Divergent relationship of circulating CTRP3 levels between obesity and gender: a cross-sectional study

C1q TNF Related Protein 3 (CTRP3) is a novel adipose tissue derived secreted factor, or adipokine, which has been linked to a number of beneficial biological effects on metabolism, inflammation, and survival signaling in a variety of tissues. However, very little is known about CTRP3 in regards to human health. The purpose of this project was to examine circulating CTRP3 levels in a clinical population, patients with symptoms requiring heart catheterization in order to identify the presence of obstructive coronary artery disease (CAD). It was hypothesized that serum CTRP3 levels would be decreased in the presence of CAD. METHODS: Body mass index (BMI), diabetes status, and plasma samples were collected from 100 patients who were >30 years of age and presented at the East Tennessee State University Heart Clinic with symptoms requiring heart catheterization in order to identify the presence of cardiovascular blockages (n = 52 male, n = 48 female). Circulating CTRP3 levels were quantified using commercially available ELISA. RESULTS: Circulating CTRP3 levels had no relationship to the presence of CAD regardless of gender. However, circulating concentrations of CTRP3 were significantly higher in normal weight (BMI < 30) females (0.88 ± 0.12 µg/ml) compared with males (0.54 ± 0.06 µg/ml). Further, obesity (BMI > 30) resulted in an increase in circulating CTRP3 levels in male subjects (0.74 ± 0.08 µg/ml) but showed a significant decrease in female subjects (0.58 ± 0.07 µg/ml). Additionally, there was a significant reduction in circulating CTRP3 levels in female subjects who were diagnosed with Type 2 diabetes compared with patients without (0.79 ± 0.08 vs. 0.42 ± 0.10 µg/ml). There was no relationship between diabetes status and circulating CTRP3 levels in male subjects. CONCLUSION: Circulating CTRP3 levels had a different relationship with diabetes and obesity status between male and female patients. It is possible that circulating CTRP3 levels are controlled by hormonal status, however more research is needed to explore this relationship. Nevertheless, future studies examining the relationship between CTRP3 levels and disease status should treat gender as an independent variable.