Metformin and Its Sulfenamide Prodrugs Inhibit Human Cholinesterase Activity

Diabetes Driven Oncogenesis and Anticancer Potential of Repurposed Antidiabetic Drug: A Systemic Review

Diabetes and cancer are two prevalent disorders, pose significant public health challenges and contribute substantially to global mortality rates, with solely 10 million reported cancer-related deaths in 2020. This review explores the pathological association between diabetes and diverse cancer progressions, examining molecular mechanisms and potential therapeutic intersections. From altered metabolic landscapes to dysregulated signaling pathways, the intricate links are delineated, offering a comprehensive understanding of diabetes as a modulator of tumorigenesis. Cancer cells develop drug resistance through mechanisms like enhanced drug efflux, genetic mutations, and altered drug metabolism, allowing them to survive despite chemotherapeutic agent. Glucose emerges as a pivotal player in diabetes progression, and serving as a crucial energy source for cancer cells, supporting their biosynthetic needs and adaptation to diverse microenvironments. Glycation, a non-enzymatic process that produces advanced glycation end products (AGEs), has been linked to the etiology of cancer and has been shown in a number of tumor forms, such as leiomyosarcomas, adenocarcinomas, and squamous cell carcinomas. Furthermore, in aggressive and metastatic breast cancer, the receptor for AGEs (RAGE) is increased, which may increase the malignancy of the tumor. Reprogramming glucose metabolism manifests as hallmark cancer features, including accelerated cell proliferation, angiogenesis, metastasis, and evasion of apoptosis. This manuscript encapsulates the dual narrative of diabetes as a driver of cancer progression and the potential of repurposed antidiabetic drugs as formidable countermeasures. The amalgamation of mechanistic understanding and clinical trial outcomes establishes a robust foundation for further translational research and therapeutic advancements in the dynamic intersection of diabetes and cancer.

The role of the cholinergic system in the memory-protecting effects of metformin in a model of scopolamine-induced memory impairment in aged rats

PURPOSE

As the elderly population grows, the prevalence of dementia is also rapidly increasing worldwide. Metformin, an antidiabetic drug, has been shown to have ameliorative effects on impaired cognitive functions in experimental models. However, studies have generally used young animals. Additionally, although it has a major role in Alzheimer's disease (AD) and memory, literature information about the effects of metformin on the cholinergic system is limited. In this study, we investigated the effects of metformin on memory in a model of scopolamine-induced memory impairment in aged rats. We also examined the effects of metformin on the cholinergic system, which is very important in cognitive functions.

METHODS

Metformin was administered orally to male Wistar rats (20-22 months old) at 100 mg/kg/day for three weeks. Morris water maze (MWM) tests were performed to assess spatial memory. Before the probe test of the MWM test, scopolamine was injected intraperitoneally at a dose of 1 mg/kg. After testing, animals were sacrificed, whole brains were removed, and hippocampus samples were separated for biochemical analysis.

RESULTS

Impaired memory associated with scopolamine administration was reversed by metformin. In addition, metformin administration ameliorated scopolamine-induced changes in acetylcholine (ACh) levels, acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and choline acetyltransferase (ChAT) activity.

CONCLUSION

Our results show that metformin may have protective effects in a scopolamine-induced memory impairment model in aged animals by improving cholinergic function. Metformin shows promise in preventing dementia with its dual cholinesterase inhibition and ChAT activation effect.

Metformin derivatives - Researchers' friends or foes?

Metformin has been used for ages to treat diabetes mellitus due to its safety profile and low cost. However, metformin has variable pharmacokinetics in patients, and due to its poor oral absorption, the therapeutic doses are relatively high, causing unpleasant gastrointestinal adverse effects. Therefore, novel derivatives of metformin have been synthesized during the past decades. Particularly, after the mid-2000 s, when organic cation transporters were identified as the main metformin carriers, metformin derivatives have been under intensive investigation. Nevertheless, due to the biguanide structure, derivatives of metformin have been challenging to synthesize. Moreover, the mechanisms of metformin's action are not fully understood to date, and since it has multifunctional properties, the interests have switched to re-purposing for other diseases. Indeed, metformin derivatives have been demonstrated in many cases to be more effective than metformin itself and have the potential to be used in different diseases, including several types of cancers and neurodegenerative diseases. On the other hand, the pleiotropic nature of metformin and its derivatives can also create challenges. Not all properties are fit for all diseases. In this review, the history of the development of metformin-like compounds is summarized, and insights into their potential for future drug discovery are discussed.

Autonomic Nervous System and Cardiac Metabolism: Links Between Autonomic and Metabolic Remodeling in Atrial Fibrillation

Simultaneous activation of the sympathetic and parasympathetic nervous systems is crucial for the initiation of paroxysmal atrial fibrillation (AF). However, unbalanced activation of the sympathetic system is characteristic of autonomic remodeling in long-standing persistent AF. Moreover, the adrenergic activation-induced metabolic derangements provide a milieu for acute AF and promote the transition from the paroxysmal to the persistent phase of AF. On the other hand, cholinergic activation ameliorates the maladaptive metabolic remodeling in the face of metabolic challenges. Selective inhibition of the sympathetic system and restoration of the balance of the cholinergic system by neuromodulation is emerging as a novel nonpharmacologic strategy for managing AF. This review explores the link between cardiac autonomic and metabolic remodeling and the potential roles of different autonomic modulation strategies on atrial metabolic aberrations in AF.

Chronic exposure to environmentally relevant concentrations of guanylurea induces neurotoxicity of Danio rerio adults

Recent studies have shown guanylurea (GUA) alters the growth and development of fish, induces oxidative stress, and disrupts the levels and expression of several genes, metabolites, and proteins related to the overall fitness of fish. Nonetheless, up to date, no study has assessed the potential neurotoxic effects that GUA may induce in non-target organisms. To fill the current knowledge gaps about the effects of this metabolite in the central nervous system of fish, we aimed to determine whether or not environmentally relevant concentrations of this metabolite may disrupt the behavior, redox status, AChE activity in Danio rerio adults. In addition, we also meant to assess if 25, 50, and 200 μg/L of GUA can alter the expression of several antioxidant defenses-, apoptosis-, AMPK pathway-, and neuronal communication-related genes in the brain of fish exposed for four months to GUA. Our results demonstrated that chronic exposure to GUA altered the swimming behavior of D. rerio, as fish remained more time frozen and traveled less distance in the tank compared to the control group. Moreover, this metabolite significantly increased the levels of oxidative damage biomarkers and inhibited the activity of acetylcholinesterase of fish in a concentration-dependent manner. Concerning gene expression, environmentally relevant concentrations of GUA downregulated the expression GRID2IP, PCDH17, and PCDH19, but upregulated Nrf1, Nrf2, p53, BAX, CASP3, PRKAA1, PRKAA2, and APP in fish after four months of exposure. Collectively, we can conclude that GUA may alter the homeostasis of several essential brain biomarkers, generating anxiety-like behavior in fish.

The Influence of Selected Antipsychotic Drugs on Biochemical Aspects of Alzheimer's Disease

The aim of this study was to assess the potency of selected antipsychotic drugs (haloperidol (HAL), bromperidol (BRMP), benperidol (BNP), penfluridol (PNF), pimozide (PIM), quetiapine (QUET) and promazine (PROM)) on the main pathological hallmarks of Alzheimer's disease (AD). Binary mixtures of donepezil and antipsychotics produce an anti-BuChE effect, which was greater than either compound alone. The combination of rivastigmine and antipsychotic drugs (apart from PNF) enhanced AChE inhibition. The tested antipsychotics (excluding HAL and PNF) significantly reduce the early stage of Aβ aggregation. BRMP, PIM, QUET and PROM were found to substantially inhibit Aβ aggregation after a longer incubation time. A test of human erythrocytes hemolysis showed that short-term incubation of red blood cells (RBCs) with QUET resulted in decreased hemolysis. The antioxidative properties of antipsychotics were also proved in human umbilical vein endothelial cells (HUVEC); all tested drugs were found to significantly increase cell viability. In the case of astrocytes, BNP, PNF, PIM and PROM showed antioxidant potential.

Biological Properties of Transition Metal Complexes with Metformin and Its Analogues

Metformin is a widely prescribed medication for the treatment and management of type 2 diabetes. It belongs to a class of biguanides, which are characterized by a wide range of diverse biological properties, including anticancer, antimicrobial, antimalarial, cardioprotective and other activities. It is known that biguanides serve as excellent N-donor bidentate ligands and readily form complexes with virtually all transition metals. Recent evidence suggests that the mechanism of action of metformin and its analogues is linked to their metal-binding properties. These findings prompted us to summarize the existing data on the synthetic strategies and biological properties of various metal complexes with metformin and its analogues. We demonstrated that coordination of biologically active biguanides to various metal centers often resulted in an improved pharmacological profile, including reduced drug resistance as well as a wider spectrum of activity. In addition, coordination to the redox-active metal centers, such as Au(III), allowed for various activatable strategies, leading to the selective activation of the prodrugs and reduced off-target toxicity.

Advances in prodrug design for Alzheimer's Disease: the state of the art

INTRODUCTION

: Alzheimer's disease (AD) is the most common cause of dementia with a memory loss and other cognitive abilities and is a complex and multifactorial neurodegenerative disease that remains today a challenge for drug discovery. Like many pathologies of the central nervous system, one of the first hurdles is the development of a compound with a sufficient brain exposure to ensure a potential therapeutic benefit. In this direction, the development of prodrugs has been an intense field of research in the last years.

AREAS COVERED

: Two main strategies of prodrugs development are analysed in this review. First, the application of the classical modulation of an active compound to incorporate a drug carrier or to prepare bioprecursor has been exemplified in the field of AD. This approach has led to several examples engaged in the clinical trials. In a second chapter, a series of innovative prodrugs based on a polypharmacological approach is described to take into account the complexity of AD.

EXPERT OPINION

: In the past 10 years, at least 6 prodrugs have been approved by the FDA for the treatment of central nervous system pathologies. Most of them have been developed in order to improve membrane permeability of the parent drugs. Facing the limitation of Alzheimer's disease drug discovery, the development of prodrugs will likely play a central role in the next years. Indeed, beside addressing the challenge of distribution, prodrug could also tackle the complex multifactorial origin of the disease with the rise of innovative pleiotropic prodrugs.

The Neuroprotective Effect of α-Lipoic Acid and/or Metformin against the Behavioral and Neurochemical Changes Induced by Hypothyroidism in Rat

OBJECTIVE

The present study evaluates the neuroprotective effect of α-lipoic acid (ALA) and/or metformin (MET) on the behavioral and neurochemical changes induced by hypothyroidism.

METHODS

Rats were divided into control, rat model of hypothyroidism induced by propylthiouracil, and rat model of hypothyroidism treated with ALA, MET, or their combination.

RESULTS

Behaviorally, hypothyroid rats revealed impaired memory and reduced motor activity as indicated from the novel object recognition test and open-field test, respectively. Hypothyroidism induced a significant increase in lipid peroxidation (malondialdehyde [MDA]) and a significant decrease in reduced glutathione (GSH) and nitric oxide (NO) in the cortex and hippocampus. These were associated with a significant increase in tumor necrosis factor-α (TNF-α) and a significant decrease in brain-derived neurotrophic factor (BDNF). Hypothyroidism decreased significantly the levels of serotonin (5-HT), norepinephrine (NE), and dopamine (DA) and reduced the activities of acetylcholinesterase (AchE) and Na+, K+-ATPase in the cortex and hippocampus. Treatment of hypothyroid rats with ALA and/or MET showed an improvement in memory function and motor activity. Moreover, ALA and/or MET prevented the increase in MDA and TNF-α, and the decline in GSH, NO, BDNF, 5-HT, NE, and DA. It also restored AchE and Na+, K+-ATPase activities in the studied brain regions.

CONCLUSION

ALA and/or MET has a potential neuroprotective effect against the adverse behavioral and neurochemical changes induced by hypothyroidism in rats.

Activation of the cardiac non-neuronal cholinergic system prevents the development of diabetes-associated cardiovascular complications

BACKGROUND

Acetylcholine (ACh) plays a crucial role in the function of the heart. Recent evidence suggests that cardiomyocytes possess a non-neuronal cholinergic system (NNCS) that comprises of choline acetyltransferase (ChAT), choline transporter 1 (CHT1), vesicular acetylcholine transporter (VAChT), acetylcholinesterase (AChE) and type-2 muscarinic ACh receptors (M2AChR) to synthesize, release, degrade ACh as well as for ACh to transduce a signal. NNCS is linked to cardiac cell survival, angiogenesis and glucose metabolism. Impairment of these functions are hallmarks of diabetic heart disease (DHD). The role of the NNCS in DHD is unknown. The aim of this study was to examine the effect of diabetes on cardiac NNCS and determine if activation of cardiac NNCS is beneficial to the diabetic heart.

METHODS

Ventricular samples from type-2 diabetic humans and db/db mice were used to measure the expression pattern of NNCS components (ChAT, CHT1, VAChT, AChE and M2AChR) and glucose transporter-4 (GLUT-4) by western blot analysis. To determine the function of the cardiac NNCS in the diabetic heart, a db/db mouse model with cardiac-specific overexpression of ChAT gene was generated (db/db-ChAT-tg). Animals were followed up serially and samples collected at different time points for molecular and histological analysis of cardiac NNCS components and prosurvival and proangiogenic signaling pathways.

RESULTS

Immunoblot analysis revealed alterations in the components of cardiac NNCS and GLUT-4 in the type-2 diabetic human and db/db mouse hearts. Interestingly, the dysregulation of cardiac NNCS was followed by the downregulation of GLUT-4 in the db/db mouse heart. Db/db-ChAT-tg mice exhibited preserved cardiac and vascular function in comparison to db/db mice. The improved function was associated with increased cardiac ACh and glucose content, sustained angiogenesis and reduced fibrosis. These beneficial effects were associated with upregulation of the PI3K/Akt/HIF1α signaling pathway, and increased expression of its downstream targets-GLUT-4 and VEGF-A.

CONCLUSION

We provide the first evidence for dysregulation of the cardiac NNCS in DHD. Increased cardiac ACh is beneficial and a potential new therapeutic strategy to prevent or delay the development of DHD.

Sulfonylurea Class of Antidiabetic Drugs Inhibit Acetylcholinesterase Activity: Unexplored Auxiliary Pharmacological Benefit toward Alzheimer's Disease

Contemporary literature documents extensive research on common causative mechanisms, pathogenic pathways and dual effective remedies for Alzheimer's disease (AD) and Type 2 diabetes mellitus (T2DM). Tolbutamide (TBM), chlorpropamide (CPM), and glyburide (GLY) are three sulfonylurea antidiabetic drugs of different generations. All these drugs were found to exhibit moderate to strong inhibitory efficiency on the neurotransmitter degrading enzyme acetylcholinesterase (AChE) with GLY (IC50 = 0.74 ± 0.02 μM) being the most potent, followed by CPM (IC50 = 5.72 ± 0.24 μM) and TBM (IC50 = 28.9 ± 1.60 μM). Notably, the inhibition efficiency of GLY is even comparable with the FDA approved AD drug, donepezil (DON). The larger size of GLY spans almost the full gorge of AChE ranging from catalytic active site (CAS) to the peripheral active site (PAS) with relatively strong binding affinity (6.0 × 105 M-1) and acts as a competitive inhibitor for AChE. On the other hand, while they show relatively weak binding ((2-6) × 104 M-1), both CPM and TBM act as noncompetitive binders. While these two drugs can bind to PAS, MD simulation results predict an alternative noncompetitive inhibition mechanism for CPM. These results open the possibility of repurposing the antidiabetic drugs, particularly GLY, in the treatment of AD. The consequential side effect of excess acetylcholine production, due to the administration of these drugs to AD-unaffected patients, can be rectified by using colloidal gold and silver nanofluids as potential AChE activity boosters.

Quetiapine and novel PDE10A inhibitors potentiate the anti-BuChE activity of donepezil

The symptoms of Alzheimer’s disease (AD) do not include only memory loss and cognitive decline but also neuropsychiatric manifestation. These AD-related symptoms are usually treated with the aid of antipsychotics; however, their effects on cognition and safety remain unexplored. The present study determines the effects of quetiapine, an atypical antipsychotic, and two imidazo[1,2-a]pyrimidine-based inhibitors of PDE10A on the activity of human cholinesterases. Quetiapine moderately inhibited BuChE (IC₅₀ = 6.08 ± 1.64 µmol/L) but improved the anti-BuChE properties of donepezil by decreasing its IC₅₀ value. Both PDE10A inhibitors were found to possess moderate anti-AChE properties. The combined mixtures of donepezil and imidazo[1,2-a]pyrimidine analogues produce a synergistic anti-BuChE effect which was greater than either compound alone, improving the IC₅₀ value by approximately six times. These favourable interactions between quetiapine, PDE10A inhibitors and clinically approved donepezil, resulting in improved anti-BuChE activity, can lead to a wider variety of potent AD treatment options.

Water soluble biguanide salts and their 1,3,5-triazine derivatives as inhibitors of acetylcholinesterase and α-glucosidase

Seven biguanide derivatives were prepared by the nucleophilic reaction between dicyandiamide and p-substitute aniline derivatives or memantine or adamantine under acidic conditions. The cyclization of the biguanide compounds were also conducted via acetone to give 1,3,5-triazine derivatives. The structures of the synthesized compounds were characterized by analytical methods. The solid state structures of [HL5]Cl, [H2L7]Cl2, [HL1a]Cl and [HL5a]Cl were investigated by X-ray diffraction study. The acetylcholinesterase and α-glucosidase inhibitor properties of the compounds were then evaluated by the spectroscopic method. The compounds were found to show considerable acetylcholinesterase and α-glucosidase inhibitory activities compared to the approved drugs. The cyclization of biguanide derivatives with acetone did not affect inhibition of acetylcholinesterase, yet increased the α-glucosidase inhibition.

Diabetes drugs in the fight against Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia, particularly in old age subjects. Hyperinsulinemia and insulin resistance, which are known as pathophysiological features of Type 2 Diabetes Mellitus (T2DM), have also been demonstrated to have a significant impact on cognitive impairment. Studies have shown that an altered insulin pathway may interact with amyloid-β protein deposition and tau protein phosphorylation, both leading factors for AD development. Drugs used for T2DM treatment from insulin and metformin through dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists may represent a promising approach to fight AD. With this review from animal to human studies, we aim at responding to the reasons why drugs for diabetes may represent potential treatments for AD.

Metformin and its sulphonamide derivative simultaneously potentiateanti-cholinesterase activity of donepezil and inhibit beta-amyloid aggregation

The aim of this study was to assess in vitro the effects of sulphenamide and sulphonamide derivatives of metformin on the activity of human acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), establish the type of inhibition, and assess the potential synergism between biguanides and donepezil towards both cholinesterases (ChEs) and the effects on the β-amyloid aggregation. Sulphonamide 5 with para-trifluoromethyl- and ortho-nitro substituents in aromatic ring inhibited AChE in a mixed-type manner at micromolar concentrations (IC50 = 212.5 ± 48.3 µmol/L). The binary mixtures of donepezil and biguanides produce an anti-AChE effect, which was greater than either compound had alone. A combination of donepezil and sulphonamide 5 improved the IC50 value by 170 times. Compound 5 at 200 µmol/L inhibited Aβ aggregation by ∼20%. In conclusion, para-trifluoromethyl-ortho-nitro-benzenesulphonamide presents highly beneficial anti-AChE and anti-Aβ aggregation properties which could serve as a promising starting point for the design and development of novel biguanide-based candidates for AD treatment.