(Edmonton) It's common enough for researchers to look at the effects of prescribed drugs on the body. And if you're a diabetes researcher who believes that exercise has great benefits for those with Type 2 diabetes, you're hoping your research will show that. But when Normand Boulé looked at the dual impacts of exercise and metformin-two of the most commonly-prescribed modalities for glucose control-on that very outcome, the hoped-for double whammy wasn't the result.
Ten men and women between 30 and 65 with Type 2 diabetes who were not taking glucose-lowering medication or insulin for their condition were recruited into the study. Participants were randomly assigned to take metformin or a placebo for the first 28 days of the study, then crossed over so those taking the placebo received metformin and vice versa for a second 28-day period. On the last two days of each time period, participants were assessed during a non-exercise and a subsequent exercise day. Exercise took place in the morning and involved a total of 35 minutes performed at three different submaximal intensities.
Boulé, a professor in the Faculty of Physical Education and Recreation, explains that metformin is thought to reduce glucose in the blood by activating exercise-like pathways. By combining exercise with metformin, Boulé says his team was looking for an outcome where the sum of the whole would be greater than the individual glucose-control paths.
"As expected, our study showed that metformin lowered the blood-glucose concentrations measured during a two-hour period after lunch," said Boulé. "But we found that on the non-exercise day, metformin led to better glucose control after lunch than on the day our participants took metformin and exercised."
Boulé theorizes that because both metformin and exercise act to lower glucose levels, the combination may have triggered a counter regulatory response by the body to prevent glucose levels from dipping too much.
"During exercise, glucagon (a hormone secreted by the pancreas that raises glucose levels) concentrations increased in the blood but when we combined exercise and metformin the glucagon levels were almost twice as elevated."
Boulé says the findings of their study were also likely effected by the timing of meals relative to the exercise session participants underwent and that the intensity of exercise may have had an effect as well, including the fact that these levels were measured after a single bout of exercise as opposed to regular daily exercise.
In terms of the other foci of the study, Boulé says this study was consistent with previous studies that saw participants experience slightly increased lactate levels, and increased use of fats as an energy source during exercise. However, he believes his study was the first to document a significantly increased heart rate-six beats per minute on average-when performing aerobic exercise of various intensities with metformin.
Boulé says despite these findings, "exercise has hundreds of benefits" and should still be an important part of a healthy approach to glucose control for those with diabetes, including those taking metformin.
"What we've learned is that the relationship between exercise and metformin is complex, and this opens the door for more research to examine how different treatments work together, especially because exercise is widely prescribed for people with diabetes and metformin is often the drug of choice for treating Type 2 diabetes."
This study was funded by the Alberta Diabetes Institute and recently published in the journal Diabetes Care.