Elevated serum IL-6 and adiponectin levels are associated with frailty and physical function in Chinese older adults

Abstract

Purpose: Frailty is associated with adverse health outcomes. Its biological markers are essential to enhance diagnostic ease and would contribute to surveillance of the condition. Considering the involvement of pro-inflammatory and nutritional states in frailty, we aimed to investigate whether inflammatory mediators and adipokines are associated with frailty and their relationship with physical function.

Patients and methods: We recruited 130 older adults (90 nonfrail participants and 40 frail participants, mean age: 72.80±8.61 years) who underwent a comprehensive medical history and frailty assessment. The biochemical indicators (eg, blood urea nitrogen [BUN], high-density lipoprotein [HDL], and hemoglobin [HGB]), insulin pathway (glucose, insulin, and insulin-like growth factor 1 [IGF-1]), circulating inflammatory biomarkers (IL-6, tumor necrosis factor receptor 1, and C-reactive protein), and adipokines (adiponectin, vaspin, and leptin) were compared between the two groups. We further analyzed their correlation with physical function.

Results: Frail older adults showed higher levels of BUN, IL-6, adiponectin, vaspin, and glucose and lower levels of IGF-1, HDL, and HGB compared with nonfrail participants. Serum IL-6 levels were negatively correlated with both grip strength (P=0.03) and gait speed (P=0.04). Levels of circulating adiponectin and leptin were adversely correlated with grip strength (P=0.01) and gait speed (P=0.03), respectively. After adjustment for age and sex, the only markers correlated with physical function were IL-6 (r=-0.180, P=0.044) and adiponectin (r=-0.195, P=0.029).

Conclusion: High levels of IL-6, adiponectin, vaspin, and glucose as well as low levels of IGF-1 were found in frail older adults. Furthermore, IL-6, adiponectin, and leptin levels were negatively correlated with physical function, suggesting that inflammatory mediators and adipokines are biomarkers for frailty and decreased function in older adults.

Keywords: IL-6; adipokine; adiponectin; biomarker; frailty; inflammation.

Figure 1

Comparison of inflammatory markers between frail and nonfrail old adults. Notes: One hundred thirty older adults were divided into two groups: nonfrail group (n=90) and frail group (n=40). Values in the figure were expressed as mean (SD) or median (IQR). Levels of IL-6 (A), TNFR1 (B), IIS (C), CRP (D), Fib (E) and WBC (F) were compared between the two groups. Abbreviations: CRP, C-reactive protein; Fib, fibrinogen; IIS, inflammation index score; TNFR1, tumor necrosis factor receptor 1; WBC, white blood cell count.

Figure 2

Comparison of circulating adipokines and insulin pathway between frail and nonfrail old adults. Notes: One hundred thirty older adults were divided into two groups: nonfrail group (n=90) and frail group (n=40). Values in the figure were expressed as mean (SD) or median (IQR). Levels of adiponectin (A), vaspin (B), leptin (C), IGF-1 (D), glucose (E) and insulin (F) were compared between the two groups. Abbreviation: IGF-1, insulin-like growth factor 1.

Figure 3

Correlation between physical function and circulating inflammatory markers and adipokines. Notes: Pearson’s correlation coefficients were calculated between grip strength and IL-6 (A) and adiponectin (B). Spearman’s correlation coefficients were calculated between gait speed and IL-6 (C) and leptin (D) in 130 older adults.