Mechanism involved in insulin resistance via accumulation of β-amyloid and neurofibrillary tangles: link between type 2 diabetes and Alzheimer's disease

Multi-target approach to Alzheimer's disease prevention and treatment: antioxidant, anti-inflammatory, and amyloid- modulating mechanisms

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) plaque accumulation, neurofibrillary tangles, neuroinflammation, and progressive cognitive decline, posing a significant global health challenge. Growing evidence suggests that dietary polyphenols may reduce the risk and progression of AD through multifaceted neuroprotective mechanisms. Polyphenols regulate amyloid proteostasis by inhibiting β/γ-secretase activity, preventing Aβ aggregation, and enhancing clearance pathways. Their strong antioxidant properties neutralize reactive oxygen species, chelate redox-active metals, and activate cytoprotective enzymes via Nrf2 signaling. This review examines the potential therapeutic targets, signaling pathways, and molecular mechanisms by which dietary polyphenols exert neuroprotective effects in AD, focusing on their roles in modulating amyloid proteostasis, oxidative stress, neuroinflammation, and cerebrovascular health. Polyphenols mitigate neuroinflammation by suppressing NF-κB signaling and upregulating brain-derived neurotrophic factor, supporting neuroplasticity and neurogenesis. They also enhance cerebrovascular health by improving cerebral blood flow, maintaining blood-brain barrier integrity, and modulating angiogenesis. This review examines the molecular and cellular pathways through which polyphenols exert neuroprotective effects, focusing on their antioxidant, anti-inflammatory, and amyloid-modulating roles. We also discuss their influence on key AD pathologies, including Aβ deposition, tau hyperphosphorylation, oxidative stress, and neuroinflammation. Insights from clinical and preclinical studies highlight the potential of polyphenols in preventing or slowing AD progression. Future research should explore personalized dietary strategies that integrate genetic and lifestyle factors to optimize the neuroprotective effects of polyphenols.

Insulin resistance in Alzheimer's disease: signalling mechanisms and therapeutics strategies

BACKGROUND

Alzheimer's disease (AD), one of the most common neurodegenerative disorders, is characterised by hallmark abnormalities such as amyloid-β plaques and neurofibrillary tangles (NFTs). Emerging evidence suggests that faulty insulin signalling contributes to these pathological features, impairing critical cellular and metabolic processes.

OBJECTIVE

This review aims to elucidate the role of insulin signalling in the central nervous system (CNS) under normal and pathological conditions and to explore therapeutic approaches targeting insulin pathways in AD and other neurodegenerative diseases.

METHODS

We reviewed studies highlighting the involvement of insulin-signalling pathways in neuronal health, with a particular focus on the key components-IRS, PI3K, Akt, and GSK-3β-predominantly expressed in cortical and hippocampal regions.

RESULTS

Insulin, an essential growth factor, regulates numerous cellular functions, including glucose metabolism, mitochondrial activity, oxidative stress response, autophagy, synaptic plasticity, and cognitive processes. Altered phosphorylation of signalling molecules in insulin pathways contributes to oxidative stress, inflammation, and the formation of AD hallmarks. Indirect modulators such as NF-κB and caspases further exacerbate neuronal damage, linking impaired insulin signalling to neurodegeneration.

CONCLUSION

Insulin signalling plays a crucial role in maintaining neuronal health and mitigating neurodegenerative processes. Targeting insulin pathways and associated molecules offers promising therapeutic avenues for AD and other neurodegenerative disorders.

Flavonoid-Rich Trianthema decandra Ameliorates Cognitive Dysfunction in the Hyperglycemic Rats

The present study was aimed at the evaluation of neuroprotective ability of methanolic extract of Trianthema decandra (METD) against hyperglycemia-related cognitive impairment in rats. The extract of T. decandra was standardized by TLC and HPTLC methods. To verify the identity and purity of isolated compounds, they were segregated and characterized using various techniques, including UV-visible spectrophotometry, FT-IR, H-NMR, and Mass spectroscopy. α-Amylase and α-glucosidase inhibition property of the extracts were assessed in-vitro. The screening of the neuroprotective effects of METD in hyperglycemic rats was done utilizing Morri's water (MWM) and elevated plus maze (EPM) model, as well as acetylcholinesterase (AChE) activity. The extracts of Trianthema decandra and its chemical constituents, namely quercetin and phytol, demonstrated a significant protective effect on enzymes like α-amylase and α-glucosidase. Methanol and hydroalcoholic extracts have shown the strongest inhibitory activity followed by chloroform extract. Quercetin and phytol were associated with the methanolic and chloroform extracts which were identified using TLC and HPTLC techniques. During the thirty days of the study, the induction of diabetes in the rats exhibited persistent hyperglycemia, hyperlipidemia, higher escape latency during training trials and reduced time spent in target quadrant in probe trial in Morris water maze test, and increased escape latency in EPM task. Regimen of METD (200 and 400 mg/kg) in the diabetic rats reduced the glucose levels in blood, lipid, and liver profile and showed positive results on Morri's water and elevated plus maze tasks. During the investigation, it was determined that Trianthema decandra extracts and the chemical constituent's quercetin and phytol in it had anti-diabetic and neuroprotective activities.

Mechanisms Linking Obesity, Insulin Resistance, and Alzheimer's Disease: Effects of Polyphenols and Omega-3 Polyunsaturated Fatty Acids

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by progressive cognitive decline, memory loss, and behavioral changes. It poses a significant global health challenge. AD is associated with the accumulation of amyloid-β (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain, along with chronic inflammation, dysfunctional neurons, and synapse loss. While the prevalence of AD continues to rise, the current FDA-approved drugs offer only limited effectiveness. Emerging evidence suggests that obesity, insulin resistance (IR), and type 2 diabetes mellitus (T2DM) are also implicated in AD pathogenesis, with epidemiological studies and animal models confirming the impact of IR on Aβ accumulation, and high-fat diets also exacerbating Aβ accumulation. Since neuroinflammation activated by Aβ involves the nuclear factor kappa-light-chain-enhancer of the activated B cell (NF-κB) pathway, the inhibition of NF-κB and NLRP3 inflammasome activation are potential therapeutic strategies in AD. Bioactive compounds, including polyphenols (resveratrol, epigallocatechin-3-gallate, curcumin, and quercetin), and omega-3 polyunsaturated fatty acids, show promising results in animal studies and clinical trials for reducing Aβ levels, improving cognition and modulating the signaling pathways implicated in AD. This review explores the interplay between obesity, IR, inflammation, and AD pathology, emphasizing the potential of dietary compounds and their role in reducing inflammation, oxidative stress, and cognitive decline, as viable strategies for AD prevention and treatment. By integrating epidemiological findings, observational studies, and clinical trials, this review aims to provide a comprehensive understating of how metabolic dysfunctions and bioactive compounds influence AD progression.

Pregnancy as a window of opportunity for dementia prevention: a narrative review

Dementia is a debilitating condition with a disproportionate impact on women. While sex differences in longevity contribute to the disparity, the role of the female sex as a biological variable in disease progression is not yet fully elucidated. Metabolic dysfunctions are drivers of dementia etiology, and cardiometabolic diseases are among the most influential modifiable risk factors. Pregnancy is a time of enhanced vulnerability for metabolic disorders. Many dementia risk factors, such as hypertension or blood glucose dysregulation, often emerge for the first time in pregnancy. While such cardiometabolic complications in pregnancy pose a risk to the health trajectory of a woman, increasing her odds of developing type 2 diabetes or chronic hypertension, it is not fully understood how this relates to her risk for dementia. Furthermore, structural and functional changes in the maternal brain have been reported during pregnancy suggesting it is a time of neuroplasticity for the mother. Therefore, pregnancy may be a window of opportunity to optimize metabolic health and support the maternal brain. Healthy dietary patterns are known to reduce the risk of cardiometabolic diseases and have been linked to dementia prevention, yet interventions targeting cognitive function in late life have largely been unsuccessful. Earlier interventions are needed to address the underlying metabolic dysfunctions and potentially reduce the risk of dementia, and pregnancy offers an ideal opportunity to intervene. This review discusses current evidence regarding maternal brain health and the potential window of opportunity in pregnancy to use diet to address neurological health disparities for women.

Neurobiological role and therapeutic potential of exercise-induced irisin in Alzheimer's disease management

Alzheimer's disease (AD) poses a significant obstacle in today's healthcare landscape, with limited effective treatments. Recent studies have revealed encouraging findings about how exercise-triggered irisin might help slow down the advancement of AD. Irisin, a myokine, released during physical activity, has garnered significant attention for its pleiotropic effects, extending beyond its traditional role in metabolic regulation. This review explores irisin's multifaceted potential in combating AD. Research indicates that irisin enhances synaptic plasticity, crucial for learning and memory, and exhibits neuroprotective properties that may slow AD progression by safeguarding neurons from degeneration. Additionally, irisin's ability to modulate inflammatory responses is significant, as neuroinflammation is a key feature of AD pathology. Irisin may also influence the metabolism and clearance of amyloid-beta plaques and tau tangles, hallmark pathological markers of AD. Furthermore, irisin boosts brain-derived neurotrophic factor expression, vital for neuronal health, and improves insulin glucose regulation, addressing impaired brain insulin signaling observed in AD. Exercise-induced irisin presents a non-pharmacological strategy, leveraging physical activity's brain health benefits. Future research should focus on elucidating irisin's mechanisms and conducting clinical trials to assess its therapeutic efficacy and safety in AD patients. Overall, irisin therapy offers a promising avenue for AD treatment, potentially slowing disease progression and enhancing cognitive function, paving the way for innovative therapeutic strategies in the fight against AD.

Unlocking the Therapeutic Potential of Natural Products for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative condition marked by memory loss and cognitive decline. With current treatments offering limited effectiveness, researchers are turning to natural products that can target various aspects of AD pathology. Clinically approved natural products, such as galantamine and huperzine A, have shown success in AD treatments. Furthermore, compounds such as epigallocatechin gallate, quercetin, and resveratrol are in clinical trials. This Perspective examines nearly 100 natural compounds with promising neuroprotective effects in preclinical and clinical studies. These compounds exhibit diverse pharmacological actions that help to prevent neurodegeneration while improving cognitive functions. Their unique structures further enhance their biological activities, making them promising candidates for drug discovery. This Perspective stresses the importance of further clinical research to maximize the medical benefits of these compounds and highlights their potential as innovative remedies for AD. Continued exploration of these compounds is crucial to fully leverage their capabilities in combating 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.

Ferroptosis in Cognitive Impairment Associated with Diabetes and Alzheimer's Disease: Mechanistic Insights and New Therapeutic Opportunities

Cognitive impairment associated with diabetes and Alzheimer's disease has become a major health issue affecting older individuals, with morbidity rates growing acutely each year. Ferroptosis is a novel form of cell death that is triggered by iron-dependent lipid peroxidation. A growing body of evidence suggests a strong correlation between the progression of cognitive impairment and diabetes, Alzheimer's disease, and ferroptosis. The pharmacological modulation of ferroptosis could be a promising therapeutic intervention for cognitive impairment associated with diabetes and Alzheimer's disease. In this review, we summarize evidence on ferroptosis in the context of cognitive impairment associated with diabetes and Alzheimer's disease and provide detailed insights into the function and potential action pathways of ferroptosis. Furthermore, we discuss the therapeutic importance of natural ferroptosis products in improving the cognitive impairment associated with diabetes and Alzheimer's disease and provide new insights for clinical treatment.

Self-Assembly of Human Fibrinogen into Microclot-Mimicking Antifibrinolytic Amyloid Fibrinogen Particles

Recent clinical studies have highlighted the presence of microclots in the form of amyloid fibrinogen particles (AFPs) in plasma samples from Long COVID patients. However, the clinical significance of these abnormal, nonfibrillar self-assembly aggregates of human fibrinogen remains debated due to the limited understanding of their structural and biological characteristics. In this study, we present a method for generating mimetic microclots in vitro. Using this approach, the self-assembly process, structural organization of AFPs, and their interactions with human plasma components were elucidated. The amyloid transition of fibrinogen occurs under acidic conditions within a pH range of 2.3-3.2. Well-dispersed amyloid oligomers of fibrinogen, ranging in size from 1 to 5 μm, can be prepared at pH 2.8 after 1 h of incubation. We tracked the dynamic self-assembly process at the single-molecule level using high-speed atomic force microscopy (HS-AFM). The arrangement of amyloid oligomers manifests as well-ordered, stacked nanodomains with striped patterns, growing perpendicular to the primary axis of the fibrinogen monomer. Upon transfer to physiological solution conditions or human plasma, these amyloid oligomers further aggregate into nonfibrillar structures at the micrometer scale, resembling the microclots observed in the bloodstream of Long COVID patients. Notably, these AFPs exhibit characteristics consistent with microclots, including positive staining in thioflavin T (ThT) assays and resistance to fibrinolysis. Proteomic analysis suggests that AFPs interact with various components of human plasma and have an enhanced binding affinity with complement C3 compared to native fibrinogen. This study enables the in vitro preparation of mimetic microclots exhibiting amyloid features. It is anticipated to facilitate further researches on the mechanisms, detection, and treatment of diseases associated with fibrinogen amyloidogenesis.

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.

AD-Like Neuropsychiatric Dysfunction in a Mice Model Induced by a Combination of High-Fat Diet and Intraperitoneal Injection of Streptozotocin

Increasing data suggest a crucial relationship between glycolipid metabolic disorder and neuropsychiatric injury. The aim of this study is to investigate the behavioral performance changes and neuropathological injuries in mice challenged with high-fat diet (HFD) and streptozotocin (STZ). The glucose metabolism indicators and behavioral performance were detected. The mRNA expression of IL-1β, IL-6, TNF-α, ocln, zo-1, and clnds and protein expression of APP, p-Tau, p-IRS1, p-AKT, p-ERK, and TREM1/2 were measured. The fluorescence intensities of MAP-2, NeuN, APP, p-Tau, GFAP, and IBA-1 were observed. The results showed that combination of HFD and STZ/I.P. could induce glucose metabolic turmoil and Alzheimer's disease (AD)-like neuropsychiatric dysfunction in mice, as indicated by the increased concentrations of fasting blood glucose and impaired learning and memory ability. Moreover, the model mice presented increased levels of APP, p-Tau, p-IRS1, TREM2, IL-1β, IL-6, TNF-α, ocln, zo-1, and clnds; decreased levels of p-AKT, p-ERK, and TREM1; and neuron damage and the hyperactivation of astrocytes and microglia in the hippocampus as compared with control mice. Only male mice were used in this study. Although AD and type 2 diabetes mellitus (T2DM) are distinct pathologies, our results suggested that combination of HFD and STZ/I.P., a widely used T2DM modeling method, could successfully induce AD-like behavioral impairments and neuropathological injuries in mice; the mechanism might be involved with neuroinflammation and its associated dysfunction of IRS1/AKT/ERK signaling pathway. Our findings further support the potential overlap between T2DM and AD pathophysiology, providing insight into the mechanisms underlying the comorbidity of these diseases.

Integrative analysis of single-nucleus RNA sequencing and Mendelian randomization to explore novel risk genes for Alzheimer's disease

In this study, we aimed to delineate cellular heterogeneity in Alzheimer's disease (AD) and identify genetic markers contributing to its pathogenesis using integrative analysis of single-nucleus RNA sequencing (sn-RNA-Seq) and Mendelian randomization (MR). The dorsolateral prefrontal cortex sn-RNA-Seq dataset (GSE243292) was sourced from the Gene Expression Omnibus (GEO) database. Data preprocessing was conducted using the Seurat R software package, employing principal component analysis (PCA) and uniform manifold approximation and projection (UMAP) for cell clustering and annotation. MR analysis was used to identify instrumental variables from expression quantitative trait loci (eQTL) and GWAS data by applying inverse variance weighting (IVW), weighted median (WM) and MR-Egger methods. This was complemented by leave-one-out sensitivity analysis to validate the causal relationship on AD risk genes. We identified 23 distinct cell clusters, which were annotated into eight subgroups, including oligodendrocytes, oligodendrocyte precursors, astrocytes, macrophage cells, endothelial cells, glutamatergic neurons, neural stem cells, and neurons. Notably, the number of macrophages significantly increased in the AD group. Using genome-wide association study (GWAS) summaries and eQTL data, MR analysis identified causal relationships for 7 genes with significant impacts on AD risk. Among these genes, CACNA2D3, INPP5D, RBM47, and TBXAS1 were associated with a decreased risk of AD, whereas EPB41L2, MYO1F, and SSH2 were associated with an increased risk. A leave-one-out sensitivity analysis confirmed the robustness of these findings. Expression analysis revealed that these genes were variably expressed across different cell subgroups. Except for the CACNA2D3 gene, the other 6 genes showed increased expression levels in the macrophages, particularly EPB41L2 and SSH2. Our findings highlight the potential of specific genetic markers identified through integrative analysis of sn-RNA-Seq and MR in guiding the diagnosis and therapeutic strategies for Alzheimer's disease.

High Mobility Group Box Protein (HMGB1): A Potential Therapeutic Target for Diabetic Encephalopathy

HMGB (high mobility group B) is one of the ubiquitous non-histone nuclear protein superfamilies that make up the HMG (high mobility group) protein group. HMGB1 is involved in a variety of physiological and pathological processes in the human body, including a structural role in the cell nucleus as well as replication, repair, DNA transcription, and assembly of nuclear proteins. It functions as a signaling regulator in the cytoplasm and a pro-inflammatory cytokine in the extracellular environment. Among several studies, HMGB1 protein is also emerging as a crucial factor involved in the development and progression of diabetic encephalopathy (DE) along with other factors such as hyperglycaemia-induced oxidative and nitrosative stress. Diabetes' chronic side effect is DE, which manifests as cognitive and psychoneurological dysfunction. The HMGB1 is released outside to the extracellular medium in diabetes condition through active or passive routes, where it functions as a damage-associated molecular pattern (DAMP) molecule to activate several signaling pathways by interacting with receptors for advanced glycosylation end-products (RAGE)/toll like receptors (TLR). HMGB1 reportedly activates inflammatory pathways, disrupts the blood-brain barrier, causes glutamate toxicity and oxidative stress, and promotes neuroinflammation, contributing to the development of cognitive impairment and neuronal damage which is suggestive of the involvement of HMGB1 in the enhancement of the diabetes-induced encephalopathic condition. Additionally, HMGB1 is reported to induce insulin resistance, further exacerbating the metabolic dysfunction associated with diabetes mellitus (DM). Thus, the present review explores the possible pathways associated with DM-induced hyperactivation of HMGB1 ultimately leading to DE.

Melatonin rescues pregnant female mice and their juvenile offspring from high fat diet-induced alzheimer disease neuropathy

High fat diet (HFD) is a prime factor, which contributes to the present epidemic of metabolic syndrome. Prolonged intake of HFD induces oxidative stress (OS) that in turn causes neuroinflammation, neurodegeneration, insulin resistance, amyloid burden, synaptic dysfunction and cognitive impairment hence leading to Alzheimer's disease neuropathy. Melatonin (secreted by the Pineal gland) has the potential to nullify the toxic effects of reactive oxygen species (ROS) and have been shown to ameliorate various complications induced by HFD in rodent models. This study aimed to assess the neurotherapeutic effects of melatonin on HFD-induced neuroinflammation and neurodegeneration mediated by OS in pregnant female mice and their offspring. Western blotting, immunohistochemistry and antioxidant enzyme assays were used for quantification of samples from the hippocampal region of the brain of pregnant albino mice and their offspring. Short- and long-term memory was assessed by Y-maze and Morris Water Maze tests. HFD significantly induced OS leading to AD like neuropathology in the pregnant mice and their offspring while melatonin administration simultaneously with the HFD significantly prevented this neuropathy. This study reports that melatonin exerts these effects through the stimulation of SIRT1/Nrf2/HO-1 pathway that in turn reduces the HFD-induced OS and its downstream signaling. In conclusion melatonin prevents HFD-induced multiple complications that ultimately leads to the memory dysfunction in pregnant female mice and their successive generation via activation of SIRT1/Nrf2 signaling pathway.

Redox imbalance and metabolic defects in the context of Alzheimer disease

Redox reactions play a critical role for intracellular processes, including pathways involved in metabolism and signaling. Reactive oxygen species (ROS) act either as second messengers or generators of protein modifications, fundamental mechanisms for signal transduction. Disturbance of redox homeostasis is associated with many disorders. Among these, Alzheimer's disease is a neurodegenerative pathology that presents hallmarks of oxidative damage such as increased ROS production, decreased activity of antioxidant enzymes, oxidative modifications of macromolecules, and changes in mitochondrial homeostasis. Interestingly, alteration of redox homeostasis is closely associated with defects of energy metabolism, involving both carbohydrates and lipids, the major energy fuels for the cell. As the brain relies exclusively on glucose metabolism, defects of glucose utilization represent a harmful event for the brain. During aging, a progressive perturbation of energy metabolism occurs resulting in brain hypometabolism. This condition contributes to increase neuronal cell vulnerability ultimately resulting in cognitive impairment. The current review discusses the crosstalk between alteration of redox homeostasis and brain energy defects that seems to act in concert in promoting Alzheimer's neurodegeneration.

Potential therapeutic natural compounds for the treatment of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a complicated neurodegenerative disease with cognitive impairment occurring in the older people, in which extracellular accumulation of β-amyloid and intracellular aggregation of hyperphosphorylated tau are regarded as the prevailing theories. However, the exact AD mechanism has not been determined. Moreover, there is no effective treatment available in phase III trials to eradicate AD, which is imperative to explore novel treatments.

PURPOSE

A number of up-to-date pre-clinical studies on cognitive impairment is beneficial to clarify the pathology of AD. This review recapitulates several advances in AD pathobiology and discusses the neuroprotective effects of natural compounds, such as phenolic compounds, natural polysaccharides and oligosaccharides, peptide, and lipids, underscoring the therapeutic potential for AD.

METHODS

Electronic databases involving PubMed, Web of Science, and Google Scholar were searched up to October 2023. Articles were conducted using the keywords like Alzheimer's disease, pathogenic mechanisms, natural compounds, and neuroprotection.

RESULT

This review summarized several AD pathologies and the neuroprotective effects of natural compounds such as natural polysaccharides and oligosaccharides, peptide, and lipids.

CONCLUSION

We have discussed the pathogenic mechanisms of AD and the effect natural products on neurodegenerative diseases particularly in treating AD. Specifically, we investigated the molecular pathways and links between natural compounds and Alzheimer's disease such as through NF-κB, Nrf2, and mTOR pathway. Further investigation is necessary in exploring the bioactivity and effectiveness of natural compounds in clinical trials, which may provide a promising treatment for AD patients.

Pterostilbene Ameliorates Cognitive Impairment in Polycystic Ovary Syndrome Rat Model through Improving Insulin Resistance via the IRS-1/PI3K/Akt/GSK-3β Pathway: A Comparative Study with Metformin

Polycystic ovary syndrome (PCOS) is an intricate endocrine disorder that targets millions of women globally. Recent research has drawn attention to its association with cognitive impairment and Alzheimer's disease (AD) risk, yet the exact mechanism remains elusive. This study aimed to explore the potential role of PCOS-associated insulin resistance (IR) and inflammation in linking PCOS to AD pathogenesis. It additionally investigated the therapeutic merits of pterostilbene (PTS) in ameliorating PCOS and associated cognitive deficits in comparison to metformin (MET). Rats were divided into five groups; vehicle group, PTS group [30 mg/kg, per os (p.o.) for 13 days], and the remaining three groups received letrozole (1 mg/kg, p.o. for 21 days) to represent the PCOS, PCOS + MET (300 mg/kg, p.o. for 13 days), and PCOS + PTS groups, respectively. Behavioral tests were conducted, along with a histopathological investigation of brains and ovaries. Assessment of serum hormonal profile and hippocampal IRS-1/PI3K/AKT/GSK-3β insulin signaling pathway components were performed. PTS rats exhibited improved insulin sensitivity and hormonal profile, besides enhanced neurobehavioral tests performance and histopathological findings. These effects may be attributed to modulation of the IRS-1/PI3K/AKT/GSK-3β pathway, reducing GSK-3β activity, and mitigating Tau hyperphosphorylation and Aβ accumulation in the brain. Likewise, PTS attenuated nuclear factor kappa B-mediated inflammation and reversed AChE elevation, suggesting multifaceted neuroprotective effects. Comparatively, PTS showed outcomes similar to those of MET in most parameters. The obtained findings validated that dysregulated insulin signaling in PCOS rats detrimentally affects cognitive function, which is halted by PTS, unveiling the potential of PTS as a novel therapy for PCOS and related cognitive deficits.

Influence of Exercise and Genistein to Mitigate the Deleterious Effects of High-Fat High-Sugar Diet on Alzheimer's Disease-Related Markers in Male Mice

The prevalence of obesity and related consequences, including insulin resistance and Alzheimer's-like neuropathology, has increased dramatically. Contributing to this prevalence is the shift in lifestyle preference away from wholesome foods and exercise to the Western-style diet and sedentarism. Despite advances in drug development, a healthy diet and regular exercise remain the most effective approaches to mitigating the unwanted sequelae of diet-induced obesity on brain health. In this study, we used the high-fat high-sugar (HFHS) mouse model of neurodegeneration to examine the effects of exercise training (HFHS+Ex), genistein treatment (HFHS+Gen), and combination treatment (HFHS+Ex+Gen) on proteins relating to neurodegeneration in the brain of male mice. After a period of 12 weeks, as expected, HFHS feeding increased body weight, adipose tissue weight, and systemic plasma inflammation (TNF-α) compared to lean mice fed a standard diet. HFHS feeding also increased protein expression of brain markers of insulin resistance (pGSK-3β, p-IR), apoptosis (caspase 3), early neurofibrillary tangles (CP13), and amyloid-beta precursor (CT20). Compared to HFHS mice, Ex decreased body weight, plasma TNF-α, and expression of pGSK-3β, caspase 3, CP13, amyloid-β precursor (22c11), and ADAM10. Treatment with Gen was equally protective on these markers and decreased the expression of p-IR. Combination treatment with Ex and Gen afforded the greatest overall benefits, and this group exhibited the greatest reduction in body and adipose tissue weight and all brain markers, except for 22c11 and ADAM10, which were decreased compared to mice fed an HFHS diet. In addition, levels of 4G8, which detects protein levels of amyloid-β, were decreased with combination treatment. Our results indicate that exercise training, genistein supplementation, or combination treatment provide varying degrees of neuroprotection from HFHS feeding-induced Alzheimer's pathology. Future perspectives could include evaluating moderate exercise regimens in combination with dietary supplementation with genistein in humans to determine whether the same benefits translate clinically.

Banxia Xiexin Decoction Alleviated Cerebral Glucose Metabolism Disorder by Regulating Intestinal Microbiota in APP/PS1 Mice

OBJECTIVE

To identify whether Banxia Xiexin Decoction (BXD) alleviates cerebral glucose metabolism disorder by intestinal microbiota regulation in APP/PS1 mice.

METHODS

Forty-five 3-month-old male APP/PS1 mice were divided into 3 groups using a random number table (n=15 per group), including a model group (MG), a liraglutide group (LG) and a BXD group (BG). Fifteen 3-month-old male C57BL/6J wild-type mice were used as the control group (CG). Mice in the BG were administered BXD granules by gavage at a dose of 6 g/(kg•d) for 3 months, while mice in the LG were injected intraperitoneally once daily with Liraglutide Injection (25 nmol/kg) for 3 months. Firstly, liquid chromatography with tandem-mass spectrometry was used to analyze the active components of BXD granules and the medicated serum of BXD. Then, the cognitive deficits, Aβ pathological change and synaptic plasticity markers, including synaptophysin (SYP) and postsynaptic density protein 95 (PSD95), were measured in APP/PS1 mice. Brain glucose uptake was detected by micropositron emission tomography. Intestinal microbial constituents were detected by 16S rRNA sequencing. The levels of intestinal glucagon-like peptide 1 (GLP-1) and cerebral GLP-1 receptor (GLP-1R), as well as the phosphoinositide-3-kinase/protein kinase B/glycogen synthase kinase-3β (PI3K/Akt/GSK3β) insulin signaling pathway were determined by immunohistochemical (IHC) staining and Western blot analysis, respectively.

RESULTS

BXD ameliorated cognitive deficits and Aβ pathological features (P<0.01). The expressions of SYP and PSD95 in the BG were higher than those in the MG (P<0.01). Brain glucose uptake in the BG was higher than that in the MG (P<0.01). The intestinal microbial composition in the BG was partially reversed. The levels of intestinal GLP-1 in the BG were higher than those in the MG (P<0.01). Compared with the MG, the expression levels of hippocampal GLP-1R, Akt, PI3K and p-PI3K in the BG were significantly increased (P<0.01), while the levels of GSK3β were reduced (P<0.01).

CONCLUSION

BXD exhibited protective effects against Alzheimer's disease by regulating the gut microbiota/GLP-1/GLP-1R, enhancing PI3K/Akt/GSK3β insulin signaling pathway, and improving brain glucose metabolism.

Canagliflozin Mitigated Cognitive Impairment in Streptozotocin-Induced Sporadic Alzheimer's Disease in Mice: Role of AMPK/SIRT-1 Signaling Pathway in Modulating Neuroinflammation

Sporadic Alzheimer's disease (SAD) represents a major health concern especially among elderly. Noteworthy, neuroinflammation and oxidative stress are highly implicated in AD pathogenesis resulting in enhanced disease progression. Moreover, most of the available anti-Alzheimer drugs have several adverse effects with variable efficacy, therefore new strategies, including agents with anti-inflammatory and antioxidant effects, are encouraged. Along these lines, canagliflozin (CAN), with its anti-inflammatory and anti-apoptotic activities, presents a promising candidate for AD treatment. Therefore, this study aimed to evaluate the therapeutic potential of CAN via regulation of AMPK/SIRT-1/BDNF/GSK-3β signaling pathway in SAD. SAD model was induced by intracerebroventricular streptozotocin injection (ICV-STZ;3 mg/kg, once), while CAN was administered (10 mg/kg/day, orally) to STZ-treated mice for 21 days. Behavioral tests, novel object recognition (NOR), Y-Maze, and Morris Water Maze (MWM) tests, histopathological examination, total adenosine monophosphate-activated protein kinase (T-AMPK) expression, p-AMPK, and silent information regulator-1 (SIRT-1) were evaluated. Furthermore, brain-derived neurotrophic factor (BDNF), glycogen synthase kinase-3β (GSK-3β), acetylcholinesterase (AChE), Tau protein, insulin-degrading enzyme (IDE), nuclear factor erythroid-2 (Nrf-2), interleukin-6 (IL-6), nuclear factor kappa-B-p65 (NFκB-p65), beta-site APP cleaving enzyme 1 (BACE-1), and amyloid beta (Aβ) plaque were assessed. CAN restored STZ-induced cognitive deficits, confirmed by improved behavioral tests and histopathological examination. Besides, CAN halted STZ-induced neurotoxicity through activation of p-AMPK/SIRT-1/BDNF pathway, subsequently reduction of GSK-3β, Tau protein, AChE, NFκB-p65, IL-6, BACE-1, and Aβ plaque associated with increased IDE and Nrf-2. Consequentially, our findings assumed that CAN, via targeting p-AMPK/SIRT-1 pathway, combated neuroinflammation and oxidative stress in STZ-induced AD. Thus, this study highlighted the promising effect of CAN for treating AD.

The protective role of carnosine against type 2 diabetes-induced cognitive impairment

The morbidity and mortality associated with type 2 diabetes mellitus (T2DM) have grown exponentially over the last 30 years. Together with its associated complications, the mortality rates have increased. One important complication in those living with T2DM is the acceleration of age-related cognitive decline. T2DM-induced cognitive impairment seriously affects memory, executive function, and quality of life. However, there is a lack of effective treatment for both diabetes and cognitive decline. Thus, finding novel treatments which are cheap, effective in both diabetes and cognitive impairment, are easily accessible, are needed to reduce impact on patients with diabetes and health-care systems. Carnosine, a histidine containing dipeptide, plays a protective role in cognitive diseases due to its antioxidant, anti-inflammation, and anti-glycation properties, all of which may slow the development of neurodegenerative diseases and ischemic injury. Furthermore, carnosine is also involved in regulating glucose and insulin in diabetes. Herein, we discuss the neuroprotective role of carnosine and its mechanisms in T2DM-induced cognitive impairment, which may provide a theoretical basis and evidence base to evaluate whether carnosine has therapeutic effects in alleviating cognitive dysfunction in T2DM patients.

Exploring the neuropharmacological potential of empagliflozin on nootropic and scopolamine-induced amnesic model of Alzheimer's like conditions in rats

BACKGROUND

Alzheimer's disease (AD) is one of the most challenging and prevalent neurodegenerative disorder globally with a rising prevalence, characterized by progressive cognitive decline, memory loss, and behavioural changes. Current research aims to determine the nootropic and anti-amnesic effect of Empagliflozin (EMPA) against scopolamine-induced amnesia in rats, by modulating the cholinergic and N-Methyl D-Aspartate (NMDA) receptors.

METHODS

Rats were treated once daily with an EMPA (5 and 10 mg/kg) and donepezil (2.5 mg/kg) for successive 26 days. During the final 13 days of treatment, a daily injection of scopolamine (1 mg/kg) was administered to induce cognitive deficits.

RESULTS

EMPA was found to be significantly reduce escape latency, increase time spent in the target quadrant, and enhanced the number of target zone crossings in the Morris water maze (MWM) test, indicating improved spatial memory. Moreover, EMPA increased the recognition index and the number of spontaneous alternations in the novel object recognition (NOR) and Y-maze tests, respectively, suggesting enhanced memory.

DISCUSSION

Interestingly doses of EMPA (5 mg/kg, 10 mg/kg) exhibited memory-enhancing effects even in the absence of scopolamine-induced impairment. Biochemical analysis revealed that EMPA elevated the levels of glutathione (GSH), a potent antioxidant, while decreasing lipid peroxidation (LPO) activity and increasing catalase (CAT) levels, indicating its antioxidative properties. Interestingly molecular docking studies revealed that EMPA fit perfectly in the active sites of M1 muscarinic acetylcholine (mACh) and NMDA receptors. These results indicated that the nootropic and antiamnesic effect of EMPA is possibly mediated via M1 and NMDA receptors and might be a remedy for AD.

The interaction between insulin resistance and Alzheimer's disease: a review article

Insulin serves multiple functions as a growth-promoting hormone in peripheral tissues. It manages glucose metabolism by promoting glucose uptake into cells and curbing the production of glucose in the liver. Beyond this, insulin fosters cell growth, drives differentiation, aids protein synthesis, and deters degradative processes like glycolysis, lipolysis, and proteolysis. Receptors for insulin and insulin-like growth factor-1 are widely expressed in the central nervous system. Their widespread presence in the brain underscores the varied and critical functions of insulin signaling there. Insulin aids in bolstering cognition, promoting neuron extension, adjusting the release and absorption of catecholamines, and controlling the expression and positioning of gamma-aminobutyric acid (GABA). Importantly, insulin can effortlessly traverse the blood-brain barrier. Furthermore, insulin resistance (IR)-induced alterations in insulin signaling might hasten brain aging, impacting its plasticity and potentially leading to neurodegeneration. Two primary pathways are responsible for insulin signal transmission: the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway, which oversees metabolic responses, and the mitogen-activated protein kinase (MAPK) pathway, which guides cell growth, survival, and gene transcription. This review aimed to explore the potential shared metabolic traits between Alzheimer's disease (AD) and IR disorders. It delves into the relationship between AD and IR disorders, their overlapping genetic markers, and shared metabolic indicators. Additionally, it addresses existing therapeutic interventions targeting these intersecting pathways.

Association between the triglyceride-glucose index and cognitive impairment in China: a community population-based cross-sectional study

INTRODUCTION

Insulin resistance (IR) is a feature of metabolic syndrome and plays an important role in cognitive impairment (CI). The triglyceride-glucose (TyG) index is a convenient and cost-effective surrogate for assessing IR. This study aimed to assess the association between the TyG index and CI.

METHODS

This community population-based cross-sectional study used a cluster-sampling methodology. All participants underwent the education-based Mini-Mental State Examination (MMSE), and those with CI were identified using standard thresholds. The fasting blood triglyceride and glucose levels were measured in the morning, and the TyG index was calculated as ln (½ fasting triglyceride level [mg/dL] × fasting blood glucose level [mg/dL]). Multivariable logistic regression and subgroup analysis were used to assess the relationship between the TyG index and CI.

RESULTS

This study included 1484 subjects, of which 93 (6.27%) met the CI criteria. Multivariable logistic regression showed that CI incidence increased by 64% per unit increase in the TyG index (odds ratio [OR] = 1.64, 95% confidence interval [CI]: 1.02-2.63, p = 0.042). CI risk was 2.64-fold higher in the highest TyG index quartile compared to the lowest TyG index quartile (OR = 2.64, 95% CI: 1.19-5.85, p = 0.016). Finally, interaction analysis showed that sex, age, hypertension, and diabetes did not significantly affect the association between the TyG index and CI.

CONCLUSION

The present study suggested that an elevated TyG index was associated with a higher CI risk. Subjects with a higher TyG index should manage and treat at an early stage to alleviate the cognitive decline.

Malondialdehyde and TNF-α lowering effects of purified gambier (Uncaria gambir Roxb.) in diabetic rats

BACKGROUND

Malondialdehyde (MDA) is one of a dominat marker in oxidative stress condition, and when inflammation occurred tumor necrosis factor- α (TNF-α) played a significant influence in the propagation this process. Purified gambier (Uncaria gambier Roxb.) contained 90% catechin which is proven to have antioxidant activity and may prevent unwanted inflammatory responses during diabetic state.

OBJECTIVE

The objective of this research was to assess how purified gambier affected plasma MDA and TNF- α levels in alloxan-induced diabetic rats.

MATERIAL AND METHODS

In this study, 35 rats were used. Alloxan 120 mg/kg BW intraperitoneal injection was administered to induce diabetes conditions in rats. All animals were divided into 5 groups, diabetic control group treated with vehicle, positive control group treated with glibenclamide dose 0.45 mg/kg BW), and treatment groups treated with purified gambier dose of 2.5; 5 and 10 mg/kg BW. All animals were treated respectively for 14 days. Plasma MDA and TNF- α levels were measured on day 3, and 14.

RESULTS

Two-way ANOVA was applied to analyze all of the data, these findings suggested that purified gambier has antioxidant-related anti-inflammation actions. possesses blood sugar-lowering activity (p<0.05). The plasma MDA and TNF- α level of treatment group were significantly reduced (p<0.05) compared to diabetes control group.

CONCLUSION

These results depicted that at doses of 2.5-10 mg/kg BW, purified gambier has antioxidant-associated anti-inflammation effects when given for 14 days on diabetic rat model by reducing plasma levels MDA and TNF-α.

SGLT2 and DPP4 inhibitors improve Alzheimer's disease-like pathology and cognitive function through distinct mechanisms in a T2D-AD mouse model

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2D) share common features, including insulin resistance. Brain insulin resistance has been implicated as a key factor in the pathogenesis of AD. Recent studies have demonstrated that anti-diabetic drugs sodium-glucose cotransporter-2 inhibitor (SGLT2-i) and dipeptidyl peptidase-4 inhibitor (DPP4-i) improve insulin sensitivity and provide neuroprotection. However, the effects of these two inhibitors on the brain metabolism and insulin resistance remain uninvestigated. We developed a T2D-AD mouse model using a high-fat diet (HFD) for 19 weeks along with a single dose of streptozotocin (100 mg/kg, intraperitoneally) at the fourth week of HFD initiation. Subsequently, the animals were treated with SGLT2-i (empagliflozin, 25 mg/kg/day orally [p.o.]) and DPP4-i (sitagliptin, 100 mg/kg/day p.o.) for 7 weeks. Subsequently, behavioral tests were performed, and the expression of insulin signaling, AD-related, and other signaling pathway proteins in the brain were examined. T2D-AD mice not only showed increased blood glucose levels and body weight but also insulin resistance. SGLT2-i and DPP4-i effectively ameliorated insulin sensitivity and reduced body weight in these mice. Furthermore, SGLT2-i and DPP4-i significantly improved hippocampal-dependent learning, memory, and cognitive functions in the T2D-AD mouse model. Interestingly, SGLT2-i and DPP4-i reduced the hyperphosphorylated tau (pTau) levels and amyloid β (Aβ) accumulation and enhanced brain insulin signaling. SGLT2-i reduced pTau accumulation through the angiotensin converting enzyme-2/angiotensin (1-7)/ mitochondrial assembly receptor axis, whereas DPP4-i reduced Aβ accumulation by increasing insulin-degrading enzyme levels. These findings suggest that SGLT2-i and DPP4-i prevent AD-like pathology and cognitive dysfunction in T2D mice potentially through affecting brain insulin signaling via different mechanisms.

Qi Fu Yin ameliorates neuroinflammation through inhibiting RAGE and TLR4/NF-κB pathway in AD model rats

The purpose of this study is to investigate the therapeutic effect of Qi Fu Yin (QFY) on Alzheimer's disease (AD) both computationally and experimentally. Network pharmacology analysis and molecular docking were conducted to identify potential targets and signaling pathways involved in QFY treating AD. Streptozotocin-induced AD rat model was used to verify important targets and predicted pathways. The components of QFY were identified using liquid chromatography-tandem mass spectrometry. The results indicate that the potential targets of QFY are highly enriched for anti-inflammatory pathways. Molecular docking analysis revealed stable structures formed between QFY's active compounds, including stigmasterol, β-sitosterol, and isorhamnetin, and the identified targets. In vivo, QFY improved cognitive memory in AD rats and reduced the mRNA expression levels of toll-like receptor 4 (TLR4), the receptor for advanced glycation end products (AGER), and the inflammatory factors interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the brains of AD rats. Furthermore, QFY effectively reduced nuclear translocation of nuclear factor-kappa B (NF-κB) and inhibited NF-κB and microglia activation. In conclusion, QFY can ameliorate neuroinflammation in AD model rats, partly via the inhibition of TLR4 and RAGE/NF-κB pathway and microglia activation, thereby enhancing learning and memory in AD model rats.

Metformin ameliorates insulin resistance, thyroid nodules and thyroid function

OBJECTIVE

To evaluate the ameliorative impact of metformin on insulin resistance (IR), as well as thyroid nodules (TNs) and function in TN patients with IR.

METHODS

The clinical data of 128 TN patients with IR admitted to Yantai Laiyang Central Hospital from July 2018 to March 2020 were retrospectively analyzed and categorized into a control group (CNG, n = 64) and a study group (SG, n = 64). Patients in the CNG received standard lifestyle intervention, while those in the SG received standard lifestyle intervention in conjunction with metformin therapy for 1 year of course. Weight-related indicators, IR, thyroid function, TN diameter, and oxidative stress levels were compared between the two groups before and after treatment. Additionally, the safety of metformin was evaluated.

RESULTS

Before treatment, no significant differences were observed between the two groups in fasting plasma glucose (FPG), 2-h postprandial glucose (2hPG), glycated hemoglobin (HbA1c), fasting insulin (FINS), homeostatic model assessment of insulin resistance (HOMA-IR), systolic blood pressure (SBP), diastolic blood pressure (DBP), thyroid-stimulating hormone (TSH), malondialdehyde (MDA), TN diameter, and thyroid volume (P > 0.05). After treatment, significant statistical differences were observed in the aforementioned indicators between the two groups (P < 0.05). After 1 year of treatment, the SG exhibited lower levels of FPG, 2hPG, HbA1c, FINS, HOMA-IR, SBP, DBP, TSH, MDA, TN diameter, and thyroid volume, and showed higher levels of HOMA-β, superoxide dismutase, and glutathione peroxidase levels compared to before treatment (P < 0.05). The incidence of adverse reactions in the SG was significantly higher than that in the CNG (P < 0.05). Taking metformin and free thyroxine (FT4) were protective factors for TSH (P < 0.05).

CONCLUSION

Metformin could significantly improve IR and oxidative stress levels, regulate TSH levels, and shrink TNs in TN patients with IR, with high safety. The administration of metformin and FT4 were identified as protective factors for positive prognosis.

Tau suppresses microtubule-regulated pancreatic insulin secretion

Tau protein is implicated in the pathogenesis of Alzheimer's disease (AD) and other tauopathies, but its physiological function is in debate. Mostly explored in the brain, tau is also expressed in the pancreas. We further explored the mechanism of tau's involvement in the regulation of glucose-stimulated insulin secretion (GSIS) in islet β-cells, and established a potential relationship between type 2 diabetes mellitus (T2DM) and AD. We demonstrate that pancreatic tau is crucial for insulin secretion regulation and glucose homeostasis. Tau levels were found to be elevated in β-islet cells of patients with T2DM, and loss of tau enhanced insulin secretion in cell lines, drosophila, and mice. Pharmacological or genetic suppression of tau in the db/db diabetic mouse model normalized glucose levels by promoting insulin secretion and was recapitulated by pharmacological inhibition of microtubule assembly. Clinical studies further showed that serum tau protein was positively correlated with blood glucose levels in healthy controls, which was lost in AD. These findings present tau as a common therapeutic target between AD and T2DM.

Identification of diagnostic biomarkers in Alzheimer's disease by integrated bioinformatic analysis and machine learning strategies

Background

Alzheimer's disease (AD) is the most prevalent form of dementia, and is becoming one of the most burdening and lethal diseases. More useful biomarkers for diagnosing AD and reflecting the disease progression are in need and of significance.

Methods

The integrated bioinformatic analysis combined with machine-learning strategies was applied for exploring crucial functional pathways and identifying diagnostic biomarkers of AD. Four datasets (GSE5281, GSE131617, GSE48350, and GSE84422) with samples of AD frontal cortex are integrated as experimental datasets, and another two datasets (GSE33000 and GSE44772) with samples of AD frontal cortex were used to perform validation analyses. Functional Correlation enrichment analyses were conducted based on Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and the Reactome database to reveal AD-associated biological functions and key pathways. Four models were employed to screen the potential diagnostic biomarkers, including one bioinformatic analysis of Weighted gene co-expression network analysis (WGCNA)and three machine-learning algorithms: Least absolute shrinkage and selection operator (LASSO), support vector machine-recursive feature elimination (SVM-RFE) and random forest (RF) analysis. The correlation analysis was performed to explore the correlation between the identified biomarkers with CDR scores and Braak staging.

Results

The pathways of the immune response and oxidative stress were identified as playing a crucial role during AD. Thioredoxin interacting protein (TXNIP), early growth response 1 (EGR1), and insulin-like growth factor binding protein 5 (IGFBP5) were screened as diagnostic markers of AD. The diagnostic efficacy of TXNIP, EGR1, and IGFBP5 was validated with corresponding AUCs of 0.857, 0.888, and 0.856 in dataset GSE33000, 0.867, 0.909, and 0.841 in dataset GSE44770. And the AUCs of the combination of these three biomarkers as a diagnostic tool for AD were 0.954 and 0.938 in the two verification datasets.

Conclusion

The pathways of immune response and oxidative stress can play a crucial role in the pathogenesis of AD. TXNIP, EGR1, and IGFBP5 are useful biomarkers for diagnosing AD and their mRNA level may reflect the development of the disease by correlation with the CDR scores and Breaking staging.

Nose-to-brain drug delivery for the treatment of CNS disease: New development and strategies

Delivering drugs to the brain has always been a challenging task due to the restrictive properties of the blood-brain barrier (BBB). Intranasal delivery is therefore emerging as an efficient method of administration, making it easy to self-administration and thus provides a non-invasive and painless alternative to oral and parenteral administration for delivering therapeutics to the central nervous system (CNS). Recently, drug formulations have been developed to further enhance this nose-to-brain transport, primarily using nanoparticles (NPs). Therefore, the purposes of this review are to highlight and describe the anatomical basis of nasal-brain pathway and provide an overview of drug formulations and current drugs for intranasal administration in CNS disease.

A review: Exploring the metabolic and structural characterisation of beta pleated amyloid fibril in human tissue using Raman spectrometry and SAXS

Amyloidosis is a deleterious condition caused by abnormal amyloid fibril build-up in living tissues. To date, 42 proteins that are linked to amyloid fibrils have been discovered. Amyloid fibril structure variation can affect the severity, progression rate, or clinical symptoms of amyloidosis. Since amyloid fibril build-up is the primary pathological basis for various neurodegenerative illnesses, characterization of these deadly proteins, particularly utilising optical techniques have been a focus. Spectroscopy techniques provide significant non-invasive platforms for the investigation of the structure and conformation of amyloid fibrils, offering a wide spectrum of analyses ranging from nanometric to micrometric size scales. Even though this area of study has been intensively explored, there still remain aspects of amyloid fibrillization that are not fully known, a matter hindering progress in treating and curing amyloidosis. This review aims to provide recent updates and comprehensive information on optical techniques for metabolic and proteomic characterization of β-pleated amyloid fibrils found in human tissue with thorough literature analysis of publications. Raman spectroscopy and SAXS are well established experimental methods for study of structural properties of biomaterials. With suitable models, they offer extended information for valid proteomic analysis under physiologically relevant conditions. This review points to evidence that despite limitations, these techniques are able to provide for the necessary output and proteomics indication in order to extrapolate the aetiology of amyloid fibrils for reliable diagnostic purposes. Our metabolic database may also contribute to elucidating the nature and function of the amyloid proteome in development and clearance of amyloid diseases.

Portulaca oleracea L. (purslane) improves the anti-inflammatory, antioxidant and autophagic actions of metformin in the hippocampus of diabetic demented rats

Great body of evidence links cognitive decline to diabetes/insulin resistance. In this study the effect of Portulaca oleracea (PUR) (100 mg/kg), Metformin (MET) (200 mg/kg), a first line diabetes mellitus type 2 therapy, and their combination on cognitive function and hippocampal markers in diabetic rats were assessed. Male rats were injected with streptozotocin (30 mg/kg on two successive weeks) followed by 4 weeks of treatment. Possible antioxidant, anti-inflammatory, and autophagy enhancing mechanisms of these drugs were investigated in the hippocampal tissue using spectrophotometry, ELISA, and western blotting. Diabetic rats suffered significant cognitive impairment in Morris's water maze, hippocampal TBARS elevation, GSH depletion, and SOD upregulation. In addition, diabetes promoted the secretion of hippocampal inflammatory cytokines, TNF-α and IL-1β, and depleted anti-inflammatory cytokines as IL-10. Such detrimental changes were reversed by MET and/or PUR. Notably, AMPK was upregulated by diabetes, then restored to normal by MET and/or PUR. The pattern of change in AMPK expression was concomitant with changes in oxidative and inflammatory burden. Hence, AMPK is believed to be a key mediator in most of the measured pre-AD markers in this study. However, from our results, PUR is believed to have non-AMPK dependent actions as well. In conclusion, antidiabetic agents as metformin and purslane extract proved to be invaluable in addressing the cognitive decline and hippocampal changes that arise as a complication of diabetes. They mainly acted through AMPK pathway; however, their usefulness was not limited to AMPK pathways since their combination was suggested to have a different mechanism.

Pharmacological and physiological roles of adipokines and myokines in metabolic-related dementia

Dementia is a detrimental neuropathologic condition with considerable physical, mental, social, and financial impact on patients and society. Patients with metabolic syndrome (MetS), a group of diseases that occur in tandem and increase the risk of neurologic diseases, have a higher risk of dementia. The ratio between muscle and adipose tissue is crucial in MetS, as these contain many hormones, including myokines and adipokines, which are involved in crosstalk and local paracrine/autocrine interactions. Evidence suggests that abnormal adipokine and myokine synthesis and release may be implicated in various MetS, such as atherosclerosis, diabetic mellitus (DM), and dyslipidemia, but their precise role is unclear. Here we review the literature on adipokine and myokine involvement in MetS-induced dementia via glucose and insulin homeostasis regulation, neuroinflammation, vascular dysfunction, emotional changes, and cognitive function.

Correlations between Cognitive Evaluation and Metabolic Syndrome

One of the most common medical diseases is metabolic syndrome (MetS), which encompasses diabetes and obesity. It has a systemic effect, which has long-lasting consequences on the body that are still not fully understood. The objectives of the study were to investigate the association between the severity of metabolic imbalances, insulin resistance, leptin concentration, and the presence of cognitive disorders and to assess the possible protective role of some classes of drugs used in the treatment of type 2 diabetes mellitus (T2D) and dyslipidemia in order to identify a viable target in the near future. The study included 148 diabetic patients. Standardized tests for the evaluation of cognition, including Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA), were applied to all study participants. Serum concentrations of leptin and insulin were determined using the enzyme-linked immunosorbent assay method (ELISA), and insulin resistance was calculated using the homeostatic model assessment for insulin resistance (HOMA-IR). We found that MMSE and MoCA scores were associated with anthropometric parameters, and MoCA was associated with glycemic control parameters and leptin levels. Further research is needed in order to establish the magnitude of the relationship between metabolic syndrome components and cognitive decline in diabetic patients.

In silico study on evaluation of corosolic acid of Lagerstroemia speciosa against Alzheimer’s disease

Purpose

Alzheimer’s disease (AD), the most common cause of dementia, is a neurodegenerative disorder caused by the aggregation of amyloid-beta (Aβ) at outside of neuron cells and also due to tau aggregation inside the cell. Corosolic acid is aimed to be selected as a main active constituent of Lagerstroemia speciosa for the study.

Design/methodology/approach

In the present study, molecular docking of corosolic acid and tau protein was examined using PyRx-v.0.8 software. Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) properties were described and a molecular dynamics study of the bound complex was performed using Desmond.

Findings

The docking score and interactions suggested that the corosolic acid (CID:6918774) could bind to tau protein to prevent the fibrillar network, to prevent AD. During simulation corosolic acid-bound protein root mean square deviation (RMSD) values showed more stability when compared to the Apo form of protein. Molecular dynamics study of tau protein and corosolic acid complex gave the insights to develop a drug-like candidate against AD.

Originality/value

The use of corosolic acid of Lagerstroemia speciosa to prevent AD is supported by preliminary analysis on a computational basis. This compound should explore in terms of experimental strategies for the further drug development process. However, in vitro and in vivo evaluation studies are required to suggest the use of corosolic acid against AD.

Association of Alzheimer's dementia with oral bacteria, vitamin B12, folate, homocysteine levels, and insulin resistance along with its pathophysiology, genetics, imaging, and biomarkers

Alzheimer's disease is a prevalent form of dementia, particularly among the elderly population. It is characterized by progressive cognitive decline and neurodegeneration. Despite numerous studies, the exact cause of Alzheimer's disease remains uncertain, and various theories have been proposed, including Aβ amyloid deposition in the brain and tau protein hyper-phosphorylation. This review article explores the potential pathogenesis of Alzheimer's disease, focusing on the effects of derangements in the levels of vitamin B12, folate, and homocysteine, as well as the impact of oral bacteria causing periodontitis and insulin resistance, and their relationship to Alzheimer's. Studies have shown that high levels of homocysteine and low levels of vitamin B12 and folate, are associated with an increased risk of developing Alzheimer's disease. The article also explores the link between Alzheimer's disease and oral bacteria, specifically dental infections and periodontitis, which contribute to the inflammatory processes in the nervous system of Alzheimer's patients. There could be derangement in the insulin signaling further causing disruption in glucose metabolism within the brain, suggesting that Alzheimer's disease may represent a form of type 2 diabetes mellitus associated with the brain, commonly known as type 3 diabetes. Neuroimaging techniques, including MRI, PET, and tau PET, can identify the predictive characteristics of Alzheimer's disease, with amyloid PET being the most useful in ruling out the disease. The article concludes by stressing the importance of understanding genetic and neuroimaging factors in the diagnosing and treating Alzheimer's disease.

Auditory or Audiovisual Stimulation Ameliorates Cognitive Impairment and Neuropathology in ApoE4 Knock-In Mice

We hypothesized that auditory stimulation could reduce the progression of Alzheimer’s disease (AD), and that audiovisual stimulation could have additional effects through multisensory integration. We exposed 12 month old Apoetm1.1(APOE*4)Adiuj mice (a mouse model of sporadic AD) to auditory (A) or audiovisual stimulation (AV) at 40 Hz for 14 days in a soundproof chamber system (no stimulation, N). Behavioral tests were performed before and after each session, and their brain tissues were assessed for amyloid-beta expression and apoptotic cell death, after 14 days. Furthermore, brain levels of acetylcholine and apoptosis-related proteins were analyzed. In the Y-maze test, the percentage relative alternation was significantly higher in group A than in group N mice. Amyloid-beta and TUNEL positivity in the hippocampal CA3 region was significantly lower in group A and group AV mice than in group N mice (p < 0.05). Acetylcholine levels were significantly higher in group A and group AV mice than in group N mice (p < 0.05). Compared to group N mice, expression of the proapoptotic proteins Bax and caspase-3 was lower in group A, and expression of the antiapoptotic protein Bcl-2 was higher in group AV. In a mouse model of early-stage sporadic AD, auditory or audiovisual stimulation improved cognitive performance and neuropathology.

"Adjust Zang and arouse spirit" electroacupuncture ameliorates cognitive impairment by reducing endoplasmic reticulum stress in db/db mice

Introduction

Diabetic cognitive impairment (DCI) is a chronic complication of the central nervous system (CNS) caused by diabetes that affects learning and memory capacities over time. Recently, acupuncture has been shown to improve cognitive impairment in streptozotocin-induced diabetic rats. However, the effects of electroacupuncture on DCI and its underlying mechanism have not yet been elucidated in detail.

Methods

In this study, we used db/db mice as DCI animal models which showed low cognitive, learning and memory functions. Electroacupuncture significantly ameliorated DCI, which is reflected by better spatial learning and memory function using behavioral tests. The db/db mice with cognitive impairment were randomly divided into a model group (Mod) and an electroacupuncture treatment group (Acup), while db/m mice were used as a normal control group (Con). First, the mice were subjected to behavioural tests using the Morris water maze (MWM), and body weight, blood glucose, insulin, triglycerides (TG) and total cholesterol (TC) were observed; HE, Nissl, and TUNEL staining were used to observe the morphological changes and neuronal apoptosis in the mice hippocampus; Finally, Western blot and rt-PCR were applied to detect the essential proteins and mRNA of ERS and insulin signalling pathway, as well as the expression levels of Tau and Aβ.

Results

Electroacupuncture significantly ameliorated DCI, which is reflected by better spatial learning and memory function using behavioral tests. Moreover, electroacupuncture attenuated diabetes-induced morphological structure change, neuronal apoptosis in the hippocampus of db/db mice. Our results revealed that electroacupuncture could regulate the expression levels of Tau and Aβ by improving hippocampal ERS levels in db/db mice, inhibiting JNK activation, attenuating IRS1 serine phosphorylation, and restoring normal transduction of the insulin signaling pathway.

Discussion

In summary, ERS and insulin signaling pathway paly causal roles in DCI development. Electroacupuncture can significantly alleviate the pathogenesis of DCI, improve mice's learning and memory ability, and improve cognitive dysfunction. This study adds to our understanding of the effect of acupuncture on DCI and opens the door to further research on DCI.

DISC1 inhibits GSK3β activity to prevent tau hyperphosphorylation under diabetic encephalopathy

Diabetic encephalopathy (DE) is a common complication of type 2 diabetes (T2D), especially in those patients with long T2D history. Persistent high glucose (HG) stimulation leads to neuron damage and manifests like Alzheimer's disease's pathological features such as neurofilament tangle. However, the precise mechanism of high-glucose-induced tau hyperphosphorylation is not fully revealed. We here gave evidence that Disrupted in schizophrenia 1 protein (DISC1) could interact with glycogen synthase kinase 3β (GSK3β) and inhibit its activity to prevent tau hyperphosphorylation. By using DB/DB mice as animal model and HG-treated N2a cell as cell model, we found that DISC1 was downregulated both in vivo and in vitro, complicated with Tau hyperphosphorylation and GSK3β activation. Further, we identified DISC1 interacted with GSK3β by its 198th-237th amino acid residues. Overexpression of full length DISC1 but not mutated DISC1 lacking this domain could prevent HG induced tau hyperphosphorylation. Taken together, our work revealed DISC1 could be an important negative modulators of tau phosphorylation, and suggested that preservation of DISC1 could prevent HG induced neuron damage.

Impact of Eating a Carbohydrate-Restricted Diet on Cortical Atrophy in a Cross-Section of Amyloid Positive Patients with Alzheimer's Disease: A Small Sample Study

BACKGROUND

A carbohydrate-restricted diet aimed at lowering insulin levels has the potential to slow Alzheimer's disease (AD). Restricting carbohydrate consumption reduces insulin resistance, which could improve glucose uptake and neural health. A hallmark feature of AD is widespread cortical thinning; however, no study has demonstrated that lower net carbohydrate (nCHO) intake is linked to attenuated cortical atrophy in patients with AD and confirmed amyloidosis.

OBJECTIVE

We tested the hypothesis that individuals with AD and confirmed amyloid burden eating a carbohydrate-restricted diet have thicker cortex than those eating a moderate-to-high carbohydrate diet.

METHODS

A total of 31 patients (mean age 71.4±7.0 years) with AD and confirmed amyloid burden were divided into two groups based on a 130 g/day nCHO cutoff. Cortical thickness was estimated from T1-weighted MRI using FreeSurfer. Cortical surface analyses were corrected for multiple comparisons using cluster-wise probability. We assessed group differences using a two-tailed two-independent sample t-test. Linear regression analyses using nCHO as a continuous variable, accounting for confounders, were also conducted.

RESULTS

The lower nCHO group had significantly thicker cortex within somatomotor and visual networks. Linear regression analysis revealed that lower nCHO intake levels had a significant association with cortical thickness within the frontoparietal, cingulo-opercular, and visual networks.

CONCLUSIONS

Restricting carbohydrates may be associated with reduced atrophy in patients with AD. Lowering nCHO to under 130 g/day would allow patients to follow the well-validated MIND diet while benefiting from lower insulin levels.

The role of transforming growth factor β1 /Smad pathway in Alzheimer's disease inflammation pathology

Alzheimer's disease (AD), a progressive disorder, has become a global health problem and is now the main cause of dementia. The aetiology of AD is complex and remains elusive making effective AD treatment difficult. Current drugs for AD only improve symptoms but do not interfere with pathogenic mechanisms. Three main hypotheses have been brought forward regarding AD aetiology, one of them being the 'inflammation hypothesis'. A number of studies have demonstrated that inflammation plays a critical role in AD. Self-limiting neuroinflammation is considered beneficial to AD, whereas chronic inflammation aggravates brain injury and neuronal death. Transforming growth factor β 1(TGF-β1) is an anti-inflammatory cytokine with neuroprotective properties. Smad proteins are downstream molecules of TGF-β signalling. They are cytoplasmic transcription factors that can regulate targeted gene expression. In AD, impairments of TGF-β1/Smad pathways have been observed. Moreover, microglia, astrocytes, inflammasomes, and insulin resistance also have been implicated in AD pathogenesis. Elucidating the molecular mechanisms underlying AD pathogenesis is a fundamental step toward designing new treatment options. In this review, we detail the changes in TGF-β1/Smad pathways in AD and hope this will facilitate further research on AD treatment.

Linking Diabetes to Alzheimer's Disease: Potential Roles of Glucose Metabolism and Alpha-Glucosidase

Alzheimer's disease (AD) and type 2 diabetes mellitus (DM) are more prevalent with ageing and cause a substantial global socio-economic burden. The biology of these two conditions is well elaborated, but whether AD and type 2 DM arise from coincidental roots in ageing or are linked by pathophysiological mechanisms remains unclear. Research findings involving animal models have identified mechanisms shared by both AD and type 2 DM. Deposition of β-amyloid peptides and formation of intracellular neurofibrillary tangles are pathological hallmarks of AD. Type 2 DM, on the other hand, is a metabolic disorder characterised by hyperglycaemia and insulin resistance. Several studies show that improving type 2 DM can delay or prevent the development of AD, and hence, prevention and control of type 2 DM may reduce the risk of AD later in life. Alpha-glucosidase is an enzyme that is commonly associated with hyperglycaemia in type 2 DM. However, it is uncertain if this enzyme may play a role in the progression of AD. This review explores the experimental evidence that depicts the relationship between dysregulation of glucose metabolism and AD. We also delineate the links between alpha-glucosidase and AD and the potential role of alpha-glucosidase inhibitors in treating AD.

The identities of insulin signaling pathway are affected by overexpression of Tau and its phosphorylation form

Introduction

Hyperphosphorylated Tau formed neurofibrillary tangles was one of the major neuropathological hallmarks of Alzheimer's disease (AD). Dysfunctional insulin signaling in brain is involved in AD. However, the effect of Tau pathology on brain insulin resistance remains unclear. This study explored the effects of overexpressing wild-type Tau (WTau) or Tau with pseudo-phosphorylation at AT8 residues (PTau) on the insulin signaling pathway (ISP).

Methods

293T cells or SY5Y cells overexpressing WTau or PTau were treated with or without insulin. The elements in ISP or the regulators of IPS were analyzed by immunoblotting, immunofluorescent staining and co-immunoprecipitation. Akt inhibitor MK2206 was used for evaluating the insulin signaling to downstream of mTOR in Tau overexpressing cells. The effects of anti-aging drug lonafarnib on ISP in WTau or PTau cells were also analyzed with immunoblotting. Considering lonafarnib is an inhibitor of FTase, the states of Rhes, one of FTase substrate in WTau or PTau cells were analyzed by drug affinity responsive target stability (DARTS) assay and the cellular thermal shift assay (CETSA).

Results

WTau or PTau overexpression in cells upregulated basal activity of elements in ISP in general. However, overexpression of WTau or PTau suppressed the ISP signaling transmission responses induced by insulin simulation, appearing relative higher response of IRS-1 phosphorylation at tyrosine 612 (IRS-1 p612) in upstream IPS, but a lower phosphorylation response of downstream IPS including mTOR, and its targets 4EPB1 and S6. This dysregulation of insulin evoked signaling transmission was more obvious in PTau cells. Suppressing Akt with MK2206 could compromise the levels of p-S6 and p-mTOR in WTau or PTau cells. Moreover, the changes of phosphatases detected in WTau and PTau cells may be related to ISP dysfunction. In addition, the effects of lonafarnib on the ISP in SY5Y cells with WTau and PTau overexpression were tested, which showed that lonafarnib treatment resulted in reducing the active levels of ISP elements in PTau cells but not in WTau cells. The differential effects are probably due to Tau phosphorylation modulating lonafarnib-induced alterations in Rhes, as revealed by DARTS assay.

Conclusion and discussion

Overexpression of Tau or Tau with pseudo-phosphorylation at AT8 residues could cause an upregulation of the basal/tonic ISP, but a suppression of insulin induced the phasic activation of ISP. This dysfunction of ISP was more obvious in cells overexpressing pseudo-phosphorylated Tau. These results implied that the dysfunction of ISP caused by Tau overexpression might impair the physiological fluctuation of neuronal functions in AD. The different effects of lonafarnib on ISP between WTau and PTau cells, indicating that Tau phosphorylation mediates an additional effect on ISP. This study provided a potential linkage of abnormal expression and phosphorylation of Tau to the ISP dysfunction in AD.

Decreased resistin plasmatic concentrations in patients with Alzheimer's disease: A case-control study

Previous studies suggested a role for adipokines in ageing and in several age-related diseases. The purpose of our study was to further elucidate adipokines involvement in neurodegeneration, investigating adiponectin, leptin and resistin in Alzheimer's disease (AD) and Frontotemporal Dementia (FTD). We enrolled for the study 70 subjects: 26 AD, 21 FTD, and 23 with other neurological (but not neurodegenerative) conditions (CTR, control group). According to a standardized protocol, we measured adipokines plasmatic levels, blood parameters of glucidic and lipidic metabolism, ESR, cerebrospinal fluid (CSF) markers of neurodegeneration (beta-amyloid, total-Tau, phosphorylated-Tau) and anthropometric parameters. In comparison with control group, we found lower resistin concentrations in patients with dementia, and in particular in AD (p < 0.001). In multivariate analysis, AD relative risk was reduced by resistin, when controlling for sex, age and anthropometric/metabolic parameters (RR = 0.71, P < 0.0001). Considering CSF biomarkers, we found a direct correlation between resistin and Aβ_1-42 CSF concentration in patients (p < 0.001, r = 0.50). Lower resistin characterized AD patients in our study and AD, but not FTD, diagnosis risk was found to be inversely associated with resistin when controlling for confounders. We hypothesize that resistin-linked metabolic profile has to be reconsidered and further investigated in AD.

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Adipose tissue has an endocrine function, releasing polypeptide hormones, the adipokines.

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Impairment of adipokines circulating levels has been shown in neurodegenerative dementias.

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We found lower resistin levels in Alzheimer's disease patients compared to control group.

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Resistin plasmatic levels correlated with liquoral amyloid β_1-42 concentrations in dementia patients.

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Resistin could interact with amyloid β_1-42 secretion and have a role in Alzheimer's disease pathogenesis.

Ocular manifestations of central insulin resistance

Central insulin resistance, the diminished cellular sensitivity to insulin in the brain, has been implicated in diabetes mellitus, Alzheimer's disease and other neurological disorders. However, whether and how central insulin resistance plays a role in the eye remains unclear. Here, we performed intracerebroventricular injection of S961, a potent and specific blocker of insulin receptor in adult Wistar rats to test if central insulin resistance leads to pathological changes in ocular structures. 80 mg of S961 was stereotaxically injected into the lateral ventricle of the experimental group twice at 7 days apart, whereas buffer solution was injected to the sham control group. Blood samples, intraocular pressure, trabecular meshwork morphology, ciliary body markers, retinal and optic nerve integrity, and whole genome expression patterns were then evaluated. While neither blood glucose nor serum insulin level was significantly altered in the experimental or control group, we found that injection of S961 but not buffer solution significantly increased intraocular pressure at 14 and 24 days after first injection, along with reduced porosity and aquaporin 4 expression in the trabecular meshwork, and increased tumor necrosis factor α and aquaporin 4 expression in the ciliary body. In the retina, cell density and insulin receptor expression decreased in the retinal ganglion cell layer upon S961 injection. Fundus photography revealed peripapillary atrophy with vascular dysregulation in the experimental group. These retinal changes were accompanied by upregulation of pro-inflammatory and pro-apoptotic genes, downregulation of anti-inflammatory, anti-apoptotic, and neurotrophic genes, as well as dysregulation of genes involved in insulin signaling. Optic nerve histology indicated microglial activation and changes in the expression of glial fibrillary acidic protein, tumor necrosis factor α, and aquaporin 4. Molecular pathway architecture of the retina revealed the three most significant pathways involved being inflammation/cell stress, insulin signaling, and extracellular matrix regulation relevant to neurodegeneration. There was also a multimodal crosstalk between insulin signaling derangement and inflammation-related genes. Taken together, our results indicate that blocking insulin receptor signaling in the central nervous system can lead to trabecular meshwork and ciliary body dysfunction, intraocular pressure elevation, as well as inflammation, glial activation, and apoptosis in the retina and optic nerve. Given that central insulin resistance may lead to neurodegenerative phenotype in the visual system, targeting insulin signaling may hold promise for vision disorders involving the retina and optic nerve.