Jan. 15, 2014 — Research carried out in two distinct communities in Colombia illustrates how coevolution between humans and bacteria can affect a person's risk of disease.
Working with colleagues in Columbia and the U.S., Scott Williams, PhD, a professor of genetics at the Geisel School of Medicine and the Institute of Quantitative Biomedical Sciences (iQBS) at Dartmouth, and his graduate student Nuri Kodaman discovered that the risk of
developing gastric cancer depends heavily on both the ancestry of the person and the ancestry of Helicobacter pylori with which that person is infected. About half of the world's population is infected with H. pylori. The microbe usually only causes minor gastric inflammation, but it is also the primary cause of gastric cancer, which is the second- leading cause of death by cancer
worldwide.
Williams' research team studied 233 people from two populations in Colombia, one located in the mountain village of Tuquerres and the other in the coastal village of Tumaco. Rates of H. pylori infection in the two communities are similar (about 90%), but the rate of gastric cancer is about 25 times higher in
the mountain community. The researchers classified the ancestry of the people in both villages and of the H. pylori in each area. In the coastal village, the human population was primarily of African descent. The dominant component of the H. pylori also came from Africa.
In the mountain village, the people were largely Amerindian and had very little African ancestry, and the H. pylori was predominantly derived from Europe.
The researchers examined the connections between human ancestry, the strains of H. pylori, and the severity of gastric disease and made several important findings:
First, among both populations, people of European or Amerindian descent were at greater risk of developing more severe lesions than were people of African descent.
Second, in the mountain community where most people were of
Amerindian or European descent, those infected with African-derived H. pylori had worse outcomes than those infected with predominantly European strains. And third, people from either village who had the lowest percentage of African ancestry had lesions that were more severe if they had H. pylori with a high proportion of African ancestry.
"The interaction between H. pylori and human ancestry entirely accounted for the difference in geographical disease risk," said Kodaman, a graduate student based
at Vanderbilt University, who is working and studying under Williams in the Department of Genetics at Geisel.
Based on their findings, the researchers concluded that coevolution among humans and H. pylori reduced gastric cancer disease risk in the people of African descent.People of Amerindian descent would have been exposed to European or African strains of H. pylori much more recently, meaning that there would not have been time for coevolution to take place and explaining the worse outcomes
among the villagers in the mountain community.
source:
http://www.sciencedaily.com/releases/2014/01/140115143707.htm
Topic: Coevolution Between Humans, Bacteria Reduces Gastric Cancer Risk, Research Suggests (Read 1759 times)