Serum 25-hydroxyvitamin D and parathyroid hormone are independent determinants of whole-body insulin sensitivity in women and may contribute to lower insulin sensitivity in African Americans

Background Circulating 25 hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) concentrations have been shown to be associated with insulin sensitivity however adiposity may con found this relation Furthermore African Americans (AAs) have lower Insulin sensitivity and 25(OH)D concentrations than do European Americans (EAs) whether these differences are associated in a cause and effect manner has not been determined Objectives The objectives of this study were to examine the re talon of 25(OH)D and PTH concentrations with whole body insulin sensitivity and to determine whether lower 25(OH)D concentrations in AAs compared with EAs contribute to the lower insulin sensitivity of AAs relative to that of EAs Design This was a cross sectional study of 25 AA and 25 EA women We determined the whole body insulin sensitivity index (S-1) with an intravenous glucose tolerance test and minimal modeling Percentage body fat was determined with dual energy X ray absorptiometry and intraabdominal adipose tissue (IAAT) was determined with computed tomography Results Multiple linear regression analysis indicated that 25(OH)D and PTH concentrations were independent determinants of S-1 [star)dardizecl beta = 024 (P = 0 04) and -0 36 (P = 0 002) respectively] after adjustment for age race and IAAT The mean ethnic difference in S-1 decreased from 2 70 [10(-4) min(-1)/(mu IU/mL)] after adjustment for IAAT and percentage body fat to 1 80 [10(-4) min(-1)/(mu IU/mL)] after further adjustment for 25(OH)D and PTH concentrations Conclusions 25(OH)D and PTH concentrations were independently associated with whole body insulin sensitivity in a cohort of healthy women which suggested that these variables may influence insulin sensitivity through independent mechanisms Further more ethnic differences in 25(OH)D concentrations may contribute to ethnic differences in insulin sensitivity Am J Clin Nut, 2010 92 1344-9