Science 101

What Happens to Your Cells As You Age and What You Can Do About It

Your cells are the building blocks of your very existence. Keeping them healthy and humming is the key to staving off aging and disease. Here’s what you should know.

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We’re used to thinking about our health on a macro level. We often consider blood pressure readings or temperatures or weight to gauge our health. But scientists know that health is really determined by the very building blocks of your body: your cells.

Cells: the Basic Structure and Function of Living Things

“Cellular health is important because it is what determines the health of each organ, which is made up of cells. The organ is sort of the unit of health,” explains Leonard Guarente, Ph.D., the Novartis Professor of Biology at Massachusetts Institute of Technology and chief scientist of Elysium Health.

All aging and disease begins on the cellular level, and often cellular function is impaired before you realize anything is off. This means that thinking about our health on the micro level can go a long way toward maintaining good health.

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“A cell is a unit of life that has a membrane on the outside and has all of the machinery to conduct metabolism on the inside,” Guarente says. Cells provide the basic structure and function of all living things. For us humans, our cells house the machinery — DNA, RNA, proteins, lipids, mitochondria — that power all of the body’s complex processes.

Not all cells are exactly the same, but “they almost all have in common the basic organization of the cell, which is that inside of the cell there's a nucleus, which has the DNA,” Guarente says. “There's the cytoplasm where proteins are made and there are the mitochondria, which produce energy for the cell.”

Each of your body’s trillions of individual cells contain your individual genes, and there are about 200 different types of human cells — blood cells, skin cells, nerve cells, to name a few — responsible for different elements of your cellular health. For example, a brain cell (called a neuron) uses electrochemical signalling to process information, while a red blood cell carries oxygen to your tissues. Aside from their specialized functions, types of cells also differ in terms of how often they can regenerate.

“Brain cells and heart cells, for example, regenerate slowly if at all,” Guarente says. “The cells in your gut turn over every few weeks.”

Why Cellular Health Matters

Good cellular health means that the all-important molecules that make up the cell — the proteins, mitochondria, and DNA — are functioning well and will be free from damage so long as the cell is working correctly.

On some level, all diseases and illnesses are some malfunction happening with your cells. For example, when you have a cold, a virus is infecting your cells, leading to symptoms like low-grade fever and runny nose. When you have Type 2 diabetes, your cells are no longer sensitive to insulin, causing an inability to manage your blood sugar.

But outside of diseases, the major thing influencing cellular health is time. “Aging causes a degradation in cellular health,” Guarente says. It sounds pretty straightforward (of course your cells degrade over time, doesn’t everything?), but it’s taken hundreds of years of research — starting from 1665, when cells were first identified — for scientists to understand what exactly is happening as we age.

“But what’s happening with aging is that over time, damage starts to outstrip the ability of repair processes to fix things, leading to a gradual accumulation of damage,” Guarente says.

In fact, aging isn’t just one process; it’s more like a cascade of various changes happening at once. A 2013 review published in the journal Cell identified nine different hallmarks of aging, things like “mitochondrial dysfunction” — which is when the cellular metabolic engine stop working correctly — and “cellular senescence” — when cells stop dividing as part of the biological process.

Each of your body’s cells is like a phone’s operating system, with many different parts that can (and do) break down over time, needing repair. One of your cells’ everyday jobs, in addition to carrying out their specialized functions, is to repair themselves to keep the operating system running smoothly.

“But what’s happening with aging is that over time, damage starts to outstrip the ability of repair processes to fix things, leading to a gradual accumulation of damage,” Guarente says.

We know that not smoking or protecting yourself from UV radiation can help protect your cells from damage. And we know that simple lifestyle changes like proper diet, regular exercise, and stress management can pay dividends on the cellular level. But scientists are also beginning to understand how we might slow aging down—or maybe even reverse it. For example, one exciting area of research centers around sirtuins, a group of proteins responsible for stability in the cell, in the form of things like DNA expression. Nicknamed the “longevity genes,” sirtuins, which were only discovered in the 1990s, are crucial for maintaining cellular health, but thanks in large part to Guarente, we know they can only function with the help of a coenzyme called nicotinamide adenine dinucleotide (NAD+). Scientists also know now that NAD+ declines over time, suggesting that supplementation of NAD+ precursors may be a way to keep your sirtuins working better and longer and thus, keeping your cells healthier longer as well. 

What’s Next for Cellular Health Research?

After many years of research, scientists have learned a lot about cellular health and how we might maintain it, but there’s still a ton we’ve yet to discover. In addition to things like NAD+ supplementation, scientists are trying to figure out how calorie restriction might play a role in slowing down aging. “A very low calorie diet increases the activity of sirtuins,” Guarente says. “Part of that may be because we've evolved in order to withstand periods when food is scarce. And one way to accomplish that is to make the animal become more stress-resistant.”

Another area scientists are honing in on is how to deal with cellular senescence through what’s known as senolytic therapies.

“Senescent cells are basically cells that get in the way. They don’t carry out their function,” Guarente explains. “Scientists think if you can eliminate them, you will make the whole animal healthier. And so there's a whole field now based on trying to design drugs that can eliminate senescent cells.”

One 2018 study published in the journal Nature Medicine, for example, found that a combination of two senolytic drugs prevented cell damage, which delayed physical dysfunction and extended the lifespan of adult mice.

How or when this kind of research will help humans shift their lifestyles before aging causes an abundance of damage to our cellular health is anyone’s guess. But as more science is discovered on the topic, it’s not hard to imagine a huge shift in how we age coming sooner rather than later.

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