糖毒性对TC1-6细胞胰升糖素分泌的影响

目的 探讨长期糖毒性对胰岛α细胞胰升糖素分泌的影响及其与α细胞胰岛素抵抗的关系.方法 TC1-6细胞(α细胞株)分别培养于含低浓度(5.5 mmoL/L)、中浓度(11.1 mmol/L)和高浓度(25 mmoL/L)葡萄糖的培养基中1～5天,检测胰升糖素分泌及其mRNA表达;加入不同浓度胰岛素6 h后,观察对培养5天的TC1-6细胞胰升糖素分泌的影响并以Western印迹检测高糖对TC1-6细胞Akt磷酸化的影响.结果 (1)与低糖培养相比,中、高浓度葡萄糖培养1天和3天的TC1-6细胞胰升糖素分泌无明显改变,而高糖培养5天时TC1-6细胞的胰升糖素分泌明显增高(136.80±10.94 vs 78.62±4.72)ng/106细胞,P<0.05];另外,培养5天时胰升糖素mRNA的表达较1天时明显升高(P<0.05);(2)10-7mol/L胰岛素抑制低糖组TC1-6细胞胰升糖素的分泌(21.59±1.30 vs 55.12±3.86)ng/106细胞],但仅能轻微抑制高糖组胰升糖素的分泌(106.58±8.53 vs 117.18±10.55)ng/106细胞];当胰岛素增至10-5mol/L时,高糖组胰升糖素的分泌也受到抑制(46.55±3.72 vs 118.61±10.68)ng/106细胞];(3)加入10-5mol/L胰岛素2h后,两组TC1-6细胞磷酸化Akt水平分别升高180%和70%,但高糖组明显低于低糖组,给予磷脂酰肌醇3激酶抑制剂后两组TC1-6细胞磷酸化Akt水平在低糖组抑制率明显高于高糖组.结论 高糖可增加TC1-6细胞胰升糖素的分泌,其可能的机制与TC1-6细胞胰岛素抵抗有关.

Impact of glucotoxicity on TC1-6 cell glucagon secretion

Objective To investigate the effects of chronic high glucose on α-cells glucagon releasing in relation to insulin resistance induced by high glucose. Methods TC1-6 cells, an α-cell line, were incubated separately in DMEM containing high (25.0 mmol/L), medium (11.1 mmol/L) and low (5.5 mmol/L) concentrations of glucose for 1 to 5 days. The secretion and gene expression of glueagon were measured. When TC1-6 cells had been cultured for 5 days, three different concentrations of insulin were added for 6 h and then glucagon secretion was detected. Western blot was used for 1 and 3 days to confirm the effect of high glucose on phosphorylation of Akt in TC1-6 cells. Results (1) Exposure of TC1-6 cells to 11.1 and 25.0 mmol/L glucose resulted in a slight increase of glucagon secretion compared with those incubated with 5.5 mmol/L. However, after 5 days in media containing 25.0 mmol/L glucose, glucagan secretion was significantly increased as compared to cells treated with low glucose (136.80±10.94 vs 78.62±4.72 ) ng/106 cells, P<0.05]; moreover, in TC1-6 cell cultured with high glucose glucagon mRNA expression was increased significantly. (2) 10-7 mol/L insulin reduced significantly glucagon secretion of TC1-6 ceils exposed to low glucose (21.59±1.30 vs 55.12±3.86) ng/106 cells], but just scarcely inhibited glucagon secretion of cells incubated with high glucose (106.58±8.53 vs 117.18±10.55) ng/106 cells]. When insulin concentration was increased to 10-5 mol/L, glucagon secretion of TC1-6 cells in high glucose was also reduced (46.55±3.72 vs 118.61±10.68 )ng/106 cells]. (3) After treated with 10-5 mol/L insulin for 2h, the levels of Akt phosphorylation in both groups of TC1-6 cells were increased by 180% and 70%, while the level in high glucose group was significantly lower than that in low glucose group. In the presence of phosphoinositide 3 kinase inhibitor, the levels of Akt phosphorylation were both lowered, but the inhibition in low glucose group was more significant than in high glucose group. Conclusion High glucose induces hypersecretion of glucagon, which may be due to the a-cell insulin resistance.