Efeitos da suplementação de magnésio na estrutura e função vascular de mulheres hipertensas em uso de diurético tiazídico

Abstract

Magnesium has been the subject of some studies on the pathogenesis of hypertension for having significant inverse correlation between its serum levels and the incidence of cardiovascular disease. The main objective of this study was to evaluate the effects of magnesium supplementation on vascular function in hypertensive patients in use of hydrochlorothiazide. Furthermore, serum and intracellular magnesium were correlated with nutritional parameters, blood pressure, metabolic, structural and functional aspects of the macro- and microcirculation. Hypertensive women, 40 to 65 years-old, in use of hydrochlorothiazide in the past 4 weeks, were selected for this project. Initially we conducted a cross-sectional study to assess the associations of low serum (<2.0 mg/dl) and intracellular (<3.75 mg/dl red blood cells) magnesium with these parameters. Subsequently, in a prospective randomized study, patients were divided into two groups according to the Ambulatory Blood Pressure Monitoring (ABPM) in: Controlled group, mean 24-h blood pressure (BP) <130x80 mmHg (without supplementation) and intervention group (supplementation) with mean 24-h BP &#8805; 130x80 mmHg. This second group was divided into placebo and magnesium (chelate of magnesium, 600 mg/day). At inclusion and after 6 months follow-up, all patients were evaluated for nutritional and biochemical parameters, BP measurement, ABPM, flow-mediated dilatation (FMD) of the brachial artery, peripheral arterial tonometry (with EndoPAT), assessment of intima-media thickness (IMT) of the carotid artery, determination of systolic aortic pressure and central hemodynamic parameters (with SphygmoCor) and pulse wave velocity (with Complior SP). On cross-sectional analysis, low serum magnesium levels were associated with increased cardiovascular risk (16±3 vs 11±1%, p=0.024), higher systolic (148±7 vs 135±3 mmHg, p=0.049) and diastolic (91±3 vs 84±2 mmHg, p = 0.042) BP and increased carotid IMT (0.92±0.09 vs 0.76±0.02mm, p=0.023). Moreover, low concentrations of intracellular magnesium have been associated with increased vascular stiffness parameters such as increased aortic pressure (20±2 vs 15±1 mmHg, p=0.032) and augmentation index (43±2 vs 33±2%, p=0.004). In the prospective study, the group receiving magnesium presented significant reduction in systolic (144±18 vs 134±14 mmHg, p=0.036) and diastolic (88±9 vs 81±8 mmHg, p=0.005) BP. There was no change on glucose and lipid metabolism, and on arterial stiffness parameters. After 6 months follow-up, the placebo group showed a significant increase in carotid IMT (0.78±0.13 vs 0.89±0.14 mm, p=0.033) while the magnesium group maintained the initial average (0.79±0.16 vs 0.79±0.19 mm, p=0.716). The magnesium group demonstrated a significant increase in variation of FMD compared to the placebo group (+3.7±2.1 vs -2.4±1.2%, p = 0.015). In addition, there was a significant correlation between the intracellular magnesium variation and FMD (r=0.44, p=0.011). In conclusion, in these hypertensive women in use of thiazide, low serum magnesium has been associated with higher BP values, while lower concentrations of intracellular magnesium have been associated with increased vascular stiffness. The magnesium supplementation for 6 months was followed by a reduction in BP, attenuating the process of subclinical atherosclerosis with improvement of endothelial function.