Intestinal permeability in patients with IgA nephropathy and other glomerular diseases: an observational study

Background A dysregulated ‘gut-kidney axis’ may contribute to immunoglobulin A nephropathy (IgAN). We studied whether IgAN patients have disturbed intestinal permeability. Methods In a prospective, cross sectional, pilot study we assessed intestinal permeability in 35 IgAN patients, 18 patients with non-IgAN glomerulonephritides (GNs) and 19 healthy controls. After an overnight fast, trial participants ingested a multi-sugar solution and samples were obtained from 0 to 2, 2 to 5- and 5 to 24-h urine portions. Urinary sugar concentrations were quantified using isocratic ion-exchange high performance liquid chromatography. Indices of small intestinal permeability (0–2-h lactulose/L-rhamnose (L/R) ratio), distal small intestinal and proximal colonic permeability (2–5-h sucralose/erythritol (S/E) ratio) and colonic permeability (5–24-h sucralose/erythritol (S/E) ratio) were evaluated. Associations between groups and indices of intestinal permeability were investigated by a linear mixed model. Results Small intestinal permeability (0–2 h L/R-ratio) was significantly increased in patients with glomerular diseases versus healthy controls. More precisely, increased small intestinal permeability was exclusively noted in non-IgAN GN patients, whereas IgAN patients exhibited a trend towards elevated small intestinal permeability. In total, 54% of patients with IgAN and 67% of non-IgAN GN patients had increased small intestinal permeability. Neither distal small intestinal and proximal colonic permeability nor colonic gut permeability indices (i.e., 2–5 h and 5–24 h S/E ratios) were significantly different between controls and any of the GN patient groups. Conclusion The present single center pilot study suggests that disturbed intestinal permeability is common in patients with glomerular diseases and is not specific for IgAN. Trial registration number German Clinical Trials Register DRKS00021533, Date: 24.04.2020. Graphical abstract