Insulin signaling pathway and related molecules: Role in neurodegeneration and Alzheimer's disease

Insulin-related traits and prostate cancer: A Mendelian randomization study

Investigating the causal relationship between insulin secretion and prostate cancer (PCa) development is challenging due to the multifactorial nature of PCa, which complicates the isolation of the specific impact of insulin-related factors. We conducted a Mendelian randomization (MR) study to investigate the associations between insulin secretion-related traits and PCa. We used 36, 60, 56, 23, 48, and 49 single nucleotide polymorphisms (SNPs) as instrumental variables for fasting insulin, insulin sensitivity, proinsulin, and proinsulin in nondiabetic individuals, individuals with diabetes, and individuals receiving exogenous insulin, respectively. These SNPs were selected from various genome-wide association studies. To clarify the causal relationship between insulin-related traits and PCa, we utilized a multivariable MR analysis to adjust for obesity and body fat percentage. Additionally, two-step Mendelian randomization was conducted to assess the role of insulin-like growth factor 1 (IGF-1) in the relationship between proinsulin and PCa. Two-sample MR analysis revealed strong associations between genetically predicted fasting insulin, insulin sensitivity, proinsulin, and proinsulin in nondiabetic individuals and the development of PCa. After adjustment for obesity and body fat percentage using multivariable MR analysis, proinsulin remained significantly associated with PCa, whereas other factors were not. Furthermore, two-step MR analysis demonstrated that proinsulin acts as a negative factor in prostate carcinogenesis, largely independent of IGF-1. This study provides evidence suggesting that proinsulin may act as a negative factor contributing to the development of PCa. Novel therapies targeting proinsulin may have potential benefits for PCa patients, potentially reducing the need for unnecessary surgical treatments.

Glymphatic system: a gateway for neuroinflammation

The glymphatic system is a relatively recently identified fluid exchange and transport system in the brain. Accumulating evidence indicates that glymphatic function is impaired not only in central nervous system disorders but also in systemic diseases. Systemic diseases can trigger the inflammatory responses in the central nervous system, occasionally leading to sustained inflammation and functional disturbance of the central nervous system. This review summarizes the current knowledge on the association between glymphatic dysfunction and central nervous system inflammation. In addition, we discuss the hypothesis that disease conditions initially associated with peripheral inflammation overwhelm the performance of the glymphatic system, thereby triggering central nervous system dysfunction, chronic neuroinflammation, and neurodegeneration. Future research investigating the role of the glymphatic system in neuroinflammation may offer innovative therapeutic approaches for central nervous system disorders.

Insulin resistance as the molecular link between diabetes and Alzheimer's disease

Diabetes mellitus (DM) and Alzheimer's disease (AD) are two major health concerns that have seen a rising prevalence worldwide. Recent studies have indicated a possible link between DM and an increased risk of developing AD. Insulin, while primarily known for its role in regulating blood sugar, also plays a vital role in protecting brain functions. Insulin resistance (IR), especially prevalent in type 2 diabetes, is believed to play a significant role in AD's development. When insulin signalling becomes dysfunctional, it can negatively affect various brain functions, making individuals more susceptible to AD's defining features, such as the buildup of beta-amyloid plaques and tau protein tangles. Emerging research suggests that addressing insulin-related issues might help reduce or even reverse the brain changes linked to AD. This review aims to explore the rela-tionship between DM and AD, with a focus on the role of IR. It also explores the molecular mechanisms by which IR might lead to brain changes and assesses current treatments that target IR. Understanding IR's role in the connection between DM and AD offers new possibilities for treatments and highlights the importance of continued research in this interdisciplinary field.

Moderate aerobic training enhances the effectiveness of insulin therapy through hypothalamic IGF1 signaling in rat model of Alzheimer's disease

Alzheimer's disease (AD) is a neurological condition that is connected with a decline in a person's memory as well as their cognitive ability. One of the key topics of AD research has been the exploration of metabolic causes. We investigated the effects of treadmill exercise and intranasal insulin on learning and memory impairment and the expression of IGF1, BDNF, and GLUT4 in hypothalamus. The animals were put into 9 groups at random. In this study, we examined the impact of insulin on spatial memory in male Wistar rats and analyzed the effects of a 4-week pretreatment of moderate treadmill exercise and insulin on the mechanisms of improved hypothalamic glucose metabolism through changes in gene and protein expression of IGF1, BDNF, and GLUT4. We discovered that rat given Aβ25-35 had impaired spatial learning and memory, which was accompanied by higher levels of Aβ plaque burden in the hippocampus and lower levels of IGF1, BDNF, and GLUT4 mRNA and protein expression in the hypothalamus. Additionally, the administration of exercise training and intranasal insulin results in the enhancement of spatial learning and memory impairments, the reduction of plaque burden in the hippocampus, and the enhancement of the expression of IGF1, BDNF, and GLUT4 in the hypothalamus of rats that were treated with Aβ25-35. Our results show that the improvement of learning and spatial memory due to the improvement of metabolism and upregulation of the IGF1, BDNF, and GLUT4 pathways can be affected by pretreatment exercise and intranasal insulin.

Glutamine stimulates the S6K/4E-BP branch of insulin signalling pathway to mitigate human poly(Q) disorders in Drosophila disease models

OBJECTIVE AND METHODS

Since, the S6K/4E-BP sub-pathway can be stimulated by various amino acids; we extended our investigation to examine if oral feeding of amino acids delivers rescue against human poly(Q) toxicity in Drosophila. We utilised Drosophila models of two different poly(Q) disorders to test our hypothesis. Glutamine was fed to the test flies orally mixed in the food. Control and treated flies were then tested for different parameters, such as formation of poly(Q) aggregates and neurodegeneration, to evaluate glutamine's proficiency in mitigating poly(Q) neurotoxicity.

RESULTS

Our study, for the first time, reports that glutamine feeding stimulates the growth promoting S6K/4E-BP branch of insulin signalling pathway and restricts pathogenesis of poly(Q) disorders in Drosophila disease models. We noted that glutamine treatment restricts the formation of neurotoxic poly(Q) aggregates and minimises neuronal deaths. Further, glutamine treatment re-establishes the chromatin architecture by improving the histone acetylation which is otherwise compromised in poly(Q) expressing neuronal cells.

DISCUSSION

Since, the insulin signalling pathway as well as mechanism of action of glutamine are fairly conserved between human and Drosophila, our finding strongly suggests that glutamine holds immense potential to be developed as an intervention therapy against the incurable human poly(Q) disorders.

Comprehensive Overview of Alzheimer's Disease: Etiological Insights and Degradation Strategies

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and affects millions of individuals globally. AD is associated with cognitive decline and memory loss that worsens with aging. A statistical report using U.S. data on AD estimates that approximately 6.9 million individuals suffer from AD, a number projected to surge to 13.8 million by 2060. Thus, there is a critical imperative to pinpoint and address AD and its hallmark tau protein aggregation early to prevent and manage its debilitating effects. Amyloid-β and tau proteins are primarily associated with the formation of plaques and neurofibril tangles in the brain. Current research efforts focus on degrading amyloid-β and tau or inhibiting their synthesis, particularly targeting APP processing and tau hyperphosphorylation, aiming to develop effective clinical interventions. However, navigating this intricate landscape requires ongoing studies and clinical trials to develop treatments that truly make a difference. Genome-wide association studies (GWASs) across various cohorts identified 40 loci and over 300 genes associated with AD. Despite this wealth of genetic data, much remains to be understood about the functions of these genes and their role in the disease process, prompting continued investigation. By delving deeper into these genetic associations, novel targets such as kinases, proteases, cytokines, and degradation pathways, offer new directions for drug discovery and therapeutic intervention in AD. This review delves into the intricate biological pathways disrupted in AD and identifies how genetic variations within these pathways could serve as potential targets for drug discovery and treatment strategies. Through a comprehensive understanding of the molecular underpinnings of AD, researchers aim to pave the way for more effective therapies that can alleviate the burden of this devastating disease.

Mind the Metabolic Gap: Bridging Migraine and Alzheimer's disease through Brain Insulin Resistance

Brain insulin resistance has recently been described as a metabolic abnormality of brain glucose homeostasis that has been proven to downregulate insulin receptors, both in astrocytes and neurons, triggering a reduction in glucose uptake and glycogen synthesis. This condition may generate a mismatch between brain's energy reserve and expenditure, mainly during high metabolic demand, which could be involved in the chronification of migraine and, in the long run, at least in certain subsets of patients, in the prodromic phase of Alzheimer's disease, along a putative metabolic physiopathological continuum. Indeed, the persistent disruption of glucose homeostasis and energy supply to neurons may eventually impair protein folding, an energy-requiring process, promoting pathological changes in Alzheimer's disease, such as amyloid-β deposition and tau hyperphosphorylation. Hopefully, the "neuroenergetic hypothesis" presented herein will provide further insight on there being a conceivable metabolic bridge between chronic migraine and Alzheimer's disease, elucidating novel potential targets for the prophylactic treatment of both diseases.

Activation of NRF2 by epiberberine improves oxidative stress and insulin resistance in T2DM mice and IR-HepG2 cells in an AMPK dependent manner

ETHNOPHARMACOLOGICAL RELEVANCE

Phytochemical compounds offer a distinctive edge in diabetes management, attributed to their multifaceted target mechanisms and minimal toxicological profiles. Epiberberine (EPI), an alkaloid derived from plants of the Rhizoma Coptidis, has been reported to have antidiabetic effects. However, the underlying molecular mechanism of EPI are not fully elucidated.

AIM OF THE STUDY

This study explored the anti-diabetic effects of EPI and the role of the NRF2/AMPK signaling pathway in improving insulin resistance.

MATERIALS AND METHODS

We utilized two distinct models: in vivo, we employed mice with type 2 diabetes mellitus (T2DM) induced by high-fat diet (HFD) and streptozotocin (STZ) to conduct a range of assessments including measuring physical parameters, conducting biochemical analyses, examining histopathology, and performing Western blot tests. In parallel, in vitro experiments were carried out using insulin resistance (IR)-HepG2 cells, through which we conducted a CCK8 assay, glucose uptake tests, Western blot analyses, and flow cytometry studies.

RESULTS

In the EPI-treated group of T2DM mice, there was a significant reduction in hyperglycemia, IR, and hyperlipidemia, accompanied by beneficial changes in the liver and pancreas, as well as enhanced glucose uptake in IR-HepG2 cells. Herein, our finding also provided evidence that EPI could increase the expression of GLUT4 and activated the IRS-1/PI3K/AKT insulin signaling pathway to improve IR in vitro and in vivo. Moreover, EPI alleviated oxidative stress by enhancing SOD and GPX-px activity, decreasing reactive oxygen species (ROS) and malondialdehyde (MDA) content, and promoting nuclear factor (erythroid-derived 2)-like 2 (NRF2), total NRF2, NAD(P)H-quinone oxidoreductase (NQO1) and heme oxygenase-1 (HO-1) expression in the liver tissue of T2DM mice and IR-HepG2 cells. Furthermore, EPI decreased oxidative stress and improved IR, but these benefits were nullified by siNRF2 transfection. In particular, AMP-activated protein kinase (AMPK) deficiency by short-hairpin RNA (shRNA) partially reversed the effects of EPI on nuclear transcription, oxidative stress, and IR of NRF2 in IR-HepG2 cells.

CONCLUSIONS

Taken together, EPI activated NRF2-dependent AMPK cascade to protect T2DM from oxidative stress, thereby alleviating IR.

Network analysis combined with experimental assessment to explore the therapeutic mechanisms of New Shenqi Pills formula targeting mitochondria on senile diabetes mellitus

Background

The escalation of global population aging has accentuated the prominence of senile diabetes mellitus (SDM) as a consequential public health concern. Oxidative stress and chronic inflammatory cascades prevalent in individuals with senile diabetes significantly amplify disease progression and complication rates. Traditional Chinese Medicine (TCM) emerges as a pivotal player in enhancing blood sugar homeostasis and retarding complication onset in the clinical management of senile diabetes. Nonetheless, an evident research gap persists regarding the integration of TCM's renal tonification pharmacological mechanisms with experimental validation within the realm of senile diabetes therapeutics.

Aims

The objective of this study was to investigate the mechanisms of action of New Shenqi Pills (SQP) in the treatment of SDM and make an experimental assessment.

Methods

Network analysis is used to evaluate target pathways related to SQP and SDM. Mitochondrial-related genes were obtained from the MitoCarta3.0 database and intersected with the common target genes of the disease and drugs, then constructing a protein-protein interaction (PPI) network making use of the GeneMANIA database. Representative compounds in the SQP were quantitatively measured using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to ensure quality control and quantitative analysis of the compounds. A type 2 diabetes mice (C57BL/6) model was used to investigate the pharmacodynamics of SQP. The glucose lowering efficacy of SQP was assessed through various metrics including body weight and fasting blood glucose (FBG). To elucidate the modulatory effects of SQP on pancreatic beta cell function, we measured oral glucose tolerance test (OGTT), insulin histochemical staining and tunel apoptosis detection, then assessed the insulin-mediated phosphoinositide 3-kinase (PI3K)/protein kinase A (Akt)/glycogen synthase kinase-3β (GSK-3β) pathway in diabetic mice via Western blotting. Additionally, we observe the structural changes of the nucleus, cytoplasmic granules and mitochondria of pancreatic islet β cells.

Results

In this investigation, we identified a total of 1876 genes associated with senile diabetes, 278 targets of SQP, and 166 overlapping target genes, primarily enriched in pathways pertinent to oxidative stress response, peptide response, and oxygen level modulation. Moreover, an intersection analysis involving 1,136 human mitochondrial genes and comorbidity targets yielded 15 mitochondria-related therapeutic targets. Quality control assessments and quantitative analyses of SQP revealed the predominant presence of five compounds with elevated concentrations: Catalpol, Cinnamon Aldehyde, Rehmanthin D, Trigonelline, and Paeonol Phenol. Vivo experiments demonstrated notable findings. Relative to the control group, mice in the model group exhibited significant increases in body weight and fasting blood glucose levels, alongside decreased insulin secretion and heightened islet cell apoptosis. Moreover, β-cells nuclear condensation and mitochondrial cristae disappearance were observed, accompanied by reduced expression levels of p-GSK-3β protein in islet cells (p < 0.05 or p < 0.01). Conversely, treatment groups administered SQP and Rg displayed augmented expressions of the aforementioned protein markers (p < 0.05 or p < 0.01), alongside preserved mitochondrial cristae structure in islet β cells.

Conclusion

Our findings suggest that SQP can ameliorate diabetes by reducing islet cell apoptosis and resist oxidative stress. These insulin-mediated PI3K/AKT/GSK-3β pathway plays an important regulatory role in this process.

Triglyceride-glucose index as a potential predictor for in-hospital mortality in critically ill patients with intracerebral hemorrhage: a multicenter, case-control study

BACKGROUND

The correlation between the triglyceride-glucose index (TyG) and the prognosis of ischemic stroke has been well established. This study aims to assess the influence of the TyG index on the clinical outcomes of critically ill individuals suffering from intracerebral hemorrhage (ICH).

METHODS

Patients diagnosed with ICH were retrospectively retrieved from the Medical Information Mart for Intensive Care (MIMIC-IV) and the eICU Collaborative Research Database (eICU-CRD). Various statistical methods, including restricted cubic spline (RCS) regression, multivariable logistic regression, subgroup analysis, and sensitivity analysis, were employed to examine the relationship between the TyG index and the primary outcomes of ICH.

RESULTS

A total of 791 patients from MIMIC-IV and 1,113 ones from eICU-CRD were analyzed. In MIMIC-IV, the in-hospital and ICU mortality rates were 14% and 10%, respectively, while in eICU-CRD, they were 16% and 8%. Results of the RCS regression revealed a consistent linear relationship between the TyG index and the risk of in-hospital and ICU mortality across the entire study population of both databases. Logistic regression analysis revealed a significant positive association between the TyG index and the likelihood of in-hospital and ICU death among ICH patients in both databases. Subgroup and sensitivity analysis further revealed an interaction between patients' age and the TyG index in relation to in-hospital and ICU mortality among ICH patients. Notably, for patients over 60 years old, the association between the TyG index and the risk of in-hospital and ICU mortality was more pronounced compared to the overall study population in both MIMIC-IV and eICU-CRD databases, suggesting a synergistic effect between old age (over 60 years) and the TyG index on the in-hospital and ICU mortality of patients with ICH.

CONCLUSIONS

This study established a positive correlation between the TyG index and the risk of in-hospital and ICU mortality in patients over 60 years who diagnosed with ICH, suggesting that the TyG index holds promise as an indicator for risk stratification in this patient population.

Phytochemicals targeting Alzheimer's disease via the AMP-activated protein kinase pathway, effects, and mechanisms of action

Alzheimer's disease (AD), characterized by cognitive dysfunction and other behavioral abnormalities, is a progressive neurodegenerative disease that occurs due to aging. Currently, effective drugs to mitigate or treat AD remain unavailable. AD is associated with several abnormalities in neuronal energy metabolism, such as decreased glucose uptake, mitochondrial dysfunction, and defects in cholesterol metabolism. Amp-activated protein kinase (AMPK) is an important serine/threonine protein kinase that regulates the energy status of cells. AMPK is widely present in eukaryotic cells and can sense and regulate energy metabolism to maintain energy supply and demand balance, making it a promising target for energy metabolism-based AD therapy. Therefore, this review aimed to discuss the molecular mechanism of AMPK in the pathogenesis of AD to provide a theoretical basis for the development of new anti-AD drugs. To review the mechanisms of phytochemicals in the treatment of AD via AMPK pathway regulation, we searched PubMed, Google Scholar, Web of Science, and Embase databases using specific keywords related to AD and phytochemicals in September 2023. Phytochemicals can activate AMPK or regulate the AMPK pathway to exert therapeutic effects in AD. The anti-AD mechanisms of these phytochemicals include inhibiting Aβ aggregation, preventing Tau hyperphosphorylation, inhibiting inflammatory response and glial activation, promoting autophagy, and suppressing anti-oxidative stress. Additionally, several AMPK-related pathways are involved in the anti-AD mechanism, including the AMPK/CaMKKβ/mTOR, AMPK/SIRT1/PGC-1α, AMPK/NF-κB/NLRP3, AMPK/mTOR, and PERK/eIF2α pathways. Notably, urolithin A, artemisinin, justicidin A, berberine, stigmasterol, arctigenin, and rutaecarpine are promising AMPK agonists with anti-AD effects. Several phytochemicals are effective AMPK agonists and may have potential applications in AD treatment. Overall, phytochemical-based drugs may overcome the barriers to the effective treatment of neurodegenerative diseases.

Types of memory, dementia, Alzheimer's disease, and their various pathological cascades as targets for potential pharmacological drugs

Alzheimer's disease (AD) is the most common type of dementia accounting for 90% of cases; however, frontotemporal dementia, vascular dementia, etc. prevails only in a minority of populations. The term dementia is defined as loss of memory which further takes several other categories of memories like working memory, spatial memory, fear memory, and long-term, and short-term memory into consideration. In this review, these memories have critically been elaborated based on context, duration, events, appearance, intensity, etc. The most important part and purpose of the review is the various pathological cascades as well as molecular levels of targets of AD, which have extracellular amyloid plaques and intracellular hyperphosphorylated tau protein as major disease hallmarks. There is another phenomenon that either leads to or arises from the above-mentioned hallmarks, such as oxidative stress, mitochondrial dysfunction, neuroinflammation, cholinergic dysfunction, and insulin resistance. Several potential drugs like antioxidants, anti-inflammatory drugs, acetylcholinesterase inhibitors, insulin mimetics or sensitizers, etc. studied in various previous preclinical or clinical reports were put as having the capacity to act on these pathological targets. Additionally, agents directly or indirectly targeting amyloid and tau were also discussed. This could be further investigated in future research.

Exploring the impacts of ketogenic diet on reversible hepatic steatosis: initial analysis in male mice

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common chronic liver disease. Ketogenic diet (KD), a diet with very low intake in carbohydrates, gained popularity as a weight-loss approach. However, in mice models, it has been reported that an excess exposition of dietary fat induces hepatic insulin resistance and steatosis. However, data published is inconsistent. Herein, we investigated in a mouse model, the metabolic effects of KD and its contribution to the pathogenesis of NALFD. Mice were exposed to KD or CHOW diet for 12 weeks while a third group was exposed to KD for also 12 weeks and then switched to CHOW diet for 4 weeks to determine if we can rescue the phenotype. We evaluated the effects of diet treatments on fat distribution, glucose, and insulin homeostasis as well as hepatic steatosis. Mice fed with KD developed glucose intolerance but not insulin resistance accompanied by an increase of inflammation. KD-fed mice showed an increase of fat accumulation in white adipose tissue and liver. This effect could be explained by an increase in fat uptake by the liver with no changes of catabolism leading to MAFLD. Interestingly, we were able to rescue the phenotype by switching KD-fed mice for 4 weeks on a CHOW diet. Our studies demonstrate that even if mice develop hepatic steatosis and glucose intolerance after 12 weeks of KD, they do not develop insulin resistance and more importantly, the phenotype can be reversed by switching the mice from a KD to a CHOW.

KAT7/HMGN1 signaling epigenetically induces tyrosine phosphorylation-regulated kinase 1A expression to ameliorate insulin resistance in Alzheimer's disease

BACKGROUND

Epidemiological studies have revealed a correlation between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2D). Insulin resistance in the brain is a common feature in patients with T2D and AD. KAT7 is a histone acetyltransferase that participates in the modulation of various genes.

AIM

To determine the effects of KAT7 on insulin patients with AD.

METHODS

APPswe/PS1-dE9 double-transgenic and db/db mice were used to mimic AD and diabetes, respectively. An in vitro model of AD was established by Aβ stimulation. Insulin resistance was induced by chronic stimulation with high insulin levels. The expression of microtubule-associated protein 2 (MAP2) was assessed using immunofluorescence. The protein levels of MAP2, Aβ, dual-specificity tyrosine phosphorylation-regulated kinase-1A (DYRK1A), IRS-1, p-AKT, total AKT, p-GSK3β, total GSK3β, DYRK1A, and KAT7 were measured via western blotting. Accumulation of reactive oxygen species (ROS), malondialdehyde (MDA), and SOD activity was measured to determine cellular oxidative stress. Flow cytometry and CCK-8 assay were performed to evaluate neuronal cell death and proliferation, respectively. Relative RNA levels of KAT7 and DYRK1A were examined using quantitative PCR. A chromatin immunoprecipitation assay was conducted to detect H3K14ac in DYRK1A.

RESULTS

KAT7 expression was suppressed in the AD mice. Overexpression of KAT7 decreased Aβ accumulation and MAP2 expression in AD brains. KAT7 overexpression decreased ROS and MDA levels, elevated SOD activity in brain tissues and neurons, and simultaneously suppressed neuronal apoptosis. KAT7 upregulated levels of p-AKT and p-GSK3β to alleviate insulin resistance, along with elevated expression of DYRK1A. KAT7 depletion suppressed DYRK1A expression and impaired H3K14ac of DYRK1A. HMGN1 overexpression recovered DYRK1A levels and reversed insulin resistance caused by KAT7 depletion.

CONCLUSION

We determined that KAT7 overexpression recovered insulin sensitivity in AD by recruiting HMGN1 to enhance DYRK1A acetylation. Our findings suggest that KAT7 is a novel and promising therapeutic target for the resistance in AD.

Revisiting the mechanisms linking blood glucose to cognitive impairment: new evidence for the potential important role of klotho

Background

The association between blood glucose and cognition is controversial. Klotho is an anti-aging protein with neural protective effects. This study aimed to use a population-based study to disentangle the relationship between blood glucose levels and cognitive function in older adults, and to explore the role of klotho in it.

Methods

A total of 1445 eligible participants from National Health and Nutrition Examination Survey (NHANES) 2011-2014 were included in our study. Cognitive function was assessed by Digit Symbol Substitution Test (DSST) and categorized into four quartiles (Q1-Q4). General characteristics and laboratory test results including serum klotho concentration and blood glucose levels were collected. Associations of cognitive function and klotho levels with blood glucose concentrations were explored through multivariate linear regression models. Mediation models were constructed to figure out the mediating role of klotho.

Results

All three multivariate linear regression models showed a negative correlation between blood glucose and cognitive function. (Model 1, β=-0.149, 95%CI: -0.202,-0.096, p=0.001; Model 2, β=-0.116, 95%CI: -0.167,-0.065, p=0.001; Model 3, β=-0.007, 95%CI: -0.118,-0.023, p=0.003). Mediation analysis showed that klotho mediated the statistical association between blood glucose level and cognitive function with proportions (%) of 12.5.

Conclusion

Higher blood glucose levels are associated with poorer cognitive performance in non-diabetic older adults, partially mediated through lower klotho levels.

Insights into the mechanism of transcription factors in Pb2+-induced apoptosis

The health risks associated with exposure to heavy metals, such as Pb2+, are increasingly concerning the public. Pb2+ can cause significant harm to the human body through oxidative stress, autophagy, inflammation, and DNA damage, disrupting cellular homeostasis and ultimately leading to cell death. Among these mechanisms, apoptosis is considered crucial. It has been confirmed that transcription factors play a central role as mediators during the apoptosis process. Interestingly, these transcription factors have different effects on apoptosis depending on the concentration and duration of Pb2+ exposure. In this article, we systematically summarize the significant roles of several transcription factors in Pb2+-induced apoptosis. This information provides insights into therapeutic strategies and prognostic biomarkers for diseases related to Pb2+ exposure.

Quercetin improved hepatic circadian rhythm dysfunction in middle-aged mice fed with vitamin D-deficient diet

We aimed to determine whether quercetin is capable of improving circadian rhythm and metabolism disorder under vitamin D-deficient condition. Middle-aged mice were randomly divided into four groups, namely, control (CON), vitamin D-deficient diet (VDD), quercetin (Q), and quercetin intervention in vitamin D-deficient diet (VDQ), with a total of 12 weeks' intervention. Mice were sacrificed at zeitgeber time1 (ZT1) and ZT13 time points. At ZT1, circadian locomotor output cycle kaput (CLOCK) protein expression from VDD, Q, and VDQ groups; CRY1 from Q group; and CRY2 from VDD group were significantly lower compared to CON group. The mRNA expression of Sirt1, Bmal1, Clock, Cry1, and Cry2 in VDQ groups, also Bmal1, Clock, and Cry1 from Q group, were significantly decreased compared to CON group. At ZT13, compared to CON group, fasting insulin and homeostasis model assessment-insulin resistance (HOMA-IR) were higher in VDD group; BMAL1 was significantly increased, while CLOCK and CRY1 protein were significantly decreased from VDD group; CLOCK protein from VDQ group was significantly higher compared to CON, VDD, and Q groups, and also, BMAL1 protein expression from VDQ group was elevated compared to CON group. The mRNA expression of Bmal1, Clock, Per2, Cry1, and Cry2 in VDQ groups were significantly increased compared to CON groups. The mRNA expression of Bmal1 from VDQ group was decreased compared to both VDD and Q group. In conclusion, vitamin D-deficient diet resulted in a disordered liver circadian rhythm, and quercetin improved the hepatic circadian desynchronization. Quercetin supplementation might be effective for balancing circadian rhythm under vitamin D-deficient condition.

Tetrahydroalstonine possesses protective potentials on palmitic acid stimulated SK-N-MC cells by suppression of Aβ1-42 and tau through regulation of PI3K/Akt signaling pathway

Alzheimer's disease (AD) is the most common neurodegenerative disease. The morbidity of Alzheimer's disease is currently on the rise worldwide, but no effective treatment is available. Cornus officinalis is an herb and edible plant used in traditional Chinese medicine, whose extract has neuroprotective properties. In this investigation, we endeavored to refine a systems pharmacology strategy combining bioinformatics analysis, drug prediction, network pharmacology, and molecular docking to screen tetrahydroalstonine (THA) from Cornus officinalis as a therapeutic component for AD. Subsequent in vitro experiments were validated using MTT assay, Annexin V-PI flow cytometry, Western blotting, and immunofluorescence analysis. In Palmitate acid-induced SK-N-MC cells, THA restored the impaired PI3K/AKT signaling pathway, regulated insulin resistance, and attenuated BACE1 and GSK3β activity. In addition, THA significantly reduced cell apoptosis rate, down-regulated relative levels of p-JNK/JNK, Bax/Bcl-2, cytochrome C, active caspase-3 and caspase-3, and attenuated Palmitate acid-induced Aβ1-42 and Tau generation. THA may regulate the phenotype of AD and reduce cell apoptosis by modulating the PI3K/AKT signaling pathway. This systematic analysis provides new ramifications concerning the therapeutic utility of tetrahydroalstonine for AD.

Assess Alzheimer's Disease via Plasma Extracellular Vesicle-derived mRNA

Alzheimer's disease (AD), the most prevalent neurodegenerative disorder globally, has emerged as a significant health concern, particularly due to the increasing aging population. Recently, it has been revealed that extracellular vesicles (EVs) originating from neurons play a critical role in AD pathogenesis and progression. These neuronal EVs can cross the blood-brain barrier and enter peripheral circulation, offering a less invasive means for assessing blood-based AD biomarkers. In this study, we analyzed plasma EV-derived messenger RNA (mRNA) from 82 subjects, including individuals with AD, mild cognitive impairment (MCI), and healthy controls, using next-generation sequencing (NGS) to profile their gene expression for functional enrichment and pathway analysis. Based on the differentially expressed genes identified in both MCI and AD groups, we established a diagnostic model by implementing a machine learning classifier. The refined model demonstrated an average diagnostic accuracy over 98% and showed a strong correlation with different AD stages, suggesting the potential of plasma EV-derived mRNA as a promising non-invasive biomarker for early detection and ongoing monitoring of AD.

From diabetic hyperglycemia to cerebrovascular Damage: A narrative review

Diabetes mellitus is a globally significant disease that can lead to systemic complications, particularly vascular damage, including cardiovascular and cerebrovascular diseases of relevance. The physiological changes resulting from the imbalance in blood glucose levels play a crucial role in initiating vascular endothelial damage. Elevated glucose levels can also penetrate the central nervous system, triggering diabetic encephalopathy characterized by oxidative damage to brain components and activation of alternative and neurotoxic pathways. This brain damage increases the risk of ischemic stroke, a leading cause of mortality worldwide and a major cause of disability among surviving patients. The aim of this review is to highlight important pathways related to hyperglycemic damage that extend to the brain and result in vascular dysfunction, ultimately leading to the occurrence of a stroke. Understanding how diabetes mellitus contributes to the development of ischemic stroke and its impact on patient outcomes is crucial for implementing therapeutic strategies that reduce the incidence of diabetes mellitus and its complications, ultimately decreasing morbidity and mortality associated with the disease.

A multi-layered network model identifies Akt1 as a common modulator of neurodegeneration

The accumulation of misfolded and aggregated proteins is a hallmark of neurodegenerative proteinopathies. Although multiple genetic loci have been associated with specific neurodegenerative diseases (NDs), molecular mechanisms that may have a broader relevance for most or all proteinopathies remain poorly resolved. In this study, we developed a multi-layered network expansion (MLnet) model to predict protein modifiers that are common to a group of diseases and, therefore, may have broader pathophysiological relevance for that group. When applied to the four NDs Alzheimer's disease (AD), Huntington's disease, and spinocerebellar ataxia types 1 and 3, we predicted multiple members of the insulin pathway, including PDK1, Akt1, InR, and sgg (GSK-3β), as common modifiers. We validated these modifiers with the help of four Drosophila ND models. Further evaluation of Akt1 in human cell-based ND models revealed that activation of Akt1 signaling by the small molecule SC79 increased cell viability in all models. Moreover, treatment of AD model mice with SC79 enhanced their long-term memory and ameliorated dysregulated anxiety levels, which are commonly affected in AD patients. These findings validate MLnet as a valuable tool to uncover molecular pathways and proteins involved in the pathophysiology of entire disease groups and identify potential therapeutic targets that have relevance across disease boundaries. MLnet can be used for any group of diseases and is available as a web tool at http://ssbio.cau.ac.kr/software/mlnet.

Iron and Targeted Iron Therapy in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide. β-amyloid plaque (Aβ) deposition and hyperphosphorylated tau, as well as dysregulated energy metabolism in the brain, are key factors in the progression of AD. Many studies have observed abnormal iron accumulation in different regions of the AD brain, which is closely correlated with the clinical symptoms of AD; therefore, understanding the role of brain iron accumulation in the major pathological aspects of AD is critical for its treatment. This review discusses the main mechanisms and recent advances in the involvement of iron in the above pathological processes, including in iron-induced oxidative stress-dependent and non-dependent directions, summarizes the hypothesis that the iron-induced dysregulation of energy metabolism may be an initiating factor for AD, based on the available evidence, and further discusses the therapeutic perspectives of targeting iron.

Quantitative Proteomics Characterization of the Effect and Mechanism of Trichostatin A on the Hippocampus of Type II Diabetic Mice

Diabetic encephalopathy (DE) is one of the complications of diabetes mellitus with mild-to-moderate cognitive impairment. Trichostatin A (TSA) has been revealed to show protective effect on central nervous systems in Alzheimer's disease (AD) and hypoxic-ischemic brain injury. However, the effect and molecular mechanism of TSA on cognitive function of DE are unknown. Here, we demonstrated that cognitive function was damaged in diabetic mice versus normal mice and treatment with TSA improved cognitive function in diabetic mice. Proteomic analysis of the hippocampus revealed 174 differentially expressed proteins in diabetic mice compared with normal mice. TSA treatment reversed the expression levels of 111 differentially expressed proteins grouped into functional clusters, including the longevity regulating pathway, the insulin signaling pathway, peroxisomes, protein processing in the endoplasmic reticulum, and ribosomes. Furthermore, protein-protein interaction network analysis of TSA-reversed proteins revealed that UBA52, CAT, RPL29, RPL35A, CANX, RPL37, and PRKAA2 were the main hub proteins. Multiple KEGG pathway-enriched CAT and PRKAA2 levels were significantly decreased in the hippocampus of diabetic mice versus normal mice, which was reversed by TSA administration. Finally, screening for potential similar or ancillary drugs for TSA treatment indicated that HDAC inhibitors ISOX, apicidin, and panobinostat were the most promising similar drugs, and the PI3K inhibitor GSK-1059615, the Aurora kinase inhibitor alisertib, and the nucleophosmin inhibitor avrainvillamide-analog-6 were the most promising ancillary drugs. In conclusion, our study revealed that CAT and PRKAA2 were the key proteins involved in the improvement of DE after TSA treatment. ISOX, apicidin, and panobinostat were promising similar drugs and that GSK-1059615, alisertib, and avrainvillamide-analog-6 were promising ancillary drugs to TSA in the treatment of DE.

Physiological Mechanisms Inherent to Diabetes Involved in the Development of Dementia: Alzheimer's Disease

Type 2 diabetes mellitus (T2D) is a metabolic disease reaching pandemic levels worldwide. In parallel, Alzheimer's disease (AD) and vascular dementia (VaD) are the two leading causes of dementia in an increasingly long-living Western society. Numerous epidemiological studies support the role of T2D as a risk factor for the development of dementia. However, few basic science studies have focused on the possible mechanisms involved in this relationship. On the other hand, this review of the literature also aims to explore the relationship between T2D, AD and VaD. The data found show that there are several alterations in the central nervous system that may be promoting the development of T2D. In addition, there are some mechanisms by which T2D may contribute to the development of neurodegenerative diseases such as AD or VaD.

Effects of Jatrorrhizine on inflammatory response induced by H2O2 in microglia by regulating the MAPK/NF-κB/NLRP3 signaling pathway

Microglia-induced neuroinflammation is a contributing factor to neurodegenerative diseases. Jatrorrhizine (JAT), an alkaloid isolated from Huanglian, has been shown to have neuroprotective effects against various neurodegenerative diseases, but its impact on microglia-induced neuroinflammation remains unclear. In this study, we investigated the role of JAT in MAPK/NF-κB/NLRP3 signaling pathway in an H2O2-induced oxidative stress model using microglia (N9 cells). We divided cells into six groups, including control, JAT, H2O2, H2O2 + 5 μmol/L JAT, H2O2 + 10 μmol/L JAT, and H2O2 + 20 μmol/L minocycline groups. Cell viability was measured using MTT assay and TNF-α levels were detected with an ELISA Kit. Western blot was used to detect NLRP3, HMGB1, NF-κB, p-NF-κB, ERK, p-ERK, p38, p-p38, p-JNK, JNK, IL-1β, and IL-18 expressions. Our results showed that JAT intervention improved H2O2-induced cytotoxicity in N9 cells and reduced the elevated expression of TNF-α, IL-1β, IL-18, p-ERK/ERK, p-p38/p38, p-JNK/JNK, p-p65/p65, NLRP3, and HMGB1 in H2O2 group. Furthermore, treatment with ERK inhibitor SCH772984 specifically blocked ERK phosphorylation, resulting in decreased protein levels of p-NF-κB, NLRP3, IL-1β, and IL-18 in H2O2 group. These results suggest that the MAPK/NF-κB signaling pathway may regulate the protein levels of NLRP3. Overall, our study indicates that JAT may have a protective effect on H2O2-treated microglia via inhibition the MAPK/NF-κB/NLRP3 pathway and could be a potential therapeutic approach for neurodegenerative diseases.

Decoding the role of gut microbiota in Alzheimer's pathogenesis and envisioning future therapeutic avenues

Alzheimer's disease (AD) emerges as a perturbing neurodegenerative malady, with a profound comprehension of its underlying pathogenic mechanisms continuing to evade our intellectual grasp. Within the intricate tapestry of human health and affliction, the enteric microbial consortium, ensconced within the milieu of the human gastrointestinal tract, assumes a role of cardinal significance. Recent epochs have borne witness to investigations that posit marked divergences in the composition of the gut microbiota between individuals grappling with AD and those favored by robust health. The composite vicissitudes in the configuration of the enteric microbial assembly are posited to choreograph a participatory role in the inception and progression of AD, facilitated by the intricate conduit acknowledged as the gut-brain axis. Notwithstanding, the precise nature of this interlaced relationship remains enshrouded within the recesses of obscurity, poised for an exhaustive revelation. This review embarks upon the endeavor to focalize meticulously upon the mechanistic sway exerted by the enteric microbiota upon AD, plunging profoundly into the execution of interventions that govern the milieu of enteric microorganisms. In doing so, it bestows relevance upon the therapeutic stratagems that form the bedrock of AD's management, all whilst casting a prospective gaze into the horizon of medical advancements.

Pesticides and insulin resistance-related metabolic diseases: Evidences and mechanisms

The use of pesticides in the past century has lot helped humankind in improving crops' field and general hygiene level. Nevertheless, there has been countless evidences on the toxic effects of pesticides on the living systems. The link of exposure to pesticides with different human chronic diseases in the context of carcinogenicity, neurotoxicity, developmental toxicity, etc., have been evaluated in various types of studies. There are also some evidences on the link of exposure to pesticides with higher incidence of metabolic diseases associated with insulin resistance like diabetes, obesity, metabolic syndrome, hypertension, polycystic ovary syndrome and chronic kidney diseases. Physiologically, weakening intracellular insulin signaling is considered as a compensatory mechanism for cells to cope with cellular stresses like xenobiotic effects, oxidative stress and inflammatory responses, but it can pathologically lead to a defective cycle with lowered sensitivity of the cells to insulin which happens in metabolic disorders. In this work, the data related to metabolic toxicity of pesticides categorized in the mentioned metabolic diseases with a focus on the effects of pesticides on insulin signaling pathway and the mechanisms of development of insulin resistance will be systematically reviewed and presented.

Sex- and APOE-specific genetic risk factors for late-onset Alzheimer's disease: Evidence from gene-gene interaction of longevity-related loci

Advanced age is the largest risk factor for late-onset Alzheimer's disease (LOAD), a disease in which susceptibility correlates to almost all hallmarks of aging. Shared genetic signatures between LOAD and longevity were frequently hypothesized, likely characterized by distinctive epistatic and pleiotropic interactions. Here, we applied a multidimensional reduction approach to detect gene-gene interactions affecting LOAD in a large dataset of genomic variants harbored by genes in the insulin/IGF1 signaling, DNA repair, and oxidative stress pathways, previously investigated in human longevity. The dataset was generated from a collection of publicly available Genome Wide Association Studies, comprising a total of 2,469 gene variants genotyped in 20,766 subjects of Northwestern European ancestry (11,038 LOAD cases and 9,728 controls). The stratified analysis according to APOE*4 status and sex corroborated evidence that pathways leading to longevity also contribute to LOAD. Among the significantly interacting genes, PTPN1, TXNRD1, and IGF1R were already found enriched in gene-gene interactions affecting survival to old age. Furthermore, interacting variants associated with LOAD in a sex- and APOE-specific way. Indeed, while in APOE*4 female carriers we found several inter-pathway interactions, no significant epistasis was found in APOE*4 negative females; conversely, in males, significant intra- and inter-pathways epistasis emerged according to APOE*4 status. These findings suggest that interactions of risk factors may drive different trajectories of cognitive aging. Beyond helping to disentangle the genetic architecture of LOAD, such knowledge may improve precision in predicting the risk of dementia and enable effective sex- and APOE-stratified preventive and therapeutic interventions for LOAD.

Insulin signaling and its application

The discovery of insulin in 1921 introduced a new branch of research into insulin activity and insulin resistance. Many discoveries in this field have been applied to diagnosing and treating diseases related to insulin resistance. In this mini-review, the authors attempt to synthesize the updated discoveries to unravel the related mechanisms and inform the development of novel applications. Firstly, we depict the insulin signaling pathway to explain the physiology of insulin action starting at the receptor sites of insulin and downstream the signaling of the insulin signaling pathway. Based on this, the next part will analyze the mechanisms of insulin resistance with two major provenances: the defects caused by receptors and the defects due to extra-receptor causes, but in this study, we focus on post-receptor causes. Finally, we discuss the recent applications including the diseases related to insulin resistance (obesity, cardiovascular disease, Alzheimer's disease, and cancer) and the potential treatment of those based on insulin resistance mechanisms.

Potential Role of Glucagon-like Peptide-1 Receptor Agonists in the Treatment of Cognitive Decline and Dementia in Diabetes Mellitus

Dementia is a permanent illness characterized by mental instability, memory loss, and cognitive decline. Many studies have demonstrated an association between diabetes and cognitive dysfunction that proceeds in three steps, namely, diabetes-associated cognitive decrements, mild cognitive impairment (MCI; both non-amnesic MCI and amnesic MCI), and dementia [both vascular dementia and Alzheimer's disease (AD)]. Based on this association, this disease has been designated as type 3 diabetes mellitus. The underlying mechanisms comprise insulin resistance, inflammation, lipid abnormalities, oxidative stress, mitochondrial dysfunction, glycated end-products and autophagy. Moreover, insulin and insulin-like growth factor-1 (IGF-1) have been demonstrated to be involved. Insulin in the brain has a neuroprotective role that alters cognitive skills and alteration of insulin signaling determines beta-amyloid (Aβ) accumulation, in turn promoting brain insulin resistance. In this complex mechanism, other triggers include hyperglycemia-induced overproduction of reactive oxygen species (ROS) and inflammatory cytokines, which result in neuroinflammation, suggesting that antidiabetic drugs may be potential treatments to protect against AD. Among these, glucagon-like peptide-1 receptor agonists (GLP-1RAs) are the most attractive antidiabetic drugs due to their actions on synaptic plasticity, cognition and cell survival. The present review summarizes the significant data concerning the underlying pathophysiological and pharmacological mechanisms between diabetes and dementia.

Cognitive dysfunction in diabetes: abnormal glucose metabolic regulation in the brain

Cognitive dysfunction is increasingly recognized as a complication and comorbidity of diabetes, supported by evidence of abnormal brain structure and function. Although few mechanistic metabolic studies have shown clear pathophysiological links between diabetes and cognitive dysfunction, there are several plausible ways in which this connection may occur. Since, brain functions require a constant supply of glucose as an energy source, the brain may be more susceptible to abnormalities in glucose metabolism. Glucose metabolic abnormalities under diabetic conditions may play an important role in cognitive dysfunction by affecting glucose transport and reducing glucose metabolism. These changes, along with oxidative stress, inflammation, mitochondrial dysfunction, and other factors, can affect synaptic transmission, neural plasticity, and ultimately lead to impaired neuronal and cognitive function. Insulin signal triggers intracellular signal transduction that regulates glucose transport and metabolism. Insulin resistance, one hallmark of diabetes, has also been linked with impaired cerebral glucose metabolism in the brain. In this review, we conclude that glucose metabolic abnormalities play a critical role in the pathophysiological alterations underlying diabetic cognitive dysfunction (DCD), which is associated with multiple pathogenic factors such as oxidative stress, mitochondrial dysfunction, inflammation, and others. Brain insulin resistance is highly emphasized and characterized as an important pathogenic mechanism in the DCD.

Taurine alleviated hepatic steatosis in oleic acid-treated-HepG2 cells and rats fed a high-fat diet

Taurine has been proven in many trials to alleviate the symptoms of metabolic associated fatty liver disease. Here its protective effect for hepatic steatosis and modulation of AMP-activated protein kinase and insulin signaling pathway were investigated. Steatotic HepG2 cell established with oleic acid (0.05 mmol/L), treated with taurine (5 mmol/L), dorsomorphin (10 μmol/L) for 24 h. Sprague Dawley rats were divided into regular and high-fat diet (HFD) groups, and their corresponding taurine (70 or 350 mg/kg BW/d) groups, fed for 8 weeks. In steatotic cell, taurine reduced the TG concentration and SREBP-1c, PPARγ, FAS, ACC, SCD1 protein levels, decreased phosphorylation of mTOR, IRS1 (Ser302), increased phosphorylation of AMPKα, LKB1, PI3K, Akt, ACC. While dorsomorphin eliminated taurine's TG-lowering effect. In HFD-fed rats, taurine reduced liver TG, serum TG, ALT, AST, IL-1β, IL-4, TNF-α. The effects of taurine on the main factors of fatty acid synthesis were mostly consistent with cell experiments, and the reduction of microRNAs (451, 33, 291b) was aligned with the improvement in LKB1 and AMPK expression in HFD rats. Taurine alleviated steatosis-induced inhibition of IRS1-PI3K-Akt pathway, but suppressed its positively regulated downstream factor mTOR. In parallel, taurine reduced steatosis by activating LKB1-AMPKα pathway via phosphorylation and no-phosphorylation manner, then inhibiting SREBP-1c directly or by suppressing mTOR phosphorylation.

The human neurosecretome: extracellular vesicles and particles (EVPs) of the brain for intercellular communication, therapy, and liquid-biopsy applications

Emerging evidence suggests that brain derived extracellular vesicles (EVs) and particles (EPs) can cross blood-brain barrier and mediate communication among neurons, astrocytes, microglial, and other cells of the central nervous system (CNS). Yet, a complete understanding of the molecular landscape and function of circulating EVs & EPs (EVPs) remain a major gap in knowledge. This is mainly due to the lack of technologies to isolate and separate all EVPs of heterogeneous dimensions and low buoyant density. In this review, we aim to provide a comprehensive understanding of the neurosecretome, including the extracellular vesicles that carry the molecular signature of the brain in both its microenvironment and the systemic circulation. We discuss the biogenesis of EVPs, their function, cell-to-cell communication, past and emerging isolation technologies, therapeutics, and liquid-biopsy applications. It is important to highlight that the landscape of EVPs is in a constant state of evolution; hence, we not only discuss the past literature and current landscape of the EVPs, but we also speculate as to how novel EVPs may contribute to the etiology of addiction, depression, psychiatric, neurodegenerative diseases, and aid in the real time monitoring of the "living brain". Overall, the neurosecretome is a concept we introduce here to embody the compendium of circulating particles of the brain for their function and disease pathogenesis. Finally, for the purpose of inclusion of all extracellular particles, we have used the term EVPs as defined by the International Society of Extracellular Vesicles (ISEV).

Integrated transcriptome and metabolome analysis to investigate the mechanism of intranasal insulin treatment in a rat model of vascular dementia

Introduction: Insulin has an effect on neurodegenerative diseases. However, the role and mechanism of insulin in vascular dementia (VD) and its underlying mechanism are unknown. In this study, we aimed to investigate the effects and mechanism of insulin on VD. Methods: Experimental rats were randomly assigned to control (CK), Sham, VD, and insulin (INS) + VD groups. Insulin was administered by intranasal spray. Cognitive function was evaluated using the Morris's water maze. Nissl's staining and immunohistochemical staining were used to assess morphological alterations. Apoptosis was evaluated using TUNEL-staining. Transcriptome and metabolome analyses were performed to identify differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs), respectively. Results: Insulin significantly improved cognitive and memory functions in VD model rats (p < 0.05). Compared with the VD group, the insulin + VD group exhibited significantly reduced the number of Nissl's bodies numbers, apoptosis level, GFAP-positive cell numbers, apoptosis rates, and p-tau and tau levels in the hippocampal CA1 region (p < 0.05). Transcriptomic analysis found 1,257 and 938 DEGs in the VD vs. CK and insulin + VD vs. VD comparisons, respectively. The DEGs were mainly enriched in calcium signaling, cAMP signaling, axon guidance, and glutamatergic synapse signaling pathways. In addition, metabolomic analysis identified 1 and 14 DEMs between groups in negative and positive modes, respectively. KEGG pathway analysis indicated that DEGs and DEMs were mostly enriched in metabolic pathway. Conclusion: Insulin could effectively improve cognitive function in VD model rats by downregulating tau and p-tau expression, inhibiting astrocyte inflammation and neuron apoptosis, and regulating genes involved in calcium signaling, cAMP signaling, axon guidance, and glutamatergic synapse pathways, as well as metabolites involved in metabolic pathway.

Apoptosis in Alzheimer's disease: insight into the signaling pathways and therapeutic avenues

Alzheimer's disease (AD) is characterized by the accumulation of hyperphosphorylated tau and amyloid-β (Aβ) protein resulting in synaptic loss and apoptosis. Aβ and tau deposition trigger apoptotic pathways that result in neuronal death. Apoptosis is considered to be responsible for manifestations associated with AD under pathological conditions. It regulates via extrinsic and intrinsic pathways. It activates various proteins including Bcl-2 family proteins like Bax, Bad, Bid, Bcl-XS, Bcl-XL and caspases comprising of initiator, effector and inflammatory caspases carried out through a cascade of events that finally lead to cell disintegration. The apoptotic elements interact with trophic factors, signaling molecules including Ras-ERK, JNK, GSK-3β, BDNF/TrkB/CREB and PI3K/AKT/mTOR. Ras-ERK signaling is involved in the progression of cell cycle and apoptosis. JNK pathway is also upregulated in AD which results in decreased expression of anti-apoptotic proteins. JAK-STAT triggers caspase-3 mediated apoptosis leading to neurodegeneration. The imbalance between autophagy and apoptosis is regulated by PI3K/Akt/mTOR pathway. GSK-3β is involved in the stimulation of pro-apoptotic factors resulting in dysregulation of apoptosis. Drugs like filgrastim, epigallocatechin gallate, curcumin, nicergoline and minocycline are under development which target these pathways and modulate the disease condition. This study sheds light on apoptotic pathways that are cardinal for neuronal survival and perform crucial role in the occurrence of AD along with the trends in therapeutics targeting apoptosis induced AD. To develop prospective treatments for AD, it is desirable to elucidate potential targets including restoration apoptotic balance, regulation of caspases, Bcl-2 and other crucial proteins involved in apoptosis mediated AD.

Insulin Resistance and Impaired Branched-Chain Amino Acid Metabolism in Alzheimer's Disease

The pathogenesis of Alzheimer's disease (AD) is complicated and involves multiple contributing factors. Mounting evidence supports the concept that AD is an age-related metabolic neurodegenerative disease mediated in part by brain insulin resistance, and sharing similar metabolic dysfunctions and brain pathological characteristics that occur in type 2 diabetes mellitus (T2DM) and other insulin resistance disorders. Brain insulin signal pathway is a major regulator of branched-chain amino acid (BCAA) metabolism. In the past several years, impaired BCAA metabolism has been described in several insulin resistant states such as obesity, T2DM and cardiovascular disease. Disrupted BCAA metabolism leading to elevation in circulating BCAAs and related metabolites is an early metabolic phenotype of insulin resistance and correlated with future onset of T2DM. Brain is a major site for BCAA metabolism. BCAAs play pivotal roles in normal brain function, especially in signal transduction, nitrogen homeostasis, and neurotransmitter cycling. Evidence from animal models and patients support the involvement of BCAA dysmetabolism in neurodegenerative diseases including Huntington's disease, Parkinson's disease, and maple syrup urine disease. More recently, growing studies have revealed altered BCAA metabolism in AD, but the relationship between them is poorly understood. This review is focused on the recent findings regarding BCAA metabolism and its role in AD. Moreover, we will explore how impaired BCAA metabolism influences brain function and participates in the pathogenesis of AD.

Comparison of the molecular mechanisms of Fuzi Lizhong Pill and Huangqin decoction in the treatment of the cold and heat syndromes of ulcerative colitis based on network pharmacology

OBJECTIVE

The aim of this study was to illuminate the similarities and differences of two prescriptions as "cold" and "heat" drugs for treating ulcerative colitis (UC) with the simultaneous occurrence of heat and cold syndrome via network pharmacology.

METHODS

(1) Active compounds of Fuzi-Lizhong Pill (FLP) and Huangqin Decoction (HQT) were retrieved from the TCMSP database, and their common active compounds were compared using the Venn diagram. (2) Potential proteins targeted to three sets of compounds either (i) shared by FLP and HQT, (ii) unique to FLP or (iii) unique to HQT were screened from the STP, STITCH and TCMSP databases, and three corresponding core compound sets were identified in Herb-Compound-Target (H-C-T) networks. (3) Targets related to UC were identified from the DisGeNET and GeneCards databases and compared with the FLP-HQT common targets to identify potential targets of FLP-HQT compounds related to UC. (4) Three potential target sets were imported into the STRING database for protein‒protein interaction (PPI) analysis, and three core target sets were defined. (5) The binding capabilities and interacting modes between core compounds and key targets were verified by molecular docking via Discovery Studio 2019 and molecular dynamics (MD) simulations via Amber 2018. (6) The target sets were enriched for KEGG pathways using the DAVID database.

RESULTS

(1) FLP and HQT included 95 and 113 active compounds, respectively, with 46 common compounds, 49 FLP-specific compounds and 67 HQT-specific compounds. (2) 174 targets of FLP-HQT common compounds, 168 targets of FLP-specific compounds, and 369 targets of HQT-specific compounds were predicted from the STP, STITCH and TCMSP databases; six core compounds specific to FLP and HQT were screened in the FLP-specific and HQT-specific H-C-T networks, respectively. (3) 103 targets overlapped from the 174 predicted targets and the 4749 UC-related targets; two core compounds for FLP-HQT were identified from the FLP-HQT H-C-T network. (4) 103 FLP-HQT-UC common targets, 168 of FLP-specific targets and 369 of HQT-specific targets had shared core targets (AKT1, MAPK3, TNF, JUN and CASP3) based on the PPI network analysis. (5) Molecular docking demonstrated that naringenin, formononetin, luteolin, glycitein, quercetin, kaempferol and baicalein of FLP and HQT play a critical role in treating UC; meanwhile, MD simulations revealed the stability of protein‒ligand interactions. (6) The enriched pathways indicated that most targets were related to anti-inflammatory, immunomodulatory and other pathways. Compared with the pathways identified using traditional methods, FLP-specific pathways included the PPAR signaling pathway and the bile secretion pathway, and HQT-specific pathways included the vascular smooth muscle contraction pathway and the natural killer cell-mediated cytotoxicity pathway etc. CONCLUSION: In this study, we clarified the common mechanisms of FLP and HQT in treating UC and their specific mechanisms in treating cold and heat syndrome in UC through compound, target and pathway distinction and a literature comparison based on network pharmacology; these results provide a new perspective on the detailed mechanism of "multidrugs and single-disease" thought in traditional Chinese medicine.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) in the central nervous system

The gene encoding proprotein convertase subtilisin/kexin type 9 (PCSK9) and its protein product have been widely studied for their role in cholesterol and lipid metabolism. PCSK9 increases the rate of metabolic degradation of low-density lipoprotein receptors, preventing the diffusion of low-density lipoprotein (LDL) from plasma into cells and contributes to high lipoprotein-bound cholesterol levels in the plasma. While most research has focused on the regulation and disease relevance of PCSK9 to the cardiovascular system and lipid metabolism, there is a growing body of evidence that PCSK9 plays a crucial role in pathogenic processes in other organ systems, including the central nervous system. PCSK9's impact on the brain is not yet fully understood, though several recent studies have sought to illuminate its impact on various neurodegenerative and psychiatric disorders, as well as its connection with ischemic stroke. Cerebral PCSK9 expression is low but is highly upregulated during disease states. Among others, PCSK9 is known to play a role in neurogenesis, neural cell differentiation, central LDL receptor metabolism, neural cell apoptosis, neuroinflammation, Alzheimer's Disease, Alcohol Use Disorder, and stroke. The PCSK9 gene contains several polymorphisms, including both gain-of-function and loss-of-function mutations which profoundly impact normal PCSK9 signaling and cholesterol metabolism. Gain-of-function mutations lead to persistent hypercholesterolemia and poor health outcomes, while loss-of-function mutations generally lead to hypocholesterolemia and may serve as a protective factor against diseases of the liver, cardiovascular system, and central nervous system. Recent genomic studies have sought to identify the end-organ effects of such mutations and continue to identify evidence of a much broader role for PCSK9 in extrahepatic organ systems. Despite this, there remain large gaps in our understanding of PCSK9, its regulation, and its effects on disease risk outside the liver. This review, which incorporates data from a wide range of scientific disciplines and experimental paradigms, is intended to describe PCSK9's role in the central nervous system as it relates to cerebral disease and neuropsychiatric disorders, and to examine the clinical potential of PCSK9 inhibitors and genetic variation in the PCSK9 gene on disease outcomes, including neurological and neuropsychiatric disease.

Research Progress on Lipocalin-2 in Diabetic Encephalopathy

Diabetic encephalopathy is a central nervous complication of diabetes mellitus which is characterized by cognitive impairment and structural and neurochemical abnormalities, which is easily neglected. Lipocalin-2 (LCN2) is a 25 kDa transporter in the lipocalin family that can transport small molecules, including fatty acids, iron, steroids, and lipopolysaccharides in the circulation. Recently, LCN2 has been found to be a significant regulator of insulin resistance and glucose homeostasis. Numerous studies have shown that LCN2 is connected to central nervous system abnormalities, including neuroinflammation and neurodegeneration, while the latest researches have found that LCN2 is closely related to the development of diabetic encephalopathy. Nevertheless, its precise role in the pathogenesis of diabetic encephalopathy remains to be determined. In this paper, we review recent evidence on the role of LCN2 in diabetic encephalopathy from multiple perspectives in order to decipher the impact of LCN2 in both the aetiology and treatment of diabetic encephalopathy.

Construction and analysis of circular RNA-associated competing endogenous RNA network in the hippocampus of aged mice for the occurrence of postoperative cognitive dysfunction

Circular RNAs are highly stable single-stranded circular RNAs and enriched in the brain. Previous studies showed that circRNAs, as part of competing endogenous RNAs (ceRNAs) network, play an important role in neurodegenerative and psychiatric diseases. However, the mechanism of circRNA-related ceRNA networks in postoperative cognitive dysfunction (POCD) has not been elucidated yet. POCD usually occurs in elderly patients and is characterized by hippocampal dysfunction. Here, aged C57BL/6 mice were subjected to exploratory laparotomy under sevoflurane anesthesia, and this POCD model was verified by Morris water maze test. Whole-transcriptome sequencing was performed on the hippocampus of control group (Con) and surgery group. One hundred and seventy-seven DEcircRNAs, 221 DEmiRNAs and 2,052 DEmRNAs were identified between two groups. A ceRNA network was established with 92 DEcircRNAs having binding sites with 76 DEmiRNAs and 549 target DEmRNAs. In functional enrichment analysis, a pathological pattern of POCD was highlighted in the ceRNA network: Abnormal metabolic process in neural cells, including oxygen metabolism, could promote apoptosis and then affect the synaptic function, which may undermine the neural plasticity and eventually lead to changes in cognitive function and other behavioral patterns. In conclusion, this specific ceRNA network of circRNAs–miRNAs–mRNAs has provided novel insights into the regulatory mechanisms of POCD and revealed potential therapeutic gene targets.

GRK5 Deficiency in the Hippocampus Leads to Cognitive Impairment via Abnormal Microglial Alterations

GRK5 is a member of the G protein-coupled receptor (GPCR) kinase family and is closely associated with heart and nervous system disease. It has been reported that GRK5 is closely related to cerebral nerve function and neurodegenerative diseases. However, the biological function of GRK5 in the brain and the influence of GRK5 deficiency on cognitive dysfunction associated with neurodegenerative diseases are unknown. Here, we reported that mice with reduced GRK5 in the hippocampus exhibit cognitive impairment and some Alzheimer's disease (AD)-related molecular pathologies, such as significant neuronal damage and loss, enhanced tau protein phosphorylation, and increased levels of Aβ peptides in the hippocampus. Mechanistically, we observed that GRK5 is located in microglia and plays an essential role in maintaining the morphology and function of microglia. GRK5 deficiency elicits microglial morphology changes and proinflammatory-associated gene increases. In addition, transcriptional analysis of hippocampal tissues revealed striking changes in neuroactive ligand‒receptor interactions and TNF signaling in GRK5-deficient mice. In conclusion, our results further confirm the vital role of GRK5 in maintaining normal cognitive function in mice. This finding suggests a possible mechanism by which GRK5 maintains microglial homeostasis, and its loss may induce microglial function deficits and cause some AD-related molecular pathogenesis.

The TgF344-AD rat: behavioral and proteomic changes associated with aging and protein expression in a transgenic rat model of Alzheimer's disease

Animal models of Alzheimer's Disease (AD) are attractive tools for preclinical, prodromal drug testing. The TgF344-AD (Tg) rat exhibits cognitive deficits and 5 major hallmarks of AD. Here we show that spatial water maze (WMZ) memory deficits and proteomic differences in dorsal CA1 were present in young Tg rats. Aged learning-unimpaired (AU) and aged learning-impaired (AI) proteome associated changes were identified and differed by sex. Levels of phosphorylated tau, reactive astrocytes and microglia were significantly increased in aged Tg rats and correlated with the WMZ learning index (LI); in contrast, no significant correlation was present between amyloid plaques or insoluble Aβ levels and LI. Neuroinflammatory markers were also significantly correlated with LI and increased in female Tg rats. The anti-inflammatory marker, triggering receptor expressed on myeloid cells-2 (TREM2), was significantly reduced in aged impaired Tg rats and correlated with LI. Identifying and understanding mechanisms that allow for healthy aging by overcoming genetic drivers for AD, and/or promoting drivers for successful aging, are important for developing successful therapeutics against AD.

Metformin mitigates amyloid β1-40-induced cognitive decline via attenuation of oxidative/nitrosative stress and neuroinflammation

Metformin is an antidiabetic medicine widely used for management of type 2 diabetes with neuroprotective effects and promising potential to attenuate cognitive impairment. The efficacy of metformin in attenuation of Alzheimer's disease (AD) pathology has not been well-documented. Thus, this study was designed to assess protective effect of metformin against Aβ_1-40-instigared cognitive impairment. After intra-CA1 microinjection of aggregated Aβ_1-40, rats received oral metformin (50 and/or 200 mg/kg/day) for two weeks. Cognition function was analyzed in various behavioral tasks besides measurement of hippocampal oxidative stress, apoptosis, and inflammation along with H&E staining and 3-nitrotyrosine (3-NT) immunohistochemistry. Obtained data showed significant improvement of discrimination score in novel object recognition test, higher alternation score in Y maze, greater latency in passive avoidance task, and lower working and reference memory errors in radial arm maze in metformin-treated Aβ-injured group. Moreover, metformin treatment attenuated hippocampal levels of nitrite, MDA, protein carbonyl, ROS, TNFα, GFAP, DNA fragmentation intensity, caspase 3 activity, AChE activity, and increased SOD activity and level of IL-10 as an anti-inflammatory factor. In addition, metformin treatment was associated with lower CA1 neuronal loss and it also decreased intensity of 3-NT immunoreactivity as an indicator of nitrosative stress. Taken together, obtained findings showed neuroprotective and anti-dementia property of metformin in male rats and this may have potential benefit in attenuation of cognitive decline and related complications in patients with neurodegenerative disorders such as AD besides diabetes mellitus.

PolyAMiner-Bulk: A Machine Learning Based Bioinformatics Algorithm to Infer and Decode Alternative Polyadenylation Dynamics from bulk RNA-seq data

More than half of human genes exercise alternative polyadenylation (APA) and generate mRNA transcripts with varying 3' untranslated regions (UTR). However, current computational approaches for identifying cleavage and polyadenylation sites (C/PASs) and quantifying 3'UTR length changes from bulk RNA-seq data fail to unravel tissue- and disease-specific APA dynamics. Here, we developed a next-generation bioinformatics algorithm and application, PolyAMiner-Bulk, that utilizes an attention-based machine learning architecture and an improved vector projection-based engine to infer differential APA dynamics accurately. When applied to earlier studies, PolyAMiner-Bulk accurately identified more than twice the number of APA changes in an RBM17 knockdown bulk RNA-seq dataset compared to current generation tools. Moreover, on a separate dataset, PolyAMiner-Bulk revealed novel APA dynamics and pathways in scleroderma pathology and identified differential APA in a gene that was identified as being involved in scleroderma pathogenesis in an independent study. Lastly, we used PolyAMiner-Bulk to analyze the RNA-seq data of post-mortem prefrontal cortexes from the ROSMAP data consortium and unraveled novel APA dynamics in Alzheimer's Disease. Our method, PolyAMiner-Bulk, creates a paradigm for future alternative polyadenylation analysis from bulk RNA-seq data.

High-fiber-diet-related metabolites improve neurodegenerative symptoms in patients with obesity with diabetes mellitus by modulating the hippocampal-hypothalamic endocrine axis

Objective

Through transcriptomic and metabolomic analyses, this study examined the role of high-fiber diet in obesity complicated by diabetes and neurodegenerative symptoms.

Method

The expression matrix of high-fiber-diet-related metabolites, blood methylation profile associated with pre-symptomatic dementia in elderly patients with type 2 diabetes mellitus (T2DM), and high-throughput single-cell sequencing data of hippocampal samples from patients with Alzheimer's disease (AD) were retrieved from the Gene Expression Omnibus (GEO) database and through a literature search. Data were analyzed using principal component analysis (PCA) after quality control and data filtering to identify different cell clusters and candidate markers. A protein-protein interaction network was mapped using the STRING database. To further investigate the interaction among high-fiber-diet-related metabolites, methylation-related DEGs related to T2DM, and single-cell marker genes related to AD, AutoDock was used for semi-flexible molecular docking.

Result

Based on GEO database data and previous studies, 24 marker genes associated with high-fiber diet, T2DM, and AD were identified. Top 10 core genes include SYNE1, ANK2, SPEG, PDZD2, KALRN, PTPRM, PTPRK, BIN1, DOCK9, and NPNT, and their functions are primarily related to autophagy. According to molecular docking analysis, acetamidobenzoic acid, the most substantially altered metabolic marker associated with a high-fiber diet, had the strongest binding affinity for SPEG.

Conclusion

By targeting the SPEG protein in the hippocampus, acetamidobenzoic acid, a metabolite associated with high-fiber diet, may improve diabetic and neurodegenerative diseases in obese people.

Insulin ameliorates dim blue light at night-induced apoptosis in hippocampal neurons via the IR/IRS1/AKT/GSK3β/β-catenin signaling pathway

In recent years, the damaging effects of night light pollution, one of the environmental pollutions, on memory has been attracting attention. However, the underlying molecular mechanisms by which light at night, especially blue light at night, impairs memory remains unclear. Here, a total of 42 C57BL6/J mice that exposed to no light at night, dim white light at night (dLAN-WL), or dim blue light at night (dLAN-BL) for 28 days. Behavioral data indicated that exposure to dLAN-BL resulted in severe recognition memory impairment, as evidenced by the reduced recognition index and discrimination index in the novel object recognition test. At the same time, we observed a decrease in plasma insulin levels. Consistent with these changes, we also observed that dLAN-BL reduced the number of neurons in the CA1, CA3 and DG regions of the hippocampus, up-regulated the mRNA expression levels of Bax, down-regulated the mRNA expression levels of Bcl-2, Bcl-xl and the protein expression level of pIRS1, pAKT, pGSK3β, β-catenin in the hippocampus. In vitro experiments, we found that insulin (10 nM) inhibited apoptosis and up-regulated the protein expression levels of pAKT, pGSK3β, β-catenin of HT22 cells induced by H₂O₂ (200 μM). However, these changes disappeared when the insulin receptors (IR) in HT22 cells were silenced. Taken together, our findings suggested that the impairment of memory in mice induced by dLAN-BL was mediated by insulin via the IR/IRS1/AKT/GSK3β/β-catenin pathway. DATA AVAILABILITY: All data generated or analyzed during this study are included in this published article.

Miracle fruit seed as a potential supplement for the treatment of learning and memory disorders in Alzheimer's disease

Currently, the treatment of Alzheimer's disease (AD) is still at the stage of symptomatic treatment due to lack of effective drugs. The research on miracle fruit seeds (MFSs) has focused on lipid-lowering and antidiabetic effects, but no therapeutic effects have been reported in AD. The purpose of this study was to provide data resources and a potential drug for treatment of AD. An AD mouse model was established and treated with MFSs for 1 month. The Morris water maze test was used to assess learning memory function in mice. Nissl staining was used to demonstrate histopathological changes. MFSs were found to have therapeutic implications in the AD mouse model, as evidenced by improved learning memory function and an increase in surviving neurons. To explore the mechanism of MFSs in treating AD, network pharmacological approaches, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and molecular docking studies were carried out. Based on the network pharmacology strategy, 74 components from MFS corresponded to 293 targets related to the AD pathology. Among these targets, AKT1, MAPK3, ESR1, PPARG, PTGS2, EGFR, PPARA, CNR1, ABCB1, and MAPT were identified as the core targets. According to the relevant number of core targets, cis-8-octadecenoic acid, cis-10-octadecenoic acid, 2-dodecenal, and tetradecane are likely to be highly correlated with MFS for AD. Enrichment analysis indicated the common targets mainly enriched in AD and the neurodegeneration-multiple disease signaling pathway. The molecular docking predictions showed that MFSs were stably bound to core targets, specifically AKT1, EGFR, ESR1, PPARA, and PPARG. MFSs may play a therapeutic role in AD by affecting the insulin signaling pathway and the Wnt pathway. The findings of this study provide potential possibilities and drug candidates for the treatment of AD.

The Role of Caspases in Alzheimer's Disease: Pathophysiology Implications and Pharmacologic Modulation

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide. Although the main cause of the onset and development of AD is not known yet, neuronal death due to pathologic changes such as amyloid-β (Aβ) deposition, tau aggregation, neuroinflammation, oxidative stress, and calcium dyshomeostasis are considered to be the main cause. At the present, there is no cure for this insidious disorder. However, accurate identification of molecular changes in AD can help provide new therapeutic goals. Caspases are a group of proteases which are known because of their role in cellular apoptosis. In addition, different caspases are involved in other cellular responses to the environment, such as induction of inflammation. Emerging evidence suggest that these proteases play a central role in AD pathophysiology due to their role in the processing of amyloid-β protein precursor, tau cleavage, and neuroinflammation. Therefore, it seems that targeting caspases may be a suitable therapeutic option to slow the progression of AD. This review focuses on the role of caspases in AD pathophysiology and introduce results from studies targeted caspases in different models of AD.

Verniciflavanol A, a profisetinidin-type-4-arylflavan-3-ol from toxicodendron vernicifluum protects SH-SY5Y cells against H2O2-Induced oxidative stress

Eleven undescribed derivatives of flavan, including flavan-3,4-diols vernicinosides A-H and profisetinidin-type-4-arylflavan-3-ols verniciflavanols A-C, together with eight known compounds were purified from the heartwood of Toxicodendron vernicifluum. The chemical structures of the undescribed compounds were characterized by spectroscopic data interpretation, including NMR (¹H and ¹³C NMR HSQC and HMBC) and HRESIMS analysis. CD data analysis was conducted to assign the absolute configurations of the undescribed compounds and the active compound verniciflavanol A was also confirmed by ECD experiment. The absolute configuration of the sugar moiety was identified by GC analysis of chiral derivatives in the hydrolysate. MTT assay was applied to test these compounds against H₂O₂-induced oxidative stress in human neuroblastoma SH-SY5Y cells. Results found that verniciflavanol A demonstrated the best potential in protecting SH-SY5Y cells against H₂O₂-induced oxidative stress by inhibiting cell apoptosis and attenuate reactive oxygen species (ROS) level and mitochondrial dysfunction. And the underlying mechanism was confirmed to be associated with Nrf2-antioxidant response element signaling and IL-6 cell survival pathways.