Alcohol abuse is a major public health problem leading to premature death, impaired hospital recovery, and dysfunction of multiple organ systems. Muscle wasting is a hallmark of sustained alcohol abuse and the associated proximal muscle weakness represents a prevalent form of skeletal muscle myopathy. During the past funding period, using established rodent models of acute alcohol intoxication and chronic alcohol ingestion, we demonstrated that alcohol impairs not only basal muscle protein synthesis but also the responsiveness of this tissue to nutrient (e.g., leucine) stimulation. This leucine (Leu) resistance results from suppression of mTOR kinase activity, which is manifested as an inhibition of protein synthesis and which appears to be largely Akt/TSC-independent. We also reported that a similar mechanism is operational in muscle cells cultured with alcohol. Our long-term goal is to elucidate the Akt/TSC-independent mechanisms underpinning Leu-induced mTOR activity in skeletal muscle per se and to determine their relative importance in the ability of alcohol to down-regulate this nutritional sensor thereby producing skeletal muscle myopathy. To address the questions implicit in this goal, the proposed research has the following specific aims: (1) Assess the importance of the alcohol-induced change in total and/or phosphorylated DEPTOR (a known negative mTOR-regulatory protein) as a mechanism for the decrease in basal and/or Leu-stimulated muscle protein synthesis;(2) Delineate the mechanism by which alcohol disrupts endosomal trafficking of mTOR complex-1 (mTORC1) and impairs amino acid sensing and protein synthesis in muscle;and (3) Elucidate the extent to which altered MAP4K3 signaling is causally linked to the alcohol-induced decrease in mTOR kinase activity under basal and nutrient-stimulated conditions. Our application exploits a number of innovative approaches made possible by the availability of novel reagents and is supported by provocative preliminary data. It is noteworthy that the proposed in vivo electroporation of lentiviral-delivered shRNA specifically to skeletal muscle permits loss- and gain-of-function experiments to be performed and to assign causality to the observed changes. Furthermore, changes in muscle mass/protein synthesis will be correlated with direct assessment of muscle strength/contractility. These in vivo methods, used in conjunction with an established model of chronic alcohol ingestion in mice and with the availability of novel phospho-specific antibodies, place us in a unique position to rapidl and significantly advance knowledge pertaining to amino acid regulation of mTORC1. Our focus on state-of-the-art in vivo approaches permits us to definitively assign physiological importance to our observations, while complementary in vitro studies will allow us to define cellular mechanisms and to prioritize future work. The expected research outcomes will have a positive impact by contributing fundamental knowledge concerning nutrient regulation at the molecular level and provide seminal mechanistic insights into the clinically significant pathology of alcohol induced muscle disease.

Public Health Relevance

Alcohol excess, both chronic abuse and acute intoxication, exacts a staggering economic cost to society and remains a major public health problem. Excessive alcohol consumption is associated not only with increased mortality, but also with premature and preventable health concerns, and impaired rehabilitation. Our study focuses on the cellular and molecular mechanisms by which excess alcohol impairs basal skeletal muscle protein synthesis and produces a resistance to the normal anabolic effects of amino acids, thereby leading to the development of alcoholic myopathy, one of the most prominent muscle diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
5R37AA011290-19
Application #
8617196
Study Section
Integrative Nutrition and Metabolic Processes Study Section (INMP)
Program Officer
Gao, Peter
Project Start
1997-05-01
Project End
2017-03-31
Budget Start
2014-04-01
Budget End
2015-03-31
Support Year
19
Fiscal Year
2014
Total Cost
$333,923
Indirect Cost
$115,673
Name
Pennsylvania State University
Department
Physiology
Type
Schools of Medicine
DUNS #
129348186
City
Hershey
State
PA
Country
United States
Zip Code
17033
Molina, Patricia E; Bagby, Gregory J; Nelson, Steve (2014) Biomedical consequences of alcohol use disorders in the HIV-infected host. Curr HIV Res 12:265-75
Gordon, Bradley S; Steiner, Jennifer L; Lang, Charles H et al. (2014) Reduced REDD1 expression contributes to activation of mTORC1 following electrically induced muscle contraction. Am J Physiol Endocrinol Metab 307:E703-11
Molina, Patricia E; Gardner, Jason D; Souza-Smith, Flavia M et al. (2014) Alcohol abuse: critical pathophysiological processes and contribution to disease burden. Physiology (Bethesda) 29:203-15
Molina, Patricia E (2014) Alcohol binging exacerbates adipose tissue inflammation following burn injury. Alcohol Clin Exp Res 38:33-5
Lang, Charles H; Derdak, Zoltan; Wands, Jack R (2014) Strain-dependent differences for suppression of insulin-stimulated glucose uptake in skeletal and cardiac muscle by ethanol. Alcohol Clin Exp Res 38:897-910
Simon, Liz; LeCapitaine, Nicole; Berner, Paul et al. (2014) Chronic binge alcohol consumption alters myogenic gene expression and reduces in vitro myogenic differentiation potential of myoblasts from rhesus macaques. Am J Physiol Regul Integr Comp Physiol 306:R837-44
Lang, Charles H; Korzick, Donna H (2014) Chronic alcohol consumption disrupts myocardial protein balance and function in aged, but not adult, female F344 rats. Am J Physiol Regul Integr Comp Physiol 306:R23-33
Molina, Patricia E; Amedee, Angela M; Veazey, Ron et al. (2014) Chronic binge alcohol consumption does not diminish effectiveness of continuous antiretroviral suppression of viral load in simian immunodeficiency virus-infected macaques. Alcohol Clin Exp Res 38:2335-44
Steiner, Jennifer L; Lang, Charles H (2014) Alcohol impairs skeletal muscle protein synthesis and mTOR signaling in a time-dependent manner following electrically stimulated muscle contraction. J Appl Physiol (1985) 117:1170-9
Hong-Brown, Ly Q; Brown, C Randell; Navaratnarajah, Maithili et al. (2013) Activation of AMPK/TSC2/PLD by alcohol regulates mTORC1 and mTORC2 assembly in C2C12 myocytes. Alcohol Clin Exp Res 37:1849-61

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