Avaliação da concentração sérica da vitamina D e sua associação com adiposidade corporal e fatores de risco para doença cardiovascular em receptores de transplante renal

Abstract

The prevalence of vitamin D deficiency is high in different regions of the world. In recent years, evidence emerged that this deficiency may be associated with increased risk of cardiovascular disease (CVD). In this context, CVD is a major cause of death in renal transplant recipients (RTR) who present contributing factors for vitamin D deficiency as the use of glucocorticoids, low sun exposure and excessive weight gain. However, the relationship of vitamin D deficiency with risk factors for CVD, including body adiposity, has not been explored adequately in RTR. This study evaluated serum levels of vitamin D and its association with body adiposity, CVD risk factors, estimated glomerular filtration rate (GFR) and proteinuria in RTR. It was a Cross-sectional observational study involving RTR under regular treatment in a specialized clinic. Patients between 18-65 years and renal transplantation for at least six months were included in the study, and were excluded those with acquired immune deficiency syndrome, cancer, autoimmune disease, dialysis therapy or in use of vitamin D supplements. The assessment of nutritional status consisted of anthropometry, bioelectrical impedance and dual-energy x-ray absorptiometry (DXA). Risk factors for CVD included hypertension, diabetes mellitus, dyslipidemia and metabolic syndrome (MS). Laboratory serum parameters included glucose, insulin, lipid profile, parathyroid hormone and 25-hidroxivitamin D [25(OH)D]. GFR was estimated by the Chronic Kidney Disease, Epidemiology Collaboration (CKD-EPI) and proteinuria in the urine sample analysis. Serum levels of 25(OH)D in ng/ml defined the status of vitamin D: <16 deficiency, 16-30 insufficiency, >30 sufficiency. 195 RTR were included in the study (58% men; n = 114) with a mean age of 47.6 ± 11.2 years and time of kidney transplant of 117.6 ± 92.6 months. It was observed that 10% (n=19) of the participants had vitamin D deficiency, 43% (n=85) insufficiency and 47% (n=91) sufficiency. Serum levels of vitamin D were inversely related to total body adiposity parameters: body mass index (BMI) (r=-0.17; p=0.02) and total body fat measured by DXA (kg) (r=-0.16; p=0.04), even after adjusting for confounders. Serum 25(OH)D was inversely and significantly associated with % of body fat in the trunk (central adiposity parameter) only before adjustments for confounding factors. There was no association of 25(OH)D with the presence of risk factors for CVD: hypertension, diabetes, dyslipidemia and metabolic syndrome. Even after adjustment for age, sex, BMI, and time of kidney transplantation, serum concentration of 25 (OH)D was associated with the estimated GFR (r=0.16; p=0.03) and urinary protein excretion (r=-0.33; p<0.0001). The present study suggests that in RTR the frequency of hypovitaminosis D is high and is associated with increased total body adiposity. Vitamin D deficiency is not associated with the presence of traditional risk factors for CVD. Serum 25(OH)D may be associated with eGFR and urinary excretion of protein, but there is a need for vitamin D supplementation studies to evaluate the possibility of a causal relationship.