Metabolic syndrome: A review of the role of vitamin D in mediating susceptibility and outcome

Abstract

Despite the well-recognised role of vitamin D in a wide range of physiological processes, hypovitaminosis is common worldwide (prevalence 30%-50%) presumably arising from inadequate exposure to ultraviolet radiation and insufficient consumption. While generally not at the very low levels associated with rickets, hypovitaminosis D has been implicated in various very different, pathophysiological processes. These include putative effects on the pathogenesis of neoplastic change, inflammatory and demyelinating conditions, cardiovascular disease (CVD) and diabetes. This review focuses on the association between hypovitaminosis D and the metabolic syndrome as well as its component characteristics which are central obesity, glucose homeostasis, insulin resistance, hypertension and atherogenic dyslipidaemia. We also consider the effects of hypovitaminosis D on outcomes associated with the metabolic syndrome such as CVD, diabetes and non-alcoholic fatty liver disease. We structure this review into 3 distinct sections; the metabolic syndrome, vitamin D biochemistry and the putative association between hypovitaminosis D, the metabolic syndrome and cardiovascular risk.

Keywords: Atherogenic dyslipidaemia; Cardiovascular disease; Hypertension; Hypovitaminosis D; Insulin resistance; Metabolic syndrome; Non-alcoholic fatty liver disease; Type 2 diabetes mellitus; Vitamin D.

Figure 1

Simplified illustrations of the component risk factors of the metabolic syndrome, the complex relationships between them and the outcomes leading to increased morbidity and mortality. We also identify the areas that may be affected by hypovitaminosis D which are covered in this review. CVD: Cardiovascular disease.

Figure 2

Simplified synthetic pathway leading to the formation of the active metabolite 1,25(OH)₂D. UVB: Ultraviolet B.