The researchers believe that measuring RBP4 would potentially be an effective way to assess body fat, and that treatment to cut levels of the protein might also have health benefits.

In previous work, they showed that cutting RBP4 levels in obese mice helped the animals to make better use of the hormone insulin - and thus reduce their risk of diabetes.

They also showed that measures to improve insulin sensitivity in human subjects resulted in a drop in RPB4 levels.

Researcher Dr Matthias Bluher said: "We believe that in the near future, measurements of RBP4 serum concentrations might serve as a novel biomarker for visceral obesity and increased risk for type 2 diabetes and other adverse outcomes of visceral obesity.

"In addition, pharmacological interventions that reduce RBP4 levels might be a new approach in the treatment of metabolic syndrome and visceral obesity."

The only known function of RBP4 is to carry vitamin A in the blood.

The fibers that make up blood clots are more elastic than rubber bands and stretchier than spider webs. They're even tougher than doctors suspected - a discovery that could lead to improved treatment of heart attacks and strokes.

Understanding how much these fibers can be stretched before they break should point to better ways to bust up blood clots on demand.

Made of a protein called fibrin, the fibers are stretchier than any other naturally occurring ones, even super-stretchy spider silk, concluded researchers who rigged up a double-microscope to measure how tough the tiny strands -- 1,000 times smaller than a human hair -- really are.

Astrocytes produce fat-like lipid neurons used to create their outer membranes and they also produce glutamate, the most abundant neurotransmitter in the nervous system and one of the most important chemical messengers in the brain.

Recent experiments, however, revealed that astrocytes form connections with blood vessels and control the flow of nutrients, including oxygen, to neurons. When brain activity increases, neurons trigger astrocytes to release calcium, which in turn affects other chemical messengers that can cause blood vessels to either dilate or contract.

The classical symptoms of memory loss and dementia associated with Alzheimer's are the result of neurons dying over a period of years. Brain scans of Alzheimer's patients show decreased blood flow to critical parts of the brain, and doctors have always assumed that this was because there was less of a demand for blood because there were fewer neurons to feed.

The new result could mean that Alzheimer's affects mainly astrocytes and not neurons and that blood flow to the brain is not decreased because the neurons are dying, but that the neurons are dying because there is decreased blood flow.

"It may be that for whatever reason, astrocytes are not doing their job properly, and then blood flow decreases," Nedergaard said. "This could lead to the death of the neurons, which would starve from a lack of nutrients, since the neurons depend on the astrocytes for their survival."

"Previous studies suggest flavonoid-rich foods, including fruits, vegetables, tea, red wine and chocolate, might offer cardiovascular benefits, but this is one of the first clinical trials to look specifically at dark chocolate's effect on lowering blood pressure among people with hypertension," said Jeffrey Blumberg of Tufts University in Boston, who led the study.

"This study is not about eating more chocolate," Blumberg added. "It suggests that cocoa flavonoids appear to have benefits on vascular function and glucose sensitivity."

"White chocolate, which has no flavonoids, was the perfect control food because it contains all the other ingredients and calories found in dark chocolate," Blumberg said.

"It's important to note that the dark chocolate we used had a high level of flavonoids, giving it a slightly bittersweet taste. Most Americans eat milk chocolate, which has a low amount of these compounds."

Writing in the journal Hypertension, Blumberg's team said when the volunteers ate the special dark chocolate, they had a 12 mm Hg decrease in systolic blood pressure (the top number in a blood pressure reading) and a 9 mm Hg decrease in diastolic blood pressure (the bottom number) on average.

Blood pressure did not change when the volunteers ate white chocolate.

"This is not only a statistically significant effect, but it's also a clinically meaningful decline," Blumberg said. "This is the kind of reduction in blood pressure often found with other healthful dietary interventions."