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.

Circadian rhythms are central to optimal physiological function as disruption contributes to the development of several chronic diseases. Alcohol (EtOH) intoxication disrupts circadian rhythms within liver, brain, and intestines, but it is unknown whether alcohol also disrupts components of the core clock in skeletal muscle. Female C57BL/6Hsd mice were randomized to receive either saline (control) or alcohol (EtOH) (5g/kg) via intraperitoneal injection at the start of the dark cycle (ZT12), and gastrocnemius was collected every 4hr from Control and EtOH treated mice for the next 48hr following isoflurane anesthetization. In addition, metyrapone was administered prior to alcohol intoxication in separate mice to determine whether the alcohol-induced increase in serum corticosterone contributed to circadian gene regulation. Finally, synchronized C2C12 myotubes were treated with alcohol (100mM) to assess the influence of centrally or peripherally mediated effects of alcohol on the muscle clock. Alcohol significantly disrupted mRNA expression of Bmal1, Per1/2, and Cry1/2 in addition to perturbing the circadian pattern of clock-controlled genes, Myod1, Dbp, Tef, and Bhlhe40 (p<0.05) in muscle. Alcohol increased serum corticosterone levels and glucocorticoid target gene, Redd1, in muscle. Metyrapone prevented the EtOH-mediated increase in serum corticosterone but did not normalize the EtOH-induced change in Per1, Cry1 and Cry2 and Myod1 mRNA expression. Core clock gene expression (Bmal, Per1/2, Cry1/2) was not changed following 4, 8, or 12hrs of alcohol treatment on synchronized C2C12 myotubes. Therefore, binge alcohol disrupted genes of the core molecular clock independently of elevated serum corticosterone or direct effects of EtOH on the muscle.

Herein, we demonstrate that acute alcohol intoxication immediately alters whole body metabolism coinciding with rapid changes in the skeletal muscle macronutrient gene signature for at least 48 h postbinge and that this response diverges from hepatic effects and those of a fasted animal.

Previous studies have shown that chronic heavy alcohol consumption and consumption of a high-fat (HF) diet can independently contribute to skeletal muscle oxidative stress and mitochondrial dysfunction, yet the concurrent effect of these risk factors remains unclear. We aimed to assess the effect of alcohol and different dietary compositions on mitochondrial activity and oxidative stress markers. Male and female mice were randomized to an alcohol (EtOH)-free HF diet, a HF + EtOH diet, or a low-Fat (LF) + EtOH diet for 6 weeks. At the end of the study, electron transport chain complex activity and expression as well as antioxidant activity and expression, were measured in skeletal muscles. Complex I and III activity were diminished in muscles of mice fed a HF + EtOH diet relative to the EtOH-free HF diet. Lipid peroxidation was elevated, and antioxidant activity was diminished, in muscles of mice fed a HF + EtOH diet as well. Consumption of a HF diet may exacerbate the negative effects of alcohol on skeletal muscle mitochondrial health and oxidative stress.

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.

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Chronic alcohol consumption has been commonly reported to induce skeletal muscle loss, however data observing the impact of diet composition and alcohol on muscle mass, particularly between sexes, remains scarce. PURPOSE To observe how differences in dietary composition influence the effects of alcohol on skeletal muscle mass in male and female mice. METHODS C57BL/6 mice (n=72; m=36; f=36) aged 12‐weeks‐old were acclimated to a liquid diet for one‐week prior to randomization into either a control (CON: 35% FAT, 47% CHO, 18% PRO) or one of three alcohol (EtOH) treatment groups of differing dietary composition: high‐fat (HF: 35% FAT, 15% CHO, 18% PRO), low‐fat (LF: 12% FAT, 38% CHO, 18% PRO) or high‐protein (PRO: 12% FAT, 31% CHO, 25% PRO). Alcohol was incorporated into the diet and increased over time to a maximum intake of 32% kcal of the diet. Daily consumption of EtOH was assessed relative to body weight. After 7 weeks, the gastrocnemius (GAS) and quadriceps (QUAD) muscles were excised, along with the heart and spleen, which were weighed and expressed relative to body weight. Blood was taken at sacrifice for blood EtOH concentration (BAC); however, feeding status and therefore alcohol intake, was ad libitum up until the time of sample collection. Data were analyzed via 2‐way ANOVA for variables across time, and unpaired t‐tests were used to detect differences between diets and control groups, and between sexes within diets. RESULTS No significant interactions nor main effects were observed for EtOH consumption between diets within each sex. A significant main effect of sex was observed for EtOH consumption within all diets, where females consumed more EtOH than males (HF: F=71.79, 5.18 ± 0.61 g/kg; LF: F=53.55, 4.37 ± 0.60 g/kg; PRO: F=38.45, 4.75 ± 0.77 g/kg; p’s <0.0001). No main effect of diet was observed for either sex for BAC (p≥0.98) at sacrifice. Female GAS was significantly reduced in HF and LF compared to CON (−8.31 ± 3.74%, p=0.043; −10.53 ± 3.74%, p=0.01 respectively), while no changes were noted for Male GAS. Female QUAD was significantly reduced in HF and LF compared to CON (−10.81 ± 4.52%, p=0.03; −13.63 ± 3.58%, p<0.01 respectively), while no changes were observed for male QUAD. Female heart weights were significantly reduced in HF and LF compared to CON (−12.35 ± 4.33%, p=0.01; −11.34 ± 3.88%, p<0.01 respectively), while an increase in LF was observed in males (9.89 ± 2.55%, p<0.01). Furthermore, female spleen weight was significantly reduced in LF and PRO (−18.39 ± 7.22%, p=0.02; −19.06 ± 6.45%, p=0.01 respectively), while no differences were noted for males. CONCLUSIONS Despite consuming equivalent amounts of EtOH between diets within each sex, females in HF and LF diets experienced significant muscle atrophy compared to CON, while no reductions were observed in PRO. However, this alcohol feeding protocol did not induce significant muscle atrophy in male mice. A possible explanation for these sex differences is that over time, female mice consumed significantly more EtOH relative to body weig...

Highlights Aerobic exercise in the heat promotes modest increases in plasma TNF-α and STNFR1. Increases in TNF-α and STNFR1 are likely driven by changes in core temperature. TNFR1 and 2 expression on non-classical monocytes is blunted one hour post-exercise. TNFR1 expression on non-classical monocytes is elevated during exercise in the heat.