Diabetes drugs in the fight against Alzheimer's disease

Assessment of sodium-glucose cotransporter 2 inhibitors (SGLT2i) and other antidiabetic agents in Alzheimer's disease: a population-based study

The lack of effective treatments for dementia has led to explore the potential of antidiabetic agents as a possible approach. This cross-sectional and population-based study aimed to investigate the relationship between each antidiabetic drug and their defined daily doses (DDDs) and the use of anti-Alzheimer's disease (AD) drugs in order to establish new possible hypotheses about the role of antidiabetic drugs in AD. For that purpose, a database containing information on medications prescribed to 233183 patients aged 50 years or older between 2018 and 2020 was used. DDDs were calculated according to the ATC/DDD index 2023. Statistical analyses, with logistic regression, were carried out to assess antidiabetic and anti-AD drugs consumption. A total of 91836 patients who were prescribed at least one antihypertensive, antidiabetic, or lipid-modifying agent were included in the study; specifically, 29260 patients were prescribed antidiabetic medication. Among the antidiabetic agents, glucagon-like peptide-1 analogs (GLP-1) DDDs were likely to have a positive association with anti-AD drugs in people aged between 70 and 80 years. Additionally, sodium-glucose cotransporter 2 inhibitors (SGLT2i) were prone to have a positive association with anti-AD drug usage across almost every age. However, insulin usage was associated with an increased usage of anti-AD agents. In conclusion, there is evidence suggesting a correlation between certain antidiabetic agents and dementia. Specifically, GLP-1 and SGLT2i might be associated with lower odds of anti-AD drugs usage, while insulins might be linked to higher odds of using anti-AD drugs.

Effects of antidiabetic agents on platelet characteristics with implications in Alzheimer's disease: Mendelian randomization and colocalization study

Background

Observational studies have found a potential link between the use of thiazolidinediones (TZDs) and a lower risk of Alzheimer's disease (AD) development. Platelets were the great source of amyloid-β (Aβ) and involved in the development of AD. This study aimed to assess the correlation between antidiabetic agents and platelet characteristics, hoping to provide a potential mechanism of TZDs neuroprotection in AD.

Method

Drug-targeted Mendelian randomization (MR) was performed to systematically illustrate the long-term effects of antidiabetic agents on platelet characteristics. Four antidiabetic agent targets were considered. Positive control analysis for type 2 diabetes (T2D) was conducted to validate the selection of instrumental variables (IVs). Colocalization analysis was used to further strengthen the robustness of the results.

Result

Positive control analysis showed an association of four antidiabetic agents with lower risk of T2D, which was consistent with their mechanisms of action and previous evidence from clinical trials. Genetically proxied TZDs were associated with lower platelet count (β[IRNT] = -0.410 [95 % CI -0.533 to -0.288], P = 5.32E-11) and a lower plateletcrit (β[IRNT] = -0.344 [95 % CI -0.481 to -0.206], P = 1.04E-6). Colocalization suggested the posterior probability of hypothesis 4 (PPH4) > 0.8, which further strengthened the MR results.

Conclusion

Genetically proxied TZDs were causally associated with lower platelet characteristics, particularly platelet count and plateletcrit, providing insight into the involvement of platelet-related pathways in the neuroprotection of TZDs against AD. Future studies are warranted to reveal the underlying molecular mechanism of TZDs' neuroprotective effects through platelet pathways.

Diabetes mellitus and Alzheimer's disease: Understanding disease mechanisms, their correlation, and promising dual activity of selected herbs

ETHNOPHARMACOLOGICAL RELEVANCE

This review explores the link between Type 2 Diabetes Mellitus (T2DM) and diabetes-induced Alzheimer's disease (AD). It emphasizes the shared pathophysiological links and mechanisms between the two conditions, focusing on reduced insulin levels and receptors, impaired glucose metabolism, insulin resistance, mitochondrial dysfunction, and oxidative damage in AD-affected brains-paralleling aspects of T2DM. The review suggests AD as a "diabetes of the brain," supported by cognitive enhancement through antidiabetic interventions. It focuses on the traditionally used Indian herbs as a means to manage both conditions while addressing developmental challenges.

AIM OF THE STUDY

This study explores the DM-AD connection, reviewing medicinal herbs with protective potential for both ailments, considering traditional uses and developmental challenges.

MATERIALS AND METHODS

Studied research, reviews, and ethnobotanical and scientific data from electronic databases and traditional books.

RESULTS

The study analyzes the pathophysiological links between DM and AD, emphasizing their interconnected factors. Eight Ayurvedic plants with dual protective effects against T2DM and AD are thoroughly reviewed with preclinical/clinical evidence. Historical context, phytoconstituents, and traditional applications are explored. Innovative formulations using these plants are examined. Challenges stemming from phytoconstituents' physicochemical properties are highlighted, prompting novel formulation development, including nanotechnology-based delivery systems. The study uncovers obstacles in formulating treatments for these diseases.

CONCLUSION

The review showcases the dual potential of chosen medicinal herbs against both diseases, along with their traditional applications, endorsing their use. It addresses formulation obstacles, proposing innovative delivery technologies for herbal therapies, while acknowledging their constraints. The review suggests the need for heightened investment and research in this area.

Alzheimer's disease, a metabolic disorder: Clinical advances and basic model studies (Review)

Alzheimer's disease (AD) is a type of neurodegenerative disease characterized by cognitive impairment that is aggravated with age. The pathological manifestations include extracellular amyloid deposition, intracellular neurofibrillary tangles and loss of neurons. As the world population ages, the incidence of AD continues to increase, not only posing a significant threat to the well-being and health of individuals but also bringing a heavy burden to the social economy. There is epidemiological evidence suggesting a link between AD and metabolic diseases, which share pathological similarities. This potential link would deserve further consideration; however, the pathogenesis and therapeutic efficacy of AD remain to be further explored. The complex pathogenesis and pathological changes of AD pose a great challenge to the choice of experimental animal models. To understand the role of metabolic diseases in the development of AD and the potential use of drugs for metabolic diseases, the present article reviews the research progress of the comorbidity of AD with diabetes, obesity and hypercholesterolemia, and summarizes the different roles of animal models in the study of AD to provide references for researchers.

Association of Triglyceride-Glucose Index With Cognitive Function and Brain Atrophy: A Population-Based Study

OBJECTIVE

To investigate the associations of triglyceride-glucose (TyG) index, a reliable surrogate marker for insulin resistance, with the function of various cognitive domains and brain structures among older adults.

DESIGN

A population-based cross-sectional study.

SETTING

Older adults living in the rural communities in China.

PARTICIPANTS

About 4,541 rural-dwelling dementia-free participants (age ≥65 years; 56.37% women) undertook examinations in March-September 2018 for MIND-China.

MEASUREMENTS

TyG index was calculated as ln[fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2]. A neuropsychological test battery was used to assess memory, attention, verbal fluency, and executive function. Volumetric brain measures were assessed on magnetic resonance imaging (MRI) in a subsample (n = 1,019). Data were analyzed with restricted cubic spline and multivariable general linear models.

RESULTS

An inverted J-shaped association was observed between TyG index and z-scores of multiple cognitive domains, such that among individuals with TyG index ≥8.57 (median), a higher TyG index was significantly associated with lower z-scores of memory, attention, verbal fluency, executive function, and global cognition (all p < 0.05); among people with TyG index <8.57, a higher TyG index was significantly associated with a higher executive function z-score (p < 0.05), but not with any of the other examined cognitive domains. In the MRI subsample, a higher TyG index was significantly associated with lower volumes of total brain tissue, gray matter, and white matter as well as greater cerebrospinal fluid volume (p < 0.05), but not with white matter hyperintensity volume.

CONCLUSIONS

Insulin resistance, as indicated by a high TyG index, was associated with poor function in multiple cognitive domains and global brain atrophy.

Anti-inflammatory role of glucagon-like peptide 1 receptor agonists and its clinical implications

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) have emerged as promising therapeutic agents with potent anti-inflammatory properties and diverse clinical implications. This in-depth review article explores the mechanisms behind the anti-inflammatory actions of GLP-1RAs and assesses their prospective applicability in a wide range of disease scenarios. The current review establishes the significance of comprehending the anti-inflammatory role of GLP-1RAs and identifies pertinent research gaps. A concise overview of inflammation and its clinical consequences underscores the critical need for effective anti-inflammatory interventions. Subsequently, the article elucidates the intricate mechanisms through which GLP-1RAs modulate immune cell signaling and regulate the nuclear factor-kappa B (NF-κB) pathway. Detailed discussions encompass their impact on inflammatory responses, cytokine production, and attenuation of oxidative stress. The exposition is substantiated by a collection of pertinent examples and an extensive array of references from both preclinical and clinical investigations. The historical trajectory of GLP-1RA drugs, including exenatide, lixisenatide, liraglutide, and semaglutide, is traced to delineate their development as therapeutic agents. Moreover, the review emphasizes the therapeutic potential of GLP-1RAs in specific disease contexts like type 2 diabetes, a neurodegenerative disorder, and inflammatory bowel disease (IBD), shedding light on their anti-inflammatory effects through rigorous examination of preclinical and clinical studies. The article also provides an outlook on future perspectives for GLP-1RAs, encompassing the domains of diabetes, neurodegenerative diseases, and IBD. In conclusion, GLP-1RAs exhibit substantial anti-inflammatory effects, rendering them promising therapeutic agents with broad clinical implications. They are very useful in a wide variety of diseases because they regulate immunological responses, block NF-κB activation, and decrease production of pro-inflammatory cytokines. Ongoing research endeavors aim to optimize their therapeutic use, delineate patient-specific treatment paradigms, and explore novel therapeutic applications. GLP-1RAs represent a significant breakthrough in anti-inflammatory therapy, offering novel treatment options, and improved patient outcomes.

Ginsenoside Rg1, lights up the way for the potential prevention of Alzheimer's disease due to its therapeutic effects on the drug-controllable risk factors of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine, Shen Nong, BenCao Jing, and Compendium of Materia Medica (Bencao Gangmu), Panax ginseng, and its prescriptions have been used for the treatment of dementia, depression, weight loss, Xiaoke disease (similar to diabetes), and vertigo. All these diseases are associated with the drug-controllable risk factors for Alzheimer's disease (AD), including depression, obesity, diabetes, and hypertension. Ginsenoside Rg1, one of the main active ingredients of P. ginseng and its congener Panax notoginseng, possesses therapeutic potentials against AD and associated diseases. This suggests that ginsenoside Rg1 might have the potential for AD prevention and treatment. Although the anti-AD effects of ginsenoside Rg1 have received more attention, a systematic review of its effects on depression, obesity, diabetes, and hypertension is not available.

AIM OF THE REVIEW

This systematic literature review comprehensively summarized existing literature on the therapeutic potentials of ginsenoside Rg1 in AD prevention for the propose of providing a foundation of future research aimed at enabling the use of such drugs in clinical practice.

METHODS

Information on ginsenoside Rg1 was collected from relevant published articles identified through a literature search in electronic scientific databases (PubMed, Science Direct, and Google Scholar). The keywords used were "Ginsenoside Rg1," "Panax ginseng," "Source," "Alzheimer's disease," "Brain disorders," "Depression," "Obesity," "Diabetes," and "Hypertension."

RESULTS

The monomer ginsenoside Rg1 can be relatively easily obtained and has therapeutic potentials against AD. In vitro and in vivo experiments have demonstrated the therapeutic potentials of ginsenoside Rg1 against the drug-controllable risk factors of AD including depression, obesity, diabetes, and hypertension. Thus, ginsenoside Rg1 alleviates diseases resulting from AD risk factors by regulating multiple targets and pathways.

CONCLUSIONS

Ginsenoside Rg1 has the potentials to prevent AD by alleviating depression, obesity, diabetes, and hypertension.

Metformin: The Winding Path from Understanding Its Molecular Mechanisms to Proving Therapeutic Benefits in Neurodegenerative Disorders

Metformin, a widely prescribed medication for type 2 diabetes, has garnered increasing attention for its potential neuroprotective properties due to the growing demand for treatments for Alzheimer's, Parkinson's, and motor neuron diseases. This review synthesizes experimental and clinical studies on metformin's mechanisms of action and potential therapeutic benefits for neurodegenerative disorders. A comprehensive search of electronic databases, including PubMed, MEDLINE, Embase, and Cochrane library, focused on key phrases such as "metformin", "neuroprotection", and "neurodegenerative diseases", with data up to September 2023. Recent research on metformin's glucoregulatory mechanisms reveals new molecular targets, including the activation of the LKB1-AMPK signaling pathway, which is crucial for chronic administration of metformin. The pleiotropic impact may involve other stress kinases that are acutely activated. The precise role of respiratory chain complexes (I and IV), of the mitochondrial targets, or of the lysosomes in metformin effects remains to be established by further research. Research on extrahepatic targets like the gut and microbiota, as well as its antioxidant and immunomodulatory properties, is crucial for understanding neurodegenerative disorders. Experimental data on animal models shows promising results, but clinical studies are inconclusive. Understanding the molecular targets and mechanisms of its effects could help design clinical trials to explore and, hopefully, prove its therapeutic effects in neurodegenerative conditions.

Developing a Two-Photon "AND" Logic Probe and Its Application in Alzheimer's Disease Differentiation

In Alzheimer's disease, hypochlorous acid involved in the clearance of invading bacteria or pathogens and butyrylcholinesterase engaged in the hydrolysis of the neurotransmitter acetylcholine are relatively significantly altered. However, there are few dual detection probes for hypochlorous acid and butyrylcholinesterase. In addition, single-response probes suffer from serious off-target effects and near-infrared probes do not easily penetrate the blood-brain barrier due to their excessive molecular weight. In this work, we constructed a two-photon fluorescent probe that recognizes hypochlorous acid and butyrylcholinesterase based on a dual-lock strategy. The thiocarbonyl group is oxidized in the presence of hypochlorous acid, and the hydrolysis occurs at the 7-position ester bond in the existence of butyrylcholinesterase, releasing a strongly fluorescent fluorophore, 4-methylumbelliferone. Excellent imaging was performed in PC12 cells using this probe, and deep two-photon imaging was observed in the brains of AD mice after tail vein injection with this probe. It indicates that the probe can provide a promising tool for the more precise diagnosis of Alzheimer's disease.

Hypericin as a potential drug for treating Alzheimer's disease and type 2 diabetes with a view to drug repositioning

AIMS

Alzheimer's disease (AD) and type 2 diabetes (T2D) are two of the most common diseases in elderly population and they have a high rate of comorbidity. Study has revealed that T2D is a major risk factor of AD, and thus exploring therapeutic approaches that can target both diseases has drawn much interest in recent years. In this study, we tried to explore drugs that could be potentially used to prevent or treat both AD and T2D via a drug repositioning approach.

METHODS

We first searched the known drugs that may be effective to T2D treatment based on the network distance between the T2D-associated genes and drugs deposited in the DrugBank database. Then, via molecular docking, we further screened these drugs by examining their interaction with islet amyloid polypeptide (IAPP) and Aβ42 peptide, the key components involved in the pathogenesis of T2D or AD. Finally, the binding between the selected drug candidates and the target proteins was verified by molecular dynamics (MD) simulation; and the potential function of the drug candidates and the corresponding targets were analyzed.

RESULTS

From multiple resources, 734 T2D-associated genes were collected, and a list of 1109 drug candidates for T2D was obtained. We found that hypericin had the lowest binding energy and the most stable interaction with either IAPP or Aβ42 peptide. In addition, we also found that the target genes regulated by hypericin were differentially expressed in the tissues related to the two diseases.

CONCLUSION

Our results show that hypericin may be able to bind with IAPP and Aβ42 stably and prevent their accumulation, and thus could be a promising drug candidate for treating the comorbidity of AD and T2D.

Myeloid Cells As a Promising Target for Brain-Bone Degenerative Diseases from a Metabolic Point of View

Brain and bone degenerative diseases such as Alzheimer's disease and osteoporosis are common in the aging population and lack efficient pharmacotherapies. Myeloid cells are a diverse group of mononuclear cells that plays important roles in development, immune defense, and tissue homeostasis. Aging drastically alters the expansion and function of myeloid cells, which might be a common pathogenesis of the brain-bone degenerative diseases. From this perspective, the role of myeloid cells in brain-bone degenerative diseases is discussed, with a particular focus on metabolic alterations in myeloid cells. Furthermore, targeting myeloid cells through metabolic regulation via drugs such as metformin and melatonin is proposed as a potential therapy for the clinical treatment of brain-bone diseases.

Glucagon-like peptide 1 (GLP-1) receptor agonists in experimental Alzheimer's disease models: a systematic review and meta-analysis of preclinical studies

Alzheimer's disease (AD) is a degenerative disease of the nervous system. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs), a drug used to treat type 2 diabetes, have been shown to have neuroprotective effects. This systematic review and meta-analysis evaluated the effects and potential mechanisms of GLP-1 RAs in AD animal models. 26 studies were included by searching relevant studies from seven databases according to a predefined search strategy and inclusion criteria. Methodological quality was assessed using SYRCLE's risk of bias tool, and statistical analysis was performed using ReviewManger 5.3. The results showed that, in terms of behavioral tests, GLP-1 RAs could improve the learning and memory abilities of AD rodents; in terms of pathology, GLP-1 RAs could reduce Aβ deposition and phosphorylated tau levels in the brains of AD rodents. The therapeutic potential of GLP-1 RAs in AD involves a range of mechanisms that work synergistically to enhance the alleviation of various pathological manifestations associated with the condition. A total of five clinical trials were retrieved from ClinicalTrials.gov. More large-scale and high-quality preclinical trials should be conducted to more accurately assess the therapeutic effects of GLP-1 RAs on AD.

Crosstalk between Alzheimer's disease and diabetes: a focus on anti-diabetic drugs

Alzheimer's disease (AD) and Type 2 diabetes mellitus (T2DM) are two of the most common age-related diseases. There is accumulating evidence of an overlap in the pathophysiological mechanisms of these two diseases. Studies have demonstrated insulin pathway alternation may interact with amyloid-β protein deposition and tau protein phosphorylation, two essential factors in AD. So attention to the use of anti-diabetic drugs in AD treatment has increased in recent years. In vitro, in vivo, and clinical studies have evaluated possible neuroprotective effects of anti-diabetic different medicines in AD, with some promising results. Here we review the evidence on the therapeutic potential of insulin, metformin, Glucagon-like peptide-1 receptor agonist (GLP1R), thiazolidinediones (TZDs), Dipeptidyl Peptidase IV (DPP IV) Inhibitors, Sulfonylureas, Sodium-glucose Cotransporter-2 (SGLT2) Inhibitors, Alpha-glucosidase inhibitors, and Amylin analog against AD. Given that many questions remain unanswered, further studies are required to confirm the positive effects of anti-diabetic drugs in AD treatment. So to date, no particular anti-diabetic drugs can be recommended to treat AD.

Insights into prevention mechanisms of bioactive components from healthy diets against Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease in which senile plaques, neurofibrillary tangles, insulin resistance, oxidative stress, chronic neuroinflammation, and abnormal neurotransmission are the potential mechanisms involved in its onset and development. Although it is still an intractable disorder, diet intervention has been developed as an innovative strategy for AD prevention. Some bioactive compounds and micronutrients from food, including soy isoflavones, rutin, vitamin B1, etc., have exhibited numerous neuronal health-promoting effects in both in vivo and in vitro studies. It is well known that their antiapoptotic, antioxidative, and anti-inflammatory properties prevent the neuronal or glial cells from injury or death, minimize oxidative damage, inhibit the production of proinflammatory cytokines by modulating typical signaling pathways of MAPK, NF-kβ, and TLR, and further reduce Aβ genesis and tau hyperphosphorylation. However, parts of the dietary components trigger AD-related proteins productions and inflammasome as well as inflammatory gene upregulation. This review summarized the neuroprotective or nerve damage-promoting role and underlying molecular mechanisms of flavonoids, vitamins, and fatty acids via the data from library databases, PubMed, and journal websites, which provides a comprehensive analysis of the prevention potential of these dietary components against AD.

Metformin alleviates the cognitive impairment induced by benzo[a]pyrene via glucolipid metabolism regulated by FTO/FoxO6 pathway in mice

Benzo[a]pyrene (B[a]P) is neurotoxic; however, the mechanism and prevention are still unclear. In this study, we assessed the intervention effect of metformin (MET) on cognitive dysfunction in mice induced by B[a]P from the perspective of glucolipid metabolism. Forty-two male healthy ICR mice were randomly categorized into 6 groups and were gavaged with B[a]P (0, 2.5, 5, or 10 mg/kg), 45 times for 90 days. The controls were gavaged with edible peanut oil, and the intervention groups were co-treated with B[a]P (10 mg/kg) and MET (200 or 300 mg/kg). We assessed the cognitive function of mice, observed the pathomorphological and ultrastructural changes, and detected neuronal apoptosis and glucolipid metabolism. Results showed that B[a]P dose-dependently induced cognitive impairment, neuronal damage, glucolipid metabolism disorder in mice, and enhanced proteins of fat mass and obesity-associated protein (FTO) and forkhead box protein O6 (FoxO6) in the cerebral cortex and liver, which were alleviated by the MET intervention. The findings indicated the critical role of glucolipid metabolism disorder in the cognitive impairment in mice caused by B[a]P and the prevention of MET against B[a]P neurotoxicity by regulating glucolipid metabolism via restraining FTO/FoxO6 pathway. The finding provides a scientific basis for the neurotoxicity and prevention strategies of B[a]P.

Remote Digital Technologies for the Early Detection and Monitoring of Cognitive Decline in Patients With Type 2 Diabetes: Insights From Studies of Neurodegenerative Diseases

Type 2 diabetes (T2D) is a risk factor for cognitive decline. In neurodegenerative disease research, remote digital cognitive assessments and unobtrusive sensors are gaining traction for their potential to improve early detection and monitoring of cognitive impairment. Given the high prevalence of cognitive impairments in T2D, these digital tools are highly relevant. Further research incorporating remote digital biomarkers of cognition, behavior, and motor functioning may enable comprehensive characterizations of patients with T2D and may ultimately improve clinical care and equitable access to research participation. The aim of this commentary article is to review the feasibility, validity, and limitations of using remote digital cognitive tests and unobtrusive detection methods to identify and monitor cognitive decline in neurodegenerative conditions and apply these insights to patients with T2D.

Triglyceride-glucose index, Alzheimer's disease plasma biomarkers, and dementia in older adults: The MIND-China study

Introduction

Population-based studies have rarely explored the associations of the triglyceride-glucose (TyG) index, a surrogate marker of insulin resistance, with dementia and plasma biomarkers for amyloid beta (Aβ) and neurodegeneration.

Methods

This population-based study included 5199 participants (age ≥ 65 years); of these, plasma Aβ, total tau, and neurofilament light chain (NfL) were measured in 1287 persons. Dementia and subtypes were diagnosed following the international criteria. TyG index was calculated as ln(fasting triglyceride(mg/dL) × fasting glucose[mg/dL]/2). Data were analyzed using logistic and general linear regression models.

Results

Dementia, Alzheimer's disease (AD), and vascular dementia (VaD) were diagnosed in 301, 195, and 95 individuals, respectively. A high TyG index was significantly associated with increased likelihoods of dementia and AD; the significant association with dementia remained among participants without cardiovascular disease or diabetes. In the biomarker subsample, a high TyG index was correlated with elevated plasma Aβ, but not with total tau or NfL.

Discussion

High TyG index is associated with dementia, possibly via Aβ pathology.

The human islet amyloid polypeptide reduces hippocampal tauopathy and behavioral impairments in P301S mice without inducing neurotoxicity or seeding amyloid aggregation

Recent evidence suggests that human islet amyloid polypeptide (h-IAPP) accumulates in the brains of Alzheimer's disease (AD) patients and may interact with Aβ or microtubule associated protein tau to associate with the neurodegenerative process. Increasing evidence indicates a potential protective effect of h-IAPP against Aβ-induced neurotoxicity in AD mouse models. However, a direct therapeutic effect of h-IAPP supplementation on tauopathy has not been established. Here, we found that long-term h-IAPP treatment attenuated tau hyperphosphorylation levels and induced neuroinflammation and oxidative damage, prevented synaptic loss and neuronal degeneration in the hippocampus, and alleviated behavioral deficits in P301S transgenic mice (a mouse model of tauopathy). Restoration of insulin sensitization, glucose/energy metabolism, and activated BDNF signaling also contributed to the underlying mechanisms. These findings suggest that seemly h-IAPP has promise for the treatment of neurodegenerative disorders with tauopathy, such as AD.

The Role of Heme and Copper in Alzheimer's Disease and Type 2 Diabetes Mellitus

Beyond the well-explored proposition of protein aggregation or amyloidosis as the central event in amyloidogenic diseases like Alzheimer's Disease (AD), and Type 2 Diabetes Mellitus (T2Dm); there are alternative hypotheses, now becoming increasingly evident, which suggest that the small biomolecules like redox noninnocent metals (Fe, Cu, Zn, etc.) and cofactors (Heme) have a definite influence in the onset and extent of such degenerative maladies. Dyshomeostasis of these components remains as one of the common features in both AD and T2Dm etiology. Recent advances in this course reveal that the metal/cofactor-peptide interactions and covalent binding can alarmingly enhance and modify the toxic reactivities, oxidize vital biomolecules, significantly contribute to the oxidative stress leading to cell apoptosis, and may precede the amyloid fibrils formation by altering their native folds. This perspective highlights this aspect of amyloidogenic pathology which revolves around the impact of the metals and cofactors in the pathogenic courses of AD and T2Dm including the active site environments, altered reactivities, and the probable mechanisms involving some highly reactive intermediates as well. It also discusses some in vitro metal chelation or heme sequestration strategies which might serve as a possible remedy. These findings might open up a new paradigm in our conventional understanding of amyloidogenic diseases. Moreover, the interaction of the active sites with small molecules elucidates potential biochemical reactivities that can inspire designing of drug candidates for such pathologies.

Causal Relationship Between Basal Metabolic Rate and Alzheimer's Disease: A Bidirectional Two-sample Mendelian Randomization Study

INTRODUCTION

Objective observational studies have shown that basal metabolic rate (BMR) decreases in patients with Alzheimer's disease (AD), but the causal relationship between BMR and AD has not been established. We determined the causal relationship between BMR and AD by two-way Mendelian randomization (MR) and investigated the impact of factors associated with BMR on AD.

METHODS

We obtained BMR (n = 454,874) and AD from a large genome-wide association study (GWAS) database (21,982 patients with AD, 41,944 controls). The causal relationship between AD and BMR was investigated using two-way MR. Additionally, we identified the causal relationship between AD and factors related with BMR, hyperthyroidism (hy/thy) and type 2 diabetes (T2D), height and weight.

RESULTS

BMR had a causal relationship with AD [451 single nucleotide polymorphisms (SNPs), odds ratio (OR) 0.749, 95% confidence intervals (CIs) 0.663-0.858, P = 2.40E-03]. There was no causal relationship between hy/thy or T2D and AD (P > 0.05). The bidirectional MR showed that there was also a causal relationship between AD and BMR (OR 0.992, Cls 0.987-0.997, N_SNPs18, P = 1.50E-03). BMR, height and weight have a protective effect on AD. Based on MVMR analysis, we found that genetically determined height and weight may be adjusted by BMR to have a causal effect on AD, not height and weight themselves.

CONCLUSION

Our study showed that higher BMR reduced the risk of AD, and patients with AD had a lower BMR. Because of a positive correlation with BMR, height and weight may have a protective effect on AD. The two metabolism-related diseases, hy/thy and T2D, had no causal relationship with AD.

Increasing brain glucose uptake by Gypenoside LXXV ameliorates cognitive deficits in a mouse model of diabetic Alzheimer's disease

We have previously reported that Gypenoside LXXV (GP-75), a novel natural PPARγ agonist isolated from Gynostemma pentaphyllum, ameliorated cognitive deficits in db/db mice. In this study, we further investigated the beneficial effects on cognitive impairment in APP/PS1 mice and a mouse model of diabetic AD (APP/PS1xdb/db mice). Interestingly, intragastric administration of GP-75 (40 mg/kg/day) for 3 months significantly attenuated cognitive deficits in APP/PS1 and APP/PS1xdb/db mice. GP-75 treatment markedly reduced the levels of glucose, HbA1c and insulin in serum and improved glucose tolerance and insulin sensitivity in APP/PS1xdb/db mice. Notably, GP-75 treatment decreased the β-amyloid (Aβ) burden, as measured by ¹¹ C-PIB PET imaging. Importantly, GP-75 treatment increased brain glucose uptake as measured by ¹⁸ F-FDG PET imaging. Moreover, GP-75 treatment upregulated PPARγ and increased phosphorylation of Akt (Ser473) and GLUT4 expression levels but decreased phosphorylation of IRS-1 (Ser616) in the hippocampi of both APP/PS1 and APP/PS1xdb/db mice. Furthermore, GP-75-induced increases in GLUT4 membrane translocation in primary hippocampal neurons from APP/PS1xdb/db mice was abolished by cotreatment with the selective PPARγ antagonist GW9662 or the PI3K inhibitor LY294002. In summary, GP-75 ameliorated cognitive deficits in APP/PS1 and APP/PS1xdb/db mice by enhancing glucose uptake via activation of the PPARγ/Akt/GLUT4 signaling pathways.

The BET inhibitor apabetalone decreases neuroendothelial proinflammatory activation in vitro and in a mouse model of systemic inflammation

Brain vascular inflammation is characterized by endothelial activation and immune cell recruitment to the blood vessel wall, potentially causing a breach in the blood - brain barrier, brain parenchyma inflammation, and a decline of cognitive function. The clinical-stage small molecule, apabetalone, reduces circulating vascular endothelial inflammation markers and improves cognitive scores in elderly patients by targeting epigenetic regulators of gene transcription, bromodomain and extraterminal proteins. However, the effect of apabetalone on cytokine-activated brain vascular endothelial cells (BMVECs) is unknown. Here, we show that apabetalone treatment of BMVECs reduces hallmarks of in vitro endothelial activation, including monocyte chemoattractant protein-1 (MCP-1) and RANTES chemokine secretion, cell surface expression of endothelial cell adhesion molecule VCAM-1, as well as endothelial capture of THP-1 monocytes in static and shear stress conditions. Apabetalone pretreatment of THP-1 downregulates cell surface expression of chemokine receptors CCR1, CCR2, and CCR5, and of the VCAM-1 cognate receptor, integrin α4. Consequently, apabetalone reduces THP-1 chemoattraction towards soluble CCR ligands MCP-1 and RANTES, and THP-1 adhesion to activated BMVECs. In a mouse model of brain inflammation, apabetalone counters lipopolysaccharide-induced transcription of endothelial and myeloid cell markers, consistent with decreased neuroendothelial inflammation. In conclusion, apabetalone decreases proinflammatory activation of brain endothelial cells and monocytes in vitro and in the mouse brain during systemic inflammation.

Type 2 Diabetes Comorbidity and Cognitive Decline in Patients with Alzheimer's Disease

BACKGROUND

Although insulin dysregulation and resistance likely participate in Alzheimer's disease (AD) etiologies, little is known about the correlation between type 2 diabetes mellitus (T2DM) and the progression of cognitive decline in patients with AD.

OBJECTIVE

To determine whether AD patients with T2DM experience more rapid cognitive decline than those without T2DM.

METHODS

All cognitive performance data and the presence or absence of T2DM comorbidity in patients with AD were derived from the US National Alzheimer's Coordinating Center's (NACC) Uniform Data Set (UDS). A search of the UDS identified 3,055 participants with AD who had more than one epoch completed. The data set culled clinically diagnosed AD dementia patients who were assessed for diabetes type identified during at least 1 visit. These patients were divided into 2 groups based on whether they had a diagnosis of T2DM. The data from these groups were then analyzed for differences in cognitive decline based on neuropsychological test battery scores and a Clinician Dementia Rating using a general linear model.

RESULTS

Comparisons of the mean scores for 16 selected tests from the neuropsychological test battery showed no significant differences in baseline scores and scores at subsequent visits between the T2DM and nondiabetic groups.

CONCLUSIONS

The results revealed no differences in cognitive decline metrics over the course of 5 visits in either study group. These data indicate that the presence of T2DM does not increase the rate of cognitive decline in AD. This finding contradicts expected disease burden and will need to be explored further.

Exploring the common pathogenesis of Alzheimer's disease and type 2 diabetes mellitus via microarray data analysis

Background

Alzheimer's Disease (AD) and Type 2 Diabetes Mellitus (DM) have an increased incidence in modern society. Although more and more evidence has supported that DM is prone to AD, the interrelational mechanisms remain fully elucidated.

Purpose

The primary purpose of this study is to explore the shared pathophysiological mechanisms of AD and DM.

Methods

Download the expression matrix of AD and DM from the Gene Expression Omnibus (GEO) database with sequence numbers GSE97760 and GSE95849, respectively. The common differentially expressed genes (DEGs) were identified by limma package analysis. Then we analyzed the six kinds of module analysis: gene functional annotation, protein-protein interaction (PPI) network, potential drug screening, immune cell infiltration, hub genes identification and validation, and prediction of transcription factors (TFs).

Results

The subsequent analyses included 339 common DEGs, and the importance of immunity, hormone, cytokines, neurotransmitters, and insulin in these diseases was underscored by functional analysis. In addition, serotonergic synapse, ovarian steroidogenesis, estrogen signaling pathway, and regulation of lipolysis are closely related to both. DEGs were input into the CMap database to screen small molecule compounds with the potential to reverse AD and DM pathological functions. L-690488, exemestane, and BMS-345541 ranked top three among the screened small molecule compounds. Finally, 10 essential hub genes were identified using cytoHubba, including PTGS2, RAB10, LRRK2, SOS1, EEA1, NF1, RAB14, ADCY5, RAPGEF3, and PRKACG. For the characteristic Aβ and Tau pathology of AD, RAPGEF3 was associated significantly positively with AD and NF1 significantly negatively with AD. In addition, we also found ADCY5 and NF1 significant correlations with DM phenotypes. Other datasets verified that NF1, RAB14, ADCY5, and RAPGEF3 could be used as key markers of DM complicated with AD. Meanwhile, the immune cell infiltration score reflects the different cellular immune microenvironments of the two diseases.

Conclusion

The common pathogenesis of AD and DM was revealed in our research. These common pathways and hub genes directions for further exploration of the pathogenesis or treatment of these two diseases.

Therapeutic approaches for improving cognitive function in the aging brain

The rapid aging of populations around the world has become an unprecedented challenge. Aging is associated with cognitive impairment, including dementia and mild cognitive impairment. Successful drug development for improving or maintaining cognition in the elderly is critically important. Although 4 drugs for improving cognition in Alzheimer's disease have been approved, a variety of potential drugs targeting age-related cognitive impairment are still in development. In addition, non-pharmacological interventions, including cognition-oriented treatments, non-invasive brain stimulation physical exercise, and lifestyle-related interventions, have also been suggested as cognitive enhancers in the last decade. In this paper, we reviewed the recent evidence of pharmacological and non-pharmacological interventions aimed at improving or maintaining cognition in the elderly.

Protective effects of Forsythiae fructus and Cassiae semen water extract against memory deficits through the gut-microbiome-brain axis in an Alzheimer's disease model

CONTEXT

Fruits of Forsythia suspensa Vahl (Oleaceae) and seeds of Cassia obtusifolia Linne (Caesalpinaceae) have been used to treat inflammation in Asia.

OBJECTIVE

We examined the alleviation of memory function in Alzheimer's disease (AD) rats fed Forsythiae Fructus (FF) and Cassiae Semen water extracts (CS) and investigated the mechanisms responsible for the effects.

MATERIALS AND METHODS

Thirty Sprague-Dawley male rats had hippocampal infusions of amyloid-β_(25-35) (AD rats; memory deficit), and ten rats were infused with amyloid-β_(35-25) (non-AD rats; no memory deficit). For eight weeks, all rats freely consumed high-fat diets (43% lard) incorporated with 200 mg/kg body weight assigned aqueous herbal extracts: AD-FF, AD-CS, or without extracts AD-CON (control), non-AD (normal-control).

RESULTS

Memory impairment was prevented in the AD-FF (0.54 ± 0.06-fold) and the AD-CS rats (0.33 ± 0.04-fold) compared to the AD-CON by inhibiting amyloid-β deposition to the levels less than one-fourth of the AD-CON group. The hippocampal pAkt→pGSK-3β→pFOXO1 pathway was attenuated by approximately 3.25-fold in the AD-CON, while AD-FF prevented the attenuation better than AD-CS. The relative intensity of hippocampal tau protein based on β-actin was suppressed with AD-FF (0.68 ± 0.09) and AD-CS (0.96 ± 0.81), compared to AD-CON (1.19 ± 0.13). AD decreased the abundance of Bacteroidales by 34.2% and Lactobacillales by 23.8% and increased Clostridiales by 181% while the AD-FF, but not the AD-CS, normalised the gut microbiota changes to be similar to the non-AD.

DISCUSSION AND CONCLUSIONS

FF improved memory deficits better than CS in an AD-induced rat model. The potential neuroprotective benefits of FF against AD may be applicable to human AD therapy with additional clinical research.

A blast from the past: To tame time with metformin

The strong evidence of metformin use in subjects affected by type 2 diabetes (T2DM) on health outcomes, together with data from pre-clinical studies, has led the gerontological research to study the therapeutic potential of such a drug as a slow-aging strategy. However, despite clinical use for over fifty years as an anti-diabetic drug, the mechanisms of action beyond glycemic control remain unclear. In this review, we have deeply examined the literature, doing a narrative review from the metformin story, through mechanisms of action to slow down aging potential, from lower organisms to humans. Based on the available evidence, we conclude that metformin, as shown in lower organisms and mice, may be effective in humans' longevity. A complete analysis and follow-up of ongoing clinical trials may provide more definitive answers as to whether metformin should be promoted beyond its use to treat T2DM as a drug that enhances both healthspan and lifespan.

Glucagon-like peptide-1 (GLP-1) receptor agonists and neuroinflammation: Implications for neurodegenerative disease treatment

Chronic, excessive neuroinflammation is a key feature of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). However, neuroinflammatory pathways have yet to be effectively targeted in clinical treatments for such diseases. Interestingly, increased inflammation and neurodegenerative disease risk have been associated with type 2 diabetes mellitus (T2DM) and insulin resistance (IR), suggesting that treatments that mitigate T2DM pathology may be successful in treating neuroinflammatory and neurodegenerative pathology as well. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that promotes healthy insulin signaling, regulates blood sugar levels, and suppresses appetite. Consequently, numerous GLP-1 receptor (GLP-1R) stimulating drugs have been developed and approved by the US Food and Drug Administration (FDA) and related global regulatory authorities for the treatment of T2DM. Furthermore, GLP-1R stimulating drugs have been associated with anti-inflammatory, neurotrophic, and neuroprotective properties in neurodegenerative disorder preclinical models, and hence hold promise for repurposing as a treatment for neurodegenerative diseases. In this review, we discuss incretin signaling, neuroinflammatory pathways, and the intersections between neuroinflammation, brain IR, and neurodegenerative diseases, with a focus on AD and PD. We additionally overview current FDA-approved incretin receptor stimulating drugs and agents in development, including unimolecular single, dual, and triple receptor agonists, and highlight those in clinical trials for neurodegenerative disease treatment. We propose that repurposing already-approved GLP-1R agonists for the treatment of neurodegenerative diseases may be a safe, efficacious, and cost-effective strategy for ameliorating AD and PD pathology by quelling neuroinflammation.

Dietary regulation in health and disease

Nutriments have been deemed to impact all physiopathologic processes. Recent evidences in molecular medicine and clinical trials have demonstrated that adequate nutrition treatments are the golden criterion for extending healthspan and delaying ageing in various species such as yeast, drosophila, rodent, primate and human. It emerges to develop the precision-nutrition therapeutics to slow age-related biological processes and treat diverse diseases. However, the nutritive advantages frequently diversify among individuals as well as organs and tissues, which brings challenges in this field. In this review, we summarize the different forms of dietary interventions extensively prescribed for healthspan improvement and disease treatment in pre-clinical or clinical. We discuss the nutrient-mediated mechanisms including metabolic regulators, nutritive metabolism pathways, epigenetic mechanisms and circadian clocks. Comparably, we describe diet-responsive effectors by which dietary interventions influence the endocrinic, immunological, microbial and neural states responsible for improving health and preventing multiple diseases in humans. Furthermore, we expatiate diverse patterns of dietotheroapies, including different fasting, calorie-restricted diet, ketogenic diet, high-fibre diet, plants-based diet, protein restriction diet or diet with specific reduction in amino acids or microelements, potentially affecting the health and morbid states. Altogether, we emphasize the profound nutritional therapy, and highlight the crosstalk among explored mechanisms and critical factors to develop individualized therapeutic approaches and predictors.

Hyperinsulinemia-induced microglial mitochondrial dynamic and metabolic alterations lead to neuroinflammation in vivo and in vitro

Numerous studies have demonstrated that type 2 diabetes (T2D) is closely linked to the occurrence of Alzheimer’s disease (AD). Nevertheless, the underlying mechanisms for this association are still unknown. Insulin resistance (IR) hallmarked by hyperinsulinemia, as the earliest and longest-lasting pathological change in T2D, might play an important role in AD. Since hyperinsulinemia has an independent contribution to related disease progressions by promoting inflammation in the peripheral system, we hypothesized that hyperinsulinemia might have an effect on microglia which plays a crucial role in neuroinflammation of AD. In the present study, we fed 4-week-old male C57BL/6 mice with a high-fat diet (HFD) for 12 weeks to establish IR model, and the mice treated with standard diet (SD) were used as control. HFD led to obesity in mice with obvious glucose and lipid metabolism disorder, the higher insulin levels in both plasma and cerebrospinal fluid, and aberrant insulin signaling pathway in the whole brain. Meanwhile, IR mice appeared impairments of spatial learning and memory accompanied by neuroinflammation which was characterized by activated microglia and upregulated expression of pro-inflammatory factors in different brain regions. To clarify whether insulin contributes to microglial activation, we treated primary cultured microglia and BV2 cell lines with insulin in vitro to mimic hyperinsulinemia. We found that hyperinsulinemia not only increased microglial proliferation and promoted M1 polarization by enhancing the production of pro-inflammatory factors, but also impaired membrane translocation of glucose transporter 4 (GLUT4) serving as the insulin-responding glucose transporter in the processes of glucose up-taking, reduced ATP production and increased mitochondrial fission. Our study provides new perspectives and evidence for the mechanism underlying the association between T2D and AD.

Targeting the liver in dementia and cognitive impairment: Dietary macronutrients and diabetic therapeutics

Many people living with dementia and cognitive impairment have dysfunctional mitochondrial and insulin-glucose metabolism resembling type 2 diabetes mellitus and old age. Evidence from human trials shows that nutritional interventions and anti-diabetic medicines that target nutrient-sensing pathways overcome these deficits in glucose and energy metabolism and can improve cognition and/or reduce symptoms of dementia. The liver is the main organ that mediates the systemic effects of diets and many diabetic medicines; therefore, it is an intermediate target for such dementia interventions. A challenge is the efficacy of these treatments in older age. Solutions include the targeted hepatic delivery of diabetic medicines using nanotechnologies and titration of macronutrients to optimize hepatic energy metabolism.

Genetic Variation in Targets of Antidiabetic Drugs and Alzheimer Disease Risk: A Mendelian Randomization Study

BACKGROUND AND OBJECTIVES

Previous studies have highlighted antidiabetic drugs as repurposing candidates for Alzheimer disease (AD), but the disease-modifying effects are still unclear.

METHODS

A 2-sample mendelian randomization study design was applied to examine the association between genetic variation in the targets of 4 antidiabetic drug classes and AD risk. Genetic summary statistics for blood glucose were analyzed using UK Biobank data of 326,885 participants, whereas summary statistics for AD were retrieved from previous genome-wide association studies comprising 24,087 clinically diagnosed AD cases and 55,058 controls. Positive control analysis on type 2 diabetes mellitus (T2DM), insulin secretion, insulin resistance, and obesity-related traits was conducted to validate the selection of instrumental variables.

RESULTS

In the positive control analysis, genetic variation in sulfonylurea targets was associated with higher insulin secretion, a lower risk of T2DM, and an increment in body mass index, waist circumference, and hip circumference, consistent with drug mechanistic actions and previous trial evidence. In the primary analysis, genetic variation in sulfonylurea targets was associated with a lower risk of AD (odds ratio [OR] = 0.38 per 1 mmol/L decrement in blood glucose, 95% CI 0.19-0.72, p = 0.0034). These results for sulfonylureas were largely unchanged in the sensitivity analysis using a genetic variant, rs757110, that has been validated to modulate the target proteins of sulfonylureas (OR = 0.35 per 1 mmol/L decrement in blood glucose, 95% CI 0.15-0.82, p = 0.016). An association between genetic variations in the glucagon-like peptide 1 (GLP-1) analogue target and a lower risk of AD was also observed (OR = 0.32 per 1 mmol/L decrement in blood glucose, 95% CI 0.13-0.79, p = 0.014). However, this result should be interpreted with caution because the positive control analyses for GLP-1 analogues did not comply with a weight-loss effect as shown in previous clinical trials. Results regarding other drug classes were inconclusive.

DISCUSSION

Genetic variation in sulfonylurea targets was associated with a lower risk of AD, and future studies are warranted to clarify the underlying mechanistic pathways between sulfonylureas and AD.

Actions of Metformin in the Brain: A New Perspective of Metformin Treatments in Related Neurological Disorders

Metformin is a first-line drug for treating type 2 diabetes mellitus (T2DM) and one of the most commonly prescribed drugs in the world. Besides its hypoglycemic effects, metformin also can improve cognitive or mood functions in some T2DM patients; moreover, it has been reported that metformin exerts beneficial effects on many neurological disorders, including major depressive disorder (MDD), Alzheimer’s disease (AD) and Fragile X syndrome (FXS); however, the mechanism underlying metformin in the brain is not fully understood. Neurotransmission between neurons is fundamental for brain functions, and its defects have been implicated in many neurological disorders. Recent studies suggest that metformin appears not only to regulate synaptic transmission or plasticity in pathological conditions but also to regulate the balance of excitation and inhibition (E/I balance) in neural networks. In this review, we focused on and reviewed the roles of metformin in brain functions and related neurological disorders, which would give us a deeper understanding of the actions of metformin in the brain.

BACE1: More than just a β-secretase

β-site amyloid precursor protein cleaving enzyme-1 (BACE1) research has historically focused on its actions as the β-secretase responsible for the production of β-amyloid beta, observed in Alzheimer's disease. Although the greatest expression of BACE1 is found in the brain, BACE1 mRNA and protein is also found in many cell types including pancreatic β-cells, adipocytes, hepatocytes, and vascular cells. Pathologically elevated BACE1 expression in these cells has been implicated in the development of metabolic diseases, including type 2 diabetes, obesity, and cardiovascular disease. In this review, we examine key questions surrounding the BACE1 literature, including how is BACE1 regulated and how dysregulation may occur in disease, and understand how BACE1 regulates metabolism via cleavage of a myriad of substrates. The phenotype of the BACE1 knockout mice models, including reduced weight gain, increased energy expenditure, and enhanced leptin signaling, proposes a physiological role of BACE1 in regulating energy metabolism and homeostasis. Taken together with the weight loss observed with BACE1 inhibitors in clinical trials, these data highlight a novel role for BACE1 in regulation of metabolic physiology. Finally, this review aims to examine the possibility that BACE1 inhibitors could provide a innovative treatment for obesity and its comorbidities.

Drug repositioning in drug discovery of T2DM and repositioning potential of antidiabetic agents

Repositioning or repurposing drugs account for a substantial part of entering approval pipeline drugs, which indicates that drug repositioning has huge market potential and value. Computational technologies such as machine learning methods have accelerated the process of drug repositioning in the last few decades years. The repositioning potential of type 2 diabetes mellitus (T2DM) drugs for various diseases such as cancer, neurodegenerative diseases, and cardiovascular diseases have been widely studied. Hence, the related summary about repurposing antidiabetic drugs is of great significance. In this review, we focus on the machine learning methods for the development of new T2DM drugs and give an overview of the repurposing potential of the existing antidiabetic agents.

Glucose-lowering drugs, cognition, and dementia: The clinical evidence

Type 2 diabetes mellitus (T2DM) is an important risk factor for dementia. The possibility to mitigate this risk by controlling T2DM is compelling; however, different glucose-lowering drugs have different effects on the brain by virtue of their different mechanisms of action. The clinical and epidemiological data appear mixed, warranting careful critical evaluation of the human studies. Here we examine the evidence in the context of dementia prevention and treatment, both for people with and without T2DM. We discuss the evidence on this scaffold of research directions, identifying methodological complexities in the extant literature (e.g. comparator discrepancies, changes in the therapeutic landscape), and the implications of different outcome measures (e.g. neuropsychological). We consider possible implications of cerebrovascular protection vs. effects on progression of neurodegenerative proteinopathy, and we present a research roadmap for glucose-lowering drugs in cognitive neurology, including neuroimaging, and fluid biomarkers. We conclude that there is great potential to advance personalized strategies to prevent and treat dementia with glucose-lowering drugs.

Type 2 diabetes mellitus-associated cognitive dysfunction: Advances in potential mechanisms and therapies

Type 2 diabetes (T2D) and its target organ injuries cause distressing impacts on personal health and put an enormous burden on the healthcare system, and increasing attention has been paid to T2D-associated cognitive dysfunction (TDACD). TDACD is characterized by cognitive dysfunction, delayed executive ability, and impeded information-processing speed. Brain imaging data suggest that extensive brain regions are affected in patients with T2D. Based on current findings, a wide spectrum of non-specific neurodegenerative mechanisms that partially overlap with the mechanisms of neurodegenerative diseases is hypothesized to be associated with TDACD. However, it remains unclear whether TDACD is a consequence of T2D or a complication that co-occurs with T2D. Theoretically, anti-diabetes methods are promising neuromodulatory approaches to reduce brain injury in patients with T2D. In this review, we summarize potential mechanisms underlying TDACD and promising neurotropic effects of anti-diabetes methods and some neuroprotective natural compounds. Constructing screening or diagnostic tools and developing targeted treatment and preventive strategies would be expected to reduce the burden of TDACD.

Association Between Specific Type 2 Diabetes Therapies and Risk of Alzheimer’s Disease and Related Dementias in Propensity-Score Matched Type 2 Diabetic Patients

Objective

We sought to determine the impact of Type 2 Diabetes Mellitus (T2D) anti-hyperglycemic medications (A-HgM) on risk of Alzheimer’s disease (AD) and related dementias (ADRD) outcomes including vascular dementia, and non-AD dementia such as frontotemporal, Lewy body, and mixed etiology dementias.

Research Design and Methods

This retrospective cohort study used the US-based Mariner claims dataset. 1,815,032 T2D participants 45 years and older with records 6 months prior and at least 3 years after the diagnosis of T2D were included. Claims were surveyed for a diagnosis of AD and ADRD 12 months post T2D diagnosis. A propensity score approach was used to minimize selection bias. Analyses were conducted between January 1st and February 28th, 2021.

Results

In this cohort study A-HgM exposure was associated with decreased diagnosis of AD (RR, 0.61; 95% CI, 0.59–0.62; p < 0.001), vascular dementia (RR, 0.72; 95% CI, 0.69–0.74; p < 0.001) and non-AD dementia (RR, 0.67; 95% CI, 0.66–0.68; p < 0.001). Metformin was associated with the greatest risk reduction and insulin with the least reduction in risk compared to patients not receiving A-HgM for ADRD risk. Of interest, patients with a diagnosis of AD, while either on metformin or insulin, were older in age and predominately female, than individuals on these drugs that did not develop AD. Mean (SD) follow-up was 6.2 (1.8) years.

Conclusion

After controlling for age, sex, and comorbidities, A-HgM in patients with T2D was associated with a reduced risk of AD and ADRD. These findings provide evidence in support of T2D as a risk factor for AD and ADRD and the beneficial impact of early and effective control of hyperglycemia to mitigate risk.

Enhancement of Impaired Olfactory Neural Activation and Cognitive Capacity by Liraglutide, but Not Dapagliflozin or Acarbose, in Patients With Type 2 Diabetes: A 16-Week Randomized Parallel Comparative Study

OBJECTIVE

The comparative neuroprotective effects of different antidiabetes drugs have not been characterized in randomized controlled trials. Here, we investigated the therapeutic effects of liraglutide, dapagliflozin, or acarbose treatment on brain functional alterations and cognitive changes in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Thirty-six patients with type 2 diabetes inadequately controlled with metformin monotherapy were randomized to receive liraglutide, dapagliflozin, or acarbose treatment for 16 weeks. Brain functional MRI (fMRI) scan and a battery of cognitive assessments were evaluated pre- and postintervention in all subjects.

RESULTS

The 16-week treatment with liraglutide significantly enhanced the impaired odor-induced left hippocampal activation with Gaussian random field correction and improved cognitive subdomains of delayed memory, attention, and executive function (all P < 0.05), whereas dapagliflozin or acarbose did not. Structural equation modeling analysis demonstrated that such improvements of brain health and cognitive function could be partly ascribed to a direct effect of liraglutide on left hippocampal activation (β = 0.330, P = 0.022) and delayed memory (β = 0.410, P = 0.004) as well as to the metabolic ameliorations of reduced waist circumference, decreased body fat ratio, and elevated fasting insulin (all P < 0.05).

CONCLUSIONS

Our head-to-head study demonstrated that liraglutide enhanced impaired brain activation and restored impaired cognitive domains in patients with type 2 diabetes, whereas dapagliflozin and acarbose did not. The results expand the clinical application of liraglutide and provide a novel treatment strategy for individuals with diabetes and a high risk of cognitive decline.

Expert Consensus on Cognitive Dysfunction in Diabetes

The incidence of diabetes is gradually increasing in China, and diabetes and associated complications, such as cognitive dysfunction have gained much attention in recent time. However, the concepts, clinical treatment, and prevention of cognitive dysfunction in patients with diabetes remain unclear. The Chinese Society of Endocrinology investigated the current national and overseas situation of cognitive dysfunction associated with diabetes. Based on research both in China and other countries worldwide, the Expert Consensus on Cognitive Dysfunction in Diabetes was established to guide physicians in the comprehensive standardized management of cognitive dysfunction in diabetes and to improve clinical outcomes in Chinese patients. This consensus presents an overview, definition and classification, epidemiology and pathogenesis, risk factors, screening, diagnosis, differential diagnosis, treatment, and prevention of cognitive dysfunction in patients with diabetes.

Impairment of the autophagy-lysosomal pathway in Alzheimer's diseases: Pathogenic mechanisms and therapeutic potential

Alzheimer's disease (AD), the most common neurodegenerative disorder, is characterized by memory loss and cognitive dysfunction. The accumulation of misfolded protein aggregates including amyloid beta (Aβ) peptides and microtubule associated protein tau (MAPT/tau) in neuronal cells are hallmarks of AD. So far, the exact underlying mechanisms for the aetiologies of AD have not been fully understood and the effective treatment for AD is limited. Autophagy is an evolutionarily conserved cellular catabolic process by which damaged cellular organelles and protein aggregates are degraded via lysosomes. Recently, there is accumulating evidence linking the impairment of the autophagy–lysosomal pathway with AD pathogenesis. Interestingly, the enhancement of autophagy to remove protein aggregates has been proposed as a promising therapeutic strategy for AD. Here, we first summarize the recent genetic, pathological and experimental studies regarding the impairment of the autophagy–lysosomal pathway in AD. We then describe the interplay between the autophagy–lysosomal pathway and two pathological proteins, Aβ and MAPT/tau, in AD. Finally, we discuss potential therapeutic strategies and small molecules that target the autophagy–lysosomal pathway for AD treatment both in animal models and in clinical trials. Overall, this article highlights the pivotal functions of the autophagy–lysosomal pathway in AD pathogenesis and potential druggable targets in the autophagy–lysosomal pathway for AD treatment.

Deciphering the Roles of Metformin in Alzheimer's Disease: A Snapshot

Alzheimer’s disease (AD) is a prevalent neurodegenerative disease predominantly affecting millions of elderly people. To date, no effective therapy has been identified to reverse the progression of AD. Metformin, as a first-line medication for Type 2 Diabetes Mellitus (T2DM), exerts multiple beneficial effects on various neurodegenerative disorders, including AD. Evidence from clinical studies has demonstrated that metformin use contributes to a lower risk of developing AD and better cognitive performance, which might be modified by interactors such as diabetic status and APOE-ε4 status. Previous mechanistic studies have gradually unveiled the effects of metformin on AD pathology and pathophysiology, including neuronal loss, neural dysfunction, amyloid-β (Aβ) depositions, tau phosphorylation, chronic neuroinflammation, insulin resistance, impaired glucose metabolism and mitochondrial dysfunction. Current evidence remains ambiguous and even conflicting. Herein, we review the current state of knowledge concerning the mechanisms of metformin in AD pathology while summarizing current evidence from clinical studies.

Targeting whole body metabolism and mitochondrial bioenergetics in the drug development for Alzheimer's disease

Aging is by far the most prominent risk factor for Alzheimer's disease (AD), and both aging and AD are associated with apparent metabolic alterations. As developing effective therapeutic interventions to treat AD is clearly in urgent need, the impact of modulating whole-body and intracellular metabolism in preclinical models and in human patients, on disease pathogenesis, have been explored. There is also an increasing awareness of differential risk and potential targeting strategies related to biological sex, microbiome, and circadian regulation. As a major part of intracellular metabolism, mitochondrial bioenergetics, mitochondrial quality-control mechanisms, and mitochondria-linked inflammatory responses have been considered for AD therapeutic interventions. This review summarizes and highlights these efforts.

Ultra-stable dextran conjugated prodrug micelles for oxidative stress and glycometabolic abnormality combination treatment of Alzheimer's disease

Sophisticated nanomedicines are continually being developed, but big obstacles remain before they finish the drug release mission. The first challenge is rupture possibility of structure when infinite dilution, competitive reaction of electrolytes and protein in blood circulation. In addition, low responsive drug release efficiency in the lesion site remains the major challenge for clinical application of nanomedicine combination treatment. In this study, we discussed the opportunities for Alzheimer's disease (AD) combination therapy based on the thermodynamically ultra-stable dextran conjugated prodrug micelles. Dextran-nateglinide conjugated prodrug micelles (NA) and dextran-vitamin E succinate conjugated prodrug micelles (VES) presented ultra-low critical micelle concentration of ~10^-5 mM and high physiological stability when challenged by NaCl, sodium dodecyl sulphate (SDS), dodecyl dimethyl benzyl ammonium chloride (DDBAC) and no rupture of structure happened. The NA/insulin polymer-drug conjugate micelles (NA/INS PDC) and VES/insulin polymer-drug conjugate micelles (VES/INS PDC) efficiently cleaved by reactive oxygen species (ROS), leading to over 80% release of the encapsulated and conjugated drugs. The combination of nateglinide and insulin, vitamin E succinate and insulin improved the glucose metabolism, reduced oxidative stress, improved the mitochondrial function and recovered the cognitive capacity of mice. This work demonstrated a paradigm for specific and high efficacy AD combination therapy.

A novel DPP-4 inhibitor Gramcyclin A attenuates cognitive deficits in APP/PS1/tau triple transgenic mice via enhancing brain GLP-1-dependent glucose uptake

Enhancing glucagon-like peptide 1 (GLP-1) signaling with a dipeptidyl peptidase IV (DPP-4) inhibitor might exert protective effects on Alzheimer's disease (AD). We found that intragastric administration of Gramcyclin A (10, 20 and 40 mg/kg), a novel DPP-4 inhibitor, for 3 months significantly reversed cognitive decline in APP/PS1/tau triple transgenic mice in a dose-dependent manner. Gramcyclin A treatment markedly reduced Aβ plaques as well as the insoluble and soluble forms of Aβ40 and Aβ42 in the hippocampus of APP/PS1/tau mice. Treatment with Gramcyclin A remarkedly decreased the level of microglia and suppressed neuroinflammation in the hippocampus of APP/PS1/tau mice. Moreover, Gramcyclin A treatment could increase brain glucose uptake in APP/PS1/tau mice, as detected by 18-fluoro-2-deoxyglucose (¹⁸ F-FDG) micro-positron emission tomography (micro-PET) imaging. Furthermore, Gramcyclin A significantly increased expression of glucagon-like peptide-1 (GLP-1), GLP-1R, proliferator-activated receptor gamma coactivator (PGC)-1α and glucose transporter 4 (GLUT4), and inhibited insulin receptor (IRS)-1 phosphorylation and tau hyperphosphorylation in the hippocampus of APP/PS1/tau mice. Collectively, Gramcyclin A conferred protective effects against AD via enhancing brain GLP-1-dependent glucose uptake. The DPP-4 inhibitor Gramcyclin A might be a potential therapeutic drug for AD.

GLP-1a: Going beyond Traditional Use

Glucagon-like peptide-1 (GLP-1) is a human incretin hormone derived from the proglucagon molecule. GLP-1 receptor agonists are frequently used to treat type 2 diabetes mellitus and obesity. However, the hormone affects the liver, pancreas, brain, fat cells, heart, and gastrointestinal tract. The objective of this study was to perform a systematic review on the use of GLP-1 other than in treating diabetes. PubMed, Cochrane, and Embase were searched, and the PRISMA guidelines were followed. Nineteen clinical studies were selected. The results showed that GLP-1 agonists can benefit defined off-medication motor scores in Parkinson’s Disease and improve emotional well-being. In Alzheimer’s disease, GLP-1 analogs can improve the brain’s glucose metabolism by improving glucose transport across the blood–brain barrier. In depression, the analogs can improve quality of life and depression scales. GLP-1 analogs can also have a role in treating chemical dependency, inhibiting dopaminergic release in the brain’s reward centers, decreasing withdrawal effects and relapses. These medications can also improve lipotoxicity by reducing visceral adiposity and decreasing liver fat deposition, reducing insulin resistance and the development of non-alcoholic fatty liver diseases. The adverse effects are primarily gastrointestinal. Therefore, GLP-1 analogs can benefit other conditions besides traditional diabetes and obesity uses.

Type 2 Diabetes Mellitus Easily Develops into Alzheimer's Disease via Hyperglycemia and Insulin Resistance

With the acceleration of population aging, the incidence of type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) is progressively increasing due to the age-relatedness of these two diseases. The association between T2DM and AD-like dementia is receiving much attention, and T2DM is reported to be a significant risk factor for AD. The aims of this review were to reveal the brain changes caused by T2DM as well as to explore the roles of hyperglycemia and insulin resistance in the development of AD.