How the Inuit adapted to life in the Arctic

The Inuit, the natives of Greenland, and their ancestors have been living in the extreme conditions of the Arctic for thousands of years and have been exposed to both cold annual temperatures and a traditional high-fat diet. We discovered that the Inuit genome has mutations in genes controlling how fat is metabolized, allowing them to physically adapt on a diet rich in omega-3 polyunsaturated fatty acids from marine mammals.

HFSP Long-Term Fellow Matteo Fumagalli and colleagues
authored on Fri, 25 September 2015

Figure: The Greenlandic village of Oqaatsut. Photo kindly provided by Ida Moltke.

The Greenland natives – the Inuit – have long been exposed to low annual temperatures typical of the Arctic, and lived on a traditional diet rich in protein mostly from marine mammals with high levels of omega-3 fatty acids.

In an effort to understand how the Inuit adapted to such conditions, we analyzed the genomes of 191 Greenlanders with low European ancestry and compared them to the genomes of 60 Europeans and 44 Han Chinese. We identified mutations occurring in a large fraction of Inuit individuals but rarely or not at all in other populations. These mutations are therefore likely to have spread throughout the Inuit because they were essential for their survival.

One cluster of these mutations was located in genes that code for enzymes that desaturate carbon-carbon bonds in fatty acids. Those genetic mutations, found in nearly 100 percent of the Inuit, are found in only 2 percent of Europeans and 15 percent of Han Chinese.

These mutations downregulate the production of omega-3 and omega-6 polyunsaturated fatty acids, possibly to account for the high intake of fatty acids from the Inuit diet. They also have other effects, as they lower “bad” LDL cholesterol, fasting insulin levels, and height, as growth is partly regulated by the fatty acid profile. Notably, the association with height was replicated in Europeans.

We identified another common mutation in the Inuit located in a gene involved in the differentiation of brown and brite fat cells. As the latter is responsible for heat generation, this mutation may have helped the Inuit adapt to a cold environment.

In this study, we provided evidence of Inuit adaptation to their environment and demonstrated the power of evolutionary analyses on locally adapted populations to elucidate the genetic basis of human phenotypic variation.

This study was co-lead by Dr Matteo Fumagalli at University College London, Dr Ida Moltke, Dr Anders Albrecthsen and Professor Torben Hansen at the University of Copenhagen, and Professor Rasmus Nielsen at UC Berkeley.

Reference

Greenlandic Inuit show genetic signatures of diet and climate adaptation. Fumagalli M, Moltke I, Grarup N, Racimo F, Bjerregaard P, Jørgensen ME, Korneliussen TS, Gerbault P, Skotte L, Linneberg A, Christensen C, Brandslund I, Jørgensen T, Huerta-Sánchez E, Schmidt EB, Pedersen O, Hansen T, Albrechtsen A, Nielsen R., Science. 349, 1343–1347 (2015).

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