Sphingosine kinase is induced in mouse 3T3-L1 cells and promotes adipogenesis

Takeshi Hashimoto, Junsuke Igarashi, and Hiroaki Kosaka

Department of Cardiovascular Physiology, Kagawa University Faculty of Medicine, Kita-gun, Kagawa 761-0793

Corresponding Author: igarashi{at}med.kagawa-u.ac.jp

Sphingosine 1-phosphate (S1P) is a lysophospholipid mediator that exerts numerous biological activities both as a receptor ligand and as an intracellular second messenger. In the present study, we explored roles of sphingosine kinase (SphK), an S1P-producing enzyme, in adipose tissue. We utilized mouse 3T3-L1 cells as an in vitro model of adipogenesis, using a mixture of insulin/dexamethasone/3-isobutyl-1-methylxanthine to induce differentiation. Quantitative real-time PCR assays revealed that the expression levels of transcripts encoding both isoforms of SphK-1 and SphK-2 are up-regulated during adipogenesis (37.6 and 6.6 folds vs. basal, p < 0.05, respectively). Concomitantly, SphK-1/SphK-2 protein abundance and S1P contents of these cells increased at 3 days after hormonal stimulation. Loss-of-function approaches by pharmacological inhibition of SphK activity as well as by transfection with small interfering RNA against SphK-1 led to significant attenuation of lipid droplet accumulation and adipocyte marker gene expression. We detected marked elevation of SphK-1 mRNA in adipose tissue derived from 13-weeks old ob/ob mice with obese phenotype than their lean littermates. These results suggest that increased expression of SphK, an S1P-producing enzyme, plays a significant role during adipogenesis, potentially providing a novel point of control in adipose tissue.

Add to CiteULike CiteULike Add to Complore Complore Add to Connotea Connotea Add to Del.icio.us Del.icio.us Add to Digg Digg Add to Reddit Reddit Add to Technorati Technorati What's this?