N-acetylneuraminic acid (sialic acid)

N-acetylneuraminic acid (2-keto-5-acetamino-3,5-dideoxy-d-glycerin-d-galactose nucleic acid; 2-keto-5-acetamino-3,5-dideoxy-d-glycerin-d-galactose nucleic acid); Neu5Ac is the most common form of sialic acid in human glycoconjugates, including glycoprotein, glycosaminoglycan, ganglioside and mucin, and is widely expressed in human body ^[1].

These negatively charged sugars are found in all vertebrate cell types, which means that they are found in almost all vertebrate tissues and bodies, but rarely in prokaryotes, plants or invertebrates. Glycoconjugates, which play important roles in neurodevelopment, synaptic transmission, cognition, memory formation and immune function, are structurally diverse and can be used as bait for invading pathogens. It is worth noting that most of the sialic acid in breast milk is N-acetylneuraminic acid ^[2].

Published scientific studies have shown that N-acetylneuraminic acid has the following functions:

   ·Enhance learning ability ^{[3] [4]}
   ·Improve the memory and intelligence level of infants ^[5]
   ·Increase cell activity and protect cells from interference of other substances ^[6]
   ·Promote the activation of immune cells, trap microorganisms and enhance human immunity ^[7]
   ·Antiviral ^[8]
   ·Anti Alzheimer's disease ^[9]
   ··Inhibition of inflammation ^[10]

Status：

Functions：

Mechanism：

N-acetylneuraminic acid can promote human health in a variety of ways, including:

   ·It acts on brain cell membrane and synapse, promotes differentiation, development and nerve regeneration of nerve cells, participates in synaptic transmission and maintains normal function of cells ^[11]
   ·Promote the growth and neurite elongation of nerve cells, prevent brain function degradation ^[9]
   ·4-amino or 4-guanidine-2-deoxy-2,3-dehydosalicylic acid, a derivative of sialic acid in human body, has been proved to have strong anti influenza virus A and B activity ^[8], while another derivative       

              9-acetyl has anti influenza virus C activity ^[12]
   ·Sialyl Lewis is an important component of leukocyte surface, which can enhance the aggregation of leukocytes in inflammatory sites, and better play the role of antibacterial and anti-inflammatory ^[13]

Safety：

Safety is crucial for vulnerable groups (such as the elderly and infants). Oral toxicity test and a large number of clinical studies have confirmed the safety of N-acetylneuraminic acid, and no adverse reactions were found among the subjects ^{[3] [4] [5] [6]}. N-acetylneuraminic acid has always been safe.

[1] Rosenberg A . Biology of the Sialic Acids[M]. Plenum Press, 1995.    

[2] Wang B . Sialic Acid Is an Essential Nutrient for Brain Development and Cognition[J]. Annual Review of Nutrition, 2009, 29(1):177-222.

[3] Morgan B ,Winick M . A possible relationship between brain N-acetylneuraminic acid content and behavior.[J]. Proceedings of the Society for Experimental Biology & Medicine Society for Experimental Biology & Medicine, 1979, 161(4):534-7.

[4] Brunngraber E G . Biochemistry, Function, and Neuropathology of the Glycoproteins in Brain Tissue[J]. Advances in Experimental Medicine & Biology, 1972, 32:109.

[5]冯君, 李宏基, 杨国宇. 牛奶中唾液酸的生物学功能研究[J]. 乳业科学与技术, 2007(05):219-220.

[5] Morgan B , Myron W . The subcellular localization of administered N-acetylneuraminic acid in the brains of well-fed and protein restricted rats[J]. British Journal of Nutrition, 1981, 46.

[6] Varki A , Gagneux P . Multifarious roles of sialic acids in immunity[J]. Annals of the New York Academy of Sciences, 2012, 1253(1).

[7] Oetke C , Vinson M C ,  Jones C , et al. Sialoadhesin-Deficient Mice Exhibit Subtle Changes in B- and T-Cell Populations and Reduced Immunoglobulin M Levels[J]. Molecular & Cellular Biology, 2006, 26(4):1549-1557.

[8] Von hzslein M, Wu WY, Kok GB, et al. Rotional design of potent sialidase- based inhibitors of in-fluenzavirus replication [J]. Nature, 1993, 383:418.

[9] 李绍顺.唾液酸及其衍生物的生物学研究进展[J].药学进展, 1997,21( 2) :70- 75

[10] WANG B,BRAND- MILLER. The roel and potential of sialic acid in human nutrition [J]. European journal of Clinical Nutrition,2003( 57) :1351- 1369.

[11] Muhsin Karim, Bing Wang. Is sialic acid in milk food for the brain [J]. Perspectives in Agriculture,Veterinary Science, Nutrition and Resources, 2006,18( 1) :1- 11.

[12] 张春,刘艺.唾液酸的生物学功能及临床意义[J].哈尔滨医科大学报,1990,24( 6) :500- 502.

[13] WANG B,BRAND- MILLER. The roel and potential of sialic acid in human nutrition [J]. European journal of Clinical Nutrition,2003( 57) :1351- 1369.