Plasma ghrelin levels in patients undergoing haemodialysis and peritoneal dialysis

Background. Ghrelin has been characterized as a relevant physiologic regulator of appetite and body weight in humans. However, the potential relationships between ghrelin levels, inflammation and malnutrition in dialysis patients have not been adequately studied. Methods. We used a cross-sectional design to study 20 haemodialysis (HD) and 21 peritoneal dialysis (PD) patients, and compared their plasma ghrelin (PGhr) levels with that of an age-matched control group. We also explored correlations between ghrelin and selected hormonal, renal adequacy, nutritional and inflammation markers in both groups. Results. PGhr levels were higher in HD (median 119.8 pg/ml, range 71.1-333.7, P = 0.001) and PD (99.3, range 45.8-578.5, P = 0.045) patients than in healthy controls (78, range 29-158) (HD is PD, not significant). Ghrelin levels were strongly and inversely correlated with age (r = -0.46, P = 0.02 for patients; r = -0.61, P = 0.001 for controls). Except for a positive correlation between ghrelin and growth hormone (r = 0.48, P = 0.002), univariate analysis failed to detect associations between PGhr and the measured hormonal values, renal adequacy, nutritional indicators and markers of inflammation. However, multivariate analysis revealed significant inverse correlations between PGhr levels and nutritional markers, including subjective global assessment (P = 0.013), albumin (P = 0.001), transferrin (P = 0.01) and protein nitrogen appearance (as an estimate of protein intake) (P = 0.035), after controlling for the confounding effect of age. Conclusions. PGhr levels were moderately and similarly increased in patients undergoing HD and PD. Age was a strong determinant of PGhr levels, both in uraemic patients and in healthy controls. Dialysis adequacy, residual renal function and inflammation did not appear to influence ghrelin levels in these patients. The negative correlation between PGhr and nutritional markers suggests that low dietary intake causes increases in ghrelin secretion in dialysis patients.