 |
|
Dragonfly's metabolic disease provides clues about human obesity
November 21, 2006Parasite-infected dragonflies suffer the same metabolic disorders that have led to an epidemic of obesity and type-2 diabetes in humans, reveal the findings of research conducted at Penn State University that are due to be published in the 5 December 2006 issue of the Proceedings of the National Academy of Science and also in the PNAS early online edition at www.pnas.org on 21 November. The discovery expands the known taxonomic breadth of metabolic disease and suggests that the study of microbes found in human intestines may provide a greater understanding of the root causes of human metabolic dysfunction.
James Marden, professor of biology and an insect physiologist at Penn State, and Ruud Schilder, who in August 2006 earned his doctorate in biology at Penn State and is now a postdoctoral fellow at the University of Nebraska, are the first to show a non-mammalian species suffering from metabolic dysfunction in ways similar to humans. "Metabolic disease isn't some strange thing having just to do with humans," said Marden. "Animals in general suffer from these symptoms."
The work is also novel because it links metabolic disease to a supposedly harmless parasite living in the dragonfly's gut. The parasites, known as gregarines, belong to the Apicomplexa, a group of microorganisms that includes protozoa, which cause diseases like malaria and cryptosporidiosis. The dragonfly species that Marden and Schilder studied is Libellula pulchella. The microbes disrupting the dragonfly metabolism may hold clues for scientists looking for the root causes of metabolic diseases in humans, according to Marden and Schilder's paper
"All of these symptoms, and the underlying processes behind these symptoms that we're seeing in these dragonflies, are pretty much identical to what you see in mammalian metabolic syndrome and obesity," said Marden. "We're seeing it all relate back to this non-invasive protozoan in the gut." The work raises a fascinating question about what role microbial communities found in human intestines may play in human metabolic disorders like insulin resistance, type-2 diabetes, and obesity. In mammals, these metabolic disorders are known to be associated with a chronic inflammatory response, thought to be triggered by an accumulation of fat.
In Marden and Schilder's dragonflies, the reverse happens. Parasitic infection triggers an inflammatory response and immediate changes in metabolism. Unable to metabolize fat, the dragonflies accumulate fat around their muscles. This finding begs the question of whether something similar might be happening in human metabolic diseases, the root causes of which remain poorly understood despite intense study.
"Might disturbances in the microbial balance of human intestines trigger an immune system response that leads to metabolic disease?" Marden and Schilder asked. "More attention should be paid to the microbial balance in the intestines of people who suffer from obesity," said Schilder. "It seems plausible that disturbance in the microbial community in humans might trigger these inflammatory responses."
There are some other clues indicating that this may be an important question. "What we're finding in insects is that they become obese when parasites cause inflammation that affects metabolism," said Marden. "That seems akin to what's happening in humans when they get type-2 diabetes. It's not because there's been a change in the genetic composition of the population. it's because something has changed in our environment." One change in the human environment is the dramatic increase in soft-drink consumption among Americans, estimated to be 500 percent over 50 years from the 1940s to the 1990s. "We looked in the literature and found that consumption of high-fructose corn syrup often is associated with gastrointestinal distress, which may be a sign that fructose affects the gut microbial flora," said Marden.
Another clue is that some AIDS patients, with compromised immune systems, have chronic problems with Cryptosporidium (a protozoan parasite closely related to the one found in dragonflies) that over time impairs their metabolism in a similar fashion to what Schilder and Marden found for infected dragonflies. "That information gave us the courage to connect the dots," said Marden. "Granted, it is a big extrapolation to think that our dragonfly results might have any relevance for human disease, but it would be irresponsible for us to not point out these possibilities. People who study metabolic disease should test the hypothesis that changes in gut microbial composition can cause these syndromes."
Marden's lab, which studies how insect muscles work and affect the animal's survival and reproductive capabilities, can mechanically isolate single flight muscles and measure their mechanical power output under conditions similar to those in nature. The researchers noted that the muscles of some dragonflies are able to perform at 80 watts per kg. while others of the same species could perform at up to 220 watts per kg. The life of a dragonfly and successful mating requires intense competition for pond territory, aerial contests, and high-performance flight. "These guys are the jet fighters of the insect world," said Marden. Flight muscle makes up 60 percent of their body mass. The large variation in muscle output was intriguing because natural selection, over time, would weed out the submissive, poor flyers if the trait were genetically based. When the researchers looked in the gut of the dragonflies with poor muscle output, they found parasites.
Healthy dragonflies can adjust their muscle performance according to how much fat they have available in their bodies, but the dragonflies infected with parasites weren't making that adjustment, Marden observed. He and Schilder began looking for an explanation and ultimately found many key differences between the tissues and performance of healthy dragonflies and parasite-infected dragonflies that match symptoms of metabolic syndrome in humans. One symptom involves the signaling molecule, p38 MAP kinase, a common indicator of stress response in humans and other animals. The signaling molecule was chronically activated in the flight muscles of parasite-infected dragonflies, but not in muscles from healthy dragonflies. Activation of p38 MAP kinase has been shown to be related to the development of insulin resistance and metabolic disease in humans. "What's more, we could induce this activation in muscles from healthy individuals by exposing them to excretory-secretory products obtained from the gregarine parasites," said Schilder.
The researchers also found that the muscles of parasite-infected dragonflies oxidized only carbohydrates instead of a carbohydrate-lipid mix. A common symptom of metabolic syndrome is that muscles metabolize fewer lipids. The researchers also found that unused lipids accumulated in the dragonflies' thorax. Humans with metabolic disease tend to accumulate fat around skeletal muscle tissue.
Marden and Schilder's experiments also found the hemolymph carbohydrate concentrations in parasite-infected dragonflies to be about double those of healthy dragonflies, and found insulin to have little effect on those concentrations. Insulin resistance is an abnormality associated with metabolic syndrome in humans. The researchers found the parasites rapidly caused effects in the dragonflies. Dragonflies that drank water containing trace amounts of excretory-secretory substances obtained from live parasites showed effects in two days. Abnormal blood glucose concentrations are a symptom of metabolic syndrome in humans. Marden and Schilder also concluded that insects may be useful models to understand more about metabolic disease in humans. Their work was supported by grants from the U.S. National Science Foundation.
Penn State
"All of these symptoms, and the underlying processes behind these symptoms that we're seeing in these dragonflies, are pretty much identical to what you see in mammalian metabolic syndrome and obesity," said Marden. "We're seeing it all relate back to this non-invasive protozoan in the gut." The work raises a fascinating question about what role microbial communities found in human intestines may play in human metabolic disorders like insulin resistance, type-2 diabetes, and obesity. In mammals, these metabolic disorders are known to be associated with a chronic inflammatory response, thought to be triggered by an accumulation of fat.
In Marden and Schilder's dragonflies, the reverse happens. Parasitic infection triggers an inflammatory response and immediate changes in metabolism. Unable to metabolize fat, the dragonflies accumulate fat around their muscles. This finding begs the question of whether something similar might be happening in human metabolic diseases, the root causes of which remain poorly understood despite intense study.
"Might disturbances in the microbial balance of human intestines trigger an immune system response that leads to metabolic disease?" Marden and Schilder asked. "More attention should be paid to the microbial balance in the intestines of people who suffer from obesity," said Schilder. "It seems plausible that disturbance in the microbial community in humans might trigger these inflammatory responses."
There are some other clues indicating that this may be an important question. "What we're finding in insects is that they become obese when parasites cause inflammation that affects metabolism," said Marden. "That seems akin to what's happening in humans when they get type-2 diabetes. It's not because there's been a change in the genetic composition of the population. it's because something has changed in our environment." One change in the human environment is the dramatic increase in soft-drink consumption among Americans, estimated to be 500 percent over 50 years from the 1940s to the 1990s. "We looked in the literature and found that consumption of high-fructose corn syrup often is associated with gastrointestinal distress, which may be a sign that fructose affects the gut microbial flora," said Marden.
Another clue is that some AIDS patients, with compromised immune systems, have chronic problems with Cryptosporidium (a protozoan parasite closely related to the one found in dragonflies) that over time impairs their metabolism in a similar fashion to what Schilder and Marden found for infected dragonflies. "That information gave us the courage to connect the dots," said Marden. "Granted, it is a big extrapolation to think that our dragonfly results might have any relevance for human disease, but it would be irresponsible for us to not point out these possibilities. People who study metabolic disease should test the hypothesis that changes in gut microbial composition can cause these syndromes."
Marden's lab, which studies how insect muscles work and affect the animal's survival and reproductive capabilities, can mechanically isolate single flight muscles and measure their mechanical power output under conditions similar to those in nature. The researchers noted that the muscles of some dragonflies are able to perform at 80 watts per kg. while others of the same species could perform at up to 220 watts per kg. The life of a dragonfly and successful mating requires intense competition for pond territory, aerial contests, and high-performance flight. "These guys are the jet fighters of the insect world," said Marden. Flight muscle makes up 60 percent of their body mass. The large variation in muscle output was intriguing because natural selection, over time, would weed out the submissive, poor flyers if the trait were genetically based. When the researchers looked in the gut of the dragonflies with poor muscle output, they found parasites.
Healthy dragonflies can adjust their muscle performance according to how much fat they have available in their bodies, but the dragonflies infected with parasites weren't making that adjustment, Marden observed. He and Schilder began looking for an explanation and ultimately found many key differences between the tissues and performance of healthy dragonflies and parasite-infected dragonflies that match symptoms of metabolic syndrome in humans. One symptom involves the signaling molecule, p38 MAP kinase, a common indicator of stress response in humans and other animals. The signaling molecule was chronically activated in the flight muscles of parasite-infected dragonflies, but not in muscles from healthy dragonflies. Activation of p38 MAP kinase has been shown to be related to the development of insulin resistance and metabolic disease in humans. "What's more, we could induce this activation in muscles from healthy individuals by exposing them to excretory-secretory products obtained from the gregarine parasites," said Schilder.
The researchers also found that the muscles of parasite-infected dragonflies oxidized only carbohydrates instead of a carbohydrate-lipid mix. A common symptom of metabolic syndrome is that muscles metabolize fewer lipids. The researchers also found that unused lipids accumulated in the dragonflies' thorax. Humans with metabolic disease tend to accumulate fat around skeletal muscle tissue.
Marden and Schilder's experiments also found the hemolymph carbohydrate concentrations in parasite-infected dragonflies to be about double those of healthy dragonflies, and found insulin to have little effect on those concentrations. Insulin resistance is an abnormality associated with metabolic syndrome in humans. The researchers found the parasites rapidly caused effects in the dragonflies. Dragonflies that drank water containing trace amounts of excretory-secretory substances obtained from live parasites showed effects in two days. Abnormal blood glucose concentrations are a symptom of metabolic syndrome in humans. Marden and Schilder also concluded that insects may be useful models to understand more about metabolic disease in humans. Their work was supported by grants from the U.S. National Science Foundation.
Penn State
Science News and Science Current Events Tag Cloud
This tag cloud is a visual representation of term frequencies of random science news topics with common terms grouped together and emphasized by their display size.
Allergic Reactions Herbicide Minimally invasive surgery Cosmic Rays Estrogen therapy Mangrove Juvenile Idiopathic Arthritis Supercomputer Copd Helicobacter pylori Hurricane Katrina Tigers Antibodies Heart Surgery Graphene Depression Motor Neurons Neanderthal Cleft Palate Defibrillator Galaxies MicroRNA Ischemic Stroke Gene Therapy Fishing
See More: Science News Tags
Metabolic Disease Current Events and Metabolic Disease News RSSExposure to phthalates may be a risk factor for low birth weight in infants
Many parents worry about their child's exposure to phthalates, the chemical compounds used as plasticizers in a wide variety of personal care products, children's toys, and medical devices.
Diabetes patients should have regular exercise, weight training
To reduce their cardiovascular risk, people with type 2 diabetes should do at least two-and-a-half hours per week of moderate-intensity or one-and-a-half hours per week of vigorous-intensity aerobic exercises, plus some weight training, according to an American Heart Association scientific statement published in Circulation: Journal of the American Heart Association.
A Biological Basis for the 8-Hour Workday?
The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly. Scientists already know that some genes are controlled by the clock and are turned on only one time during each 24-hour cycle.
Discovery offers new understanding of diabetes drug target
Scientists at the University of Leicester have published findings about a new advance in the study of major diabetes drug target.
'Healthy' individuals may be at risk for heart disease
In the face of a growing obesity epidemic in the United States, researchers at Wake Forest University Baptist Medical Center have new study results that indicate that how much fat a person has is not as important as where that fat is located when assessing risk for cardiovascular events and metabolic disease.
Safer and more effective way to treat Crohn's disease
An international research study, published in The Lancet, has thrown into question the current method of treating Crohn's disease - opening the door to a safer and more effective treatment option for sufferers of the chronic disease.
SAGE's American Journal of Lifestyle Medicine looks at the health benefit of oats
The first issue of Volume 2 (January/February 2008) explores the results of the "Oats at 10 Years" study, marking the 10th anniversary of the U.S. Food and Drug Administration claim that oats, as part of an overall heart healthy diet, could lower the risk of heart disease.
UCSD researchers discover inflammation, not obesity, cause of insulin resistance
Researchers at the University of California, San Diego (UCSD) School of Medicine have discovered that inflammation provoked by immune cells called macrophages leads to insulin resistance and Type 2 diabetes.
Once-fatal metabolic disorders treatable, says Stanford/Packard researcher
People with a class of rare genetic disorders that often lead to brain damage, coma and death can be successfully treated with drugs, says a researcher at the Stanford University School of Medicine and Lucile Packard Children's Hospital.
Metabolic disease too easily missed
Dutch researcher Terry Derks has demonstrated that the metabolic disease MCAD deficiency can be detected at an early stage. At present the disease is only found in half of the expected number of patients.
More Metabolic Disease Current Events and Metabolic Disease News Articles
 |
Inborn Metabolic Diseases: Diagnosis and Treatment by John Fernandes (Editor), Jean-Marie Saudubray (Editor), Georges van den Berghe (Editor), John H. Walter (Editor) This henceforth classical textbook has become indispensable for those in the front line dealing with metabolic disorders. As with previous editions the book is aimed at all those involved with this specialty including pediatricians, biochemists, dieticians, neurologists, internists, geneticists, psychologists, nurses, and social workers. This 4th edition has been thoroughly updated and revised and John Walter has joined the three other editors. One new chapter on Neonatal screening by tandem MS/MS has been added and several new groups of disorders have been included; for example defects involving the pentose phosphate pathway (polyols metabolism) and disorders of glucose transport. The first chapter presents the clinical approach to inherited metabolic disease using many... |
 |
Neurology of Hereditary Metabolic Disease of Children by Gilles Lyon (Author), Edwin Kolodny (Author), Gregory Pastores (Author) The expert, up-to-date guidance you need to identify, understand, and treat neurogenetic disorders in children Written in a readily-accessible, highly-readable style, this unique reference offers a sound starting point and clinical step-by-step approach to treating the complex and often baffling neurogenetic diseases found in children. Conveniently organized by age groups from prenatal diagnosis to neonate to childhood, each chapter begins by describing symptoms (similar to the way a patient would present), and then guides you through confirming the diagnosis and choosing the appropriate course of therapy. Completely updated to reflect the significant advances made following the discovery of the DNA sequence on the human genome, the Third Edition of... |
 |
Physician's Guide to the Treatment and Follow-Up of Metabolic Diseases by Springer This clinical reference provides concise information on the treatment and management of inherited metabolic diseases. World experts cover all commonalities of therapy giving practical advice and guidance. All established treatment protocols in this quickly developing area of medicine are clearly described, including follow-up protocols and monitoring. Alternative and experimental therapies are also described and evaluated. Numerous tables and figures allow rapid access to specific details. This book is invaluable to anyone dealing with patients with inherited metabolic diseases, pediatricians, internists, neurologists, and clinical geneticists. |
 |
A Clinical Guide to Inherited Metabolic Diseases by Joe T. R. Clarke (Author) This user-friendly clinical handbook provides a clear and concise overview of how to recognize and diagnose inherited metabolic diseases. The reader is led through the diagnostic process from the identification of those features of an illness suggesting that it might be metabolic through the selection of appropriate laboratory investigation to a final diagnosis. The new edition provides more in-depth coverage on mitochondrial disease and congenital disorders of glycosylation. The chapters on neurological syndrome and newborn screening are greatly expanded, as well as those on laboratory investigation and treatment. |
|
Primer on Metabolic Bone Diseases and Disorders of Mineral M by Amer Soc Bone Mineral Research Published by the American Society for Bone and Mineral Research. Discusses principals of bone biology, bone anatomy, roots of bone disorders and much more! | |
 |
Atlas of Metabolic Diseases (A Hodder Arnold Publication)(2nd Edition) by William L. Nyhan M.D. (Author), Bruce A. Barshop M.D. (Author), Pinar T. Ozand M.D. (Author) In a field where even experts may find that years have elapsed since they last encountered a child with a given disorder, it is essential for the clinician to have a comprehensive source of practical and highly illustrated information covering the whole spectrum of metabolic disease to refer to. The second edition of this highly regarded book, authored by three of the foremost authorities in pediatric metabolic medicine, fulfils this need by providing an invaluable insight into the problems associated with metabolic diseases. For ease of reference, Atlas of Metabolic Disease is divided into sections of related disorders, such as disorders of amino acid metabolism, lipid storage disorders and mitochondrial diseases, with an introductory outline where appropriate summarizing the biochemical... |
 |
Heart Disease and South Asians: A Population at Risk Why are South Asians a higher risk group for cardiovascular disease and type 2 diabetes? What lifestyle changes can lower the risk to you and your family? How should you discuss this risk with your doctor? Dr.Gerald Reaven, world-renowned researcher on the importance of abnormal insulin action in type 2 diabetes and heart disease and Dr. Meenakshi Aggarwal, specialist in cardiovascular diseases, outline the problems faced by this population and present the latest research to help you monitor and minimize your risk. |
 |
Metabolic Syndrome and Cardiovascular Disease: Epidemiology, Assessment, and Management by Informa HealthCare Addressing a topic of utmost importance in the field, this text addresses the epidemiology, diagnosis, assessment, and management of patients with metabolic syndrome-focusing on implications for cardiovascular disease risk. With an abundance of clearly organized tables, flowcharts, and practice guidelines, this blue-ribbon source succinctly analyzes recent clinical trials, compares and assesses recent and emerging therapies, and provides recommendations for the improved assessment and treatment of patients, while supplying a state-of-the-art overview of approaches to optimize and enhance patient care. |
 |
Professional Guide to Diseases Hardbound, 8th Edition by Anatomical Chart Company 1-58255-370-X: Professional Guide to Diseases: full descriptionProfessional Guide to Diseases, Eighth Edition is the newest edition of the health care professional's guide to disease management and patient care. This complete yet concise reference covers over 600 disorders, including emerging diseases such as metabolic syndrome, monkeypox, SARS, Creutzfeldt-Jakob (mad cow) disease, and antibiotic-resistant infections. Coverage also includes terrorist agents such as anthrax.The easy-to-use format presents comprehensive disease information ranging from causes, signs and symptoms, and diagnosis through treatment and special considerations. Helpful tips, charts, anatomic drawings, and other illustrations supplement the text. This edition includes expanded information on obesity treatments and... |
 |
Primer on the Metabolic Bone Diseases And Disorders of Mineral Metabolism by Clifford J. Rosen (Author), Clifford J. Rosen (Editor) This comprehensive yet concise handbook is an indispensable reference for the many clinicians who see patients with disorders of bone formation, metabolic bone diseases, or disorders of stone formation. It is also a crucial tool for researchers, students, and all other professionals working in the bone field. In a format designed for quick reference, it provides complete information on the symptoms, pathophysiology, diagnosis, and treatment of all common and rare bone and mineral disorders. New in this edition: detailed coverage of osteonecrosis of the jaw, more in-depth coverage of cancer and bone including new approaches to pathogenesis, diagnosis, and treatment; new approaches to anabolic therapy of osteoporosis; the latest research on Vitamin D; expanded coverage of international... |
| © 2009 BrightSurf.com |