Macroautophagy/autophagy has profound implications for aging. However, the true features of autophagy in the progression of aging remain to be clarified. In the present study, we explored the status of autophagic flux during the development of cell senescence induced by oxidative stress. In this system, although autophagic structures increased, the degradation of SQSTM1/p62 protein, the yellow puncta of mRFP-GFP-LC3 fluorescence and the activity of lysosomal proteolytic enzymes all decreased in senescent cells, indicating impaired autophagic flux with lysosomal dysfunction. The influence of autophagy activity on senescence development was confirmed by both positive and negative autophagy modulators; and MTOR-dependent autophagy activators, rapamycin and PP242, efficiently suppressed cellular senescence through a mechanism relevant to restoring autophagic flux. By time-phased treatment of cells with the antioxidant N-acetylcysteine (NAC), the mitochondria uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and ambroxol, a reagent with the effect of enhancing lysosomal enzyme maturation, we found that mitochondrial dysfunction plays an initiating role, while lysosomal dysfunction is more directly responsible for autophagy impairment and senescence. Interestingly, the effect of rapamycin on autophagy flux is linked to its role in functional revitalization of both mitochondrial and lysosomal functions. Together, this study demonstrates that autophagy impairment is crucial for oxidative stressinduced cell senescence, thus restoring autophagy activity could be a promising way to retard senescence.

Summary AMPK activation is beneficial for cellular homeostasis and senescence prevention. However, the molecular events involved in AMPK activation are not well defined. In this study, we addressed the mechanism underlying the protective effect of AMPK on oxidative stress‐induced senescence. The results showed that AMPK was inactivated in senescent cells. However, pharmacological activation of AMPK by metformin and berberine significantly prevented the development of senescence and, accordingly, inhibition of AMPK by Compound C was accelerated. Importantly, AMPK activation prevented hydrogen peroxide‐induced impairment of the autophagic flux in senescent cells, evidenced by the decreased p62 degradation, GFP‐RFP‐LC3 cancellation, and activity of lysosomal hydrolases. We also found that AMPK activation restored the NAD + levels in the senescent cells via a mechanism involving mostly the salvage pathway for NAD + synthesis. In addition, the mechanistic relationship of autophagic flux and NAD + synthesis and the involvement of mTOR and Sirt1 activities were assessed. In summary, our results suggest that AMPK prevents oxidative stress‐induced senescence by improving autophagic flux and NAD + homeostasis. This study provides a new insight for exploring the mechanisms of aging, autophagy and NAD + homeostasis, and it is also valuable in the development of innovative strategies to combat aging.

Global germ line loss of fat mass- and obesity-associated (FTO) gene results in both the reduction of fat mass and lean mass in mice. The role of FTO in adipogenesis has been proposed, however, that in myogenesis has not. Skeletal muscle is the main component of body lean mass, so its connection with FTO physiologic significance need to be clarified. Here, we assessed the impact of FTO on murine skeletal muscle differentiation by in vitro and in vivo experiments. We found that FTO expression increased during myoblasts differentiation, while the silence of FTO inhibited the differentiation; in addition, skeletal muscle development was impaired in skeletal muscle FTO-deficient mice. Significantly, FTO-promoted myogenic differentiation was dependent on its m6A demethylase activity. Mechanically, we found that FTO downregulation suppressed mitochondria biogenesis and energy production, showing as the decreased mitochondria mass and mitochondrial DNA (mtDNA) content, the downregulated expression of mtDNA-encoding genes and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) gene, together with declined ATP level. Moreover, the involvement of mTOR-PGC-1α pathway in the connection between FTO and muscle differentiation is displayed, since the expression of FTO affected the activity of mTOR and rapamycin blocked FTO-induced PGC-1α transcription, along with the parallel alteration pattern of FTO expression and mTOR phosphorylation during myoblasts differentiation. Summarily, our findings provide the first evidence for the contribution of FTO for skeletal muscle differentiation and a new insight to study the physiologic significance of RNA methylation.

Mitochondrial DNA (mtDNA) damage is associated with the development of cardiovascular diseases. Cardiac aging plays a central role in cardiovascular diseases. There is accumulating evidence linking cardiac aging to mtDNA damage, including mtDNA mutation and decreased mtDNA copy number. Current wisdom indicates that mtDNA is susceptible to damage by mitochondrial reactive oxygen species (mtROS). This review presents the cellular and molecular mechanisms of cardiac aging, including autophagy, chronic inflammation, mtROS, and mtDNA damage, and the effects of mitochondrial biogenesis and oxidative stress on mtDNA. The importance of nucleoid-associated proteins (Pol γ), nuclear respiratory factors (NRF1 and NRF2), the cGAS-STING pathway, and the mitochondrial biogenesis pathway concerning the development of mtDNA damage during cardiac aging is discussed. Thus, the repair of damaged mtDNA provides a potential clinical target for preventing cardiac aging.

Atherosclerotic cardiovascular disease may share the risk factors for low bone mineral density (BMD), one of which is dyslipidemia. The association between serum cholesterol and BMD remains controversial. Thus, the correlation between serum lipids and BMD in women was explored in the current study. Materials and Methods: This cross-sectional study included 1116 Chinese female participants. Serum samples were collected to evaluate total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and other laboratory markers. Dual-energy X-ray absorptiometry was used to assess lumbar spine, femoral neck, and total hip BMD. Results: In the postmenopausal women, a non-linear relationship was detected between TC, LDL-C, HDL-C, and lumbar spine BMD. Using segmented linear regression, the inflection points were 5.86 mmol/L, 3.52 mmol/L, and 2.37 mmol/L, respectively. To the left of the inflection point, the higher the serum lipid level, the lower the value for lumbar spine BMD. To the right of the inflection point, the higher the serum level of TC and LDL-C, the higher the value for lumbar spine BMD. In the premenopausal women, the association between HDL-C and femoral neck BMD was non-linear. In addition, LDL-C had a positive association with BMD of the femoral neck and HDL-C had an inverse association with BMD of the femoral neck in postmenopausal women. Conclusion: In postmenopausal women, the relationship between TC, LDL-C, HDL-C, and lumbar spine BMD was non-linear. TC, LDL-C, and HDL-C were negatively associated with lumbar spine BMD when the values were less than 5.86 mmol/L, 3.52 mmol/L, and 2.37 mmol/L, respectively. The mechanisms of the association were unclear, and further research is warranted to clarify the relationship.