Soy pinitol acts partly as an insulin sensitizer or insulin mediator in 3T3-L1 preadipocytes

Abstract

The blood glucose-lowering property of pinitol is mediated via the insulin signaling pathway. This study was carried out to evaluate the effects of soy pinitol on adipogenesis in a 3T3-L1 cell line; 3T3-L1 preadipocytes were treated with pinitol (0-1 mM) together with insulin for 9 days. The regulation of lipid metabolism was assessed by oil-red-O staining of intracellular lipids and real-time PCR of adipogenesis-related factors. The inhibition of cell proliferation was estimated by MTT assay. Pinitol treatment did not inhibit lipid accumulation, nor did it affect expression of adipogenesis-related factors, including ADD1, aP2 and FAS, in a dose-dependent manner. Expression of adiponectin, GLUT4, IRS, C/EBPalpha and PPARgamma mRNAs, however, increased in cells treated with 0.5 mM and/or 1 mM pinitol. Pinitol treatment did not affect the inhibition of cell growth and proliferation in a dose-dependent manner. Accordingly, we suggest that pinitol is nontoxic to this cell line, and that it enhances adipogenesis by acting as an insulin sensitizer or insulin mediator via the upregulation of adiponectin, GLUT4, IRS, C/EBPalpha and PPARgamma in 3T3-L1 preadipocytes.

Fig. 1

The structure of pinitol

Fig. 2

Pinitol slightly inhibits 3T3-L1 differentiation induced by differentiation medium (DM). The cells were stained with oil-red-O at day 9. Pinitol (0–1 mM) was added at the beginning of DM induction of 3T3-L1 cells, with additional treatment every 2 days

Fig. 3

Real time reverse transcriptase coupled polymerase chain reaction (RT-PCR) analysis of several adipogenesis-related factors. mRNAs were quantified using GAPDH as an internal standard. The results represent means ± SD (n = 5)

Fig. 4

Effect of pinitol on the inhibition of cell population growth in 3T3-L1 preadipocytes. Cells were treated with 0–1 mM pinitol for 9 days. Reported values are means ± SD (n = 5)