Relationship between total vitamin D metabolites and complications in patients with type 2 diabetes
Lina Ahmed, Alexandra E. Butler, Soha R. Dargham, Aishah Latif, Elhadi Abdalla Ahmed, Abubaker Hassan, Stephen L. Atkin
Abstract
In our previous study, it was shown that endogenous vitamin D<sub>3</sub> and its metabolites are associated with diabetic microvascular complications and cardiovascular risk factors. The aim of the present study was to determine if the relationship between total vitamin D (vitamin D<sub>2</sub> supplements plus endogenous vitamin D<sub>3</sub>) was a better predictor of complications in type 2 diabetes (T2DM). A total of 460 patients with T2DM participated in the present cross‑sectional study. Plasma levels of total vitamin D and its metabolites (1,25‑dihydroxyvitamin D (1,25(OH)D), 25‑hydroxyvitamin D (25(OH)D) and 24,25‑dihydroxyvitamin D (24,25(OH)D) were measured by isotope‑dilution liquid chromatography tandem mass spectrometry analysis. 1,25‑dihydroxyvitamin D<sub>3</sub> and 25‑hydroxyvitamin D<sub>3</sub> were associated with diabetic retinopathy and coronary artery disease, but total 1,25‑dihydroxyvitamin D and total 25‑hydroxyvitamin D levels were not statistically associated with any complications. Total 1,25‑dihydroxyvitamin D showed the same positive association as 1,25‑dihydroxyvitamin D<sub>3</sub> for hypertension and dyslipidemia, and total 25‑hydroxyvitamin D showed the same positive association as 25‑hydroxyvitamin D<sub>3</sub> for dyslipidemia. Total 24,25‑dihydroxyvitamin D showed the same positive association only with dyslipidemia as did 24,25‑dihydroxyvitamin D<sub>3</sub>. However, total 25‑hydroxyvitamin D was associated with hypertension, whereas 25‑hydroxyvitamin D<sub>3</sub> was not. Vitamin D<sub>3</sub> metabolites were associated with diabetic retinopathy, whereas total vitamin D levels were not, suggesting that endogenous vitamin D<sub>3</sub> metabolites are a better measure of diabetic microvascular complications. However, both total vitamin D and vitamin D<sub>3</sub> metabolites were associated with cardiovascular risk factors in patients with type 2 diabetes.