mTOR in Brain Physiology and Pathologies

Consecutive skeletal muscle PGC-1α overexpression: A double-edged sword for mitochondrial health in the aging brain

Mitochondrial dysfunction is a critical contributor to age-related functional declines in skeletal muscle and brain. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is essential for mitochondrial biogenesis and function during aging. While skeletal muscle-specific overexpression of PGC-1α is known to mimic exercise-induced benefits in young animals, its chronic systemic effects on aging tissues remain unclear. This study aimed to determine the lifelong impact of skeletal muscle-specific PGC-1α overexpression on mitochondrial health, oxidative stress, inflammation, and cognitive function in aged mice. We established three experimental groups: young wild-type mice (3-4 months old), aged wild-type mice (25-27 months old), and aged mice with skeletal muscle-specific PGC-1α overexpression (24-27 months old). In skeletal muscle, aging led to significant reductions in mitochondrial biogenesis markers, including PGC-1α, FNDC5, and mtDNA content. PGC-1α overexpression reversed this decline, elevating the expression of PGC-1α, SIRT1, LONP1, SDHA, CS, TFAM, eNOS, and mtDNA levels, suggesting preserved mitochondrial biogenesis. However, FNDC5 and SIRT3 were paradoxically suppressed, indicating potential compensatory feedback mechanisms. PGC-1α overexpression also enhanced anabolic signaling, as evidenced by increased phosphorylation of mTOR and S6, and reduced FOXO1 expression, favoring a muscle growth-promoting environment. Moreover, aging impaired mitochondrial dynamics by downregulating MFN1, MFN2, OPA1, FIS1, and PINK1. While PGC-1α overexpression did not restore fusion-related proteins, it further reduced fission-related protein and enhanced mitophagy proteins, as evidenced by increased PINK1 phosphorylation. In contrast, in the hippocampus, muscle-specific PGC-1α overexpression exacerbated age-associated mitochondrial biogenesis decline. Expression levels of key mitochondrial markers, including PGC-1α, SIRT1, CS, FNDC5, Cytochrome C, and TFAM, were further reduced compared to aged wild-type controls. mTOR phosphorylation was also significantly suppressed, whereas cognition-related proteins (BDNF, VEGF, eNOS) and performance in behavioral tests remained unchanged. Importantly, skeletal muscle-specific PGC-1α overexpression triggered pronounced oxidative stress and inflammatory responses in both skeletal muscle and the hippocampus. In skeletal muscle, elevated levels of protein carbonyls, IκB-α, NF-κB, TNF-α, SOD2, and NRF2 were observed, accompanied by a reduction in the DNA repair enzyme OGG1. Notably, similar patterns were detected in the hippocampus, including increased expression of protein carbonyls, iNOS, NF-κB, TNF-α, SOD2, GPX1, and NRF2, alongside decreased OGG1 levels. These findings suggest that the overexpression of PGC-1α in skeletal muscle may have contributed to systemic oxidative stress and inflammation. In conclusion, skeletal muscle-specific PGC-1α overexpression preserves mitochondrial biogenesis and enhances anabolic signaling in aging muscle but concurrently induces oxidative stress and inflammatory responses, which may adversely affect mitochondrial health in the brain. These results emphasize the complex role of the skeletal muscle PGC-1α during aging.

(-)-Epicatechin Rescues Memory Deficits by Activation of Autophagy in a Mouse Model of Tauopathies

In tauopathies, defects in autophagy-lysosomal protein degradation are thought to contribute to the abnormal accumulation of aggregated tau. Recent studies have shown that (-)-Epicatechin (Epi), a dietary flavonoid belonging to the flavan-3-ol subgroup, improves blood flow, modulates metabolic profiles, and prevents oxidative damage. However, less research has explored the effects of Epi on tauopathies. Here, we found that Epi rescued cognitive deficits in P301S tau transgenic mice, a model exhibiting characteristics of tauopathies like frontotemporal dementia and Alzheimer's disease, and attenuated tau pathology through autophagy activation. Proteomic and biochemical analyses revealed that P301S mice exhibit deficits in autophagosome formation via modulating mTOR, consequently inhibiting autophagy. Epi inhibited the mTOR signaling pathway to promote autophagosome formation, which is essential for the clearance of tau aggregation. By using chloroquine (CQ) to inhibit autophagy in vivo, we further confirmed that Epi induced tau degradation via the autophagy pathway. Lastly, Epi administration was also found to improve cognition by reversing spine decrease and neuron loss, as well as attenuating neuroinflammation. Our findings suggest that Epi promoted tau clearance by activating autophagy, indicating its potential as a promising therapeutic candidate for tauopathies.

Brain volumes in genetic syndromes associated with mTOR dysregulation: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES

Dysregulation of molecular pathways associated with mechanistic target of rapamycin (mTOR) and elevated rates of neurodevelopmental disorders are implicated in the genetic syndromes neurofibromatosis type 1 (NF1), tuberous sclerosis complex (TSC), fragile X syndrome (FXS), and Noonan syndrome (NS). Given shared molecular and clinical features, understanding convergent and divergent implications of these syndromes on brain development may offer unique insights into disease mechanisms. While an increasing number of studies have examined brain volumes in these syndromes, the effects of each syndrome on global and subcortical brain volumes are unclear. Therefore, the aim of the current study was to conduct a systematic review and meta-analysis to synthesize existing literature on volumetric brain changes across TSC, FXS, NF1, and NS. Study outcomes were the effect sizes of the genetic syndromes on whole brain, gray and white matter, and subcortical volumes compared to typically developing controls.

SUBJECTS/METHODS

We performed a series of meta-analyses synthesizing data from 23 studies in NF1, TSC, FXS, and NS (pooled N = 1556) reporting whole brain volume, gray and white matter volumes, and volumes of subcortical structures compared to controls.

RESULTS

Meta-analyses revealed significantly larger whole brain volume, gray and white matter volumes, and subcortical volumes in NF1 compared to controls. FXS was associated with increased whole brain, and gray and white matter volumes relative to controls, but effect sizes were smaller than those seen in NF1. In contrast, studies in NS indicated smaller whole brain and gray matter volumes, and reduced subcortical volumes compared to controls. For individuals with TSC, there were no significant differences in whole brain, gray matter, and white volumes compared to controls. Volumetric effect sizes were not moderated by age, sex, or full-scale IQ.

CONCLUSIONS

This meta-analysis revealed that dysregulation of mTOR signaling across pre- and post-natal periods of development can result in convergent and divergent consequences for brain volume among genetic syndromes. Further research employing advanced disease modeling techniques with human pluripotent stem cell-derived in vitro models is needed to further refine our understanding of between and within syndrome variability on early brain development and identify shared molecular mechanisms for the development of pharmaceutical interventions.

Progressive Alcohol-Related Brain Atrophy and White Matter Pathology Are Linked to Long-Term Inhibitory Effects on mTOR Signaling

BACKGROUND

Alcohol-related brain damage (ARBD) causes cognitive-behavioral impairments that can lead to dementia. White matter is a major target in ARBD. Additional research is needed to better understand the mechanisms of ARBD progression to advanced stages with permanent disability. Potential contributing factors include neuroinflammation and altered signaling through pathways that regulate cell survival, neuronal plasticity, myelin maintenance, and energy metabolism.

OBJECTIVES

This study characterizes the time course-related effects of chronic heavy ethanol feeding on white matter myelin protein expression, neuroinflammation, and molecules that mediate signaling through the mechanistic target of rapamycin (mTOR) pathways.

METHODS

Adult Long Evans rats (8-12/group) were fed with isocaloric liquid diets containing 0% (control) or 36% ethanol. Experimental endpoints spanned from 1 day to 8 weeks. The frontal lobes were used for histopathology and molecular and biochemical analyses.

RESULTS

Chronic ethanol feeding caused significant brain atrophy that was detected within 4 weeks and sustained over the course of the study. Early exposure time points, i.e., 2 weeks or less, were associated with global increases in the expression of non-myelinating, myelinating, and astrocyte markers, whereas at 6 or 8 weeks, white matter oligodendrocyte/myelin/glial protein expression was reduced. These effects were not associated with shifts in neuroinflammatory markers. Instead, the early stages of ARBD were accompanied by increases in several mTOR proteins and phosphoproteins, while later phases were marked by inhibition of downstream mTOR signaling through P70S6K.

CONCLUSIONS

Short-term versus long-term ethanol exposures differentially altered white matter glial protein expression and signaling through mTOR's downstream mediators that have known roles in myelin maintenance. These findings suggest that strategic targeting of mTOR signaling dysregulation may be critical for maintaining the functional integrity of white matter and ultimately preventing long-term ARBD-related cognitive impairment.

Novel 5-HT6R modulators as mTOR-dependent neuronal autophagy inductors

Autophagy is a natural process in which the cell degrades substances through the lysosomal pathway. One of the most studied mechanisms for regulating autophagy is the mTOR signaling pathway. Recent research has shown that the 5-HT6 receptor is linked to the mTOR pathway and can affect cognition in various neurodevelopmental models. Therefore, developing 5-HT6 receptor antagonists could improve cognition by inducing autophagy through the inhibition of the mTOR pathway. Our study reports two in-house-designed 5-HT6R antagonists, PUC-10 and its indazole analogue PUC-55, that induce mTOR-dependent autophagy. PUC-10, an indole-based 5-HT6 receptor antagonist with high binding affinity (Ki = 14.6 nM) and antagonist potency (IC50 = 32 nM), demonstrated more than 90% at 25 µM cellular viability and a high capacity to induce autophagy in the neuroblastoma SH-SY5Y cell line. Similarly, its indazole analogue, PUC-55 (Ki = 37.5 nM), exhibited high cellular viability and potent autophagy-inducing activity. Both compounds induced overexpression of the 5-HT6 receptor after 24 h of stimulation, contrasting with the effects observed with Rapamycin (100 nM), a well-known mTOR inhibitor. Additionally, the signaling pathway was characterized, showing that both PUC-10 and PUC-55 induce autophagy by inhibiting the mTOR pathway, suggesting their potential therapeutic applications for neurological disorders.

A Combined GLP-1/PPARa/CB1-Based Therapy to Restore the Central and Peripheral Metabolic Dysregulation Induced by a High-Fructose High-Fat Diet

Obesity remains a major epidemic in developed countries, with a limited range of effective pharmacological treatments. The pharmacological modulation of PPARα, CB1, or GLP-1 receptor activity has demonstrated beneficial effects, including anti-obesity actions. In this study, we evaluated a novel amide derivative of oleic acid and tyrosol (Oleyl hydroxytyrosol ether, OLHHA), a PPARα agonist, and CB1 antagonist, in combination with the GLP-1 agonist liraglutide (LIG), as an effective multitarget therapy to improve both the peripheral and central alterations in an animal model of diet-induced obesity. In rats, exposure to a high-fat high-fructose diet (HFHFD) induced weight gain and increased plasma triglycerides, LDL, and hepatic parameters. In the brain, the HFHFD provoked disruptions in the expression of proteins regulating food intake, the endocannabinoid system, the insulin pathway, and inflammation and resulted in altered tau expression and phosphorylation, thus indicating neurodegenerative changes. Based on our results, the administration of LIG or OLHHA alone was insufficient to completely reverse the alterations noticed at the peripheral and central levels. On the other hand, the combined treatment with both compounds (OLHHA+LIG) was the most effective in promoting body weight loss and ameliorating both the central and peripheral alterations induced by HFHFDs in rats. This multitarget therapeutic approach could represent a promising strategy for treating obesity and associated comorbidities.

Intracerebellar upregulation of Rheb(S16H) ameliorates motor dysfunction in mice with SCA2

Cerebellar ataxia (CA) is characterized by impaired balance and coordination due to the loss of cerebellar neurons caused by various factors, and effective treatments are currently lacking. Recently, we observed reduced expression of signaling molecules in the mammalian target of rapamycin complex 1 (mTORC1) pathway in the cerebellum of mice with spinocerebellar ataxia type 2 (SCA2) compared with wild-type mice. To investigate the effects of mTORC1 upregulation on motor dysfunction in mice with SCA2, we administered an intracerebellar injection of adeno-associated virus serotype 1 carrying a constitutively active form of Ras homolog enriched in brain [Rheb(S16H)], which is an upstream activator of mTORC1. This treatment led to increased Rheb(S16H) expression in calbindin-D28K-positive Purkinje cells and increased levels of neurotrophic factors. Additionally, Rheb(S16H) upregulation reduced abnormal behaviors and protected Purkinje cells in mice with SCA2. Our findings suggest that upregulating Rheb(S16H) in the cerebellum may be a promising therapeutic strategy for hereditary CA.

Engrams across diseases: Different pathologies - unifying mechanisms?

Memories are our reservoir of knowledge and thus, are crucial for guiding decisions and defining our self. The physical correlate of a memory in the brain is termed an engram and since decades helps researchers to elucidate the intricate nature of our imprinted experiences and knowledge. Given the importance that memories have for our lives, their impairment can present a tremendous burden. In this review we aim to discuss engram malfunctioning across diseases, covering dementia-associated pathologies, epilepsy, chronic pain and psychiatric disorders. Current neuroscientific tools allow to witness the emergence and fate of engram cells and enable their manipulation. We further suggest that specific mechanisms of mnemonic malfunction can be derived from engram cell readouts. While depicting the way diseases act on the mnemonic component - specifically, on the cellular engram - we emphasize a differentiation between forms of amnesia and hypermnesia. Finally, we highlight commonalities and distinctions of engram impairments on the cellular level across diseases independent of their pathogenic origins and discuss prospective therapeutic measures.

Paradoxical mTORC1-Dependent microRNA-mediated Translation Repression in the Nucleus Accumbens of Mice Consuming Alcohol Attenuates Glycolysis

mTORC1 promotes protein translation, learning and memory, and neuroadaptations that underlie alcohol use and abuse. We report that activation of mTORC1 in the nucleus accumbens (NAc) of mice consuming alcohol promotes the translation of microRNA (miR) machinery components and the upregulation of microRNAs (miRs) expression including miR-34a-5p. In parallel, we detected a paradoxical mTORC1-dependent repression of translation of transcripts including Aldolase A, an essential glycolytic enzyme. We found that miR-34a-5p in the NAc targets Aldolase A for translation repression and promotes alcohol intake. Our data further suggest that glycolysis is inhibited in the NAc manifesting in an mTORC1-dependent attenuation of L-lactate, the end product of glycolysis. Finally, we show that systemic administration of L-lactate attenuates mouse excessive alcohol intake. Our data suggest that alcohol promotes paradoxical actions of mTORC1 on translation and glycolysis which in turn drive excessive alcohol use.

RICTOR variants are associated with neurodevelopmental disorders

RICTOR is a key component of the mTORC2 signaling complex which is involved in the regulation of cell growth, proliferation and survival. RICTOR is highly expressed in neurons and is necessary for brain development. Here, we report eight unrelated patients presenting with intellectual disability and/or development delay and carrying variants in the RICTOR gene. The phenotypic presentation is diverse with associated features including growth failure, feeding difficulties, abnormal behavior, seizure, hypertonia, brain anomalies and various other congenital organ and skeletal malformations. All patients carried de novo or heterozygous variants inherited from one affected parent, including three missense variants, four loss-of-function variants and one 3 kb deletion encompassing RICTOR. The mTORC2 pathway was hyperactivated in a patient's fibroblasts carrying a missense variant, while the expression of RICTOR remained unchanged, indicating a gain-of-function mechanism. RNA sequencing on RICTOR knock-out mouse embryonic fibroblasts confirmed the potential role of RICTOR in neuronal cell development.

mTOR signaling pathway as a pathophysiologic mechanism in preclinical models of autism spectrum disorder

Autism spectrum disorder (ASD) is a highly prevalent multifactorial disorder characterized by social deficits and stereotypies. Despite extensive research efforts, the etiology of ASD remains poorly understood. However, studies using preclinical models have identified the mechanistic target of rapamycin kinase (mTOR) signaling pathway as a key player in ASD-related features. This review examines genetic and environmental models of ASD, focusing on their association with the mTOR pathway. We organize findings on alterations within this pathway, providing insights about the potential mechanisms involved in the onset and maintenance of ASD symptoms. Our analysis highlights the central role of mTOR hyperactivation in disrupting autophagic processes, neural organization, and neurotransmitter pathways, which collectively contribute to ASD phenotypes. The review also discusses the therapeutic potential of mTOR pathway inhibitors, such as rapamycin, in mitigating ASD characteristics. These insights underscore the importance of the mTOR pathway as a target for future research and therapeutic intervention in ASD. This review innovates by bringing the convergence of disrupted mTOR signaling in preclinical models and clinical data associated with ASD.

Lipid metabolism: Novel approaches for managing idiopathic epilepsy

Epilepsy is a common neurological condition characterized by abnormal neuronal activity, often leading to cellular damage and death. There is evidence to suggest that lipid imbalances resulting in cellular death play a key role in the development of epilepsy, including changes in triglycerides, cholesterol, sphingolipids, phospholipids, lipid droplets, and bile acids (BAs). Disrupted lipid metabolism acts as a crucial pathological mechanism in epilepsy, potentially linked to processes such as cellular ferroptosis, lipophagy, and immune modulation of gut microbiota (thus influencing the gut-brain axis). Understanding these mechanisms could open up new avenues for epilepsy treatment. This study investigates the association between disturbances in lipid metabolism and the onset of epilepsy.

Brain insulin resistance in Down syndrome: Involvement of PI3K-Akt/mTOR axis in early-onset of Alzheimer's disease and its potential as a therapeutic target

Down syndrome (DS) is the most common genetic cause of intellectual impairment, characterised by an extra copy of chromosome 21. After the age of 40, DS individuals are highly susceptible to accelerated ageing and the development of early-onset Alzheimer-like neuropathology. In the context of DS, the brain presents a spectrum of neuropathological mechanisms and metabolic anomalies. These include heightened desensitisation of brain insulin and insulin-like growth factor-1 (IGF-1) reactions, compromised mitochondrial functionality, escalated oxidative stress, reduced autophagy, and the accumulation of amyloid beta and tau phosphorylation. These multifaceted factors intertwine to shape the intricate landscape of DS-related brain pathology. Altered brain insulin signalling is linked to Alzheimer's disease (AD). This disruption may stem from anomalies in the extracellular aspect (insulin receptor) or the intracellular facet, involving the inhibition of insulin receptor substrate 1 (IRS1). Both domains contribute to the intricate mechanism underlying this dysregulation. The PI3K-Akt/mammalian target of the rapamycin (mTOR) axis is a crucial intracellular element of the insulin signalling pathway that connects numerous physiological processes in the cell cycle. In age-related neurodegenerative disorders like AD, aberrant modulation of the PI3K-Akt signalling cascade is a key factor contributing to their onset. Aberrant and sustained hyperactivation of the PI3K/Akt-mTOR axis in the DS brain is implicated in early symptoms of AD development. Targeting the PI3K-Akt/mTOR pathway may help delay the onset of early-onset AD in individuals with DS, offering a potential way to slow disease progression and enhance their quality of life.

Dysregulated mTOR networks in experimental sporadic Alzheimer's disease

Background

Beyond the signature amyloid-beta plaques and neurofibrillary tangles, Alzheimer's disease (AD) has been shown to exhibit dysregulated metabolic signaling through insulin and insulin-like growth factor (IGF) networks that crosstalk with the mechanistic target of rapamycin (mTOR). Its broad impact on brain structure and function suggests that mTOR is likely an important therapeutic target for AD.

Objective

This study characterizes temporal lobe (TL) mTOR signaling abnormalities in a rat model of sporadic AD neurodegeneration.

Methods

Long Evans rats were given intracerebroventricular injections of streptozotocin (ic-STZ) or saline (control), and 4 weeks later, they were administered neurobehavioral tests followed by terminal harvesting of the TLs for histopathological study and measurement of AD biomarkers, neuroinflammatory/oxidative stress markers, and total and phosphorylated insulin/IGF-1-Akt-mTOR pathway signaling molecules.

Results

Rats treated with ic-STZ exhibited significantly impaired performance on Rotarod (RR) and Morris Water Maze (MWM) tests, brain atrophy, TL and hippocampal neuronal and white matter degeneration, and elevated TL pTau, AβPP, Aβ, AChE, 4-HNE, and GAPDH and reduced ubiquitin, IL-2, IL-6, and IFN-γ immunoreactivities. In addition, ic-STZ reduced TL pY1135/1136-IGF-1R, Akt, PTEN, pS380-PTEN, pS2448-mTOR, p70S6K, pT412-p70S6K, p/T-pT412-p70S6K, p/T-Rictor, and p/T-Raptor.

Conclusion

Experimental ic-STZ-induced sporadic AD-type neurodegeneration with neurobehavioral dysfunctions associated with inhibition of mTOR signaling networks linked to energy metabolism, plasticity, and white matter integrity.

5-HT6 receptor neutral antagonists protect astrocytes: A lesson from 2-phenylpyrrole derivatives

The serotonin type 6 receptor (5-HT6R) displays a strong constitutive activity, suggesting it participates largely in the physiological and pathological processes controlled by the receptor. The active states of 5-HT6R engage particular signal transduction pathways that lead to different biological responses. In this study, we present the development of 5-HT6R neutral antagonists at Gs signaling built upon the 2-phenylpyrrole scaffold. Using molecular dynamics simulations, we outline the relationship between the exposure of the basic center of the molecules and their ability to target the agonist-activated state of the receptor. Our study identifies compound 30 as a potent and selective neutral antagonist at 5-HT6R-operated Gs signaling. Furthermore, we demonstrate the cytoprotective effects of 30 and structurally diverse 5-HT6R neutral antagonists at Gs signaling in C8-D1A cells and human astrocytes exposed to rotenone. This effect is not observed for 5-HT6R agonists or inverse agonists. In light of these findings, we propose compound 30 as a valuable molecular probe to study the biological effects associated with the agonist-activated state of 5-HT6R and provide insight into the glioprotective properties of 5-HT6R neutral antagonists at Gs signaling.

Role of FMRP in AKT/mTOR pathway-mediated hippocampal autophagy in fragile X syndrome

Fragile X syndrome (FXS) is caused by epigenetic silencing of the Fmr1 gene, leading to the deletion of the coding protein FMRP. FXS induces abnormal hippocampal autophagy and mTOR overactivation. However, it remains unclear whether FMRP regulates hippocampal autophagy through the AKT/mTOR pathway, which influences the neural behavior of FXS. Our study revealed that FMRP deficiency increased the protein levels of p-ULK-1 and p62 and decreased LC3II/LC3I level in Fmr1 knockout (KO) mice. The mouse hippocampal neuronal cell line HT22 with knockdown of Fmr1 by lentivirus showed that the protein levels of p-ULK-1 and p62 were increased, whereas LC3II/LC3I was unchanged. Further observations revealed that FMRP deficiency obstructed autophagic flow in HT22 cells. Therefore, FMRP deficiency inhibited autophagy in the mouse hippocampus and HT22 cells. Moreover, FMRP deficiency increased reactive oxygen species (ROS) level, decreased the co-localization between the mitochondrial outer membrane proteins TOM20 and LC3 in HT22 cells, and caused a decrease in the mitochondrial autophagy protein PINK1 in HT22 cells and Fmr1 KO mice, indicating that FMRP deficiency caused mitochondrial autophagy disorder in HT22 cells and Fmr1 KO mice. To explore the mechanism by which FMRP deficiency inhibits autophagy, we examined the AKT/mTOR signaling pathway in the hippocampus of Fmr1 KO mice, found that FMRP deficiency caused overactivation of the AKT/mTOR pathway. Rapamycin-mediated mTOR inhibition activated and enhanced mitochondrial autophagy. Finally, we examined whether rapamycin affected the neurobehavior of Fmr1 KO mice. The Fmr1 KO mice exhibited stereotypical behavior, impaired social ability, and learning and memory impairment, while rapamycin treatment improved behavioral disorders in Fmr1 KO mice. Thus, our study revealed the molecular mechanism by which FMRP regulates autophagy function, clarifying the role of hippocampal neuron mitochondrial autophagy in the pathogenesis of FXS, and providing novel insights into potential therapeutic targets of FXS.

The interplay between BDNF and PGC-1 alpha in maintaining brain health: role of exercise

Throughout our evolutionary history, physical activity has played a significant role in shaping our physiology. Advances in exercise science have further reinforced this concept by highlighting how exercise can change gene expression and molecular signaling to achieve various beneficial outcomes. Several studies have shown that exercise can alter neuronal functions to prevent neurodegenerative conditions like Parkinson's and Alzheimer's diseases. However, individual genotypes, phenotypes, and varying exercise protocols hinder the prescription of exercise as standard therapy. Moreover, exercise-induced molecular signaling targets can be double-edged swords, making it difficult to use exercise as the primary candidate for beneficial effects. For example, activating PGC-1 alpha and BDNF through exercise could produce several benefits in maintaining brain health, such as plasticity, neuronal survival, memory formation, cognition, and synaptic transmission. However, higher expression of BDNF might play a negative role in bipolar disorder. Therefore, further understanding of a specific mechanistic approach is required. This review focuses on how exercise-induced activation of these molecules could support brain health and discusses the potential underlying mechanisms of the effect of exercise-induced PGC-1 alpha and BDNF on brain health.

Boolean Modeling of Biological Network Applied to Protein-Protein Interaction Network of Autism Patients

Cellular molecules interact with one another in a structured manner, defining a regulatory network topology that describes cellular mechanisms. Genetic mutations alter these networks' pathways, generating complex disorders such as autism spectrum disorder (ASD). Boolean models have assisted in understanding biological system dynamics since Kauffman's 1969 discovery, and various analytical tools for regulatory networks have been developed. This study examined the protein-protein interaction network created in our previous publication of four ASD patients using the SPIDDOR R package, a Boolean model-based method. The aim is to examine how patients' genetic variations in INTS6L, USP9X, RSK4, FGF5, FLNA, SUMF1, and IDS affect mTOR and Wnt cell signaling convergence. The Boolean network analysis revealed abnormal activation levels of essential proteins such as β-catenin, MTORC1, RPS6, eIF4E, Cadherin, and SMAD. These proteins affect gene expression, translation, cell adhesion, shape, and migration. Patients 1 and 2 showed consistent patterns of increased β-catenin activity and decreased MTORC1, RPS6, and eIF4E activity. However, patient 2 had an independent decrease in Cadherin and SMAD activity due to the FLNA mutation. Patients 3 and 4 have an abnormal activation of the mTOR pathway, which includes the MTORC1, RPS6, and eIF4E genes. The shared mTOR pathway behavior in these patients is explained by a shared mutation in two closely related proteins (SUMF1 and IDS). Diverse activities in β-catenin, MTORC1, RPS6, eIF4E, Cadherin, and SMAD contributed to the reported phenotype in these individuals. Furthermore, it unveiled the potential therapeutic options that could be suggested to these individuals.

Signaling pathways in the treatment of Alzheimer's disease with acupuncture: a narrative review

BACKGROUND

To date, there is no effective treatment for Alzheimer's disease (AD), a progressive neurodegenerative disorder that is increasing in prevalence worldwide. The objective of this review was to summarize the core targets and signaling pathways involved in acupuncture treatment for AD.

METHODS

We reviewed numerous signaling pathways, including mammalian target of rapamycin (mTOR), phosphatidylinositol 3-kinase-protein kinase B (PI3 K/Akt), adenosine monophosphate-activated protein kinase (AMPK), mitogen-activated protein kinase (MAPK), nuclear factor (NF)-kB, p53, Wnt, nitric oxide (NO), Janus kinase / signal transducer and activator of transcription (JAK/ STAT), RhoA/ROCK (Rho-associated protein kinase) and Ca2+/ calmodulin-dependent protein kinase II (CaMKII) / cyclic adenosine monophosphate-response element-binding protein (CREB). The relevant data were obtained from PubMed, EMBASE, Web of Science, China National Knowledge Infrastructure (CNKI) and Wanfang databases.

RESULTS

In summary, the effects of acupuncture are mediated by multiple targets and pathways. Furthermore, acupuncture can improve pathological changes associated with AD (such as abnormal deposition of amyloid (A)β, tau hyperphosphorylation, synaptic dysfunction and neuronal apoptosis) through multiple signaling pathways.

CONCLUSION

Overall, our findings provide a basis for future research into the effects of acupuncture on AD.

Nanoparticles for inducing Gaucher disease-like damage in cancer cells

Nutrient avidity is one of the most distinctive features of tumours. However, nutrient deprivation has yielded limited clinical benefits. In Gaucher disease, an inherited metabolic disorder, cells produce cholesteryl-glucoside which accumulates in lysosomes and causes cell damage. Here we develop a nanoparticle (AbCholB) to emulate natural-lipoprotein-carried cholesterol and initiate Gaucher disease-like damage in cancer cells. AbCholB is composed of a phenylboronic-acid-modified cholesterol (CholB) and albumin. Cancer cells uptake the nanoparticles into lysosomes, where CholB reacts with glucose and generates a cholesteryl-glucoside-like structure that resists degradation and aggregates into microscale crystals, causing Gaucher disease-like damage in a glucose-dependent manner. In addition, the nutrient-sensing function of mTOR is suppressed. It is observed that normal cells escape severe damage due to their inferior ability to compete for nutrients compared with cancer cells. This work provides a bioinspired strategy to selectively impede the metabolic action of cancer cells by taking advantage of their nutrient avidity.

Resistance training boosts lactate transporters and synaptic proteins in insulin-resistance mice

Background

This investigation delineates the influence of resistance training on the expression of synaptic plasticity-related proteins in the hippocampi of insulin-resistant mice and explores the underlying molecular mechanisms.

Methods

Six-week-old male C57BL/6 J mice were stratified into a control group and a high-fat diet group to induce insulin resistance over a 12-week period. Subsequently, the mice were further divided into sedentary and resistance training cohorts, with the latter engaging in a 12-week ladder-climbing regimen. Post-intervention, blood, and hippocampal specimens were harvested for analytical evaluation.

Results

In the insulin-resistant mice, elevated blood lactate levels were observed alongside diminished expression of synaptic plasticity-related proteins, monocarboxylate transporters (MCTs), and reduced phosphorylation of protein kinase B (Akt) and mechanistic target of rapamycin (mTOR). In contrast, the expression of eukaryotic translation initiation factor 4 E-binding protein 2 was significantly augmented. Resistance training mitigated insulin resistance, decreased blood lactate levels, and enhanced the expression and phosphorylation of mTOR, regulatory-associated protein of mTOR, MCTs, and synaptic plasticity-related proteins.

Conclusions

Resistance training mitigates insulin resistance and improves hippocampal synaptic plasticity by normalizing blood lactate levels and enhancing mTOR, MCTs, and synaptic plasticity-related proteins. It may also activate mTORC1 via the PI3K/Akt pathway, promote lactate utilization, and enhance synaptic plasticity proteins, potentially alleviating peripheral insulin resistance. Further research is needed to confirm these mechanisms.

Astaxanthin Rescues Memory Impairments in Rats with Vascular Dementia by Protecting Against Neuronal Death in the Hippocampus

Vascular dementia (VaD) is a cognitive disorder characterized by a decline in cognitive function resulting from cerebrovascular disease. The hippocampus is particularly susceptible to ischemic insults, leading to memory deficits in VaD. Astaxanthin (AST) has shown potential therapeutic effects in neurodegenerative diseases. However, the mechanisms underlying its protective effects in VaD and against hippocampal neuronal death remain unclear. In this study, We used the bilateral common carotid artery occlusion (BCCAO) method to establish a chronic cerebral hypoperfusion (CCH) rat model of VaD and administered a gastric infusion of AST at 25 mg/kg per day for 4 weeks to explore its therapeutic effects. Memory impairments were assessed using Y-maze and Morris water maze tests. We also performed biochemical analyses to evaluate levels of hippocampal neuronal death and apoptosis-related proteins, as well as the impact of astaxanthin on the PI3K/Akt/mTOR pathway and oxidative stress. Our results demonstrated that AST significantly rescued memory impairments in VaD rats. Furthermore, astaxanthin treatment protected against hippocampal neuronal death and attenuated apoptosis. We also observed that AST modulated the PI3K/Akt/mTOR pathway, suggesting its involvement in promoting neuronal survival and synaptic plasticity. Additionally, AST exhibited antioxidant properties, mitigating oxidative stress in the hippocampus. These findings provide valuable insights into the potential therapeutic effects of AST in VaD. By elucidating the mechanisms underlying the actions of AST, this study highlights the importance of protecting hippocampal neurons and suggests potential targets for intervention in VaD. There are still some unanswered questions include long-term effects and optimal dosage of the use in human. Further research is warranted to fully understand the therapeutic potential of AST and its application in the clinical treatment of VaD.

Differential effects of moderate chronic ethanol consumption on neurobehavior, white matter glial protein expression, and mTOR pathway signaling with adolescent brain maturation

Background: Adolescent brains are highly vulnerable to heavy alcohol exposure. Increased understanding of how alcohol adversely impacts brain maturation may improve treatment outcomes.Objectives: This study characterizes short-term versus long-term effects of ethanol feeding on behavior, frontal lobe glial proteins, and mTOR signaling.Methods: Adolescent rats (8/group) were fed liquid diets containing 26% or 0% ethanol for 2 or 9 weeks, then subjected to novel object recognition (NOR) and open field (OF) tests. Frontal lobes were used for molecular assays.Results: Significant ethanol effects on OF performance occurred in the 2-week model (p < .0001). Further shifts in OF and NOR performance were unrelated to ethanol exposure in the 9-week models (p < .05 to p < .0001). Ethanol inhibited MAG1 (p < .01) and MBP (p < .0001) after 2 but not 9 weeks. However, both control and ethanol 9-week models had significantly reduced MAG1 (p < .001-0.0001), MBP (p < .0001), PDGFRA (p < .05-0.01), and PLP (p < .001-0.0001) relative to the 2-week models. GFAP was the only glial protein significantly inhibited by ethanol in both 2- (p < .01) and 9-week (p < .05) models. Concerning the mTOR pathway, ethanol reduced IRS-1 (p < .05) and globally inhibited mTOR (p < .01 or p < .001) in the 9- but not the 2-week model.Conclusions: Short-term versus long-term ethanol exposures differentially alter neurobehavioral function, glial protein expression, and signaling through IRS-1 and mTOR, which have known roles in myelination during adolescence. These findings suggest that strategies to prevent chronic alcohol-related brain pathology should consider the increased maturation-related vulnerability of adolescent brains.

Spatial omics reveals molecular changes in focal cortical dysplasia type II

Focal cortical dysplasia (FCD) represents a group of diverse localized cortical lesions that are highly epileptogenic and occur due to abnormal brain development caused by genetic mutations, involving the mammalian target of rapamycin (mTOR). These somatic mutations lead to mosaicism in the affected brain, posing challenges to unravel the direct and indirect functional consequences of these mutations. To comprehensively characterize the impact of mTOR mutations on the brain, we employed here a multimodal approach in a preclinical mouse model of FCD type II (Rheb), focusing on spatial omics techniques to define the proteomic and lipidomic changes. Mass Spectrometry Imaging (MSI) combined with fluorescence imaging and label free proteomics, revealed insight into the brain's lipidome and proteome within the FCD type II affected region in the mouse model. MSI visualized disrupted neuronal migration and differential lipid distribution including a reduction in sulfatides in the FCD type II-affected region, which play a role in brain myelination. MSI-guided laser capture microdissection (LMD) was conducted on FCD type II and control regions, followed by label free proteomics, revealing changes in myelination pathways by oligodendrocytes. Surgical resections of FCD type IIb and postmortem human cortex were analyzed by bulk transcriptomics to unravel the interplay between genetic mutations and molecular changes in FCD type II. Our comparative analysis of protein pathways and enriched Gene Ontology pathways related to myelination in the FCD type II-affected mouse model and human FCD type IIb transcriptomics highlights the animal model's translational value. This dual approach, including mouse model proteomics and human transcriptomics strengthens our understanding of the functional consequences arising from somatic mutations in FCD type II, as well as the identification of pathways that may be used as therapeutic strategies in the future.

mTOR and neuroinflammation in epilepsy: implications for disease progression and treatment

Epilepsy remains a major health concern as anti-seizure medications frequently fail, and there is currently no treatment to stop or prevent epileptogenesis, the process underlying the onset and progression of epilepsy. The identification of the pathological processes underlying epileptogenesis is instrumental to the development of drugs that may prevent the generation of seizures or control pharmaco-resistant seizures, which affect about 30% of patients. mTOR signalling and neuroinflammation have been recognized as critical pathways that are activated in brain cells in epilepsy. They represent a potential node of biological convergence in structural epilepsies with either a genetic or an acquired aetiology. Interventional studies in animal models and clinical studies give strong support to the involvement of each pathway in epilepsy. In this Review, we focus on available knowledge about the pathophysiological features of mTOR signalling and the neuroinflammatory brain response, and their interactions, in epilepsy. We discuss mitigation strategies for each pathway that display therapeutic effects in experimental and clinical epilepsy. A deeper understanding of these interconnected molecular cascades could enhance our strategies for managing epilepsy. This could pave the way for new treatments to fill the gaps in the development of preventative or disease-modifying drugs, thus overcoming the limitations of current symptomatic medications.

Autophagy-related genes in mesial temporal lobe epilepsy: an integrated bioinformatics analysis

BACKGROUND

Autophagy plays essential roles in the development and pathogenesis of mesial temporal lobe epilepsy (mTLE). In this research, we aim to identify and validate the autophagy-related genes associated with mTLE through bioinformatics analysis and experimental validations.

METHODS

We obtained the dataset GSE143272 and high-throughput sequencing results of mTLE from public databases. Potential differentially expressed autophagy-related genes related to mTLE were identified using R software. Subsequently, genomes pathway enrichment analysis, protein-protein interactions (PPIs), and the gene ontology (GO) enrichment were performed for the selected autophagy-related genes. The mRNA expression profiles of hub genes were then used to establish a least absolute shrinkage and selection operator (LASSO) model. Finally, seven hub candidate autophagy-related genes were confirmed in hippocampus using the lithium-pilocarpine chronic epilepsy model.

RESULTS

A total of 40 differential expression genes (DEGs) among the core autophagy-related genes were identified. The analysis results of PPI revealed that interactions among these DEGs. KEGG pathway and GO analysis of selected candidate autophagy-related genes indicated that those enriched terms mainly focused on macroautophagy, regulation of autophagy, cellular response to extracellular stimulus and mitochondrion disassembly. The results suggested that SQSTM1, VEGFA, BNIP and WIPI2 were consistent with the bioinformatics analysis. The expression levels of SQSTM1 and VEGFA in epilepsy model samples were significantly higher than those in normal control, while BNIP and WIPI2 expression levels were notably decreased. The final hub gene-based LASSO regression model accurately predicted the occurrence of epilepsy (AUC = 0.88).

CONCLUSIONS

Through bioinformatics analysis of public data, we identified 40 candidate autophagy-related genes associated with mTLE. SQSTM1, VEGFA, BNIP and WIPI2 may play significant roles in autophagy, influencing the onset and development of mTLE by regulating autophagy pathway. These findings deepen our understanding of mTLE, and may serve as sensitive and valuable indicators for the prognosis and diagnosis of this condition.

Selective disruption of mTORC1 and mTORC2 in VTA astrocytes induces depression and anxiety-like behaviors in mice

Dysfunction of the mechanistic target of rapamycin (mTOR) signaling pathway is implicated in neuropsychiatric disorders including depression and anxiety. Most studies have been focusing on neurons, and the function of mTOR signaling pathway in astrocytes is less investigated. mTOR forms two distinct complexes, mTORC1 and mTORC2, with key scaffolding protein Raptor and Rictor, respectively. The ventral tegmental area (VTA), a vital component of the brain reward system, is enrolled in regulating both depression and anxiety. In the present study, we aimed to examine the regulation effect of VTA astrocytic mTOR signaling pathway on depression and anxiety. We specifically deleted Raptor or Rictor in VTA astrocytes in mice and performed a series of behavioral tests for depression and anxiety. Deletion of Raptor and Rictor both decreased the immobility time in the tail suspension test and the latency to eat in the novelty suppressed feeding test, and increased the horizontal activity and the movement time in locomotor activity. Deletion of Rictor decreased the number of total arm entries in the elevated plus-maze test and the vertical activity in locomotor activity. These data suggest that VTA astrocytic mTORC1 plays a role in regulating depression-related behaviors and mTORC2 is involved in both depression and anxiety-related behaviors. Our results indicate that VTA astrocytic mTOR signaling pathway might be new targets for the treatment of psychiatric disorders.

mTOR signaling and Alzheimer's disease: What we know and where we are?

Despite the great body of research done on Alzheimer's disease, the underlying mechanisms have not been vividly investigated. To date, the accumulation of amyloid-beta plaques and tau tangles constitutes the hallmark of the disease; however, dysregulation of the mammalian target of rapamycin (mTOR) seems to be significantly involved in the pathogenesis of the disease as well. mTOR, as a serine-threonine protein kinase, was previously known for controlling many cellular functions such as cell size, autophagy, and metabolism. In this regard, mammalian target of rapamycin complex 1 (mTORC1) may leave anti-aging impacts by robustly inhibiting autophagy, a mechanism that inhibits the accumulation of damaged protein aggregate and dysfunctional organelles. Formation and aggregation of neurofibrillary tangles and amyloid-beta plaques seem to be significantly regulated by mTOR signaling. Understanding the underlying mechanisms and connection between mTOR signaling and AD may suggest conducting clinical trials assessing the efficacy of rapamycin, as an mTOR inhibitor drug, in managing AD or may help develop other medications. In this literature review, we aim to elaborate mTOR signaling network mainly in the brain, point to gaps of knowledge, and define how and in which ways mTOR signaling can be connected with AD pathogenesis and symptoms.

Termination of convulsion seizures by destabilizing and perturbing seizure memory engrams

Epileptogenesis, arising from alterations in synaptic strength, shares mechanistic and phenotypic parallels with memory formation. However, direct evidence supporting the existence of seizure memory remains scarce. Leveraging a conditioned seizure memory (CSM) paradigm, we found that CSM enabled the environmental cue to trigger seizure repetitively, and activating cue-responding engram cells could generate CSM artificially. Moreover, cue exposure initiated an analogous process of memory reconsolidation driven by mammalian target of rapamycin-brain-derived neurotrophic factor signaling. Pharmacological targeting of the mammalian target of rapamycin pathway within a limited time window reduced seizures in animals and interictal epileptiform discharges in patients with refractory seizures. Our findings reveal a causal link between seizure memory engrams and seizures, which leads us to a deeper understanding of epileptogenesis and points to a promising direction for epilepsy treatment.

Diet-induced hyperhomocysteinemia causes sex-dependent deficiencies in offspring musculature and brain function

Hyperhomocysteinemia (HHcy), characterized by elevated homocysteine (Hcy) levels, is a known risk factor for cardiovascular, renal, and neurological diseases, as well as pregnancy complications. Our study aimed to investigate whether HHcy induced by a high-methionine (high-Met) diet exacerbates cognitive and behavioral deficits in offspring and leads to other breeding problems. Dietary HHcy was induced four weeks before mating and continued throughout gestation and post-delivery. A battery of behavioral tests was conducted on offspring between postnatal days (PNDs) 5 and 30 to assess motor function/activity and cognition. The results were correlated with brain morphometric measurements and quantitative analysis of mammalian target of rapamycin (mTOR)/autophagy markers. The high-Met diet significantly increased parental and offspring urinary tHcy levels and influenced offspring behavior in a sex-dependent manner. Female offspring exhibited impaired cognition, potentially related to morphometric changes observed exclusively in HHcy females. Male HHcy pups demonstrated muscle weakness, evidenced by slower surface righting, reduced hind limb suspension (HLS) hanging time, weaker grip strength, and decreased activity in the beaker test. Western blot analyses indicated the downregulation of autophagy and the upregulation of mTOR activity in HHcy cortexes. HHcy also led to breeding impairments, including reduced breeding rate, in-utero fetal death, lower pups' body weight, and increased mortality, likely attributed to placental dysfunction associated with HHcy. In conclusion, a high-Met diet impairs memory and cognition in female juveniles and weakens muscle strength in male pups. These effects may stem from abnormal placental function affecting early neurogenesis, the dysregulation of autophagy-related pathways in the cortex, or epigenetic mechanisms of gene regulation triggered by HHcy during embryonic development.

Advanced Model-based Approach to Evaluate Human Plasma, Cerebrospinal Fluid, and Neuronal mTORC1 Activation Biomarkers After NV-5138 Administration in Healthy Volunteers

PURPOSE

NV-5138 ([S]-2-amino-5,5-difluoro-4,4-dimethylpentanoic acid) is an orally bioavailable, small-molecule activator of the mechanistic target of rapamycin complex 1 (mTORC1) pathway in development for treatment-resistant depression. The authors established a model to describe the relationship between plasma and cerebrospinal fluid (CSF) concentrations of NV-5138 and between CSF concentrations and potential biomarkers thought to be associated with mTORC1 activity (ie, orotic acid, N-acetylmethionine, and N-formylmethionine).

METHODS

Data were collected from a randomized, double-blind, placebo-controlled, tolerability, and pharmacokinetic (PK) parameter study of 5 ascending (400, 800, 1600, 2400, and 3000 mg), once-daily oral doses of NV-5138 in healthy subjects. NV-5138 plasma PK parameter samples were collected at 15 time points over 24 hours on days 1 and 7, and at pre dose on days 2-6 for all doses. NV-5138 CSF PK parameter and CSF biomarker samples were collected on days 1 and 7 at pre dose and 4, 8, and 12 hours post dose for all doses except 3000 mg. A model-based approach was used to develop and validate a model that describes the relationship between NV-5138 in CSF and biomarker concentrations.

FINDINGS

Twenty-four of the 42 enrolled subjects had simultaneous plasma and CSF measurements of NV-5138 and CSF biomarker concentrations and were included in the PK parameter and pharmacodynamic (PD) analyses. A 2-compartment plasma and CSF PK parameter, with indirect PD effects, model was developed and validated. NV-5138 plasma concentrations were positively correlated with those in CSF, although CSF concentrations lagged slightly behind those in plasma, as indicated by a counterclockwise hysteresis effect. Similarly, the relationship between the PD measures of mTORC1 activation and NV-5138 was also characterized by counterclockwise hysteresis, when the increase in CSF biomarker concentrations lagged behind those of NV-5138, consistent with a signaling intermediary/cascade, such as mTORC1. Maximal biomarker activation was achieved at NV-5138 CSF concentrations of approximately 3 µg/mL, which were associated with daily doses of 1600 mg NV-5138. The safety profile analysis (n = 42) found that most of the reported adverse events were mild in severity, with no severe, serious, unusual, or unexpected adverse events or any dissociative effects; 2 subjects (400-mg cohort) discontinued due to adverse events that were judged to be unrelated to study medication.

IMPLICATIONS

The model will be used for designing future efficacy and tolerability studies. Consecutive daily doses of NV-5138 were well tolerated in this healthy volunteer study.

Comorbidity Genes of Alzheimer's Disease and Type 2 Diabetes Associated with Memory and Cognitive Function

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) are comorbidities that result from the sharing of common genes. The molecular background of comorbidities can provide clues for the development of treatment and management strategies. Here, the common genes involved in the development of the two diseases and in memory and cognitive function are reviewed. Network clustering based on protein-protein interaction network identified tightly connected gene clusters that have an impact on memory and cognition among the comorbidity genes of AD and T2DM. Genes with functional implications were intensively reviewed and relevant evidence summarized. Gene information will be useful in the discovery of biomarkers and the identification of tentative therapeutic targets for AD and T2DM.

Latest advances in mechanisms of epileptic activity in Alzheimer's disease and dementia with Lewy Bodies

Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) stand as the prevailing sources of neurodegenerative dementia, impacting over 55 million individuals across the globe. Patients with AD and DLB exhibit a higher prevalence of epileptic activity compared to those with other forms of dementia. Seizures can accompany AD and DLB in early stages, and the associated epileptic activity can contribute to cognitive symptoms and exacerbate cognitive decline. Aberrant neuronal activity in AD and DLB may be caused by several mechanisms that are not yet understood. Hyperexcitability could be a biomarker for early detection of AD or DLB before the onset of dementia. In this review, we compare and contrast mechanisms of network hyperexcitability in AD and DLB. We examine the contributions of genetic risk factors, Ca2+ dysregulation, glutamate, AMPA and NMDA receptors, mTOR, pathological amyloid beta, tau and α-synuclein, altered microglial and astrocytic activity, and impaired inhibitory interneuron function. By gaining a deeper understanding of the molecular mechanisms that cause neuronal hyperexcitability, we might uncover therapeutic approaches to effectively ease symptoms and slow down the advancement of AD and DLB.

Transient anticonvulsant effects of time-restricted feeding in the 6-Hz mouse model

INTRODUCTION

Intermittent fasting enhances neural bioenergetics, is neuroprotective, and elicits antioxidant effects in various animal models. There are conflicting findings on seizure protection, where intermittent fasting regimens often cause severe weight loss resembling starvation which is unsustainable long-term. Therefore, we tested whether a less intensive intermittent fasting regimen such as time-restricted feeding (TRF) may confer seizure protection.

METHODS

Male CD1 mice were assigned to either ad libitum-fed control, continuous 8 h TRF, or 8 h TRF with weekend ad libitum food access (2:5 TRF) for one month. Body weight, food intake, and blood glucose levels were measured. Seizure thresholds were determined at various time points using 6-Hz and maximal electroshock seizure threshold (MEST) tests. Protein levels and mRNA expression of genes, enzyme activity related to glucose metabolism, as well as mitochondrial dynamics were assessed in the cortex and hippocampus. Markers of antioxidant defence were evaluated in the plasma, cortex, and liver.

RESULTS

Body weight gain was similar in the ad libitum-fed and TRF mouse groups. In both TRF regimens, blood glucose levels did not change between the fed and fasted state and were higher during fasting than in the ad libitum-fed groups. Mice in the TRF group had increased seizure thresholds in the 6-Hz test on day 15 and on day 19 in a second cohort of 2:5 TRF mice, but similar seizure thresholds at other time points compared to ad libitum-fed mice. Continuous TRF did not alter MEST seizure thresholds on day 28. Mice in the TRF group showed increased maximal activity of pyruvate dehydrogenase in the cortex, which was accompanied by increased protein levels of mitochondrial pyruvate carrier 1 in the cortex and hippocampus. There were no other major changes in protein or mRNA levels associated with energy metabolism and mitochondrial dynamics in the brain, nor markers of antioxidant defence in the brain, liver, or plasma.

CONCLUSIONS

Both continuous and 2:5 TRF regimens transiently increased seizure thresholds in the 6-Hz model at around 2 weeks, which coincided with stability of blood glucose levels during the fed and fasted periods. Our findings suggest that the lack of prolonged anticonvulsant effects in the acute electrical seizure models employed may be attributed to only modest metabolic and antioxidant adaptations found in the brain and liver. Our findings underscore the potential therapeutic value of TRF in managing seizure-related conditions.

The brain serotonin system in autism

Autism spectrum disorders (ASDs) are among the most common neurodevelopmental diseases. These disorders are characterized by lack of social interaction, by repetitive behavior, and often anxiety and learning disabilities. The brain serotonin (5-HT) system is known to be crucially implicated in a wide range of physiological functions and in the control of different kinds of normal and pathological behavior. A growing number of studies indicate the involvement of the brain 5-HT system in the mechanisms underlying both ASD development and ASD-related behavioral disorders. There are some review papers describing the role of separate key players of the 5-HT system in an ASD and/or autistic-like behavior. In this review, we summarize existing data on the participation of all members of the brain 5-HT system, namely, 5-HT transporter, tryptophan hydroxylase 2, MAOA, and 5-HT receptors, in autism in human and various animal models. Additionally, we describe the most recent studies involving modern techniques for in vivo regulation of gene expression that are aimed at identifying exact roles of 5-HT receptors, MAOA, and 5-HT transporter in the mechanisms underlying autistic-like behavior. Altogether, results of multiple research articles show that the brain 5-HT system intimately partakes in the control of some types of ASD-related behavior, and that specific changes in a function of a certain 5-HT receptor, transporter, and/or enzyme may normalize this aberrant behavior. These data give hope that some of clinically used 5-HT-related drugs have potential for ASD treatment.

Long and Short-Term Effect of mTOR Regulation on Cerebral Organoid Growth and Differentiations

BACKGROUND

The mammalian target of rapamycin (mTOR) signaling is critical for the maintenance and differentiation of neurogenesis, and conceivably for many other brain developmental processes. However, in vivo studies of mTOR functions in the brain are often hampered due to the essential role of the associated signaling in brain development.

METHODS

We monitored the long- and short-term effects of mTOR signaling regulation on cerebral organoids growth, differentiation and function using an mTOR inhibitor (everolimus) and an mTOR activator (MHY1485).

RESULTS

Short-term treatment with MHY1485 induced faster organoid growth and differentiation, while long-term treatment induced the maturation of cerebral organoids.

CONCLUSION

These data suggest that the optimal activity of mTOR is crucial in maintaining normal brain development, and its role is not confined to the early neurogenic phase of brain development.

Microglial stimulation triggered by intranasal lipopolysaccharide administration produces antidepressant-like effect through ERK1/2-mediated BDNF synthesis in the hippocampus

We recently reported that reversing the chronic stress-induced decline of microglia in the dentate gyrus (DG) of the hippocampus by intraperitoneal injection of a low dose of lipopolysaccharide (LPS) ameliorated depression-like behavior in chronically stressed mice. In this study, we found that a single intranasal administration of LPS dose-dependently improved depression-like behavior in mice treated with chronic unpredictable stress (CUS), as evidenced by the reduction of immobility time in the tail suspension test (TST) and forced swimming test (FST) and by the increase of sucrose uptake in the sucrose preference test (SPT). The antidepressant effects of intranasal administration of LPS could be abolished by inhibition of brain-derived neurotrophic factor (BDNF) signaling by infusion of an anti-BDNF antibody, by knock-in of the mutant BDNF Val68Met allele, or by the BDNF receptor antagonist K252a. In addition, intranasal administration of LPS was found to exert antidepressant effects in a BDNF-dependent manner via promotion of BDNF synthesis mediated by extracellular signal-regulated kinase 1/2 (ERK1/2) signaling but not protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling in DG. Inhibition of microglia by minocycline or depletion of microglia by PLX3397 was able to abolish the reversal effect of intranasal LPS administration on CUS-induced depression-like behaviors as well as the CUS-induced decrease in phospho-ERK1/2 and BDNF protein levels in DG. These results demonstrate that stimulation of hippocampal microglia by intranasal LPS administration can induce antidepressant effects via ERK1/2-dependent synthesis of BDNF protein, providing hope for the development of new strategies for the treatment of depression.

The Neuroprotective Effects and Probable Mechanisms of Everolimus in a Rat Model of Intracerebral Hemorrhage

Mammalian target of rapamycin (mTOR) is a central regulator of cellular growth and homeostasis. Changes in mTOR activity are often observed in many neurological diseases, such as stroke. Intracerebral hemorrhage (ICH) is associated with high mortality and morbidity. However, there are currently no treatments that have been shown to enhance outcomes following ICH, so new treatments are urgently required. In this study, a selective mTOR inhibitor, everolimus, was applied to investigate the outcome after ICH and the possible underlying mechanism. The ICH model was established by autologous blood injection. Everolimus (50 and 100 µg/kg) was administered intraperitoneally for 14 consecutive days' post-operation. The neurological functions were examined at 3, 7, and 14 days' post-ICH. Samples of brain tissue were collected to perform histopathological and immunohistochemical (NF-k-positive cell) examinations. Besides, the striatum was used to evaluate parameters related to oxidative stress (superoxide dismutase (SOD) activity, malondialdehyde (MDA), and total thiol levels) and inflammation markers (TNF-α and NO). Everolimus ameliorated ICH-induced neurological deficits. In addition, treatment with everolimus reduced infarct volume and NF-k-β positive cells as compared to the ICH group. Furthermore, everolimus significantly increased total thiol content and SOD activity while significantly reducing MDA, NO, and TNF- levels as compared to the ICH group. Collectively, our investigation showed that everolimus improves ICH outcome and modulates oxidative stress and inflammation after ICH. Treatment with rapamycin reduced neurological deficient, oxidative stress, and inflammation in a rat model of intracerebral hemorrhage.

CEGA: a method for inferring natural selection by comparative population genomic analysis across species

We developed maximum likelihood method for detecting positive selection or balancing selection using multilocus or genomic polymorphism and divergence data from two species. The method is especially useful for investigating natural selection in noncoding regions. Simulations demonstrate that the method outperforms existing methods in detecting both positive and balancing selection. We apply the method to population genomic data from human and chimpanzee. The list of genes identified under selection in the noncoding regions is prominently enriched in pathways related to the brain and nervous system. Therefore, our method will serve as a useful tool for comparative population genomic analysis.

Insights into the neurobiology of suicidality: explicating the role of glutamatergic systems through the lens of ketamine

Suicidality is a prevalent mental health condition, and managing suicidal patients is one of the most challenging tasks for health care professionals due to the lack of rapid-acting, effective psychopharmacological treatment options. According to the literature, suicide has neurobiological underpinnings that are not fully understood, and current treatments for suicidal tendencies have considerable limitations. To treat suicidality and prevent suicide, new treatments are required; to achieve this, the neurobiological processes underlying suicidal behavior must be thoroughly investigated. Although multiple neurotransmitter systems, particularly serotonergic systems, have been studied in the past, less has been reported in relation to disruptions in glutamatergic neurotransmission, neuronal plasticity, and neurogenesis that result from stress-related abnormalities of the hypothalamic-pituitary-adrenal system. Informed by the literature, which reports robust antisuicidal and antidepressive properties of subanaesthetic doses of ketamine, this review aims to provide an examination of the neurobiology of suicidality (and relevant mood disorders) with implications of pertinent animal, clinical, and postmortem studies. We discuss dysfunctions in the glutamatergic system, which may play a role in the neuropathology of suicidality and the role of ketamine in restoring synaptic connectivity at the molecular levels.

Neuroprotective effects of hesperetin on H2O2-induced damage in neuroblastoma SH-SY5Y cells

BACKGROUND/OBJECTIVES

Oxidative stress is a fundamental neurodegenerative disease trigger that damages and decimates nerve cells. Neurodegenerative diseases are chronic central nervous system disorders that progress and result from neuronal degradation and loss. Recent studies have extensively focused on neurodegenerative disease treatment and prevention using dietary compounds. Heseperetin is an aglycone hesperidin form with various physiological activities, such as anti-inflammation, antioxidant, and antitumor. However, few studies have considered hesperetin's neuroprotective effects and mechanisms; thus, our study investigated this in hydrogen peroxide (H2O2)-treated SH-SY5Y cells.

MATERIALS/METHODS

SH-SY5Y cells were treated with H2O2 (400 µM) in hesperetin absence or presence (10-40 µM) for 24 h. Three-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assays detected cell viability, and 4',6-diamidino-2-phenylindole staining allowed us to observe nuclear morphology changes such as chromatin condensation and apoptotic nuclei. Reactive oxygen species (ROS) detection assays measured intracellular ROS production; Griess reaction assays assessed nitric oxide (NO) production. Western blotting and quantitative polymerase chain reactions quantified corresponding mRNA and proteins.

RESULTS

Subsequent experiments utilized various non-toxic hesperetin concentrations, establishing that hesperetin notably decreased intracellular ROS and NO production in H2O2-treated SH-SY5Y cells (P < 0.05). Furthermore, hesperetin inhibited H2O2-induced inflammation-related gene expression, including interluekin-6, tumor necrosis factor-α, and nuclear factor kappa B (NF-κB) p65 activation. In addition, hesperetin inhibited NF-κB translocation into H2O2-treated SH-SY5Y cell nuclei and suppressed mitogen-activated protein kinase protein expression, an essential apoptotic cell death regulator. Various apoptosis hallmarks, including shrinkage and nuclear condensation in H2O2-treated cells, were suppressed dose-dependently. Additionally, hesperetin treatment down-regulated Bax/Bcl-2 expression ratios and activated AMP-activated protein kinase-mammalian target of rapamycin autophagy pathways.

CONCLUSION

These results substantiate that hesperetin activates autophagy and inhibits apoptosis and inflammation. Hesperetin is a potentially potent dietary agent that reduces neurodegenerative disease onset, progression, and prevention.

Hippocampus protection from apoptosis by Baicalin in a LiCl-pilocarpine-induced rat status epilepticus model through autophagy activation

BACKGROUND

Autophagy is associated with hippocampal injury following status epilepticus (SE) and is considered a potential therapeutic mechanism. Baicalin, an emerging multitherapeutic drug, has shown neuroprotective effects in patients with nervous system diseases due to its antioxidant properties.

AIM

To investigate the potential role of autophagy in LiCl-pilocarpine-induced SE.

METHODS

The drugs were administered 30 min before SE. Nissl staining showed that Baicalin attenuated hippocampal injury and reduced neuronal death in the hippocampus. Western blotting and terminal deoxynucleotidyl transferase dUTP nick end labeling assay confirmed that Baicalin reversed the expression intensity of cleaved caspase-3 and apoptosis in hippocampal CA1 following SE. Fur-thermore, western blotting and immunofluorescence staining were used to measure the expression of autophagy markers (p62/SQSTM1, Beclin 1, and LC3) and apoptotic pathway markers (cleaved caspase-3 and Bcl-2).

RESULTS

Baicalin significantly upregulated autophagic activity and downregulated mitochondrial apoptotic pathway markers. Conversely, 3-methyladenine, a commonly used autophagy inhibitor, was simultaneously administered to inhibit the Baicalin-induced autophagy, abrogating the protective effect of Baicalin on the mitochondrial apoptotic level.

CONCLUSION

We illustrated that Baicalin-induced activation of autophagy alleviates apoptotic death and protects the hippocampus of SE rats.

Altered Expression of Autophagy Biomarkers in Hippocampal Neurons in a Multiple Sclerosis Animal Model

Multiple Sclerosis (MS) is a chronic inflammatory disease that affects the brain and spinal cord. Inflammation, demyelination, synaptic alteration, and neuronal loss are hallmarks detectable in MS. Experimental autoimmune encephalomyelitis (EAE) is an animal model widely used to study pathogenic aspects of MS. Autophagy is a process that maintains cell homeostasis by removing abnormal organelles and damaged proteins and is involved both in protective and detrimental effects that have been seen in a variety of human diseases, such as cancer, neurodegenerative diseases, inflammation, and metabolic disorders. This study is aimed at investigating the autophagy signaling pathway through the analysis of the main autophagic proteins including Beclin-1, microtubule-associated protein light chain (LC3, autophagosome marker), and p62 also called sequestosome1 (SQSTM1, substrate of autophagy-mediated degradation) in the hippocampus of EAE-affected mice. The expression levels of Beclin-1, LC3, and p62 and the Akt/mTOR pathway were examined by Western blot experiments. In EAE mice, compared to control animals, significant reductions of expression levels were detectable for Beclin-1 and LC3 II (indicating the reduction of autophagosomes), and p62 (suggesting that autophagic flux increased). In parallel, molecular analysis detected the deregulation of the Akt/mTOR signaling. Immunofluorescence double-labeling images showed co-localization of NeuN (neuronal nuclear marker) and Beclin-1, LC3, and p62 throughout the CA1 and CA3 hippocampal subfields. Taken together, these data demonstrate that activation of autophagy occurs in the neurons of the hippocampus in this experimental model.

mTOR pathway - a potential therapeutic target in stroke

Stroke is ranked as the second leading cause of death worldwide and a major cause of long-term disability. A potential therapeutic target that could offer favorable outcomes in stroke is the mammalian target of rapamycin (mTOR) pathway. mTOR is a serine/threonine kinase that composes two protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), and is regulated by other proteins such as the tuberous sclerosis complex. Through a significant number of signaling pathways, the mTOR pathway can modulate the processes of post-ischemic inflammation and autophagy, both of which play an integral part in the pathophysiological cascade of stroke. Promoting or inhibiting such processes under ischemic conditions can lead to apoptosis or instead sustained viability of neurons. The purpose of this review is to examine the pathophysiological role of mTOR in acute ischemic stroke, while highlighting promising neuroprotective agents such as hamartin for therapeutic modulation of this pathway. The therapeutic potential of mTOR is also discussed, with emphasis on implicated molecules and pathway steps that warrant further elucidation in order for their neuroprotective properties to be efficiently tested in future clinical trials.

Simufilam suppresses overactive mTOR and restores its sensitivity to insulin in Alzheimer's disease patient lymphocytes

Introduction: Implicated in both aging and Alzheimer's disease (AD), mammalian target of rapamycin (mTOR) is overactive in AD brain and lymphocytes. Stimulated by growth factors such as insulin, mTOR monitors cell health and nutrient needs. A small molecule oral drug candidate for AD, simufilam targets an altered conformation of the scaffolding protein filamin A (FLNA) found in AD brain and lymphocytes that induces aberrant FLNA interactions leading to AD neuropathology. Simufilam restores FLNA's normal shape to disrupt its AD-associated protein interactions. Methods: We measured mTOR and its response to insulin in lymphocytes of AD patients before and after oral simufilam compared to healthy control lymphocytes. Results: mTOR was overactive and its response to insulin reduced in lymphocytes from AD versus healthy control subjects, illustrating another aspect of insulin resistance in AD. After oral simufilam, lymphocytes showed normalized basal mTOR activity and improved insulin-evoked mTOR activation in mTOR complex 1, complex 2, and upstream and downstream signaling components (Akt, p70S6K and phosphorylated Rictor). Suggesting mechanism, we showed that FLNA interacts with the insulin receptor until dissociation by insulin, but this linkage was elevated and its dissociation impaired in AD lymphocytes. Simufilam improved the insulin-mediated dissociation. Additionally, FLNA's interaction with Phosphatase and Tensin Homolog deleted on Chromosome 10 (PTEN), a negative regulator of mTOR, was reduced in AD lymphocytes and improved by simufilam. Discussion: Reducing mTOR's basal overactivity and its resistance to insulin represents another mechanism of simufilam to counteract aging and AD pathology. Simufilam is currently in Phase 3 clinical trials for AD dementia.

mTOR/α-ketoglutarate signaling: impact on brain cell homeostasis under ischemic conditions

The multifunctional molecules mechanistic target of rapamycin (mTOR) and α-ketoglutarate (αKG) are crucial players in the regulatory mechanisms that maintain cell homeostasis in an ever-changing environment. Cerebral ischemia is associated primarily with oxygen-glucose deficiency (OGD) due to circulatory disorders. Upon exceeding a threshold of resistance to OGD, essential pathways of cellular metabolism can be disrupted, leading to damage of brain cells up to the loss of function and death. This mini-review focuses on the role of mTOR and αKG signaling in the metabolic homeostasis of brain cells under OGD conditions. Integral mechanisms concerning the relative cell resistance to OGD and the molecular basis of αKG-mediated neuroprotection are discussed. The study of molecular events associated with cerebral ischemia and endogenous neuroprotection is relevant for improving the effectiveness of therapeutic strategies.

mTOR pathway: Insights into an established pathway for brain mosaicism in epilepsy

The mechanistic target of rapamycin (mTOR) signaling pathway is an essential regulator of numerous cellular activities such as metabolism, growth, proliferation, and survival. The mTOR cascade recently emerged as a critical player in the pathogenesis of focal epilepsies and cortical malformations. The 'mTORopathies' comprise a spectrum of cortical malformations that range from whole brain (megalencephaly) and hemispheric (hemimegalencephaly) abnormalities to focal abnormalities, such as focal cortical dysplasia type II (FCDII), which manifest with drug-resistant epilepsies. The spectrum of cortical dysplasia results from somatic brain mutations in the mTOR pathway activators AKT3, MTOR, PIK3CA, and RHEB and from germline and somatic mutations in mTOR pathway repressors, DEPDC5, NPRL2, NPRL3, TSC1 and TSC2. The mTORopathies are characterized by excessive mTOR pathway activation, leading to a broad range of structural and functional impairments. Here, we provide a comprehensive literature review of somatic mTOR-activating mutations linked to epilepsy and cortical malformations in 292 patients and discuss the perspectives of targeted therapeutics for personalized medicine.

A multi-organ analysis of the role of mTOR in fetal alcohol spectrum disorders

Alcohol exposure during gestation can lead to fetal alcohol spectrum disorders (FASD), an array of cognitive and physical developmental impairments. Over the past two and a half decades, Mammalian Target of Rapamycin (mTOR) has emerged at the nexus of many fields of study, and has recently been implicated in FASD etiology. mTOR plays an integral role in modulating anabolic and catabolic activities, including protein synthesis and autophagy. These processes are vital for proper development and can have long lasting effects following alcohol exposure, such as impaired hippocampal and synapse formation, reduced brain size, as well as cognitive, behavioral, and memory impairments. We highlight recent advances in the field of FASD, primarily with regard to animal model discoveries and discuss the interaction between alcohol and mTOR in the context of various tissues, including brain, placenta, bone, and muscle, with respect to developmental alcohol exposure paradigms. The current review focuses on novel FASD research within the context of the mTOR signaling and sheds light on mechanistic etiologies at various biological levels including molecular, cellular, and functional, across multiple stages of development and illuminates the dichotomy between the different mTOR complexes and their unique signaling roles.

Insulin Resistance and Impaired Branched-Chain Amino Acid Metabolism in Alzheimer's Disease

The pathogenesis of Alzheimer's disease (AD) is complicated and involves multiple contributing factors. Mounting evidence supports the concept that AD is an age-related metabolic neurodegenerative disease mediated in part by brain insulin resistance, and sharing similar metabolic dysfunctions and brain pathological characteristics that occur in type 2 diabetes mellitus (T2DM) and other insulin resistance disorders. Brain insulin signal pathway is a major regulator of branched-chain amino acid (BCAA) metabolism. In the past several years, impaired BCAA metabolism has been described in several insulin resistant states such as obesity, T2DM and cardiovascular disease. Disrupted BCAA metabolism leading to elevation in circulating BCAAs and related metabolites is an early metabolic phenotype of insulin resistance and correlated with future onset of T2DM. Brain is a major site for BCAA metabolism. BCAAs play pivotal roles in normal brain function, especially in signal transduction, nitrogen homeostasis, and neurotransmitter cycling. Evidence from animal models and patients support the involvement of BCAA dysmetabolism in neurodegenerative diseases including Huntington's disease, Parkinson's disease, and maple syrup urine disease. More recently, growing studies have revealed altered BCAA metabolism in AD, but the relationship between them is poorly understood. This review is focused on the recent findings regarding BCAA metabolism and its role in AD. Moreover, we will explore how impaired BCAA metabolism influences brain function and participates in the pathogenesis of AD.

Irisin Attenuates Apoptosis Following Ischemia-Reperfusion Injury Through Improved Mitochondria Dynamics and ROS Suppression Mediated Through the PI3K/Akt/mTOR Axis

Irisin is a muscle-derived hormone that promotes the survival of motor neurons and enhances muscle size following injury. In this study, we investigated the beneficial effects and mechanism(s) of action of irisin in response to cerebral ischemia-reperfusion injury (CIRI). Right-middle cerebral artery occlusion (MCAO) and hypoxia/reoxygenation (H/R) models were generated in C57BL/6 J mice. Mouse neuronal cell lines (NSC-34) were used to confirm the molecular mechanisms of the protection afforded by irisin in response to CIRI. We found that irisin (250 μg/kg) improved cerebral function and reduced the cerebral infarct volume following CIRI. Irisin also protected neuronal cells against ischemia-reperfusion (I/R) induced apoptosis, assessed via TUNEL, and cleaved Caspase-3 staining. Western blotting of neuronal tissue from irisin treated I/R mice showed lower expression of pro-apoptotic Bax and caspase-9 (P < 0.001 and P < 0.01) and increased levels of the pro-survival protein Bcl-2 (P < 0.01 & P < 0.001 vs. I/R). Irisin also reduced the levels of reactive oxygen species (ROS) characterized through malondialdehyde (MDA) assays. Irisin was found to maintain mitochondrial homeostasis through the suppression of mitochondrial fission-linked dynamin-related protein 1 in CIRI mice (P < 0.01 and P < 0.05 v. I/R cohort). Moreover, mitochondrial fusion-related protein (Mfn2) and Opa1 expression were rescued following irisin treatment (P < 0.001 and P < 0.01 v. I/R cohort). Cell-based assays showed that irisin activates PI3K/AKT/mTOR signaling in the neurons of CIRI mice. Furthermore, the beneficial effects of irisin on NSC-34 cell-survival, mitochondrial function, and ROS generation were reversed by VS-5584, a highly specific PI3K/AKT/mTOR inhibitor. Collectively, these data highlight the ability of irisin to alleviate CIRI in vivo and in vitro. The mechanisms of action of irisin include the attenuation of apoptosis through the prevention of mitochondrial fission and increased mitochondrial fusion and the alleviation of oxidative stress through activation of the PI3K/AKT/mTOR axis. We therefore identify irisin as a much-needed therapeutic for CIRI.