Pancreatic β-cells secrete insulin when blood glucose levels become high. However, when β-cells are chronically exposed to hyperglycemia, their function gradually deteriorates. Although such phenomena are called as β-cell glucose toxicity, its molecular mechanism remained unclear. This manuscript describes the possible mechanism for such β-cell dysfunction. In the diabetic state, nuclear expression levels of pancreatic transcription factors PDX-1 and MafA are decreased. In addition, incretin receptor expression in β- cells is decreased, which is likely involved in the impairment of incretin effects in diabetes. Taken together, it is likely that down-regulation of pancreatic transcription factors and/or incretin receptors are involved in β-cell dysfunction observed in type 2 diabetes.