Vitamin D status, body composition and hypertensive target organ damage in primary hypertension

Abstract

Overweight/obesity and high blood pressure during growth period are important risk factors of cardiovascular disease later in life. Cardiovascular system, fat and muscles are among target tissues for vitamin D and low 25(OH)D levels are likely to attenuate potential benefits of its action. The study was aimed to evaluate vitamin D status and body composition in children and adolescents with primary hypertension (PH). The study population comprised 78 patients aged 15.4±2.3yrs (9-18yrs; 15 girls) with diagnosed PH. Total 25(OH)D and parathyroid hormone (PTH) were assayed by Cobas e411 machine (Roche Diagnostics). DXA (Prodigy, GE Lunar) was used to assess total body bone mineral content (TBBMC; g), total body bone mineral density (TBBMD; g/cm(2)), lean body mass (LBM; g), % lean body mass (%LBM), fat mass (FM; g), % fat mass (% FM), Android %Fat, Gynoid %Fat and Trunk fat mass (Trunk FM; g). Hypertensive cases (BMI=25.6±4.2kg/m(2)), compared to reference, had slightly increased TBBMD and TBBMC Z-scores (+0.40±0.91 and +0.59±0.96; both p<0.001), and had markedly increased FM and FM/body weight ratio Z-scores of ±1.83±1.63 (p<0.0001) and +1.43±1.05 (p<0.0001). LBM Z-scores were slightly increased as well (+0.34±1.08, p<0.001). In contrast, markedly reduced LBM/body weight ratio Z-scores of -1.47±0.90 (p<0.0001) and disturbed relationship between FM and LBM as assessed by FM/LBM ratio Z-score of +1.53±1.29 (p<0.0001) were noted. The average serum levels of 25(OH)D of 17.8±6.9ng/mL and PTH of 34.8±16.8pg/mL were noted in PH group. 91% PH cases showed 25(OH)D levels lower than 30ng/mL. 71% of PH subjects revealed vitamin D deficiency (25(OH)D<20ng/ml). 10% of PH cases showed 25(OH)D levels lower than 10ng/mL. 25(OH)D levels negatively correlated with PTH showing r=-0.24 (p=0.03). Absolute LBM/body weight ratio values positively correlated with 25(OH)D levels (r=0.31; p=0.01). In contrast, absolute FM/body weight ratio values correlated negatively with 25(OH)D levels (r=-0.32; p<0.01). Moreover, 25(OH)D levels negatively correlated with absolute Trunk FM (r=-0.29; p<0.05), Android %Fat (r=-0.32; p<0.01) and with Gynoid %Fat (r=-0.28; p<0.05). PTH and 25(OH)D concentrations did not differ when severity of hypertension, left ventricular mass and carotid intima-media thickness were controlled for. Concluding, higher muscle mass stores in body weight coincided with higher 25(OH)D levels. Higher fat mass stores coincided with lower 25(OH)D levels in PH group. Whether vitamin D insufficiency/deficiency in PH group should be considered as a cause of disease or epiphenomenon remains unknown. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Keywords: 25(OH)D level; Body composition; Carotid intima-media thickness; Left ventricular hypertrophy; Primary hypertension; Vitamin D.