Digestive Diseases News
Winter 2008
NIH Roadmap Initiative Focuses on Microorganisms
A major research project involving the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) will help scientists understand the role bacteria, fungi, and other microbes play in human health and disease. The Human Microbiome Project (HMP) will help develop research tools and strategies to improve understanding, treatment, and prevention of inflammatory bowel disease, obesity, diabetes, and other health conditions.
“The Human Microbiome Project will help us understand the microbial environment in the gut, as well as provide us with the tools and technology to expand our exploration into this field of research,” said NIDDK Director Griffin P. Rodgers, M.D., M.A.C.P., co-chair of the HMP’s Implementation Group.
The estimated 10 to 100 trillion microorganisms that inhabit the human body actually outnumber the body’s own cells by a factor of 10. The human microbiome is the genetic sum of this community of microorganisms. Scientists are finding some surprising ways human-associated microbes influence human health and vice versa.
For example, NIDDK-funded research led by Jeffrey Gordon, M.D., at Washington University in St. Louis, suggests gut bacteria may affect body weight. Gordon’s group correlated weight loss in obese individuals with a change in the relative abundance of the two major types of gut bacteria—Firmicutes and Bacteroidetes. As study participants lost weight on either of two types of low-calorie diets, the proportional representation of the Bacteroidetes increased significantly. In studies using mice, Gordon’s group has shown that gut bacteria not only affect the body’s ability to extract calories from food but also regulate host genes involved in energy metabolism.
Major Scientific Resource
The HMP, with $115 million in funding for 5 years, officially became an NIH Roadmap for Medical Research initiative last May. Roadmap initiatives address major opportunities or gaps in research that no single institute can tackle alone.
The HMP’s first goal is to assemble a reference database containing the genomes of human-associated microorganisms. The HMP has already begun sequencing the genomes of human-associated microbes that are cultivable. Later on, the project will focus on strategies to cultivate and sequence organisms that do not grow in a lab. With the help of various partners, the HMP plans to sequence the genomes of about 1,000 different organisms.
“The Human Microbiome Project is essentially an enormous survey of the bacteria that populate our gut and other sites and what they are doing there,” said Robert Karp, Ph.D., the NIDDK’s director of the Genetics and Genomics Programs, Division of Digestive Diseases and Nutrition, and representative for the NIH Human Microbiome Working Group. “It is going to be a major scientific resource for researchers.”
Like the Human Genome Project, which deciphered the human DNA code, data from the HMP will be a public resource available not only to NIH researchers but to scientists around the globe.
Microbial Diversity
The project will also begin to examine the diversity of the human microbiome by sampling
a number of specific body sites including the gut, vagina, mouth, nose, and skin of volunteers. This process will help scientists gauge the breadth of the human microbiome and begin to answer the following questions:
- Do humans have a core microbiome, or a set of microbes that is fundamentally different from other host species?
- What factors, such as diet and the use of antibiotics, influence the microbiome?
- Does the microbiome change with age?
- How does the microbiome correlate with health and disease?
“This is a pilot project,” said Jane Peterson, Ph.D., HMP program director and associate director of extramural research at the NIH National Human Genome Research Institute. According to Peterson, the HMP will not define the microbiome for all people and health conditions but will establish the resources and demonstrate strategies researchers need to conduct disease-specific research.
New Research Tools
Hopefully, new technologies will emerge from the project that will allow scientists to study microorganisms within the context of the human microenvironment and complex human microbe interactions. The HMP also will develop new computational analysis tools to make sense of the very complex data the project will generate.
In December 2007, HMP working group members met with scientists outside the United States to discuss the creation of an international consortium to coordinate efforts to characterize the human microbiome. For more information about the HMP and the NIH Roadmap project, go to www.nihroadmap.nih.gov.
Probiotics: Friendly Bacteria
Probiotics—sold as supplements in capsule form and as ingredients in foods such as yogurt, cheese, baby food, and energy bars—are live microorganisms that people consume for anticipated health benefits. Prebiotics are foods or ingestible substances that stimulate the growth or activity of probiotics.
The idea of ingesting microorganisms for the sake of health has been around at least since the early twentieth century. And judging by the millions of dollars in the sale of products containing probiotics, American consumers have embraced the idea despite minimal manufacturer evidence that probiotics work. Only recently have scientists begun testing probiotics in controlled, clinical trials.
In December 2007, the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health (NIH) co-sponsored the Gastrointestinal Microbiota and Advances in Prebiotic and Probiotic Research meeting to discuss the state of the science around microbial gut ecology, host-microbe interactions, and pre- and probiotics. Other sponsors included the NIH Division of Nutrition Research Coordination, the National Institute of Allergy and Infectious Diseases, the National Cancer Institute, the National Center for Complementary and Alternative Medicine, and the Office of Dietary Supplements.
Some evidence supports the use of probiotics to treat some digestive diseases, including certain types of diarrhea, a form of inflammatory bowel disease called pouchitis, and necrotizing enterocolitis in preterm infants. Most scientists at the meeting want to see more clinical trials of probiotics. Tools and data from the Human Microbiome Project will go a long way toward a better understanding of probiotics.
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NIH Publication No. 08–4552
March 2008
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