Vitamin D and cardiovascular diseases: A narrative review

Abstract

Cardiovascular diseases (CVD) and vitamin D deficiency are becoming highly prevalent among general populations. Despite plausible biological mechanisms for the role of vitamin D in cardio-protection, a cause-and-effect relationship has not yet been established. The interest in vitamin D as a potential therapeutic target to attenuate cardiovascular risk has been raised. The question about the benefit of vitamin D supplementation for cardiovascular outcomes cannot be answered certainly for the moment. The association between hypovitaminosis D and CVD has been proven by some studies while other studies deny any such link. The present narrative review gives a comprehensive overview of studies on the potential impact of hypovitaminosis D on CVD. The potential role of vitamin D supplementation in the management of CVD is also evaluated. Particular emphasis is paid to those studies that achieve a high level of scientific evidence.

Keywords: 1,25-dihydroxyvitamin D; 25-Hydroxyvitamin D; coronary artery diseases; hypovitaminosis D; vitamin D supplementation.

Figure 1

Vitamin D synthesis and metabolism. Endogenous vitamin D synthesis occurs primarily through sunlight exposure, which produces pre-vitamin D3. It is hydroxylated by 1 of 4 cytochrome P450 enzymes (most importantly CYP2R1) in the liver producing 25-hydroxyvitamin D, the form usually considered as a circulating biomarker of vitamin D status. Subsequent conversion by 1α-hydroxylase (another cytochrome P450 enzyme; CYP27B1) into the physiologically active form, 1α,25-dihydroxyvitamin D or calcitriol, occurs primarily in the kidney. 1,25(OH)₂D acts in target sites in bone and immune cells, as well as liver cells. Abbreviations: CYP (cytochrome P450), UVB (ultraviolet B), hν (denotes photochemical reaction). Printed with permission[13]

Figure 2

Hypothesized mechanisms underlying the interrelationships among vitamin D deficiency and cardiovascular disease risk factors such as insulin resistance, hypertension, and diabetes. Abbreviations: 1,25(OH) 2D: 1,25-dihydroxyvitamin D, 25(OH) D: 25-hydroxyvitamin D, CVD: cardiovascular diseases, DM: diabetes mellitus, HTN: hypertension, IL-2: interleukin-2, IL-6: interleukin-6, IL-12: interleukin-12, IR: insulin resistance, LDL: low-density lipoprotein, PTH: parathyroid hormone, TG: triglycerides, TNF-α: tumor necrosis factor-α, TNF-β: tumor necrosis factor-β