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Leucine metabolism during chronic ethanol consumption
C A Bernal1, J A Vazquez, S A Adibi
1Department of Medicine, University of Pittsburgh School of Medicine, PA.
Metabolism: Clinical and Experimental
|September 1, 1993
Summary
Chronic ethanol consumption elevates branched-chain amino acids (BCAA) by reducing protein synthesis and increasing breakdown. This leads to higher BCAA oxidation and plasma levels in rats.
Area of Science:
- Biochemistry
- Metabolism
- Toxicology
Background:
- Chronic ethanol consumption is linked to increased plasma branched-chain amino acids (BCAA) in humans and rats.
- The underlying mechanisms for elevated BCAA levels due to ethanol intake remain unclear.
Purpose of the Study:
- To investigate the impact of chronic ethanol consumption on BCAA metabolism in rats.
- To determine if altered protein turnover or BCAA oxidation contributes to increased BCAA levels.
Main Methods:
- Rats were fed liquid diets with or without 36% ethanol (calories) for 21 days.
- Plasma and tissue (muscle, liver, jejunal mucosa) BCAA concentrations were measured.
- Leucine turnover, oxidation, and protein incorporation rates were assessed.
Main Results:
- Ethanol-fed rats showed twofold increases in plasma BCAA and significant increases in tissue BCAA concentrations.
- Whole-body leucine turnover and oxidation rates were significantly elevated in ethanol-fed rats.
- Leucine incorporation into muscle and liver proteins was significantly decreased, while jejunal mucosa incorporation remained unchanged.
Conclusions:
- Chronic ethanol consumption leads to reduced protein synthesis and/or increased protein breakdown.
- These alterations in protein turnover contribute to elevated tissue and plasma BCAA concentrations.
- Increased BCAA oxidation is a consequence of elevated tissue BCAA levels in chronic ethanol consumers.