Vitamina D e aterosclerosi

Amongst the numerous actions of vitamin D, its effects on the immune system, adipose tissue, glucose and lipid metabolism, and vascular endothelium are pivotal in determining its effects on the pathophysiology of atherosclerosis. In particular, vitamin D acts on the adipose tissue by stimulating lipolysis, insulin sensitivity and reducing lipogenesis and inflammation; it reduces the formation of foam cells by the macrophages of the atherosclerotic plaque, and the expression of adhesion molecules, oxidative stress and dysfunction at the endothelial level. These mechanisms, demonstrated by pre-clinical studies, were substantially confirmed by observational and epidemiological studies. They demonstrated that there is an inverse relationship between serum 25(OH)D levels, the main marker of vitamin D status, and the increased prevalence of arterial hypertension, poor lipid profile, insulin resistance, poor glucose control in diabetic subjects, non-alcoholic fatty liver disease (NAFLD), atherosclerotic plaques and coronary calcifications. However, these data were not corroborated by clinical intervention studies, including a number of randomised controlled trials (RCT) and their meta-analyses. The latter demonstrated a possible significant effect of vitamin D supplementation on some risk factors for atherosclerotic disease, such as amelioration of the lipid profile and, probably, reduction of the progression to type 2 diabetes in pre-diabetic subjects. As far as other factors predisposing to atherosclerosis are concerned, data are negative or controversial and leave room for future research focused on whether vitamin D could reduce the progression of atherosclerosis. In this context, lower heterogeneity in the study design and focus on subjects who require vitamin D supplementation, namely those who are frankly deficient, in association with adequate calcium intake, seems to be the way forward.