Vascular Function, Insulin Sensitivity, and Vitamin D

The overall objectives of this study are to examine the relationships between circulating
vitamin D, insulin sensitivity, and multiple indices of vascular function and to examine
whether vitamin D deficiency in African Americans (AA) and White Hispanics (WH) is
responsible for ethnic differences in insulin sensitivity and hypertension in AA, WH and
European Americans (EA), as well as mechanisms underlying the association between insulin
resistance and blood pressure. We hypothesize that 1) serum 25(OH)D is associated with
insulin sensitivity and vascular functioning, independent of adiposity, 2) lower insulin
sensitivity and vascular functioning in AA and WH relative to EA is due to lower circulating
25(OH)D in AA, and 3) the relationship between insulin resistance and vascular dysfunction
is mediated by 25(OH)D.

Acronyms: African American (AA), European American (EA), White Hispanics (WH), Serum
25-hydroxy vitamin D (25()H)D, Body mass index (BMI), Alabama (AL).