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Irish Traveller Gut Microbiomes Reveal Effect of Lifestyle Change on Microbial Makeup, Disease Risk

NEW YORK – Irish Travellers who had to abandon their traditional lifestyle have gut microbiomes that fall between those of individuals from industrialized and non-industrialized populations, according to a new study, which might have implications for their health.

Irish Travellers make up about 1 percent of the population of Ireland. They have a separate culture, language, and history, as well as a nomadic lifestyle, and were recognized in 2017 as a separate ethnic group. While Irish Travellers are genetically similar to the non-nomadic, settled Irish population, years of social separation and endogamous relationships have led to genetic drift.

In 2002, legislation in Ireland led Irish Travellers to live at halting sites or in state-sponsored housing. Researchers from University College Cork examined the gut microbiomes of Irish Travellers to ascertain how a change from a nomadic lifestyle, marked by large families and close association with domesticated animals, to a settled one affected their gut microbiomes and related chronic disease. As they reported in Nature Medicine on Monday, the researchers observed hints that the gut microbiomes of Irish Travellers remained somewhat different, to varying degrees, from that of the surrounding Irish population but showed changes that may place them at greater risk of metabolic disease.

"Retention of a non-industrialized microbiome correlated inversely with the degree to which the Travellers adopted the lifestyle of the background community," Cork's Fergus Shanahan and his colleagues wrote in their paper. "This suggests that the Traveller subpopulation and its microbiome are in transition and represent an informative model for further study of the relationships between lifestyle, the microbiome, and health."

The researchers gathered fecal samples from 118 Irish Travellers. Of these individuals, 87 percent had been nomadic in childhood and since adopted a settled lifestyle to varying degrees.

When compared to previously published fecal microbiomes from 190 elderly and 141 young non-Traveller Irish, the Irish Traveller population's microbiome remained separated. Additionally, in comparison to the microbiomes of global populations, the Irish Traveller microbiomes in general fell between the microbiomes of non-industrialized and industrialized populations.

Based on how their microbiomes fell along this continuum, the researchers identified three subgroups of Irish Travellers: a non-industrialized-like, an industrialized-like, and an intermediate group. They traced these differences in microbiome profiles to changes in living conditions.

Of the about two dozen host demographic factors they examined, eight could explain a non-industrialized-like versus an industrialized-like gut microbiome among Irish Travellers. Three — housing conditions, number of siblings, and animal ownership — could distinguish Irish Travellers from other Irish. Diet, the researchers noted, was not one of the microbiome determinants.

The differences in microbiome composition were also associated with functional changes, the researchers noted, some of which appear to be associated with an increased risk of chronic disease. For instance, they noted changes in the production of the short-chain fatty acid butyrate and in the metabolism of carbohydrates, bile acids, and trimethylamine (TMA). TMA, the researchers noted, is a precursor metabolite of trimethylamine-N-oxide, which is a risk factor for atherosclerosis, fatty liver disease, and type 2 diabetes.

The researchers noted, however, that the mean age of their Irish Traveller cohort was young, about 39 years, so they had not developed many metabolic diseases yet, though the scientists did uncover a hint of an association between a non-industrialized-like gut microbiome and high-density lipoprotein levels, lean mass, bone density, and perceived well being.

Further studying the Irish Traveller gut microbiome could help in the understanding of how adopting a Western lifestyle affects the microbiome and chronic disease and how to prevent it.

"Moreover, while societal lifestyle changes usually occur gradually over generations, they have been abrupt, recent, and enforced for the Irish Travellers and reveal the wider public health concerns when ethnic minorities are pressured to change or to move en masse due to famine, war, or natural disaster," Shanahan and his colleagues wrote.