Glucose regulation and association with Vitamin D and parathyroid hormone – differences across Middle Eastern and Caucasian ethnicities

Abstract

Background Middle Eastern (ME) immigrants to Europe have a heavy burden of metabolic disorders including a higher prevalence of insulin resistance, T2D and obesity as compared to native-born Europeans. Vitamin D insufficiency and deficiency are prevalent conditions in people originating from the ME. Aims To study the differences in the levels of 25(OH)D and parathyroid hormone (PTH) across ME and European ethnicity, and the effect of 25(OH)D and PTH on insulin action and secretion. Methods Vitamin D and PTH levels were assessed in a population-based cohort of 918 participants (449 Swedes and 469 Iraqis) aged 30–75 years. The differences between the groups in the adjusted levels of Vitamin D and PTH were studied using multiple regression analysis. Differences in insulin action and secretion, in relation to risk markers including Vitamin D and PTH, were assessed using multiple regression analysis. Results Vitamin D and PTH adjusted levels differed significantly between the groups; 92% of the Iraqi-born versus 45% of the Swedish-born individuals had Vitamin D levels below 50 nmol/L. The mean levels of PTH (SD) were higher in Iraqi-born compared to native Swedish-born (5.1 (2.3) vs. 3.8 (1.6) pmol/L, p = < 0.001). Insulin sensitivity was lower in Iraqi-born (79.16 vs. 98.97, β -0.085, 95% CI −.163 to −.007) but after adjustment for the confounding effect of Vitamin D, the differences in insulin action observed between the groups were no longer significant. Conclusion The ethnic differences in insulin action could be explained by differences in the levels of Vitamin D.