Evidence of growth hormone effect on plasma leptin in diet-induced obesity and diet-resistant rats

Abstract

Background Plasma leptin is regulated by several factors, including growth hormone (GH), which influences the pathophysiology of obesity. Objective To demonstrate the short-term effect of GH on plasma leptin levels in 3 conditions in vivo with the different amount of body fat mass. Methods Adult male Wistar rats were fed with standard chow or hypercaloric diet (HC). The HC rats were demonstrated as HC-feeding obese (HC-O) and HC-feeding resistant (HC-R) rats. Then, they were treated with GH or saline for 3 days. Basal plasma leptin levels were measured at 24 and 32 h. For meal-induced condition, all rats were fed for 2 hand plasma leptin was measured. Further 16-h fasting period, plasma leptin, insulin, and insulin sensitivity indexes were determined. Results The short-term GH treatment decreased basal plasma leptin at 32 h after the first GH injection in HC-O rats. However, GH treatment had no effect on meal-induced plasma leptin in all rats. Furthermore, GH treatment attenuated fasting effect on plasma leptin in control and HC-R rats. The insulin resistance (IR) induced by the short-term GH treatment was demonstrated by higher fasting plasma insulin and the increased homeostasis model of IR in HC-R rats. Conclusions The study demonstrates the important role of greater fat mass in HC-O rats, which results in decreased basal plasma leptin after short-term GH treatment. For meal-induced condition, GH had no effect on plasma leptin in all rats. Interestingly, GH could attenuate fasting effect on plasma leptin in rats that have lower fat mass.

Effects of oleic acid and/or exercise on diet-induced thermogenesis and obesity in rats

“…Obesity stimulates chronic low-degree inflammation and intrinsic immune system activation( 35 ). Obese adipose tissue includes further immune cells, involving M1-polarized pro-inflammatory macrophages which generate pro-inflammatory cytokines like IL-6, TNF-α, and IL-Ιβ( 36 ).…”

Short-Term Growth Hormone Administration Mediates Hepatic Fatty Acid Uptake and De Novo Lipogenesis Gene Expression in Obese Rats

“…However, long-term GH treatment promoted insulin resistance in hypophysectomized animals and GH-deficient subjects [ 12 , 13 ]. On the other hand, short-term GH treatment (5 days) did not increase plasma insulin levels in obese animals [ 14 ] and did not affect fat accumulation [ 15 ]. In addition, short-term GH treatment (5 days) promoted the anorectic effect of obese rats [ 14 ].…”