While the role of the circadian rhythm and the anti-aging benefits of NAD+ are already well-known a new ground-breaking study , published just a week ago, provides new insights into:[i]

- To what extent NAD+ can alter gene expression of the circadian rhythm.
- How NAD+, with the help of SIRT1, stabilizes BMAL1 activity by repressing PER2 and how this boosts circadian transcription.
- How NAD+ supplementation altering the circadian rhythm, restores repressed BMAL1 binding, cellular oscillations, respiration rhythms, and activity rhythms back to youthful levels.

What is the Circadian Rhythm?

The circadian rhythm is sometimes also described as your body’s internal clock, which regulates sleepiness and wakefulness throughout the day. The circadian rhythm is controlled by a region in the brain that is highly responsive to light changes. This is why we are most alert when the sun is shining and get tired, as it gets dark.

What is NAD+?

NAD+ is an essential molecule that can be found all throughout your body. It is a key component for around 500 different enzymatic reactions happening in our bodies [ii]. NAD+ can be supplemented through precursors, such as NMN (Nicotinamide mononucleotide) and NR (Nicotinamide Riboside) [iii].

What is currently known about the circadian rhythm and NAD+?

As we age, our circadian rhythm starts to decline – we feel less awake when exposed to sunlight and less sleepy when it’s dark. Essentially our body’s internal clock gets dampened [i]. Along with the decline of the circadian rhythm, NAD+ levels also decline as we age, so naturally, scientists have been curious whether there is a two-way correlation between NAD+ levels and the circadian rhythm.

In vivo and in vitro studies have demonstrated that NMN supplementation (which increases the NAD+ levels) extends the lifespan of organisms such as mice [ii] and worms and microorganisms, such as yeast [iii]. In addition, NMN supplementation has been shown to protect against physical decline, attributed to aging, such as muscle regeneration, a decline in physical fitness, mitochondrial dysfunction, diminishing vision, insulin resistance, arterial dysfunction, and more [iv].

A study published on May 4th, 2020, provides us with new insights into how NAD+ affects the circadian rhythm.

This in vivo study, looked at NR (nicotinamide riboside) supplementation (400 mg/kg/ day) in mice over a period of four months and compared it to a control group of mice, which was fed plain water instead. NR is another NAD+ precursor, just like the aforementioned NMN. After four months, the mice’s genes were examined; their gene expression changed drastically. Around 50% of the mice’s genes showed a significant change in expression. Some genes:

1. Showed a loss in circadian rhythm oscillation
2. Showed an increase in circadian rhythm oscillation
3. Showed a shift in circadian rhythm expression
4. Were unaffected (around 50%)

While these were remarkable findings, a more important question arose. How does NAD+ achieve these changes?
 

The study started examining the role of BMAL1, which is a protein that is involved in the transcription of various genes that affect the circadian clock mechanisms in all mammals, including humans. Mice were divided into two groups. One of them had normal NAD+ and BMAL1 levels, whereas the second group consisted of mice deficient in BMAL1. Both groups were injected with 500mg/kg of NMN (NAD+ precursor), and DNA samples were collected four hours later. After examining the BMAL1 bindings in the samples, it was concluded that NAD+ boosts circadian transcription by stabilizing BMAL1.

However, for NAD+ to effectively stabilize BMAL1 bindings, the presence of SIRT1 is required. SIRT1 is a sirtuin, a group of NAD+ dependent proteins. SIRT1 is also a protein deacetylase. Protein deacetylases are enzymes that remove acetyl groups from lysine (a common amino acid/protein). By looking at cells that do not contain SIRT1, they identified increased levels of PER2 in the nucleus of these cells. PER2 is a protein known to suppress BMAL1 activity.

Based on these findings they derived a conclusion that: SIRT1 removes the acetyl group from PER2 proteins, which alters PER2, thus reducing its effectiveness in repressing BMAL1 activity. BMAL1 activity can remain stable and therefore help to reprogram circadian function.

So, while it is now known how NAD+ affects the circadian rhythm, the researchers wanted to find out whether this is actually the root cause of NAD+ well-known health benefits.

To examine this, two groups of mice were given NR for two months. One group was young, ten months old mice with high NAD+ levels, the other group consisted of older, 22-month-old mice, with low NAD+ levels. Both groups were given NR for six months. After these six months, they found that the old mice’ repressed BMAL1 binding, cellular oscillations, respiration rhythms, and activity rhythms were restored back to youthful levels comparable to the younger control group.

References:

[i] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5272178/

[ii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5668137/

[iii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112140/

[iv] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5795269/

[i] https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx

[ii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6342515/

[i] https://www.sciencedirect.com/science/article/abs/pii/S1097276520302367