Early decrease in Cx36 is associated with increased cell adhesion molecules (CAMs) junctional content in mouse pancreatic islets after short-term high-fat diet feeding.

Cell-to-cell interactions mediated by intercellular junctions (IJs) are crucial for beta-cell functioning and proper insulin secretion, however, their role in type-2 diabetes is still unclear. This work aimed to evaluate the cellular distribution and expression of proteins associated with adherens (AJs) and gap junctions (GJs) in pancreatic islets of C57BL6 mice fed a high-fat (HF) diet. The administration of HF diet for 30 days induced an increase in body weight, post-prandial glycemia, insulinemia, glucose intolerance, and moderate insulin resistance associated with mild perturbations in insulin secretion. The intercellular content of the AJ-associated proteins (namely, E-, N-cadherins, and α-, ß-catenins) was significantly higher in islet cells of HF-fed mice. Inversely, the gap junctional content of Cx36 was significantly decreased, as revealed by immunofluorescence, which was paralleled by a reduction in the frequency of calcium oscillations in islets of prediabetic mice. In conclusion, the endocrine pancreas displays significant changes in the content of several junctional proteins at the cell-cell contact region following short-term HF diet administration, indicating that IJs may be involved in the adaptive response of beta cells seen during this state.

Translational Science: How experimental research has contributed to the understanding of spontaneous Physical Activity and Energy Homeostasis

Abstract Spontaneous physical activity (SPA) consists of all daily living activities other than volitional exercise (e.g. sports and fitness-related activities). SPA is an important component of energy expenditure and may protect from overweight and obesity. Little is known about the biological regulation of SPA, but animal researchhas contributedsignificantly to expand our knowledge in this field. Studies in rodents have shown that SPA is influenced by nutrients and volitional exercise. High-fat diet seems to decrease SPA, which contributes to weigh gain. Volitional exercisemayalso reduce SPA, helping to explain the commonly reported low efficiency of exercise to cause weight loss, and highlighting the need to finda volume/intensity of exercise to maximize total daily energy expenditure. Animal studieshave also allowed for the identification of some brain areas and chemical mediatorsinvolved in SPA regulation. These discoveries could enable the development of new therapeutics aiming to enhance SPA.(AU)