Einfluss von Glukose auf die HMGB-1-Regulation der ß-Inselzellen

In the present study the influence of glucose was examined for the HMGB1-regulation of glucose ß-islet cells. We treated INS-1 cells with 10 and 30 mM glucose and then separat-ed the proteins by 2-D gel electrophoresis. We investigated the proteins HMGB1 and caspase-3, which was subsequently verified by means of Western blot. Under hypergly-cemia we showed a downregulation of HMGB1 and an activation of caspase 3. Under hy-perglycemic conditions we observed a significant decrease in cell proliferation by MTT-Assay. By cell fractionation a reduction of HMGB1 both in the nucleus and in the cytosol could be shown at elevated glucose levels. Interestingly an additional treatment with pioglitazone could interestingly prevent the downregulation of HMGB1. Combined treatment with 10 mM glucose and pioglitazone of INS cells showed a significant under-expression and a strong impairment of the cell proliferation. In summary pioglitazone exerts its protective effect under elevated glucose conditions. In the diabetic patients decreased HMGB1 levels were detected before and after pioglitazone therapy. An increase in HMGB1 levels could not be achieved under the influence of pioglitazone. The date lead to the assumption that pioglitazone exerts its protective effect in the late stage of diabetes mellitus. Furthermore pioglitazone exerts its protective effect on carci-noma cells possibly leading to bladder cancer or colon carcinoma. On the bases of facts glitazones were taken off the market in 2011. But pioglitazone could possibly be effective in MS. To investigate possible anti-apoptotic functions of HMGB1 we used RT-PCR cloning, then performed a stable transfection. In the performed Western blots we showed low grade HMGB1 overexpression. We went from a slight over-expression, as the stably transfected INS-1 cells compared to the normal INS-1 cells behaved differently. Under elevated glucose levels no downregulation of HMGB1 was found and cell proliferation of INS-1 clones was significant-ly improved. A caspase-3 cleavage under elevated glucose conditions could not be de-tected, thus HMGB1 overexpression prevents the activation of caspase 3.