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Mutation Challenges Theories on Evolution and High-Carb Diets

A single mitochondrial DNA mutation that is common in animals, including humans, could help to tailor diets that combat obesity and other health problems associated with a carbohydrate-rich diet, according to the authors of a study published in PLoS Genetics (https://goo.gl/MaB6tu).

The study found that fruit fly larvae with a mitochondrial DNA (mtDNA) mutation showed a pronounced increase in development when eating a high-carbohydrate diet of banana, but stagnated on a high-protein diet of passionfruit. Conversely, fruit fly larvae without the mtDNA mutation thrived on the high-protein diet but dropped in frequency when put on carbohydrates.

The study challenges the neutral theory of molecular evolution, which says that changes in species at the molecular level are random, not caused by natural selection and provide no benefit or disadvantage to the species.

Sam Towarnicki, a University of NSW PhD student who is equal first author of the paper, explained why this was more than just a random, neutral mutation. “The selective advantage is this: the larvae possessing the mutation fed on a high-carbohydrate diet grow up nice and early, and become adults before the others on the protein diet [also with a mutation],” he says. “We found a 10% difference in the development just in one generation between those two groups, which is huge. And because we followed 25 generations, those increases compound over time, which delivers much bigger numbers and a huge selective advantage.”

Given that humans share 75% of the same genes as fruit flies, and have the same mtDNA genes, the same mutation inherited in human mtDNA may metabolise carbohydrates in a similar way.

Prof Bill Ballard, who led the research, says knowledge of a person’s “mitotype” could explain why a diet high in carbohydrates may induce obesity and diabetes in some but not others. “The most obvious implication from our work is that people should start to manage their diets to match their genotypes,” Ballard says. “Knowing a person’s mitotype will help each person optimise their diet.

“Our energetic goals change over time, and so the food we feed our body should also change. A goal for some might be to increase fertility, while increasing longevity may be the goal for older folks,” Ballard says.