You probably know someone who seems grow old slowly, looking years younger than his date of birth 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 during their golden years and others struggle physiologically in middle age?
I have worked in the area of aging throughout my scientific career and teaching cellular and molecular biology of aging at the University of Michigan. Aging research doesn’t tend to be about finding the cure that solves everything that might ail you in old age. Instead, the last two decades of work point 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 some common characteristics: Aging is a time-dependent process that results in increased vulnerability to disease, injury and death. This process is intrinsic, when your own body causes new problems, and extrinsic, when environmental insults damage your tissues.
Your body is made up of trillions of cells, and each is not only responsible for one or more specific functions of the tissue in which it resides, but must also do all the work to stay alive. This includes metabolizing nutrients, getting rid of waste, exchanging signals with other cells, and adapting to stress.
The problem is that every process and component in every one of your cells may be interrupted or damaged. Therefore, your cells spend a lot of energy every day preventing, recognizing and solving these problems.
Aging can be thought of as a gradual loss of the ability to maintain homeostasis – a state of balance between the body’s systems – either by not being able to prevent or recognize damage and malfunction, or by not adequately or quickly resolving problems as they occur. Aging results from a combination of these problems. Decades of research have shown that almost all cellular processes become 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 address the potential roles that many other important biomolecules in the cell also play in aging.
One of the cell’s main functions is to maintain its DNA – the instruction manual that the cell’s machinery reads to produce specific proteins. DNA maintenance involves the protection and precise repair of damage to the genetic material and the molecules attached to it.
Proteins are the workers of the cell. They carry out chemical reactions, provide structural support, send and receive messages, retain and release energy, and more. If the protein is damaged, the cell uses mechanisms involving special proteins who try to fix the broken protein or send it for recycling. Similar mechanisms move proteins out of the way or destroy them when they are no longer needed. This way, its components can later be used to build a new protein.
Aging disrupts a delicate biological network
The cross-talk between components within cells, cells as a whole, organs, and the environment is a complex, ever-changing network of information.
When all the processes involved in creating and maintaining the function of DNA and proteins are functioning normally, the different compartments within a cell perform specialized functions – called organelles – can maintain cell health and function. For an organ to function well, most of the cells that make it up need to function well. And for an entire organism to survive and thrive, every organ in your body needs to function well.
Aging can lead to dysfunction at any of these levels, from the subcellular to the organism. Maybe one gene that codes for a protein important for DNA repair has been damaged and now every other gene in the cell is more likely to be repaired incorrectly. Or maybe the cell phone recycling systems can no longer degrade dysfunctional components. Even the communication systems between cells, tissues and organs can be compromised, leaving the organism less able to respond to changes within the body.
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 designed to correct it also accumulate damage. This leads to a increasing wear cycle as cells age.
Anti-aging interventions
The interdependence of the cellular processes of life is a double-edged sword: Sufficiently damage one process and all other processes that interact with or depend on it are impaired. However, this interconnectedness also means that strengthening a highly interconnected process could also improve related functions. In fact, this is how the most successful anti-aging interventions work.
There is no magic solution to stop aging, but certain interventions appear to slow aging in the laboratory. Although there are ongoing clinical trials investigating different approaches in people, most existing data comes from animals such as nematodes, flies, mice and non-human primates.
One of the best studied interventions is calorie restriction, which involves reducing the amount of calories an animal would normally consume without depriving it of necessary nutrients. An FDA-approved drug used in organ transplants and some cancer treatments called rapamycin seems to work using at least one subset of the same paths that calorie restriction is activated in the cell. Both affect signaling centers that guide the cell to preserve the biomolecules it has, instead of growing and building new biomolecules. Over time, this cellular version of “reduce, reuse, recycle” removes damaged components and leaves behind a greater proportion of functional components.
Other interventions include changing the levels of certain metabolitesselectively destroying senescent cells that stopped dividing, changing the gut microbiome It is behavioral modifications.
What all of these interventions have in common is that they affect central processes that are critical 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 of the mechanisms that protect the body’s DNA and proteins.
There is no single cause for aging. No two people age the same way and, in fact, no two cells age. There are countless ways that your basic biology can go wrong over time, and these add up to create a unique network of aging-related factors for each person that make finding a anti-aging treatment one size fits all extremely challenging.
However, researching interventions that target multiple important cellular processes simultaneously could help improve and maintain health across a greater part of life. These advances could help people live longer lives in the process.
This article was republished from The conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you understand our complex world. It was written by: Ellen Quarles, University of Michigan
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Ellen Quarles does not work for, consult with, 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.
