Circulating Interleukin-6 Is Associated with Skeletal Muscle Strength, Quality, and Functional Adaptation with...

Area of Science:

• Gerontology and Exercise Physiology
• Biomedical Science
• Inflammation Research

Background:

• Aging is associated with chronic, low-grade inflammation, termed
• inflammaging
• which may impair skeletal muscle health and adaptive responses to exercise.
• Interleukin-6 (IL-6) is a key inflammatory cytokine implicated in age-related muscle decline.

Purpose of the Study:

• To examine the relationship between circulating IL-6 levels, skeletal muscle characteristics, and exercise adaptation in mobility-limited older adults.
• To determine if IL-6 influences the effectiveness of a structured physical activity intervention.

Main Methods:

• A 6-month randomized controlled trial involving 99 mobility-limited older adults (Short Physical Performance Battery score ≤9).
• Intervention included structured physical activity, with or without protein and vitamin D supplementation.
• Measurements comprised circulating IL-6, skeletal muscle size, composition, strength, power, specific force, and physical function (gait speed, stair climb, SPPB).

Main Results:

• Baseline IL-6 was inversely correlated with muscle composition, strength, power, specific force, and positively with stair climb time.
• The exercise intervention did not alter IL-6 levels.
• In individuals with higher baseline IL-6, reductions in IL-6 correlated with gait speed improvements; baseline IL-6 was also inversely associated with lean mass gains and SPPB improvements.

Conclusions:

• Elevated circulating IL-6 in older adults is linked to reduced skeletal muscle strength, quality, function, and impaired adaptation to exercise training.
• Targeting IL-6 reduction presents a potential therapeutic strategy for preserving skeletal muscle health and enhancing exercise benefits in the aging population.