It may be old news that people who work the night shift tend to have higher rates of certain medical conditions. But researchers say they have established a direct link between an abnormal sleep cycle and altered hormone levels, which can disrupt metabolism and increase the risk of heart disease, diabetes, and obesity. As soon as their circadian rhythms became separated from a day-night cycle, test subjects’ levels of key metabolic hormones went haywire—the most compelling evidence yet that shift work isn’t just an inconvenience, but an occupational hazard [Wired News].
The study, published in the Proceedings of the National Academy of Sciences, maps a clear path from work-sleep cycles to metabolic disregulation to disease [Wired News]. Scientists cannot yet explain the exact connection between metabolism and the circadian rhythm, the roughly 24-hour cycle that biological and behavioral processes are based on. But they believe the trigger to be a decrease in the hormone leptin, which the body uses to regulate appetite, that results when the circadian rhythm is disrupted.
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Spikes in blood sugar levels seem to be linked to memory problems, and may be a major factor in the normal memory and cognitive problems that crop up as people age, according to a new study. People’s ability to regulate blood sugar begins to deteriorate by their third or fourth decade and continues to decline, so older people are more prone to these sugar spikes. “This would suggest that anything to improve regulation of blood glucose would potentially be a way to ameliorate age-related memory decline,” said senior study author Dr. Scott Small…. The findings may also help explain why people who exercise don’t have as many cognitive problems as they age: Exercise helps stabilize blood glucose levels [HealthDay News].
The findings have important implications for the increasing number of overweight children who are at risk of diabetes, commented neuroscientist Bruce McEwen. “When we think about diabetes, we think about heart disease and all the consequences for the rest of the body, but we usually don’t think about the brain,” he said. “This is something we’ve got to be really worried about. We need to think about their ultimate risks not only for cardiovascular disease and metabolic disorders, but also about their cognitive skills, and whether they will be able to keep up with the demands of education and a fast-paced complex society. That’s the part that scares the heck out of me” [The New York Times].
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For the first time, scientists have derived and cultured embryonic stem (ES) cells from rats, paving the way for genetically engineered rats that would more accurately model some human diseases than the currently available genetically engineered mice. Two collaborating teams developed a new approach to derive the ES cells, using a new cocktail of molecules to protect their precious pluripotency, the ability to differentiate into any type of cell. “This is a major development in stem cell research because we know that rats are much more closely related to humans than mice in many aspects of biology. The research direction of many labs around the world will change because of the availability of rat ES cells,” says Qilong Ying [Xinhua], who led one of the teams.
ES cells from mice have been available since 1981, and different researchers have created hundreds of different strains of “knock-out” mice—ones raised from ES cells in which certain genes are silenced to make apparent the genes’ functions. With mice, ES cells were grown with a mixture of growth signals to make them divide without differentiating. But transferring the same technique to rats and other mammals proved surprisingly difficult. To the great frustration of researchers, stem cells isolated from rat embryos and cultured with growth signals would quickly lose their pluripotency. The new strategy, reported in two studies in Cell [subscription required], involves growing the ES cells in a mixture of three key molecules that block the signals that normally induce differentiation. “Our discovery was that if you want to maintain cells in the undifferentiated state, you must block signals, not activate them,” says Ying… By repressing differentiation, the researchers could hold the cells in what they call a “ground state,” a blank slate ready to turn into any tissue in the body [Science News].
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A drug that mimics the effects of a compound found in red wine has been shown to prevent obesity and diabetes in mice that were fed a high-calorie diet and prevented from exercising, taking another step towards the target of a anti-obesity pill. The natural compound found in grapes and red wine, called resveratrol, is believed to have numerous health benefits related to longevity, heart health, and metabolism. But tests in mice suggested gallons of wine would be necessary for humans to stand a chance of getting the same benefits. The scientists turned their attention to creating a more potent drug [BBC News].
The new experimental drug, called SRT1720, was developed by the pharmaceutical company GlaxoSmithKline. Researchers explain that mice fed a high-fat diet were tricked into switching their metabolisms to a fat-burning mode that normally takes over when energy levels are low…. “We are activating the same enzymes that are activated when people go to the gym,” said Peter Elliott, a vice president at Sirtris Pharmaceuticals, the Glaxo unit that developed the drug. “That is why we believe the profile for this drug is very safe” [Reuters].
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While the nation decides on the fate of Barack Obama and John McCain tomorrow, residents of Michigan will also decide on the fate of thousands of human embryos. They will be voting on Proposition 2, an amendment to the state constitution that would lift a 30-year-old ban on the destruction of human embryos to get stem cells for medical research. Currently, researchers in the state must import embryonic stem cell lines from other states or countries. (Research on embryonic stem cells is legal in Michigan, but not the destruction of embryos.) The nationwide ban on federal funding for most embryonic stem cell research, instituted in 2001, will still hold, although both Obama and McCain have stated they would lift the ban if elected.
Proposition 2 pits the state’s powerful public and private biological research centers against large, conservative Catholic and evangelical populations who oppose destroying embryos, a form of human life [Wall Street Journal]. The proposition is sponsored by the bipartisan group Cure Michigan. Proponents argue embryos in fertility clinics are routinely thrown away, so why not donate them to science [Detroit Free Press]? The U. S. currently has 400,000 frozen embryos in storage, most of which will be discarded. Supporters say embryonic stem cell research could lead to therapies for degenerative diseases like Alzheimer’s and juvenile diabetes, and that lifting the ban would advance the state’s biomedical industry and create thousands of new jobs.
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In a discovery that’s being hailed as a leap forward in regenerative medicine, researchers have found a way to transform common pancreatic cells in an adult mouse into the rare, insulin-producing beta cells that are destroyed in type 1 diabetes. Previously, researchers believed that the only way to transmute an adult cell was to first coax it back into stem cell form and then to reprogram it; this new research removes the first step entirely.
The accomplishment raises the tantalizing prospect that patients suffering from not only diabetes but also heart disease, strokes and many other ailments could eventually have some of their cells reprogrammed to cure their afflictions without the need for drugs, transplants or other therapies. “It’s kind of an extreme makeover of a cell,” said [lead researcher] Douglas A. Melton…. “The goal is to create cells that are missing or defective in people. It’s very exciting” [Washington Post].
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A new study has shown that people with small amounts of arsenic in their urine are more likely to suffer from diabetes, and raises the possibility that drinking tap water contaminated with trace amounts of arsenic may be a risk factor for the disease. The [diabetes] risk was apparent at levels generally considered harmless and grew with increasing exposure [Bloomberg].
“It seems there is may be no safe level of arsenic,” [lead researcher Ana] Navas-Acien said in a telephone interview. “Worldwide it’s a huge problem” [Reuters]. Previous epidemiological studies in Bangladesh, Mexico, and Taiwan have shown that drinking water with high levels of arsenic in linked to high rates of diabetes. While safety standards for drinking water are much stricter in the United States, researchers say that 13 million Americans may be drinking water with arsenic levels that exceed federal guidelines. People in rural areas who drink well water may be particularly at risk, researchers say.
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At a scientific meeting of the American Diabetes Association this weekend, researchers had some disappointing and some downright confusing news. Two new studies showed that contrary to expectations, drastically cutting blood-sugar levels in diabetic patients did nothing to reduce their risk of heart disease and strokes.
In the most disquieting result, one of the studies was halted early because the patients who were given intensive treatment to lower their blood sugar had a higher death rate. Researchers say they don’t know whether to blame the treatment regimen, a mix of diabetes drugs and insulin, or the patients’ reduced blood-sugar levels. However, the second study showed no similar increase in mortality rates.
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