Chronological Age Does not Influence Ex-vivo Mitochondrial Respiration and Quality Control in Skeletal Muscle.
BACKGROUND
Considerable debate continues to surround the concept of mitochondrial dysfunction in aging muscle. We tested the overall hypothesis that age per se does not influence mitochondrial function and markers of mitochondria quality control, that is, expression of fusion, fission, and autophagy proteins. We also investigated the influence of cardiorespiratory fitness (VO2max) and adiposity (body mass index) on these associations.


METHODS
Percutaneous biopsies of the vastus lateralis were obtained from sedentary young (n = 14, 24±3 years), middle-aged (n = 24, 41±9 years) and older adults (n = 20, 78±5 years). A physically active group of young adults (n = 10, 27±5 years) was studied as a control. Mitochondrial respiration was determined in saponin permeabilized fiber bundles. Fusion, fission and autophagy protein expression was determined by Western blot. Cardiorespiratory fitness was determined by a graded exercise test.


RESULTS
Mitochondrial respiratory capacity and expression of fusion (OPA1 and MFN2) and fission (FIS1) proteins were not different among sedentary groups despite a wide age range (21 to 88 years). Mitochondrial respiratory capacity and fusion and fission proteins were, however, negatively associated with body mass index, and mitochondrial respiratory capacity was positively associated with cardiorespiratory fitness. The young active group had higher respiration, complex I and II respiratory control ratios, and expression of fusion and fission proteins. Finally, the expression of fusion, fission, and autophagy proteins were linked with mitochondrial respiration.


CONCLUSIONS
Mitochondrial respiration and markers of mitochondrial dynamics (fusion and fission) are not associated with chronological age per se, but rather are more strongly associated with body mass index and cardiorespiratory fitness.
Division of Endocrinology and Metabolism, Department of Medicine.|Department of Physical Therapy, University of Pittsburgh, Pennsylvania and.
Giovanna
G
Distefano
Division of Endocrinology and Metabolism, Department of Medicine.
Robert A
RA
Standley
Division of Endocrinology and Metabolism, Department of Medicine.
John J
JJ
Dubé
Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando.
Elvis A
EA
Carnero
Division of Endocrinology and Metabolism, Department of Medicine.
Vladimir B
VB
Ritov
Division of Endocrinology and Metabolism, Department of Medicine.
Maja
M
Stefanovic-Racic
Division of Endocrinology and Metabolism, Department of Medicine.
Frederico G S
FG
Toledo
Department of Physical Therapy, University of Pittsburgh, Pennsylvania and.
Sara R
SR
Piva
Division of Endocrinology and Metabolism, Department of Medicine.
Bret H
BH
Goodpaster
Division of Endocrinology and Metabolism, Department of Medicine.
Paul M
PM
Coen
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D000072599:Cardiorespiratory Fitness; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D055815:Young Adult
Aging; Body composition; Mitochondria; Muscle; Physical activity