Relação entre zinco e leptina e seus efeitos na ingestão alimentar e no estado nutricional de pacientes submetidos à hemodiálise

Abstract

Anorexia, a common complication in hemodialysis patients (HD), contributes to protein-energy wasting and increased risk of mortality. Several factors are involved with diminished appetite in chronic kidney disease (CKD); however, its causes are unknown. Recent evidences suggested that zinc can be a mediator in leptin production indicating a possible relationship between zinc deficiency and leptin levels in pathogenesis of anorexia in chronic kidney disease (CKD). The aim of this study was to describe the correlation between zinc and leptin levels and their influence on food intake and nutritional status of hemodialysis patients. The study was a cross-sectional where fifty patients (mean age 54.3 ± 12.7 years old, BMI of 24.4 ± 4.1 kg/m2, 62% men) treated at RenalCor clinic in Rio de Janeiro were studied and compared to 21 healthy volunteers (50.7 ± 15.7 years, BMI of 25.6 ± 4.0 Kg/m2, 43% men). Blood samples were collected at fasting, before a regular HD session. Plasma zinc concentration was measured by atomic absorption spectrometry. Plasma leptin levels, IL-6 (interleukin 6) and TNF- (tumor necrosis factor-alpha) were determined using multiplex kits (R & D System) run on the Luminex platform and CRP (C-reactive protein) levels, by immunoturbidimetric method. Appetite was measured using a specific questionnaire and food intake was evaluated via 24h recall, carried in 3 distinct occasions. Anthropometric, biochemical and parameters dietary were used to evaluate the nutritional status. The leptin levels were significantly higher in patients (16.1μg/mL (0.21 - 118.25) than to those in healthy individuals (6.0 μg/mL (0.50 - 23.10) (p = 0.04), whereas plasma zinc levels were significantly lower (54.5 ± 16.3 μg/dL vs 78.4 ± 9.4 μg/dL, respectivelly) (p = 0.0001) and 80% of patients had zinc deficiency. Plasma leptin was correlated negatively with energy intake (r= -0.38; p=0.002) and protein intake (r = -0.34; p=0.006) and positively correlated with BMI (r=0.54; p = 0.0001), % body fat (%BF) (r =0.70 p=0.0001), conicity index (Ci) (r=0.46; p=0.001) and CRP (r=0.38; p=0.014). Plasma zinc was associated with hemoglobin (r = 0.30; p=0.04) and negatively associated with leptin (r= -0.33; p=0.007), TNF α (r = -0.37; p=0.002) and CRP (r= -0.37; p=0.004) when analysed with health subjects. CRP levels were positively correlated with BMI (r=0.34; p=0.028), waist circumference (r=0.39; p=0.017), % BF (r=0.46; p=0.004) and Ci (r=0.33; p=0.046). In conclusion, most patients had zinc deficiency and high levels of plasma leptin, in addition, this study showed that plasma zinc is possibly associated with leptin levels in HD patients. Studies are required to investigate the regulatory pathways by which zinc and leptin regulate energy intake and body composition in HD patients