Proteasome activation by insulin-like growth factor-1/nuclear factor erythroid 2-related factor 2 signaling promotes exercise-induced neurogenesis

The Deficiency of the ASD-Related Gene CHD8 Disrupts Behavioral Patterns and Inhibits Hippocampal Neurogenesis in Mice

Chromodomain helicase DNA-binding 8 (CHD8) is a gene that poses a high risk for autism spectrum disorder (ASD) and neurological development delay. Nevertheless, the impact of CHD8 haploinsufficiency on both hippocampus neurogenesis and behavior remains uncertain. Here, we performed behavioral assessments on male and female CHD8 heterozygous mice. The study discovered that both male and female CHD8 heterozygous mice displayed an impairment in preference for social novelty. Concurrently, CHD8 heterozygous mice exhibited anxiety-like behavior. However, its cognitive capacity for learning and memory is within the expected range. Furthermore, we discovered a reduction in the number of both immature and mature new neurons in mice with CHD8 heterozygous, resulting in an impeded neurogenesis process in the hippocampus. Taken together, our findings indicate that CHD8 plays a crucial role in the regulation of hippocampal neurogenesis, and further suggest that ASD-like behaviors observed in CHD8 heterozygous mice may be associated with disruptions in hippocampal neurogenesis.

Adult neurogenesis research in China

Neural stem cells are multipotent stem cells that generate functional newborn neurons through a process called neurogenesis. Neurogenesis in the adult brain is tightly regulated and plays a pivotal role in the maintenance of brain function. Disruption of adult neurogenesis impairs cognitive function and is correlated with numerous neurologic disorders. Deciphering the mechanisms underlying adult neurogenesis not only advances our understanding of how the brain functions, but also offers new insight into neurologic diseases and potentially contributes to the development of effective treatments. The field of adult neurogenesis is experiencing significant growth in China. Chinese researchers have demonstrated a multitude of factors governing adult neurogenesis and revealed the underlying mechanisms of and correlations between adult neurogenesis and neurologic disorders. Here, we provide an overview of recent advancements in the field of adult neurogenesis due to Chinese scientists.

Adipose transplantation improves olfactory function and neurogenesis via PKCα-involved lipid metabolism in Seipin Knockout mice

BACKGROUND

Lipodystrophy-associated metabolic disorders caused by Seipin deficiency lead to not only severe lipodystrophy but also neurological disorders. However, the underlying mechanism of Seipin deficiency-induced neuropathy is not well elucidated, and the possible restorative strategy needs to be explored.

METHODS

In the present study, we used Seipin knockout (KO) mice, combined with transcriptome analysis, mass spectrometry imaging, neurobehavior test, and cellular and molecular assay to investigate the systemic lipid metabolic abnormalities in lipodystrophic mice model and their effects on adult neurogenesis in the subventricular zone (SVZ) and olfactory function. After subcutaneous adipose tissue (AT) transplantation, metabolic and neurological function was measured in Seipin KO mice to clarify whether restoring lipid metabolic homeostasis would improve neurobehavior.

RESULTS

It was found that Seipin KO mice presented the ectopic accumulation of lipids in the lateral ventricle, accompanied by decreased neurogenesis in adult SVZ, diminished new neuron formation in the olfactory bulb, and impaired olfactory-related memory. Transcriptome analysis showed that the differentially expressed genes (DEGs) in SVZ of adult Seipin KO mice were significantly enriched in lipid metabolism. Mass spectrometry imaging showed that the levels of glycerophospholipid and diglyceride (DG) were significantly increased. Furthermore, we found that AT transplantation rescued the abnormality of peripheral metabolism in Seipin KO mice and ameliorated the ectopic lipid accumulation, concomitant with restoration of the SVZ neurogenesis and olfactory function. Mechanistically, PKCα expression was up-regulated in SVZ tissues of Seipin KO mice, which may be a potential mediator between lipid dysregulation and neurological disorder. DG analogue (Dic8) can up-regulate PKCα and inhibit the proliferation and differentiation of neural stem cells (NSCs) in vitro, while PKCα inhibitor can block this effect.

CONCLUSION

This study demonstrates that Seipin deficiency can lead to systemic lipid disorder with concomitant SVZ neurogenesis and impaired olfactory memory. However, AT restores lipid homeostasis and neurogenesis. PKCα is a key mediator mediating Seipin KO-induced abnormal lipid metabolism and impaired neurogenesis in the SVZ, and inhibition of PKCα can restore the impaired neurogenesis. This work reveals the underlying mechanism of Seipin deficiency-induced neurological dysfunction and provides new ideas for the treatment of neurological dysfunction caused by metabolic disorders.

Insulin-like growth factor 1 in heat stress-induced neuroinflammation: novel perspective about the neuroprotective role of chromium

Heat stress (HS) can cause a series of stress responses, resulting in numerous negative effects on the body, such as the diminished food intake, carcass quality and reproductive capacity. In addition to the negative effects on the peripheral system, HS leads to central nervous system (CNS) disorders given its toll on neuroinflammation. This neuroinflammatory process is mainly mediated by microglia and astrocytes, which are involved in the activation of glial cells and the secretion of cytokines. While the regulation of inflammatory signaling has a close relationship with the expression of heat shock protein 70 (Hsp70), HS-induced neuroinflammation is closely related to the activation of the TLR4/NF-κB pathway. Moreover, oxidative stress and endoplasmic reticulum (ER) stress are key players in the development of neuroinflammation. Chromium (Cr) has been widely shown to have neuroprotective effects in both humans and animals, despite the lack of mechanistic evidence. Evidence has shown that Cr supplementation can increase the levels of insulin-like growth factor 1 (IGF-1), a major neurotrophic factor with anti-inflammatory and antioxidant effects. This review highlights recent advances in the attenuating effects and potential mechanisms of Cr-mediated IGF-1 actions on HS-induced neuroinflammation, providing presently existing evidence supporting the neuroprotective role of Cr.

NRF2: An emerging role in neural stem cell regulation and neurogenesis

The birth of new neurons from neural stem cells (NSC)s during developmental and adult neurogenesis arises from a myriad of highly complex signalling cascades. Emerging as one of these is the nuclear factor erythroid 2-related factor (NRF2)-signaling pathway. Regulation by NRF2 is reported to span the neurogenic process from early neural lineage specification and NSC regulation to neuronal fate commitment and differentiation. Here, we review these reports selecting only those where NRF2 signaling was directly manipulated to provide a clearer case for a direct role of NRF2 in embryonic and adult neurogenesis. With few studies providing mechanistic insight into this relationship, we lastly discuss key pathways linking NRF2 and stem cell regulation outside the neural lineage to shed light on mechanisms that may also be relevant to NSCs and neurogenesis.

Exercise Preconditioning Ameliorates Cognitive Impairment in Mice with Ischemic Stroke by Alleviating Inflammation and Modulating Gut Microbiota

Several studies have demonstrated that exercise preconditioning is an effective means of alleviating poststroke cognitive impairment (PSCI). Mechanisms of regulating cognitive function have not been fully elucidated. Herein, the present study is aimed at exploring the effect of the microbiota-gut-inflammasome-brain axis in the process of exercise preconditioning moderating cognitive impairment after ischemic stroke. We observed that exercise preconditioning decreased infarct size, reduced the degree of neuronal damage, and alleviated cognitive impairment in mice with ischemic stroke. In addition, exercise preconditioning also reduced the expression of inflammatory cytokines, as well as NLRP3, Caspase-1, IL-18, and IL-1β protein expressions. Ischemic stroke could downregulate the abundance of Roseburia while increasing the abundance of the Helicobacter at the level of genus. As a comparison, exercise preconditioning increased the abundance of the Lactobacillus, which was beneficial for mice at the genus level. In conclusion, exercise preconditioning can improve cognitive dysfunction after ischemic stroke through alleviating inflammation and regulating the composition and diversity of the gut microbiota, which might provide a new strategy for the prevention of PSCI.

Antioxidant Molecular Brain Changes Parallel Adaptive Cardiovascular Response to Forced Running in Mice

Physically active lifestyle has huge implications for the health and well-being of people of all ages. However, excessive training can lead to severe cardiovascular events such as heart fibrosis and arrhythmia. In addition, strenuous exercise may impair brain plasticity. Here we investigate the presence of any deleterious effects induced by chronic high-intensity exercise, although not reaching exhaustion. We analyzed cardiovascular, cognitive, and cerebral molecular changes in young adult male mice submitted to treadmill running for eight weeks at moderate or high-intensity regimens compared to sedentary mice. Exercised mice showed decreased weight gain, which was significant for the high-intensity group. Exercised mice showed cardiac hypertrophy but with no signs of hemodynamic overload. No morphological changes in the descending aorta were observed, either. High-intensity training induced a decrease in heart rate and an increase in motor skills. However, it did not impair recognition or spatial memory, and, accordingly, the expression of hippocampal and cerebral cortical neuroplasticity markers was maintained. Interestingly, proteasome enzymatic activity increased in the cerebral cortex of all trained mice, and catalase expression was significantly increased in the high-intensity group; both first-line mechanisms contribute to maintaining redox homeostasis. Therefore, physical exercise at an intensity that induces adaptive cardiovascular changes parallels increases in antioxidant defenses to prevent brain damage.

Exogenous IGF-1 improves tau pathology and neuronal pyroptosis in high-fat diet mice with cognitive dysfunction

Insulin-like growth factor-1 (IGF-1) improves obesity-induced cognitive dysfunction, but its mechanism is not fully clarified. The aim of the study was to reveal whether IGF-1 treated cognitive dysfunction by improving tau pathology and neuronal pyroptosis in high-fat diet mice. During in vitro experiment, C57BL/6J mice were fed with high-fat diet, and were treated with PEG-IGF-1, IGF-1 receptor blocker AXL1717, HO-1 blocker Znpp IX or their combinations. Cognitive function was evaluated using Morris water maze. Expression of Nrf2, HO-1, p-tau, NLRP3, caspase-1 and IL-1β in hippocampus was determined using western blotting. Pyroptosis rate in hippocampus was measured using flow cytometry. During in vivo experiment, HN-h cells were treated with palmitic acid, pyroptosis blocker nonecrosulfonamide or their combinations. The expression of the proteins and rate of pyroptosis were also measured using western blotting and flow cytometry. During in vitro experiment, high-fat diet mice showed cognitive dysfunction, significant hyperphosphorylation of tau protein and neuronal pyroptosis in hippocampus compared with the sham mice. After exogenous IGF-1 treatment, these abnormalities were reversed and Nrf2/HO-1 signaling pathway was activated. Inhibition of the signaling pathway using AXL1717 or Znpp IX re-deteriorated cognitive function, tau pathology and neuronal pyroptosis in hippocampus. During in vivo experiment, inhibition of pyroptosis using nonecrosulfonamide improved tau pathology in palmitic acid-treated HN-h cells. Exogenous IGF-1 improved tau pathology induced by high-fat diet through inhibition of neuronal pyroptosis and activation of Nrf2/HO-1 signaling pathway.

Activation of Autophagy Ameliorates Age-Related Neurogenesis Decline and Neurodysfunction in Adult Mice

Adult neurogenesis is the ongoing generation of functional new neurons from neural progenitor cells (NPCs) in the mammalian brain. However, this process declines with aging, which is implicated in the recession of brain function and neurodegeneration. Understanding the mechanism of adult neurogenesis and stimulating neurogenesis will benefit the mitigation of neurodegenerative diseases. Autophagy, a highly conserved process of cellular degradation, is essential for maintaining cellular homeostasis and normal function. Whether and how autophagy affects adult neurogenesis remains poorly understood. In present study, we revealed a close connection between impaired autophagy and adult neurogenetic decline. Expression of autophagy-related genes and autophagic activity were significantly declined in the middle-adult subventricular/subgranular zone (SVZ/SGZ) homogenates and cultured NPCs, and inhibiting autophagy by siRNA interference resulted in impaired proliferation and differentiation of NPCs. Conversely, stimulating autophagy by rapamycin not only revitalized the viability of middle-adult NPCs, but also facilitated the neurogenesis in middle-adult SVZ/SGZ. More importantly, autophagic activation by rapamycin also ameliorated the olfactory sensitivity and cognitional capacities in middle-adult mice. Taken together, our results reveal that compromised autophagy is involved in the decline of adult neurogenesis, which could be reversed by autophagy activation. It also shed light on the regulation of adult neurogenesis and paves the way for developing a therapeutic strategy for aging and neurodegenerative diseases.

The impact of physical exercise on hippocampus, in physiological condition and ageing-related decline: current evidence from animal and human studies

Physical exercise (PE), notoriously, promotes a state of general well-being, throughout the entire human lifespan. Moreover, maintaining an adequate and regular PE habit results to be a powerful preventive factor towards many diseases and may also help in managing existing pathological conditions. PE induces structural and functional changes in various districts of the body, determining biological and psychological benefits. Additionally, in elderly, PE might represent a remarkable tool reducing cognitive impairments related to the normal aging processes and it has also been found to have an impact in neurodegenerative diseases such as Alzheimer's disease. The present review aims to provide an overview about PE effects on hippocampus, since it is one of the brain regions most susceptible to aging and, therefore, involved in diseases characterized by cognitive impairment.

Physical exercise promotes brain remodeling by regulating epigenetics, neuroplasticity and neurotrophins

Exercise has been shown to have beneficial effects on brain functions in humans and animals. Exercise can improve memory and learning in age-related neurodegenerative diseases. In animal models, physical exercise regulates epigenetics, promotes synaptic plasticity and hippocampal neurogenesis, regulates the expression levels of neurotrophic factors, and improves cognitive function. Therefore, exercise is very important for brain rehabilitation and remodeling. The purpose of this review is to explore the mechanisms by which exercise exerts positive effects on brain function. This knowledge implies that physical exercise can be used as a non-drug therapy for neurological diseases.

Maternal Protein Restriction in Rats Alters the Expression of Genes Involved in Mitochondrial Metabolism and Epitranscriptomics in Fetal Hypothalamus

Fetal brain development is closely dependent on maternal nutrition and metabolic status. Maternal protein restriction (PR) is known to be associated with alterations in the structure and function of the hypothalamus, leading to impaired control of energy homeostasis and food intake. The objective of this study was to identify the cellular and molecular systems underlying these effects during fetal development. We combined a global transcriptomic analysis on the fetal hypothalamus from a rat model of maternal PR with in vitro neurosphere culture and cellular analyses. Several genes encoding proteins from the mitochondrial respiratory chain complexes were overexpressed in the PR group and mitochondrial metabolic activity in the fetal hypothalamus was altered. The level of the N6-methyladenosine epitranscriptomic mark was reduced in the PR fetuses, and the expression of several genes involved in the writing/erasing/reading of this mark was indeed altered, as well as genes encoding several RNA-binding proteins. Additionally, we observed a higher number of neuronal-committed progenitors at embryonic day 17 (E17) in the PR fetuses. Together, these data strongly suggest a metabolic adaptation to the amino acid shortage, combined with the post-transcriptional control of protein expression, which might reflect alterations in the control of the timing of neuronal progenitor differentiation.