Δ⁹-tetrahydrocannabinol, a cannabis sativa–derived natural product, as a probe of endocannabinoid system plasticity in type 1 diabetes: a receptor-level, testable hypothesis

Abstract

Type 1 diabetes (T1D) is a chronic autoimmune disease in which receptor-level regulation of the endocannabinoid system (ECS) remains largely unmapped. While ECS perturbations have been extensively described in obesity and type 2 diabetes, a directed experimental interrogation of receptor adaptability in autoimmune diabetes is still lacking. Within the framework of natural-product pharmacology, plant-derived Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the principal psychoactive constituent of Cannabis sativa L., provides a uniquely suitable experimental probe of this gap, owing to its partial CB1 agonism, high lipophilicity, oral bioavailability, and documented tolerability in chronic human exposure paradigms. This hypothesis-driven article advances a receptor-level testable framework in which chronic, dose-escalating oral Δ⁹-THC exposure is hypothesized to induce GRK2/3-mediated CB1 phosphorylation, β-arrestin–driven receptor desensitization, and a relative shift of ECS tone toward CB2-associated regulatory signaling. The framework integrates evidence on intestinal barrier dynamics, immune polarization, the blood–pancreas barrier as a structurally analogous ECS-sensitive interface, and β-cell metabolic plasticity, but is deliberately confined to receptor-level adaptations as the central, testable claim. Δ⁹-THC is introduced strictly as a purified plant-derived probe administered orally under controlled experimental conditions, not as a therapeutic candidate. Alternative pharmacological tools—including synthetic CB1 agonists and inhibitors of endocannabinoid degradation (FAAH, MAGL) — are explicitly acknowledged; however, Δ⁹-THC is positioned as the natural-product–compatible probe most aligned with the editorial scope of this article. By formalizing a set of falsifiable predictions in NOD mouse models, isolated islets, intestinal organoids, and human cross-sectional cohorts, this work converts an analogical and extrapolative literature into a discrete preclinical research agenda. The ECS-centred framework is explicitly framed as complementary to—not in competition with—established mechanistic axes in T1D pathogenesis, including HLA-associated genetic susceptibility, viral triggers, and β-cell intrinsic stress responses.

1 Introduction

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by HLA-restricted, T-cell–mediated immune-mediated destruction of pancreatic β-cells and lifelong dependence on exogenous insulin. Its pathogenesis is driven by loss of self-tolerance to β-cell autoantigens (insulin, GAD65, IA-2, ZnT8), seroconversion to islet autoantibodies, expansion of β-cell–reactive CD4⁺ and CD8⁺ T-cell clones, and a relative deficit in regulatory T-cell restraint, with established environmental contributors including enteroviral exposures. Despite major advances in glucose management, no currently available therapy reliably modifies disease progression or prevents β-cell loss (Cnop et al., 2005). Increasing evidence suggests that T1D extends beyond a strictly β-cell–centric process and involves systemic mechanisms, including chronic inflammation, mitochondrial dysfunction, and impaired tissue barrier integrity, which together shape disease susceptibility and progression (Gruden et al., 2016; Łukowski, 2025).

The endocannabinoid system (ECS) is a lipid signaling network that integrates immune regulation, metabolic control, mitochondrial function, and epithelial barrier stability. Dysregulation of ECS signaling has been documented in metabolic disorders and across multiple autoimmune diseases, where it is associated with altered immune cell activity, redox imbalance, and compromised barrier control (Gruden et al., 2016; Di Marzo, 2018; Chiurchiù et al., 2015). In contrast, the ECS remains insufficiently characterized in autoimmune diabetes, and its role in T1D pathophysiology is largely unexplored (Howlett, 2017; Pertwee et al., 2010).

The historical discovery of the ECS is inseparably linked to plant-based natural product research. Cannabis sativa L. (in older botanical and pharmacognostic literature also referred to as Cannabis indica), long used in traditional medical systems for gastrointestinal disturbances and inflammatory conditions, provided the phytochemical basis for receptor identification. The mid-20th century isolation and structural characterization of Δ⁹-tetrahydrocannabinol (THC) from Cannabis indica represented a pivotal advance in natural product chemistry (Osei-Hyiaman et al., 2005; Silvestri et al., 2013). Transition from heterogeneous botanical extracts to a purified, structurally defined secondary metabolite enabled reproducible receptor-binding studies, leading to the identification of CB1 and CB2 receptors and the subsequent discovery of endogenous ligands such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG) (Battista et al., 2013; Giorgi et al., 2021).

Thus, the purification of a plant-derived molecule revealed a conserved physiological signaling system with broad immunometabolic relevance. Despite this origin, systematic investigation of phytocannabinoid-mediated receptor plasticity in autoimmune diabetes has not been undertaken. Most ECS research in diabetes has focused on type 2 diabetes and obesity-related insulin resistance, conditions linked to chronic endocannabinoid overactivity, particularly at CB1. Whether ECS alterations in T1D represent compensatory adaptation to inflammatory stress or contribute to disease amplification remains unknown (Lazenka et al., 2014; Noble, 2024).

Across multiple autoimmune diseases—including inflammatory bowel disease, multiple sclerosis, and rheumatoid arthritis—ECS dysregulation has been associated with shifts in CB1/CB2 balance, altered endocannabinoid tone, and mitochondrial vulnerability. These observations suggest that the ECS functions as an integrative inflammatory rheostat linking barrier tissues, immune polarization, and metabolic stress. However, receptor-level ECS plasticity under sustained phytocannabinoid engagement has not been systematically interrogated in T1D (Łukowski, 2025; Battista et al., 2013; Chiurchiù et al., 2018; Rozanc et al., 2024).

In the present framework, Δ⁹-tetrahydrocannabinol is introduced strictly as a purified phytochemical probe rather than as a therapeutic agent. Importantly, this work refers exclusively to controlled oral administration of purified THC and does not involve inhalational or smoked cannabis preparations. Oral exposure permits standardized dosing and sustained systemic engagement while minimizing variability associated with combustion and rapid pulmonary absorption (Huestis and Pertwee, 2005; Pertwee et al., 2010).

The aim of this work is to define a structured preclinical research gap at the intersection of T1D, ECS dysregulation, and sustained oral phytocannabinoid exposure. As illustrated in Figure 1, by integrating evidence from autoimmune comorbidities, metabolic disease models, gut–immune interactions, and pancreatic β-cell biology, we propose a mechanistic framework to guide future experimental studies without advancing therapeutic claims (Łukowski, 2025).

FIGURE 1

Several ECS-related terms (ECS tone, CB1 dominance, receptor recalibration) are used recurrently in this manuscript. To prevent ambiguity, working definitions are summarized in Box 1.

2 Materials and methods

2.1 Study design and scope

This manuscript is a narrative, hypothesis-generating mechanistic review aimed at integrating fragmented evidence on endocannabinoid system (ECS) signaling and cannabinoid biology—particularly Δ⁹-tetrahydrocannabinol (THC)—across autoimmune, metabolic, and inflammatory disease contexts, with specific relevance to type 1 diabetes (T1D).

The primary objective was not to evaluate therapeutic efficacy or generate new experimental data, but to construct a coherent conceptual framework linking ECS plasticity, barrier dysfunction, immune activation, and pancreatic β-cell vulnerability in autoimmune diabetes.

No new experimental studies, animal interventions, human trials, datasets, or computational analyses were performed as part of this work.

2.2 Literature search strategy

A structured literature search was conducted between August and December 2025 using the PubMed, Scopus, and Web of Science databases. Search terms included combinations of:

“Δ⁹-tetrahydrocannabinol”, “endocannabinoid system”, “cannabinoids”, “CB1”, “CB2”, “FAAH”, “MAGL”, “FABP”, “autoimmunity”, “type 1 diabetes”, “autoimmune diabetes”, “type 2 diabetes”, “β-cell”, “insulin secretion”, “mitochondria”, “oxidative stress”, “gut microbiota”, and “intestinal barrier”.

Additional manual searches were performed by screening reference lists of relevant reviews and primary research articles to capture foundational studies and mechanistic reports not retrieved by database queries.

Only peer-reviewed articles published in English were considered.

2.3 Inclusion of adjacent disease models

This strategy reflects a mechanism-driven rather than disease-label–driven approach, acknowledging that many ECS-dependent cellular processes are conserved across tissues and disease states, even when clinical phenotypes differ.

The resulting fragmentation and partial overlap of evidence across metabolic and autoimmune domains is explicitly summarized in Figure 2, which illustrates the current preclinical research gap motivating this framework.

FIGURE 2

Chiurchiù et al., 2015; Di Marzo and Piscitelli, 2015; O’Sullivan, 2016; Cani et al., 2016). Figure created with BioRender.com.

2.4 Evidence integration and conceptual mapping

Identification of testable preclinical hypotheses.

2.5 Methodological limitations

Because no published studies have systematically examined chronic, dose-escalating THC exposure in autoimmune diabetes—either in humans or in NOD mouse models—certain elements of this framework necessarily rely on analogical reasoning from adjacent autoimmune and metabolic contexts. These extrapolations are explicitly framed as hypothesis-generating and require empirical validation (Lazenka et al., 2014; Battista et al., 2013).

The inclusion of older foundational studies reflects the limited number of original investigations into cannabinoid-mediated immunometabolic regulation rather than a methodological omission.

Among these older foundational studies, the work of Li et al. (2001) represents the closest available preclinical precedent for the present framework, although it does not directly model spontaneous autoimmune diabetes. In the multiple-low-dose streptozotocin (MLD-STZ) model, oral Δ⁹-THC transiently attenuated hyperglycemia, preserved pancreatic insulin content, reduced insulitis and CD3⁺ inflammatory cell infiltration, and lowered pancreatic IFN-γ, IL-12, and TNF-α mRNA expression. However, the MLD-STZ model combines immune-mediated β-cell injury with direct STZ cytotoxicity and is therefore not equivalent to spontaneous autoimmune diabetes. For this reason, Li et al. should be interpreted as the nearest available proof-of-principle that Δ⁹-THC can modulate the immune component of experimental diabetes, while dedicated studies in NOD mice remain necessary to test receptor-level ECS plasticity during genetically driven autoimmune β-cell destruction.

3 Δ⁹-tetrahydrocannabinol as a cannabis sativa–derived natural product: phytochemistry, pharmacokinetics, and pharmacodynamics

Because the central hypothesis advanced in this article positions Δ⁹-tetrahydrocannabinol (Δ⁹-THC) as a receptor-level probe administered orally and chronically, the pharmacokinetic (PK) and pharmacodynamic (PD) properties of this Cannabis sativa–derived natural product require explicit treatment. The features outlined below are not incidental: they directly determine whether the proposed receptor adaptations (GRK2/3-mediated CB1 phosphorylation, β-arrestin recruitment, internalization, and CB2 re-emergence) can plausibly be induced and detected within the time frame of a typical NOD-mouse experiment or controlled human exposure paradigm (Lazenka et al., 2014; Huestis and Pertwee, 2005; Elmes et al., 2019).

3.1 Cannabis sativa as the botanical source of Δ⁹-THC

Cannabis sativa L. is a botanically variable annual plant whose secondary metabolome includes more than one hundred structurally related C21 prenylated polyketides collectively termed phytocannabinoids (Pertwee et al., 2010). Among them, Δ⁹-tetrahydrocannabinol (Δ⁹-THC) is the predominant psychoactive constituent of high-THC chemovars (colloquially designated as C. sativa subsp. Indica or as drug-type C. sativa, although the precise taxonomic status of these designations remains contested in modern cannabis chemistry). Δ⁹-THC is biosynthesized through prenylation and oxidative cyclization of olivetolic acid, yielding tetrahydrocannabinolic acid (THCA-A), which is subsequently converted to neutral Δ⁹-THC by non-enzymatic decarboxylation upon heating or prolonged storage (Schurman et al., 2020).

For the purposes of the present framework, Δ⁹-THC is treated strictly as a purified, plant-derived natural product whose chemical identity and ligand properties are well-characterized across species and exposure routes, in contrast to crude Cannabis extracts, whose pharmacological profile is modulated by accompanying minor cannabinoids (cannabidiol, cannabigerol, cannabinol) and terpene constituents. Pharmaceutical-grade purified Δ⁹-THC therefore provides the analytical control required for the receptor-level mechanistic claims advanced in this work, and is the form in which the natural-product probe is operationalized throughout the manuscript. The receptor-level adaptations induced by chronic exposure to this natural product are addressed at the pharmacokinetic level in Section 3.2 and at the pharmacodynamic level in Section 3.3, before the analysis turns, in Section 4, to the endocannabinoid system as the biological substrate upon which the probe is intended to act (Huestis and Pertwee, 2005; Izzo et al., 2009; Di et al., 2011).

3.2 Pharmacokinetics: absorption, distribution, metabolism, and elimination

Δ⁹-THC is highly lipophilic (logP ≈ 6–7), which dominates its pharmacokinetic profile across all administration routes. Following oral administration, absorption is variable and substantially reduced compared with inhalation, with reported bioavailability between approximately 6% and 20% depending on formulation (oil-based, encapsulated, or food matrix) and individual factors (Huestis and Pertwee, 2005). After absorption, Δ⁹-THC undergoes extensive hepatic first-pass metabolism, primarily by CYP2C9 and CYP3A4, producing the psychoactive active metabolite 11-hydroxy-Δ⁹-THC (11-OH-THC) and, subsequently, the inactive carboxylic acid metabolite 11-nor-9-carboxy-Δ⁹-THC. Importantly, intracellular trafficking of Δ⁹-THC and its metabolites is regulated in part by fatty-acid-binding proteins (FABPs), notably FABP1 in hepatocytes (Kaczocha et al., 2012), with direct relevance for the receptor-level framework advanced here (Elmes et al., 2019).

Three pharmacokinetically distinct time scales should be explicitly distinguished, because they are frequently conflated in the cannabinoid literature: (I) the distribution half-life of Δ⁹-THC (minutes), governing initial uptake into well-perfused tissues; (II) the plasma elimination half-life of Δ⁹-THC itself, typically reported as 1.five to three h following a single oral dose but variable with formulation and prior exposure; and (III) the terminal elimination half-life, which is markedly prolonged (commonly 24–36 h after acute use, and substantially longer in chronic users) and reflects slow redistribution from adipose depots (Huestis and Pertwee, 2005). Under chronic oral exposure paradigms relevant to the present framework, this terminal kinetic compartment, rather than peak plasma concentration, is the principal determinant of sustained receptor exposure and therefore of the receptor-level adaptations interrogated in this manuscript.

The principal active metabolite of Δ⁹-THC, 11-OH-THC, displays comparable or higher CB1 affinity than the parent compound and contributes appreciably to the in vivo pharmacological effect of oral Δ⁹-THC, particularly in chronic dosing regimens with substantial first-pass metabolism (Huestis and Pertwee, 2005). Together with the FABP-mediated cytosolic transport of Δ⁹-THC (Elmes et al., 2019), this active-metabolite contribution implies that effective receptor exposure under oral chronic administration cannot be inferred from parent-compound plasma kinetics alone and must be evaluated jointly with 11-OH-THC and lipidomic measurements.

The principal pharmacokinetic parameters relevant to chronic, dose-escalating oral exposure paradigms are summarized in Table 1.

3.3 Pharmacodynamics, CB1 partial agonism, signaling bias, and implications for chronic oral exposure paradigms

Pharmacodynamically, Δ⁹-THC acts as a partial agonist at both CB1 and CB2 receptors, with relatively higher CB1 efficacy in most cellular systems and tissue contexts (Pertwee et al., 2010). Partial agonism is mechanistically important for the present hypothesis: in contrast to full synthetic agonists (e.g., WIN55,212-2 or CP55,940), partial agonist exposure typically results in submaximal but persistent receptor activation, which has been more consistently associated with phosphorylation, β-arrestin recruitment, and signaling bias than with abrupt receptor saturation (Howlett, 2017). Direct experimental evidence supports the capacity of repeated Δ⁹-THC administration to induce regional CB1 desensitization and downregulation through these mechanisms (Lazenka et al., 2014).

In addition to CB1 and CB2, Δ⁹-THC engages several non-canonical targets relevant to the broader ECS, including GPR55, PPARγ, and TRPV1 (Rafacho et al., 2011), with implications for cellular calcium handling, mitochondrial dynamics, and transcriptional regulation (Pertwee et al., 2010). The present framework does not require simultaneous engagement of all these targets but does require that the dominant signaling output under chronic oral exposure converge on receptor-level adaptation of CB1 and a relative shift of effective signaling toward CB2-associated regulatory pathways.

From the convergent PK and PD properties summarized above, several practical implications for experimental design follow. First, single-dose plasma kinetics are insufficient to characterize cumulative receptor exposure under the chronic oral paradigm proposed here; longitudinal sampling across days to weeks, combined with quantification of active metabolites and tissue endocannabinoid pools, is required. Second, because partial-agonist receptor adaptation is dose- and time-dependent, dose-escalation rather than fixed-dose administration is preferable to interrogate the dynamic range of receptor recalibration (Lazenka et al., 2014). Third, the natural-product origin of Δ⁹-THC introduces inter-batch variability (chemovar, terpene profile, residual minor cannabinoids) that must be controlled by using pharmaceutical-grade purified Δ⁹-THC rather than crude extracts. Fourth, the documented tolerability of chronic high-dose oral Δ⁹-THC in humans supports the translational feasibility of this experimental framework, although in the present manuscript Δ⁹-THC is positioned strictly as a mechanistic probe and not as a therapeutic candidate (Lazenka et al., 2014; Huestis and Pertwee, 2005).

3.4 Comparative pharmacology of cannabinoid ligands and rationale for Δ⁹-THC as a natural-product probe

To determine which cannabinoid ligands are theoretically capable of engaging the mechanistic axis outlined above, key physicochemical and pharmacokinetic parameters governing sustained CB1 receptor engagement are considered.

The capacity of cannabinoids to modulate ECS signaling is strongly influenced by their physicochemical properties, including lipophilicity, membrane permeability, metabolic stability, and receptor-binding affinity. Endogenous ligands such as AEA and 2-AG are synthesized on demand and act locally, with signaling duration tightly constrained by rapid enzymatic degradation via FAAH and MAGL, respectively (Blankman and Cravatt, 2013; Di Marzo, 2008). This ensures transient receptor engagement and limits prolonged adaptive responses under physiological conditions. These key physicochemical and pharmacokinetic parameters are summarized in Table 2 (Huestis and Pertwee, 2005; Elmes et al., 2019; Izzo et al., 2009; Pacher et al., 2006).

In contrast, phytocannabinoids—particularly THC—exhibit markedly higher lipophilicity, enhanced diffusion across biological membranes, and prolonged tissue retention. These properties facilitate access not only to plasma membrane CB1 and CB2 receptors but also to intracellular and mitochondrial receptor pools (Bénard et al., 2012). As summarized in Table 2, THC displays a distinctive combination of receptor affinity, bioavailability, and residence time that distinguishes it from both endogenous cannabinoids and other phytocannabinoids. Importantly, the comparatively high binding affinity of THC enables prolonged CB1 receptor engagement, which in experimental settings has been associated with receptor phosphorylation and adaptive downregulation processes, particularly in contexts of sustained CB1 activation (Sim-Selley, 2003; Breivogel et al., 1999).

These characteristics do not imply superior physiological relevance, but they render THC particularly suitable for experimentally probing ECS plasticity. Sustained receptor engagement enabled by THC allows observation of adaptive processes—such as receptor desensitization, signaling bias, and metabolic reprogramming—that are difficult to capture using rapidly degraded endogenous ligands (Lazenka et al., 2014; Noble, 2024).

4 Endocannabinoid system plasticity in autoimmune and metabolic disease

Having outlined the pharmacokinetic and pharmacodynamic profile of Δ⁹-THC as a Cannabis sativa–derived natural product in Section 3, the following section turns to the biological substrate on which this probe is intended to act. Endocannabinoid system (ECS) plasticity is examined here in the specific context of type 1 diabetes (T1D), with attention to the receptor-level adaptations and tissue-specific reorganizations that motivate the experimental framework developed in subsequent sections.

4.1 Endocannabinoid system imbalance in T1D: motivation and scope

Although direct, longitudinal studies of endocannabinoid system (ECS) dynamics in autoimmune diabetes remain scarce, indirect evidence converges on the view that ECS plasticity is engaged at multiple levels of T1D pathogenesis. In particular, sustained inflammatory pressure has been associated with shifts in 2-arachidonoylglycerol (2-AG) and anandamide (AEA) tone, alterations in cannabinoid receptor expression, and changes in barrier and immune cell signaling. Several of the upstream events most often discussed in this context—microbiota–ECS interactions, intestinal barrier remodeling, and inter-organ lipid mediator propagation—are addressed as a network-level lipid signaling problem in a parallel manuscript by the present author. The present article focuses, by deliberate scope, on the receptor-level layer of this larger picture, and specifically on how a plant-derived cannabinoid agonist may be used to interrogate it (Łukowski, 2025; Cani et al., 2016).

In framing the present work, ECS plasticity in T1D is positioned as a deliberate experimental gap rather than as a settled mechanism, and the analytical scope is intentionally narrowed to receptor-level adaptations under sustained ligand exposure. The phytochemical, pharmacokinetic, and pharmacodynamic foundations that allow Δ⁹-THC to serve as a tractable probe of this receptor layer are addressed in dedicated Section 3, whereas the upstream gut-derived and downstream β-cell consequences of ECS remodeling—together with their relative contribution to T1D pathogenesis alongside HLA-conferred susceptibility, viral triggers, and β-cell intrinsic stress—are integrated only insofar as they shape the receptor-level readouts proposed in this manuscript (Gruden et al., 2016; Łukowski, 2025; Pertwee et al., 2010).

4.2 Cannabis research for type 1 diabetes: current evidence and a mechanistic gap

Cannabinoids have been extensively investigated across metabolic, inflammatory, and autoimmune disease models, with reported effects on glucose regulation, insulin sensitivity, oxidative stress, and immune signaling. As summarized in Table 3, these effects span diverse compound classes—including Δ⁹-tetrahydrocannabinol (THC), cannabidiol (CBD), tetrahydrocannabivarin (THCV), cannabigerol (CBG), and synthetic CB1 or CB2 ligands—and converge on partial recalibration of the endocannabinoid system (ECS), most commonly characterized by reduced CB1 signaling and engagement of CB2- or PPARγ-associated pathways (Gruden et al., 2016; Pertwee et al., 2010; Di et al., 2011; Horváth et al., 2012).

Despite this breadth, the majority of available data derive from chemically induced diabetes or metabolic disease models that lack the autoimmune component central to type 1 diabetes (T1D). Consequently, while these studies provide important insights into β-cell toxicity and metabolic stress, they offer limited resolution with respect to immune–metabolic feedback and receptor-level adaptation in autoimmune contexts (Gruden et al., 2016; Łukowski, 2025; Di et al., 2011; Horváth et al., 2012).

The earliest preclinical demonstration that purified Δ⁹-THC can modulate the immune component of experimental diabetes comes from Li et al. (2001). In a multiple-low-dose streptozotocin (MLD-STZ) model, oral Δ⁹-THC transiently attenuated hyperglycemia, preserved pancreatic insulin content, reduced insulitis and CD3⁺ inflammatory cell infiltration in the islets, and lowered pancreatic IFN-γ, IL-12, and TNF-α mRNA expression. This work remains the closest available preclinical precedent for the receptor-level framework proposed here, in that it pairs an oral, repeated-dose Δ⁹-THC exposure paradigm with immune-readout endpoints in an immune-mediated diabetes model. Two qualifications are nonetheless essential. First, the MLD-STZ model combines direct β-cell cytotoxicity with secondary T-cell–driven injury and is therefore not equivalent to the spontaneous, HLA-restricted autoimmunity that defines T1D in NOD mice or in humans; the immune component is induced rather than genetically programmed. Second, the study did not assess receptor-level adaptations such as CB1 phosphorylation status, β-arrestin recruitment, or relative CB2 re-emergence under sustained exposure. Li et al. should accordingly be read as a proof-of-principle that Δ⁹-THC can dampen the immune limb of experimental β-cell injury, while the question of whether the same compound induces adaptive ECS recalibration during genuinely autoimmune β-cell destruction—the central question of the present framework—remains open.

Only recently has cannabinoid research begun to directly engage autoimmune-relevant models. González-Mariscal et al. (2022) demonstrated that abnormal cannabidiol (abn-CBD), acting through CB1-independent and CB2-biased mechanisms, attenuates insulitis and preserves β-cell mass in non-obese diabetic (NOD) mice. Garcia-Luna et al. (2023) subsequently showed that Δ⁹-THC modulates β-cell function and glucose-stimulated insulin secretion in C57BL/6 prediabetic mice maintained on a hypercaloric diet; although not performed in an autoimmune model, this work established the feasibility of short-term oral Δ⁹-THC exposure in pancreatic islets under metabolic stress. Together, these studies indicate growing experimental traction for cannabinoid-based modulation of autoimmune diabetes, while remaining limited to fixed-dose paradigms (Horváth et al., 2012).

In parallel, translational human data have established the feasibility of chronic and dose-escalating THC exposure. A comprehensive review by Rozanc et al. (2024) summarized controlled human laboratory studies employing oral THC doses ≥30 mg, including intra-subject dose-escalation designs, demonstrating general tolerability under controlled conditions. Although not conducted in autoimmune disease settings, these data provide methodological precedent for sustained and escalating THC exposure aimed at inducing adaptive cannabinoid receptor regulation rather than acute intoxication (Lazenka et al., 2014; Huestis and Pertwee, 2005).

Taken together, current evidence suggests that cannabinoid research in T1D is advancing in a coherent direction, yet remains largely descriptive with respect to ECS adaptation. What remains unexamined is a unified mechanistic framework focused on receptor-level plasticity—specifically GRK/β-arrestin–dependent CB1 phosphorylation, functional CB1 downregulation, and relative CB2 upregulation—as a regulatory axis in autoimmune diabetes. Leveraging established feasibility data, chronic dose-escalating THC paradigms, complemented by integrated endocannabinoid and gut microbiota profiling in humans, represent a logical next step toward mechanistic resolution (Rozanc et al., 2024).

4.3 Central mechanistic axis: CB1 phosphorylation and receptor downregulation

At the core of the present framework lies a single, explicitly testable mechanistic hypothesis: that GRK/β-arrestin–dependent phosphorylation and functional downregulation of CB1 receptors constitutes a critical lever for resetting pathological endocannabinoid system (ECS) tone in type 1 diabetes (T1D) (Lazenka et al., 2014; Howlett, 2017; Pacher et al., 2006).

Importantly, cannabinoid receptors do not operate in isolation. CB1 and CB2 form functional heterodimers and higher-order signaling complexes, allowing changes in CB1 phosphorylation state to propagate across ECS signaling networks, including immune, epithelial, endothelial, and β-cell compartments. From this perspective, chronic, escalating THC exposure is not intended to “activate” the ECS, but rather to force the system into a desensitized, reweighted configuration, revealing whether pathological CB1 dominance represents a reversible adaptive state or a locked pathological attractor (broader CB1/CB2 pharmacology has been comprehensively reviewed in 2017 by Howlett et al. (2017) and Li et al., 2001.

Despite extensive literature on cannabinoids in metabolic disease, inflammation, and autoimmunity, no study has systematically examined chronic, orally administered THC using progressively escalating doses in autoimmune diabetes, particularly in NOD mice. Existing work has focused on chemically induced β-cell toxicity models or CB1-independent cannabinoids such as abnormal cannabidiol (abn-CBD). Consequently, the impact of sustained CB1 phosphorylation pressure on ECS plasticity in an authentic autoimmune context remains undefined (Łukowski, 2025; González-Mariscal et al., 2022).

It should be acknowledged that Δ⁹-THC is not the only experimental tool capable of inducing CB1 receptor adaptations. A range of complementary pharmacological strategies exist, including synthetic full and partial CB1 agonists (e.g., WIN55,212-2, CP55,940, HU-210), inhibitors of endocannabinoid degradation that elevate endogenous AEA and 2-AG (e.g., the FAAH inhibitor URB597 and the MAGL inhibitor JZL184) (Kozela et al., 2013), and CB1-selective peripherally restricted inverse agonists (Ghosh et al., 2023). Each class engages CB1 signaling differently, and several have been used to dissect receptor desensitization, β-arrestin recruitment, and downstream effector pathways under controlled conditions. The choice of Δ⁹-THC in the present framework is therefore not based on uniqueness in pharmacological terms, but on a defined combination of features relevant to the specific question and journal scope: as a Cannabis sativa–derived natural product with documented oral bioavailability and chronic-use feasibility in humans, prolonged tissue residence due to high lipophilicity, partial agonism that supports sustained rather than maximal receptor activation, and inclusion within the editorial scope of natural-product pharmacology. Synthetic ligands and MAGL/FAAH inhibitors are valuable complementary probes and remain natural targets for follow-up experimental work, but fall outside the natural-product framework of the present hypothesis (Pertwee et al., 2010; Schurman et al., 2020; Karwad et al., 2017; Dagon et al., 2007).

4.4 Receptor preferences and plasticity of the cannabinoid system under inflammatory stress

The purpose of chronic, dose-escalating THC exposure within this framework is to impose sustained CB1 ligand pressure sufficient to trigger GRK/β-arrestin–dependent phosphorylation, internalization, and signaling bias of hyperactive CB1 receptors—an adaptive mechanism observed in other autoimmune and inflammatory diseases but untested in type 1 diabetes (Borrelli et al., 2013).

Under physiological conditions, endocannabinoid system (ECS) signaling is governed by ligand-specific receptor preferences and tightly regulated temporal dynamics. Anandamide (AEA) and 2-arachidonoylglycerol (2-AG) exert short-lived, spatially restricted effects, with functional selectivity across CB1, CB2, and TRPV1 receptors. In this balanced state, ECS signaling integrates metabolic cues with immune tone, while parallel receptor pools at the plasma membrane and mitochondria coordinate calcium handling, redox balance, and energy homeostasis (Chiurchiù et al., 2015; Di Marzo and Piscitelli, 2015; Wu et al., 2008). An overview of these receptor–ligand preferences and the associated pharmacological distinctions is provided in Figure 3 (Pertwee et al., 2010; Schurman et al., 2020; Pacher et al., 2006).

FIGURE 3

Bermúdez-Silva et al., 2008). Figure created with BioRender.com.

In autoimmune and inflammatory contexts relevant to type 1 diabetes (T1D), this equilibrium becomes progressively destabilized. Intestinal dysbiosis and barrier dysfunction have been proposed to promote sustained elevation of 2-AG, shifting ECS tone toward chronic receptor engagement rather than transient signaling. Hypothesized, persistent 2-AG excess favors prolonged CB1 activation, enhanced GRK-dependent receptor phosphorylation, and β-arrestin recruitment, ultimately driving receptor desensitization and signaling bias toward metabolically and oxidatively stressful pathways (Silvestri et al., 2013; Cani et al., 2016). At the same time, chronic ligand pressure alters receptor trafficking and degradation dynamics, contributing to functional attenuation of CB2-mediated immunoregulatory signaling (Gruden et al., 2016; Łukowski, 2025; Chiurchiù et al., 2015; R et al., 2008; Silva-Picazo and Allan, 2025).

Crucially, cannabinoid receptor expression itself is dynamically regulated by the prevailing endocannabinoid environment. Sustained 2-AG overproduction is conceptually proposed to promote a transcriptional and post-translational landscape favoring CB1 expression and dominance, with the potential to reinforce pro-inflammatory signaling loops. In T1D, where CB2-dependent immune restraint may be insufficient or progressively lost, such a ligand-driven shift could further predispose target tissues—particularly pancreatic β-cells—to immune-mediated damage. The proposed CB1-dominant ECS state in T1D and the hypothesized THC-induced receptor recalibration are conceptually summarized in Figure 4. It must be explicitly acknowledged, however, that direct experimental evidence for a stably CB1-dominant ECS state specifically in autoimmune diabetes is currently lacking. This construct is derived by analogy from chemically induced diabetes, type 2 diabetes, and adjacent autoimmune models, and is advanced here as a falsifiable hypothesis to be probed—rather than as an established feature of T1D pathophysiology. The experimental predictions outlined in Section 8 and Table 4 are designed precisely to test, rather than presuppose, the validity of this construct (Howlett, 2017; Schurman et al., 2020).

FIGURE 4

Breivogel et al., 1999; Silva-Picazo and Allan, 2025). THC/FABP1 interactions may reduce AEA trafficking toward FAAH degradation, increase local AEA availability, normalize MAGL-dependent 2-AG turnover, and support PPARγ-linked anti-inflammatory and metabolic transcriptional responses (O’Sullivan, 2016; Elmes et al., 2019; Blankman and Cravatt, 2013; Marche et al., 2017; Gurevich and Gurevich, 2020), thereby attenuating CB1-driven calcium and mitochondrial stress (Blankman and Cravatt, 2013; Kaczocha et al., 2015). The diagram is intended as a conceptual integration of receptor-level adaptations rather than a depiction of therapeutic outcomes. Figure created with BioRender.com.

The methodological basis for this hypothesis is abductive inference from three independent evidence domains. First, sustained CB1 overactivity has been extensively documented in metabolic-inflammatory contexts (obesity, type 2 diabetes), where CB1 antagonism reverses dysmetabolic phenotypes (Osei-Hyiaman et al., 2005; Silvestri et al., 2013; Di et al., 2011; Horváth et al., 2012; Borrelli et al., 2013; Després et al., 2005). Second, ECS dysregulation involving CB1/CB2 shifts has been independently documented in autoimmune conditions frequently comorbid with T1D—including celiac disease (Battista et al., 2013), multiple sclerosis (Chiurchiù et al., 2018), inflammatory bowel disease (Kozela et al., 2013), and rheumatoid arthritis (Laprairie et al., 2015) — establishing autoimmunity as a context in which ECS plasticity is engaged. Third, within T1D-relevant preclinical systems, cannabinoid modulation has been shown to influence disease trajectory: cannabidiol arrests T1D onset in NOD mice (Jadoon et al., 2016), abnormal cannabidiol attenuates insulitis and preserves β-cell mass (González-Mariscal et al., 2022), and Δ⁹-THC modulates pancreatic islet function in non-autoimmune metabolic stress models (Garcia-Luna et al., 2023); complementary direct evidence in human T1D documents TRPV1 channel dysregulation (R et al., 2008; Silva-Picazo and Allan, 2025). None of these data prove a stably CB1-dominant ECS state specifically in T1D, but their convergence provides sufficient mechanistic plausibility to motivate dedicated empirical interrogation—which the present framework, together with the falsifiable predictions in Section 8 and Table 4, is designed to enable.

4.5 Cell-type-specific ECS expression and signaling across tissues relevant to T1D

A consistent limitation of analogical extrapolation from chemically induced diabetes and type 2 diabetes models is that ECS components are not uniformly expressed across the cell populations relevant to T1D, and the predicted receptor-level adaptations therefore cannot be assumed to occur with equal magnitude or directionality in every tissue. To clarify the cell-type resolution required for testing the present framework, the principal ECS components reported in T1D-relevant cellular compartments are briefly summarized below.

Pancreatic β-cells express functional CB1 and CB2 receptors together with the principal endocannabinoid-synthesizing (DAGLα/β, NAPE-PLD) and -degrading (FAAH, MAGL) enzymes, and these components have been localized to both plasma-membrane and intracellular pools, including mitochondria-associated compartments that couple CB1 engagement to oxidative phosphorylation and glucose-stimulated insulin secretion (Hebert-Chatelain et al., 2016; Li et al., 2021; Aseer and Egan, 2021; Cortes-Justo et al., 2023). Within this compartment, CB1 activation has been associated with impaired insulin receptor signaling and proapoptotic mitochondrial signaling, whereas CB2 and PPARγ engagement have been associated with cytoprotective and anti-inflammatory effects (Hebert-Chatelain et al., 2016; Aseer and Egan, 2021; González-Mariscal and Egan, 2018; Bermúdez-Silva et al., 2008; Kim et al., 2011). Pancreatic α-cells also express CB1, where receptor activation modulates glucagon secretion, although this compartment remains substantially less characterized than the β-cell in autoimmune contexts (Hebert-Chatelain et al., 2016; Aseer and Egan, 2021).

Within the immune compartment, CB1 and CB2 are differentially expressed across innate and adaptive populations. CB2 predominates on monocytes, macrophages, dendritic cells, B cells, and on activated T-cell subsets, and is generally regarded as the principal immunoregulatory cannabinoid receptor; CB1 expression on resting T cells is lower but is upregulated upon activation. Reported functional consequences include attenuation of Th1 and Th17 polarization and partial preservation of regulatory T-cell function under cannabinoid engagement, together with downregulation of antigen-presenting-cell maturation and effector cytokine output (Chiurchiù et al., 2015; Klein et al., 1998; Weiss et al., 2008; Osei-Hyiaman et al., 2008). These cell-type distinctions are directly relevant to T1D, where pathogenesis is dominated by Th1- and Th17-biased CD4⁺ responses, β-cell-reactive CD8⁺ cytotoxic T cells, and a relative deficit in functional Treg restraint; the predicted directionality of ECS adaptations therefore cannot be assumed to be identical across all immune subsets and should be evaluated subset by subset rather than as a single aggregate readout.

In intestinal epithelial cells, CB1 and CB2 are co-expressed with TRPV1 and contribute to tight-junction stability, paracellular permeability, and mucosal immune tone, with CB1 overactivation linked to junctional destabilization and CB2-biased signaling linked to barrier preservation (Battista et al., 2013; Cani et al., 2016; Kozela et al., 2013). Endothelial cells of the blood–brain barrier, and—by structural analogy advanced in Section 7—the blood–pancreas barrier, also express functional ECS components that couple sustained CB1 engagement to oxidative stress and junctional remodeling (Kim et al., 2016; Shin et al., 2018). Across these compartments, the prevailing direction of receptor-level adaptation under chronic ligand pressure is not uniform: CB1 is the dominant driver of pro-inflammatory and pro-apoptotic signaling in β-cells and barrier endothelia, while CB2 is the dominant regulatory node in macrophages, dendritic cells, and lymphocytes. The cell-type-specific framing summarized here is intended to make explicit that the receptor-level predictions advanced in this manuscript are not interchangeable across compartments and that experimental designs should resolve, rather than average over, these distinctions.

5 Gut-driven endocannabinoid system dysregulation as an upstream event

Accumulating evidence from longitudinal, mechanistic, and systems-level studies indicates that intestinal dysbiosis and early epithelial barrier dysfunction represent upstream events in the development of autoimmune diseases, including type 1 diabetes (T1D). Large prospective cohorts have demonstrated that individuals progressing toward T1D exhibit an early reduction in short-chain fatty acid (SCFA)–producing bacterial taxa—particularly butyrate- and propionate-producing genera such as Faecalibacterium, Roseburia, and Eubacterium—preceding islet autoantibody seroconversion and clinical onset (Łukowski, 2025; Cani et al., 2016; Klein et al., 1998). SCFA deficiency compromises epithelial energy metabolism, tight junction stability, and immune tolerance, thereby creating a permissive pro-inflammatory environment at the intestinal interface (Kozela et al., 2013; Brook et al., 2019).

As illustrated in Figure 5, loss of barrier integrity enables translocation of luminal microbial products, most notably lipopolysaccharide (LPS), into the lamina propria and systemic circulation. LPS-driven activation of innate immune cells—particularly intestinal macrophages—has been associated with state-dependent remodeling of local endocannabinoid system (ECS) signaling. The intestine is one of the most active sites of endocannabinoid synthesis, exhibits high capacity for 2-arachidonoylglycerol (2-AG) production, and activated immune cells represent a major source of excessive 2-AG under dysbiotic conditions (Chiurchiù et al., 2015; Cani et al., 2016; Brook et al., 2019). Sustained immune cell–derived 2-AG overproduction is hypothesized to shift ECS tone from transient, homeostatic signaling toward a pro-inflammatory, CB1-dominant state, amplifying metabolic and oxidative stress pathways relevant to autoimmune priming (Łukowski, 2025; Kozela et al., 2013).

FIGURE 5

Cani et al., 2016; Klein et al., 1998; Brook et al., 2019). Figure created with BioRender.com.

Recent integrative analyses propose that this microbiota-dependent cascade—linking SCFA depletion, epithelial barrier disruption, LPS-driven immune activation, and ECS remodeling—constitutes a critical upstream interface between environmental cues and systemic immune dysregulation in T1D (Łukowski, 2025; Cani et al., 2016; Klein et al., 1998). In this framework, gut-derived ECS imbalance is positioned not merely as a secondary consequence of inflammation but as a candidate driver of immune amplification with downstream relevance for pancreatic β-cell vulnerability (Łukowski, 2025).

It should be explicitly acknowledged that intestinal dysbiosis represents only one of several parallel and partially overlapping triggers of ECS dysregulation in vivo. Beyond the gut axis emphasized in this section, the ECS is responsive to (I) viral exposures, including enteroviral infections such as Coxsackie B variants long implicated in T1D etiology and capable of triggering β-cell endoplasmic reticulum stress and innate immune activation (Addissouky, 2024) that secondarily reshape lipid mediator signaling; (II) systemic bacterial endotoxin exposure independent of intestinal barrier integrity, with ECS engagement now documented across diverse infection contexts (Rajesh et al., 2010); (III) chronic glucocorticoid signaling and HPA axis dysregulation, which modulate endocannabinoid synthesis and receptor expression in immune and metabolic tissues; (IV) metabolic stressors including high-fat diet, obesity-driven adipose remodeling, and hyperglycemia, all of which acting on ECS tone through receptor- and ligand-level mechanisms (Vatanen et al., 2018); (V) environmental and xenobiotic exposures, including pesticides with documented endocrine and pro-diabetogenic effects (Acharya et al., 2017); and (VI) β-cell intrinsic stress responses and HLA-conferred autoimmune susceptibility, which interact with ECS dysregulation downstream rather than acting as primary upstream triggers (Noble, 2024; Barker and Ferraro, 2024). The gut axis is given particular attention in this section because it is the upstream limb with the most direct and longitudinally documented evidence in T1D-relevant cohorts and because its products (lipopolysaccharide, short-chain fatty acids, bile acid derivatives) interface most directly with the immune ECS at the levels addressed in the present receptor-level framework (Łukowski, 2025; Cani et al., 2016). Within this broader landscape of ECS-dysregulating inputs, the THC-as-probe approach advanced here is intended to interrogate adaptive receptor responses that are likely shared across multiple triggers, rather than to test a gut-specific hypothesis in isolation.

5.1 Tight junction destabilization, LPS translocation, and the LPS–macrophage–2-AG–CB1 axis

Tight junctions (TJs) of the intestinal epithelium are highly dynamic, ECS-sensitive structures whose integrity depends on coordinated lipid signaling, calcium flux, and redox control. Balanced endocannabinoid tone supports TJ assembly by maintaining CB1/CB2 equilibrium and controlled TRPV1-dependent Ca²⁺ signaling, thereby preserving epithelial polarity and limiting paracellular permeability (Battista et al., 2013; Cani et al., 2016; Kozela et al., 2013). Detailed molecular architecture of the TJ complex (claudin/occludin/ZO-1, with adjacent gap and adherens junctions and TRPV1 calcium handling) is provided in Figure 6 (Szanda et al., 2022).

FIGURE 6

Loss of TJ regulatory control enables translocation of microbial products such as LPS into the lamina propria, triggering innate immune activation. LPS-stimulated intestinal macrophages have been shown to exhibit excessive 2-AG production, which is hypothesized to shift ECS dynamics toward sustained CB1 engagement and pro-inflammatory signaling (Chiurchiù et al., 2015; Cani et al., 2016; Kozela et al., 2013). Persistent 2-AG excess has been associated with a CB1-dominant ECS signaling state characterized by chronic receptor engagement, calcium dysregulation, mitochondrial stress, and amplification of pro-inflammatory transcriptional pathways. In intestinal epithelial cells, CB1 overactivation has been proposed to destabilize tight junction architecture, reinforcing barrier leakage in a feed-forward manner, while in macrophages it has been associated with cytokine production and loss of regulatory restraint (Łukowski, 2025; Kozela et al., 2013; Brook et al., 2019). Together, these processes have been hypothesized to transform the intestinal barrier from a protective interface into a systemic amplifier of immunometabolic stress, facilitating propagation of inflammatory signals beyond the gut.

Emerging systems-level frameworks summarized in Figure 7 propose that this LPS–macrophage–2-AG–CB1 axis constitutes a mechanistic bridge linking gut dysbiosis to extra-intestinal autoimmune vulnerability, including pancreatic β-cell stress in type 1 diabetes (Gruden et al., 2016; Łukowski, 2025; Cani et al., 2016). In this context, barrier disruption is positioned not merely as a consequence of inflammation but as a putative active driver of ECS remodeling and disease propagation, providing a rationale for interrogating ECS plasticity at the intestinal interface as part of the broader receptor-level framework advanced in this manuscript.

FIGURE 7

Chiurchiù et al., 2015; Di Marzo and Piscitelli, 2015; Cani et al., 2016; Klein et al., 1998; Brook et al., 2019). Figure created with BioRender.com.

5.2 Δ⁹-tetrahydrocannabinol–ECS interactions at the intestinal barrier in type 1 diabetes

Although direct studies examining Δ⁹-tetrahydrocannabinol (THC) at the intestinal barrier in type 1 diabetes (T1D) are currently lacking, converging evidence from inflammatory bowel disease, autoimmune gastrointestinal models, and isolated epithelial systems indicates that THC engages the same ECS components implicated in dysbiosis-driven barrier failure described above. THC-mediated effects on the gut have been shown to be ECS-dependent, involving CB1 attenuation, CB2 engagement, and TRPV1 modulation, with reported reductions in epithelial inflammatory cytokine release and partial preservation of paracellular permeability under inflammatory challenge (Howlett, 2017; Pertwee et al., 2010; Battista et al., 2013; Kozela et al., 2013).

Within the receptor-level framework advanced here, intestinal barrier stabilization is therefore hypothesized to represent one of the earliest measurable consequences of chronic, dose-escalating oral Δ⁹-THC exposure. Because intestinal barrier failure directly conditions immune cell activation and polarization, ECS-dependent barrier stabilization may attenuate downstream immune drivers of T1D progression, providing a mechanistic rationale for the gut-focused experimental predictions outlined in Table 4 (Łukowski, 2025; Cani et al., 2016; Kozela et al., 2013).

6 Immune ECS dysregulation following barrier failure

Disruption of intestinal barrier function exposes the immune system to persistent microbial and lipid-derived inflammatory signals. Within innate and adaptive immune compartments, sustained 2-AG elevation and chronic CB1 engagement have been associated with NF-κB activation, pro-inflammatory cytokine release, M1 macrophage polarization, dendritic cell activation, and a Th1/Th17-biased adaptive response. In parallel, regulatory T-cell function and CB2-mediated counter-regulation appear to become progressively less effective under chronic ligand pressure. The progressive immune polarization arising from this ECS imbalance—from physiological surveillance to autoimmune amplification within the islet microenvironment—is summarized in Figure 8 (Chiurchiù et al., 2015; Brook et al., 2019).

FIGURE 8

Chiurchiù et al., 2015; Giorgi et al., 2021; Cani et al., 2016; Blankman and Cravatt, 2013; Wu et al., 2008; Eizirik et al., 2020; Iannotti et al., 2014; Miller et al., 2020). Figure created with BioRender.com.

Although a comprehensive treatment of immune ECS dynamics in T1D is beyond the scope of the present receptor-focused manuscript and is developed in detail in the companion network-level paper, the implication for the present framework is direct: chronic immune-cell-derived endocannabinoid pressure provides a plausible source of sustained CB1 agonism, against which the receptor-level adaptations probed by chronic phytocannabinoid exposure should be evaluated (Łukowski, 2025).

The inflammatory pressure generated within the systemic immune compartment ultimately converges on the pancreas through a specialized vascular interface—the blood–pancreas barrier (BPB) — formed by islet capillary endothelium, pericytes, and inter-endothelial tight-junction complexes. Activated immune cells have been shown to engage analogous vascular barriers via chemokine-driven endothelial adhesion, transmigration of autoreactive CD4⁺ and CD8⁺ T cells, and accumulation of innate cells within the perivascular space, while persistent immune-cell-derived endocannabinoid output (notably 2-AG) may propagate ligand pressure across the same interface (Chiurchiù et al., 2015). Whether ECS-mediated remodeling of the BPB precedes, accompanies, or follows the canonical insulitic infiltrate remains experimentally unresolved, but the structural and pharmacological vulnerability of this interface places it within the same receptor-level framework advanced for upstream barriers, and motivates the analogical treatment developed in Section 7.1.

7 ECS dysregulation in pancreatic β-cells under inflammatory stress

Following disruption of the blood–pancreas barrier and sustained immune activation, pathological signaling converges on pancreatic β-cells—the central and symbolic target of type 1 diabetes (T1D). Beyond immune-mediated cytotoxicity, β-cells may exhibit intrinsic vulnerability to inflammatory and metabolic stress, in which the endocannabinoid system (ECS) has been proposed to play a regulatory role that remains incompletely characterized in autoimmune diabetes. Pancreatic β-cells express functional ECS components, including CB1 and CB2 receptors (Malenczyk et al., 2015; Kim et al., 2023), ECS enzymes, and intracellular signaling partners that have been implicated in calcium flux, mitochondrial metabolism, redox balance, and insulin secretion (Hebert-Chatelain et al., 2016; Li et al., 2021; Aseer and Egan, 2021; Barker and Ferraro, 2024).

Under physiological conditions, balanced endocannabinoid tone is thought to support glucose-stimulated insulin secretion (GSIS) and mitochondrial coupling, although the precise directionality and magnitude of these effects remain incompletely resolved in primary human β-cells. In inflammatory environments characteristic of early T1D, ECS regulation has been hypothesized to become progressively distorted, potentially rendering β-cells metabolically more vulnerable—though this temporal relationship has yet to be empirically established in pre-diagnostic T1D cohorts (Howlett, 2017; Hebert-Chatelain et al., 2016; Li et al., 2021; Aseer and Egan, 2021; Cortes-Justo et al., 2023).

7.1 The blood–pancreas barrier as a structurally analogous, ECS-sensitive interface

The pancreatic islet microenvironment is protected by a specialized vascular structure—the blood–pancreas barrier (BPB) — formed by endothelial cells, pericytes, and tight junction complexes that regulate molecular and cellular exchange between the systemic circulation and the endocrine pancreas. Despite its functional importance, the BPB remains substantially less characterized than its counterparts in the central nervous system and the gastrointestinal tract, and most experimental models of type 1 diabetes have focused on intra-islet immune activation rather than on upstream barrier integrity (Hebert-Chatelain et al., 2016). Among biological barriers, both the blood–brain barrier (BBB) and the intestinal epithelial barrier have been independently documented as endocannabinoid-modulable structures. Endocannabinoid signaling at the BBB has been implicated in cerebrovascular tight junction stability and inflammation-driven permeability changes, with cannabinoid receptor activation modulating endothelial integrity in models of metabolic and neurodegenerative disease (Kim et al., 2016). At the intestinal interface, ECS signaling coordinates microbiota-driven regulation of tight junction proteins, paracellular permeability, and mucosal immune tone, with extensive evidence linking gut-derived endocannabinoid dynamics to host metabolic and inflammatory states (Cani et al., 2016). In both systems, sustained CB1 engagement under inflammatory stress has been associated with junctional destabilization, while CB2-biased signaling and balanced endocannabinoid tone support barrier preservation (Cortes-Justo et al., 2023; Shin et al., 2018).

The BPB shares fundamental architectural features with these two well-characterized barriers—claudin/occludin/ZO-1-based tight junction scaffolding, endothelial–pericyte coupling, and the presence of cannabinoid receptors and ECS-metabolizing enzymes within barrier-forming cells. On the basis of this structural and molecular homology, we propose, strictly by analogy, that the BPB plausibly belongs to the same class of ECS-sensitive vascular interfaces, and that its permeability may be similarly modulable by cannabinoid receptor engagement. It must, however, be explicitly stated that no direct experimental studies of cannabinoid-mediated BPB modulation in type 1 diabetes have, to our knowledge, been performed. The argument advanced here is therefore an analogical extrapolation rather than a mechanistic claim, and is presented as a hypothesis to be tested rather than as an established feature of T1D pathophysiology (Kozela et al., 2013; Kim et al., 2016).

Figure 9 summarizes this analogical framework, juxtaposing healthy ECS-balanced barrier conditions with the hypothesized CB1-dominant disruption pattern proposed to operate at the BPB by analogy with BBB and intestinal barrier biology (Shin et al., 2018).

FIGURE 9

This analogical framing carries direct experimental implications for autoimmune diabetes models. If the BPB indeed behaves as an ECS-sensitive interface, chronic oral Δ⁹-tetrahydrocannabinol exposure in NOD mice should produce measurable changes in islet vascular permeability—assessable by Evans Blue extravasation, fluorescent dextran tracer leakage, ZO-1 and occludin immunofluorescence, and pericyte coverage scoring—alongside the receptor-level adaptations (CB1 phosphorylation, β-arrestin recruitment) described in earlier sections. A positive result would validate the analogical extension and identify an upstream, ECS-modulable vascular checkpoint relevant to the timing of insulitis. A negative result would refine the framework by excluding BPB plasticity from the set of receptor-level adaptations elicited by chronic phytocannabinoid exposure. Either outcome would convert what is presently an analogical hypothesis into testable mechanistic territory, and this testability is the principal justification for retaining the BPB as a conceptual node within the framework proposed here (Chen et al., 2020; Kozela et al., 2013; Kim et al., 2016; Shin et al., 2018).

7.2 CB1 signaling, mitochondrial stress, and redox imbalance

As illustrated in Figure 10, early inflammatory stress induces a compensatory increase in intracellular 2-arachidonoylglycerol (2-AG) production within β-cells. Transient CB1 engagement and TRPV1-linked Ca²⁺ influx initially support insulin exocytosis under metabolic strain. This adaptive phase, however, is short-lived.

FIGURE 10

Chiurchiù et al., 2015; Li et al., 2001; Ligresti et al., 2016; Garcia-Luna et al., 2023; Aseer and Egan, 2021; Cortes-Justo et al., 2023; Odenwald and Turner, 2017; Cristino et al., 2014)]. Figure created with BioRender.com.

Sustained CB1 dominance has been associated with a rapid shift toward a maladaptive signaling state marked by excessive mitochondrial Ca²⁺ loading, impaired oxidative phosphorylation, and increased reactive oxygen species (ROS) generation. CB1 overactivation further suppresses CB2- and PPARγ-associated protective pathways, amplifying redox imbalance and endoplasmic reticulum stress, ultimately disrupting proinsulin processing and GSIS (Blagov et al., 2023; Aseer and Egan, 2021). These changes establish functional β-cell failure that can precede direct immune cytotoxicity (Gruden et al., 2016; Hebert-Chatelain et al., 2016; González-Mariscal and Egan, 2018; Bermúdez-Silva et al., 2008; Kim et al., 2011).

A key distinction emerging from ECS-centric models is that β-cell dysfunction in T1D is not solely a consequence of immune attack but may actively contribute to autoimmune amplification. Metabolically stressed β-cells exhibit altered membrane excitability, aberrant Ca²⁺ signaling, and mitochondrial distress, leading to the release of damage-associated molecular patterns and β-cell antigens (Hebert-Chatelain et al., 2016). This intrinsic dysfunction enhances antigen presentation and immune visibility, effectively converting metabolic failure into an immunogenic signal. ECS imbalance thus acts as a molecular bridge linking intracellular stress to adaptive immune engagement, positioning β-cells as active participants—rather than passive victims—in disease propagation (Łukowski, 2025; Howlett, 2017; Acharya et al., 2017).

7.3 Experimental observations of THC effects on β-cells and islets

Experimental studies in isolated islets, β-cell lines, and non-autoimmune diabetic models demonstrate that Δ⁹-tetrahydrocannabinol (THC) profoundly modulates β-cell ECS signaling. As summarized in Figure 11 (multi-state β-cell schematic), sustained THC exposure induces GRK/β-arrestin–dependent CB1 phosphorylation, desensitization, and internalization, thereby attenuating excessive Ca²⁺ influx and partially rebalancing CB1-dominant signaling (Gruden et al., 2016; Hirvonen et al., 2012; Sim-Selley, 2003; Breivogel et al., 1999; Garcia-Luna et al., 2023; Hebert-Chatelain et al., 2016; González-Mariscal and Egan, 2018; Bermúdez-Silva et al., 2008; Kim et al., 2011); in a complementary INS-1 β-cell model, Δ⁹-THC together with four minor phytocannabinoids (CBD, THCV, CBC, CBG) reduced apoptosis under high-glucose/high-lipid stress via decreased TXNIP expression, with THC and three minor phytocannabinoids additionally preserving cellular function (Maccarrone et al., 2015).

FIGURE 11

Di Marzo, 2008; Sim-Selley, 2003; Brook et al., 2019; Barker and Ferraro, 2024). Figure created with BioRender.com.

These changes are associated with reduced mitochondrial stress, improved redox stability, and transient preservation of GSIS under inflammatory conditions in experimental settings (Laychock et al., 1986; Coskun and Bolkent; Hebert-Chatelain et al., 2016; Maccarrone et al., 2015). Importantly, such effects do not constitute restoration of normal β-cell physiology and do not reverse established ER stress or immune recognition. Crucially, no studies have examined chronic, orally administered THC using progressively escalating doses in type 1 diabetes, nor have ECS remodeling trajectories in β-cells been characterized under sustained ligand pressure in autoimmune contexts. Existing data derive from acute exposure paradigms, non-autoimmune models, or indirect metabolic settings, underscoring a major translational gap (Garcia-Luna et al., 2023; Hebert-Chatelain et al., 2016; Li et al., 2021).

8 Discussion: research gaps and translationally testable hypotheses

Despite decades of research on cannabinoids, endocannabinoids, and metabolic regulation, the role of sustained endocannabinoid system (ECS) modulation in type 1 diabetes (T1D) remains insufficiently defined. As synthesized throughout this work, disruption of intestinal barrier integrity, immune dysregulation, blood–pancreas barrier destabilization, and β-cell stress converge on a shared signaling architecture that is highly sensitive to ECS tone. Experimental and clinical evidence further indicates that ECS regulation is tightly coupled to gut microbiota composition and gut-derived inflammatory signaling, positioning the ECS as an integrative interface between metabolic, immune, and epithelial compartments rather than an isolated receptor system (Cani et al., 2016). Nevertheless, existing studies remain fragmented across disease models, cannabinoid classes, exposure paradigms, and experimental endpoints, limiting the ability to draw mechanistically integrative conclusions in the context of autoimmune diabetes (Gruden et al., 2016; Łukowski, 2025; Di et al., 2011; Horváth et al., 2012).

A central limitation emerging from the current literature is the lack of longitudinal, mechanistically oriented studies designed to interrogate ECS plasticity under sustained ligand pressure. This gap is particularly evident for Δ⁹-tetrahydrocannabinol (THC), a compound whose pharmacological profile is well suited to probing GRK/β-arrestin–dependent receptor phosphorylation, signaling bias, and adaptive receptor downregulation rather than acute receptor blockade or nonspecific immunosuppression (Marche et al., 2017). Within the framework proposed here, THC is not conceptualized as a therapeutic intervention, but rather as an experimental probe to test whether ECS dysregulation hypothesized in T1D reflects a reversible stress-adaptive state or a more rigid pathological configuration (Łukowski, 2025; Chen et al., 2020).

From a translational standpoint, this question is not purely theoretical. Controlled human laboratory studies demonstrate that high-dose oral THC is generally well tolerated under supervised conditions, with predictable pharmacokinetics and manageable adverse effects even at doses exceeding typical recreational exposure (Rozanc et al., 2024). Although these data were not generated in autoimmune or metabolic disease contexts, they provide methodological precedent indicating that mechanistic investigations—distinct from therapeutic applications—are not intrinsically precluded on safety grounds (Huestis and Pertwee, 2005).

Resolving the mechanistic role of ECS plasticity in T1D will therefore likely require a stepwise experimental strategy. An initial priority is integrative endocannabinoid profiling in human cohorts, interpreted in parallel with gut microbiota composition, intestinal barrier markers, and immune phenotyping, to establish whether a CB1-dominant, 2-AG–enriched ECS signature consistently associates with disease stage or progression (Di Marzo, 2018). In parallel, autoimmune-relevant preclinical systems—such as chronic, dose-escalating THC exposure in NOD mice—can directly test whether sustained CB1 ligand pressure induces adaptive receptor downregulation and functional reweighting of ECS signaling in vivo. Complementary in vitro studies using β-cell and immune cell models under chronic cannabinoid exposure may further disentangle cell-autonomous from system-level adaptations. Only following such mechanistic validation would consideration of carefully controlled human studies be scientifically justified (Łukowski, 2025; Chen et al., 2020).

Figure 12 summarizes the central mechanistic hypothesis developed in this work and is intended as a predictive framework rather than a depiction of therapeutic outcomes. Specifically, the schematic integrates multiple, independently testable axes of endocannabinoid system (ECS) adaptation that may emerge under conditions of sustained CB1 ligand pressure. If ECS dysregulation in type 1 diabetes reflects a reversible stress-adaptive state, chronic, escalating THC exposure would be expected to induce GRK/β-arrestin–dependent CB1 downregulation, relative CB2 resensitization, and a shift in endocannabinoid tone away from 2-AG dominance. In parallel, adaptive changes in mitochondrial ECS signaling, nuclear PPARγ–NR2 transcriptional pathways, and barrier-associated tight junction stability would be anticipated as downstream correlates rather than primary intervention targets (Łukowski, 2025; Pacher et al., 2006; Li et al., 2021).

FIGURE 12

Chiurchiù et al., 2015; Rozanc et al., 2024; Cani et al., 2016; Li et al., 2001; Breivogel et al., 1999; Wu et al., 2008). Figure created with BioRender.com.

It must also be emphasized that the ECS-centered framework outlined here represents only one component of the broader pathobiology of T1D, and should be positioned squarely within the established immunopathology of the disease. Type 1 diabetes is fundamentally a T-cell–driven autoimmune disorder, in which loss of central and peripheral tolerance to β-cell autoantigens (insulin, GAD65, IA-2, ZnT8) precedes seroconversion to multiple islet autoantibodies, followed by progressive expansion of β-cell–reactive CD4⁺ and CD8⁺ T-cell clones, relative deficits in regulatory T-cell restraint, and immune-mediated β-cell destruction within the insulitic lesion. The receptor-level ECS adaptations advanced in this framework are not proposed as substitutes for any of these processes; rather, they are intended to operate as one modifier among many, plausibly contributing to the inflammatory milieu and to β-cell metabolic vulnerability without driving autoreactive T-cell repertoire selection or HLA-restricted antigen presentation. Within this broader landscape, the receptor-level ECS framework presented here is not advanced as an exclusive or dominant explanatory model. The HLA class II region remains the strongest single genetic determinant of T1D risk and continues to be refined as new haplotype-resolution data accumulate (Noble, 2024). Enterovirus exposures, particularly Coxsackie B variants, have been repeatedly implicated as environmental triggers; β-cell intrinsic stress responses, including endoplasmic reticulum stress, defective unfolded protein response, and aberrant autoantigen presentation, are well documented; and broader mechanisms of immunological tolerance and T-cell repertoire selection remain central to current models of disease initiation. The receptor-level ECS framework presented here is therefore intended to complement, not displace, these established mechanistic axes, and would ideally be evaluated jointly with them in any integrated model of T1D pathogenesis (Gruden et al., 2016; Barker and Ferraro, 2024).

To support translational uptake of the framework, the central testable predictions arising from the receptor-level hypothesis are summarized in Table 4. Each prediction is paired with a defined experimental model, primary readouts, and a falsifiable negative outcome, with the explicit aim of converting analogical and extrapolative arguments into discrete, evaluable mechanistic claims (Łukowski, 2025; Chen et al., 2020).

9 Conclusion

Despite substantial advances in cannabinoid research and metabolic immunology, the adaptive role of sustained endocannabinoid system (ECS) modulation in type 1 diabetes (T1D) remains fundamentally unresolved. No studies to date have systematically examined chronic, dose-escalating oral Δ⁹-tetrahydrocannabinol (THC) exposure in autoimmune-relevant models of T1D to interrogate receptor-level plasticity under sustained ligand pressure. Existing evidence from metabolic and inflammatory disease contexts indicates that prolonged CB1 engagement can induce receptor phosphorylation, desensitization, and adaptive remodeling of ECS signaling networks. Whether similar mechanisms operate in autoimmune diabetes—and whether ECS recalibration would attenuate, exacerbate, or neutrally modulate immunometabolic stress—remains unknown. Importantly, the potential restoration of ECS balance cannot be assumed to yield predictable biological outcomes and must be empirically determined (Gruden et al., 2016; Łukowski, 2025).

The framework proposed here defines a structured preclinical research gap at the intersection of plant-derived cannabinoid pharmacology, receptor-level ECS plasticity, and autoimmune diabetes. By conceptualizing purified, orally administered THC as a mechanistic probe rather than a therapeutic intervention, this work outlines experimentally testable hypotheses addressing receptor recalibration, endocannabinoid tone dynamics, and downstream barrier and mitochondrial adaptations (Łukowski, 2025; Huestis and Pertwee, 2005; Horváth et al., 2012).

Clarifying ECS plasticity in T1D may have implications beyond cannabinoid biology alone. Mechanistic insights derived from such investigations could inform broader translational contexts, including β-cell replacement strategies, stem cell–based therapies, immune modulation approaches, and microbiota-targeted interventions, where immunometabolic balance and barrier integrity are critical determinants of outcome (Łukowski, 2025; Chiurchiù et al., 2018; Pacher et al., 2006; Horváth et al., 2012).

Until these mechanistic questions are addressed through carefully designed, stepwise experimental studies, the role of sustained ECS modulation in autoimmune diabetes will remain speculative despite its strong biological plausibility. Closing this gap represents a necessary step toward integrating plant-derived molecular tools with modern systems immunometabolism in the study of T1D (Łukowski, 2025; Chen et al., 2020).

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