β-cell mass in people with type 2 diabetes

The early occurrence of β-cell dysfunction has been broadly recognized as a critical determinant of the development and progression of type2 diabetes. β-cell dysfunction might be induced by insufficient β-cell mass, by a dysfunction of the β-cells, or both. Whether or not β-cell dysfunction constitutes a cause of reduced β-cells or vice-versa currently remains unclear. The results of some studies have measured the loss of β-cells in type2 diabetic patients at between 22 and 63% by planimetric measurements. Because β-cell hypertrophy has been noted in type2 diabetic patients, the loss of β-cell number should prove more profound than what has thus far been reported. Furthermore, β-cell volumes are reduced even in patients with impaired fasting glucose. Such defects in β-cell mass are associated with increased apoptosis rather than insufficient replication or neogenesis of β-cells. With these results, although they still require clarification, the peak β-cell mass might be determined at quite an early stage of life, and then might decline progressively over time as the result of exposure to harmful environmental influences over one's lifetime. In this review, we have summarized the relevant studies regarding β-cell mass in patients with type2 diabetes, and then presented a review of the various causes of β-cell loss in adults.