Metformin Protects against Experimental Acrylamide Neuropathy in Rats

Cornerstone Cellular Pathways for Metabolic Disorders and Diabetes Mellitus: Non-Coding RNAs, Wnt Signaling, and AMPK

Metabolic disorders and diabetes (DM) impact more than five hundred million individuals throughout the world and are insidious in onset, chronic in nature, and yield significant disability and death. Current therapies that address nutritional status, weight management, and pharmacological options may delay disability but cannot alter disease course or functional organ loss, such as dementia and degeneration of systemic bodily functions. Underlying these challenges are the onset of aging disorders associated with increased lifespan, telomere dysfunction, and oxidative stress generation that lead to multi-system dysfunction. These significant hurdles point to the urgent need to address underlying disease mechanisms with innovative applications. New treatment strategies involve non-coding RNA pathways with microRNAs (miRNAs) and circular ribonucleic acids (circRNAs), Wnt signaling, and Wnt1 inducible signaling pathway protein 1 (WISP1) that are dependent upon programmed cell death pathways, cellular metabolic pathways with AMP-activated protein kinase (AMPK) and nicotinamide, and growth factor applications. Non-coding RNAs, Wnt signaling, and AMPK are cornerstone mechanisms for overseeing complex metabolic pathways that offer innovative treatment avenues for metabolic disease and DM but will necessitate continued appreciation of the ability of each of these cellular mechanisms to independently and in unison influence clinical outcome.

Cellular Metabolism: A Fundamental Component of Degeneration in the Nervous System

It is estimated that, at minimum, 500 million individuals suffer from cellular metabolic dysfunction, such as diabetes mellitus (DM), throughout the world. Even more concerning is the knowledge that metabolic disease is intimately tied to neurodegenerative disorders, affecting both the central and peripheral nervous systems as well as leading to dementia, the seventh leading cause of death. New and innovative therapeutic strategies that address cellular metabolism, apoptosis, autophagy, and pyroptosis, the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), growth factor signaling with erythropoietin (EPO), and risk factors such as the apolipoprotein E (APOE-ε4) gene and coronavirus disease 2019 (COVID-19) can offer valuable insights for the clinical care and treatment of neurodegenerative disorders impacted by cellular metabolic disease. Critical insight into and modulation of these complex pathways are required since mTOR signaling pathways, such as AMPK activation, can improve memory retention in Alzheimer's disease (AD) and DM, promote healthy aging, facilitate clearance of β-amyloid (Aß) and tau in the brain, and control inflammation, but also may lead to cognitive loss and long-COVID syndrome through mechanisms that can include oxidative stress, mitochondrial dysfunction, cytokine release, and APOE-ε4 if pathways such as autophagy and other mechanisms of programmed cell death are left unchecked.

Type 2 Diabetes (T2DM) and Parkinson's Disease (PD): a Mechanistic Approach

Growing evidence suggest that there is a connection between Parkinson's disease (PD) and insulin dysregulation in the brain, whilst the connection between PD and type 2 diabetes mellitus (T2DM) is still up for debate. Insulin is widely recognised to play a crucial role in neuronal survival and brain function; any changes in insulin metabolism and signalling in the central nervous system (CNS) can lead to the development of various brain disorders. There is accumulating evidence linking T2DM to PD and other neurodegenerative diseases. In fact, they have a lot in common patho-physiologically, including insulin dysregulation, oxidative stress resulting in mitochondrial dysfunction, microglial activation, and inflammation. As a result, initial research should focus on the role of insulin and its molecular mechanism in order to develop therapeutic outcomes. In this current review, we will look into the link between T2DM and PD, the function of insulin in the brain, and studies related to impact of insulin in causing T2DM and PD. Further, we have also highlighted the role of various insulin signalling pathway in both T2DM and PD. We have also suggested that T2DM-targeting pharmacological strategies as potential therapeutic approach for individuals with cognitive impairment, and we have demonstrated the effectiveness of T2DM-prescribed drugs through current PD treatment trials. In conclusion, this investigation would fill a research gap in T2DM-associated Parkinson's disease (PD) with a potential therapy option.

The Anti-Inflammatory, Anti-Apoptotic and Antioxidant Effects of a Pomegranate-Peel Extract against Acrylamide-Induced Hepatotoxicity in Rats

The Acrylamide is a toxic compound generated under oxidative stress arising from intracellular ROS production and induced toxicity. It is frequently used in industry and generated through the heating of tobacco and foods high in carbohydrates. The exact mechanism of its toxicity is still unclear. In this study, an extract of the peels of pomegranate (Punica granatum L.), a nutritious and visually appealing fruit with a diverse bioactive profile, was examined for its potential anti-apoptotic, antioxidant, and anti-inflammatory effects. A total of 40 adult male Wistar rats were allocated into four groups of 10 rats each: Group 1 was a negative-control group (CNT) and received normal saline; Group 2 was a positive-control acrylamide group and received acrylamide orally at a dose of 20 mg/kg/bw; in Group 3, the rats were supplemented with pomegranate-peel extract (P.P; 150 mg/kg/bw) orally on a daily basis for 3 weeks, administered simultaneously with the acrylamide treatment described for Group 2; Group 4 was a protective group, and the animals received the pomegranate-peel extract and acrylamide as stated for Groups 2 and 3, with the pomegranate-peel extract (P.P. extract) administered 1 week earlier than the acrylamide. The results indicate that acrylamide exposure increased the serum levels of AST, ALT, creatinine, interleukin-1 beta, and interleukin-6 in an extraordinary manner. In addition, it increased the lipid peroxidation marker malondialdehyde (MDA) and simultaneously weakened antioxidant biomarker activities (SOD, GSH, and catalase) and reduced the levels of interleukin-10. The pomegranate-peel extract was shown to reduce the inflammatory blood markers of interleukin-1 beta and IL-6. Glutathione peroxidase, superoxide dismutase, catalase, and interleukin-10 were all significantly elevated in comparison to the acrylamide-treatment group as a result of the significant reduction in MDA levels induced by the P.P extract. In addition, the pomegranate-peel extract normalized the cyclooxygenase-2 (COX2), transforming growth factor-beta 1 (TGF-β1), and caspase-3 levels, with a significant upregulation of the mRNA expression of heme oxygenase-1 (HO-1), nuclear factor erythroid 2 (Nrf2), and Bcl-2. Therefore, these data reveal that pomegranate peel has anti-inflammatory, antiapoptotic, free-radical-scavenging, and powerful antioxidant activity that protects against acrylamide toxicity.

Metformin treatment confers protection of the optic nerve following photoreceptor degeneration

Acquired or inherited or photoreceptor loss causes retinal ganglion cell loss and ultimately axonal transport alteration. Thus, therapies should be applied early during photoreceptors degeneration before the remodeling process reaches the inner retina. This study aimed to evaluate the protective effect of metformin on the rat optic nerve following photoreceptors loss induced by N-Ethyl-N-nitrosourea (ENU). Eighteen adults male Wistar rats were divided into two groups. Group I: normal vehicle control (n=6). Group II: ENU-induced photoreceptors degeneration (n=12) received a single intraperitoneal injection of ENU at a dose of 600 mg/kg. Rats in group II were equally divided into two subgroups: IIa: photoreceptor degeneration induced group and IIb: metformin treated group (200 mg/kg) for 7 days. Specimens from the optic nerve were processed for light and electron microscopy. In ENU treated group, the optic nerve revealed reduction in the diameter of the optic nerve fibers and thinning of myelin sheath with morphological changes in the glia (astrocytes, oligodendrocytes, and microglia). Caspase-3 (apoptotic marker), iNOS (oxidative stress marker) and CD68 (macrophage marker) expression increased. In metformin-treated group, the diameter of optic nerve fibers and myelin sheath thickness increased with improvement of the deterioration in the glia. Caspase-3, iNOS and CD68 expression decreased. Metformin ameliorates the histological changes of the rat optic nerve following photoreceptors loss induced by ENU.

Vitamin E and 5-amino salicylic acid ameliorates acrylamide-induced peripheral neuropathy by inhibiting caspase-3 and inducible nitric oxide synthase immunoexpression

Acrylamide is a fundamental cause of accidental toxicity in humans. This study aimed to investigate the neuroprotective effect of vitamin E (Vit. E), 5-amino salicylic acid (5-ASA), and their combination against acrylamide-induced sciatic nerve toxicity. For this purpose, 25 male Wister rats were divided into 5 groups: control, acrylamide, acrylamide + Vit. E, acrylamide + 5-ASA, and acrylamide + Vit. E + 5-ASA. Food intake and body weight were assessed after 7 days. Furthermore, the gait score was also evaluated for each rat. The sciatic nerve was dissected, fixed, and processed for routine light and electron microscopic examination. Haematoxylin and eosin, osmium tetroxide for myelin sheath, and toluidine blue for semithin section were used. In addition, immunohistochemistry for caspase-3 and inducible nitric oxide synthase (iNOS) were performed. The results showed reduced food intake and body weight in acrylamide rats. Abnormal gait score was also recorded in acrylamide rats with significant improvement in Vit. E, and Vit. E + 5-ASA groups. Histologically, Vit. E and 5-ASA provided potential protection against decreased sciatic nerve axon density, disrupted myelination, and the alteration in the immunohistochemistry induced by acrylamide. Vit. E and its combination with 5-ASA provided more evident protection compared to 5-ASA alone. 5-ASA significantly decreased apoptotic cell death (caspase-3 immunoexpression) while Vit. E failed. Both Vit. E and 5-ASA significantly decreased iNOS immunoexpression in the sciatic nerve, where 5-ASA was superior to Vit. E. These findings concluded that both Vit. E and 5-ASA protect against acrylamide-induced peripheral neuropathy through downregulation of both caspase-3 and iNOS immunoexpression.

Peripheral Neuropathic Pain: From Experimental Models to Potential Therapeutic Targets in Dorsal Root Ganglion Neurons

Neuropathic pain exerts a global burden caused by the lesions in the somatosensory nerve system, including the central and peripheral nervous systems. The mechanisms of nerve injury-induced neuropathic pain involve multiple mechanisms, various signaling pathways, and molecules. Currently, poor efficacy is the major limitation of medications for treating neuropathic pain. Thus, understanding the detailed molecular mechanisms should shed light on the development of new therapeutic strategies for neuropathic pain. Several well-established in vivo pain models were used to investigate the detail mechanisms of peripheral neuropathic pain. Molecular mediators of pain are regulated differentially in various forms of neuropathic pain models; these regulators include purinergic receptors, transient receptor potential receptor channels, and voltage-gated sodium and calcium channels. Meanwhile, post-translational modification and transcriptional regulation are also altered in these pain models and have been reported to mediate several pain related molecules. In this review, we focus on molecular mechanisms and mediators of neuropathic pain with their corresponding transcriptional regulation and post-translational modification underlying peripheral sensitization in the dorsal root ganglia. Taken together, these molecular mediators and their modification and regulations provide excellent targets for neuropathic pain treatment.

Metformin attenuates renal interstitial fibrosis through upregulation of Deptor in unilateral ureteral obstruction in rats

Renal interstitial fibrosis (RIF) is a common pathological process that accompanies chronic kidney disease (CKD) and that progresses to end-stage renal failure (ESRD). Accumulating evidence has revealed that persistent mammalian target of rapamycin (mTOR) activation in kidneys is closely associated with the occurrence and progression of CKD. The DEP domain-containing mTOR interacting protein (Deptor) is an endogenous negative regulator of mTOR. Metformin can attenuate renal fibrosis in an animal model of diabetic nephropathy. Previous studies demonstrated that metformin can attenuate renal fibrosis in several models of CKD. However, the precise mechanisms of this effect are not well understood. The present study aimed to examine the mechanism of action of metformin on unilateral ureteral obstruction (UUO)-induced RIF in rats in vivo. Sprague-Dawley rats were randomly divided into a sham-operated group, three UUO groups examined at different time points (3, 7 and 14 days after UUO surgery), and three metformin-treated groups, treated with three different concentrations of metformin. The metformin-treated groups were administered metformin orally every day for 14 consecutive days following surgery. The protein expression levels of Deptor, α-smooth muscle actin (α-SMA), phosphorylated (p-)mTOR, p-ribosomal protein S6 kinase (p-p70S6K) and CD68 were assessed. The present results suggested that, following UUO, there was a significant reduction of Deptor expression, and an increase in collagen deposition in the extracellular matrix over time, accompanied by an increased expression of several proteins including CD68, α-SMA, p-mTOR and p-p70S6K. Notably, metformin treatment reversed these effects. In conclusion, the present results suggested that metformin attenuated RIF of UUO rats, and the mechanism of action was found to be associated with the increase in Deptor expression and inhibition of the mTOR/p70S6K pathway in the kidneys of UUO rats.

Dysregulation of metabolic flexibility: The impact of mTOR on autophagy in neurodegenerative disease

Non-communicable diseases (NCDs) that involve neurodegenerative disorders and metabolic disease impact over 400 million individuals globally. Interestingly, metabolic disorders, such as diabetes mellitus, are significant risk factors for the development of neurodegenerative diseases. Given that current therapies for these NCDs address symptomatic care, new avenues of discovery are required to offer treatments that affect disease progression. Innovative strategies that fill this void involve the mechanistic target of rapamycin (mTOR) and its associated pathways of mTOR complex 1 (mTORC1), mTOR complex 2 (mTORC2), AMP activated protein kinase (AMPK), trophic factors that include erythropoietin (EPO), and the programmed cell death pathways of autophagy and apoptosis. These pathways are intriguing in their potential to provide effective care for metabolic and neurodegenerative disorders. Yet, future work is necessary to fully comprehend the entire breadth of the mTOR pathways that can effectively and safely translate treatments to clinical medicine without the development of unexpected clinical disabilities.

New Insights for nicotinamide: Metabolic disease, autophagy, and mTOR

Metabolic disorders, such as diabetes mellitus (DM), are increasingly becoming significant risk factors for the health of the global population and consume substantial portions of the gross domestic product of all nations. Although conventional therapies that include early diagnosis, nutritional modification of diet, and pharmacological treatments may limit disease progression, tight serum glucose control cannot prevent the onset of future disease complications. With these concerns, novel strategies for the treatment of metabolic disorders that involve the vitamin nicotinamide, the mechanistic target of rapamycin (mTOR), mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP activated protein kinase (AMPK), and the cellular pathways of autophagy and apoptosis offer exceptional promise to provide new avenues of treatment. Oversight of these pathways can promote cellular energy homeostasis, maintain mitochondrial function, improve glucose utilization, and preserve pancreatic beta-cell function. Yet, the interplay among mTOR, AMPK, and autophagy pathways can be complex and affect desired clinical outcomes, necessitating further investigations to provide efficacious treatment strategies for metabolic dysfunction and DM.

Chemotherapy-induced peripheral neuropathy: where are we now?

Chemotherapy-induced peripheral neuropathy (CIPN) is a major challenge, with increasing impact as oncological treatments, using potentially neurotoxic chemotherapy, improve cancer cure and survival. Acute CIPN occurs during chemotherapy, sometimes requiring dose reduction or cessation, impacting on survival. Around 30% of patients will still have CIPN a year, or more, after finishing chemotherapy. Accurate assessment is essential to improve knowledge around prevalence and incidence of CIPN. Consensus is needed to standardize assessment and diagnosis, with use of well-validated tools, such as the EORTC-CIPN 20. Detailed phenotyping of the clinical syndrome moves toward a precision medicine approach, to individualize treatment. Understanding significant risk factors and pre-existing vulnerability may be used to improve strategies for CIPN prevention, or to use targeted treatment for established CIPN. No preventive therapies have shown significant clinical efficacy, although there are promising novel agents such as histone deacetylase 6 (HDAC6) inhibitors, currently in early phase clinical trials for cancer treatment. Drug repurposing, eg, metformin, may offer an alternative therapeutic avenue. Established treatment for painful CIPN is limited. Following recommendations for general neuropathic pain is logical, but evidence for agents such as gabapentinoids and amitriptyline is weak. The only agent currently recommended by the American Society of Clinical Oncology is duloxetine. Mechanisms are complex with changes in ion channels (sodium, potassium, and calcium), transient receptor potential channels, mitochondrial dysfunction, and immune cell interactions. Improved understanding is essential to advance CIPN management. On a positive note, there are many potential sites for modulation, with novel analgesic approaches.

Metformin as a protective agent against natural or chemical toxicities: a comprehensive review on drug repositioning

BACKGROUND

Metformin is the first prescribed drug for hyperglycemia in type 2 diabetes mellitus. Mainly by activating AMPK pathway, this drug exerts various functions that among them protective effects are of the interest.

PURPOSE

Herein, we aimed to gather data about the protective impacts of metformin against various natural or chemical toxicities.

RESULTS

An extensive search among PubMed, Scopus, and Google Scholar was conducted by keywords related to protection, toxicity, natural and chemical toxins and, metformin. Our literature review showed metformin alongside its anti-hyperglycemic effect has a wide range of anti-toxic effects against anti-tumour and routine drugs, natural and chemical toxins, herbicides and, heavy metals.

CONCLUSION

It is evident that metformin is a potent drug against the toxicity of a broad spectrum of natural, chemical toxic agents which is proved by a vast number of studies. Metformin mainly through AMPK axis can protect different organs against toxicities. Moreover, metformin preserves DNA integrity and can be an option for adjuvant therapy to ameliorate side effect of other therapeutics.

The Mechanistic Target of Rapamycin (mTOR): Novel Considerations as an Antiviral Treatment

Multiple viral pathogens can pose a significant health risk to individuals. As a recent example, the β-coronavirus family virion, SARS-CoV-2, has quickly evolved as a pandemic leading to coronavirus disease 2019 (COVID-19) and has been declared by the World Health Organization as a Public Health Emergency of International Concern. To date, no definitive treatment or vaccine application exists for COVID-19. Although new investigations seek to repurpose existing antiviral treatments for COVID-19, innovative treatment strategies not normally considered to have antiviral capabilities may be critical to address this global concern. One such avenue that may prove to be exceedingly fruitful and offer exciting potential as new antiviral therapy involves the mechanistic target of rapamycin (mTOR) and its associated pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), and AMP activated protein kinase (AMPK). Recent work has shown that mTOR pathways in conjunction with AMPK may offer valuable targets to control cell injury, oxidative stress, mitochondrial dysfunction, and the onset of hyperinflammation, a significant disability associated with COVID-19. Furthermore, pathways that can activate mTOR may be necessary for anti-hepatitis C activity, reduction of influenza A virus replication, and vital for type-1 interferon responses with influenza vaccination. Yet, important considerations for the development of safe and effective antiviral therapy with mTOR pathways exist. Under some conditions, mTOR can act as a double edge sword and participate in virion replication and virion release from cells. Future work with mTOR as a potential antiviral target is highly warranted and with a greater understanding of this novel pathway, new treatments against several viral pathogens may successfully emerge.

Nicotinamide: Oversight of Metabolic Dysfunction Through SIRT1, mTOR, and Clock Genes

Metabolic disorders that include diabetes mellitus present significant challenges for maintaining the welfare of the global population. Metabolic diseases impact all systems of the body and despite current therapies that offer some protection through tight serum glucose control, ultimately such treatments cannot block the progression of disability and death realized with metabolic disorders. As a result, novel therapeutic avenues are critical for further development to address these concerns. An innovative strategy involves the vitamin nicotinamide and the pathways associated with the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), the mechanistic target of rapamycin (mTOR), mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP activated protein kinase (AMPK), and clock genes. Nicotinamide maintains an intimate relationship with these pathways to oversee metabolic disease and improve glucose utilization, limit mitochondrial dysfunction, block oxidative stress, potentially function as antiviral therapy, and foster cellular survival through mechanisms involving autophagy. However, the pathways of nicotinamide, SIRT1, mTOR, AMPK, and clock genes are complex and involve feedback pathways as well as trophic factors such as erythropoietin that require a careful balance to ensure metabolic homeostasis. Future work is warranted to gain additional insight into these vital pathways that can oversee both normal metabolic physiology and metabolic disease.

Long-Term Moderate Exercise Combined with Metformin Treatment Induces an Hormetic Response That Prevents Strength and Muscle Mass Loss in Old Female Wistar Rats

Sarcopenia is a syndrome characterized by a progressive and generalized skeletal muscle mass and strength loss, as well as a poor physical performance, which as strongly been associated with aging. Sedentary lifestyle in the elderly contributes to this condition; however, physical activity improves health, reducing morbidity and mortality. Recent studies have shown that metformin (MTF) can also prevent muscle damage promoting muscular performance. To date, there is great controversy if MTF treatment combined with exercise training improves or nullifies the benefits provided by physical activity. This study is aimed at evaluating the effect of long-term moderate exercise combined with MTF treatment on body composition, strength, redox state, and survival rate during the life of female Wistar rats. In this study, rats performed moderate exercise during 20 of their 24 months of life and were treated with MTF for one year or for 6 months, i.e., from 12 to 24 months old and 18 to 24 months old. The body composition (percentage of fat, bone, and lean mass) was determined using a dual-energy X-ray absorption scanner (DXA), and grip strength was determined using a dynamometer. Likewise, medial and tibial nerve somatosensory evoked potentials were evaluated and the redox state was measured by HPLC, calculating the GSH/GSSG ratio in the gastrocnemius muscle. Our results suggest- that the MTF administration, both in the sedentary and the exercise groups, might activate a mechanism that is directly related to the induction of the hormetic response through the redox state modulation. MTF treatment does not eliminate the beneficial effects of exercise throughout life, and although MTF does not increase muscle mass, it increases longevity.

Apoptosis and astrogliosis perturbations and expression of regulatory inflammatory factors and neurotransmitters in acrylamide-induced neurotoxicity under ω3 fatty acids protection in rats

This study was aimed to investigate the potential ameliorative effects of omega-3 (ω3) fatty acids against acrylamide (ACR)-induced neurotoxicity. Thirty-two adult male Sprague Dawley rats were randomly assigned into four groups (n = 8) as follows: control, ω3 fatty acids (1000 mg/kg bwt/day orally), ACR-treated (50 mg/kg bwt/day IP) and ACR plus ω3 fatty acids group. Treatments were performed every other day for 21 consecutive days. ACR induced abnormal gait and elevated serum levels of proinflammatory cytokines (IL-6 and TNF-α), brain and spinal cord MDA levels and decreased brain and spinal cord GSH levels. Moreover, it reduced neurotransmitters (acetylcholine, GABA, serotonin and noradrenaline levels) and increased AChE activity in brain tissues. Histopathologically, ACR caused various degenerative changes, necrosis and glial cell activation in the cerebrum, cerebellum, hippocampus, spinal cord and sciatic nerve. Likewise, the histomorphometric analysis was constant with ACR-induced neurotoxicity. The ACR induced axonal atrophy and myelin disruption and decreased g-ratio of the sciatic nerve. Immunohistochemically, strong positive expressions of apoptotic marker caspase-3 and astroglial GFAP in the examined tissues were detected. Contrariwise, concurrent administration of ω3 fatty acids partially attenuated ACR impacts, as it improved the gait performance, reduced oxidative stress and pro-inflammatory cytokines, and modulate the levels of the neurotransmitters. It also ameliorated the intensity of ACR-induced histopathological and histomorphometric alterations within the examined nervous tissues. It could be concluded that ω3 fatty acids have antioxidant, anti-inflammatory and anti-apoptotic potentials against ACR neurotoxicity via suppression of oxidative stress, lipid peroxidation and pro-inflammatory cytokines, and inhibition of AChE activity and downregulation of caspase-3 and GFAP expressions in the nervous tissues.