The brain link: researchers have discovered an amazing connection between how the brain is involved in obesity and drug addiction.Dear Teacher: As someone who sees adolescents every day, you are no doubt concerned that the number of teens battling health-threatening weight problems is growing. What you may not realize is that NIDA NIDA National Institute on Drug Abuse NIDA National Institute of Dramatic Arts (Australia) NIDA Northern Ireland Development Agency (UK) NIDA Northern Ireland Dairy Association researchers are discovering fascinating connections between obesity and another key teen health issue: drug addiction drug addiction or chemical dependency Physical and/or psychological dependency on a psychoactive (mind-altering) substance (e.g., alcohol, narcotics, nicotine), defined as continued use despite knowing that the substance causes harm. . Amazingly, drug abusers drug abuser n → chi fa uso di droghe and those who suffer from obesity appear to have a similarity in brain chemistry that seems partly responsible for these compulsive behaviors Compulsive behavior is behavior which a person does "compulsively", i.e., not because he enjoys it but because he feels he "has to". The two most common forms are: The common link is the neurotransmitter neurotransmitter, chemical that transmits information across the junction (synapse) that separates one nerve cell (neuron) from another nerve cell or a muscle. Neurotransmitters are stored in the nerve cell's bulbous end (axon). dopamine dopamine (dōp`əmēn), one of the intermediate substances in the biosynthesis of epinephrine and norepinephrine. See catecholamine. dopamine One of the catecholamines, widely distributed in the central nervous system. , the brain chemical responsible for stimulating feelings of pleasure. This year's fourth and final installment of Heads Up discusses this link, as well as obesity research and treatment. Like all of the articles in the series this year, this one reinforces our understanding of addiction as a brain disease--a disease that can be treated, understood, and, most important, prevented. Learning about the seemingly unlikely link between obesity and drug addiction will give students an intricate view of how science works. It will also teach them that researchers can never know for sure where the facts will lead them. NIDA-sponsored scientists started out doing work on drug addiction but soon found themselves researching obesity, as well. Thank you for taking time to share the lessons of Heads Up with your students. You have helped set the stage for a healthier, smarter, and drug-free generation of young adults. Sincerely, Nora D. Volkow, M.D. Director of NIDA Ask experts to name the biggest health threats for teens today, and these two answers will rise to the top: obesity and drug addiction. Are you surprised by the first answer? You shouldn't be. More and more teens weigh far too much, and the problem is growing. It's no joke. Check out these numbers: 16 percent of young people between the ages of 12 and 19 are overweight, according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. a 1999-2002 federal study by the Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. . That's more than triple what the rate was between 1976 and 1980. The same study revealed that an additional 15 percent of teens are at risk of becoming overweight. What's so bad about being overweight or obese? For starters, it can cause diabetes, a life-shortening disease in which the body loses its ability to metabolize me·tab·o·lize v. 1. To subject to metabolism. 2. To produce by metabolism. 3. To undergo change by metabolism. metabolize to subject to or be transformed by metabolism. sugar. It can also lead to asthma and can cause heart disease. Most obese people just aren't healthy, overall. HEADS UP: A WILD CONNECTION What do you think? Could the health threats of drug addiction and obesity be connected? If you're like most people, you probably think, "No way." Well, you--and most people--are wrong! Think about it. People addicted ad·dict·ed adj. 1. Physiologically or psychologically dependent on a habit-forming substance. 2. Compulsively or habitually involved in a practice or behavior, such as gambling. to drugs and those who suffer from obesity have at least one thing in common. It can be extremely hard for them to stop doing things that they know are harming them. For the drug abuser, it's taking drugs. For the obese person, it's usually excessive eating (although there are other factors as well, as we'll learn). NIDA researchers decided to find out if and how the two disorders could be related. Their amazing a·maze v. a·mazed, a·maz·ing, a·maz·es v.tr. 1. To affect with great wonder; astonish. See Synonyms at surprise. 2. Obsolete To bewilder; perplex. v.intr. new findings indicate that there is a link. If you think back to what you've learned from earlier articles in this series, you can probably guess what the link is. Got it? It's dopamine and the brain. Researchers are discovering that obesity (like drug addiction) is, at least in part, a brain disease. HEADS UP: SEE SCIENCE IN ACTION! How did researchers find the obesity-addiction link? They started by reviewing what they already knew: Dopamine is a brain chemical that stimulates pleasurable feelings. When dopamine binds to special structures in your brain--called D2 receptors--it activates the brain's reward circuits. The end result? You feel good. For some time now, researchers have known that people who are addicted to alcohol, cocaine, and other drugs tend to have a lower-than-average number of D2 receptors in their brains. That makes sense when you think about it. If you have a shortage of D2 receptors, it's harder for you to feel good. It's harder for dopamine to find a D2 receptor to bind to to contract; as, to bind one's self to a wife s>. See also: Bind , so it takes more dopamine for you to feel pleasure. As it happens, most drugs of abuse cause a flood of dopamine in the brain. Taking drugs makes people feel better--in the immediate short term. Researchers also knew that eating can stimulate the production of dopamine in the brain. Could it be that obese people suffer from a shortage of D2 receptors? They might need to overeat o·ver·eat v. To eat to excess, especially habitually. to get feelings of pleasure from food. Using PET scanners PET scanner n. A device that produces cross-sectional x-rays of metabolic processes by means of positron emission tomography. PET scanning n. to look inside the brains of obese and non-obese people, researchers Nora Volkow Nora Volkow is director of the National Institute of Drug Abuse. She is Leon Trotsky's great-granddaughter. Sources
New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of showed that the more obese the person, the lower the number of D2 receptors. "The low number of receptors in obese people might be causing them to overeat," says Dr. Wang. "They might be doing it to compensate for reduced stimulation in their brain's reward circuits." Dr. Volkow adds, "An individual who has low sensitivity to normal stimuli learns behaviors, such as abusing drugs or overeating overeating eating too much food too quickly; leads to acute gastric dilatation in dogs and horses, acute carbohydrate engorgement in ruminants, dietetic (dietary) diarrhea in young calves and foals, abomasal tympany in bottle fed lambs and calves. , that will activate them." HEADS UP: ADDICTION MAY CAUSE THE DAMAGE Just because obese people and drug addicts share a shortage of D2 receptors, does that mean their disorders are caused by the lack of receptors? Not necessarily. It's a classic "chicken-and-egg" question. In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , which comes first--the addictive behavior Addictive behavior is any activity, substance, object, or behavior that has become the major focus of a person's life to the exclusion of other activities, or that has begun to harm the individual or others physically, mentally, or socially. or the D2 shortage? Maybe the addictive behavior causes the shortage. Or ... maybe the shortage causes the behavior? Dr. Wang says an experiment with animals indicates that "having plenty, of D2 receptors does protect against drug abuse and obesity." So, that's some evidence that the D2 shortage causes the behavior. The experiment Dr. Wang is talking about worked like this: Panayotis K. Thanes, a Brookhaven National Laboratory researcher, trained rats to regularly take alcohol, then introduced additional D2 receptors into their brains. As soon as the receptors took hold, the rats' consumption of alcohol decreased. Dr. Wang says researchers have had similar findings involving cocaine and food. Case closed? Not exactly. Scientists also know that the flood of dopamine in the brain that drug abuse causes can overstimulate the reward pathways--and cause a reduction in D2 receptors in abusers' brains. "In the end, people who become addicted could be much worse off biologically than when they started," says Joseph Frascella, Ph.D., of NIDA'S Division of Treatment Research and Development. HEADS UP: CHECK OUT THE DIFFERENCES Of course, there are major differences between drug addiction and obesity. For one, according to Dr. Wang, obesity is not all about the brain. "You have to consider a person's metabolism and other genetic issues," he says. "The brain chemistry is just part of the picture." Dr. Wang adds that it's not accurate to describe an obese person as a "food addict Any individual who habitually uses any narcotic drug so as to endanger the public morals, health, safety, or welfare, or who is so drawn to the use of such narcotic drugs as to have lost the power of self-control with reference to his or her drug use. ." Rather, one should say that overeating is an "addictive behavior." Also, drug addiction seems to cause more wide-ranging brain damage than obesity. For example, in people who are addicted to drugs, the drop in D2 receptors is often accompanied by a loss in functioning of the prefrontal prefrontal /pre·fron·tal/ (-fron´t'l) situated in the anterior part of the frontal lobe or region. pre·fron·tal adj. 1. cortex--the part of the brain responsible for judgment and impulse control impulse control Psychology The degree to which a person can control the desire for immediate gratification or other; IC may be the single most important indicator of a person's future adaptation in terms of number of friends, school performance and future . "In obesity, we didn't see any problems in the prefrontal cortex Noun 1. prefrontal cortex - the anterior part of the frontal lobe prefrontal lobe cerebral cortex, cerebral mantle, cortex, pallium - the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum ," says Dr. Wang. This probably explains why obese people, though compulsive when it comes to eating, have more control over their behavior than drug abusers. HEADS UP: KNOWLEDGE IS POWER NIDA scientists have made amazing discoveries Amazing Discoveries was a series of infomercials hosted by Mike Levey and produced by Levey's production company, Positive Response Television. It was also produced under the title Ask Mike. about the connection between drug addiction and obesity. Although these discoveries are fascinating, can they help people? Yes, definitely. This new information can help people addicted to drugs, obese people, and healthy teens who want to avoid drug addiction or obesity. How? First, the research shows us that having a healthy supply of D2 receptors in the brain can help stave off stave n. 1. A narrow strip of wood forming part of the sides of a barrel, tub, or similar structure. 2. A rung of a ladder or chair. 3. A staff or cudgel. 4. Music See staff1. addictive behaviors. So, anything that increases D2 levels could be a valuable weapon in the battle against drug abuse and obesity. With this in mind, NIDA researchers are looking to develop new medications. But is there anything safe and available now that can boost the level of D2 receptors in your brain? "Yes!" says Dr. Wang. "Exercise has been found to increase dopamine release and to raise the number of dopamine receptors Dopamine receptors are a class of metabotropic G protein-coupled receptors that are prominent in the vertebrate central nervous system (CNS). The neurotransmitter dopamine is the primary endogenous ligand for dopamine receptors. ," he says. "This suggests that obese people might be able to boost their dopamine response through exercise instead of eating--which is just one more reason to exercise if you are trying to lose weight." He feels that exercise can be helpful for recovering addicts, as well. Dr. Wang also notes that animal studies have revealed that group interactions can increase D2 receptor levels. So, exercising and spending time "Spending Time" is the first single released by Christian artist Stellar Kart. The lyrics describe the band members desire to spend "more time with God". "Sometimes it’s a real struggle to spend time with God. with family and friends can help you keep your mind and body healthy--and help you avoid developing addictive behaviors. That's all good to know. But according to Dr. Wang, perhaps the most important way the research can help is by giving people an understanding of their own behavior. It helps remove the mystery and stigma that surround addictive behaviors. "When you know the reason why," says Dr. Wang, "it makes everything much easier." Cutting Edge How Do You Design an Experiment? By using their knowledge of addiction and how the brain works, Dr. Volkow and her colleagues had an idea: Maybe obese people have low numbers of D2 dopamine receptors in their brains--just like drug addicts. How did the researchers test their theory? They used the scientific method. The scientific method--which scientists in all disciplines have followed for hundreds of years--has four steps. 1. OBSERVE Researchers observed that D2 receptor levels are lower than normal in many drug abusers. 2. QUESTION Researchers raised the question of whether obese people, whose behavior can be described as "addictive," might also have low D2 levels. 3. PREDICT Researchers came up with a hypothesis: People suffering from obesity will have lower D2 levels than people whose weight is normal. 4. TEST Researchers took PET scans PET scan (pĕt) or positron emission tomography (pŏz`ĭtrŏn' ĭmĭsh`ən təmŏg`rəfē) of obese adults to see how many D2 receptors they had. The researchers validated the experiment by testing a control group--a similarly made up group of non-obese people. Accurate results from the obese group are only obtainable by looking at the results from the control group. The researchers also made sure the experiment was quantitative. In other words, they made exact measurements. (It wouldn't have been enough to say, "There were oodles of D2 receptors in that thin woman's brain.") Finally, the experiment was valid because it was set up in a way that was replicable--it could be repeated and tested by other scientists. Wake-Up Call How Much is Too Much? What's the difference between being overweight and "just a bit chunky chunk·y adj. chunk·i·er, chunk·i·est 1. Short and thick; stocky. 2. Containing small thick pieces: chunky peanut butter; chunky soup. "? The Centers for Disease Control and Prevention has very strict definitions of weight-related terms. They're net based on hew hew v. hewed, hewn or hewed, hew·ing, hews v.tr. 1. To make or shape with or as if with an ax: hew a path through the underbrush. 2. a person looks in jeans, they're calculated using height, weight, and--for people under 21--age and gender. If you're worried that you have a weight problem, you should talk to a health professional. He or she will likely determine your body mass index (BMI BMI body mass index. BMI abbr. body mass index Body mass index (BMI) A measurement that has replaced weight as the preferred determinant of obesity. ) using this formula: BMI = (Weight in Pounds) / ((Height in Inches) x (Height in Inches)) x 703 With your BMI and a specially made chart, the health professional can determine what percentile percentile, n the number in a frequency distribution below which a certain percentage of fees will fall. E.g., the ninetieth percentile is the number that divides the distribution of fees into the lower 90% and the upper 10%, or that fee level your BMI falls into. The percentile shows how your BMI compares with that of other teens of the same gender and age. * BMI value at or above the 95th percentile is considered overweight. * BMI value between the 85th and 95th percentiles is considered at risk for becoming overweight. * BMI value between the 6th and 84th percentiles is considered healthy. * BMI value below the 6th percentile is considered underweight Underweight An situation where a portfolio does not hold a sufficient amount of securities to satisfy the accepted benchmark of the portfolio's asset allocation strategy. Notes: . As you may have noticed, there is no "obese" category for teens. That's because, unlike adults, young people's bodies are growing and changing. Once you reach adulthood, your body levels off. But teens who are overweight not only face health problems, they are also at higher risk for becoming obese as adults. As BMI increases in adults, so does risk of the following: * premature death Premature Death occurs when a living thing dies of a cause other than old age. A premature death can be the result of injury, illness, violence, suicide, poor nutrition (often stemming from low income), starvation, dehydration, or other factors. * diabetes * cardiovascular disease Cardiovascular disease Disease that affects the heart and blood vessels. Mentioned in: Lipoproteins Test cardiovascular disease * high blood pressure * arthritis * certain cancers If it turns out that you de have a weight problem, you and your parents can talk with your health professional about what actions you can take to improve your health. Facts for Real Life Q. Why is the number of overweight teens growing so rapidly? A. Nobody knows for sure. It could be that today's teens are less physically active than those a generation ago. It may be that people are eating bigger portions of food than ever before. Dr. Volkow thinks one factor is the increasing ease with which people can get food today. Researchers are finding that there's a region of the brain--called the dorsal dorsal /dor·sal/ (dor´s'l) 1. pertaining to the back or to any dorsum. 2. denoting a position more toward the back surface than some other object of reference; a synonym of posterior striatum--that is programmed to draw people to food even when they're not hungry. "This system was once very important for survival," says Dr. Volkow. "It was important to want food whenever you could get it, because you never knew when it was going to be around." In the contemporary United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. , though, where there are fast-food outlets and convenience stores The following is a list of convenience stores organized by geographical location. Stores are grouped by the lowest heading that contains all locales in which the brands have significant presence. on every corner, "the system doesn't serve any purpose anymore," says Dr. Volkow. Now, with food so easy to get, people who follow their brains' instructions to eat, eat, eat are not staving off starvation--they're growing overweight. Lesson 1: Obesity and Drug Addiction--What Do You Know? OBJECTIVE To give students information about the connection between drug addiction and obesity; to increase students' understanding of addiction and the brain; to broaden students' understanding of the scientific process; and to assess students' knowledge of the topics before and after reading the article NATIONAL SCIENCE EDUCATION STANDARDS The National Science Education Standards (NSES) are a set of guidelines for the science education in primary and secondary schools in the United States, as established by the National Research Council in 1996. Life Science; Technology; Science in Personal and Social Perspective WHAT YOU WILL DO * Before beginning the lesson, hold a class discussion based on these questions: "Are there more teens who have weight problems now than in the past?" "How big of a problem is obesity?" "Could there be a connection between obesity and drug addiction?" * Tell students that they are going to find out how much they know about food addiction and its connection to drug abuse. Distribute copies of Student Activity Reproducible 1. Tell students to write their names on the paper and label it No. 1. Then have them answer the questions. Collect and grade the papers. * Have students read the article, "Obesity and Drug Addiction: The Brain Link." Next, hold a discussion based on these questions: "What is the connection between obesity and drug addiction?" "How can this connection help scientists understand how to treat and prevent both conditions?" * Next, tell students it's time It's Time was a successful political campaign run by the Australian Labor Party (ALP) under Gough Whitlam at the 1972 election in Australia. Campaigning on the perceived need for change after 23 years of conservative (Liberal Party of Australia) government, Labor put forward a to find out how much they've learned. Give them a second copy of Student Activity Reproducible 1. Tell them to write their names on the paper and label it No. 2. When students have finished, collect the papers, score them, and record your data in the Assessment Guide below. * Wrap up the lesson by discussing the "chicken-and-egg" question from the article: "What comes first, obesity or drug addiction, or a low level of D2 receptors in the brain?" ANSWERS TO QUIZ QUESTIONS: 1. d; 2. c; 3. c; 4. b; 5. d; 6. b; 7. c; 8. c; 9. d; 10. a. Lesson 2: Dangerous Cravings and the Brain OBJECTIVE Students use scientific data to draw conclusions about the effect of increasing D2 dopamine receptor levels in the brain. NATIONAL SCIENCE EDUCATION STANDARDS Science as Inquiry; Science in Personal and Social Perspective WHAT YOU WILL DO * Tell students that scientists know that D2 receptor levels are lower in people who suffer from obesity or drug or alcohol addiction. Ask students why they believe this is so. * Explain that students will read about an experiment in which alcohol-addicted and non-alcohol-addicted rats were medically altered to increase D2 receptor levels in their brains. The researchers compared the alcohol intake of the rats before and after the treatment. Ask students: "If increasing the D2 receptors causes the alcohol-addicted rats to stop drinking, what might be the implications for humans?" * Distribute Student Activity Reproducible 2. Have students complete it. * Wrap up the lesson by asking students to speculate on how this experiment and others like it might lead to useful treatments for addiction. ANSWERS TO REPRODUCIBLE: 1. Yes, the increase in DE receptors led to a drop in alcohol consumption. 2. Alcohol consumption fell in both groups, but the percentage drop was larger among the alcohol-addicted rats. In the non-alcohol-preferring rats, the D2 increase almost totally abolished alcohol consumption. In the rats that preferred alcohol, it reduced alcohol consumption to the level normally seen in non-alcohol-preferring rats. 3. This was done as a control to show that it wasn't the pressure of the needle itself but the D2 receptor gene causing the change in consumption. Obesity and Drug Addiction--What Do You Know? Test your knowledge of obesity, drug addiction, and the possible connection between the two by taking this quiz. Circle the correct answer to each question. 1. Between 1980 and 2002, the proportion of overweight teens in the United States a. didn't change. b. doubled. c. fell by half. d. tripled. 2. What percentage of U.S. teens is at risk for becoming overweight or obese? a. 5 percent b. 10 percent c. 15 percent d. 20 percent 3. Which of the following health problems is not associated with obesity? a. diabetes b. arthritis c. schizophrenia d. heart disease 4. In what organ did researchers find similarities between obese people and people addicted to drugs? a. stomach b. brain c. skin d. lungs 5. Which natural chemical activates the brain's reward circuits? a. insulin b. norepinephrine norepinephrine (nôr'ĕpīnĕf`rən), a neurotransmitter in the catecholamine family that mediates chemical communication in the sympathetic nervous system, a branch of the autonomic nervous system. c. endorphins endorphins (ĕndôr`fĭnz), neurotransmitters found in the brain that have pain-relieving properties similar to morphine. There are three major types of endorphins: beta endorpins, found primarily in the pituitary gland; and enkephalins and d. dopamine 6. People addicted to drugs and obese people tend to have lower-than-normal numbers of a. brain cells. b. D2 receptors. c. insulin receptors insulin receptor A heterodimeric membrane receptor composed of α and β chains, which has tyrosine kinase activity after binding insulin; IR deficiency is a rare cause of DM and may be due to a gene rearrangement, causing a deletion in the . d. family members. 7. People addicted to drugs tend to have damage to a part of the brain responsible for judgment and impulse control. It is a. the brain stem brain stem, lower part of the brain, adjoining and structurally continuous with the spinal cord. The upper segment of the human brain stem, the pons, contains nerve fibers that connect the two halves of the cerebellum. . b. the hypothalamus hypothalamus (hī'pəthăl`əməs), an important supervisory center in the brain, rich in ganglia, nerve fibers, and synaptic connections. It is composed of several sections called nuclei, each of which controls a specific function. . c. the prefrontal cortex. d. the cerebrum cerebrum: see brain. cerebrum Largest part of the brain. The two cerebral hemispheres consist of an inner core of myelinated nerve fibres, the white matter, and a heavily convoluted outer cortex of gray matter (see cerebral cortex). . 8. Teens with a body mass index (BMI) above the 95th percentile are considered a. underweight. b. normal weight. c. overweight. d. obese. 9. Which of these boosts the number of D2 receptors in the brain? a. overeating b. drinking alcohol c. reading d. exercise 10. If you think you are overweight, you should a. check with your doctor. b. buy a diet book. c. diet immediately. d. run 10 miles. Dangerous Cravings and the Brain Researchers have found that people suffering from obesity, alcohol addiction, and drug addiction tend to have lower- than-average numbers of D2 (dopamine) receptors in their brains. In 2001, researchers at Brookhaven National Laboratory in New York conducted an experiment using rats to find out if increasing the number of D2 receptors in rats' brains would decrease the amount of alcohol consumed by rats that had been trained to prefer alcohol over water. The experiment was conducted with two groups: normal rats and rats that had been trained to prefer alcohol. Rats, D2 Receptors, and Alcohol Intake Hypothesis: An increase in the number of D2 receptors in the brains of rats trained to prefer alcohol will make alcohol less appealing and cause them to drink less of it. Brief Description of Experiment: The researchers, led by Panayotis K. Thanes, injected a virus carrying the D2 receptor gene into the nucleus accumbens The nucleus accumbens (NAcc), also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus leaning against the septum), is a collection of neurons within the forebrain, located where the head of the caudate and the anterior (the pleasure center of the brain) of rats. This caused their brains to produce more D2 receptors. Brain imaging techniques were used to measure the increase. Of the 15 rats that received injections, six had been trained to prefer alcohol over water. (On average, 60 percent of the liquid they chose to drink was alcohol.) Nine rats preferred water. The experiment began when the needle that would carry the gene was implanted in the rats' brains as a control. After eight days with the needle in place, the virus-carrying gene was injected. Each day, scientists measured the rats' alcohol intake. The rats could choose from two bottles: one filled with water and the other with alcohol. The Results of the Experiment [ILLUSTRATION OMITTED] D2 Receptor Levels In both alcohol-addicted and non-alcohol-addicted rats, D2 receptor levels rose--in most cases there was an approximate 50 percent increase about four days after injection of the virus-carrying gene. The D2 receptor level fell to about 8 percent above normal levels by the tenth day after the injection. Now that you have read about the experiment, answer these questions. Write your answers on the back of this page. 1. Did the researchers prove their hypothesis? 2. How did the results differ in the alcohol-addicted and non-alcohol-addicted rats? Are the results permanent? 3. Why do you think researchers waited eight days before injecting the D2 receptor gene? |
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