Laetitia Koppe1,2, Pascaline M Alix1,3, Marine L Croze1, Stéphane Chambert3, Raymond Vanholder4, Griet Glorieux4, Denis Fouque1,2, Christophe O Soulage1. 1. Univ. Lyon, CarMeN lab, INSERM U1060, INRA U1397, INSA-Lyon, Université Claude Bernard Lyon 1, Villeurbanne, France. 2. Hospices Civils de Lyon, Department of Nephrology, Centre Hospitalier Lyon-Sud, Pierre-Bénite, France. 3. Hospices Civils de Lyon, Department of Nephrology, Hôpital E. Herriot, Lyon, France, Univ. Lyon, INSA-Lyon, UMR 5246 CNRS, ICBMS, Villeurbanne, France. 4. Nephrology Section, Department of Internal Medicine, Ghent University Hospital, Ghent, Belgium.
Abstract
BACKGROUND: The role of uraemic toxins in insulin resistance associated with chronic kidney disease (CKD) is gaining interest. p-Cresol has been defined as the intestinally generated precursor of the prototype protein-bound uraemic toxins p-cresyl sulphate (p-CS) as the main metabolite and, at a markedly lower concentration in humans, p-cresyl glucuronide (p-CG). The objective of the present study was to evaluate the metabolism of p-cresol in mice and to decipher the potential role of both conjugates of p-cresol on glucose metabolism. METHODS: p-CS and p-CG were measured by high performance liquid chromatography-fluorescence in serum from control, 5/6 nephrectomized mice and mice injected intraperitoneously with either p-cresol or p-CG. The insulin sensitivity in vivo was estimated by insulin tolerance test. The insulin pathway in the presence of p-cresol, p-CG and/or p-CS was further evaluated in vitro on C2C12 muscle cells by measuring insulin-stimulated glucose uptake and the insulin signalling pathway (protein kinase B, PKB/Akt) by western blot. RESULTS: In contrast to in humans, where p-CS is the main metabolite of p-cresol, in CKD mice both conjugates accumulated, and after chronic p-cresol administration with equivalent concentrations but a substantial difference in protein binding (96% for p-CS and <6% for p-CG). p-CG exhibited no effect on insulin sensitivity in vivo or in vitro and no synergistic inhibiting effect in combination with p-CS. CONCLUSIONS: The relative proportion of the two p-cresol conjugates, i.e. p-CS and p-CG, is similar in mouse, in contrast to humans, pinpointing major inter-species differences in endogenous metabolism. Biologically, the sulpho- (i.e. p-CS) but not the glucuro- (i.e. p-CG) conjugate promotes insulin resistance in CKD.
BACKGROUND: The role of uraemic toxins in insulin resistance associated with chronic kidney disease (CKD) is gaining interest. p-Cresol has been defined as the intestinally generated precursor of the prototype protein-bound uraemic toxins p-cresyl sulphate (p-CS) as the main metabolite and, at a markedly lower concentration in humans, p-cresyl glucuronide (p-CG). The objective of the present study was to evaluate the metabolism of p-cresol in mice and to decipher the potential role of both conjugates of p-cresol on glucose metabolism. METHODS: p-CS and p-CG were measured by high performance liquid chromatography-fluorescence in serum from control, 5/6 nephrectomized mice and mice injected intraperitoneously with either p-cresol or p-CG. The insulin sensitivity in vivo was estimated by insulin tolerance test. The insulin pathway in the presence of p-cresol, p-CG and/or p-CS was further evaluated in vitro on C2C12 muscle cells by measuring insulin-stimulated glucose uptake and the insulin signalling pathway (protein kinase B, PKB/Akt) by western blot. RESULTS: In contrast to in humans, where p-CS is the main metabolite of p-cresol, in CKD mice both conjugates accumulated, and after chronic p-cresol administration with equivalent concentrations but a substantial difference in protein binding (96% for p-CS and <6% for p-CG). p-CG exhibited no effect on insulin sensitivity in vivo or in vitro and no synergistic inhibiting effect in combination with p-CS. CONCLUSIONS: The relative proportion of the two p-cresol conjugates, i.e. p-CS and p-CG, is similar in mouse, in contrast to humans, pinpointing major inter-species differences in endogenous metabolism. Biologically, the sulpho- (i.e. p-CS) but not the glucuro- (i.e. p-CG) conjugate promotes insulin resistance in CKD.