Neu5Gc was in the news last week because it was identified as one of the likely causal links between increased consumption of red meat and some forms of cancer.
Most reports stated, "...Neu5Gc is found in lamb, beef, pork and other red meats." Very few reports actually listed the Neu5Gc levels. This report from U-T San Diego does.
Three facts stand out:
1.) There is a huge range of Neu5Gc levels within "red meat". The highest levels seen in beef are 33 times greater than the lowest levels seen in pork.
2.) There are huge ranges within species. Beef has a range of almost 10X while pork has a range of almost 6X.
3.) The causes of these ranges are not explained.
Families of variationThe most intriguing possibility is that genetic lines may have already been identified that have very low, or no, Neu5Gc. The first places I would look would be those animal lines that are used to produce porcine and bovine replacement heart valves. The person or organization that can find and patent this mutation for the production of low carcinogen red meats will be very, very rich.
Variation by cut-of-meatNeu5Gc concentration varies by organ. Brains, for instance, have almost no Neu5Gc. Does it vary by cut-of-meat?
Variation by family lineHumans do not produce Neu5Gc due to a simple mutation. Given the number of hogs and cattle in the world there are probably many animals that exhibit this same mutation. It is simply a matter of finding them.
The most intriguing possibility is that genetic lines may have already been identified that have very low, or no, Neu5Gc. The first places I would look would be those animal lines that are used to produce porcine and bovine replacement heart valves. Because of the extreme fecundity of swine, you could see low Neu5Gc pork on supermarket shelves in 24 months. The person or organization that can finds and patents this mutation for the production of low carcinogen red meats will be very, very rich.
Variation due to stressful environmentsNeu5Gc acts like traffic lights for immune responses. Cities increase the number of traffic lights when there is more demand for resources. It is plausible that bodies produce more Neu5Gc when the animals are exposed to more pathogen pressure and environmental stressors....like when they are in a close confinment feedlot. Maybe it is not the beef but the stress.
Variation due to time-of-yearMany biological functions are paced by day length. Perhaps Neu5Gc
Variation due to dietPerhaps a diet of clover and bluegrass makes low Neu5Gc meat.
Evolutionary biologists speculate that humans gained two benefits from the null-Neu5Gc mutation.
One of the benefits was that pathogens that looked for host cells based on the Neu5Gc molecules would be blind to those with Neu5Ga molecules. The other benefit was that Neu5Ga is even more efficient at traffic lighting immune responses.
A disadvantage to having hogs and cattle with Neu5Ga sialic acid is that humans will lose their "stealth" immunity advantage to pathogens that evolve in those animals. That is a public health policy issue.