Sarcopenic obesity and inflammation in the InCHIANTI study

TLDR

Aging is accompanied by muscle loss and fat gain, and when extreme, leads to sarcopenic obesity, a condition in which visceral adipose‑derived inflammatory cytokines accelerate muscle catabolism and perpetuate the cycle. The study tested whether obesity and reduced muscle strength in older adults are linked to elevated circulating proinflammatory cytokines. The cross‑sectional analysis included 871 participants aged 65+ from Tuscany, classified by sex‑specific tertiles of waist circumference and grip strength and by BMI ≥ 30 kg/m². After adjustment, sarcopenic obesity components were associated with higher IL‑6, CRP, IL‑1RA, and soluble IL‑6R, indicating that obesity‑driven inflammation impairs muscle strength and drives sarcopenic obesity.

Abstract

The aging process is often paralleled by decreases in muscle and increases in fat mass. At the extreme these two processes lead to a condition known as "sarcopenic obesity" (Roubenoff R. Ann NY Acad Sci 904: 553-557, 2000). Research suggests that inflammatory cytokines produced by adipose tissue, especially visceral fat, accelerate muscle catabolism and thus contribute to the vicious cycle that initiates and sustains sarcopenic obesity. We tested the hypothesis that obesity and poor muscle strength, hallmarks of sarcopenic obesity, are associated with high circulating levels of proinflammatory cytokines in a random sample of the residents of two municipalities in the Chianti geographic area (Tuscany, Italy). The study sample consisted of 378 men and 493 women 65 yr and older with complete data on anthropometrics, handgrip strength, and inflammatory markers. Participants were cross-classified according to sex-specific tertiles of waist circumference and grip strength and according to a cut point for obesity of body mass index > or =30 kg/m(2). After adjusting for age, sex, education, smoking history, physical activity, and history of comorbid diseases, components of sarcopenic obesity were associated with elevated levels of IL-6, C-reactive protein, IL-1 receptor antagonist, and soluble IL-6 receptor (P < 0.05). Our findings suggest that global obesity and, to a greater extent, central obesity directly affect inflammation, which in turn negatively affects muscle strength, contributing to the development and progression of sarcopenic obesity. These results suggest that proinflammatory cytokines may be critical in both the development and progression of sarcopenic obesity.