Journal
FRONTIERS IN ENDOCRINOLOGY
Volume 13, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fendo.2022.905703
Keywords
podocyte; Cdc42; apoptosis; co-culture; beta-cells
Categories
Funding
- National Natural Science Foundation of China
- [82170847]
- [81770822]
- [82170824]
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Cdc42 in podocytes plays a crucial role in insulin secretion by beta-cells and may serve as a new therapeutic target to prevent the deterioration of beta-cell function in T2DM.
Objectives: The progressive impairment of beta-cell function results in prolonged deterioration in patients with type 2 diabetes mellitus (T2DM). Interestingly, the finding on pancreatitis secondary to renal injury suggests that potential communication exists between kidney and pancreas. Therefore, we aimed to investigate cell division cycle 42 (Cdc42)-mediated podocyte apoptosis and its effect on insulin secretion in islet beta-cells. Methods: Type 2 diabetic nephropathy mouse models were established to identify the expression of Cdc42 in podocytes by immunohistochemistry. An in vitro co-culture of mouse podocyte MPC5 and beta-TC6 cells was preliminarily established. Subsequently, podocyte apoptosis induced by high glucose and Cdc42 was detected by TUNEL staining and western blotting. In addition, the JNK pathway was examined to determine the mechanism of apoptosis in MPC5 cells. Finally, insulin secretion and expression in beta-TC6 cells as well as malondialdehyde (MDA) and superoxide dismutase (SOD) levels in both cell types were examined after the regulation of Cdc42 in MPC5 cells. Results: Cdc42 was highly expressed in the podocytes of diabetic nephropathy mice. Exposure to 25 mM glucose for 48 h induced a significant upregulation of Cdc42, Bax, and cleaved caspase-3 as well as a decreased Bcl-2 expression. In addition, marked apoptosis of MPC5 cells was observed compared to normal glucose treatment. After transfection with Cdc42 plasmid, apoptosis of MPC5 cells was enhanced with an increased expression of p-JNK, whereas inhibition of Cdc42 significantly alleviated podocyte apoptosis accompanied by a downregulation of p-JNK. The glucose-stimulated insulin secretion level of beta-TC6 cells decreased after the upregulation of Cdc42 in MPC5 cells. Immunofluorescence staining for insulin showed that co-culture with MPC5 cells carrying the Cdc42 plasmid significantly reduced insulin expression, whereas inhibition of Cdc42 in MPC5 cells alleviated the above-mentioned abnormality of beta-TC6 cells. The expression of Cdc42 and p-p38 in beta-TC6 cells increased following the upregulation of Cdc42 in MPC5 cells; this was concurrent with augmented MDA levels and decreased SOD activity. The opposite result was observed for Cdc42 knockdown in MPC5 cells. Conclusions: Cdc42 in podocytes plays a crucial role in insulin secretion by beta-cells, which may provide a new therapeutic target to prevent the vicious cycle of beta-cell dysfunction in T2DM.
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