Chronic disuse and skeletal muscle structure in older adults: sex-specific differences and relationships to contractile function.

Abstract

In older adults, we examined the effect of chronic muscle disuse on skeletal muscle structure at the tissue, cellular, organellar, and molecular levels and its relationship to muscle function. Volunteers with advanced-stage knee osteoarthritis (OA, n = 16) were recruited to reflect the effects of chronic lower extremity muscle disuse and compared with recreationally active controls (n = 15) without knee OA but similar in age, sex, and health status. In the OA group, quadriceps muscle and single-fiber cross-sectional area were reduced, with the largest reduction in myosin heavy chain IIA fibers. Myosin heavy chain IIAX fibers were more prevalent in the OA group, and their atrophy was sex-specific: men showed a reduction in cross-sectional area, and women showed no differences. Myofibrillar ultrastructure, myonuclear content, and mitochondrial content and morphology generally did not differ between groups, with the exception of sex-specific adaptations in subsarcolemmal (SS) mitochondria, which were driven by lower values in OA women. SS mitochondrial content was also differently related to cellular and molecular functional parameters by sex: greater SS mitochondrial content was associated with improved contractility in women but reduced function in men. Collectively, these results demonstrate sex-specific structural phenotypes at the cellular and organellar levels with chronic disuse in older adults, with novel associations between energetic and contractile systems.

• Authors: Damien M Callahan, Timothy W Tourville, Mark S Miller, Sarah B Hackett, Himani Sharma, Nicholas C Cruickshank, James R Slauterbeck, Patrick D Savage, Philip A Ades, David W Maughan, Bruce D Beynnon, Michael J Toth
• Journal: American journal of physiology. Cell physiology (Am J Physiol Cell Physiol) Vol. 308 Issue 11 Pg. C932-43 (Jun 01 2015) ISSN: 1522-1563 [Electronic] United States
• PMID: 25810256 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
• Copyright: Copyright © 2015 the American Physiological Society.

Chemical References

• Protein Isoforms
• Myosin Heavy Chains

Topics

• Aged
• Case-Control Studies
• Exercise
• Female
• Gene Expression
• Humans
• Knee (pathology, physiopathology)
• Male
• Mitochondria (metabolism, ultrastructure)
• Muscle Contraction
• Muscle Fibers, Skeletal (metabolism, pathology, ultrastructure)
• Muscular Atrophy (complications, metabolism, pathology, physiopathology)
• Myosin Heavy Chains (genetics, metabolism)
• Osteoarthritis, Knee (complications, metabolism, pathology, physiopathology)
• Protein Isoforms (genetics, metabolism)
• Quadriceps Muscle (metabolism, physiopathology, ultrastructure)
• Sex Factors