A new study presented at the American Society of Human Genetics has associated a humans immunity-related pathways to the composition of the microbiome. The microbiome refers to bacteria and other microbes that live in and on the body and form a biological network.“These genes are significantly enriched in inflammatory and immune pathways and form an interaction network highly enriched with immunity-related functions,” said Ran Blekhman, Ph.D., Assistant Professor, Department of Genetics, Cell Biology, and Development at the University of Minnesota, Minneapolis.
The investigators highlighted the interaction between genetic variants and the different microbes that live on and in the human body on the skin, genital areas, mouth and other areas of the human body including the intestines colonized by trillions of bacteria and other micro-organisms.
Their study specifically detected that the human genetic variants correlated with the microbiome at two different levels: 1. the individual level where the genetic variation correlated with the overall structure of a person’s microbiome and 2. at the species level, where host human genetic variation linked to one particular bacterial species was identified.
To examine the specific bacterial species that inhabited each human body site, the researchers mined sequence data from the Human Microbiome Project (HMP), an international program to genetically catalog the microbial residents of the human body. They found that variation in genes related to immune system pathways was correlated with microbiome composition in 15 body sites.
“The results highlight the role of host immunity in determining bacteria levels across the body and support a possible role for the microbiome in driving the evolution of bacteria-associated host genes,” Dr. Blekhman said.
Another study which confirmed the link to an immune response based on the intestinal microbiome was published in the PLOS ONE journal. In this study researchers demonstrated that mice fed a gluten-free diet had a dramatic reduction in type 1 diabetes development.These mice were non-obese diabetic mice, or mice that grow to develop Type 1 diabetes and the gluten-free diet worked to protect the mice against Type 1 diabetes. When gluten was added back to the diet there was a measurable change in the composition of the bacterial flora.
“These changes suggest that the presence of gluten is directly responsible for the diabetes-creating effects of diet and determines the gut microflora,” said Govindarajan Rajagopalan, Ph.D., a Mayo Clinic immunologist and study author.
Eric V. Marietta, Andres M. Gomez, Carl Yeoman, Ashenafi Y. Tilahun, Chad R. Clark, David H. Luckey, Joseph A. Murray, Bryan A. White, Yogish C. Kudva, Govindarajan Rajagopalan. Low Incidence of Spontaneous Type 1 Diabetes in Non-Obese Diabetic Mice Raised on Gluten-Free Diets Is Associated with Changes in the Intestinal Microbiome. PLoS ONE, 2013; 8 (11): e78687 DOI: 10.1371/journal.pone.0078687
American Society of Human Genetics. “Gene variants in immune system pathways correlated with composition of microbes of human body.”