Acting in the
hypothalamus, tumor necrosis factor-alpha (
TNF-alpha) produces a potent anorexigenic effect. However, the molecular mechanisms involved in this phenomenon are poorly characterized. In this study, we investigate the capacity of
TNF-alpha to activate signal transduction in the hypothalamus through elements of the pathways employed by the anorexigenic
hormones insulin and
leptin. High dose
TNF-alpha promotes a reduction of 25% in 12h food intake, which is an inhibitory effect that is marginally inferior to that produced by
insulin and
leptin. In addition, high dose
TNF-alpha increases body temperature and respiratory quotient, effects not reproduced by
insulin or
leptin.
TNF-alpha, predominantly at the high dose, is also capable of activating canonical pro-inflammatory signal transduction in the hypothalamus, inducing JNK, p38, and NFkappaB, which results in the transcription of early responsive genes and expression of
proteins of the SOCS family. Also,
TNF-alpha activates signal transduction through JAK-2 and STAT-3, but does not activate signal transduction through early and intermediary elements of the
insulin/
leptin signaling pathways such as IRS-2, Akt, ERK and FOXO1. When co-injected with
insulin or
leptin,
TNF-alpha, at both high and low doses, partially impairs signal transduction through IRS-2, Akt, ERK and FOXO1 but not through JAK-2 and STAT-3. This effect is accompanied by the partial inhibition of the anorexigenic effects of
insulin and
leptin, when the low, but not the high dose of
TNF-alpha is employed. In conclusion,
TNF-alpha, on a dose-dependent way, modulates
insulin and
leptin signaling and action in the hypothalamus.