Unlike all other animals, humans have an unfortunate tendency to drop dead from heart attacks that have no apparent cause. According to a new study in the Proceedings of the National Academy of Sciences, this inconvenient ticker malfunction can all be blamed on a single gene, which became deactivated in humans thanks to a mutation that occurred in one of our ancestors, between 2 and 3 million years ago.
Atherosclerosis is a form of cardiovascular disease characterized by the clogging of arteries, and is the leading cause of human death worldwide, accounting for around a third of all fatalities. In many cases, it is brought on by factors such as obesity, hypertension, smoking, and blood cholesterol, although around 15 percent of heart attacks due to atherosclerosis occur with none of these risk factors.
These sudden, unexplained heart attacks are virtually non-existent in all other species, including many of our closest relatives such as chimpanzees. And the reason, it seems, is all down to a single sugar molecule called Neu5Gc that is found on the surface of cells in all animals apart from humans.
The gene that codes for Neu5Gc is called CMAH, and appears to have been deactivated in one of our early ancestors several million years ago. One theory is that the elimination of Neu5Gc occurred as an evolutionary response to a particular form of malaria, which attached to the molecule in order to infect apes.
Fast-forward to today, and modern humans remain immune to certain malaria strains that chimps and other apes are susceptible to, yet the results of this latest research bring home just how high a price we are having to pay for our resistance to the disease.
The study authors deactivated the CMAH gene in lab mice, resulting in a deficiency of Neu5Gc. Compared to regular mice, these rodents were found to be 1.9 times more likely to suffer from atherosclerosis.
Things got even worse for the mutant mice when they were put on a diet that was high in red meat, resulting in a 2.4-fold increase in atherosclerosis compared to normal mice. This is because red meat contains high levels of Neu5Gc, which prompts an immune response called xenosialitis, whereby antibodies that are designed to detect and destroy Neu5Gc kick-start a process of inflammation, which appears to carry a heart attack risk.
Overall, these results seem to suggest that eating too much red meat can significantly increase your chances of cardiovascular disease, but that even super fit, non-smoking vegetarians are genetically predisposed to kicking the bucket for no apparent reason.