The research team from McMaster and York universities analysed muscle biopsies of young adults with and without type 1 diabetes who exceed Diabetes Canada's recommended weekly levels for physical activity.
The researchers found structural and functional changes in the power generation parts of the cell, or mitochondria, of those with diabetes. Not only were the mitochondria less capable of producing energy for the muscle, they were also releasing high amounts of toxic reactive oxygen species, related to cell damage.
These changes could result in reduced metabolism, greater difficulty controlling blood glucose and, if left unchecked, an accelerated rate of developing a disability. The study findings add poor muscle health to the list of better-known complications of type 1 diabetes, including nerve damage, heart disease and kidney disorders.
"Now we know that even active people with diabetes have changes in their muscles that could impair their ability to manage blood sugar," said Thomas Hawke, corresponding author of the study. "Knowing in the long term that this could contribute to faster development of disability, we can start to address it early on."
Christopher Perry, study co-senior author, added, "Skeletal muscle is our largest metabolic organ and is the primary tissue for clearing blood sugar after eating a meal, so we need to keep muscle as healthy as possible."
With regular aerobic exercise, the amount of mitochondria in muscle increases, thereby helping muscle cells to use more glucose and become more efficient. Given this new data, Perry added that their study suggests that current guidelines for Type 1 diabetics may also need to be revised.
"We believe these dysfunctional mitochondria are what's causing the muscle to not use glucose properly and to also damage muscle cells in the process. We were surprised to see the muscles were this unhealthy in young adults with Type 1 diabetes who were regularly active."
Researchers say while further study is needed, revising evidence-based exercise guidelines, specific for those with Type 1 diabetes, may be required to keep them in the best health.
The paper was published in Diabetologia, the journal of the European Association for the Study of Diabetes.