When you eat beats what you eat in staying healthy

Preventing obesity may be down to timing, in mice, at least. Mice allowed meals only within an 8-hour period were healthier than those that munched freely through the day, even when they consumed more fat.

A link between obesity and the time you eat meals makes sense, says Satchidananda Panda of the Salk Institute in La Jolla, California, as food choices generally get less healthy as the day progresses. Breakfast may include healthy fruits and grains, but late-night snacks are more likely to involve high-fat ice cream or high-calorie alcohol. Furthermore, research has shown that our internal clocks are closely tied to our metabolism; disrupting them can cause weight gain and diabetes.

Panda and colleagues fed two groups of mice a high-fat diet. One group could snack whenever they liked, the other could only eat during an 8-hour window. Both groups consumed the same number of calories each day. Two other groups were fed a healthy diet under the same conditions.

Three months later, the weight of mice on the all-day, high-fat diet had increased by 28 per cent. Their blood sugar levels had gone up – a risk factor for diabetes – and they also had liver damage. In contrast, mice eating a high-fat diet for only 8 hours a day stayed healthy and didn't become obese. They also had better balance than mice on a healthy diet.

Panda reckons the shortened feeding period gives metabolic systems longer to perform their function uninterrupted by a new influx of nutrients.

RNA breakthrough transforms idea of gene control

Tiny chemical changes that do not alter the sequence of our DNA but modulate how it works have been found to act on a new part of our genetic machinery. The discovery could provide insights into many health problems, including obesity.

It has been long known that DNA can be altered "epigenetically" – where changes occur without altering the sequence of DNA but leave chemical marks on genes that dictate how active they are by adding chemical methyl groups that silence genes, for example. Numerous environmental factors, such as stress and smoking, have been shown to influence these epigenetic marks.

Now, researchers have discovered that messenger RNA, the mirror-image copy of DNA from which all proteins are manufactured, can be methylated too.

"We've discovered something fundamental to biology," says Samie Jaffrey of Cornell University in New York, and head of the team that made the discovery. "It was there all the time and no-one knew about it."

Fundamental discovery

Jaffrey's team found that around a fifth of the RNA produced in cells from rat brains and human kidneys contained methylated versions of adenosine, one of the four building blocks of our genetic code. "It was exciting to find that 20 per cent had methyl groups, so it must be a pretty fundamental regulatory mechanism," says Jaffrey.

Separate analyses of assorted rat tissues demonstrated that the methylated RNA was concentrated in the brain, liver and kidneys. Also, samples from rat embryos showed that concentrations rose 70-fold in the brain as it reached the final stages of growth, therefore they are likely to play a fundamental role in development.

The team also discovered that the methyl groups are stripped off the RNA by an enzyme linked with obesity. The enzyme is made by a gene called FTO, one variant of which raises the risk of obesity by 70 per cent. People with an overactive copy of the gene are most at risk, suggesting that stripping the methyl groups from RNA might somehow alter our metabolism.

The researchers found that methylated adenosine tended to cluster close to the point on the RNA strand where protein manufacture reaches completion, and on regions where other proteins bind to the strand to alter or halt production. The suggestion is that methylation may therefore dictate how much protein gets made, and when. "It's not changing what would be made, but it might govern how much and when it's made," says Jaffrey. This, he says, could in turn have a big impact on a multitude of physiological processes and disease.

International Space Station enters 2001's star gate

Just because you're sitting in the most expensive bit of kit on the planet (well, orbiting the planet) it doesn't mean you can overcome all the technical glitches of digital photography.

This is what Expedition 31 flight engineer Don Pettit on the International Space Station has found while trying to create star trail photos. Such photos capture the night sky in exposures so long that the imperceptibly slow movements of the stars around the poles become bright streaks. To get this effect using film-based cameras, astrophotographers need to leave their camera's shutter open for 10 to 15 minutes.

However, most digital cameras are unable to have their shutters open for more than about 30 seconds at a time. So instead of one long exposure, amateur star photographers take a series of 30-second shots and later combine them together on a computer. Pettit used this technique to stack 18 photos taken by a stationary camera on the ISS.

Often the appeal of star trail images lies in the sharpness of the foreground - often a remote, still and beautiful landscape - contrasted with the whirling energy of the stars moving above. For Pettit's photo the Earth is spinning past quickly too, and the only still point of reference is part of the space station itself at the top of the photograph.

Lots of nail biting on the eve of a historic launch

With the first commercial spacecraft to attempt docking with the International Space Station waiting on the launch pad, nerves and excitement are high. And hours before the historic launch, officials from NASA and private company SpaceX are managing expectations.

"It bears repeating that this is a test flight," said director for NASA Commercial Spaceflight Development Phil McAlister in a press conference today, where he was reluctant to even use the word "success". "NASA views test flights as learning opportunities."

The cargo-carrying Dragon capsule has a long list of firsts to achieve in the next few days. It's scheduled to launch at 4:15 am eastern time tomorrow, and will spend the first 24 hours catching up with the International Space Station in low-Earth orbit. At around hour 40, it will begin a choreographed dance around the space station to make sure it's sufficiently under control to attempt docking. Astronauts on the space station will test communications with the Dragon and can abort the mission at any time.

If everything goes well, Dragon will dock to the space station by 75 hours after launch, early morning on Tuesday 22 May.

"If successful, there's no question this is the historic flight," said SpaceX president Gwynne Shotwell. "I think we're going to be biting off our fingers between now and hour 75."

Shotwell also stressed that this is a test flight and things could go wrong.

"Success is not going to mean the success of the commercial space industry, and failure is not going to mean the failure of the commercial space industry," she said. "We'd hope that every flight is successful, that would make my job incredibly easy. But I don't want to say that, I don't think that's realistic."

Despite that, she has an optimistic view of the future. The company has 17 launches planned in the next three years, and could be bringing astronauts into space as early as 2015, Shotwell says - although McAlister says it may be more like 2017 before they're certified to fly NASA astronauts.

And the transition from big government organizations to private companies navigating the skies may be inevitable, he added.

"Once we get the private sector out there, there will be no turning back," he said. "[Spaceflight] will no longer be subject to the prevailing political winds. It will just push further and further out, no more looking backwards, only looking forwards."