Beta cell failure is caused by loss of cell mass, mostly by apoptosis, but also by simple dysfunction (decline of glucose-stimulated insulin secretion, downregulation of specific gene expression). Apoptosis is a key mechanism of beta cell loss in diabetes. The current understanding of beta cell failure is based on the concept of apoptosis as a major mechanism of beta cell loss. However, recent studies have shown that beta cell dysfunction is also a significant contributor to diabetes. The role of apoptosis in beta cell failure is complex and multifaceted, and further research is needed to fully understand its mechanisms. Understanding the mechanisms of beta cell failure is crucial for the development of effective treatments for diabetes.