Protein energy wasting (PEW) is a complex syndrome associated with different underlying illnesses and characterized by loss of muscle, with or without loss of fat. It is a highly prevalent condition among patients with chronic kidney disease (CKD), associated with increased morbidity and mortality.

The pathophysiology of PEW in CKD is multifactorial and not yet completely understood. The potential role in uremic PEW of two of hormones involved in orexigenic/anorexigenic balance, ghrelin and obestatin, both derived from the ghrelin gene (GHRL), has been investigated in adults and, less extensively, in children. Aim of our study was to measure AG, UAG and obestatin concentrations in children with CKD and to assess their potential contribution to the development of pediatric uremic PEW.

This is a cross-sectional case-control study. Between January 2013 and June 2015 children and adolescents aged 5-20 years, referred to the Pediatric Nephrology, Dialysis and Transplant Unit of Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico - Milan, Italy were enrolled. Subjects with CKD stages II-V under conservative treatment (CKD-CT), or undergoing hemodialysis treatment (CKD-HD), or being renal transplant recipients (RTx) were included in the study. Data about age, primary renal disease and concomitant medications were collected for each subject.

CKD stages were defined using the K/DOQI criteria of the US National Kidney Foundation.

Control subjects were outpatients of the Pediatric Surgery Unit of the Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico - Milan, Italy, aged 1-20 years, who underwent a blood sample collection before a surgical intervention for the treatment of minor diseases that did not impair renal or endocrine function (i.e. phimosis, hydrocele, inguinal hernia).

Biochemical and hormonal parameters Blood samples were collected between 7:00 and 8:00 a.m. after an overnight fast, and before dialysis in CKD-HD patients. Routine biochemical parameters [creatinine, urea] were measured in all subjects. Glomerular filtration rate was estimated (eGFR) by the Schwartz formula, with k = 0.413, as appropriate for standardized creatinine.

In all subjects, plasma AG and UAG concentrations were measured by the Human Acylated / Unacylated Ghrelin ELISA kit (BioVendor, Laboratorni Medicina a.s., Brno, Czech Republic) according to manufacture procedures, and AG/UAG ratio was calculated. Serum obestatin concentrations were determined using the Human Obestatin ELISA kit (BioVendor, Laboratorni Medicina a.s., Brno, Czech Republic).

Inclusion Criteria:

• the CKD-HD patients should have been on hemodialysis treatment for at least 3 months
• the RTx patients should have received renal transplantation at least 6 months before

Exclusion Criteria:

• treatment with growth hormone
• the presence of neurologic disability or syndromic diseases affecting per se food intake
• for controls: they should have no history of chronic diseases and should not receive any medication. They should be on unrestricted diet.

A total of 154 subjects were included (M:F=100:54), 111 patients and 43 controls. Out of 111 patients, 43 had CKD stages II-V under conservative treatment (CKD-CT), 20 were on hemodialysis (CKD-HD), 48 were renal transplant recipients (RTx).