Peroxisome proliferator-activated receptor gamma thiazolidinedione agonists increase glucose metabolism in astrocytes

Nuclear receptor PPARγ targets GPNMB to promote oligodendrocyte development and remyelination

Myelin injury occurs in brain ageing and in several neurological diseases. Failure of spontaneous remyelination is attributable to insufficient differentiation of oligodendrocyte precursor cells (OPCs) into mature myelin-forming oligodendrocytes in CNS demyelinated lesions. Emerging evidence suggests that peroxisome proliferator-activated receptor γ (PPARγ) is the master gatekeeper of CNS injury and repair and plays an important regulatory role in various neurodegenerative diseases. Although studies demonstrate positive effects of PPARγ in oligodendrocyte ontogeny in vitro, the cell-intrinsic role of PPARγ and the molecular mechanisms involved in the processes of OPC development and CNS remyelination in vivo are poorly understood. Here, we identify PPARγ as an enriched transcription factor in the dysfunctional OPCs accumulated in CNS demyelinated lesions. Its expression increases during OPC differentiation and myelination and is closely related to the process of CNS demyelination/remyelination. Administration of pharmacological agonists of PPARγ not only promotes OPC differentiation and CNS myelination, but also causes a significant increase in remyelination in both cuprizone- and lysophosphatidylcholine-induced demyelination models. In contrast, the attenuation of PPARγ function, either through the specific knockout of PPARγ in oligodendrocytes in vivo or through its inhibition in vitro, leads to decreased OPC maturation, hindered myelin generation and reduced therapeutic efficacy of PPARγ agonists. At a mechanistic level, PPARγ induces myelin repair by directly targeting glycoprotein non-metastatic melanoma protein B (GPNMB), a novel regulator that drives OPCs to differentiate into oligodendrocytes, promotes myelinogenesis in the developing CNS of postnatal mice and enhances remyelination in mice with lysophosphatidylcholine-induced demyelination. In conclusion, our evidence reveals that PPARγ is a positive regulator of endogenous OPC differentiation and CNS myelination/remyelination and suggests that PPARγ and/or its downstream sensor (GPNMB) might be a candidate pharmacological target for regenerative therapy in the CNS.

The role of PPAR-γ in memory deficits induced by prenatal and lactation alcohol exposure in mice

Patients diagnosed with fetal alcohol spectrum disorder (FASD) show persistent cognitive disabilities, including memory deficits. However, the neurobiological substrates underlying these deficits remain unclear. Here, we show that prenatal and lactation alcohol exposure (PLAE) in mice induces FASD-like memory impairments. This is accompanied by a reduction of N-acylethanolamines (NAEs) and peroxisome proliferator-activated receptor gamma (PPAR-γ) in the hippocampus specifically in a childhood-like period (at post-natal day (PD) 25). To determine their role in memory deficits, two pharmacological approaches were performed during this specific period of early life. Thus, memory performance was tested after the repeated administration (from PD25 to PD34) of: i) URB597, to increase NAEs, with GW9662, a PPAR-γ antagonist; ii) pioglitazone, a PPAR-γ agonist. We observed that URB597 suppresses PLAE-induced memory deficits through a PPAR-γ dependent mechanism, since its effects are prevented by GW9662. Direct PPAR-γ activation, using pioglitazone, also ameliorates memory impairments. Lastly, to further investigate the region and cellular specificity, we demonstrate that an early overexpression of PPAR-γ, by means of a viral vector, in hippocampal astrocytes mitigates memory deficits induced by PLAE. Together, our data reveal that disruptions of PPAR-γ signaling during neurodevelopment contribute to PLAE-induced memory dysfunction. In turn, PPAR-γ activation during a childhood-like period is a promising therapeutic approach for memory deficits in the context of early alcohol exposure. Thus, these findings contribute to the gaining insight into the mechanisms that might underlie memory impairments in FASD patients.

Pioglitazone Use and Reduced Risk of Dementia in Patients With Diabetes Mellitus With a History of Ischemic Stroke

BACKGROUND AND OBJECTIVES

Previous studies have reported the protective effect of pioglitazone on dementia in patients with type 2 diabetes mellitus (DM). Recent studies have shown that pioglitazone also lowers the risk of primary and recurrent stroke. Understanding the characteristics of patients particularly associated with the benefits of pioglitazone would facilitate its personalized use by specifying subpopulations during routine clinical care. The aim of this study was to examine the effects of pioglitazone use on dementia in consideration of stroke occurrence.

METHODS

Using nationwide longitudinal data of patients with DM from the Korean National Health Insurance Service DM cohort (2002-2017), we investigated the association of pioglitazone use with incident dementia in patients with new-onset type 2 DM. The heterogeneity of the treatment effect was examined using exploratory analyses. Using a multistate model, we assessed the extent to which incident stroke affects the association between pioglitazone use and dementia.

RESULTS

Pioglitazone use was associated with a reduced risk of dementia, compared with nonuse (adjusted hazard ratio [aHR] = 0.84, 95% CI 0.75-0.95); the risk reduction in dementia was greater among patients with a history of ischemic heart disease or stroke before DM onset (aHR = 0.46, 95% CI 0.24-0.90; aHR = 0.57, 95% CI 0.38-0.86, respectively). The incidence of stroke was also reduced by pioglitazone use (aHR = 0.81, 95% CI 0.66-1.00). However, when the stroke developed during the observation period of pioglitazone use, such lowered risk of dementia was not observed (aHR = 1.27, 95% CI 0.80-2.04).

DISCUSSION

Pioglitazone use is associated with a lower risk of dementia in patients with DM, particularly in those with a history of stroke or ischemic heart disease, suggesting the possibility of applying a personalized approach when choosing pioglitazone to suppress dementia in patients with DM.

Development of PPARγ Agonists for the Treatment of Neuroinflammatory and Neurodegenerative Diseases: Leriglitazone as a Promising Candidate

Increasing evidence suggests that the peroxisome proliferator-activated receptor γ (PPARγ), a member of the nuclear receptor superfamily, plays an important role in physiological processes in the central nervous system (CNS) and is involved in cellular metabolism and repair. Cellular damage caused by acute brain injury and long-term neurodegenerative disorders is associated with alterations of these metabolic processes leading to mitochondrial dysfunction, oxidative stress, and neuroinflammation. PPARγ agonists have demonstrated the potential to be effective treatments for CNS diseases in preclinical models, but to date, most drugs have failed to show efficacy in clinical trials of neurodegenerative diseases including amyotrophic lateral sclerosis, Parkinson's disease, and Alzheimer's disease. The most likely explanation for this lack of efficacy is the insufficient brain exposure of these PPARγ agonists. Leriglitazone is a novel, blood-brain barrier (BBB)-penetrant PPARγ agonist that is being developed to treat CNS diseases. Here, we review the main roles of PPARγ in physiology and pathophysiology in the CNS, describe the mechanism of action of PPARγ agonists, and discuss the evidence supporting the use of leriglitazone to treat CNS diseases.

Cannabidiol enhances cerebral glucose utilization and ameliorates psychopathology and cognition: A case report in a clinically high-risk mental state

Adolescent individuals often present with subtle, sub-threshold psychiatric syndromes that fluctuate or persist for years. These symptoms have been classified as Clinically High-Risk mental states (CHR), negatively affecting these individuals' psychosocial development and integration by reducing performance and affecting interpersonal relations. The pathophysiological underpinnings have not been studied in detail, contributing to the current lack of appropriate intervention strategies. This case report sheds new light on potential pathophysiological mechanisms of this condition, which may be addressed by novel treatment approaches such as cannabidiol. A 19-year-old student presented to our early intervention center with a marked cognitive decline within 6 months, anhedonia, ambivalence, social withdrawal, poverty of speech, and brief intermittent psychotic symptoms (delusions and hallucinations). He was diagnosed with CHR state, and we decided to treat him with the non-psychotomimetic phytocannabinoid cannabidiol. Cannabidiol is a promising compound carrying an orphan drug approval for rare certain childhood epilepsy types and is under investigation as an antipsychotic compound with a new mechanism of action compared to existing antipsychotics. We investigated the effect of oral cannabidiol (600  mg per day) over 4 weeks on psychopathology and cerebral glucose utilization. We observed no relevant side effects but a significant clinical improvement. In addition, positron emission tomography (PET) showed a considerable increase in cerebral [¹⁸F]fluoro-2-deoxyglucose (FDG) uptake in various brain regions. This finding suggests that cannabidiol may enhance cerebral glucose utilization, possibly via activation of peroxisome proliferator-activated receptor-gamma (PPAR-γ) by its endogenous ligand anandamide or related N-acylethanolamines. This mechanism may represent a new innovative treatment approach for CHR, especially given that many individuals with CHR and early psychosis do not substantially benefit from current psychopharmacological interventions.

Schizophrenia: a disorder of broken brain bioenergetics

A substantial and diverse body of literature suggests that the pathophysiology of schizophrenia is related to deficits of bioenergetic function. While antipsychotics are an effective therapy for the management of positive psychotic symptoms, they are not efficacious for the complete schizophrenia symptom profile, such as the negative and cognitive symptoms. In this review, we discuss the relationship between dysfunction of various metabolic pathways across different brain regions in relation to schizophrenia. We contend that several bioenergetic subprocesses are affected across the brain and such deficits are a core feature of the illness. We provide an overview of central perturbations of insulin signaling, glycolysis, pentose-phosphate pathway, tricarboxylic acid cycle, and oxidative phosphorylation in schizophrenia. Importantly, we discuss pharmacologic and nonpharmacologic interventions that target these pathways and how such interventions may be exploited to improve the symptoms of schizophrenia.

Astrocyte Bioenergetics and Major Psychiatric Disorders

Ongoing research continues to add new elements to the emerging picture of involvement of astrocyte energy metabolism in the pathophysiology of major psychiatric disorders, including schizophrenia, mood disorders, and addictions. This review outlines what is known about the energy metabolism in astrocytes, the most numerous cell type in the brain, and summarizes the recent work on how specific perturbations of astrocyte bioenergetics may contribute to the neuropsychiatric conditions. The role of astrocyte energy metabolism in mental health and disease is reviewed on the organism, organ, and cell level. Data arising from genomic, metabolomic, in vitro, and neurobehavioral studies is critically analyzed to suggest future directions in research and possible metabolism-focused therapeutic interventions.

Elucidating the Neuroprotective Role of PPARs in Parkinson's Disease: A Neoteric and Prospective Target

One of the utmost frequently emerging neurodegenerative diseases, Parkinson's disease (PD) must be comprehended through the forfeit of dopamine (DA)-generating nerve cells in the substantia nigra pars compacta (SN-PC). The etiology and pathogenesis underlying the emergence of PD is still obscure. However, expanding corroboration encourages the involvement of genetic and environmental factors in the etiology of PD. The destruction of numerous cellular components, namely oxidative stress, ubiquitin-proteasome system (UPS) dysfunction, autophagy-lysosome system dysfunction, neuroinflammation and programmed cell death, and mitochondrial dysfunction partake in the pathogenesis of PD. Present-day pharmacotherapy can alleviate the manifestations, but no therapy has been demonstrated to cease disease progression. Peroxisome proliferator-activated receptors (PPARs) are ligand-directed transcription factors pertaining to the class of nuclear hormone receptors (NHR), and are implicated in the modulation of mitochondrial operation, inflammation, wound healing, redox equilibrium, and metabolism of blood sugar and lipids. Numerous PPAR agonists have been recognized to safeguard nerve cells from oxidative destruction, inflammation, and programmed cell death in PD and other neurodegenerative diseases. Additionally, various investigations suggest that regular administration of PPAR-activating non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen, indomethacin), and leukotriene receptor antagonists (montelukast) were related to the de-escalated evolution of neurodegenerative diseases. The present review elucidates the emerging evidence enlightening the neuroprotective outcomes of PPAR agonists in in vivo and in vitro models experiencing PD. Existing articles up to the present were procured through PubMed, MEDLINE, etc., utilizing specific keywords spotlighted in this review. Furthermore, the authors aim to provide insight into the neuroprotective actions of PPAR agonists by outlining the pharmacological mechanism. As a conclusion, PPAR agonists exhibit neuroprotection through modulating the expression of a group of genes implicated in cellular survival pathways, and may be a propitious target in the therapy of incapacitating neurodegenerative diseases like PD.

Reassessment of Pioglitazone for Alzheimer's Disease

Alzheimer's disease is a quintessential 'unmet medical need', accounting for ∼65% of progressive cognitive impairment among the elderly, and 700,000 deaths in the United States in 2020. In 2019, the cost of caring for Alzheimer's sufferers was $244B, not including the emotional and physical toll on caregivers. In spite of this dismal reality, no treatments are available that reduce the risk of developing AD or that offer prolonged mitiagation of its most devestating symptoms. This review summarizes key aspects of the biology and genetics of Alzheimer's disease, and we describe how pioglitazone improves many of the patholophysiological determinants of AD. We also summarize the results of pre-clinical experiments, longitudinal observational studies, and clinical trials. The results of animal testing suggest that pioglitazone can be corrective as well as protective, and that its efficacy is enhanced in a time- and dose-dependent manner, but the dose-effect relations are not monotonic or sigmoid. Longitudinal cohort studies suggests that it delays the onset of dementia in individuals with pre-existing type 2 diabetes mellitus, which small scale, unblinded pilot studies seem to confirm. However, the results of placebo-controlled, blinded clinical trials have not borne this out, and we discuss possible explanations for these discrepancies.

Inhibition of the Soluble Epoxide Hydrolase as an Analgesic Strategy: A Review of Preclinical Evidence

Chronic pain is a complicated condition which causes substantial physical, emotional, and financial impacts on individuals and society. However, due to high cost, lack of efficacy and safety problems, current treatments are insufficient. There is a clear unmet medical need for safe, nonaddictive and effective therapies in the management of pain. Epoxy-fatty acids (EpFAs), which are natural signaling molecules, play key roles in mediation of both inflammatory and neuropathic pain sensation. However, their molecular mechanisms of action remain largely unknown. Soluble epoxide hydrolase (sEH) rapidly converts EpFAs into less bioactive fatty acid diols in vivo; therefore, inhibition of sEH is an emerging therapeutic target to enhance the beneficial effect of natural EpFAs. In this review, we will discuss sEH inhibition as an analgesic strategy for pain management and the underlying molecular mechanisms.

Immune Modulatory Treatments for Autism Spectrum Disorder

Several lines of evidence from family history studies, immunogenetics, maternal immune activation, neuroinflammation, and systemic inflammation support an immune subtype of autism spectrum disorder (ASD). Current Food and Drug Administration-approved medications for ASD do not address the underlying pathophysiology of ASD, have not consistently been shown to address the core symptoms of ASD, and are currently only approved for treating irritability in children and adolescents. In this article, we review the immune modulatory effects of the 2 currently Food and Drug Administration-approved treatments for ASD. We then provide an overview of current data on emerging treatments for ASD from multiple fields of medicine with immune modulatory effects. Although further research is needed to more clearly establish the efficacy and safety of immune modulatory treatments, early data on repurposing medications used to treat systemic inflammation for ASD demonstrate potential benefit and further research is warranted.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Nutritional ketosis as an intervention to relieve astrogliosis: Possible therapeutic applications in the treatment of neurodegenerative and neuroprogressive disorders

Nutritional ketosis, induced via either the classical ketogenic diet or the use of emulsified medium-chain triglycerides, is an established treatment for pharmaceutical resistant epilepsy in children and more recently in adults. In addition, the use of oral ketogenic compounds, fractionated coconut oil, very low carbohydrate intake, or ketone monoester supplementation has been reported to be potentially helpful in mild cognitive impairment, Parkinson’s disease, schizophrenia, bipolar disorder, and autistic spectrum disorder. In these and other neurodegenerative and neuroprogressive disorders, there are detrimental effects of oxidative stress, mitochondrial dysfunction, and neuroinflammation on neuronal function. However, they also adversely impact on neurone–glia interactions, disrupting the role of microglia and astrocytes in central nervous system (CNS) homeostasis. Astrocytes are the main site of CNS fatty acid oxidation; the resulting ketone bodies constitute an important source of oxidative fuel for neurones in an environment of glucose restriction. Importantly, the lactate shuttle between astrocytes and neurones is dependent on glycogenolysis and glycolysis, resulting from the fact that the astrocytic filopodia responsible for lactate release are too narrow to accommodate mitochondria. The entry into the CNS of ketone bodies and fatty acids, as a result of nutritional ketosis, has effects on the astrocytic glutamate–glutamine cycle, glutamate synthase activity, and on the function of vesicular glutamate transporters, EAAT, Na⁺, K⁺-ATPase, K_ir4.1, aquaporin-4, Cx34 and K_ATP channels, as well as on astrogliosis. These mechanisms are detailed and it is suggested that they would tend to mitigate the changes seen in many neurodegenerative and neuroprogressive disorders. Hence, it is hypothesized that nutritional ketosis may have therapeutic applications in such disorders.

Lessons from the Trials for the Desirable Effects of Sodium Glucose Co-Transporter 2 Inhibitors on Diabetic Cardiovascular Events and Renal Dysfunction

Recent large placebo-controlled trials of sodium glucose co-transporter 2 (SGLT2) inhibitors revealed desirable effects on heart failure (HF) and renal dysfunction; however, the mechanisms underlying these effects are unknown. The characteristic changes in the early stage of diabetic cardiomyopathy (DCM) are myocardial and interstitial fibrosis, resulting in diastolic and subsequent systolic dysfunction, which leads to clinical HF. Pericytes are considered to play crucial roles in myocardial and interstitial fibrosis. In both DCM and diabetic retinopathy (DR), microaneurysm formation and a decrease in capillaries occur, triggered by pericyte loss. Furthermore, tubulointerstitial fibrosis develops in early diabetic nephropathy (DN), in which pericytes and mesangial cells are thought to play important roles. Previous reports indicate that pericytes and mesangial cells play key roles in the pathogenesis of DCM, DR and DN. SGLT2 is reported to be functionally expressed in pericytes and mesangial cells, and excessive glucose and Na+ entry through SGLT2 causes cellular dysfunction in a diabetic state. Since SGLT2 inhibitors can attenuate the high glucose-induced dysfunction of pericytes and mesangial cells, the desirable effects of SGLT2 inhibitors on HF and renal dysfunction might be explained by their direct actions on these cells in the heart and kidney microvasculature.

Effects of PPAR-γ agonist, pioglitazone on brain tissues oxidative damage and learning and memory impairment in juvenile hypothyroid rats

Aim: The effect of peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist pioglitazone on the brain tissues oxidative damage and learning and memory impairment in the juvenile hypothyroid rats was evaluated. Main methods: Rats were classified as: ( 1 ) Control; (2) Propylthiouracil (PTU); (3) PTU-Pio 10 and (4) PTU-Pio 20. PTU was given in drinking water (0.05%) during 6 weeks. Pioglitazone (10 or 20 mg/kg) was daily injected intraperitoneally. Passive avoidance (PA) and Morris water maze (MMW) were conducted. Later, the animals were sacrificed and the brain tissues were removed for biochemical measurements. Key funding: The results indicated that in the MWM escape latency as well as traveled path increased in the PTU group as compared to the control group. Also, the time spent in the target quadrant in the probe test of MWM and step-through latency in the PA test were decreased in the PTU group as compared to the control group. Pioglitazone reversed all the negative behavioral effects of hypothyroidism. Administration of PTU attenuated thiol and superoxide dismutase (SOD), and catalase (CAT) activities in the brain tissues, whereas increased malondialdehyde (MDA) and nitric oxide (NO) metabolites. PPARγ agonist improved thiol, SOD and CAT, while diminished MDA concentration. Significance: Our finding in the present study indicated that PPARγ agonist pioglitazone prevented the brain tissues from oxidative damage and learning and memory impairments in juvenile hypothyroid rats.

Exercise and metformin counteract altered mitochondrial function in the insulin-resistant brain

Insulin resistance associates with increased risk for cognitive decline and dementia; however, the underpinning mechanisms for this increased risk remain to be fully defined. As insulin resistance impairs mitochondrial oxidative metabolism and increases ROS in skeletal muscle, we considered whether similar events occur in the brain, which - like muscle - is rich in insulin receptors and mitochondria. We show that high-fat diet-induced (HFD-induced) brain insulin resistance in mice decreased mitochondrial ATP production rate and oxidative enzyme activities in brain regions rich in insulin receptors. HFD increased ROS emission and reduced antioxidant enzyme activities, with the concurrent accumulation of oxidatively damaged mitochondrial proteins and increased mitochondrial fission. Improvement of insulin sensitivity by both aerobic exercise and metformin ameliorated HFD-induced abnormalities. Moreover, insulin-induced enhancement of ATP production in primary cortical neurons and astrocytes was counteracted by the insulin receptor antagonist S961, demonstrating a direct effect of insulin resistance on brain mitochondria. Further, intranasal S961 administration prevented exercise-induced improvements in ATP production and ROS emission during HFD, supporting that exercise enhances brain mitochondrial function by improving insulin action. These results support that insulin sensitizing by exercise and metformin restores brain mitochondrial function in insulin-resistant states.

Pioglitazone improves working memory performance when administered in chronic TBI

Traumatic brain injury (TBI) is a leading cause of long-term disability in the United States. Even in comparatively mild injuries, cognitive and behavioral symptoms can persist for years, and there are currently no established strategies for mitigating symptoms in chronic injury. A key feature of TBI-induced damage in acute and chronic injury is disruption of metabolic pathways. As neurotransmission, and therefore cognition, are highly dependent on the supply of energy, we hypothesized that modulating metabolic activity could help restore behavioral performance even when treatment was initiated weeks after TBI. We treated rats with pioglitazone, a FDA-approved drug for diabetes, beginning 46 days after lateral fluid percussion injury and tested working memory performance in the radial arm maze (RAM) after 14 days of treatment. Pioglitazone treated TBI rats performed significantly better in the RAM test than untreated TBI rats, and similarly to control animals. While hexokinase activity in hippocampus was increased by pioglitazone treatment, there was no upregulation of either the neuronal glucose transporter or hexokinase enzyme expression. Expression of glial markers GFAP and Iba-1 were also not influenced by pioglitazone treatment. These studies suggest that targeting brain metabolism, in particular hippocampal metabolism, may be effective in alleviating cognitive symptoms in chronic TBI.

Neuron-specific deficits of bioenergetic processes in the dorsolateral prefrontal cortex in schizophrenia

Schizophrenia is a devastating illness that affects over 2 million people in the United States and costs society billions of dollars annually. New insights into the pathophysiology of schizophrenia are needed to provide the conceptual framework to facilitate development of new treatment strategies. We examined bioenergetic pathways in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia and control subjects using western blot analysis, quantitative real-time polymerase chain reaction, and enzyme/substrate assays. Laser-capture microdissection-quantitative polymerase chain reaction was used to examine these pathways at the cellular level. We found decreases in hexokinase (HXK) and phosphofructokinase (PFK) activity in the DLPFC, as well as decreased PFK1 mRNA expression. In pyramidal neurons, we found an increase in monocarboxylate transporter 1 mRNA expression, and decreases in HXK1, PFK1, glucose transporter 1 (GLUT1), and GLUT3 mRNA expression. These results suggest abnormal bioenergetic function, as well as a neuron-specific defect in glucose utilization, in the DLPFC in schizophrenia.

Pharmacological Treatment of Chemotherapy-Induced Neuropathic Pain: PPARγ Agonists as a Promising Tool

Chemotherapy-induced neuropathic pain (CINP) is one of the most severe side effects of anticancer agents, such as platinum- and taxanes-derived drugs (oxaliplatin, cisplatin, carboplatin and paclitaxel). CINP may even be a factor of interruption of treatment and consequently increasing the risk of death. Besides that, it is important to take into consideration that the incidence of cancer is increasing worldwide, including colorectal, gastric, lung, cervical, ovary and breast cancers, all treated with the aforementioned drugs, justifying the concern of the medical community about the patient’s quality of life. Several physiopathological mechanisms have already been described for CINP, such as changes in axonal transport, mitochondrial damage, increased ion channel activity and inflammation in the central nervous system (CNS). Another less frequent event that may occur after chemotherapy, particularly under oxaliplatin treatment, is the central neurotoxicity leading to disorders such as mental confusion, catatonia, hyporeflexia, etc. To date, no pharmacological therapy has shown satisfactory effect in these cases. In this scenario, duloxetine is the only drug currently in clinical use. Peroxisome proliferator-activated receptors (PPARs) belong to the class of nuclear receptors and are present in several tissues, mainly participating in lipid and glucose metabolism and inflammatory response. There are three PPAR isoforms: α, β/δ and γ. PPARγ, the protagonist of this review, is expressed in adipose tissue, large intestine, spleen and neutrophils. This subtype also plays important role in energy balance, lipid biosynthesis and adipogenesis. The effects of PPARγ agonists, known for their positive activity on type II diabetes mellitus, have been explored and present promising effects in the control of neuropathic pain, including CINP, and also cancer. This review focuses largely on the mechanisms involved in chemotherapy-induced neuropathy and the effects of the activation of PPARγ to treat CINP. It is the aim of this review to help understanding and developing novel CINP therapeutic strategies integrating PPARγ signalling.

Connectivity Analyses of Bioenergetic Changes in Schizophrenia: Identification of Novel Treatments

We utilized a cell-level approach to examine glycolytic pathways in the DLPFC of subjects with schizophrenia (n = 16) and control (n = 16) and found decreased mRNA expression of glycolytic enzymes in pyramidal neurons, but not astrocytes. To replicate these novel bioenergetic findings, we probed independent datasets for bioenergetic targets and found similar abnormalities. Next, we used a novel strategy to build a schizophrenia bioenergetic profile by a tailored application of the Library of Integrated Network-Based Cellular Signatures data portal (iLINCS) and investigated connected cellular pathways, kinases, and transcription factors using Enrichr. Finally, with the goal of identifying drugs capable of "reversing" the bioenergetic schizophrenia signature, we performed a connectivity analysis with iLINCS and identified peroxisome proliferator-activated receptor (PPAR) agonists as promising therapeutic targets. We administered a PPAR agonist to the GluN1 knockdown model of schizophrenia and found it improved long-term memory. Taken together, our findings suggest that tailored bioinformatics approaches, coupled with the LINCS library of transcriptional signatures of chemical and genetic perturbagens, may be employed to identify novel treatment strategies for schizophrenia and related diseases.

Dissecting the Brain/Islet Axis in Metabesity

The high prevalence of type 2 diabetes mellitus (T2DM), together with the fact that current treatments are only palliative and do not avoid major secondary complications, reveals the need for novel approaches to treat the cause of this disease. Efforts are currently underway to identify therapeutic targets implicated in either the regeneration or re-differentiation of a functional pancreatic islet β-cell mass to restore insulin levels and normoglycemia. However, T2DM is not only caused by failures in β-cells but also by dysfunctions in the central nervous system (CNS), especially in the hypothalamus and brainstem. Herein, we review the physiological contribution of hypothalamic neuronal and glial populations, particularly astrocytes, in the control of the systemic response that regulates blood glucose levels. The glucosensing capacity of hypothalamic astrocytes, together with their regulation by metabolic hormones, highlights the relevance of these cells in the control of glucose homeostasis. Moreover, the critical role of astrocytes in the response to inflammation, a process associated with obesity and T2DM, further emphasizes the importance of these cells as novel targets to stimulate the CNS in response to metabesity (over-nutrition-derived metabolic dysfunctions). We suggest that novel T2DM therapies should aim at stimulating the CNS astrocytic response, as well as recovering the functional pancreatic β-cell mass. Whether or not a common factor expressed in both cell types can be feasibly targeted is also discussed.

A novel mouse model overexpressing Nocturnin results in decreased fat mass in male mice

Nocturnin (NOCT) belongs to the Mg²⁺ dependent Exonucleases, Endonucleases, Phosphatase (EEP) family of enzymes that exhibit various functions in vitro and in vivo. NOCT is known to function as a deadenylase, cleaving poly-A tails from mRNA (messenger RNA) transcripts. Previously, we reported a role for NOCT in regulating bone marrow stromal cell differentiation through its interactions with PPARγ. In this study, we characterized the skeletal and adipose tissue phenotype when we globally overexpressed Noct in vivo. After 12 weeks of Noct overexpression, transgenic male mice had lower fat mass compared to controls, with no significant differences in the skeleton. Based on the presence of a mitochondrial target sequence in NOCT, we determined that mouse NOCT protein localizes to the mitochondria; subsequently, we found that NOCT overexpression led to a significant increase in the preadipocytes ability to utilize oxidative phosphorylation for ATP (adenosine triphosphate) generation. In summary, the effects of NOCT on adipocytes are likely through its novel role as a mediator of mitochondrial function.

Pioglitazone reversed the fructose-programmed astrocytic glycolysis and oxidative phosphorylation of female rat offspring

Excessive maternal high-fructose diet (HFD) during pregnancy and lactation has been reported to cause metabolic disorders in the offspring. Whether the infant's brain metabolism is disturbed by maternal HFD is largely unknown. Brain energy metabolism is elevated dramatically during fetal and postnatal development, whereby maternal nutrition is a key factor that determines cellular metabolism. Astrocytes, a nonneuronal cell type in the brain, are considered to support the high-energy demands of neurons by supplying lactate. In this study, the effects of maternal HFD on astrocytic glucose metabolism were investigated using hippocampal primary cultures of female infants. We found that glycolytic capacity and mitochondrial respiration and electron transport chain were suppressed by maternal HFD. Mitochondrial DNA copy number and mitochondrial transcription factor A expression were suppressed by maternal HFD. Western blots and immunofluorescent images further indicated that the glucose transporter 1 was downregulated whereas the insulin receptor-α, phospho-insulin receptor substrate-1 (Y612) and the p85 subunit of phosphatidylinositide 3-kinase were upregulated in the HFD group. Pioglitazone, which is known to increase astrocytic glucose metabolism, effectively reversed the suppressed glycolysis, and lactate release was restored. Moreover, pioglitazone also normalized oxidative phosphorylation with an increase of cytosolic ATP. Together, these results suggest that maternal HFD impairs astrocytic energy metabolic pathways that were reversed by pioglitazone.

Metabolic Plasticity of Astrocytes and Aging of the Brain

As part of the blood-brain-barrier, astrocytes are ideally positioned between cerebral vasculature and neuronal synapses to mediate nutrient uptake from the systemic circulation. In addition, astrocytes have a robust enzymatic capacity of glycolysis, glycogenesis and lipid metabolism, managing nutrient support in the brain parenchyma for neuronal consumption. Here, we review the plasticity of astrocyte energy metabolism under physiologic and pathologic conditions, highlighting age-dependent brain dysfunctions. In astrocytes, glycolysis and glycogenesis are regulated by noradrenaline and insulin, respectively, while mitochondrial ATP production and fatty acid oxidation are influenced by the thyroid hormone. These regulations are essential for maintaining normal brain activities, and impairments of these processes may lead to neurodegeneration and cognitive decline. Metabolic plasticity is also associated with (re)activation of astrocytes, a process associated with pathologic events. It is likely that the recently described neurodegenerative and neuroprotective subpopulations of reactive astrocytes metabolize distinct energy substrates, and that this preference is supposed to explain some of their impacts on pathologic processes. Importantly, physiologic and pathologic properties of astrocytic metabolic plasticity bear translational potential in defining new potential diagnostic biomarkers and novel therapeutic targets to mitigate neurodegeneration and age-related brain dysfunctions.

Rosiglitazone up-regulates glial fibrillary acidic protein via HB-EGF secreted from astrocytes and neurons through PPARγ pathway and reduces apoptosis in high-fat diet-fed mice

The anti-diabetic drug and peroxisome proliferator-activated receptor-gamma (PPARγ) agonist, rosiglitazone, alters astrocyte activation; however, its mechanism remains less-known. We hypothesized participation of epidermal growth factor receptor (EGFR), known to control astrocyte reactivity. We first detected that rosiglitazone promoted glial fibrillary acidic protein (GFAP) expression in primary astrocytes as well as the mouse cerebral cortex, associated with increased EGFR activation. Screening for EGFR ligands revealed a rosiglitazone-mediated increase of heparin-binding epidermal growth factor (HB-EGF) in astrocytes, resulting in HB-EGF release into culture medium and mouse cerebrospinal fluid too. Treatment with HB-EGF-siRNA and EGFR inhibitors showed that the rosiglitazone-induced HB-EGF and p-EFGR were interdependent, which participated in GFAP increase. Interestingly, we observed that rosiglitazone could induce cellular and secreted-HB-EGF in neurons also, contributing toward the activated EGFR-induced GFAP in astrocytes. Probing whether these effects of rosiglitazone were PPARγ-linked, revealed potential PPARγ-responsive elements within HB-EGF gene. Moreover, gel-shift, site-directed mutagenesis, chromatin-immunoprecipitation and luciferase-reporter assays demonstrated a PPARγ-dependent HB-EGF transactivation. Subsequently, we examined effects of rosiglitazone in a high-fat diet-fed diabetes mouse model, and supporting observations in the normal cortical cells, identified a rosiglitazone-induced GFAP, astrocyte and neuronal HB-EGF and secreted-HB-EGF in the cerebral cortex of diabetic mice. Moreover, assessing relevance of increased HB-EGF and GFAP revealed an anti-apoptotic role of rosiglitazone in the cerebral cortex, supported by a GFAP-siRNA as well as HB-EGF-siRNA-mediated increase in cleaved-caspase 3 and 9 levels in the rosiglitazone-treated astrocyte-neuron coculture. Overall, our study indicates that rosiglitazone may protect the brain, via a PPARγ-dependent HB-EGF/EGFR signaling and increased GFAP.

Treating Hepatic Steatosis and Fibrosis by Modulating Mitochondrial Pyruvate Metabolism

A hepatic comorbidity of metabolic syndrome, known as nonalcoholic fatty liver disease (NAFLD), is increasing in prevalence in conjunction with the pandemics of obesity and diabetes. The spectrum of NAFLD ranges from simple hepatic fat accumulation to a more severe disease termed nonalcoholic steatohepatitis (NASH), involving inflammation, hepatocyte death, and fibrosis. Importantly, NASH is linked to a much higher risk of cirrhosis, liver failure, and hepatocellular carcinoma, as well as an increased risk for nonhepatic malignancies and cardiovascular disease. Interest in the understanding of the disease processes and search for treatments for the spectrum of NAFLD-NASH has increased exponentially, but there are no approved pharmacologic therapies. In this review, we discuss the existing literature supporting insulin-sensitizing thiazolidinedione compounds as potential drug candidates for the treatment of NASH. In addition, we put these results into new context by summarizing recent studies suggesting these compounds alter mitochondrial metabolism by binding and inhibiting the mitochondrial pyruvate carrier.

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

Astrocyte-Specific Deletion of Peroxisome-Proliferator Activated Receptor-γ Impairs Glucose Metabolism and Estrous Cycling in Female Mice

Mice lacking peroxisome-proliferator activated receptor-γ (PPARγ) in neurons do not become leptin resistant when placed on a high-fat diet (HFD). In male mice, this results in decreased food intake and increased energy expenditure, causing reduced body weight, but this difference in body weight is not observed in female mice. In addition, estrous cycles are disturbed and the ovaries present with hemorrhagic follicles. We observed that PPARγ was more highly expressed in astrocytes than neurons, so we created an inducible, conditional knockout of PPARγ in astrocytes (AKO). The AKO mice had impaired glucose tolerance and hepatic steatosis that did not worsen with HFD. Expression of gluconeogenic genes was elevated in the mouse livers, as was expression of several genes involved in lipogenesis, lipid transport, and storage. The AKO mice also had a reproductive phenotype with fewer estrous cycles, elevated plasma testosterone levels, reduced corpora lutea formation, and alterations in hypothalamic and ovarian gene expression. Thus, the phenotypes of the AKO mice were very different from those seen in the neuronal knockout mice, suggesting distinct roles for PPARγ in these two cell types.

Protective Effect of PPARγ Agonists on Cerebellar Tissues Oxidative Damage in Hypothyroid Rats

The aim of the current study was to investigate the effects of peroxisome proliferator-activated receptor gamma (PPARγ) agonists on cerebellar tissues oxidative damage in hypothyroid rats. The animals included seven groups: group I (control), the animals received drinking water; group II, the animals received 0.05% propylthiouracil (PTU) in drinking water; besides PTU, the animals in groups III, IV, V, VI, and VII, were injected with 20 mg/kg vitamin E (Vit E), 10 or 20 mg/kg pioglitazone, and 2 or 4 mg/kg rosiglitazone, respectively. The animals were deeply anesthetized and the cerebellar tissues were removed for biochemical measurements. PTU administration reduced thiol content, superoxide dismutase (SOD), and catalase (CAT) activities in the cerebellar tissues while increasing malondialdehyde (MDA) and nitric oxide (NO) metabolites. Vit E, pioglitazone, and rosiglitazone increased thiol, SOD, and CAT in the cerebellar tissues while reducing MDA and NO metabolites. The results of present study showed that, similar to Vit E, both rosiglitazone and pioglitazone as PPARγ agonists exerted protective effects against cerebellar tissues oxidative damage in hypothyroid rats.

PPARγ as a therapeutic target to rescue mitochondrial function in neurological disease

There is increasing evidence for the involvement of mitochondrial dysfunction and oxidative stress in the pathogenesis of many of the major neurodegenerative and neuroinflammatory diseases, suggesting that mitochondrial and antioxidant pathways may represent potential novel therapeutic targets. Recent years have seen a rapidly growing interest in the use of therapeutic strategies that can limit the defects in, or even to restore, mitochondrial function while reducing free radical generation. The peroxisome proliferation-activated receptor gamma (PPARγ), a ligand-activated transcription factor, has a wide spectrum of biological functions, regulating mitochondrial function, mitochondrial turnover, energy metabolism, antioxidant defence and redox balance, immune responses and fatty acid oxidation. In this review, we explore the evidence for potential beneficial effects of PPARγ agonists in a number of neurological disorders, including Parkinson's disease, Alzheimer's disease, Amyotrophic lateral sclerosis and Huntington's disease, ischaemia, autoimmune encephalomyelitis and neuropathic pain. We discuss the mechanisms underlying those beneficial effects in particular in relation to mitochondrial function, antioxidant defence, cell death and inflammation, and suggest that the PPARγ agonists show significant promise as therapeutic agents in otherwise intractable neurological disease.

Escherichia coli K1 Modulates Peroxisome Proliferator-Activated Receptor γ and Glucose Transporter 1 at the Blood-Brain Barrier in Neonatal Meningitis

Escherichia coli K1 meningitis continues to be a major threat to neonatal health. Previous studies demonstrated that outer membrane protein A (OmpA) of E. coli K1 interacts with endothelial cell glycoprotein 96 (Ecgp96) in the blood-brain barrier to enter the central nervous system. Here we show that the interaction between OmpA and Ecgp96 downregulates peroxisome proliferator-activated receptor γ (PPAR-γ) and glucose transporter 1 (GLUT-1) levels in human brain microvascular endothelial cells, causing disruption of barrier integrity and inhibition of glucose uptake. The suppression of PPAR-γ and GLUT-1 by the bacteria in the brain microvessels of newborn mice causes extensive pathophysiology owing to interleukin 6 production. Pretreatment with partial or selective PPAR-γ agonists ameliorate the pathological outcomes of infection by suppressing interleukin 6 production in the brain. Thus, inhibition of PPAR-γ and GLUT-1 by E. coli K1 is a novel pathogenic mechanism in meningitis, and pharmacological upregulation of PPAR-γ and GLUT-1 levels may provide novel therapeutic avenues.

NF-κB signaling pathway as target for antiplatelet activity

In different nucleated cells, NF-κB has long been considered a prototypical proinflammatory signaling pathway with the expression of proinflammatory genes. Although platelets lack a nucleus, a number of functional transcription factors are involved in activated platelets, such as NF-κB. In platelet activation NF-κB regulation events include IKKβ phosphorylation, IκBα degradation, and p65 phosphorylation. Multiple pathways contribute to platelet activation and NF-κB is a common pathway in this activation. Therefore, in platelet activation the modulation of NF-κB pathway could be a potential new target in the treatment of inflammation-related vascular disease therapy (antiplatelet and antithrombotic activities).

Insulin receptor sensitizer, dicholine succinate, prevents both Toll-like receptor 4 (TLR4) upregulation and affective changes induced by a high-cholesterol diet in mice

BACKGROUND

High cholesterol intake in mice induces hepatic lipid dystrophy and inflammation, signs of non-alcoholic fatty liver disease (NAFLD), depressive- and anxiety-like behaviors, and the up-regulation of brain and liver Toll-like receptor 4 (Tlr4). Here, we investigated whether dicholine succinate (DS), an insulin receptor sensitizer and mitochondrial complex II substrate would interact with these effects.

METHODS

C57BL/6J mice were given a 0.2%-cholesterol diet for 3 weeks, alone or along with oral DS administration, or a control feed. Outcomes included behavioral measures of anxiety/depression, and Tlr4 and peroxisome-proliferator-activated-receptor-gamma coactivator-1b (PPARGC1b) expression.

RESULTS

50mg/kg DS treatment for 3 weeks partially ameliorated the cholesterol-induced anxiety- and depressive-like changes. Mice were next treated at the higher dose (180mg/kg), either for the 3-week period of dietary intervention, or for the last two weeks. Three-week DS administration normalized behaviors in the forced swim and O-maze tests and abolished the Tlr4 up-regulation in the brain and liver. The delayed, 2-week DS treatment had similar effects on Tlr4 expression and largely rescued the above-mentioned behaviors. Suppression of PPARGC1b, a master regulator of mitochondrial biogenesis, by the high cholesterol diet, was prevented with the 3-week administration, and markedly diminished by the a 2-week administration of DS. None of treatments prevented hepatic dystrophy and triglyceride accumulation.

LIMITATIONS

Other conditions have to be tested to define possible limitations of reported effects of DS.

CONCLUSIONS

DS treatment did not alter the patho-morphological substrates of NAFLD syndrome in mice, but ameliorated its molecular and behavioral consequences, likely by activating mitochondrial functions and anti-inflammatory mechanisms.

Metabolic and Inflammatory Adaptation of Reactive Astrocytes: Role of PPARs

Astrocyte-mediated inflammation is associated with degenerative pathologies such as Alzheimer's and Parkinson's diseases and multiple sclerosis. The acute inflammation and morphological and metabolic changes that astrocytes develop after the insult are known as reactive astroglia or astrogliosis that is an important response to protect and repair the lesion. Astrocytes optimize their metabolism to produce lactate, glutamate, and ketone bodies in order to provide energy to the neurons that are deprived of nutrients upon insult. Firstly, we review the basis of inflammation and morphological changes of the different cell population implicated in reactive gliosis. Next, we discuss the more active metabolic pathways in healthy astrocytes and explain the metabolic response of astrocytes to the insult in different pathologies and which metabolic alterations generate complications in these diseases. We emphasize the role of peroxisome proliferator-activated receptors isotypes in the inflammatory and metabolic adaptation of astrogliosis developed in ischemia or neurodegenerative diseases. Based on results reported in astrocytes and other cells, we resume and hypothesize the effect of peroxisome proliferator-activated receptor (PPAR) activation with ligands on different metabolic pathways in order to supply energy to the neurons. The activation of selective PPAR isotype activity may serve as an input to better understand the role played by these receptors on the metabolic and inflammatory compensation of astrogliosis and might represent an opportunity to develop new therapeutic strategies against traumatic brain injuries and neurodegenerative diseases.

Pioglitazone

Pioglitazone is a thiazolidinedione antidiabetic with actions similar to those of rosiglitazone. It is used in the management of type 2 diabetes mellitus and is prepared by reducing 5-[4-[2-(5-ethyl-2-pyridyl)ethoxy]benzilidene]-2,4-thiazolidinedione with sodium borohydride in the presence of a cobalt ion and dimethyl glyoxime. Ultraviolet spectroscopy shows maximum absorption at 270nm. Infrared spectroscopy shows principal peaks at wave numbers 3082, 2964, 1736, 1690, 1472, 1331, 1254, 1040, 841, 728cm(-1) (KBr disk). The determination method by high-performance liquid chromatography was linear over the range of 25-1500ng/mL of pioglitazone in plasma (r(2)>0.999). The within- and between-day precision values were in the range of 2.4-6.8%. The limit of quantitation of the method was 25ng/mL. It is well absorbed with a mean absolute bioavailability of 83% and reaching maximum concentrations in around 1.5h. It is metabolized by the hepatic cytochrome P450 enzyme system. Following oral administration, approximately 15-30% of the pioglitazone dose is recovered in the urine. Renal elimination of pioglitazone is negligible, and the drug is excreted primarily as metabolites and their conjugates. It is presumed that most of the oral dose is excreted into the bile either unchanged or as metabolites and eliminated in the feces.

The Impact of Sperm Metabolism during In Vitro Storage: The Stallion as a Model

In vitro sperm storage is a necessary part of many artificial insemination or in vitro fertilization regimes for many species, including the human and the horse. In many situations spermatozoa are chilled to temperatures between 4 and 10°C for the purpose of restricting the metabolic rate during storage, in turn, reducing the depletion of ATP and the production of detrimental by-products such as reactive oxygen species (ROS). Another result of lowering the temperature is that spermatozoa may be "cold shocked" due to lipid membrane phase separation, resulting in reduced fertility. To overcome this, a method of sperm storage must be developed that will preclude the need to chill spermatozoa. If a thermally induced restriction-of-metabolic-rate strategy is not employed, ATP production must be supported while ameliorating the deleterious effects of ROS. To achieve this end, an understanding of the nature of energy production by the spermatozoa of the species of interest is essential. Human spermatozoa depend predominantly on glycolytic ATP production, producing significantly less ROS than oxidative phosphorylation, with the more efficient pathway predominantly employed by stallion spermatozoa. This review provides an overview of the implications of sperm metabolism for in vitro sperm storage, with a focus on ambient temperature storage in the stallion.

Pioglitazone rapidly reduces neuropathic pain through astrocyte and nongenomic PPARγ mechanisms

Repeated administration of peroxisome proliferator-activated receptor gamma (PPARγ) agonists reduces neuropathic pain-like behavior and associated changes in glial activation in the spinal cord dorsal horn. As PPARγ is a nuclear receptor, sustained changes in gene expression are widely believed to be the mechanism of pain reduction. However, we recently reported that a single intrathecal (i.t.) injection of pioglitazone, a PPARγ agonist, reduced hyperalgesia within 30 minutes, a time frame that is typically less than that required for genomic mechanisms. To determine the very rapid antihyperalgesic actions of PPARγ activation, we administered pioglitazone to rats with spared nerve injury and evaluated hyperalgesia. Pioglitazone inhibited hyperalgesia within 5 minutes of injection, consistent with a nongenomic mechanism. Systemic or i.t. administration of GW9662, a PPARγ antagonist, inhibited the antihyperalgesic actions of intraperitoneal or i.t. pioglitazone, suggesting a spinal PPARγ-dependent mechanism. To further address the contribution of nongenomic mechanisms, we blocked new protein synthesis in the spinal cord with anisomycin. When coadministered intrathecally, anisomycin did not change pioglitazone antihyperalgesia at an early 7.5-minute time point, further supporting a rapid nongenomic mechanism. At later time points, anisomycin reduced pioglitazone antihyperalgesia, suggesting delayed recruitment of genomic mechanisms. Pioglitazone reduction of spared nerve injury-induced increases in GFAP expression occurred more rapidly than expected, within 60 minutes. We are the first to show that activation of spinal PPARγ rapidly reduces neuropathic pain independent of canonical genomic activity. We conclude that acute pioglitazone inhibits neuropathic pain in part by reducing astrocyte activation and through both genomic and nongenomic PPARγ mechanisms.

Impaired mitochondrial homeostasis and neurodegeneration: towards new therapeutic targets?

The sustained integrity of the mitochondrial population of a cell is critical for maintained cell health, and disruption of that integrity is linked strongly to human disease, especially to the neurodegenerative diseases. These are appalling diseases causing untold levels of suffering for which treatment is woefully inadequate. Understanding the mechanisms that disturb mitochondrial homeostasis may therefore prove key to identification of potential new therapeutic pathways. Mechanisms causing mitochondrial dysfunction include the acute catastrophic loss of function caused by opening of the mitochondrial permeability transition pore (mPTP), which collapses bioenergetic function and initiates cell death. This is best characterised in ischaemic reperfusion injury, although it may also contribute to a number of other diseases. More insidious disturbances of mitochondrial homeostasis may result from impaired balance in the pathways that promote mitochondrial repair (biogenesis) and pathways that remove dysfunctional mitochondria (mitophagy). Impaired coordination between these processes is emerging as a key feature of a number of neurodegenerative and neuromuscular disorders. Here we review pathways that may prove to be valuable potential therapeutic targets, focussing on the molecular mechanisms that govern the coordination of these processes and their involvement in neurodegenerative diseases.

PPARγ and PGC-1α as therapeutic targets in Parkinson's

The peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated transcriptional factor that belongs to the nuclear hormone receptor superfamily. PPARγ was initially identified through its role in the regulation of glucose and lipid metabolism and cell differentiation. It also influences the expression or activity of a number of genes in a variety of signalling networks. These include regulation of redox balance, fatty acid oxidation, immune responses and mitochondrial function. Recent studies suggest that the PPARγ agonists may serve as good candidates for the treatment of several neurodegenerative disorders including Parkinson’s disease (PD), Alzheimer’s disease, Huntington’s disease and amyotrophic lateral sclerosis, even though multiple etiological factors contribute to the development of these disorders. Recent reports have also signposted a role for PPARγ coactivator-1α (PGC-1α) in several neurodegenerative disorders including PD. In this review, we explore the current knowledge of mechanisms underlying the beneficial effects of PPARγ agonists and PGC-1α in models of PD.

Regulatory mechanisms of cAMP levels as a multiple target for antiplatelet activity and less bleeding risk

Platelet activation is a critical component of atherothrombosis. The multiple pathways of platelet activation limit the effect of specific receptor/pathway inhibitors, resulting in limited clinical efficacy. Recent research has confirmed that combination therapy results in enhanced antithrombotic efficacy without increasing bleeding risk. In this way, the best-known inhibitor and turn off signaling in platelet activation is cAMP. In this article we discuss the mechanisms of regulation of intraplatelet cAMP levels, a) platelet-dependent pathway: Gi/Gs protein-coupled receptors, phosphodiesterase inhibition and activation of PPARs and b) platelet-independent pathway: inhibition of adenosine uptake by erythrocytes. With respect to the association between intraplatelet cAMP levels and bleeding risk it is possible to establish that compounds/drugs with pleitropic effect for increased intraplatelet cAMP level could have an antithrombotic activity with less risk of bleeding.

CDK5-induced p-PPARγ(Ser 112) downregulates GFAP via PPREs in developing rat brain: effect of metal mixture and troglitazone in astrocytes

The peroxisome proliferator-activated receptor gamma (PPARγ), a group of ligand-activated transcriptional factors, is expressed in glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes. Here, we investigated the role of PPARγ in regulating GFAP using a mixture of As, Cd and Pb (metal mixture, MM) that induces apoptosis and aberrant morphology in rat brain astrocytes. We observed a phospho PPARγ (serine 112 (S112)) (p-PPARγ (S112))-mediated downregulation of GFAP in the MM-exposed astrocytes. We validated this using pure PPARγ agonist, troglitazone (TZ). As reported with MM, TZ induced astrocyte damage owing to reduced GFAP. In silico analysis in the non-coding region of GFAP gene revealed two PPARγ response elements (PPREs); inverted repeat 10 and direct repeat 1 sequences. Gel shift and chromatin immunoprecipitation assays demonstrated enhancement in binding of p-PPARγ (S112) to the sequences, and luciferase reporter assay revealed strong repression of GFAP via PPREs, in response to both MM and TZ. This indicated that suppression in GFAP indeed occurs through direct regulation of these elements by p-PPARγ (S112). Signaling studies proved that MM, as well as TZ, activated the cyclin-dependent kinase 5 (CDK5) and enhanced its interaction with PPARγ resulting into increased p-PPARγ (S112). The p-CDK5 levels were dependent on proximal activation of extracellular signal-regulated protein kinase 1/2 and downstream Jun N-terminal kinase. Taken together, these results are the first to delineate downregulation of GFAP through genomic and non-genomic signaling of PPARγ. It also brings forth a resemblance of TZ with MM in terms of astrocyte disarray in developing brain.

PPARγ activation rescues mitochondrial function from inhibition of complex I and loss of PINK1

Parkinson's disease has long been associated with impaired mitochondrial complex I activity, while several gene defects associated with familial Parkinson's involve defects in mitochondrial function or 'quality control' pathways, causing an imbalance between mitochondrial biogenesis and removal of dysfunctional mitochondria by autophagy. Amongst these are mutations of the gene for PTEN-induced kinase 1 (PINK1) in which mitochondrial function is abnormal. Peroxisome proliferator-activated receptor gamma (PPARγ), a nuclear receptor and ligand-dependent transcription factor, regulates pathways of inflammation, lipid and carbohydrate metabolism, antioxidant defences and mitochondrial biogenesis. We have found that inhibition of complex I in human differentiated SHSY-5Y cells by the complex I inhibitor rotenone irreversibly decrease mitochondrial mass, membrane potential and oxygen consumption, while increasing free radical generation and autophagy. Similar changes are seen in PINK1 knockdown cells, in which potential, oxygen consumption and mitochondrial mass are all decreased. In both models, all these changes were reversed by pre-treatment of the cells with the PPARγ agonist, rosiglitazone, which increased mitochondrial biogenesis, increased oxygen consumption and suppressed free radical generation and autophagy. Thus, rosiglitazone is neuroprotective in two different models of mitochondrial dysfunction associated with Parkinson's disease through a direct impact on mitochondrial function.