title: Changes in IL-15 expression and death-receptor apoptotic signaling in rat  gastrocnemius muscle with aging and life-long calorie restriction.
abstract: TNF-alpha-mediated apoptosis is enhanced in aged rodent muscles, suggesting that this pathway may be involved in sarcopenia. Interleukin-15 (IL-15), a muscle-derived anabolic cytokine, mitigates muscle wasting and apoptosis in cachectic rats. This effect is thought to occur through inhibition of TNF-alpha-triggered apoptosis. We investigated IL-15 signaling and the TNF-alpha-mediated pathway of apoptosis in the gastrocnemius muscle of Fischer344xBrown Norway rats across the ages of 8, 18, 29 and 37 months, in relation to life-long calorie restriction (CR, 40% calorie intake reduction). Aging caused loss of muscle mass and increased apoptotic DNA fragmentation, which were mitigated by CR. Protein levels of IL-15 and mRNA abundance of IL-15 receptor a-chain decreased in senescent ad libitum (AL) fed rats, but were maintained in CR rodents. Elevations of TNF-alpha, TNF-receptor 1, cleaved caspase-8 and -3 were observed at advanced age in AL rats. These changes were prevented or mitigated by CR. Our results indicate that aging is associated with decreased IL-15 signaling in rat gastrocnemius muscle, which may contribute to sarcopenia partly through enhanced TNF-alpha-mediated apoptosis. Preservation of IL-15 signaling by CR may therefore represent a further mechanism contributing to the anti-aging effect of this dietary intervention in skeletal muscle.
authors.affiliation: Department of Aging and Geriatric Research, Institute on Aging, Division of Biology of Aging, University of Florida, Gainesville, FL 32610-0143, USA. emarzetti@aging.ufl.edu
authors.forename: Emanuele
authors.initials: E
authors.lastname: Marzetti
authors.forename: Christy S
authors.initials: CS
authors.lastname: Carter
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Wohlgemuth
authors.forename: Hazel A
authors.initials: HA
authors.lastname: Lees
authors.forename: Silvia
authors.initials: S
authors.lastname: Giovannini
authors.forename: Barbara
authors.initials: B
authors.lastname: Anderson
authors.forename: LeBris S
authors.initials: LS
authors.lastname: Quinn
authors.forename: Christiaan
authors.initials: C
authors.lastname: Leeuwenburgh
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D001835:Body Weight; D031204:Caloric Restriction; D020169:Caspases / Q000378:metabolism; D019409:Interleukin-15 / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism*; D009929:Organ Size; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D053218:Receptors, Death Domain / Q000378:metabolism*; D053647:Receptors, Interleukin-15 / Q000378:metabolism; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D019409:Interleukin-15; D021122:Protein Subunits; D053218:Receptors, Death Domain; D053647:Receptors, Interleukin-15; D014409:Tumor Necrosis Factor-alpha; D020169:Caspases