Impact of vitamin D insufficiency on insulin homeostasis and beta cell function in nondiabetic male HIV ‐infected patients

Objectives Vitamin D is thought to play a role in glucose homeostasis and beta cell function. Our aim was to examine the impact of plasma 25‐hydroxyvitamin D [25( OH ) D ] upon in vivo insulin sensitivity and beta cell function in HIV ‐infected male patients without diabetes. Methods A cross‐sectional study was carried out involving a cohort of HIV ‐infected patients undergoing regular assessment in a tertiary hospital. Eighty‐nine patients [mean (± standard deviation) age 42 ± 8 years] were included in the study: 14 patients were antiretroviral therapy ( ART )‐naïve, while 75 were on ART . Vitamin D insufficiency ( VDI ) was defined as 25( OH ) D  < 75 nmol/L; insulin sensitivity was determined using a 2‐h continuous infusion of glucose model assessment with homeostasis ( CIGMA‐HOMA ), using the trapezoidal model to calculate the incremental insulin and glucose areas under the curve ( AUCins and AUGglu , respectively). Beta cell function was assessed using the disposition index ( DI ). Abdominal visceral adipose tissue ( VAT ) and hepatic triglyceride content ( HTGC ) were measured by magnetic resonance imaging ( MRI ) and 1‐ H magnetic resonance spectroscopy. Multivariate linear regression analysis was performed. Results VDI was associated with insulin resistance ( IR ), as indicated by a higher CIGMA‐HOMA index (odds ratio 1.1) [1.01–1.2]. This association was independent of the main confounders, such as age, C enters for D isease C ontrol and P revention ( CDC ) stage, ART , lipodystrophy, body mass index, VAT :subcutaneous adipose tissue ratio and HTGC , as confirmed by multivariate analysis ( B  = 12.3; P  = 0.01; r 2  = 0.7). IR in patients with VDI was compensated by an increase in insulin response. However, beta cell function was lower in the VDI subpopulation (33% decrease in DI ). Conclusions VDI in nondiabetic HIV ‐positive male patients is associated with impaired insulin sensitivity and a decrease in pancreatic beta cell function.