Min Thar Htut (University of Medicine 2, Yangon, Myanmar)| May Pyone Kyaw (University of Medicine 2, Yangon, Myanmar)
Obesity becomes one of the major health problems worldwide. Adipose tissue morphology changes in obesity and expression of pro-inflammatory adipocytokines increases in both adipocytes and adipose tissue macrophages. Regarded as pro-inflammatory cytokine, leptin could be part of cytokine network that induces pro-inflammatory cytokine (IL-6) production from adipose tissue macrophages. Although interleukin-6 (IL-6) is a pro-inflammatory cytokine, some studies reported its anti-inflammatory role. The present study aimed to investigate the association of plasma leptin and IL-6 levels in obese and non-obese adults. A comparative cross-sectional study was designed for apparently healthy non-obese (BMI – 18.5 – 22.9 kg/m2, n=60) and obese adults (BMI ≥ 25 kg/m2, n=60) age ranged between 25–50 years. Anthropometric measurements including BMI, wrist circumference and blood pressure were performed. Plasma leptin and IL-6 levels were determined by enzyme-linked immunosorbent assay (ELISA). The variables were compared between non-obese and obese groups and between genders. The correlation of plasma leptin and IL-6 levels was determined and compared between obese and non-obese groups. Plasma leptin and IL-6 levels were significantly higher in obese than in non-obese adults (leptin: 31.65 ± 19.16 ng/ml vs. 9.02 ± 10.29 ng/ml, p<0.01) (IL-6: 2.64 ± 0.9 pg/ml vs. 1.22 ± 0.48 pg/ml, p<0.01). Higher plasma leptin level was observed in women (30.62 ± 19.74 ng/ml) compared to men (10.06 ± 11.36 ng/ml) (p < 0.01). There was no significant difference between plasma IL-6 levels of men (1.8 ± 0.99 pg/ml) and women (2.06 ± 1.03 pg/ml) (p=0.168). Significant positive correlation was seen between plasma leptin and IL-6 levels (r=0.547, p<0.05) in the whole study group. Stronger positive correlation between plasma leptin and IL-6 was observed in non-obese group (r=0.313, p<0.05) than in obese group (r=0.18, p=0.169). The present study pointed out that obesity is a state of chronic inflammation with increased plasma levels of pro-inflammatory adipocytokines, leptin and IL-6. The positive correlation between plasma leptin and IL-6 was diminished in obese compared to non-obese adults and this may be due to peripheral leptin resistance that reduces effectiveness of stimulatory effect of leptin on IL-6 production from adipose tissue.
Table 1. Demographic characteristics and biochemical parameters of non-obese and obese groups Table 2. Correlation between plasma leptin and plasma IL-6 level in non-obese, obese and the whole study group