You probably know someone who ages slowly, aging years earlier than their birth date suggests. And you’ve probably seen the opposite—someone whose body and mind seem to be ravaged by time far more than others. Why do some people seem to glide through their golden years while others seem to struggle physiologically in middle age?
I have worked in the field of aging my entire scientific career and teach the cellular and molecular biology of aging at the University of Michigan. Aging research is not generally about finding a single treatment that will fix everything that ails you in old age. Instead, the last decade or two of work has shown that aging is a multifactorial process and no single intervention can stop everything.
What is aging?
There are many different definitions of aging, but scientists generally agree on some common characteristics: Aging is a time-dependent process that results in increased susceptibility to disease, injury, and death. This process is both internal, when your own body creates new problems, and external, when environmental insults 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 located in, but it also has to do the job of keeping itself alive. This includes metabolizing nutrients, removing waste, signaling with other cells, and adapting to stress.
The problem is that every single process and component in your cells can be disrupted or damaged, so your cells spend a lot of energy every day trying to prevent, recognize, and fix these problems.
Aging can be thought of as the gradual loss of the ability to maintain homeostasis (the state of balance between body systems) through the inability to prevent or recognize damage and poor function, or to adequately or quickly correct problems as they arise. Aging results from a combination of these problems. Decades of research have shown that nearly every cellular process deteriorates with age.
Repairing DNA and recycling proteins
Most research on cellular aging focuses on how DNA and proteins change with age. Scientists are also beginning to address the potential roles that many other important biomolecules in the cell play in aging.
One of the cell’s primary jobs is to maintain its DNA, the instruction manual that the cell’s machinery reads to produce specific proteins. DNA maintenance involves protecting against damage to the genetic material and the molecules that bind to it and repairing them correctly.
Proteins are the workhorses of the cell. They perform chemical reactions, provide structural support, send and receive messages, store and release energy, and much more. If a protein is damaged, the cell employs mechanisms that include specialized proteins that attempt to repair the broken protein or send it for recycling. Similar mechanisms remove proteins or destroy them when they are no longer needed. In this way, their components can be used later to build a new protein.
Aging disrupts a delicate biological network
The cross-talk between components within cells, entire cells, organs, and the environment is a complex and constantly changing information network.
When all the processes involved in creating and maintaining DNA and protein function are functioning normally, different compartments within the cell with specialized roles, called organelles, can maintain the health and function of the cell. For an organ to function well, most of the cells that make it up must function well. And for an entire organism to survive and thrive, all of the organs in its body must function well.
Aging can lead to dysfunction at any of these levels, from the subcellular to the organism. Perhaps a gene that codes for a protein important for DNA repair has been damaged, and now all other genes in the cell are more likely to be repaired incorrectly. Or perhaps the cell’s recycling systems can no longer break down dysfunctional components. Even communication systems between cells, tissues, and organs can be compromised, diminishing the organism’s ability to respond to changes in the body.
Random chance can lead to an increasing burden of molecular and cellular damage that is progressively less repaired over time. As this damage accumulates, the systems that are supposed to repair it also accumulate damage. 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 enough, and all the other processes that interact with it or depend on it are disrupted. However, this connection also means that supporting a highly interconnected process can also improve related functions. In fact, the most successful anti-aging interventions work this way.
There’s no surefire way to stop aging, but some interventions do appear to slow it down in the lab. While there are ongoing clinical trials investigating different approaches in humans, most of the available data comes from animals like nematodes, flies, mice, and non-human primates.
One of the best-studied interventions is calorie restriction, which involves reducing the number of calories an animal would normally eat without depriving them of essential nutrients. An FDA-approved drug called rapamycin, used in organ transplants and some cancer treatments, appears to work by using at least a subset of the pathways that calorie restriction activates in the cell. Both affect signaling centers that direct the cell to preserve the biomolecules it has rather than to create and grow new ones. Over time, this cellular version of “reduce, reuse, recycle” eliminates damaged components, leaving behind more highly functional components.
Other interventions include altering levels of certain metabolites, selectively destroying senescent cells that have stopped dividing, changing the gut microbiome, and behavioral changes.
What all of these interventions have in common is that they affect fundamental processes that are critical to cellular homeostasis, that often become dysregulated or dysfunctional with age, and that depend on other cellular maintenance systems—often the central drivers of mechanisms that maintain DNA and proteins in the body.
There is no single cause of aging. No two people age the same way, and in fact, no two cells age the same way. There are countless ways your basic biology can go wrong over time, creating a unique web of aging-related factors for each person, making it extremely difficult to find a single anti-aging treatment.
But exploring interventions that target multiple important cellular processes simultaneously could help improve and maintain health across a larger portion of life. These advances could help people live longer in the process.
This article is republished from The Conversation, a nonprofit, independent news organization that brings you facts and trusted analysis to help you understand our complex world. By Ellen Quarles University of Michigan
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Ellen Quarles does not work for, consult, own shares in, or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond her academic appointment.