Sialic acid: an attractive biomarker with promising biomedical applications

Abstract

This broad, narrative review highlights the roles of sialic acids as acidic sugars found on cellular membranes. The role of sialic acids in cellular communication and development has been well established. Recently, attention has turned to the fundamental role of sialic acids in many diseases, including viral infections, cardiovascular diseases, neurological disorders, diabetic nephropathy, and malignancies. Sialic acid may be a target for developing new drugs to treat various cancers and inflammatory processes. We recommend the routine measurement of serum sialic acid as a sensitive inflammatory marker in various diseases.

Keywords: cardiovascular diseases; diabetic nephropathies; molecular targeted therapy; neoplasms; neuraminic acids; sialic acid; virus diseases.

Figure 1

(A) Chemical structure of the 3 main sialic acids, N-acetylneuraminic acid (Neu5Ac), N-glycolylneuraminic acid (Neu5Gc), and deaminoneuraminic acid (KDN). (B) Sialic acids are transferred onto acceptor glycans via sialyl transferase enzymes that use the activated cytidine-5′-monophosphate-sialic acid (CMP-Sia) as a donor molecule. Sialyl residues may be added terminally to galactose residues in α-2,3 or α-2,6 linkage, or to sialic acid residues in α-2,8 connection. Such glycan chains may be attached to glycoproteins via asparagine (N-glycan) or serine or threonine residues (O-glycans). Sialic acids may be released via hydrolytic enzymes called neuraminidases. (C) Examples of pathobiological interactions involving sialic acids with viruses, bacteria, hormones, and toxins. Gal, galactose; GalNAc, N-acetylgalactosamine; Man, mannose; Glc, glucose; GlcNAc, N-acetylglucosamine; Fuc, fucose.

Figure 2

Flowchart showing that increased sialic acid level in plasma predicts diabetic nephropathy. RBC, red blood cell.