Cardiac overexpression of metallothionein rescues chronic alcohol intake-induced cardiomyocyte dysfunction: role of Akt, mammalian target of rapamycin and ribosomal p70s6 kinase.
OBJECTIVE
Reduced insulin sensitivity following alcohol intake plays a role in alcohol-induced organ damage although its precise mechanism is undefined. This study was designed to examine the effect of cardiac overexpression of the antioxidant metallothionein on alcohol-induced cardiac contractile dysfunction and post-receptor insulin signaling.


METHODS
FVB and metallothionein mice were fed a 4% alcohol diet for 16 weeks. Cardiomyocyte contractile function was evaluated including peak shortening (PS), time-to-PS (TPS), and time-to-relengthening (TR(90)). Post-insulin receptor signaling molecules Akt, mammalian target of rapamycin (mTOR), and ribosomal p70s6 kinase (p70s6k) were evaluated using western blot analysis. Akt1 kinase activity was assayed with a phosphotransferase kit.


RESULTS
Alcohol intake dampened whole body glucose tolerance, depressed PS, shortened TPS, and prolonged TR(90), which were abrogated by metallothionein with the exception of glucose intolerance. Our results revealed reduced expression of total Akt, phosphorylated mTOR, and phosphorylated p70s6k-to-p70s6k ratio as well as Akt1 kinase activity in alcohol consuming FVB mice. Phosphorylated Akt, total mTOR, and phosphorylated p70s6k were unaffected by alcohol. Metallothionein ablated reduced Akt protein and kinase activity without affecting any other proteins or their phosphorylation.


CONCLUSIONS
In summary, our data suggest that chronic alcohol intake interrupted cardiac contractile function and Akt/mTOR/p70s6k signaling. Akt but unlikely mTOR and p70s6k may contribute to metallothionein-elicited cardiac protective response.
Li
Qun
Q
Division of Pharmaceutical Sciences, Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA.
Ren
Jun
J
D000428:Alcohol Drinking / Q000453:epidemiology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D015153:Blotting, Western; D002310:Cardiomyopathy, Alcoholic / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D002908:Chronic Disease; D005947:Glucose / Q000378:metabolism; D047468:Immunoprecipitation; D007328:Insulin / Q000378:metabolism; D008668:Metallothionein / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects* / Q000235:genetics*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000187:drug effects* / Q000235:genetics*; D020123:Sirolimus / Q000008:administration & dosage / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D007328:Insulin; D008668:Metallothionein; C514862:Akt1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D005947:Glucose; D020123:Sirolimus