Pancreatic changes in obese mice supplemented with vitamin D

This study investigates the impact of vitamin D supplementation on insulin secretion and pancreatic islet morphometry in a high-fat diet-induced obese mouse model. Male C57BL/6 mice were randomly assigned to two groups: a control group receiving a standard diet (C) and an obese group receiving a high-fat diet (H). After 12 weeks, the obese group was subdivided, with one subset continuing on the high-fat diet (H) and the other receiving vitamin D supplementation (HD) at 500 IU/kg via oral gavage for four weeks. Glucose tolerance tests, insulin sensitivity assessments, insulin secretion assays, and histological and immunohistochemical analyses for glucagon and PCNA were conducted. Vitamin D supplementation led to a reduction in fasting blood glucose levels and a significant increase in insulin secretion at 20 mM glucose, as indicated by an improved HOMA%B index, suggesting enhanced β-cell protection. Additionally, vitamin D treatment resulted in a β-cell percentage comparable to the control group and a notable increase in α-cell population relative to the untreated obese group. However, elevated circulating cholesterol levels were observed in both obese groups, with a significant rise in hepatic triglycerides in the vitamin D-treated group. These findings highlight the potential of vitamin D to improve pancreatic secretory function in obese mice.