Leptin receptor-deficient obese Zucker rats reduce their food intake in response to a systemic supply of calories from glucose

It has been established that leptin exerts a negative control on food intake, allowing one to maintain stable caloric intake over time. The aim of the present study was to investigate whether leptin regulates food intake when a supply of calories is provided by the systemic route. Experiments were carried out in leptin receptor-deficient obese fa/fa rats and lean Fa/fa controls. In both groups, 48 It of glucose infusion reduced food intake in proportion to caloric supply, resulting in virtually no change in total caloric intake as compared to before the infusion. This hypophagic response was reproduced without adding systemic calories, but by increasing glucose and insulin concentrations specifically in the brain through carotid artery infusion. Concomitant intracere-broventricular administration of 5-(tetradecyloxy)-2-furoic acid, an acetyl CoA carboxylase inhibitor that precludes malonyl-CoA synthesis, abolished the restriction of feeding in carotid-infused lean and obese rats. These data indicate that a supply of calories via glucose infusion induces a hypophagic response independent of leptin signaling in the rat, and support the hypothesis that a rise in central malonyl-CoA, triggered by increased glucose and insulin concentrations, participates in this adaptation. This process could contribute to the limiting of hyperphagia, primarily when leptin signaling is altered, as in the obese state.