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Tuesday, December 21, 2010

Sedentary lifestyle does not necessarily lead to insulin resistance

As everyone knows, the two key components to maintaining healthy weight are diet and exercise. But what happens to people who don’t exercise? Are they doomed to suffer weight gain and diabetes? In order to answer that question, researchers have created mice that are incapable of exercising. Surprisingly, the mice are not at greater risk for diabetes than their calisthenics-practicing counterparts.

The mice in question are lacking the transcription coactivator PGC-1. Briefly, PGC-1 is responsible for regulating genes involved in energy metabolism. Without PGC-1, mitochondria cannot function normally, leading to cells that garner much less energy from the fuel they take in. That limited energy is funneled strictly into cell maintenance and growth, leaving little for exercise. The afflicted mice can develop normally, but cannot run on their exercise wheels.

Even though the PGC-1 negative mice were not exercising, they did not suffer from either obesity or insulin resistance. This surprised many scientists, who expected the lack of exercise to lead directly to such health risks. The new thinking is that the insulin resistance came first, and that this triggered the decline in mitochondrial function, rather than the other way around. In other words, it isn’t the sedentary lifestyle that leads to diabetes, but rather diabetes that leads to being sedentary. More specifically, obesity may trigger a decline in PGC-1, which makes it more difficult for people to exercise.