Physicians and dietitians have often encouraged and prescribed exercise as a treatment to manage diabetes mellitus. Even though the World Health Organization suggests that regular physical activity can prevent or delay the onset of type II diabetes, current evidence shows some moderate benefits regarding exercise’s effectiveness in maintaining long-term normal blood sugar levels. In normal blood-sugar regulation, the pancreas produces insulin to help the body store glucose for energy, either in skeletal muscles or the liver. This hormone is released when a meal with carbohydrates is consumed. Among those with diabetes mellitus, the pancreas either does not make insulin at all because the beta cells in the pancreas that makes insulin no longer functions (type I), or the body just does not respond well to insulin (type II).
Among type II diabetics, exercise may increase insulin sensitivity and blood glucose uptake in skeletal muscles, according to a 2013 study published in American Journal of Physiology, Endocrinology and Metabolism. However, researchers find that insulin uptake did not occur in fat tissues, which shows that those who are obese with low muscle mass may be more susceptible to diabetes mellitus. Although most studies have focused mostly on aerobic exercise, this study shows evidence that strength training is also necessary to build muscle mass to help increase insulin sensitivity among diabetics.
An Australian meta-analysis performed at the University of Newcastle reviewed 23 articles from eight studies that examined the effects of aerobic and resistance exercise on diabetes mellitus. The median length of the study was 12 months (range four to 48 months) with a median follow-up of 18 months (range 6.5 to 48 months). Researchers Elroy J. Aguilar and colleagues found that diet and a combination of aerobics and resistance exercise are essential to any lifestyle change to prevent type II diabetes. However, they said that more “rigorous studies” are needed, and they should include “long-term follow-ups, muscular fitness outcomes, risk reduction, and diabetes incidences.” Another meta-analysis that reviewed 24 studies among childhood diabetics also found a similar benefit in lowering insulin resistance with exercise. However, the review — published in Pediatrics, January 1, 2014 — did not mention the type of exercise intervention used.
Even though exercise could help those with diabetes mellitus, diabetics may likely have cellular respiratory dysfunctions that can inhibit their exercise performance. Scientists at the University of California, Los Angeles, recently found that a special protein called heat shock protein 72 (HSP72) in skeletal muscles could prevent glucose intolerance and obesity in mice when that protein has an increase expression. It works with another protein called Parkin, which regulates the removal of damaged mitochondria prior to a cell’s death, to maintain the normal process of cell cycle. In the experiment, scientists removed HSP72 from mice, which impaired Parkin’s function. This resulted in “enlarged, dysmorphic mitochondria,” which caused reduced muscle respiratory activity, high fat accumulation, and increased muscle insulin resistance. This further lead to decreased oxygen intake and impaired insulin activity and response. Although much is still not known about HSP72’s mechanisms, UCLA researchers stated that these data could provide better strategies to “enhance mitochondrial quality and insulin action” to improve type II diabetes mellitus and other metabolic diseases. This can help minimize fatigue and other complications that diabetics may get during exercise.
Better understanding of diabetes mellitus — on a molecular and macro level — can help exercise and medical professionals give the appropriate strategies and interventions to work with diabetics. While the amount, intensity, and type of exercise vary from each individual, diabetics still need to stay active everyday for other health benefits, such as improving mood, cholesterol levels, cardiovascular function, and muscle and joint strength and flexibility.
By Nick Ng
Journal of Primary Care Community & Health
International Journal of Behavioral Nutrition and Physical Activity
Biomedical Society Transactions
American Journal of Physiology, Endocrinology and Metabolism