Lower Circulating C1q/TNF-Related Protein-3 (CTRP3) Levels Are Associated with Obesity: A Cross-Sectional Study

PURPOSE C1q/TNF-related protein-3 (CTRP3) is a novel adipokine that lowers blood glucose levels, reduces liver triglyceride synthesis, and is protective against hepatic steatosis in diet-induced obese mouse models. We hypothesized that higher circulating serum levels of CTRP3 would be associated with a lean body mass index (BMI) and a more favorable metabolic profile in humans. The aim of this study was to investigate CTRP3 levels in lean individuals compared to obese individuals. METHODS This was a cross-sectional study of obese (n=44) and lean control patients (n=60). Fasting metabolic parameters were measured in all patients and serum CTRP3 levels were measured by ELISA. RESULTS BMI of the lean group was 21.9 ± 0.2 kg/m2 and obese group was 45.2 ± 1.1 kg/m2. We found significantly lower circulating levels of CTRP3 in obese individuals (405 ± 8.3 vs. 436 ± 6.7 ng/mL, p=0.004) compared to the lean group. Serum CTRP3 levels were inversely correlated with BMI (p=0.001), and triglycerides (p<0.001), and significantly associated with gender (p<0.01), ethnicity (p=0.05), HDL-cholesterol (p<0.01), and adiponectin (p<0.01). We found BMI (p<0.01), gender (p<0.01), and ethnicity (p<0.05) to be significant predictors of CTRP3 levels when controlling for age in multiple regression analysis. CONCLUSIONS CTRP3 is a beneficial adipokine whose circulating levels are significantly lower in obese individuals. Obesity causes dysregulation in adipokine production, including the down-regulation of CTRP3. Lower CTRP3 levels may contribute to the pathophysiology of metabolic disorders associated with obesity. Optimizing CTRP3 levels through novel therapies may improve obesity and its comorbidities.