Relation of plasma selenium and lipid peroxidation end products in patients with Alzheimer's disease

Lipophilic fluorescent products as a potential biomarker of oxidative stress: A link between central (brain) and peripheral (blood)

Oxidative stress plays a key role in brain damage because of the sensitivity of brain tissue to oxidative damage. Biomarkers with easy measurement can be a candidate for reflecting the oxidative stress issue in humans. For this reason, we need to focus on specific metabolic products of the brain. End products of free radical reactions such as malondialdehydes form fluorescent products known as lipophilic fluorescent products (LFPs). The distinctive feature of LFPs is their autofluorescent properties. LFPs are detectable in the brain and cerebrospinal fluid. Furthermore, because of the diffusion into the bloodstream, these lipophilic molecules can be detected in the blood. Accumulations of these compounds produce more reactive oxygen species and increase the sensitivity of cells to oxidative damage. Hence, LFPs can be considered a danger signal for neurons and can be introduced as a strong index of oxidative damage both in the central and in the peripheral.

Multi-element Exposure and Cognitive Function in Rural Elderly Chinese

To investigate the relationship between selenium (Se) based multi-element combined exposure and cognitive function in rural elderly individuals, a cross-sectional study was conducted. The study involved 416 older adults aged 60 and above, residing in four different areas of Enshi county, China, with varying soil Se levels. Inductively coupled plasma mass spectrometry (ICP-MS) was employed to measure the concentrations of Se, copper (Cu), iron (Fe), zinc (Zn), calcium (Ca), magnesium (Mg), cadmium (Cd), arsenic (As), and lead (Pb) in whole blood. Nine standard cognitive tests were applied to assess cognitive function. Analysis of the least absolute shrinkage and selection operator regression (LASSO), covariance (ANCOVA), and generalized linear model (GLM) were utilized to investigate the relationship between element exposure and cognitive function. The results of LASSO revealed that Se, Cu, Fe, Zn, Ca, and Pb were independently identified to be associated with cognition. Both ANCOVA and GLM demonstrated that Se and Ca were correlated with cognitive function. The multi-element model showed higher composite Z scores of 0.32 (95% CI: 0.09 to 0.55) for log-transformed Se (P = 0.007), 0.75 (95% CI: 0.01 to 1.49) for log-transformed Cu (P = 0.048), and a lower score of - 0.67 (95% CI: - 1.26 to - 0.08) for log-transformed Ca (P = 0.025). Furthermore, there was evidence that Se could counteract the negative impact of Ca on cognitive function (P for interaction = 0.031). Our findings suggested that higher levels of Se and Cu were associated with better cognitive function in the elderly and Se can counteract the cognitive damage caused by Ca.

Association of Selenium Levels with Neurodegenerative Disease: A Systemic Review and Meta-Analysis

BACKGROUND

Neurodegenerative diseases (NDs) have posed significant challenges to public health, and it is crucial to understand their mechanisms in order to develop effective therapeutic strategies. Recent studies have highlighted the potential role of selenium in ND pathogenesis, as it plays a vital role in maintaining cellular homeostasis and preventing oxidative damage. However, a comprehensive analysis of the association between selenium and NDs is still lacking.

METHOD

Five public databases, namely PubMed, Web of Science, EMBASE, Cochrane and Clinical Trials, were searched in our research. Random model effects were chosen, and Higgins inconsistency analyses (I2), Cochrane's Q test and Tau2 were calculated to evaluate the heterogeneity.

RESULT

The association of selenium in ND patients with Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD) was studied. A statistically significant relationship was only found for AD patients (SMD = -0.41, 95% CI (-0.64, -0.17), p < 0.001), especially for erythrocytes. However, no significant relationship was observed in the analysis of the other four diseases.

CONCLUSION

Generally, this meta-analysis indicated that AD patients are strongly associated with lower selenium concentrations compared with healthy people, which may provide a clinical reference in the future. However, more studies are urgently needed for further study and treatment of neurodegenerative diseases.

Iron and Ferroptosis More than a Suspect: Beyond the Most Common Mechanisms of Neurodegeneration for New Therapeutic Approaches to Cognitive Decline and Dementia

Neurodegeneration is a multifactorial process that involves multiple mechanisms. Examples of neurodegenerative diseases are Parkinson's disease, multiple sclerosis, Alzheimer's disease, prion diseases such as Creutzfeldt-Jakob's disease, and amyotrophic lateral sclerosis. These are progressive and irreversible pathologies, characterized by neuron vulnerability, loss of structure or function of neurons, and even neuron demise in the brain, leading to clinical, functional, and cognitive dysfunction and movement disorders. However, iron overload can cause neurodegeneration. Dysregulation of iron metabolism associated with cellular damage and oxidative stress is reported as a common event in several neurodegenerative diseases. Uncontrolled oxidation of membrane fatty acids triggers a programmed cell death involving iron, ROS, and ferroptosis, promoting cell death. In Alzheimer's disease, the iron content in the brain is significantly increased in vulnerable regions, resulting in a lack of antioxidant defenses and mitochondrial alterations. Iron interacts with glucose metabolism reciprocally. Overall, iron metabolism and accumulation and ferroptosis play a significant role, particularly in the context of diabetes-induced cognitive decline. Iron chelators improve cognitive performance, meaning that brain iron metabolism control reduces neuronal ferroptosis, promising a novel therapeutic approach to cognitive impairment.

Metals in Alzheimer's Disease

The role of metals in the pathogenesis of Alzheimer's disease (AD) is still debated. Although previous research has linked changes in essential metal homeostasis and exposure to environmental heavy metals to the pathogenesis of AD, more research is needed to determine the relationship between metals and AD. In this review, we included human studies that (1) compared the metal concentrations between AD patients and healthy controls, (2) correlated concentrations of AD cerebrospinal fluid (CSF) biomarkers with metal concentrations, and (3) used Mendelian randomization (MR) to assess the potential metal contributions to AD risk. Although many studies have examined various metals in dementia patients, understanding the dynamics of metals in these patients remains difficult due to considerable inconsistencies among the results of individual studies. The most consistent findings were for Zn and Cu, with most studies observing a decrease in Zn levels and an increase in Cu levels in AD patients. However, several studies found no such relation. Because few studies have compared metal levels with biomarker levels in the CSF of AD patients, more research of this type is required. Given that MR is revolutionizing epidemiologic research, additional MR studies that include participants from diverse ethnic backgrounds to assess the causal relationship between metals and AD risk are critical.

Advanced Overview of Biomarkers and Techniques for Early Diagnosis of Alzheimer's Disease

The development of early non-invasive diagnosis methods and identification of novel biomarkers are necessary for managing Alzheimer's disease (AD) and facilitating effective prognosis and treatment. AD has multi-factorial nature and involves complex molecular mechanism, which causes neuronal degeneration. The primary challenges in early AD detection include patient heterogeneity and lack of precise diagnosis at the preclinical stage. Several cerebrospinal fluid (CSF) and blood biomarkers have been proposed to show excellent diagnosis ability by identifying tau pathology and cerebral amyloid beta (Aβ) for AD. Intense research endeavors are being made to develop ultrasensitive detection techniques and find potent biomarkers for early AD diagnosis. To mitigate AD worldwide, understanding various CSF biomarkers, blood biomarkers, and techniques that can be used for early diagnosis is imperative. This review attempts to provide information regarding AD pathophysiology, genetic and non-genetic factors associated with AD, several potential blood and CSF biomarkers, like neurofilament light, neurogranin, Aβ, and tau, along with biomarkers under development for AD detection. Besides, numerous techniques, such as neuroimaging, spectroscopic techniques, biosensors, and neuroproteomics, which are being explored to aid early AD detection, have been discussed. The insights thus gained would help in finding potential biomarkers and suitable techniques for the accurate diagnosis of early AD before cognitive dysfunction.

Non-Enzymatic Antioxidants against Alzheimer's Disease: Prevention, Diagnosis and Therapy

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. Although substantial research has been conducted to elucidate the complex pathophysiology of AD, the therapeutic approach still has limited efficacy in clinical practice. Oxidative stress (OS) has been established as an early driver of several age-related diseases, including neurodegeneration. In AD, increased levels of reactive oxygen species mediate neuronal lipid, protein, and nucleic acid peroxidation, mitochondrial dysfunction, synaptic damage, and inflammation. Thus, the identification of novel antioxidant molecules capable of detecting, preventing, and counteracting AD onset and progression is of the utmost importance. However, although several studies have been published, comprehensive and up-to-date overviews of the principal anti-AD agents harboring antioxidant properties remain scarce. In this narrative review, we summarize the role of vitamins, minerals, flavonoids, non-flavonoids, mitochondria-targeting molecules, organosulfur compounds, and carotenoids as non-enzymatic antioxidants with AD diagnostic, preventative, and therapeutic potential, thereby offering insights into the relationship between OS and neurodegeneration.

A study of the oxidative processes in human plasma by time-resolved fluorescence spectroscopy

The aim of this study was to examine the usefulness of time-resolved fluorescence spectroscopy in the evaluation of the oxidative processes in human plasma. To investigate the impact of oxidative stress on the fluorescence of plasma, five studied markers (thiobarbituric acid-reactive substances, ischemia modified albumin, carbonyl groups, hydrogen peroxide, advanced oxidation protein products) were chosen as oxidative damage approved markers. Our method presents several advantages over traditional methods as it is a direct, non-time-consuming, repeatable, and non-invasive technique that requires only simple pre-treatment of samples without additional reagents and the sample size needed for analysis is small. In principle, each modification of the protein in plasma can be expected to modify its fluorescence properties and hence its lifetime or intensity. The study involved 59 blood donors with no evidence of disease. The research was conducted at excitation wavelengths of 280 nm and 360 nm, and emission was measured at wavelengths of 350 nm and 440 nm, respectively. Our results, although preliminary, suggest that the application of fluorescence measurements can be considered as an effective marker of oxidative stress. Regression analyses showed that a notable growth in fluorescence intensity at 440 nm and a simultaneous decrease in fluorescence intensity and mean fluorescence lifetime at 350 nm are associated with higher levels of oxidative stress.

Ferroptosis, a Potential Therapeutic Target in Alzheimer's Disease

Cell death is a common phenomenon in the progression of Alzheimer’s disease (AD). However, the mechanism of triggering the death of neuronal cells remains unclear. Ferroptosis is an iron-dependent lipid peroxidation-driven cell death and emerging evidences have demonstrated the involvement of ferroptosis in the pathological process of AD. Moreover, several hallmarks of AD pathogenesis were consistent with the characteristics of ferroptosis, such as excess iron accumulation, elevated lipid peroxides, and reactive oxygen species (ROS), reduced glutathione (GSH), and glutathione peroxidase 4 (GPX4) levels. Besides, some ferroptosis inhibitors can relieve AD-related pathological symptoms in AD mice and exhibit potential clinical benefits in AD patients. Therefore, ferroptosis is gradually being considered as a distinct cell death mechanism in the pathogenesis of AD. However, direct evidence is still lacking. In this review, we summarize the features of ferroptosis in AD, its underlying mechanisms in AD pathology, and review the application of ferroptosis inhibitors in both AD clinical trials and mice/cell models, to provide valuable information for future treatment and prevention of this devastating disease.

Selenium concentrations in elderly people with Alzheimer's disease: a cross-sectional study with control group

OBJECTIVE

To investigate possible differences in plasma and erythrocyte concentrations of selenium among elderly with and without a diagnosis of Alzheimer's disease (AD).

METHODS

Cross-sectional study, performed with an elderly group with Alzheimer's disease, diagnosed by a geriatric doctor, and compared to an elderly group without the disease, equaling gender, education, and age. Atomic absorption spectrophotometry determined plasma and erythrocyte concentrations of total selenium (Set).

RESULTS

The mean age was 74.41±7.1 years in the Alzheimer's disease group and 71.46±5.1 years among the control group. The Alzheimer's disease group presented lower plasma concentrations (mean of 45.29±14.51 µg/dL vs. 55.14±14.01 µg/dL; p=0.004), and erythrocyte Set (median of 56.36 µg/L vs. 76.96 µg/L; p<0.001). The logistic regression model indicated an association between erythrocyte Set concentrations and diagnosis of Alzheimer's disease (p=0.028).

CONCLUSION

Elderly with Alzheimer's disease present lower selenium concentrations in the evaluated organic compartments.

Lipid Peroxidation Assessment in Preclinical Alzheimer Disease Diagnosis

BACKGROUND

Alzheimer disease (AD) is an increasingly common neurodegenerative disease, especially in countries with aging populations. Its diagnosis is complex and is usually carried out in advanced stages of the disease. In addition, lipids and oxidative stress have been related to AD since the earliest stages. A diagnosis in the initial or preclinical stages of the disease could help in a more effective action of the treatments.

METHODS

Isoprostanoid biomarkers were determined in plasma samples from preclinical AD participants (n = 12) and healthy controls (n = 31) by chromatography and mass spectrometry (UPLC-MS/MS). Participants were accurately classified according to cerebrospinal fluid (CSF) biomarkers and neuropsychological examination.

RESULTS

Isoprostanoid levels did not show differences between groups. However, some of them correlated with CSF biomarkers (t-tau, p-tau) and with cognitive decline. In addition, a panel including 10 biomarkers showed an area under curve (AUC) of 0.96 (0.903-1) and a validation AUC of 0.90 in preclinical AD prediction.

CONCLUSIONS

Plasma isoprostanoids could be useful biomarkers in preclinical diagnosis for AD. However, these results would require a further validation with an external cohort.

Ferroptosis as a New Mechanism in Parkinson's Disease Therapy Using Traditional Chinese Medicine

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. To date, among medications used to treat PD, only levodopa exhibits a limited disease-modifying effect on early-onset PD, but it cannot delay the progression of the disease. In 2018, for the first time, the World Health Organization included traditional Chinese medicine (TCM) in its influential global medical compendium. The use of TCM in the treatment of PD has a long history. At present, TCM can help treat and prevent PD. Iron metabolism is closely associated with PD. Ferroptosis, which is characterized by the accumulation of lipid peroxides, is a recently discovered form of iron-dependent cell death. The research literature indicates that ferroptosis in dopaminergic neurons is an important pathogenetic mechanism of PD. TCM may thus play unique roles in the treatment of PD and provide new ideas for the treatment of PD by regulating pathways associated with ferroptosis.

Clinical Utility of Plasma Lipid Peroxidation Biomarkers in Alzheimer's Disease Differential Diagnosis

BACKGROUND

Differential diagnosis of Alzheimer's disease (AD) is a complex task due to the clinical similarity among neurodegenerative diseases. Previous studies showed the role of lipid peroxidation in early AD development. However, the clinical validation of potential specific biomarkers in minimally invasive samples constitutes a great challenge in early AD diagnosis.

METHODS

Plasma samples from participants classified into AD (n = 138), non-AD (including MCI and other dementias not due to AD) (n = 70) and healthy (n = 50) were analysed. Lipid peroxidation compounds (isoprostanes, isofurans, neuroprostanes, neurofurans) were determined by ultra-performance liquid chromatography coupled with tandem mass spectrometry. Statistical analysis for biomarkers' clinical validation was based on Elastic Net.

RESULTS

A two-step diagnosis model was developed from plasma lipid peroxidation products to diagnose early AD specifically, and a bootstrap validated AUC of 0.74 was obtained.

CONCLUSION

A promising AD differential diagnosis model was developed. It was clinically validated as a screening test. However, further external validation is required before clinical application.

Selenium Status in Elderly People: Longevity and Age-Related Diseases

BACKGROUND

Selenium (Se) is a trace element active in selenoproteins, which can regulate oxidative stress. It is generally perceived as an import factor for maintaining health in the elderly.

METHODS

The goal of this review is to discuss selenium concentration in biological samples, primarily serum or plasma, as a function of age and its relation with longevity. The elemental level in various age-related diseases is reviewed.

CONCLUSION

Highest selenium values were observed in healthy adults, while in an elderly population significantly lower concentrations were reported. Variables responsible for contradictory findings are mentioned. Risk and benefits of Se-supplementation still remain under debate.

NGF protects neuroblastoma cells against β-amyloid-induced apoptosis via the Nrf2/HO-1 pathway

As one of the main neurotrophic factors, nerve growth factor (NGF) participates in various processes related to viability, plasticity, and neuronal growth. NGF is known to protect against cell death and toxicity triggered by β‐amyloid (Aβ), but the underlying mechanism remains unclear. Here, we investigated this process in SKNSH neuroblastoma, in which NGF reduced cell death induced by Aβ25–35. Furthermore, NGF suppressed the production of reactive oxygen species (ROS) and promoted antioxidant function via Aβ25–35. Additionally, we demonstrated that NGF impaired the activation of the JNK/c‐Jun signaling pathway and significantly increased Nrf2 nuclear translocation and HO‐1 expression. Nrf2 elimination abolished the protective effect of NGF‐1 on Aβ25–35‐induced ROS generation, apoptosis, and activation of the JNK/c‐Jun pathway. The results of our study indicate that NGF protects neuroblastoma against injury triggered by Aβ25–35 via suppression of ROS–JNK/c‐Jun pathway stimulation through the Nrf2/HO‐1 pathway.

Nerve growth factor (NGF) promotes the nuclear translocation of Nrf2 and subsequently upregulates HO‐1 expression. This reduces the levels of reactive oxygen species (ROS), which attenuates the activation of JNK/c‐Jun pathway and eventually contributes to deceased cell apoptosis. The present discovery of this novel NGF/Nrf2/HO‐1 pathway and ROS–JNK/c‐Jun pathway identifies new clinical targets for therapeutic intervention of Alzheimer's disease.

Systems Biology of Selenium and Complex Disease

Selenium is an essential trace element for maintenance of overall health, whose deficiency and dyshomeostasis have been linked to a variety of diseases and disorders. The majority of previous researches focused on characterization of genes encoding selenoproteins or proteins involved in selenium metabolism as well as their functions. Many studies in humans also investigated the relationship between selenium and complex diseases, but their results have been inconsistent. In recent years, systems biology and "-omics" approaches have been widely used to study complex and global variations of selenium metabolism and function in physiological and different pathological conditions. The present paper reviews recent progress in large-scale and systematic analyses of the relationship between selenium status or selenoproteins and several complex diseases, mainly including population-based cohort studies and meta-analyses, genetic association studies, and some other omics-based studies. Advances in ionomics and its application in studying the interaction between selenium and other trace elements in human health and diseases are also discussed.

Lipid peroxidation in neurodegeneration

Neurodegenerative diseases have great social and economic impact and cause millions of deaths every year. The potential molecular mechanisms in these pathologies have been widely studied and implicate lipid peroxidation as an important factor in the development of neurodegenerative disorders such as Alzheimer's, Parkinson's and Huntington's diseases. Data indicates that pathologic mechanisms specifically involve ferroptosis and mitochondrial dysfunction. Here we review the molecular mechanisms related to the lipid peroxidation that involve the development of neurodegeneration, as well as the utility of some biomarkers in diagnosis, prognosis and evaluation of new therapies for neurodegenerative diseases.

Changing levels of selenium and zinc in cadmium-exposed workers: probable association with the intensity of inflammation

Inflammation is a response mediated by multiple cytokines, such as IL-6, IL-10 and TNF-α. Cadmium (Cd) has been involved in the etiopathogenesis of many diseases via inflammation. Selenium (Se) and zinc (Zn) play a pivotal role in maintaining many physiological functions of cells as well as inhibiting Cd-induced cytotoxicity. This study investigated the anti-inflammatory effects of Se and Zn in cadmium-exposed workers by measuring the levels of IL-6, IL-10 and TNF-α cytokines in 68 control and 91 Cd-exposed subjects. Blood samples were obtained from each participant for immunological, toxicological and routine analysis. All samples were digested by microwave oven and analysed by inductively coupled plasma mass spectrometry (ICP-MS). IL-6, IL-10 and TNF-α cytokine levels were found to be statistically different (p < 0.001) between the control and Cd-exposed groups (23.50 ± 7.70 pg/mL vs. 69.05 ± 19.06 pg/mL; 28.61 ± 9.83 pg/mL vs. 51.79 ± 11.77 pg/mL; 3.44 ± 1.14 pg/mL vs. 5.79 ± 1.04 pg/mL, respectively). High positive correlations were found between Cd levels of participants and IL-6, IL-10, TNF-α and CRP levels (r = 0.568, r = 0.615, r = 0.614 and r = 0.296, respectively, p < 0.01). In terms of the regression analysis results, there were significant effects of Cd on IL-6, IL-10 and TNF-α levels (p < 0.05). The Cd, Zn and Se levels between control and exposed group were significantly different [0.26 ± 0.15 µg/L vs. 3.36 ± 1.80 µg/L; 143.91 ± 71.13 µg/dL vs. 121.09 ± 59.88 µg/dL; 92.98 ± 17.03 µg/L vs. 82.72 ± 34.46 µg/L (p < 0.001, p < 0.03, p < 0.015), respectively]. In conclusion, increasing levels of Se and Zn decreases the intensity of inflammation as measured by IL-6, IL-10 and TNF-α levels.

Assessment of lipid peroxidation and artificial neural network models in early Alzheimer Disease diagnosis

OBJECTIVE

Lipid peroxidation constitutes a molecular mechanism involved in early Alzheimer Disease (AD) stages, and artificial neural network (ANN) analysis is a promising non-linear regression model, characterized by its high flexibility and utility in clinical diagnosis. ANN simulates neuron learning procedures and it could provide good diagnostic performances in this complex and heterogeneous disease compared with linear regression analysis.

DESIGN AND METHODS

In our study, a new set of lipid peroxidation compounds were determined in urine and plasma samples from patients diagnosed with early Alzheimer Disease (n = 70) and healthy controls (n = 26) by means of ultra-performance liquid chromatography coupled with tandem mass-spectrometry. Then, a model based on ANN was developed to classify groups of participants.

RESULTS

The diagnostic performances obtained using an ANN model for each biological matrix were compared with the corresponding linear regression model based on partial least squares (PLS), and with the non-linear (radial and polynomial) support vector machine (SVM) models. Better accuracy, in terms of receiver operating characteristic-area under curve (ROC-AUC), was obtained for the ANN models (ROC-AUC 0.882 in plasma and 0.839 in urine) than for PLS and SVM models.

CONCLUSION

Lipid peroxidation and ANN constitute a useful approach to establish a reliable diagnosis when the prognosis is complex, multidimensional and non-linear.

Plasma lipid peroxidation biomarkers for early and non-invasive Alzheimer Disease detection

INTRODUCTION

Alzheimer Disease (AD) standard diagnosis is based on evaluations and biomarkers that are non-specific, expensive, or requires invasive sampling. Therefore, an early, and non-invasive diagnosis is required. As regards molecular mechanisms, recent research has shown that lipid peroxidation plays an important role.

METHODS

Well-defined participants groups were recruited. Lipid peroxidation compounds were determined in plasma using a validated analytical method. Statistical studies consisted of an elastic-net-penalized logistic regression adjustment.

RESULTS

The regression model fitted to the data included six variables (lipid peroxidation biomarkers) as potential predictors of early AD. This model achieved an apparent area under the receiver operating characteristics (AUC-ROCs) of 0.883 and a bootstrap-validated AUC-ROC of 0.817. Calibration of the model showed very low deviations from real probabilities.

CONCLUSION

A satisfactory early diagnostic model has been obtained from plasma levels of 6 lipid peroxidation compounds, indicating the individual probability of suffering from early AD.