Trim67 alleviates lipotoxicity-induced β-cell dysfunction by modulating Sirt1-mediated mitochondrial function

β-cell dysfunction is a key factor in the progression of diabetes. It was reported that lipotoxicity impaired β-cell mitochondrial function. However, the molecular mechanisms regulating lipotoxicity-induced β-cell mitochondrial dysfunction remain unclear.

Islet cells were isolated from diabetic db/db and control db/m mice. Palmitic acid (PA) was used to treat MIN6 cells to construct a lipotoxicity-induced β-cell model. Co-IP was employed to verify the interaction between Sirt1 and Trim67. Enrichment of Klf5, Klf2, Klf6, and Ahr on the Trim67 promoter was analyzed using DNA pull-downs. Binding of Klf6 to the Trim67 promoter region was detected using ChIP and dual-luciferase reporter assays. Cell proliferative capacity and mitochondrial function were measured by CCK-8, EdU, JC-1, Seahorse XF-96 and ATP detection kits. Protein expression was tested using RT-qPCR and western blotting. Sirt1 deacetylase activity was measured fluorometrically. Ubiquitination sites were mapped using site-directed mutagenesis. In vivo experiments were performed using AAV8-mediated Trim67 overexpression in the db/db mice.

Trim67 was downregulated in pancreatic islet of diabetic mice and in PA-induced β-cells. AAV8-mediated Trim67 overexpression in db/db mice significantly improved glucose tolerance, enhanced insulin secretion, and preserved islet integrity. Overexpression of Trim67 alleviated PA-induced mitochondrial dysfunction in β-cells. Moreover, Trim67 was transcriptionally activated by Klf6 in PA-induced β-cells. Trim67 increased Sirt1 stability through K63-linked ubiquitination at lysines 491 and 591 to mediate the Sirt1/Pgc-1α pathway, which in turn alleviates PA-induced mitochondrial dysfunction in β-cells.

Klf6 transcriptionally activated Trim67 to regulate the Sirt1/Pgc-1α axis, thereby alleviating PA-induced mitochondrial dysfunction in β-cells. This study offers new insights into the treatment of diabetes.