The ratio of estrogen receptor α to β is associated with the expression of lipoprotein lipase and hormone-sensitive lipase in human adipose tissue

Abstract

Lipoprotein lipase (LPL) is a key enzyme regulating fat metabolism by catabolizing plasma triglyceride (TG) into free fatty acid (FFA) (lipogenesis). Hormone-sensitive lipase (HSL) is rate-limiting enzyme for lipolysis by hydrolysis of stored TG in fat into FFA and glycerol. Current evidence has suggested that estrogen have regulatory effect on determining the amount and distribution of adipose tissue, but the mechanism remains unclear. Estrogen performs its biological activities through binding to its two receptors, ER-alpha (ERα) and ER-beta (ERβ), which are expressed in adipocytes. In this study, we investigate the association between ER expression and LPL or HSL in human adipose tissue. Exploratory, pilot study. We obtained small pieces (5-10g) of subcutaneous and omental adipose tissue from thirty-eight women who have had a gynecologic surgery. Total RNA was extracted from the fat samples, and a real-time RT-PCR was performed to measure and quantify the mRNA expression of ER, LPL, and HSL. Correlation and regression tests were performed for the variables. All subjects were premenopausal women aged 20 to 50 (median age: 39.2 years-old). In subcutaneous fat, neither ERα nor ERβ showed a correlation with the mRNA levels of LPL or HSL. However, the ER ratio (α/β) showed a negative correlation with the HSL (r = -0.553, P < 0.001). In omental fat, the mRNA of ERα was significantly correlated with both LPL and HSL (P = 0.001 and P = 0.017). In addition, the ER ratio was positively correlated with LPL mRNA level (r = 0.471, P < 0.001). The results of present study showed that both subtypes of ER were associated with the expression of LPL or HSL. Our findings imply that the ratio of ERα to ERβ in human subcutaneous and omental adipose tissue is an important regulatory factor involved in fat metabolism by interacting with LPL and HSL.