SIRT6 Protein Reversed the Aging Clock in the Livers of Old Mice

Once every few years, a study is published that moves the entire field of aging forward, and this time it came from Israel. A team of researchers from Bar-Ilan University published findings in Nature Communications that sound like science fiction: they took old mice, at an age equivalent to 70-80 years in humans, and restored their livers to a youthful molecular pattern in just one month.

The tool they used was the SIRT6 protein, a protein from the family that gained global fame through longevity research, but SIRT6 itself remains less known to the general public than its famous sibling SIRT1. The study, led by Prof. Haim Cohen and doctoral students Ron Nagar and Zachary Schwartz from the Faculty of Life Sciences and the Sagol Center for Healthy Longevity, places Israel at the forefront of a new field: rejuvenation biology.

The main achievement: Boosting SIRT6 in old mice reversed 80% of age-related chromatin changes, and when the protein was boosted from birth, it prevented 95% of these changes from occurring in the first place. In other words, the epigenetic aging of the liver, once thought to be a one-way process, turned out to be reversible.

What is SIRT6 and Why is it Called a Guardian Protein?

SIRT6 is one of seven members of the sirtuin family (SIRT1 to SIRT7), a group of proteins at the center of aging biology. Sirtuins are the enzymes that David Sinclair from Harvard made famous, but each specializes in a different role:

• SIRT1, the most famous member, is involved in metabolism and the effects of caloric restriction.
• SIRT3 primarily acts in mitochondria and maintains energy production.
• SIRT6, the hero of this study, is the expert in DNA repair and genome stability. It sits on the chromatin itself and maintains proper DNA packaging.

SIRT6 has three main roles that make it a true 'guardian protein': repairing DNA breaks, maintaining genome stability (including protecting chromosome ends), and metabolic regulation of sugar and fat levels. The problem: SIRT6 levels decline with age, and just when we need it most, it becomes less available.

The Connection to Chromatin: The Surprising Mechanism

To understand why the finding is so significant, one must understand what chromatin is. Our DNA does not float freely in the cell; it is tightly packed around proteins called histones, and this entire structure is chromatin. The packaging determines which genes are active and which are silenced: open regions allow gene reading, closed regions silence them.

One of the most profound signs of aging is loss of chromatin order. With age, regions that should remain closed open up, and regions that should be open close. The result: genes turn on and off in the wrong places. The study found that in the aging liver, inflammatory pathways become overactive, while the metabolic programs that define a healthy liver weaken.

This is where SIRT6 comes in. The researchers discovered that it directly acts on an epigenetic mark called H3K9ac (histone acetylation), which is linked to abnormal opening of chromatin regions during aging. SIRT6 removes this acetylation and returns the regions to their youthful closed state. This is not a deletion of genetic information, but a rewriting of the operating instructions, restoring the expression pattern to the youthful version.

The Current Evidence

Study 1: Boosting SIRT6 from Birth, Preventing 95% of Changes

In the group of mice where SIRT6 was boosted from birth, the researchers found that 95% of age-related chromatin changes simply did not occur. The liver remained in a youthful molecular state even as the mouse aged chronologically. This is evidence that when the guardian is constantly present, it prevents damage from the start.

Study 2: Boosting SIRT6 in Old Mice, Reversing 80% in One Month

This is the most dramatic finding. In mice that were already old, at an age equivalent to 70-80 in humans, activating SIRT6 reversed 80% of chromatin changes back to a youthful pattern in just one month. In other words, even a liver that had already aged responded to treatment and rejuvenated. This is proof that epigenetic aging is not a death sentence.

Study 3: The Long-Term Context, 30% Lifespan Extension

The new finding builds on previous studies by the same group. Mice engineered to overexpress SIRT6 lived about 30% longer, with improved metabolic function and reduced cancer risk. SIRT6 also regulates the production of hydrogen sulfide, a molecule linked to the benefits of caloric restriction.

International Collaboration

The study was conducted in collaboration with researchers from Tel Aviv University and the National Institute on Aging (NIA) in the US, including Prof. Rafael de Cabo and his team, among the world's leading names in caloric restriction and aging research. This is not an isolated study but part of a global research network, with Israel at its center.

Why the Liver Specifically?

The choice of the liver is not coincidental. The liver is the body's central metabolic organ, processing fats and sugars, detoxifying, and regulating energy levels. When the liver ages, the impact is felt throughout the body, from insulin resistance to chronic inflammation.

Another advantage: The liver is an exceptionally regenerative organ. It is one of the few organs capable of significant regeneration even in adulthood. If its regeneration station is stuck due to aging chromatin, releasing this blockage can restore its natural regenerative ability. The combination of metabolic importance and regenerative capacity makes the liver an ideal model for demonstrating aging reversal.

Should We Start Looking for SIRT6 Activators?

Here, caution is required. Despite the excitement, the study is far from being translated into a human treatment, and several important warnings apply:

• This is a study in mice only. Most interventions that extend lifespan in mice do not successfully translate to humans. Human biology is more complex and slower.
• The finding is specific to the liver. What works in the liver may not work the same way in the brain, heart, or muscles, where chromatin structure differs.
• Safe activation of SIRT6 in humans has not been proven. SIRT6 is involved in growth regulation and cancer suppression, but aggressively altering its activity could disrupt a delicate balance. We need to know exactly how much and when.
• There is no approved drug yet. The Israeli company SirTLab, founded by the researchers, is developing a drug targeting these mechanisms and preparing for clinical trials, but the path to approval is long.

In short: This is a true scientific breakthrough, but not an invitation to start taking random supplements claiming to activate SIRT6. There is still no proven and safe molecule for human use.

What Can We Take from the Study?

Even without a drug, one can support SIRT6 activity and liver health through lifestyle based on known mechanisms:

1. Caloric restriction and intermittent fasting. SIRT6, like other sirtuins, is activated in states of energy deficit. Moderate fasting naturally increases its expression, and this is also the mechanism through which caloric restriction extends lifespan.
2. Certain polyphenols. Natural compounds like fucoidan (from brown algae) and specific types of polyphenols are being studied as potential SIRT6 activators. The evidence is still preliminary, but a plant-rich diet supports the mechanism.
3. Regular physical activity. Aerobic and strength training improve insulin sensitivity and reduce liver fat, two factors that affect the same metabolic pathways regulated by SIRT6.
4. Maintaining liver health. Avoiding excess alcohol, processed sugar, and fatty liver reduces the inflammatory burden that the study indicates accelerates aging.
5. Scientific monitoring. If you are interested in the field, follow the progress of SirTLab and clinical studies. This is a field that will develop rapidly in the coming years.

The Broader Perspective

This study is part of a profound conceptual revolution. For decades, we thought of aging as accumulated damage, irreversible wear and tear like rust. The Bar-Ilan finding joins a growing wave of evidence, along with Yamanaka factors and partial reprogramming, showing that part of aging is software, not hardware. If the problem is a faulty pattern of gene activation, the pattern can be rewritten.

And there is also a story of Israeli pride. While American tech giants pour billions into longevity research, an academic lab in Ramat Gan laid one of the strongest cornerstones of the field, and did so in collaboration with leading institutions worldwide. SIRT6 is not just a protein; it is a reminder that Israeli science is at the forefront of the aging race.

Still, the bottom line is cautious science: what works in a mouse liver in a month will need a decade or more to prove itself in humans. But for the first time, we have clear proof that the very idea is possible, and that the aging clock of an entire organ can, at least in principle, be turned back.

References:
Ynet News: Can aging be reversed? Israeli scientists uncover major longevity breakthrough
Nature Communications: SIRT6 overexpression counteracts chromatin aging in the murine liver (Nagar, Schwartz, Cohen et al., Bar-Ilan University, 2026)