In African American Type 2 Diabetic Patients, Is Vitamin D Deficiency Associated with Lower Blood Levels of Hydrogen Sulfide and Cyclic Adenosine Monophosphate, and Elevated Oxidative Stress?

Abstract

African Americans (AA) have a higher incidence of cardiovascular disease and vitamin D (VD) deficiency compared with Caucasians. Hydrogen sulfide (H(2)S) is an important signaling molecule. This study examined the hypothesis that blood levels of H(2)S are lower in AA type 2 diabetic patients (T2D). Fasting blood was obtained from T2D and healthy controls. Results showed a significant decrease in plasma levels of cyclic adenosine monophosphate (cAMP) and H(2)S in AA T2D but not in Caucasian T2D when compared with those of respective age- and race-matched healthy controls. Plasma VD levels were significantly lower in AA T2D compared with Caucasian T2D. Cell culture studies demonstrate that 1,25(OH)(2)-VD supplementation significantly increased expression of cystathionine-γ-lyase (CSE), H(2)S formation, and cAMP secretion, but decreased reactive oxygen species in high glucose-treated U937 monocytes. This suggests that VD supplementation upregulates CSE and H(2)S formation and decreases oxidative stress, and that VD deficiency may contribute to the malfunctioning of H(2)S signaling and thus a higher incidence of vascular inflammation in AA. These results lead to the hypothesis that VD supplementation can replenish blood concentrations of H(2)S and cAMP and lower oxidative stress and cardiovascular disease in AA T2D.