Stimulation by leptin of ³H GDP binding to brown adipose tissue of fasted but not fed rats

Abstract

OBJECTIVES: To assess the effects of intracerebroventricular (icv) leptin administration on rats fed ad libitum or fasted on ³H GDP binding to brown adipose tissue (BAT).

SUBJECTS: Groups of 5–6 ten-week-old male Wistar rats.

EXPERIMENTAL DESIGN: An icv cannula was inserted and unilateral denervation of interscapular brown adipose tissue (BAT) was performed 5 d before each study. Thereafter, leptin was infused icv during 72 h while rats were fed ad libitum or fasted. Vehicle-infused, pair-fed or fasted rats were used as controls.

MEASUREMENTS: ³H GDP binding to innervated and denervated BAT mitochondria.

RESULTS: ³H GDP binding to innervated or denervated BAT of rats fed ab libitum compared to vehicle-infused, pair-fed rats was not increased by icv leptin. ³H GDP binding was lower in fasted than in fed rats, and the difference was larger in innervated than denervated BAT. Icv leptin increased ³H GDP binding by 30% in innervated, and by 51% in denervated BAT (P<0.05) in fasted rats.

CONCLUSIONS: Icv leptin does not increase ³H GDP binding to BAT of rats fed ad libitum compared to pair-fed (food-restricted) rats. In contrast, icv leptin produces a mild stimulation of ³H GDP binding to BAT of fasted rats. This effect is not mediated by the sympathetic nervous system, because it is observed in both innervated and denervated BAT. These results are compatible with the concept that, in fasting rats, the decrease in leptin secretion contributes to the reduction in ³H GDP binding to BAT mitochondria.