Treadmill exercise training alleviates diabetes-induced depressive-like behavior and cognitive impairment by improving hippocampal CA1 neurons injury in db/db mice

KLK8/HGF/Met signaling pathway mediates diabetes-associated hippocampal neuroinflammation in male mice

Rationale: Neuroinflammation plays a critical role in the pathogenesis of diabetes-associated depression. Tissue kallikrein-related peptidase 8 (KLK8), a secreted serine protease, has been implicated in the pathogenesis of depression- and anxiety-related behaviors across various etiologies, however the underlying mechanisms remain largely unexplored. This study elucidates a novel mechanism by which KLK8 upregulation contributes to diabetes-induced microglial activation and neuroinflammation in the hippocampus through modulating the hepatocyte growth factor (HGF)/Met signaling pathway. Methods and Results: Streptozotocin (STZ)-induced diabetic mice exhibited increased KLK8 expression in the hippocampus, an effect that was mitigated in KLK8-deficient or aerobic running-exercised mice. KLK8 deficiency significantly reduced depression-like behaviors, microglial activation, and neuroinflammation in diabetic mice. In BV2 mouse microglial cells, adenovirus-mediated overexpression of KLK8 (Ad-KLK8) was sufficient to induce microglial activation. Co-immunoprecipitation (Co-IP) coupled with mass spectrometry revealed that CD44 might interact with KLK8. KLK8 overexpression decreased CD44 levels in microglial cells. However, the CD44 activator Angstrom6 further exacerbated KLK8-induced microglial activation. Conversely, transcriptional profiling of KLK8-overexpressing microglial cells and subsequent validation demonstrated that the Met/Src/Btk/NF-κB signaling pathway played a central role in mediating the stimulatory effects of KLK8 on microglial activation in both Ad-KLK8-treated BV2 cells and human microglial cell line HMC3 cells stably transfected with KLK8 lentivirus (Lv-KLK8). The Met receptor is activated upon binding to its ligand HGF, which exists as an inactive precursor (pro-HGF). Our findings showed that KLK8 cleaved pro-HGF, promoting HGF release and subsequently activating the Met/Src/Btk/NF-κB signaling pathway in microglial cells. High glucose conditions increased KLK8 expression and enhanced HGF release, thereby stimulating the Met/Src/Btk/NF-κB signaling pathway and microglial activation in a KLK8-dependent manner. Systemic administration of a Met inhibitor inactivated the Met/Src/Btk/NF-κB pathway, reducing depression-like behaviors, microglial activation, and neuroinflammation in STZ-induced diabetic mice. Both Met inhibitor and KLK8 deficiency enhanced hippocampal neuroplasticity in STZ-induced diabetic mice. Finally, we demonstrated that running exercise reversed KLK8 upregulation and inactivated Met/Src/Btk/NF-κB signaling pathways, thereby attenuating neuroinflammation, improving neuroplasticity, and alleviating depression-like behaviors in STZ-induced diabetic mice. Conclusions: This study provides evidence that the KLK8/HGF/Met signaling pathway mediates diabetes-associated hippocampal neuroinflammation and depression-like behaviors, highlighting the therapeutic potential of targeting this pathway in diabetes-associated depression.

Scientific status analysis of exercise benefits for vascular cognitive impairment: Evidence of neuroinflammation

Vascular cognitive impairment (VCI) is a syndrome characterized by cognitive decline resulting from insufficient perfusion to the entire brain or specific brain regions. The lack of a clear understanding of the mechanisms linking cerebrovascular disease to cognitive impairment has impeded the development of targeted treatments for VCI. Increasing evidence indicates that exercise may offer significant benefits for patients with VCI. This study explores how neuroinflammatory mechanisms mediate the effects of exercise on VCI, focusing on the broader biological processes involved. Exercise plays a crucial role in mitigating vascular risk factors, reducing oxidative stress, and promoting neurogenesis. Furthermore, exercise influences neuroinflammatory mediators and central immune cells via various signaling pathways. Different types and intensities of exercise, including resistance and endurance training, have been shown to differentially modulate neuroinflammation during the progression of VCI. This paper summarizes the current mechanisms of action and proposes exercise interventions targeting neuroinflammatory pathways, along with biomarker studies, to enhance our understanding of VCI pathogenesis and inform clinical practice. A more in-depth understanding of the inflammatory mechanisms underlying VCI may facilitate the development of targeted therapeutic interventions.

Risk Factors, Pathological Changes, and Potential Treatment of Diabetes-Associated Cognitive Dysfunction

BACKGROUND

Diabetes is a prevalent public health issue worldwide, and the cognitive dysfunction and subsequent dementia caused by it seriously affect the quality of life of patients.

METHODS

Recent studies were reviewed to provide a comprehensive summary of the risk factors, pathogenesis, pathological changes and potential drug treatments for diabetes-related cognitive dysfunction (DACD).

RESULTS

Several risk factors contribute to DACD, including hyperglycemia, hypoglycemia, blood sugar fluctuations, hyperinsulinemia, aging, and others. Among them, modifiable risk factors for DACD include blood glucose control, physical activity, diet, smoking, and hypertension management, while non-modifiable risk factors include age, genetic predisposition, sex, and duration of diabetes. At the present, the pathogenesis of DACD mainly includes insulin resistance, neuroinflammation, vascular disorders, oxidative stress, and neurotransmitter disorders.

CONCLUSIONS

In this review, we provide a comprehensive summary of the risk factors, pathogenesis, pathological changes and potential drug treatments for DACD, providing information from multiple perspectives for its prevention and management.

Aerobic exercise and metformin attenuate the cognitive impairment in an experimental model of type 2 diabetes mellitus: focus on neuroinflammation and adult hippocampal neurogenesis

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder that increases the prevalence of cognitive impairment in the geriatric population. Aerobic exercise is an excellent non-pharmacological therapeutic strategy to prevent Alzheimer's disease, the most common form of dementia. The exact molecular mechanism of aerobic exercise (Exe) as an intervention to counter cognitive decline is far from clear. Metformin is a first-line agent against T2DM with neuroprotective properties. The present study assessed the role of treadmill exercise in combination with a low dose of metformin (Met; 70 mg/kg) in cognitive impairment and its associated molecular mechanism in T2DM rats. The experimental model of T2DM-associated cognitive decline was created by administration of a high-fat diet (HFD) with a low dose of streptozotocin (STZ; 35 mg/kg). Neurobehavioral assessments were performed to evaluate spatial recognition and fear-conditioned memory across the groups: control, HFD + STZ, HFD + STZ + Exe, and HFD + STZ + Exe + Met. In addition, we performed immunohistochemistry and western blotting on the rat hippocampal tissue from the above groups for protein expression studies. T2DM rats showed a significant cognitive decline compared to the control group, which improved in the long-term exercise and metformin co-administered animals. The level of neuroinflammation was significantly elevated in the hippocampal tissue of T2DM rats compared to the control and lowered after exercise and metformin treatment. T2DM reduced mature neurons and neurogenesis while increasing astrogliosis and microgliosis, ameliorated by exercise and metformin treatment. Moreover, T2DM impaired hippocampal neurogenesis by reducing the canonical Wnt/β-catenin pathway, which got upregulated in exercise and metformin-co-administered rats. Long-term aerobic exercise with metformin treatment ameliorated neuroinflammation and promoted adult hippocampal neurogenesis via upregulating the canonical Wnt/β-catenin pathway in T2DM rats.

Jaranol alleviates cognitive impairment in db/db mice through the PI3K/AKT pathway

The widely used Radix Astragali (RA) has significant therapeutic effects on cognitive impairment (CI) caused by type 2 diabetes (T2DM). However, the effective active ingredients and the precise mechanism underly RA alleviation of T2DM-induced CI still require further study. In this study, we aim to elucidate whether and how jaranol, a key effective active ingredient in RA, influences CI in db/db mice. We used various online databases and Cytoscape to screen jaranol as the most active ingredient of RA in the treatment of T2DM-induced CI. The fear conditioning experiment, new object recognition (NOR) test, and Morris water maze (MWM) test were conducted to assess the improvement effect of jaranol on CI in diabetic mice. The protein-protein interaction (PPI) network, Cytoscape, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to identify key genes. The levels of AKT and caspase-3 were determined by Western blotting. The number of surviving hippocampal neurons was verified through Nissl staining. AutoDock was utilized for predicting potential binding sites between jaranol and key genes.As a result, jaranol attenuated CI in db/db mice probably through activation of PI3K-AKT signaling pathway by inhibiting cell apoptosis in hippocampus. Furthermore, A329 near the active site of AKT1 had hydrogen bond with jaranol. In conclusion, we suggest that jaranol may have therapeutic applications in T2DM-induced CI by targeting the PI3K-AKT signaling pathway directly via key sites. Our study provides alternative drugs and potential therapeutic targets for the prevention and treatment of T2DM-induced CI.

Acute 2-phenyl-3-(phenylselanyl)benzofuran treatment reverses the neurobehavioral alterations induced by sleep deprivation in mice

Sleep is a fundamental state for maintaining the organism homeostasis. Disruptions in sleep patterns predispose to the appearance of memory impairments and mental disorders, including depression. Recent pre-clinical studies have highlighted the antidepressant-like properties of the synthetic compound 2-phenyl-3-(phenylselanyl)benzofuran (SeBZF1). To further investigate the neuromodulatory effects of SeBZF1, this study aimed to assess its therapeutic efficacy in ameliorating neurobehavioral impairments induced by sleep deprivation (SD) in mice. For this purpose, a method known as multiple platforms over water was used to induce rapid eye movement (REM) SD. Two hours after acute SD (24 h), male Swiss mice received a single treatment of SeBZF1 (5 mg/kg, intragastric route) or fluoxetine (a positive control, 20 mg/kg, intraperitoneal route). Subsequently, behavioral tests were conducted to assess spontaneous motor function (open-field test), depressive-like behavior (tail suspension test), and memory deficits (Y-maze test). Brain structures were utilized to evaluate oxidative stress markers, monoamine oxidase (MAO) and acetylcholinesterase (AChE) activities. Our findings revealed that SD animals displayed depressive-like behavior and memory impairments, which were reverted by SeBZF1 and fluoxetine treatments. SeBZF1 also reverted the increase in lipoperoxidation levels and glutathione peroxidase activity in the pre-frontal cortex in mice exposed to SD. Besides, the increase in hippocampal AChE activity induced by SD was overturned by SeBZF1. Lastly, cortical MAO-B activity was reestablished by SeBZF1 in mice that underwent SD. Based on the main findings of this study, it can be inferred that the compound SeBZF1 reverses the neurobehavioral alterations induced by sleep deprivation in male Swiss mice.

Microglial gp91phox-mediated neuroinflammation and ferroptosis contributes to learning and memory deficits in rotenone-treated mice

Apart from dopaminergic neurotoxicity, exposure to rotenone, a commonly used insecticide in agriculture, also adversely affects hippocampal and cortical neurons, resulting in cognitive impairments in mice. We recently established a role of microglia-mediated neuroinflammation in rotenone-elicited deficits of cognition, yet the mechanisms remain elusive. Here, we investigated the involvement of NADPH oxidase 2 (NOX2) catalytic subunit gp91phox in rotenone-induced cognitive deficits and the associated mechanisms. Our study demonstrated that rotenone exposure elevated expression of gp91phox and phosphorylation of the NOX2 cytosolic subunit p47phox, along with NADPH depletion in the hippocampus and cortex of mice, indicating NOX2 activation. Specific knockdown of gp91phox in microglia via adeno-associated virus delivery resulted in reduced microglial activation, proinflammatory gene expression and improved learning and memory capacity in rotenone-intoxicated mice. Genetic deletion of gp91phox also reversed rotenone-elicited cognitive dysfunction in mice. Furthermore, microglial gp91phox knockdown attenuated neuronal damage and synaptic loss in mice. This intervention also suppressed iron accumulation, disruption of iron-metabolism proteins and iron-dependent lipid peroxidation and restored the balance of ferroptosis-related parameters, including GPX4, SLC711, PTGS2, and ACSL4 in rotenone-lesioned mice. Intriguingly, pharmacological inhibition of ferroptosis with liproxstatin-1 conferred protection against rotenone-induced neurodegeneration and cognitive dysfunction in mice. In summary, our findings underscored the contribution of microglial gp91phox-dependent neuroinflammation and ferroptosis to learning and memory dysfunction in rotenone-lesioned mice. These results provided valuable insights into the pathogenesis of cognitive deficits associated with pesticide-induced Parkinsonism, suggesting potential therapeutic avenues for intervention.

Jiao-tai-wan and its effective component-berberine improve diabetes and depressive disorder through the cAMP/PKA/CREB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Jiao-tai-wan (JTW), a classic herbal formula of traditional Chinese medicine recorded in Han Shi Yi Tong, has been used to alleviate sleep disorders since ancient times. In modern pharmacological research, JTW has been adopted for treating diabetes mellitus and even exerts antidepressant effects. However, the potential mechanisms deserve further elucidation.

AIM OF THE STUDY

The prevalence of diabetes mellitus combined with depressive disorder (DD) is continuing to increase, yet it is currently under-recognized and its treatment remains inadequate. The present study aims to explore the underlying therapeutics and mechanisms of JTW on DD.

MATERIALS AND METHODS

Chronic restraint stress was used on db/db mice to construct a mouse model of DD. The therapeutic effects of JTW were assessed by glucolipid metabolic indexes, behavioral tests, and depression-related neurotransmitter levels. The inflammatory status and cell apoptosis of different mice were investigated and the changes in the cAMP/PKA/CREB pathway were detected. Combining the results of fingerprinting with molecular docking, the active components of JTW were screened. A cellular model was constructed by intervention of glucose combined with corticosterone (CORT). The levels of apoptosis and depression-related neurotransmitters in HT-22 cells were examined, and the changes in the cAMP/PKA/CREB pathway were tested. Finally, the activator and inhibitor of the PKA protein were used for reverse validation experiments.

RESULTS

JTW could improve the impaired glucose tolerance, lipid metabolism disorders, and depression-like symptoms in DD mice. Meanwhile, JTW could alleviate the inflammatory status, suppress the microglia activation, and improve hippocampal neuron apoptosis in DD mice. The dual effects of JTW might be associated with the activation of the cAMP/PKA/CREB pathway. Berberine (Ber) was identified for the in vitro experiment, it could reverse the apoptosis of HT-22 cells and up-regulate the depression-related neurotransmitter levels, and the effects of Ber were related to the activation of the cAMP/PKA/CREB pathway as well.

CONCLUSION

JTW could exert both hypoglycemic and antidepressant effects through activating the cAMP/PKA/CREB signaling pathway, its active component, Ber, could improve the damage to HT-22 cells induced by glucose combined with CORT via the activation of the cAMP/PKA/CREB pathway. Ber may be one of the effective components of the dual effects of JTW.

The gut-brain axis and cognitive control: A role for the vagus nerve

Survival requires the integration of external information and interoceptive cues to effectively guide advantageous behaviors, particularly foraging and other behaviors that promote energy acquisition and consumption. The vagus nerve acts as a critical relay between the abdominal viscera and the brain to convey metabolic signals. This review synthesizes recent findings from rodent models and humans revealing the impact of vagus nerve signaling from the gut on the control of higher-order neurocognitive domains, including anxiety, depression, reward motivation, and learning and memory. We propose a framework where meal consumption engages gastrointestinal tract-originating vagal afferent signaling that functions to alleviate anxiety and depressive-like states, while also promoting motivational and memory functions. These concurrent processes serve to favor the encoding of meal-relevant information into memory storage, thus facilitating future foraging behaviors. Modulation of these neurocognitive domains by vagal tone is also discussed in the context of pathological conditions, including the use of transcutaneous vagus nerve stimulation for the treatment of anxiety disorders, major depressive disorder, and dementia-associated memory impairments. Collectively, these findings highlight the contributions of gastrointestinal vagus nerve signaling to the regulation of neurocognitive processes that shape various adaptive behavioral responses.

Systematic review and meta-analysis of the effects of exercise on cognitive impairment and neuroprotective mechanisms in diabetes mellitus animal models

This study aims to assess the effects of exercise on cognitive impairment behavioral performance and neuroprotective mechanisms in diabetes mellitus (DM) animal models. PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang Database, VIP Database (VIP), and China Biomedical Literature Database (CBM) were systematically searched for studies investigating the impact of exercise on cognitive impairment in animal models of diabetes mellitus (DM) from the inception of these databases through July 2023. Rigorous quality assessments were conducted on the included literature. Primary outcome measures comprised fasting blood glucose (FBG) levels and performance in the Morris water maze test, while secondary outcomes focused on mechanisms related to neuroprotection. Statistical analysis of outcome data was conducted using RevMan 5.3 and R software. A total of 17 studies were included, encompassing 399 animals. The results of the meta-analysis of primary outcome measures revealed that, compared to the control group, exercise effectively reduced fasting blood glucose (FBG) levels in diabetic animal models. In the Morris water maze experiment, exercise also significantly decreased the escape latency of diabetic animal models, increased the number of platform crossings, improved the percentage of time spent in the target quadrant, extended the time spent in the target quadrant, and enhanced swimming speed. Meta-analysis of secondary outcome measures indicated that exercise effectively reduced Aβ deposition, attenuated oxidative stress, enhanced synaptic function, suppressed cellular apoptosis and neuroinflammation, and promoted neurogenesis. Exercise represents a promising non-pharmacological therapy with a positive impact on diabetes-related cognitive function and neuroprotection. Moreover, this study provides a theoretical foundation for further preclinical and clinical trials.

NTRK1 knockdown induces mouse cognitive impairment and hippocampal neuronal damage through mitophagy suppression via inactivating the AMPK/ULK1/FUNDC1 pathway

Hippocampal neuronal damage may induce cognitive impairment. Neurotrophic tyrosine kinase receptor 1 (NTRK1) reportedly regulates neuronal damage, although the underlying mechanism remains unclear. The present study aimed to investigate the role of NTRK1 in mouse hippocampal neuronal damage and the specific mechanism. A mouse NTRK1-knockdown model was established and subjected to pre-treatment with BAY-3827, followed by a behavioral test, Nissl staining, and NeuN immunofluorescence (IF) staining to evaluate the cognitive impairment and hippocampal neuronal damage. Next, an in vitro analysis was conducted using the CCK-8 assay, TUNEL assay, NeuN IF staining, DCFH-DA staining, JC-1 staining, ATP content test, mRFP-eGFP-LC3 assay, and LC3-II IF staining to elucidate the effect of NTRK1 on mouse hippocampal neuronal activity, apoptosis, damage, mitochondrial function, and autophagy. Subsequently, rescue experiments were performed by subjecting the NTRK1-knockdown neurons to pre-treatment with O304 and Rapamycin. The AMPK/ULK1/FUNDC1 pathway activity and mitophagy were detected using western blotting (WB) analysis. Resultantly, in vivo analysis revealed that NTRK1 knockdown induced mouse cognitive impairment and hippocampal tissue damage, in addition to inactivating the AMPK/ULK1/FUNDC1 pathway activity and mitophagy in the hippocampal tissues of mice. The treatment with BAY-3827 exacerbated the mouse depressive-like behavior induced by NTRK1 knockdown. The results of in vitro analysis indicated that NTRK1 knockdown attenuated viability, NeuN expression, ATP production, mitochondrial membrane potential, and mitophagy, while enhancing apoptosis and ROS production in mouse hippocampal neurons. Conversely, pre-treatment with O304 and rapamycin abrogated the suppression of mitophagy and the promotion of neuronal damage induced upon NTRK1 silencing. Conclusively, NTRK1 knockdown induces mouse hippocampal neuronal damage through the suppression of mitophagy via inactivating the AMPK/ULK1/FUNDC1 pathway. This finding would provide insight leading to the development of novel strategies for the treatment of cognitive impairment induced due to hippocampal neuronal damage.

Intermittent fasting alleviates type 1 diabetes-induced cognitive dysfunction by improving the frontal cortical metabolic disorder

Intermittent fasting (IF) is an ecological strategy to control various metabolic disorder symptoms, but its protective effect on type 1 diabetes (T1D)-induced cognitive dysfunction and the underlying mechanisms remain poorly defined. Herein, we examined the efficacy of IF in altering the behaviors and brain metabolome in T1D mice and investigated the potential molecular mechanisms. We demonstrated that IF remarkably improved frontal cortical-dependent memory in T1D mice and reduced the loss of neuronal cells. Metabolomics and targeted mass spectrometry assay showed that IF reprogrammed the frontal cortical metabolome composition, including activated the aspartate and glutamate pathway and reversed glycerophospholipid and sphingolipid depositions in T1D mice. Mechanistically, IF attenuated the levels of oxidative stress proteins, such as NOX2, NOX4, 8-OHdG, 4-HNE, and inhibited the levels of pro-apoptotic factors Bax and cleaved Caspase-3, finally improved the memory ability of T1D mice. In vitro studies confirmed the protective effect of the supplemented N-acetylaspartate, a pivotal metabolite involved in IF-regulated T1D-induced cognitive dysfunction, in high glucose-stimulated SH-SY5Y cells by eliminating toxic lipids accumulation, oxidative stress and apoptosis. To conclude, the frontal cortical metabolites mediated the protective effects of IF against T1D-induced cognitive dysfunction by attenuating oxidative stress and apoptotic signaling. Thus, IF can be a potential therapeutic strategy for T1D-induced cognitive dysfunction.

A study of the influence of sports venues on the intra-city population layout based on multi-source data-Taking Xi'an city and Zhengzhou city as examples

Revealing the influence of sports sports venues on the population in the built-up areas of cities contributes to the high-quality development of cities and the well-being of people. This study applies kernel density estimation to characterize the distribution of sports venues using reclassified POI (Point of Information) data, visualizes the distribution of intra-city population using population raster data from the WorldPop database, and analyses the distribution of sports venues and the urban population in Xi'an and Zhengzhou cities in 2020 from both the general and local perspectives based on various regression methods, such as MGWR, GWR, and linear fitting. The results show that the distribution of sports venues in Xi'an and Zhengzhou cities in 2020 was a good indicator of the population. The spatial distribution of sports venues and the population within the cities have a centre-periphery structure. From the global perspective, the distribution of sports venues is positively correlated with the intra-city population, and the promoting effect is significant. From the local perspective, the effect is spatially heterogeneous. Finally, this study explores the rationality of the complex impact and indicates that the research methodology can provide a reliable reference for other cities.