Muscle atrophy, insulin resistance and reduced muscle phosphoinositide 3‐kinase‐Akt signalling are common characteristics of patients undergoing maintenance haemodialysis (MHD). Disruption to the transmembrane protein linkage between the cytoskeleton and the extracellular matrix in skeletal muscle may contribute to reduced amino acid metabolism and insulin resistance in MHD patients. Eight MHD patients (age: 56 ± 5 years: body mass index: 32 ± 2 kg m–2) and non‐diseased controls (age: 50 ± 2 years: body mass index: 31 ± 1 kg m–2) received primed continuous l‐[ring‐2H5]phenylalanine before consuming a mixed meal. Phenylalanine metabolism was determined using two‐compartment modelling. Muscle biopsies were collected prior to the meal and at 300 min postprandially. In a separate experiment, skeletal muscle tissue from muscle‐specific Rac1 knockout (Rac1 mKO) was harvested to investigate whether Rac1 depletion disrupted the cytoskeleton‐integrin linkage, allowing for cross‐model examination of proteins of interest. ILK, PINCH1 and pFAKTyr397 were significantly lower in MHD (P < 0.01). Rac1 and Akt showed no difference between groups for the human trial. Rac1 deletion in the Rac1 mKO model did not alter the expression of integrin‐associated proteins. Phenylalanine rates of appearance and disappearance, as well as metabolic clearance rates, were lower in the MHD group at 30 and 60 min post meal ingestion compared to controls (P < 0.05). Both groups showed similar levels of insulin sensitivity and β‐cell function. Key proteins in the integrin–cytoskeleton linkage are reduced in MHD patients, suggesting for the first time that integrin‐associated proteins dysfunction may contribute to reduced phenylalanine flux without affecting insulin resistance in haemodialysis patients.
This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors. We sincerely thank Dr Lykke Sylow and Professor Erik A. Ritcher of the Department of Nutrition, Exercise and Sport, University of Copenhagen, who have supported this project and shared their materials and facilities for the experiments. Our personal thanks are extended to Mona Sadek-Ali from Dr Sylow's laboratory for her constant help and support. Moreover, we thank Dr Nicholas A. Burd and his group from the University of Illinois for sharing their materials for this project.
© 2020 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society