Repurposing of Anti-Diabetic Agents as a New Opportunity to Alleviate Cognitive Impairment in Neurodegenerative and Neuropsychiatric Disorders

Assessment of Cognitive Flexibility in Jordanian Diabetic Patients by Wisconsin Card Sorting and Trail Making Tests: Implications with Demographic, Anthropometric and Therapeutic Variables

Purpose

Cognitive flexibility is a mental ability that aids in smoothly alternating between them tasks in the brain. Diabetes Mellitus (DM) is a, common disorder that has been associated with impairments in cognitive functions. This research is a retrospective case-control study aimed at establishing a clear relationship between cognitive flexibility and diabetes among Jordanians, considering demographic, anthropometric, and therapeutic variables.

Patients and Methods

The Wisconsin Card Sorting Test (WCST)-64 item and the Trail Making Test (TMT) assessed cognitive flexibility in 268 people with diabetes and healthy control. Demographic, therapeutic data were collected. We also measured waist-to-hip ratio (WHR) and body mass index (BMI). As the variables were non-normally distributed, non-parametric statistical tests were used to examine differences (Kruskal-Wallis) and correlation (Spearman) between variables.

Results

The patient group did worse on the WCST In contrast to the control group, patients exhibited more significant delays for both Part A and Part B of the TMT (p<0.05). Males had higher WCST conceptual level responses than females. In addition, participants with professional jobs showed less delay in TMT Part A (p<0.05). Age was positively correlated with WCST's total errors and TMT's Parts A and B (p<0.05). BMI was negatively correlated with the WCST's conceptual level of responses and positively correlated with TMT's Part B (p<0.05). In addition, urea and albumin levels were positively correlated with TMT's Part A (p<0.05). Furthermore, creatinine was positively correlated with WCST's total errors and TMT's Part A (p<0.05).

Conclusion

Some measures of cognitive flexibility are associated with DM status in the studied sample of Jordanians and other variables (educational levels, occupation, lifestyle, average duration of illness, and age).

Reconsidering repurposing: long-term metformin treatment impairs cognition in Alzheimer's model mice

Metformin, a primary anti-diabetic medication, has been anticipated to provide benefits for Alzheimer's disease (AD), also known as "type 3 diabetes". Nevertheless, some studies have demonstrated that metformin may trigger AD pathology and even elevate AD risk in humans. Despite this, limited research has elucidated the behavioral outcomes of metformin treatment, which would hold significant translational value. Thus, we aimed to perform thorough behavioral research on the prolonged administration of metformin to mice: We administered metformin (300 mg/kg/day) to transgenic 3xTg-AD and non-transgenic (NT) C57BL/6 mice over 1 and 2 years, respectively, and evaluated their behaviors across multiple domains via touchscreen operant chambers, including motivation, attention, memory, visual discrimination, and cognitive flexibility. We found metformin enhanced attention, inhibitory control, and associative learning in younger NT mice (≤16 months). However, chronic treatment led to impairments in memory retention and discrimination learning at older age. Furthermore, metformin caused learning and memory impairment and increased levels of AMPKα1-subunit, β-amyloid oligomers, plaques, phosphorylated tau, and GSK3β expression in AD mice. No changes in potential confounding factors on cognition, including levels of motivation, locomotion, appetite, body weight, blood glucose, and serum vitamin B12, were observed in metformin-treated AD mice. We also identified an enhanced amyloidogenic pathway in db/db mice, as well as in Neuro2a-APP695 cells and a decrease in synaptic markers, such as PSD-95 and synaptophysin in primary neurons, upon metformin treatment. Our findings collectively suggest that the repurposing of metformin should be carefully reconsidered when this drug is used for individuals with AD.

Alzheimer's Disease: The Past, Present, and Future of a Globally Progressive Disease

Alzheimer's disease (AD) is a significant 21st-century public health challenge. This article delves into AD's neurodegenerative complexities, highlighting cognitive decline, memory impairment, and societal burdens. Mechanistically, protein misfolding, amyloid-beta (Aβ) pathway abnormalities, and genetic/environmental factors are discussed. The pivotal amyloid hypothesis is dissected, focusing on Aβ aggregation's role in synaptic dysfunction and neurodegeneration. The review showcases promising therapeutic strategies, including anti-amyloid antibodies and β/γ-secretase inhibitors targeting Aβ production. Notably, the FDA-approved Lecanemab signifies a breakthrough, slowing disease progression. Anti-Tau therapies' emergence is highlighted, addressing late-stage intervention. Tau aggregation blockers and anti-Tau antibodies offer potential against intracellular tau pathology. The review underscores collaborative efforts to uncover AD's secrets and pave the way for memory preservation.

Antipsychotic-Induced Weight Gain in Severe Mental Illness: Risk Factors and Special Considerations

PURPOSE OF REVIEW

Weight gain is a disconcerting issue experienced by patients treated with antipsychotics (APs). This review summarizes current knowledge on the prevalence, etiology, and risk factors for antipsychotic-induced weight gain (AIWG), and evidence for interventions, including special considerations.

RECENT FINDINGS

Predisposing risk factors for AIWG include lack of prior AP exposure, sex, and age. AP dose and duration of exposure are additional treatment-related factors that may contribute to this issue. Among current approaches to target AIWG, metformin has the most evidence to support its use, and this is increasingly reflected in clinical guidelines. While lifestyle approaches are recommended, cost-effectiveness and scalability represent limitations. More research is needed to identify newer treatment options and inform clinical recommendations for AIWG. Concerns around scope of practice in psychiatry to address AIWG and related comorbidities will require enhanced training opportunities and interdisciplinary collaborations, as well as updated position statements/practice guidelines emphasizing prevention.

Meta-analysis of Association between Newer Glucose-Lowering Drugs and Risk of Parkinson's Disease

Background

The association between newer classes of glucose-lowering drugs (GLDs) and the risk of Parkinson's disease (PD) remains unclear.

Objective

The aim was to examine the effect of newer GLDs on the risk of PD through a meta-analysis of randomized outcome trials.

Methods

The methods included randomized placebo-controlled outcome trials that reported PD events associated with three newer classes of GLDs (ie, dipeptidyl peptidase-4 inhibitors, glucagon-like peptide-1 receptor agonists, and sodium-glucose co-transporter-2 inhibitors) in participants with or without type 2 diabetes. The pooled odds ratio (OR) and 95% confidence interval (CI) were estimated using Peto's method.

Results

The study included 24 trials involving 33 PD cases among 185,305 participants during a median follow-up of 2.2 years. Newer GLDs were significantly associated with a lower PD risk (OR: 0.50; 95% CI: 0.25-0.98) than placebo.

Conclusion

Newer GLDs may possibly be associated with a decreased risk of PD; however, larger datasets are required to confirm or refute this notion.

Exploring the Potential of Antidiabetic Agents as Therapeutic Approaches for Alzheimer's and Parkinson's Diseases: A Comprehensive Review

Alzheimer's and Parkinson's are two prevalent neurodegenerative disorders with significant societal and healthcare burdens. The search for effective therapeutic approaches to combat these diseases has led to growing interest in exploring the potential of antidiabetic agents. This comprehensive review aims to provide a detailed overview of the current literature on using antidiabetic agents as therapeutic interventions for Alzheimer's and Parkinson's diseases. We discuss the underlying pathological mechanisms of these neurodegenerative diseases, including protein misfolding, inflammation, oxidative stress, and mitochondrial dysfunction. We then delve into the potential mechanisms by which antidiabetic agents may exert neuroprotective effects, including regulation of glucose metabolism and insulin signaling, anti-inflammatory effects, modulation of oxidative stress, and improvement of mitochondrial function and bioenergetics. We highlight in vitro, animal, and clinical studies that support the potential benefits of antidiabetic agents in reducing disease pathology and improving clinical outcomes. However, we also acknowledge these agents' limitations, variability in treatment response, and potential side effects. Furthermore, we explore emerging therapeutic targets and novel approaches, such as glucagon-like peptide-1 receptor (GLP-1R) agonists, insulin sensitizer drugs, neuroinflammation-targeted therapies, and precision medicine approaches. The review concludes by emphasizing the need for further research, including large-scale clinical trials, to validate the efficacy and safety of antidiabetic agents in treating Alzheimer's and Parkinson's disease. The collaboration between researchers, clinicians, and pharmaceutical companies is essential in advancing the field and effectively treating patients affected by these debilitating neurodegenerative disorders.

Research landscape and emerging trends of diabetes-associated cognitive dysfunction: a bibliometric analysis

Background

Diabetes-associated cognitive dysfunction (DACD) is a common and serious complication in diabetes and has a high impact on the lives of both individuals and society. Although a number of research has focused on DACD in the past two decades, there is no a study to systematically display the knowledge structure and development of the field. Thus, the present study aimed to show the landscape and identify the emerging trends of DACD research for assisting researchers or clinicians in grasping the knowledge domain faster and easier and focusing on the emerging trends in the field.

Methods

We searched the Web of Science database for all DACD-related studies between 2000 and 2022. Bibliometric analysis was conducted using the VOSviewer, CiteSpace, Histcite, and R bibliometric package, revealing the most prominent research, countries, institutions, authors, journals, co-cited references, and keywords.

Results

A total of 4,378 records were selected for analysis. We found that the volume of literature on DACD has increased over the years. In terms of the number of publications, the USA ranked first. The most productive institutions were the University of Washington and the University of Pittsburgh. Furthermore, Biessels GJ was the most productive author. Journal of Alzheimers Disease, Diabetes Care, and Frontiers in Aging Neuroscience had the most publications in this field. The keywords"dementia," "alzheimers-disease," "cognitive impairment" and "diabetes" are the main keywords. The burst keywords in recent years mainly included "signaling pathway" and "cognitive deficit."

Conclusion

This study systematically illustrated advances in DACD over the last 23 years. Current findings suggest that exploring potential mechanisms of DACD and the effect of anti-diabetes drugs on DACD are the hotspots in this field. Future research will also focus on the development of targeted drugs that act on the DACD signaling pathway.

Exploring Rosiglitazone's Potential to Treat Alzheimer's Disease through the Modulation of Brain-Derived Neurotrophic Factor

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that debilitates over 55 million individuals worldwide. Currently, treatments manage and alleviate its symptoms; however, there is still a need to find a therapy that prevents or halts disease progression. Since AD has been labeled as "type 3 diabetes" due to its similarity in pathological hallmarks, molecular pathways, and comorbidity with type 2 diabetes mellitus (T2DM), there is growing interest in using anti-diabetic drugs for its treatment. Rosiglitazone (RSG) is a peroxisome proliferator-activated receptor-gamma agonist that reduces hyperglycemia and hyperinsulinemia and improves insulin signaling. In cellular and rodent models of T2DM-associated cognitive decline and AD, RSG has been reported to improve cognitive impairment and reverse AD-like pathology; however, results from human clinical trials remain consistently unsuccessful. RSG has also been reported to modulate the expression of brain-derived neurotrophic factor (BDNF), a protein that regulates neuroplasticity and energy homeostasis and is implicated in both AD and T2DM. The present review investigates RSG's limitations and potential therapeutic benefits in pre-clinical models of AD through its modulation of BDNF expression.

Linagliptin and Empagliflozin Inhibit Microtubule Affinity Regulatory Kinase 4: Repurposing Anti-Diabetic Drugs in Neurodegenerative Disorders Using In Silico and In Vitro Approaches

Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) are significant public health burdens. Many studies have revealed the possibility of common pathophysiology between T2DM and AD. Thus, in recent years, studies deciphering the action mechanism of anti-diabetic drugs with their future use in AD and related pathologies are on high demand. Drug repurposing is a safe and effective approach owing to its low cost and time-saving attributes. Microtubule affinity regulating kinase 4 (MARK4) is a druggable target for various diseases and is found to be linked with AD and diabetes mellitus. MARK4 plays a vital role in energy metabolism and regulation and thus serves as an irrefutable target to treat T2DM. The present study was intended to identify the potent MARK4 inhibitors among FDA-approved anti-diabetic drugs. We performed structure-based virtual screening of FDA-approved drugs to identify the top hits against MARK4. We identified five FDA-approved drugs having an appreciable affinity and specificity toward the binding pocket of MARK4. Among these identified hits, two drugs, linagliptin, and empagliflozin, favorably bind to the MARK4 binding pocket, interacting with its critical residues and thus subjected to detailed analysis. All-atom detailed molecular dynamics (MD) simulations revealed the dynamics of binding of linagliptin and empagliflozin with MARK4. Kinase assay showed significant inhibition of MARK4 kinase activity in the presence of these drugs, implying them as potent MARK4 inhibitors. In conclusion, linagliptin and empagliflozin may be promising MARK4 inhibitors, which can further be exploited as potential lead molecules against MARK4-directed neurodegenerative diseases.

Association between prediabetes and cognitive function in Parkinson's disease

INTRODUCTION

It remains largely unknown whether prediabetes is related to cognitive impairment in Parkinson's disease (PD). This study aimed to assess the association between prediabetes and cognitive function in PD patients.

METHODS

In this cross-sectional study, 262 PD patients (age, 69.8 ± 10.3 years; Hoehn-Yahr stage, 2.3 ± 0.8) were classified into diabetes (glycated hemoglobin [HbA1c] ≥6.5% or previously diagnosed, n = 76), prediabetes (5.7%-6.4%, n = 90), or diabetes free (≤5.6%, n = 96) groups. Cognitive function was measured using the Montreal Cognitive Assessment (MoCA) test.

RESULTS

Both the diabetes and prediabetes groups had significantly lower MoCA scores (17.0 ± 6.6 and 18.0 ± 6.1, respectively) than the diabetes free group (20.0 ± 5.7), even after adjusting for potential confounders (p = .002 and p = .008, respectively). In the combined group of prediabetes and diabetes free patients, higher HbA1c levels significantly correlated with lower MoCA scores (p = .031). There was a significant interaction of diabetes status with age, but not with the duration of PD, on cognitive function.

CONCLUSION

In addition to diabetes, prediabetes may negatively affect cognitive function in PD patients. Further prospective longitudinal studies are necessary to clarify the impact of prediabetes on the cognitive trajectory of these patients.

Metformin alleviates neurocognitive impairment in aging via activation of AMPK/BDNF/PI3K pathway

Slowing down age-related neurocognitive impairment has been a challenge. We evaluated the therapeutic effects of metformin in D-galactose-induced aging. Additionally, we studied the potential molecular mechanisms that could be responsible for metformin's anti-aging effects. Thirty male rats were equally divided into: 1-control group, which received saline solution, 2-D-galactose (D-gal) group, which received D-galactose (100 mg/kg/day) by gastric lavage for eight weeks, and 3-D-galactose + Metformin (D-gal + Met) treated group, which received D-galactose + metformin (200 mg/kg/day) by gastric lavage for eight weeks. Neurocognitive assessment was done. Measurement of inflammatory, oxidative stress, and BDNF biomarkers was performed. AMPK and PI3K genes expression were assessed. Hippocampal tissues were dissected for histopathological and immunohistochemical studies. D-gal resulted in neurocognitive impairments, elevation of inflammatory biomarkers, altered oxidative stress markers, decreased BDNF, decreased expression of synaptophysin and Bcl2 with increased expression of Caspase-3, and down-regulation of AMPK and PI3K genes. Neurodegenerative changes were present in the hippocampus. Metformin restored significantly D-gal induced neurodegenerative changes. We concluded that metformin could alleviate age-induced neurocognitive deficit via amelioration of neuroinflammation, attenuation of oxidative stress, reduction of apoptosis, as well as promotion of synaptic plasticity. These mechanisms could be mediated via the activation of the AMPK/BDNF/PI3K pathway.

An Update on Treatment of Cognitive Impairment Associated with Schizophrenia

Cognitive impairment associated with schizophrenia (CIAS) is widely regarded as a critically important treatment target for schizophrenia. Despite major efforts and a number of promising findings, we do not yet have an approved drug for CIAS. Similarly, promising cognitive remediation approaches are limited in their ability to help patients achieve real-world functional gains on a wide scale. This article provides an update and critical evaluation of recent treatment development activities for CIAS. First, we provide update on pharmacological approaches, which include a glutamatergic drug that is currently in Phase III trials for CIAS, and discuss factors that may have impacted past efforts to identify efficacious drugs. Second, we review positive findings, limitations, and current trends involving cognitive remediation approaches. Third, we consider newer transdiagnostic approaches aimed at looking beyond, or identifying more homogenous subgroups within, the diagnostic category schizophrenia to advance treatment development. Despite its many challenges, treatment development for CIAS remains a major public health issue and research continues to push forward on several encouraging fronts.

A Tale of Two Diseases: Exploring Mechanisms Linking Diabetes Mellitus with Alzheimer's Disease

Dementias, including the type associated with Alzheimer's disease (AD), are on the rise worldwide. Similarly, type 2 diabetes mellitus (T2DM) is one of the most prevalent chronic diseases globally. Although mechanisms and treatments are well-established for T2DM, there remains much to be discovered. Recent research efforts have further investigated factors involved in the etiology of AD. Previously perceived to be unrelated diseases, commonalities between T2DM and AD have more recently been observed. As a result, AD has been labeled as "type 3 diabetes". In this review, we detail the shared processes that contribute to these two diseases. Insulin resistance, the main component of the pathogenesis of T2DM, is also present in AD, causing impaired brain glucose metabolism, neurodegeneration, and cognitive impairment. Dysregulation of insulin receptors and components of the insulin signaling pathway, including protein kinase B, glycogen synthase kinase 3β, and mammalian target of rapamycin are reported in both diseases. T2DM and AD also show evidence of inflammation, oxidative stress, mitochondrial dysfunction, advanced glycation end products, and amyloid deposition. The impact that changes in neurovascular structure and genetics have on the development of these conditions is also being examined. With the discovery of factors contributing to AD, innovative treatment approaches are being explored. Investigators are evaluating the efficacy of various T2DM medications for possible use in AD, including but not limited to glucagon-like peptide-1 receptor agonists, and peroxisome proliferator-activated receptor-gamma agonists. Furthermore, there are 136 active trials involving 121 therapeutic agents targeting novel AD biomarkers. With these efforts, we are one step closer to alleviating the ravaging impact of AD on our communities.

Failure of the Brain Glucagon-Like Peptide-1-Mediated Control of Intestinal Redox Homeostasis in a Rat Model of Sporadic Alzheimer's Disease

The gastrointestinal system may be involved in the etiopathogenesis of the insulin-resistant brain state (IRBS) and Alzheimer's disease (AD). Gastrointestinal hormone glucagon-like peptide-1 (GLP-1) is being explored as a potential therapy as activation of brain GLP-1 receptors (GLP-1R) exerts neuroprotection and controls peripheral metabolism. Intracerebroventricular administration of streptozotocin (STZ-icv) is used to model IRBS and GLP-1 dyshomeostasis seems to be involved in the development of neuropathological changes. The aim was to explore (i) gastrointestinal homeostasis in the STZ-icv model (ii) assess whether the brain GLP-1 is involved in the regulation of gastrointestinal redox homeostasis and (iii) analyze whether brain-gut GLP-1 axis is functional in the STZ-icv animals. Acute intracerebroventricular treatment with exendin-3(9-39)amide was used for pharmacological inhibition of brain GLP-1R in the control and STZ-icv rats, and oxidative stress was assessed in plasma, duodenum and ileum. Acute inhibition of brain GLP-1R increased plasma oxidative stress. TBARS were increased, and low molecular weight thiols (LMWT), protein sulfhydryls (SH), and superoxide dismutase (SOD) were decreased in the duodenum, but not in the ileum of the controls. In the STZ-icv, TBARS and CAT were increased, LMWT and SH were decreased at baseline, and no further increment of oxidative stress was observed upon central GLP-1R inhibition. The presented results indicate that (i) oxidative stress is increased in the duodenum of the STZ-icv rat model of AD, (ii) brain GLP-1R signaling is involved in systemic redox regulation, (iii) brain-gut GLP-1 axis regulates duodenal, but not ileal redox homeostasis, and iv) brain-gut GLP-1 axis is dysfunctional in the STZ-icv model.

The Candidate Schizophrenia Risk Gene Tmem108 Regulates Glucose Metabolism Homeostasis

BACKGROUND

Schizophrenia (SCZ) is a severe psychiatric disease affected by genetic factors and environmental contributors, and premorbid abnormality of glucose metabolism is one of the SCZ characteristics supposed to contribute to the disease's pathological process. Transmembrane protein 108 (Tmem108) is a susceptible gene associated with multiple psychiatric diseases, including SCZ. Moreover, Tmem108 mutant mice exhibit SCZ-like behaviors in the measurement of sensorimotor gating. However, it is unknown whether Tmem108 regulates glucose metabolism homeostasis while it involves SCZ pathophysiological process.

RESULTS

In this research, we found that Tmem108 mutant mice exhibited glucose intolerance, insulin resistance, and disturbed metabolic homeostasis. Food and oxygen consumption decreased, and urine production increased, accompanied by weak fatigue resistance in the mutant mice. Simultaneously, the glucose metabolic pathway was enhanced, and lipid metabolism decreased in the mutant mice, consistent with the elevated respiratory exchange ratio (RER). Furthermore, metformin attenuated plasma glucose levels and improved sensorimotor gating in Tmem108 mutant mice.

CONCLUSIONS

Hyperglycemia occurs more often in SCZ patients than in control, implying that these two diseases share common biological mechanisms, here we demonstrate that the Tmem108 mutant may represent such a comorbid mechanism.