Impact of Food on the Oral Absorption of N-Acetyl-D-Mannosamine in Healthy Men and Women.

N-Acetyl-D-mannosamine (ManNAc) is an endogenous monosaccharide and precursor of N-acetylneuraminic acid (Neu5Ac), a critical sialic acid. ManNAc is currently under clinical development to treat GNE myopathy, a rare muscle-wasting disease. In this randomized, open-label, 2-sequence, crossover study, 16 healthy women and men were administered a single oral dose of ManNAc under fasting and fed conditions. Blood samples were collected for 48 hours after dosing for quantification of plasma ManNAc and Neu5Ac concentrations. Noncompartmental pharmacokinetic and deconvolution analyses were performed using baseline-corrected plasma concentration data. Administration of ManNAc in the fed state resulted in a 1.6-fold increase in ManNAc exposure, compared to fasting conditions. A concurrent increase in Neu5Ac exposure was observed in the presence of food. Deconvolution analysis indicated that the findings were attributed to prolonged absorption rather than an enhanced rate of absorption. The impact of food on ManNAc pharmacokinetics was greater in women than men (fed/fasted area under the concentration-time curve from time 0 to infinity mean ratio: 198% compared to 121%). It is hypothesized that the presence of food slows gastric emptying, allowing a gradual release of ManNAc into the small intestine, translating into improved ManNAc absorption. The results suggest that taking ManNAc with food may enhance its therapeutic activity and/or reduce the daily dosage requirement.

Study on the fabrication and controlled release behavior of N-Acetylneuraminic acid-loaded hydrogels stabilized by gelatin/whey protein isolate.

Gelatin (GEL), pectin (PEC), carboxymethyl cellulose (CMC), and whey protein isolate (WPI) were employed to formulate hydrogels for stabilizing N-Acetylneuraminic Acid (NeuAc). GEL/WPI-NeuAc hydrogels, irrespective of the ratio, exhibited a flexible and smooth surface with a continuous three-dimensional network structure internally. Porosity of the three types of hydrogels increased from 3.69% to 86.92% (GEL/WPI), 41.67% (PEC/WPI), and 87.62% (CMC/WPI), rendering them suitable as carriers for NeuAc encapsulation. The dynamic swelling behavior of all hydrogels followed Schott's second-order kinetics model. The degradation performance of GEL, PEC, and CMC/WPI-NeuAc hydrogels was optimal at a 5: 5 ratio, with degradation rates of 80.39 ± 1.26%, 82.38 ± 1.96%, and 81.39 ± 1.57%, respectively. GEL, PEC, CMC/WPI-NeuAc hydrogels demonstrated decreased release rates of 44.56%, 31.04%, and 41.26%, respectively, compared to free NeuAc, post gastric digestion. The present investigation suggests the potential of GEL/WPI hydrogels as effective carriers for delivering NeuAc encapsulation.

Multi-omics analysis of five species of milk and specific composition links within each species.

The gold standard of milk is human milk, not cow milk. The present study expects to explored the comprehensive nutritional value of different kinds of milk and the differences between them through multi-omics analysis and found functional components that are more similar to human milk. This study employed untargeted LC-MS/MS metabolomics, untargeted LC-MS/MS lipidomics, and 4D label-free proteomics analysis techniques. The findings revealed substantial disparities in metabolites, lipids, and proteins among the five types of milk. Notably, pig milk exhibited a remarkable abundance of N-acetylneuraminic acid (Neu5Ac) and specific polar lipids. Yak milk stood out with significantly elevated levels of creatine and lipoprotein lipase (LPL) compared to other species. Buffalo milk boasted the highest concentrations of L-isoleucine, echinocystic acid, and alkaline phosphatase, tissue-nonspecific isozyme (ALPL). The concentrations of iminostilbene and osteopontin (OPN) were higher in cow milk.

Establishment of Swine Primary Nasal, Tracheal, and Bronchial Epithelial Cell Culture Models for the Study of Influenza Virus Infection.

We established primary porcine nasal, tracheal, and bronchial epithelial cells that recapitulate the physical and functional properties of the respiratory tract and have the ability to fully differentiate. Trans-well cultures demonstrated increased transepithelial electrical resistance over time the presence of tight junctions as demonstrated by immunohistochemistry. The nasal, tracheal, and bronchial epithelial cells developed cilia, secreted mucus, and expressed sialic acids on surface glycoproteins, the latter which are required for influenza A virus infection. Swine influenza viruses were shown to replicate efficiently in the primary epithelial cell cultures, supporting the use of these culture models to assess swine influenza and other virus infection. Primary porcine nasal, tracheal, and bronchial epithelial cell culture models enable assessment of emerging and novel influenza viruses for pandemic potential as well as mechanistic studies to understand mechanisms of infection, reassortment, and generation of novel virus. As swine are susceptible to infection with multiple viral and bacterial respiratory pathogens, these primary airway cell models may enable study of the cellular response to infection by pathogens associated with Porcine Respiratory Disease Complex.

The essential malaria protein PfCyRPA targets glycans to invade erythrocytes.

Plasmodium falciparum is a human-adapted apicomplexan parasite that causes the most dangerous form of malaria. P. falciparum cysteine-rich protective antigen (PfCyRPA) is an invasion complex protein essential for erythrocyte invasion. The precise role of PfCyRPA in this process has not been resolved. Here, we show that PfCyRPA is a lectin targeting glycans terminating with α2-6-linked N-acetylneuraminic acid (Neu5Ac). PfCyRPA has a >50-fold binding preference for human, α2-6-linked Neu5Ac over non-human, α2-6-linked N-glycolylneuraminic acid. PfCyRPA lectin sites were predicted by molecular modeling and validated by mutagenesis studies. Transgenic parasite lines expressing endogenous PfCyRPA with single amino acid exchange mutants indicated that the lectin activity of PfCyRPA has an important role in parasite invasion. Blocking PfCyRPA lectin activity with small molecules or with lectin-site-specific monoclonal antibodies can inhibit blood-stage parasite multiplication. Therefore, targeting PfCyRPA lectin activity with drugs, immunotherapy, or a vaccine-primed immune response is a promising strategy to prevent and treat malaria.

High-Performance Production of N-Acetyl-d-Neuraminic Acid with Whole Cells of Fast-Growing Vibrio natriegens via a Thermal Strategy.

High performance is the core objective that biotechnologists pursue, of which low efficiency, low titer, and side products are the chief obstacles. Here, a thermal strategy is proposed for simultaneously addressing the obstacles of whole-cell catalysis that is widely applied in the food industry. The strategy, by combining fast-growing Vibrio natriegens, thermophilic enzymes, and high-temperature whole-cell catalysis, was successfully applied for the high-performance production of N-acetyl-d-neuraminic acid (Neu5Ac) that plays essential roles in the fields of food (infant formulas), healthcare, and medicine. By using this strategy, we realized the highest Neu5Ac titer and productivity of 126.1 g/L and up to 71.6 g/(L h), respectively, 7.2-fold higher than the productivity of Escherichia coli. The major byproduct acetic acid was also eliminated via quenching complex metabolic side reactions enabled by temperature elevation. This study offers a broadly applicable strategy for producing chemicals relevant to the food industry, providing insights for its future development.

The effect of long-term moderate exercise on myocardial metabolome in rats.

Regular moderate physical exercise is beneficial for the cardiovascular system. Our prior study has demonstrated a long-term moderate exercise (4-week of 60-min 74.0% V̇O2max treadmill running) is optimal in protecting from exhaustive exercise-induced cardiac ischemic injury. This study is aimed to investigate the effect of long-term moderate exercise on myocardial metabolome in rats. Thirteen male Sprague-Dawley rats were randomly assigned into the control group (C) and the long-term moderate exercise group (E). The targeted metabolomics of the myocardium was analyzed by ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) system. Results showed that the metabolites categories of bile acids (BAs), fatty acids (FAs), and phenylpropanoic acids were significantly decreased. The biosynthesis of unsaturated FAs pathway was significantly downregulated. The altered metabolites in the E Group included decreased FAs (pentadecanoic acid, 10Z-heptadecenoic acid, dihomo-gamma-linolenic acid, docosahexaenoic acid, docosapentaenoic acid, and 10Z-nonadecenoic acid), decreased BAs (chenodeoxycholic acid and beta-muricholic acid), decreased organic acids (glycolic acid and 2-hydroxyglutaric acid), decreased carbohydrate (N-acetylneuraminic acid, Neu5Ac), decreased amino acids (α-aminobutyric acid and norvaline), decreased phenylpropanoic acids (hydroxyphenyllactic acid), and benzoic acids (4-hydroxybenzoic acid and phthalic acid). The results indicated that long-term moderate exercise has promoted lipids utilization in myocardium while exerted little influence on carbohydrate metabolism and diminished many detrimental metabolites. Notably, decrease of myocardial carbohydrate Neu5Ac after long-term moderate exercise might predict a prospective metabolomics biomarker for cardioprotection. This research has displayed the effect of long-term moderate exercise on myocardial metabolomic profiling in rats and indicated some promising metabolites which can be applied for exercise benefits in future.

Enhanced phagocytosis and complement-mediated killing of Mannheimia haemolytica serotype 1 following in-frame CMP-sialic acid synthetase (neuA) gene deletion.

IMPORTANCE: The Gram-negative coccobacillus Mannheimia haemolytica is a natural inhabitant of the upper respiratory tract in ruminants and the most common bacterial agent involved in bovine respiratory disease complex development. Key virulence factors harbored by M. haemolytica are leukotoxin, lipopolysaccharide, capsule, adhesins, and neuraminidase which are involved in evading innate and adaptive immune responses. In this study, we have shown that CMP-sialic acid synthetase (neuA) is necessary for the incorporation of sialic acid onto the membrane, and inactivation of neuA results in increased phagocytosis and complement-mediated killing of M. haemolytica, thus demonstrating that sialylation contributes to the virulence of M. haemolytica.

Changes in the levels of free sialic acid during ex vivo lung perfusion do not correlate with pulmonary function. Experimental model.

BACKGROUND: Ex vivo lung perfusion (EVLP) constitutes a tool with great research potential due to its advantages over in vivo and in vitro models. Despite its important contribution to lung reconditioning, this technique has the disadvantage of incurring high costs and can induce pulmonary endothelial injury through perfusion and ventilation. The pulmonary endothelium is made up of endothelial glycocalyx (EG), a coating of proteoglycans (PG) on the luminal surface. PGs are glycoproteins linked to terminal sialic acids (Sia) that can affect homeostasis with responses leading to edema formation. This study evaluated the effect of two ex vivo perfusion solutions on lung function and endothelial injury. METHODS: We divided ten landrace swine into two groups and subjected them to EVLP for 120 min: Group I (n = 5) was perfused with Steen® solution, and Group II (n = 5) was perfused with low-potassium dextran-albumin solution. Ventilatory mechanics, histology, gravimetry, and sialic acid concentrations were evaluated. RESULTS: Both groups showed changes in pulmonary vascular resistance and ventilatory mechanics (p < 0.05, Student's t-test). In addition, the lung injury severity score was better in Group I than in Group II (p < 0.05, Mann-Whitney U); and both groups exhibited a significant increase in Sia concentrations in the perfusate (p < 0.05 t-Student) and Sia immunohistochemical expression. CONCLUSIONS: Sia, as a product of EG disruption during EVLP, was found in all samples obtained in the system; however, the changes in its concentration showed no apparent correlation with lung function.

Crosstalk between Breast Milk N-Acetylneuraminic Acid and Infant Growth in a Gut Microbiota-Dependent Manner.

The healthy growth of infants during early life is associated with lifelong consequences. Breastfeeding has positive impacts on reducing obesity risk, which is likely due to the varied components of breast milk, such as N-acetylneuraminic acid (Neu5Ac). However, the effect of breast milk Neu5Ac on infant growth has not been well studied. In this study, targeted metabolomic and metagenomic analyses were performed to illustrate the association between breast milk Neu5Ac and infant growth. Results demonstrated that Neu5Ac was significantly abundant in breast milk from infants with low obesity risk in two independent Chinese cohorts. Neu5Ac from breast milk altered infant gut microbiota and bile acid metabolism, resulting in a distinct fecal bile acid profile in the high-Neu5Ac group, which was characterized by reduced levels of primary bile acids and elevated levels of secondary bile acids. Taurodeoxycholic acid 3-sulfate and taurochenodeoxycholic acid 3-sulfate were correlated with high breast milk Neu5Ac and low obesity risk in infants, and their associations with healthy growth were reproduced in mice colonized with infant-derived microbiota. Parabacteroides might be linked to bile acid metabolism and act as a mediator between Neu5Ac and infant growth. These results showed the gut microbiota-dependent crosstalk between breast milk Neu5Ac and infant growth.

Recent advances on N-acetylneuraminic acid: Physiological roles, applications, and biosynthesis.

N-Acetylneuraminic acid (Neu5Ac), the most common type of Sia, generally acts as the terminal sugar in cell surface glycans, glycoconjugates, oligosaccharides, lipo-oligosaccharides, and polysaccharides, thus exerting numerous physiological functions. The extensive applications of Neu5Ac in the food, cosmetic, and pharmaceutical industries make large-scale production of this chemical desirable. Biosynthesis which is associated with important application potential and environmental friendliness has become an indispensable approach for large-scale synthesis of Neu5Ac. In this review, the physiological roles of Neu5Ac was first summarized in detail. Second, the safety evaluation, regulatory status, and applications of Neu5Ac were discussed. Third, enzyme-catalyzed preparation, whole-cell biocatalysis, and microbial de novo synthesis of Neu5Ac were comprehensively reviewed. In addition, we discussed the main challenges of Neu5Ac de novo biosynthesis, such as screening and engineering of key enzymes, identifying exporters of intermediates and Neu5Ac, and balancing cell growth and biosynthesis. The corresponding strategies and systematic strategies were proposed to overcome these challenges and facilitate Neu5Ac industrial-scale production.

Efficient Production of N-Acetylneuraminic Acid in Escherichia coli Based on the UDP-N-Acetylglucosamine Biosynthetic Pathway.

N-Acetylneuraminic acid (NeuAc) is the predominant sialic acid found in human cells and a human-identical milk monosaccharide. Due to its numerous health benefits, it has great commercial potential in the pharmaceutical, cosmetic, and food industries. Microbial synthesis via metabolic engineering strategies is an important approach to its large-scale production. In this study, a NeuAc synthetic pathway was constructed in Escherichia coli BL21(DE3) by deleting the competitive pathway genes and introducing two genes encoding UDP-N-acetylglucosamine (GlcNAc) 2-epimerase (NeuC) and NeuAc synthase (NeuB). UDP-GlcNAc pathway genes, glmS, glmM, and glmU, were overexpressed to strengthen precursor supply for enhancement of NeuAc synthesis. The microbial source of neuC and neuB was optimized, and their expression was fine-tuned. In addition, glycerol as the carbon source showed a much better effect on NeuAc synthesis than glucose. The final engineered strain produced 7.02 g/L NeuAc by shake-flask cultivation. The titer was enhanced to 46.92 g/L by fed-batch cultivation, with the productivity of 0.82 g/L/h and 1.05 g/g DCW.

[Development of biosensors highly responsive to N-acetylneuraminic acid in Bacillus subtilis].

Bacillus subtilis is recognized as a generally-regarded-as-safe strain, and has been widely used in the biosynthesis of high value-added products, including N-acetylneuraminic acid (NeuAc) which is widely used as a nutraceutical and a pharmaceutical intermediate. Biosensors responding to target products are widely used in dynamic regulation and high-throughput screening in metabolic engineering to improve the efficiency of biosynthesis. However, B. subtilis lacks biosensors that can efficiently respond to NeuAc. This study first tested and optimized the transport capacity of NeuAc transporters, and obtained a series of strains with different transport capacities for testing NeuAc-responsive biosensors. Subsequently, the binding site sequence of Bbr_NanR responding to NeuAc was inserted into different sites of the constitutive promoter of B. subtilis, and active hybrid promoters were obtained. Next, by introducing and optimizing the expression of Bbr_NanR in B. subtilis with NeuAc transport capacity, we obtained an NeuAc-responsive biosensor with wide dynamic range and higher activation fold. Among them, P535-N2 can sensitively respond to changes in intracellular NeuAc concentration, with the largest dynamic range (180-20 245) AU/OD. P566-N2 shows a 122-fold of activation, which is 2 times of the reported NeuAc-responsive biosensor in B. subtilis. The NeuAc-responsive biosensor developed in this study can be used to screen enzyme mutants and B. subtilis strains with high NeuAc production efficiency, providing an efficient and sensitive analysis and regulation tool for biosynthesis of NeuAc in B. subtilis.

Antiobesity Effect of N-Acetylneuraminic Acid by Enhancing Antioxidative Capacity in Mice Fed a High-Fat Diet.

The sialic acid N-acetylneuraminic acid (NANA), an essential factor in bioregulation, is a functional food component that is known to have beneficial health effects, but its antiobesity effect has not been clearly understood. Adipocyte dysfunction in obesity involves a decrease in the level of NANA sialylation. In this study, we investigated the antiobesity effect of NANA in mice fed a high-fat diet (HFD) and in 3T3-L1 adipocytes. Male C57BL/6J mice were randomly divided into three groups and administered the following diets: a normal diet, an HFD, and an HFD with 1% NANA supplementation for 12 weeks. NANA supplementation significantly reduced body weight gain; epididymal adipose tissue hypertrophy; and serum lipid, fasting glucose, and aspartate transaminase levels compared with those in HFD mice. The percentage of lipid droplets in hepatic tissue was also decreased by NANA supplementation in HFD mice. The downregulation of Adipoq expression and upregulation of Fabp4 expression induced by HFD in epididymal adipocytes were improved by NANA supplementation. The downregulation of Sod1 expression and increase in malondialdehyde level were induced by HFD, and they were significantly improved in the liver by NANA supplementation, but not in epididymal adipocytes. However, NANA supplementation had no effect on sialylation and antioxidant enzyme levels in mouse epididymal adipocytes and 3T3-L1 adipocytes. Overall, NANA exerts antiobesity and antihypolipidemic effects and may be beneficial in suppressing obesity-related diseases.

The generation of 5-N-glycolylneuraminic acid as a consequence of high levels of reactive oxygen species.

The presence of N-glycolylneuraminic acid (Neu5Gc), a non-human sialic acid in cancer patients, is currently attributed to the consumption of red meat. Excess dietary red meat has been considered a risk factor causing chronic inflammation and for the development of cancers. However, it remains unknown whether Neu5Gc can be generated via a chemical reaction rather than via a metabolic pathway in the presence of high levels of reactive oxygen species (ROS) found in the inflammatory and tumor environments. In this study, the conversion of N-acetylneuraminic acid (Neu5Ac) to Neu5Gc has been assessed in vitro under conditions mimicking the hydroxyl radical-rich humoral environment found in inflammatory and cancerous tissues. As a result, Neu5Gc has been detected via liquid chromatography-multiple reaction monitoring mass spectrometry. Furthermore, this conversion has also been found to take place in serum biomatrix containing ROS and in cancer cell cultures with induced ROS production.

Correlation of Serum N-Acetylneuraminic Acid with the Risk of Moyamoya Disease.

N-acetylneuraminic acid (Neu5Ac) is a functional metabolite and has been demonstrated to be a risk factor for cardiovascular diseases. It is not clear whether Neu5Ac is associated with a higher risk of cerebrovascular disorders, especially moyamoya disease (MMD). We sought to elucidate the association between serum Neu5Ac levels and MMD in a case-control study and to create a clinical risk model. In our study, we included 360 MMD patients and 89 matched healthy controls (HCs). We collected the participants' clinical characteristics, laboratory results, and serum Neu5Ac levels. Increased level of serum Neu5Ac was observed in the MMD patients (p = 0.001). After adjusting for traditional confounders, the risk of MMD (odds ratio [OR]: 1.395; 95% confidence interval [CI]: 1.141-1.706) increased with each increment in Neu5Ac level (per µmol/L). The area under the curve (AUC) values of the receiver operating characteristic (ROC) curves of the basic model plus Neu5Ac binary outcomes, Neu5Ac quartiles, and continuous Neu5Ac are 0.869, 0.863, and 0.873, respectively. Furthermore, including Neu5Ac in the model offers a substantial improvement in the risk reclassification and discrimination of MMD and its subtypes. A higher level of Neu5Ac was found to be associated with an increased risk of MMD and its clinical subtypes.

Increasing brain N-acetylneuraminic acid alleviates hydrocephalus-induced neurological deficits.

AIMS: This metabolomic study aimed to evaluate the role of N-acetylneuraminic acid (Neu5Ac) in the neurological deficits of normal pressure hydrocephalus (NPH) and its potential therapeutic effect. METHODS: We analyzed the metabolic profiles of NPH using cerebrospinal fluid with multivariate and univariate statistical analyses in a set of 42 NPH patients and 38 controls. We further correlated the levels of differential metabolites with severity-related clinical parameters, including the normal pressure hydrocephalus grading scale (NPHGS). We then established kaolin-induced hydrocephalus in mice and treated them using N-acetylmannosamine (ManNAc), a precursor of Neu5Ac. We examined brain Neu5Ac, astrocyte polarization, demyelination, and neurobehavioral outcomes to explore its therapeutic effect. RESULTS: Three metabolites were significantly altered in NPH patients. Only decreased Neu5Ac levels were correlated with NPHGS scores. Decreased brain Neu5Ac levels have been observed in hydrocephalic mice. Increasing brain Neu5Ac by ManNAc suppressed the activation of astrocytes and promoted their transition from A1 to A2 polarization. ManNAc also attenuated the periventricular white matter demyelination and improved neurobehavioral outcomes in hydrocephalic mice. CONCLUSION: Increasing brain Neu5Ac improved the neurological outcomes associated with the regulation of astrocyte polarization and the suppression of demyelination in hydrocephalic mice, which may be a potential therapeutic strategy for NPH.

One-pot biosynthesis of N-acetylneuraminic acid from chitin via combination of chitin-degrading enzymes, N-acetylglucosamine-2-epimerase, and N-neuraminic acid aldolase.

N-acetylneuraminic acid (Neu5Ac) possesses the ability to promote mental health and enhance immunity and is widely used in both medicine and food fields as a supplement. Enzymatic production of Neu5Ac using N-acetyl-D-glucosamine (GlcNAc) as substrate was significant. However, the high-cost GlcNAc limited its development. In this study, an in vitro multi-enzyme catalysis was built to produce Neu5Ac using affordable chitin as substrate. Firstly, exochitinase SmChiA from Serratia proteamaculans and N-acetylglucosaminosidase CmNAGase from Chitinolyticbacter meiyuanensis SYBC-H1 were screened and combined to produce GlcNAc, effectively. Then, the chitinase was cascaded with N-acetylglucosamine-2-epimerase (AGE) and N-neuraminic acid aldolase (NanA) to produce Neu5Ac; the optimal conditions of the multi-enzyme catalysis system were 37°C and pH 8.5, the ratio of AGE to NanA (1:4) and addition of pyruvate (70 mM), respectively. Finally, 9.2 g/L Neu5Ac could be obtained from 20 g/L chitin within 24 h along with two supplementations with pyruvate. This work will lay a good foundation for the production of Neu5Ac from cheap chitin resources.

Analysis of the intramolecular 1,7-lactone of N-acetylneuraminic acid using HPLC-MS: relationship between detection and stability.

A subclass of the sialic acid family consists of intramolecular lactones that may function as key indicators of physiological and pathological states. However, the existence of these compounds in free form is highly improbable, since they are unlikely to exist in an aqueous solution due to their lability. Current analytical method used to detect them in biological fluids has not recognized their reactivity in solution and is prone to misidentification. However, recent advances in synthetic methods for 1,7-lactones have allowed the preparation of these sialic acid derivatives as authentic reference standards. We report here the development of a new HPLC-MS method for the simultaneous detection of the 1,7-lactone of N-acetylneuraminic acid, its γ-lactone derivative, and N-acetylneuraminic acid that overcomes the limitations of the previous analytical procedure for their identification.

Bacterial Sialic Acid Catabolism at the Host-Microbe Interface.

Sialic acids consist of nine-carbon keto sugars that are commonly found at the terminal end of mucins. This positional feature of sialic acids contributes to host cell interactions but is also exploited by some pathogenic bacteria in evasion of host immune system. Moreover, many commensals and pathogens use sialic acids as an alternative energy source to survive within the mucus-covered host environments, such as the intestine, vagina, and oral cavity. Among the various biological events mediated by sialic acids, this review will focus on the processes necessary for the catabolic utilization of sialic acid in bacteria. First of all, transportation of sialic acid should be preceded before its catabolism. There are four types of transporters that are used for sialic acid uptake; the major facilitator superfamily (MFS), the tripartite ATP-independent periplasmic C4-dicarboxilate (TRAP) multicomponent transport system, the ATP binding cassette (ABC) transporter, and the sodium solute symporter (SSS). After being moved by these transporters, sialic acid is degraded into an intermediate of glycolysis through the well-conserved catabolic pathway. The genes encoding the catabolic enzymes and transporters are clustered into an operon(s), and their expression is tightly controlled by specific transcriptional regulators. In addition to these mechanisms, we will cover some researches about sialic acid utilization by oral pathogens.