β-cell golgy body stress response to glucolipotoxicity

Başkent University Institute of Health Sciences, Medical Biology Doctorate Thesis, 2019 Type 2 Diabetes Mellitus is an important disease with diverse polygenetic and enviromental factors in etiopathogenesis. Over the past decades, the central role of pancreatic β-cell dysfunction and loss have become increasingly appreciated. Glucolipotoxicity and its contribution to endoplasmic reticulum stress has been postulated to the worsening β-cell function and survival. In cells with high capacity of secretory function, work load on ER is assumed to be reflected to Golgi apparatus. Factors leading to ER stress is expected to converge adaptive and/or maladaptive changes in Golgi structural proteins, enzymes and secretory function. In this regard, there are documented Golgi stress proteins (TFE , HSP 47 CREB3/Luman, and ARF4,) of which genetic expression and/or activity have been increased after derangement of Golgi function with golcisides like Brefeldin A, Golciside A etc. We hypothesized that glucolipotoxicity in diabetes can trigger a Golgi stress response in pancreatic β-cells. In order to test a Golgi stress response in β-cells of a diabetic metabolic millue, we tried to create lipotoxicity/glucotoxcitiy/glucolipotoxicity in INS-1E rat β-cells with palmitic acid, glucose and both together and investigated the expression of the genes documented as Golgi stress proteins before in the literature. In this context palmitic acid, glucose and both together were applied to INS-1E rat β-cells and analysed at 8th, 16th, 24th and 48th hours. MTT assay was used for cell viability analysis. Expression rates of Golgi structural proteins, Golgi glycosylation enzymes, ARF1, HSP47, CREB3 ve ARF4 proteins were measured in all experimental conditions. In our study we determined an increase in expression levels of Golgi glycosylation enzyme stgal1 and HSP47 in the 8th hour of all experimental conditions. In the 48th hour, when the viability of most cells were lost, expression rate of CREB3 was found to be increased. Our study is the first one in English literature which investigated Golgi stress response in β-cells under lipotoxicity/glucotoxicity/glucolipotoxicity. HSP47 and CREB3 were found to be important mediators of Golgi stress response in β-cells under metabolic stress. In this regard, this study will form basis for further studies dealing with Golgi stress in diabetes mellitus.