Analysis of the adiponectin paradox in healthy older people

BACKGROUND: It remains unknown why adiponectin levels are associated with poor physical functioning, skeletal muscle mass and increased mortality in older populations. METHODS: In 190 healthy adults (59–86 years, BMI 17–37 kg/m(2), 56.8% female), whole body skeletal muscle mass (normalized by height, SMI, kg/m(2)), muscle and liver fat were determined by magnetic resonance imaging. Bone mineral content (BMC) and density (BMD) were assessed by dual X‐ray absorptiometry (n = 135). Levels of insulin‐like growth factor 1 (IGF‐1), insulin, inflammation markers, leptin and fibroblast growth factor 21 were measured as potential determinants of the relationship between adiponectin and body composition. RESULTS: Higher adiponectin levels were associated with a lower SMI (r = −0.23, P < 0.01), BMC (r = −0.17, P < 0.05) and liver fat (r = −0.20, P < 0.05) in the total population and with higher muscle fat in women (r = 0.27, P < 0.01). By contrast, IGF‐1 showed positive correlations with SMI (r = 0.33), BMD (r = 0.37) and BMC (r = 0.33) (all P < 0.01) and a negative correlation with muscle fat (r = −0.17, P < 0.05). IGF‐1 was negatively associated with age (r = −0.21, P < 0.01) and with adiponectin (r = −0.15, P < 0.05). Stepwise regression analyses revealed that IGF‐1, insulin and leptin explained 18% of the variance in SMI, and IGF‐1, leptin and age explained 16% of the variance in BMC, whereas adiponectin did not contribute to these models. CONCLUSIONS: Associations between higher adiponectin levels and lower muscle or bone mass in healthy older adults may be explained by a decrease in IGF‐1 with increasing adiponectin levels.