Some Candidate Drugs for Pharmacotherapy of Alzheimer's Disease

Ankaflavin and Monascin Prevent Fibrillogenesis of Hen Egg White Lysozyme: Focus on Noncovalent and Covalent Interactions

Misfolding and amyloid fibrillogenesis of proteins have close relationships with several neurodegenerative diseases. The present work investigates the inhibitive activities of ankaflavin (AK) and monascin (MS), two yellow pigments separated from Monascus-fermented rice, on hen egg white lysozyme (HEWL) fibrillation. The results demonstrated that AK/MS suppressed HEWL fibrillation through interfering with the nucleation period and AK was more potent. Fluorescence quenching and in silico docking studies revealed that AK/MS bond to HEWL by the formation of noncovalent forces with some critical amino acid residues that tend to form fibrils. Compared to those of AK, hydrogen bonding interactions between MS and Asn46, Trp62, and Trp63 residues in HEWL were slightly weaker. Besides, the covalent interaction between MS and HEWL with the binding site of Arg68 was found. These observations offered reasonable explanations for the difference in the mechanisms of AK and MS inhibiting HEWL fibrillogenesis. In a word, all data acquired herein indicated AK/MS as potent candidates for the improvement and treatment of neurological disorders.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Exploring the most promising anti - Depressant drug targeting Microtubule Affinity Receptor Kinase 4 involved in Alzheimer's Disease through molecular docking and molecular dynamics simulation

Alzheimer's Disease (AD) is the prevailing type of neurodegenerative illness, characterised by the accumulation of amyloid beta plaques. The symptoms associated with AD are memory loss, emotional variability, and a decline in cognitive functioning. To date, the pharmaceuticals currently accessible in the marketplace are limited to symptom management. According to several research, antidepressants have demonstrated potential efficacy in the management of AD. In this particular investigation, a total of 24 anti-depressant medications were selected as ligands, while the Microtubule Affinity Receptor Kinase 4 (MARK4) protein was chosen as the focal point of our study. The selection of MARK4 was based on its known involvement in the advancement of AD and other types of malignancies, rendering it a highly prospective target for therapeutic interventions. The initial step involved doing ADMET analysis, which was subsequently followed by molecular docking of 24 drugs. This was succeeded by molecular dynamics simulation and molecular mechanics generalised Born surface area (MMGBSA) calculations. Upon conducting molecular docking experiments, it has been determined that the binding affinities observed fall within the range of -5.5 kcal/mol to -9.0 kcal/mol. In this study, we selected six anti-depressant compounds (CID ID - 4184, 2771, 4205, 5533, 4543, and 2160) based on their binding affinities, which were determined to be -9.0, -8.7, -8.4, -8.3, -8.2, and -8.2, respectively. Molecular dynamics simulations were conducted for all six drugs, with donepezil serving as the control drug. Various analyses were performed, including basic analysis and post-trajectory analysis such as free energy landscape (FEL), polarizable continuum model (PCM), and MMGBSA calculations. Based on the findings from molecular dynamics simulations and the MMGBSA analysis, it can be inferred that citalopram and mirtazapine exhibit considerable potential as anti-depressant agents. Consequently, these compounds warrant further investigation through in vitro and in vivo investigations in the context of treating AD.

Evaluation of Anticholinesterase Activity of the Fungicides Mefentrifluconazole and Pyraclostrobin

Triazoles are compounds with various biological activities, including fungicidal action. They became popular through cholinesterase studies after the successful synthesis of the dual binding femtomolar triazole inhibitor of acetylcholinesterase (AChE, EC 3.1.1.7) by Sharpless et al. via in situ click chemistry. Here, we evaluate the anticholinesterase effect of the first isopropanol triazole fungicide mefentrifluconazole (Ravystar®), developed to overcome fungus resistance in plant disease management. Mefentrifluconazole is commercially available individually or in a binary fungicidal mixture, i.e., with pyraclostrobin (Ravycare®). Pyraclostrobin is a carbamate that contains a pyrazole ring. Carbamates are known inhibitors of cholinesterases and the carbamate rivastigmine is already in use for the treatment of Alzheimer's disease. We tested the type and potency of anticholinesterase activity of mefentrifluconazole and pyraclostrobin. Mefentrifluconazole reversibly inhibited human AChE and BChE with a seven-fold higher potency toward AChE (Ki = 101 ± 19 μM). Pyraclostrobin (50 μM) inhibited AChE and BChE progressively with rate constants of (t1/2 = 2.1 min; ki = 6.6 × 103 M-1 min-1) and (t1/2 = 1.5 min; ki = 9.2 × 103 M-1 min-1), respectively. A molecular docking study indicated key interactions between the tested fungicides and residues of the lipophilic active site of AChE and BChE. Additionally, the physicochemical properties of the tested fungicides were compared to values for CNS-active drugs to estimate the blood-brain barrier permeability. Our results can be applied in the design of new molecules with a lesser impact on humans and the environment.

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.

Crocin nano-chitosan-coated compound improves anxiety disorders, learning, and spatial memory in Alzheimer's model induced by beta-amyloid in rats

Objectives

Alzheimer's disease (AD) is a neurodegenerative disease that results in the gradual breakdown of brain tissue, causing the deterioration of intellectual function and ability. Crocin is a saffron carotenoid compound proven to have excellent neuroprotective and anti-inflammation properties, although it has some limitations such as low stability and bioavailability. Therefore, in the current research, we tried to improve these limitations by using nanotechnology and chitosan as the carrier. Our study examined the therapeutic effects of crocin nano-chitosan-coated compound and compared it with intact crocin in lower dosages than other studies in AD rat models.

Materials and Methods

Encapsulating crocin into chitosan nanoparticles was done through a modified technique to improve its limitations. The AD rat model was induced by bilaterally injecting beta-amyloid (Aβ) peptide into the frontal lobe using a stereotaxic device. To evaluate memory, we conducted the Barnes maze test, and to evaluate anxiety, we used the elevated plus maze test. Also, histological tests were conducted to evaluate neuronal damage in each group.

Results

Crocin nano-chitosan-coated administration significantly improved specific memory indicators compared to the Aβ and other treated groups. A significant decrease in anxiety indicators was detected compared to the Aβ and other treated groups. Finally, the results of hippocampus staining indicated a meaningful difference between the Aβ group and other treated groups, compared to the crocin nano-chitosan-coated group.

Conclusion

Treatment with low dosages of crocin in the nano-coated form exhibited great efficacy in reducing AD's adverse effects compared to the same dosage of intact crocin.

Protein aggregation: Consequences, mechanism, characterization and inhibitory strategies

Proteins play a major role in the regulation of various cellular functions including the synthesis of structural components. But proteins are stable under physiological conditions only. A slight variation in environmental conditions can cost them huge in terms of conformational stability ultimately leading to aggregation. Under normal conditions, aggregated proteins are degraded or removed from the cell by a quality control system including ubiquitin-proteasomal machinery and autophagy. But they are burdened under diseased conditions or are impaired by the aggregated proteins leading to the generation of toxicity. The misfolding and aggregation of protein such as amyloid-β, α-synuclein, human lysozyme etc., are responsible for certain diseases including Alzheimer, Parkinson, and non- neuropathic systemic amyloidosis respectively. Extensive research has been done to find the therapeutics for such diseases but till now we have got only symptomatic treatment that will reduce the disease severity but will not target the initial formation of nucleus responsible for disease progression and propagation. Hence there is an urgent need to develop the drugs targeting the cause of the disease. For this, a wide knowledge related to misfolding and aggregation under the same heading is required as described in this review alongwith the strategies hypothesized and implemented till now. This will contribute a lot to the work of researchers in the field of neuroscience.

Hot Spots for the Use of Intranasal Insulin: Cerebral Ischemia, Brain Injury, Diabetes Mellitus, Endocrine Disorders and Postoperative Delirium

A decrease in the activity of the insulin signaling system of the brain, due to both central insulin resistance and insulin deficiency, leads to neurodegeneration and impaired regulation of appetite, metabolism, endocrine functions. This is due to the neuroprotective properties of brain insulin and its leading role in maintaining glucose homeostasis in the brain, as well as in the regulation of the brain signaling network responsible for the functioning of the nervous, endocrine, and other systems. One of the approaches to restore the activity of the insulin system of the brain is the use of intranasally administered insulin (INI). Currently, INI is being considered as a promising drug to treat Alzheimer's disease and mild cognitive impairment. The clinical application of INI is being developed for the treatment of other neurodegenerative diseases and improve cognitive abilities in stress, overwork, and depression. At the same time, much attention has recently been paid to the prospects of using INI for the treatment of cerebral ischemia, traumatic brain injuries, and postoperative delirium (after anesthesia), as well as diabetes mellitus and its complications, including dysfunctions in the gonadal and thyroid axes. This review is devoted to the prospects and current trends in the use of INI for the treatment of these diseases, which, although differing in etiology and pathogenesis, are characterized by impaired insulin signaling in the brain.

Aging and aging-related diseases: from molecular mechanisms to interventions and treatments

Aging is a gradual and irreversible pathophysiological process. It presents with declines in tissue and cell functions and significant increases in the risks of various aging-related diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic diseases, musculoskeletal diseases, and immune system diseases. Although the development of modern medicine has promoted human health and greatly extended life expectancy, with the aging of society, a variety of chronic diseases have gradually become the most important causes of disability and death in elderly individuals. Current research on aging focuses on elucidating how various endogenous and exogenous stresses (such as genomic instability, telomere dysfunction, epigenetic alterations, loss of proteostasis, compromise of autophagy, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, deregulated nutrient sensing) participate in the regulation of aging. Furthermore, thorough research on the pathogenesis of aging to identify interventions that promote health and longevity (such as caloric restriction, microbiota transplantation, and nutritional intervention) and clinical treatment methods for aging-related diseases (depletion of senescent cells, stem cell therapy, antioxidative and anti-inflammatory treatments, and hormone replacement therapy) could decrease the incidence and development of aging-related diseases and in turn promote healthy aging and longevity.

Linking the Amyloid, Tau, and Mitochondrial Hypotheses of Alzheimer's Disease and Identifying Promising Drug Targets

Damage or loss of brain cells and impaired neurochemistry, neurogenesis, and synaptic and nonsynaptic plasticity of the brain lead to dementia in neurodegenerative diseases, such as Alzheimer's disease (AD). Injury to synapses and neurons and accumulation of extracellular amyloid plaques and intracellular neurofibrillary tangles are considered the main morphological and neuropathological features of AD. Age, genetic and epigenetic factors, environmental stressors, and lifestyle contribute to the risk of AD onset and progression. These risk factors are associated with structural and functional changes in the brain, leading to cognitive decline. Biomarkers of AD reflect or cause specific changes in brain function, especially changes in pathways associated with neurotransmission, neuroinflammation, bioenergetics, apoptosis, and oxidative and nitrosative stress. Even in the initial stages, AD is associated with Aβ neurotoxicity, mitochondrial dysfunction, and tau neurotoxicity. The integrative amyloid-tau-mitochondrial hypothesis assumes that the primary cause of AD is the neurotoxicity of Aβ oligomers and tau oligomers, mitochondrial dysfunction, and their mutual synergy. For the development of new efficient AD drugs, targeting the elimination of neurotoxicity, mutual potentiation of effects, and unwanted protein interactions of risk factors and biomarkers (mainly Aβ oligomers, tau oligomers, and mitochondrial dysfunction) in the early stage of the disease seems promising.

The Transcranial Light Therapy Improves Synaptic Plasticity in the Alzheimer’s Disease Mouse Model

Alzheimer’s disease (AD) is the main cause of dementia worldwide. Emerging non-invasive treatments such as photobiomodulation target the mitochondria to minimize brain damage, improving cognitive functions. In this work, an experimental design was carried out to evaluate the effect of transcranial light therapy (TLTC) on synaptic plasticity (SP) and cognitive functions in an AD animal model. Twenty-three mice were separated into two general groups: an APP/PS1 (ALZ) transgenic group and a wild-type (WT) group. Each group was randomly subdivided into two subgroups: mice with and without TLTC, depending on whether they would undergo treatment with TLTC. Cognitive function, measured through an object recognition task, showed non-significant improvement after TLTC. SP, on the other hand, was evaluated using four electrophysiological parameters from the Schaffer-CA1 collateral hippocampal synapses: excitatory field potentials (fEPSP), paired pulse facilitation (PPF), long-term depression (LTD), and long-term potentiation (LTP). An improvement was observed in subjects treated with TLTC, showing higher levels of LTP than those transgenic mice that were not exposed to the treatment. Therefore, the results obtained in this work showed that TLTC could be an efficient non-invasive treatment for AD-associated SP deficits.

GJA1/CX43 High Expression Levels in the Cervical Spinal Cord of ALS Patients Correlate to Microglia-Mediated Neuroinflammatory Profile

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting motoneurons (MNs) with a fatal outcome. The typical degeneration of cortico-spinal, spinal, and bulbar MNs, observed in post-mortem biopsies, is associated with the activation of neuroimmune cells. GJA1, a member of the connexins (Cxs) gene family, encodes for connexin 43 (Cx43), a core gap junctions (GJs)- and hemichannels (HCs)-forming protein, involved in cell death, proliferation, and differentiation. Recently, Cx43 expression was found to play a role in ALS pathogenesis. Here, we used microarray and RNA-seq datasets from the NCBI of the spinal cord of control (NDC) and ALS patients, which were stratified according to the GJA1 gene expression. Genes that positively or negatively correlated to GJA1 expression were used to perform a genomic deconvolution analysis (GDA) using neuroimmune signatures. Expression analysis revealed a significantly higher GJA1 expression in the MNs of ALS patients as compared to NDC. Gene deconvolution analysis revealed that positively correlated genes were associated with microglia activation, whereas negatively correlated genes were associated with neuronal activation profiles. Moreover, gene ontology analysis, performed on genes characterizing either microglia or neuronal signature, indicated immune activation or neurogenesis as main biological processes. Finally, using a synthetic analysis of drugs able to revert the GJA1 transcriptomic signatures, we found a specific drug profile for ALS patients with high GJA1 expression levels, composed of amlodipine, sertraline, and prednisolone. In conclusion, our exploratory study suggests GJA1 as a new neuro-immunological gene correlated to microglial cellular profile in the spinal cord of ALS patients. Further studies are warranted to confirm these results and to evaluate the therapeutic potential of drugs able to revert typical GJA1/CX43 signature in ALS patients

Medha Plus - A novel polyherbal formulation ameliorates cognitive behaviors and disease pathology in models of Alzheimer's disease

Alzheimer's disease (AD) is a multi-faceted neurodegenerative disorder that leads to drastic cognitive impairments culminating in death. Pathologically, it is characterized by amyloid-β (Aβ) plaques, neurofibrillary tangles and neurodegeneration in brain. Complete cure of AD remains elusive to date. Available synthetic drugs only provide symptomatic reliefs targeting single molecule, hence, are unable to address the multi-factorial aspects in AD pathogenesis. It is imperative to develop combinatorial drugs that address the multiple molecular targets in AD. We show a unique polyherbal formulation of Brahmi, Mandukaparni, Shankhpushpi, Yastimadhu, Kokilaksha and Shunthi called 'Medha Plus' (MP), conventionally used for improving memory and reducing anxiety, was able to ameliorate cognitive deficits and associated pathological hallmarks of AD. Viability assays revealed that MP prevented Aβ-induced loss of neurites as well as neuronal apoptosis in cellular models. An array of behavioral studies showed that MP was able to recover AD-associated memory deficits in both Aβ-injected rats and 5XFAD mice. Immunohistochemical studies further revealed that MP treatment reduced Aβ depositshpi and decreased apoptotic cell death in the hippocampus. Enzymatic assays demonstrated anti-oxidative and anti-acetyl cholinesterase properties of MP especially in hippocampus of Aβ-injected rats. An underlying improvement in synaptic plasticity was observed with MP treatment in 5XFAD mice along with an increased expression of phospho-Akt at serine 473 indicating a role of PI3K/Akt signaling in correcting these synaptic deficits. Thus, our strong experiment-driven approach shows that MP is an incredible combinatorial drug that targets multiple molecular targets with exemplary neuroprotective properties and is proposed for clinical trial.

The Role of Resveratrol in Mild Cognitive Impairment and Alzheimer's Disease: A Systematic Review

Advancing age is one of the risk factors for developing many diseases, including cancer, cardiovascular disorders, and neurodegenerative alterations, such as mild cognitive impairment (MCI), and Alzheimer's Disease (AD). Studies have indicated that supplementation with resveratrol (RSV) might improve cerebrovascular function and reduce the risk of developing dementia. Thus, the aim of this systematic review was to assess the effects of RSV on MCI and AD. MEDLINE-PubMed, Cochrane, and EMBASE were used to perform the search, and PRISMA guidelines were followed. Five studies met the eligible criteria; three with AD and two with MCI. In AD patients, the use of RSV reduces Aβ levels, improves brain volume, reduces the Mini-mental status score, and improves AD scores. In patients with MCI, this polyphenol prevents decline in Standard Volumes of Interest and increases the Resting-state Functional Connectivity score. RSV can activate the human silent information regulator 2/sirtuin 1 (Sirt-1) and can inhibit the cyclooxygenase-2 (COX-2), 5-lipoxygenase, and nuclear factor-κB, resulting in the reduction of the proinflammation pathways. It is also associated with the increase in the levels of interleukin (IL)-10 and reduction of interferon-γ and IL-17. Both anti-inflammatory and antioxidant effects can be related to preventing neurodegenerative diseases, doing maintenance, and enabling the recovery of these conditions directly related to inflammation and oxidative stress. We suggest that the use of RSV can bring beneficial effects to patients with MCI or AD.

Insulin and α-Tocopherol Enhance the Protective Effect of Each Other on Brain Cortical Neurons under Oxidative Stress Conditions and in Rat Two-Vessel Forebrain Ischemia/Reperfusion Injury

Clinical trials show that insulin administered intranasally is a promising drug to treat neurodegenerative diseases, but at high doses its use may result in cerebral insulin resistance. Identifying compounds which could enhance the protective effects of insulin, may be helpful to reduce its effective dose. Our aim was thus to study the efficiency of combined use of insulin and α-tocopherol (α-T) to increase the viability of cultured cortical neurons under oxidative stress conditions and to normalize the metabolic disturbances caused by free radical reaction activation in brain cortex of rats with two-vessel forebrain ischemia/reperfusion injury. Immunoblotting, flow cytometry, colorimetric, and fluorometric techniques were used. α-T enhanced the protective and antioxidative effects of insulin on neurons in oxidative stress, their effects were additive. At the late stages of oxidative stress, the combined action of insulin and α-T increased Akt-kinase activity, inactivated GSK-3beta and normalized ERK1/2 activity in cortical neurons, it was more effective than either drug action. In the brain cortex, ischemia/reperfusion increased the lipid peroxidation product content and caused Na⁺,K⁺-ATPase oxidative inactivation. Co-administration of insulin (intranasally, 0.25 IU/rat) and α-T (orally, 50 mg/kg) led to a more pronounced normalization of the levels of Schiff bases, conjugated dienes and trienes and Na⁺,K⁺-ATPase activity than administration of each drug alone. Thus, α-T enhances the protective effects of insulin on cultured cortical neurons in oxidative stress and in the brain cortex of rats with cerebral ischemia/reperfusion injury.

Aducanumab: evidence from clinical trial data and controversies

Alzheimer's disease (AD) is the most common cause for dementia worldwide. Until recently, all approved treatments for AD were symptomatic and not disease modifying. On 7 June 2021, the US FDA approved aducanumab, a human IgG1 anti-Aβ monoclonal antibody selective for Aβ aggregates, as the first disease-modifying treatment for AD. Aducanumab is approved in the United States for the treatment of mild cognitive impairment or mild-dementia stage of AD. In this Editorial, we review the trial data for aducanumab in the treatment of AD and the controversies that its approval has generated.

Antidepressants in Alzheimer's Disease: A Focus on the Role of Mirtazapine

Mirtazapine belongs to the category of antidepressants clinically used mainly in major depressive disorder but also used in obsessive-compulsive disorders, generalized anxiety, and sleep disturbances. This drug acts mainly by antagonizing the adrenergic α2, and the serotonergic 5-HT2 and 5-HT3 receptors. Neuropsychiatric symptoms, such as depression and agitation, are strongly associated with Alzheimer’s disease, reducing the life quality of these patients. Thus, it is crucial to control depression in Alzheimer’s patients. For this purpose, drugs such as mirtazapine are important in the control of anxiety, agitation, and other depressive symptoms in these patients. Indeed, despite some contradictory studies, evidence supports the role of mirtazapine in this regard. In this review, we will focus on depression in Alzheimer’s disease, highlighting the role of mirtazapine in this context.

The Rhesus Macaque as a Translational Model for Neurodegeneration and Alzheimer's Disease

A major obstacle to progress in understanding the etiology of normative and pathological human brain aging is the availability of suitable animal models for experimentation. The present article will highlight our current knowledge regarding human brain aging and neurodegeneration, specifically in the context of Alzheimer's disease (AD). Additionally, it will examine the use of the rhesus macaque monkey as a pragmatic translational animal model in which to study underlying causal mechanisms. Specifically, the discussion will focus on behavioral and protein-level brain changes that occur within the central nervous system (CNS) of aged monkeys, and compare them to the changes observed in humans during clinically normative aging and in AD.

Metformin a Potential Pharmacological Strategy in Late Onset Alzheimer's Disease Treatment

Alzheimer's disease (AD) is one of the most devastating brain disorders. Currently, there are no effective treatments to stop the disease progression and it is becoming a major public health concern. Several risk factors are involved in the progression of AD, modifying neuronal circuits and brain cognition, and eventually leading to neuronal death. Among them, obesity and type 2 diabetes mellitus (T2DM) have attracted increasing attention, since brain insulin resistance can contribute to neurodegeneration. Consequently, AD has been referred to "type 3 diabetes" and antidiabetic medications such as intranasal insulin, glitazones, metformin or liraglutide are being tested as possible alternatives. Metformin, a first line antihyperglycemic medication, is a 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) activator hypothesized to act as a geroprotective agent. However, studies on its association with age-related cognitive decline have shown controversial results with positive and negative findings. In spite of this, metformin shows positive benefits such as anti-inflammatory effects, accelerated neurogenesis, strengthened memory, and prolonged life expectancy. Moreover, it has been recently demonstrated that metformin enhances synaptophysin, sirtuin-1, AMPK, and brain-derived neuronal factor (BDNF) immunoreactivity, which are essential markers of plasticity. The present review discusses the numerous studies which have explored (1) the neuropathological hallmarks of AD, (2) association of type 2 diabetes with AD, and (3) the potential therapeutic effects of metformin on AD and preclinical models.