Can regular aerobic exercise literally reverse the effects of aging? According to a new study published online ahead of print in a journal from the American Physiology Association, the answer appears to be yes, at least for mice, and possibly for humans.
The study, conducted by a University of Colorado at Boulder research team, examined the effects of voluntary exercise in young and old laboratory mice, and found that the old mice who engaged in voluntary wheel running during the 14-week study period showed cellular changes in heart and surrounding artery tissues that closely matched with corresponding tissue samples from the young mice in the study.
According to the study authors, researchers have long known that moderate exercise helps boost antioxidant capacity, reduce inflammation and improve cardiovascular function in humans. What’s been less clear to scientists is how these positive benefits translate to the aging of heart tissue and the surrounding coronary arteries. Since the aging of cardiovascular tissue is believed to be strongly linked to the development of chronic heart disease and other forms of cardiovascular disease, a finding that demonstrates the ability of regular exercise to offset the effects of aging on cardiovascular tissues is groundbreaking.
To assess the potential of exercise to reverse coronary artery aging, the research team selected seven “young” male mice and 11 “old” male mice and sequestered them in separate mouse cages without an exercise wheel. They also selected another group of five young male mice and eight old male mice and placed them in cages with an exercise wheel.
The young mice averaged five to six months of age (which is roughly comparable to 11-12 years old for humans based on the relative average life spans of mice and humans). The old mice averaged 31-32 months of age (approximately comparable to a 65-66-year-old human).
All of the mice received the same diet and had the same living conditions within their respective cages with the exception of the running wheel in half of the cages. The young and old mice who were in cages with exercise wheels were not forced to use them, but researchers did track the average use of the wheels by the mice in these cages. Over the course of the study, the young mice ran 8.2 kilometers per day (which seems like an awful lot of running for a mouse, but that’s what the researchers reported), while the old mice ran an average of 2.1 kilometers per day.
At the end of the study, all the mice were put down and their hearts and surrounding arteries were removed to examine for known inflammation markers, arterial tissue composition and arterial function (hence the reason why scientists use mice for this kind of study versus humans).
A number of the tissue tests conducted by the study team produced extraordinary results. For example, when comparing known inflammation markers (inflammation signaling proteins called cytokines) between the non-exercising old mice and exercising old mice, the researchers found in excess of 60 percent reductions in the counts of the cytokines in the exercising old mice. Further, those 60 percent-plus drops in inflammation-related proteins resulted in absolute levels that were the same or below both the young exercising and young non-exercising mice.
In another measure of arterial aging, the researchers isolated and counted the number of macrophages (white blood cells) that had penetrated the outermost wall of artery and heart tissues. Macrophages are called to the sites of inflammation in the body by cytokines and are typically found in large number in the outer walls of aged aortic and carotid artery tissues. Sure enough, the number of macrophages present in the outer walls of the artery tissues of older mice who did not exercise was three to four times higher than in either young mice (whether they exercised or not) or older mice who exercised. The older exercising mice had macrophage counts consistent with the two younger mice groups.
The researchers concluded, “The overall novel finding of the present study is that regular aerobic exercise ameliorates inflammation with aging in mice. Specifically, our results show that the anti-inflammatory effects of aerobic exercise on aging arteries include normalization of IKK-NFxB activation, pro-inflammatory cytokines and adventitial-perivascular macrophage infiltration. These anti-inflammatory effects are associated with amelioration of age-associated vascular dysfunction … To our knowledge, this is the first direct evidence for anti-inflammatory effects of aerobic exercise in arterial tissues per se in the context of aging or any other state associated with vascular dysfunction.”
The study authors went on to offer their speculation of the mechanism at work. They suggested that the anti-inflammatory effect of aerobic exercise inhibits the infiltration of macrophages into the inner layers of arteries, and in so doing, limits damage of the arteries. In other words, inflammation and the body’s response to it breaks down the tissues of arteries and this is what causes them to become aged or diseased. Exercise seems to reduce artery inflammation and boost antioxidant capacity which in turn reduces the inflammation-signaling cytokines which in turn reduces the number of macrophages. Macrophages in turn don’t penetrate the layers of the arteries and the integrity of artery tissues is preserved (at least in mice).
That said, the researchers leading the study suggested regular aerobic exercise in middle-aged and older humans may confer similar benefits: reduced aging of tissues, improved cardiovascular function and lower inflammation. One more reason to start and maintain a regular aerobic exercise program, wouldn’t you say?
For those of you who are interested in beginning an aerobic exercise program, we’ve published a number of articles within the last few months describing different approaches shown to be effective in recent research studies. Understanding that each of us has different preferences for type of exercise and varying amounts of free time to devote to a program, we’ve tried to provide a range of alternatives. On the Peak Health Advocate home page, enter the keyword “exercise” in the search box in the right-hand sidebar to view our exercise-related articles.
 Lesniewski LA, et al. Aerobic Exercise Reverses Arterial Inflammation with Aging in Mice. Am J Phsyiol Heart Circ Phsyiol. May 27, 2011. Epub ahead of print.