Race or vitamin D: A determinant of intima media thickness in obese adolescents?

Objective: Carotid intima media thickness (IMT), a predictor of cardiovascular events, is reported to be higher in African-American (AA) vs White (AW) individuals. We investigated whether racial differences in IMT in obese adolescents could be explained by differences in 25 hydroxy-vitamin D [25(OH) D]. Research Design and Methods: A total of 63 obese adolescents had 25(OH) D levels, determination of IMT, body composition, insulin sensitivity (IS) by hyperinsulinemic-euglycemic clamp, lipids and blood pressure (BP). Results: IMT was higher and 25(OH) D lower in AA vs AW. IMT correlated with 25(OH) D level (r = -0.38, P = .002) but not with IS. In multiple regression analysis, race, HbA1c, BP and age, and not 25(OH) D, BMI or IS, were the significant determinants of IMT (R-2 = 0.44, P < .001). Without race in the model, 25(OH) D (beta = -0.36, P = .009) contributed to the variance in IMT (R-2 = 0.32, P = .007). Conclusion: Obese AA adolescents vs AW, have higher IMT, explained by race, BP, and HbA1c. Although 25(OH) D levels contribute to the variance in IMT, the observed racial difference in IMT could be mediated through other unknown race-related factors besides 25(OH) D.