Genes that conquered cold blamed for disease, fat

By Julie Steenhuysen

CHICAGO (Reuters) - Genes that helped early humans adapt to cold climates may be driving metabolism-related diseases such as obesity or diabetes in many countries, U.S. researchers said on Thursday.

They found a strong correlation between climate and genetic adaptations that influence the risk of metabolic syndrome, a group of related disorders such as obesity, high cholesterol, heart disease and diabetes.

"Climate over a long period of time has shaped the distribution of genetic variants that may be associated with the risk of these common metabolic disorders," said Anna Di Rienzo, a professor of human genetics at the University of Chicago.

Anthropologists have long made the case that certain traits such as differences in skin pigmentation reflect early human migration from equatorial Africa to cooler climates -- for instance, the link between paler skin and an ability to synthesize vitamin D from sunlight.

"There are all of these traits, body mass or skin pigmentation, that we know are strongly correlated with environmental variables," Di Rienzo said in a telephone interview.

Di Rienzo and colleagues wanted to see if genes that were once useful for tolerating cold climates were playing a role in diseases of the metabolism.

"To survive in these climates, they had to adapt," said Di Rienzo, whose study appears in PLoS Genetics, a journal published by the Public Library of Science. (http://genetics.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pgen.0040032).