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Human neuromuscular aging: Sex differences revealed at the myocellular level
Brandon M Roberts1, Kaleen M Lavin1, Gina M Many1
1UAB Center for Exercise Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, United States; Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, United States.
Experimental Gerontology
|February 27, 2018
Summary
Age-related muscle loss, or sarcopenia, impacts men and women, causing weakness and disability. This study reveals distinct sex-based mechanisms of muscle aging, with females experiencing myofiber atrophy and males myofiber loss.
Area of Science:
- Gerontology
- Skeletal Muscle Physiology
- Sex Differences in Aging
Background:
- Age-related muscle loss (sarcopenia) is a significant health issue, leading to weakness, disability, and reduced quality of life.
- Current definitions of sarcopenia do not fully capture the complex age-related changes in skeletal muscle.
- Understanding the influence of aging and sex on skeletal muscle health is crucial for developing effective interventions.
Purpose of the Study:
- To investigate the impact of aging and sex on skeletal muscle health.
- To analyze myocellular aging through histopathological examination.
- To assess age and sex-related differences in neuromuscular performance.
Main Methods:
- Histopathological analysis of skeletal muscle from 221 untrained males and females across four age cohorts (25, 37, 61, 72 years).
- Assessment of neuromuscular performance, including knee extensor strength and power, and explosive sit-to-stand power.
- Evaluation of myocellular changes, such as fiber type atrophy and myofiber size heterogeneity.
Main Results:
- Significant reductions in total, leg, and arm lean mass were observed in older adults (61 and 72 years) compared to younger cohorts.
- Knee extensor strength and power decreased significantly in older adults, while explosive power declined by age 37.
- Histological analysis revealed type IIx atrophy by age 37 and type IIa atrophy by age 61, primarily driven by females.
- Aged female muscle showed greater myofiber size heterogeneity and type I myofiber grouping compared to males.
- Distinct sex-specific mechanisms of muscle atrophy were identified: myofiber atrophy in females versus myofiber loss in males.
Conclusions:
- The predominant mechanisms driving whole muscle atrophy differ between aging males and females.
- Females exhibit progressive myofiber atrophy (type IIa and IIx), while males appear to experience myofiber loss.
- Further research is needed to elucidate the mechanisms behind sex differences in myocellular aging.
- Optimizing exercise prescriptions and treatments requires consideration of these sex-specific aging processes.
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