Document Type : Original Article
Authors
1
PhD Student in Exercise Physiology, Department of Exercise Physiology, Ka.C., Islamic Azad University, Karaj, Iran.
2
Assistant Professor at Department of Exercise Physiology, Ka.C., Islamic Azad University, Karaj, Iran.
10.22077/jpsbs.2026.11899.2070
Abstract
Background and Aim: Type 2 diabetes mellitus is characterized by chronic hyperglycemia, insulin resistance, and progressive pancreatic beta-cell dysfunction. In addition to oxidative stress, low-grade inflammation, mitochondrial impairment, and endoplasmic-reticulum stress, disruption of intra-islet signaling may contribute to the deterioration of insulin secretion. Melatonin receptor 1B (MTNR1B), which is expressed in pancreatic islets, is coupled to inhibitory G proteins and can suppress adenylyl cyclase, cyclic adenosine monophosphate (cAMP) production, and protein kinase A-dependent insulin secretion. Increased MTNR1B expression or activity may therefore intensify beta-cell dysfunction. Resistance training can reduce peripheral insulin demand by improving skeletal-muscle glucose uptake and insulin sensitivity, whereas the proanthocyanidins in black grape seed extract may protect beta cells by attenuating oxidative and endoplasmic-reticulum stress. Nanoliposomal encapsulation with a chitosan coating may further improve polyphenol stability, controlled release, and intestinal uptake. Whether these interventions interact on the pancreatic MTNR1B–cAMP axis, however, remains uncertain. This study examined the independent and interactive effects of resistance training and chitosan-coated nanoliposomal black grape seed extract on pancreatic MTNR1B gene expression, tissue cAMP, fasting glucose, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and body weight in rats with experimentally induced type 2 diabetes.
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