Salivary lactoferrin as biomarker for Alzheimer's disease: Brain-immunity interactions

Preadsorbed Particles with Cross-Shaped DNA Scaffolds Enable Spherical Nucleic Acid to Directly Respond to Protein in Complex Matrices

Spherical nucleic acids (SNAs) usually suffer from an undesired protein corona and disrupt the function of nucleic acids (e.g., aptamer), thereby compromising recognition and response to proteins in the biological environment. To overcome the unexpected protein interference, specific proteins were initially adsorbed onto magnetic particles (MPs) as a customized protein corona "shield" with fabricated nucleic acid scaffolds, forming a preadsorbed particle-based spherical nucleic acid (pap-SNA). By comparing with AuNPs-SNA or COOH-MPs, it was found that such a protein corona "shield" of pap-SNA significantly eliminated the adsorption of nonspecific proteins or other biomolecules onto the MPs' interface, thereby enabling the SNA to directly respond to proteins in complex matrices. To further reduce the interference of protein on SNA performance, a series of nucleic acid scaffolds (Z-type, dsDNA type, circle type, T-type, and cross-shaped type) were designed by changing the rigidity and thermal stability of functional nucleic acids on the MPs. As a consequence, the pap-SNA with a cross-shaped scaffold improved the sensitivity of the pap-SNA-based detection platform in that the orderly arrangement of functional nucleic acids provides a steric hindrance to interferents. Moreover, the presence of the cross-shaped scaffold not only enables pap-SNA to exhibit a proportional response to varied protein concentrations but also enhances the detection sensitivity of pap-SNA by 160% in serum and by 190% in urine. Therefore, incorporating optimized DNA scaffolds maintained and facilitated the function of a probe (aptamer) on the surface of SNA. This approach offers a pathway for creating SNA with direct response and anti-interference capability applicable to detecting diverse biomolecules such as nucleic acids and proteins in biological matrices.

Pilot: Salivary Lactoferrin as a Biomarker of Alzheimer's Disease

Background

Alzheimer's disease (AD) research has focused on developing accessible biomarkers that accurately detect disease pathology and progression before symptoms present. Lactoferrin (Lf) is an iron-binding antimicrobial glycoprotein found in all biological fluids, and its concentration in saliva has been correlated with AD symptoms. This pilot project aimed to determine whether salivary lactoferrin (sLF) has potential as a biomarker for AD.

Methods

Participants were middle to older-aged non-Hispanic white (NHW) and Black Americans (BA) at risk for AD due to parental history. We collected saliva samples after an 8-hour fast and administered a cognitive battery assessing executive function, memory, visuospatial ability, attention, and verbal fluency. We examined the relationship between sLF and cognitive performance and evaluated protein concentration across races.

Results

Seventeen middle-to-older-aged (age = 60.29 ± 9.7 years) BA and NHWs were enrolled. After controlling for age, sex, race, and years of education, we found a significant r between sLF and Digit Span Memory Test (DSMT) scores (P = 0.013) and a modest correlation with Mental Rotation Test scores (P = 0.194). We found no difference in average concentration across races.

Conclusions

Memory concerns and a worsening in visuospatial ability are early signs of cognitive decline in AD patients, and this pilot suggests a correlation of these symptoms with sLF. Bigger-scale longitudinal studies to examine the relationship between sLF and established AD biomarkers in diverse populations are needed to assess its clinical usefulness as an early biomarker for AD.

Data-independent LC-MS/MS analysis of ME/CFS plasma reveals a dysregulated coagulation system, endothelial dysfunction, downregulation of complement machinery

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic condition that is characterized by unresolved fatigue, post-exertion symptom exacerbation (PESE), cognitive dysfunction, orthostatic intolerance, and other symptoms. ME/CFS lacks established clinical biomarkers and requires further elucidation of disease mechanisms. A growing number of studies demonstrate signs of hematological and cardiovascular pathology in ME/CFS cohorts, including hyperactivated platelets, endothelial dysfunction, vascular dysregulation, and anomalous clotting processes. To build on these findings, and to identify potential biomarkers that can be related to pathophysiology, we measured differences in protein expression in platelet-poor plasma (PPP) samples from 15 ME/CFS study participants and 10 controls not previously infected with SARS-CoV-2, using DIA LC-MS/MS. We identified 24 proteins that are significantly increased in the ME/CFS group compared to the controls, and 21 proteins that are significantly downregulated. Proteins related to clotting processes - thrombospondin-1 (important in platelet activation), platelet factor 4, and protein S - were differentially expressed in the ME/CFS group, suggestive of a dysregulated coagulation system and abnormal endothelial function. Complement machinery was also significantly downregulated, including C9 which forms part of the membrane attack complex. Additionally, we identified a significant upregulation of lactotransferrin, protein S100-A9, and an immunoglobulin variant. The findings from this experiment further implicate the coagulation and immune system in ME/CFS, and bring to attention the pathology of or imposed on the endothelium. This study highlights potential systems and proteins that require further research with regards to their contribution to the pathogenesis of ME/CFS, symptom manifestation, and biomarker potential, and also gives insight into the hematological and cardiovascular risk for ME/CFS individuals affected by diabetes mellitus.

Prodromic Inflammatory-Oxidative Stress in Peritoneal Leukocytes of Triple-Transgenic Mice for Alzheimer's Disease

Inflammatory-oxidative stress is known to be pivotal in the pathobiology of Alzheimer's disease (AD), but the involvement of this stress at the peripheral level in the disease's onset has been scarcely studied. This study investigated the pro-inflammatory profile and oxidative stress parameters in peritoneal leukocytes from female triple-transgenic mice for AD (3xTgAD) and non-transgenic mice (NTg). Peritoneal leukocytes were obtained at 2, 4, 6, 12, and 15 months of age. The concentrations of TNFα, INFγ, IL-1β, IL-2, IL-6, IL-17, and IL-10 released in cultures without stimuli and mitogen concanavalin A and lipopolysaccharide presence were measured. The concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), lipid peroxidation, and Hsp70 were also analyzed in the peritoneal cells. Our results showed that although there was a lower release of pro-inflammatory cytokines by 3xTgAD mice, this response was uncontrolled and overstimulated, especially at a prodromal stage at 2 months of age. In addition, there were lower concentrations of GSH in leukocytes from 3xTgAD and higher amounts of lipid peroxides at 2 and 4 months, as well as, at 6 months, a lower concentration of Hsp70. In conclusion, 3xTgAD mice show a worse pro-inflammatory response and higher oxidative stress than NTg mice during the prodromal stages, potentially supporting the idea that Alzheimer's disease could be a consequence of peripheral alteration in the leukocyte inflammation-oxidation state.

Unlocking the power of Lactoferrin: Exploring its role in early life and its preventive potential for adult chronic diseases

Nutrition during the early postnatal period exerts a profound impact on both infant development and later-life health. Breast milk, which contains lactoferrin, a dynamic protein, plays a crucial role in the growth of various biological systems and in preventing numerous chronic diseases. Based on the relationship between early infant development and chronic diseases later in life, this paper presents a review of the effects of lactoferrin in early life on neonates intestinal tract, immune system, nervous system, adipocyte development, and early intestinal microflora establishment, as well as the preventive and potential mechanisms of early postnatal lactoferrin against adult allergy, inflammatory bowel disease, depression, cancer, and obesity. Furthermore, we summarized the application status of lactoferrin in the early postnatal period and suggested directions for future research.

Salivary Biomarkers for Parkinson's Disease: A Systematic Review with Meta-Analysis

Parkinson's Disease (PD) is a common neurodegenerative disease which manifests with motor features, such as bradykinesia, resting tremor, rigidity, and postural instability. Using the non-invasive technique of saliva collection, we designed a systematic review to answer the question "Are salivary biomarkers reliable for the diagnosis of Parkinson's Disease?". Following inclusion and exclusion criteria, 30 studies were included in this systematic review (according to the PRISMA statement guidelines). Mostly proteins were reported as potential biomarkers in saliva. Based on meta-analysis, in PD patients, salivary levels of total alpha-synuclein were significantly decreased, and those of oligomeric alpha-synuclein were significantly increased. Also, according to pooled AUC, heme oxygenase-1 demonstrated significant predictive value for saliva-based PD diagnosis. In conclusion, some potential biomarkers, especially alpha-synuclein, can be altered in the saliva of PD patients, which could be reliably useful for early diagnosis of this neurodegenerative disease differentiating other synucleopathies.

A Scoping Review of Alzheimers Disease Hypotheses: An Array of Uni- and Multi-Factorial Theories

Background

There is a common agreement that Alzheimers disease (AD) is inherently complex; otherwise, a general disagreement remains on its etiological underpinning, with numerous alternative hypotheses having been proposed.

Objective

To perform a scoping review of original manuscripts describing hypotheses and theories of AD published in the past decades.

Results

We reviewed 131 original manuscripts that fulfilled our inclusion criteria out of more than 13,807 references extracted from open databases. Each entry was characterized as having a single or multifactorial focus and assigned to one of 15 theoretical groupings. Impact was tracked using open citation tools.

Results

Three stages can be discerned in terms of hypotheses generation, with three quarter of studies proposing a hypothesis characterized as being single-focus. The most important theoretical groupings were the Amyloid group, followed by Metabolism and Mitochondrial dysfunction, then Infections and Cerebrovascular. Lately, evidence towards Genetics and especially Gut/Brain interactions came to the fore.

Conclusions

When viewed together, these multi-faceted reports reinforce the notion that AD affects multiple sub-cellular, cellular, anatomical, and physiological systems at the same time but at varying degree between individuals. The challenge of providing a comprehensive view of all systems and their interactions remains, alongside ways to manage this inherent complexity.

Developing an improved optical biosensing system based on gold nanoparticles acting as interferometric enhancers in Lactoferrin detection

We report for the first time the whole development of a biosensing system based on the Interferometric Optical Detection Method (IODM) enriched with gold nanoparticles (AuNPs), acting as interferometric enhancers for improving the performance of immunoassays. For this purpose, the Lactoferrin sandwich immunoassay model was employed. We describe in detail the entire value chain from the AuNPs production, its functionalization, and characterization with anti-Lactoferrin (anti-LF), the biosensing response of these conjugates as well as their corresponding calculation of the kinetic constants, performance comparison of the readout interferometric signals versus Scanning Electron Microscopy (SEM) and the percentage of the sensing surface covered. Finally, a Lactoferrin sandwich immunoassay was carried out and correlated with Enzyme-Linked ImmunoSorbent Assay (ELISA), and the Limit of Detection and sensitivity figures were obtained. As a result, we demonstrate how the AuNPs act as interferometric amplifiers of the IODM for improving the biosensing response, opening the possibility of being applied in multiple biological detection applications.

Clinical evidence of human pathogens implicated in Alzheimer's disease pathology and the therapeutic efficacy of antimicrobials: an overview

A wealth of pre-clinical reports and data derived from human subjects and brain autopsies suggest that microbial infections are relevant to Alzheimer's disease (AD). This has inspired the hypothesis that microbial infections increase the risk or even trigger the onset of AD. Multiple models have been developed to explain the increase in pathogenic microbes in AD patients. Although this hypothesis is well accepted in the field, it is not yet clear whether microbial neuroinvasion is a cause of AD or a consequence of the pathological changes experienced by the demented brain. Along the same line, the gut microbiome has also been proposed as a modulator of AD. In this review, we focus on human-based evidence demonstrating the elevated abundance of microbes and microbe-derived molecules in AD hosts as well as their interactions with AD hallmarks. Further, the direct-purpose and potential off-target effects underpinning the efficacy of anti-microbial treatments in AD are also addressed.

Employing nanoparticle tracking analysis of salivary neuronal exosomes for early detection of neurodegenerative diseases

Neurodegenerative diseases are a set of progressive and currently incurable diseases that are primarily caused by neuron degeneration. Neurodegenerative diseases often lead to cognitive impairment and dyskinesias. It is now well recognized that molecular events precede the onset of clinical symptoms by years. Over the past decade, intensive research attempts have been aimed at the early diagnosis of these diseases. Recently, exosomes have been shown to play a pivotal role in the occurrence and progression of many diseases including cancer and neurodegenerative diseases. Additionally, because exosomes can cross the blood-brain barrier, they may serve as a diagnostic tool for neural dysfunction. In this review, we detail the mechanisms and current challenges of these diseases, briefly review the role of exosomes in the progression of neurodegenerative diseases, and propose a novel strategy based on salivary neuronal exosomes and nanoparticle tracking analysis that could be employed for screening the early onset of neurodegenerative diseases.

Saliva - a new opportunity for fluid biopsy

Saliva is a complex biological fluid with a variety of biomolecules, such as DNA, RNA, proteins, metabolites and microbiota, which can be used for the screening and diagnosis of many diseases. In addition, saliva has the characteristics of simple collection, non-invasive and convenient storage, which gives it the potential to replace blood as a new main body of fluid biopsy, and it is an excellent biological diagnostic fluid. This review integrates recent studies and summarizes the research contents of salivaomics and the research progress of saliva in early diagnosis of oral and systemic diseases. This review aims to explore the value and prospect of saliva diagnosis in clinical application.

Lactoferrin for Mental Health: Neuro-Redox Regulation and Neuroprotective Effects across the Blood-Brain Barrier with Special Reference to Neuro-COVID-19

Overall mental health depends in part on the blood-brain barrier, which regulates nutrient transfer in-and-out of the brain and its central nervous system. Lactoferrin, an innate metal-transport protein, synthesized in the substantia nigra, particularly in dopaminergic neurons and activated microglia is vital for brain physiology. Lactoferrin rapidly crosses the blood-brain barrier via receptor-mediated transcytosis and accumulates in the brain capillary endothelial cells. Lactoferrin receptors are additionally present on glioma cells, brain micro-vessels, and neurons. As a regulator of neuro-redox, microglial lactoferrin is critical for protection/repair of neurons and healthy brain function. Iron imbalance and oxidative stress are common among patients with neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease, dementia, depression, and multiple sclerosis. As an endogenous iron-chelator, lactoferrin prevents iron accumulation and dopamine depletion in Parkinson's disease patients. Oral lactoferrin supplementation could modulate the p-Akt/PTEN pathway, reduce Aβ deposition, and ameliorate cognitive decline in Alzheimer's disease. Novel lactoferrin-based nano-therapeutics have emerged as effective drug-delivery systems for clinical management of neurodegenerative disorders. Recent emergence of the Coronavirus disease-2019 (COVID-19) pandemic, initially considered a respiratory illness, demonstrated a broader virulence spectrum with the ability to cross the blood-brain barrier and inflict a plethora of neuropathological manifestations in the brain - the Neuro-COVID-19. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are widely reported in Parkinson's disease, Alzheimer's disease, dementia, and multiple sclerosis patients with aggravated clinical outcomes. Lactoferrin, credited with several neuroprotective benefits in the brain could serve as a potential adjuvant in the clinical management of Neuro-COVID-19.

[Developments in Research on Salivary Biomarkers in the Diagnosis of Systemic Diseases]

Saliva, an important biological fluid secreted by oral glands, serves multiple functions. It performs cleaning and protective functions for oral tissues, safeguarding against biological, mechanical and chemical stimuli, while allowing for the sensory perception of taste and temperature. It is also responsible for the preliminary digestion of food. These functions and properties of saliva are attributed to the presence of electrolytes, buffers, proteins, glycoproteins, and lipids in saliva. Recent studies have found that saliva contains biomarkers that are closely connected with the pathophysiological status of the human body, suggesting that saliva makes an ideal biological fluid for drug monitoring and biomarker screening. Therefore, salivary biomarkers can be used as an instrument for physical monitoring and localization of the occurrence of diseases, thereby accomplishing early diagnosis of diseases and assessment of the overall health status of patients. However, the actual application of salivary biomarkers in the diagnosis and treatment of systemic diseases is still not widely available, and the establishment of evaluation criteria and the exploration of its mechanism are not sufficiently investigated. Herein, we reviewed the latest research findings on applying the salivary biomarkers in the diagnosis of systemic diseases.

Can Lactoferrin, a Natural Mammalian Milk Protein, Assist in the Battle against COVID-19?

Notwithstanding mass vaccination against specific SARS-CoV-2 variants, there is still a demand for complementary nutritional intervention strategies to fight COVID-19. The bovine milk protein lactoferrin (LF) has attracted interest of nutraceutical, food and dairy industries for its numerous properties-ranging from anti-viral and anti-microbial to immunological-making it a potential functional ingredient in a wide variety of food applications to maintain health. Importantly, bovine LF was found to exert anti-viral activities against several types of viruses, including certain SARS-CoV-2 variants. LF's potential effect on COVID-19 patients has seen a rapid increase of in vitro and in vivo studies published, resulting in a model on how LF might play a role during different phases of SARS-CoV-2 infection. Aim of this narrative review is two-fold: (1) to highlight the most relevant findings concerning LF's anti-viral, anti-microbial, iron-binding, immunomodulatory, microbiota-modulatory and intestinal barrier properties that support health of the two most affected organs in COVID-19 patients (lungs and gut), and (2) to explore the possible underlying mechanisms governing its mode of action. Thanks to its potential effects on health, bovine LF can be considered a good candidate for nutritional interventions counteracting SARS-CoV-2 infection and related COVID-19 pathogenesis.

Prospective biomarkers of Alzheimer's disease: A systematic review and meta-analysis

OBJECTIVE

Alzheimer's disease (AD) involves a series of pathological changes and some biomarkers were reported to assist in monitoring and predicting disease progression before the emergence of clinical symptoms. We aimed to identify prospective biomarkers and quantify their effect on AD progression.

METHODS

PubMed, EMBASE and Web of Science databases were searched for prospective cohort studies published up to October 2021. Eligible studies were included, and the available data were extracted. Meta-analyses were conducted based on random-effect models. Relative risk (RR) with 95% confidence interval (CI) was adopted as the final effect size.

RESULTS

Totally 48,769 articles were identified, of which 84 studies with 20 prospective biomarkers were included in meta-analyses. In the present study, 15 biomarkers were associated with AD progression, comprising CSF Aβ42 (RR=2.49, 95%CI=1.68-3.69), t-tau (RR=1.88, 95%CI=1.49-2.37), p-tau (RR=1.74, 95%CI=1.37-2.21), tau/Aβ42 ratio (RR=5.11, 95%CI=2.01-13.00); peripheral blood Aβ42/Aβ40 (RR=1.26, 95%CI=1.05-1.51), t-tau (RR=1.33, 95%CI=1.08-1.64), NFL (RR=1.75, 95%CI=1.07-2.87); whole, left and right hippocampal volume (HV) (whole: RR=1.65, 95%CI=1.39-1.95; left: RR=2.60, 95%CI=1.02-6.64; right: RR=1.43, 95%CI=1.23-1.66), entorhinal cortex (EC) volume (RR=1.69, 95%CI=1.24-2.30), medial temporal lobe atrophy (MTA) (RR=1.52, 95%CI=1.33-1.74), 18 F-FDG PET (RR=2.24, 95%CI=1.29-3.89), 11 C-labeled Pittsburgh Compound B PET (11 C-PIB PET) (RR=3.91, 95%CI=1.06-14.41); APOE ε4 (RR=2.16, 1.83-2.55). A total of 70 articles were included in the qualitative review, in which 61 biomarkers were additionally associated with AD progression.

CONCLUSION

CSF Aβ42, t-tau, p-tau, tau/Aβ42; peripheral blood t-tau, Aβ42/Aβ40, NFL; whole, left and right HV, EC volume, MTA, 18 F-FDG PET, 11 C-PIB PET; APOE ε4 may be promising prospective biomarkers for AD progression.

Fluorescence Resonance Energy Transfer-Based Aptasensor Made of Carbon-Based Nanomaterials for Detecting Lactoferrin at Low Concentrations

Lactoferrin in the saliva is recently considered a biomarker for the diagnosis of Alzheimer's disease. In this paper, a solution-based, user-friendly biosensing system has been developed to quickly measure lactoferrin at low concentrations. This aptasensor is applied to the fluorescence resonance energy transfer (FRET) quenching mechanism, in which carbon quantum dots (CDs) act as the FRET donor; the FRET quenching element is made of graphene oxide (GO) nanosheets which show good quenching capability. CDs bioconjugated with a chosen aptamer (CDs-aptamer) have the strongest emission (λ_em) at 447 nm when excitation (λ_ex) is 365 nm. Due to the interaction of the aptamer and GO through the π-π* interaction, GO can approach CDs, resulting in FRET quenching. In the presence of lactoferrin, the fluorescence intensity of CDs-aptamer is restored as the binding affinity between lactoferrin and the aptamer is stronger than the π-π* interaction between the aptamer and GO. A linear relationship between the restored fluorescence intensity and the concentration of lactoferrin in artificial saliva with a range from 4 to 16 μg/mL is observed. The limit of detection of the solution-based aptasensor is estimated at 2.48 μg/mL. In addition, the sensing performance of the aptasensor made of carbon nanomaterials has been evaluated to test different proteins including major salivary proteins. The results show that this aptasensor has a high selectivity to detect LF with a low concentration, <16 μg/mL.

Neuroprotective Role of Lactoferrin during Early Brain Development and Injury through Lifespan

Early adverse fetal environments can significantly disturb central nervous system (CNS) development and subsequently alter brain maturation. Nutritional status is a major variable to be considered during development and increasing evidence links neonate and preterm infant impaired brain growth with neurological and psychiatric diseases in adulthood. Breastfeeding is one of the main components required for healthy newborn development due to the many "constitutive" elements breastmilk contains. Maternal intake of specific nutrients during lactation may alter milk composition, thus affecting newborn nutrition and, potentially, brain development. Lactoferrin (Lf) is a major protein present in colostrum and the main protein in human milk, which plays an important role in the benefits of breastfeeding during postnatal development. It has been demonstrated that Lf has antimicrobial, as well as anti-inflammatory properties, and is potentially able to reduce the incidence of sepsis and necrotizing enterocolitis (NEC), which are particularly frequent in premature births. The anti-inflammatory effects of Lf can reduce birth-related pathologies by decreasing the release of pro-inflammatory factors and inhibiting premature cervix maturation (also related to commensal microbiome abnormalities) that could contribute to disrupting brain development. Pre-clinical evidence shows that Lf protects the developing brain from neuronal injury, enhances brain connectivity and neurotrophin production, and decreases inflammation in models of perinatal inflammatory challenge, intrauterine growth restriction (IUGR) and neonatal hypoxia-ischemia (HI). In this context, Lf can provide nutritional support for brain development and cognition and prevent the origin of neuropsychiatric diseases later in life. In this narrative review, we consider the role of certain nutrients during neurodevelopment linking to the latest research on lactoferrin with respect to neonatology. We also discuss new evidence indicating that early neuroprotective pathways modulated by Lf could prevent neurodegeneration through anti-inflammatory and immunomodulatory processes.

Differentially Aquaporin 5 Expression in Submandibular Glands and Cerebral Cortex in Alzheimer’s Disease

Impaired brain clearance mechanisms may result in the accumulation of aberrant proteins that define Alzheimer’s disease (AD). The water channel protein astrocytic aquaporin 4 (AQP4) is essential for brain amyloid-β clearance, but it is known to be abnormally expressed in AD brains. The expression of AQPs is differentially regulated during diverse brain injuries, but, whereas AQP4 expression and function have been studied in AD, less is known about AQP5. AQP5 functions include not only water transport but also cell migration mediated by cytoskeleton regulation. Moreover, AQP5 has been reported to be expressed in astrocytes, which are regulated after ischemic and traumatic injury. Additionally, AQP5 is particularly abundant in the salivary glands suggesting that it may be a crucial factor in gland dysfunction associated with AD. Herein, we aim to determine whether AQP5 expression in submandibular glands and the brain was altered in AD. First, we demonstrated impaired AQP5 expression in submandibular glands in APP/PS1 mice and AD patients. Subsequently, we observed that AQP5 expression was upregulated in APP/PS1 cerebral cortex and confirmed its expression both in astrocytes and neurons. Our findings propose AQP5 as a significant role player in AD pathology, in addition to AQP4, representing a potential target for the treatment of AD.

The health status: the ignored risk factor in dementia incidence. NEDICES cohort

BACKGROUND

The causes of the dementia decrease in affluent countries are not well known but health amelioration could probably play a major role. Nevertheless, although many vascular and systemic disorders in adult life are well-known risk factors (RF) for dementia and Alzheimer disease (AD), health status is rarely considered as a single RF.

AIM

To analyse whether the health status and the self-perceived health (SPH) could be RF for dementia and AD and to discuss its biological basis.

METHODS

We analysed different objective health measures and SPH as RF for dementia and AD incidence in 4569 participants of the NEDICES cohort by means of Cox-regression models. The mean follow-up period was 3.2 (range: 0.03-6.6) years.

RESULTS

Ageing, low education, history of stroke, and "poor" SPH were the main RF for dementia and AD incidence, whereas physical activity was protective. "Poor" SPH had a hazard ratio = 1.66 (95% CI 1.17-2.46; p = 0.012) after controlling for different confounders.

DISCUSSION

According to data from NEDICES cohort, SPH is a better predictor of dementia and AD than other more objective health status proxies. SPH should be considered a holistic and biologically rooted indicator of health status, which can predict future development of dementia and AD in older adults.

CONCLUSIONS

Our data indicate that it is worthwhile to include the SPH status as a RF in the studies of dementia and AD incidence and to explore the effect of its improvement in the evolution of this incidence.

Lactoferrin as Immune-Enhancement Strategy for SARS-CoV-2 Infection in Alzheimer's Disease Patients

Coronavirus 2 (SARS-CoV2) (COVID-19) causes severe acute respiratory syndrome. Severe illness of COVID-19 largely occurs in older people and recent evidence indicates that demented patients have higher risk for COVID-19. Additionally, COVID-19 further enhances the vulnerability of older adults with cognitive damage. A balance between the immune and inflammatory response is necessary to control the infection. Thus, antimicrobial and anti-inflammatory drugs are hopeful therapeutic agents for the treatment of COVID-19. Accumulating evidence suggests that lactoferrin (Lf) is active against SARS-CoV-2, likely due to its potent antiviral and anti-inflammatory actions that ultimately improves immune system responses. Remarkably, salivary Lf levels are significantly reduced in different Alzheimer's disease (AD) stages, which may reflect AD-related immunological disturbances, leading to reduced defense mechanisms against viral pathogens and an increase of the COVID-19 susceptibility. Overall, there is an urgent necessity to protect AD patients against COVID-19, decreasing the risk of viral infections. In this context, we propose bovine Lf (bLf) as a promising preventive therapeutic tool to minimize COVID-19 risk in patients with dementia or AD.

Lactoferrin of oral fluid is normal and in Alzheimer's disease: laboratory and diagnostic aspects (review of literature)

The article discusses the clinical value of determining the lactoferrin protein in oral fluid - one of the representatives of the saliva proteome. The review is based on the analysis of modern literature, including systematic reviews, the results of multicenter prospective studies, review and original articles by leading experts in this field, presented in the databases PubMed, Scopus, CyberLeninka. The problems of the preanalytical stage, methods for determining lactoferrin are highlighted and information about its content in mixed saliva according to various authors is provided. Special attention is paid to the clinical and diagnostic value of the level of salivary lactoferrin in Alzheimer's disease. According to most authors, the diagnostic sensitivity of this parameter ranges from 87 to 100%. Some mechanisms of the relationship between this protein and the central nervous system (CNS) are shown. In conclusion, it is concluded that salivary lactoferrin can be an "indicator" of the formation of amyloid plaques and can be considered as one of the reliable biomarkers of Alzheimer's disease. This opinion is based both on fundamental ideas about the global relationship between innate immunity and the central nervous system, and on clinical data. The special advantage of this laboratory test is its non-invasiveness, which makes it more preferable in comparison with the determination of amyloid and tau proteins in the cerebrospinal fluid and blood.

Impact of the Glycemic Level on the Salivary Proteome of Middle-Aged and Elderly People With Type 2 Diabetes Mellitus: An Observational Study

Type 2 diabetes mellitus (T2DM) is an increasing global public health concern, but its impact on the salivary proteome is still unclear. To evaluate the effect of glycemic levels in middle-aged and elderly individuals with T2DM on salivary proteomics, we compared the differences by liquid chromatography tandem mass spectrometry (LC–MS/MS). Unstimulated whole saliva samples from 8 T2DM patients with good glycemic control (G group, HbA1c <6.5%) and 16 patients with poor control (P group, HbA1c ≥6.5%) were analyzed by LC–MS/MS in the data-independent acquisition mode (Clinical register number: ChiCTR1900023582.). After functional annotation, cluster analysis and receiver operating characteristic (ROC) curve analysis were carried out to screen and evaluate candidate proteins. A total of 5,721 proteins were quantified, while 40 proteins differed significantly. In the P group, proteins involved in oxidative stress-related processes were upregulated, whereas proteins related to salivary secretion were downregulated. The combination of thioredoxin domain-containing protein 17, zymogen granule protein 16B, and FAM3 metabolism regulating signaling molecule D yielded an area under the curve of 0.917 which showed a robust ability to distinguish the P and G groups. In conclusion, poorly controlled hyperglycemia may affect salivary proteins through various pathways, including oxidative stress and glandular secretion. Furthermore, the differentially expressed proteins, especially the three proteins with the best differentiation, might serve as an anchor point for the further study of hyperglycemia and oral diseases.

The effect of lactoferrin in aging: role and potential

Aging is frequently accompanied by various types of physiological deterioration, which increases the risk of human pathologies. Global public health efforts to increase human lifespan have increasingly focused on lowering the risk of aging-related diseases, such as diabetes, neurodegenerative diseases, cardiovascular disease, and cancers. Dietary intervention is a promising approach to maintaining human health during aging. Lactoferrin (LF) is known for its physiologically pleiotropic properties. Anti-aging interventions of LF have proven to be safe and effective for various pharmacological activities, such as anti-oxidation, anti-cellular senescence, anti-inflammation, and anti-carcinogenic. Moreover, LF has a pivotal role in modulating the major signaling pathways that influence the longevity of organisms. Thus, LF is expected to be able to attenuate the process of aging and greatly ameliorate its effects.

Salivary Lactoferrin Expression in a Mouse Model of Alzheimer's Disease

In the last few years, microbial infection and innate immune theories have been proposed as an alternative approach explaining the etiopathogenesis and origin of Alzheimer's disease (AD). Lactoferrin, one of the main antimicrobial proteins in saliva, is an important modulator of immune response and inflammation, and represents an important defensive element by inducing a broad spectrum of antimicrobial effects against microbial infections. We demonstrated that lactoferrin levels in saliva are decreased in prodromal and dementia stages of AD compared with healthy subjects. That finding seems to be specific to cerebral amyloid-β (Aβ) load as such observation was not observed in healthy elderly controls or those subjects with frontotemporal dementia. In the present study, we analysed salivary lactoferrin levels in a mouse model of AD. We observed robust and early reduction of lactoferrin levels in saliva from 6- and 12-month-old APP/PS1 mice. Because saliva is secreted by salivary glands, we presume that deregulation in salivary glands resulting in reduced salivary lactoferrin levels may occur in AD. To test this hypothesis, we collected submandibular glands from APP/PS1 mice, as well as submandibular gland tissue from AD patients and we analysed the expression levels of key components of the salivary protein signalling pathway. A significant reduction in M3 receptor levels was found along with decreased acetylcholine (Ach) levels in submandibular glands from APP/PS1 mice. Similarly, a reduction in M3 receptor levels was observed in human submandibular glands from AD patients but in that case, the Ach levels were found increased. Our data suggest that the ACh-mediated M3 signalling pathway is impaired in salivary glands in AD, resulting in salivary gland dysfunction and reduced salivary lactoferrin secretion.

Salivary lactoferrin is associated with cortical amyloid-beta load, cortical integrity, and memory in aging

BACKGROUND

Aging is associated with declining protective immunity and persistent low-grade inflammatory responses, which significantly contribute to Alzheimer's disease (AD) pathogenesis. Detecting aging-related cerebral vulnerability associated with deterioration of the immune system requires from non-invasive biomarkers able to detect failures in the brain-immunity connection. Reduced levels of salivary lactoferrin (sLF), an iron-binding protein with immunomodulatory activity, have been related to AD diagnosis. However, it remains unknown whether decreased sLF is associated with increased cortical amyloid-beta (Aβ) load and/or with loss of cortical integrity in normal aging.

METHODS

Seventy-four cognitively normal older adults (51 females) participated in the study. We applied multiple linear regression analyses to assess (i) whether sLF is associated with cortical Aβ load measured by 18F-Florbetaben (FBB)-positron emission tomography (PET), (ii) whether sLF-related variations in cortical thickness and cortical glucose metabolism depend on global Aβ burden, and (iii) whether such sLF-related cortical abnormalities moderate the relationship between sLF and cognition.

RESULTS

sLF was negatively associated with Aβ load in parieto-temporal regions. Moreover, sLF was related to thickening of the middle temporal cortex, increased FDG uptake in the posterior cingulate cortex, and poorer memory. These associations were stronger in individuals showing the highest Aβ burden.

CONCLUSIONS

sLF levels are sensitive to variations in cortical Aβ load, structural and metabolic cortical abnormalities, and subclinical memory impairment in asymptomatic older adults. These findings provide support for the use of sLF as a non-invasive biomarker of cerebral vulnerability in the general aging population.

The fluid biomarkers of Alzheimer’s disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder. However, it still has no available disease‐modifying therapies. Its pathology cascade begins decades before symptomatic presentation. For these reasons, highly sensitive and highly specific fluid biomarkers should be developed for the early diagnosis of AD. In this study, the well‐established and emerging fluid biomarkers of AD are summarized, and recent advances on their role in early diagnosis and progression monitoring as well as their correlations with AD pathology are highlighted. Future prospects and related research directions are also discussed.

Standardizing salivary lactoferrin measurements to obtain a robust diagnostic biomarker for Alzheimer's disease

The search for new, robust, and reproducible biomarkers for Alzheimer's disease (AD) diagnosis is a challenge. We recently reported that salivary lactoferrin (Lf) could be presented as new biomarker candidate for AD, being both non-invasive and cost-effective, as well as having appropriate diagnostic performance for the clinical detection of AD subjects. Saliva is an attractive sample type for biomarker-based testing approaches for several other diseases; however, its composition may change under certain circumstances. It is therefore critical to maintain a consistent salivary handling protocol, considering possible extrinsic factors that may influence salivary Lf concentration. In this work, we analyzed salivary Lf concentration under different handling conditions and donor-dependent factors including age, inter-diurnal variations, physical activity, and pharmacological treatments. Our aim was to evaluate the influence of such conditions on salivary Lf concentration. In conclusion, we found that most of these extrinsic factors should be considered in the future when using Lf as a predictive biomarker for AD.

The Evolving Landscape of Exosomes in Neurodegenerative Diseases: Exosomes Characteristics and a Promising Role in Early Diagnosis

Neurodegenerative diseases (ND) remains to be one of the biggest burdens on healthcare systems and serves as a leading cause of disability and death. Alzheimer's disease (AD) is among the most common of such disorders, followed by Parkinson's disease (PD). The basic molecular details of disease initiation and pathology are still under research. Only recently, the role of exosomes has been linked to the initiation and progression of these neurodegenerative diseases. Exosomes are small bilipid layer enclosed extracellular vesicles, which were once considered as a cellular waste and functionless. These nano-vesicles of 30-150 nm in diameter carry specific proteins, lipids, functional mRNAs, and high amounts of non-coding RNAs (miRNAs, lncRNAs, and circRNAs). As the exosomes content is known to vary as per their originating and recipient cells, these vesicles can be utilized as a diagnostic biomarker for early disease detection. Here we review exosomes, their biogenesis, composition, and role in neurodegenerative diseases. We have also provided details for their characterization through an array of available techniques. Their updated role in neurodegenerative disease pathology is also discussed. Finally, we have shed light on a novel field of salivary exosomes as a potential candidate for early diagnosis in neurodegenerative diseases and compared the biomarkers of salivary exosomes with other blood/cerebrospinal fluid (CSF) based exosomes within these neurological ailments.

Low levels of salivary lactoferrin may affect oral dysbiosis and contribute to Alzheimer's disease: A hypothesis

Recently it has been reported that reduced levels of salivary lactoferrin (LF) can be a plausible biomarker for amyloid beta (Aβ) accumulation in Alzheimer's disease (AD) brains. This could mean that reduced levels of salivary LF act as a trigger for oral dysbiosis and that low LF levels could change the oral microbiota. A chemical change in the composition of saliva has not yet been considered as a cause for microbial dysbiosis but does present an opportunity to view oral dysbiosis as a plausible contributory factor in the development of AD pathophysiology. Oral dysbiosis has largely been reported as a result of inadequate oral hygiene and dry mouth in elderly subjects. Here we discuss if the deficiency of LF in saliva and gingival fluid of AD patients can facilitate proliferation of oral pathogens, and as a result their spread elsewhere in the body. Additionally, we ask if LF in the AD brain could be overexposed as a result of chronic infection. Together these outcomes will indicate if reduced levels of salivary LF can act as a trigger of oral dysbiosis.

Decreased salivary lactoferrin levels are specific to Alzheimer's disease

BACKGROUND

Evidences of infectious pathogens in Alzheimer's disease (AD) brains may suggest a deteriorated innate immune system in AD pathophysiology. We previously demonstrated reduced salivary lactoferrin (Lf) levels, one of the major antimicrobial proteins, in AD patients.

METHODS

To assess the clinical utility of salivary Lf for AD diagnosis, we examine the relationship between salivary Lf and cerebral amyloid-β (Aβ) load using amyloid-Positron-Emission Tomography (PET) neuroimaging, in two different cross-sectional cohorts including patients with different neurodegenerative disorders.

FINDINGS

The diagnostic performance of salivary Lf in the cohort 1 had an area under the curve [AUC] of 0•95 (0•911-0•992) for the differentiation of the prodromal AD/AD group positive for amyloid-PET (PET⁺) versus healthy group, and 0•97 (0•924-1) versus the frontotemporal dementia (FTD) group. In the cohort 2, salivary Lf had also an excellent diagnostic performance in the health control group versus prodromal AD comparison: AUC 0•93 (0•876-0•989). Salivary Lf detected prodromal AD and AD dementia distinguishing them from FTD with over 87% sensitivity and 91% specificity.

INTERPRETATION

Salivary Lf seems to have a very good diagnostic performance to detect AD. Our findings support the possible utility of salivary Lf as a new non-invasive and cost-effective AD biomarker.

FUNDING

Instituto de Salud Carlos III (FIS15/00780, FIS18/00118), FEDER, Comunidad de Madrid (S2017/BMD-3700; NEUROMETAB-CM), and CIBERNED (PI2016/01) to E.C.; Spanish Ministry of Economy and Competitiveness (SAF2017-85310-R) to J.L.C., and (PSI2017-85311-P) to M.A.; International Centre on ageing CENIE-POCTEP (0348_CIE_6_E) to M.A.; Instituto de Salud Carlos III (PIE16/00021, PI17/01799), to H.B.

Salivary lactoferrin as biomarker for Alzheimer's disease: Brain-immunity interactions

Objective

We aim to explain why salivary lactoferrin (Lf) levels are reduced in patients suffering mild cognitive impairment (MCI) and sporadic Alzheimer's disease (sAD).¹ We also will discuss if such Lf decrease could be due to a downregulation of the sAD associated systemic immunity.

Background

Several non‐neurological alterations have been described in sAD, mainly in skin, blood cell, and immunological capacities. We reviewed briefly the main pathophysiological theories of sAD (amyloid cascade, tau, unfolder protein tau, and amyloid deposits) emphasizing the most brain based hypotheses such as the updated tau‐related neuron skeletal hypothesis; we also comment on the systemic theories that emphasize the fetal origin of the complex disorders that include the low inflammatory and immunity theories of sAD.

New/updated hypothesis

Lf has important anti‐infectious and immunomodulatory roles in health and disease. We present the hypothesis that the reduced levels of saliva Lf could be an effect of immunological disturbances associated to sAD. Under this scenario, two alternative pathways are possible: first, whether sAD could be a systemic disorder (or disorders) related to early immunological and low inflammatory alterations; second, if systemic immunity alterations of sAD manifestations could be downstream of early sAD brain affectations.

Major challenges for the hypothesis

The major challenge of the Lf as early sAD biomarker would be its validation in other clinical and population‐based studies. It is possible the decreased salivary Lf in early sAD could be related to immunological modulation actions, but other different unknown mechanisms could be the origin of such reduction.

Linkage to other major theories

This hypothesis is in agreement with two physiopathological explanations of the sAD as a downstream process determined by the early lesions of the hypothalamus and autonomic vegetative system (neurodegeneration), or as a consequence of low neuroinflammation and dysimmunity since the early life aggravated in the elderly (immunosenescence).