Effects of age and sedentary lifestyle on skeletal muscle NF-kappaB signaling in men.
BACKGROUND
Nuclear factor kappa B (NF-kappaB) is a critical signaling molecule of disuse-induced skeletal muscle atrophy. However, few studies have carefully investigated whether similar pathways are modulated with physical activity and age.


METHODS
The present study examined lean mass, maximal force production, and skeletal muscle NF-kappaB signaling in 41 men categorized as sedentary (OS, N = 13, 63.85 +/- 6.59 year), physically active (OA, N = 14, 60.71 +/- 5.54 year), or young and sedentary (YS, N = 14, 21.35 +/- 3.84 year). Muscle tissue from the vastus lateralis was assayed for messenger RNA (mRNA) expression of the beta subunit of IkB kinase (IKKbeta), cytosolic protein content of phosphorylated inhibitor of kappa B alpha (pIKBalpha), and nuclear content of NF-kappaB subunits p50 and p65.


RESULTS
When compared with YS, OS demonstrated age-related muscle atrophy and reduced isokinetic knee extension torque. Physical activity in older individuals preserved maximal isokinetic knee extension torque. OS muscle contained 50% more pIKBalpha than OA and 61% more pIKBalpha than YS. Furthermore, nuclear p65 was significantly elevated in OS compared with YS. OS muscle did not differ from either of the other two groups for nuclear p50 or for mRNA expression of IKKbeta.


CONCLUSIONS
These results indicate that skeletal muscle content of nuclear-bound p65 is elevated by age in humans. The elevation in nuclear-bound p65 appears to be at least partially due to significant increases in pIKBalpha. A sedentary lifestyle appears to play some role in increased IKBalpha; however, further research is needed to identify downstream effects of this increase.
Buford
Thomas W
TW
Department of Health, Human Performance, and Recreation, Exercise and Biochemical Nutrition Laboratory, Baylor University, Waco, TX 76798, USA.
Cooke
Matthew B
MB
Manini
Todd M
TM
Leeuwenburgh
Christiaan
C
Willoughby
Darryn S
DS
D000368:Aged; D000375:Aging / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000737:chemistry / Q000502:physiology*; D016328:NF-kappa B / Q000032:analysis / Q000502:physiology*; D052002:NF-kappa B p50 Subunit / Q000032:analysis / Q000502:physiology; D016133:Polymerase Chain Reaction; D016059:Range of Motion, Articular / Q000502:physiology; D057185:Sedentary Behavior; D015398:Signal Transduction / Q000502:physiology; D051996:Transcription Factor RelA / Q000032:analysis / Q000502:physiology
D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D051996:Transcription Factor RelA