Isomer-specific effects of conjugated linoleic acid on proliferative activity of cultured neural progenitor cells.

Conjugated linoleic acid (CLA) has been shown to have a variety of biological activities. However, the effects of CLA on the proliferation of neural progenitor cells (NPCs) are not clear. The objective of this study was to determine the effects of cis-9 trans-11 CLA and trans-10 cis-12 CLA, the predominant individual isomers, on the proliferative activity of NPCs in vitro. Cell counts showed that treatment of NPCs with cis-9 trans-11 CLA increased the cell number in a dose- and time- dependent manner while significant inhibition effect of trans-10 cis-12 CLA was observed. Western blot analysis revealed the elevated expression of cyclin D1 induced by cis-9 trans-11 CLA treatment and the decreased expression of cyclin D1 by trans-10 cis-12 CLA treatment in NPCs. Cyclin D1-siRNA transfection significantly inhibited the promotion of cell proliferation by cis-9 trans-11 CLA. In addition, trans-10 cis-12 CLA inhibited the phosphorylation of protein kinase B (PKB/Akt), while cis-9 trans-11 CLA had no effect on phospho Akt levels. Furthermore, immunofluorescence assay showed that after CLA treatment, the cells retained their functional characteristics of neural progenitors. These results indicated that cis-9 trans-11 CLA can effectively enhance the proliferation of hADSCs. The effect of cis-9 trans-11 CLA may be associated with the up-regulation of cyclin D1 expression.