Impact of glucotoxicity on TC1-6 cell glucagon secretion / 中华内分泌代谢杂志

ABSTRACT

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.