Neuroinflammation: A Modifiable Pathway Linking Obesity, Alzheimer's disease, and Depression

Waist-to-weight index and cognitive impairment: Understanding the link through depression mediation in the NHANES

BACKGROUND

In recent years, several studies have suggested that obesity may play an important role in cognitive impairment. Individuals with cognitive impairment often also exhibit depressive symptoms. This study aimed to explore the association between obesity and cognitive impairment and to elucidate the mediating role of depressive symptoms in this association.

METHODS

Older participants in the U.S. were examined in this cross-sectional study (n = 2391). The WWI was computed as follows: WWI = waist circumference/square root of body weight. The Consortium for Alzheimer's Disease Word Learning (CERAD-WL), the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST) were used to evaluate cognitive function. Depression symptoms were evaluated with the Patient Health Questionnaire 9 (PHQ-9). Subgroup analysis and multiple logistic regression analysis were utilized to investigate the relationships between the WWI and depressive symptoms and cognitive decline. Threshold effects were computed using a two-segment linear regression model. To ascertain whether depression mediates the relationship between the WWI and cognitive impairment, mediation analysis was also employed.

RESULTS

A total of 2391 participants were included, 33.29 % of whom had cognitive impairment. There was a significant correlation between the WWI and depressive symptoms and cognitive function (P < 0.05). With increasing WWI quartiles, the prevalence of cognitive impairment increased (Q1: 27.09 %, Q2: 33.00 %, Q3: 31.44 %, Q4: 41.64 %). It was highly likely that the WWI and cognitive impairment were positively correlated (OR = 1.34, 95 % CI = 1.13, 1.59), and this link was steady across all subgroups (P for trend >0.05). A nonlinear curve with an inflection point of 10.71 connected the WWI and cognitive deterioration. A significant correlation was found between the WWI and cognitive impairment on the left side of the inflection point (OR = 3.58, 95 % CI = 1.57, 8.15). With a 5.4 % mediation rate, mediation analysis revealed that depressive symptoms mediated the relationship between cognitive impairment and the WWI.

CONCLUSIONS

There was a positive association between the WWI and the incidence of cognitive impairment in older Americans. Among other factors, depressive symptoms slightly mediated the association between the WWI and cognitive impairment. However, large-scale prospective studies are still needed to analyse the interactions between the three factors in depth.

Exploring the Interplay of Genetics and Nutrition in the Rising Epidemic of Obesity and Metabolic Diseases

Background: Obesity has become a significant global health issue. This multifaceted condition is influenced by genetic, environmental, and lifestyle factors, significantly influenced by nutrition. Aim: The study's objective is to elucidate the relationship between obesity-related genes, nutrient intake, and the development of obesity and the importance of other metabolic diseases. Methods: A comprehensive literature review spanning the past two decades was conducted to analyze the contributions of genetic variants-including FTO, MC4R, and LEPR-and their associations with dietary habits, highlighting how specific nutrients affect gene expression and obesity risk and how the coexistence of metabolic diseases such as type 2 diabetes and osteoporosis may modulate these factors. Moreover, the role of epigenetic factors, such as dietary patterns that encourage the development of obesity, was explored. Discussion and Conclusions: By understanding the intricate relationships among genetics, nutrients, and obesity development, this study highlights the importance of personalized dietary strategies in managing obesity. Overall, an integrated approach that considers genetic predispositions alongside environmental influences is essential for developing effective prevention and treatment methodologies, ultimately contributing to better health outcomes in diverse populations.

Microbiota-gut-brain axis in perioperative neurocognitive and depressive disorders: Pathogenesis to treatment

An increasing number of people undergo anesthesia and surgery. Perioperative neurocognitive and depressive disorders are common central nervous system complications with similar pathogeneses. These conditions pose a deleterious threat to human health and a significant societal burden. In recent years, numerous studies have focused on the role of the gut microbiota and its metabolites in the central nervous system via the gut-brain axis. Its involvement in perioperative neurocognitive and depressive disorders has attracted considerable attention. This review aimed to elucidate the role of the gut microbiota and its metabolites in the pathogenesis of perioperative neurocognitive and depressive disorders, as well as the value of targeted interventions and treatments.

Iron accumulation/overload and Alzheimer's disease risk factors in the precuneus region: A comprehensive narrative review

Alzheimer's disease (AD) is a neurodegenerative disease that is characterized by amyloid plaques, neurofibrillary tangles, and neuronal loss. Early cerebral and body iron dysregulation and accumulation interact with AD pathology, particularly in the precuneus, a crucial functional hub in cognitive functions. Quantitative susceptibility mapping (QSM), a novel post-processing approach, provides insights into tissue iron levels and cerebral oxygen metabolism and reveals abnormal iron accumulation early in AD. Increased iron deposition in the precuneus can lead to oxidative stress, neuroinflammation, and accelerated neurodegeneration. Metabolic disorders (diabetes, non-alcoholic fatty liver disease (NAFLD), and obesity), genetic factors, and small vessel pathology contribute to abnormal iron accumulation in the precuneus. Therefore, in line with the growing body of literature in the precuneus region of patients with AD, QSM as a neuroimaging method could serve as a non-invasive biomarker to track disease progression, complement other imaging modalities, and aid in early AD diagnosis and monitoring.

Withania somnifera (Ashwagandha) Improves Spatial Memory, Anxiety and Depressive-like Behavior in the 5xFAD Mouse Model of Alzheimer's Disease

Withania somnifera (WS), also known as ashwagandha, is a popular botanical supplement used to treat various conditions including memory loss, anxiety and depression. Previous studies from our group showed an aqueous extract of WS root (WSAq) enhances cognition and alleviates markers for depression in Drosophila. Here, we sought to confirm these effects in the 5xFAD mouse model of β-amyloid (Aβ) accumulation. Six- to seven-month-old male and female 5xFAD mice were treated with WSAq in their drinking water at 0 mg/mL, 0.5 mg/mL or 2.5 mg/mL for four weeks. In the fourth week of treatment, spatial memory, anxiety and depressive-like symptoms were evaluated. At the conclusion of behavioral testing, brain tissue was harvested, immunohistochemistry was performed, and the cortical expression of antioxidant response genes was evaluated. Both concentrations of WSAq improved spatial memory and reduced depressive and anxiety-related behavior. These improvements were accompanied by a reduction in Aβ plaque burden in the hippocampus and cortex and an attenuation of activation of microglia and astrocytes. Antioxidant response genes were upregulated in the cortex of WSAq-treated mice. Oral WSAq treatment could be beneficial as a therapeutic option in AD for improving disease pathology and behavioral symptoms. Future studies focused on dose optimization of WSAq administration and further assessment of the mechanisms by which WSAq elicits its beneficial effects will help inform the clinical potential of this promising botanical therapy.

Factors Associated with the Development of Depression and the Influence of Obesity on Depressive Disorders: A Narrative Review

Depression affects several aspects of life, including socioeconomic status, relationships, behavior, emotions, and overall health. The etiology of depression is complex and influenced by various factors, with obesity emerging as a significant contributor. This narrative review aims to investigate the factors associated with the development of depression, with a particular focus on the role of obesity. The literature search was conducted on PubMed, Embase, and PsycINFO from May to July 2024. The review highlights the impact of environmental and socioeconomic conditions; lifestyle choices, including physical activity and dietary habits; stress; traumatic experiences; neurotransmitter imbalances; medical and psychological conditions; hormone fluctuations; and epigenetic factors on depression. A key emphasis is placed on the inflammatory processes linked to obesity, which may drive the bidirectional relationship between obesity and depression. The findings suggest that obesity is associated with an increased risk of depression, potentially due to chronic inflammation, neurochemical dysregulation, and the emotional and social challenges related to weight stigma and obesity management. Understanding these interconnected factors is important for developing targeted interventions to address both obesity and depression, leading to improved quality of life for those affected.

Association between Life's Essential 8 and cognitive function among older adults in the United States

The American Heart Association (AHA) recently redefined cardiovascular health (CVH) with the introduction of Life's Essential 8 (LE8), which encompasses eight areas (diet, physical activity, nicotine exposure, sleep duration body mass index, non-HDL cholesterol, blood glucose, and blood pressure). This study aimed to explore the relationships between both the aggregate and individual CVH metrics, as defined by Life's Essential 8, and cognitive function in older adults in the United States. This cross-sectional, population-based study analyzed data from the National Health and Nutrition Examination Survey conducted between 2011 and 2014, focusing on individuals aged 60 years and older. CVH was categorized as low (0-49), moderate (50-79), or high (80-100). Cognitive function was assessed through the CERAD tests, Animal Fluency test, and Digit Symbol Substitution test. Multivariable logistic models and restricted cubic spline models were employed to investigate these associations. This study included a total of 2279 older adults in the United States. Only 11% of adults achieved a high total CVH score, while 12% had a low score. After further adjustment for potential confounding factors, higher LE8 scores were significantly associated with higher scores on CERAD: delayed recall score (0.02[0.01, 0.03]; P < 0.001), CERAD: total score (3 recall trials) (0.04[0.02, 0.06]; P < 0.001), animal fluency: total score (0.09[0.05, 0.12]; P < 0.001), and digit symbol: score (0.29[0.18, 0.41]; P < 0.001), demonstrating a linear dose-response relationship. Similar patterns were also observed in the associations between health behavior and health factor scores with cognitive function tests. LE8 scores exhibited positive linear associations with cognitive function. Maintaining better levels of CVH may be associated with higher levels of cognitive function in older Americans, but further research is needed to confirm the causal and temporal relationships between LE8 and cognitive function.

Psychiatric Disease as a Potential Risk Factor for Dementia: A Narrative Review

Neurodegenerative disease is a major global health problem with 150 million people predicted to have dementia by 2050. Genetic factors, environmental factors, demographics, and some diseases have been associated with dementia. In addition to associations between diseases such as hypertension and cerebrovascular disease and dementia, emerging findings associate some psychiatric disorders with incident dementia. Because of the high and increasing global prevalence of dementia and the high worldwide prevalence of psychiatric disorders, the primary objective of this narrative review was to evaluate published findings that evaluate the association between bipolar disorder, depression, anxiety, post-traumatic stress disorder, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism spectrum disorder, schizophrenia and other psychosis syndromes, and personality disorders and personality traits and incident dementia. Here, we highlight findings indicating possible associations between these psychiatric disorders and subsequent dementia and suggest that some psychiatric disorders may be risk factors for incident dementia. Further research, including more large longitudinal studies and additional meta-analyses, however, is needed to better characterize the associations between psychiatric disorders and incident dementia, to identify possible mechanisms for these putative associations, and to identify risk factors within psychiatric disorders that predispose some people with a psychiatric disorder but not others to subsequent dementia. Additional important questions concern how the treatment of psychiatric disorders might affect the risk of incident dementia.

Frequent Occurrence of Alzheimer Disease in Patients With IgE-mediated Allergies

Alzheimer disease and allergic diseases are common health problems. The aim of the study was to check the hypothesis that older patients with IgE-mediated allergies have a higher prevalence of Alzheimer disease. It was a retrospective, multicenter cohort observation. In total, 7129 people were examined, including 3566 women and 2558 men (mean 64.9±6.9 y). The diagnosis of Alzheimer disease is based on the ICD-10 code and appropriate medical documentation. The proportion of patients with confirmed Alzheimer disease in the group of patients with diagnosed allergy compared to the group of those without allergy was as follows: 13.9% (168) versus 8.2% (484) with P=0.001. There was a positive correlation between the presence of Alzheimer disease and high serum total IgE, eosinophilia, and asthma or the presence of atopic polymorphic disease (P<0.05). IgE-dependent allergic diseases, in particular allergic asthma, and the presence of high serum IgE levels may favor the development of Alzheimer disease.

Unveiling the Complex Role of Exosomes in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative illness, characterized by memory loss and cognitive decline, accounting for 60-80% of dementia cases. AD is characterized by senile plaques made up of amyloid β (Aβ) protein, intracellular neurofibrillary tangles caused by hyperphosphorylation of tau protein linked with microtubules, and neuronal loss. Currently, therapeutic treatments and nanotechnological developments are effective in treating the symptoms of AD, but a cure for the illness has not yet been found. Recently, the increased study of extracellular vesicles (EVs) has led to a growing awareness of their significant involvement in neurodegenerative disorders, including AD. Exosomes are small extracellular vesicles that transport various components including messenger RNAs, non-coding RNAs, proteins, lipids, DNA, and other bioactive compounds from one cell to another, facilitating information transmission and material movement. There is growing evidence indicating that exosomes have complex functions in AD. Exosomes may have a dual role in Alzheimer's disease by contributing to neuronal death and also helping to alleviate the pathological progression of the disease. Therefore, the primary aim of this review is to outline the updated understandings on exosomes biogenesis and many functions of exosomes in the generation, conveyance, distribution, and elimination of hazardous proteins related to Alzheimer's disease. This review is intended to provide novel insights for understanding the development, specific treatment, and early detection of Alzheimer's disease.

Gender differences in plasma S100B levels of patients with major depressive disorder

BACKGROUND

Low concentrations of S100B have neurotrophic effects and can promote nerve growth and repair, which plays an essential role in the pathophysiological and histopathological alterations of major depressive disorder (MDD) during disease development. Studies have shown that plasma S100B levels are altered in patients with MDD. In this study, we investigated whether the plasma S100B levels in MDD differ between genders.

METHODS

We studied 235 healthy controls (HCs) (90 males and 145 females) and 185 MDD patients (65 males and 120 females). Plasma S100B levels were detected via multifactor assay. The Mahalanobis distance method was used to detect the outliers of plasma S100B levels in the HC and MDD groups. The Kolmogorov-Smirnov test was used to test the normality of six groups of S100B samples. The Mann-Whitney test and Scheirer-Ray-Hare test were used for the comparison of S100B between diagnoses and genders, and the presence of a relationship between plasma S100B levels and demographic details or clinical traits was assessed using Spearman correlation analysis.

RESULTS

All individuals in the HC group had plasma S100B levels that were significantly greater than those in the MDD group. In the MDD group, males presented significantly higher plasma S100B levels than females. In the male group, the plasma S100B levels in the HC group were significantly higher than those in the MDD group, while in the female group, no significant difference was found between the HC and MDD groups. In the male MDD subgroup, there was a positive correlation between plasma S100B levels and years of education. In the female MDD subgroup, there were negative correlations between plasma S100B levels and age and suicidal ideation.

CONCLUSIONS

In summary, plasma S100B levels vary with gender and are decreased in MDD patients, which may be related to pathological alterations in glial cells.

Evaluation of daytime sleepiness and insomnia symptoms in OSA patients with a characterization of symptom-defined phenotypes and their involvement in depression comorbidity-a cross-sectional clinical study

Introduction

Recent research highlights the significance of insomnia and sleepiness, shifting from obstructive sleep apnea (OSA) severity and sleep structure, in defining OSA phenotypes.

Objectives

This study aimed to characterize insomnia and sleepiness associated with OSA phenotypes and assess their involvement in depression symptoms (DS) in OSA.

Materials and methods

This cross-sectional, clinical study included 181 participants who underwent polysomnography (PSG) and filled out questionnaires, including the Epworth Sleepiness Scale (ESS), Insomnia Severity Index (ISI), Pittsburgh Sleep Quality Index (PSQI), and Beck Depression Index (BDI). They were categorized into phenotypes: insomnia-sleepiness (I + S; ESS ≥ 11; ISI ≥ 15; n = 20), sleepiness (S; ESS ≥ 11; ISI < 15; n = 22), insomnia (I; ESS < 11; ISI ≥ 15), and asymptomatic (A; ESS < 11; ISI<15; n=55).

Results

A linear regression model for the BDI score (R2 = 0.357, p < 0.001) included ISI score and subjective-to-objective sleep latency ratio. The ISI score was a predictive factor for mild and moderate DS [OR = 1.23 (95% CI: 1.09-1.38), p < 0.001 and OR = 1.39 (95% CI: 1.13-1.72), p = 0.002]. The I and I + S phenotypes are characterized by higher BDI scores (p < 0.001 and p = 0.02), longer subjective sleep latency (p = 0.008 and p = 0.04), and shorter subjective total sleep time (TST; p = 0.049 and p = 0.006) compared to A. Furthermore, the I and I + S groups had shorter subjective TST than S (p = 0.03 and p = 0.047). The I and I + S had higher BDI scores than A (p < 0.001 and p = 0.02, respectively) and S (p < 0.001 and p = 0.02, respectively). The I phenotype was associated with the risk of mild and moderate DS (OR = 5.61 (95% CI: 1.91-16.53), p < 0.001 and OR = 9.55 (95% CI: 1.81-50.48), p = 0.008 respectively). Moreover, the I + S phenotype presented an even greater risk for mild DS (OR = 10.29 (95% CI: 2.95-35.85), p < 0.001).

Conclusion

Using clinical features for OSA phenotyping holds promise for finding OSA individuals with increased risk for DS occurrence.

A Cross-Sectional Study of Protein Changes Associated with Dementia in Non-Obese Weight Matched Women with and without Polycystic Ovary Syndrome

Dysregulated Alzheimer's disease (AD)-associated protein expression is reported in polycystic ovary syndrome (PCOS), paralleling the expression reported in type 2 diabetes (T2D). We hypothesized, however, that these proteins would not differ between women with non-obese and non-insulin resistant PCOS compared to matched control subjects. We measured plasma amyloid-related proteins levels (Amyloid-precursor protein (APP), alpha-synuclein (SNCA), amyloid P-component (APCS), Pappalysin (PAPPA), Microtubule-associated protein tau (MAPT), apolipoprotein E (apoE), apoE2, apoE3, apoE4, Serum amyloid A (SAA), Noggin (NOG) and apoA1) in weight and aged-matched non-obese PCOS (n = 24) and control (n = 24) women. Dementia-related proteins fibronectin (FN), FN1.3, FN1.4, Von Willebrand factor (VWF) and extracellular matrix protein 1 (ECM1) were also measured. Protein levels were determined by Slow Off-rate Modified Aptamer (SOMA)-scan plasma protein measurement. Only APCS differed between groups, being elevated in non-obese PCOS women (p = 0.03) relative to the non-obese control women. This differed markedly from the elevated APP, APCS, ApoE, FN, FN1.3, FN1.4 and VWF reported in obese women with PCOS. Non-obese, non-insulin resistant PCOS subjects have a lower AD-associated protein pattern risk profile versus obese insulin resistant PCOS women, and are not dissimilar to non-obese controls, indicating that lifestyle management to maintain optimal body weight could be beneficial to reduce the long-term AD-risk in women with PCOS.

Pros and Cons of APOE4 Homozygosity and Effects on Neuroplasticity, Malnutrition, and Infections in Early Life Adversity, Alzheimer's Disease, and Alzheimer's Prevention

Fortea et al.'s. (2024) recent data analysis elegantly calls attention to familial late-onset Alzheimer's disease (AD) with APOE4 homozygosity. The article by Grant (2024) reviews the factors associated with AD, particularly the APOE genotype and lifestyle, and the broad implications for prevention, both for individuals with the lifestyles associated with living in resource-rich countries and for those enduring environmental adversity in poverty settings, including high exposure to enteric pathogens and precarious access to healthcare. Grant discusses the issue of APOE genotype and its implications for the benefits of lifestyle modifications. This review highlights that bearing APOE4 could constitute an evolutionary benefit in coping with heavy enteric infections and malnutrition early in life in the critical formative first two years of brain development. However, the critical issue may be that this genotype could be a health concern under shifts in lifestyle and unhealthy diets during aging, leading to severe cognitive impairments and increased risk of AD. This commentary supports the discussions of Grant and the benefits of improving lifestyle for decreasing the risks for AD while providing further understanding and modelling of the early life benefits of APOE4 amidst adversity. This attention to the pathophysiology of AD should help further elucidate these critical, newly appreciated pathogenic pathways for developing approaches to the prevention and management in the context of the APOE genetic variations associated with AD.

Assessing the Global, Regional, and National Impact of High Body Mass Index on Alzheimer's Disease and Other Dementias Between 1990 and 2019

BACKGROUND

Obesity significantly increases Alzheimer's disease (AD) and dementia risk. Understanding the link between a high body mass index (BMI) and these conditions is crucial for effective management and prevention.

OBJECTIVE

We aimed to estimate the burden of AD and other dementias attributed to high BMI from 1990 to 2019 based on sex, age, and socio-demographic indicators (SDI) at global, regional, and national levels.

METHODS

We collected data on deaths, disability-adjusted life years (DALYs), age-standardized mortality rates (ASMR), and age-standardized DALY rates (ASDR) from the 2019 Global Burden of Disease study for AD and dementia attributed to high BMI. We explored the correlation between SDI levels and ASDR.

RESULTS

In 2019, there were 198,476.2 deaths (95% UI: 32,695.4-593,366.4) and 3,159,912.4 DALYs (848,330.5-8,042,531) attributed to high BMI. Numbers of deaths, DALYs, ASMR, and ASDR increased since 1990. Females had higher deaths, ASMR, and ASDR than males. Mortality and DALYs rates increased with age. ASMR and ASDR increased across five SDI levels, with the highest rise in Low-middle SDI. High-income North America had the most deaths [30,993.9 (5,101.7-89,912.9)], while North Africa and the Middle East had the highest ASMR [4.61 (0.79-13.64)] and ASDR [72.56 (20.98-181.16)] in 2019.

CONCLUSIONS

The burden of AD and other dementias attributed to high BMI increased since 1990 globally and is still heaviest in developed regions. Females accounted predominantly for the burden than males. Timely measures are needed to against high BMI.

A Brief History of the Progress in Our Understanding of Genetics and Lifestyle, Especially Diet, in the Risk of Alzheimer's Disease

The two major determining factors for Alzheimer's disease (AD) are genetics and lifestyle. Alleles of the apolipoprotein E (APOE) gene play important roles in the development of late-onset AD, with APOEɛ4 increasing risk, APOEɛ3 being neutral, and APOEɛ2 reducing risk. Several modifiable lifestyle factors have been studied in terms of how they can modify the risk of AD. Among these factors are dietary pattern, nutritional supplements such as omega-3 fatty acids, and B vitamins, physical exercise, and obesity, and vitamin D. The Western diet increases risk of AD, while dietary patterns such as the Mediterranean and vegetarian/vegan diets reduce risk. Foods associated with reduced risk include coffee, fruits and vegetables, whole grains and legumes, and fish, while meat and ultraprocessed foods are associated with increased risk, especially when they lead to obesity. In multi-country ecological studies, the amount of meat in the national diet has the highest correlation with risk of AD. The history of research regarding dietary patterns on risk of AD is emphasized in this review. The risk of AD can be modified starting at least by mid-life. People with greater genetic risk for AD would benefit more by choosing lifestyle factors to reduce and/or delay incidence of AD.

Simufilam Reverses Aberrant Receptor Interactions of Filamin A in Alzheimer's Disease

Simufilam is a novel oral drug candidate in Phase 3 clinical trials for Alzheimer's disease (AD) dementia. This small molecule binds an altered form of filamin A (FLNA) that occurs in AD. This drug action disrupts FLNA's aberrant linkage to the α7 nicotinic acetylcholine receptor (α7nAChR), thereby blocking soluble amyloid beta1-42 (Aβ42)'s signaling via α7nAChR that hyperphosphorylates tau. Here, we aimed to clarify simufilam's mechanism. We now show that simufilam reduced Aβ42 binding to α7nAChR with a 10-picomolar IC50 using time-resolved fluorescence resonance energy transfer (TR-FRET), a robust technology to detect highly sensitive molecular interactions. We also show that FLNA links to multiple inflammatory receptors in addition to Toll-like receptor 4 (TLR4) in postmortem human AD brains and in AD transgenic mice: TLR2, C-X-C chemokine receptor type 4 (CXCR4), C-C chemokine receptor type 5 (CCR5), and T-cell co-receptor cluster of differentiation 4 (CD4). These aberrant FLNA linkages, which can be induced in a healthy control brain by Aβ42 incubation, were disrupted by simufilam. Simufilam reduced inflammatory cytokine release from Aβ42-stimulated human astrocytes. In the AD transgenic mice, CCR5-G protein coupling was elevated, indicating persistent activation. Oral simufilam reduced both the FLNA-CCR5 linkage and the CCR5-G protein coupling in these mice, while restoring CCR5's responsivity to C-C chemokine ligand 3 (CCL3). By disrupting aberrant FLNA-receptor interactions critical to AD pathogenic pathways, simufilam may promote brain health.