Doctors are concerned about the growing numbers of men and women that will need medical care during old age. We are all living longer, and as a result Alzheimer’s, sarcopenia, diabetes and osteoporosis are taking on epidemic proportions. Researchers at the Joslin Diabetes Center in the US published an animal study which suggests that the numbers of elderly people with weak muscles are likely to grow more than we had expected.
The researchers performed experiments with mice. They gave some pregnant females normal food [C] and underfed others [UN]. After the young had been born and weaned, they were given either ordinary food, consisting of approximately 20 percent energy derived from fat, or a high-fat diet consisting of 60 percent energy derived from fat. Mice become fat when fed a fatty diet.
After three weeks the researchers counted the number of stem cells in the mice's muscles. The stem cells are not part of the muscle tissue, but are still capable of dividing, after which they form muscle cells that do then become part of the muscle tissue. Physical exercise, anabolic hormones and serious damage to muscle tissue all stimulate stem cell division.
The researchers discovered that the offspring of the underfed females had fewer stem cells. That was not unexpected. However, the researchers also discovered that overfeeding after birth had the same effect – and that was unexpected. The overfed mice had 27 percent fewer stem cells in their muscles than the animals that had been given regular chow.
The researchers damaged muscle tissue in their lab animals by exposing it to extremely low temperatures. They then examined the tissues three days later to see how well they had recovered. In the mice whose mothers had had enough to eat, overfeeding reduced the recovery ability by 42 percent. The recovery ability of the offspring of underfed mothers was 64 percent less.
"Such reductions in muscle stem cell number and function may contribute to alterations in muscle mass and body composition associated with developmentally mediated risk for adult disease", the researchers write.
It is clear that they are referring to the increasing numbers of children who are too fat. It seems likely that these children in older age may lose muscle mass and strength more quickly, and will therefore need more help.
In many developing countries overweight is also on the increase. In these countries underfeeding and overfeeding go hand in hand – and for these countries the relationships that the Americans have uncovered are even more worrying.
Stem Cells Dev. 2011 Oct;20(10):1763-9.