Association of serum soluble leptin receptor and leptin levels with breast cancer

Leptin plays a key role in the regulation of energy expenditure and is known to circulate in both free and bound forms. Soluble leptin receptor (sOB-R) is a unique circulating form of leptin receptor that can bind to leptin. Leptin and leptin receptor have been implicated in processes leading to breast cancer initiation and progression. Our study was aimed to investigate the relationship between serum levels of sOB-R and leptin with breast cancer. Serum leptin and sOB-R levels were measured by enzyme-linked immunosorbent assay in 100 women with breast cancer cases compared with 100 age and body mass index (BMI)-matched controls without cancer. Lipid profiles were measured by enzymatic method. The median serum levels of sOB-R in controls were significantly higher than that in breast cancer cases (odds ratio [OR], 1.98; 95% confidence interval [CI] = 0.77-188.2) versus (OR, 0.140; 95% CI = 0.09-98.1). Conversely, the median serum level of leptin in breast cancer cases was significantly higher than that in controls (OR, 67.90; 95% CI = 2.77-129.9) vs. (OR, 28.30; 95% CI = 0.60-113.1). Breast cancer was significantly associated with higher serum level of leptin (OR = 1.027, 95% CI = 1.017-1.038). Conversely, breast cancer was correlated with lower serum level of sOB-R (OR = 0.983, 95% CI = 0.969-0.997). Moreover, free leptin index (FLI) (leptin/sOB-R ratio) was associated with breast cancer (OR = 1.028, 95% CI = 1.015-1.042). The serum sOB-R level was negatively associated with leptin, BMI, and high density lipoprotein (r = −0.238, −0.186, and −0.168, respectively). Our results suggested that FLI and serum leptin level rather than serum level of sOB-R was associated with the breast cancer.