Neurohumoral stimulation of lipogenesis during altered states of energy balance

Abstract

Acid extracts of bovine hypothalamus stimulate lipogenic activity in adipose tissue. We employed a rat fat cell bioassay system to determine whether tissue concentrations of the active material vary as a function of spontaneous alterations in energy balance in hibernators and/or the obesity resulting from bilateral electrolytic lesions of the ventromedial area of the hypothalamus in rats. When hypothalamic extracts and partially purified plasma were fractionated using reverse-phase high-pressure liquid chromatography, both the void volume and material eluting 17 min after the start of a 25-min linear methanol gradient enhanced glucose incorporation into total lipid. Activities eluting with these two fractions were positively correlated with one another and were independent of insulin. The results indicate that a hypothalamic lipogenic factor (LHF) is detectable in plasma, that hypothalamic and circulating LHF concentrations vary in a reciprocal manner, and that elevations in plasma LHF concentration are associated with insulin resistance. The data suggest that the central regulation of lipogenesis is at least partially mediated by a hypothalamic humoral factor reaching fat depots via the circulation.