Friday, February 10, 2012

Science Friday: Miracle Cures

A new study identifies a hormone that may reproduce some of the effects of exercise.
Bruce Spiegelman’s group at the Dana Farber Cancer Institute found a hormone that is secreted from muscle cells following exercise and acts on fat cells, turning them from white adipose tissue cells (the bad kind of fat cell that stores fat) to brown adipose tissue cells (the good kind that burns fat.)

They identified this hormone by looking at the effects of PGC1-alpha, a protein produced during exercise that is known to increase mitochondria and regulate switching between muscle fiber types. Mice genetically engineered to express PGC1-alpha in muscles had increased conversion of white adipose tissue to brown adipose tissue, similar to mice that exercised. They sought to identify what could be responding to PGC1 in fat cells, reasoning there must be a factor that muscles were releasing that affected fat cells. After narrowing their search, they checked their candidates in humans who underwent a ten-week exercise program and found increases in the mRNA (the stuff that makes proteins) of these proteins. One protein in particular, FNDC5, had significant effects on the expression of genes that regulate brown fat. Cells treated with FNDC5 had increased mitochondria and oxygen consumption (a measure of energy expenditure.) Importantly, they found that FNDC5 is cut and part of it is released outside the cell. The secreted part is what they called irisin, and since it travels from muscle cells to fat cells, it’s characterized as a hormone. They named their newly identified hormone after the Greek messenger goddess Iris (personally, I would have gone with Pheidippides for a Greek messenger.) They found elevated levels of irisin in the blood of mice and humans following endurance exercise (they defined this as 10 weeks of 20-35 minutes of biking 4-5 times a week.) Finally, mice injected with FNDC5 had increased irisin and browning of white adipose tissue. In obese mice, there was also a decrease in body weight, an increase in oxygen consumption, and reduced insulin after fasting. 

The paper ends with the obligatory plug for how this finding could lead to better therapeutics for people who struggle with diabetes or obesity. But, I have to say, I’m not convinced. Too often we hear talk about some miracle drug that will burn fat while you lay on the couch watching reruns of Real Housewives. Photoshopped images try to convince us that this miracle drug leads to dropped pounds, lost inches, and happier lives. And while I absolutely hope we can find a way to cure America’s obesity problem, I don’t think giving people this hormone or any other drug will ever replace the benefits of exercise. Even if irisin does promote fat conversion and increase energy expenditure, there is a whole host of other things exercise does that one hormone won’t be able to mimic. I predict that even if we do discover the miracle weight loss drug, it will only be a matter of time before we realize some benefit of exercise we missed and start trying to design new drugs. In John J. Ratey’s book Spark: The Revolutionary New Science of Exercise and the Brain, he describes a whole slew of neurological and psychological disorders and details how exercise helps alleviate symptoms in all of them. A few chapters in, it becomes a bit repetitive (ADHD, cured by exercise! Alzheimer’s disease, cured by exercise! Depression, cured by exercise!) but it is filled with studies proving what us runners already know: running is the ultimate miracle cure. Dropped pounds, lost inches, happier lives. Why are we searching for drugs when we already have good old-fashioned exercise?

Dream big,

1 comment :

  1. Runner Teal:

    Informative and persuasive. What other running blog pulls together so many interesting threads?

    Keep at it!