Researchers at the University of California, San Diego School of Medicine (CA, USA) have demonstrated the potential tumor-forming role of the sugar Neu5Gc. Their results, which were published in December in the Proceedings of the National Academy of Sciences, demonstrated that Neu5Gc, a nonhuman sugar, was found to promote inflammation and cancer progression in rodents.
Neu5Gc is found in other mammals and red meat has been shown to have high levels of the sugar. Humans who consume large quantities of red meat are known to be at increased risk for certain cancers, whereas other carnivores are not. This pattern prompted the investigators at the San Diego School of Medicine to explore the possible link between Neu5Gc and the development of cancer.
The researchers engineered mice to be Neu5Gc deficient and demonstrated that subsequent feeding of Neu5Gc to these mice significantly promoted spontaneous cancers. The study did not include exposure to carcinogens and artificially induced cancers, strengthening the support for a link between Neu5Gc, red meat consumption and cancer development.
It is known that animal Neu5Gc can be absorbed into human tissues and it was hypothesized that red meat consumption could cause inflammation due to the constant requirement to produce antibodies against animal Neu5Gc , a foreign molecule.
Mice were engineered to mimic humans, in that they were unable to produce their own Neu5Gc and consequently produced antibodies against Neu5Gc. The mice were then fed Neu5Gc resulting in the development of systemic inflammation, which led to a five-fold increase in spontaneous tumor formation and the accumulation of Neu5Gc in the tumors.
Lead author on the study, Ajit Varki (University of California), explained “Until now, all of our evidence linking Neu5Gc to cancer was circumstantial or indirectly predicted from somewhat artificial experimental setups.” He added that this is the first time it had been demonstrated that spontaneous cancers in mice are increased by mimicking the exact situation that occurs in humans – feeding nonhuman Neu5Gc and inducing anti-Neu5Gc antibodies.
Prior to the experiments, the research team completed a systematic survey of common foods. Red meats, including beef, pork and lamb, were discovered to have high levels of bioavailable Neu5Gc. This confirmed that foods of mammalian origin are the primary sources of Neu5Gc in the human diet.
The investigators believe that the final proof in humans will be more difficult to obtain, but hope their work will help explain the possible link between red meat consumption and other diseases, such as atherosclerosis and Type 2 diabetes, in which chronic inflammation is a key factor.
“Of course, moderate amounts of red meat can be a source of good nutrition for young people. We hope that our work will eventually lead the way to practical solutions for this catch-22.” Varki commented.