Characterization of GLUT4 and calpain expression in healthy human skeletal muscle during fasting and refeeding

• Published in: Acta Physiologica Vol. 189; no. 3; pp. 233 - 240
• Main Authors: Norton, L., Parr, T., Bardsley, R. G., Ye, H., Tsintzas, K.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.2007; Blackwell
• Subjects: Adult; Analysis of Variance; Ankyrin Repeat - genetics; Biological and medical sciences; Blotting, Western - methods; Calpain - analysis; Calpain - genetics; calpains; diabetes ankyrin repeat protein; Dietary Carbohydrates - administration & dosage; Fasting - metabolism; Fundamental and applied biological sciences. Psychology; Glucose Transporter Type 4 - analysis; Glucose Transporter Type 4 - genetics; GLUT4; Humans; Insulin Resistance; Male; Muscle Proteins - analysis; Muscle Proteins - genetics; Muscle, Skeletal - chemistry; Muscle, Skeletal - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - analysis; skeletal muscle; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Endocrinopathy; Human; diabetes ankyrin repeat protein; Fasting; Refeeding; Enzyme; Cysteine endopeptidases; Diabetes mellitus; Calpain; Striated muscle; Protein; Characterization; Peptidases; Vertebrata; Mammalia; Hydrolases; Insulin resistance; Ankyrin; calpains; GLUT4; skeletal muscle
• ISSN: 1748-1708; 1748-1716
• DOI: 10.1111/j.1748-1716.2006.01639.x

Aims:  Calpain‐10 and calpain‐3 and the diabetes ankyrin repeat protein (DARP) have all been linked to insulin resistance and type 2 diabetes. We set out to measure the expression of these genes in human skeletal muscle and relate them to functional measurements of insulin action during fasting (which induces insulin resistance) and refeeding (which reverses it). Methods:  Ten healthy male volunteers underwent 48 h of starvation followed by 24 h of high carbohydrate refeeding. On three occasions, before and after starvation and after refeeding, subjects underwent a 16 min insulin tolerance test to quantify insulin sensitivity. Muscle biopsies were obtained before and after fasting and after refeeding for the analysis of calpain‐10 and calpain‐3, GLUT4 and DARP expression by Western blotting and real‐time PCR. Results:  Fasting led to a marked reduction in whole body insulin sensitivity by approx. 45% (P < 0.01) and skeletal muscle GLUT4 gene expression by approx. 40% (P < 0.05). However, fasting had no effect on calpain‐10 and calpain‐3 mRNA or protein levels, or DARP mRNA expression. Refeeding only partly restored insulin sensitivity and GLUT4 gene expression to their pre‐fast values, but did not effect the expression of calpain‐10, calpain‐3 or DARP. Conclusions:  These findings demonstrate that in healthy non‐diabetic humans induction of insulin resistance by fasting and its reversal by refeeding with a high CHO diet is mirrored by changes in skeletal muscle GLUT4 but not calpain‐10 and calpain‐3 expression.