Differential effects of alcohol consumption on eukaryotic elongation factors in heart, skeletal muscle, and liver.
BACKGROUND
Acute and chronic alcohol administration diminishes rates of protein synthesis in a variety of tissues including skeletal muscle, heart, and liver, through a diminished translational efficiency rather than a reduction in the number of ribosomes.


METHODS
The purpose of the present study was to examine the effect of chronic alcohol exposure (8, 12, or 16 weeks) on elongation factors (eEF) as a potential mechanism for controlling mRNA translation in psoas, soleus, heart, and liver. The cellular content of eEF1A and eEF2 and the phosphorylation state of eEF2 in each tissue was measured using immunoblot techniques.


RESULTS
The protein content of eEF1A was reduced in psoas, heart, and liver (but not soleus) from rats fed a diet containing alcohol for 16 weeks, but not for 8 or 12 weeks, compared with time-matched pair-fed controls. eEF2 content was only reduced in myocardium after feeding rats an alcohol-containing diet for 16 weeks. In other tissues, no change in eEF2 content was observed. The decreases in eEF protein content were not associated with a concomitant reduction in the mRNA abundance for eEF1A or eEF2. The phosphorylation state of eEF2 was not affected by chronic alcohol consumption in the skeletal muscle or heart. In contrast, the level of eEF2 phosphorylation in the liver was reduced after 8, 12, and 16 weeks of feeding rats an alcohol-containing diet. In contrast, acute alcohol intoxication failed to modulate the content of eEF1A or eEF2 in any of the tissues examined. The phosphorylation state of eEF2 was reduced in psoas following acute alcohol intoxication.


CONCLUSIONS
A decreased eEF1A protein content could account, in part, for the inhibition of translational efficiency following chronic (16 weeks) alcohol feeding but not the response to acute alcohol intoxication.