Chapter 9. Homeostasis: Active Regulation of the Internal Environment
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
By Brady Dennis The Food and Drug Administration on Wednesday approved a device aimed at helping obese people shed weight in a novel way – by targeting the nerve pathway between the brain and the stomach that controls feelings of hunger and fullness. The Maestro Rechargeable System, as it is known, consists of an electrical charge generator, wire leads and electrodes that are implanted surgically into a patient’s abdomen. It sends electrical pulses designed to interfere with the vagus nerve, which signals to the brain when the stomach is full or empty. Though researchers don't know exactly how such electrical stimulation leads to weight loss, the approach seems promising. In a year-long clinical trial involving 233 patients with a body-mass index, or BMI, of 35 or greater, those who received a working Maestro device lost 8.5 percent more weight than those without it. About half those in the experimental group lost at least 20 percent of their excess weight, and more than a third lost more than 25 percent of their excess weight. The overall figure was below the original goal of the trial, which was to show weight loss of 10 percent more excess weight in the control group than in those using the new device. Nevertheless, an FDA advisory group said the data showed sustained weight loss among participants and argued that the benefits of the device outweigh its risks for certain patients. In the clinical trial, some patients experienced nausea, vomiting, surgical complications and other side effects. The FDA is requiring the device's manufacturer, EnteroMedics, to conduct a five-year, post-approval study to gather additional data about its safety and effectiveness.
Link ID: 20488 - Posted: 01.15.2015
Carl Zimmer Among scientists who study how our DNA affects our weight, a gene called FTO stands out. “It’s the poster child for the genetics of obesity,” said Struan F. Grant, an associate professor of pediatrics at the University of Pennsylvania School of Medicine. In 2007, researchers discovered that people with a common variant of FTO tend to be heavier than those without it. Since then, studies have repeatedly confirmed the link. On average, one copy of the risky variant adds up to 3.5 extra pounds of weight. Two copies of the gene bring 7 extra pounds — and increase a person’s risk of becoming obese by 50 percent. But the gene doesn’t seem to have always been a problem. If scientists had studied FTO just a few decades ago, they would have found no link to weight whatsoever. A new study shows that FTO became a risk only in people born after World War II. The research, published this week in the Proceedings of the National Academy of Sciences, raises questions that extend far beyond obesity. Genes clearly influence our health in many ways, but so does our environment; often, it is the interplay between them that makes the difference in whether we develop obesity or cancer or another ailment. But the relative importance of certain genes may shift over the years, the new study suggests, as our environment changes. James Niels Rosenquist of Massachusetts General Hospital and his colleagues were inspired to conduct the study by recent research documenting how people’s experiences alter the effects of their genes. A variant of a gene called AKT1, for example, can raise the risk of psychosis — but only if the carrier smokes a lot of marijuana. If he avoids smoking, the AKT1 variant doesn’t cause a problem. © 2015 The New York Times Company
By James Gallagher Health editor, BBC News website Higher rates of obesity and ill-health have been found in shift workers than the general population. Health Survey for England data showed they were in worse health despite often being young. The lead researcher told the BBC that the rise of zero-hours contracts may be increasing the numbers doing shift work and could raise "pretty serious problems" for the nation's health. Scientists said it was "fairly clear now" that shift work was unhealthy. The report, by the Health and Social Care Information Centre, showed 33% of men and 22% of women of working age were doing shift work. They defined shifts as employment outside 0700-1900. Rachel Craig, the research director for the Health Survey for England, told the BBC: "Overall, people who are doing shift work are not quite as healthy as their counterparts doing regular working hours." The data showed 30% of shift workers were obese, compared with 24% of men and 23% of women doing normal hours. Meanwhile, 40% of men and 45% of women on shifts had long-standing health conditions such as back-pain, diabetes or chronic obstructive pulmonary disease compared with 36% and 39% of the rest of the population. Younger people Shift working is most common in the 16-24 age group with nearly half of men and a third of women having this working pattern. The rates fell with age so that fewer than a third of men and a fifth of women were working shifts after the age of 55. Ms Craig said that, overall, young people should be in better health: "You'd expect less ill-health and fewer long-standing conditions that reflect lifestyle like obesity, so it makes it an even stronger relationship [between shifts and poor health]." BBC © 2014
by Andy Coghlan It may not sound very appetising, but an edible powder made from waste excreted by bacteria in our guts may help people to avoid gaining weight. Stabilising a person's weight could have a major health impact, says Gary Frost of Imperial College London, because as people on Western diets grow older, they tend to put on between 0.3 and 0.8 kilograms per year on average. A fatty acid called propionate is released when the bacteria in our gut digest fibre. Propionate makes people feel full by activating cells in the large intestine that produce the satiety hormones GLP-1 and PYY: these tell the brain that it's time to stop eating. But to trigger a big enough dose of this appetite-suppressing signal from gut bacteria alone, people would have to eat extremely large amounts of fibre. To get around that, Frost and his team made the molecule in a concentrated form called inulin-propionate ester (IPE). "That gives you eight times the amount of someone following a typical Western diet," he says. To test its appetite-stemming properties, the team gave powdered IPE, mixed in with fruit juice or a milkshake, to a group of overweight volunteers every day for six months. A type of ordinary fibre was given to another set of people, who acted as controls. Only one of the 25 volunteers taking IPE put on more than 3 per cent of their body weight over that time, compared with six of the 24 controls. One reason for this might be that the IPE recipients ate around 9 per cent less over the six months. © Copyright Reed Business Information Ltd.
Link ID: 20416 - Posted: 12.13.2014
By Dr. Mitesh Popat It’s common knowledge that eating better, exercising more, limiting alcohol intake and not smoking can lead to a healthier, longer life. For many, sustaining healthy behaviors is not easy. For diabetics, maintaining healthy behaviors is even more challenging, although it is critical. If well managed, the disease can be held in check; if not, it can be devastating, leading to kidney failure, blindness, stroke and even death. It may be a surprise that there is strong association between depression, anxiety and diabetes. Not only can depression and anxiety seriously affect the ability to manage the disease, but there also is evidence that, for some, depression plays a role in actually causing diabetes. Research indicates that depression is unrecognized and untreated in approximately two-thirds of patients with diabetes. Whether cause or effect, the medical profession needs to do more to address the psychological issues associated with the disease. As a family medicine physician, I see the association on daily basis. Some patients are so overwhelmed by the necessary daily self-care that comes with diabetes that they become highly anxious and depressed. Others who are suffering from complications or are having trouble managing their blood sugar levels may feel a loss of control and get anxious or depressed. These symptoms are often compounded in people who live in poverty, including the low-income Latinos, African Americans and seniors whom we care for at Marin Community Clinics. Diabetes has become an epidemic in these groups. Working three jobs and constantly worrying about making ends meet can trigger depression and anxiety in anyone. Add to that the need to adopt a disciplined healthy lifestyle, and it can be a real struggle.
Link ID: 20410 - Posted: 12.13.2014
By Nsikan Akpan Gut surgery is often the only option for life-threatening obesity and diabetes, but what if doctors could cut the pounds without using a knife? Scientists have engineered an antiobesity drug that rivals the dramatic benefits seen with surgery, dropping excess body weight by a third. Though the work was done only in rodents, the drug is the first to influence three obesity-related hormones in the gut at once. Bariatric surgery, including gastric bypass, typically involves limiting food intake by removing part of the stomach or intestines. Yet it does more than shrink the size of patient’s stomach or intestines. It also changes the release of multiple gut-related hormones, explains clinical endocrinologist Stephen O'Rahilly of the University of Cambridge in the United Kingdom, who wasn’t involved with the study. That’s important, because years of eating a diet high in fat and sugar can throw a person’s metabolism into disarray. Cells undergo genetic reprogramming that negatively impacts how they process sugar and store fat, locking in obesity. This pattern makes it harder and harder to lose weight, even if a person changes their diet and begins exercising. Bariatric surgery interrupts that cycle by stimulating the production of several hormones that reduce blood sugar, burn fat, and curb appetite. (It may also change the composition of the gut’s microbes.) Three of these hormones are called glucagon-like peptide-1 (GLP-1), gastric inhibitory peptide (GIP), and glucagon. Cells in your gut release GLP-1 and GIP after a meal to keep your body’s blood sugar levels in a normal range. GLP-1 also curbs appetite, signaling to your brain that you are full. In type 2 diabetes, the body stops responding to GLP-1 and GIP, which contributes to hyperglycemia, or too much blood sugar. Hyperglycemia causes the devastating hallmarks of diabetes, such as kidney injury, cardiovascular disease, and nerve damage. © 2014 American Association for the Advancement of Science.
Link ID: 20408 - Posted: 12.10.2014
by Michael Slezak The elusive link between obesity and high blood pressure has been pinned down to the action of leptin in the brain, and we might be able to block it with drugs. We've known for more than 30 years that fat and high blood pressure are linked, but finding what ties them together has been difficult. One of the favourite candidates has been leptin – a hormone produced by fat cells. Under normal circumstances, when fat cells produce leptin, the hormone sends the message that you've had enough food. But in people with obesity, the body stops responding to this message, and large levels of leptin build up. Leptin is known to activate the regulatory network called the sympathetic nervous system, and it's the activation of sympathetic nerves on the kidneys that seem to be responsible for raising blood pressure. Leptin has thus been linked to blood pressure. However, conclusive evidence has been hard to come by. Michael Cowley of Monash University in Melbourne, Australia, and his colleagues have now conducted a string of experiments that provide some evidence. Through genetic and drug experiments in mice, they have pinpointed an area in the mouse brain that increases blood pressure when it is exposed to high leptin levels. This region is called the dorsomedial hypothalamus, and is thought to be involved in controlling energy consumption. Their findings show that high levels in leptin do indeed boost blood pressure, via this brain region. © Copyright Reed Business Information Ltd.
Link ID: 20398 - Posted: 12.06.2014
By Nicholas Bakalar Researchers have found that people diagnosed with diabetes in their 50’s are significantly more likely than others to suffer mental decline by their 70’s. The study, published Monday in the Annals of Internal Medicine, started in 1990. Scientists examined 13,351 black and white adults, aged 48 to 67, for diabetes and prediabetes using self-reported physician diagnoses and glucose control tests. They also administered widely used tests of memory, reasoning, problem solving and planning. About 13 percent had diabetes at the start. The researchers followed them with five periodic examinations over the following 20 years. By that time, 5,987 participants were still enrolled. After adjusting for numerous health and behavioral factors, and for the large attrition in the study, the researchers found people with diabetes suffered a 30 percent larger decline in mental acuity than those without the disease. Diabetes can impair blood circulation, and the authors suggest that the association of diabetes with thinking and memory problems may be the result of damage to small blood vessels in the brain. “People may think cognitive decline with age is inevitable, but it’s not,” said the senior author, Elizabeth Selvin, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. “Factors like diabetes are potentially modifiable. If we can better control diabetes we can stave off cognitive decline and future dementia.” © 2014 The New York Times Company
By Elizabeth Pennisi The microbes that live in your body outnumber your cells 10 to one. Recent studies suggest these tiny organisms help us digest food and maintain our immune system. Now, researchers have discovered yet another way microbes keep us healthy: They are needed for closing the blood-brain barrier, a molecular fence that shuts out pathogens and molecules that could harm the brain. The findings suggest that a woman's diet or exposure to antibiotics during pregnancy may influence the development of this barrier. The work could also lead to a better understanding of multiple sclerosis, in which a leaky blood-brain barrier may set the stage for a decline in brain function. The first evidence that bacteria may help fortify the body’s biological barriers came in 2001. Researchers discovered that microbes in the gut activate genes that code for gap junction proteins, which are critical to building the gut wall. Without these proteins, gut pathogens can enter the bloodstream and cause disease. In the new study, intestinal biologist Sven Pettersson and his postdoc Viorica Braniste of the Karolinska Institute in Stockholm decided to look at the blood-brain barrier, which also has gap junction proteins. They tested how leaky the blood-brain barrier was in developing and adult mice. Some of the rodents were brought up in a sterile environment and thus were germ-free, with no detectable microbes in their bodies. Braniste then injected antibodies—which are too big to get through the blood-brain barrier—into embryos developing within either germ-free moms or moms with the typical microbes, or microbiota. © 2014 American Association for the Advancement of Science
Link ID: 20338 - Posted: 11.20.2014
By Nicholas Bakalar Exposure to secondhand smoke and roadway traffic may be tied to increased body mass index in children and adolescents, a new study suggests. Researchers studied 3,318 children in 12 Southern California communities beginning at an average age of 10, and then followed them through age 18. They used parental questionnaires to establish exposure to smoking, and data on traffic volume and levels of nitrogen dioxide, ozone and particulates to track pollution. The study, in Environmental Health Perspectives, controlled for many other factors: sex, initial B.M.I., asthma, physical activity, insurance status, parental education and income, acres of parks and open space nearby, percentage of people living in poverty in each community. But even after accounting for these issues and more, they found that compared with children exposed to no secondhand smoke or near-roadway air pollution, B.M.I. was 0.80 higher in children exposed to pollution alone, 0.85 higher in those exposed to secondhand smoke alone, and 2.15 higher in those exposed to both. A normal B.M.I. for adults is 18.5 to 24.9. Higher than 25 is considered overweight, and above 30 obese. “It would be interesting to know more about the mechanism,” said the lead author, Dr. Rob McConnell, a professor of preventive medicine at the University of Southern California. “But the finding challenges the view that obesity is due solely to increased caloric intake and reduced physical activity. That’s not the whole story.” © 2014 The New York Times Company
By Adam Brimelow Health Correspondent, BBC News A Mediterranean diet may be a better way of tackling obesity than calorie counting, leading doctors have said. Writing in the Postgraduate Medical Journal (PMJ), the doctors said a Mediterranean diet quickly reduced the risk of heart attacks and strokes. And they said it may be better than low-fat diets for sustained weight loss. Official NHS advice is to monitor calorie intake to maintain a healthy weight. Last month NHS leaders stressed the need for urgent action to tackle obesity and the health problems that often go with it. The PMJ editorial argues a focus on food intake is the best approach, but it warns crash dieting is harmful. Signatories of the piece included the chair of the Academy of Medical Royal Colleges, Prof Terence Stephenson, and Dr Mahiben Maruthappu, who has a senior role at NHS England. They criticise the weight-loss industry for focusing on calorie restriction rather than "good nutrition". And they make the case for a Mediterranean diet, including fruit and vegetables, nuts and olive oil, citing research suggesting it quickly reduces the risk of heart attacks and strokes, and may be better than low-fat diets for sustained weight loss. The lead author, cardiologist Dr Aseem Malhotra, says the scientific evidence is overwhelming. "What's more responsible is that we tell people to concentrate on eating nutritious foods. "It's going to have an impact on their health very quickly. We know the traditional Mediterranean diet, which is higher in fat, proven from randomised controlled trials, reduces the risk of heart attack and stroke even within months of implementation." The article also says adopting a Mediterranean diet after a heart attack is almost three times as effective at reducing deaths as taking cholesterol-lowering statin medication. BBC © 2014
Link ID: 20316 - Posted: 11.17.2014
Sara Reardon Companies selling ‘probiotic’ foods have long claimed that cultivating the right gut bacteria can benefit mental well-being, but neuroscientists have generally been sceptical. Now there is hard evidence linking conditions such as autism and depression to the gut’s microbial residents, known as the microbiome. And neuroscientists are taking notice — not just of the clinical implications but also of what the link could mean for experimental design. “The field is going to another level of sophistication,” says Sarkis Mazmanian, a microbiologist at the California Institute of Technology in Pasadena. “Hopefully this will shift this image that there’s too much commercial interest and data from too few labs.” This year, the US National Institute of Mental Health spent more than US$1 million on a new research programme aimed at the microbiome–brain connection. And on 19 November, neuroscientists will present evidence for the link in a symposium at the annual Society for Neuroscience meeting in Washington DC called ‘Gut Microbes and the Brain: Paradigm Shift in Neuroscience’. Although correlations have been noted between the composition of the gut microbiome and behavioural conditions, especially autism1, neuroscientists are only now starting to understand how gut bacteria may influence the brain. The immune system almost certainly plays a part, Mazmanian says, as does the vagus nerve, which connects the brain to the digestive tract. Bacterial waste products can also influence the brain — for example, at least two types of intestinal bacterium produce the neurotransmitter γ-aminobutyric acid (GABA)2. © 2014 Nature Publishing Group
By Katy Waldman How much control do you have over how much control you think you have? The researchers Michael R. Ent and Roy F. Baumeister have been studying what makes a person more or less likely to believe in free will. Is it a deep connection to the philosophy of David Hume? An abiding faith in divine omnipotence? Try a really, really full bladder. In an online survey, 81 adults ages 18 to 70 reported the extent to which they felt hungry, tired, desirous of sex, and desirous of a toilet. They then rated the extent to which they considered themselves in command of their destinies. People experiencing intense physical needs were less likely to say they believed in free will. People who were not inexplicably taking an online survey while desperately holding in their pee (or starving, or wanting sex, or trying to stay awake) mostly claimed that the universe had handed them the keys to their lives. Also, people who brought their laptops with them into the bathroom to fill out the survey reported that they were God. (I kid on that last part.) Ent and Baumeister also used a survey to take the free will temperature of 23 people with panic disorder, 16 people with epilepsy, and 35 healthy controls. Those suffering from the two conditions—both of which can unpredictably plunge the mind into chaos—tended to put less stock in the notion of mental autonomy. There was a third experiment, too. I said earlier that people not taking an online survey while jonesing for various creature comforts mostly claimed that they wore the metaphysical pants. However, despite robust results for horniness, fatigue, and needing-to-go-ness, Ent and Baumeister didn’t initially see much correlation between people’s philosophical visions and their hunger levels. So they re-administered the survey to 112 new volunteers, some of whom were dieting and some of whom were not. © 2014 The Slate Group LLC.
Link ID: 20294 - Posted: 11.10.2014
By James Gallagher Health editor, BBC News website Weight loss surgery can dramatically reduce the odds of developing type 2 diabetes, according to a major study. Doctors followed nearly 5,000 people as part of a trial to assess the health impact of the procedure. The results, published in the Lancet Diabetes and Endocrinology journal, showed an 80% reduction in type 2 diabetes in those having surgery. The UK NHS is considering offering the procedure to tens of thousands of people to prevent diabetes. Obesity and type 2 diabetes are closely tied - the bigger someone is, the greater the risk of the condition. The inability to control blood sugar levels can result in blindness, amputations and nerve damage. Around a tenth of NHS budgets are spent on managing the condition. Surgery The study followed 2,167 obese adults who had weight loss - known as bariatric - surgery. They were compared to 2,167 fellow obese people who continued as they were. There were 38 cases of diabetes after surgery compared with 177 in people left as they were - a reduction of nearly 80%. Around 3% of morbidly obese people develop type 2 each year, however, surgery reduced the figure to around 0.5%, which is the background figure for the whole population. Bariatric surgery, also known as weight loss surgery, is used as a last resort to treat people who are dangerously obese and carrying an excessive amount of body fat. This type of surgery is available on the NHS only to treat people with potentially life-threatening obesity when other treatments have not worked. Around 8,000 people a year currently receive the treatment. The two most common types of weight loss surgery are: Gastric band, where a band is used to reduce the size of the stomach so a smaller amount of food is required to make someone feel full Gastric bypass, where the digestive system is re-routed past most of the stomach so less food is digested to make someone feel full BBC © 2014
Link ID: 20269 - Posted: 11.03.2014
Daniel Duane, Men's Journal For more than half a century, the conventional wisdom among nutritionists and public health officials was that fat is dietary enemy No. 1 — the leading cause of obesity and heart disease. It appears the wisdom was off. And not just off. Almost entirely backward. According to a new study from the National Institutes of Health, a diet that reduces carbohydrates in favor of fat — including the saturated fat in meat and butter — improves nearly every health measurement, from reducing our waistlines to keeping our arteries clear, more than the low-fat diets that have been recommended for generations. "The medical establishment got it wrong," says cardiologist Dennis Goodman, director of Integrative Medicine at New York Medical Associates. "The belief system didn't pan out." It's not the conclusion you would expect given the NIH study's parameters. Lead researcher Lydia Bazanno, of the Tulane University School of Public Health, pitted this high-fat, low-carb diet against a fat-restricted regimen prescribed by the National Cholesterol Education Program. "We told both groups to get carbs from green, leafy vegetables, because those are high in nutrients and fiber to keep you sated," Bazanno says. "We also told everyone to stay away from trans fats." The fat-restricted group continued to eat carbs, including bread and cereals, while keeping saturated fat — common in animal products — below 7 percent of total calories. By contrast, the high-fat group cut carbs in half and did not avoid butter, meat, and cheese. Most important, both groups ate as much as they wanted — no calorie counting, no going hungry.
Link ID: 20251 - Posted: 10.28.2014
By Gary Stix Scott Small, a professor of neurology at Columbia University’s College of Physicians and Surgeons, researches Alzheimer’s, but he also studies the memory loss that occurs during the normal aging process. Research on the commonplace “senior moments” focuses on the hippocampus, an area of the brain involved with formation of new memories. In particular, one area of the hippocampus, the dentate gyrus, which helps distinguish one object from another, has lured researchers on age-related memory problems. In a study by Small and colleagues published Oct. 26 in Nature Neuroscience, naturally occurring chemicals in cocoa increased dentate gyrus blood flow. Psychological testing showed that the pattern recognition abilities of a typical 60-year-old on a high dose of the cocoa phytochemicals in the 37-person study matched those of a 30-or 40-year old after three months. The study received support from the food company Mars, but Small cautions against going out to gorge on Snickers Bars, as most of the beneficial chemicals, or flavanols, are removed when processing cocoa. An edited transcript of an interview with Small follows: Can you explain what you found in your study? The main motive of the study was to causally establish an anatomical source of age-related memory loss. A number of labs have shown in the last 10 years that there’s one area of the brain called the dentate gyrus that is linked to the aging process. But no one has tested that concept. Until now the observations have been correlational. There is decreased function in that region and, to prove causation, we were trying to see if we could reverse that. © 2014 Scientific American
Keyword: Learning & Memory
Link ID: 20245 - Posted: 10.27.2014
By GABRIELE OETTINGEN MANY people think that the key to success is to cultivate and doggedly maintain an optimistic outlook. This belief in the power of positive thinking, expressed with varying degrees of sophistication, informs everything from affirmative pop anthems like Katy Perry’s “Roar” to the Mayo Clinic’s suggestion that you may be able to improve your health by eliminating “negative self-talk.” But the truth is that positive thinking often hinders us. More than two decades ago, I conducted a study in which I presented women enrolled in a weight-reduction program with several short, open-ended scenarios about future events — and asked them to imagine how they would fare in each one. Some of these scenarios asked the women to imagine that they had successfully completed the program; others asked them to imagine situations in which they were tempted to cheat on their diets. I then asked the women to rate how positive or negative their resulting thoughts and images were. A year later, I checked in on these women. The results were striking: The more positively women had imagined themselves in these scenarios, the fewer pounds they had lost. My colleagues and I have since performed many follow-up studies, observing a range of people, including children and adults; residents of different countries (the United States and Germany); and people with various kinds of wishes — college students wanting a date, hip-replacement patients hoping to get back on their feet, graduate students looking for a job, schoolchildren wishing to get good grades. In each of these studies, the results have been clear: Fantasizing about happy outcomes — about smoothly attaining your wishes — didn’t help. Indeed, it hindered people from realizing their dreams. © 2014 The New York Times Company
Clare Pain Eating a high fat and high carb diet resulted in inflammation in the brain - at least in male mice. We'll have to wait to see if the same process applies to male humans. The detrimental impact of junk food seems to be connected to inflammation in the brains of male mice, with the brains of females protected by oestrogen, according to research published today in Cell Reports. Dr Deborah Clegg, who led the study while at University of Texas Southwestern Medical Centre, Dallas, USA, was building on existing research that links brain inflammation with obesity and heart disease in male mice. "We embarked on this research because [the link with inflammation] had been shown in male mice, so we asked ourselves, do the same processes occur in females?" explains Clegg. Previous research has shown that one cause of inflammation in the hypothalamus - the part of the brain that controls energy balance - is palmitic acid, a saturated fatty acid found in palm oil, dairy products and meat, and common in high fat food. The team looked at male and female mice, fed either their normal diet or a 'high fat' diet. Besides containing 42 per cent fat, the high fat diet was also high in carbohydrates making it a good correlate of human junk food, says Clegg. © 2014 ABC
By ALEX STONE Smell is one of the oldest human faculties, yet it was one of the last to be understood by scientists. It was not until the early 1990s that biologists first described the inner workings of olfactory receptors — the chemical sensors in our noses — in a discovery that won a Nobel Prize. Since then, the plot has thickened. Over the last decade or so, scientists have discovered that odor receptors are not solely confined to the nose, but found throughout body — in the liver, the heart, the kidneys and even sperm — where they play a pivotal role in a host of physiological functions. Now, a team of biologists at Ruhr University Bochum in Germany has found that our skin is bristling with olfactory receptors. “More than 15 of the olfactory receptors that exist in the nose are also found in human skin cells,” said the lead researcher, Dr. Hanns Hatt. Not only that, but exposing one of these receptors (colorfully named OR2AT4) to a synthetic sandalwood odor known as Sandalore sets off a cascade of molecular signals that appears to induce healing in injured tissue. In a series of human tests, skin abrasions healed 30 percent faster in the presence of Sandalore, a finding the scientists think could lead to cosmetic products for aging skin and to new treatments to promote recovery after physical trauma. The presence of scent receptors outside the nose may seem odd at first, but as Dr. Hatt and others have observed, odor receptors are among the most evolutionarily ancient chemical sensors in the body, capable of detecting a multitude of compounds, not solely those drifting through the air. “If you think of olfactory receptors as specialized chemical detectors, instead of as receptors in your nose that detect smell, then it makes a lot of sense for them to be in other places,” said Jennifer Pluznick, an assistant professor of physiology at Johns Hopkins University who in 2009 found that olfactory receptors help control metabolic function and regulate blood pressure in the kidneys of mice. © 2014 The New York Times Company
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20206 - Posted: 10.14.2014
By MOISES VELASQUEZ-MANOFF WHEN Andre H. Lagrange, a neurologist at Vanderbilt University in Nashville, saw the ominous white spots on the patient’s brain scan, he considered infection or lymphoma, a type of cancer. But tests ruled out both. Meanwhile, anti-epilepsy drugs failed to halt the man’s seizures. Stumped, Dr. Lagrange turned to something the mother of the 30-year-old man kept repeating. The fits coincided, she insisted, with spells of constipation and diarrhea. That, along with an odd rash, prompted Dr. Lagrange to think beyond the brain. Antibody tests, followed by an intestinal biopsy, indicated celiac disease, an autoimmune disorder of the gut triggered by the gluten proteins in wheat and other grains. Once on a gluten-free diet, the man’s seizures stopped; those brain lesions gradually disappeared. He made a “nearly complete recovery,” Dr. Lagrange told me. I began encountering case descriptions like this some years ago as I researched autoimmune disease. The first few seemed like random noise in an already nebulous field. But as I amassed more — describing seizures, hallucinations, psychotic breaks and even, in one published case, what looked like regressive autism, all ultimately associated with celiac disease — they began to seem less like anomalies, and more like a frontier in celiac research. They tended to follow a similar plot. What looked like neurological or psychiatric symptoms appeared suddenly. The physician ran through a diagnostic checklist without success. Drugs directed at the brain failed. Some clue suggestive of celiac disease was observed. The diagnosis was made. And the patient recovered on a gluten-free diet. The cases highlighted, in an unusually concrete fashion, the so-called gut-brain axis. The supposed link between the intestinal tract and the central nervous system is much discussed in science journals, often in the context of the microbial community inhabiting the gut. But it’s unclear how, really, we can leverage the link to improve health. © 2014 The New York Times Company
Link ID: 20200 - Posted: 10.13.2014