Lateral hypothalamic serotonin is not stimulated during central leptin hypophagia

Abstract

Whether leptin targets the hypothalamic serotonergic system to inhibit food intake is not established. We examined the effect of a short-term i.c.v. leptin treatment on serotonin microdialysate levels in rat lateral hypothalamus. Adipose tissue gene expression was also evaluated. Male rats received four daily injections of leptin (5 μg) or vehicle (with pair-feeding to leptin-induced intake) and a fifth injection during collection of LH microdialysates. We found that serotonin and 5-HIAA levels were not affected by the leptin pre-treatment, as basal levels were similar between the leptin and the pair-fed group. These levels remained unaltered after the acute leptin injection. For gene expression studies, rats were pre-treated with five daily injections of either leptin (5 μg) or vehicle (with either pair-feeding or ad libitum intake). mRNA levels of resistin, adiponectin, lipoprotein lipase, and PPAR-gamma were unaltered by either leptin or pair-feeding. Leptin gene expression was significantly reduced by leptin but not by pair-feeding, in both the retroperitoneal (-74%) and the epididymal (-99%) depots while no differences were observed in the subcutaneous depot. The observations confirmed the absence of an acute stimulatory effect of central leptin on serotonin release in the lateral hypothalamus and showed that the pre-treatment with leptin failed to modify this pattern. This indicates that components of the serotonergic system are probably not directly affected by leptin. Additionally, the central effect of leptin was able to downregulate its own adipose tissue gene expression in a depot-specific manner while other adipokine genes were not affected.

Ginkgo biloba Extract Improves Insulin Signaling and Attenuates Inflammation in Retroperitoneal Adipose Tissue Depot of Obese Rats

“…It is possible that the GbE treatment duration was not sufficient to affect the other cytokine levels rather than TNF- α . In addition, it is well known that the white adipose tissue presents a depot-specific response to different stimuli [ 31 , 32 ]. It allows to speculate that other fat depots rather than the retroperitoneal one might present altered levels of IL-6 and IL-10 in response to GbE treatment.…”

Restricción alimentaria intermitente: repercusiones en la regulación de la homeostasis energética hipotalámica y tejido adiposo

“…En estudios en modelo animal con programación metabólica, donde las ratas gestantes fueron someti das a restricción alimentaria por periodos prolongados, se observaron alteraciones en los efectos anorexígenos hipotalámicos de la insulina, lepti na y serotonina de la prole. Por consiguiente, los autores concluyeron que periodos de restricción de nutrientes conti nuos o intermitentes, causan resistencia a la acción de estos anorexígenos, comprometi endo así la señalización de estas vías en esa generación 42,43,44 .…”