Vitamin D may prolong survival

COLON CANCER
Vitamin D has been linked to numerous health benefits: Several studies have suggested that it may help prevent the progression of diseases like osteoporosis and multiple sclerosis. Now, research from the Dana-Farber Cancer Institute reveals that vitamin D may also may reduce mortality from colon cancer. The vitamin helps to shuttle the calcium we eat from the gut to the rest of the body. However, it probably also acts as a conductor of a cellular orchestra - telling our cells when to grow and when to stop dividing. If the body becomes deficient of vitamin D, cellular division may go awry, leading to cancer development. Lead researcher Dr. Kimme Ng and colleagues decided to investigate whether patients with higher levels of vitamin D in their blood had lower rates of mortality from colon cancer. They identified 304 patients diagnosed with colorectal cancer from the large Nurses' Health Study and the Health Professionals Follow-up Study, and between 1991 and 2005, 96 of the patients died from this cancer.Patients with higher levels of vitamin D had nearly a 50 percent reduction in their risk of death.

BOTTOM LINE: Higher vitamin D levels are associated with better survival of colorectal cancer patients. CAUTIONS: The study could not rule out other explanations for the reduced death rates among patients with higher vitamin D levels. More rigorous studies need to be done. "The data is still too premature to recommend vitamin D for colon cancer patients," Ng said.

WHAT'S NEXT: Randomized controlled trials are planned to assess vitamin D as a potential therapeutic agent in colorectal cancer.

WHERE TO FIND IT: The Journal of Clinical Oncology, June 20. SUSHRUT JANGI

NEUROSCIENCE

A hundred years after star-shaped cells called astrocytes were found in the brain, MIT scientists say they have finally discovered the function of these pervasive cells. The finding also seems to explain how a widely used scanning technique that has transformed neuroscience measures brain activity. Much of what we know about the brain has come from using microelectrodes to record the electrical activity of neurons, but astrocytes have remained mysterious because they do not generate electrical spikes. Mriganka Sur and colleagues from the Department of Brain and Cognitive Sciences and the Picower Institute for Learning and Memory got around this problem using a powerful imaging technique called two-photon microscopy, which allowed them to monitor intracellular calcium levels of astrocytes in the visual cortex of ferret brains. They discovered, to their amazement, that the astrocytes had precise responses to visual stimuli and were actually "blinking" when stimulated, just like neurons. They observed that the astrocytes, whose tendrils extend around the synapses where neurons communicate with one another and along blood vessels, were "listening" in at the synapses and regulating blood flow. This reveals why brain scans like functional MRIs, which record changes in blood flow, are accurate depictions of brain activity. Because astrocytes are now seen to be a crucial element of neuronal networks, better understanding their role may also help explain the development of brain disorders like autism or Alzheimer's disease.

BOTTOM LINE: "After a century we have understood the function of astrocytes," said Sur. "They are not silent components of the brain."

CAUTIONS: The study recorded astrocytes in just the visual cortex. It's not known whether astrocytes in the rest of the brain behave similarly.

WHAT'S NEXT: "Next we plan to examine the influences of astrocyte activity on the processing of visual stimuli by neurons in the visual cortex," said James Schummers, the study's co-author.

WHERE TO FIND IT: Science, June 20

SENA DESAI GOPAL