A popular diabetes drug sometimes taken to slow aging may diminish some of the expected health benefits of aerobic exercise in healthy older adults, according to a new report. The drug, metformin, can blunt certain physical changes from exercise that normally help people to age well. …
… The researchers measured the volunteers’ current aerobic fitness, blood-sugar levels, insulin sensitivity and body mass. They also took tiny leg-muscle biopsies and randomly assigned the volunteers to start taking either metformin or a placebo.
All of the volunteers then began a supervised exercise program, visiting the lab three times a week to jog on a treadmill or pedal a bike for 45 minutes, a routine that lasted for four months.
Afterward, the researchers repeated all of the measurements from the study’s start and compared the two groups.
It turned out, to no one’s surprise, that most of the volunteers now had better aerobic fitness and blood-sugar control than before, as well as improved insulin sensitivity. Each of these physiological changes would be expected to improve how well the volunteers aged.
But there were notable disparities between the two groups. Over all, the men and women taking metformin gained less fitness, upping their endurance by about half as much as those swallowing the placebo. Many of those taking the drug also showed slighter, if any, improvements in insulin sensitivity. (Hardly anyone’s weight changed much, in either group.)
The scientists next looked microscopically inside their volunteers’ muscles and found telling discrepancies between the two groups. The muscle cells of the exercisers on placebo teemed with active mitochondria, which are the cells’ powerhouses. Mitochondria transform oxygen and sugar into cellular fuel in a process referred to as mitochondrial respiration. Higher respiration generally means better cellular health.
In the muscle cells from the men and women on placebo, mitochondrial respiration rose by about 25 percent, compared to levels at the study’s start. But not so in the muscle cells from the metformin group, which showed little if any upswing in mitochondrial respiration.
In effect, metformin had road-blocked the normal exercise-related gains in muscle-cell mitochondrial respiration, says Benjamin Miller, a principal investigator in the aging and metabolism research program at the Oklahoma Medical Research Foundation, who oversaw the study. …
… metformin and exercise “did not seem to play together very well.” …