The investigation on sialic acid-modified pectin nanoparticles loaded with oxymatrine for orally targeting and inhibiting the of ulcerative colitis.

The aim of the study was to develop an oral targeting drug delivery system (OTDDS) of oxymatrine (OMT) to effectively treat ulcerative colitis (UC). The OTDDS of OMT (OMT/SA-NPs) was constructed with OMT, pectin, Ca2+, chitosan (CS) and sialic acid (SA). The obtained particles were characterized in terms of particle size, zeta potential, morphology, drug loading, encapsulation efficiency, drug release and stability. The average size of OMT/SA-NPs was 255.0 nm with a zeta potential of -12.4 mV. The loading content and encapsulation efficiency of OMT/SA-NPs were 14.65% and 84.83%, respectively. The particle size of OMT/SA-NPs changed slightly in the gastrointestinal tract. The nanoparticles can delivery most of the drug to the colon region. In vitro cell experiments showed that the SA-NPs had excellent biocompatibility and anti-inflammation, and the uptake of SA-NPs by RAW 264.7 cells was time and concentration-dependent. The conjugated SA can help the internalization of NPs into target cells. In vivo experiments showed that OMT/SA-NPs had a superior anti-inflammation effect and the effect of reducing UC, which was attributed to the delivery most of OMT to the colonic lumen, the specific targeting and retention in colitis site and the combined anti-inflammation of OMT and NPs.

GNE deficiency impairs Myogenesis in C2C12 cells and cannot be rescued by ManNAc supplementation.

GNE myopathy (GNEM) is a late-onset muscle atrophy, caused by mutations in the gene for the key enzyme of sialic acid biosynthesis, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE). With an incidence of one to nine cases per million it is an ultra-rare, so far untreatable, autosomal recessive disease. Several attempts have been made to treat GNEM patients by oral supplementation with sialic acid precursors (e.g. N-acetylmannosamine, ManNAc) to restore sarcolemmal sialylation and muscle strength. In most studies, however, no significant improvement was observed. The lack of a suitable mouse model makes it difficult to understand the exact pathomechanism of GNEM and many years of research have failed to identify the role of GNE in skeletal muscle due to the lack of appropriate tools. We established a CRISPR/Cas9-mediated Gne-knockout cell line using murine C2C12 cells to gain insight into the actual role of the GNE enzyme and sialylation in a muscular context. The main aspect of this study was to evaluate the therapeutic potential of ManNAc and N-acetylneuraminic acid (Neu5Ac). Treatment of Gne-deficient C2C12 cells with Neu5Ac, but not with ManNAc, showed a restoration of the sialylation level back to wild type levels-albeit only with long-term treatment, which could explain the rather low therapeutic potential. We furthermore highlight the importance of sialic acids on myogenesis, for C2C12 Gne-knockout myoblasts lack the ability to differentiate into mature myotubes.

Sialic acid in human milk and infant formulas in China: concentration, distribution and type.

This study compared the concentrations, types and distributions of sialic acid (SA) in human milk at different stages of the postnatal period with those in a range of infant formulas. Breast milk from mothers of healthy, full-term and exclusively breastfed infants was collected on the 2nd (n 246), 7th (n 135), 30th (n 85) and 90th (n 48) day after birth. The SA profiles of human milk, including their distribution, were analysed and compared with twenty-four different infant formulas. Outcome of this observational study was the result of natural exposure. Only SA of type Neu5Ac was detected in human milk. Total SA concentrations were highest in colostrum and reduced significantly over the next 3 months. Approximately 68·7­76·1 % of all SA in human milk were bound to oligosaccharides. Two types of SA, Neu5Ac and Neu5Gc, have been detected in infant formulas. Most SA was present in infant formulas combined with protein. Breastfed infants could receive more SA than formula-fed infants with the same energy intake. Overall, human milk is a preferable source of SA than infant formulas in terms of total SA content, dynamics, distribution and type. These SA profiles in the natural state are worth to be considered by the production of formulas because they may have a great effect on infant nutrition and development.

Sialic Acid Engineered Prodrug Nanoparticles for Codelivery of Bortezomib and Selenium in Tumor Bearing Mice.

Most cancer patients rarely benefit from monodrug therapy because of both cancer complexity and tumor environment. One of the main reasons for this failure is insufficient accumulation of the optimal dose at the tumorous site. Our investigation implies a promising strategy to engineer prodrug nanoparticles (NPs) of bortezomib (BTZ) and selenium (Se) using sialic acid (SAL) as a ligand to improve breast cancer therapy. BTZ was conjugated with SAL and HPMA (N-2-hydroxypropyl methacrylamide) to prepare a prodrug conjugate; BTZ-SAL-HPMA (BSAL-HP) and then fabricated into prodrug NPs with Se (Se_BSAL-HP prodrug NPs). The self-assembly of prodrug NPs functionalized with Se showed size (204.13 ± 0.02 nm) and zeta potential (-31.0 ± 0.11 mV) in dynamic light scattering (DLS) experiments and spherical shape in TEM and SEM analysis. Good stability and low pH drug release profile were characterized by Se_BSAL-HP prodrug NPs. The tumor-selective boronate-ester-based prodrug NPs of BTZ in combination with Se endowed a synergistic effect against cancer cells. Compared to prodrug conjugate, Se_BSAL-HP prodrug NPs exhibited higher cell cytotoxicity and enhanced cellular internalization with significant changes in mitochondria membrane potential (MMP). Elevated apoptosis was observed in the (G2/M) phase of the cell cycle for Se_BSAL-HP prodrug NPs (2.7-fold) higher than BTZ. In vivo studies were performed on Sprague-Dawley rats and resulted in positive trends. The increased therapeutic activity of Se_BSAL-HP prodrug NPs inhibited primary tumor growth and showed 43.05 fold decrease in tumor volume than the control in 4T1 tumor bearing mice. The surprising and remarkable outcomes for Se_BSAL-HP prodrug NPs were probably due to the ROS triggering effect of boronate ester and selenium given together.

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.

Oral sialic acid supplementation in NANS-CDG: Results of a single center, open-label, observational pilot study.

NANS-CDG is a congenital disorder of glycosylation (CDG) caused by biallelic variants in NANS, encoding an essential enzyme in de novo sialic acid synthesis. It presents with intellectual developmental disorder (IDD), skeletal dysplasia, neurologic impairment, and gastrointestinal dysfunction. Some patients suffer progressive intellectual neurologic deterioration (PIND), emphasizing the need for a therapy. In a previous study, sialic acid supplementation in knockout nansa zebrafish partially rescued skeletal abnormalities. Here, we performed the first in-human pre- and postnatal sialic-acid study in NANS-CDG. In this open-label observational study, 5 patients with NANS-CDG (range 0-28 years) were treated with oral sialic acid for 15 months. The primary outcome was safety. Secondary outcomes were psychomotor/cognitive testing, height and weight, seizure control, bone health, gastrointestinal symptoms, and biochemical and hematological parameters. Sialic acid was well tolerated. In postnatally treated patients, there was no significant improvement. For the prenatally treated patient, psychomotor and neurologic development was better than two other genotypically identical patients (one treated postnatally, one untreated). The effect of sialic acid treatment may depend on the timing, with prenatal treatment potentially benefiting neurodevelopmental outcomes. Evidence is limited, however, and longer-term follow-up in a larger number of prenatally treated patients is required.

Chitosan-sialic acid nanoparticles of selenium: Statistical optimization of production, characterization, and assessment of cytotoxic effects against two human glioblastoma cell lines.

According to the favorable antitumor properties of selenium, this study aimed to design a novel form of selenium nanoparticles (Se NPs) functionalized with chitosan (Cs) and sialic acid to assess their antitumor effects on the human glioblastoma cell lines (T98 and A172). Se NPs were synthesized in the presence of chitosan and ascorbic acid (Vc) and the synthesis conditions were optimized using response surface methodology. Se NPs@Cs were obtained with a monoclinic structure with an average diameter of 23 nm under the optimum conditions (reaction time = 30 min, chitosan concentration = 1 % w/v, Vc/Se molar ratio = 5). To modify Se NP@Cs for glioblastoma treatment, sialic acid was used to cover the surface of the NPs. Sialic acid was successfully attached to the surface of Se NPs@Cs, and Se NPs@Cs-sialic acid were formed in the size range of 15-28 nm. Se NPs@Cs-sialic acid were stable for approximately 60 days at 4 ℃. The as-synthesized NPs exerted inhibitory effects on T98 greater than 3 T3 > A172 cells in a dose- and time-dependent manner. Additionally, sialic acid ameliorated the blood biocompatibility of Se NPs@Cs. Taken together, sialic acid improved both the stability and biological activity of Se NPs@Cs.

Low vitamin B12 level in relation to trace element, total sialic acid and antioxidant enzymes in children with vitamin B12 deficiency anemia.

In this study, children with vitamin B12 deficiency anemia (V-B12DA) and control subjects were evaluated for erythrocyte glutathione peroxidase, catalase and superoxide dismutase enzyme activities, glutathione, malondialdehyde, serum total sialic acid, total antioxidant status, cobalt, chromium, copper, selenium, vanadium, zinc, iron, lead, magnesium, calcium, sodium, potassium, chloride, phosphorus levels, and the associations of these variables were assessed. The study included 50 children with V-B12DA and 50 control subjects. It was found that the V-B12DA group was significantly lower than the control group, with regard to the mean±the standard error of the mean levels of cobalt (0.089±0.009; 0.058±0.0063 µmol/L, p<0.01), selenium (2.19±0.087; 1.88±0.057 µmol/L, p<0.01), vanadium (1.31±0.053; 1.18±0.035 µmol/L, p<0.05), magnesium (3.02±0.15; 2.73±0.068 µmol/L, p<0.05), zinc (50.76±1.96; 42.23± 1.53 µmol/L, p<0.001), and vitamin B12 (427.20±21.45; 157.08±3.96 pg/mL, p<0.001). Moreover, a significant elevation in total sialic acid (1.44±0.050; 1.61±0.043 mmol/L, p<0.01), and mean corpuscular volume (MCV) (75.37±0.95; 79.91±1.14 fL, p<0.01). It was observed that in the V-B12DA, significantly linear correlations were observed between cobalt - vitamin B12 (r=0.334; p=0.025), vanadium - MCV (r=0.315; p=0.017), vitamin B12 - MCV (r=-0.297; p=0.026). The findings of the study indicated that the levels of cobalt, vanadium significantly associated with traditional vitamin B12-deficiency parameters. Vitamin B12 and MCV should be measured together with cobalt, vanadium for monitoring the vitamin B12 deficiency anemia.

Switching azide and alkyne tags on bioorthogonal reporters in metabolic labeling of sialylatedglycoconjugates: a comparative study.

Sialylation of cell surface glycans plays an essential role in cell-cell interaction and communication of cells with their microenvironment. Among the tools that have been developed for the study of sialylation in living cells, metabolic oligosaccharide engineering (MOE) exploits the biosynthetic pathway of sialic acid (Sia) to incorporate unnatural monosaccharides into nascent sialylatedglycoconjugates, followed by their detection by a bioorthogonal ligation of a molecular probe. Among bioorthogonal reactions, the copper-catalyzed azide-alkyne cycloaddition (CuAAC) is the only ligation where both reactive tags can be switched on the chemical reporter or on the probe, making this reaction very flexible and adaptable to various labeling strategies. Azide- and alkyne-modified ManNAc and Sia reporters have been widely used, but per-O-acetylated ManNAz (Ac4ManNAz) remains the most popular choice so far for tracking intracellular processing of sialoglycans and cell surface sialylation in various cells. Taking advantage of CuAAC, we compared the metabolic incorporation of ManNAl, ManNAz, SiaNAl, SiaNAz and Ac4ManNAz in the human colon cell lines CCD841CoN, HT29 and HCT116, and in the two gold standard cell lines, HEK293 and HeLa. Using complementary approaches, we showed marked differences in the efficiency of labeling of sialoglycoproteins between the different chemical reporters in a given cell line, and that switching the azide and alkyne bioorthogonal tags on the analogs highly impacted their metabolic incorporation in the human colon cell lines. Our results also indicated that ManNAz was the most promiscuous metabolized reporter to study sialylation in these cells.

Comparison of dental caries experience and salivary parameters among children with Down syndrome and healthy controls in Chennai, Tamil Nadu.

Background: Although there have been numerous studies on dental caries in children with Down syndrome, the reports are conflicting. Studies on salivary chemical composition of children with Down syndrome are limited. Aim: The study aims to evaluate and compare the dental caries experience, salivary flow rate, pH, buffering capacity, and concentration of sodium, potassium, calcium, phosphorus, total proteins, and sialic acid in children with Down syndrome and healthy controls. Settings and Design: This was a cross-sectional study. Materials and Methods: Forty subjects with Down syndrome aged 5-18 years fulfilling the eligibility criteria from six special schools were selected by snowball sampling. Sixty healthy controls from six neighborhood schools fulfilling the eligibility criteria were selected by simple random sampling by matching the age, gender, and socioeconomic status. Sociodemographic data, oral hygiene practices, diet history and dental caries experience were recorded. About 6 mL of stimulated whole saliva was collected. Salivary flow rate, salivary pH, buffering capacity, and the concentration of sodium, potassium, calcium, phosphorus, total proteins, and sialic acid were determined. Results: There was no significant difference in the mean proportional caries rate between the study and control group (P = 0.90). Salivary pH (P = 0.00) and salivary sodium concentration (P = 0.02) were significantly low in the study group than the control group. Salivary buffering capacity was significantly higher in the study group than the control group (P = 0.001). Conclusions: Dental caries experience of children with Down syndrome was similar to the healthy controls. School health programs could be implemented in special schools to improve oral and general health of special children.

N-linked glycoproteomic profiling in esophageal squamous cell carcinoma.

BACKGROUND: Mass spectrometry-based proteomics and glycomics reveal post-translational modifications providing significant biological insights beyond the scope of genomic sequencing. AIM: To characterize the N-linked glycoproteomic profile in esophageal squamous cell carcinoma (ESCC) via two complementary approaches. METHODS: Using tandem multilectin affinity chromatography for enrichment of N-linked glycoproteins, we performed N-linked glycoproteomic profiling in ESCC tissues by two-dimensional gel electrophoresis (2-DE)-based and isobaric tags for relative and absolute quantification (iTRAQ) labeling-based mass spectrometry quantitation in parallel, followed by validation of candidate glycoprotein biomarkers by Western blot. RESULTS: 2-DE-based and iTRAQ labeling-based quantitation identified 24 and 402 differentially expressed N-linked glycoproteins, respectively, with 15 in common, demonstrating the outperformance of iTRAQ labeling-based quantitation over 2-DE and complementarity of these two approaches. Proteomaps showed the distinct compositions of functional categories between proteins and glycoproteins with differential expression associated with ESCC. Western blot analysis validated the up-regulation of total procathepsin D and high-mannose procathepsin D, and the down-regulation of total haptoglobin, high-mannose clusterin, and GlcNAc/sialic acid-containing fraction of 14-3-3ζ in ESCC tissues. The serum levels of glycosylated fractions of clusterin, proline-arginine-rich end leucine-rich repeat protein, and haptoglobin in patients with ESCC were remarkably higher than those in healthy controls. CONCLUSION: Our study provides insights into the aberrant N-linked glycoproteome associated with ESCC, which will be a valuable resource for future investigations.

Synthesis of 2-Acetamido-1,3,4-Tri-O-Acetyl-2-Deoxy-D-Mannopyranose -6-Phosphate Prodrugs as Potential Therapeutic Agents.

Sugar phosphates are emerging as potential therapeutic candidates for certain diseases. However, their high polarity makes them poorly absorbed by the body and their penetration inside the cell is even more difficult without a proper transporter. Amino sugar phosphates (n-amino-n-deoxy-sugars, carbohydrates in which a hydroxyl group has been replaced with an amine group), such as N-acetyl-D-mannosamine (ManNac)-6-phosphate have shown potential as a treatment for a muscular disease called GNE myopathy caused by a deficiency in the production of sialic acid. However, its high polarity leads to poor absorption and consequent high dosage in humans, causing unwanted side effects. Herein, we describe the application of phosphoramidate prodrug chemistry to 1,3,4-O-acetylated N-acetylmannosamine (Ac3ManNAc) to deliver ManNAc-6-phosphate (ManNAc-6-P), a critical intermediate in sialic acid biosynthesis. Sialic acid deficiency is a hallmark of GNE myopathy, a rare congenital disorder of glycosylation (CDG), caused by mutations in the gene "GNE," that limit the production of ManNAc-6-P. Synthetic methods were developed to provide a library of Ac3ManNAc-6-phosphoramidates that were evaluated in a series of studies for their potential as a treatment for GNE myopathy. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Synthesis of 2-Acetamido-1,3,4-tri-O-acetyl-2-deoxy-D-mannopyranose. Basic Protocol 2: Preparation of 3-acetamido-6-((((((S)-1-ethoxy-4-methyl-1-oxo-pentan-2-yl) amino) (phenoxy)phosphoryl) oxy) methyl) tetrahydro-2H-pyran-2,4,5-triyl triacetate (5). Support Protocol: Preparation of ethyl (chloro(phenoxy)phosphoryl)-l-leucinate.

Novel multifunctional bionanoparticles modified with sialic acid for stroke treatment.

Oxidative stress and inflammation are two key pathophysiological mechanisms that lead to neuronal apoptosis and brain damage following ischemia/reperfusion (I/R) injury. Because of their complex pathological mechanisms and the presence of the blood-brain barrier, the treatment of I/R is severely limited. Inspired by the fact that Macrophage membranes (MM) can cross the blood-brain barrier, we have developed a new multifunctional bionic particle (MSAOR@Cur). The modification of Sialic acid (SA) on the surface of Angelica polysaccharides (APS), the attachment of Resveratrol (Res) using the ROS-responsive bond oxalate bond as a linker arm, constitutes amphiphilic nanoparticles with an inner core encapsulated with curcumin (SAOR@Cur), and finally the use of MM camouflage to integrate the neuroprotection of APS, the free radical scavenging of Res, and the anti-inflammation of curcumin (Cur) in one strategy. Interestingly, the experimental results show that MSAOR@Cur can successfully deliver curcumin to the area of ischemia-reperfusion injury.

A nanohybrid of Prussian blue supported by boracic acid-modified g-C3N4 for Raman recognition of cell surface sialic acid and photothermal/photodynamic therapy.

Theranostic nanoplatforms with accurate diagnosis and effective therapy show a bright prospect for tumor treatments. Herein, a novel boracic acid-modified graphite carbon nitride and Prussian blue nanohybrid (PB@B-g-C3N4) was developed, which provides sialic acid-targeted Raman recognition and synergistic photothermal/photodynamic therapy in the near-infrared region. Owing to the specific interaction between boracic acid and sialic acid and Raman response at 2157 cm-1 of PB, the nanohybrids exhibit high specificity and Raman sensitivity for detection of the overexpressed sialic acid on tumor cells. Moreover, the photothermal conversion efficiency of PB@B-g-C3N4 is as high as 47.0% with 808 nm laser irradiation due to the enhanced absorbance of PB@B-g-C3N4. PB@B-g-C3N4 also possesses excellent photodynamic activity, which is attributed to the energy transfer of PB (type I) and electron transfer between PB and B-g-C3N4 (type II). This nanotheranostic agent for Raman recognition of cancer markers and synergistic photothermal/photodynamic therapy holds great potential for the development of efficient theranostic nanoplatforms.

COVID-19, Cation Dysmetabolism, Sialic Acid, CD147, ACE2, Viroporins, Hepcidin and Ferroptosis: A Possible Unifying Hypothesis.

Background: iron and calcium dysmetabolism, with hyperferritinemia, hypoferremia, hypocalcemia and anemia have been documented in the majority of COVID-19 patients at later/worse stages. Furthermore, complementary to ACE2, both sialic acid (SA) molecules and CD147 proved relevant host receptors for SARS-CoV-2 entry, which explains the viral attack to multiple types of cells, including erythrocytes, endothelium and neural tissue. Several authors advocated that cell ferroptosis may be the core and final cell degenerative mechanism. Methods: a literature research was performed in several scientific search engines, such as PubMed Central, Cochrane Library, Chemical Abstract Service. More than 500 articles were retrieved until mid-December 2021, to highlight the available evidence about the investigated issues. Results: based on COVID-19 literature data, we have highlighted a few pathophysiological mechanisms, associated with virus-based cation dysmetabolism, multi-organ attack, mitochondria degeneration and ferroptosis. Our suggested elucidated pathological sequence is: a) spike protein subunit S1 docking with sialylated membrane glycoproteins/receptors (ACE2, CD147), and S2 subunit fusion with the lipid layer; b) cell membrane morpho-functional changes due to the consequent electro-chemical variations and viroporin action, which induce an altered ion channel function and intracellular cation accumulation; c) additional intracellular iron concentration due to a deregulated hepcidin-ferroportin axis, with higher hepcidin levels. Viral invasion may also affect erythrocytes/erythroid precursors, endothelial cells and macrophages, through SA and CD147 receptors, with relative hemoglobin and iron/calcium dysmetabolism. AB0 blood group, hemochromatosis, or environmental elements may represent possible factors which affect individual susceptibility to COVID-19.     Conclusions: our literature analysis confirms the combined role of SA molecules, ACE2, CD147, viroporins and hepcidin in determining the cation dysmetabolism and final ferroptosis in the cells infected by SARS-CoV-2. The altered ion channels and electrochemical gradients of the cell membrane have a pivotal role in the virus entry and cell dysmetabolism, with subsequent multi-organ immune-inflammatory degeneration and erythrocyte/hemoglobin alterations.

Synthesis of sialic acid conjugates of the clinical near-infrared dye as next-generation theranostics for cancer phototherapy.

Cancer is a multifaceted global health problem that requires continuous action to develop next-generation cancer theranostics. Inspired by the emerging use of indocyanine green (ICG), the only clinically approved near-infrared (NIR) dye for cancer phototherapy, here we synthesized two ICG conjugate theranostics by coupling ICG to sialic acid (Sia) through the C2 and C9 positions of Sia, respectively, referred to as Sia-C2-ICG and Sia-C9-ICG. Encouragingly, Sia-C2/C9-ICGs show superior in vitro properties, including enhanced stability, reduced non-specific binding to serum proteins, and improved blood compatibility, highlighting the benefits of Sia coupling. Notably, in vivo NIR imaging shows that Sia-C9-ICG significantly promotes tumor targeting and effectively prolongs the circulation time in the body, while Sia-C2-ICG is superior to ICG but inferior to Sia-C9-ICG in targeting tumors. Furthermore, Sia-C9-ICG combined with NIR laser irradiation can lead to excellent photothermal and photodynamic therapies for cancer cells, resulting in superior solid tumor ablation. To our knowledge, this is the first report of Sia-NIR conjugates achieving significant tumor reduction in vivo. Together, these advances render Sia-C9-ICG an attractive lead as next-generation cancer theranostics that can be translated clinically to treat human patients.

Negative-mode mass spectrometry in the analysis of invertebrate, fungal, and protist N-glycans.

The approaches for analysis of N-glycans have radically altered in the last 20 years or so. Due to increased sensitivity, mass spectrometry has become the predominant method in modern glycomics. Here, we summarize recent studies showing that the improved resolution and detection by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has contributed greatly to the discovery of a large range of anionic and zwitterionic N-glycan structures across the different kingdoms of life, whereby MALDI-TOF MS in negative mode is less widely performed than in positive mode. However, its use enables the detection of key fragments indicative of certain sugar modifications such as sulfate, (methyl) phosphate, phosphoethanolamine, (methyl)aminoethylphosphonate, glucuronic, and sialic acid, thereby enabling certain isobaric glycan variations to be distinguished. As we also discuss in this review, complementary approaches such as negative-mode electrospray ionization-MS/MS, Fourier-transform ion cyclotron resonance MS, and ion mobility MS yield, respectively, cross-linkage fragments, high accuracy masses, and isomeric information, thus adding other components to complete the jigsaw puzzle when defining unusual glycan modifications from lower organisms.

Dietary Neu5Ac Intervention Protects Against Atherosclerosis Associated With Human-Like Neu5Gc Loss-Brief Report.

Objective: Species-specific pseudogenization of the CMAH gene during human evolution eliminated common mammalian sialic acid N-glycolylneuraminic acid (Neu5Gc) biosynthesis from its precursor N-acetylneuraminic acid (Neu5Ac). With metabolic nonhuman Neu5Gc incorporation into endothelia from red meat, the major dietary source, anti-Neu5Gc antibodies appeared. Human-like Ldlr-/-Cmah-/- mice on a high-fat diet supplemented with a Neu5Gc-enriched mucin, to mimic human red meat consumption, suffered increased atherosclerosis if human-like anti-Neu5Gc antibodies were elicited. Approach and Results: We now ask whether interventional Neu5Ac feeding attenuates metabolically incorporated Neu5Gc-mediated inflammatory acceleration of atherogenesis in this Cmah-/-Ldlr-/- model system. Switching to a Neu5Gc-free high-fat diet or adding a 5-fold excess of Collocalia mucoid-derived Neu5Ac in high-fat diet protects against accelerated atherosclerosis. Switching completely from a Neu5Gc-rich to a Neu5Ac-rich diet further reduces severity. Remarkably, feeding Neu5Ac-enriched high-fat diet alone has a substantial intrinsic protective effect against atherosclerosis in Ldlr-/- mice even in the absence of dietary Neu5Gc but only in the human-like Cmah-null background. Conclusions: Interventional Neu5Ac feeding can mitigate or prevent the red meat/Neu5Gc-mediated increased risk for atherosclerosis, and has an intrinsic protective effect, even in the absence of Neu5Gc feeding. These findings suggest that similar interventions should be tried in humans and that Neu5Ac-enriched diets alone should also be investigated further.

A preliminary study on isomer-specific quantification of sialylated N-glycans released from whey glycoproteins in human colostrum and mature milk using a glycoqueuing strategy.

Sialylated N-glycans are an integral component of whey proteins in human milk and play an irreplaceable role in infant growth and development. Currently, there are few studies on quantitative comparison of sialylated N-glycans in milk obtained at different lactation stages. Here, a preliminary isomer-specific quantification of whey sialylated N-glycans of human colostrum milk (CM) and mature milk (MM) was performed by using our recently developed glycoqueuing strategy. Such a preliminary comparison revealed that the whey sialylated N-glycan content was 86.4% lower in MM than in CM. Twenty-three α2,6-linked sialylated N-glycan isomers were detected with no α2,3-linked isomer observed. For the first time, three mono-sialylated and four bi-sialylated glycan isomers were reported. With the prolongation of lactation, the relative abundance of mono-sialylated glycans increased, whilst the relative abundance of bi-sialylated glycans decreased significantly. These findings contribute to the understanding of the structure-function relationship of sialylated N-glycans in the human whey fraction.

Analysis of biomarkers and metabolic pathways in patients with unstable angina based on ultra­high­performance liquid chromatography­quadrupole time­of­flight mass spectrometry.

Unstable angina (UA) is a coronary disease with a high mortality and morbidity worldwide. The present study aimed to use non­invasive techniques to identify urine biomarkers in patients with UA, so as to provide more information for the early diagnosis and treatment of the disease. Based on metabolomics, urine samples from 28 patients with UA and 28 healthy controls (HCs) were analyzed using ultra­high­performance liquid chromatography­quadrupole time­of­flight mass spectrometry (UPLC­Q­TOF/MS). A total of 16 significant biomarkers that could distinguish between patients with UA and HCs, including D­glucuronic acid, creatinine, succinic acid and N­acetylneuraminic acid, were identified. The major metabolic pathways associated with UA were subsequently analyzed by non­targeted metabolomics. The results demonstrated that amino acid and energy metabolism, fatty acid metabolism, purine metabolism and steroid hormone biosynthetic metabolism may serve important roles in UA. The results of the current study may provide a theoretical basis for the early diagnosis of UA and novel treatment strategies for clinicians. The trial was registered with the Chinese Clinical Trial Registration Center (registration no. ChiCTR­ROC­17013957) at Tianjin University of Traditional Chinese Medicine.