Observational pilot study: A comparison of amino acids and derangement of intestinal function between healthy ageing subjects and patients affected by chronic kidney disease stage CKD3b-4 in conservative management

Abstract

A comparison of the amino acid (AA) plasma profile and markers of intestinal absorption-inflammation between healthy subjects aged 65-70 years and age-matched patients affected by stage 3b-4 chronic kidney disease (CKD3b-4) was performed. Eleven healthy volunteers were compared with 12 CKD3b-4 patients at their first outpatient control (T0) and after 12-months (T12). Adherence to a low protein diet (LPD, 0.6±0.1g/kg/day) was assessed by Urea Nitrogen Appearance. The following parameters were assessed: renal function, nutritional parameters, bioelectrical impedance analysis, plasma levels of 20 total amino acids (TAAs), both essential (EAAs) including branched-chain amino acids (BCAAs) and non-essential (NEAAs). Zonulin and faecal Calprotectin markers were used to evaluate intestinal permeability/inflammation. Four patients dropped out of the study; in the remaining 8 residual kidney function (RKF) remained stable, their LPD adherence had risen to 0.89g/kg/day, anaemia had worsened and extracellular body fluid had increased. In comparison to healthy subjects, TAA levels of histidine, arginine, asparagine, threonine, glycine, and glutamine had all increased. No variation in BCAAs was observed. A significant increase was detected in faecal calprotectin and zonulin levels in CKD patients as the disease progressed. This study confirms the finding in aged patients of an alteration in plasmatic levels of several AAs secondary to uraemia. Intestinal markers provide confirmation of a relevant alteration to the intestinal function in CKD patients.