Sialic Acid Research Articles

Multiplex Sensing of Biomarkers on the Cancer Cell Surface by an Epithelial-Mesenchymal Transition (EMT) Sensing Panel Enables Precise Differentiating of Cancer Cells at Various EMT Stages.

Epithelial-mesenchymal transition (EMT) is a complex process that plays a critical role in tumor progression. In this study, we present an EMT sensing panel for the classification of cancer cells at different EMT stages. This sensing panel consists of three types of fluorescent probes based on boronic acid-functionalized carbon-nitride nanosheet (BCN) derivatives. The selective response toward different EMT-associated biomarkers, namely, EpCAM, N-cadherin, and sialic acid (SA), was achieved by conjugating the corresponding antibodies to each BCN derivative, whereas the rare-earth-doping ensures simultaneous sensing of the three biomarkers with fluorescent emission of the three probes at different wavelengths. Sensitive sensing of the three biomarkers was achieved at the protein level with LODs reaching 1.35 ng mL-1 for EpCAM, 1.62 ng mL-1 for N-cadherin, and 1.54 ng mL-1 for SA. The selective response of these biomarkers on the cell surface also facilitated sensitive detection of MCF-7 cells and MDA-MB-231 cells with LODs of 2 cells/mL and 2 cells/mL, respectively. Based on the simultaneous sensing of the three biomarkers on cancer cells that underwent different extents of EMT, precise discrimination and classification of cells at various EMT stages were also achieved with an accuracy of 93.3%. This EMT sensing panel provided a versatile tool for monitoring the EMT evolution process and has the potential to be used for the evaluation of the EMT-targeting therapy and metastasis prediction.

1, 6-dilauroyl-D-fructofuranose ameliorates lipopolysaccharide induced sepsis acute kidney injury via inhibiting caspase 1-mediated pyroptosis formation in rat

Background: Sepsis is a systemic inflammatory state associated with acute kidney injury (AKI) and high mortality. However, sepsis induced AKI cannot be efficiently prevented or cured using current antimicrobial therapies and supportive measures. We explored the therapeutic effect of newly developed fructose esters on sepsis-induced AKI (S-AKI). Methods: We used the surface plasmon resonance technique and ultrasensitive chemiluminescence analyzer to characterize the lipopolysaccharide (LPS)/endotoxin binding activity and antioxidant capability of fructose esters. We evaluated the degree of fructose ester gastrointestinal digestion using rat intestinal acetone powder. We examined the therapeutic effect of fructose esters on LPS-induced S-AKI by evaluating the blood and renal reactive oxygen species (ROS) amounts, Caspase 1 mediated pyroptosis, inflammation, microcirculation, and renal dysfunction. Results: Our data showed that the fructose esters are not easily hydrolyzed by the rat intestinal acetone powder implicating its high stability in the gastrointestinal tract. 1,6-dilauroyl-D-fructofuranose (FDL) dose-dependently scavenged H2O2 activity displayed a higher binding affinity to LPS than sialic acid and fructose did. LPS significantly enhanced Caspase 1 mediated pyroptosis and increased leukocyte infiltration, blood and renal ROS amount and BUN and creatinine level, whereas FDL significantly depressed these LPS-enhanced parameters. In addition, the increased plasma inflammatory cytokines levels using LPS could be reduced by intravenous fructose ester FDL treatment. Conclusion: Our data suggest that FDL with antioxidant H2O2 activity can neutralize LPS toxicity using a high binding affinity, and attenuate S-AKI by inhibiting Caspase 1 mediated pyroptosis resulting in ameliorating renal oxidative stress and dysfunction.

Sequencing Sialic Acid Positioning in Gangliosides by High-Resolution Cyclic Ion Mobility Separations Coupled with Multiple Collision-Induced Dissociation-Based Tandem Mass Spectrometry Strategies.

Gangliosides, a diverse class of glycosphingolipids, are highly abundant in neural tissue and have been implicated in numerous aging-related diseases. Their characterization with methods such as liquid chromatography-tandem mass spectrometry is often precluded by their structural complexity, isomeric heterogeneity, and lack of commercially available authentic standards. In this work, we coupled high-resolution cyclic ion mobility spectrometry with multiple collision-induced dissociation-based tandem mass spectrometry strategies to sequence the sialic acid positions in various ganglioside isomers. Initially, as a proof-of-concept demonstration, we were able to characterize the sialic acid positions in several GD1 and GT1 species. From there, we extended our approach to identify the location of N-glycolylneuraminic acid (NeuGc) residues in previously uncharacterized GD1 and GQ1 isomers. Our results highlight the potential of this presented methodology for the de novo characterization of gangliosides within complex biological matrices without the need for authentic standards.

Targeting Neuraminidase 4 Attenuates Kidney Fibrosis in Mice.

Despite significant progress in therapy, there remains a lack of substantial evidence regarding the molecular factors that lead to renal fibrosis. Neuraminidase 4 (NEU4), an enzyme that removes sialic acids from glycoconjugates, has an unclear role in chronic progressive fibrosis. Here, this study finds that NEU4 expression is markedly upregulated in mouse fibrotic kidneys induced by folic acid or unilateral ureter obstruction, and this elevation is observed in patients with renal fibrosis. NEU4 knockdown specifically in the kidney attenuates the epithelial-to-mesenchymal transition, reduces the production of pro-fibrotic cytokines, and decreases cellular senescence in male mice. Conversely, NEU4 overexpression exacerbates the progression of renal fibrosis. Mechanistically, NEU4254-388aa interacts with Yes-associated protein (YAP) at WW2 domain (231-263aa), promoting its nucleus translocation and activation of target genes, thereby contributing to renal fibrosis. 3,5,6,7,8,3',4'-Heptamethoxyflavone, a natural compound, is identified as a novel NEU4 inhibitor, effectively protecting mice from renal fibrosis in a NEU4-dependent manner. Collectively, the findings suggest that NEU4 may represent a promising therapeutic target for kidney fibrosis.

Sialidase-Chimeric Bioengineered Bacteria for Tumor-Sialoglycan-Triggered Solid Tumor Therapy.

Adoptive cell therapies for solid tumors are usually limited by off-target antigens, incapable tissue infiltration, and cell function exhaustion. In contrast, bacterial cells possess the inherent competencies of preferential tumor targeting, deep tissue penetration, and high intratumoral bioactivity and represent promising alternatives to overcome these challenges. Here, a sialic-acid-responsive regulatory gene circuit is engineered into Escherichia coli MG1655 to express cytolysin of hemolysin E (HlyE). Furthermore, sialidases are bioorthogonally decorated onto the surface of azido-functionalized bioengineered bacteria for recognizing tumor sialoglycans and cleaving their sialosides into free sialic acids. As chemical inducers, sialic acids feedbackingly activate the bacterial gene circuit to produce HlyE and lyse tumor cells. This study mimics the tumor antigen-induced cytotoxin production and cell lysis that occurs in chimeric antigen receptor T (CAR-T) cells yet surmounts the intrinsic limitations of adoptive cell therapies. Moreover, sialidase-mediated tumor cell desialylation also reverses the immunosuppressive effect of glycoimmune checkpoints and further improves the therapeutic effect of solid tumors.

A bioinspired supramolecular nanoprodrug for precision therapy of B-cell non-Hodgkin’s lymphoma

Fludarabine (FA) is still considered as a first-line chemotherapy drug for hematological tumors related to B lymphocytes. However, it is worth noting that the non-specific distribution and non-different cytotoxicity of FA may lead to irreversible consequences such as central nervous system damage such as blindness, coma, and even death. Therefore, it is very important to develop a system to targeting delivery FA. In preliminary studies, it was found that B lymphoma cells would specific highly expressing the sialic acid-binding immunoglobulin-like lectin 2 (known as CD22). Inspired by the specific recognition of sialic acid residues and CD22, we have developed a supramolecular prodrug based on polysialic acid, an endogenous biomacromolecule, achieving targeted-therapy of B-cell non-Hodgkin’s lymphoma (B-NHL). Specifically, the prepared hydrophobic reactive oxygen species-responsive FA dimeric prodrug (F2A) interacts with the TPSA, which polysialic acid were modified by the thymidine derivatives, through non-covalent intermolecular interactions similar to “Watson–Crick” base pairing, resulting in the formation of nanoscale supramolecular prodrug (F@TPSA). Cell experiments have confirmed that F@TPSA can be endocytosed by CD22+ B lymphoma cells including Raji and Ramos cells, and there is a significant difference of endocytosis in other leukocytes. Furthermore, in B-NHL mouse model, compared with FA, F@TPSA is determined to have a stronger tumor targeting and inhibitory effect. More importantly, the distribution of F@TPSA in vivo tends to be enriched in lymphoma tissue rather than nonspecific, thus reducing the leukopenia of FA. The targeted delivery system based on PSA provides a new prodrug modification strategy for targeted treatment of B-NHL.Graphical abstract

Human apolipoprotein E glycosylation and sialylation: from structure to function.

Human apolipoprotein E (ApoE) was first identified as a polymorphic gene in the 1970s; however, the genetic association of ApoE genotypes with late-onset sporadic Alzheimer's disease (sAD) was only discovered 20 years later. Since then, intensive research has been undertaken to understand the molecular effects of ApoE in the development of sAD. Despite three decades' worth of effort and over 10,000 papers published, the greatest mystery in the ApoE field remains: human ApoE isoforms differ by only one or two amino acid residues; what is responsible for their significantly distinct roles in the etiology of sAD, with ApoE4 conferring the greatest genetic risk for sAD whereas ApoE2 providing exceptional neuroprotection against sAD. Emerging research starts to point to a novel and compelling hypothesis that the sialoglycans posttranslationally appended to human ApoE may serve as a critical structural modifier that alters the biology of ApoE, leading to the opposing impacts of ApoE isoforms on sAD and likely in the peripheral systems as well. ApoE has been shown to be posttranslationally glycosylated in a species-, tissue-, and cell-specific manner. Human ApoE, particularly in brain tissue and cerebrospinal fluid (CSF), is highly glycosylated, and the glycan chains are exclusively attached via an O-linkage to serine or threonine residues. Moreover, studies have indicated that human ApoE glycans undergo sialic acid modification or sialylation, a structural alteration found to be more prominent in ApoE derived from the brain and CSF than plasma. However, whether the sialylation modification of human ApoE has a biological role is largely unexplored. Our group recently first reported that the three major isoforms of human ApoE in the brain undergo varying degrees of sialylation, with ApoE2 exhibiting the most abundant sialic acid modification, whereas ApoE4 is the least sialylated. Our findings further indicate that the sialic acid moiety on human ApoE glycans may serve as a critical modulator of the interaction of ApoE with amyloid β (Aβ) and downstream Aβ pathogenesis, a prominent pathologic feature in AD. In this review, we seek to provide a comprehensive summary of this exciting and rapidly evolving area of ApoE research, including the current state of knowledge and opportunities for future exploration.

Structural Characterization of Human Bufavirus 1: Receptor Binding and Endosomal pH-Induced Changes.

Bufaviruses (BuV) are members of the Parvoviridae of the Protoparvovirus genus. They are non-enveloped, T = 1 icosahedral ssDNA viruses isolated from patients exhibiting acute diarrhea. The lack of treatment options and a limited understanding of their disease mechanisms require studying these viruses on a molecular and structural level. In the present study, we utilize glycan arrays and cell binding assays to demonstrate that BuV1 capsid binds terminal sialic acid (SIA) glycans. Furthermore, using cryo-electron microscopy (cryo-EM), SIA is shown to bind on the 2/5-fold wall of the capsid surface. Interestingly, the capsid residues stabilizing SIA binding are conserved in all human BuVs identified to date. Additionally, biophysical assays illustrate BuV1 capsid stabilization during endo-lysosomal (pH 7.4-pH 4) trafficking and capsid destabilization at pH 3 and less, which correspond to the pH of the stomach. Hence, we determined the cryo-EM structures of BuV1 capsids at pH 7.4, 4.0, and 2.6 to 2.8 Å, 3.2 Å, and 2.7 Å, respectively. These structures reveal capsid structural rearrangements during endo-lysosomal escape and provide a potential mechanism for this process. The structural insights gained from this study will add to the general knowledge of human pathogenic parvoviruses. Furthermore, the identification of the conserved SIA receptor binding site among BuVs provides a possible targetable surface-accessible pocket for the design of small molecules to be developed as anti-virals for these viruses.

The Role of NEU1 in Coronavirus Infection and Pathogenesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the coronavirus disease 2019 (COVID-19) pandemic, resulting in millions of infections and deaths worldwide. Although vaccines are available, they appear to be less efficacious against newly emerging variants of the virus. Thus, therapeutic modalities are urgently needed. The coronavirus genome encodes four major structural proteins: the spike (S) protein, nucleocapsid (N) protein, membrane (M) protein, and envelope (E) protein, all of which are required to produce a structurally complete viral particle. N protein is one of the most abundant structural proteins, participates in the regulation of viral replication and virion assembly, and is a major immunogen in coronavirus infection-induced disease. Sialylation is the addition of sialic acids to the terminal glycans of glycoproteins and glycolipids, which act as key components for biological functions of glycoproteins or glycolipids. Sialidases (or neuraminidases) are glycosidases that remove sialic acid residues (desialylation) from glycan portions of glycoproteins or glycolipids. Through desialylation, sialidases modulate the functionality of sialic acid-containing molecules and are involved in both physiological and pathological pathways. This review aims to explore the current understanding of NEU1's involvement in coronavirus infection and pathogenesis, synthesizing available research and identifying areas for future investigation.

Co-expression of human sialyltransferase improves N-glycosylation in Leishmania tarentolae and optimizes the production of humanized therapeutic glycoprotein IFN-beta

The production of therapeutic glycoproteins is primarily expensive due to the necessity of culturing mammalian cells. These systems often require complex and costly culture media and typically yield low amounts of protein. Leishmania tarentolae, a non-pathogenic protozoan to mammals, has emerged as a cost-effective alternative system for heterologous glycoprotein expression due to its suitability for large-scale production using low-cost culture media, and its ability to perform mammalian-like post-translational modifications, including glycosylation. Nevertheless, differences in the carbohydrate residues at the end of N-glycan chains are observed in Leishmania compared to mammalian cells due to the absence of biosynthetic enzymes in Leishmania that are required for the incorporation of terminal sialic acid. In this study, a genetically optimized L. tarentolae cell line was engineered for the production of recombinant interferon-β (IFN-β) featuring a complete mammalian N-glycosylation profile. Genomic and metabolomic analyses revealed that heterologous expression of the sialyltransferase enzyme and cultivation in a medium containing sialic acid were sufficient to generate mammalian-like protein N-glycosylation. N-glycan mass spectrometry analysis demonstrated a glycosylation pattern compatible with the incorporation of sialic acid into the glycan structure. In vitro IFN-β activity indicated that the expressed protein exhibited reduced inflammatory effects compared to IFN-beta produced by other platforms, such as bacteria, non-optimized L. tarentolae, and mammalian cells.

Characterization of Histophilus somni sialic acid uptake mutant (ΔnanP-ΔnanU) using a mouse septicemia and mortality model

Histophilus somni is an important pathogen of the bovine respiratory disease complex, yet the mechanisms underlying its virulence remain poorly understood. It is known that H. somni can incorporate sialic acid into lipooligosaccharide (LOS), and sialylated H. somni is more resistant to phagocytosis and complement-mediated killing by serum compared to non-sialylated bacteria in vitro. However, the virulence of non-sialylated H. somni has not been evaluated in vivo using an animal model. In this study, we investigated the contribution of sialic acid to virulence by constructing an H. somni sialic acid uptake mutant (ΔnanP-ΔnanU) and comparing the parent and mutant strains in a mouse septicemia and mortality model. Intraperitoneal challenge of mice with wildtype H. somni (1 × 108 colony forming units/mouse, CFU) was lethal to all animals. Mice challenged with three different doses (1, 2, or 5 × 108 CFU/mouse) of an H. somni ΔnanP-ΔnanU sialic acid uptake mutant exhibited survival rates of 90 %, 60 %, and 0 % respectively. High-performance anion exchange chromatography analyses revealed that LOS prepared from both parent and the ΔnanP-ΔnanU mutant strains of H. somni were sialylated. These findings suggest the presence of de novo sialic acid synthesis pathway, although the genes associated with de novo sialic acid synthesis (neuB and neuC) were not identified by genomic analysis. The lower attenuation in mice is most likely attributed to the sialylated LOS of H. somni nanPU mutant.

Neu5Gc-mediated high-affinity interaction is dispensable for CD22 cis-ligands to regulate B cell signaling

CD22 (also known as Siglec-2) is an inhibitory receptor expressed in B cells. CD22 specifically recognizes α2,6 sialic acid and interacts with α2,6 sialylated membrane proteins expressed on the same cell (cis-ligands) and those derived from outside of the cell (trans-ligands). Previously, CD22 cis-ligands were shown to regulate the activity of CD22, thereby regulating both BCR ligation-induced signaling and low-level "tonic" signaling in the absence of BCR ligation that regulates the survival and differentiation of B cells. Mouse CD22 prefers Neu5Gc to Neu5Ac thereby binding to α2,6-linked Neu5Gc with high affinity. Although human CD22 binds to a distinct α2,6 sialylated glycan with high affinity, expression of high-affinity ligands is regulated in a conserved and stringent manner. However, how high- versus low-affinity CD22 ligands regulate B cells is poorly understood. Here we demonstrate that the interaction of CD22 with the endogenous ligands enhances BCR ligation-induced signaling but reduces tonic signaling in Cmah-/- mouse B cells deficient in Neu5Gc as well as wild-type B cells. Moreover, Cmah-/- B cells do not show alterations in the phenotypes correlated to tonic signaling. These results indicate that low-affinity interaction of the CD22 cis-ligands with CD22 is sufficient for the regulation of B cell signaling, and suggest that expression of high-affinity CD22 ligands might be involved in the regulation of B cells by competing for the binding of CD22 with exogenous trans-ligands of CD22.

Bovine H5N1 influenza virus binds poorly to human-type sialic acid receptors.

Clade 2.3.4.4b highly pathogenic H5N1 avian influenza (HPAI) viruses started circulating widely in lactating dairy cattle in the United States at the end of 2023. Avian influenza viruses enter cells after binding to glycan receptors with terminally linked α2-3 sialic acid, whereas human influenza viruses typically bind to glycan receptors terminally linked α2-6 sialic acid in the upper respiratory tract. Here, we evaluated the receptor binding properties of hemagglutinin (HA) trimers from a clade 2.3.4.4b avian isolate (A/American Wigeon/South Carolina/22-000345-001/2021) and a cattle isolate (A/dairy cattle/Texas/24-008749-002-v/2024). Using two different methods, we found that both of the 2.3.4.4b H5s bound efficiently to glycan receptors with terminally linked α2-3 sialic acid with no detectable binding to glycan receptors with terminally linked α2-6 sialic acid. Our data suggest that clade 2.3.4.4b H5N1 viruses bind poorly to human receptors. It will be important to continue evaluating receptor binding properties of these viruses as they evolve in cattle.

Abstract Mo134: Restoring NaV1.5 Mutant Functionality in Arrhythmia with ManNAc Supplementation

The SCN5A gene encodes the human cardiac sodium channel NaV1.5, essential for cardiac excitability and action potential propagation. Mutations in SCN5A are linked to various cardiac disorders, including Brugada Syndrome (BrS), typically leading to channel loss-of-function. Understanding alterations in NaV1.5 expression and sodium current density is vital for comprehending arrhythmogenesis and formulating therapeutic strategies. Post-translational modifications, especially sialylation, significantly impact channel functionality. We previously demonstrated that BrS patients show decreased protein sialylation, correlating with reduced sodium channel activity. This study aimed to investigate sialic acid's role in regulating NaV1.5 activity, testing if sialylation induction via mannosamine (ManNAc) supplementation could restore channel activity in-vitro. Preliminary tests with exogenous sialidases and ManNAc supplementation affirmed our hypothesis. We examined ManNAc's effect on NaV1.5 mutants common in BrS, which typically exhibit partial functional loss. We overexpressed mutations p.A344S, p.K1479A, and p.G1406R in HEK293A cells and measured sodium currents before and after ManNAc supplementation to stimulate sialic acid synthesis. ManNAc effectively restored sodium currents in mutants with intracellular and extracellular loop mutations. However, the p.1406G>A mutant, affecting the pore structure, showed no improvement, suggesting that sialic acid mainly influences channel membrane trafficking rather than direct glycosylation. This underscores the complexity of sialic acid's role and points to trafficking pathways as potential therapeutic targets. Notably, the treatment neither increased nor decreased sodium currents in wild-type NaV1.5 channels or in the CaV3.2 calcium channel, underscoring its specificity. In summary, our findings demonstrate that ManNAc supplementation can selectively restore the function of certain NaV1.5 mutants without affecting wild-type channels, highlighting the potential of targeting sialylation pathways for SCN5A-related arrhythmia treatments. Future research should aim to unravel these mechanisms further, providing insights into novel treatments for SCN5A-related arrhythmias.

Abstract Tu131: Counteracting Cardiac Ischemia and Reperfusion Injury: the role of Sialidase Neu3

Coronary reperfusion procedures are crucial for restoring blood flow to the heart tissue after an acute myocardial infarction. However, they also lead to ischemia and reperfusion injury (IRI), which exacerbate the damage and promote heart failure. Despite the urgent need for cardioprotective strategies against IRI, none have been clinically implemented, emphasizing the need for a comprehensive understanding of the pathophysiology of IRI. Our research team found that sialidase Neu3, an enzyme responsible for the removal of sialic acid from glycosphingolipids, is modulated during IRI in vivo. Constitutive overexpression of Neu3 in rat cardiomyoblasts was shown to attenuate IRI through activation of the reperfusion injury salvage kinase (RISK) and HIF-1α signaling pathways. To further investigate the role of Neu3 in promoting cardioprotection, in this study we developed an inducible Neu3 overexpression model in human cardiac cells and mice. Inducible upregulation of Neu3 significantly improved cell resistance and reduced oxidative stress in AC16 cells exposed to IRI in vitro. These effects were attributed to Neu3-mediated maintenance of mitochondrial membrane potential, which was impaired in control cells. When looking at the upregulated genes exclusively in cells overexpressing the sialidase Neu3, RNAseq analysis revealed the predominant activation of MAP kinases typical of the RISK pathway. We also generated, for the first time, αMHC-Cre/LSL-Neu3 mice overexpressing Neu3 in an inducible and cardiomyocyte-specific manner. These mice showed no significant differences in cardiac morphology and functionality compared to wild-type animals. However, the Neu3-overexpressing mice exhibited a significant reduction in infarct size and improved cardiac functionality after surgical induction of IRI. These results suggest that Neu3 is a promising target for improving cardioprotection and attenuating the incidence and severity of myocardial infarction.

Brain-derived gangliosides prime human platelet aggregation and induce platelet-leukocyte aggregate formation

BackgroundPlatelet activation and interaction with leukocytes are crucial in inflammation. Gangliosides, sialic acid–containing glycosphingolipids, have been linked to different inflammatory conditions related to cardio- and neurodegenerative disorders. The role of gangliosides in platelet and leukocyte function, although reported, still needs further investigation. ObjectivesWe aimed to study the role of gangliosides in platelet activation and platelet-leukocyte interaction in vitro. MethodsPlatelet activation was studied through aggregometry in platelet-rich plasma from apparently healthy human volunteers. Signaling protein phosphorylation was analyzed by immunoblotting. Platelet P-selectin expression and platelet-leukocyte aggregate formation were measured by flow cytometry. ResultsThe gangliosides monosialoganglioside GM1, disialoganglioside GD1a, and trisialoganglioside GT1b did not induce by themselves any platelet aggregation. Conversely, when preincubated with platelets, they potentiate platelet aggregation induced by submaximal adenosine diphosphate and collagen concentrations and increased P-selectin expression. Incubation of platelets with free sialic acid and the soluble part of monosialoganglioside GM1 induced a similar potentiating effect on platelet aggregation but not on platelet P-selectin expression. Consistently, analyzing the signaling protein phosphorylation, only the entire gangliosides activated extracellular stimuli–responsive kinase 1/2 suggesting that a complete ganglioside is crucial for its action on platelets. Both the priming effect on platelet aggregation and ERK1/2 activation were prevented by aspirin. Moreover, incubation of citrated whole blood with gangliosides induced platelet-leukocyte aggregate formation accompanied by increased expression of granulocyte and monocyte CD11b compared with untreated blood, suggesting a primary leukocyte activation. ConclusionGangliosides may act in vitro both on platelet and leukocyte activation and on their interaction. The observed effects might contribute to inflammatory processes in clinical conditions.

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 48hours 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.

Genetic risk factors for COVID-19 and influenza are largely distinct

Coronavirus disease 2019 (COVID-19) and influenza are respiratory illnesses caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza viruses, respectively. Both diseases share symptoms and clinical risk factors1, but the extent to which these conditions have a common genetic etiology is unknown. This is partly because host genetic risk factors are well characterized for COVID-19 but not for influenza, with the largest published genome-wide association studies for these conditions including >2 million individuals2 and about 1,000 individuals3–6, respectively. Shared genetic risk factors could point to targets to prevent or treat both infections. Through a genetic study of 18,334 cases with a positive test for influenza and 276,295 controls, we show that published COVID-19 risk variants are not associated with influenza. Furthermore, we discovered and replicated an association between influenza infection and noncoding variants in B3GALT5 and ST6GAL1, neither of which was associated with COVID-19. In vitro small interfering RNA knockdown of ST6GAL1—an enzyme that adds sialic acid to the cell surface, which is used for viral entry—reduced influenza infectivity by 57%. These results mirror the observation that variants that downregulate ACE2, the SARS-CoV-2 receptor, protect against COVID-19 (ref. 7). Collectively, these findings highlight downregulation of key cell surface receptors used for viral entry as treatment opportunities to prevent COVID-19 and influenza.

Deep mutational scanning of H5 hemagglutinin to inform influenza virus surveillance.

H5 influenza is a potential pandemic threat. Previous studies have identified molecular phenotypes of the viral hemagglutinin (HA) protein that contribute to pandemic risk, including cell entry, receptor preference, HA stability, and reduced neutralization by polyclonal sera. Here we use pseudovirus deep mutational scanning to measure how all mutations to a clade 2.3.4.4b H5 HA affect each phenotype. We identify mutations that allow HA to better bind a2-6-linked sialic acids, and show that some viruses already carry mutations that stabilize HA. We also identify recent viral strains with reduced neutralization to sera elicited by candidate vaccine virus. Overall, the systematic nature of deep mutational scanning combined with the safety of pseudoviruses enables comprehensive characterization of mutations to inform surveillance of H5 influenza.

Impact of processed and ultra-processed foods on colorectal cancer risk: Mechanisms, dietary factors, and protective compound

Colorectal cancer (CRC) is the third most common malignant neoplasm worldwide, linked to behavioral factors such as a sedentary lifestyle and smoking, environmental factors like pollution, and nutritional factors including a diet rich in red and processed meats. Some foods are associated with potential carcinogenicity, while others act as protective factors. This review aims to report the contribution of processed and ultra-processed foods to the etiopathogenesis of CRC and explore the role of protective diets. The article is an integrative review conducted in PubMed and VHL databases using the descriptors “colorectal cancer” and “processed foods.” Studies published in the last five years addressing the relationship between these foods and CRC development were included. Potentially carcinogenic substances in processed foods, such as heterocyclic amines, nitrosamines, heme iron, industrial fatty acids, aromatic hydrocarbons, sialic acid sugar, and additives like titanium dioxide, were associated with colon and rectal neoplasms. Additional associations were found with the human microbiome, packaging materials, and food preparation methods. Conversely, several food components can protect against CRC. The consumption of processed and ultra-processed foods can significantly increase CRC risk through mechanisms like inflammation, oxidative stress, gene expression changes, and genetic material damage. The intestinal flora profile may be protective against CRC but is altered when processed and ultra-processed foods are included in the diet. Fiber, phytochemicals, and spices present in plant foods are consistently reported to have anticarcinogenic effects.