Circulating MMP9, vitamin D and variation in the TIMP-1 response with VDR genotype: mechanisms for inflammatory damage in chronic disorders?

Background: Vitamin-D deficiency and vitamin-D receptor genotype (VDR) are risk factors for several disorders with inflammatory components, including coronary heart disease (CHD) and diabetes, though the mechanisms involved are unclear. Aim: To examine the hypothesis that vitamin D status modulates the matrix metalloproteinase (MMP) system in a population with a high prevalence of vitamin D deficiency, a situation affecting susceptibility to CHD and diabetes. Design: Prospective cross-sectional, interventional and embedded studies. Methods: Circulating MMP2,9, the inhibitor TIMP-1 and C-reactive protein (CRP) were measured during studies of vitamin-D deficiency as a risk factor for type 2 diabetes and CHD in 171 healthy British Bangladeshi adults, free of known diabetes or major illness. Vitamin D status, VDR genotype, body-build, blood pressure, lipid and insulin profiles, glucose tolerance, fibrinogen, PAI-1, folate and homocysteine were measured. Vitamin-D-deficient subjects were re-assessed after 1 years' supplementation. MMP, TIMP-1 and CRP levels were measured in 41 subjects halfway through 5-year follow-up. Independent determinants of circulating concentrations of MMP9, TIMP-1 and CRP were assessed by multiple regression analysis. Results: Vitamin D status was the sole determinant of circulating MMP9 (inversely) and an independent determinant of CRP (inversely). Determinants of TIMP-1 were MMP9, systolic blood-pressure (directly) and VDR genotype (TaqI). Significant reductions in MMP9 (-68%), TIMP-1 (-38%) and CRP (-23%) concentrations followed vitamin-D supplementation. Discussion: Vitamin-D insufficiency is associated with increased circulating MMP2,9 and CRP, correctable by supplementation. This finding provides a possible mechanism for tissue damage in chronic inflammatory conditions, including CHD and diabetes.