Hormone injection lets ageing muscles run harder and longer

Wind back the clock. We’ve found a hormone that can make ageing muscles more youthful and active – in mice at least.

Once overlooked as the passive scaffolding of the body, we are beginning to understand that our bones can communicate with and influence other organs.

Now Gerard Karsenty of Columbia University and his colleagues have shown that a hormone secreted by bone – called osteocalcin – boosts the ability of muscles to burn fuel and generate energy.

When they injected the hormone into old mice, the animals were able to run as far as their younger counterparts, despite being up to a year older – a long time in mouse years. Old mice that did not receive the hormone ran about half as far. “It was extremely surprising,” says Karsenty...

Fountain of youth?

The team found that in both mice and humans, physical exercise significantly increases the level of osteocalcin in the blood. The release of this hormone increases the availability of two primary fuels, glucose and fatty acids, to the muscles.

Osteocalcin gives the muscles an extra kick by promoting fuel uptake as well as boosting the muscles’ ability to break down that fuel to use as energy, making it easier to run longer and harder, says Karsenty.

They found that osteocalcin levels gradually decrease in men and women as they age, flatlining at ages 50 and 30, respectively. “If you look backwards during evolution, men were much more active than women – for example, in hunting and fishing. That may be an explanation for why the decrease in circulating osteocalcin occurs later in men than in women,” Karsenty suggests.

The team now plans to test whether the hormone improves muscle function in people as well as mice.

The results are exciting, but there are many “big ifs”, says Graham Kemp at the University of Liverpool. “Notably, if osteocalcin has the same effect in humans, and if there are any side effects.”

There is also the risk that osteocalcin could be used as a doping agent in sport, Kemp says. “Anything, especially a natural endocrine factor, with these potential effects in humans, couldn’t fail to attract interest from would-be dopers.”

Why you really are extra tasty to mosquitoes

With the exception of maybe a mosquito's mother, the world is unified in its hatred of the little critters. But the world seems divided by those the bugs ignore and those who too often become the blood soup du jour.

This may seem random, but scientist say there is a real reason for it: blame your parents.

For the first time, scientists discovered a possible genetic reason why some of us are mosquito magnets, at least according to a pilot study from the London School of Hygiene &Tropical Medicine. It's published in the recent edition of PLOS ONE.

To figure this out, scientists released Aedes aegypti, also known as dengue mosquitoes, into a tube. The tube was divided into two sections. The bugs were essentially given a choice to swipe left or swipe right and fly down either side.

At the other end of the tube were a pair of twins. Eighteen identical and 19 nonidentical female twins volunteered to be mosquito meat. With these pairs, scientists saw a difference in who the bugs chose. When the twins were identical, the two would either be equally attractive or not attractive to the mosquitoes. When the twins were not identical, the choice varied. That, scientists say, suggests there is a genetic component to the mosquito law of attraction. Identical twins have identical genes. With fraternal twins, there are differences.

This gene that makes people more attractive might influence how someone smells to the insect.

This research builds on earlier studies that show a person's body odor may play a role in who gets bitten more. Earlier studies have found people with a particular type and volume of bacteria that naturally occurs on skin may make people more of a target. Same with people with Type O blood, which is linked to a particular odorant marker in sweat.

Pregnant women sweat more because pregnancy raises their average body temperature about 1.26 degrees, so they are bitten more often. The same has been shown with people who are heavier.

Knowing how this works will not keep you safe from the little buggers this summer, scientists need to do more research. But eventually, this may mean researchers could figure out a way to neutralize this particular odor, if that's what the mosquitoes like. This could mean fewer mosquito bites, and it may mean fewer cases of yellow fever and dengue since these particular bugs are often the carriers of these viruses.

In the meantime, Missy Henriksen from the National Pest Management Association suggests people wear the bug repellant that is on the market any time you go outside.

"We've gotten pretty good about sun screen, but people need to get better about protecting themselves against insects as well, since mosquitoes are more than just a nuisance. They carry disease."

Henriksen and the Centers for Disease Control and Prevention recommend using products that have one of four active ingredients. Check the label for DEET, picaridin, IR3535 and/or lemon eucalyptus and para-methane-diol products. These products are effective, and they are registered with the EPA (meaning the EPA believes the chemical will only hurt the mosquitoes not you).

Henriksen also suggests you may want to wear shirts with long sleeves and long pants if you can stand it in the heat of summer.

"Bugs (are less likely to) bite what they can't access," she said. And hopefully someday, bugs won't be able to suck what they can't smell.

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