Effects of chronic alcohol intoxication on aerobic exercise-induced adaptations in female mice

Chronic alcohol intoxication decreases muscle strength/function and causes mitochondrial dysfunction. Aerobic exercise training improves mitochondrial oxidative capacity and increases muscle mass and strength. Presently, the impact of chronic alcohol on aerobic exercise-induced adaptations was investigated. Female C57BL/6Hsd mice were randomly assigned to one of four groups: control sedentary (CON SED; n = 26), alcohol sedentary (ETOH SED; n = 27), control exercise (CON EX; n = 28), and alcohol exercise (ETOH EX; n = 25). Exercise mice had running wheel access for 2 h a day, 7 days a week. All mice were fed either control or an alcohol-containing liquid diet. Grip strength testing and EchoMRI were performed before and after the interventions. After 6 wk, hindlimb muscles were collected for molecular analyses. A subset of mice performed a treadmill run to fatigue (RTF), then abstained from alcohol for 2 wk and repeated the RTF. Alcohol decreased lean mass and forelimb grip strength compared with control-fed mice. Alcohol blunted the exercise-induced increase in muscle mass (plantaris and soleus), type IIa fiber percentage in the plantaris, and run time to fatigue. Mitochondrial markers (Citrate synthase activity and Complex I-IV, COXIV and Cytochrome C protein expression) were increased with exercise regardless of ETOH in the gastrocnemius but not tibialis anterior muscle. Two weeks of alcohol abstinence improved RTF time in ETOH EX but not in ETOH SED. These data suggest that alcohol impairs some exercise-induced adaptations in skeletal muscle, but not all were negatively affected, indicating that exercise may be a beneficial behavior even while consuming alcohol.NEW & NOTEWORTHY Alcohol consumption during an aerobic exercise training period prevented training-induced increases in run to fatigue time and grip strength. Cessation of alcohol allowed for recovery of endurance performance within 2 wk. The worsened exercise performance after alcohol was unrelated to impairments in markers of mitochondrial health. Therefore, some adaptations to exercise training are impaired with alcohol use (endurance performance, muscle growth, and strength), while others remain mostly unaffected (mitochondrial health).

Chronic Alcohol Consumption Disrupts the Skeletal Muscle Circadian Clock in Female Mice

The intrinsic skeletal muscle core clock has emerged as a key feature of metabolic control and influences several aspects of muscle physiology. Acute alcohol intoxication disrupts the core molecular clock, but whether chronic consumption, like that leading to alcoholic myopathy, is also a zeitgeber for skeletal muscle remains unknown. The purpose of this work was to determine whether chronic alcohol consumption dysregulates the skeletal muscle core molecular clock and clock-controlled genes (CCGs). C57BL/6Hsd female mice (14 weeks old) were fed a control (CON) or alcohol (EtOH) containing liquid diet for 6 weeks. Gastrocnemius muscles and serum were collected from CON and EtOH mice every 4-h for 24-h. Chronic alcohol consumption disrupted genes of the core clock including suppressing the rhythmic peak of expression of Bmal1, Per1, Per2, and Cry2. Genes involved in the regulation of Bmal1 also exhibited lower rhythmic peaks including Reverb α and Myod1. The CCGs, Dbp, Lpl, Hk2, and Hadh were also suppressed by alcohol. The nuclear expression patterns of MYOD1, DBP, and REVERBα were shifted by alcohol, while no change in BMAL1 was detected. Overall, these data indicate that alcohol disrupted the skeletal muscle core clock but whether these changes in the core clock are causative or a consequence of alcoholic myopathy requires future mechanistic confirmation.

Effects of alcohol on skeletal muscle contractile performance in male and female mice

Background

Acute and chronic alcohol use can cause skeletal muscle myopathy in concert with impairments in skeletal muscle strength, function and fatigue resistance. However, the fundamental contractile deficits induced in the presence of alcohol versus those observed in the recovery period following the clearance of alcohol have not yet been characterized nor is it known whether sex influences these outcomes.

Methods

Male and female mice received an intraperitoneal injection of either saline (Control) or ethanol (EtOH; 5g/kg body weight). Muscle force, fatigue, fatigue recovery and twitch characteristics of the posterior crural muscle complex were measured in situ 1 hour and 24 hours post alcohol.

Results

In the presence of alcohol (1-hour post treatment) absolute and normalized force generated at 80–150 Hertz was decreased in male and female mice with concurrent reductions in the rate of force development and increases in ½ relaxation time. When expressed as a percentage of maximum force, both males and females also displayed an alcohol-induced leftward shift in the force frequency curve indicative of a type I contractile phenotype. Alcohol enhanced fatigue in both males and females but had no effect on force recovery. Following clearance of alcohol (24-hour post treatment), contractile function was completely restored in females while alcohol treated males experienced sustained reductions in absolute force and had enhanced fatigue compared with male controls.

Conclusions

In the presence of alcohol, both males and females exhibited significant declines in muscle force production and enhanced fatigue; however, following complete clearance of the alcohol, females recovered all functional parameters, while males did not.