Chronic Alcohol Consumption, but not Acute Intoxication, Decreases In Vitro Skeletal Muscle Contractile Function

• Published in: Alcoholism, clinical and experimental research Vol. 43; no. 10; pp. 2090 - 2099
• Main Authors: Crowell, Kristin T., Laufenberg, Lacee J., Lang, Charles H.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-10-2019
• Subjects: Acute intoxication; Alcohol use; Alcoholic beverages; ATP; Calcium-binding protein; Contractile Proteins; Ethanol; Fatigability; Ingestion; Intoxication; Muscle Contractility; Muscle contraction; Muscle Force; Muscles; Musculoskeletal system; Myopathy; Myosin; Oxidative phosphorylation; Phosphorylation; Protein biosynthesis; Protein synthesis; Skeletal muscle; Troponin; Muscle Force; ATP; Fatigability; Muscle Contractility; Contractile Proteins
• ISSN: 0145-6008; 1530-0277
• DOI: 10.1111/acer.14179

Background
Skeletal muscle myopathy accompanying chronic alcohol misuse results in part from a decrease in protein synthesis typically observed in type II‐rich muscles that leads to muscle weakness. However, there is a paucity of studies investigating whether the alcohol‐induced weakness is intrinsic to the muscle or results primarily from the loss of muscle mass. The present study determines whether acute alcohol (ethanol) intoxication or chronic alcohol consumption decreases the intrinsic contractile function of muscle.
Methods
Adult male mice were randomly assigned to the chronic alcohol group or given a binge dose of alcohol, and contractile characteristics of the extensor digitorum longus (EDL) were determined in vitro.
Results
The weight and physiological cross‐sectional area (PCSA) of the EDL were decreased in alcohol‐fed mice. Maximum twitch and tetanic tension were also reduced, and there was a downward shift of the absolute force–frequency curve in alcohol‐fed mice. However, no alcohol‐induced changes were noted when these contractile parameters were normalized for the lower PCSA. Alcohol‐fed mice demonstrated greater fatigability, and alcohol‐induced decreases in postfatigue specific twitch and tetanic force were independent of a decreased PCSA. Furthermore, postfatigue recovery of muscle force over time was reduced. While alcohol did not alter the content of high‐energy phosphates or oxidative phosphorylation complexes I‐V, it did reduce myosin heavy chain and troponin‐T content. In contrast, contractile properties were not altered when examined 2 hours after binge alcohol.
Conclusions
These data demonstrate chronic alcohol consumption decreases isometric and tetanic tension development due to a reduction in muscle CSA, whereas the increased fatigability observed was independent of muscle mass. As none of the functional changes were produced by acute alcohol, which produced higher blood alcohol levels than chronic ingestion, our data suggest defects in intrinsic muscle contractility require sustained intake and appear independent of defects in basal energy production.
Chronic alcohol consumption impairs skeletal muscle contractile properties. Some defects, such as isometric and tetanic tension development, result from a reduction in muscle cross‐sectional area. Other defects, such as increased fatigability, are independent of muscle mass. No contractile defects are noted by acute binge alcohol drinking that yielded higher blood alcohol levels than chronic ingestion. Our data suggest defects in intrinsic muscle contractility require sustained consumption of alcohol and contribute to the observed muscle weakness that characterizes alcoholic myopathy.