The Lipoprivic Control of Feeding Is Governed by Fat Metabolism, Not by Leptin or Adipose Depletion

Abstract

A lipoprivic control of feeding has been proposed based on the finding that appetite is stimulated by drugs such as β-mercaptoacetate (MA) that reduce fatty acid oxidation. The adipose-derived hormone, leptin, has effects on feeding and fat oxidation that are opposite those produced by MA. However, effects of this hormone on MA-induced feeding are not known. Here we examined the effects of endogenous leptin levels and of acute central and peripheral leptin administration on MA-induced feeding. We also examined leptin-induced changes in feeding, body weight, and plasma fuels after capsaicin-induced deletion of the lipoprivic control. MA-induced feeding was not altered under any of these conditions, and leptin’s effects were not altered by capsaicin. We then examined MA-induced feeding during chronic leptin treatment. Because chronic leptin produces several distinct metabolic states as body adiposity is reduced, we tested MA before, during, and after leptin treatment at times that coincided with these states. MA-induced feeding was unchanged on d 3 of leptin treatment when rats were in a lipolytic state and rapidly metabolizing body fat stores but reduced on d 10 when they were adipose deplete and their level of fat oxidation was reduced. Together results suggest that the lipoprivic control is normally less active in the fat deplete state than during states associated with fat availability. If so, its insensitivity to leptin would enable the lipoprivic control to operate when dietary fat, adiposity, and leptin levels are elevated. The role played by the lipoprivic control under such conditions remains uncertain.