Associations between serum apelin-12 levels and obesity-related markers in Chinese children

Abstract

Objective: To investigate possible correlations between apelin-12 levels and obesity in children in China and associations between apelin-12 and obesity-related markers, including lipids, insulin sensitivity and insulin resistance index (HOMA-IR).

Methods: Forty-eight obese and forty non-obese age- and gender-matched Chinese children were enrolled between June 2008 and June 2009. Mean age was 10.42 ± 2.03 and 10.86±2.23 years in obesity and control groups, respectively. Main outcome measures were apelin-12, BMI, lipids, glucose and insulin. HOMA-IR was calculated for all subjects.

Results: All obesity group subjects had significantly higher total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), insulin levels and HOMA-IR (all P<0.05). In separate analyses, obese girls had significantly higher LDL-C, insulin and HOMA-IR than controls, and obese boys had significantly higher TC, TG, insulin and HOMA-IR than controls (all P<0.05). Apelin-12 levels were significantly higher in obese girls compared to controls (P = 0.024), and correlated positively with TG in all obese subjects. Among obese girls, apelin-12 levels correlated positively with TG, insulin and HOMA-IR after adjusting for age and BMI. In all boys (obese and controls) apelin-12 was positively associated with fasting plasma glucose (FPG). No significant correlations were found in either group between apelin-12 levels and other characteristics after adjusting for age, sex, and BMI.

Conclusions: Apelin-12 levels are significantly higher in obese vs. non-obese girls in China and correlate significantly with obesity-related markers insulin, HOMA-IR, and TG. Increased apelin-12 levels may be involved in the pathological mechanism of childhood obesity.

Figure 1. Associations between apelin levels, fasting insulin, triglycerides and HOMA-IR.

Figure 1 depicts the association between apelin levels and (A) fasting insulin, (B) TG, and (C) HOMA-IR in female subjects and the association between apelin levels and (D) fasting insulin, (E) TG, and (F) HOMA-IR in male subjects. Correlation coefficients with respective P-values are presented through partial correlation analysis after adjusting for age and BMI. The apelin levels were positively correlated with fasting insulin, TG, and HOMA-IR in females; No significant results were observed in males. TG, triglycerides; HOMA_IR, homeostasis model assessment of insulin resistance; BMI, body mass index.