Naked Mole Rats Defy Aging. One Scientist Has Dedicated Her Career to Finding Out How.
Eve Herold is a science writer specializing in issues at the intersection of science and society. She has written and spoken extensively about stem cell research and regenerative medicine and the social and bioethical aspects of leading-edge medicine. Her 2007 book, Stem Cell Wars, was awarded a Commendation in Popular Medicine by the British Medical Association. Her 2016 book, Beyond Human, has been nominated for the Kirkus Prize in Nonfiction, and a forthcoming book, Robots and the Women Who Love Them, will be released in 2019.
Naked mole rats have extraordinarily long lifespans and are extremely resistant to cancer.
Rochelle "Shelley" Buffenstein has one of the world's largest, if not the largest, lab-dwelling colonies of the naked mole rat. (No one has done a worldwide tabulation, but she has 4,500 of them.) Buffenstein has spent decades studying the little subterranean-dwelling rodents. Over the years, she and her colleagues have uncovered one surprising discovery after another, which has led them to re-orient the whole field of anti-aging research.
Naked mole rats defy everything we thought we knew about aging. These strange little rodents from arid regions of Africa, such as Kenya, Ethiopia and Somalia, live up to ten times longer than their size would suggest. And unlike virtually every other animal, they don't lose physical or cognitive abilities with age, and even retain their fertility up until the end of life. They appear to have active defenses against the ravages of time, suggesting that aging may not be inevitable. Could these unusual creatures teach humans how to extend life and ameliorate aging?
Buffenstein, who is senior principle investigator at Calico Life Sciences, has dedicated her life to finding out. Her early interest in the animals of what is now Zimbabwe led to her current position as a cutting-edge anti-aging researcher at Calico, the Google-funded health venture launched in 2013. The notoriously secretive company is focused on untangling the mysteries of why animals and people age, and whether there are ways to slow or temporarily arrest the process.
The small, wrinkly animal, which lives in underground burrows in the hot, arid regions of Africa, is hardly the beauty queen of the mammalian kingdom. Furless, buck-toothed and tiny-eyed, the creatures look like they could use a good orthodontist, a protective suit of clothes and possibly, some spectacles to enhance their eyesight. But these rats more than make up for their unimpressive looks with their superlative ability to adapt to some of the most inhospitable conditions on earth.
Based on the usual rule that body size predicts lifespan, naked mole rats shouldn't live that long. After all, similarly-sized rodents like mice have a life expectancy of two years or less. But Buffenstein was one of the first scientists to recognize that naked mole rats live an extraordinarily long time, with her oldest animal approaching 39 years of age. In addition, they never become geriatric in the human sense, defying the common signs of aging — age-related diseases, cognitive decline and even menopause. In fact, the queens, or females that do all the breeding in a bee-like underground colony, remain fertile and give birth to healthy pups up until what would be considered very old age in humans. And the naked mole rat has other curious abilities, such as the ability to endure extreme low-oxygen, or hypoxic, conditions like those they encounter in their underground nests.
"One thing we've learned from these animals is that they stay healthy until the very end."
It's not that the naked mole rat isn't subject to the vicissitudes of life, or the normal wear and tear of biological processes. Over the years, Buffenstein and her colleagues have discovered that, while the process of oxidative stress — thought for 50 years to be the main cause of aging — occurs in the naked mole rat just as in any other animal, its damage does not accumulate with age. Oxidative stress occurs during normal cell metabolism when oxygen "free radicals" with one or more unpaired electrons wreak havoc on large cellular molecules, leaving microscopic debris in their wake that clogs up the gears of healthy cell function. Somehow, naked mole rats have an enhanced ability to clear out the damaged cells and molecules before they can set off the usual chain reaction of cell dysfunction and death, according to a 2013 paper in which Buffenstein is the lead author.
Oxidative stress is not the only factor known to be problematic in aging. Slowly accumulating damage to DNA typically leads to protein malfunction and improper folding. In humans and most other animals, these protein fragments can accumulate in cells and gum up the works. Only not so much in naked mole rats, which are able to maintain normal protein folding throughout their long life. After years of discoveries like these, Buffenstein has gradually reframed her focus from "what goes wrong to produce aging?" to "what goes right in the naked mole rat to help it defy the normal wear and tear of life?" Buffenstein's research suggests that the tiny mammals have a unique ability to somehow clear out damaged protein fragments and other toxic debris before they can cause disease and aging.
How She Got Here
Buffenstein ascribes her initial acquaintance with the naked mole rat to serendipity. Back in 1979, her postgraduate mentor Jenny Jarvis at the University of Cape Town in South Africa kept a small colony of rats in her office while studying the mechanisms that lead to the animals' unusual adaptive capabilities. It was Buffenstein's job to take care of them. Working with Jarvis, Buffenstein focused on understanding their unique adaptations to the extreme conditions of their natural habitat.
They studied the unusual behaviors regulating the rat colonies. For instance, they observed that designated "workers" dig the entire colony's underground tunnels and a single reproducing female breeds with only a small number of males. Buffenstein also examined how these animals are able to survive without the "sunshine hormone" — vitamin D — and their unusual modes of regulating their internal temperatures and converting food into energy. Though classified as mammals, the rodents simply don't conform to the mammalian handbook, having found ingenuous ways to alter their bodies and behavior that is fine-tuned to the scorching heat and aridity of their environment.
To escape the heat, they simply burrow underground and live in elaborate tunnels. To cope with the low-oxygen conditions underground, they slowed their metabolism and learned to live for extended periods of time in such hypoxic conditions that an ordinary animal would quickly suffocate. But it was slowly dawning on Buffenstein that the small creatures were exceptional in additional ways.
When Buffenstein got her first academic position at the University of Witwatersrand in Johannesburg, Jarvis said she could take some of the naked mole rats with her. When she did, Buffenstein noticed that the animals were living far longer than similarly sized rodents. "At that stage, they were about ten years old. Little did I know how long they would eventually show us they could live," she says.
In 1997, after accepting a position at the City College of New York, Buffenstein moved to the U.S. and took her rat colony with her. There she was able to pursue an evolving narrative about the humble naked mole rat that continued to defy expectations. As the years passed, it was becoming more and more evident that her observations could have major implications for aging research. Eventually, she took a position at the Barshop Institute for Aging and Longevity Studies in San Antonio, Texas.
One early observation of Buffenstein's suggested that the species most often used in aging research—mice, roundworms, fruit flies and yeast—have short lifespans and poor defenses against aging. These animals provide important insights into how aging works, and have revealed possible targets for intervention. But they don't show what goes right in apparently non-aging animals like the naked mole rat.
Buffenstein's years of studying the rats has laid the foundation for a whole new perspective in aging research.
"My hypothesis," she says, "is that naked mole rats are very good at removing damaged macromolecules and cells, thereby maintaining homeostasis and cell and tissue function. All the repair pathways examined by us and others in the field point to more efficient repair and more rapid responses to damaging agents." These include things like free radicals and radiation.
Buffenstein’s Legacy
Some researchers today are building on Buffenstein's foundational discoveries to home in on possible anti-aging mechanisms that lead to the extraordinary resilience of naked mole rats. University of Cambridge researcher and co-founder of the institution's Naked Mole-Rat Initiative, Ewan St. John Smith, is studying the animal's resistance to cancer.
In a 2020 paper published in Nature, Smith and his colleagues established that naked mole rats harbor cancer-causing genes, and these genes occasionally create cancer cells. But something in the rats shuts the multiplication process down before the cells can grow out of control and form tumors. Now, scientists want to know what mechanisms, exactly, are at play in preventing the cells from invading healthy tissues. Smith has hypothesized that the answer is somehow embedded in interactions in the cells' microenvironment.
He also thinks the animal's immune system could just be very effective at seeking out and destroying cancer cells. Several current cancer therapies work by boosting the body's immune system so it can attack and eliminate the toxic cells. It's possible that the naked mole rat's immune system naturally goes into hyper-drive when cancer cells appear, enabling it to nip the disease in the bud before tumors can form. A pharmacologist by training, Smith thinks that if there is some chemical mediator in the naked mole rat that supercharges its immune cells, perhaps that mediator can be synthesized in a drug to treat humans for cancer.
The naked mole rat's extreme tolerance to hypoxia could also play a role. "Interestingly," he says, "when cells become cancerous, they also become hypoxic, and naked mole rats are known to be very resistant to hypoxia.
He notes that a form of low-level hypoxia is also present in the bodies and brains of both aged mice and older humans. It's commonly seen in the brains of humans with Alzheimer's disease and other forms of age-related dementia. This suggests that hypoxia in humans — and in other mammals — may have a role to play in Alzheimer's and the aging process itself. Resistance to hypoxia could be why the naked mole rat, in Smith's words, "chugs along quite happily" in conditions that in humans are associated with disease and decline.
Smith cheerfully acknowledges his debt to Buffenstein for laying so much of the groundwork in a field rife with possible implications for anti-aging. "Shelley is amazing," he says. "Naked mole rats have a queen and I always refer to her as the queen of the naked mole rat world." In fact, Buffenstein gave Smith his first colony of rats, which he's since grown to about 150. "Some of them will still be around when I retire," he jokes.
Vera Gorbunova, a professor of biology and oncology at the University of Rochester who studies both longevity and cancer in naked mole rats, credits Buffenstein with getting others to study the animals for anti-aging purposes. Gorbunova believes that "cancer and aging go hand-in-hand" and that longer-lived animals have better, more accurate DNA repair.
Gorbunova is especially interested in the naked mole rat's ability to secrete a superabundance of a "super-sugar" molecule called hyaluronan, a ubiquitous additive to skin creams for its moisturizing effect. Gorbunova and others have observed that the presence of high concentrations of hyaluronan in the naked mole rat's extracellular matrix — the chemical-rich solution between cells — prevents the overcrowding of cells. This, perhaps, could be the key to the animal's ability to stop tumors from forming.
Hyaluronan is also present in the extracellular matrix of humans, but the naked mole rat molecule is more than five times larger than the versions found in humans or mice, and is thought to play a significant part in the animal's DNA repair. But just rubbing a cream containing hyaluronan over your skin won't stop cancer or aging. High concentrations of the substance in the extracellular matrix throughout your body would likely be needed.
Gorbunova notes that the naked mole rat offers a multitude of possibilities that could eventually lead to drugs to slow human aging. "I'm optimistic that there are many different strategies, because the naked mole rat likely has many processes going on that fight aging," she says. "I think that in a relatively short time, there will be bonafide treatments to test in animals. One thing we've learned from these animals is that they stay healthy until the very end."
So if naked mole rats don't become frail with age or develop age-related diseases, what does kill them? The answer, unfortunately, is usually other naked mole rats. Buffenstein has long noted that even though they live in highly cooperative colonies, they can be quite cantankerous when there's a disruption in the hierarchy, a sentiment echoed by Gorbunova. "Sometimes there are periods of peace and quiet, but if something happens to the queen, all hell breaks loose," she says. "If the queen is strong, everybody knows their place," but if the queen dies, the new queen is inevitably decided by violent competition.
To the casual observer, a strange, wrinkly rodent like the naked mole rat might seem to have little to teach us about ourselves, but Buffenstein is confident that her discoveries could have major implications for human longevity research. Today, at Calico's labs in San Francisco, she's focused entirely on the determining how anti-aging defense mechanisms in the rats could lead to similar defenses being stimulated or introduced in humans.
"The million-dollar question is, what are the mechanisms protecting against aging, and can these be translated into therapies to delay or abrogate human aging, too?"
Buffenstein fired up a new generation of scientists with multiple discoveries, especially the fundamental one that naked mole rats are subject to the same wear and tear over time as the rest of us, but somehow manage to reverse it. These days, the trailblazer is at work on untangling the molecular mechanisms involved in the animal's resistance to cardiac aging. On top of everything else, the small creature has a unique ability to fight off the scourge of heart disease, which is the leading cause of death in the industrialized world.
After all, the point is not to extend old age, but to slow down aging itself so that frailty and disability are compressed into a brief period after a long-extended period of vitality. By switching the focus from what goes wrong to mechanisms that defend against aging in the first place, the discoveries of Buffenstein and a new generation of researchers who are building on her groundbreaking research promise to be a driving force in the quest to extend not only life, but healthy, vigorous life in humans.
Eve Herold is a science writer specializing in issues at the intersection of science and society. She has written and spoken extensively about stem cell research and regenerative medicine and the social and bioethical aspects of leading-edge medicine. Her 2007 book, Stem Cell Wars, was awarded a Commendation in Popular Medicine by the British Medical Association. Her 2016 book, Beyond Human, has been nominated for the Kirkus Prize in Nonfiction, and a forthcoming book, Robots and the Women Who Love Them, will be released in 2019.
Patients voice hope and relief as FDA gives third-ever drug approval for ALS
On Sept. 29, the FDA approved Relyvrio, a new drug for ALS, even though a study of 137 ALS patients did not result in “substantial evidence” that Relyvrio was effective.
At age 52, Glen Rouse suffered from arm weakness and a lot of muscle twitches. “I first thought something was wrong when I could not throw a 50-pound bag of dog food over the tailgate of my truck—something I use to do effortlessly,” said the 54-year-old resident of Anderson, California, about three hours north of San Francisco.
In August, Rouse retired as a forester for a private timber company, a job he had held for 31 years. The impetus: amyotrophic lateral sclerosis, or ALS, a progressive neuromuscular disease that is commonly known as Lou Gehrig’s disease, named after the New York Yankees’ first baseman who succumbed to it less than a month shy of his 38th birthday in 1941. ALS eventually robs an individual of the ability to talk, walk, chew, swallow and breathe.
Rouse is now dependent on ventilation through a nasal mask and uses a powerchair to get around. “I can no longer walk or use my arms very well,” he said. “I can still move my wrists and fingers. I can also transfer from my chair to the toilet if I have two of my friends help me.”
It’s “shocking” that modern medicine has very little to offer to people with this devastating condition, Rouse said. But there is hope on the horizon. Yesterday, the U.S. Food and Drug Administration approved Relyvrio, a drug made up of two parts, sodium phenylbutyrate and taurursodiol, to treat patients with ALS.
“This approval provides another important treatment option for ALS, a life-threatening disease that currently has no cure,” said Billy Dunn, director of the Office of Neuroscience in the FDA’s Center for Drug Evaluation and Research, in a statement. “The FDA remains committed to facilitating the development of additional ALS treatments.”
Until this point, the FDA had approved only two other medications—Riluzole (rilutek) in 1995 and Radicava (edaravone) in 2017—to extend life in patients with ALS, which typically kills within two to five years after diagnosis. That’s why earlier this week, Rouse was optimistic about the FDA’s likely approval of a controversial new drug for ALS.
When Relyvrio is taken in addition to Riluzole, it appears to slow functional decline by an additional 25 percent and extend life by another 6 to 10 months, said Richard Bedlak, director of the Duke ALS Clinic. “It is not a cure, but it is definitely a step forward.”
“The whole ALS community is extremely excited about it,” he said the day before Relyvrio’s expected approval. “We are very hopeful. We’re on pins and needles.”
A study of 137 ALS patients did not result in “substantial evidence” that Relyvrio was effective, the agency’s Peripheral and Central Nervous System Drugs Advisory Committee concluded in March. However, after some persuasion from FDA officials, patients and their families, the committee met again and decided to recommend approving the drug.
In January 2019, following an ALS diagnosis at age 58 in October the previous year, Jeff Sarnacki, of Chester, Maryland, was accepted into a trial for Relyvrio. “Because of the trial, we did experience hope and a greater sense of help than had we not had that opportunity,” said Juliet Taylor, his wife and caregiver. They both believed the drug “worked for him in giving him more time.”
In June 2019, Sarnacki chose an open-label extension, offered to patients by drug researchers after a study ends, and took the active drug until he died peacefully at home under hospice care in May 2020, five days after his 60th birthday. A retired agent with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives who later worked as a security consultant, Sarnacki lived about 19 months after diagnosis, which is shorter than the typical prognosis.
His symptoms began with leg cramps in fall 2017 and foot drop in early 2018. A feeding tube was placed in 2019, as it became necessary early in his illness, Taylor said. He also took Radicava and Riluzole, the two previously approved drugs, for his ALS. “We were both incredulous that, so many years after Lou Gehrig’s own diagnosis, there were so few treatments available,” she said.
The dearth of successful treatments for ALS is “certainly not for lack of trying,” said Karen Raley Steffens, a registered nurse and ALS support services coordinator at the Les Turner ALS Foundation in Skokie, Ill. “There are thousands of researchers and scientists all over the world working tirelessly to try to develop treatments for ALS.”
Unfortunately, she added, research takes time and exorbitant amounts of funding, while bureaucratic challenges persist. The rare disease also manifests and progresses in many different ways, so many treatments are needed.
As of 2017, the Centers for Disease Control and Prevention estimated that more than 31,000 people in the U.S. live with ALS, and an average of 5,000 people are newly diagnosed every year. It is slightly more common in men than women. Most people are diagnosed between the ages of 55 and 75.
Most cases of ALS are sporadic, meaning that doctors don’t know the cause. There is about a one-year interval between symptom onset and an ALS diagnosis for most patients, so many motor neurons are lost by the time individuals can enroll in a clinical trial, said Richard Bedlack, professor of neurology and director of the Duke ALS Clinic in Durham, North Carolina.
Bedlack found the new drug, Relyvrio, to be “very promising,” which is why he testified to the FDA in favor of approval. (He’s a consultant and disease state speaker for multiple companies including Amylyx, manufacturer of Relyvrio.)
The “drug has different mechanisms of action than the currently approved treatments,” Bedlack said. He added that, when Relyvrio is taken in addition to Riluzole, it appears to slow functional decline by an additional 25 percent and extend life by another 6 to 10 months. “It is not a cure, but it is definitely a step forward.”
T. Scott Diesing, a neurohospitalist and director of general neurology at the University of Nebraska Medical Center in Omaha, said he hopes the drug is “as good as people anticipated it should be, because there are not too many options for these patients.”
"FDA went out on a limb in approving Relyvrio based on limited results from a small trial while a larger study remains in progress," said Florian P. Thomas, co-director of the ALS Center at Hackensack University Medical Center and the Meridian School of Medicine. "While it is definitely promising, clearly, the last word on this drug has not been spoken."
So far, Rouse's voice is holding up, but he knows the day will come when ALS will steal that and much more from him.
ALS is 100 percent fatal, with some patients dying as soon as a year after diagnosis. A few have lasted as long as 15 years, but those are the exceptions, Diesing said.
“If this drug can provide even months of additional life, or would maintain quality of life, that’s a big deal,” he noted, adding that “the patients are saying, ‘I know it’s not proven conclusively, but what do we have to lose?’ So, they would like to try it while additional studies are ongoing.” The drug has already been conditionally approved in Canada.
As his disease progresses, Rouse hopes to get a speech-to-text voice-generating computer that he can control with his eyes. So far, his voice is holding up, but he knows the day will come when ALS will steal that and much more from him. He works at I AM ALS, a patient-led community, and six of his friends have already died of the disease.
“Every time I lose a friend to ALS, I grieve and am sad but I resolve myself to keep working harder for them, myself and others,” Rouse said. “People living with ALS find great purpose in life advocating and trying to make a difference.”
Friday Five Podcast: New drug may slow the rate of Alzheimer's disease
On September 27, pharmaceuticals Biogen and Eisai announced that their drug, lecanemab, can slow the rate of Alzheimer's disease, according to a clinical trial. Today's Friday Five episode covers this story and other health research over the month of September.
The Friday Five covers important stories in health and science research that you may have missed - usually over the previous week, but today's episode is a lookback on important studies over the month of September.
Most recently, on September 27, pharmaceuticals Biogen and Eisai announced that a clinical trial showed their drug, lecanemab, can slow the rate of Alzheimer's disease. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on scientific creativity and progress to give you a therapeutic dose of inspiration headed into the weekend and the new month.
Listen on Apple | Listen on Spotify | Listen on Stitcher | Listen on Amazon | Listen on Google
This Friday Five episode covers the following studies published and announced over the past month:
- A new drug is shown to slow the rate of Alzheimer's disease
- The need for speed if you want to reduce your risk of dementia
- How to refreeze the north and south poles
- Ancient wisdom about Neti pots could pay off for Covid
- Two women, one man and a baby
Matt Fuchs is the editor-in-chief of Leaps.org. He is also a contributing reporter to the Washington Post and has written for the New York Times, Time Magazine, WIRED and the Washington Post Magazine, among other outlets. Follow him on Twitter @fuchswriter.