Chronic and heavy alcohol consumption is one of the causes of
heart diseases. However, the effects of
ethanol on
insulin sensitivity in myocardium has been unclear. To investigate the effects of
ethanol on the expression of
AMP-activated protein kinase (AMPK),
myocyte enhancer factor 2 (MEF2) and
glucose transporter 4 (GLUT4), all of which are involved in the regulation of
insulin sensitivity, in the myocardium, we performed three parts of experiments in vivo and in vitro. I: Rats were injected with 5-amino-4-imidazolecarboxamide
ribonucleotide (
AICAR, 0.8 mg.kg(-l)) for 2 h. II: Rats received different dose (0.5, 2.5 or 5 g.kg(-l).d(-l)) of
ethanol for 22-week. III: Primary neonatal rat cardiomyocytes were isolated and treated with or without 100 mM
ethanol or 1 mM
AICAR for 4 h. The cardiac
protein and
mRNA expression of AMPKalpha subunits, MEF2 and GLUT4 were observed by western-blotting and RT-PCR, respectively. Serum
TNFalpha levels were assessed by ELISA. The results showed chronic
ethanol exposure induced
insulin resistance.
Ethanol decreased the
mRNA levels of AMPKalpha1 and alpha2, the
protein levels of total- and phospho-AMPKalpha in cardiomyocytes. Similarly,
ethanol showed inhibitory effects on both the
mRNA and
protein levels of MEF2A and 2D, and GLUT4 in a dose-response-like fashion. Correlation analysis implied an association between phospho-AMPKalpha and MEF2A or MEF2D, and between the levels of MEF2
protein and GLUT4 transcription. In addition,
ethanol elevated serum
TNFalpha level. Taken together, chronic
ethanol exposure decreases the expression of AMPKalpha and MEF2, and is associated with GLUT4 decline in rat myocardium.