Tier 3 — preclinical

SIRT6 overexpression counteracts chromatin aging in the male murine liver

Ron Nagar, Zacharia Schwartz, Almog Katz, Noga Touitou, Efrat Sharon, Kobi Tzdaka, Odeya Waner, Noam Shalev, Rotem Clo, Leah Weiss, Benjamin Epstein, Michel Bernier, Roni B Shtark, Nirad Banskota, Kwan-Wood G Lam, Supriyo De, Nathan L Price, Batia Lerrer, Daniel Z Bar, Rafael de Cabo, Haim Y Cohen

Nature Communications 2026 Volume 17, issue 1, article 6449

Bibliography

DOI: 10.1038/s41467-026-73115-y
PubMed: PMID 42135312
PubMed Central: PMC13376905
Funding: This study was supported by the Israel Science Foundation (777/16 and 890/21), The U.S.–Israel Binational Science Foundation (BSF) (2019312, 2023151), MINERVA (AZ5746940769), ICRF-SWCRF, and the SAGOL center of healthy human aging. The research was supported in part by the Intramural Research Program at the National Institute on Aging, NIH. R.N. is supported by Bracha Levy Foundation and Teva BioInnovators Forum. Z.S. is supported by the Office of the President of Israel.
Competing interests: H.Y.C. advises SIRTLAB Inc., the rest of the authors declare no conflict of interest.

Study snapshot

Design	Comparative multi-omic study of chromatin architecture, DNA methylation and transcription in young and old wild-type and SIRT6-transgenic mouse livers, followed by liver-targeted AAV8 delivery of SIRT6 to aged wild-type mice to test therapeutic reversal.
Model	Male C57BL/6 wild-type mice and male SIRT6-transgenic (SIRT6 TG) mice at 5–7 months (young) and 18–21 months (old). Separate AAV8 delivery experiment in 24-month-old male C57BL/6 wild-type mice using liver-specific hcApoE.EhAAT1 promoter driving SIRT6 or GFP, analysed at 25 months (one month post-injection).
Sample	ATAC-seq/RNA-seq cohort: n = 8 for wild-type, n = 6 for SIRT6 TG. DNA methylation cohort: n = 7 for young WT and old TG, n = 8 for young TG and old WT. AAV cohort: n = 7 for GFP and n = 8 for SIRT6 injection.
Intervention	Constitutive transgenic SIRT6 overexpression (SIRT6 TG line); liver-specific AAV8-hcApoE.EhAAT1-SIRT6-WPRE (versus AAV8-GFP control) delivered intravenously to 24-month-old male mice.
Duration	Cross-sectional comparison across life stages for TG cohort; AAV experiment terminated one month after injection.
Endpoints	Chromatin accessibility (ATAC-seq peak log₂ fold change); ageing-associated domain (AAD) identification and reversal on SIRT6 overexpression; whole-genome DNA methylation at opened and closed AADs; transcriptional signatures (RNA-seq, GSEA); transcription-factor motif enrichment (HOMER); histone modification levels (H3K9ac, H3K56ac, H3K27me3 and others by Western blot); differentially accessible regions (DARs) in AAV-injected livers.

What the study showed, in plain terms

Chromatin is the way DNA is packaged inside cells. When DNA is tightly wound around histones, genes are silent; when the packaging loosens, genes get read. In the ageing liver, this packaging drifts — inflammation genes open up and get switched on, metabolism genes close down and get silenced. The result is chronic low-grade inflammation and a fatty, poorly functioning organ.

This study asked whether SIRT6 — a longevity enzyme that removes acetyl groups from histones — could reverse that drift. The team compared young and old livers from ordinary mice and from mice engineered to make extra SIRT6 throughout life. They mapped which parts of the genome were open or closed (ATAC-seq), how heavily DNA was methylated, and which genes were being expressed. They then delivered SIRT6 directly to the livers of 24-month-old ordinary mice using a liver-targeted gene-therapy vector, one month before harvest, to test whether the same effect could be produced late in life.

Both approaches worked. Lifelong SIRT6 overexpression prevented most age-related chromatin drift. Late-life SIRT6 delivery reversed it. Inflammation genes closed back down. Liver metabolism genes reopened. The chromatin looked young again — evidence that at least in mice, epigenetic ageing is not a one-way process.

Key findings

The ageing liver shows a globally more open chromatin landscape. Of 247,709 ATAC-seq peaks compared between old and young wild-type mice, 60.1% opened with age and only 1.7% closed. Ageing-associated domains (AADs) — regions with the largest accessibility change — showed the same directional bias.
Lifelong SIRT6 overexpression reversed 34.7% of opened AADs (they were condensed in old TG livers) with matched effects on DNA methylation at those sites.
Opened AADs were enriched for ETS-family transcription factor motifs (PU.1, ELF4, ELF5, SPIB, ETS1), all linked to immune activation. Closed AADs were enriched for liver-enriched transcription factors (HNF6, HNF1, HNF6B, CUX2) that maintain hepatic identity.
GSEA showed old wild-type livers upregulated the interferon alpha response and downregulated oxidative phosphorylation, fatty acid beta-oxidation and TCA cycle pathways. All were reversed in old SIRT6 TG livers.
ChIP-seq identified H3K9ac, but not H3K56ac, as the histone modification associated with the age-related opening. SIRT6 overexpression maintained young-like H3K9ac levels at those sites.
One month of AAV-mediated hepatic SIRT6 delivery in 24-month-old wild-type mice produced a similar reversal pattern to lifelong overexpression: 27.9% of AADs were rejuvenated (opened with age, closed by SIRT6). DARs opened by SIRT6 in the AAV cohort were enriched for LETFs; DARs closed by SIRT6 were enriched for ETS factors, replicating the transgenic phenotype.
H3K27me3 was significantly reduced by SIRT6 AAV delivery (p = 0.0036) with a non-significant trend toward reduced H3K9ac.

What this study can and cannot tell us

All experiments were performed exclusively in male mice. The authors state upfront that SIRT6's lifespan effect is more pronounced in males and that whether SIRT6's role in global chromatin regulation is sex-dependent remains unknown from this dataset.

The AAV rescue endpoint was one month post-injection — long enough to demonstrate chromatin remodelling, but not to test whether the rejuvenated chromatin translates into meaningful survival, healthspan or functional liver improvement in aged mice.

No human liver samples or human-derived hepatocyte data appear in the study. Findings are entirely rodent. Translation to a human dose, route and safety profile is not yet established, and one senior author (H.Y.C.) advises SIRTLAB Inc., a commercial SIRT6 activator entity — relevant context for how the paper's translational framing should be read.

The "rejuvenation" claim is measured at the level of chromatin accessibility, methylation and transcription. It has not been shown that a chromatin state indistinguishable from young by these assays produces a young-like liver phenotype across other hallmarks of ageing.

Tier 3

SIRT6 is a key regulator of mitochondrial function in the brain

Smirnov D et al. · Cell Death and Disease · 2023