Resistin serum levels are increased but not correlated with insulin resistance in chronic hemodialysis patients.

BACKGROUND/AIMS: Insulin resistance is a well-known phenomenon in uremia. Resistin, a recently discovered insulin inhibitor secreted by adipocytes, is associated with obesity and insulin resistance in mice. Adiponectin, also secreted by adipocytes, is known to reduce insulin resistance in humans. The aim of the present study was to address the hypothesis that changes in resistin or adiponectin serum levels may relate to body composition and to insulin resistance in patients with end-stage renal disease.

METHODS: In a cross-sectional study, 33 non-diabetic patients (24 males and 9 females, mean age 61.5+/-15.8 years) with end-stage renal disease on chronic hemodialysis (treatment duration 41+/-31 months) that lacked signs of infection were enrolled. The control group consisted of 33, matched for age, sex and body mass index (BMI), healthy volunteers (22 males, 11 females, mean age 62.6+/-12.1 years). BMI (kg/m(2)) was calculated from body weight and height. Body fat (%) was measured by means of bioelectrical impedance. Blood samples were taken always in the morning after a 12-hour fasting period before and after the hemodialysis session. Resistin and adiponectin serum concentrations were measured by enzyme immunoassays and insulin by an electrochemiluminescence immunoassay. The post-treatment values were corrected regarding the hemoconcentration. The homeostasis model assessment index (HOMA-R) was calculated as an estimate of insulin resistance from the fasting glucose and insulin serum levels.

RESULTS: Pre-treatment resistin serum levels were significantly increased in hemodialysis patients compared to healthy controls (19.2+/-6.2 vs. 3.9+/-1.8 ng/ml; p<0.001). Hemodialysis did not alter resistin levels, as pre- and post-treatment levels were not different when corrected for hemoconcentration (19.2+/-6.2 vs. 18.7+/-5.0 ng/ml; p=0.54). Adiponectin levels were also increased in hemodialysis patients compared to healthy controls (25.4+/-21.5 vs. 10.5+/-5.9 microg/ml; p<0.001). A significant inverse correlation was observed between the serum adiponectin levels before the hemodialysis session on the one hand and the BMI (r=-0.527, p=0.002), the HOMA-R (r=-0.378, p<0.05) and the fasting insulin levels (r=-0.397, p<0.05) on the other. However, no significant correlation was observed between serum resistin levels on the one hand versus HOMA-R index (3.2+/-3.9 mmol.microIU/ml; r=-0.098, p=0.59), insulin levels (13.3+/-14.4 mU/l; r=-0.073, p=0.69), glucose levels (89+/-13 mg/dl; r=-0.049, p=0.78), BMI (25.6+/-3.7 kg/m(2); r=-0.041, p=0.82) and body fat content (26.4+/-8.4%; r=-0.018, p=0.94) on the other hand.

CONCLUSION: Resistin serum levels are significantly elevated in non-diabetic patients with end-stage renal disease that are treated by hemodialysis. The hemodialysis procedure does not affect the resistin levels. Along with previous observations in patients with renal insufficiency in the pre-dialysis stage, our findings implicate an important role of the kidney in resistin elimination. However, increased resistin serum levels in hemodialysis patients are not related to reduced insulin sensitivity encountered in uremia.