Creatine kinase as a marker of obesity in a multi-ethnic population

Objective: Creatine kinase (CM), the central regulatory enzyme of energy metabolism, is particularly high in type II skeletal muscle fibers, which are associated with insulin resistance and obesity. As resting plasma CK is mainly derived from skeletal muscle, we assessed whether plasma CM is associated with markers of obesity. Methods: In this cross-sectional study, we analyzed a random sample of the multi-ethnic population of Amsterdam, the Netherlands, consisting of 1444 subjects aged 34-60 years. The primary outcome was the independent association between plasma CM after rest and waist circumference. Other outcomes included waist-to-hip ratio and body mass index. Results: Mean waist circumference increased from the first through the third CK tertile, respectively 90.3 (SD 13.4), 93.2 (SD 14.3), and 94.4 (SD 13.3) cm (p < 0.001 for differences between tertiles). The increase in waist circumference was 8.91 (95% CI 5.35 to 12.47) cm per log CM increase after adjustment for age, sex, African ethnicity, educational level, physical activity and plasma creatinine. Similarly, CM was independently associated with waist-to-hip ratio and body mass index, with an increase of respectively 0.05 (95% CI 0.03 to 0.07) and 3.6 (95% CI 2.3 to 5.0) kg/m(2) per log CM increase. Conclusions: Plasma CM is independently associated with measures of obesity in a multi-ethnic population. This is in line with the central role of type II skeletal muscle fibers in energy metabolism and obesity. Prospective studies should assess whether resting plasma CK could be an easy accessible marker of CK rich type II fiber predominance that helps identify individuals at risk for obesity. (C) 2016 Elsevier Ireland Ltd. All rights reserved.