Leucine metabolism during chronic ethanol consumption

Bernal, Claudio; Vazquez, Jorge A.; Adibi, Siamak A.

doi:10.1016/0026-0495(93)90262-m

Cited by 27 publications

(9 citation statements)

References 14 publications

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“…Likewise, under well-controlled experimental conditions, inhibitor studies have demonstrated that the suppressive effects of alcohol are not due to elevations in the plasma corticosterone concentration (49, 55). Finally, there are no differences in the concentration of total amino acids, branched-chain amino acids or leucine between control and alcohol-fed rats (3, 59). Hence, the consensus from the available literature suggests that changes in the concentration of selected hormones and protein substrates are not causally related to the reduction in muscle protein synthesis.…”

Section: Alcoholic Myopathymentioning

confidence: 88%

Mechanisms Underlying Muscle Protein Imbalance Induced by Alcohol

Kimball¹,

Lang

2018

Annu. Rev. Nutr.

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Both acute intoxication and longer-term cumulative ingestion of alcohol negatively impact the metabolic phenotype of both skeletal and cardiac muscle, independent of overt protein calorie malnutrition, resulting in loss of skeletal muscle strength and cardiac contractility. In large part, these alcohol-induced changes are mediated by a decrease in protein synthesis that in turn is governed by impaired activity of a protein kinase, the mechanistic target of rapamycin (mTOR). Herein, we summarize recent advances in understanding mTOR signal transduction, similarities and differences between the effects of alcohol on this central metabolic controller in skeletal muscle and in the heart, and the effects of acute versus chronic alcohol intake. While alcohol-induced alterations in global proteolysis via activation of the ubiquitin-proteasome pathway are equivocal, emerging data suggest alcohol increases autophagy in muscle. Further studies are necessary to define the relative contributions of these bidirectional changes in protein synthesis and autophagy in the etiology of alcoholic myopathy in skeletal muscle and the heart.

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Section: Alcoholic Myopathymentioning

confidence: 88%

Mechanisms Underlying Muscle Protein Imbalance Induced by Alcohol

Kimball¹,

Lang

2018

Annu. Rev. Nutr.

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“…In this regard, it is interesting to underline the result of the increased plasma KIC concentration during the absorptive state of the (35), suggesting that these amino acids are subsequently lost through oxidation. However, the habitual consumption of ethanol would lead to a steady expansion of the free amino acid pool according to studies in alcoholic humans (36,37) or chronically ethanol fed rats (38,39), showing increased concentrations of branched chain amino acids in plasma (36)(37)(38)(39) and tissues (38,39).…”

Section: Methodsmentioning

confidence: 99%

Ethanol impairs post-prandial hepatic protein metabolism.

Feo¹,

Volpi²,

Lucidi³

et al. 1995

J. Clin. Invest.

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The effects of acute ethanol ingestion on whole body and hepatic protein metabolism in humans are not known. To simulate social drinking, we compared the effects of the association of a mixed meal (632 kcal, 17% amino acids, 50% glucose, 33% lipids) with a bottle of either table wine (ethanol content 71 g) or water on the estimates ([1-'4C]-leucine infusion) of whole body protein breakdown, oxidation, and synthesis, and on the intravascular fractional secretory rates (FSR) of hepatically (albumin, fibrinogen) and extrahepatically (IgG) synthesized plasma proteins in two randomized groups (ethanol n = 7, water n = 7) of healthy nonalcoholic volunteers. Each study was carried out for 8 h. Protein kinetics were measured in the overnight post-absorptive state, over the first 4 h, and during a meal infusion (via a nasogastric feeding tube at constant rate) combined with the oral ingestion of wine or water, over the last 4 h. When compared with water, wine ingestion during the meal reduced (P < 0.03) by 24% the rate of leucine oxidation, did not modify the estimates of whole body protein breakdown and synthesis, reduced (P < 0.01) by -30% the FSR of albumin and fibrinogen, but did not affect IgG FSR. In conclusion, 70 g of ethanol, an amount usual among social drinkers, impairs hepatic protein metabolism. The habitual consumption of such amounts by reducing the synthesis and/or secretion of hepatic proteins might lead to the progressive development of liver injury and to hypoalbuminemia also in the absence of protein malnutrition. (J. Clin. Invest. 1995Invest. . 95:1472Invest. -1479

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“…L-leucine appears to be one of the strongest autophagic suppressors in this group. It is noteworthy that reports indicate that chronic ethanol administration in rats increases the intrahepatic levels of leucine by 1.4 to 1.8-fold over pairfed controls [27,42] . Thus, the association of an ethanolinduced reduction in autophagy with higher levels of intrahepatic leucine may partially explain autophagic suppression in the ethanol-fed state.…”

Section: Suppression Of Autophagymentioning

confidence: 99%

“…It is also paradoxical that ethanol feeding results in higher levels of leucine during a slowdown in protein catabolism when one would expect the opposite situation. Still, leucine accumulation could reflect a reduced ability of the liver to synthesize proteins, which indeed occurs in ethanol-fed animals [42,43] . A third likely mechanism of autophagic suppression by ethanol is its well-documented ability to disrupt protein trafficking in the liver.…”

Section: Suppression Of Autophagymentioning

confidence: 99%

Autophagy and ethanol-induced liver injury

Donohue¹

2009

WJG

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The majority of ethanol metabolism occurs in the liver. Consequently, this organ sustains the greatest damage from ethanol abuse. Ethanol consumption disturbs the delicate balance of protein homeostasis in the liver, causing intracellular protein accumulation due to a disruption of hepatic protein catabolism. Evidence indicates that ethanol or its metabolism impairs trafficking events in the liver, including the process of macroautophagy, which is the engulfment and degradation of cytoplasmic constituents by the lysosomal system. Autophagy is an essential, ongoing cellular process that is highly regulated by nutrients, endocrine factors and signaling pathways. A great number of the genes and gene products that govern the autophagic response have been characterized and the major metabolic and signaling pathways that activate or suppress autophagy have been identified. This review describes the process of autophagy, its regulation and the possible mechanisms by which ethanol disrupts the process of autophagic degradation. The implications of autophagic suppression are discussed in relation to the pathogenesis of alcohol-induced liver injury.

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Leucine metabolism during chronic ethanol consumption

Cited by 27 publications

References 14 publications

Mechanisms Underlying Muscle Protein Imbalance Induced by Alcohol

Mechanisms Underlying Muscle Protein Imbalance Induced by Alcohol

Ethanol impairs post-prandial hepatic protein metabolism.

Autophagy and ethanol-induced liver injury

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