Connection between the Altered HDL Antioxidant and Anti-Inflammatory Properties and the Risk to Develop Alzheimer's Disease: A Narrative Review

Clinical and Diagnostic Value of High-Density Lipoprotein-Based Inflammatory Indices and Lipid Ratios in Young Adults with Schizophrenia

Purpose

This study aimed to assess High-density Lipoprotein (HDL)-based Inflammatory Indices and lipid profile changes in antipsychotic-naive first-episode schizophrenia (AN-FES) patients, chronic schizophrenia (CS) patients, and explore the clinical and predictive value of these parameters for schizophrenia.

Patients and Methods

The study cohort included 52 AN-FES patients, 46 CS patients, and 52 healthy controls (HCs), with an average age of 24 years. Upon admission, patients underwent complete blood count and lipid profile analyses. Various ratios were calculated, including neutrophil-to-HDL (NHR), monocyte-to-HDL (MHR), lymphocyte-to-HDL (LHR), and platelet-to-HDL (PHR), as well as lipid ratios like triglycerides/HDL, non-HDL/HDL, total cholesterol/HDL, and low-density lipoprotein/HDL. For the AN-FES group, these evaluations were repeated after two months of treatment with atypical antipsychotics. Statistical analyses included correlation analysis, Receiver Operating Characteristic (ROC) curve analysis, and univariate and multivariate regression.

Results

Compared to HCs, CS patients exhibited significantly higher MHR and NHR values, while AN-FES patients showed elevated levels of PHR, MHR, and NHR. No significant differences were observed in LHR or lipid ratios across the three groups. In the AN-FES cohort, MHR correlated positively with neutrophil counts, and NHR with monocyte counts. Additionally, white blood cell counts were positively associated with both MHR and NHR. Following treatment, NHR levels decreased, whereas TG/HDL ratios increased, with MHR and PHR remaining elevated. ROC analysis highlighted NHR as the most diagnostically valuable parameter (AUC = 0.799), with 86.5% specificity at an optimal cutoff of 3.534, outperforming MHR and PHR. Regression analyses recognized NHR (OR=2.225) as an independent risk factor for schizophrenia, even after adjusting for confounders.

Conclusion

HDL-based inflammatory indices, particularly NHR, may serve as valuable diagnostic and prognostic markers in young adults with schizophrenia, even though significant alterations in lipid ratios were not observed in this demographic.

Association between lipoprotein-associated phospholipase A2 and 25-hydroxy-vitamin D on early stage diabetic kidney disease in patients with type-2 diabetes mellitus

Objective

This study aimed to analyse the association between lipoprotein-associated phospholipase A2 (Lp-PLA2) and 25-hydroxy-vitamin D (25[OH]D) and early diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM) and evaluate the potential roles of these two biomarkers in the clinical diagnosis of DKD.

Methods

A total of 422 inpatients with T2DM were retrospectively enrolled between January 2018 and March 2022 at the First Affiliated Hospital of Nanjing Medical University. The baseline clinical parameters of each patient were determined, and their demographic characteristics were extracted from the hospital information system. The patients were separated into groups according to serum Lp-PLA2 and 25(OH)D levels and binary logistic regression analysis was used to determine independent predictors of early DKD incidence.

Results

Levels of Lp-PLA2 significantly increased and those of 25(OH)D significantly decreased with DKD progression (both P < 0.001). Lp-PLA2 concentrations were positively correlated with albuminuria levels (r = 0.37, P < 0.001), whereas 25(OH)D levels were negatively correlation (r = -0.34, P < 0.001). The incidence of DKD was higher in the Lp-PLA2 elevated and 25(OH)D deficient groups (all P < 0.001). Body mass index, systemic immune-inflammatory index, serum uric acid, C-peptide, and triglyceride-glucose indices were positively associated with Lp-PLA2 levels (all P < 0.001) and negatively associated with 25(OH)D (all P < 0.05). Furthermore, Lp-PLA2 was an independent risk factor (OR = 1.003, P = 0.015), and 25(OH)D was an independent protective factor (OR = 0.937, P = 0.008) for early DKD occurrence in binary logistic regression analysis. The area under the curve for the combination of Lp-PLA2 and 25(OH)D for diagnosing DKD was 0.867, with a sensitivity of 70.4 % and a specificity of 89.5 %.

Conclusions

Increased serum Lp-PLA2 and decreased 25(OH)D levels are risk factors for early DKD in patients with T2DM. The combined detection of Lp-PLA2 and 25(OH)D may enhance the diagnostic efficacy of DKD.

Post-GWAS multiomic functional investigation of the TNIP1 locus in Alzheimer's disease highlights a potential role for GPX3

INTRODUCTION

Recent genome-wide association studies (GWAS) have reported a genetic association with Alzheimer's disease (AD) at the TNIP1/GPX3 locus, but the mechanism is unclear.

METHODS

We used cerebrospinal fluid (CSF) proteomics data to test (n = 137) and replicate (n = 446) the association of glutathione peroxidase 3 (GPX3) with CSF biomarkers (including amyloid and tau) and the GWAS-implicated variants (rs34294852 and rs871269).

RESULTS

CSF GPX3 levels decreased with amyloid and tau positivity (analysis of variance P = 1.5 × 10-5) and higher CSF phosphorylated tau (p-tau) levels (P = 9.28 × 10-7). The rs34294852 minor allele was associated with decreased GPX3 (P = 0.041). The replication cohort found associations of GPX3 with amyloid and tau positivity (P = 2.56 × 10-6) and CSF p-tau levels (P = 4.38 × 10-9).

DISCUSSION

These results suggest variants in the TNIP1 locus may affect the oxidative stress response in AD via altered GPX3 levels.

HIGHLIGHTS

Cerebrospinal fluid (CSF) glutathione peroxidase 3 (GPX3) levels decreased with amyloid and tau positivity and higher CSF phosphorylated tau. The minor allele of rs34294852 was associated with lower CSF GPX3. levels when also controlling for amyloid and tau category. GPX3 transcript levels in the prefrontal cortex were lower in Alzheimer's disease than controls. rs34294852 is an expression quantitative trait locus for GPX3 in blood, neutrophils, and microglia.

Systemic inflammation and oxidative stress markers in patients with unipolar and bipolar depression: A large-scale study

OBJECTIVE

Numerous studies have demonstrated that neutrophil/HDL ratio (NHR), lymphocyte/HDL ratio (LHR), monocyte/HDL (MHR) ratio, platelet/HDL ratio (PHR), neutrophil/ALB ratio (NAR) and platelet/ALB ratio (PAR) can serve as systemic inflammation and oxidative stress markers in a variety of diseases. However, few studies have estimated the associations of these markers with unipolar depression (UD) and bipolar depression (BD), as well as psychotic symptoms in UD and BD.

METHODS

6297 UD patients, 1828 BD patients and 7630 healthy subjects were recruited. The differences in these indicators among different groups were compared, and the influencing factors for the occurrence of UD or BD and psychotic symptoms were analyzed.

RESULTS

These ratios displayed unique variation patterns across different diagnostic groups. BD group exhibited higher NHR, LHR, MHR, NAR and lower PAR than UD and HC groups, UD group showed higher MHR than HC group. The psychotic UD group had higher NHR, LHR, MHR and NAR than non-psychotic UD group. Higher LHR, MHR, NAR and lower PAR were risk factors in BD when compared to UD group.

CONCLUSIONS

Our study demonstrated differences in inflammation and oxidative stress profile between UD and BD patients, as well as between subjects with or without psychotic symptom exist, highlighting the role of inflammation and oxidative stress in the pathophysiology of UD and BD.

Evaluation of the relationship among gene expressions and enzyme activities with antioxidant role and presenilin 1 expression in Alzheimer's disease

It is known that oxidative stress originating from reactive oxygen species plays a role in the pathogenesis of Alzheimer's disease. In this study, the role of antioxidant status associated with oxidative stress in Alzheimer's disease was investigated. Peripheral blood samples were obtained from 28 healthy individuals (as control) and 28 Alzheimer's patients who met the National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association criteria. Catalase, glutathione S-transferase and paraoxonase 1 enzyme activities in blood plasma and glutathione S-transferase enzyme activities in erythrocytes were determined by spectrophotometer. Catalase, glutathione S-transferase and presenilin 1 gene expressions in leukocytes were determined using qRT-PCR. Data were analysed with SPSS one-way anova, a LSD post hoc test at p < 0.05. The activity of each enzyme was significantly reduced in Alzheimer's patients compared to control. The catalase gene expression level did not change compared to the control. Glutathione S-transferase and presenilin 1 gene expression levels were increased compared to the control.

Inflammation Markers in Patients with Bipolar Disorder Who Have Committed Offenses and Their Relationship with Criminal Behavior

Background and Objectives: This study aimed to examine the function of various inflammation parameters and their interactions in the pathology of Bipolar disorder (BD) and to assess whether they could be biomarkers in the relationship between criminal behavior and BD. Materials and Methods: Overall, 1029 participants, including 343 patients with BD who have committed offenses, 343 nonoffending patients with BD, and 343 healthy controls, were included in this retrospective study. Neutrophil, lymphocyte, monocyte, and platelet counts; high-density lipoprotein (HDL-c) levels; systemic immune-inflammatory index (SII), systemic inflammatory response index (SIRI), neutrophil to high-density lipoprotein ratio (NHR), lymphocyte to high-density lipoprotein ratio (LHR), monocyte to high-density lipoprotein ratio (MHR), platelet to high-density lipoprotein ratio (PHR) were measured. Results: Significant differences were observed between the groups in terms of SII, SIRI, NHR, LHR, MHR, PHR, neutrophil, and monocyte values (p < 0.001). The lymphocyte counts were significantly higher in the patients with BD who committed offenses (p = 0.04). The platelet counts were significantly lower in the patients with BD who committed offenses compared to nonoffending patients with BD (p = 0.015). The HDL-c levels were significantly lower in the patients with BD who have committed offenses than those of nonoffending patients with BD (p < 0.001). Bipolar disorder, not receiving active psychiatric treatment, having a diagnosis of bipolar manic episodes, and having low platelet and HDL values constitute a risk of involvement in crime. Conclusions: The present study emphasizes the role of systemic inflammation in the pathophysiology of patients with BD with and without criminal offenses and the relationship between inflammation and criminal behavior.

Modulation of the Cellular microRNA Landscape: Contribution to the Protective Effects of High-Density Lipoproteins (HDL)

High-density lipoproteins (HDL) play an established role in protecting against cellular dysfunction in a variety of different disease contexts; however, harnessing this therapeutic potential has proved challenging due to the heterogeneous and relative instability of this lipoprotein and its variable cargo molecules. The purpose of this study is to examine the contribution of microRNA (miRNA; miR) sequences, either delivered directly or modulated endogenously, to these protective functions. This narrative review introduces the complex cargo carried by HDL, the protective functions associated with this lipoprotein, and the factors governing biogenesis, export and the uptake of microRNA. The possible mechanisms by which HDL can modulate the cellular miRNA landscape are considered, and the impact of key sequences modified by HDL is explored in diseases such as inflammation and immunity, wound healing, angiogenesis, dyslipidaemia, atherosclerosis and coronary heart disease, potentially offering new routes for therapeutic intervention.

Paraoxonase 1 activity in patients with Alzheimer disease: Systematic review and meta-analysis

Cumulating evidence links environmental toxicants, such as organophosphate (OP) pesticides, to the pathogenesis of Alzheimer's disease (AD). The calcium-dependent Paraoxonase 1 (PON1) can neutralize these toxicants with good catalytic efficiency, thus protecting from OP-induced biological damage. Although different previous studies have already partially described an association between PON1 activity and AD, this intriguing relationship has not yet been comprehensively examined. To fill this gap, we performed a meta-analysis of existing data comparing the PON1 arylesterase activity in AD and healthy subjects from the general population. Data were obtained by searching MEDLINE, Embase and CENTRAL, Google Scholar, and SCOPUS electronic databases for all studies published at any time up to February 2023, reporting and comparing the PON1- paraoxonase activity between AD patients and controls. Seven studies, based on 615 subjects (281 AD and 356 controls) met the inclusion criteria and were included into the final analysis. A random effect model revealed that PON1 arylesterase activity was significantly lower in the AD group compared to controls, exhibiting low level of heterogeneity (SMD = - 1.62, 95% CI = -2.65 to -0.58, p = 0.0021, I2 = 12%). These findings suggest that PON1 activity might be reduced in AD reflecting a major susceptibility to OPs neurotoxicity. Further studies should be conducted to definitely ascertain this link and to establish the cause-effect relationship between PON1 reduction and AD onset.

A Current Update on the Role of HDL-Based Nanomedicine in Targeting Macrophages in Cardiovascular Disease

High-density lipoproteins (HDL) are complex endogenous nanoparticles involved in important functions such as reverse cholesterol transport and immunomodulatory activities, ensuring metabolic homeostasis and vascular health. The ability of HDL to interact with a plethora of immune cells and structural cells places it in the center of numerous disease pathophysiologies. However, inflammatory dysregulation can lead to pathogenic remodeling and post-translational modification of HDL, rendering HDL dysfunctional or even pro-inflammatory. Monocytes and macrophages play a critical role in mediating vascular inflammation, such as in coronary artery disease (CAD). The fact that HDL nanoparticles have potent anti-inflammatory effects on mononuclear phagocytes has opened new avenues for the development of nanotherapeutics to restore vascular integrity. HDL infusion therapies are being developed to improve the physiological functions of HDL and to quantitatively restore or increase the native HDL pool. The components and design of HDL-based nanoparticles have evolved significantly since their initial introduction with highly anticipated results in an ongoing phase III clinical trial in subjects with acute coronary syndrome. The understanding of mechanisms involved in HDL-based synthetic nanotherapeutics is critical to their design, therapeutic potential and effectiveness. In this review, we provide a current update on HDL-ApoA-I mimetic nanotherapeutics, highlighting the scope of treating vascular diseases by targeting monocytes and macrophages.

Paraoxonases at the Heart of Neurological Disorders

Paraoxonase enzymes serve as an important physiological redox system that participates in the protection against cellular injury caused by oxidative stress. The PON enzymes family consists of three members (PON-1, PON-2, and PON-3) that share a similar structure and location as a cluster on human chromosome 7. These enzymes exhibit anti-inflammatory and antioxidant properties with well-described roles in preventing cardiovascular disease. Perturbations in PON enzyme levels and their activity have also been linked with the development and progression of many neurological disorders and neurodegenerative diseases. The current review summarizes the available evidence on the role of PONs in these diseases and their ability to modify risk factors for neurological disorders. We present the current findings on the role of PONs in Alzheimer's disease, Parkinson's disease, and other neurodegenerative and neurological diseases.

Lipoprotein-Associated Phospholipase A2 Activity as Potential Biomarker of Vascular Dementia

A wealth of evidence suggests that Lipoprotein-associated phospholipase A2 (Lp-PLA2) plays a relevant role in atherogenesis and inflammation, which in turn are associated with the risk of developing dementia. The aim of this study was to evaluate whether serum Lp-PLA2 activity might be an early and/or late biomarker for different forms of dementia. Serum Lp-PLA2 activity was assessed in older patients with mild cognitive impairment (MCI, n = 166; median clinical follow-up = 29 months), Late-Onset Alzheimer's disease (LOAD, n = 176), vascular dementia (VAD, n = 43), dementia characterized by an overlap between LOAD and VAD (AD-VAD MIXED dementia) (n = 136), other dementia subtypes (n = 45), and cognitively normal controls (n = 151). We found a significant trend towards higher levels of Lp-PLA2 activity in VAD compared with the other groups (ANOVA, p = 0.028). Similarly, Lp-PLA2 activity was greater in MCI converting to VAD compared with those that did not or did convert to the other types of dementia (ANOVA, p = 0.011). After adjusting for potential confounders, high levels of Lp-PLA2 activity were associated with the diagnosis of VAD (O.R. = 2.38, 95% C.I. = 1.06-5.10), but not with other types of dementia. Our data suggest that increased serum Lp-PLA2 activity may represent a potential biomarker for the diagnosis of VAD.

Alzheimer's Disease Is a Multi-Organ Disorder: It May Already Be Preventable

In this commentary, we offer an overview of the several environmental and metabolic factors that have been identified as contributing to the development of Alzheimer's disease (AD). Many of these factors involve extracranial organ systems including immune system dysfunction accompanied by neuroinflammation (inflammaging), gastrointestinal dysbiosis, insulin resistance, and hepatic dysfunction. A variety of microbial factors including mouth flora, viruses, and fungi appear to play a significant role. There is a role for the colonic microbiome becoming dysbiotic and producing toxic metabolites. Declining hepatic function contributes diminished neuronal precursors and reduces toxin elimination. Environmental toxins especially metals play an important role in impairing the blood-brain barrier and acting synergistically with biotoxins and other toxic chemicals. Prevention and treatment of AD appears to require measuring several of these biomarkers and implementing corrective actions regarding such toxicants and correcting metabolic dysfunction at early or preclinical stages of this disorder.

Lipids at the Nexus between Cerebrovascular Disease and Vascular Dementia: The Impact of HDL-Cholesterol and Ceramides

Cerebrovascular diseases and the subsequent brain hypoperfusion are at the basis of vascular dementia. Dyslipidemia, marked by an increase in circulating levels of triglycerides and LDL-cholesterol and a parallel decrease in HDL-cholesterol, in turn, is pivotal in promoting atherosclerosis which represents a common feature of cardiovascular and cerebrovascular diseases. In this regard, HDL-cholesterol has traditionally been considered as being protective from a cardiovascular and a cerebrovascular prospective. However, emerging evidence suggests that their quality and functionality play a more prominent role than their circulating levels in shaping cardiovascular health and possibly cognitive function. Furthermore, the quality of lipids embedded in circulating lipoproteins represents another key discriminant in modulating cardiovascular disease, with ceramides being proposed as a novel risk factor for atherosclerosis. This review highlights the role of HDL lipoprotein and ceramides in cerebrovascular diseases and the repercussion on vascular dementia. Additionally, the manuscript provides an up-to-date picture of the impact of saturated and omega-3 fatty acids on HDL circulating levels, functionality and ceramide metabolism.

A Nutraceutical Compound Containing a Low Dose of Monacolin K, Polymethoxyflavones, Phenolic Acids, Flavonoids, and Hydroxytyrosol Improves HDL Functionality

BACKGROUND

In earlier studies, it has been observed that 8-week treatment with a novel nutraceutical compound (NC) containing low monacolin K dose, polymethoxyflavones, phenolic acids, flavonoids, and hydroxytyrosol improves lipid profile and endothelial function and reduces the level of oxidized low-density lipoprotein (oxLDL). We hypothesize that this effect might be, at least in part, explained by positive modulation exerted by the NC on the atheroprotective function of high-density lipoprotein (HDL).

AIM

This study aimed to evaluate whether the NC could influence determinants of HDL function.

METHODS

Forty-five subjects with low-moderate dyslipidaemia were enrolled and treated for 8 weeks with the NC, followed by 4 weeks of washout. Blood samples were collected at every time point to evaluate changes in lipid profile, endothelial function, oxLDL, and markers of HDL function, such as the anti-oxidant activities of paraoxonase-1, glutathione peroxidase-3 (Gpx3), lipoprotein-phospholipase A2 (Lp-PLA2), and pro-oxidant activity of myeloperoxidase (MPO).

RESULTS

Although the concentration of HDL-C did not change, the activity of Lp-PLA2 significantly decreased upon treatment (-11.6%, p<0.001) and returned to baseline level 4 weeks after the end of treatment. In contrast, Gpx3 increased after treatment (+5%, p<0.01) and remained unvaried after 4 weeks. Both MPO activity and concentration significantly decreased after the washout period (-33 and 32%, p<0.001).

CONCLUSION

For the first time, it was found that the administration of an NC with beneficial effects on lipid homeostasis also positively impacts HDL function by improving the balance between protective and damaging determinants. Further investigation is required to corroborate our findings.

Oxidized High-Density Lipoprotein Induces Endothelial Fibrosis Promoting Hyperpermeability, Hypotension, and Increased Mortality

During systemic inflammation, reactive oxygen species (ROS) are generated in the bloodstream, producing large amounts of oxidized HDL (oxHDL). OxHDL loses the vascular protective features of native HDL, acquiring detrimental actions. Systemic inflammation promotes endothelial fibrosis, characterized by adhesion protein downregulation and fibrotic-specific gene upregulation, disrupting endothelial monolayer integrity. Severe systemic inflammatory conditions, as found in critically ill patients in the intensive care unit (ICU), exhibit endothelial hyperpermeability, hypotension, and organ hypoperfusion, promoting organ dysfunction and increased mortality. Because endothelial fibrosis disturbs the endothelium, it is proposed that it is the cellular and molecular origin of endothelial hyperpermeability and the subsequent deleterious consequences. However, whether oxHDL is involved in this process is unknown. The aim of this study was to investigate the fibrotic effect of oxHDL on the endothelium, to elucidate the underlying molecular and cellular mechanism, and to determine its effects on vascular permeability, blood pressure, and mortality. The results showed that oxHDL induces endothelial fibrosis through the LOX-1/NOX-2/ROS/NF-κB pathway, TGF-β secretion, and ALK-5/Smad activation. OxHDL-treated rats showed endothelial hyperpermeability, hypotension, and an enhanced risk of death and mortality, which was prevented using an ALK-5 inhibitor and antioxidant diet consumption. Additionally, the ICU patients showed fibrotic endothelial cells, and the resuscitation fluid volume administered correlated with the plasma oxHDL levels associated with an elevated risk of death and mortality. We conclude that oxHDL generates endothelial fibrosis, impacting blood pressure regulation and survival.

Effect of Obesity and High-Density Lipoprotein Concentration on the Pathological Characteristics of Alzheimer's Disease in High-Fat Diet-Fed Mice

The typical pathological features of Alzheimer's disease (AD) are the accumulation of amyloid plaques in the brain and reactivity of glial cells such as astrocytes and microglia. Clinically, the development of AD and obesity are known to be correlated. In this study, we analyzed the changes in AD pathological characteristics in 5XFAD mice after obesity induction through a high-fat diet (HFD). Surprisingly, high-density lipoprotein and apolipoprotein AI (APOA-I) serum levels were increased without low-density lipoprotein alteration in both HFD groups. The reactivity of astrocytes and microglia in the dentate gyrus of the hippocampus and fornix of the hypothalamus in 5XFAD mice was decreased in the transgenic (TG)-HFD high group. Finally, the accumulation of amyloid plaques in the dentate gyrus region of the hippocampus was also significantly decreased in the TG-HFD high group. These results suggest that increased high-density lipoprotein level, especially with increased APOA-I serum level, alleviates the pathological features of AD and could be a new potential therapeutic strategy for AD treatment.

Microencapsulated curcumin from Curcuma longa modulates diet-induced hypercholesterolemia in Sprague Dawley rats

Hypercholesterolemia is one of the major causes of cardiovascular ailments. The study has been conducted on the hypothesis that hypercholesterolemia can be modulated by microencapsulated curcumin due to its enhanced bioavailability. In this context, curcumin obtained from fresh rhizomes of Curcuma longa by conventional (CSE) and supercritical fluid (SFE) extractions, has been successfully microencapsulated using a mixture of gelatin and maltodextrin. The microencapsulated curcumin _CSE&SFE, has been added as supplemented diet and has been resulted in maximum plasma concentration of curcumin at 100 min as 529.31 ± 8.73 and 405.23 ± 7.12 μg/mL, respectively compared to non-encapsulated turmeric powder used as control. During the bio evaluation trial, turmeric powder (3%), microencapsulated curcumin_CSE (1%) and microencapsulated curcumin_SFE (0.5%) were provided to designate rat groups categorized by normal; N₁, N₂, and N₃ and hypercholesterolemic; H₁, H₂, and H₃ conditions, respectively. The incorporation of microencapsulated curcumin_SFE in the supplemented diet caused a reduction in serum cholesterol, low density lipoprotein (LDL) and triglycerides, athrogenic index (AI) and cardiac risk ration (CRR) as 5.42 and 12.81%, 7.25 and 15.42%, 3.17 and 9.38%, 15.38 and 29.28%, and 10.98 19.38% in normo- and hypercholesterolemic rat groups. Additionally, high-density lipoprotein (HDL) and anti-atherogenic index (AAI) indicated a significant increase in all treated rat groups. Conclusively, the inclusion of turmeric and curcumin microencapsulates in the dietary module has been proven effective to alleviate hyperlipidemia. Therefore, the present study is proven that curcumin absorption via the gastrointestinal tract and its stability toward metabolization in the body increased via microencapsulation using maltodextrin and gelatin. Microencapsulated curcumin reaches the target site via oral administration because of sufficient gastrointestinal residence period and stability in the digestive tract.

Emerging role of HDL in brain cholesterol metabolism and neurodegenerative disorders

High-density lipoproteins (HDLs play a key role in cholesterol homeostasis maintenance in the central nervous system (CNS), by carrying newly synthesized cholesterol from astrocytes to neurons, to support their lipid-related physiological functions. As occurs for plasma HDLs, brain lipoproteins are assembled through the activity of membrane cholesterol transporters, undergo remodeling mediated by specific enzymes and transport proteins, and finally deliver cholesterol to neurons by a receptor-mediated internalization process. A growing number of evidences indicates a strong association between alterations of CNS cholesterol homeostasis and neurodegenerative disorders, in particular Alzheimer's disease (AD), and a possible role in this relationship may be played by defects in brain HDL metabolism. In the present review, we summarize and critically examine the current state of knowledge on major modifications of HDL and HDL-mediated brain cholesterol transport in AD, by taking into consideration the individual steps of this process. We also describe potential and encouraging HDL-based therapies that could represent new therapeutic strategies for AD treatment. Finally, we revise the main plasma and brain HDL modifications in other neurodegenerative disorders including Parkinson's disease (PD), Huntington's disease (HD), and frontotemporal dementia (FTD).

Punicic Acid and Its Role in the Prevention of Neurological Disorders: A Review

Millions of people worldwide are affected by neurodegenerative diseases (NDs). NDs are characterized by progressive damage and death of nerve cells accompanied by high levels of inflammatory biomarkers and oxidative stress conditions. Punicic acid, the main bioactive component of pomegranate (Punica granatum) seed oil, is an omega-5 isomer of conjugated α-linoleic acid that has shown strong anti-oxidative and anti-inflammatory effects that contributes towards its positive effect against a wide arrange of diseases. Punicic acid decreases oxidative damage and inflammation by increasing the expression of peroxisome proliferator-activated receptors. In addition, it can reduce beta-amyloid deposits formation and tau hyperphosphorylation by increasing the expression of GLUT4 protein and the inhibition of calpain hyperactivation. Microencapsulated pomegranate, with high levels of punicic acid, increases antioxidant PON1 activity in HDL. Likewise, encapsulated pomegranate formulations with high levels of punicic acid have shown an increase in the antioxidant PON1 activity in HDL. Because of the limited brain permeability of punicic acid, diverse delivery formulations have been developed to enhance the biological activity of punicic acid in the brain, diminishing neurological disorders symptoms. Punicic acid is an important nutraceutical compound in the prevention and treatment of neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's disease.

Investigation of systemic immune-inflammation index, neutrophil/high-density lipoprotein ratio, lymphocyte/high-density lipoprotein ratio, and monocyte/high-density lipoprotein ratio as indicators of inflammation in patients with schizophrenia and bipolar disorder

BACKGROUND

The systemic immune-inflammation index (SII), system inflammation response index (SIRI), neutrophil/high-density lipoprotein (HDL) ratio (NHR), lymphocyte/HDL ratio (LHR), monocyte/HDL ratio (MHR), and platelet/HDL ratio (PHR) have been recently investigated as new markers for inflammation. The purpose of this research is to use large-scale clinical data to discuss and compare the predictive ability of the SII, SIRI, NHR, LHR, MHR, and PHR in patients with schizophrenia (SCZ) and bipolar disorder (BD), to investigate potential biomarkers.

MATERIALS AND METHODS

In this retrospective, naturalistic, cross-sectional study, we collected the hematological parameter data of 13,329 patients with SCZ, 4,061 patients with BD manic episodes (BD-M), and 1,944 patients with BD depressive episodes (BD-D), and 5,810 healthy subjects served as the healthy control (HC) group. The differences in the SII, SIRI, NHR, LHR, MHR, and PHR were analyzed, and a receiver operating characteristic (ROC) curve was used to analyze the diagnostic potential of these parameters.

RESULTS

Compared with the HC group, the values of the SII, SIRI, NHR, LHR, MHR, and PHR and the levels of neutrophils, monocytes, and triglycerides (TG) were higher in SCZ and BD groups, and levels of platelets, cholesterol (CHO), HDL, low-density lipoprotein (LDL), and apoprotein B (Apo B) were lower in SCZ and BD groups. Compared to the BD group, the values of the SIRI, lymphocytes, monocytes, and HDL were lower and the values of the SII, NHR, PHR, and platelet were higher in the SCZ group. In contrast to the BD-D group, the values of the SII; SIRI; NHR; and MHR; and levels of neutrophils, monocytes, and platelets were higher in the BD-M group, and the levels of CHO, TG, LDL, and Apo B were lower in the BD-M group. The MHR and NHR were predictors for differentiating the SCZ group from the HC group; the SIRI, NHR, and MHR were predictors for differentiating the BD-M group from the HC group; and the MHR was a predictor for differentiating the BD-D group from the HC group. The combination model of the indicators improved diagnostic effectiveness.

CONCLUSION

Our study highlights the role of systemic inflammation in the pathophysiology of SCZ, BD-M, and BD-D, the association between inflammation and lipid metabolism, and these inflammation and lipid metabolism indicators showed different variation patterns in SCZ, BD-D, and BD-M.

Anti-Inflammatory Properties of Statin-Loaded Biodegradable Lecithin/Chitosan Nanoparticles: A Step Toward Nose-to-Brain Treatment of Neurodegenerative Diseases

Nasal delivery has been indicated as one of the most interesting alternative routes for the brain delivery of neuroprotective drugs. Nanocarriers have emerged as a promising strategy for the delivery of neurotherapeutics across the nasal epithelia. In this work, hybrid lecithin/chitosan nanoparticles (LCNs) were proposed as a drug delivery platform for the nasal administration of simvastatin (SVT) for the treatment of neuroinflammatory diseases. The impact of SVT nanoencapsulation on its transport across the nasal epithelium was investigated, as well as the efficacy of SVT-LCNs in suppressing cytokines release in a cellular model of neuroinflammation. Drug release studies were performed in simulated nasal fluids to investigate SVT release from the nanoparticles under conditions mimicking the physiological environment present in the nasal cavity. It was observed that interaction of nanoparticles with a simulated nasal mucus decreased nanoparticle drug release and/or slowed drug diffusion. On the other hand, it was demonstrated that two antibacterial enzymes commonly present in the nasal secretions, lysozyme and phospholipase A2, promoted drug release from the nanocarrier. Indeed, an enzyme-triggered drug release was observed even in the presence of mucus, with a 5-fold increase in drug release from LCNs. Moreover, chitosan-coated nanoparticles enhanced SVT permeation across a human cell model of the nasal epithelium (×11). The nanoformulation pharmacological activity was assessed using an accepted model of microglia, obtained by activating the human macrophage cell line THP-1 with the Escherichia coli–derived lipopolysaccharide (LPS) as the pro-inflammatory stimulus. SVT-LCNs were demonstrated to suppress the pro-inflammatory signaling more efficiently than the simple drug solution (−75% for IL-6 and −27% for TNF-α vs. −47% and −15% at 10 µM concentration for SVT-LCNs and SVT solution, respectively). Moreover, neither cellular toxicity nor pro-inflammatory responses were evidenced for the treatment with the blank nanoparticles even after 36 h of incubation, indicating a good biocompatibility of the nanomedicine components in vitro. Due to their biocompatibility and ability to promote drug release and absorption at the biointerface, hybrid LCNs appear to be an ideal carrier for achieving nose-to-brain delivery of poorly water-soluble drugs such as SVT.

l-Glutamine supplementation enhances glutathione peroxidase and paraoxonase-1 activities in HDL of exercising older individuals

BACKGROUND

Oxidative stress is an important factor in the formation of atherosclerotic plaques. High-density lipoprotein (HDL) harbors paraoxonase-1 (PON-1) and glutathione peroxidase (GPx), key enzymes in the protection against the harmful effects of oxidative stress. Although exercise training can increase both HDL-c content and its antioxidant action, and glutamine (Gln) intake also promotes GPx-based defenses, the association between exercise training and Gln in the regulation of PON-1 activity was not explored. Therefore, the objective of this study was to investigate the effects of Gln supplementation on the redox balance and on the total HDL antioxidant capacity by evaluation of the activity of PON-1 and GPx enzymes in physically exercised elderly individuals compared to non-exercised ones.

METHODS

Fifty-one practitioners of a combined exercise training program (CET, age: 71.9 ± 5.7 years) and 32 non-practitioners (NP, age: 73 ± 6.3 years) participated in the study. CET and NP groups were separated into 2 subgroups according to the supplementation: Gln, 0.3 g/kg/day + 10 g maltodextrin (CET-Gln, n = 26; and NP-Gln, n = 16) or placebo, 10 g maltodextrin (CET-PL, n = 25; and NP-PL, n = 16). Blood samples were drawn at baseline and after 30 days after commencement of the supplementation for biochemical and enzyme activity analyses.

RESULTS

Increased HDL-c, total peroxidase (PRx), and GPx activities were found in both CET-Gln and NP-Gln after the supplementation period, compared to baseline, in opposition to CET-PL and NP-PL groups. PON-1 activity increased only in CET-Gln. In both CET-Gln and NP-Gln groups, there was a reduction of the total peroxides/PRx, iron/PRx, and total peroxides/GPX ratios after supplementation. In CET-Gln, thiobarbituric acid-reactive substances (TBARS)/PRx and TBARS/GPx ratios were also lower after supplementation. CET-Gln and CET-PL subgroups had lower glycemia than NP-Gln and NP-PL, either at baseline or after the supplementation periods. The other parameters were unchanged after supplementation [total cholesterol, LDL-c, triglycerides, non-HDL cholesterol, total peroxides, TBARS, iron serum, Trolox-equivalent antioxidant capacity (TEAC), and uric acid].

CONCLUSIONS

Gln supplementation can increase glutathione peroxidase activity regardless the individuals were physically active or sedentary, but the PON-1 activity only increased in physically active individuals. These results show the potential of Gln supplementation in the maintenance of the vascular redox balance, with potential implications for atherogenesis protection.

Role of Oxidative Damage in Alzheimer's Disease and Neurodegeneration: From Pathogenic Mechanisms to Biomarker Discovery

Alzheimer’s disease (AD) is a neurodegenerative disorder accounting for over 50% of all dementia patients and representing a leading cause of death worldwide for the global ageing population. The lack of effective treatments for overt AD urges the discovery of biomarkers for early diagnosis, i.e., in subjects with mild cognitive impairment (MCI) or prodromal AD. The brain is exposed to oxidative stress as levels of reactive oxygen species (ROS) are increased, whereas cellular antioxidant defenses are decreased. Increased ROS levels can damage cellular structures or molecules, leading to protein, lipid, DNA, or RNA oxidation. Oxidative damage is involved in the molecular mechanisms which link the accumulation of amyloid-β and neurofibrillary tangles, containing hyperphosphorylated tau, to microglia response. In this scenario, microglia are thought to play a crucial role not only in the early events of AD pathogenesis but also in the progression of the disease. This review will focus on oxidative damage products as possible peripheral biomarkers in AD and in the preclinical phases of the disease. Particular attention will be paid to biological fluids such as blood, CSF, urine, and saliva, and potential future use of molecules contained in such body fluids for early differential diagnosis and monitoring the disease course. We will also review the role of oxidative damage and microglia in the pathogenesis of AD and, more broadly, in neurodegeneration.

Long-Term Treatment of Cuban Policosanol Attenuates Abnormal Oxidative Stress and Inflammatory Response via Amyloid Plaques Reduction in 5xFAD Mice

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder resulting in cognitive decline or dementia, the number of patients with AD is continuously increasing. Although a lot of great progress has been made in research and development of AD therapeutics, there is no fundamental cure for this disease yet. This study demonstrated the memory-improving effects of Cuban policosanol (PCO) in 5xFAD mice, which is an animal model of AD. Following 4-months of treatment with PCO in 5xFAD mice, we found that the number of amyloid plaques decreased in the brain compared to the vehicle-treated 5xFAD mice. Long-term PCO treatment in 5xFAD mice resulted in the reduction of gliosis and abnormal inflammatory cytokines level (interleukin [IL]-1β, IL-6, and tumor necrosis factor [TNF]-α) in the cortex and hippocampus. Levels of lipid peroxide (4-hydroxynonenal [4-HNE]) and superoxide dismutase (SOD1 and SOD2) levels were also recoverd in the brains of PCO-treated 5xFAD mice. Notably, PCO administration reduced memory deficits in the passive avoidance test, as well as synaptic loss (PSD-95, synaptophysin) in 5xFAD mice. Collectively, we identified the potential effects of PCO as a useful supplement to delay or prevent AD progression by inhibiting the formation of Aβ plaques in the brain.

Serum Apo J as a potential marker of conversion from mild cognitive impairment to dementia

BACKGROUND

Apolipoprotein J (ApoJ) is present in both plasma and tissues, including brain. Growing evidence suggest that this protein may play an early role on the development of the two most common forms of dementia, Alzheimer's disease (AD) and vascular dementia (VD).

OBJECTIVE

To evaluate whether serum ApoJ levels might be able to predict the progression to AD, VD, or mixed dementia (AD&VD) in individuals with mild cognitive impairment (MCI).

METHODS

Serum ApoJ was measured in 196 MCI subjects (aged ≥60 years) with a median follow up of 2.9 years.

RESULTS

One hundred thirty-two of the enrolled MCI subjects converted to dementia. Among these, 45% developed AD, 33% mixed dementia, 13% VD (VD), and 9% other forms of dementia. A significant trend toward a progressive reduction in the incidence of dementia, regardless of the type, from tertile I (83.1%), to tertile II (63.1%), to tertile III (56.1%) was observed (p = 0.003). After adjustment for potential confounders, a twofold increase in the risk of conversion to dementia was found in subjects belonging to tertile I of Apo J compared with tertile III; the risk increased after two years of follow up, while no differences emerged within the first 2 years.

CONCLUSIONS

Our results suggest that in MCI subjects, low APOJ levels may be associated with increased risk of developing dementia.

Association between Serum Concentrations of Apolipoprotein A-I (ApoA-I) and Alzheimer's Disease: Systematic Review and Meta-Analysis

BACKGROUND

A wealth of experimental and epidemiological evidence suggest that Apolipoprotein A-I (ApoA-I), the main protein constituent of high-density lipoprotein (HDL), may protect against Alzheimer disease (AD). To investigate this potential role, we conducted a meta-analysis of the published studies on the relationship between serum ApoA-I and AD occurrence.

METHODS

We screened MEDLINE, EMBASE, Web of Science, and Scopus, for cross-sectional studies published from inception to 1 March 2021, comparing the ApoA-I serum levels between patients with AD and cognitively normal controls.

RESULTS

From an initial screening of 245 articles, 5 studies, including 397 AD patients (mean age 75.0 years, 234 females) and 367 controls (mean age 69.2 years, 182 females), met the inclusion criteria. Compared to healthy controls, AD subjects had a lower ApoA-I serum level. The pooled weighted mean difference from a random-effects model was -0.31 g/L (p < 0.0001) (95% Confidence Interval: [-0.62-0.01], with high heterogeneity (I2 = 100%). The Egger's test confirmed an absence of publication bias (t = 0.62, p = 0.576).

CONCLUSIONS

Our study showed that AD patients present lower serum levels of ApoA-I compared to cognitively normal individuals. Further studies on large population samples are required to support this finding.