Activation of AMP-activated protein kinase by metformin protects against global cerebral ischemia in male rats: interference of AMPK/PGC-1α pathway

Promising use of metformin in treating neurological disorders: biomarker-guided therapies

Neurological disorders are a diverse group of conditions that affect the nervous system and include neurodegenerative diseases (Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease), cerebrovascular conditions (stroke), and neurodevelopmental disorders (autism spectrum disorder). Although they affect millions of individuals around the world, only a limited number of effective treatment options are available today. Since most neurological disorders express mitochondria-related metabolic perturbations, metformin, a biguanide type II antidiabetic drug, has attracted a lot of attention to be repurposed to treat neurological disorders by correcting their perturbed energy metabolism. However, controversial research emerges regarding the beneficial/detrimental effects of metformin on these neurological disorders. Given that most neurological disorders have complex etiology in their pathophysiology and are influenced by various risk factors such as aging, lifestyle, genetics, and environment, it is important to identify perturbed molecular functions that can be targeted by metformin in these neurological disorders. These molecules can then be used as biomarkers to stratify subpopulations of patients who show distinct molecular/pathological properties and can respond to metformin treatment, ultimately developing targeted therapy. In this review, we will discuss mitochondria-related metabolic perturbations and impaired molecular pathways in these neurological disorders and how these can be used as biomarkers to guide metformin-responsive treatment for the targeted therapy to treat neurological disorders.

Rhoa/ROCK, mTOR and Secretome-Based Treatments for Ischemic Stroke: New Perspectives

Ischemic stroke triggers a complex cascade of cellular and molecular events leading to neuronal damage and tissue injury. This review explores the potential therapeutic avenues targeting cellular signaling pathways implicated in stroke pathophysiology. Specifically, it focuses on the articles that highlight the roles of RhoA/ROCK and mTOR signaling pathways in ischemic brain injury and their therapeutic implications. The RhoA/ROCK pathway modulates various cellular processes, including cytoskeletal dynamics and inflammation, while mTOR signaling regulates cell growth, proliferation, and autophagy. Preclinical studies have demonstrated the neuroprotective effects of targeting these pathways in stroke models, offering insights into potential treatment strategies. However, challenges such as off-target effects and the need for tissue-specific targeting remain. Furthermore, emerging evidence suggests the therapeutic potential of MSC secretome in stroke treatment, highlighting the importance of exploring alternative approaches. Future research directions include elucidating the precise mechanisms of action, optimizing treatment protocols, and translating preclinical findings into clinical practice for improved stroke outcomes.

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

Anxiolytic effect of antidiabetic metformin is mediated by AMPK activation in mPFC inhibitory neurons

Diabetic patients receiving the antidiabetic drug metformin have been observed to exhibit a lower prevalence of anxiety disorders, yet the precise mechanism behind this phenomenon is unclear. In our study, we found that anxiety induces a region-specific reduction in AMPK activity in the medial prefrontal cortex (mPFC). Concurrently, transgenic mice with brain-specific AMPK knockout displayed abnormal anxiety-like behaviors. Treatment with metformin or the overexpression of AMPK restored normal AMPK activity in the mPFC and mitigated social stress-induced anxiety-like behaviors. Furthermore, the specific genetic deletion of AMPK in the mPFC not only instigated anxiety in mice but also nullified the anxiolytic effects of metformin. Brain slice recordings revealed that GABAergic excitation and the resulting inhibitory inputs to mPFC pyramidal neurons were selectively diminished in stressed mice. This reduction led to an excitation-inhibition imbalance, which was effectively reversed by metformin treatment or AMPK overexpression. Moreover, the genetic deletion of AMPK in the mPFC resulted in a similar defect in GABAergic inhibitory transmission and a consequent hypo-inhibition of mPFC pyramidal neurons. We also generated a mouse model with AMPK knockout specific to GABAergic neurons. The anxiety-like behaviors in this transgenic mouse demonstrated the unique role of AMPK in the GABAergic system in relation to anxiety. Therefore, our findings suggest that the activation of AMPK in mPFC inhibitory neurons underlies the anxiolytic effects of metformin, highlighting the potential of this primary antidiabetic drug as a therapeutic option for treating anxiety disorders.

Neuroprotective Effects of Zerumbone on H2O2-Induced Oxidative Injury in Human Neuroblastoma SH-SY5Y Cells

Oxidative stress is recognized as one of the main reasons for cellular damage and neurodegenerative diseases. Zerumbone is one of the sesquiterpenoid compounds in the essential oil of Zingiber zerumbet Smith. Zerumbone exhibits various physiological activities, such as anticancer, antioxidant, and antibacterial effects. However, studies on the neuroprotective efficacy of zerumbone and the mechanism behind it are lacking. In this study, we explored the neuroprotective efficacy of zerumbone and its mechanism in hydrogen peroxide-treated human neuroblastoma SH-SY5Y cells. H2O2 treatment (400 μM) for 24 h enhanced the generation of intracellular reactive oxygen species (ROS) compared to untreated cells. By contrast, zerumbone treatment significantly suppressed the production of intracellular ROS. Zerumbone significantly inhibited H2O2-induced nitric oxide production and expression of inflammation-related genes. Moreover, zerumbone decreased H2O2-induced mitogen-activated protein kinase (MAPK) protein expression. Various hallmarks of apoptosis in H2O2-treated cells were suppressed in a dose-dependent manner through downregulation of the Bax/Bcl-2 expression ratio by zerumbone. Since activation of AMP-activated kinase (AMPK) is a promising therapeutic target for neurodegenerative diseases, we also investigated the mammalian target of rapamycin (mTOR) as part of the autophagy mechanism in H2O2-treated SH-SY5Y cells. In this study, zerumbone upregulated the expression of Sirtuin 1 (SIRT1) and p-AMPK (which were downregulated by the H2O2 treatment) and downregulated p-mTOR. Altogether, our results propose that inhibition of apoptosis and inflammation by autophagy activation plays an important neuroprotective role in H2O2-treated SH-SY5Y cells. Zerumbone may thus be a potent dietary agent that reduces the onset and progression, as well as prevents neurodegenerative diseases.

Punicalagin protects against impaired skeletal muscle function in high-fat-diet-induced obese mice by regulating TET2

The function of skeletal muscles can be markedly hampered by obesity. Ten-eleven translocation 2 (TET2) is an important therapeutic target for ameliorating skeletal muscle dysfunction. Our previous study revealed that punicalagin (PUN) regulated TET2 in obese mice; however, whether PUN can prevent obesity-induced skeletal muscle dysfunction by regulating TET2 remains unclear. In the present study, 40 male C57BL/6J mice were divided into four groups (n = 10 per group): the control (CON) group, the high-fat-diet (HFD, negative control) group, the resveratrol (positive control) group, and the PUN group. The ratio of gastrocnemius weight to body weight (0.0097 ± 0.0016 vs. 0.0080 ± 0.0011), the grip strength (120.04 g ± 11.10 vs. 98.89 g ± 2.79), and the muscle fiber count (314.56 per visual field ± 92.73 vs. 236.44 per visual field ± 50.58) in the PUN group were higher than those in the HFD group. Moreover, the levels of the TET2 protein, 5-hydroxymethylcytosine (5hmC), and 5-formylcytosine (5fC) in skeletal muscles were significantly lower in the HFD group than those in the CON group; these levels increased after PUN treatment. Compared with the HFD group, the phosphorylation level of AMP-activated protein kinase (AMPK) α in the PUN group was higher, which effectively enhanced the stability of the TET2 protein. Besides, the ratio of (succinic acid + fumaric acid)/α-ketoglutarate in the PUN group was lower than that in the HFD group (43.21 ± 12.42 vs. 99.19 ± 37.07), and a lower ratio led to a higher demethylase activity of TET2 in the PUN group than in the HFD group. This study highlights that PUN supplementation protects against obesity-induced impairment of the skeletal muscle function via regulating the protein stability of TET2 and the enzymatic activity of TET2 demethylation.

Dapagliflozin as an autophagic enhancer via LKB1/AMPK/SIRT1 pathway in ovariectomized/D-galactose Alzheimer's rat model

Autophagy and mitochondrial deficits are characteristics of early phase of Alzheimer's disease (AD). Sodium-glucose cotransporter-2 inhibitors have been nominated as a promising class against AD hallmarks. However, there are no available data yet to discuss the impact of gliflozins on autophagic pathways in AD. Peripherally, dapagliflozin's (DAPA) effect is mostly owed to autophagic signals. Thus, the goal of this study is to screen the power of DAPA centrally on LKB1/AMPK/SIRT1/mTOR signaling in the ovariectomized/D-galactose (OVX/D-Gal) rat model. Animals were arbitrarily distributed between 5 groups; the first group undergone sham operation, while remaining groups undergone OVX followed by D-Gal (150 mg/kg/day; i.p.) for 70 days. After 6 weeks, the third, fourth, and fifth groups received DAPA (1 mg/kg/day; p.o.); concomitantly with the AMPK inhibitor dorsomorphin (DORSO, 25 µg/rat, i.v.) in the fourth group and the SIRT1 inhibitor EX-527 (10 µg/rat, i.v.) in the fifth group. DAPA mitigated cognitive deficits of OVX/D-Gal rats, as mirrored in neurobehavioral task with hippocampal histopathological examination and immunohistochemical aggregates of p-Tau. The neuroprotective effect of DAPA was manifested by elevation of energy sensors; AMP/ATP ratio and LKB1/AMPK protein expressions along with autophagic markers; SIRT1, Beclin1, and LC3B expressions. Downstream the latter, DAPA boosted mTOR and mitochondrial function; TFAM, in contrary lessened BACE1. Herein, DORSO or EX-527 co-administration prohibited DAPA's actions where DORSO elucidated DAPA's direct effect on LKB1 while EX-527 mirrored its indirect effect on SIRT1. Therefore, DAPA implied its anti-AD effect, at least in part, via boosting hippocampal LKB1/AMPK/SIRT1/mTOR signaling in OVX/D-Gal rat model.

Intermittent hypoxia promotes the recovery of motor function in rats with cerebral ischemia by regulating mitochondrial function

Hypoxia preconditioning is neuroprotective, but the therapeutic effects of intermittent hypoxia were not fully considered. The present study investigated the neuroprotective effect and mechanism of intermittent hypoxia on motor function after cerebral ischemia and explored alternative clinical treatment options. In total, 36 8-week-old male Sprague-Dawley rats were subjected to 60 min of transient middle cerebral artery occlusion (tMCAO) and then randomly divided into a sham-operated group (SHAM), tMCAO-sedentary group (SED), and tMCAO-intermittent hypoxia group (IH). The intervention was performed 1 week after tMCAO and lasted 4 weeks. Rats in the IH group were placed in an animal hypoxic chamber (altitude 5000 m and oxygen concentration of 13%) for 4 h/day and 7 days/week, and rats in the SED group were placed in a normoxic environment for 4 weeks. Body weights, neurological deficit scores, cerebral infarction volume ratios, gait analyses, mitochondrial structure, adenosine triphosphate (ATP) content and AMO-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1α), and silencing regulatory protein 3 (Sirt3) expression in the peri-ischemic region brain tissues were detected during the intervention. Compared with the SED group, the body weight of the IH group gradually recovered, and the neurological deficit scores were significantly reduced (P < 0.05). The gait analysis results showed that the pressure of the affected paw and the maximum content area, swing speed, stride length, and other parameters were significantly restored (P < 0.05). The cerebral infarction volume ratio was significantly reduced (P < 0.01). Mitochondrial morphological structure damage in the peri-ischemic region brain tissues recovered, the number was significantly increased (P < 0.05), and the expression of AMPK, PGC-1α, and Sirt3 proteins (P < 0.05), and ATP content were significantly increased (P < 0.05). Intermittent hypoxia may activate the AMPK-PGC-1α-Sirt3 signaling pathway, promote mitochondrial biogenesis, repair mitochondrial ultrastructural damage, and improve mitochondrial function to reduce brain damage and promote motor function recovery in rats with cerebral ischemia.

The effect of chronic exposure to metformin in a new type-2 diabetic NONcNZO10/LtJ mouse model of stroke

BACKGROUND

Diabetes is an independent risk factor of stroke and previous studies have confirmed that diabetic patients and animals experience poorer clinical outcomes following stroke. In this study, we aim to determine the effect of chronic exposure of the first-line antidiabetic agent, metformin, to restore euglycemia and to impact brain cell death following stroke in a new type-2 diabetes, NONcNZO10/LtJ (RCS-10) mouse model of stroke.

METHODS

Male RCS-10 mice received a moderate (11%) fat diet post-weaning, at 4 weeks of age, and became diabetic by 12-14 weeks, thus resembling human maturity-onset diabetes. The mice received either metformin or vehicle for 4 weeks before undergoing a hypoxic/ischemic (HI) insult. Blood samples were collected pre-, post-treatment, and post HI for glucose and lipid measurements, and brains were analyzed for infarct size, glial activation, neuronal cell death, and metformin-mediated adenosine monophosphate-activated protein kinase (AMPK) signaling at 48 h post HI.

RESULTS

Pretreatment with metformin maintained euglycemia for 4 weeks but did not change body weight or lipid profile. Metformin treatment significantly enhanced the microglial Bfl-1 mRNA expression and showed a non-significant increase in GFAP mRNA, however, GFAP protein levels were reduced. Metformin treatment slightly increased neuronal NeuN and MAP-2 protein levels and significantly reduced overall mortality post HI but did not elicit any significant change in infarct size.

CONCLUSION

The study suggests that the prolonged effect of metformin-induced euglycemia promoted the microglial activation, reduced neuronal cell death, and improved the overall survival following stroke, without any change in infarct size.

Low-dose sodium-glucose cotransporter 2 inhibitor ameliorates ischemic brain injury in mice through pericyte protection without glucose-lowering effects

Antidiabetic sodium-glucose cotransporter 2 (SGLT2) inhibitors have attracted attention for their cardiorenal-protective properties beyond their glucose-lowering effect. However, their benefits in ischemic stroke remain controversial. Here we show the effects of luseogliflozin, a selective SGLT2 inhibitor, in acute ischemic stroke, using a permanent middle cerebral artery occlusion (pMCAO) model in non-diabetic mice. Pretreatment with low-dose luseogliflozin, which does not affect blood glucose levels, significantly attenuated infarct volume, blood-brain barrier disruption, and motor dysfunction after pMCAO. SGLT2 was expressed predominantly in brain pericytes and was upregulated in peri- and intra-infarct areas. Notably, luseogliflozin pretreatment reduced pericyte loss in ischemic areas. In cultured pericytes, luseogliflozin activated AMP-activated protein kinase α and increased mitochondrial transcription factor A expression and number of mitochondria, conferring resistance to oxygen-glucose deprivation. Collectively, pre-stroke inhibition of SGLT2 induces ischemic tolerance in brain pericytes independent of the glucose-lowering effect, contributing to the attenuation of ischemic brain injury.

Pre-treatment of non-diabetic mice with the SGLT2 inhibitor, luseogliflozin, reduces brain damage and neurological dysfunction following middle cerebral artery occlusion by acquiring ischemic tolerance in pericytes.

Poly (ADP-ribose) polymerase: An Overview of Mechanistic Approaches and Therapeutic Opportunities in the Management of Stroke

Stroke is one of the leading causes of morbidity and mortality accompanied by blood supply loss to a particular brain area. Several mechanistic approaches such as inhibition of poly (ADP-ribose) polymerase, therapies against tissue thrombosis, and neutrophils lead to stroke's therapeutic intervention. Evidence obtained with the poly (ADP-ribose) polymerase (PARP) inhibition and animals having a deficiency of PARP enzymes; represented the role of PARP in cerebral stroke, ischemia/reperfusion, and neurotrauma. PARP is a nuclear enzyme superfamily with various isoforms, each with different structural domains and functions, and out of all, PARP-1 is the best-characterized member. It has been shown to perform multiple physiological as well as pathological processes, including its role in inflammation, oxidative stress, apoptosis, and mitochondrial dysfunction. The enzyme interacts with NF-κB, p53, and other transcriptional factors to regulate survival and cell death and modulates multiple downstream signaling pathways. Clinical trials have also been conducted using PARP inhibitors for numerous disorders and have shown positive results. However, additional information is yet to be established for the therapeutic intervention of PARP inhibitors in stroke. These agents' utilization appears to be challenging due to their unknown potential long-term side effects. PARP activity increased during ischemia, but its inhibition provided significant neuroprotection. Despite the increased interest in PARP as a pharmacological modulator for novel therapeutic therapies, the current review focused on stroke and poly ADP-ribosylation.

Glutamate excitotoxicity: Potential therapeutic target for ischemic stroke

Glutamate-mediated excitotoxicity is an important mechanism leading to post ischemic stroke damage. After acute stroke, the sudden reduction in cerebral blood flow is most initially followed by ion transport protein dysfunction and disruption of ion homeostasis, which in turn leads to impaired glutamate release, reuptake, and excessive N-methyl-D-aspartate receptor (NMDAR) activation, promoting neuronal death. Despite extensive evidence from preclinical studies suggesting that excessive NMDAR stimulation during ischemic stroke is a central step in post-stroke damage, NMDAR blockers have failed to translate into clinical stroke treatment. Current treatment options for stroke are very limited, and there is therefore a great need to develop new targets for neuroprotective therapeutic agents in ischemic stroke to extend the therapeutic time window. In this review, we highlight recent findings on glutamate release, reuptake mechanisms, NMDAR and its downstream cellular signaling pathways in post-ischemic stroke damage, and review the pathological changes in each link to help develop viable new therapeutic targets. We then also summarize potential neuroprotective drugs and therapeutic approaches for these new targets in the treatment of ischemic stroke.

Acute Administration of Metformin Protects Against Neuronal Apoptosis Induced by Cerebral Ischemia-Reperfusion Injury via Regulation of the AMPK/CREB/BDNF Pathway

Metformin is a first-line anti-diabetic agent with a powerful hypoglycemic effect. Several studies have reported that metformin can improve the prognosis of stroke patients and that this effect is independent of its hypoglycemic effect; however, the specific mechanism remains unclear. In this research, we explored the effect and specific mechanism of metformin in cerebral ischemia-reperfusion (I/R) injury by constructing a transient middle cerebral artery occlusion model in vivo and a glucose and oxygen deprivation/reoxygenation (OGD/R) model in vitro. The results of the in vivo experiments showed that acute treatment with low-dose metformin (10 mg/kg) ameliorated cerebral edema, reduced the cerebral infarction volume, improved the neurological deficit score, and ameliorated neuronal apoptosis in the ischemic penumbra. Moreover, metformin up-regulated the brain-derived neurotrophic factor (BDNF) expression and increased phosphorylation levels of AMP-activated protein kinase (AMPK) and cAMP-response element binding protein (CREB) in the ischemia penumbra. Nevertheless, the above-mentioned effects of metformin were reversed by Compound C. The results of the in vitro experiments showed that low metformin concentrations (20 μM) could reduce apoptosis of human umbilical vein endothelial cells (HUVECs) under OGD/R conditions and promote cell proliferation. Moreover, metformin could further promote BDNF expression and release in HUVECs under OGD/R conditions via the AMPK/CREB pathway. The Transwell chamber assay showed that HUVECs treated with metformin could reduce apoptosis of SH-SY5Y cells under OGD/R conditions and this effect could be partially reversed by transfection of BDNF siRNA in HUVECs. In summary, our results suggest that metformin upregulates the level of BDNF in the cerebral ischemic penumbra via the AMPK/CREB pathway, thereby playing a protective effect in cerebral I/R injury.

AMP-activated protein kinase(AMPK) channel: A Global Bibliometric analysis From 2012 to 2021

In recent years, AMPK channel has gained considerable attention in a variety of research areas, and several academic journals have published articles on AMPK research. However, few attempts have been made to thoroughly assess the scientific output and current status systematically in this topic from a worldwide viewpoint. As a result, it is critical to adopt an appropriate visualization method to reveal the global status, future research trends, and hotspots in AMPK channel research. To investigate research hotspots/frontiers in certain domains, bibliometric analysis has been frequently utilized to determine the productivity of nations, institutions, authors, and the frequency of keywords. In this work, we used CiteSpace and VOSviewer to conduct a bibliometric analysis of AMPK channel studies from 2012 to 2021 in order to perform researchers with some directions for AMPK channel research.

Metformin Inhibits NLR Family Pyrin Domain Containing 3 (NLRP)-Relevant Neuroinflammation via an Adenosine-5′-Monophosphate-Activated Protein Kinase (AMPK)-Dependent Pathway to Alleviate Early Brain Injury After Subarachnoid Hemorrhage in Mice

Neuroinflammation plays a key role in the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Previous studies have shown that metformin exerts anti-inflammatory effects and promotes functional recovery in various central nervous system diseases. We designed this study to investigate the effects of metformin on EBI after SAH. Our results indicate that the use of metformin alleviates the brain edema, behavioral disorders, cell apoptosis, and neuronal injury caused by SAH. The SAH-induced NLRP3-associated inflammatory response and the activation of microglia are also suppressed by metformin. However, we found that the blockade of AMPK with compound C weakened the neuroprotective effects of metformin on EBI. Collectively, our findings indicate that metformin exerts its neuroprotective effects by inhibiting neuroinflammation in an AMPK-dependent manner, by modulating the production of NLRP3-associated proinflammatory factors and the activation of microglia.

Metformin Treatment Attenuates Brain Inflammation and Rescues PACAP/VIP Neuropeptide Alterations in Mice Fed a High-Fat Diet

High-fat diet (HFD)-induced comorbid cognitive and behavioural impairments are thought to be the result of persistent low-grade neuroinflammation. Metformin, a first-line medication for the treatment of type-2 diabetes, seems to ameliorate these comorbidities, but the underlying mechanism(s) are not clear. Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) are neuroprotective peptides endowed with anti-inflammatory properties. Alterations to the PACAP/VIP system could be pivotal during the development of HFD-induced neuroinflammation. To unveil the pathogenic mechanisms underlying HFD-induced neuroinflammation and assess metformin’s therapeutic activities, (1) we determined if HFD-induced proinflammatory activity was present in vulnerable brain regions associated with the development of comorbid behaviors, (2) investigated if the PACAP/VIP system is altered by HFD, and (3) assessed if metformin rescues such diet-induced neurochemical alterations. C57BL/6J male mice were divided into two groups to receive either standard chow (SC) or HFD for 16 weeks. A further HFD group received metformin (HFD + M) (300 mg/kg BW daily for 5 weeks) via oral gavage. Body weight, fasting glucose, and insulin levels were measured. After 16 weeks, the proinflammatory profile, glial activation markers, and changes within the PI3K/AKT intracellular pathway and the PACAP/VIP system were evaluated by real-time qPCR and/or Western blot in the hypothalamus, hippocampus, prefrontal cortex, and amygdala. Our data showed that HFD causes widespread low-grade neuroinflammation and gliosis, with regional-specific differences across brain regions. HFD also diminished phospho-AKT^(Ser473) expression and caused significant disruptions to the PACAP/VIP system. Treatment with metformin attenuated these neuroinflammatory signatures and reversed PI3K/AKT and PACAP/VIP alterations caused by HFD. Altogether, our findings demonstrate that metformin treatment rescues HFD-induced neuroinflammation in vulnerable brain regions, most likely by a mechanism involving the reinstatement of PACAP/VIP system homeostasis. Data also suggests that the PI3K/AKT pathway, at least in part, mediates some of metformin’s beneficial effects.

Icariin improves brain function decline in aging rats by enhancing neuronal autophagy through the AMPK/mTOR/ULK1 pathway

CONTEXT

Icariin (ICA) is the main active ingredient of Epimedium brevicornu Maxim (Berberidaceae), which is used in the immune, reproductive, neuroendocrine systems, and anti-aging.

OBJECTIVE

To evaluate the effect of ICA on natural aging rat.

MATERIALS AND METHODS

16-month-old Sprague-Dawley (SD) rats were randomly divided into aging, low and high-dose ICA groups (n = 8); 6-month-old rats were taken as the adult control (n = 8). Rats were fed regular feed (aging and adult control) or feed containing ICA (ICA 2 and 6 mg/kg group) for 4 months. HE and Nissl staining were used to assess pathological changes. Western blot was used to test the expression of autophagy (LC3B, p62, Atg5, Beclin1) and p-AMPK, p-mTOR and p-ULK1 (ser 757). Immunofluorescence was used to detect the co-localization of LC3 and neurons.

RESULTS

ICA improved neuronal degeneration associated with aging and increased the staining of Nissl bodies. Western blot showed that ICA up-regulated autophagy-related proteins LC3B (595%), Beclin1 (73.5%), p-AMPK (464%) protein (p < 0.05 vs. 20 M) in the cortex and hippocampus of aging rats, down-regulated the expression of p62 (56.9%), p-mTOR (53%) and p-ULK1 (ser 757) (65.4%) protein (p < 0.05 vs. 20 M). Immunofluorescence showed that the fluorescence intensity of LC3 decreased in the aging rat brain, but increased and mainly co-localized with neurons after ICA intervention.

CONCLUSIONS

Further research needs to verify the expression changes of AMPK/mTOR/ULK1 and the improvement effect of ICA in elderly. These results will further accelerate the applications of ICA and the treatment for senescence.

Novel treatments in epilepsy guided by genetic diagnosis

In recent years, precision medicine has emerged as a new paradigm for improved and more individualized patient care. Its key objective is to provide the right treatment, to the right patient at the right time, by basing medical decisions on individual characteristics, including specific genetic biomarkers. In order to realize this objective researchers and physicians must first identify the underlying genetic cause; over the last 10 years, advances in genetics have made this possible for several monogenic epilepsies. Through next generation techniques, a precise genetic aetiology is attainable in 30-50% of genetic epilepsies beginning in the paediatric age. While committed in such search for novel genes carrying disease-causing variants, progress in the study of experimental models of epilepsy has also provided a better understanding of the mechanisms underlying the condition. Such advances are already being translated into improving care, management and treatment of some patients. Identification of a precise genetic aetiology can already direct physicians to prescribe treatments correcting specific metabolic defects, avoid antiseizure medicines that might aggravate functional consequences of the disease-causing variant or select the drugs that counteract the underlying, genetically determined, functional disturbance. Personalized, tailored treatments should not just focus on how to stop seizures but possibly prevent their onset and cure the disorder, often consisting of seizures and its comorbidities including cognitive, motor and behaviour deficiencies. This review discusses the therapeutic implications following a specific genetic diagnosis and the correlation between genetic findings, pathophysiological mechanisms and tailored seizure treatment, emphasizing the impact on current clinical practice.

Effects of co-administration of metformin and evogliptin on cerebral infarct volume in the diabetic rat

Patients with diabetes suffer more severe ischemic stroke. A combination of metformin and dipeptidyl peptide-4 inhibitors is commonly prescribed to treat diabetes. Therefore, we aimed to determine if pretreatment with a combination of metformin and evogliptin, a dipeptidyl peptidase-4 inhibitor, could reduce cerebral infarct volume in rats with streptozotocin-induced diabetes. After confirming diabetes induction, the rats were treated with vehicle, evogliptin, metformin, or evogliptin/metformin combination for 30 days. Then, stroke was induced by transient middle cerebral artery occlusion (tMCAO). Infarct volume, oxidative stress, levels of methylglyoxal-modified protein, glucagon-like peptide-1 receptor (GLP-1R), AMPK, and Akt/PI3K pathway-related proteins, and post-stroke pancreatic islet cell volume were evaluated. Compared to vehicle, only the co-administration group had significantly reduced infarct volume from the effects of tMCAO; the regimen also improved glycemic control, whereas the individual treatments did not. Co-administration also significantly reduced methylglyoxal-modified protein level in the core of the brain cortex, and the expression of 4-HNE and 8-OHdG was reduced. Co-administration increased p-Akt levels in the ischemic core and mitigated the suppression of Bcl-2 expression. Plasma GLP-1 and dipeptidyl peptidase-4 levels and brain GLP-1R expression remained unaltered. In the pancreas, islet cell damage was reduced by co-administration. These results reveal that metformin and evogliptin co-administration ameliorates cerebral infarction associated with prolonged glycemic control and pancreatic beta cell sparing. Other potential protective mechanisms may be upregulation of insulin receptor signaling or reduction of methylglyoxal-induced neurotoxicity. The combination of metformin and evogliptin should be tested further for its potential against focal cerebral ischemia in diabetes patients.

Regulation of blood-brain barrier permeability by Salvinorin A via alleviating endoplasmic reticulum stress in brain endothelial cell after ischemia stroke

Inhibition of endoplasmic reticulum (ER) stress reduces blood-brain barrier (BBB) injury caused by ischemia/reperfusion (I/R), with indistinct mechanisms. Salvinorin A (SA) relieves I/R-induced BBB leakage; however, whether it is related to the suppression of ER stress is yet unclear. To address this question, we have used both a rat model of middle cerebral artery occlusion (MCAO) and human brain microvascular endothelial cells (HBMECs) with oxygen-glucose deprivation (OGD). SA was injected by tail vein at the terminal of ischemia; Norbinaltorphimine (NB), a kappa opioid antagonist, was administered 30 min prior to SA; 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, was injected intraperitoneally after the onset of ischemia; adenylate-activated protein kinase (AMPK)-specific small interfering RNAs (siRNAs) were transfected to HBMECs before OGD. The assessment was as follows: infarct volume, brain water gain, Evans blue leakage, and modified neurological severity score (mNSS) after MCAO; HBMECs apoptosis rate and permeability, ER stress-related protein, and reactive oxygen species (ROS) and calcium levels after OGD. The results showed that SA significantly reduced the BBB leakage in vivo; SA relieved the apoptotic rates and ER stress in HBMECs, protected the permeability of HBMECs, and reduced ROS and calcium ion level after OGD. Moreover, the SA function was blocked by NB in vivo and AMPK- siRNAs in vitro. We conclude that SA mitigated BBB damage and HBMEC injury after I/R and alleviated ER stress in endothelial cells via AMPK pathway.

Highlighting the protective or degenerative role of AMPK activators in dementia experimental models

AMP-activated protein kinase (AMPK) is a serine/threonine kinase and a driving or deterrent factor in the development of neurodegenerative diseases and dementia. AMPK affects intracellular proteins like the mammalian target of rapamycin (mTOR). Peroxisome proliferator-activated receptor-γ coactivator 1-α (among others) contributes to a wide range of intracellular activities based on its downstream molecules such as energy balancing (ATP synthesis), extracellular inflammation, cell growth, and neuronal cell death (such as apoptosis, necrosis, and necroptosis). Several studies have looked at the dual role of AMPK in neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington disease (HD) but the exact effect of this enzyme on dementia, stroke, and motor neuron dysfunction disorders has not been elucidated yet. In this article, we review current research on the effects of AMPK on the brain to give an overview of the relationship. More specifically, we review the neuroprotective or neurodegenerative effects of AMPK or AMPK activators like metformin, resveratrol, and 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside on neurological diseases and dementia, which exert through the intracellular molecules involved in neuronal survival or death.

Metformin Protects against NMDA-Induced Retinal Injury through the MEK/ERK Signaling Pathway in Rats

Metformin, an anti-hyperglycemic drug of the biguanide class, exerts positive effects in several non-diabetes-related diseases. In this study, we aimed to examine the protective effects of metformin against N-methyl-D-aspartic acid (NMDA)-induced excitotoxic retinal damage in rats and determine the mechanisms of its protective effects. Male Sprague–Dawley rats (7 to 9 weeks old) were used in this study. Following intravitreal injection of NMDA (200 nmol/eye), the number of neuronal cells in the ganglion cell layer and parvalbumin-positive amacrine cells decreased, whereas the number of CD45-positive leukocytes and Iba1-positive microglia increased. Metformin attenuated these NMDA-induced responses. The neuroprotective effect of metformin was abolished by compound C, an inhibitor of AMP-activated protein kinase (AMPK). The AMPK activator, AICAR, exerted a neuroprotective effect in NMDA-induced retinal injury. The MEK1/2 inhibitor, U0126, reduced the neuroprotective effect of metformin. These results suggest that metformin protects against NMDA-induced retinal neurotoxicity through activation of the AMPK and MEK/extracellular signal-regulated kinase (ERK) signaling pathways. This neuroprotective effect could be partially attributable to the inhibitory effects on inflammatory responses.

Metformin prevents stroke damage in non-diabetic female mice with chronic kidney disease

Chronic kidney disease (CKD) worsens ischemic stroke severity in both patients and animals. In mice, these poorer functional outcomes are associated with decreased brain activity of AMP-activated protein kinase (AMPK), a molecule that recently emerged as a potential therapeutic target for ischemic stroke. The antidiabetic drug metformin, a well-known activator of AMPK, has improved stroke outcomes in diabetic patients with normal renal function. We investigated whether chronic metformin pre-conditioning can rescue AMPK activity and prevent stroke damage in non-diabetic mice with CKD. Eight-week-old female C57BL/6J mice were assigned to CKD or SHAM groups. CKD was induced through right kidney cortical electrocautery, followed by left total nephrectomy. Mice were then allocated to receive metformin (200 mg/kg/day) or vehicle for 5 weeks until stroke induction by transient middle cerebral artery occlusion (tMCAO). The infarct volumes were lower in CKD mice exposed to metformin than in vehicle-treated CKD mice 24 h after tMCAO. Metformin pre-conditioning of CKD mice improved their neurological score, grip strength, and prehensile abilities. It also enhanced AMPK activation, reduced apoptosis, increased neuron survival and decreased microglia/macrophage M1 signature gene expression as well as CKD-induced activation of the canonical NF-κB pathway in the ischemic lesions of CKD mice.

Repurposing metformin to treat age-related neurodegenerative disorders and ischemic stroke

Aging is a risk factor for major central nervous system (CNS) disorders. More specifically, aging can be inked to neurodegenerative diseases (NDs) because of its deteriorating impact on neurovascular unit (NVU). Metformin, a first line FDA-approved anti-diabetic drug, has gained increasing interest among researchers for its role in improving aging-related neurodegenerative disorders. Additionally, numerous studies have illustrated metformin's role in ischemic stroke, a cerebrovascular disorder in which the NVU becomes dysfunctional which can lead to permanent life-threatening disabilities. Considering metformin's beneficial preclinical actions on various disorders, and the drug's role in alleviating severity of these conditions through involvement in commonly characterized cellular pathways, we discuss the potential of metformin as a suitable drug candidate for repurposing in CNS disorders.

Metformin protects against myocardial ischemia-reperfusion injury and cell pyroptosis via AMPK/NLRP3 inflammasome pathway

Ischemia/reperfusion (I/R) injury is a life-threatening vascular emergency following myocardial infarction. Our previous study showed cardioprotective effects of metformin against myocardial I/R injury. In this study, we further examined the involvement of AMPK mediated activation of NLRP3 inflammasome in this cardioprotective effect of metformin. Myocardial I/R injury was simulated in a rat heart Langendorff model and neonatal rat ventricle myocytes (NRVMs) were subjected to hypoxi/reoxygenation (H/R) to establish an in vitro model. Outcome measures included myocardial infarct size, hemodynamic monitoring, myocardial tissue injury, myocardial apoptotic index and the inflammatory response. myocardial infarct size and cardiac enzyme activities. First, we found that metformin postconditioning can not only significantly alleviated myocardial infarct size, attenuated cell apoptosis, and inhibited myocardial fibrosis. Furthermore, metformin activated phosphorylated AMPK, decreased pro-inflammatory cytokines, TNF-α, IL-6 and IL-1β, and decreased NLRP3 inflammasome activation. In isolated NRVMs metformin increased cellular viability, decreased LDH activity and inhibited cellular apoptosis and inflammation. Importantly, inhibition of AMPK phosphorylation by Compound C (CC) resulted in decreased survival of cardiomyocytes mainly by inducing the release of inflammatory cytokines and increasing NLRP3 inflammasome activation. Finally, in vitro studies revealed that the NLRP3 activator nigericin abolished the anti-inflammatory effects of metformin in NRVMs, but it had little effect on AMPK phosphorylation. Collectively, our study confirmed that metformin exerts cardioprotective effects by regulating myocardial I/R injury-induced inflammatory response, which was largely dependent on the enhancement of the AMPK pathway, thereby suppressing NLRP3 inflammasome activation.

Comparison of Effects of Metformin, Phenformin, and Inhibitors of Mitochondrial Complex I on Mitochondrial Permeability Transition and Ischemic Brain Injury

Damage to cerebral mitochondria, particularly opening of mitochondrial permeability transition pore (MPTP), is a key mechanism of ischemic brain injury, therefore, modulation of MPTP may be a potential target for a neuroprotective strategy in ischemic brain pathologies. The aim of this study was to investigate whether biguanides-metformin and phenformin as well as other inhibitors of Complex I of the mitochondrial electron transfer system may protect against ischemia-induced cell death in brain slice cultures by suppressing MPTP, and whether the effects of these inhibitors depend on the age of animals. Experiments were performed on brain slice cultures prepared from 5-7-day (premature) and 2-3-month old (adult) rat brains. In premature brain slice cultures, simulated ischemia (hypoxia plus deoxyglucose) induced necrosis whereas in adult rat brain slice cultures necrosis was induced by hypoxia alone and was suppressed by deoxyglucose. Phenformin prevented necrosis induced by simulated ischemia in premature and hypoxia-induced-in adult brain slices, whereas metformin was protective in adult brain slices cultures. In premature brain slices, necrosis was also prevented by Complex I inhibitors rotenone and amobarbital and by MPTP inhibitor cyclosporine A. The latter two inhibitors were protective in adult brain slices as well. Short-term exposure of cultured neurons to phenformin, metformin and rotenone prevented ionomycin-induced MPTP opening in intact cells. The data suggest that, depending on the age, phenformin and metformin may protect the brain against ischemic damage possibly by suppressing MPTP via inhibition of mitochondrial Complex I.

The Modulatory Effect of Metformin on Ethanol-Induced Anxiety, Redox Imbalance, and Extracellular Matrix Levels in the Brains of Wistar Rats

The study investigated the potential neuroprotective effects of metformin (MET) on alcohol-induced neurotoxicity in adult Wistar rats. The animals were randomized in four groups (n = 10): control, alcohol (ALC), ALC + MET, and MET. ALC (2 g/kg b.w.) and MET (200 mg/kg b.w.) were orally administered for 21 days, once daily. For the ALC + MET group, MET was administered 2 h after ALC treatment. On day 22, the open field test (OFT) and elevated plus maze (EPM) were performed. MET improved global activity and increased the time spent in unprotected open arms, decreased oxidative stress, both in the frontal lobe and in the hippocampus, and increased neuroglobin expression in the frontal cortex. Histopathologically, an increased neurosecretory activity in the frontal cortex in the ALC + MET group was noticed. Thus, our findings suggest that metformin has antioxidant and anxiolytic effects and may partially reverse the neurotoxic effects induced by ethanol.

Bioactive peptides attenuate cardiac apoptosis in spontaneously hypertensive rat hearts through activation of autophagy and mitochondrial biogenesis pathway

Alcalase potato protein hydrolysate (APPH) might have a very important role in therapeutic effects. This study aims to examine the beneficial effects of bioactive peptides (DIKTNKPVIF [DI] and IF) from APPH supplement in the regulation of cardiac apoptosis, autophagy, and mitochondrial biogenesis pathway in spontaneously hypertensive rats (SHR). We have investigated ejection fraction, fractional shortening, Tunel assay, apoptosis, autophagy, and mitochondrial biogenesis pathway marker expression to show the efficacy of bioactive peptides in an SHR model. Bioactive peptides significantly upregulate ejection fraction and fractional shortening in SHR rats. SHR rats exhibited higher protein expression of apoptotic markers such as BAD, cytochrome c, and caspase 3. Finally, the bioactive peptides upregulate survival proteins (p-AKT/p-PI3K), autophagy (Beclin1/LC3B), and mitochondrial biogenesis (p-AMPKα/SIRT1/PGC1α/p-Foxo3a/Nrf2/CREB) marker expressions compared with the SHR groups. In summary, the bioactive peptides protect the heart tissues through the activation of autophagy and mitochondrial biogenesis pathway and thereby attenuate cardiac apoptosis in a spontaneously hypertensive rat model.

Gonadal hormones and stroke risk: PCOS as a case study

It is well known that stroke incidence and outcome is sex-dependent and influenced by age and gonadal hormones. In post-menopausal and/or aged females, declining estrogen levels increases stroke risk. However, women who experience early menopause also have an increase in stroke risk. This suggests that, regardless of age, gonadal hormones regulate stroke risk and severity. This review discusses prolonged gonadal hormone dysfunction in a common female endocrine disorder known as polycystic ovarian syndrome, PCOS, and the associated increased risk of stroke due to resulting hyperandrogenism and metabolic comorbidities.

Metformin as a Potential Neuroprotective Agent in Prodromal Parkinson's Disease-Viewpoint

To date, there are no clinically effective neuroprotective or disease-modifying treatments that can halt Parkinson's disease (PD) progression. The current clinical approach focuses on symptomatic management. This failure may relate to the complex neurobiology underpinning the development of PD and the absence of true translational animal models. In addition, clinical diagnosis of PD relies on presentation of motor symptoms which occur when the neuropathology is already established. These multiple factors could contribute to the unsuccessful development of neuroprotective treatments for PD. Prodromal symptoms develop years prior to formal diagnosis and may provide an excellent tool for early diagnosis and better trial design. Patients with idiopathic rapid eye movement behavior disorder (iRBD) have the highest risk of developing PD and could represent an excellent group to include in neuroprotective trials for PD. In addition, repurposing drugs with excellent safety profiles is an appealing strategy to accelerate drug discovery. The anti-diabetic drug metformin has been shown to target diverse cellular pathways implicated in PD progression. Multiple studies have, additionally, observed the benefits of metformin to counteract other age-related diseases. The purpose of this viewpoint is to discuss metformin's neuroprotective potential by outlining relevant mechanisms of action and the selection of iRBD patients for future clinical trials in PD.

Investigation of the effects of dichlorvos poisoning on AMPK signaling pathway in chicken brain tissues

Dichlorvos is a common crop insecticide widely used by people which causes extensive and serious environmental pollution. However, it has been shown that organophosphorus poisoning causes energy metabolism and neural disorders. The overall purpose of this study was to investigate the damage to brain tissue and the changes in AMPK signaling pathway-related gene expression after dichlorvos poisoning in chickens. White-feathered broiler chickens, as the research subjects of this experiment, were divided into three groups: control group, low-dose group (77.5% dichlorvos at 1.13 mg/kg dose) and high-dose group (77.5% dichlorvos at 10.2 mg/kg dose). Clinical symptoms were observed after modeling, and an integrative analysis was conducted using HE staining microscopy, immune-histochemical microscopy, electron microscopy and PCR arrays. The results showed that the high-dose group had more obvious dyspnea, salivation, convulsion and other neurological phenomena. Pathological sections showed that nuclear disintegration of neurons was most obvious in the low-dose group, and apoptosis of brain cells was most obvious in the high-dose group, and the mitochondrial structure was destroyed in the two poisoned group, i.e. low-dose group and high-dose group. PCR arrays showed that AMPK signaling pathway was inhibited and the expressions of genes involved in energy metabolism (ACACA and PRKAA1) were significantly changed. Furthermore, genes associated with protein synthesis (EIF4EBP1) were significantly upregulated. FASN and HMGCR expressions were significantly increased. There were significant changes in the expressions of cell cycle-related genes (STK11, TP53 and FOXO3). Organophosphate poisoning can cause a lot of nuclear disintegration of brain neurons, increases cell apoptosis, disrupts the energy metabolism of mitochondrial structure, and inhibits the AMPK signaling pathway. These results provide a certain idea and basis for studying the mechanism of AMPK signaling after organophosphorus poisoning and provide a research basis for the prevention and treatment of organophosphorus poisoning.

The Anti-Diabetic Drug Metformin Rescues Aberrant Mitochondrial Activity and Restrains Oxidative Stress in a Female Mouse Model of Rett Syndrome

Metformin is the first-line therapy for diabetes, even in children, and a promising attractive candidate for drug repurposing. Mitochondria are emerging as crucial targets of metformin action both in the periphery and in the brain. The present study evaluated whether treatment with metformin may rescue brain mitochondrial alterations and contrast the increased oxidative stress in a validated mouse model of Rett syndrome (RTT), a rare neurologic disorder of monogenic origin characterized by severe behavioral and physiological symptoms. No cure for RTT is available. In fully symptomatic RTT mice (12 months old MeCP2-308 heterozygous female mice), systemic treatment with metformin (100 mg/kg ip for 10 days) normalized the reduced mitochondrial ATP production and ATP levels in the whole-brain, reduced brain oxidative damage, and rescued the increased production of reactive oxidizing species in blood. A 10-day long treatment with metformin also boosted pathways related to mitochondrial biogenesis and antioxidant defense in the brain of metformin-treated RTT mice. This treatment regimen did not improve general health status and motor dysfunction in RTT mice at an advanced stage of the disease. Present results provide evidence that systemic treatment with metformin may represent a novel, repurposable therapeutic strategy for RTT.

Antidiabetic Drug Metformin Ameliorates Depressive-Like Behavior in Mice with Chronic Restraint Stress via Activation of AMP-Activated Protein Kinase

Depression is one of the most prevalent neuropsychiatric disorders in modern society. However, traditional drugs, such as monoaminergic agents, have defect showing lag response requiring several weeks to months. Additionally, these drugs have limited efficacy and high resistance rates in patients with depression. Thus, there is an urgent need to develop novel drugs or approaches for the treatment of depression. Here, using biochemical, pharmacological, genetic and behavioral methods, we demonstrate that metformin imparts a fast-acting antidepressant-like effect in naïve mice as well as stressed mice subjected to chronic restraint stress model. Moreover, inhibition of AMP-activated protein kinase (AMPK) activity by compound C or knock down of hippocampal AMPKα occluded the antidepressant-like effect induced by metformin. Our results suggest that metformin may be a viable therapeutic drug for the treatment of stress-induced depression via activation of AMPK.

Metformin and cognition from the perspectives of sex, age, and disease

Metformin is the safest and the most widely prescribed first-line therapy for managing hyperglycemia due to different underlying causes, primarily type 2 diabetes mellitus. In addition to its euglycemic properties, metformin has stimulated a wave of clinical trials to investigate benefits on aging-related diseases and longevity. Such an impact on the lifespan extension would undoubtedly expand the therapeutic utility of metformin regardless of glycemic status. However, there is a scarcity of studies evaluating whether metformin has differential cognitive effects across age, sex, glycemic status, metformin dose, and duration of metformin treatment and associated pathological conditions. By scrutinizing the available literature on animal and human studies for metformin and brain function, we expect to shed light on the potential impact of metformin on cognition across age, sex, and pathological conditions. This review aims to provide readers with a broader insight of (a) how metformin differentially affects cognition and (b) why there is a need for more translational and clinical studies examining multifactorial interactions. The outcomes of such comprehensive studies will streamline precision medicine practices, avoiding "fit for all" approach, and optimizing metformin use for longevity benefit irrespective of hyperglycemia.

Involvement of AMP-activated protein kinase in neuroinflammation and neurodegeneration in the adult and developing brain

Microglial activation followed by neuroinflammation is a defense mechanism of the brain to eliminate harmful endogenous and exogenous materials including pathogens and damaged tissues, while excessive or chronic neuroinflammation may cause or exacerbate neurodegeneration observed in brain injuries and neurodegenerative diseases. Depending on conditions/environments during activation, microglia acquire distinct phenotypes, such as pro-inflammatory, anti-inflammatory, and disease-associated phenotypes, and show their ability to phagocytose various objects and produce pro-and anti-inflammatory mediators. Prevention of excessive inflammation by regulating the microglia's pro/anti-inflammatory balance is important for alleviating progression of brain injuries and diseases. Among many factors involved in the regulation of microglial phenotypes, cellular energy status plays an important role. Adenosine monophosphate-activated protein kinase (AMPK), which serves as a master sensor and regulator of energy balance, is considered a candidate molecule. Accumulating evidence from adult rodent studies indicates that AMPK activation promotes anti-inflammatory responses in microglia exposed to danger signals or various stressors mainly through inhibition of the nuclear factor κB (NF-κB) signaling and activation of the nuclear factor erythroid-2-related factor-2 (Nrf2) pathway. However, AMPK activation in neurons exposed to stressors/insults may exacerbate neuronal damage if AMPK activation is excessive or prolonged. While AMPK affects microglial activation states and neuronal cell survival rates in both the adult and the developing brain, studies in the developing brain are still scarce, even though activated AMPK is highly expressed especially in the neonatal brain. More in depth studies in the developing brain are important, because neuroinflammation/neurodegeneration occurred during development can result in long-lasting brain damage.

Lafora disease - from pathogenesis to treatment strategies

Lafora disease is a severe, autosomal recessive, progressive myoclonus epilepsy. The disease usually manifests in previously healthy adolescents, and death commonly occurs within 10 years of symptom onset. Lafora disease is caused by loss-of-function mutations in EPM2A or NHLRC1, which encode laforin and malin, respectively. The absence of either protein results in poorly branched, hyperphosphorylated glycogen, which precipitates, aggregates and accumulates into Lafora bodies. Evidence from Lafora disease genetic mouse models indicates that these intracellular inclusions are a principal driver of neurodegeneration and neurological disease. The integration of current knowledge on the function of laforin-malin as an interacting complex suggests that laforin recruits malin to parts of glycogen molecules where overly long glucose chains are forming, so as to counteract further chain extension. In the absence of either laforin or malin function, long glucose chains in specific glycogen molecules extrude water, form double helices and drive precipitation of those molecules, which over time accumulate into Lafora bodies. In this article, we review the genetic, clinical, pathological and molecular aspects of Lafora disease. We also discuss traditional antiseizure treatments for this condition, as well as exciting therapeutic advances based on the downregulation of brain glycogen synthesis and disease gene replacement.

Treatment with metformin in twelve patients with Lafora disease

Background

Lafora disease (LD) is a rare, lethal, progressive myoclonus epilepsy for which no targeted therapy is currently available. Studies on a mouse model of LD showed a good response to metformin, a drug with a well known neuroprotective effect. For this reason, in 2016, the European Medicines Agency granted orphan designation to metformin for the treatment of LD. However, no clinical data is available thus far.

Methods

We retrospectively collected data on LD patients treated with metformin referred to three Italian epilepsy centres.

Results

Twelve patients with genetically confirmed LD (6 EPM2A, 6 NHLRC1) at middle/late stages of disease were treated with add-on metformin for a mean period of 18 months (range: 6–36). Metformin was titrated to a mean maintenance dose of 1167 mg/day (range: 500–2000 mg). In four patients dosing was limited by gastrointestinal side-effects. No serious adverse events occurred. Three patients had a clinical response, which was temporary in two, characterized by a reduction of seizure frequency and global clinical improvement.

Conclusions

Metformin was overall safe in our small cohort of LD patients. Even though the clinical outcome was poor, this may be related to the advanced stage of disease in our cases and we cannot exclude a role of metformin in slowing down LD progression. Therefore, on the grounds of the preclinical data, we believe that treatment with metformin may be attempted as early as possible in the course of LD.

The beneficial roles of metformin on the brain with cerebral ischaemia/reperfusion injury

Cerebral ischaemia/reperfusion (I/R) injury is the transient loss, followed by rapid return, of blood flow to the brain. This condition is often caused by strokes and heart attacks. The underlying mechanisms resulting in brain damage during cerebral I/R injury include mitochondrial dysregulation, increased oxidative stress/reactive oxygen species, blood-brain-barrier breakdown, inflammation of the brain, and increased neuronal apoptosis. Metformin is the first-line antidiabetic drug which has recently been shown to be capable of acting through the aforementioned pathways to improve recovery following cerebral I/R injury. However, some studies have suggested that metformin therapy may have no effect or even worsen recovery following cerebral I/R injury. The present review will compile and examine the available in vivo, in vitro, and clinical data concerning the neuroprotective effects of metformin following cerebral I/R injury. Any contradictory evidence will also be assessed and presented to determine the actual effectiveness of metformin treatment in stroke recovery.

Identifying New AMP-Activated Protein Kinase Inhibitors That Protect against Ischemic Brain Injury

We recently reported that AMP-activated protein kinase (AMPK) contributes to zinc-induced neuronal death by inducing Bim, a pro-apoptotic Bcl-2 homology domain 3-only protein, in a liver kinase B1 (LKB1)-dependent manner. Current data suggest AMPK plays key roles in excitotoxicity and ischemic brain injury, with zinc neurotoxicity representing at least one mechanism of ischemic neuronal death. Inhibition of AMPK could be a viable therapeutic strategy to prevent ischemic brain injury following stroke. This prompted our search for novel inhibitors of AMPK activity and zinc-induced neuronal death using cultured mouse cortex and a rat model of brain injury after middle cerebral artery occlusion (MCAO). In structure-based virtual screening, 118 compounds were predicted to bind the active site of AMPK α2, and 40 showed in vitro AMPK α2 inhibitory activity comparable to compound C (a well-known, potent AMPK inhibitor). In mouse cortical neuronal cultures, 7 of 40 compound reduced zinc-induced neuronal death at levels comparable to compound C. Ultimately, only agents 2G11 and 1H10 significantly attenuated various types of neuronal death, including oxidative stress, excitotoxicity, and apoptosis. When administered as intracerebroventricular injections prior to permanent MCAO in rats, 2G11 and 1H10 reduced brain infarct volumes, whereas compound C did not. Therefore, these novel AMPK inhibitors could be drug development candidates to treat stroke.

Sestrins at the Interface of ROS Control and Autophagy Regulation in Health and Disease

Reactive oxygen species (ROS) and autophagy are two highly complex and interrelated components of cell physiopathology, but our understanding of their integration and their contribution to cell homeostasis and disease is still limited. Sestrins (SESNs) belong to a family of highly conserved stress-inducible proteins that orchestrate antioxidant and autophagy-regulating functions protecting cells from various noxious stimuli, including DNA damage, oxidative stress, hypoxia, and metabolic stress. They are also relevant modulators of metabolism as positive regulators of the key energy sensor AMP-dependent protein kinase (AMPK) and inhibitors of mammalian target of rapamycin complex 1 (mTORC1). Since perturbations in these pathways are central to multiple disorders, SESNs might constitute potential novel therapeutic targets of broad interest. In this review, we discuss the current understanding of regulatory and effector networks of SESNs, highlighting their significance as potential biomarkers and therapeutic targets for different diseases, such as aging-related diseases, metabolic disorders, neurodegenerative diseases, and cancer.

Rescue of Retinal Degeneration in rd1 Mice by Intravitreally Injected Metformin

Retinitis pigmentosa (RP) is a progressive hereditary retinal degenerative disease in which photoreceptor cells undergo degeneration and apoptosis, eventually resulting in irreversible loss of visual function. Currently, no effective treatment exists for this disease. Neuroprotection and inflammation suppression have been reported to delay the development of RP. Metformin is a well-tested drug used to treat type 2 diabetes, and it has been reported to exert beneficial effects in neurodegenerative diseases, such as Parkinson’s disease and Alzheimer’s disease. In the present study, we used immunofluorescence staining, electroretinogram (ERG) recordings and RNA-Seq to explore the effects of metformin on photoreceptor degeneration and its mechanism in rd1 mice. We found that metformin significantly reduced apoptosis in photoreceptors and delayed the degeneration of photoreceptors and rod bipolar cells in rd1 mice, thus markedly improving the visual function of rd1 mice at P14, P18, and P22 when tested with a light/dark transition test and ERG. Microglial activation in the outer nuclear layer (ONL) of the retina of rd1 mice was significantly suppressed by metformin. RNA-Seq showed that metformin markedly downregulated inflammatory genes and upregulated the expression of crystallin proteins, which have been demonstrated to be important neuroprotective molecules in the retina, revealing the therapeutic potential of metformin for RP treatment. αA-crystallin proteins were further confirmed to be involved in the neuroprotective effects of metformin in a Ca²⁺ ionophore-damaged 661W photoreceptor-like cell line. These data suggest that metformin exerts a protective effect in rd1 mice via both immunoregulatory and new neuroprotective mechanisms.

Metformin treatment improves the spatial memory of aged mice in an APOE genotype-dependent manner

Aging and apolipoprotein E4 (ApoE4) can increase the risk of cognitive impairment and neurodegenerative disorders, including Alzheimer's disease (AD), and patients with type 2 diabetes mellitus are highly susceptible to cognitive dysfunction. Recent research has indicated that metformin, a prescribed drug for type 2 diabetes, may affect cognitive function; however, findings regarding its efficacy are largely controversial. The current study reported that a 5-mo metformin administration (300 mg/kg/d) starting at 13 mo old improved the spatial memory of ApoE3-target replacement (TR) mice, not ApoE4-TR mice. It found that in aged ApoE3-TR mice, metformin treatment, at a molecular level, inhibited AMPK activity, increased insulin signaling, and activated mammalian target of rapamycin signaling, resulting in an enhanced expression of postsynaptic proteins; but the response of the neuronal AMPK activity and insulin signaling to metformin was blunt in aged ApoE4-TR mice. Meanwhile, metformin treatment also increased the phosphorylation of tau in both ApoE3-TR and ApoE4-TR mice, implying that metformin may have side effects in human. These findings suggest that metformin can improve the cognitive performance of aged mice in an APOE genotype-dependent manner, which provides empirical insights into the clinical value of metformin for ApoE4- and age-related AD prevention and treatment.-Zhang, J., Lin, Y., Dai, X., Fang, W., Wu, X., Chen, X. Metformin treatment improves the spatial memory of aged mice in an APOE genotype-dependent manner.