Neurovascular protection by peroxisome proliferator-activated receptor α in ischemic stroke

Combining fecal 16 S rRNA sequencing and spinal cord metabolomics analysis to explain the modulatory effect of PPARα on neuropathic pain

BACKGROUND

Existing evidence suggests that the composition of the gut microbiota is associated with neuropathic pain (NP), but the mechanistic link is elusive. Peroxisome proliferator-activated receptor α (PPARα) has been shown to be a pharmacological target for the treatment of metabolic disorders, and its expression is also involved in inflammatory regulation. The aim of this study was to investigate the important modulatory effects of PPARα on gut microbiota and spinal cord metabolites in mice subjected to chronic constriction injury.

METHODS

We analyzed fecal microbiota and spinal cord metabolic alterations in mice from the sham, CCI, GW7647 (PPARα agonist) and GW6471 (PPARα antagonist) groups by 16 S rRNA amplicon sequencing and untargeted metabolomics analysis. On this basis, the intestinal microbiota and metabolites that were significantly altered between treatment groups were analyzed in a combined multiomics analysis. We also investigated the effect of PPARα on the polarization fractionation of spinal microglia.

RESULTS

PPARα agonist significantly reduce paw withdrawal threshold and paw withdrawal thermal latency, while PPARα antagonist significantly increase paw withdrawal threshold and paw withdrawal thermal latency. 16 S rRNA gene sequencing showed that intraperitoneal injection of GW7647 or GW6471 significantly altered the abundance, homogeneity and composition of the gut microbiome. Analysis of the spinal cord metabolome showed that the levels of spinal cord metabolites were shifted after exposure to GW7647 or GW6471. Alterations in the composition of gut microbiota were significantly associated with the abundance of various spinal cord metabolites. The abundance of Licheniformes showed a significant positive correlation with nicotinamide, benzimidazole, eicosanoids, and pyridine abundance. Immunofluorescence results showed that intraperitoneal injection of GW7647 or GW6471 altered microglial activation and polarization levels.

CONCLUSION

Our study shows that PPARα can promote M2-type microglia polarization, as well as alter gut microbiota and metabolites in CCI mice. This study enhances our understanding of the mechanism of PPARα in the treatment of neuropathic pain.

Ischemic stroke pathophysiology: A bibliometric and visualization analysis from 1990 to 2022

Background

Pathophysiology plays a significant role in the scientific study of ischemic stroke, and has attracted increasing interest from researchers in the field. However, a comprehensive bibliometric analysis is lacking in this field. The purpose of this study is to identify the current research status and hotspots of ischemic stroke pathophysiology from a bibliometric perspective.

Methods

The Web of Science Core Collection database was searched for articles published from 1990 to 2022. CiteSpace, VOSviewer, and R package "bibliometrix" software were used to analyze countries/regions, institutions, journals, authors, papers, and keywords to predict the latest trends in ischemic stroke pathophysiology research.

Results

This analysis collected 7578 records of ischemic stroke pathophysiology. China and America emerged as the leading countries in this field, with Harvard University being the most active institution. Among journals and authors in this field, journal Stroke and author Gregory YH Lip published the most papers, while Nature Medicine was the journal with the highest citation per article. Keywords and co-citation clusters were closely related to "central nervous system", "mechanisms", "biochemistry & molecular biology" and "radiology, nuclear medicine & medical imaging", while other related fields, such as peripheral organs damage induced by the central nervous system and rehabilitation after ischemic stroke, require further research efforts.

Conclusion

This is the first bibliometric study that comprehensively mapped out the knowledge structure and development trends of ischemic stroke pathophysiology in recent 32 years, which may provide a reference for scholars to explore ischemic stroke pathophysiology.

Paraoxonases at the Heart of Neurological Disorders

Paraoxonase enzymes serve as an important physiological redox system that participates in the protection against cellular injury caused by oxidative stress. The PON enzymes family consists of three members (PON-1, PON-2, and PON-3) that share a similar structure and location as a cluster on human chromosome 7. These enzymes exhibit anti-inflammatory and antioxidant properties with well-described roles in preventing cardiovascular disease. Perturbations in PON enzyme levels and their activity have also been linked with the development and progression of many neurological disorders and neurodegenerative diseases. The current review summarizes the available evidence on the role of PONs in these diseases and their ability to modify risk factors for neurological disorders. We present the current findings on the role of PONs in Alzheimer's disease, Parkinson's disease, and other neurodegenerative and neurological diseases.

NLRP3 inflammasome activation increases brain oxidative stress after transient global cerebral ischemia in rats

Pupurpose of the study: Oxidative stress has been reported to be an important mechanism for brain damage following ischemic stroke. Recently, the involvement of cytosolic receptors capable of forming protein complexes called inflammasomes has been demonstrated to perpetuate oxidative stress. Herein, we report the effect of NLRP3 inhibition with MCC950 on brain oxidative stress in an animal model of transient global cerebral ischemia.Materials and methods: Male Wistar rats received an intracerebroventricularly (icv) injection of MCC950 (140 ng/kg) or saline and were subjected to sham procedure or ischemia/reperfusion (I/R). Twenty-four hours after I/R, myeloperoxidase (MPO) activity, nitrite/nitrate (N/N) concentration, lipid peroxidation, protein carbonyls formation, superoxide dismutase (SOD) and catalase (CAT) activity were determined in the prefrontal cortex, hippocampus, cortex, cerebellum and striatum. Results: After I/R, MPO activity increased in the prefrontal cortex, hippocampus, cortex and cerebellum and N/N concentration elevated in the prefrontal cortex, hippocampus and cortex, while MCC950 decreased this level except in hippocampus. After I/R, lipid peroxidation enhanced in the prefrontal cortex and cerebellum and increased the oxidative protein damage in both structures and hippocampus. MCC950 decreased lipid peroxidation in the prefrontal cortex and decreased protein oxidative damage in all brain structures except in the striatum. SOD activity decreased in the cortex after I/R and MCC950 reestablished these levels. CAT activity decreased in the prefrontal cortex, hippocampus and cerebellum after I/R and MCC950 reestablished these levels in the prefrontal cortex.Conclusion: Our data provide novel demonstration that inhibiting NLRP3 activation with MCC950 reduces brain oxidative damage after cerebral I/R in rats.

PPARα Inhibits Astrocyte Inflammation Activation by Restoring Autophagic Flux after Transient Brain Ischemia

Astrocyte inflammation activation is an important cause that hinders the recovery of motor function after cerebral ischemia. However, its molecular mechanism has not yet been clearly clarified. The peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated nuclear transcriptional factor. This study aims to further clarify the role of PPARα in astrocyte inflammation activation after cerebral ischemia and to explore the underlying mechanism. Astrocyte activation was induced in an in vivo model by transient middle cerebral artery occlusion (tMCAO) in mice. The in vitro model was induced by an oxygen-glucose deprivation/reoxygenation (OGD/R) in a primary culture of mouse astrocyte. PPARα-deficient mice were used to observe the effects of PPARα on astrocyte activation and autophagic flux. Our results showed that PPARα was mainly expressed in activated astrocytes during the chronic phase of brain ischemia and PPARα dysfunction promoted astrocyte inflammatory activation. After cerebral ischemia, the expressions of LC3-II/I and p62 both increased. Autophagic vesicle accumulation was observed by electron microscopy in astrocytes, and the block of autophagic flux was indicated by an mRFP-GFP-LC3 adenovirus infection assay. A PPARα deficit aggravated the autophagic flux block, while PPARα activation preserved the lysosome function and restored autophagic flux in astrocytes after OGD/R. The autophagic flux blocker bafilomycin A1 and chloroquine antagonized the effect of the PPARα agonist on astrocyte activation inhibition. This study identifies a potentially novel function of PPARα in astrocyte autophagic flux and suggests a therapeutic target for the prevention and treatment of chronic brain ischemic injury.

Neuroprotective Effects and Metabolomics Study of Protopanaxatriol (PPT) on Cerebral Ischemia/Reperfusion Injury In Vitro and In Vivo

Stroke, one of the leading causes of disability and death worldwide, is a severe neurological disease that threatens human life. Protopanaxatriol (PPT), panaxatriol-type saponin aglycone, is a rare saponin that exists in Panax ginseng and Panax Noto-ginseng. In this study, we established an oxygen-glucose deprivation (OGD)-PC12 cell model and middle cerebral artery occlusion/reperfusion (MCAO/R) model to evaluate the neuroprotective effects of PPT in vitro and in vivo. In addition, metabolomics analysis was performed on rat plasma and brain tissue samples to find relevant biomarkers and metabolic pathways. The results showed that PPT could significantly regulate the levels of LDH, MDA, SOD, TNF-α and IL-6 factors in OGD-PC12 cells in vitro. PPT can reduce the neurological deficit score and infarct volume of brain tissue in rats, restore the integrity of the blood-brain barrier, reduce pathological damage, and regulate TNF-α, IL-1β, IL-6, MDA, and SOD factors. In addition, the results of metabolomics found that PPT can regulate 19 biomarkers involving five metabolic pathways, including amino acid metabolism, arachidonic acid metabolism, sphingolipid metabolism, and glycerophospholipid metabolism. Thus, it could be inferred that PPT might serve as a novel natural agent for MCAO/R treatment.

Effects of Different Doses of Clopidogrel plus Early Rehabilitation Therapy on Motor Function and Inflammatory Factors in Patients with Ischemic Stroke

This prospective randomized controlled study was intended to assess the effects of different doses of clopidogrel plus early rehabilitation therapy on motor function and inflammatory factors in patients with ischemic stroke. Between August 2018 and October 2020, 90 cases of ischemic stroke treated in the Second People's Hospital of Yibin were randomized at a ratio of 1 : 1 to receive either oral 50 mg/d clopidogrel plus early rehabilitation therapy (low-dose group) or oral 75 mg/d clopidogrel plus early rehabilitation therapy (high-dose group), with 45 cases in each group. The outcome measures including the Barthel Index (BI), National Institutes of Health Stroke Scale (NIHSS), Fugl-Meyer simplified scale, hypersensitive C-reactive protein (hs-CRP), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and occurrence of adverse events were collected. After treatment, the high-dose group had higher BI results than the low-dose group. All eligible patients showed significantly declined NIHSS scores, and the high-dose group had markedly lower results (P < 0.05). After treatment, the Fugl-Meyer scores of both upper and lower extremities of the high-dose group were significantly higher than those in the low-dose group. The high-dose group achieved a greater decrease in inflammatory factor levels after treatment versus the low-dose group. The two groups showed a similar incidence of adverse events. High-dose clopidogrel plus early rehabilitation outperforms the low-dose treatment for patients with ischemic stroke by effectively mitigating the inflammatory response in the body, promoting the restoration of neurological function, improving the level of motor function, and enhancing the patient's quality of life, with manageable safety.

Role of Semaphorins in Ischemic Stroke

Ischemic stroke is one of the major causes of neurological morbidity and mortality in the world. Although the management of ischemic stroke has been improved significantly, it still imposes a huge burden on the health and property. The integrity of the neurovascular unit (NVU) is closely related with the prognosis of ischemic stroke. Growing evidence has shown that semaphorins, a family of axon guidance cues, play a pivotal role in multiple pathophysiological processes in NVU after ischemia, such as regulating the immune system, angiogenesis, and neuroprotection. Modulating the NVU function via semaphorin signaling has a potential to develop a novel therapeutic strategy for ischemic stroke. We, therefore, review recent progresses on the role of semphorin family members in neurons, glial cells and vasculature after ischemic stroke.

A new nitronyl nitroxide radical with salicylic acid framework attenuates blood-brain barrier disruption and oxidative stress in a rat model of middle cerebral artery occlusion

OBJECTIVES

A new nitronyl nitroxide radical with a salicylic acid framework (SANR) has been demonstrated to exert antioxidant effects in the previous study by our team. The current study has assessed the protective effect of SANR on cerebral ischemia and reperfusion (I/R) in rat models.

METHODS

Sprague-Dawley rats were randomly divided into four groups: sham, I/R, 10, and 20 mg/kg SANR + I/R groups. A total of 120 min of middle cerebral artery occlusion (MCAO) caused cerebral ischemia. Survival rates were calculated, and neurological deficits were evaluated by a blinded experimenter. Cerebral infarct area, apoptosis cells, and blood-brain barrier (BBB) leakage were measured by 2,3,5-triphenyltetrazolium chloride staining, terminal deoxynucleotidyl transferase dUTP nick-end labeling, and Evans blue assay, respectively. Reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and 8-hydroxy-2-deoxyguanosine (8-OHdG) also were detected to assess oxidation damage caused by cerebral I/R.

RESULTS

Treatment with SANR significantly promoted survival of rats with cerebral I/R injury. SANR meliorated neurologic deficit and infarct area, improved BBB permeability, and reduced neuronal apoptosis. SANR also reduced ROS levels and the content of MDA and increased SOD and GSH-Px activity in a dose-dependent manner. Furthermore, SANR could inhibit the expression of 8-OHdG.

CONCLUSION

Our results suggested that SANR has a neuroprotective effect against cerebral I/R injury, and its effect mechanism is related to the antioxidant function.

Systematic Understanding of Mechanism of Danggui Shaoyao San against Ischemic Stroke Using a Network Pharmacology Approach

Purpose

Danggui Shaoyao San (DSS) was developed to treat the ischemic stroke (IS) in patients and animal models. The purpose of this study was to explore its active compounds and demonstrate its mechanism against IS through network pharmacology, molecular docking, and animal experiment.

Methods

All the components of DSS were retrieved from the pharmacology database of TCM system. The genes corresponding to the targets were retrieved using OMIM, CTD database, and TTD database. The herb-compound-target network was constructed by Cytoscape software. The target protein-protein interaction network was built using the STRING database. The core targets of DSS were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Then, we achieved molecular docking between the hub proteins and the key active compounds. Finally, animal experiments were performed to verify the core targets. Triphenyltetrazolium chloride (TTC) staining was used to calculate the infarct size in mice. The protein expression was determined using the Western blot.

Results

Compound-target network mainly contained 51 compounds and 315 corresponding targets. Key targets contained MAPK1, SRC, PIK3R1, HRAS, AKT1, RHOA, RAC1, HSP90AA1, and RXRA FN1. There were 417 GO items in GO enrichment analysis (p < 0.05) and 119 signaling pathways (p < 0.05) in KEGG, mainly including negative regulation of apoptosis, steroid hormone-mediated signaling pathway, neutrophil activation, cellular response to oxidative stress, and VEGF signaling pathway. MAPK1, SRC, and PIK3R1 docked with small molecule compounds. According to the Western blot, the expression of p-MAPK 1, p-AKT, and p-SRC was regulated by DSS.

Conclusions

This study showed that DSS can treat IS through multiple targets and routes and provided new insights to explore the mechanisms of DSS against IS.

Promoting the hippocampal PPARα expression participates in the antidepressant mechanism of reboxetine, a selective norepinephrine reuptake inhibitor

Reboxetine, the first selective norepinephrine (NA) reuptake inhibitor used in the treatment of depression, mainly acts by binding to the NA transporter and blocking reuptake of extracellular NA. Recently, some other pharmacological targets beyond the NA transporter are being demonstrated for reboxetine. Peroxisome proliferator activated receptor α (PPARα) is a member of the nuclear hormone receptor family of ligand-dependent transcription factors. Previous reports have demonstrated the role of hippocampal PPARα in the pathophysiology of depression. Here we assume that hippocampal PPARα may participate in the antidepressant mechanism of reboxetine. Therefore, the chronic social defeat stress (CSDS) model of depression, various behavioral tests, the western blotting and adenovirus associated virus (AAV)-mediated genetic knockdown methods were used together in the present study. Our results showed that repeated reboxetine treatment markedly restored the decreasing effects of CSDS on the expression of hippocampal PPARα, brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element binding protein (pCREB). Pharmacological blockade of PPARα notably prevented the antidepressant-like effects of reboxetine in the CSDS model. Furthermore, genetic knockdown of hippocampal PPARα also fully abolished the antidepressant-like effects of reboxetine in the CSDS model. Taken together, promoting the hippocampal PPARα expression participates in the antidepressant mechanism of reboxetine.

Protective Properties of the Extract of Chrysanthemum on Patients with Ischemic Stroke

Investigation of the protective effect of chrysanthemum extract in ischemic strokes patients is among the challenging issues with the traditional hospital system in general and smart technology-based hospitals in particular. In this study, we have evaluated the protective effect of chrysanthemum extract on patients with ischemic stroke by detecting the severity of stroke, neuronal indexes, and oxidative stress biomarkers. For this purpose, forty-six patients with ischemic stroke were randomly divided into the control group (n = 30) and chrysanthemum group (n = 30). The control group received standard stroke treatment, and the chrysanthemum group was treated with chrysanthemum extract 400 mg/day (200 mg/day, twice/day) on the basis of standard treatment. The groups were compared the effect of saffron capsules using the National Institute of Health Stoke Scale (NIHSS), serum neuron specific enolase (NSE), S100, brain-derived neurotrophic factor (BDNF), malondialdehyde (MDA), Su-peroxide dismutase (SOD), and total antioxidant capacity (TAC ) levels, at the time of first day and fourth day after treatment. On the first day after treatment, there was no significant difference in the NIHSS score, serum NSE, S100, BDNF, MDA, SOD, and TAC levels between the chrysanthemum group and the control group (P > 0.05). On the fourth day after treatment, the NIHSS, serum NSE, S100, and MDA levels were significantly reduced in the chrysanthemum group compared to the control group, while the BDNF, SOD, and TAC levels were higher (P < 0.05). In addition, compared to the levels on the first day, the NIHSS, serum NSE, S100, and MDA levels were significantly reduced, and the BDNF, SOD, and TAC levels were increased in the chrysanthemum group on the fourth day (P < 0.05). Chrysanthemum extract has the effects of scavenging oxygen free radicals and antioxidation and has a neuroprotective effect on ischemic stroke patients.

Effects of Txk‑mediated activation of NF‑κB signaling pathway on neurological deficit and oxidative stress after ischemia‑reperfusion in rats

Ischemic stroke is an extremely mortal cerebrovascular disease, and neuroinflammation and oxidative stress emerge as important traits of ischemic stroke. However, as an inflammation‑associated factor, Txk tyrosine kinases (Txk) has been poorly studied in neuroscience research. The aim of the present study was to investigate the role of Txk after ischemia‑reperfusion (I/R) in vivo and in vitro, observe the association between Txk knockdown and neurological deficit and oxidative stress, and to explore whether the process was mediated by the activation of nuclear factor (NF)‑κB signaling pathway. Middle cerebral artery occlusion (MCAO), oxygen and glucose deprivation/reperfusion (OGD/R) model and western blotting have been used to simulate the I/R injury to analyze the expression, and to approximate the localization of Txk, respectively. Brain infarct volume, neurological score, brain water content, apoptosis and oxidative stress assays in vivo and apoptosis, cellular viability, the LDH release and oxidative stress assays in vitro were observed using a Txk‑knockdown lentivirus. Finally, NF‑κB overexpression lentivirus was applied to discuss whether the role of Txk following I/R was regulated by the NF‑κB signaling pathway. The results show that the Txk expression peaked at 24 h after MCAO and 6 h after OGD/R, respectively. Txk molecules gradually entered the nucleus after MCAO and OGD/R. The Txk‑knockdown lentivirus resulted in decreased brain infarct volume, neurological score, brain water content, apoptosis and oxidative stress after MCAO in vivo. Besides, Txk knockdown decreased apoptosis, LDH release, oxidative stress, and increased cellular viability, after ODG in vitro. Finally, NF‑κB overexpression reversed the process of neurological deficit and oxidative stress after Txk regulation in vivo and vitro. Overall, the present study suggests that Txk potentially regulates apoptosis, neurological deficit, and oxidative stress after I/R, by entering the nucleus. NF‑κB maybe the downstream target factor of Txk.

Baicalin Inhibits NLRP3 Inflammasome Activity Via the AMPK Signaling Pathway to Alleviate Cerebral Ischemia-Reperfusion Injury

Baicalin has been reported to have ameliorative effects on nerve-induced hypoxic ischemia injury; however, its role in the NLRP3 inflammasome-dependent inflammatory response during cerebral ischemia-reperfusion remains unclear. To investigate the molecular mechanisms involved in baicalin alleviating cerebral ischemia-reperfusion injury, we investigated the AMPK signaling pathway which regulates NLRP3 inflammasome activity. SD rats were treated with baicalin at doses of 100 mg/kg and 200 mg/kg, respectively, after middle cerebral artery occlusion at 2 h and reperfusion for 24 h (MCAO/R). MCAO/R treatment significantly increased cerebral infarct volume, changed the ultrastructure of nerve cells, and activated the NLRP3 inflammasome, manifesting as significantly increased expression of NLRP3, ASC, cleaved caspase-1, IL-1β, and IL-18. Our results demonstrated that baicalin treatment effectively reversed these phenomena in a dose-dependent manner. Additionally, inhibition of NLRP3 expression was found to promote the neuroprotective effects of baicalin on cortical neurons. Furthermore, baicalin remarkably increased the expression of p-AMPK following oxygen glucose deprivation/reperfusion (OGD/R). The expression of the NLRP3 inflammasome was also increased when the AMPK pathway was blocked by compound C. Taken together, our findings reveal that baicalin reduces the activity of the NLRP3 inflammasome and consequently inhibits cerebral ischemia-reperfusion injury through activation of the AMPK signaling pathway.

Transcriptomic and Metabolomic Profiling Reveals the Protective Effect of Acanthopanax senticosus (Rupr. & Maxim.) Harms Combined With Gastrodia elata Blume on Cerebral Ischemia-Reperfusion Injury

The effects of current treatment strategies used in ischemic stroke are weakened by cerebral ischemia-reperfusion (CIR) injury. Suitable treatment regimens targeting CIR injury are still lacking. Two herbs, namely, Acanthopanax senticosus (Rupr. & Maxim.) Harms (ASE) and Gastrodia elata Blume (GEB), have been used as traditional Chinese medicine and are indicated in the treatment of stroke and cerebrovascular diseases. However, there are no studies that report the effects of ASE combined with GEB in the treatment of CIR injury. In this study, we used the Zea Longa method to induce CIR injury in male Wistar rats. Results of the pharmacodynamic studies revealed that co-administration of ASE and GEB may improve neuronal injury and prevent neuronal apoptosis by reducing oxidative stress and inflammation, and also help prevent CIR injury. On the basis of our hypothesis, we combined the results from transcriptomic and metabonomic analyses and found that ASE and GEB could prevent CIR injury by targeting phenylalanine, pyrimidine, methionine, and sphingolipid metabolism. Therefore, our study provides the basis for the compatibility and efficacy of ASE and GEB.

Receptors, Channel Proteins, and Enzymes Involved in Microglia-mediated Neuroinflammation and Treatments by Targeting Microglia in Ischemic Stroke

Stroke is the largest contributor to global neurological disability-adjusted life-years, posing a huge economic and social burden to the world. Though pharmacological recanalization with recombinant tissue plasminogen activator and mechanical thrombectomy have greatly improved the prognosis of patients with ischemic stroke, clinically, there is still no effective treatment for the secondary injury caused by cerebral ischemia. In recent years, more and more evidences show that neuroinflammation plays a pivotal role in the pathogenesis and progression of ischemic cerebral injury. Microglia are brain resident innate immune cells and act the role peripheral macrophages. They play critical roles in mediating neuroinflammation after ischemic stroke. Microglia-mediated neuroinflammation is not an isolated process and has complex relationships with other pathophysiological processes as oxidative/nitrative stress, excitotoxicity, necrosis, apoptosis, pyroptosis, autophagy, and adaptive immune response. Upon activation, microglia differentially express various receptors, channel proteins, and enzymes involved in promoting or inhibiting the inflammatory processes, making them the targets of intervention for ischemic stroke. To inhibit microglia-related neuroinflammation and promote neurological recovery after ischemic stroke, numerous biochemical agents, cellular therapies, and physical methods have been demonstrated to have therapeutic potentials. Though accumulating experimental evidences have demonstrated that targeting microglia is a promising approach in the treatment of ischemic stroke, the clinical progress is slow. Till now, no clinical study could provide convincing evidence that any biochemical or physical therapies could exert neuroprotective effect by specifically targeting microglia following ischemic stroke.

Insulin Resistance and Blood-Brain Barrier Dysfunction Underlie Neuroprogression in Bipolar Disorder

Bipolar disorder (BD) often progresses to a more chronic and treatment resistant (neuroprogressive) course. Identifying which patients are at risk could allow for early intervention and prevention. Bipolar disorder is highly comorbid with metabolic disorders including type II diabetes mellitus (T2DM), hypertension, obesity, and dyslipidemia. Our studies have shown that insulin resistance (IR) is present in over 50% of patients with BD and that IR might underlie the progression of BD. While no confirmed predictors exist for identifying which patients with BD are likely to develop a more chronic course, emerging evidence including our own studies suggest that IR and related inflammatory pathways lead to impairments in blood-brain barrier (BBB) functioning. For the first time in living psychiatric patients, we have shown that the severity of BBB leakage is proportional to BD severity and is associated with IR. In this hypothesis paper we (i) highlight the evidence for a key role of IR in BD, (ii) show how IR in BD relates to shared inflammatory pathways, and (iii) hypothesize that these modulations result in BBB leakage and worse outcomes in BD. We further hypothesize that (iv) reversing IR through lifestyle changes or the actions of insulin sensitizing medications such as metformin, or optimizing BBB function using vascular protective drugs, such as losartan, could provide novel strategies for the prevention or treatment of neuroprogressive BD.

Repairing blood-CNS barriers: Future therapeutic approaches for neuropsychiatric disorders

Central nervous system (CNS) drug development faces significant difficulties that translate into high rates of failure and lack of innovation. The pathophysiology of neurological and psychiatric disorders often results in the breakdown of blood-CNS barriers, disturbing the CNS microenvironment and worsening disease progression. Therefore, restoring the integrity of blood-CNS barriers may have a beneficial influence in several CNS disorders and improve treatment outcomes. In this review, pathways that may be modulated to protect blood-CNS barriers from neuroinflammatory and oxidative insults are featured. First, the participation of the brain endothelium and glial cells in disruption processes is discussed. Then, the relevance of regulatory systems is analysed, specifically the hypothalamic-pituitary axis, the renin-angiotensin system, sleep and circadian rhythms, and glutamate neurotransmission. Lastly, compounds of endogenous and exogenous origin that are known to mediate the repair of blood-CNS barriers are presented. We believe that enhancing the protection of blood-CNS barriers is a promising therapeutic strategy to pursue in the future.