Circulating Interleukin-6 Is Associated with Skeletal Muscle Strength, Quality, and Functional Adaptation with Exercise Training in Mobility-Limited Older Adults

• Published in: The Journal of frailty & aging Vol. 9; no. 1; pp. 57 - 63
• Main Authors: Grosicki, G J, Barrett, B B, Englund, D A, Liu, C, Travison, T G, Cederholm, T, Koochek, A, von Berens, Å, Gustafsson, T, Benard, T, Reid, K F, Fielding, R A
• Format: Journal Article
• Language: English
• Published: France Springer Nature B.V 01.01.2020
• Subjects: Adaptation; Age differences; Aged; Aging; Clinical trials; Cytokines; Density; Dietary supplements; Exercise; Exercise - physiology; Fitness training programs; Gait; Health sciences; Humans; IL-6; Immunoassay; Inflammation; Interleukin-6 - blood; Intervention; Medicin och hälsovetenskap; Mobility; Mobility Limitation; Muscle strength; Muscle Strength - physiology; Muscle, Skeletal - physiology; Musculoskeletal system; Nutrition research; older adults; Older people; Physical ability; Physical activity; Physical fitness; Power; sarcopenia; Strength training; Treatment methods; Vitamin D; Sweden; older adults; Inflammation; aging; IL-6; sarcopenia
• ISSN: 2260-1341; 2273-4309; 2273-4309
• DOI: 10.14283/jfa.2019.30

Human aging is characterized by a chronic, low-grade inflammation suspected to contribute to reductions in skeletal muscle size, strength, and function. Inflammatory cytokines, such as interleukin-6 (IL-6), may play a role in the reduced skeletal muscle adaptive response seen in older individuals. To investigate relationships between circulating IL-6, skeletal muscle health and exercise adaptation in mobility-limited older adults. Randomized controlled trial. Exercise laboratory on the Health Sciences campus of an urban university. 99 mobility-limited (Short Physical Performance Battery (SPPB) ≤9) older adults. 6-month structured physical activity with or without a protein and vitamin D nutritional supplement. Circulating IL-6, skeletal muscle size, composition (percent normal density muscle tissue), strength, power, and specific force (strength/CSA) as well as physical function (gait speed, stair climb time, SPPB-score) were measured pre- and post-intervention. At baseline, Spearman's correlations demonstrated an inverse relationship (P<0.05) between circulating IL-6 and thigh muscle composition (r = -0.201), strength (r = -0.311), power (r = -0.210), and specific force (r = -0.248), and positive association between IL-6 and stair climb time (r = 0.256; P<0.05). Although the training program did not affect circulating IL-6 levels (P=0.69), reductions in IL-6 were associated with gait speed improvements (r = -0.487; P<0.05) in "higher" IL-6 individuals (>1.36 pg/ml). Moreover, baseline IL-6 was inversely associated (P<0.05) with gains in appendicular lean mass and improvements in SPPB score (r = -0.211 and -0.237, respectively). These findings implicate age-related increases in circulating IL-6 as an important contributor to declines in skeletal muscle strength, quality, function, and training-mediated adaptation. Given the pervasive nature of inflammation among older adults, novel therapeutic strategies to reduce IL-6 as a means of preserving skeletal muscle health are enticing.