Decreased Sirt3 contributes to cyclic production of reactive oxygen species and islet β-cell apoptosis in high glucose conditions

Downregulation of Sirt3 contributes to β-cell dedifferentiation via FoxO1 in type 2 diabetic mellitus

AIMS

FoxO1 is an important factor in the β-cell differentiation in type 2 diabetes mellitus (T2DM). Sirt3 is found to be involved in FoxO1 function. This study investigated the role of Sirt3 in the β-cell dedifferentiation and its mechanism.

METHODS

Twelve-week-old db/db mice and INS1 cells transfected with Sirt3-specific short hairpin RNA (shSirt3) were used to evaluate the dedifferentiation of β-cell. Insulin levels were measured by enzyme linked immunosorbent assay. The proteins of Sirt3, T-FoxO1, Ac-FoxO1 and differentiation indexes such as NGN3, OCT4, MAFA were determined by western blot or immunofluorescence staining. The combination of Sirt3 and FoxO1 was determined by the co-immunoprecipitation assay. The transcriptional activity of FoxO1 was detected by dual luciferase reporter assay.

RESULTS

Both the in vivo and in vitro results showed that Sirt3 was decreased along with β-cell dedifferentiation and decreased function of insulin secretion under high glucose conditions. When Sirt3 was knocked down in INS1 cells, increased β-cell dedifferentiation and lowered insulin secretion were observed. This effect was closely related to the amount loss and the decreased deacetylation of FoxO1, which resulted in a reduction in transcriptional activity.

CONCLUSION

Downregulation of Sirt3 contributes to β-cell dedifferentiation in high glucose via FoxO1. Intervention of Sirt3 may be an effective approach to prevent β-cell failure in T2DM.

Pancreatic Beta-cell Dysfunction in Type 2 Diabetes

Pancreatic β-cells produce and secrete insulin to maintain blood glucose levels within a narrow range. Defects in the function and mass of β-cells play a significant role in the development and progression of diabetes. Increased β-cell deficiency and β-cell apoptosis are observed in the pancreatic islets of patients with type 2 diabetes. At an early stage, β-cells adapt to insulin resistance, and their insulin secretion increases, but they eventually become exhausted, and the β-cell mass decreases. Various causal factors, such as high glucose, free fatty acids, inflammatory cytokines, and islet amyloid polypeptides, contribute to the impairment of β-cell function. Therefore, the maintenance of β-cell function is a logical approach for the treatment and prevention of diabetes. In this review, we provide an overview of the role of these risk factors in pancreatic β-cell loss and the associated mechanisms. A better understanding of the molecular mechanisms underlying pancreatic β-cell loss will provide an opportunity to identify novel therapeutic targets for type 2 diabetes.