Effect of gold thioglucose and gold thiomalate on the norepinephrine-induced lipolysis in brown adipose tissue of mice.

Abstract

The ventromedial hypothalamus(VMH) may play an important regulatory role in peripheral lipid mobilization. Gold thioglucose (GTG) is known to produce damage in the VMH, causing hyper-phagia and consequent obesity. We studied changes in lipolytic response to norepinephrine(NE) in brown(interscapular :IBAT) and white(epididymal:EWAT) adipose tissues after GTG and gold thiomalate(GTM) treatment. Male ddY mice were injected i.p. with either GTG(800 mg/kg) or GTM(800 mg/kg). At varying times after GTG injection(5-24h,7,30d), slices of IBAT and EWAT were incubated in KRP buffer with added NE (10−4-10−8M). After incubation, FFA released into the medium was determined colorimetri-cally. The body weight of GTG group increased to almost twice the control group after 30 days. The weight of IBAT and EWAT from these obese mice increased markedly. At 5 hr after GTG treatment, significant hyperphagia was obtained, and its degree increased progressively during the 24 hrs examined. Thirty days after GTG injection, basal lipolytic activity of the EWAT was significantly higher than that of the control group, whereas this elevation was not observed in the IBAT of GTG-treated mice. In contrast to the IBAT, the EWAT from GTG-treated obese mice was not responsive to exogenous NE. This insensitivity to NE in the EWAT from GTG-treated mice may be affected by the hypothalamic obesity caused by GTG injection.