Complete neural stem cell (NSC) neuronal differentiation requires a branched chain amino acids-induced persistent metabolic shift towards energy metabolism

Unraveling the Molecular Mechanisms of the Neurodevelopmental Consequences of Fetal Protein Deficiency: Insights From Rodent Models and Public Health Implications

Fetal brain development requires increased maternal protein intake to ensure that offspring reach their optimal cognitive potential in infancy and adulthood. While protein deficiency remains a prevalent issue in developing countries, it is also reemerging in Western societies due to the growing adoption of plant-based diets, some of which are monotonous and may fail to provide sufficient amino acids crucial for the brain's critical developmental phase. Confounding variables in human nutritional research have impeded our understanding of the precise impact of protein deficiency on fetal neurodevelopment, as well as its implications for childhood neurocognitive performance. Moreover, it remains unclear whether such deficiency could predispose to mental health problems in adulthood, mirroring observations in individuals exposed to prenatal famine. In this review, we sought to evaluate mechanistic data derived from rodent models, placing special emphasis on the involvement of neuroendocrine axes, the influence of sex and timing, epigenetic modifications, and cellular metabolism. Despite notable progress, critical knowledge gaps remain, including understanding the long-term reversibility of effects due to fetal protein restriction and the interplay between genetic predisposition and environmental factors. Enhancing our understanding of the precise mechanisms that connect prenatal nutrition to brain development in future research endeavors can be significantly advanced by integrating multiomics approaches and utilizing additional alternative models such as nonhuman primates. Furthermore, it is crucial to investigate potential interventions aimed at alleviating adverse outcomes. Ultimately, this research has profound implications for guiding public health strategies aimed at raising awareness about the crucial role of optimal maternal nutrition in supporting fetal neurodevelopment.

Cellular and Molecular Insights into the Divergence of Neural Stem Cells on Matrigel and Poly-l-lysine Interfaces

Poly-l-lysine (PLL) and Matrigel, both classical coating materials for culture substrates in neural stem cell (NSC) research, present distinct interfaces whose effect on NSC behavior at cellular and molecular levels remains ambiguous. Our investigation reveals intriguing disparities: although both PLL and Matrigel interfaces are hydrophilic and feature amine functional groups, Matrigel stands out with lower stiffness and higher roughness. Based on this diversity, Matrigel surpasses PLL, driving NSC adhesion, migration, and proliferation. Intriguingly, PLL promotes NSC differentiation into astrocytes, whereas Matrigel favors neural differentiation and the physiological maturation of neurons. At the molecular level, Matrigel showcases a wider upregulation of genes linked to NSC behavior. Specifically, it enhances ECM-receptor interaction, activates the YAP transcription factor, and heightens glycerophospholipid metabolism, steering NSC proliferation and neural differentiation. Conversely, PLL upregulates genes associated with glial cell differentiation and amino acid metabolism and elevates various amino acid levels, potentially linked to its support for astrocyte differentiation. These distinct transcriptional and metabolic activities jointly shape the divergent NSC behavior on these substrates. This study significantly advances our understanding of substrate regulation on NSC behavior, offering novel insights into optimizing and targeting the application of these surface coating materials in NSC research.

Neuroprotective effect of the RNS60 in a mouse model of transient focal cerebral ischemia

BACKGROUND

Stroke is a major cause of death, disability, and public health problems. Its intervention is limited to early treatment with thrombolytics and/or endovascular clot removal with mechanical thrombectomy without any available subacute or chronic neuroprotective treatments. RNS60 has reduced neuroinflammation and increased neuronal survival in several animal models of neurodegeneration and trauma. The aim here was to evaluate whether RNS60 protects the brain and cognitive function in a mouse stroke model.

METHODS

Male C57BL/6J mice were subjected to sham or ischemic stroke surgery using 60-minute transient middle cerebral artery occlusion (tMCAo). In each group, mice received blinded daily administrations of RNS60 or control fluids (PNS60 or normal saline [NS]), beginning 2 hours after surgery over 13 days. Multiple neurobehavioral tests were conducted (Neurological Severity Score [mNSS], Novel Object Recognition [NOR], Active Place Avoidance [APA], and the Conflict Variant of APA [APAc]). On day 14, cortical microvascular perfusion (MVP) was measured, then brains were removed and infarct volume, immunofluorescence of amyloid beta (Aβ), neuronal density, microglial activation, and white matter damage/myelination were measured. SPSS was used for analysis (e.g., ANOVA for parametric data; Kruskal Wallis for non-parametric data; with post-hoc analysis).

RESULTS

Thirteen days of treatment with RNS60 reduced brain infarction, amyloid pathology, neuronal death, microglial activation, white matter damage, and increased MVP. RNS60 reduced brain pathology and resulted in behavioral improvements in stroke compared to sham surgery mice (increased memory-learning in NOR and APA, improved cognitive flexibility in APAc).

CONCLUSION

RNS60-treated mice exhibit significant protection of brain tissue and improved neurobehavioral functioning after tMCAo-stroke. Additional work is required to determine mechanisms, time-window of dosing, and multiple dosing volumes durations to support clinical stroke research.

Histone H3 Acetylation Is Involved in Retinoid Acid-Induced Neural Differentiation through Increasing Mitochondrial Function

Histone acetylation and mitochondrial function contribute importantly to neural differentiation, which is critically associated with neurodevelopmental disorders such as Down Syndrome (DS). However, whether and how histone acetylation regulates mitochondrial function and further affects neural differentiation has not been well described. In this study, when treated with retinoid acid (RA), the human neuroblastoma SH-SY5Y cell line was used as a neural differentiation model. We found that the acetylation of histone H3, especially H3 lysine 14 acetylation (H3K14ac), and mitochondrial function, including biogenesis and electron transport chain, were enhanced during neural differentiation. Specific inhibition of histone acetyltransferases (HATs) induced neural differentiation deficits, accompanied by downregulation of mitochondrial function. Furthermore, RA receptors (RARs) interacting with HATs were involved in the increased H3K14ac and the enhanced mitochondrial function during the neural differentiation process. Finally, receptor-interacting protein 140 (RIP140), a co-repressor of RARs, was also involved in regulating histone acetylation. RIP140 overexpression inhibited histone acetylation and mediated negative feedback on target genes which are involved in RA signaling. These findings evidenced that when interacting with RARs which had been negatively regulated by RIP140, RA promoted neural differentiation by promoting H3K14ac and enhanced mitochondrial function. This provides a molecular foundation for further investigations into abnormal neural development.

Generation of mouse hippocampal brain organoids from primary embryonic neural stem cells

Here we present a protocol to generate standardized cerebral organoids with hippocampal regional specification using morphogen WNT3a. We describe steps for isolating mouse embryonic (E14.5) neural stem cells from the brain subgranular zone, preparing organoids samples for immunofluorescence, calcium imaging, and metabolic profiling. This protocol can be used to generate mouse brain organoids for developmental studies, modeling disease, and drug screening. Organoids can be obtained in one month, thus providing a rapid tool for high-throughput data validation. For complete details on the use and execution of this protocol, please refer to Ciarpella et al. "Murine cerebral organoids develop network of functional neurons and hippocampal brain region identity".1.

Amino acids contribute to adaptive thermogenesis. New insights into the mechanisms of action of recent drugs for metabolic disorders are emerging

Adaptive thermogenesis is the heat production by muscle contractions (shivering thermogenesis) or brown adipose tissue (BAT) and beige fat (non-shivering thermogenesis) in response to external stimuli, including cold exposure. BAT and beige fat communicate with peripheral organs and the brain through a variegate secretory and absorption processes - controlling adipokines, microRNAs, extracellular vesicles, and metabolites - and have received much attention as potential therapeutic targets for managing obesity-related disorders. The sympathetic nervous system and norepinephrine-releasing adipose tissue macrophages (ATM) activate uncoupling protein 1 (UCP1), expressed explicitly in brown and beige adipocytes, dissolving the electrochemical gradient and uncoupling tricarboxylic acid cycle and the electron transport chain from ATP production. Mounting evidence has attracted attention to the multiple effects of dietary and endogenously synthesised amino acids in BAT thermogenesis and metabolic phenotype in animals and humans. However, the mechanisms implicated in these processes have yet to be conclusively characterized. In the present review article, we aim to define the principal investigation areas in this context, including intestinal microbiota constitution, adipose autophagy modulation, and secretome and metabolic fluxes control, which lead to increased brown/beige thermogenesis. Finally, also based on our recent epicardial adipose tissue results, we summarise the evidence supporting the notion that the new dual and triple agonists of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon (GCG) receptor - with never before seen weight loss and insulin-sensitizing efficacy - promote thermogenic-like amino acid profiles in BAT with robust heat production and likely trigger sympathetic activation and adaptive thermogenesis by controlling amino acid metabolism and ATM expansion in BAT and beige fat.

A balanced formula of essential amino acids promotes brain mitochondrial biogenesis and protects neurons from ischemic insult

Mitochondrial dysfunction plays a key role in the aging process, and aging is a strong risk factor for neurodegenerative diseases or brain injury characterized by impairment of mitochondrial function. Among these, ischemic stroke is one of the leading causes of death and permanent disability worldwide. Pharmacological approaches for its prevention and therapy are limited. Although non-pharmacological interventions such as physical exercise, which promotes brain mitochondrial biogenesis, have been shown to exert preventive effects against ischemic stroke, regular feasibility is complex in older people, and nutraceutical strategies could be valuable alternatives. We show here that dietary supplementation with a balanced essential amino acid mixture (BCAAem) increased mitochondrial biogenesis and the endogenous antioxidant response in the hippocampus of middle-aged mice to an extent comparable to those elicited by treadmill exercise training, suggesting BCAAem as an effective exercise mimetic on brain mitochondrial health and disease prevention. In vitro BCAAem treatment directly exerted mitochondrial biogenic effects and induced antioxidant enzyme expression in primary mouse cortical neurons. Further, exposure to BCAAem protected cortical neurons from the ischemic damage induced by an in vitro model of cerebral ischemia (oxygen-glucose deprivation, OGD). BCAAem-mediated protection against OGD was abolished in the presence of rapamycin, Torin-1, or L-NAME, indicating the requirement of both mTOR and eNOS signaling pathways in the BCAAem effects. We propose BCAAem supplementation as an alternative to physical exercise to prevent brain mitochondrial derangements leading to neurodegeneration and as a nutraceutical intervention aiding recovery after cerebral ischemia in conjunction with conventional drugs.

Nitric Oxide Attenuates Human Cytomegalovirus Infection yet Disrupts Neural Cell Differentiation and Tissue Organization

Human cytomegalovirus (HCMV) is a prevalent betaherpesvirus that is asymptomatic in healthy individuals but can cause serious disease in immunocompromised patients. HCMV is also the leading cause of virus-mediated birth defects. Many of these defects manifest within the central nervous system and include microcephaly, sensorineural hearing loss, and cognitive developmental delays. Nitric oxide is a critical effector molecule produced as a component of the innate immune response during infection. Congenitally infected fetal brains show regions of brain damage, including necrotic foci with infiltrating macrophages and microglia, cell types that produce nitric oxide during infection. Using a 3-dimensional cortical organoid model, we demonstrate that nitric oxide inhibits HCMV spread and simultaneously disrupts neural rosette structures, resulting in tissue disorganization. Nitric oxide also attenuates HCMV replication in 2-dimensional cultures of neural progenitor cells (NPCs), a prominent cell type in cortical organoids that differentiate into neurons and glial cells. The multipotency factor SOX2 was decreased during nitric oxide exposure, suggesting that early neural differentiation is affected. Nitric oxide also reduced maximal mitochondrial respiration in both uninfected and infected NPCs. We determined that this reduction likely influences neural differentiation, as neurons (Tuj1⁺ GFAP^- Nestin^-) and glial populations (Tuj1^- GFAP⁺ Nestin^-) were reduced following differentiation. Our studies indicate a prominent, immunopathogenic role of nitric oxide in promoting developmental defects within the brain despite its antiviral activity during congenital HCMV infection. IMPORTANCE Human cytomegalovirus (HCMV) is the leading cause of virus-mediated congenital birth defects. Congenitally infected infants can have a variety of symptoms manifesting within the central nervous system. The use of 3-dimensional (3-D) cortical organoids to model infection of the fetal brain has advanced the current understanding of development and allowed broader investigation of the mechanisms behind disease. However, the impact of the innate immune molecule nitric oxide during HCMV infection has not been explored in neural cells or cortical 3-D models. Here, we investigated the effect of nitric oxide on cortical development during HCMV infection. We demonstrate that nitric oxide plays an antiviral role during infection yet results in disorganized cortical tissue. Nitric oxide contributes to differentiation defects of neuron and glial cells from neural progenitor cells despite inhibiting viral replication. Our results indicate that immunopathogenic consequences of nitric oxide during congenital infection promote developmental defects that undermine its antiviral activity.

Role of Diet in Stem and Cancer Stem Cells

Diet and lifestyle factors greatly affect health and susceptibility to diseases, including cancer. Stem cells’ functions, including their ability to divide asymmetrically, set the rules for tissue homeostasis, contribute to health maintenance, and represent the entry point of cancer occurrence. Stem cell properties result from the complex integration of intrinsic, extrinsic, and systemic factors. In this context, diet-induced metabolic changes can have a profound impact on stem cell fate determination, lineage specification and differentiation. The purpose of this review is to provide a comprehensive description of the multiple “non-metabolic” effects of diet on stem cell functions, including little-known effects such as those on liquid-liquid phase separation and on non-random chromosome segregation (asymmetric division). A deep understanding of the specific dietetic requirements of normal and cancer stem cells may pave the way for the development of nutrition-based targeted therapeutic approaches to improve regenerative and anticancer therapies.

3-Bromo-Isoxazoline Derivatives Inhibit GAPDH Enzyme in PDAC Cells Triggering Autophagy and Apoptotic Cell Death

A growing interest in the study of aerobic glycolysis as a key pathway for cancer-cell energetic metabolism, favouring tumour progression and invasion, has led to consider GAPDH as an effective drug target to specifically hit cancer cells. In this study, we have investigated a panel of 3-bromo-isoxazoline derivatives based on previously identified inhibitors of Plasmodium falciparum GAPDH (PfGAPDH). The compounds are active, to a different extent, as inhibitors of human-recombinant GAPDH. They showed an antiproliferative effect on pancreatic ductal-adenocarcinoma cells (PDAC) and pancreatic-cancer stem cells (CSCs), and among them two promising compounds were selected to be tested in vivo. Interestingly, these compounds were not effective in fibroblasts. The AXP-3019 derivative was able to block PDAC-cell growth in mice xenograft without apparent toxicity. The overall results support the assumption that selective inhibition of the glycolytic pathway, by targeting GAPDH, is an effective therapy for pancreatic cancer and that 3-bromo-isoxazoline derivatives represent a new class of anti-cancer compounds targeting glycolysis.

Protective effect and mechanism of Lycium barbarum L. polyphenol on cognitive impairment induced by ethanol in mice

BACKGROUND

Chronic excessive ethanol consumption damages the central nervous system and causes neurobehavioral changes, such as cognitive impairment, which is related to oxidative stress and inhibition of neurogenesis in the hippocampus. It is known that promoting neurogenesis improves learning memory, anxiety and depression. Lycium barbarum L. polyphenol (LBP) is the main active ingredient of Lycium barbarum L., which has excellent neuroprotective effects. However, the effects and mechanisms of LBP on ethanol-induced cognitive impairment are unclear.

PURPOSE

To assess the effects and mechanisms of LBP on ethanol-induced cognitive impairment in mice.

METHODS

Eight-weeks-old adult C57BL/6J mice were allowed to drink ethanol (10%) to establish a model of ethanol-induced cognitive impairment. From the 29th day of LBP (25, 50, 100, 200, 400 mg/kg, intragastric administration), the locomotor activity, novel object recognition (NOR), Y maze and Morris water maze (MWM) were sequentially performed to investigate the effect of LBP on ethanol-induced cognitive impairment in mice. Next, enzyme-linked immunosorbent assay, immunofluorescence, and western blotting were used to study the underlying mechanism of LBP on ethanol-induced cognitive impairment.

RESULTS

LBP significantly decreased the escape latency and increased the number of crossings of the original platform in MWM, increased the spontaneous alteration behavior in the Y maze, and increased the preference index in the NOR in ethanol-induced mice. Notably, LBP significantly promoted the proliferation of neural stem cells, neural progenitor cells and neuroblasts, and increased the proportion of activated NSCs in mice with ethanol-induced cognitive impairment. Similarly, LBP significantly increased the number of newborn immature neurons and mature neurons. Moreover, LBP increased the levels of nuclear factor erythroid2-related factor 2 (Nrf2) and the downstream heme oxygenase-1(HO-1) protein expression, which led to a decrease of oxidative stress levels.

CONCLUSION

LBP significantly improves cognitive impairment in ethanol-induced mice, which is attributed to the promotion of hippocampal neurogenesis and reduction of oxidative stress.

Mitochondria and Other Organelles in Neural Development and Their Potential as Therapeutic Targets in Neurodegenerative Diseases

The contribution of organelles to neural development has received increasing attention. Studies have shown that organelles such as mitochondria, endoplasmic reticulum (ER), lysosomes, and endosomes play important roles in neurogenesis. Specifically, metabolic switching, reactive oxygen species production, mitochondrial dynamics, mitophagy, mitochondria-mediated apoptosis, and the interaction between mitochondria and the ER all have roles in neurogenesis. Lysosomes and endosomes can regulate neurite growth and extension. Moreover, metabolic reprogramming represents a novel strategy for generating functional neurons. Accordingly, the exploration and application of mechanisms underlying metabolic reprogramming will be beneficial for neural conversion and regenerative medicine. There is adequate evidence implicating the dysfunction of cellular organelles—especially mitochondria—in neurodegenerative disorders, and that improvement of mitochondrial function may reverse the progression of these diseases through the reinforcement of adult neurogenesis. Therefore, these organelles have potential as therapeutic targets for the treatment of neurodegenerative diseases. In this review, we discuss the function of these organelles, especially mitochondria, in neural development, focusing on their potential as therapeutic targets in neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis.

Therapeutic Induction of Energy Metabolism Reduces Neural Tissue Damage and Increases Microglia Activation in Severe Spinal Cord Injury

Neural tissue has high metabolic requirements. Following spinal cord injury (SCI), the damaged, tissue suffers from a severe metabolic impairment, which aggravates axonal degeneration and, neuronal loss. Impaired cellular energetic, tricarboxylic acid (TCA) cycle and oxidative, phosphorylation metabolism in neuronal cells has been demonstrated to be a major cause of neural tissue death and regeneration failure following SCI. Therefore, rewiring the spinal cord cell metabolism may be an innovative therapeutic strategy for the treatment of SCI. In this study, we evaluated the therapeutic effect of the recovery of oxidative metabolism in a mouse model of severe contusive SCI. Oral administration of TCA cycle intermediates, co-factors, essential amino acids, and branched-chain amino acids was started 3 days post-injury and continued until the end of the experimental procedures. Metabolomic, immunohistological, and biochemical analyses were performed on the injured spinal cord sections. Administration of metabolic precursors enhanced spinal cord oxidative metabolism. In line with this metabolic shift, we observed the activation of the mTORC1 anabolic pathway, the increase in mitochondrial mass, and ROS defense which effectively prevented the injury-induced neural cell apoptosis in treated animals. Consistently, we found more choline acetyltransferase (ChAT)-expressing motor neurons and increased neurofilament positive corticospinal axons in the spinal cord parenchyma of the treated mice. Interestingly, oral administration of the metabolic precursors increased the number of activated microglia expressing the CD206 marker suggestive of a, pro-resolutive, M2-like phenotype. These molecular and histological modifications observed in treated animals ultimately led to a significant, although partial, improvement of the motor functions. Our data demonstrate that rewiring the cellular metabolism can represent an effective strategy to treat SCI.

From the Bench to the Bedside: Branched Amino Acid and Micronutrient Strategies to Improve Mitochondrial Dysfunction Leading to Sarcopenia

With extended life expectancy, the older population is constantly increasing, and consequently, so too is the prevalence of age-related disorders. Sarcopenia, the pathological age-related loss of muscle mass and function; and malnutrition, the imbalance in nutrient intake and resultant energy production, are both commonly occurring conditions in old adults. Altered nutrition plays a crucial role in the onset of sarcopenia, and both these disorders are associated with detrimental consequences for patients (e.g., frailty, morbidity, and mortality) and society (e.g., healthcare costs). Importantly, sarcopenia and malnutrition also share critical molecular alterations, such as mitochondrial dysfunction, increased oxidative stress, and a chronic state of low grade and sterile inflammation, defined as inflammageing. Given the connection between malnutrition and sarcopenia, nutritional interventions capable of affecting mitochondrial health and correcting inflammageing are emerging as possible strategies to target sarcopenia. Here, we discuss mitochondrial dysfunction, oxidative stress, and inflammageing as key features leading to sarcopenia. Moreover, we examine the effects of some branched amino acids, omega-3 PUFA, and selected micronutrients on these pathways, and their potential role in modulating sarcopenia, warranting further clinical investigation.

Cell Biology Meets Cell Metabolism: Energy Production Is Similar in Stem Cells and in Cancer Stem Cells in Brain and Bone Marrow

Energy production by means of ATP synthesis in cancer cells has been investigated frequently as a potential therapeutic target in this century. Both (an)aerobic glycolysis and oxidative phosphorylation (OXPHOS) have been studied. Here, we review recent literature on energy production in glioblastoma stem cells (GSCs) and leukemic stem cells (LSCs) versus their normal counterparts, neural stem cells (NSCs) and hematopoietic stem cells (HSCs), respectively. These two cancer stem cell types were compared because their niches in glioblastoma tumors and in bone marrow are similar. In this study, it became apparent that (1) ATP is produced in NSCs and HSCs by anaerobic glycolysis, whereas fatty acid oxidation (FAO) is essential for their stem cell fate and (2) ATP is produced in GSCs and LSCs by OXPHOS despite the hypoxic conditions in their niches with FAO and amino acids providing its substrate. These metabolic processes appeared to be under tight control of cellular regulation mechanisms which are discussed in depth. However, our conclusion is that systemic therapeutic targeting of ATP production via glycolysis or OXPHOS is not an attractive option because of its unwanted side effects in cancer patients.

Murine cerebral organoids develop network of functional neurons and hippocampal brain region identity

Brain organoids are in vitro three-dimensional (3D) self-organized neural structures, which can enable disease modeling and drug screening. However, their use for standardized large-scale drug screening studies is limited by their high batch-to-batch variability, long differentiation time (10-20 weeks), and high production costs. This is particularly relevant when brain organoids are obtained from human induced pluripotent stem cells (iPSCs). Here, we developed, for the first time, a highly standardized, reproducible, and fast (5 weeks) murine brain organoid model starting from embryonic neural stem cells. We obtained brain organoids, which progressively differentiated and self-organized into 3D networks of functional neurons with dorsal forebrain phenotype. Furthermore, by adding the morphogen WNT3a, we generated brain organoids with specific hippocampal region identity. Overall, our results showed the establishment of a fast, robust and reproducible murine 3D in vitro brain model that may represent a useful tool for high-throughput drug screening and disease modeling.

Contribution of Mitochondrial Dysfunction Combined with NLRP3 Inflammasome Activation in Selected Neurodegenerative Diseases

Alzheimer's disease and Parkinson's disease are the most common forms of neurodegenerative illnesses. It has been widely accepted that neuroinflammation is the key pathogenic mechanism in neurodegeneration. Both mitochondrial dysfunction and enhanced NLRP3 (nucleotide-binding oligomerization domain (NOD)-like receptor protein 3) inflammasome complex activity have a crucial role in inducing and sustaining neuroinflammation. In addition, mitochondrial-related inflammatory factors could drive the formation of inflammasome complexes, which are responsible for the activation, maturation, and release of pro-inflammatory cytokines, including interleukin-1β (IL-1β) and interleukin-18 (IL-18). The present review includes a broadened approach to the role of mitochondrial dysfunction resulting in abnormal NLRP3 activation in selected neurodegenerative diseases. Moreover, we also discuss the potential mitochondria-focused treatments that could influence the NLRP3 complex.

Mitochondria in neurogenesis: Implications for mitochondrial diseases

Mitochondria are organelles with recognized key roles in cellular homeostasis, including bioenergetics, redox, calcium signaling, and cell death. Mitochondria are essential for neuronal function, given the high energy demands of the human brain. Consequently, mitochondrial diseases affecting oxidative phosphorylation (OXPHOS) commonly exhibit neurological impairment. Emerging evidence suggests that mitochondria are important not only for mature postmitotic neurons but also for the regulation of neural progenitor cells (NPCs) during the process of neurogenesis. These recent findings put mitochondria as central regulator of cell fate decisions during brain development. OXPHOS mutations may disrupt the function of NPCs and thereby impair the metabolic programming required for neural fate commitment. Promoting the mitochondrial function of NPCs could therefore represent a novel interventional approach against incurable mitochondrial diseases.

Environmental Enrichment Induces Meningeal Niche Remodeling through TrkB-Mediated Signaling

Neural precursors (NPs) present in the hippocampus can be modulated by several neurogenic stimuli, including environmental enrichment (EE) acting through BDNF-TrkB signaling. We have recently identified NPs in meninges; however, the meningeal niche response to pro-neurogenic stimuli has never been investigated. To this aim, we analyzed the effects of EE exposure on NP distribution in mouse brain meninges. Following neurogenic stimuli, although we did not detect modification of the meningeal cell number and proliferation, we observed an increased number of neural precursors in the meninges. A lineage tracing experiment suggested that EE-induced β3-Tubulin⁺ immature neuronal cells present in the meninges originated, at least in part, from GLAST⁺ radial glia cells. To investigate the molecular mechanism responsible for meningeal reaction to EE exposure, we studied the BDNF-TrkB interaction. Treatment with ANA-12, a TrkB non-competitive inhibitor, abolished the EE-induced meningeal niche changes. Overall, these data showed, for the first time, that EE exposure induced meningeal niche remodeling through TrkB-mediated signaling. Fluoxetine treatment further confirmed the meningeal niche response, suggesting it may also respond to other pharmacological neurogenic stimuli. A better understanding of the neurogenic stimuli modulation for meninges may be useful to improve the effectiveness of neurodegenerative and neuropsychiatric treatments.

Role of PITRM1 in Mitochondrial Dysfunction and Neurodegeneration

Mounting evidence shows a link between mitochondrial dysfunction and neurodegenerative disorders, including Alzheimer Disease. Increased oxidative stress, defective mitodynamics, and impaired oxidative phosphorylation leading to decreased ATP production, can determine synaptic dysfunction, apoptosis, and neurodegeneration. Furthermore, mitochondrial proteostasis and the protease-mediated quality control system, carrying out degradation of potentially toxic peptides and misfolded or damaged proteins inside mitochondria, are emerging as potential pathogenetic mechanisms. The enzyme pitrilysin metallopeptidase 1 (PITRM1) is a key player in these processes; it is responsible for degrading mitochondrial targeting sequences that are cleaved off from the imported precursor proteins and for digesting a mitochondrial fraction of amyloid beta (Aβ). In this review, we present current evidence obtained from patients with PITRM1 mutations, as well as the different cellular and animal models of PITRM1 deficiency, which points toward PITRM1 as a possible driving factor of several neurodegenerative conditions. Finally, we point out the prospect of new diagnostic and therapeutic approaches.

Essential amino acid formulations to prevent mitochondrial dysfunction and oxidative stress

PURPOSE OF REVIEW

Both restriction and supplementation of specific amino acids or branched-chain amino acids (BCAAs) are described to improve metabolic homeostasis, energy balance, and health span. This review will discuss the recent findings of the role of amino acid supplements in the regulation of mitochondrial health.

RECENT FINDINGS

A mixture of essential amino acids (EAAs), BCAA enriched mixture, was found to extend healthy life span in elderly mice and prevent multiple diseases associated with an energy deficit, similarly to caloric restriction or fasting-mimicking diets. A growing body of evidence highlights mitochondria as the central target of this supplement: it promotes mitochondrial biogenesis and the activation of antioxidant defence systems in different physiological (e.g., exercise or ageing) or pathological conditions (e.g., sarcopenia, muscular dystrophy, liver steatosis, or impaired cognition). Based on these results, new formulas have been created enriched with Krebs cycle substrates, behaving more efficiently than BCAA enriched mixture.

SUMMARY

EAA-BCAA balanced supplements might be valuable not only for healthy individuals undergoing to energy deficit (e.g., athletes) during strenuous exercise or training but also against diseases characterized by a dysregulated catabolic state or mitochondrial dysfunction, such as age-related disorders. The associated mechanistic processes should be identified as potential pharmacological targets.

The role of Nrf2 in neural stem/progenitors cells: From maintaining stemness and self-renewal to promoting differentiation capability and facilitating therapeutic application in neurodegenerative disease

Neurodegenerative diseases (NDs) cause progressive loss of neurons in nervous system. NDs are categorized as acute NDs such as stroke and head injury, besides chronic NDs including Alzheimer's, Parkinson's, Huntington's diseases, Friedreich's Ataxia, Multiple Sclerosis. The exact etiology of NDs is not understood but oxidative stress, inflammation and synaptic dysfunction are main hallmarks. Oxidative stress leads to free radical attack on neural cells which contributes to protein misfolding, glia cell activation, mitochondrial dysfunction, impairment of DNA repair system and subsequently cellular death. Neural stem cells (NSCs) support adult neurogenesis in nervous system during injuries which is limited to certain regions in brain. NSCs can differentiate into the neurons, astrocytes or oligodendrocytes. Impaired neurogenesis and inadequate induction of neurogenesis are the main obstacles in treatment of NDs. Protection of neural cells from oxidative damages and supporting neurogenesis are promising strategies to treat NDs. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a transcriptional master regulator that maintains the redox homeostasis in cells by provoking expression of antioxidant, anti-inflammatory and cytoprotective genes. Nrf2 can strongly influence the NSCs function and fate determination by reducing levels of reactive oxygen species in benefit of NSC survival and neurogenesis. In this review we will summarize the role of Nrf2 in NSC function, and exogenous and endogenous therapeutic strategies in treatment of NDs.

Therapeutic Approaches to Treat Mitochondrial Diseases: "One-Size-Fits-All" and "Precision Medicine" Strategies

Primary mitochondrial diseases (PMD) refer to a group of severe, often inherited genetic conditions due to mutations in the mitochondrial genome or in the nuclear genes encoding for proteins involved in oxidative phosphorylation (OXPHOS). The mutations hamper the last step of aerobic metabolism, affecting the primary source of cellular ATP synthesis. Mitochondrial diseases are characterized by extremely heterogeneous symptoms, ranging from organ-specific to multisystemic dysfunction with different clinical courses. The limited information of the natural history, the limitations of currently available preclinical models, coupled with the large variability of phenotypical presentations of PMD patients, have strongly penalized the development of effective therapies. However, new therapeutic strategies have been emerging, often with promising preclinical and clinical results. Here we review the state of the art on experimental treatments for mitochondrial diseases, presenting "one-size-fits-all" approaches and precision medicine strategies. Finally, we propose novel perspective therapeutic plans, either based on preclinical studies or currently used for other genetic or metabolic diseases that could be transferred to PMD.

Manipulation of Dietary Amino Acids Prevents and Reverses Obesity in Mice Through Multiple Mechanisms That Modulate Energy Homeostasis

Reduced activation of energy metabolism increases adiposity in humans and other mammals. Thus, exploring dietary and molecular mechanisms able to improve energy metabolism is of paramount medical importance because such mechanisms can be leveraged as a therapy for obesity and related disorders. Here, we show that a designer protein-deprived diet enriched in free essential amino acids can 1) promote the brown fat thermogenic program and fatty acid oxidation, 2) stimulate uncoupling protein 1 (UCP1)-independent respiration in subcutaneous white fat, 3) change the gut microbiota composition, and 4) prevent and reverse obesity and dysregulated glucose homeostasis in multiple mouse models, prolonging the healthy life span. These effects are independent of unbalanced amino acid ratio, energy consumption, and intestinal calorie absorption. A brown fat-specific activation of the mechanistic target of rapamycin complex 1 seems involved in the diet-induced beneficial effects, as also strengthened by in vitro experiments. Hence, our results suggest that brown and white fat may be targets of specific amino acids to control UCP1-dependent and -independent thermogenesis, thereby contributing to the improvement of metabolic health.

Meninges: A Widespread Niche of Neural Progenitors for the Brain

Emerging evidence highlights the several roles that meninges play in relevant brain functions as they are a protective membrane for the brain, produce and release several trophic factors important for neural cell migration and survival, control cerebrospinal fluid dynamics, and embrace numerous immune interactions affecting neural parenchymal functions. Furthermore, different groups have identified subsets of neural progenitors residing in the meninges during development and in the adulthood in different mammalian species, including humans. Interestingly, these immature neural cells are able to migrate from the meninges to the neural parenchyma and differentiate into functional cortical neurons or oligodendrocytes. Immature neural cells residing in the meninges promptly react to brain disease. Injury-induced expansion and migration of meningeal neural progenitors have been observed following experimental demyelination, traumatic spinal cord and brain injury, amygdala lesion, stroke, and progressive ataxia. In this review, we summarize data on the function of meninges as stem cell niche and on the presence of immature neural cells in the meninges, and discuss their roles in brain health and disease. Furthermore, we consider the potential exploitation of meningeal neural progenitors for the regenerative medicine to treat neurological disorders.