Fermented vegetables include fruits (edible part of a tree/plant) and vegetables (root/plant cultivated for food) (Medina-Pradas et al., 2017). While fruits are regarded as acidic foods, vegetables fall in the category of low acidic food. Nevertheless, the microorganisms involved in vegetable fermentation contribute to the acidity of the fermented product, irrespective of the raw material (Medina-Pradas et al., 2017). Fresh vegetables and fruits are liable to be spoilt by microorganisms and in few cases by pathogenic microorganisms contracted during their cultivation and harvest, thereby decreasing their shelf-life (Di Cagno et al., 2013; Di Cagno et al., 2015). Although various techniques like pasteurization, cooking, etc. may guarantee their safety yet, their long-term storage and escape from the unwanted change in the physical and chemical composition depends on the fermentation process (Di Cagno et al., 2013; Di Cagno et al., 2015). Lactic acid fermentation is one among the fermentation techniques to ensure safe fermented vegetables and fruits with extended shelf-life (Di Cagno et al., 2013; Di Cagno et al., 2015). Lactic acid-fermented vegetables like Sauerkraut, Kimchi and fermented cucumbers are the most studied owing to their commercial significance (Di Cagno et al., 2013; Di Cagno et al., 2015).

Lactobacillus spp. have multiple contributions in the fermentation process (Peng et al., 2018). They improve the nutritional aspect of the fermented vegetable by bringing about reduction in the nitrite and other harmful substance built-up and also inhibit the growth of harmful microorganisms (Peng et al., 2018). In addition to this, Lactobacillus contributes to the palatability of the fermented food (Peng et al., 2018). They are crucial microorganisms having major physiological functions in animals and human beings (Peng et al., 2018). Lactobacillus is a highly salt tolerant genera (Peng et al., 2018). It can ferment the sugars present in the vegetables to produce acid thereby creating an acidic environment that inhibits the growth of other spoilage bacteria (Peng et al., 2018). Besides this, the metabolic by-products of Lactobacillus such as hydrogen peroxide, diacetyl, nisin, carbon dioxide, bacteriocin, etc. also add to their anti-microbial property (Peng et al., 2018). Further, the vegetables also contain particular chemicals like isothiocyanates and allyldisulphide that selectively favor Lactobacillus over the other microorganisms (Peng et al., 2018). Even though Lactobacillus spp. are found in lesser number in the plant’s native microbiotic community, yet they predominate the vegetable fermentation process (Peng et al., 2018). Also, they represent the microbes having health-promoting effects (Peng et al., 2018). Apart from being a source of health-boosting compounds, plants also contain numerous anti-nutritional factors (Peng et al., 2018). However, the combined effects of plant enzymes and the metabolic activity of Lactobacillus increase the bioavailability and activity of phytochemicals, which in-turn results in a significant increase in the number of functional microbial metabolites, exerting beneficial health-promoting effects (Peng et al., 2018).

Currently, vegetable-based fermented foods gain much focus not only because of its health benefits, industrial applications, prebiotic property and as a source of probiotics/synbiotics, but also due to its use as a non-dairy alternative (Table 1) (Medina-Pradas et al., 2017; Wuyts et al., 2020). Unlike the dairy-based food products, vegetable-based fermented foods are favorable for the lactose-intolerant people, vegans, and people allergic to milk (Wuyts et al., 2020). Vegetable-based fermented foods may also find application in various industries. The food industry can thereby exploit these microbial strains to be used as starter cultures and their productions as enzymes, food additives and antibiotics, etc. For instance, the exopolysaccharides secreted may be used to enhance the texture of the food produced in the food industries. The pharmaceutical industry on the other hand can use these exopolysaccharides in reducing the viscosity of the blood (Wuyts et al., 2020). Thus, plant-based fermented foods contributes significantly to the human well-being by providing nourishment, vitamins, minerals, nutrients, etc. (Sivamaruthi et al., 2018). In anticipation, the future of fermented vegetable products are promising.

Fermentation is a traditional method of food preservation that enhances the organoleptic, nutritional, and health-promoting qualities of foods while also improving their safety (Macori and Cotter, 2019). Fermented dairy products are made by fermenting milk with different kinds of microorganisms which generally are regarded as safe (GRAS). During the fermentation process beneficial substances as well as bacterium-derived metabolites are produced. Fermented dairy products are an excellent matrix for the incorporation of additives and/or nutrients, which addsnutrition to the final product, thereby making them actual functional foods that are intriguing in a balanced diet (García-Burgos et al., 2020). Fermented dairy products are gaining popularity among consumers due to their associated health benefits and nutritional benefits (Table 2). The impact of fermented dairy products on the intestinal microbiota is related to the improvement of gut system leading to a healthy lifestyle and longer life expectancy (Chen et al., 2019). It was observed that Lactobacillus brevis and Lactobacillus pentosusisolated from the Iranian butter reduce the cholesterol (Ostadzadeh et al., 2022). Lactobacillus paracasei and Lactobacillus plantarum isolated from the traditional fermented dairy product of Tibet can prevent and alleviate T2D (Zhao et al., 2022). Specific lactic acid bacterial strains may be able to remove toxic or anti-nutritional components from fermented milks, and also alleviate the symptoms of lactose intolerance and galactose buildup (Shiby and Mishra, 2013). Many fermented dairy products, including yoghurt, kumys, skyr, sweetened probiotic milk, and kefir, which is the best studied fermented dairy product, include probiotics and prebiotics (Bourrie et al., 2016). Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Bacillus, Propionibacterium, and Bifidobacterium are among the bacteria found in fermented dairy products (Ghosh et al., 2019).

Lactobacilli occupy nutrient-rich habitats such as fermented foods and animal feed, the environment, which includes the surface of plants, soil, and the bodies of invertebrate and vertebrate animals, and the environment (Duar et al., 2017) (Figure 3).

In-vivo studies including animal and human models have been in trend in recent times. Numerous studies on animal models (rats, hamsters, guinea pigs, mice and pigs) have been conducted owing to their similarities with humans in terms of lipid and bile metabolism, regulation of hepatic cholesterol enzymes and plasma lipoprotein distribution. Further, the model animals used possess almost similar nutrient requirements, digestive anatomy and physiology and metabolic processes with humans, making them beneficial experimental representation for research purposes (Table 3). However, the in-vitro experiments has its own benefit as it provides a clue to whether the proposed in-vivo experiment may lead a fruitful result or not (Ooi and Liong, 2010).

Gao et al. (2011) evaluated the antioxidant and hypolipidemic activity of LAB isolated from pickled Chinese cabbage. Out of the 28 LAB strains isolated, two strains namely, L. plantarum and L. brevis, having high tolerance to acid and bile salt were further screened for the antioxidant and hypolipidemic activity (Gao et al., 2011). Numerous studies have shown a link between an increase in free radicals and lipid peroxidation, LDL-C and blood glucose (Tanaka et al., 2002). Free radicals can trigger a cascade of detrimental metabolic reactions, resulting in a variety of illnesses such as cancer, diabetes, neurological disease, and cardiovascular disease. Also, Intracellular diffusion of free radicals is possible. This diffusion of free radicals leads to mitochondrial enzyme damage and DNA breaks, impairment of cellular function (Bonnefont-Rousselot et al., 2000). SOD and glutathione peroxidase (GSH-px) being an anti-oxidant (scavenger of free radicals) has the potency to control oxidation reactions in the body. In this study, when the SOD and glutathione peroxidase (GSH-px) concentration in the tissues of kidney and liver of the experimental rats were studied, Gao et al. (2011) observed the increase in SOD and GSH-px in L. plantarum and L. brevis fed animal groups when compared with the control groups. Thus, the results indicated that both the strains could become potent agents for anti-oxidation and hypocholesterolemia (Gao et al., 2011).

In an invivo evaluation conducted by Costabile et al. (2017) the cholesterol-lowering ability of Lactobacillusplantarum ECGC 13110402, a dairy isolate possessing a high bile salt hydrolase activity was assessed in normal to mildly hpercholesterolaemic individuals. Males and females of age 18–50 years; BMI 18.5–29.9 kg/m²; TC ranging from 200 to 300 mg/dl were selected and randomly grouped into active group and placebo control group. The active group consumed 2 × 10⁹ CFU of encapsulated Lactobacillusplantarum ECGC 13110402 twice daily. This daily intake of the probiotic bacteria led to a statistically significant lowering of the LDL-C (13.9%, p = 0.030) in the volunteers during a period of 0–12 weeks when compared to the placebo group. Also, the TC levels in the volunteers fed with the probiotic also decreased to a significant value (36.7%, p = 0.045). In contrast, an increase in HDL-C (14.7%, p = 0.007) was observed in a period of 6–12 weeks. Thus, this study suggests that Lactobacillusplantarum ECGC 13110402 can be opted as a suitable candidate to be used in mitigating hypercholesterolaemia (Costabile et al., 2017).

Probiotic characteristics of LAB isolated from fermented yak milk products, which includes Chhurpi, Shyow and Thara/Khachu that are indigenous to the Dukpa and the Bhutia community of the Sikkim Himalayan regions were assessed by Ghatani and Tamang (2017). Out of the 170 LAB isolates screened for their probiotic properties, 70 isolates were found to lower cholesterol levels in-vitro. Moreover, six isolates were identified as the best strains for possessing cholesterol-reducing potential. Their cholesterol-reducing potential in terms of percentage were as follows; L. plantarum YD5S (85%) and YD9S (70%), L. pentosus YD8S (70%), L. paraplantarum YD11S (55%), Enterococcuslactis YHC20 (65%) and Enterococcusfaecium YY1 (65%) showed the best cholesterol-reducing potential. This finding highlights the cholesterol-reducing ability of the Lactic acid bacteria, especially the Lactobacillus species (Ghatani and Tamang, 2017).

In an in-vitro study conducted by Albano et al. (2018) on the activity of Lactic Acid bacterial members isolated from traditional Italian cheeses resulted a significant lowering of the cholesterol in broth. L. casei VC199, L. paracasei SE160 and VC213, L. plantarum VS.166 and VS.513, Enterococcus faecium VC223, and E. lactis BT161 resulted in a 42%–55% reduction of the cholesterol level in broth. When these strains were subjected to cheese manufacturing process, all the strains showed a decreased cholesterol content in the cheeses. However, Lb. Paracasei VC213 and E. lactis BT161 showed the best result i.e., a cholesterol reduction percent of upto 23%. Further, the sensory properties of the cheese were unaffected by these cultures (Albano et al., 2018).

Wa et al. (2019) evaluated the mechanism by which the single probiotic- and combined probiotic-fermented milk plays role in lipid metabolism. Numerous studies have revealed that farnesoid X receptor (FXR), 5′-AMP-activated protein kinase (AMPK) and liver X receptors (LXRs) play vital role in the metabolism of lipids thus, this study investigated the gene transcriptions modulated by the FXR, AMPK and LXRs. In comparison to Sprague Dawley rats fed with high fat diet, the group of High-fat rats supplemented with a single probiotic (L. rhamnosus LV108) fermented milk and those fed with combined probiotics (L. rhamnosus LV108, L. casei grx12 and L. fermentum grx08) fermented milk showed significant reduction in the levels of serum TC and TG. Also, an increase in bile acids in the liver and the small intestine of the probiotic fed high-fat rats were observed. Further, the quantitative PCR (qPCR) investigation revealed the up-regulation of transcription of LXR axis genes in the liver and small intestines of high-fat rats fed with probiotic-fermented milk, thereby suggesting the pathway of cholesterol balance. Although, the comparison of the upregulation of FXR gene transcription of probiotic fed high-fat rats were not significantly compared with the high-fat control rats but, a significant low upregulation of FXR genes in high-fat rats fed with mixed-probiotics fermented milk was observed. This observation suggested that the probiotics may not lower the TC via the FXR axis. Also, no significant differences in the transcription of AMPK genes of the high-fat rats and those groups fed with probiotics were noticed, which also suggested that probiotics may not directly activate AMPK. However, the conclusion drawn by Wa et al. (2019) through their findings suggested that the lipid-metabolism-related gene modulation of single probiotics was more efficacious in comparison to the combined probiotics (Wa et al., 2019).

Yi et al. (2020) evaluated the lipid reduction effects and mechanism of action of L. fermentum CQPC04, isolated from traditional naturally fermented vegetable, Sichuan pickle. In this in-vivo study conducted in 6-week-old C57BL/6J mice, the Lactobacillus fermentum CQPC04 showed reduction in abnormal weight gain and abnormal visceral index of mice caused by a high-fat diet. Lactobacillusfermentum CQPC04 could efficiently lower TG, TC, LDL-C, AST, ALT, and AKP (alkaline phosphatase) levels, while increasing the HDL-C levels in the serum of high-fat diet fed mice. Since abnormal levels of ALT, AST, AKP are markers of liver damage, their reduction in this finding suggested that Lactobacillusfermentum CQPC04 could prevent liver damage and as a result prevent obesity and obesity-related disorders. Further, this Lactobacillus strain could also decrease the levels of inflammatory cytokines, like IL-6 (interleukin-6), IL-1β (interleukin-1 beta), TNF-α (tumor necrosis factor alpha), and IFN-γ (interferon gamma) in the serum of high-fat mice (Yi et al., 2020).

Mu et al. (2020) studied the in-vivo lipid-reducing property of L. plantarum KFY02 isolated from naturally fermented yogurt on C57BL/6J mice. They observed the reduction in the levels of AKP, ALT, AST, TG, TC and LDL-C in the serum of high-fat-induced C57BL/6J mice. Further, qPCR experiments revealed that L. plantarum KFY02 could significantly upregulate the mRNA expression of lipid-accumulation regulated enzymes like cholesterol 7α-hydroxylase (CYP7A1), lipoprotein lipase (LPL), peroxisome proliferative-activating receptor α (PPAR-α), carnitinepalmitoyltransferase 1A (CPT1A) in the liver and epididymal adipose tissues, while downregulating the mRNA expression of adipocyte differentiation factors like CCAAT enhancer-binding proteins (C/EBP-α) and peroxisome proliferative-activating receptor γ (PPAR-γ). These results indicated that L. plantarum KFY02 possessed a significant regulatory potential for reducing hyperlipidemia and obesity (Mu et al., 2020).

In an investigation carried out by Kim et al. (2021), four strains of LAB (Pediococcuspentosaceus SMFM2017-GK1, Lactobacillusfermentum SMFM2017-NK3, L. plantarum SMFM2017-NK2, and L. fermentum SMFM2017-NK4), isolated from Kimchi were selected and administered to differently grouped obesity-induced SPF C57BL/6J mice. The findings revealed that the total cholesterol (TC), triglycerides (TG), alanine aminotransferase (ALT) and aspartate transaminase (AST) levels in the serum of LFNK4 group (obesity-induced mice treated with L. fermentum SMFM2017-NK4 were lower than that in the control group (obesity-induced mice treated with phosphate buffer saline) as well as in those groups fed with probiotic strains other than L. fermentum SMFM2017-NK4. Furthermore, on the analysis of the lipid-metabolism associated genes (FAS and Cpt-2), low levels of FAS and high levels of carnitinepalmitoyltransferase (Cpt)-2 in the liver of LFNK4 group when compared with the control group was observed. Also, the levels of expression of anti-oxidant protein Superoxide dismutase (SOD) enzyme -2, CAT, and GPx-1 in the liver were found to be higher in the LFNK4 group, comparatively. This investigation thus indicated the superiority and potency of L. fermentum SMFM2017-NK4 over the other groups in regulating the lipid balance in the mice models (Kim et al., 2021).

L. paracasei HII01, isolated from northern Thai pickles were assessed by Chaiyasut et al. (2021) for their effect on lipid- and carbohydrate-metabolism, inflammation, oxidative stress and digestion. For this purpose 52 hypercholesterolemic Thai human volunteers were randomly grouped into a placebo group and a group treated with L. paracasei HII01 (1.25 × 10¹⁰ CFU/ml/day). The outcome of the results revealed a significant reduction in the TC, TG, lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-α of the Lactobacillus treated group when compared to the placebo group. Comparatively, the total antioxidant capacity (TAC), propionic acid, lactic acid, interleukin (IL-10), interferon (IFN-γ) and HDL-C also increased in the lactobacillus treated group. Thus, this double-blind placebo experiment thus explored the hypolipidemic potential of L. paracasei HII01 (Chaiyasut et al., 2021).

The hypocholesterolemic property of L. johnsonii BFE6154, procured from Maasai traditional fermented milk was studied using high-fat high-cholesterol (HFHC) fed C57BL/6 J mice model. In comparison to the mice fed only with HFHC (control), those that were also supplemented with 5 × 109 CFU/day of L. johnsonii BFE6154 apart from receiving a HFHC diet, gained weight slowly upto 2 weeks. Unlike the control group no change in the weight of adipose tissue was observed in those groups supplemented with BFE6154. Moreover, lipid profile tests exhibited that the supplementation of BFE6154 could lower the TC and LDL-C levels while increasing the levels of HDL-C. For further understanding the molecular mechanism involved in the lowering of cholesterol levels via the administration of BFE6154 was analyzed. The results revealed that the BFE6154 supplementation significantly upregulated the gene expression of ATP-binding cassette transporter (ABC) G5, which pumps the cholesterol from the enterocytes into the lumen of the intestine. Also, a decrease in the Intestinal Niemann-Pick C1-Like1 (NPC1L1) with BFE6154 supplementation suggested a suppression of cholesterol absorption in the intestine mediated by NPC1L1. Furthermore, increased cholesterol excretion in the feces of BFE6154 supplemented mice unlike to those of the HFHC control mice, confirmed the Lipid regulating potency of BFE6154 (Yoon et al., 2021).

In an investigation carried out by Yadav et al. (2007)probiotic dahi containing Lactobacillus acidophilus and Lactobacillus casei supplemented diet significantly delayed the progression of high fructose-induced glucose intolerance, hyperglycemia, hyperinsulinemia, dyslipidemia, and oxidative stress in rats. White male Wistar rats aged 6–8 weeks (150–160 g body weight) were divided into three groups: a normal control group (NCG) supplemented with standard diet and normal drinking water, a high fructose-fed control group (HFCG) that supplemented with standard diet and 21% fructose solution along with drinking water, and a dahi- and high fructose-treated group (DHFG) that treated with standard diet supplemented with 15% dahi and 21% fructose (Yadav et al., 2007). The liver glycogen level was higher in the HFCG group in the current study due to the high load of fructose mobilized to the liver (Yadav et al., 2007). In general, glycogen in the liver is beneficial; however, presence of excess sugars may result in high levels of LDL and VLDL, which may contribute to the development of diabetic dyslipidemia. The DHFG group accumulated less glycogen than the HFCG group. Lactobacillus casei remarkably delayed the progression of high fructose-induced glucose intolerance, hyperglycemia, hyperinsulinemia (Yadav et al., 2007).

Experiment was conducted by Yadav et al. (2008)where Male Wistar rats aged 6–8 weeks and weighing 91 g were housed in a cage in a small animal house. The effect of oral administration and the impact of dahi comprising probiotic Lactobacillus acidophilus NCDC14 and Lactobacilluscasei NCDC19 (73 × 10⁸ cfu/g) on the progression of streptozotocin (STZ)-induced diabetes in rats (15 g/day/rat) was examined for 28 days (Yadav et al., 2008). Furthermore, probiotic dahi significantly reduced STZ-induced oxidative damage in pancreatic tissues by hindering lipid peroxidation and nitric oxide formation while maintaining antioxidant pools such as glutathione content and superoxide dismutase, catalase, and glutathione peroxidase activities (Yadav et al., 2008). The findings suggest that combining probiotic L. acidophilus and L. casei with dahi cultures increased dahi’s ability to suppress STZ-induced diabetes in rats by inhibiting insulin depletion, preserving diabetic dyslipidemia, and inhibiting lipid peroxidation and nitrite formation which may strengthen the antioxidant system of β-cells and slow the reduction of insulin and rise in blood glucose levels (Yadav et al., 2008).

Study revealed by Hsieh et al. (2013) Lactobacilli Lr 263 (2 × 10⁹ CFU/rat) was orally administered to Male sprague–Dawley by an oral gavage on a daily basis for 14 weeks. This study found a reduction in PPAR-mRNA expression in the adipose tissue of High fat diet rats. Lr263 administration, on the other hand, restored the PPAR-mRNA expression that had been reduced by high fructose treatment. Furthermore, GLUT1 and GLUT4 mRNA expression in HFD rats’ adipose tissue was lower than in the control group (Hsieh et al., 2013). While GLUT1 mRNA expression remained unchanged, Lr263 treatment significantly increased GLUT4 mRNA expression. These findings suggest that Lr263 may improve insulin resistance, enhance glycemic control, and maintain glucose homeostasis in adipose tissue by increasing PPAR- γ. Lr263 administration also significantly reduced adipose tissue TNF- and IL-6 production in HFD rats, implying that Lr263 improved insulin resistance by lowering oxidative stress and pro-inflammatory cytokine production and GLUT4 expression (Hsieh et al., 2013).

In an in-vivo study conducted by Li et al. (2014) where Male Wistar rats were randomly divided into four groups as follows: untreated diabetes mellitus (DM), DM treated with 10⁹ CFU/mL L plantarum NCU116 (NCU), DM treated with fermented carrot juice with L. plantarum NCU116 (FCJ, 10⁹ CFU/ml), and DM treated with non-fermented carrot juice (NFCJ). The effect of fermented carrot juice with Lactobacillus plantarum NCU116 on high-fat and low-dose STZ-induced type 2 diabetes in rats was investigated. For 5 weeks, treatments of DM plus L. plantarum NCU116 (NCU) and DM plus fermented carrot juice with L. plantarum NCU116 (FCJ) were found to favorably control blood glucose, hormones, and lipid metabolism in diabetic rats, with an increase in short-chain fatty acid (SCFA) in the colon (Li et al., 2014). Furthermore, NCU and FCJ improved the antioxidant potential and morphological characteristics of the pancreas and kidney and also upregulated the mRNA of the low-density lipoprotein (LDL) receptor, cholesterol 7-hydroxylase (CYP7A1), glucose transporter-4 (GLUT-4), peroxisome proliferator-activated receptor-α (PPAR-α), and peroxisome proliferator-activated receptor-γ (PPAR-γ). These findings show that L. plantarum NCU116 and fermented carrot juice have the potential to alleviate type 2 diabetes in rats for the initial time (Li et al., 2014).

Lactobacillus is being used in fruit and vegetable fermentation to boost nutritional content, sensory properties, and lifespan. L. plantarum NCU116, isolated from Chinese sauerkraut brine, has been effectively used to boost carrot juice’s anti-diabetic properties (Li et al., 2014). Momordicacharantia also known as bitter melon, is a Cucurbitaceae plant that is green in colour and extremely bitter. It is said to have anti-diabetic properties and has long been used in traditional medicine to alleviate diabetic illnesses. A prior analysis revealed that fermenting Momordicacharantia with L. plantarum improved the anti-diabetic activity in vitro, but further in vivo research is needed (Mazlan et al., 2015).

In a study Male C57BL/6J mice (3 weeks old, inbred-specific, pathogen-free) were grouped as follows; L. plantarum X1(X1) group: mice with T2DM and oral administration of 0.25 ml 2 × 10⁹ L. plantarum X1; L. plantarum CCFM30 (CCFM30) group: mice with T2DM and oral administration of 0.25 ml 2 × 10⁹ L. plantarum CCFM30. In vitro, the cell-free supernatant of Lactobacillus plantarum X1 demonstrated potential anti-diabetic activity by inhibiting -glucosidase activity (Li et al., 2016). L. plantarum X1 was found to improve hyperglycemia, glucose tolerance, insulin resistance, hormone levels, and lipid metabolism when taken orally. In type 2 diabetic mice, L. plantarum X1 partially increased antioxidant capacity and improved cytokine secretion. Furthermore, L. plantarum X1 significantly increased the levels of butyric acid and recovered the levels of acetic acid in the faeces of diabetic mice (Li et al., 2016). Furthermore, oral administration of L. plantarum X1 significantly decreased TNF- and IL-6 levels while increasing IL-10 in T2DM mice, similar to the effect of pioglitazone (diabetes drug). TNF- and IL-6 levels decreased, while IL-10 levels increased, possibly due to SCFA production regulation from oral supplementation with L. plantarum X1. These findings showed that L. plantarum X1 had the potential to alleviate type 2 diabetes and the hypoglycemic ability was closely related to modifications in short-chain fatty acids and gut microbiota (Li et al., 2016).

In a study the mRNA expression levels of phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt), glycogen synthesis kinase-3 (GSK-3) and glycogen synthesis (GS) in the livers of mice were evaluated using RT-qPCR to further investigate the molecular mechanism of L. casei CCFM419 in alleviating insulin resistance. Three-week old male C57BL/6J mice were grouped into four groups according to body weight as follows: normal control (NC) Diabetic control (DC) group, pioglitazone (P) group, and L. casei CCFM419 (LC) group. The mRNA expression of PI3K and GS was clearly down-regulated in diabetic mice, whereas L. casei CCFM419 intake efficiently increased the expression of the two genes comparative to the DC (Diabetic control) group (Li et al., 2017). Simultaneously, a statistically significant decrease in GSK3 mRNA expression was observed after L. casei CCFM419 treatment compared to the DC (Diabetic control) group. There was no discernible difference in AKT mRNA expression between the four groups (Li et al., 2017).

Among hundreds of LABs isolated from fermented foods, researchers suggested that L. plantarum Ln4 isolates obtained from napa cabbage kimchi has the best ability to reduce diet-induced body weight and insulin resistance. The beneficial effect of the strain on obesity and insulin resistance leads to the recovery of the associated proteins that regulate glucose and lipid metabolism. Administration of Ln4 can alter the levels of mRNA that associated with the glucose and lipid metabolism, as well as the insulin-responsive signaling pathway in in-vitro studies. As a result, Ln4 has the potential to be developed as a therapeutic probiotic for obesity and type 2 diabetes (Lee et al., 2018).

In a study the probiotics L. rhamnosus MTCC: 5957 and L. rhamnosus MTCC: 5897 were isolated from domestic curd and showing bile acid tolerance, hydrophobicity, adhesion, and immunomodulatory capabilities. Probiotic Fermented Milk (PFM) made with Lactobacillus rhamnosus MTCC: 5957, Lactobacillus rhamnosus MTCC: 5897, and their combination improved the health of diabetic male albino rats of Wistar strain (8 weeks old). Enhanced non-enzymatic glycation is one plausible hypothesis connecting high blood sugar and diabetic vascular complications. During diabetes, excess glucose in blood reacts with haemoglobin to form high levels of HbA1c compared to the normal rats, indicating poor glycemic control. According to this research diabetic rats treated with probiotics had significantly lower levels HbA1c which may be the result of improved glucose metabolism. Furthermore, it was also observed that the actions of reactive oxygen scavenging enzymes such as CAT, SOD, and GPx were disrupted in the liver and kidneys of diabetic rats, resulting in the generation of free radicals. Moreover, these free radicals caused lipid peroxidation, which was demonstrated by a significant increase in TBARS concentrations in the liver and kidney of untreated diabetic rats. The findings of this study demonstrated that probiotics improved the hepatic and renal antioxidative enzyme profiles, which can help to reduce the complications of type 1 diabetes over time. Probiotic fermented milks have indeed reported as dietary sources of natural antioxidants that increase the body’s intrinsic antioxidant properties. In diabetic rats, feeding these PFM reduced blood glucose and HbA1c levels while increasing body weight, serum insulin, and HDL-C levels. (Yadav et al., 2018).

Lipid metabolism, oxidative stress, and glucose metabolism were all improved after the administration of oral dose of L. paracasei TD062, which had high -glucosidase inhibitory action. In term of hypoglycemic processes it was observed that in diabetic mice produced by a combination of high-glucose-fat diets and STZ, genes involved in gluconeogenesis and the PI3K/Akt pathway were altered. These results suggested that L. paracasei TD062 might be useful in treating of T2DM (Dang et al., 2018; Feng et al., 2018). L. paracasei isolates have been tested in vitro for their -glucosidase inhibiting properties. The anti-diabetic efficacy of L. paracasei TD062, which had a significant -glucosidase inhibitory activity (31.9%) could persist in simulated gastrointestinal fluids (Dang et al., 2018).

L.brevis strains KLDS 1.0727 and KLDS 1.0373, isolated from dairy products proved to survive in vitro digesting models and had a high level of virulence against foodborne pathogenic microorganisms. Furthermore, the KLDS 1.0727 and KLDS 1.0373 strains produced sufficient GABA, demonstrating an excellent physiological effect in an in vivo testing and considerable impact on reducing blood glucose and insulin levels (Abdelazez et al., 2018).

Fermented foods, including Chinese sauerkraut (Dandong, China), pickled cabbage (Nanjing, China), kipper (Guiyang, China), milk curd (XilinGol League, China), and kefir yogurt (Tibet, China), are the local fermented foods of China. The findings revealed that L. plantarum EPS may effectively lower -amylase activity and could be used as a possible functional food for hyperglycemia treatment (Huang et al., 2020). α-Amylase could efficiently hydrolyze α-1,4-O-glycosidic bonds in starch and produce glucose so, inhibition of α-amylase activity could reduce the blood glucose level. Insulin promotes glucose utilization and consumption in hepatocytes by causing GLUT-4 vesicles to translocate to the plasma membrane, and GLUT-4 translocation is involved in the PI3K/Akt pathway. As previously stated, the most common cause of T2DM is insulin resistance, which results from a failure in the translocation of GLUT-4 vesicles to the plasma membrane. Increases plasma membrane GLUT-4 expression and increases glucose consumption in an insulin-independent manner by upregulating the activity of the PI3K/Akt signalling pathway (Huang et al., 2020). Lactobacillus plantarum EPS inhibited -amylase activity while increasing GLUT-4, Akt-2, and AMPK gene expression in insulin-resistant HepG2 cells in in-vitro study. However, this experiments were conducted in vitro, it is unknown whether it is applicable in vivo or whether this EPS can regulate other metabolic pathways (Huang et al., 2020).

The most common species is pomegranate, or Punica granatum, which originally belonged to the Punicaceae family. Punica is a small genus of deciduous fruits bearing shrubs and it is a nutrient-dense fruit that is high in phytochemicals. The findings were intriguing, especially the preparation technique for improving nutrient value of P. granatum juice by using L. casei as probiotics. The synthesis of quercetin-3-glucoside was linked with suppression of DPPH radicals and DPP4 by L. casei fermented juice (Mustafa et al., 2020). In the therapeutic mechanism of diabetes treatment, fermented P. granatum juice is expected to be an essential source of phytonutrients. The bacterial strain’s capacity to use fruit sugars for fast development without the need for food supplements. P. granatum juice with L. casei might be used for candidates who are allergic to medicine (Mustafa et al., 2020).

α-Glucosidase is an enymethat helps in carbohydrate metabolism found in the brush border membrane. Inhibiting α-glucosidase activity has been shown to prevent T2D by lowering glucose absorption and blood glucose levels. A study was conducted to find a strain with remarkable hypoglycemic ability and the effects of LAB strains on anti-glucosidase activity was studied. It was observed that the rate of α-glucosidase inhibition varied when compared to the control from 19.8% to 72.3%. The -glucosidase inhibition rates of L. gasseriMG4524, L. rhamnosus MG4502, and L. reuteri MG5149 were determined. Inhibition rates were found to be 63.8 1.1%, 63.4 4.7%, and 60.3 1.2% (Jeong et al., 2021).

L. paracasei NL41, which was isolated from a traditional Chinese dairy product in the Xinjiang area of China had the ability to alter the main species of gut microbiome that were linked to production of SCFA (short chain fatty acid) and have anti-inflammation mechanisms. As a consequence it was suggested that the an-tidiabetic mechanism of L. paracasei NL41 was partly linked to the maintenance of the gut microbiomeecosystem, leading to an improvement in gut barrier function, reducing LPS permeation and inhibiting inflammation, and thus alleviating insulin resistance property (Zeng et al., 2021).

In another study isolated from dairy product were selected based on their potential probiotic properties that improved glucose and lipid profiles. L. fermentum MCC2760 applied to Wistar rats (female) were reduced pro-inflammatory cytokines in the liver, gut, MAT (Methionine adenosyltransferases), and muscle tissue, and improved gut barrier and expressions of GLUT4 (Glucose transporter type 4), GLP1 (Glucagon-like peptide 1) and adiponectin in HFD and type 2 diabetic rats.L. fermentum MCC2760can elevated TNF-, IL-1, and IL-6 expression levels in the tissues of the HFD control group and diabetic control group. In both studies, however, groups treated with L. fermentum showed a decrease in TNF- while increasing the expression of the anti-inflammatory marker IL-10. (Archer et al., 2021).