Relationship between 25-hydroxyvitamin D and microalbuminuria in patients with newly diagnosed essential hypertension

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

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.

Relationship between serum 25-hydroxyvitamin D and target organ damage in children with essential hypertension

Researchers have shown that 25-hydroxyvitamin D (25[OH] D), a kind of active vitamin D in the human body, plays a role in cardiovascular disease (CVD). Low serum 25(OH) D levels have been found to be associated with elevated blood pressure (BP) in adults. However, measurement of 25(OH) D in hypertensive children has not been documented. The aim of this study was to investigate the relationship between 25(OH) D and target organ damage (TOD) in children with essential hypertension. We recruited a total of 346 children with essential hypertension and analyzed the correlation between serum 25(OH) D and TOD. Serum 25(OH) D concentration was significantly lower in the TOD than in the no-TOD group (t = 2.416, P = 0.016), as well as significantly lower in the two-organ damage than in the single-organ damage group (t = 3.140, P = 0.002). Pearson’s correlation coefficient (PCC) indicated that serum 25(OH) D levels were negatively correlated with left ventricular mass index (LVMI; r = −0.110, P = 0.041) and albuminuria (r = −0.120, P = 0.026). Linear- regression analysis showed that 25(OH) D was a risk factor for left ventricular hypertrophy (LVH; β ± s.e. =−0.074 ± 0.036; 95% confidence interval [CI], − 0.145 to –0.003; P < 0.001) and renal damage (β ± s.e.= −0.018 ± 0.008; 95% CI, − 0.035 to –0.002; P = 0.004). In total, our data revealed that serum 25(OH) D was independently associated with hypertensive cardiac and renal damage, meaning that it was a risk factor for LVH and albuminuria in childhood hypertension.