Feeding Stimulates Sphingosine-1-Phosphate Mobilization in Mouse Hypothalamus

Valentina Vozella,Daniele Piomelli,Alessandra Misto,Natalia Realini

doi:10.3390/ijms20164008

Abstract

Previous studies have shown that the sphingolipid-derived mediator sphingosine-1-phosphate (S1P) reduces food intake by activating G protein-coupled S1P receptor-1 (S1PR1) in the hypothalamus. Here, we examined whether feeding regulates hypothalamic mobilization of S1P and other sphingolipid-derived messengers. We prepared lipid extracts from the hypothalamus of C57Bl6/J male mice subjected to one of four conditions: free feeding, 12 h fasting, and 1 h or 6 h refeeding. Liquid chromatography/tandem mass spectrometry was used to quantify various sphingolipid species, including sphinganine (SA), sphingosine (SO), and their bioactive derivatives SA-1-phosphate (SA1P) and S1P. In parallel experiments, transcription of S1PR1 (encoded in mice by the S1pr1 gene) and of key genes of sphingolipid metabolism (Sptlc2, Lass1, Sphk1, Sphk2) was measured by RT-PCR. Feeding increased levels of S1P (in pmol-mg−1 of wet tissue) and SA1P. This response was accompanied by parallel changes in SA and dihydroceramide (d18:0/18:0), and was partially (SA1P) or completely (S1P) reversed by fasting. No such effects were observed with other sphingolipid species targeted by our analysis. Feeding also increased transcription of Sptlc2, Lass1, Sphk2, and S1pr1. Feeding stimulates mobilization of endogenous S1PR1 agonists S1P and SA1P in mouse hypothalamus, via a mechanism that involves transcriptional up-regulation of de novo sphingolipid biosynthesis. The results support a role for sphingolipid-mediated signaling in the central control of energy balance.

Highlights

The hypothalamus controls feeding behavior and energy metabolism by integrating a complex array of neural and humoral signals [1,2,3,4]
To determine whether feeding status influences the mobilization of sphingolipid-derived messengers in the hypothalamus, we used a liquid chromatography/mass spectrometry (LC/MS-MS) protocol that allows the simultaneous quantification of up to 25 sphingolipid species, including the sphingoid bases sphinganine (SA) and sphingosine (SO) and their bioactive phosphorylated derivatives, sphinganine-1-phoshate (SA1P) and S1P (Figure 1)
Pharmacological experiments in rats have shown that intracerebroventricular infusions of the sphingolipid-derived mediator S1P produce a behaviorally selective inhibition of food intake by activating G protein-coupled S1P receptor-1 (S1PR1) receptors in the hypothalamus [9]

Summary

Introduction

The hypothalamus controls feeding behavior and energy metabolism by integrating a complex array of neural and humoral signals [1,2,3,4]. Peptide neurotransmitters are known to play crucial roles in this process. Neurons housed in the hypothalamic arcuate nucleus secrete either orexigenic or anorexic neuropeptides [5], such as agouti-related protein (AgRP) [6] and α-melanocyte-stimulating hormone (α-MSH) [7], which interact functionally to regulate feeding and maintain energy homeostasis. While the functions served by peptide transmitters in the central control of feeding behavior are well established, much less is known about the roles that lipid-derived mediators may play in this process. A recent study suggested that sphingolipids—a quantitatively major but still poorly understood lipid class in the mammalian brain [8]—contribute to the hypothalamic regulation of energy homeostasis [9]. Silva and collaborators reported that intracerebroventricular infusions of the bioactive sphingoid base sphingosine-1-phosphate (S1P) decrease food intake, whereas genetic disruption of S1PR1, the G protein-coupled receptor engaged by S1P, exerts an opposite effect [9]

Methods

Results

Conclusion