Irisin ~ Just the Pill for Low Carbers

There was an article in the NYT that was passed along to me the other day:

Exercise Hormone May Fight Obesity and Diabetes

A newly discovered hormone produced in response to exercise may be turning people’s white fat brown, a groundbreaking new study suggests, and in the process lessening their susceptibility to obesity, diabetes and other health problems.

... in the new study, scientists closely examined the operations of a substance called PGC1-alpha, which is produced in abundance in muscles during and after exercise.

... Mice bred to produce preternaturally large amounts of PGC1a in their muscles are typically resistant to age-related obesity and diabetes, much as people who regularly exercise are.

... increases in PCG1a in muscles caused a subsequent bump in the expression of a protein known as Fndc5.

The Harvard researchers realized that one thing the protein did was break apart into different pieces, one of which was a hormone that had never before been identified. With uncharacteristic whimsy, the scientists dubbed it “irisin,” after Iris, the messenger goddess of Greek mythology.

Unlike most substances birthed in the muscles, irisin does not completely remain there, the scientists noted. It apparently enters the bloodstream and surfs to fat cells, where, by providing various biochemical signals or messages, it begins turning regular fat — especially deep, visceral fat clustered around organs — into brown fat.

... Brown fat, as many of us have heard, is physiologically desirable. While white fat cells are essentially inert storehouses for fat, brown fat cells are metabolically active. They use oxygen and require energy. They burn calories.

... And it may be that irisin, and exercise, partially determine how much brown fat each of us contains, the new study suggests. In perhaps the most compelling of the many separate experiments detailed in the Nature paper, the scientists injected irisin into white fat cells removed from mice. Afterward, genetic changes in the cells signified that they were browning. The fat cells also increased their respiratory rate, an indication that they were burning more energy.

The brown fat is also the stuff that does that thermogenic uncoupling we hear so much about.  I wonder, in those for whom exercise does preserve metabolic rate if irisin isn't behind that by altering fat metabolism more than increasing lean mass in any appreciable fashion? 

... In essence, irisin appears to be one of the more important missing links in our understanding of how exercise improves health.

But while irisin appears to have a critical impact on metabolism, it does not appear to play any discernible role in the effects that exercise has on the heart or the brain. And various issues remain unresolved. Why, for instance, if exercise increases levels of irisin and irisin increases the body’s stores of energy-burning brown fat, does exercise so rarely produce significant weight loss? The mice injected with irisin lost little weight.

If you do a Google search on irisin, the headlines you'll find are like this:

• New pill that 'helps you to stay fit without exercise' 
• Irisin Hormone Could Lead To 'Exercise Pill' 
• Newfound Hormone Irisin Could Fight Obesity and Diabetes ..

Those first two sound familiar, and the prospects of that magical "exercise pill" are mentioned in the NYT piece as well.  Ahhhh .... but it won't make you thinner probably.  See?  Exercise is useless for weight loss.  But if we learned anything from Tara Parker-Pope, it's that obesity is hard to reverse ... so best to prevent it to begin with.  And ...

On the other hand, Dr. Spiegelman notes, they resisted weight gain, even on a high-fat diet, and their blood sugar levels remained stable. So it would seem that exercise, through the actions of irisin, can render you healthy, if not svelte.

I don't suppose irisin might also help one resist REgain?   The article goes on to caution that a pill would be years in the making.   Wonder if Fred Hahn will be telling his audience in May the *whole truth* (so help me Fred ... gag, barf) about exercise.  Because this seems pretty groundbreaking here!  Maybe all those MD's who tell their prediabetic patients to move their butts a little more aren't such bad eggs after all ... could that advice actually be right?  Yeah ... but that just makes you healthy it won't make you lean.  For that just eat gobs of fat and protein and do some slow burn for a few minutes every week.  And when that fails, there will likely be an exercise pill sometime on the horizon.  Or ...

...But already, he says, it’s safe to say that “physical activity increases irisin levels in healthy people,” altering the hue of their fat cells and the tenor of their health, a message worth remembering.

I'm going with the above.  That Eat Less Move More advice sounds more brilliant every day.

And isn't this irisin amazing?  Insulin only traps fat in fat cells ... it can't turn your white fat brown!  I'm being a little cheeky there, because since humans have far less brown fat than rodents (as a proportion) I tend to think that whatever the effects of irisin, they will be less in humans and/or it will have far more varying effects depending on how our fat developed to begin with.  But just to be a wise ass, if wheat = visceral fat, and exercise turns white visceral fat into brown fat, maybe a toasted wheat belly isn't so bad after all!  ;-)