Circulating Growth Arrest-Specific 6 Protein Is Associated With Adiposity, Systemic Inflammation, and Insulin Resistance Among Overweight and Obese Adolescents

Context: Growth arrest-specific 6 (Gas6) is a vitamin K-dependent protein secreted by immune cells, endothelial cells, vascular smooth muscle cells, and adipocytes. Preclinical studies indicate that Gas6 and its receptors of the TAM (Tyro-3, Axl, Mer) family may be involved in the pathogenesis of obesity and its complications, including systemic inflammation and insulin resistance. Until now, little has been known about the clinical significance of the Gas6/TAM system in childhood obesity. Objectives: This study aimed to determine whether circulating Gas6 and soluble Axl (sAxl) levels are associated with adiposity, inflammation, and insulin resistance status among Taiwanese adolescents. Methods: Cross-sectional analyses using the data from the Taipei Children Heart Study-III were performed. A total of 832 adolescents (average age, 13.3 years) were included; they were divided into 3 groups: lean, overweight, and obese. Circulating Gas6 and sAxl levels, adiposity, inflammatory markers, and insulin resistance status were examined. Results: Levels of circulating Gas6 and sAxl were significantly higher in overweight and obese adolescents than in the lean group (both P < .05). Circulating Gas6 levels were significantly positively correlated with body mass index Z-score (P = .045), waist circumference (P < .001), waist to hip circumference ratio (P < .001), body fat mass (P = .02), serum high-sensitivity C-reactive protein (P = .005), and tumor necrosis factor-alpha levels (P = .039) among overweight and obese adolescents. The correlations remained significant after adjusting for age, gender, Tanner stage, smoking status, and drinking status. In addition, every 1 ng/mL increase in circulating Gas6 concentration corresponded to a 15% to 19% increase in the risk of developing insulin resistance among overweight and obese adolescents. Conclusions: Circulating Gas6 levels are strongly associated with adiposity, inflammation, and insulin resistance status among overweight and obese adolescents. The potential role of the Gas6/TAM system in the initiation of childhood obesity and obesity-associated complications deserves further attention. (J Clin Endocrinol Metab 98: E267-E274, 2013)