Characterization of GLUT4 and calpain expression in healthy human skeletal muscle during fasting and refeeding.
OBJECTIVE
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.
Norton
L
L
Centre for Integrated Systems Biology and Medicine, School of Biomedical Sciences, Nottingham University Medical School, Queens Medical Centre, Nottingham, UK.
Parr
T
T
Bardsley
R G
RG
Ye
H
H
Tsintzas
K
K
D000328:Adult; D000704:Analysis of Variance; D017089:Ankyrin Repeat / Q000235:genetics; D015153:Blotting, Western / Q000379:methods; D002154:Calpain / Q000032:analysis* / Q000235:genetics; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D005215:Fasting / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000032:analysis* / Q000235:genetics; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D009124:Muscle Proteins / Q000032:analysis* / Q000235:genetics; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D004040:Dietary Carbohydrates; D051275:Glucose Transporter Type 4; D009124:Muscle Proteins; D012333:RNA, Messenger; C105884:CAPN3 protein, human; D002154:Calpain; C415197:calpain 10