Changes In Fat Mass, Interleukin-6, And C-reactive Protein In Postmenopausal Women

Abstract

The association between body fat and systemic inflammation is well known. Less is known about the extent to which changes in body fat are accompanied by changes in circulating inflammatory mediators and markers in postmenopausal women. PURPOSE To determine whether one year changes in body fat are associated with one year changes in serum interleukin-6 (IL-6) and C-reactive protein (CRP) in postmenopausal women. METHODS Hormone therapy (HT) users (N=117) and non-users (N=104) were randomly assigned to a resistance training exercise program or to no exercise: HT-exercise (N=65), HT-no exercise (N=52), no HT-exercise (N=54), and no HT-no exercise (N=50). The exercise program included three 60–75 minute sessions per week wherein 8 different exercises were performed in 2 sets of 6 to 8 repetitions at 70–80% of 1RM. For each subject, baseline and 1-year serum IL-6 and CRP were measured using highly-sensitive, enzyme-linked immunosorbent assays. The inter-assay coefficients of variation were at or below 7.2% for IL-6 and at or below 6.2% for CRP. Fat mass was assessed by dual-energy X-ray absorptiometry. ANCOVA was used to determine whether changes in fat mass and serum CRP differed by tertiles of serum IL-6 change while controlling for such potential confounders as age, experimental group assignment (exercise vs. control), and HT use. RESULTS The tertiles of serum IL-6 change were indicative of small reductions in IL-6 in the 1st tertile (−0.572 ± 0.609 pg/ml, N=73), no change in IL-6 in the 2nd tertile (0.063 ± 0.093 pg/ml, N=74), and small increases in IL-6 in the 3rd tertile (+0.942 ± 1.053 pg/ml, N=74). Adjusted mean fat mass changes were significantly different between the first and the third tertiles of IL-6 change (−0.9 ± 0.3 kg vs. +0.4 ± 0.3 kg, p<0.05). Adjusted mean serum CRP changes were also significantly different between the first and third tertiles of IL-6 change (−0.690 ± 0.326 mg/l vs. +0.614 ± 0.323 mg/l, p<0.05). CONCLUSIONS Small one year changes in serum IL-6 were associated with like changes in fat mass and serum CRP independent of age, exercise status and HT use in postmenopausal women. NIH AR 39559, Mission Pharmacal and National Osteoporosis Foundation