suspect that alterations in the human microbiome, caused by changes in
modern life styles and medicines, have be contributing to an increase in
obesity and autoimmune disorders.
"The Ultimate Social Network," a story by Jennifer Ackerman in the June 2012 issue of Scientific American,
describes research into the functioning of the complex ecosystem of
bacteria and other microorganisms that inhabit our bodies. Biologist Sarkis Mazmanian at the California Institute of Technology has studied the intestinal organism bactericides fragilis and its role in the human immune system. It is pathogenic and can cause trouble, but as part of a community of commensals-the trillions of microbial cells and the genes they contain that make up our microbiome, b. fragilis help regulate the immune system. Read an article by Mazmanian and others here. B. fragilis
seems to help produce a balance between the activities of T cells that
provoke inflammation and T cells that counteract inflammation.
Over the last century, life style changes have decreased the incidence of b. fragilis
and other regulatory bacteria in the gut, and Mazmanian thinks that
maybe be one cause of an increase in autoimmune disorders as Crohn's
disease, Type I diabetes, and multiple sclerosis.
Martin Blaser, a professor of internal medicine and microbiology at New York University, has studied the role of Helicobactor pylori, which
got a bad reputation some years ago for being the cause of peptic
ulcers. Three decades ago, more than 80 percent of Americans were host
to H. pylori, but now fewer than six percent of American children test positive for it. It turns out that H. pylori helps regulate two hormones that impact appetite-ghrelin, which tells the brain we're hungry, and leptin, which signals that we're full. The Scientific American story reports on a study that showed 92 veterans treated with antibiotics to eliminate H. pylori
gained more weight than their uninfected peers who still had the
bacteria. Blaser speculates that widespread use of antibiotics to treat
childhood ear infections has caused alterations in their intestinal
microbiomes that may help explain the rise in childhood obesity. A New York Times story on
the good that bad bugs can do reports Blaser's belief that antibiotics
are causing complex and alarming changes in our microbiomes.
too worries about the loss of poorly understood bacteria through
antibiotic use and other life style changes and our tendency to think of
all bacteria as pathogenic. "What we've done as a society over a short
period is completely change our association with the microbial world,"
he told the Scientific American. He believes autoimmune diseases have both genetic and environmental components, and he thinks the
environmental component is microbiotic and the changes that are
effecting our immune systems.