Enhancing Acsl4 In Absence Of Mtorc2/Rictor Drove Beta-Cell Dedifferentiation Via Inhibiting Foxo1 And Promoting Ros Production

Rapamycin insensitive companion of mechanistic target of Rapamycin (Rictor), the key component of mTOR complex 2 (mTORC2), controls both beta-cell proliferation and function. We sought to study whether long chain acyl-CoA synthetase 4 (Acs14) worked downstream of Rictor/mTORC2 to maintain beta-cell functional mass. We found Acs14 was positively regulated by Rictor at transcriptional and posttranslational levels in mouse beta-cell. Infecting adenovirus expressing Acs14 in beta-cell-specific-Rictor-knockout (beta RicKO) islets and Min6 cells knocking down Rictor with lentivirus-expressing siRNA-oligos targeting Rictor(siRic), recovered the beta-cell dysplasia but not dysfunction. Cell bioenergetic experiment performed with Seahorse XF showed that Acs14 could not rescue the dampened glucose oxidation in Rictor-lacking beta-cell, but further promoted lipid oxidation. TransposaseAccessible Chromatin (ATAC) and H3K27Ac chromatin immunoprecipitation (ChIP) sequencing studies reflected the epigenetic elevated molecular signature for beta-cell dedifferentiation and mitigated oxidative defense/response. These results were confirmed by the observations of elevated acetylation and ubiquitination of FoxO1, increased protein levels of Gpxl and Hiflan, excessive reactive oxygen species (ROS) production and diminished MafA in Acs14 overexpressed Rictor-lacking beta-cells. In these cells, antioxidant treatment significantly recovered MafA level and insulin content. Inducing lipid oxidation alone could not mimic the effect of Acs14 in Rictor lacking beta-cell. Our study suggested that Acs14 function in (beta-cell was context dependent and might facilitate beta-cell dedifferentiation with attenuated Rictor/mTORC2 activity or insulin signaling via posttranslational inhibiting FoxO1 and epigenetically enhancing ROS induced MafA degradation.