Chapter 9. Homeostasis: Active Regulation of the Internal Environment

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McKenzie Prillaman The hotel ballroom was packed to near capacity with scientists when Susan Yanovski arrived. Despite being 10 minutes early, she had to manoeuvre her way to one of the few empty seats near the back. The audience at the ObesityWeek conference in San Diego, California, in November 2022, was waiting to hear the results of a hotly anticipated drug trial. The presenters — researchers affiliated with pharmaceutical company Novo Nordisk, based in Bagsværd, Denmark — did not disappoint. They described the details of an investigation of a promising anti-obesity medication in teenagers, a group that is notoriously resistant to such treatment. The results astonished researchers: a weekly injection for almost 16 months, along with some lifestyle changes, reduced body weight by at least 20% in more than one-third of the participants1. Previous studies2,3 had shown that the drug, semaglutide, was just as impressive in adults. The presentation concluded like no other at the conference, says Yanovski, co-director of the Office of Obesity Research at the US National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland. Sustained applause echoed through the room “like you were at a Broadway show”, she says. This energy has pervaded the field of obesity medicine for the past few years. After decades of work, researchers are finally seeing signs of success: a new generation of anti-obesity medications that drastically diminish weight without the serious side effects that have plagued previous efforts. These drugs are arriving in an era in which obesity is growing exponentially. Worldwide obesity has tripled since 1975; in 2016, about 40% of adults were considered overweight and 13% had obesity, according to the World Health Organization (WHO). With extra weight often comes heightened risk of health conditions such as type 2 diabetes, heart disease and certain cancers. The WHO recommends healthier diets and physical activity to reduce obesity, but medication might help when lifestyle changes aren’t enough. The new drugs mimic hormones known as incretins, which lower blood sugar and curb appetite. Some have already been approved for treating type 2 diabetes, and they are starting to win approval for inducing weight loss. © 2023 Springer Nature Limited

Keyword: Obesity
Link ID: 28621 - Posted: 01.04.2023

By Laurie McGinley and  Lenny Bernstein Rachel Graham has battled excess weight for years, cycling through trendy diets, various drugs, even bariatric surgery. Nothing worked for long. But last summer, she started a new medication, and today is 40 pounds lighter — and still shedding weight. “It used to be that if I saw food, I would want to eat it,” said the 54-year-old Graham, who is 5-foot-7 and 190 pounds. “Now, if I have three or four bites of food, I don’t want to eat more.” The drug she’s taking, Mounjaro by Eli Lilly, is part of a new crop of therapies that experts are hailing as a medical milestone — a long-sought way to transform the treatment of obesity, one of the nation’s most serious health threats. Designed for diabetes but used for obesity at higher doses, the medications induce loss of 15 to 22 percent of body weight on average — more than enough to significantly reduce cardiovascular and other health risks. That makes them far superior to old-style diet pills that delivered smaller benefits along with nasty side effects such as high blood pressure and loose stools. But during the past year, soaring demand for the drugs has ignited a mad scramble, exposing some of the most persistent problems in the nation’s health-care system, including supply shortages, high costs and health-care inequities. Tensions are surging as patients with diabetes and those with weight problems sometimes compete for the same medications, which are self-administered in weekly injections. Some doctors worry that the drugs, which might have to be taken for life, will overshadow the need for lifestyle changes involving diet and exercise.

Keyword: Obesity
Link ID: 28606 - Posted: 12.21.2022

ByElizabeth Pennisi Willpower might be key to getting off the couch to exercise, but bacteria may lend a helping hand. Studies in mice reported today in Nature suggest microbes in the gut may be behind differences in the desire to work out. A research team has homed in on specific microbial molecules that stimulate a rodent’s desire to run—and keep running. By revealing exactly how these molecules talk to the brain, this group has set the stage for finding out whether similar signals help keep humans active. The work “establishes just how critical the microbiome is for exercise and goes incredibly deep in providing a new gut-brain [connection],” says Aleksandar Kostic, a microbiologist at Harvard Medical School who is co-founder of FitBiomics, a company developing probiotics to improve fitness. Kostic, who wasn’t involved in the research, and others speculate that exercise-inducing commands from the microbes might one day be packaged into pills people could take. To explore why some people like to exercise and others don’t, University of Pennsylvania microbiologist Christoph Thaiss studied mice bred to have a lot of genetic and behavioral variation. His team found more than a fivefold difference in how far the mice ran on wheels in their cages—some covered more than 30 kilometers in 48 hours, whereas others rarely moved in their wheels. The active and lazy mice didn’t show any significant differences in their genetics or biochemistry. But the researchers did notice one clue: When treated with antibiotics, mice that were normally highly energetic tended to exercise less. Follow-up studies showed the antibiotic treatment affected the brains of the formerly active mice. The activity of certain brain genes declined, along with levels of dopamine, a neurotransmitter that has been linked to “runner’s high”—that sense of wellbeing that comes with prolonged exercise.

Keyword: Obesity
Link ID: 28596 - Posted: 12.15.2022

By Allison Gasparini Are you drinking enough water? The question seems like it should have a straightforward answer — a specific amount of water you need to drink daily to combat dehydration.      But the rate and way in which the human body takes in and excretes water is not as universal as you might expect. By studying more than 5,000 people living in 23 countries and ranging in age from 8 days to 96 years, researchers have found that the turnover of water in a person’s body varies widely depending on the individual’s physical and environmental factors. The results, published in the Nov. 24 Science, suggest that the idea that a person should ideally consume eight 8-ounce glasses of water a day is not a one-size-fits-all solution to peak hydration.     Even within the calculations, “individual variabilities could be huge,” says biomedical engineer Kong Chen, director of the metabolic research program at the National Institutes of Health’s Clinical Center. Yosuke Yamada, a physiologist at the National Institute of Biomedical Innovation, Health and Nutrition in Japan, and colleagues used a stable isotope of hydrogen known as deuterium to track the movement of water through people’s bodies. Drinking water accounts for only half of the total water intake by humans, with the rest coming from food. Simply measuring the amount of water that a person drinks in a day is not enough to accurately gauge water turnover or the amount of water used by the body daily. © Society for Science & the Public 2000–2022.

Keyword: Obesity
Link ID: 28592 - Posted: 12.13.2022

By Joanna Thompson Two recent papers have shown that during a critical early period of brain development, the gut’s microbiome — the assortment of bacteria that grow within in it — helps to mold a brain system that’s important for social skills later in life. Scientists found this influence in fish, but molecular and neurological evidence plausibly suggests that some form of it could also occur in mammals, including humans. In a paper published in early November in PLOS Biology, researchers found that zebra fish who grew up lacking a gut microbiome were far less social than their peers with colonized colons, and the structure of their brains reflected the difference. In a related article in BMC Genomics in late September, they described molecular characteristics of the neurons affected by the gut bacteria. Equivalents of those neurons appear in rodents, and scientists can now look for them in other species, including humans. In recent decades, scientists have come to understand that the gut and the brain have powerful mutual influences. Certain types of intestinal ulcers, for example, have been linked to worsening symptoms in people with Parkinson’s disease. And clinicians have long known that gastrointestinal disorders are more common in people who also have neurodevelopmental disorders, such as ADHD and autism spectrum disorder. “Not only does the brain have an impact on the gut, but the gut can also profoundly affect the brain,” said Kara Margolis, a pediatric gastroenterologist at New York University’s Langone Health, who was not involved in the new research. How these anatomically separate organs exert their effects, however, is far less clear. Philip Washbourne, a molecular biologist at the University of Oregon and one of the principal co-authors of the new studies, has been studying genes implicated in autism and the development of social behaviors for over two decades. But he and his lab were looking for a new model organism, one that displayed social behavior but was quicker and easier to breed than their go-to, mice. “Can we do this in fish?” he recalls thinking, and then: “Let’s get really quantitative about it and see if we can measure how friendly the fish get.” All Rights Reserved © 2022

Keyword: Sexual Behavior; Obesity
Link ID: 28557 - Posted: 11.16.2022

By Gina Kolata What if an uncontrollable urge to rapidly eat large amounts of food is rooted in an impaired brain circuit? If that were the case, people who live with binge eating disorder — a psychiatric diagnosis — might be no more at fault for overeating than a patient with Parkinson’s disease is for their tremors. That question led doctors to try a new treatment different from anything ever attempted to help people with this common but underreported eating disorder. At least 3 percent of the population has it, said Dr. Casey Halpern, a neurosurgeon at the University of Pennsylvania. He and his colleagues decided to try deep brain stimulation, a method routinely used to quell tremors in patients with Parkinson’s. It involves placing electrodes in the brain to regulate aberrant signals. The wires, connected to the electrodes, are placed under the scalp, where they are invisible and unobtrusive. For the binge eating treatment, the device only stimulates neurons when the device detects a signal to start a binge. The pilot study, funded by the National Institutes of Health and published earlier this year in the journal Nature Medicine, involves two women and will be expanded in a few months to include four more people living with binge eating disorder who regained the weight they lost after bariatric surgery. Before the treatment can be approved by the Food and Drug Administration, researchers will need to rigorously test the method in at least 100 people in multiple medical centers. Such a study would take several years to complete. The two women whose devices were implanted a year ago will be followed for up to three years. They had the option to have their devices removed after 12 months, but both wanted to keep them because they no longer felt irresistible urges to binge. One of them, Robyn Baldwin, 58, of Citrus Heights, Calif., described herself as a “chunko child” who had “always been big.” She tried a wide range of diets. Once, she consumed only protein shakes for a month. In 2003 she had bariatric surgery, which usually involves altering the digestive system so that the stomach is smaller and food is more difficult to digest. It has enabled many people to lose weight when other methods failed. But for Ms. Baldwin, the weight she lost came back. © 2022 The New York Times Company

Keyword: Anorexia & Bulimia
Link ID: 28545 - Posted: 11.09.2022

By Veronique Greenwood Anyone who’s had a shady oyster or a mushroom soup that didn’t sit well remembers the ominous queasiness heralding impending bad times. Bacteria release toxins that start the body’s process of speedily evacuating the contents of the stomach. It’s a protective mechanism of sorts — getting rid of the invaders en masse is probably helpful in the long term, even if it’s unpleasant in the short. But it has remained something of a mystery how the brain gets the alarm signal, then sends another one to tell the stomach to initiate a technicolor yawn. Your next bout of food poisoning isn’t the only reason to understand this particular neural pathway. Figuring out how to counter it could be helpful for people who develop nausea caused by chemotherapy medication and other drugs. As if fighting cancer isn’t painful and scary enough, patients are often so turned off by food that keeping their weight up becomes a major struggle. In a new study, researchers report that both bacteria and chemotherapy drugs appear to trigger the same molecular pathways in the gut. The findings, which were based on experiments with mice and published Tuesday in the journal Cell, showed that a bacterial toxin and a chemo medication both set in motion a cascade of similar neural messages that cause queasiness. Choosing mice for the study was unusual. Mice, it turns out, can’t puke — a little foible that typically makes it difficult to use them to study nausea. Researchers have used cats and dogs in the past, but the biology of mice in general is so much better understood, with much better tools available to scientists to do so. Cao Peng, a professor at Tsinghua University in Beijing, and his colleagues wondered whether mice might still be capable of feeling ill in the way people do after ingesting a chemo drug or a bad salad — or close enough, anyway, that researchers could use the creatures to understand the origins of the sensation. © 2022 The New York Times Company

Keyword: Obesity; Stress
Link ID: 28537 - Posted: 11.02.2022

Kate Siber Sharon Maxwell spent much of her life trying to make herself small. Her family put her on her first diet when she was 10. Early on Saturday mornings, she and her mother would drive through the empty suburban streets of Hammond, Ind., to attend Weight Watchers meetings. Maxwell did her best at that age to track her meals and log her points, but the scale wasn’t going down fast enough. So she decided to barely eat anything on Fridays and take laxatives that she found in the medicine cabinet. Food had long been a fraught subject in the Maxwell household. Her parents were also bigger-bodied and dieted frequently. They belonged to a fundamentalist Baptist megachurch where gluttony was seen as a sin. To eat at home was to navigate a labyrinth of rules and restrictions. Maxwell watched one time as her mother lost 74 pounds in six months by consuming little more than carrot juice (her skin temporarily turned orange). Sometimes her father, seized with a new diet idea, abruptly ransacked shelves in the kitchen, sweeping newly forbidden foods into the trash. Maxwell was constantly worried about eating too much. She started to eat alone and in secret. She took to chewing morsels and spitting them out. She hid food behind books, in her pockets, under mattresses and between clothes folded neatly in drawers. Through Maxwell’s teenage years and early 20s, eating became even more stressful. Her thoughts constantly orbited around food: what she was eating or not eating, the calories she was burning or not burning, the size of her body and, especially, what people thought of it. Her appearance was often a topic of public interest. When she went grocery shopping for her family, other customers commented on the items in her cart. “Honey, are you sure you want to eat that?” one person said. Other shoppers offered unsolicited advice about diets. Strangers congratulated her when her cart was filled with vegetables. As she grew older, people at the gym clapped and cheered for her while she worked out. “People would say: ‘Go! You can lose the weight!’” she says. While eating in public, other diners offered feedback — and still do to this day — on her choices, a few even asking if she wanted to join their gym. Some would call her names: Pig, Fatty. Sometimes people told her she was brave for wearing shorts, while others said she should cover up. She was always aware, whether she wanted to be or not, of how others viewed her body. © 2022 The New York Times Company

Keyword: Anorexia & Bulimia
Link ID: 28519 - Posted: 10.19.2022

By Greg Miller If you’re lucky enough to live to 80, you’ll take up to a billion breaths in the course of your life, inhaling and exhaling enough air to fill about 50 Goodyear blimps or more. We take about 20,000 breaths a day, sucking in oxygen to fuel our cells and tissues, and ridding the body of carbon dioxide that builds up as a result of cellular metabolism. Breathing is so essential to life that people generally die within minutes if it stops. It’s a behavior so automatic that we tend to take it for granted. But breathing is a physiological marvel — both extremely reliable and incredibly flexible. Our breathing rate can change almost instantaneously in response to stress or arousal and even before an increase in physical activity. And breathing is so seamlessly coordinated with other behaviors like eating, talking, laughing and sighing that you may have never even noticed how your breathing changes to accommodate them. Breathing can also influence your state of mind, as evidenced by the controlled breathing practices of yoga and other ancient meditative traditions. In recent years, researchers have begun to unravel some of the underlying neural mechanisms of breathing and its many influences on body and mind. In the late 1980s, neuroscientists identified a network of neurons in the brainstem that sets the rhythm for respiration. That discovery has been a springboard for investigations into how the brain integrates breathing with other behaviors. At the same time, researchers have been finding evidence that breathing may influence activity across wide swaths of the brain, including ones with important roles in emotion and cognition. “Breathing has a lot of jobs,” says Jack L. Feldman, a neuroscientist at the University of California, Los Angeles, and coauthor of a recent article on the interplay of breathing and emotion in the Annual Review of Neuroscience. “It’s very complicated because we’re constantly changing our posture and our metabolism, and it has to be coordinated with all these other behaviors.” © 2022 Annual Reviews

Keyword: ADHD
Link ID: 28508 - Posted: 10.08.2022

By Claudia Lopez Lloreda If you look at parts of the circulatory system of whales and dolphins, you might think that you are looking at a Jackson Pollock painting, not blood vessels. These cetaceans have especially dense, complex networks of blood vessels mainly associated with the brain and spine, but scientists didn’t know why. A new analysis suggests that the networks protect cetaceans’ brains from the pulses of blood pressure that the animals endure while diving deep in the ocean, researchers report in the Sept. 23 Science. Whales and dolphins “have gone through these really amazing vascular adaptations to support their brain,” says Ashley Blawas, a marine scientist at the Duke University Marine Lab in Beaufort, N.C., who was not involved with the research. Called retia mirabilia, which means “wonderful nets,” the blood vessel networks are present in some other animals besides cetaceans, including giraffes and horses. But the networks aren’t found in other aquatic vertebrates that move differently from whales, such as seals. So scientists had suspected that the cetaceans’ retia mirabilia play a role in controlling blood pressure surges. When whales and dolphins dive, they move their tail up and down in an undulating manner, which creates surges in blood pressure. Land animals that experience similar surges, like galloping horses, are able to release some of this pressure by exhaling. But some cetaceans hold their breath to dive for long periods of time (SN: 9/23/20). Without a way to relieve that pressure, those blasts could tear blood vessels and harm other organs, including the brain. In the new study, biomechanics researcher Margo Lillie of the University of British Columbia in Vancouver and colleagues used data on the morphology of 11 cetacean species to create a computational model that can simulate the animals’ retia mirabilia. It revealed that the arteries and veins in this tangle of blood vessels are really close and may even sometimes be joined. As a result, the retia mirabilia could equalize the differences in blood pressure generated by diving, perhaps by redistributing the blood pulses from arteries to veins and vice versa. This way, the networks get rid of, or at least weaken, huge blood pressure surges that might otherwise reach and devastate the brain. © Society for Science & the Public 2000–2022.

Keyword: Brain imaging
Link ID: 28499 - Posted: 10.05.2022

By Alice Callahan Katherine Flegal wanted to be an archaeologist. But it was the 1960s, and Flegal, an anthropology major at the University of California, Berkeley, couldn’t see a clear path to this profession at a time when nearly all the summer archaeology field schools admitted only men. “The accepted wisdom among female archaeology students was that there was just one sure way for a woman to become an archaeologist: marry one,” Flegal wrote in a career retrospective published in the 2022 Annual Review of Nutrition. And so Flegal set her archaeology aspirations aside and paved her own path, ultimately serving nearly 30 years as an epidemiologist at the National Center for Health Statistics (NCHS), part of the US Centers for Disease Control and Prevention. There, she spent decades crunching numbers to describe the health of the nation’s people, especially as it related to body size, until she retired from the agency in 2016. At the time of her retirement, her work had been cited in 143,000 books and articles. In the 1990s, Flegal and her CDC colleagues published some of the first reports of a national increase in the proportion of people categorized as overweight based on body mass index (BMI), a ratio of weight and height. The upward trend in BMI alarmed public health officials and eventually came to be called the “obesity epidemic.” But when Flegal, along with other senior government scientists, published estimates on how BMI related to mortality — reporting that being overweight was associated with a lower death rate than having a “normal” BMI — she became the subject of intense criticism and attacks. Flegal and her coauthors were not the first to publish this seemingly counterintuitive observation, but they were among the most prominent. Some researchers in the field, particularly from the Harvard School of Public Health, argued that the findings would detract from the public health message that excess body fat was hazardous, and they took issue with some of the study’s methods. Flegal’s group responded with several subsequent publications reporting that the suggested methodological adjustments didn’t change their findings. © 2022 Annual Reviews

Keyword: Obesity
Link ID: 28469 - Posted: 09.10.2022

Short ribs glazed in a sweet sticky sauce and slow-cooked to perfection, potato chips hand-fried and tossed with a generous coating of sour cream, chicken wings battered and double-fried so that they stay crispy for hours. What is it about these, and other, mouth-watering — but incredibly fatty — foods that makes us reach out, and keep coming back for more? How they taste on the tongue is one part of the story, but to really understand what drives “our insatiable appetite for fat,” we have to examine what happens after fat is consumed, says Columbia University’s Charles Zuker, a neuroscientist and molecular geneticist who has been a Howard Hughes Medical Institute (HHMI) Investigator since 1989. Two years ago, Zuker and his team reported how sugar, upon reaching the gut, triggers signals that are sent to the brain, thus fueling cravings for sweet treats. Now, in an article published in Nature on September 7, 2022, they describe a similar gut-to-brain circuit that underlies a preference for fat. “The gut is the source of our great desire for fat and sugar,” says Zuker. The topic in question is an incredibly timely one, given the current global obesity epidemic. An estimated 13 percent of adults worldwide are obese — thrice that in 1975. In the US, that figure is even higher — at a staggering 42 percent. “It’s a very significant and important health problem,” says Zuker. Having a high body-mass index is a risk factor for stroke, diabetes, and several other diseases. “It’s clear that if we want to help make a difference here, we need to understand the biological basis for our strong appetite for fat and sugar,” he says. Doing so will help us design interventions in the future to “suppress this strong drive to consume” and combat obesity.

Keyword: Obesity; Hormones & Behavior
Link ID: 28468 - Posted: 09.10.2022

Sascha Pare Homer Simpson may not be the only one with a region of the brain dedicated to doughnuts: researchers have found that images of food appear to trigger a specific set of neurons. Previous research found that similar regions of the brain are highly specialised to identify and remember faces, places, bodies and words. The team, based at the Massachusetts Institute of Technology (MIT), say they stumbled upon the food-sensitive neurons by accident – and they could have evolved due to the evolutionary and cultural importance of food for humans. “Our most novel result is the discovery of a new neural response that has not been reported previously for the ventral visual pathway and that is highly selective for images of food,” the scientists wrote in the journal Current Biology. The researchers examined brain scans of eight participants taken as they viewed 10,000 images. Pictures of food appeared to trigger a population of neurons in the ventral visual cortex, which processes visual information. “We were quite puzzled by this because food is not a visually homogenous category,” said Meenakshi Khosla, one of the lead authors of the study. “Things like apples and corn and pasta all look so unlike each other, yet we found a single population that responds similarly to all these diverse food items.” Cooked meals such as a cheesy slice of pizza provoked a slightly stronger reactions than raw fruit and vegetables, the researchers noted. To test whether this was due to warmer colours in prepared food, they compared participants’ reactions with cool-toned images of food and richly coloured non-food objects. They found food caused a sharper signal. © 2022 Guardian News & Media Limited

Keyword: Obesity; Brain imaging
Link ID: 28452 - Posted: 08.27.2022

By Kate Golembiewski Humans spend about 35 minutes every day chewing. That adds up to more than a full week out of every year. But that’s nothing compared to the time spent masticating by our cousins: Chimps chew for 4.5 hours a day, and orangutans clock 6.6 hours. The differences between our chewing habits and those of our closest relatives offer insights into human evolution. A study published Wednesday in the journal Science Advances explores how much energy people use while chewing, and how that may have guided — or been guided by — our gradual transformation into modern humans. Chewing, in addition to keeping us from choking, makes the energy and nutrients in food accessible to the digestive system. But the very act of chewing requires us to expend energy. Adaptations to teeth, jaws and muscles all play a part in how efficiently humans chew. Adam van Casteren, an author of the new study and a research associate at the University of Manchester in England, says that scientists haven’t delved too deeply into the energetic costs of chewing partly because compared with other things we do, such as walking or running, it’s a thin slice of the energy-use pie. But even comparatively small advantages can play a big role in evolution, and he wanted to find out if that might be the case with chewing. To measure the energy that goes into chewing, Dr. van Casteren and his colleagues outfitted study participants in the Netherlands with plastic hoods that look like “an astronaut’s helmet,” he said. The hoods were connected to tubes to measure oxygen and carbon dioxide from breathing. Because metabolic processes are fueled by oxygen and produce carbon dioxide, gas exchange can be a useful measure for how much energy something takes. The researchers then gave the subjects gum. The participants didn’t get the sugary kind, though; the gum bases they chewed were flavorless and odorless. Digestive systems respond to flavors and scents, so the researchers wanted to make sure they were only measuring the energy associated with chewing and not the energy of a stomach gearing up for a tasty meal. The test subjects chewed two pieces of gum, one hard and one soft, for 15 minutes each. The results surprised researchers. The softer gum raised the participants’ metabolic rates about 10 percent higher than when they were resting; the harder gum caused a 15 percent increase. © 2022 The New York Times Company

Keyword: Evolution
Link ID: 28440 - Posted: 08.20.2022

By Carolyn Gramling Hot or not? Peeking inside an animal’s ear — even a fossilized one — may tell you whether it was warm- or cold-blooded. Using a novel method that analyzes the size and shape of the inner ear canals, researchers suggest that mammal ancestors abruptly became warm-blooded about 233 million years ago, the team reports in Nature July 20. Warm-bloodedness, or endothermy, isn’t unique to mammals — birds, the only living dinosaurs, are warm-blooded, too. But endothermy is one of mammals’ key features, allowing the animals to regulate their internal body temperatures by controlling their metabolic rates. This feature allowed mammals to occupy environmental niches from pole to equator, and to weather the instability of ancient climates (SN: 6/7/22). When endothermy evolved, however, has been a mystery. Based on fossil analyses of growth rates and oxygen isotopes in bones, researchers have proposed dates for its emergence as far back as 300 million years ago. The inner ear structures of mammals and their ancestors hold the key to solving that mystery, says Ricardo Araújo, a vertebrate paleontologist at the University of Lisbon. In all vertebrates, the labyrinth of semicircular canals in the inner ear contains a fluid that responds to head movements, brushing against tiny hair cells in the ear and helping to maintain a sense of balance. That fluid can become thicker or thinner depending on body temperature. “Mammals have very unique inner ears,” Araújo says. Compared with cold-blooded vertebrates of similar size, the dimensions of mammals’ semicircular canals — such as thickness, length and radius of curvature — is particularly small, he says. “The ducts are very thin and tend to be very circular compared with other animals.” By contrast, fish have the largest for their body size. © Society for Science & the Public 2000–2022.

Keyword: Hearing; Evolution
Link ID: 28408 - Posted: 07.23.2022

By Linda Searing People who drink a moderate amount of coffee — up to 3½ cups a day — might have a better chance at a longer life span, even if their coffee is lightly sweetened with sugar, according to research published in Annals of Internal Medicine. For about seven years, the researchers tracked the coffee consumption and health of 171,616 participants, who were an average of nearly 56 years old and were free of cancer and cardiovascular disease when the study started. They found that those who regularly drank 1½ to 3½ cups of coffee a day, whether plain or sweetened with about a teaspoon of sugar, were up to 30 percent less likely to die in that time frame from any cause, including cancer and cardiovascular disease, than were those who did not drink coffee. The type of coffee — whether instant, ground or decaffeinated — made no difference, but the results were described as inconclusive for the use of artificial sweeteners. The latest research does not prove that coffee alone was responsible for participants’ lowered mortality risk. Still, over the years, research has revealed a variety of health benefits for coffee, linking its consumption to a reduced risk for Type 2 diabetes, Parkinson’s disease, depression and more. Nutritionists often attribute the benefits of coffee to the abundance of antioxidants in coffee beans, which may help reduce internal inflammation and cell damage and protect against disease. Drinking caffeinated coffee also provides an energy boost and increased alertness. Caffeine, however, can disrupt sleep and be risky during pregnancy.

Keyword: Drug Abuse; Obesity
Link ID: 28406 - Posted: 07.23.2022

Linda Geddes Science correspondent Summer sunshine can leave us feeling hot, sweaty and a bit burnt – but it may also make men hungrier, by triggering the release of an appetite-boosting hormone from fat stores in their skin, data suggests. The study, which was published in the journal Nature Metabolism, adds to growing evidence that the effects of sun exposure may be more complex than first thought. Excessive exposure is well known to increase the risk of skin cancer, but recent studies have suggested moderate exposure may increase life expectancy, on average, by helping to protect against cardiovascular disease and other causes of death. One possibility is that it lowers blood pressure through the release of nitric oxide from the skin, a process that causes blood vessels to relax. Other scientists have attributed the health benefits of sunlight to vitamin D production. Advertisement Wondering whether food consumption could also provide some clues, Carmit Levy, a professor at Tel Aviv University’s department of human molecular genetics and biochemistry, and his colleagues analysed data from 3,000 participants who were enrolled in a national nutrition survey. The researchers found men but not women increased their food intake during the summer months. The effect was not huge – equivalent to eating an extra 300 calories a day – but over time this could be enough to cause weight gain. To investigate further, they exposed male and female volunteers to 25 minutes of midday sunlight on a clear day, and found it triggered an increase in levels of the appetite-boosting hormone ghrelin in the men’s blood but not in women’s. Experiments in mice similarly found that when males were exposed to UVB rays, they ate more, were more motivated to search for food and had increased levels of ghrelin in their blood. No such change was seen in female mice. The trigger for ghrelin release appeared to be DNA damage in skin cells. Oestrogen blocked this effect, which may be why sunlight did not affect females in the same way. © 2022 Guardian News & Media Limited

Keyword: Biological Rhythms; Obesity
Link ID: 28393 - Posted: 07.12.2022

Shogo Sato Anyone who has suffered from jet lag or struggled after turning the clock forward or back an hour for daylight saving time knows all about what researchers call your biological clock, or circadian rhythm – the “master pacemaker” that synchronizes how your body responds to the passing of one day to the next. This “clock” is made up of about 20,000 neurons in the hypothalamus, the area near the center of the brain that coordinates your body’s unconscious functions, like breathing and blood pressure. Humans aren’t the only beings that have an internal clock system: All vertebrates – or mammals, birds, reptiles, amphibians and fish – have biological clocks, as do plants, fungi and bacteria. Biological clocks are why cats are most active at dawn and dusk, and why flowers bloom at certain times of day. Circadian rhythms are also essential to health and well-being. They govern your body’s physical, mental and behavioral changes over each 24-hour cycle in response to environmental cues like light and food. They’re why more heart attacks and strokes occur early in the morning. They’re also why mice that are missing their biological clocks age faster and have shorter lifespans, and people with a mutation in their circadian clock genes have abnormal sleep patterns. Chronic misalignment of your circadian rhythm with external cues, as seen in night-shift workers, can lead to a wide range of physical and mental disorders, including obesity, Type 2 diabetes, cancer and cardiovascular diseases. In short, there is ample evidence that your biological clock is critical to your health. And chronobiologists like me are studying how the day-night cycle affects your body to better understand how you can modify your behaviors to use your internal clock to your advantage. © 2010–2022, The Conversation US, Inc.

Keyword: Biological Rhythms
Link ID: 28386 - Posted: 07.05.2022

By Rachel Nuwer Whether we’ve got the flu or have had too much to drink, most of us have experienced nausea. Unlike other universal sensations such as hunger and thirst, however, scientists still don’t understand the biology behind the feeling—or how to stop it. A new study in mice identifies a possible key player: specialized brain cells that communicate with the gut to turn off the feeling of nausea. It’s an “elegant” study, says Nancy Thornberry, CEO of Kallyope, a biotechnology company focused on the interplay between the gut and the brain. Further research is needed to translate the finding into antinausea therapies, says Thornberry, who was not involved with the work, but the data suggest possible leads for designing new interventions. To conduct the research, Chuchu Zhang, a neuroscience postdoc at Harvard University, and her colleagues focused on the “area postrema,” a tiny structure in the brainstem first linked to nausea in the 1950s. Electrical stimulation of the region induces vomiting in animals. Last year, Zhang’s team identified two types of specialized excitatory neurons in the area postrema that induce nausea behavior in mice. Rodents can’t throw up, but they curl up in discomfort when they feel nauseous. Zhang and her colleagues showed the excitatory neurons in the area postrema are responsible for these behaviors by stimulating the cells. Genetic sequencing of cells in the area postrema also revealed inhibitory neurons in the region, which the scientists suspected may suppress the activity of the excitatory neurons and play a role in stopping the feeling of nausea. So in the new study, Zhang’s team injected mice with glucose insulinotropic peptide (GIP), a gut-derived hormone that humans and other animals produce after we ingest sugar and fat. Previous research in ferrets has shown GIP inhibits vomiting, and Zhang hypothesizes it may suppress nausea to prevent us from losing precious nutrients. She also thought it might play a role in activating nausea-inhibiting neurons. © 2022 American Association for the Advancement of Science.

Keyword: Miscellaneous
Link ID: 28384 - Posted: 06.30.2022

Allison Whitten When our phones and computers run out of power, their glowing screens go dark and they die a sort of digital death. But switch them to low-power mode to conserve energy, and they cut expendable operations to keep basic processes humming along until their batteries can be recharged. Our energy-intensive brain needs to keep its lights on too. Brain cells depend primarily on steady deliveries of the sugar glucose, which they convert to adenosine triphosphate (ATP) to fuel their information processing. When we’re a little hungry, our brain usually doesn’t change its energy consumption much. But given that humans and other animals have historically faced the threat of long periods of starvation, sometimes seasonally, scientists have wondered whether brains might have their own kind of low-power mode for emergencies. Now, in a paper published in Neuron in January, neuroscientists in Nathalie Rochefort’s lab at the University of Edinburgh have revealed an energy-saving strategy in the visual systems of mice. They found that when mice were deprived of sufficient food for weeks at a time — long enough for them to lose 15%-20% of their typical healthy weight — neurons in the visual cortex reduced the amount of ATP used at their synapses by a sizable 29%. But the new mode of processing came with a cost to perception: It impaired how the mice saw details of the world. Because the neurons in low-power mode processed visual signals less precisely, the food-restricted mice performed worse on a challenging visual task. “What you’re getting in this low-power mode is more of a low-resolution image of the world,” said Zahid Padamsey, the first author of the new study. All Rights Reserved © 2022

Keyword: Vision
Link ID: 28376 - Posted: 06.15.2022