Insulin and Insulin Resistance in Alzheimer's Disease

Type 2 Diabetes Mellitus Exacerbates Pathological Processes of Parkinson's Disease: Insights from Signaling Pathways Mediated by Insulin Receptors

Parkinson's disease (PD), a chronic and common neurodegenerative disease, is characterized by the progressive loss of dopaminergic neurons in the dense part of the substantia nigra and abnormal aggregation of alpha-synuclein. Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by chronic insulin resistance and deficiency in insulin secretion. Extensive evidence has confirmed shared pathogenic mechanisms underlying PD and T2DM, such as oxidative stress caused by insulin resistance, mitochondrial dysfunction, inflammation, and disorders of energy metabolism. Conventional drugs for treating T2DM, such as metformin and glucagon-like peptide-1 receptor agonists, affect nerve repair. Even drugs for treating PD, such as levodopa, can affect insulin secretion. This review summarizes the relationship between PD and T2DM and related therapeutic drugs from the perspective of insulin signaling pathways in the brain.

Multi-Ancestry Transcriptome-Wide Association Studies of Cognitive Function, White Matter Hyperintensity, and Alzheimer's Disease

Genetic variants increase the risk of neurocognitive disorders in later life, including vascular dementia (VaD) and Alzheimer's disease (AD), but the precise relationships between genetic risk factors and underlying disease etiologies are not well understood. Transcriptome-wide association studies (TWASs) can be leveraged to better characterize the genes and biological pathways underlying genetic influences on disease. To date, almost all existing TWASs on VaD and AD have been conducted using expression studies from individuals of a single genetic ancestry, primarily European. Using the joint likelihood-based inference framework in Multi-ancEstry TRanscriptOme-wide analysis (METRO), we leveraged gene expression data from European ancestry (EA) and African ancestry (AA) samples to identify genes associated with general cognitive function, white matter hyperintensity (WMH), and AD. Regions were fine-mapped using Fine-mapping Of CaUsal gene Sets (FOCUS). We identified 266, 23, 69, and 2 genes associated with general cognitive function, WMH, AD (using EA GWAS summary statistics), and AD (using AA GWAS), respectively (Bonferroni-corrected alpha = p < 2.9 × 10-6), some of which had been previously identified. Enrichment analysis showed that many of the identified genes were in pathways related to innate immunity, vascular dysfunction, and neuroinflammation. Further, the downregulation of ICA1L was associated with a higher WMH and with AD, indicating its potential contribution to overlapping AD and VaD neuropathology. To our knowledge, our study is the first TWAS on cognitive function and neurocognitive disorders that used expression mapping studies for multiple ancestries. This work may expand the benefits of TWASs beyond a single ancestry group and help to identify gene targets for pharmaceuticals or preventative treatments for dementia.

Role of acute exposure to environmental stressors in the gut-brain-periphery axis in the presence of cognitive resilience

Climate change-induced environmental stressors, including ambient particulate matter (PM2.5) and extreme heat stress (HS), pose serious health risks, particularly for neurodegenerative diseases. PM2.5 exacerbates cardiovascular and neurodegenerative conditions, while HS increases mortality and worsens air pollution. Combined exposure may amplify these effects, especially in vulnerable populations at risk for Alzheimer's disease (AD). In our experimental study using a mouse model of early-onset Alzheimer's disease (EOAD), we explored the combined effects of extreme weather conditions, particularly exposure to ambient PM2.5 and HS. Our research indicated that even short, repeated exposure to these environmental stressors disrupts brain energy metabolism and mitochondrial respiratory functions, which we found to be associated with altered hippocampal synaptic functions. Additionally, we find that key mechanisms associated with impaired intestinal permeability and gut dysbiosis are affected, supporting the hypothesis that exposure to climate change communication may also disrupt the gut-brain axis, as in part evidenced in our study by peripheral changes in immune and inflammatory signaling. Moreover, despite significant disruptions in metabolic and immune-inflammatory pathways, we observed no acceleration of cognitive decline in the young asymptomatic EOAD mice subjected to short, repeated exposure to extreme heat and environmental PM2.5. These findings highlight the potential role of climate change in promoting risk factors like neuroinflammation and gut-brain axis dysfunction due to gut microbiome dysbiosis in the onset and progression of AD, particularly in asymptomatic individuals at risk for developing the condition.

Microfluidics in neural extracellular vesicles characterization for early Alzheimer's disease diagnosis

Dementia is a general term for conditions impairing cognitive abilities including perception, reasoning, attention, judgment, memory, and daily brain function. Early diagnosis of Alzheimer's disease (AD), the most common form of dementia, using neural extracellular vesicles (nEVs) is the focus of the current study. These nEVs carry AD biomarkers including β-amyloid proteins and phosphorylated tau proteins. The novelty of this review lies in developing a microfluidic perspective by introducing the techniques using a microfluidic platform for early diagnosis of AD. A microfluidic device can detect small sample sizes with significantly low concentrations. These devices combine nEV isolation, enrichment, and detection, which makes them ideal candidates for early AD diagnosis.

Repurposing Drugs: A Promising Therapeutic Approach against Alzheimer's Disease

Alzheimer's disease (AD) is an insidious, irreversible, complex neurodegenerative disorder characterized by progressive cognitive decline and memory loss; affecting millions worldwide. Despite decades of research, no effective disease-modifying treatment exists. However, drug repurposing is a progressive step in identifying new therapeutic uses of existing drugs. It has emerged as a promising strategy in the quest to combat AD. Various classes of repurposed drugs, such as antidiabetic, antihypertensive, antimicrobial, and anti-inflammatory, have shown potential neuroprotective effects in preclinical and clinical studies. These drugs act by combating free radicals generation, neuroinflammation, amyloid-beta aggregation, and tau hyper-phosphorylation. Furthermore, repurposing offers several advantages, including reduced time and cost compared to de novo drug development. It holds immense promise as a complementary approach to traditional drug discovery. Future research efforts should focus on elucidating the underlying mechanisms of repurposed drugs in AD, optimizing drug combinations, and conducting large-scale clinical trials to validate their efficacy and safety profiles. This review overviews recent advancements and findings in preclinical and clinical fields of different repurposed drugs for AD treatment.

IRS gene polymorphisms in Turkish patients with late-onset Alzheimer's disease

BACKGROUND

Factors that cause changes in insulin signaling in the brain are thought to affect the synaptic plasticity and accelerate the process of brain aging and neurodegeneration. Insulin receptor substrate (IRS) molecules are key mediators in insulin signaling. The aim of the current study is to determine whether there is an association between IRS gene polymorphisms, which are critical for insulin signaling, and the late-onset Alzheimer's disease in Turkish patients.

METHODS AND RESULTS

Demographic and clinical characteristics of 115 patients with late-onset Alzheimer's disease (age of onset ≥ 65 years) and 107 age-matched control subjects were obtained. DNAs were isolated from patient and control groups, IRS-1 and IRS-2 gene polymorphisms were investigated and genotyped according to the PCR-RFLP method. No statistically significant difference was observed in the genotypes for IRS-1 Gly972Arg (rs1801278) (p = 0.499) and IRS-2 Gly1057Asp (rs1805097) polymorphism between late-onset Alzheimer's disease patients and controls (p = 0.658). However, when the compliance of IRS-2 polymorphism with Hardy- Weinberg distribution was tested, in the case-control comparison, G allele frequency of IRS-2 polymorphisms was significantly higher in the patient population than in the control group in the Turkish population of the Thrace region.

CONCLUSIONS

Despite the potential role of insulin resistance and hyperinsulinemia in the development of Alzheimer's disease, we did not find any association between polymorphism of the IRS-1 and IRS-2 genes and late-onset Alzheimer's disease. However, compared to the healthy subjects, Gly/Gly genotypes and the G allele in the IRS-2 were significantly more frequent in patients with late-onset Alzheimer's disease.

Lancao decoction in the treatment of alzheimer's disease via activating PI3K/AKT signaling to promote ERK involving in enhancing neuronal activities in the hippocampus

ETHNOPHARMACOLOGICAL RELEVANCE

Previous study has demonstrated lancao decoction (LC), a traditional Chinese medicine (TCM) fomula and recorded in "Huangdineijing", has a therapeutic effect on cognitive impairment (early clinical manifestations of alzheimer's disease (AD), which suggests that LC may have potential therapeutic advantages for AD. Whether LC has the therapeutic effect on AD and its potential mechanisms were still further indicated.

AIM OF THE STUDY

In this study, we aimed to uncover the potential advantage and neuronal mechanisms of LC in the treatment of AD in APP/PS1 mice in the hippocampus.

METHODS AND MATERIALS

We chose APP/PS1 mice to combing with behavioral tests including morris water maze (MWM) or y-maze to determine the role of LC in the therapeutic actions of AD. Network pharmacology was used to screen potential targets and pathways involving in LC's treatments of AD. Western blot was used to detect the phosphorylated expressions of proteins in hippocampus in APP/PS1 mice in the hippocampus. Pharmacological interventions were used to elucidate the relationship between the role of LC in the treatment of AD and the pathway, as well as the upstream and downstream interactions with neuronal activities.

RESULTS

According to our previous LC effective dose (2.5 g/kg), the dose was also able to significantly reduce the latency to the platform, and significantly increase the number of crossing times and time spend in the target quadrant in APP/PS1 mice in MWM, which was consistent with donepezil (DON) after 14 days chronic treatments. Network pharmacology showed that PI3K/AKT and MAPK pathways were closely associated with LC's treatments of AD, and protein autophosphorylation played a role in this process. The phosphorylated expressions of PI3K and AKT were obviously reduced in APP/PS1 mice in the hippocampus, which were both reversed by LC or DON. The phosphorylated expressions of MAPK including P38, JNK and ERK were also significantly reduced in APP/PS1 mice hippocampus, but only the phosphorylated expression of ERK was reversed by LC or DON. Inhibiting the activities of PI3K/AKT pathway by LY294002 blocked LC's improvement of behavioral deficits in APP/PS1 mice, including reducing latency to platform and increasing the number of crossings time in MWM in APP/PS1 mice, which also blunted LC's up-regulated phosphorylated expressions of PI3K, AKT and ERK in the hippocampus. Moreover, suppressing the activities of ERK by PD98059 also blocked LC's improvement of AD-related behavioral deficits including decreasing latency to new arm and increasing time in new arm in y-maze test, which also inhibited LC's enhancement of synaptic proteins (PSD95 and synapsin1) in the hippocampus and the number of EGR1-positive cells in the hippocampal dentate gyrus (DG).

CONCLUSIONS

Take together, our study revealed that LC had the therapeutic effects on AD by activating the PI3K/AKT pathway to enhance ERK activity and further strengthened neuronal activities in the hippocampus.

Metabolic Signature of Insulin Resistance and Risk of Alzheimer's Disease

BACKGROUND

Substantial evidence supports the relationship between peripheral insulin resistance (IR) and the development of Alzheimer's disease (AD)-dementia. However, the mechanisms explaining these associations are only partly understood. We aimed to identify a metabolic signature of IR associated with the progression from mild cognitive impairment (MCI) to AD-dementia.

METHODS

This is a case-control study on 400 MCI subjects, free of type 2 diabetes, within the ACE cohort, including individuals ATN + and ATN-. After a median of 2.1 years of follow-up, 142 subjects converted to AD-dementia. IR was assessed using the homeostasis model assessment for insulin resistance (HOMA-IR). A targeted multiplatform approach profiled over 600 plasma metabolites. Elastic net penalized linear regression with 10-fold cross-validation was employed to select those metabolites associated with HOMA-IR. The prediction ability of the signature was assessed using support vector machine and performance metrics. The metabolic signature was associated with AD-dementia risk using a multivariable Cox regression model. Using counterfactual-based mediation analysis, we investigated the mediation role of the metabolic signature between HOMA-IR and AD-dementia. The metabolic pathways in which the metabolites were involved were identified using MetaboAnalyst.

RESULTS

The metabolic signature comprised 18 metabolites correlated with HOMA-IR. After adjustments by confounders, the signature was associated with increased AD-dementia risk (HR = 1.234; 95% CI = 1.019-1.494; p < .05). The metabolic signature mediated 35% of the total effect of HOMA-IR on AD-dementia risk. Significant metabolic pathways were related to glycerophospholipid and tyrosine metabolism.

CONCLUSIONS

We have identified a blood-based metabolic signature that reflects IR and may enhance our understanding of the biological mechanisms through which IR affects AD-dementia.

Metabolic Syndrome and the Risk of Alzheimer's Disease: A Meta-Analysis

Purpose: The relationship between metabolic syndrome (MetS) and the risk of Alzheimer's disease (AD) remains unclear. This meta-analysis aims to clarify the prospective association between MetS and AD risk and to explore how individual MetS components contribute to this relationship. Methods: Comprehensive searches of MEDLINE, Web of Science, and Embase were conducted up to April 12, 2024. Relevant prospective cohort studies were included. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated to assess the associations. A random-effects model was used to incorporate the potential impact of heterogeneity. Findings: Six prospective cohort studies with seven datasets, including 484,994 participants and a follow-up of 3.5 to 13.0 years, were included. The pooled analysis showed no significant association between MetS and AD risk (HR: 0.96, 95% CI: 0.89-1.04, P = 0.37; I2 = 0%). Sensitivity and subgroup analyses confirmed these findings. Individual MetS components exhibited varied effects as follows: abdominal obesity was linked to a reduced AD risk (Risk ratio (RR): 0.70, 95% CI: 0.56-0.88, P = 0.002), whereas high blood pressure (BP) (RR: 1.15, 95% CI: 1.04-1.27, P = 0.007) and hyperglycemia (RR: 1.24, 95% CI: 1.08-1.42, P = 0.002) were associated with an increased risk. Low high-density lipoprotein cholesterol and high triglycerides showed no significant associations. Conclusions: This meta-analysis found no significant overall association between MetS and AD risk. However, specific MetS components, such as abdominal obesity, high BP, and hyperglycemia, may influence AD risk differently.

Neuron-derived extracellular vesicles as a liquid biopsy for brain insulin dysregulation in Alzheimer's disease and related disorders

Extracellular vesicles (EVs) have emerged as novel blood-based biomarkers for various pathologies. The development of methods to enrich cell-specific EVs from biofluids has enabled us to monitor difficult-to-access organs, such as the brain, in real time without disrupting their function, thus serving as liquid biopsy. Burgeoning evidence indicates that the contents of neuron-derived EVs (NDEs) in blood reveal dynamic alterations that occur during neurodegenerative pathogenesis, including Alzheimer's disease (AD), reflecting a disease-specific molecular signature. Among these AD-specific molecular changes is brain insulin-signaling dysregulation, which cannot be assessed clinically in a living patient and remains an unexplained co-occurrence during AD pathogenesis. This review is focused on delineating how NDEs in the blood may begin to close the gap between identifying molecular changes associated with brain insulin dysregulation reliably in living patients and its connection to AD. This approach could lead to the identification of novel early and less-invasive diagnostic molecular biomarkers for AD. HIGHLIGHTS: Neuron-derived extracellular vesicles (NDEs) could be isolated from peripheral blood. NDEs in blood reflect the molecular signature of Alzheimer's disease (AD). Brain insulin-signaling dysregulation plays a critical role in AD. NDEs in blood could predict brain insulin-signaling dysregulation. NDEs offer novel early and less-invasive diagnostic biomarkers for AD.

Insulin signaling and oxidative stress: Bridging the gap between type 2 diabetes mellitus and Alzheimer's disease

BACKGROUND

Type 2 diabetes mellitus (T2D) and Alzheimer's disease (AD) are two prevalent chronic diseases that pose significant global health challenges. Increasing evidence suggests a complex bidirectional relationship between these conditions, where T2D elevates the risk of AD, and AD exacerbates glucose metabolism abnormalities in T2D.

OBJECTIVE

This review explores the molecular mechanisms linking T2D and AD, focusing on the role of insulin signaling pathways and oxidative stress.

METHODS

A comprehensive literature search from PubMed, Web of Science, and other relevant databases was conducted and analyzed.

RESULTS

Insulin resistance in T2D leads to impaired insulin signaling in the brain, contributing to cognitive decline and the development of AD. Hyperglycemia-induced oxidative stress exacerbates neuronal damage, promoting the formation of amyloid-β plaques and neurofibrillary tangles characteristic of AD. Clinically antidiabetic drugs such as metformin show potential against AD in preclinical studies; Many natural products such as Dendrobium nobile Lindl. have anti-T2D efficacy and are also effective against AD in various in vivo and in vitro models.

CONCLUSIONS

Improving insulin resistance and reducing oxidative stress are important strategies in the treatment of T2D and AD. To understand the bridging role of insulin singling and oxidative stress in T2D and AD will provide insights and broader applications in alleviating T2D and AD.

Association between the triglyceride glucose-body mass index and memory-related diseases: A nationwide cohort study

OBJECTIVES

This study aimed to examine the longitudinal association between the triglyceride glucose-body mass index (TyG-BMI) index and memory-related diseases (MDs) among Chinese adults.

STUDY DESIGN

Nationwide cohort study.

METHODS

Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS), which is an ongoing nationally representative prospective cohort study. The exposure was the participants' TyG-BMI index at baseline from 2011 to 2012. MDs were acquired by self-reporting questions in 2018. Cox proportional hazards regression models were conducted to assess the relationship between the TyG-BMI index and MDs.

RESULTS

During a median follow-up of 7.0 years, a total of 197 incident MDs events occurred. After multivariate adjustments for established MD-related risk factors, participants with the highest tertile of the TyG-BMI index had a higher risk of MDs (HR: 1.65; 95 % CI: 1.02-2.09; P-trend <0.001) relative to individuals with the lowest tertile. Furthermore, the subgroup analyses of the association remained consistent.

CONCLUSION

A high TyG-BMI index was associated with an increased risk of MDs. Our study suggests that monitoring long-term changes in the TyG-BMI index could assist with the early identification and prevention of MDs among individuals at high risk.

Nutrition: A non-negligible factor in the pathogenesis and treatment of Alzheimer's disease

Alzheimer's disease (AD) is a degenerative disease characterized by progressive cognitive dysfunction. The strong link between nutrition and the occurrence and progression of AD pathology has been well documented. Poor nutritional status accelerates AD progress by potentially aggravating amyloid beta (Aβ) and tau deposition, exacerbating oxidative stress response, modulating the microbiota-gut-brain axis, and disrupting blood-brain barrier function. The advanced stage of AD tends to lead to malnutrition due to cognitive impairments, sensory dysfunctions, brain atrophy, and behavioral and psychological symptoms of dementia (BPSD). This, in turn, produces a vicious cycle between malnutrition and AD. This review discusses how nutritional factors and AD deteriorate each other from the early stage of AD to the terminal stages of AD, focusing on the potential of different levels of nutritional factors, ranging from micronutrients to diet patterns. This review provides novel insights into reducing the risk of AD, delaying its progression, and improving prognosis. HIGHLIGHTS: Two-fifths of Alzheimer's disease (AD) cases worldwide have been attributed to potentially modifiable risk factors. Up to ≈26% of community-dwelling patients with AD are malnourished, compared to 7%∼76% of institutionalized patients. Undernutrition effects the onset, progression, and prognosis of AD through multiple mechanisms. Various levels of nutritional supports were confirmed to be protective factors for AD via specific mechanisms.

Inflammatory signaling pathways in Alzheimer's disease: Mechanistic insights and possible therapeutic interventions

The complex pathophysiology of Alzheimer's disease (AD) poses challenges for the development of therapies. Recently, neuroinflammation has been identified as a key pathogenic mechanism underlying AD, while inflammation has emerged as a possible target for the management and prevention of AD. Several prior studies have demonstrated that medications modulating neuroinflammation might lessen AD symptoms, mostly by controlling neuroinflammatory signaling pathways such as the NF-κB, MAPK, NLRP3, etc, and their respective signaling cascade. Moreover, targeting these inflammatory modalities with inhibitors, natural products, and metabolites has been the subject of intensive research because of their anti-inflammatory characteristics, with many studies demonstrating noteworthy pharmacological capabilities and potential clinical applications. Therefore, targeting inflammation is considered a promising strategy for treating AD. This review comprehensively elucidates the neuroinflammatory mechanisms underlying AD progression and the beneficial effects of inhibitors, natural products, and metabolites in AD treatment.

Unveiling FOXO3's metabolic contribution to menopause and Alzheimer's disease

The increasing prevalence of Alzheimer's disease (AD) calls for a comprehensive exploration of its complex etiology, with a focus on sex-specific vulnerability, particularly the heightened susceptibility observed in postmenopausal women. Neurometabolic alterations during the endocrine transition emerge as early indicators of AD pathology, including reduced glucose metabolism and increased amyloid-beta (Aβ) deposition. The fluctuating endocrine environment, marked by declining estradiol levels and reduced estrogen receptor beta (ERβ) activity, further exacerbates this process. In this context, here we explore the potential of forkhead box O3 (FOXO3) as a critical mediator linking metabolic disturbances to hormonal decline. We propose that FOXO3 plays a key role in the intersection of menopause and AD, given its dysregulation in both AD patients and postmenopausal women, modulating cellular metabolism through interactions with the AMPK/AKT/PI3K pathways. This relationship highlights the intersection between hormonal changes and increased AD susceptibility. This review aims to open a discussion on FOXO3's contribution to the metabolic dysregulation seen in menopause and its impact on the progression of AD. Understanding the functional role of FOXO3 in menopause-associated metabolic changes could lead to targeted therapeutic strategies, offering novel insights for managing for this condition.

Evidence from NHANES 2011-2014: a correlation between the weight-adjusted-waist index and cognitive abilities in the United States

Background

Obesity exerts a significant detrimental impact on cognitive function. The weight-adjusted waist index (WWI) serves as a more precise indicator of visceral obesity that is independent of weight, in contrast to body mass index (BMI). Still, little research has been conducted on the interrelation between WWI and cognitive abilities. This investigation explored the link between WWI and older Americans' cognitive function.

Methods

Utilizing data from the 2011-2014 National Health and Nutrition Examination Cross-Sectional Survey, multiple linear regression analysis was used to assess the influence of WWI on cognitive abilities in those over 60. Three cognitive assessments were administered: the Animal Fluency Test (AFT), the Digit Symbol Substitution Test (DSST), and the Word Learning and Recall Module from the Coalition to Establish a Registry for Alzheimer's Disease (CERAD). We implemented threshold effects analysis and smoothed curve fitting to elucidate the nonlinear relationship. Additionally, we analyzed subgroups to check for variability.

Results

There were 2,762 participants, including1,504 (54.45%) females and 1,258 (45.55%) males. 53.77% of them had completed high school or above, and their average age was 69.05 ± 6.62. After controlling for confounding variables, the improved model predicted a negative connection between WWI and CERAD-Total, AFT, and DSST scores (all p < 0.05). Furthermore, we performed a smoothenable curve fitting between WWI and cognitive function scores, resulting in a nonlinear connection and a threshold saturation effect. We also executed subgroup analyses and interaction tests based on gender, race, educational background, marital status, diabetes, body mass index, alcohol consumption, hypertension, smoking habits, stroke, depression, and sleep quality to assess whether the relationship between WWI and cognitive function was affected by heterogeneity across different population segments. The subgroup analysis found no significant differences in cognitive performance associated with WWI across the various subgroups.

Conclusion

Higher WWI levels are associated with impaired cognitive function in Americans aged 60 and older.

Association between domain-specific physical activity and triglyceride‑glucose (TyG) index among US adults: Evidence from NHANES 2007-2018

OBJECTIVES

The triglyceride-glucose (TyG) index is not only a reliable marker for insulin resistance, but also has broad applications in assessing the risk of various diseases, including cardiovascular disease, stroke, depression, and Alzheimer's disease. The study aims to investigate the relationship between domain-specific moderate- or vigorous-intensity physical activity (MVPA) and TyG index among US adults.

METHODS

The participants from the US National Health and Nutrition Examination Survey (NHANES) (2007-2018) were included. Different PA domains, including occupation-related MVPA (O-MVPA), transportation-related MVPA (T-MVPA), and leisure-time MVPA (LT-MVPA), were assessed by the Global Physical Activity Questionnaire. Weighted multivariable linear regression and the propensity score matching (PSM) method were used to determine the relationship between domain-specific MVPA and TyG index. Furthermore, stratified and mediation analyses were employed to assess the potential effect modifications and mediators on the association.

RESULTS

A total of 12,069 participants were included. The participants had a weighted mean age of 47.43 ± 16.91 years and a weighted mean TyG index of 8.58 ± 0.67. Weighted multivariable linear regression showed that leisure-time MVPA (LT-MVPA), whether at any amount or achieving physical activity guidelines, was negatively associated with TyG index (β = -0.10, 95%CI: -0.13- -0.07, P < 0.001, and β = -0.13, 95%CI: -0.17- -0.10, P < 0.001, respectively). O-MVPA and T-MVPA were not correlated with the TyG index, even at the recommended amount (β = 0.01, 95%CI: -0.02-0.03, P = 0.59 for O-MVPA, and β = -0.02, 95%CI: -0.07-0.02, P = 0.32 for T-MVPA). After PSM, the results were still robust. Furthermore, the stratified analysis found that the correlation between LT-MVPA and TyG index was stronger in females, those with higher family incomes, and non-smokers. Finally, mediation analyses indicated a significant joint mediation effect of BMI on the relationships between LT-MVPA (≥ 150 min/week) and the TyG index, accounting for 31.48% of the total effect.

CONCLUSIONS

LT-MVPA was associated with a decreased TyG index in US adults, while no such association was observed with O-MVPA or T-MVPA. Specific recommendations for PA categories should be provided, especially for populations at risk of diseases linked to a high TyG index or insulin resistance.

Diabetes-related cognitive impairment: Mechanisms, symptoms, and treatments

Background

Diabetes-related cognitive impairment is increasingly recognized as a significant complication, profoundly impacting patients' quality of life. This review aims to examine the pathophysiological mechanisms, clinical manifestations, risk factors, assessment and diagnosis, management strategies, and future research directions of cognitive impairment in diabetes.

Methodology

A comprehensive literature search was conducted using PubMed, Medline, and other medical databases to identify, review, and evaluate published articles on cognitive impairment in diabetes. The search focused on studies examining pathophysiology, clinical presentations, risk factors, diagnostic approaches, and management strategies.

Results

The review of current literature revealed that chronic hyperglycemia, insulin resistance, and vascular factors are major contributing factors to cognitive deficits in diabetes. Clinical manifestations include impairments in attention, memory, executive function, visuospatial abilities, and language. Risk factors encompass disease duration, glycemic control, presence of complications, age, education level, and comorbidities. Assessment tools include cognitive screening instruments, neuropsychological testing, and neuroimaging techniques. Management strategies involve glycemic control optimization, lifestyle modifications, cognitive training, and pharmacological interventions.

Conclusion

This review highlights the significant prevalence and impact of cognitive impairment in diabetes, resulting from complex metabolic and vascular disturbances. Early detection and multifaceted interventions are crucial for preserving cognitive function and improving patient outcomes. Future research should focus on neuroprotective strategies, biomarker identification, and personalized approaches. Collaborative efforts between clinicians and researchers are essential to effectively address this growing healthcare challenge and enhance the quality of life for individuals with diabetes-related cognitive impairment.

Two- and Three-Dimensional In Vitro Models of Parkinson's and Alzheimer's Diseases: State-of-the-Art and Applications

In vitro models play a pivotal role in advancing our understanding of neurodegenerative diseases (NDs) such as Parkinson's and Alzheimer's disease (PD and AD). Traditionally, 2D cell cultures have been instrumental in elucidating the cellular mechanisms underlying these diseases. Cultured cells derived from patients or animal models provide valuable insights into the pathological processes at the cellular level. However, they often lack the native tissue environment complexity, limiting their ability to fully recapitulate their features. In contrast, 3D models offer a more physiologically relevant platform by mimicking the 3D brain tissue architecture. These models can incorporate multiple cell types, including neurons, astrocytes, and microglia, creating a microenvironment that closely resembles the brain's complexity. Bioengineering approaches allow researchers to better replicate cell-cell interactions, neuronal connectivity, and disease-related phenotypes. Both 2D and 3D models have their advantages and limitations. While 2D cultures provide simplicity and scalability for high-throughput screening and basic processes, 3D models offer enhanced physiological relevance and better replicate disease phenotypes. Integrating findings from both model systems can provide a better understanding of NDs, ultimately aiding in the development of novel therapeutic strategies. Here, we review existing 2D and 3D in vitro models for the study of PD and AD.

Associations Between Diabetes Mellitus and Neurodegenerative Diseases

Diabetes mellitus (DM) and neurodegenerative diseases/disturbances are worldwide health problems. The most common chronic conditions diagnosed in persons 60 years and older are type 2 diabetes mellitus (T2DM) and cognitive impairment. It was found that diabetes mellitus is a major risk for cognitive decline, dementia, Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and other neurodegenerative disorders. Different mechanisms of associations between these diseases and diabetes mellitus have been suggested. For example, it is postulated that an impaired intracellular insulin signaling pathway, together with hyperglycemia and hyperinsulinemia, may cause pathological changes, such as dysfunction of the mitochondria, oxidative stress inflammatory responses, etc. The association between diabetes mellitus and neurodegenerative diseases, as well as the mechanisms of these associations, needs further investigation. The aim of this review is to describe the associations between diabetes mellitus, especially type 1 (T1DM) and type 2 diabetes mellitus, and selected neurodegenerative diseases, i.e., Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. Suggested mechanisms of these associations are also described.

AdipoRon's Impact on Alzheimer's Disease-A Systematic Review and Meta-Analysis

Alzheimer's disease (AD) remains a leading cause of cognitive decline and mortality worldwide, characterized by neurodegeneration, synaptic deficiencies, and neuroinflammation. Despite advancements in early detection, diagnosis, and treatment, AD presents substantial challenges due to its complex pathology, heterogeneity, and the limited efficacy of current therapies. Consequently, there is a pressing need for novel therapeutic agents to target the multifaceted aspects of AD pathology, enhance current treatments, and minimize adverse effects. AdipoRon, an adiponectin receptor agonist, has garnered interest for its potential neuroprotective effects, including reducing neuroinflammation, improving mitochondrial function, and mitigating tau hyperphosphorylation. This review aimed to evaluate the effects of AdipoRon-based adiponectin replacement therapy against AD, using a comprehensive approach grounded in the PICO framework-Population, Intervention, Comparison, and Outcomes. A total of six studies were reviewed, including in vitro and in vivo investigations examining AdipoRon's impact on various AD models. These studies involved different cell lines and transgenic mouse models, assessing various outcomes such as cognitive function, neuroinflammation, tau phosphorylation, synaptic deficiencies, and relevant molecular pathways. By synthesizing data from these studies, our review thoroughly explains AdipoRon's neuroprotective effects, mechanisms of action, and potential as a therapeutic agent for AD. This analysis aims to highlight the current state of knowledge, identify gaps in the research, and suggest directions for future studies and clinical applications.

Insulin potential in preventing brain damage after traumatic brain injury: What we know

Traumatic brain injury (TBI) is a major global cause of disability and mortality. TBI results in a spectrum of primary and secondary injuries that impact neural function and overall survival. Insulin, beyond its well-known role in regulating blood glucose levels, plays critical roles in the central nervous system (CNS). These roles include the modulation of synaptic plasticity, neurotransmitter levels, neurogenesis, and neuroprotection. Central insulin resistance, a reduced sensitivity to insulin in the brain, has been observed in TBI patients. This insulin resistance impairs insulin function in the brain and increases the risk of neurodegenerative processes. This review will delve into the central role of insulin resistance in the pathological changes observed after TBI and explore the potential benefits of insulin therapy as a treatment approach for TBI.

The Gut Microbiota-Brain Axis: A New Frontier in Alzheimer's Disease Pathology

Dr. Aloysius Alzheimer, a German neuropathologist and psychiatrist, recognized the primary instance of Alzheimer's disease (AD) for a millennium, and this ailment, along with its related dementias, remains a severe overall community issue related to health. Nearly fifty million individuals worldwide suffer from dementia, with Alzheimer's illness contributing to between 60 and 70% of the instances, estimated through the World Health Organization. In addition, 82 million individuals are anticipated to be affected by the global dementia epidemic by 2030 and 152 million by 2050. Furthermore, age, environmental circumstances, and inherited variables all increase the likelihood of acquiring neurodegenerative illnesses. Most recent pharmacological treatments are found in original hypotheses of disease, which include cholinergic (drugs that show affective cholinergic system availability) as well as amyloid-accumulation (a single drug is an antagonist receptor of Nmethyl D-aspartate). In 2020, the FDA provided approval on anti-amyloid drugs. According to mounting scientific data, this gut microbiota affects healthy physiological homeostasis and has a role in the etiology of conditions that range between obesity and neurodegenerative disorders like Alzheimer's. The microbiota-gut-brain axis might facilitate interconnection among gut microbes as well as the central nervous system (CNS). Interaction among the microbiota-gut system as well as the brain occurs through the "two-way" microbiota-gut-brain axis. Along this axis, the stomach as well as the brain develop physiologically and take on their final forms. This contact is constant and is mediated by numerous microbiota-derived products. The gut microbiota, for instance, can act as non-genetic markers to set a threshold for maintaining homeostasis or getting ill. The scientific community has conducted research and found that bowel dysbiosis and gastrointestinal tract dysregulation frequently occur in Alzheimer's disease (AD) patients. In this review, the effects of the microbiota- gut-brain axis on AD pathogenesis will be discussed.

Therapeutic impact of a benzofuran derivative on Aluminium chloride-induced Alzheimer's disease-like neurotoxicity in rats via modulating apoptotic and Insulin 1 genes

Neurodegenerative disorders such as Alzheimer's disease (AD) are age-related and are fatal in advanced cases. There is a limited efficacy of drugs used for the management of these diseases. Herein, the neurotherapeutic efficacy of a benzofuran-derivative-7 (BF-7) was investigated. Aluminum chloride (AlCl3) was employed to induce AD-like brain toxicity in rats. The rats were divided into four groups: Negative control, AlCl3-induced AD rats (100 mg/kg body weight, orally), AlCl3-AD induced rats treated with BF-7 (10 mg/kg body weight, orally), AlCl3-AD-induced rats treated with the standard drug "Donepezil" (10 mg/kg body weight, orally). The behavioral performance was tested using a beam-balance test. Brain and serum acetylcholinesterase (AChE) activities and the brain levels of norepinephrine, dopamine (DA), and serotonin (5-HT) were measured. The genetic expression of Bcl-2, Bax, caspase-3, and insulin 1 were assayed. The histopathological imaging and the immunohistochemical evaluation of Glial Fibrillary Acidic Protein (GFAP) were investigated in the cerebral cortex. Treatment of AD-rats with BF-7 mitigated AlCl3-induced neurotoxicity by improving motor functions, counteracting apoptosis, and exerting cholinergic functions. In addition, the genetic expression of Insulin 1 was upregulated significantly in AD-induced rats treated with BF-7. This compound could be used as a promising candidate for neurotherapeutic drug discovery against AD or any other toxic brain disorders.

Studying targeted oxidation in diabetic cognitive dysfunction based on scientometrics analysis: research progress of natural product approaches

Purpose

The aim is to provide new insights for researchers studying the pathogenesis of diabetic cognitive dysfunction and promoting the wider use of natural products in their treatment.

Method

First, the Web of Science Core Collection was selected as the data source for a computerized literature search on oxidative stress and diabetic cognitive dysfunction (DCD). Next, Biblimetrix and VOSviewer performed statistical analysis focusing on publication countries, institutions, authors, research hotspots, and emerging directions in the field. Then, through the analysis of keywords and key articles, the forefront of the field is identified. Finally, we discussed the pathogenesis of DCD, the influence of oxidative stress on DCD and the antioxidant effect of natural products on DCD.

Result

293 valid papers were obtained. Bibliometrics showed that oxidative stress, diabetes, Alzheimer's disease (AD), cognitive decline, insulin resistance and quercetin were the key words of the symbiotic network.

Conclusion

The antioxidant effects of natural products in improving DCD have been extensively studied in preclinical studies, providing potential for their treatment in DCD, but their evaluation in clinical trials is currently uncommon.

Dysregulation of energy metabolism in Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. Its etiology and associated mechanisms are still unclear, which largely hinders the development of AD treatment strategies. Many studies have shown that dysregulation of energy metabolism in the brain of AD is closely related to disease development. Dysregulation of brain energy metabolism in AD brain is associated with reduced glucose uptake and utilization, altered insulin signaling pathways, and mitochondrial dysfunction. In this study, we summarized the relevant pathways and mechanisms regarding the dysregulation of energy metabolism in AD. In addition, we highlight the possible role of mitochondrial dysfunction as a central role in the AD process. A deeper understanding of the relationship between energy metabolism dysregulation and AD may provide new insights for understanding learning memory impairment in AD patients and in improving AD prevention and treatment.

Lifestyle empowerment for Alzheimer's prevention prescribed by physicians: Methods and adaptations to COVID-19

The health care system is insufficiently capitalizing on the benefits of physical exercise in America's aging population. Few tools exist to help clinicians incorporate physical activity into their clinical care, and barriers limit older adults from initiating and maintaining exercise programs. The Lifestyle Empowerment for Alzheimer's Prevention (LEAP! Rx) Program has been designed to support providers and participants in lifestyle change. LEAP! Rx uses two forms of participant enrollment: physician referrals through electronic health records and self-referrals to test the efficacy of delivering a community-based exercise and healthy lifestyle program to older adults. After referral into the program, participants are randomized to receive the LEAP! Rx Program or are placed in a standard-of-care group to receive the program later. The LEAP! Rx program consists of a personalized and structured exercise program, lifestyle education, and mobile health monitoring. This includes a 12-week Empowerment phase with coaching and supervised exercise training, followed by a 40-week Lifestyle phase with intermittent supervised exercise and coaching. Lifestyle education includes monthly, evidence-based classes on optimal aging. The evaluation of LEAP! Rx focuses on 1) the assessment of implementation and scalability of the LEAP!Rx Program for clinicians and patients 2) the effect of the LEAP! Rx Program on cardiorespiratory fitness, 3) the impact of the LEAP! Rx Program on secondary intervention outcome measures of chronic disease risk factors, including insulin resistance, body composition, and lipids. If successful, this study's findings could advance future healthcare practices, providing a new and practical approach to aging and chronic disease prevention.

Exploring the role of miR-125b-5p as a pro-inflammatory factor in Alzheimer's disease pathology

BACKGROUND

Alzheimer's disease (AD) is a common neurodegenerative disease, where neuroinflammation significantly influences its pathophysiology by driving the disease's pathological cascade. As a pro-inflammatory regulator, miR-125b-5p contributes to AD progression, though its precise role and mechanisms remain unclear.

OBJECTIVE

We aims to identify mRNAs significantly regulated by pro-inflammatory miR-125b-5p in AD and uncover key neuroinflammatory pathways.

METHODS

Target mRNAs regulated by miR-125b-5p were predicted using online databases and analyzed with two mRNA datasets to identify differentially expressed mRNAs (DEmRNAs). Enrichment analysis was conducted to explore their biological functions and pathways. The significance of DEmRNAs expression in AD-related inflammatory pathways was verified by the Wilcoxon test, predictive accuracy was assessed via area under the curves (AUCs), and novel mRNAs were identified through positive control analysis.

RESULTS

A total of 613 miR-125b-5p target mRNAs were identified, and 44 DEmRNAs were detected to be regulated by miR-125b-5p in two datasets. The 44 target DEmRNAs associated with AD include three key pathways: insulin signaling (EXOC7, FLOT2, MKNK2), phosphatidylinositol signaling (IP6K1, MTMR3), and phospholipase D signaling (CYTH1, GAB2). Correlation analysis indicated strong correlations among 7 mRNAs, all showing significant differential expression, with AUCs above 0.5, confirming their predictive value. Three mRNAs (EXOC7, IP6K1, CYTH1) were identified as novel AD-related genes. MiR-125b-5p binding sites in the 3'-UTRs of these 7 mRNAs suggest their potential roles in AD-related inflammation and signaling pathways.

CONCLUSIONS

This study investigates the pro-inflammatory miR-125b-5p's role in the pathological processes of AD, highlighting its regulation of key target mRNAs and critical pathways.

β-Carotene Impacts the Liver MicroRNA Profile in a Sex-Specific Manner in Mouse Offspring of Western Diet-Fed Mothers: Results from Microarray Analysis by Direct Hybridization

Maternal unbalanced diets cause adverse metabolic programming and affect the offspring's liver microRNA (miRNA) profile. The liver is a site of β-carotene (BC) metabolism and a target of BC action. We studied the interaction of maternal Western diet (WD) and early-life BC supplementation on the epigenetic remodeling of offspring's liver microRNAs. Mouse offspring of WD-fed mothers were given a daily placebo (controls) or BC during suckling. Biometric parameters and liver miRNAome by microarray hybridization were analyzed in newly weaned animals. BC sex-dependently impacted the liver triacylglycerol content. The liver miRNAome was also differently affected in male and female offspring, with no overlap in differentially expressed (DE) miRNAs between sexes and more impact in females. Bioinformatic analysis of DE miRNA predicted target genes revealed enrichment in biological processes/pathways related to metabolic processes, regulation of developmental growth and circadian rhythm, liver homeostasis and metabolism, insulin resistance, and neurodegeneration, among others, with differences between sexes. Fifty-five percent of the overlapping target genes in both sexes identified were targeted by DE miRNAs changed in opposite directions in males and females. The results identify sex-dependent responses of the liver miRNA expression profile to BC supplementation during suckling and may sustain further investigations regarding the long-term impact of early postnatal life BC supplementation on top of an unbalanced maternal diet.

Trends in hyperinsulinemia and insulin resistance among nondiabetic US adults, NHANES, 1999-2018

Hyperinsulinemia and insulin resistance (IR) are critical predictors of cardiometabolic diseases, disproportionately affecting various sociodemographic groups in the United States. This study aimed to estimate and analyze trends in the prevalence of hyperinsulinemia and IR among nondiabetic adults from 1999 to 2018, using data from the National Health and Nutrition Examination Survey (NHANES). The study included 17,310 nondiabetic men and nonpregnant women aged 20 years or older. Hyperinsulinemia was defined as fasting serum insulin levels ≥10 U/ml, while IR was measured using the HOMA-IR index (≥2.6, 66.7th percentile). The age-standardized prevalence of hyperinsulinemia increased from 28.2% in 1999-2000 to 41.4% in 2017-2018, while IR prevalence rose from 24.8% to 38.4% during the same period. Higher prevalence rates were consistently observed among males, non-Hispanic Blacks, Hispanics, and individuals with lower education or income levels. Trends indicated increases across all sociodemographic groups during at least some time periods. The findings suggest a growing prevalence of hyperinsulinemia and IR in the U.S., particularly among vulnerable populations, underscoring the importance of targeted public health interventions to address these disparities and reduce the risk of cardiometabolic diseases.

From Fundamentals to Innovation in Alzheimer's Disease: Molecular Findings and Revolutionary Therapies

Alzheimer's disease (AD) is a global health concern and the leading cause of dementia in the elderly. The prevalence of this neurodegenerative condition is projected to increase concomitantly with increased life expectancy, resulting in a significant economic burden. With very few FDA-approved disease-modifying drugs available for AD, there is an urgent need to develop new compounds capable of impeding the progression of the disease. Given the unclear etiopathogenesis of AD, this review emphasizes the underlying mechanisms of this condition. It explores not only well-studied aspects, such as the accumulation of Aβ plaques and neurofibrillary tangles, but also novel areas, including glymphatic and lymphatic pathways, microbiota and the gut-brain axis, serotoninergic and autophagy alterations, vascular dysfunction, the metal hypothesis, the olfactory pathway, and oral health. Furthermore, the potential molecular targets arising from all these mechanisms have been reviewed, along with novel promising approaches such as nanoparticle-based therapy, neural stem cell transplantation, vaccines, and CRISPR-Cas9-mediated genome editing techniques. Taking into account the overlap of these various mechanisms, individual and combination therapies emerge as the future direction in the AD strategy.

Alzheimer's Disease as Type 3 Diabetes: Understanding the Link and Implications

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) are two prevalent conditions that present considerable public health issue in aging populations worldwide. Recent research has proposed a novel conceptualization of AD as "type 3 diabetes", highlighting the critical roles of insulin resistance and impaired glucose metabolism in the pathogenesis of the disease. This article examines the implications of this association, exploring potential new avenues for treatment and preventive strategies for AD. Key evidence linking diabetes to AD emphasizes critical metabolic processes that contribute to neurodegeneration, including inflammation, oxidative stress, and alterations in insulin signaling pathways. By framing AD within this metabolic context, we can enhance our understanding of its etiology, which in turn may influence early diagnosis, treatment plans, and preventive measures. Understanding AD as a manifestation of diabetes opens up the possibility of employing novel therapeutic strategies that incorporate lifestyle modifications and the use of antidiabetic medications to mitigate cognitive decline. This integrated approach has the potential to improve patient outcomes and deepen our comprehension of the intricate relationship between neurodegenerative diseases and metabolic disorders.

AKT1 and MAPK8: New Targets for Gestational Diabetes Mellitus?

Objective: Gestational diabetes mellitus (GDM) disrupts placental function and increases risks for pregnancy. This study investigates the potential involvement of AKT1 and MAPK8 genes, known for their roles in insulin resistance and cell signaling, in GDM pathophysiology. Methods: Placental tissues from GDM patients and healthy controls were analyzed using real-time PCR to quantify gene expression levels. In silico analysis further explored the functional implications of expression changes. Results: AKT1 and MAPK8 displayed significantly altered expression in GDM placentas compared to controls (p = 0.047 and p = 0.007, respectively). In silico analysis suggests potential functional consequences related to diabetes-associated pathways. Conclusion: This study identifies differential expression of AKT1 and MAPK8 in GDM placentas, suggesting their potential roles in the disease process. Further investigation into their functional contributions could provide valuable insights into GDM pathophysiology and potential therapeutic targets.

Microglia and gut microbiota: A double-edged sword in Alzheimer's disease

The strong association between gut microbiota (GM) and brain functions such as mood, behaviour, and cognition has been well documented. Gut-brain axis is a unique bidirectional communication system between the gut and brain, in which gut microbes play essential role in maintaining various molecular and cellular processes. GM interacts with the brain through various pathways and processes including, metabolites, vagus nerve, HPA axis, endocrine system, and immune system to maintain brain homeostasis. GM dysbiosis, or an imbalance in GM, is associated with several neurological disorders, including anxiety, depression, and Alzheimer's disease (AD). Conversely, AD is sustained by microglia-mediated neuroinflammation and neurodegeneration. Further, GM and their products also affect microglia-mediated neuroinflammation and neurodegeneration. Despite the evidence connecting GM dysbiosis and AD progression, the involvement of GM in modulating microglia-mediated neuroinflammation in AD remains elusive. Importantly, deciphering the mechanism/s by which GM regulates microglia-dependent neuroinflammation may be helpful in devising potential therapeutic strategies to mitigate AD. Herein, we review the current evidence regarding the involvement of GM dysbiosis in microglia activation and neuroinflammation in AD. We also discuss the possible mechanisms through which GM influences the functioning of microglia and its implications for therapeutic intervention. Further, we explore the potential of microbiota-targeted interventions, such as prebiotics, probiotics, faecal microbiota transplantation, etc., as a novel therapeutic strategy to mitigate neuroinflammation and AD progression. By understanding and exploring the gut-brain axis, we aspire to revolutionize the treatment of neurodegenerative disorders, many of which share a common theme of microglia-mediated neuroinflammation and neurodegeneration.

A Comprehensive Review of Membrane Transporters and MicroRNA Regulation in Alzheimer's Disease

Alzheimer's disease (AD) is a distressing neurodegenerative condition characterized by the accumulation of amyloid-beta (Aβ) plaques and tau tangles within the brain. The interconnectedness between membrane transporters (SLCs) and microRNAs (miRNAs) in AD pathogenesis has gained increasing attention. This review explores the localization, substrates, and functions of SLC transporters in the brain, emphasizing the roles of transporters for glutamate, glucose, nucleosides, and other essential compounds. The examination delves into the significance of SLCs in AD, their potential for drug development, and the intricate realm of miRNAs, encompassing their transcription, processing, functions, and regulation. MiRNAs have emerged as significant players in AD, including those associated with mitochondria and synapses. Furthermore, this review discusses the intriguing nexus of miRNAs targeting SLC transporters and their potential as therapeutic targets in AD. Finally, the review underscores the interaction between SLC transporters and miRNA regulation within the context of Alzheimer's disease, underscoring the need for further research in this area. This comprehensive review aims to shed light on the complex mechanisms underlying the causation of AD and provides insights into potential therapeutic approaches.

Alzheimer's Disease, Obesity, and Type 2 Diabetes: Focus on Common Neuroglial Dysfunctions (Critical Review and New Data on Human Brain and Models)

BACKGROUND/OBJECTIVES

Obesity, type 2 diabetes (T2D), and Alzheimer's disease (AD) are pathologies that affect millions of people worldwide. They have no effective therapy and are difficult to prevent and control when they develop. It has been known for many years that these diseases have many pathogenic aspects in common. We highlight in this review that neuroglial cells (astroglia, oligodendroglia, and microglia) play a vital role in the origin, clinical-pathological development, and course of brain neurodegeneration. Moreover, we include the new results of a T2D-AD mouse model (APP+PS1 mice on a high-calorie diet) that we are investigating.

METHODS

Critical bibliographic revision and biochemical neuropathological study of neuroglia in a T2D-AD model.

RESULTS

T2D and AD are not only "connected" by producing complex pathologies in the same individual (obesity, T2D, and AD), but they also have many common pathogenic mechanisms. These include insulin resistance, hyperinsulinemia, hyperglycemia, oxidative stress, mitochondrial dysfunction, and inflammation (both peripheral and central-or neuroinflammation). Cognitive impairment and AD are the maximum exponents of brain neurodegeneration in these pathological processes. both due to the dysfunctions induced by metabolic changes in peripheral tissues and inadequate neurotoxic responses to changes in the brain. In this review, we first analyze the common pathogenic mechanisms of obesity, T2D, and AD (and/or cerebral vascular dementia) that induce transcendental changes and responses in neuroglia. The relationships between T2D and AD discussed mainly focus on neuroglial responses. Next, we present neuroglial changes within their neuropathological context in diverse scenarios: (a) aging involution and neurodegenerative disorders, (b) human obesity and diabetes and obesity/diabetes models, (c) human AD and in AD models, and (d) human AD-T2D and AD-T2D models. An important part of the data presented comes from our own studies on humans and experimental models over the past few years. In the T2D-AD section, we included the results of a T2D-AD mouse model (APP+PS1 mice on a high-calorie diet) that we investigated, which showed that neuroglial dysfunctions (astrocytosis and microgliosis) manifest before the appearance of amyloid neuropathology, and that the amyloid pathology is greater than that presented by mice fed a normal, non-high-caloric diet A broad review is finally included on pharmacological, cellular, genic, and non-pharmacological (especially diet and lifestyle) neuroglial-related treatments, as well as clinical trials in a comparative way between T2D and AD. These neuroglial treatments need to be included in the multimodal/integral treatments of T2D and AD to achieve greater therapeutic efficacy in many millions of patients.

CONCLUSIONS

Neuroglial alterations (especially in astroglia and microglia, cornerstones of neuroinflammation) are markedly defining brain neurodegeneration in T2D and A, although there are some not significant differences between each of the studied pathologies. Neuroglial therapies are a very important and p. promising tool that are being developed to prevent and/or treat brain dysfunction in T2D-AD. The need for further research in two very different directions is evident: (a) characterization of the phenotypic changes of astrocytes and microglial cells in each region of the brain and in each phase of development of each isolated and associated pathology (single-cell studies are mandatory) to better understand the pathologies and define new therapeutic targets; (b) studying new therapeutic avenues to normalize the function of neuroglial cells (preventing neurotoxic responses and/or reversing them) in these pathologies, as well as the phenotypic characteristics in each moment of the course and place of the neurodegenerative process.

Chronically Increased Levels of Circulating Insulin Secondary to Insulin Resistance: A Silent Killer

Despite all the progress made by science in the prevention and treatment of cardiovascular diseases and cancers, these are still the main reasons for hospitalizations and death in the Western world. Among the possible causes of this situation, disorders related to hyperinsulinemia and insulin resistance (Hyperin/IR) are still little-known topics. An analysis of the literature shows that this condition is a multiple risk factor for type 2 diabetes, cardiovascular diseases, cellular senescence and cancer, and neurodegenerative diseases. Hyperin/IR is progressively increasing worldwide, and its prevalence has now exceeded 50% of the general population and in overweight children. Asymptomatic or poorly symptomatic, it can last for many years before manifesting itself as diabetes, cardiovascular disease, neoplasm, cognitive deficit, or dementia, therefore leading to enormous social and healthcare costs. For these reasons, a screening plan for this pathology should be implemented for the purpose of identifying people with Hyperin/IR and promptly starting them on preventive treatment.

Pathology of Amyloid-β (Aβ) Peptide Peripheral Clearance in Alzheimer's Disease

Although Alzheimer's disease (AD) is traditionally viewed as a central nervous system disorder driven by the cerebral accumulation of toxic beta-amyloid (Aβ) peptide, new interpretations of the amyloid cascade hypothesis have led to the recognition of the dynamic equilibrium in which Aβ resides and the importance of peripheral Aβ production and degradation in maintaining healthy Aβ levels. Our review sheds light on the critical role of peripheral organs, particularly the liver, in the metabolism and clearance of circulating Aβ. We explore the mechanisms of Aβ transport across the blood-brain barrier (BBB) via transport proteins such as LRP1 and P-glycoprotein. We also examine how peripheral clearance mechanisms, including enzymatic degradation and phagocytic activity, impact Aβ homeostasis. Our review also discusses potential therapeutic strategies targeting peripheral Aβ clearance pathways. By enhancing these pathways, we propose a novel approach to reducing cerebral Aβ burden, potentially slowing AD progression.

The Hidden Dangers of Sedentary Living: Insights into Molecular, Cellular, and Systemic Mechanisms

With the aging of the global population, neurodegenerative diseases are emerging as a major public health issue. The adoption of a less sedentary lifestyle has been shown to have a beneficial effect on cognitive decline, but the molecular mechanisms responsible are less clear. Here we provide a detailed analysis of the complex molecular, cellular, and systemic mechanisms underlying age-related cognitive decline and how lifestyle choices influence these processes. A review of the evidence from animal models, human studies, and postmortem analyses emphasizes the importance of integrating physical exercise with cognitive, multisensory, and motor stimulation as part of a multifaceted approach to mitigating cognitive decline. We highlight the potential of these non-pharmacological interventions to address key aging hallmarks, such as genomic instability, telomere attrition, and neuroinflammation, and underscore the need for comprehensive and personalized strategies to promote cognitive resilience and healthy aging.

MAD-microbial (origin of) Alzheimer's disease hypothesis: from infection and the antimicrobial response to disruption of key copper-based systems

Microbes have been suspected to cause Alzheimer's disease since at least 1908, but this has generally remained unpopular in comparison to the amyloid hypothesis and the dominance of Aβ and Tau. However, evidence has been accumulating to suggest that these earlier theories are but a manifestation of a common cause that can trigger and interact with all the major molecular players recognized in AD. Aβ, Tau and ApoE, in particular appear to be molecules with normal homeostatic functions but also with alternative antimicrobial functions. Their alternative functions confer the non-immune specialized neuron with some innate intracellular defenses that appear to be re-appropriated from their normal functions in times of need. Indeed, signs of infection of the neurons by biofilm-forming microbial colonies, in synergy with herpes viruses, are evident from the clinical and preclinical studies we discuss. Furthermore, we attempt to provide a mechanistic understanding of the AD landscape by discussing the antimicrobial effect of Aβ, Tau and ApoE and Lactoferrin in AD, and a possible mechanistic link with deficiency of vital copper-based systems. In particular, we focus on mitochondrial oxidative respiration via complex 4 and ceruloplasmin for iron homeostasis, and how this is similar and possibly central to neurodegenerative diseases in general. In the case of AD, we provide evidence for the microbial Alzheimer's disease (MAD) theory, namely that AD could in fact be caused by a long-term microbial exposure or even long-term infection of the neurons themselves that results in a costly prolonged antimicrobial response that disrupts copper-based systems that govern neurotransmission, iron homeostasis and respiration. Finally, we discuss potential treatment modalities based on this holistic understanding of AD that incorporates the many separate and seemingly conflicting theories. If the MAD theory is correct, then the reduction of microbial exposure through use of broad antimicrobial and anti-inflammatory treatments could potentially alleviate AD although this requires further clinical investigation.

Brain uptake pharmacokinetics of albiglutide, dulaglutide, tirzepatide, and DA5-CH in the search for new treatments of Alzheimer's and Parkinson's diseases

BACKGROUND

A number of peptide incretin receptor agonists (IRAs) show promise as therapeutics for Alzheimer's disease (AD) and Parkinson's disease (PD). Transport across the blood-brain barrier (BBB) is one way for IRAs to act directly within the brain. To determine which IRAs are high priority candidates for treating these disorders, we have studied their brain uptake pharmacokinetics.

METHODS

We quantitatively measure the ability of four IRAs to cross the BBB. We injected adult male CD-1 mice intravenously with 125I- or 14C-labeled albiglutide, dulaglutide, DA5-CH, or tirzepatide and used multiple-time regression analyses to measure brain kinetics up to 1 hour. For those IRAs failing to enter the brain 1 h after intravenous injection, we also investigated their ability to enter over a longer time frame (i.e., 6 h).

RESULTS

Albiglutide and dulaglutide had the fastest brain uptake rates within 1 hour. DA5-CH appears to enter the brain rapidly, reaching equilibrium quickly. Tirzepatide does not appear to cross the BBB within 1 h after iv injection but like albumin, did so slowly over 6 h, presumably via the extracellular pathways.

CONCLUSIONS

We find that IRAs can cross the BBB by two separate processes; one that is fast and one that is slow. Three of the four IRAs investigated here have fast rates of transport and should be taken into consideration for testing as AD and PD therapeutics as they would have the ability to act quickly and directly on the brain as a whole.

Sex-dependent susceptibility to brain metabolic dysfunction and memory impairment in response to pre and postnatal high-fat diet

The developing brain is sensitive to the impacts of early-life nutritional intake. This study investigates whether maternal high fat diet (HFD) causes glucose metabolism impairment, neuroinflammation, and memory impairment in immature and adult offspring, and whether it may be affected by postweaning diets in a sex-dependent manner in adult offspring. After weaning, female rats were fed HFD (55.9% fat) or normal chow diet (NCD; 10% fat) for 8 weeks before mating, during pregnancy, and lactation. On postnatal day 21 (PND21), the male and female offspring of both groups were split into two new groups, and NCD or HFD feeding was maintained until PND180. On PND21 and PND180, brain glucose metabolism, inflammation, and Alzheimer's pathology-related markers were by qPCR. In adult offspring, peripheral insulin resistance parameters, spatial memory performance, and brain glucose metabolism (18F-FDG-PET scan and protein levels of IDE and GLUT3) were assessed. Histological analysis was also performed on PND21 and adult offspring. On PND21, we found that maternal HFD affected transcript levels of glucose metabolism markers in both sexes. In adult offspring, more profoundly in males, postweaning HFD in combination with maternal HFD induced peripheral and brain metabolic disturbances, impaired memory performance and elevated inflammation, dementia risk markers, and neuronal loss. Our results suggest that maternal HFD affects brain glucose metabolism in the early ages of both sexes. Postweaning HFD sex-dependently causes brain metabolic dysfunction and memory impairment in later-life offspring; effects that can be worsened in combination with maternal HFD.

Dysregulated mTOR networks in experimental sporadic Alzheimer's disease

Background

Beyond the signature amyloid-beta plaques and neurofibrillary tangles, Alzheimer's disease (AD) has been shown to exhibit dysregulated metabolic signaling through insulin and insulin-like growth factor (IGF) networks that crosstalk with the mechanistic target of rapamycin (mTOR). Its broad impact on brain structure and function suggests that mTOR is likely an important therapeutic target for AD.

Objective

This study characterizes temporal lobe (TL) mTOR signaling abnormalities in a rat model of sporadic AD neurodegeneration.

Methods

Long Evans rats were given intracerebroventricular injections of streptozotocin (ic-STZ) or saline (control), and 4 weeks later, they were administered neurobehavioral tests followed by terminal harvesting of the TLs for histopathological study and measurement of AD biomarkers, neuroinflammatory/oxidative stress markers, and total and phosphorylated insulin/IGF-1-Akt-mTOR pathway signaling molecules.

Results

Rats treated with ic-STZ exhibited significantly impaired performance on Rotarod (RR) and Morris Water Maze (MWM) tests, brain atrophy, TL and hippocampal neuronal and white matter degeneration, and elevated TL pTau, AβPP, Aβ, AChE, 4-HNE, and GAPDH and reduced ubiquitin, IL-2, IL-6, and IFN-γ immunoreactivities. In addition, ic-STZ reduced TL pY1135/1136-IGF-1R, Akt, PTEN, pS380-PTEN, pS2448-mTOR, p70S6K, pT412-p70S6K, p/T-pT412-p70S6K, p/T-Rictor, and p/T-Raptor.

Conclusion

Experimental ic-STZ-induced sporadic AD-type neurodegeneration with neurobehavioral dysfunctions associated with inhibition of mTOR signaling networks linked to energy metabolism, plasticity, and white matter integrity.

From Brain to Muscle: The Role of Muscle Tissue in Neurodegenerative Disorders

Neurodegenerative diseases (NDs), like amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Parkinson's disease (PD), primarily affect the central nervous system, leading to progressive neuronal loss and motor and cognitive dysfunction. However, recent studies have revealed that muscle tissue also plays a significant role in these diseases. ALS is characterized by severe muscle wasting as a result of motor neuron degeneration, as well as alterations in gene expression, protein aggregation, and oxidative stress. Muscle atrophy and mitochondrial dysfunction are also observed in AD, which may exacerbate cognitive decline due to systemic metabolic dysregulation. PD patients exhibit muscle fiber atrophy, altered muscle composition, and α-synuclein aggregation within muscle cells, contributing to motor symptoms and disease progression. Systemic inflammation and impaired protein degradation pathways are common among these disorders, highlighting muscle tissue as a key player in disease progression. Understanding these muscle-related changes offers potential therapeutic avenues, such as targeting mitochondrial function, reducing inflammation, and promoting muscle regeneration with exercise and pharmacological interventions. This review emphasizes the importance of considering an integrative approach to neurodegenerative disease research, considering both central and peripheral pathological mechanisms, in order to develop more effective treatments and improve patient outcomes.

Zeaxanthin and Lutein Ameliorate Alzheimer's Disease-like Pathology: Modulation of Insulin Resistance, Neuroinflammation, and Acetylcholinesterase Activity in an Amyloid-β Rat Model

Alzheimer's disease (AD) is characterized by impaired insulin/insulin-like growth factor-1 signaling in the hippocampus. Zeaxanthin and lutein, known for their antioxidant and anti-inflammatory properties, have been reported to protect against brain damage and cognitive decline. However, their mechanisms related to insulin signaling in AD remain unclear. This study investigated the efficacy and mechanisms of zeaxanthin, lutein, and resveratrol in modulating an AD-like pathology in an amyloid-β rat model. Rats were administered hippocampal infusions of 3.6 nmol/day amyloid-β (Aβ)(25-35) for 14 days to induce AD-like memory deficits (AD-CON). Normal control rats received Aβ(35-25) (Normal-CON). All rats had a high-fat diet. Daily, AD rats consumed 200 mg/kg body weight of zeaxanthin (AD-ZXT), lutein (AD-LTN), and resveratrol (AD-RVT; positive-control) or resistant dextrin as a placebo (AD-CON) for eight weeks. The AD-CON rats exhibited a higher Aβ deposition, attenuated hippocampal insulin signaling (reduced phosphorylation of protein kinase B [pAkt] and glycogen synthase kinase-3β [pGSK-3β]), increased neuroinflammation, elevated acetylcholinesterase activity, and memory deficits compared to the Normal-CON group. They also showed systemic insulin resistance and high hepatic glucose output. Zeaxanthin and lutein prevented memory impairment more effectively than the positive-control resveratrol by suppressing acetylcholinesterase activity, lipid peroxidation, and pro-inflammatory cytokines (TNF-α, IL-1β). They also potentiated hippocampal insulin signaling and increased brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CTNF) mRNA expression to levels comparable to the Normal-CON rats. Additionally, zeaxanthin and lutein improved glucose disposal, reduced hepatic glucose output, and normalized insulin secretion patterns. In conclusion, zeaxanthin and lutein supplementation at doses equivalent to 1.5-2.0 g daily in humans may have practical implications for preventing or slowing human AD progression by reducing neuroinflammation and maintaining systemic and central glucose homeostasis, showing promise even when compared to the established neuroprotective compound resveratrol. However, further clinical trials are needed to evaluate their efficacy and safety in human populations.

Breaking Barriers in Alzheimer's Disease: the Role of Advanced Drug Delivery Systems

Alzheimer's disease (AD), characterized by cognitive impairment, brain plaques, and tangles, is a global health concern affecting millions. It involves the build-up of amyloid-β (Aβ) and tau proteins, the formation of neuritic plaques and neurofibrillary tangles, cholinergic system dysfunction, genetic variations, and mitochondrial dysfunction. Various signaling pathways and metabolic processes are implicated in AD, along with numerous biomarkers used for diagnosis, risk assessment, and research. Despite these, there is no cure or effective treatment for AD. It is critically important to address this immediately to develop novel drug delivery systems (NDDS) capable of targeting the brain and delivering therapeutic agents to modulate the pathological processes of AD. This review summarizes AD, its pathogenesis, related signaling pathways, biomarkers, conventional treatments, the need for NDDS, and their application in AD treatment. It also covers preclinical, clinical, and ongoing trials, patents, and marketed AD formulations.

Methylglyoxal induces death in human brain neuronal cells (SH-SY5Y), prevented by metformin and dapagliflozin

Diabetes mellitus is a metabolic disorder caused by a dysfunction in insulin action or secretion, leading to an elevation in blood glucose levels. It is a highly prevalent condition and as a result, the NHS spends 10 % of its entire budget on diabetes mellitus care, that is equivalent to £10 billion a year. Diabetes mellitus has been linked with vascular and neurological complications which may be associated with the progression of neurodegeneration and Alzheimer's disease. Chronic hyperglycaemia increases the production of the reactive oxidant species (ROS) such as methylglyoxal (MGO). MGO has been linked with vascular complications, neuropathy and cytotoxicity. The main aim of this study was to investigate the potential beneficial effect of antidiabetic agents such as metformin and dapagliflozin on human brain neuronal cells (SH-SY5Y) treated with MGO. SH-SY5Y cells were cultured in DMEM/F12 media and subjected overnight incubation with one of the following treatment conditions: Control (untreated); MGO (1 μM); MGO (100 μM); metformin (100 μM) + MGO (100 μM); and dapagliflozin (10 μM) + MGO (100 μM). Several assays were conducted to explore the effect of the treatment groups on the SH-SY5Y cells. These included: MTT assay; LDH assay, peroxynitrite fluorescence assay, and laser scanning confocal microscopy. MGO (100 μM) led to significant cell injury and damage and significantly reduced the survival of the cells by approximately 50-75 %, associated with significant increase in peroxynitrite. The addition of metformin (100 μM) or dapagliflozin (10 μM) represented significant protective effects on the cells and prevented the cell damage caused by the high MGO concentration. As a result, the findings of this research reveal that MGO-induced cell damage may partly be mediated by the generation of peroxynitrite, while the antidiabetic agents such as metformin and dapagliflozin prevent brain cell death, which potentially may play prophylactic roles against the risk of dementia in diabetic patients.

Biological aging mediates the associations of metabolic score for insulin resistance with all-cause and cardiovascular disease mortality among US adults: A nationwide cohort study

AIM

To investigate the associations of metabolic score for insulin resistance (METS-IR) with all-cause and cardiovascular disease (CVD)-specific mortality and the potential mediating role of biological ageing.

METHODS

A cohort of 19 204 participants from the National Health and Nutrition Examination Survey (NHANES) 1999-2018 was recruited for this study. Cox regression models, restricted cubic splines, and Kaplan-Meier survival curves were used to determine the relationships of METS-IR with all-cause and CVD-specific mortality. Mediation analyses were performed to explore the possible intermediary role of biological ageing markers, including phenotypic age (PhenoAge) and biological age (BioAge).

RESULTS

During a median follow-up of 9.17 years, we observed 2818 deaths, of which 875 were CVD-specific. Multivariable Cox regression showed that the highest METS-IR level (Q4) was associated with increased all-cause (hazard ratio [HR] 1.38, 95% confidence interval [CI] 1.14-1.67) and CVD mortality (HR 1.52, 95% CI 1.10-2.12) compared with the Q1 level. Restricted cubic splines showed a nonlinear relationship between METS-IR and all-cause mortality. Only METS-IR above the threshold (41.02 μg/L) was positively correlated with all-cause death. METS-IR had a linear positive relationship with CVD mortality. In mediation analyses, we found that PhenoAge mediated 51.32% (p < 0.001) and 41.77% (p < 0.001) of the association between METS-IR and all-cause and CVD-specific mortality, respectively. For BioAge, the mediating proportions of PhenoAge were 21.33% (p < 0.001) and 15.88% (p < 0.001), respectively.

CONCLUSIONS

This study highlights the detrimental effects of insulin resistance, as measured by METS-IR, on all-cause and CVD mortality. Moreover, it underscores the role of biological ageing in mediating these associations, emphasizing the need for interventions targeting both insulin resistance and ageing processes to mitigate mortality risks in metabolic disorders.

Hindlimb immobilization induces insulin resistance and elevates mitochondrial ROS production in the hippocampus of female rats

Alzheimer's disease (AD) is the fifth leading cause of death in older adults, and treatment options are severely lacking. Recent findings demonstrate a strong relationship between skeletal muscle and cognitive function, with evidence supporting that muscle quality and cognitive function are positively correlated in older adults. Conversely, decreased muscle function is associated with a threefold increased risk of cognitive decline. Based on these observations, the purpose of this study was to investigate the negative effects of muscle disuse [via a model of hindlimb immobilization (HLI)] on hippocampal insulin sensitivity and mitochondrial function and identify the potential mechanisms involved. HLI for 10 days in 4-mo-old female Wistar rats resulted in the following novel findings: 1) hippocampal insulin resistance and deficits in whole body glucose homeostasis, 2) dramatically increased mitochondrial reactive oxygen species (ROS) production in the hippocampus, 3) elevated markers for amyloidogenic cleavage of amyloid precursor protein (APP) and tau protein in the hippocampus, 4) and reduced brain-derived neurotrophic factor (BDNF) expression. These findings were associated with global changes in iron homeostasis, with muscle disuse producing muscle iron accumulation in association with decreased serum and whole brain iron levels. We report the novel finding that muscle disuse alters brain iron homeostasis and reveal a strong negative correlation between muscle and brain iron content. Overall, HLI-induced muscle disuse has robust negative effects on hippocampal insulin sensitivity and ROS production in association with altered brain iron homeostasis. This work provides potential novel mechanisms that may help explain how loss of muscle function contributes to cognitive decline and AD risk.NEW & NOTEWORTHY Muscle disuse via hindlimb immobilization increased oxidative stress and insulin resistance in the hippocampus. These findings were in association with muscle iron overload in connection with iron dysregulation in the brain. Overall, our work identifies muscle disuse as a contributor to hippocampal dysfunction, potentially through an iron-based muscle-brain axis, highlighting iron dysregulation as a potential novel mechanism in the relationship between muscle health, cognitive function, and Alzheimer's disease risk.

Advancing the understanding of diabetic encephalopathy through unravelling pathogenesis and exploring future treatment perspectives

Diabetic encephalopathy (DE), a significant micro-complication of diabetes, manifests as neurochemical, structural, behavioral, and cognitive alterations. This condition is especially dangerous for the elderly because aging raises the risk of neurodegenerative disorders and cognitive impairment, both of which can be made worse by diabetes. Despite its severity, diagnosis of this disease is challenging, and there is a paucity of information on its pathogenesis. The pivotal roles of various cellular pathways, activated or influenced by hyperglycemia, insulin sensitivity, amyloid accumulation, tau hyperphosphorylation, brain vasculopathy, neuroinflammation, and oxidative stress, are widely recognized for contributing to the potential causes of diabetic encephalopathy. We also reviewed current pharmacological strategies for DE encompassing a comprehensive approach targeting metabolic dysregulations and neurological manifestations. Antioxidant-based therapies hold promise in mitigating oxidative stress-induced neuronal damage, while anti-diabetic drugs offer neuroprotective effects through diverse mechanisms, including modulation of insulin signaling pathways and neuroinflammation. Additionally, tissue engineering and nanomedicine-based approaches present innovative strategies for targeted drug delivery and regenerative therapies for DE. Despite significant progress, challenges remain in translating these therapeutic interventions into clinical practice, including long-term safety, scalability, and regulatory approval. Further research is warranted to optimize these approaches and address remaining gaps in the management of DE and associated neurodegenerative disorders.