title: Chronic inflammation and the effect of IGF-I on muscle strength and power in older persons.
abstract: Deregulation of the inflammatory response plays a major role in the age-related decline of physical performance. The causal pathway leading from inflammation to disability has not been fully clarified, but several researches suggest that interleukin-6 (IL-6) causes a reduction of physical performance in elderly through its effect on muscle function. In vitro studies demonstrated that IL-6 inhibits the secretion of insulin-like growth factor I (IGF-I) and its biological activity, suggesting that the negative effect of IL-6 on muscle function might be mediated through IGF-I. We evaluated the joint effect of IGF-I and IL-6 on muscle function in a population-based sample of 526 persons with a wide age range (20-102 yr). After adjusting for potential confounders, such as age, sex, body mass index, IL-6 receptor, and IL-6 promoter polymorphism, IL-6, IGF-I, and their interaction were significant predictors of handgrip and muscle power. In analyses stratified by IL-6 tertiles, IGF-I was an independent predictor of muscle function only in subjects in the lowest IL-6 tertile, suggesting that the effect of IGF-I on muscle function depends on IL-6 levels. This mechanism may explain why IL-6 is a strong risk factor for disability.
authors.affiliation: Department of Geriatric Medicine and Metabolic Diseases, II University of Naples, Italy.
authors.forename: Michelangela
authors.initials: M
authors.lastname: Barbieri
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
authors.forename: Emilia
authors.initials: E
authors.lastname: Ragno
authors.forename: Annamaria
authors.initials: A
authors.lastname: Corsi
authors.forename: Stefania
authors.initials: S
authors.lastname: Bandinelli
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Bonafè
authors.forename: Fabiola
authors.initials: F
authors.lastname: Olivieri
authors.forename: Simona
authors.initials: S
authors.lastname: Giovagnetti
authors.forename: Claudio
authors.initials: C
authors.lastname: Franceschi
authors.forename: Jack M
authors.initials: JM
authors.lastname: Guralnik
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Paolisso
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002908:Chronic Disease; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000503:physiopathology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D011446:Prospective Studies
chemical_list: D015850:Interleukin-6; D007334:Insulin-Like Growth Factor I