Low muscle mass has been associated with insulin resistance and the development of type 2 diabetes (T2DM). Serum creatinine is a metabolite of creatine present in the skeletal muscle. The creatinine concentration is stable and directly proportional to skeletal muscle mass. Low levels of creatinine have been shown to be associated with the development of T2DM. The underlying mechanism of low creatinine and its risk for the development of diabetes is not known. Nonhuman primates (NHPs), maintained on a healthy diet, frequently develop spontaneous middle-aged obesity, metabolic syndrome (MetSyn), and T2DM similar to humans. In the present study, longitudinal evaluation of the associations between creatinine and the development of obesity, MetSyn, and T2DM in 125 male rhesus monkeys were studied. In addition, 7 male monkeys with long term calorie-restriction (CR) to maintain a healthy lean mass were used as a comparison group. Creatinine decreased as age (r=-0.39, p\0.001), body fat percent (r=-0.27, p\0.001), HbA1c% (r=-32, p\0.001) increased. Decrease in insulin sensitivity was significantly (r=0.07, p\0.001) associated with a decrease in percent fat free mass. Creatinine also declined with decreasing insulin sensitivity (r=0.23, p\0.05) and fat free mass (FFM) (r=0.26, p\001) indicating that monkeys with higher lean muscle mass exhibited better insulin sensitivity. Creatinine was significantly decreased in monkeys with T2DM compared to both MetSyn and metabolically normal monkeys (p\0.001). Longitudinal data analysis showed progressive decline of creatinine with MetSyn and the development of T2DM. CR monkeys showed no significant change in creatinine throughout the lifelong duration of calorie restriction. Also unchanged during CR were fasting plasma glucose, body fat, FFM, or body weight. This is the first longitudinal study showing the association of creatinine with the development of T2DM. Serum creatinine levels declined with decrease in fat free mass and insulin sensitivity.
U.K. Chaudhari: None. J.D. Newcomb: None. B.C. Hansen: None.