Insulin Resistance and Vitamin D Deficiency: A Link Beyond the Appearances

Abstract

Vitamin D is a steroid hormone that plays a key role in the regulation of body homeostasis, including cardiovascular function. Although the chronic deficiency of vitamin D is associated with cardiovascular risk factors, as well as with an adverse prognosis, randomized controlled trials have failed in demonstrating that dietary vitamin D supplementation could ameliorate the prognosis of patients with cardiovascular diseases, and suggested that vitamin D deficiency is the expression of the effects of other determinants of cardiovascular risk. Thus, the supplementation of vitamin D is not sufficient to improve the cardiovascular risk profile and prognosis. Insulin resistance is a complex phenomenon that plays a key role in the pathogenesis of conventional cardiovascular risk factors. Interestingly, defects of vitamin D and insulin resistance have a superimposable epidemiological distribution. According to the common view, Insulin resistance is considered the direct or indirect consequence of vitamin D deficiency. However, it is also reasonable to speculate that the deficit or the impaired action of vitamin D, in some circumstances, could be the result of the same pathogenic mechanisms responsible of insulin resistance development. In this case, vitamin D deficiency could be considered an epiphenomenon of insulin resistance. Insulin resistance is a reversible condition, being possibly ameliorated by physical activity and hypocaloric diets. Notably, both physical exercise and energy-restricted dietary regimens are associated with an increase of vitamin D levels. These findings indicate that improving insulin resistance condition is a necessary step to ameliorate vitamin D supplementation-based strategies in cardiovascular prevention.

Evaluation of patient profiles, treatment paradigms and clinical efficacy, and safety outcomes in adult patients with vitamin D deficiency or insufficiency in India: A multicenter, prospective, non-interventional study

“…32 Vitamin D deficiency/insufficiency has been associated with metabolic abnormalities like hypertension and diabetes. 33,34 In our study, the mean blood pressure in hypertensive patients receiving vitamin D supplements was decreased significantly from baseline and remained normal. These patients were also on stable anti-hypertensive treatment for two months prior to enrolment.…”

“…There is an association between vitamin D levels and glycemic control, which has been reported in studies suggesting that poor vitamin D status is a potential risk modifier for both types of diabetes. 34,[36][37][38] We assessed the effect on QoL of patients after vitamin D supplementation using the SF-20 questionnaire where we observed improvement in four QoL domains, namely, physical functioning, role functioning, body pain, and health perception. This modest effect may be due to the relatively short duration of exposure to vitamin D or may be due to other confounding factors.…”

Investigating the relationship between vitamin-D deficiency and glycemia status and lipid profile in nondiabetics and prediabetics in Saudi population

“…Clinical studies have demonstrated a link between IR and vitamin D deficiency. [12] Dyslipidemia (abnormal lipid profile levels) is a health issue worldwide in adults, especially in those with unhealthy lifestyles, obesity, and postmenopausal women. Individuals with dyslipidemia are at high risk of developing hypertension, atherosclerosis, and cardiovascular disorders.…”

Vitamin D Supplementation Has No Impact on Cardiorespiratory Fitness, but Improves Inflammatory Status in Vitamin D Deficient Young Men Engaged in Resistance Training

“…Low-grade inflammation is an important factor involved in the pathogenesis of insulin resistance [82] and chronic Vit-D deficiency parallels with the clinical manifestations of this condition [83]. Six-month Vit-D supplementation in obese adolescents with variable baseline Vit-D status [84] and 12-week RT in obese middle-aged men with uncontrolled Vit-D status [85] significantly reduced HOMA-IR index, i.e., improved insulin resistance.…”