Abstract
SIRT1 is an NAD+-dependent deacetylase that is implicated in prevention of many age-related diseases including metabolic disorders. As SIRT1 deacetylase activity is dependent on NAD+ levels and the development of compounds that directly activate SIRT1 has been controversial, indirectly activating SIRT1 through enhancing NAD+ bioavailability has received increasing attention. NAD+ levels are reduced in obesity and the aged, but the underlying mechanisms remain unclear. We recently showed that hepatic microRNA-34a (miR-34a), which is elevated in obesity, directly targets and decreases SIRT1 expression. Here, we further show that miR-34a reduces NAD+ levels and SIRT1 activity by targeting NAMPT, the rate-limiting enzyme for NAD+ biosynthesis. A functional binding site for miR-34a is present in the 3′ UTR of NAMPT mRNA. Hepatic overexpression of miR-34a reduced NAMPT/NAD+ levels, increased acetylation of the SIRT1 target transcriptional regulators, PGC-1α, SREBP-1c, FXR, and NF-κB, and resulted in obesity-mimetic outcomes. The decreased NAMPT/NAD+ levels were independent of miR-34a effects on SIRT1 levels as they were also observed in SIRT1 liver-specific knockout mice. Further, the miR-34a-mediated decreases were reversed by treatment with the NAD+ intermediate, nicotinamide mononucleotide. Conversely, antagonism of miR-34a in diet-induced obese mice restored NAMPT/NAD+ levels and alleviated steatosis, inflammation, and glucose intolerance. Anti-miR-34a-mediated increases in NAD+ levels were attenuated when NAMPT was downregulated. Our findings reveal a novel function of miR-34a in reducing both SIRT1 expression and activity in obesity. The miR-34a/NAMPT axis presents a potential target for treating obesity- and aging-related diseases involving SIRT1 dysfunction like steatosis and type 2 diabetes.
Original language | English (US) |
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Pages (from-to) | 1062-1072 |
Number of pages | 11 |
Journal | Aging Cell |
Volume | 12 |
Issue number | 6 |
DOIs | |
State | Published - Dec 2013 |
Externally published | Yes |
Keywords
- Deacetylation
- Diabetes
- MiR-34a
- Resveratrol
- Sirtuins
- Steatosis
ASJC Scopus subject areas
- Aging
- Cell Biology