In an interesting look at evolution in action, a research team led by University College London has discovered around 50 percent of people carry a gene mutation that helps lower blood sugar levels. It is suggested humans evolved this mutation as we developed cooking and farming practices, and it may protect against the onset of diabetes.
The research grew out of an investigation into a gene called CLTC1, which controls production of a protein called CHC22. This protein regulates the mechanism by which glucose moves out of our blood and into our fat and muscle tissue. Looking at ancient human DNA, a number of different animal species, and the genomes of more than 2,500 modern humans, the researchers discovered the mutation in the CLTC1 gene seemed to appear in humans around the time we started cooking our food 450,000 years ago.
The gene mutation produces an altered expression of the CHC22 protein which lowers the efficacy of this glucose transportation process between blood and muscle or fat. This essentially means the mutation helps clear glucose more rapidly from our blood after a meal.
"The older version of this genetic variant likely would have been helpful to our ancestors as it would have helped maintain higher levels of blood sugar during periods of fasting, in times when we didn't have such easy access to carbohydrates, and this would have helped us evolve our large brains," says Matteo Fumagalli, first author on the new study.
The newer mutation in the CLTC1 gene was found to initially arise in ancient humans, but the researchers note it becoming more frequent as farming increased in prevalence over 10,000 years ago. As carbohydrates became more readily accessible in our diets, the need to more efficiently clear glucose from our blood increased the spread of this highly specific gene mutation.
"Our analyses strongly suggest that we have found yet another example of how prehistoric changes in dietary habits have shaped human evolution," explains Mark Thomas, co-author on the study. "Understanding how we have adapted to these changes doesn't only inform us about why people lived or died in the past, but also helps us to better understand the relationship between diet, health and disease today."
Interestingly, the new genetic mutation has not completely dominated human evolution, with the researchers saying around half of the current human genomes studied still contained the older version of the CLTC1 gene. It is unclear how significant the role of the newer gene variant is in humans today, and it is noted that the older genetic variant does not seem to play a direct role in the development of diabetes. However, the researchers do note the older genetic variant could exacerbate insulin resistance in some people and put them at a greater risk of developing type 2 diabetes.
"People with the older variant may need to be more careful of their carb intake, but more research is needed to understand how the genetic variant we found can impact our physiology," says lead author on the research, Frances Brodsky.
The study was published in the journal eLife.
Source: University College London
