Red Meat Derived Glycan, N-acetylneuraminic Acid (Neu5Ac) Is a Major Sialic Acid in Different Skeletal Muscles and Organs of Nine Animal Species-A Guideline for Human Consumers

Sialic acids (Sias) are acidic monosaccharides and red meat is a notable dietary source of Sia for humans. Among the Sias, N-acetylneuraminic acid (Neu5Ac) and 2-keto-3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) play multiple roles in immunity and brain cognition. On the other hand, N-glycolylneuraminic acid (Neu5Gc) is a non-human Sia capable of potentiating cancer and inflammation in the human body. However, their expression within the animal kingdom remains unknown. We determined Neu5Ac and KDN in skeletal muscle and organs across a range (n = 9) of species using UHPLC and found that (1) caprine skeletal muscle expressed the highest Neu5Ac (661.82 +/- 187.96 mu g/g protein) following by sheep, pig, dog, deer, cat, horse, kangaroo and cattle; (2) Among organs, kidney contained the most Neu5Ac (1992-3050 mu g/g protein) across species; (3) similar to 75-98% of total Neu5Ac was conjugated, except for in dog and cat muscle (54-58%); (4) <1% of total Sia was KDN, in which similar to 60-100% was unconjugated, with the exception of sheep liver and goat muscle (similar to 12-25%); (5) Neu5Ac was the major Sia in almost all tested organs. This study guides consumers to the safest red meat relating to Neu5Ac and Neu5Gc content, though the dog and cat meat are not conventional red meat globally.

Automated summary

Sialic acids (Sias) derived from red meat, including Neu5Ac and KDN, have various roles in immunity and brain cognition, while Neu5Gc may increase the risk of cancer and inflammation. A study using UHPLC determined the content of Neu5Ac and KDN in skeletal muscle and organs of different species, revealing that goat skeletal muscle had the highest Neu5Ac content, followed by kidney. This study provides guidance for consumers to choose red meat with lower Neu5Ac and Neu5Gc content.