Active Voice: Exercise Speeds Healing in Obese Mice
By Brandt Pence, Ph.D. and Jeffrey Woods, Ph.D., FACSM
Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.
Brandt Pence, Ph.D., is a postdoctoral researcher in the Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign. He is a member of ACSM, with research interests in the broad area of exercise, obesity, and immune function, including defects in wound healing and impairments in anti-viral immunity associated with the obese state.
Jeffrey Woods, Ph.D., FACSM, is a professor of exercise physiology in the Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign. His research career has been focused on the impact of exercise on immune function in conditions as diverse as obesity, normal aging, cancer and infection. His current research is focused on the neuroimmunological and behavioral impacts of exercise and nutrition during the aging process.
The following commentary reflects Dr. Pence’s and Dr. Woods’ views relating to their and colleagues’ research article, which appears in the October 2012 issue of Medicine and Science in Sports and Exercise®, “Exercise Speeds Cutaneous Wound Healing in High-Fat Diet-Induced Obese Mice.”
Obesity has become a nationwide (and indeed worldwide) concern, with recent estimates of more than two-thirds of adults in the United States being classified as overweight or obese. Obesity, while itself a concern, also brings with it a large number of related problems. From recent evidence of impaired immune responses to influenza H1N1/09 (the “swine flu”) in individuals with obesity, to the more well-known relationship between obesity and type 2 diabetes, comorbidities associated with obesity create a great strain on healthcare systems in the United States and around the world.
While certainly appreciated by physicians, the fact that obesity impairs wound healing is not necessarily common knowledge. Indeed, the development of non-healing wounds in diabetics is the leading cause of limb amputation in the United States. Chronic wounds are a major area of research, but even defects in the healing of acute wounds in patients with obesity, such as those occurring after bariatric surgery, are of importance. Wounds that heal more slowly both prolong discomfort in patients and lead to increased risk of wound site complications such as infection. Thus, speeding the healing of these wounds is of paramount importance. Our research question, as presented in our recent MSSE article, was simple. We asked if a short-term exercise intervention could speed wound healing in an animal model of obesity. Our exercise paradigm was equally simple. We ran obese mice on a motorized treadmill for 30 minutes at a moderate (jogging) intensity for 3 days prior to cutaneous wounding, then continued this exercise treatment for 5 days post-wounding. We tracked healing rate in these mice daily, beginning immediately after the wound was applied, and compared that healing rate with a group of mice that remained sedentary during the same period. We found that mice in the exercise group healed more quickly than mice in the sedentary group, supporting our hypothesis that exercise would speed healing rate. We also investigated whether exercise would have similar positive effects in non-obese mice, but here, exercise failed to speed healing rate. This suggests to us that, at least in our model, some type of deficiency in the healing process must exist for exercise to speed the healing rate. That is, mice that already heal normally may not be positively affected by exercise.
At first glance, our exercise paradigm may seem somewhat odd. After all, exercise in our mice did not result in significant weight loss due to the abbreviated training period. It is likely, of course, that longer-term exercise which results in significant weight loss (and perhaps reduction in classification from obese to overweight or below) might have a greater impact on wound healing rate. However, we chose our exercise paradigm for two reasons. First, previous research into psychological stressors has shown that, in mice, exposure to stress for a similar period significantly impairs the wound-healing response. Second, and perhaps more important, we designed this study with the potential for future exercise prescription in mind. If such a short exercise training period is shown in the future to be similarly successful in humans, this type of approach may be prescribed by physicians to obese individuals that are soon to undergo surgery in order to help their surgical wounds heal after the operation. Thus, although human research remains to be performed, our study has taken the first steps towards defining an achievable exercise routine intended to help patients with obesity heal surgical wounds more quickly.