Ketogenic Diet–Induced Changes in Methylation Status and Neuropeptide Signaling: Relationships Between S-adenosylmethionine (AdoMet), Orexin-A, and Metabolic Health

Giovanni Messina¹Laura Mosca²Antonietta Monda²Antonietta Messina²Francesca Cadoni²Fiorenzo Moscatelli³Marco La Marra²Vincenzo Monda²Girolamo Di Maio³Salvatore Allocca²Claudia Casella⁴Maria Casillo²Rita Polito^3*Marcellino Monda²Marina Porcelli²

• ¹University of Foggia, Foggia, Italy
• ²university of campania, luigi vanvitelli, naples, Italy
• ³Pegaso Telematic University, naples, Italy
• ⁴Universita degli Studi di Napoli Federico II, Naples, Italy

S-Adenosylmethionine (AdoMet) is the principal methyl donor in numerous biochemical reactions, influencing lipid and glucose metabolism, inflammatory pathways, and neurotransmitter synthesis. Orexin-A, a hypothalamic neuropeptide regulating arousal, feeding, and energy expenditure, also plays an important role in metabolic homeostasis. Although evidence suggests potential crosstalk between methylation pathways and orexinergic signaling, this interaction has not been investigated in the context of nutritional ketosis induced by a ketogenic diet. This study aimed to evaluate the effects of a structured ketogenic dietary intervention on circulating AdoMet, anthropometric indices, lipid and glucose metabolism, and Orexin-A levels, and to examine correlations between AdoMet and metabolic parameters. A total of 21 adults (11 males, 10 females) were recruited from the Unit of Dietetics, Sports Medicine, and Psychophysical Well-being, University Hospital "L. Vanvitelli" of Naples, Italy. The study was approved by the Ethics Committee of the University of Campania "Luigi Vanvitelli" (Protocol No. 0003232/I del 01/02/2023). Participants followed a ketogenic diet for 8 weeks. Anthropometric data, body composition, fasting biochemical parameters, AdoMet, and Orexin-A levels were measured at baseline (T0) and after 8 weeks of intervention (T1)." Anthropometric data, body composition, fasting biochemical parameters, AdoMet, and Orexin-A levels were measured at baseline (T0) and post-intervention (T1). Paired t-tests assessed changes, and linear regression analyses explored correlations between AdoMet and metabolic variables. Significant reductions were observed in AdoMet (−75.7%), Orexin-A (−7.2%), body weight, BMI, visceral adipose tissue, total cholesterol, fasting glycemia, triglycerides, and HbA1c (all p < 0.05). AdoMet levels showed significant positive correlations with body weight, BMI, visceral adipose tissue, total cholesterol, fasting glycemia, triglycerides, HbA1c, and notably Orexin-A (R² = 0.3848, p < 0.0001). A ketogenic dietary intervention significantly improved anthropometric and metabolic parameters while reducing circulating AdoMet and Orexin-A levels. The strong association between AdoMet and Orexin-A suggests an interaction between methylation status and neuropeptide signaling in metabolic regulation. These findings support the potential role of AdoMet as an integrated biomarker of metabolic health and highlight the relevance of ketogenic-induced neuro-metabolic adaptations.