You probably know someone who seems to be aging slowly, who looks years younger than their birth date suggests. And you’ve probably seen the opposite: someone whose body and mind seem much more ravaged by time than others. Why do some people seem to glide through their golden years while others struggle physiologically in midlife?
I’ve worked in the field of aging my entire scientific career, and I teach the cellular and molecular biology of aging at the University of Michigan. Aging research is not usually about finding the one cure that will fix everything that ails you as you get older. Instead, the work of the last decade or two has pointed to aging as a multifactorial process—and no single intervention can stop it all.
What is aging?
There are many different definitions of aging, but scientists generally agree on a few common characteristics: Aging is a time-dependent process that results in increased vulnerability to disease, injury, and death. This process is both intrinsic, when your own body creates new problems, and extrinsic, when environmental influences damage your tissues.
Your body is made up of trillions of cells, and each one is not only responsible for one or more functions specific to the tissue it is in, but must also do all the work to keep itself alive. This includes metabolizing nutrients, removing waste, exchanging signals with other cells, and adapting to stress.
The problem is that every single process and component in every one of your cells can be interrupted or damaged, so your cells spend a lot of energy every day trying to prevent, recognize, and fix those problems.
Aging can be thought of as a gradual loss of the ability to maintain homeostasis—a state of balance between body systems—either by failing to prevent or recognize damage and dysfunction, or by failing to resolve problems adequately or promptly when they occur. Aging results from a combination of these problems. Decades of research have shown that nearly every cellular process becomes more impaired with age.
Repairing DNA and recycling proteins
Most research on cellular aging focuses on studying how DNA and proteins change with age. Scientists are also beginning to investigate the possible roles that many other important biomolecules in the cell play in aging.
One of the cell’s most important jobs is to maintain its DNA—the instruction manual that a cell’s machinery reads to produce specific proteins. DNA maintenance involves protecting against, and accurately repairing, damage to genetic material and the molecules that bind to it.
Proteins are the workers of the cell. They carry out chemical reactions, provide structural support, send and receive messages, store and release energy, and much more. If the protein is damaged, the cell uses mechanisms involving special proteins that either attempt to repair the damaged protein or send it away for recycling. Similar mechanisms put proteins out of the way or destroy them when they are no longer needed. That way, their components can be used later to build a new protein.
Aging disrupts a delicate biological network
The communication between the components within cells, cells as a whole, organs and the environment forms a complex and constantly changing network of information.
When all of the processes involved in creating and maintaining DNA and protein function are working normally, the various compartments within a cell that perform specialized roles—called organelles—can maintain the health and function of the cell. For an organ to function properly, the majority of the cells that make it up must function properly. And for an entire organism to survive and thrive, all of the organs in the body must function properly.
Aging can lead to dysfunction at any of these levels, from the subcellular to the organism. Perhaps a gene that codes for a key protein for DNA repair has become damaged, making it more likely that all other genes in the cell are being repaired incorrectly. Or perhaps the cell’s recycling systems are no longer able to break down dysfunctional components. Even the communication systems between cells, tissues, and organs can be compromised, making the organism less able to respond to changes in the body.
Random chance can lead to a growing burden of molecular and cellular damage that is less and less repaired over time. As this damage accumulates, the systems that are supposed to repair it also become damaged. This leads to a cycle of increasing wear and tear as cells age.
Anti-aging interventions
The interdependence of life’s cellular processes is a double-edged sword: damage one process sufficiently and all other processes that interact with or depend on it are affected. However, this interconnectedness also means that strengthening one highly interconnected process can also improve related functions. This is, in fact, how most successful anti-aging interventions work.
There is no magic bullet to stop aging, but certain interventions do appear to slow aging in the lab. While clinical trials are underway investigating various approaches in humans, most of the existing data come from animals such as roundworms, flies, mice, and nonhuman primates.
One of the best-studied interventions is calorie restriction, which involves reducing the number of calories an animal would normally eat without depriving the animal of necessary nutrients. An FDA-approved drug used in organ transplantation and some cancer treatments, called rapamycin, appears to work by using at least a subset of the same pathways that calorie restriction activates in the cell. Both affect signaling hubs that direct the cell to conserve the biomolecules it has rather than grow and build new ones. Over time, this cellular version of “reduce, reuse, recycle” removes damaged components and leaves behind a greater proportion of functional components.
Other interventions include altering the levels of certain metabolites, selectively destroying senescent cells that have stopped dividing, altering the gut microbiome, and behavioral changes.
What all these interventions have in common is that they affect core processes that are crucial for cellular homeostasis, often become dysregulated or dysfunctional with age, and are linked to other cellular maintenance systems. Often these processes are the central drivers for mechanisms that protect DNA and proteins in the body.
There is no single cause of aging. No two people age the same, and no two cells do either. There are countless ways your basic biology can go wrong over time, and these add up to a unique network of aging-related factors for each person, making finding an anti-aging treatment that works for everyone extremely challenging.
However, research into interventions that target multiple key cellular processes simultaneously may help improve and maintain health for a greater portion of life. These developments may help people live longer.
This article is republished from The Conversation, a nonprofit, independent news organization that brings you facts and reliable analysis to help you understand our complex world. It was written by: Ellen Quarles, University of Michigan
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Ellen Quarles is not employed by, consulted with, owns stock in, or receives funding from any company or organization that would benefit from this article, nor has she disclosed any relevant affiliations beyond her academic appointment.