Abstract
Nicotinamide adenine dinucleotide (NAD+) is indispensable for the anti-aging activity of the sirtuin (SIRT) family enzymes. AMP-activated protein kinase (AMPK) upregulates NAD+ synthesis and SIRT activity in a nicotinamide phosphoribosyltransferase (NAMPT)-dependent manner. However, the molecular mechanisms that affect AMPK-driven NAMPT expression and NAD+/SIRT activation remain unclear. In this study, we tried to identify senescence-associated microRNAs (miRNAs) that negatively regulate the cascade linking AMPK and NAMPT expression. miRNA-screening experiments showed that the expression of miR-146a increased in senescent cells but decreased following AMPK activation. Additionally, miR-146a overexpression weakened the metformin-mediated upregulation of NAMPT expression, NAD+ synthesis, SIRT activity, and senescence protection, whereas treatment with the miR-146a inhibitor reversed this effect. Importantly, these findings were observed both in vitro and in vivo. Mechanistically, miR-146a directly targeted the 3′-UTR of Nampt mRNA to reduce the expression of NAMPT. AMPK activators metformin and 5-aminoimidazole-4-carboxamide (AICAR) hindered miR-146a expression at the transcriptional level by promoting IκB kinase (IKK) phosphorylation to attenuate nuclear factor-kappaB (NF-κB) activity. These findings identified a novel cascade that negatively regulates the NAD+/SIRT pathway by suppressing miR-146a-mediated NAMPT downregulation. Furthermore, our results showed that miR-146a impedes the anti-aging effect of AMPK. This mutual inhibitory relationship between miR-146a and AMPK enriches our understanding of the molecular connections between AMPK and SIRT and provides new insight into miRNA-mediated NAD+/SIRT regulation and an intervention point for the prevention of aging and age-related diseases.
Highlights
Aging is characterized by an irreversible decline in biological function, adaptability, and resistance
Regarding the regulation of nicotinamide phosphoribosyltransferase (NAMPT) expression, previous studies have mostly focused on the transcriptional level, and the results indicate that NAMPT expression can be regulated by transcription factors such as forkhead box O1 (FOXO1), CLOCK, and MYC.[18,20,21]
The anti-senescence effect of metformin was confirmed by increased phosphorylation of AMPactivated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), a target protein of AMPK (Fig. 1b), reduced SA-β-gal-positive cells, and decreased p16 levels (Fig. 1a, b)
Summary
Aging is characterized by an irreversible decline in biological function, adaptability, and resistance. Mechanistic studies of aging can provide important theoretical support for resisting or delaying the aging process. The study of the metabolic imbalance theory has developed rapidly, with evidence showing that caloric restriction can delay aging and prolong the lifespan of many animals.[4,5]. Based on this theory, relevant molecules and signaling pathways have been discovered. The AMP-activated protein kinase (AMPK) pathway and nicotinamide adenine dinucleotide (NAD+)dependent Sirtuin (SIRT) pathway significantly affect the occurrence and development of aging.[4–6]. The AMP-activated protein kinase (AMPK) pathway and nicotinamide adenine dinucleotide (NAD+)dependent Sirtuin (SIRT) pathway significantly affect the occurrence and development of aging.[4–6] the relationship between AMPK and SIRT has not been fully elucidated
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
