4E-BP1 counteracts human mesenchymal stem cell senescence via maintaining mitochondrial homeostasis

Although the mTOR-4E-BP1 signaling pathway is implicated in aging and aging-related disorders, the role of 4E-BP1 in regulating human stem cell homeostasis remains largely unknown. Here, we report that the expression of 4E-BP1 decreases along with the senescence of human mesenchymal stem cells (hMSCs). Genetic inactivation of 4E-BP1 in hMSCs compromises mitochondrial respiration, increases mitochondrial reactive oxygen species (ROS) production, and accelerates cellular senescence. Mechanistically, the absence of 4E-BP1 destabilizes proteins in mitochondrial respiration complexes, especially several key subunits of complex III including UQCRC2. Ectopic expression of 4E-BP1 attenuates mitochondrial abnormalities and alleviates cellular senescence in 4E-BP1-deficient hMSCs as well as in physiologically aged hMSCs. These f indings together demonstrate that 4E-BP1 functions as a geroprotector to mitigate human stem cell senescence and maintain mitochondrial homeostasis, particularly for the mitochondrial respiration complex III, thus providing a new potential target to counteract human stem cell senescence.

Effects of Chaihu Shugan powder on hepatic lipid metabolism and AMPK/SIRT1 pathway in rats with non-alcoholic fatty liver disease / 中国病理生理杂志

[ ABSTRACT] AIM:To investigate the effects of Chaihu Shugan powder ( CSP) on lipid metabolism and the pro-teins involved in adenosine 5’-monophosphate-activated protein kinase (AMPK)/sirtuin 1 (SIRT1) pathway in the liver tissues of the rats with non-alcoholic fatty liver disease (NAFLD).METHODS: Sprague-Dawley rats were randomly di-vided into normal control ( NC) group, with HFD ( HFD) group and CSP group.The NAFLD models were established by feeding with HFD for 16 weeks in the rats.The rats in CSP group were intragastrically administered with CSP extracts (9.6 g· kg-1 · d-1 ) , and blood and liver samples were collected 16 weeks later.Serum and liver levels of total cholesterol ( TC) and triglyceride ( TG) , and serum levels of alanine aminotransferase ( ALT) and aspartate aminotransferase ( AST) were measured using an automatic biochemical analyzer.The histological changes of liver tissues were observed with HE staining, while the lipid deposition was observed with Oil Red O staining.The ultrastructural changes of the liver tissues were observed under transmission electron microscope.Moreover, the protein levels of AMPK, phosphorylated AMPK (pAMPK), SIRT1 and uncoupling protein 2 (UCP2) in the liver were detected by Western blot.RESULTS:The results of HE staining, Oil Red O staining and electron microscopy demonstrated that NAFLD rat model was successfully estab-lished.Compared with NC group, the serum and liver levels of TC and TG, and serum level of AST in model group were markedly elevated ( P<0.01) .Moreover, the protein levels of pAMPK and SIRT1 in HFD group were markedly reduced (P<0.01), whereas UCP2 level was elevated (P<0.01).Furthermore, liver levels of TC and TG, and serum level of AST in GSP group were markedly reduced as compared with HFD group ( P<0.05 ) .The protein levels of pAMPK and SIRT1 were elevated ( P<0.05 ) , whereas the UCP2 level was reduced as compared with HFD group ( P<0.01 ) .The protein level of AMPK between the 3 groups had no significant difference.CONCLUSION: CSP attenuates hepatic lipid disorder and hepatic lipid deposition in NAFLD rats induced by feeding with HFD for 16 weeks, which is associated with the activation of AMPK/SIRT1 pathway.