Free Sialic Acid Research Articles

Clinical and Diagnostic Significance of Sialic Acids Determination in Biological Material.

Sialic acids (SA) are neuraminic acid derivatives, located at the terminal position in the chains of monosaccharide residues of various glycoconjugates. SA play a dual role: they either mask recognition sites, or, on the contrary, represent biological targets that can be recognized by receptor proteins and serve as ligands. The desialylation/sialylation processes can be considered as a dynamic modification regulated by sialyltransferases and sialidases in response to external or internal stimuli. This review describes the structural and functional diversity and the potential use of SA fractions as biomarkers for various pathological conditions. Almost any extreme impact on the body and inflammatory processes are accompanied by an increase in the level of both total and free SA in the blood and tissues. Possible reasons for the increase of sialoglycoconjugate metabolism indicators in biological material include: (i) activation of the hepatocyte synthesis and secretion of various acute-phase proteins, many of which are sialoglycoproteins, (ii) impaired membrane integrity and destruction of body cells, (iii) high activity of sialidases (neurominidases) and sialyltransferases. Most acute and chronic liver diseases are characterized by the decrease in the total level of SA in the blood serum (because many plasma proteins are synthesized and glycosylated in hepatocytes). Aberrant sialylation results in changes of sialoglycoconjugate structure, its ability to perform biological functions and sialoglycoconjugate half-life. Glycosylation is the most common post-translational modification of proteins in the virus, which not only promotes the formation of specific conformation of viral proteins, but also modulates their interaction with receptors and affects host cell recognition, viral replication and infectivity. Serum total SA concentration increases in some benign and inflammatory conditions, which indicates a lack of specificity and limits their use for early detection and screening of neoplastic diseases. Clinical and diagnostic value of determining the sialoglycoconjugate metabolic indicators, including changes in the content of both SA fractions and specific proteins in various biological fluids and tissues, consists in establishing the causes and mechanisms of biochemical changes in the body in certain diseases. In combination with the measurement of existing markers, they can be used to improve diagnosis, staging and monitoring of therapeutic response in some pathological conditions where the need for specificity is less than for specific diagnostics.

A Cross-Sectional Study of Sialic Acids Level in Breast Cancer Patients Attending Ahmadu Bello University Teaching Hospital Zaria, North-Western Nigeria: Preliminary investigations and Implications on Disease Subtypes, Grade and Chemotherapy Courses

Abstract Due to the challenges associated with breast cancer prognosis, this study examined sialic acid levels based on subtypes, grades and therapeutic courses among breast cancer patients presenting at Ahmadu Bello University Teaching Hospital (ABUTH) in North-Western Nigeria between June 2019 and December 2020. This was a cross-sectional study. Sociodemographic characteristics, total sialic acid (TSA), free sialic acid (FSA), bound sialic acid (BSA) and haematological parameters were determined. The mean age of the respondents was 47.46 ± 10.71 years, and the modal age range was 41-50 years. About 40% of the patients had triple-negative breast cancer subtype, and 83.1% had invasive carcinoma. There was an association between breast cancer grade and body mass index (χ2= 26.306, P= 0.001). The TSA, FSA and BSA concentrations were significantly (P<0.05) higher in luminal A and triple-negative breast cancer patients when compared to apparently healthy controls and were highest in stage IV patients. The TSA correlated with the third and sixth chemotherapy courses. Significant (P<0.05) decrease was observed in PCV and Hb among the breast cancer patients irrespective of subtype compared to healthy control. The results suggest that TSA, FSA and BSA were higher in breast cancer patients, necessitating further research on their possible prognostic implications.

O-acetylesterase activity of Bifidobacterium bifidum sialidase facilities the liberation of sialic acid and encourages the proliferation of sialic acid scavenging Bifidobacterium breve.

Bifidobacterium bifidum possesses two extracellular sialidases (SiaBb1 and SiaBb2) that release free sialic acid from mucin sialoglycans, which can be utilized via cross-feeding by Bifidobacterium breve that, otherwise, is prevented from utilizing this nutrient source. Modification of sialic acids with O-acetyl esters is known to protect mucin glycans from degradation by bacterial sialidases. Compared to SiaBb2, SiaBb1 has an additional O-acetylesterase (Est) domain. We aimed to elucidate the role of the SiaBb1 Est domain from B. bifidum in sialic acid cross-feeding within Bifidobacterium. Pre-treatment of mucin secreted from bovine submaxillary glands (BSM) using His6 -tagged-Est and -SiaBb2 released a higher amount of sialic acid compared to the pre-treatment by His6 -SiaBb2. Growth of B. breve increased with an increase in nanE expression when supplemented with both His6 -Est- and His6 -SiaBb2-treated BSM. These results indicate that the esterase activity of the SiaBb1 Est domain enhances the efficiency of SiaBb2 to cleave sialic acid from mucin. This free sialic acid can be utilized by coexisting sialic acid scavenging B. breve via cross-feeding. Here, we provide the molecular mechanism underlying the unique sialoglycan degradation property of B. bifidum which is mediated by the complementary activities of SiaBb1 and SiaBb2 in the context of sialic acid cross-feeding.

A novel C-domain-dependent inhibition of the rainbow trout CMP-sialic acid synthetase activity by CMP-deaminoneuraminic acid

The CMP-sialic acid synthetase (CSS) activates free sialic acid (Sia) to CMP-Sia using CTP, and is prerequisite for the sialylation of cell surface glycoconjugates. The vertebrate CSS consists of two domains, a catalytic N-domain and a non-catalytic C-domain. Although the C-domain is not required for the CSS enzyme to synthesize CMP-Sia, its involvement in the catalytic activity remains unknown. First, the real-time monitoring of CSS-catalyzed reaction was performed by 31P NMR using the rainbow trout CSS (rtCSS). While a rtCSS lacking the C-domain (rtCSS-N) similarly activated both deaminoneuraminic acid (Kdn) and N-acetylneuraminic acid (Neu5Ac), the full-length rtCSS (rtCSS-FL) did not activate Kdn as efficiently as Neu5Ac. These results suggest that the C-domain of rtCSS affects the enzymatic activity, when Kdn was used as a substrate. Second, the enzymatic activity of rtCSS-FL and rtCSS-N was measured under various concentrations of CMP-Kdn. Inhibition by CMP-Kdn was observed only for rtCSS-FL, but not for rtCSS-N, suggesting that the inhibition was C-domain-dependent. Third, the inhibitory effect of CMP-Kdn was also investigated using the mouse CSS (mCSS). However, no inhibition was observed with mCSS even at high concentrations of CMP-Kdn. Taken together, the data demonstrated that the C-domain is involved in the CMP-Kdn-dependent inhibition of rtCSS, which is a novel regulation of the Sia metabolism in rainbow trout.

Catabolism of sialic acids in an environmental microbial community.

Sialic acids are a family of nine-carbon negatively charged carbohydrates. In animals, they are abundant on mucosa surfaces as terminal carbohydrates of mucin glycoproteins. Some commensal and pathogenic bacteria are able to release, take up and catabolize sialic acids. Recently, sialic acids have been discovered to be widespread among most microorganisms. Although the catabolism of sialic acids has been intensively investigated in the field of host-microbe interactions, very limited information is available on microbial degradation of sialic acids produced by environmental microorganisms. In this study, the catabolic pathways of sialic acids within a microbial community dominated by 'Candidatus Accumulibacter' were evaluated. Protein alignment tools were used to detect the presence of the different proteins involved in the utilization of sialic acids in the flanking populations detected by 16S rRNA gene amplicon sequencing. The results showed the ability of Clostridium to release sialic acids from the glycan chains by the action of a sialidase. Clostridium and Chryseobacterium can take up free sialic acids and utilize them as nutrient. Interestingly, these results display similarities with the catabolism of sialic acids by the gut microbiota. This study points at the importance of sialic acids in environmental communities in the absence of eukaryotic hosts.

Chemotherapeutic potentials of β-ionone against Trypanosoma congolense infection: Inhibitionofparasite proliferation, anemia development, trans-sialidase (TconTS3 and TconTS4) gene expressions, and phospholipase A2.

Trypanosoma congolense is a pathogenic African animal trypanosome species causing devastating conditions leading to death of an infected host. The drawbacks of the existing trypanocidal drugs have led to the search for new drug candidates. In this study, β-ionone at 15 and 30mg/kg body weight (BW) was orally administered to T.congolense infected rats for 14days followed by an assessment of anemia, organ damages, and the expression of T.congolense trans-sialidase gene variants. A significant decrease in parasitemia (p<.05) was observed in the animals treated with 15mg/kg BW β-ionone besides increased animal survival rate. A trypanosome-induced decrease in packed cell volume (PCV) and histopathological changes across tissues was significantly (p<.05) ameliorated following treatment with both doses of β-ionone. This is in addition to reversing the parasite-induced upsurge in free serum sialic acid (FSA) and expression of T.congolense trans-sialidase gene variants (TconTS1, TconTS3, and TconTS4). Correlation analysis revealed a positive correlation (p>.05) between FSA with the TconTS gene expressions. In addition, the compound inhibited partially purified T.congolense sialidase and phospholipase A2 via mixed inhibition pattern with inhibition binding constants of 25.325 and 4.550µM, respectively, while molecular docking predicted binding energies of -5.6kcal/mol for both enzymes. In conclusion, treatment with β-ionone suppressed T.congolense proliferation and protected the animals against some of the parasite-induced pathologies whilst the effect on anemia development might be due to inhibition of sialidase and PLA2 activities as well as the expression levels of TconTS3 and TconTS4.

IDF21-0217 Sialidase and sialyltransferase activities are modulated in some organs of type 1 and type 2 diabetic rats

Background: Diabetes mellitus leads to an aberrant metabolism of sialoglycoconjugates. One of the main features of the pathophysiology of diabetes is elevated serum level of free sialic acids. The source of serum free sialic acid during diabetes is debatable, although the contribution of endothelial damage has been recognised. Aim: The aim of this study is to investigate the association between the level of sialic acids and activities of sialidase and sialyltranferase in the serum and some diabetes-related organs in animal model of type 1 (T1D) and type 2 (T2D) diabetes. Method: Both types of diabetes induced in albino rats using high and low dose streptozotocin respectively. The level of sialic acid and activities of sialidase and sialyltransferase were measured in the serum, liver, pancreas, skeletal muscle and kidney of the diabetic rats and matching controls at early (3rd week) and late (9th week) phases of the diseases. Results: Serum sialic acid level and sialidase activity were significantly elevated at late stage of both T1D and T2D. The activity of sialyltransferase was not significantly changed in the diabetic animals compared to the non-diabetic controls. The total sialic acid content of the pancreas and kidney significantly increased from the early phase of both T1D and T2D to the late phase. On the other hand, the sialic acid content of the liver significantly decreased in the early phase of T2D and the late phase of T1D.The sialic acid content of the skeletal muscle significantly increased in the late phase of both diabetes types. In the early phase of both T1D and T2D, sialidase activity significantly increased in most of the organs whereas sialyltransfease activity was unchanged. A multiple regression analysis revealed the contribution of the liver to the serum level of sialic acid and the contribution of the pancreas and kidney to the serum activity of sialidase. Discussion: It was concluded that the released of sialic acid from the liver and sialidase from the pancreas and kidney may contribute to the increased serum level of sialic acid during diabetes.

How bacteria utilize sialic acid during interactions with the host: snip, snatch, dispatch, match and attach.

N -glycolylneuraminic acid (Neu5Gc), and its precursor N-acetylneuraminic acid (Neu5Ac), commonly referred to as sialic acids, are two of the most common glycans found in mammals. Humans carry a mutation in the enzyme that converts Neu5Ac into Neu5Gc, and as such, expression of Neu5Ac can be thought of as a ‘human specific’ trait. Bacteria can utilize sialic acids as a carbon and energy source and have evolved multiple ways to take up sialic acids. In order to generate free sialic acid, many bacteria produce sialidases that cleave sialic acid residues from complex glycan structures. In addition, sialidases allow escape from innate immune mechanisms, and can synergize with other virulence factors such as toxins. Human-adapted pathogens have evolved a preference for Neu5Ac, with many bacterial adhesins, and major classes of toxin, specifically recognizing Neu5Ac containing glycans as receptors. The preference of human-adapted pathogens for Neu5Ac also occurs during biosynthesis of surface structures such as lipo-oligosaccharide (LOS), lipo-polysaccharide (LPS) and polysaccharide capsules, subverting the human host immune system by mimicking the host. This review aims to provide an update on the advances made in understanding the role of sialic acid in bacteria-host interactions made in the last 5–10 years, and put these findings into context by highlighting key historical discoveries. We provide a particular focus on ‘molecular mimicry’ and incorporation of sialic acid onto the bacterial outer-surface, and the role of sialic acid as a receptor for bacterial adhesins and toxins.

A concerted action to explore therapies for free sialic acid storage disease (FSASD)

A concerted action to explore therapies for free sialic acid storage disease (FSASD)

A novel experimental mouse model to investigate a free sialic acid storage disorder (Salla disease)

A novel experimental mouse model to investigate a free sialic acid storage disorder (Salla disease)

Generation of an induced pluripotent stem cell line from a patient with free sialic acid storage disorder

Generation of an induced pluripotent stem cell line from a patient with free sialic acid storage disorder

Clinical application of liver diseases diagnosis using ultrahigh-sensitive liquid chromatography-mass spectrometry for sialic acids detection

Sialic acids are a group of nine-carbon N-acetylated derivatives of neuraminic acid containing a keto group at position C2 (ketononose), which play important roles in many biological processes. The simultaneous detection of free sialic acid (FSA) and total sialic acid (TSA) is always challenging due to three orders of magnitude difference. An accurate and robust chemical derivatization-based liquid chromatography-mass spectrometry (LC-MS) method was proposed here to quantify both TSA and FSA in human serum with only 1 μL human serum consumption. The derivatization method with Girard's P (GP) reagent provided an ultrasensitive analysis of sialic acids as only [GP+SA-H2O]+ ions derivatized from SA could be detected by LC-MS. The limit of quantification (LOQ) of SA was less than 5 fg (S/N = 47), which was the most sensitive measurement published for SAs in biomatrices. In addition, no matrix effect existed after 10000-fold dilution of serum extracts. The recovery rates were in the range of 98.1–114.0% and the coefficient of variations (CV) was within 5%. The method has been successfully applied for the quantification of TSA and FSA in serums of patients with different liver diseases. The specificities of TSA and FSA for the early diagnosis of severe hepatopathies were higher than most of the lab blood test indicators with area under the curve (AUC) of 0.900 and 0.882.

Phloroglucinol as a Potential Candidate against Trypanosoma congolense Infection: Insights from In Vivo, In Vitro, Molecular Docking and Molecular Dynamic Simulation Analyses.

Sub-Saharan Africa is profoundly challenged with African Animal Trypanosomiasis and the available trypanocides are faced with drawbacks, necessitating the search for novel agents. Herein, the chemotherapeutic potential of phloroglucinol on T. congolense infection and its inhibitory effects on the partially purified T. congolense sialidase and phospholipase A2 (PLA2) were investigated. Treatment with phloroglucinol for 14 days significantly (p < 0.05) suppressed T. congolense proliferation, increased animal survival and ameliorated anemia induced by the parasite. Using biochemical and histopathological analyses, phloroglucinol was found to prevent renal damages and splenomegaly, besides its protection against T. congolense-associated increase in free serum sialic acids in infected animals. Moreover, the compound inhibited bloodstream T. congolense sialidase via mixed inhibition pattern with inhibition binding constant (Ki) of 0.181 µM, but a very low uncompetitive inhibitory effects against PLA2 (Ki > 9000 µM) was recorded. Molecular docking studies revealed binding energies of −4.9 and −5.3 kcal/mol between phloroglucinol with modeled sialidase and PLA2 respectively, while a 50 ns molecular dynamics simulation using GROMACS revealed the sialidase-phloroglucinol complex to be more compact and stable with higher free binding energy (−67.84 ± 0.50 kJ/mol) than PLA2-phloroglucinol complex (−77.17 ± 0.52 kJ/mol), based on MM-PBSA analysis. The sialidase-phloroglucinol complex had a single hydrogen bond interaction with Ser453 while none was observed for the PLA2-phloroglucinol complex. In conclusion, phloroglucinol showed moderate trypanostatic activity with great potential in ameliorating some of the parasite-induced pathologies and its anti-anemic effects might be linked to inhibition of sialidase rather than PLA2.

Variations in the Serum Sialic Acid Profiles of Malaria Patients in Zaria, Nigeria: A Cross-Sectional Study.

Understanding some variations in specialized molecules during malaria could facilitate adequate monitoring of patients and reduce the fatalities caused by the disease. The present study reports changes in the levels of free serum sialic acid (FSSA) among Plasmodium-infected individuals in Zaria, Nigeria, in a cross-sectional study with 170 individuals. The FSSA and total sialic acid (TSA) in the blood were determined using the thiobarbituric acid method and the white blood cells (WBC) count, haemoglobin concentration and packed cell volumes were assessed using an automated haematological analyser. The results showed that, in the patients aged > 5years the level of TSA was significantly elevated (P < 0.05) compared to apparently healthy age-matched controls whereas TSA was slightly lower in patients aged < 5years compared to controls. The ratio of FSSA to TSA was not different between patients aged > 5years compared to their age-matched controls whereas FSSA/TSA was significantly elevated (P < 0.05) in patients aged < 5years compared to their aged-matched controls. The level of FSSA/TSA in the patients aged < 5years was not correlated with parasite density, white blood cell count, haemoglobin concentration or packed cell volume. We concluded that, metabolism and/or physiology of serum sialo-glycoconjugates is affected by malaria and FSSA is mainly elevated in children < 5years of age but not among older patients suggesting the possible usefulness of FSSA in the analysis of uncomplicated malaria in under five children.

Association between Serum Sialic Acid Levels and Disease Severity in Psoriasis: A Case-control Study

Introduction: Psoriasis is a chronic inflammatory disease distributed worldwide with varying prevalence among different geographical areas and ethnic groups. It has been recently found that oxidative stress is one of the important factors in the pathogenesis of psoriasis. The varied effects of oxidative stress include changes in cellular uptake, altered enzymatic activity of proteins, increased predisposition to aggregation and proteolysis, which subsequently alter their immunogenicity. Sialic Acid (SA) is an acetylated derivative of neuramic acid. It is a marker for acute phase inflammatory response, with increased levels observed in inflammatory diseases. Aim: To estimate the levels of SA in psoriasis patients and to correlate with the severity of the disease. Materials and Methods: This case-control study was conducted among 50 patients, diagnosed with psoriasis, and 50 age and sex-matched subjects without psoriasis. General, systemic and dermatological examination was carried out. The severity of psoriasis was assessed according to Psoriasis Area Severity Index (PASI). The serum was treated with ethanol and centrifugation to precipitate proteins. The SA of both the precipitate and supernatant was estimated based on the reaction of SA with the ninhydrin reagent. Calculation of sialic acid was done by the formula: OD of test/ OD of standard x Concentration of the standard. To establish a correlation student’s t-test was used. Results: There were 39 males and 11 females in each case and control group. The mean±SD age of cases and controls was 44.04±10.9 years and 44.10±9.996, respectively. The mean PASI value was 23.1666 ± 18.47. Mean SA in cases and controls were 35.792±2.124 and 28.556±3.854 (p-values &lt;0.001). A positive correlation was observed between the free SA and psoriasis severity (p-value &lt;0.001, r = 0.460). Conclusion: Higher levels of free serum SA were significantly associated with more severe forms of psoriasis.

Clinical and diagnostic significance of sialic acids determination in biological material

Sialic acids (SA) are derivatives of neuraminic acid; they are located at the terminal position in the chains of monosaccharide residues of various glycoconjugates. SA play a dual role, they either mask recognition sites, or, on the contrary, represent biological targets that can be recognized by receptor proteins and serve as ligands. The desialylation/sialylation processes can be viewed as a dynamic modification regulated by sialyltransferases and sialidases in response to external or internal stimuli. This review describes the structural and functional diversity and the potential use of SA fractions as biomarkers for various pathological conditions. Almost any extreme effects on the body and inflammatory processes lead to an increase in the level of both total and free SA in the blood and tissues. Possible reasons for the increase of sialoglycoconjugate metabolism indicators in biological material include activation of the hepatocyte synthesis and secretion of various acute-phase proteins, many of which are sialoglycoproteins, violation of the membrane integrity and destruction of body cells, and also high activity of sialidases (neurominidases) and sialyltransferases. Most acute and chronic liver diseases are characterized by the decrease in the total level of SA in the blood serum (because many plasma proteins are synthesized and glycosylated in hepatocytes). Aberrant sialylation results in changes of sialoglycoconjugate structure, its ability to perform biological functions and half-life. Glycosylation is the most common post-translational modification of proteins in the virus, which not only promotes the formation of specific conformation of viral proteins, but also modulates their interaction with receptors and affects host cell recognition, viral replication and infectivity. Serum total SA concentration increases in some benign and inflammatory conditions, which indicates a lack of specificity and limits their use for early detection and screening of neoplastic diseases. Nevertheless, determining blood SA level and measuring concentration of existing biomarkers can be used to improve diagnostic indicators, to stage and monitor therapeutic response in some types of cancer, when the need for specificity is less than for diagnosis. Clinical and diagnostic value of determining the sialoglycoconjugate metabolic indicators, including changes in the content of both SA fractions and specific proteins in various biological fluids and tissues, lies in establishing the causes and mechanisms of biochemical changes in the body in certain diseases.

Chemomodulatory Effect of Capsaicin Encapsulated Chitosan Nanoparticles on Lipids, Lipoproteins and Glycoprotein Components in DMBA Induced Mammary Carcinogenesis in Rats

Objectives: Breast cancer is a dreadful public health issue that kills plenty of women all around the world. The peril of breast cancer is strongly linked to lipids, lipoproteins, and glycoproteins. Capsaicin (CAP), a natural alkaloid isolated from chilies, has been reported to possess excellent anti-cancer activity. Unfortunately, the clinical application of this compound is strictly limited due to its low solubility and poor bioavailability. Nanoparticle-based drug delivery systems have set the path for a revolution in cancer therapy by improving its therapeutic value. The aim of the present study was to investigate the effect of CAP encapsulated chitosan nanoparticles (CAP@CS-NP) on lipids, lipoproteins and glycoproteins abnormalities in 7,12-dimethylbenz(a)anthracene (DMBA) induced mammary carcinogenesis. Methods: A mammary tumor was induced by a single dose of DMBA 25mg/kg b.wt injected subcutaneously near the mammary gland. The levels of lipid profile, lipoproteins and glycoprotein components were analyzed in the plasma, liver and mammary tissues. Results: We observed higher levels of total cholesterol (TC), triglycerides (TG), phospholipids (PL), free fatty acids (FFA), hexose, hexosamine and sialic acid in DMBA induced tumor-bearing rats. Moreover, low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C) levels were raised and high-density lipoprotein cholesterol (HDL-C) levels were dropped in tumor-bearing rats. The result shows that, CAP@CS-NP 4mg/kg b.wt administration significantly recouped abnormal levels to near-normal levels. It was additionally verified by histological staining in mammary tissues. Conclusion: Our findings suggest that nanoencapsulation of CAP@CS-NP successfully regulates lipid profile, lipoproteins, and glycoproteins levels. Keywords: Breast cancer, Capsaicin, Nanoparticle, Glycoproteins, Lipids

A Study on the Skin Whitening Activity of Digesta from Edible Bird's Nest: A Mucin Glycoprotein.

Edible bird’s nest (EBN) is an unusual mucin glycoprotein. In China, it is popular among consumers due to its skin whitening activity. However, the relationship between protein, sialic acid, and the whitening activity of EBN after digestion is still unclear. In the present work, the whitening activity (antioxidant activity and tyrosinase inhibitory activity) of digested EBN were studied by HepG2 and B16 cell models. The dissolution rate of protein and sialic acid was 49.59% and 46.45% after the simulated digestion, respectively. The contents of free sialic acid and glycan sialic acid in EBN digesta were 17.82% and 12.24%, respectively. HepG2 cell experiment showed that the digested EBN had significant antioxidant activity, with EC50 of 1.84 mg/mL, and had a protective effect on H2O2-induced oxidative damage cells. The results of H2O2-induced oxidative damage showed that the cell survival rate increased from 40% to 57.37% when the concentration of digested EBN was 1 mg/mL. The results of the B16 cell experiment showed that the digested EBN had a significant inhibitory effect on tyrosinase activity, and the EC50 value of tyrosinase activity was 7.22 mg/mL. Cell experiments showed that free sialic acid had stronger antioxidant activity and tyrosinase inhibitory activity than glycan sialic acid. The contribution rate analysis showed that protein component was the main antioxidant component in digestive products, and the contribution rate was 85.87%; free sialic acid was the main component that inhibited tyrosinase activity, accounting for 63.43%. The products of the complete digestion of EBN are suitable for the development of a new generation of whitening health products.

The effect of dynamic high‐pressure microfluidization on the physicochemical and digestive properties of proteins in insoluble fraction of edible bird's nest

AbstractDynamic high‐pressure microfluidization (DHPM) has been demonstrated as an effective method to increase the solubility of proteins in water‐insoluble fraction of edible bird's nests (EBNIP). Here, we further explored the effects of DHPM treatment on the physicochemical and digestive properties of EBNIP. The results showed that DHPM treatment led to the increases in fat absorption capacities, foaming properties, and emulsifying properties of EBNIP with decreased water‐holding capacity being observed. This might result from the mechanical force during DHPM treatment can unfold the protein molecular chain, destroy the hydrogen bonds and inter‐linkage between protein molecules. In addition, the EBNIP samples with DHPM treatment exhibited increased in vitro digestibility, the degree of hydrolysis and free sialic acid release in in vitro gastrointestinal digestion assay. In conclusion, DHPM could be applied as a novel and effective processing method to modify protein macromolecules in production of edible bird's nest (EBN)‐related food.

Cerebellum and temporal lobes of Alzheimer's disease patients present with an altered glycobiological state.

A major challenge facing Alzheimer's Disease (AD) research is the slowing or prevention of synaptic pruning, a pathology associated with driving the progression of AD's clinical symptoms. Currently, the mechanism by which pruning occurs is not well understood and whilst the complement cascade has been implicated (Hong etal., 2016), there are still questions regarding cellular targets and regulation. Therefore, exploration of additional regulatory factors is likely to offer novel targets for future therapeutic strategies. One key regulatory factor we propose is glycosylation, specifically the role of sialic acid 'caps'. Here, we show that glycobiological status of individual brain regions appears to be tied to AD pathology, suggesting an exciting avenue for novel therapeutic approaches. Temporal lobe and cerebellar tissue samples from AD (n=20) and age matched control (n=20) brains were homogenised in RIPA lysis buffer supplemented with phosphatase and protease inhibitors and assessed for Neuraminidase 2-4 and sialic acid levels. Neuraminidase levels were assessed using western blot whilst total, bound and free sialic acid levels were assessed using a fluorometric assay. Significant increases in free sialic acid were observed in the temporal lobes of AD patients compared to controls, with no significant differences detected in total and bound sialic acid. Conversely, both total and bound sialic acid were significantly increased in the cerebellum, while levels of free sialic acid were unchanged. Moreover, reductions in Neu 2 and Neu 4 were observed in the temporal region during AD, with no significant changes in the cerebellum. These findings show that mild increases in free sialic acid are associated with AD pathology in vulnerable brain regions such as the temporal lobe. Crucially, they show significant increases in total and bound sialic acid in the cerebellum, a region minimally impacted by AD pathology (Larner, 1997). This suggests there are key differences between cerebellar and temporal lobe sialylation in AD, that may in turn underpin the differential vulnerability of these brain regions to disease linked degenerative processes. Understanding more about the mechanisms that drive this sialylation may prove valuable in the quest for novel therapeutic targets for AD.