A Broad and Reversible Threshold for Hair Greying
This research into the fine details of hair greying is interesting but of limited practical application, I suspect. It is nonetheless a good illustration of the point that there are few sharp dividing lines in the biochemistry of aging. Even seemingly binary changes such as hair going grey represent a broad threshold that is crossed slowly, and under the hood there are likely numerous competing and conflicting mechanisms and regulatory systems that only incrementally come to a consensus on cell behavior. None of this really changes the best way forward for the treatment of any part of aging: identify the causative damage and repair that damage, in the expectation that many of the consequences that make up degenerative aging will reverse themselves as cell behavior returns to a youthful state.
Hair greying is a visible sign of aging that affects everyone. The loss of hair color is due to the loss of melanin, a pigment found in the skin, eyes and hair. Research in mice suggests stress may accelerate hair greying, but there is no definitive research on this in humans. This is because there are no research tools to precisely map stress and hair color over time. But, just like tree rings hold information about past decades, and rocks hold information about past centuries, hairs hold information about past months and years.
Hair growth is an active process that happens under the skin inside hair follicles. It demands lots of energy, supplied by structures inside cells called mitochondria. While hairs are growing, cells receive chemical and electrical signals from inside the body, including stress hormones. It is possible that these exposures change proteins and other molecules laid down in the growing hair shaft. As the hair grows out of the scalp, it hardens, preserving these molecules into a stable form. This preservation is visible as patterns of pigmentation. Examining single-hairs and matching the patterns to life events could allow researchers to look back in time through a person's biological history.
Researchers here report a new way to digitize and measure small changes in color along single human hairs. This method revealed that some white hairs naturally regain their color, something that had not been reported in a cohort of healthy individuals before. Aligning the hair pigmentation patterns with recent reports of stress in the hair donors' lives showed striking associations. When one donor reported an increase in stress, a hair lost its pigment. When the donor reported a reduction in stress, the same hair regained its pigment. Researchers mapped hundreds of proteins inside the hairs to show that white hairs contained more proteins linked to mitochondria and energy use. This suggests that metabolism and mitochondria may play a role in hair greying.
The new method for measuring small changes in hair coloring opens up the possibility of using hair pigmentation patterns like tree rings. This could track the influence of past life events on human biology. In the future, monitoring hair pigmentation patterns could provide a way to trace the effectiveness of treatments aimed at reducing stress or slowing the aging process. Understanding how 'old' white hairs regain their 'young' pigmented state could also reveal new information about the malleability of human aging more generally.
This could be another rabbit hole without a root cause. My cousin had grey hairs since he was 17 and many others have the same issue. This surely was not related to "stress" or a sign of aging..
The stress could be a physical stressor, such as an illness or injury. My 2 year old got a gray hair -- we never figured out what the stressor was -- but eventually it returned to brown.
This 2021 article summarizes our best understanding of grey hair so far. If anyone gleans any practical advice for reversing let us know. Apparently early graying can be reversed but a point is reached when it can't…." Eventually, the bulge MSC pool becomes depleted as well, at which stage greying becomes largely irreversible."
https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12648
I'm 51 and rode my bicycle to work every day for years on top of working out on my elliptical runner 45 minutes most days. I had no gray hairs until I moved to a new location a couple years ago where I couldn't ride my bike anymore and also didn't get to exercise. Gray hair started to creep in slowly and I thought it was just aging catching up with me.
I finally got my elliptical from under the dust again several months ago and started working out again most days and doing 100 to 300 pushups every day. My hair is clearly starting to get darker again!!!
I shouldn't be surprised but didn't think this would happen. I wonder if my renewed love for exercise will be able to push back the gray completely again.
https://medicalxpress.com/news/2021-07-biochemical-pathway-skin-darkening-implications.html
Through their laboratory work with skin from humans and animal models, the MGH researchers mimicked the natural protection that exists in people with dark pigments. In the process, they gained a fuller understanding of the biochemical mechanism involved along with their drivers, and how they might be influenced by a topical agent independent of UV radiation, sun exposure, or genetics.
"We had assumed that the enzymes that make melanin by oxidizing the amino acid tyrosine in the melanosome (the synthesis and storage compartment of the cell) are largely regulated by gene expression," explains Fisher. They were surprised to learn, however, that the amount of melanin being produced is in large part regulated by a much different chemical mechanism, one that can ultimately be traced to an enzyme in the mitochondria, the inner chamber of the cell, with the ability to alter skin pigmentation.
That enzyme is nicotinamide nucleotide transhydrogenase, or NNT. Researchers found that topical application of small molecule inhibitors of NNT resulted in skin darkening in human skin, and that mice with decreased NNT function displayed increased fur pigmentation. To test their discovery, they challenged the skin with UV radiation and found that the skin with darker pigments was indeed protected from DNA damage inflicted by ultraviolet rays.
"We're excited by the discovery of a distinct pigmentation mechanism because it could pave the way, after additional studies and safety assessments, for a new approach to skin darkening and protection by targeting NNT," says Elisabeth Roider, MD, previously an investigator with MGH, and lead author and co-corresponding author of the study. "The overarching goal, of course, is to improve skin cancer prevention strategies and to offer effective new treatment options to the millions of people suffering from pigmentary disorders."
Sounds like Grey hair is mitochodrial.