CHICAGO — Exercise turns on a host of metabolism-boosting genes in fat in both humans and animals, that — at least in mice — boost glucose tolerance and mitigate the effect of a fatty diet, a series of experiments showed.
Gene assays showed a big change in gene expression in subcutaneous fat among 10 healthy men after 3 months of vigorous exercise for about an hour a day, 5 days a week, Laurie Goodyear, PhD, of the Joslin Diabetes Center in Boston, and colleagues found.
Active mice showed a similar significant shift in 1,800 different genes compared with sedentary mice, the group reported here at the American Diabetes Association meeting.
Involved pathways for both species included metabolism, mitochondrial biogenesis, oxidant stress and signaling, and membrane transport.
“Most of the research has focused on how exercise or exercise training can affect skeletal muscle,” Goodyear noted at the press briefing. “We think the changes in the muscle are important to what happens to blood glucose levels. But exercise doesn’t just affect muscle, it doesn’t just affect the heart, it actually affects probably every tissue in the body.”
It’s not clear how much exercise might be needed for those effects on diabetic or obese individuals, noted press conference moderator Steven Smith, MD, of the Sanford-Burnham Medical Research Institute in Orlando.
The study looked at a lean, fit group of men who weren’t just hitting the gym for a half hour on the treadmill, he pointed out.
However, achieving the same 10% increase in maximal aerobic capacity achieved by these lean, fit men in the study probably wouldn’t take as much exercise in a sedentary individual, Goodyear noted.
“Exercise really can train your fat,” co-author Kristin Stanford, PhD, also of Joslin, told reporters at a press briefing.
The mouse model portion of the study showed that along with the genetic changes after 11 days of exercise training came histologic changes known as “browning.” Their adipose cells shrank, shedding some of the lipids inside, and increasing in mitochondria (which contain pigment that gives a brown appearance).
Moreover, there might be a way to get the same effect without the exercise, Stanford noted.
When those exercise-trained fat cells were transplanted into sedentary mice, glucose tolerance improved compared with sham-treated mice and those given a transplant from sedentary mice despite the fact that there were no differences in body weight or food consumption.
When the transplant recipients were put on a high-fat diet, glucose levels remained significantly lower than sham treated mice either on a standard or high-fat diet.
Insulin uptake also increased in skeletal muscle and brown adipose tissue in the exercise-exposed fat cell transplant mice, “suggesting the transplanted subcutaneous white adipose tissue exerted endocrine effects,” the researchers said.
Exercise might be leading fat cells to secrete proteins that act as a signal for other tissues, Stanford explained.
However, exercise has many other health benefits and is likely the best route, said Goodyear, who “wouldn’t recommend that [transplantation procedure] for humans.”
The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the ADA.
Primary source: American Diabetes Association
Stanford KI, et al “Exercise training alters subcutaneous white adipose tissue (scWAT) In mice and humans” ADA2013; Abstract 17-OR.