To follow on from yesterday's set of exercise related research, here is an interesting note on what exercise does to the basis for heart tissue maintenance. The heart is one of the least regenerative organs in mammals, not capable of repairing itself to any significant degree following injury. Nonetheless, within those limited bounds, exercise makes a sizable difference. This is supported by the evidence showing that heart disease patients have a better prognosis when they maintain a program of exercise, even to the lesser degree that they are capable of sustaining.
In a new study performed in mice, researchers uncovered one explanation for why exercise might be beneficial: It stimulates the heart to make new muscle cells, both under normal conditions and after a heart attack. The human heart has a relatively low capacity to regenerate itself. Young adults can renew around 1 percent of their heart muscle cells every year, and that rate decreases with age. Losing those cells is linked to heart failure, so interventions that increase cell formation have the potential to help prevent it.
"We wanted to know whether there is a natural way to enhance the regenerative capacity of heart muscle cells. So we decided to test the one intervention we already know to be safe and inexpensive: exercise." To test its effects, the researchers gave one group of healthy mice voluntary access to a treadmill. When left to their own devices, the mice ran about 5 kilometers each day. The other healthy group had no such gym privileges, and remained sedentary.
To measure heart regeneration in the mouse groups, the researchers administered a labeled chemical that was incorporated into newly made DNA as cells prepared to divide. By following the labeled DNA in the heart muscle, the researchers could see where cells were being produced. They found that the exercising mice made more than 4.5 times the number of new heart muscle cells as did the mice without treadmill access. After experiencing heart attacks, mice with treadmill access still ran 5 kilometers a day, voluntarily. Compared with their sedentary counterparts, the exercising mice showed an increase in the area of heart tissue where new muscle cells are made. The researchers now plan to pinpoint which biological mechanisms link exercise with increased regenerative activity in the heart.