Chapter 9. Homeostasis: Active Regulation of the Internal Environment

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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

By Gina Kolata Maya Cohen’s entree into the world of obesity medicine came as a shock. In despair over her weight, she saw Dr. Caroline Apovian, an obesity specialist at Brigham and Women’s Hospital, who prescribed Saxenda, a recently approved weight-loss drug. Ms. Cohen, who is 55 and lives in Cape Elizabeth, Maine, hastened to get it filled. Then she saw the price her pharmacy was charging: $1,500 a month. Her insurer classified it as a “vanity drug” and would not cover it. “I’m being treated for obesity,” she complained to her insurer, but to no avail. While Ms. Cohen was stunned by her insurer’s denial, Dr. Apovian was not. She says it is an all too common response from insurers when she prescribes weight-loss drugs and the universal response from Medicare drug plans. Obesity specialists despair but hope that with the advent of highly effective drugs, the situation will change. Novo-Nordisk, the maker of the medicine Dr. Apovian prescribed, and patient advocacy groups have been aggressively lobbying insurers to pay for weight-loss drugs. They also have been lobbying Congress to pass a bill that has languished through three administrations that would require Medicare to pay for the drugs. But for now, the status quo has not budged. No one disputes the problem — more than 40 percent of Americans have obesity, and most have tried repeatedly to lose weight and keep it off, only to fail. Many suffer from medical conditions that are linked to obesity, including diabetes, joint and back pain and heart disease, and those conditions often improve with weight loss. © 2022 The New York Times Company

Keyword: Obesity
Link ID: 28342 - Posted: 06.01.2022

By Gina Kolata An experimental drug has enabled people with obesity or who are overweight to lose about 22.5 percent of their body weight, about 52 pounds on average, in a large trial, the drug’s maker announced on Thursday. The company, Eli Lilly, has not yet submitted the data for publication in a peer-reviewed medical journal or presented them in a public setting. But the claims nonetheless amazed medical experts. “Wow (and a double Wow!)” Dr. Sekar Kathiresan, chief executive of Verve Therapeutics, a company focusing on heart disease drugs, wrote in a tweet. Drugs like Eli Lilly’s, he added, are “truly going to revolutionize the treatment of obesity!!!” Dr. Kathiresan has no ties to Eli Lilly or to the drug. Dr. Lee Kaplan, an obesity expert at the Massachusetts General Hospital, said that the drug’s effect “appears to be significantly better than any other anti-obesity medication that is currently available in the U.S.” The results, he added, are “very impressive.” Dr. Kaplan who consults for a dozen pharmaceutical companies, including Eli Lilly, said he was not involved in the new trial or in the development of this drug. On average, participants in the study weighed 231 pounds at the outset and had a body mass index, or B.M.I. — a commonly used measure of obesity — of 38. (Obesity is defined as a B.M.I. of 30 and higher. At the end of the study, those taking the higher doses of the Eli Lilly drug, called tirzepatide, weighed about 180 pounds and had a B.M.I. just below 30, on average. The results far exceed those usually seen in trials of weight-loss medications and are usually seen only in surgical patients. Some trial participants lost enough weight to fall into the normal range, said Dr. Louis J. Aronne, director of the comprehensive weight control program at Weill Cornell Medical Center, who worked with Eli Lilly as the study’s principal investigator. Most of the people in the trial did not qualify for bariatric surgery, which is reserved for people with a B.M.I. over 40, or those with a B.M.I. from 35 to 40 with sleep apnea or Type 2 diabetes. The risk of developing diabetes is many times higher for people with obesity than for people without it. © 2022 The New York Times Company

Keyword: Obesity
Link ID: 28311 - Posted: 04.30.2022

pmByElizabeth Pennisi With more microbes than cells in our body, it’s not surprising that bacteria and other invisible “guests” influence our metabolism, immune system, and even our behavior. Now, researchers studying mice have worked out how bacteria in the mammalian gut can ping the brain to regulate an animal’s appetite and body temperature—and it involves the same molecular pathway the immune system uses to detect bacterial pathogens. “It’s quite an important finding,” says Antoine Adamantidis, a neuroscientist at the University of Bern who was not involved with the work. “Our life depends on food intake, and this is one more [thing] that bacteria can [influence].” Over the past 20 years, researchers have uncovered connections between the human gut and the rest of the body. They have linked certain intestinal microbes to conditions such as depression, multiple sclerosis, and immune system disorders; they have also documented nervous system connections between the gut and the brain. But researchers have been hard pressed to understand exactly how gut microbes—or the molecules they make—influence the brain. When certain gut bacteria infiltrate the rest of the body, our immune system picks up on them by sensing fragments of their cell walls, known as muropeptides. Our molecular detectors for these muropeptides, proteins called Nod2, coat the surfaces of cells involved in the body’s first line of defense. Ilana Gabanyi, a neuroimmunologist at the Pasteur Institute, wanted to know whether these molecular detectors also exist in the brain’s nerve cells. © 2022 American Association for the Advancement of Science.

Keyword: Obesity
Link ID: 28293 - Posted: 04.20.2022

Linda Geddes Setting daily meat reduction goals and keeping an online diary of intake helped frequent meat eaters to halve their consumption in just over nine weeks, a trial has found. The trial, by researchers at the University of Oxford’s Livestock, Environment and People (Leap) programme, also found the routine was popular with participants, who felt it supported them to change their diet. Many people wish to reduce their meat consumption, whether for health or environmental reasons, or animal welfare concerns. Leap researchers wondered whether tapping into psychological principles employed by weight-loss apps, such as Noom, could help boost participants’ resolve. They developed an online platform called the Optimise meat tracker (standing for online programme to tackle individuals’ meat intake through self-regulation). Users log on and pick one meat reduction strategy from a list to focus on for that day, such as “try a new vegetarian recipe”, or “eat no processed meat”. The next morning they report whether they achieved this and record how much fish, poultry, red and processed meat they consumed. They receive weekly feedback on how they have done. The approach is based on self-regulation theory: the idea that people monitor and contextualise their own behaviour, reflect on it in relation to their goals, and try to modify it in response to feedback. “We know that people tend to underestimate the amount of meat they eat, the health and environmental impacts of their meat consumption; we also know that our meat-eating habits are strongly engrained. This process of self-regulation tries to tap into all of that,” said Dr Cristina Stewart at the University of Oxford, who led the research. © 2022 Guardian News & Media Limited

Keyword: Obesity
Link ID: 28231 - Posted: 03.05.2022

By Diana Kwon People with a rare genetic disorder known as Prader-Willi syndrome never feel full, and this insatiable hunger can lead to life-threatening obesity. Scientists studying the problem have now found that the fist-shaped structure known as the cerebellum—which had not previously been linked to hunger—is key to regulating satiation in those with this condition. This finding is the latest in a series of discoveries revealing that the cerebellum, long thought to be primarily involved in motor coordination, also plays a broad role in cognition, emotion and behavior. “We’ve opened up a whole field of cerebellar control of food intake,” says Albert Chen, a neuroscientist at the Scintillon Institute in California. The project began with a serendipitous observation: Chen and his team noticed they could make mice stop eating by activating small pockets of neurons in regions known as the anterior deep cerebellar nuclei (aDCN), within the cerebellum. Intrigued, the researchers contacted collaborators at Harvard Medical School. Scientists there had gathered data using functional MRI to compare brain activity in 14 people who had Prader-Willi syndrome with activity in 14 unaffected people while each subject viewed images of food—either immediately following a meal or after fasting for at least four hours. New analysis of these scans revealed that activity in the same regions Chen’s group had pinpointed in mice, the aDCN, appeared to be significantly disrupted in humans with Prader-Willi syndrome. In healthy individuals, the aDCN were more active in response to food images while fasting than just after a meal, but no such difference was identifiable in participants with the disorder. The result suggested that the aDCN were involved in controlling hunger. Further experiments on mice, conducted by researchers from several different institutions, demonstrated that activating the animals’ aDCN neurons dramatically reduced food intake by blunting how the brain’s pleasure center responds to food. The findings were recently detailed in Nature. © 2022 Scientific American,

Keyword: Obesity
Link ID: 28219 - Posted: 02.26.2022

By Matt Richtel During the pandemic, emergency rooms across the country reported an increase in visits from teenage girls dealing with eating and other disorders, including anxiety, depression and stress, according to new data from the Centers for Disease Control and Prevention. The report provides new detail about the kinds of mental health issues affecting a generation of adolescents. Mental health experts hypothesize that the pandemic prompted some youth to feel isolated, lonely and out-of-control. Some coped by seeking to have control over their own behavior, said Emily Pluhar, a pediatric psychologist at Boston Children’s Hospital and instructor at Harvard Medical School. “You take a very vulnerable group and put on a global pandemic,” she said. “The eating disorders are out of control.” In the C.D.C. study, the agency said that the proportion of eating disorder visits doubled among teenage girls, set off by pandemic-related risk factors, like the “lack of structure in daily routine, emotional distress and changes in food availability.” The agency said that the increase in tic disorders was “atypical,” as these disorders often present earlier, and are more common in boys. But the C.D.C., reinforcing speculation from other clinicians and researchers, said that some teenage girls may be developing tics after seeing the phenomenon spread widely on social media, notably on TikTok. “Stress of the pandemic or exposure to severe tics, highlighted on social media platforms, might be associated with increases in visits with tics and tic-like behavior among adolescent females,” the C.D.C. wrote. In a related report, the C.D.C. also said on Friday that the increase in visits for mental health issues occurred as emergency rooms reported sharp declines overall in visits during the pandemic. As compared with 2019, overall visits fell by 51 percent in 2020 and by 22 percent in 2021, declines that the agency attributed in part to families delaying care, and a drop in physical injuries from activities like swimming and running. © 2022 The New York Times Company

Keyword: Anorexia & Bulimia; Stress
Link ID: 28213 - Posted: 02.19.2022

by Angie Voyles Askham Mice chemically coaxed to produce high levels of an autism-linked gut molecule have anxiety-like behavior and unusual patterns of brain connectivity, according to a study published today in Nature. The findings present a direct mechanism by which the gut could send signals to the brain and alter development, the researchers say. “It’s a true mechanistic paper, [like] the field has been asking for,” says Jane Foster, professor of psychiatry and behavioral neurosciences at McMaster University in Hamilton, Canada, who was not involved in the study. Although it’s not clear that this exact signaling pathway is happening in people, she says, “this is the sort of work that’s going to get us that answer.” The molecule, 4-ethylphenol (4EP), is produced by gut microbes in mice and people. An enzyme in the colon and liver converts 4EP to 4-ethylphenyl sulfate (4EPS), which then circulates in the blood. Mice exposed to a maternal immune response in the womb have atypically high blood levels of 4EPS, as do some autistic people, previous research shows. And injecting mice with the molecule increases behaviors indicative of anxiety. But it wasn’t clear how the molecule could contribute to those traits. In the new work, researchers show that 4EPS can enter the brain and that its presence is associated with altered brain connectivity and a decrease in myelin — the insulation around axons that helps conduct electrical signals. Boosting the function of myelin-producing cells, the team found, eases the animals’ anxiety. “This is one of the first — maybe, arguably, the first — demonstrations of a specific microbe molecule that has such a profound impact on a complex behavior,” says lead researcher Sarkis Mazmanian, professor of microbiology at the California Institute of Technology in Pasadena. “How it’s doing it, we still need to understand.” without the engineered enzymes, they showed increased anxiety-like behaviors, © 2022 Simons Foundation

Keyword: Development of the Brain; Neuroimmunology
Link ID: 28205 - Posted: 02.16.2022

Ian Sample Science editor Getting an hour or so more sleep each night can help people to cut calories, according a small clinical trial in overweight adults. Researchers in the US found that people who typically slept for less than 6.5 hours a night shed an average of 270 calories from their daily intake when they got an extra 1.2 hours of sleep. Sustained over three years, the reduction in calories could lead people to lose about 12kg (26lbs) without changing their diet during the day, the scientists believe. Some participants in the study consumed 500 fewer calories a day after improving their sleep. The study was not designed to look at weight loss, but researchers noticed the fall in calories within two weeks of patients changing their sleep patterns. “If healthy sleep habits are maintained over longer duration, this would lead to clinically important weight loss over time,” said Dr Esra Tasali, of the University of Chicago’s sleep centre. “Many people are working hard to find ways to decrease their caloric intake to lose weight – well, just by sleeping more, you may be able to reduce it substantially.” The trial studied 80 adults aged 21 to 40 with a body mass index between 25 and 29.9, meaning they were overweight. Half of the participants were randomly assigned to receive personalised sleep hygiene counselling aimed at extending the amount of time they slept each night. © 2022 Guardian News & Media Limited

Keyword: Sleep; Obesity
Link ID: 28191 - Posted: 02.09.2022

ByElizabeth Pennisi The trillions of bacteria in and on our bodies can bolster our health and contribute to disease, but just which microbes are the key actors has been elusive. Now, a study involving thousands of people in Finland has identified a potential microbial culprit in some cases of depression. The finding, which emerged from a study of how genetics and diet affect the microbiome, “is really solid proof that this association could have major clinical importance,” says Jack Gilbert, a microbial ecologist at the University of California, San Diego, who was not involved with the work. Researchers are finding ever more links between brain conditions and gut microbes. People with autism and mood disorders, for example, have deficits of certain key bacteria in their guts. Whether those microbial deficits actually help cause the disorders is unclear, but the findings have spawned a rush to harness gut microbes and the substances they produce as possible treatments for a variety of brain disorders. Indeed, researchers recently reported in Frontiers in Psychiatry that fecal transplants improved symptoms in two depressed patients. Guillaume Méric didn’t set out to find microbes that cause depression. A microbial bioinformatician at the Baker Heart & Diabetes Institute, he and his colleagues were analyzing data from a large health and lifestyle study from Finland. Part of a 40-year effort to track down underlying causes of chronic disease in Finnish people, the 2002 study assessed the genetic makeup of 6000 participants, identified their gut microbes, and compiled extensive data about their diets, lifestyles, prescription drug use, and health. Researchers tracked the health of participants until 2018. Méric and his colleagues combed the data for clues to how a person’s diet and genetics affect the microbiome. “There have been very few studies that have examined [all these factors] in such detail,” Gilbert says. Two sections of the human genome seemed to strongly influence which microbes are present in the gut, the researchers report this week in Nature Genetics. One contains the gene for digesting the milk sugar lactose, and the other helps specify blood type. (A second study, also published today in Nature Genetics, identified the same genetic loci by analyzing the relationship between the genomes and gut microbes of 7700 people in the Netherlands.) © 2022 American Association for the Advancement of Science.

Keyword: Depression; Obesity
Link ID: 28188 - Posted: 02.05.2022

By Veronique Greenwood Few pleasures compare to a long cool drink on a hot day. As a glass of water or other tasty drink makes its way to your digestive tract, your brain is tracking it — but how? Scientists have known for some time that thirst is controlled by neurons that send an alert to put down the glass when the right amount has been guzzled. What precisely tells them that it is time, though, is still a bit mysterious. In an earlier study, a team of researchers found that the act of gulping a liquid — really anything from water to oil — is enough to trigger a temporary shutdown of thirst. But they knew that gulping was not the only source of satisfaction. There were signals that shut down thirst coming from deeper within the body. In a paper published Wednesday in Nature, scientists from the same lab report that they’ve followed the signals down the neck, through one of the body’s most important nerves, into the gut, and finally to an unexpected place for this trigger: a set of small veins in the liver. The motion of gulping might provide a quick way for the body to monitor fluid intake. But whatever you swallowed will swiftly arrive in the stomach and gut, and then its identity will become clear to your body as something that can fulfill the body’s need for hydration, or not. Water changes the concentration of nutrients in your blood, and researchers believe that this is the trigger for real satiation. “There is a mechanism to ensure that what you’re drinking is water, not anything else,” said Yuki Oka, a professor at Caltech and an author of both studies. To find out where the body senses changes to your blood’s concentration, Dr. Oka and his colleagues first ran water into the intestines of mice and watched the behavior of nerves that connect the brain to the gut area, which are believed to work similarly in humans. One major nerve, the vagus nerve, fired the closest in time with the water’s arrival in the intestines, suggesting that this is the route the information takes on the way to the brain. © 2022 The New York Times Company

Keyword: Obesity
Link ID: 28178 - Posted: 01.29.2022