The Intervening Effects Of Pioglitazone On The Free Fatty Acids-induced Impairment On GPR40 Gene Expression And Insulin Secretion Function In βTC-3 Cell

Objective1.To study the effects of free fatty acids(FFAs) on gene expression of G protein coupled receptor 40 (GPR40) and the insulin secreting function inβTC-3 cell in vitro.2. To observe the effects of pioglitazone in restoring a normal secretory pattern and the protection action on gene expression of GPR40 inβTC-3 which function has been impaired by chronic exposure to abnormal FFAs levels.Methods1.βTC-3 cells were cultured in vitro and intervened by FFAs of different concentration(0.25mmol/L,0.5mmol/L,1.0mmol/L )for 12h,24h,48h, and then insulin leves were examined in every group by radioimmunoassay,the mRNA of GPR40 was detected by semi-quantitative reberse transcription polymerase chain reaction (RT-PCR).2.βTC-3 cells were incubated with pioglitazone of different concentration (0.1μmol/L,1.0μmol/L,10.0μmol/L)for 48h, and then insulin secretion and gene expression of GPR40 were measured by the same methods.3. We culturedβTC-3 cells with 1.0mmol/L FFAs in the presence or absence of pioglitazone (0.1μmol/L,1.0μmol/L,10.0μmol/L) for 48h , and then insulin levels and gene expression of GPR40 were measured. Results1. At the same intervening time, gene expression of GPR40 was decreased after the treatment of FFAs in the range of 0.25–1.0mmol/L. At the same concentration, GPR40 expression was also reduced with the prolongation of intervening duration(12,24,48h). GPR40 mRNA expression was reduced inβTC-3 cells in a dose- and time-dependent manner after cultivation with FFAs.2. The effects of FFAs on insulin secreting function inβTC-3 cell:(1)Basal linsulin secretion(BIS) was increased in the groups of 0.25 mmol/L FFAs after cultivation for 12,24,48h.(2) BIS was enhanced after cultivation for 12,24h, but decreased after 48h in the 0.5 mmol/L FFAs groups.(3) BIS was decreased in the groups of 1.0 mmol/L FFAs after cultivation for 12,24,48h.(4) ThatβTC-3 cells were exposed to FFAs showed a decreased glucose stimulated insulin secretion (GSIS) with the prolongation of duration(12,24,48h),and the higher concentration, the lower GSIS.3. Pioglitazone had no effect on gene expression of GPR40 and the insulin secreting function without FFAs.4. When the cells were cultured with 1.0mmol/L FFAs in the presence of 0.1-10μmol/L pioglitazone, a dose-dependent increase of gene expression of GPR40 and insulin secretion were induced in the co-treated groups compared with the cells incubated with 1.0mmol/L FFAs alone.Conclusions1. Elevated FFAs may inhibit the gene expression of GPR40, and impaire insulin secreticn function ofβTC-3 cells, these effects show a manner of a dose- and time-dependent.2. Pioglitazone is able to protect the expression of GPR40 and to restore a normal secretory pattern inβTC-3 cells which has been impaired by chronic exposure to elevated FFAs, and these intervening effects indicat a dose-dependent manner from 0.1μmol/L to 10.0μmol/L.3. The effects of FFAs and pioglitazone on insulin secreticn function inβTC-3 cell maybe relate with their regulation of GPR40 gene expression.