Adiponectin protects hippocampal neurons against kainic acid-induced excitotoxicity

Melatonin regulates microglial polarization to M2 cell via RhoA/ROCK signaling pathway in epilepsy

BACKGROUND

Melatonin (MEL), an endogenous hormone, has been widely investigated in neurological diseases. Microglia (MG), a resident immunocyte localizing in central nervous system is reported to play important functions in the animal model of temporal lobe epilepsy (TLE). Some evidence showed that MEL influenced activation of MG, but the detailed model of action that MEL plays in remains uncertain.

METHODS

In this study, we established a model of TLE in mice by stereotactic injection of kainic acid (KA). We treated the mice with MEL. Lipopolysaccharide, ROCK2-knockdown (ROCK-KD) and -overexpression (ROCK-OE) of lentivirus-treated cells were used in cell experiments to simulate an in vitro inflammatory model.

RESULTS

The results of electrophysiological tests showed that MEL reduced frequency and severity of seizure. The results of behavioral tests indicated MEL improved cognition, learning, and memory ability. Histological evidences demonstrated a significant reduction of neuronal death in the hippocampus. In vivo study showed that MEL changed the polarization status of MG from a proinflammatory M1 phenotype to an anti-inflammatory M2 phenotype by inversely regulating the RhoA/ROCK signaling pathway. In cytological study, we found that MEL had a significant protective effect in LPS-treated BV-2 cells and ROCK-KD cells, while the protective effect of MEL was significantly attenuated in ROCK-OE cells.

CONCLUSION

MEL played an antiepileptic role in the KA-induced TLE modeling mice both in behavioral and histological levels, and changed MG polarization status by regulating the RhoA/ROCK signaling pathway.

PPARγ/Adiponectin axis attenuates methamphetamine-induced conditional place preference via the hippocampal AdipoR1 signaling pathway

Methamphetamine (METH) is a highly addictive psychostimulant. The adipocyte-derived hormone adiponectin has a broad spectrum of functions in the brain. However, limited research has been conducted on the effect of adiponectin signaling on METH-induced conditioned place preference (CPP) and knowledge of the underlying neural mechanisms is scarce. The METH induced adult male C57/BL6J mice model were used for testing the therapeutic activities of intraperitoneal injection of AdipoRon or Rosiglitazone, and AdipoR1 overexpression in hippocampal dentate gyrus (DG), and chemogenetic inhibiting the neural activity of DG, and the changes of neurotrophic factors, synaptic molecules, and glutamate receptors, and inflammatory cytokines were also measured. We found that adiponectin expression was significantly reduced in METH addicted patients and mice. Our findings also showed that injection of AdipoRon or Rosiglitazone alleviated the METH-induced CPP behavior. Moreover, the expression of AdipoR1 in the hippocampus was also reduced, and AdipoR1 overexpression blocked the development of METH-induced CPP behavior through regulatory effects on neurotrophic factors, synaptic molecules, and glutamate receptors. The observed inhibitory neural activity of the hippocampal dentate gyrus (DG) induced via a chemogenetic approach produced a therapeutic effect on the METH-induced CPP behavior. Finally, we identified an abnormal expression of some key inflammatory cytokines through the PPARγ/Adiponectin/AdipoR1 axis. This study demonstrates that adiponectin signaling is a promising diagnostic and therapeutic target for METH addiction.

Regulatory Basis of Adipokines Leptin and Adiponectin in Epilepsy: from Signaling Pathways to Glucose Metabolism

Epilepsy is a common and severe neurological disorder in which impaired glucose metabolism leads to changes in neuronal excitability that slow or promote the development of epilepsy. Leptin and adiponectin are important mediators regulating glucose metabolism in the peripheral and central nervous systems. Many studies have reported a strong association between epilepsy and these two adipokines involved in multiple signaling cascades and glucose metabolism. Due to the complex regulatory mechanisms between them and various signal activation networks, their role in epilepsy involves many aspects, including the release of inflammatory mediators, oxidative damage, and neuronal apoptosis. This paper aims to summarize the signaling pathways involved in leptin and adiponectin and the regulation of glucose metabolism from the perspective of the pathogenesis of epilepsy. In particular, we discuss the dual effects of leptin in epilepsy and the relationship between antiepileptic drugs and changes in the levels of these two adipokines. Clinical practitioners may need to consider these factors in evaluating clinical drugs. Through this review, we can better understand the specific involvement of leptin and adiponectin in the pathogenesis of epilepsy, provide ideas for further exploration, and bring about practical significance for the treatment of epilepsy, especially for the development of personalized treatment according to individual metabolic characteristics.

Central Adiponectin Signaling – A Metabolic Regulator in Support of Brain Plasticity

Brain plasticity and metabolism are tightly connected by a constant influx of peripheral glucose to the central nervous system in order to meet the high metabolic demands imposed by neuronal activity. Metabolic disturbances highly affect neuronal plasticity, which underlies the prevalent comorbidity between metabolic disorders, cognitive impairment, and mood dysfunction. Effective pro-cognitive and neuropsychiatric interventions, therefore, should consider the metabolic aspect of brain plasticity to achieve high effectiveness. The adipocyte-secreted hormone, adiponectin, is a metabolic regulator that crosses the blood-brain barrier and modulates neuronal activity in several brain regions, where it exerts neurotrophic and neuroprotective properties. Moreover, adiponectin has been shown to improve neuronal metabolism in different animal models, including obesity, diabetes, and Alzheimer’s disease. Here, we aim at linking the adiponectin’s neurotrophic and neuroprotective properties with its main role as a metabolic regulator and to summarize the possible mechanisms of action on improving brain plasticity via its role in regulating the intracellular energetic activity. Such properties suggest adiponectin signaling as a potential target to counteract the central metabolic disturbances and impaired neuronal plasticity underlying many neuropsychiatric disorders.

The Effect of the Ketogenic Diet on Adiponectin, Omentin and Vaspin in Children with Drug-Resistant Epilepsy

Background: Changes in adipokine secretion may be involved in the anti-epileptic effect of a ketogenic diet (KD) in drug-resistant epilepsy (DRE). Objectives: The assessment of the influence of KD on serum adiponectin, omentin-1, and vaspin in children with DRE. Methods: Anthropometric measurements (weight, height, BMI, and waist-to-hip circumference ratio) were performed in 72 children aged 3–9 years, divided into 3 groups: 24 children with DRE treated with KD, 26—treated with valproic acid (VPA), and a control group of 22 children. Biochemical tests included fasting glucose, insulin, beta-hydroxybutyric acid, lipid profile, aminotransferases activities, and blood gasometry. Serum levels of adiponectin, omentin-1 and vaspin were assayed using commercially available ELISA tests. Results: Serum levels of adiponectin and omentin-1 in the KD group were significantly higher and vaspin—lower in comparison to patients receiving VPA and the control group. In all examined children, serum adiponectin and omentin-1 correlated negatively with WHR and serum triglycerides, insulin, fasting glucose, and HOMA-IR. Vaspin levels correlated negatively with serum triglycerides and positively with body weight, BMI, fasting glucose, insulin, and HOMA-IR. Conclusion: One of the potential mechanisms of KD in children with drug-resistant epilepsy may be a modulation of metabolically beneficial and anti-inflammatory adipokine levels.

Adiponectin Modulation by Genotype and Maternal Choline Supplementation in a Mouse Model of Down Syndrome and Alzheimer's Disease

Down syndrome (DS) is a genetic disorder caused by the triplication of human chromosome 21, which results in neurological and physiological pathologies. These deficits increase during aging and are exacerbated by cognitive decline and increase of Alzheimer's disease (AD) neuropathology. A nontoxic, noninvasive treatment, maternal choline supplementation (MCS) attenuates cognitive decline in mouse models of DS and AD. To evaluate potential underlying mechanisms, laser capture microdissection of individual neuronal populations of MCS offspring was performed, followed by RNA sequencing and bioinformatic inquiry. Results at ~6 months of age (MO) revealed DS mice (the well-established Ts65Dn model) have significant dysregulation of select genes within the Type 2 Diabetes Mellitus (T2DM) signaling pathway relative to normal disomic (2N) littermates. Accordingly, we interrogated key T2DM protein hormones by ELISA assay in addition to gene and encoded protein levels in the brain. We found dysregulation of adiponectin (APN) protein levels in the frontal cortex of ~6 MO trisomic mice, which was attenuated by MCS. APN receptors also displayed expression level changes in response to MCS. APN is a potential biomarker for AD pathology and may be relevant in DS. We posit that changes in APN signaling may be an early marker of cognitive decline and neurodegeneration.

Exploring the New Horizon of AdipoQ in Obesity-Related Alzheimer's Dementia

Alzheimer's disease (AD) is the most common form of dementia, which causes abnormalities in learning, thinking, memory, as well as behavior. Generally, symptoms of AD develop gradually and aggravate over time, and consequently severely interfere with daily activities. Furthermore, obesity is one of the common risk factors for dementia. Dysregulation of adipokine and adipocyte dysfunction are assumed to be accountable for the high risk of obesity in people that develop many related disorders such as AD. Moreover, it has been observed that the dysfunction of adipose is connected with changes in brain metabolism, brain atrophy, cognitive decline, impaired mood, neuroinflammation, impaired insulin signaling, and neuronal dysfunction in people with obesity. Conversely, the pathological mechanisms, as well as the molecular players which are involved in this association, have been unclear until now. In this article, we discuss the impact of adiponectin (AdipoQ) on obesity-related Alzheimer's dementia.

Lipocalin-2 Deficiency Reduces Oxidative Stress and Neuroinflammation and Results in Attenuation of Kainic Acid-Induced Hippocampal Cell Death

The hippocampal cell death that follows kainic acid (KA)-induced seizures is associated with blood–brain barrier (BBB) leakage and oxidative stress. Lipocalin-2 (LCN2) is an iron-trafficking protein which contributes to both oxidative stress and inflammation. However, LCN2′s role in KA-induced hippocampal cell death is not clear. Here, we examine the effect of blocking LCN2 genetically on neuroinflammation and oxidative stress in KA-induced neuronal death. LCN2 deficiency reduced neuronal cell death and BBB leakage in the KA-treated hippocampus. In addition to LCN2 upregulation in the KA-treated hippocampus, circulating LCN2 levels were significantly increased in KA-treated wild-type (WT) mice. In LCN2 knockout mice, we found that the expressions of neutrophil markers myeloperoxidase and neutrophil elastase were decreased compared to their expressions in WT mice following KA treatment. Furthermore, LCN2 deficiency also attenuated KA-induced iron overload and oxidative stress in the hippocampus. These findings indicate that LCN2 may play an important role in iron-related oxidative stress and neuroinflammation in KA-induced hippocampal cell death.

Acute Phase Serum Leptin, Adiponectin, Interleukin-6, and Visfatin Are Altered in Chinese Children With Febrile Seizures: A Cross-Sectional Study

Adipokines, including leptin, visfatin, adiponectin, and interleukin-6 (IL)-6, play multiple roles in the pathophysiology of epilepsy and febrile seizures (FS). We aimed to investigate the associations among plasma adipokines, mainly leptin, visfatin, adiponectin, or IL-6, and the prognosis of FS. This prospective cross-sectional study was conducted from January 2017 to December 2018 at the Wuxi Second People' Hospital China. The levels of serum leptin, visfatin, adiponectin, and IL-6 in 55 children with FS (FS group) were compared with 42 febrile children without seizure (FC group) and 48 healthy children (HC group) in an acute phase. The correlation with clinical indicators was determined by logistic regression analysis. Serum adiponectin and IL-6 levels were significantly higher in the FS group than in the FC and HC groups (p < 0.05), but there was no statistical difference between the FC and HC groups. In addition, logistic regression analysis showed that high concentrations of adiponectin and IL-6 were significantly associated with the occurrence of FS. For leptin and visfatin, they were significantly lower in the FS and FC groups than in the normal control group, but there was no statistical difference between the FS and FC groups. Our results suggest that higher plasma levels of IL-6 and adiponectin may serve as an additional biomarker in the early treatment or follow-up of the FS children.

Physiological role of adiponectin in different tissues: a review

Adiponectin is the most important adipokine secreted by the adipose tissue. It carries out an important role in setting up the metabolism and improving the function of various organs. Adiponectin in the kidneys prevents degradation of the renal arteries, reduces protein excretion, and improves filtration. This role is accomplished by regulating anabolic pathways and reducing oxidative stress in the renal tissue. This hormone in the liver prevents the accumulation of fat and free radicals that cause damage to liver cells and tissue. This adipokine, by preventing inflammatory processes, oxidative stress, obesity and insulin resistance, improves vascular function and prevents the development of atherosclerosis. It seems that adiponectin can also be a therapeutic target for many metabolic diseases. This study aims to clarify the adipose tissue discharge. Here, the diverse physiological actions of adiponectin were reviewed to provide an overview of its therapeutic potential in different metabolic disorders.

Adiponectin Paradox in Alzheimer's Disease; Relevance to Amyloidogenic Evolvability?

Adiponectin (APN) is a multi-functional adipokine which sensitizes the insulin signals, stimulates mitochondria biogenesis, and suppresses inflammation. By virtue of these beneficial properties, APN may protect against metabolic syndrome, including obesity and type II diabetes mellitus. Since these diseases are associated with hypoadiponectinemia, it is suggested that loss of function of APN might be involved. In contrast, despite beneficial properties for cardiovascular cells, APN is detrimental in circulatory diseases, including chronic heart failure (CHF) and chronic kidney disease (CKD). Notably, such an APN paradox might also be applicable to neurodegeneration. Although APN is neuroprotective in various experimental systems, APN was shown to be associated with the severity of amyloid accumulation and cognitive decline in a recent prospective cohort study in elderly. Furthermore, Alzheimer's disease (AD) was associated with hyperadiponectinemia in many studies. Moreover, APN was sequestered by phospho-tau into the neurofibrillary tangle in the postmortem AD brains. These results collectively indicate that APN might increase the risk of AD. In this context, the objective of the present study is to elucidate the mechanism of the APN paradox in AD. Hypothetically, APN might be involved in the stimulation of the amyloidogenic evolvability in reproductive stage, which may later manifest as AD by the antagonistic pleiotropy mechanism during aging. Given the accumulating evidence that AD and CHF are mechanistically overlapped, it is further proposed that the APN paradox of AD might be converged with those of other diseases, such as CHF and CKD.

Adiponectin Protects Against Cerebral Ischemic Injury Through AdipoR1/AMPK Pathways

Excitotoxicity induced by excessive N-methyl-D-aspartate (NMDA) receptor activation underlies the pathology of ischemic injury. Adiponectin (APN) is an adipocyte-derived protein hormone that modulates a number of metabolic processes. APN exerts a wide range of biological functions in the central nervous system. However, the role of APN and its receptors in cerebral ischemia/reperfusion (I/R)-induced injury and the related mechanisms remain to be clarified. Here, we found that APN and APN receptor agonist AdipoRon (APR) were protective against excitotoxicity induced by oxygen and glucose deprivation/reperfusion (OGD/R) and NMDA in primary neurons. Adiponectin receptor 1 (AdipoR1) knockdown reversed the protection conferred by either APN or APR. Moreover, the protective effects offered by both APN and APR were compromised by compound C, an inhibitor of amp-activated protein kinase (AMPK) phosphorylation. Both APN and APR protected the dissipation of the ΔΨm caused by OGD/R. They also up-regulated the PGC-1α expression, which was reversed by compound C. Furthermore, both APN and APR ameliorated but APN knockout aggravated the infarct volume and neurological deficient induced by transient middle cerebral artery occlusion (tMCAO) in vivo. Taken together, these findings show that APN and APR protect against ischemic injury in vitro and in vivo. The protective mechanism is mainly related to AdipoR1-dependent AMPK phosphorylation and PGC-1α up-regulation.

Effects of running on adiponectin, insulin and cytokines in cerebrospinal fluid in healthy young individuals

Exercise can prevent the sedentary lifestyle-related risk of metabolic and cognitive decline, but mechanisms and mediators of exercise effects on human brain are relatively unexplored. We measured acute exercise-induced changes in adiponectin, insulin and other bioactive molecules in cerebrospinal fluid (CSF) and serum from young lean individuals. Samples of serum and CSF were obtained before and 1-h after the 90-min run (75–80% HRmax; maximal heart rate), additional serum was taken at finish-line. Body composition, physical fitness, metabolic rate, cognitive functions, food preference, glucose, insulin and albumin were measured. The spectrum of 174 cytokines was assessed by protein arrays, adiponectin was also determined by ELISA and immunoblotting. CSF adiponectin decreased post-exercise by 21.3% (arrays) and 25.8% (ELISA) (p < 0.009). Immunoblotting revealed reduction in a low-molecular-weight-adiponectin (p < 0.005). CSF adiponectin positively correlated with CSF/serum albumin ratio (p < 0.022), an indicator of blood-brain-barrier permeability. CSF and serum adiponectin were positively associated with memory and running-induced changes in insulinemia and CSF insulin. Additionally, running modulated CSF levels of 16 other cytokines. Acute running reduced CSF adiponectin and modulated insulin and albumin in CSF and serum. Associations of adiponectin with memory and metabolism indicate the potential role of this bioactive molecule in mediating exercise-induced adaptive response in human brain.

The Role of Leptin and Adiponectin in Obesity-Associated Cognitive Decline and Alzheimer's Disease

Cross-talk between adipose tissue and central nervous system (CNS) underlies the increased risk of obese people to develop brain diseases such as cognitive and mood disorders. Detailed mechanisms for how peripheral changes caused by adipose tissue accumulation in obesity impact the CNS to cause brain dysfunction are poorly understood. Adipokines are a large group of substances secreted by the white adipose tissue to regulate a wide range of homeostatic processes including, but not limited to, energy metabolism and immunity. Obesity is characterized by a generalized change in the levels of circulating adipokines due to abnormal accumulation and dysfunction of adipose tissue. Altered adipokine levels underlie complications of obesity as well as the increased risk for the development of obesity-related comorbidities such as type 2 diabetes, cardiovascular and neurodegenerative diseases. Here, we review the literature for the role of adipokines as key mediators of the communication between periphery and CNS in health and disease. We will focus on the actions of leptin and adiponectin, two of the most abundant and well studied adipokines, in the brain, with particular emphasis on how altered signaling of these adipokines in obesity may lead to cognitive dysfunction and augmented risk for Alzheimer's disease. A better understanding of adipokine biology in brain disorders may prove of major relevance to diagnostic, prevention and therapy.

Circulating levels of adipokines are altered in patients with temporal lobe epilepsy

OBJECTIVE

A persistent low-grade inflammatory state has been described in patients with temporal lobe epilepsy (TLE) in the interictal period. Adipokines are cytokines produced by the adipose tissue that can influence inflammatory response. The purpose of this study was to evaluate the plasma levels of adipokines in patients with TLE in comparison with controls. In addition, we sought to investigate whether the levels of adipokines were associated with clinical parameters in TLE.

METHODS

Forty patients with TLE and 40 controls were enrolled in this study. All participants were subjected to clinical assessment that included the Mini International Neuropsychiatric Interview (MINI) and the Hamilton Depression Rating Scale (HAM-D). Peripheral blood was drawn, and plasma levels of adipokines (adiponectin, leptin, and resistin) were measured by enzyme-linked immunoassay (ELISA).

RESULTS

People with TLE presented higher leptin and lower adiponectin and resistin levels in comparison with controls. The levels of these adipokines correlated negatively with illness length but not with other clinical parameters. In a binary logistic regression model, higher leptin and lower adiponectin levels remained as significant predictors of TLE diagnosis.

CONCLUSIONS

These results corroborate the view that TLE is a multisystemic condition associated with low-grade inflammation.

Adiponectin and sporadic Alzheimer's disease: Clinical and molecular links

Obesity has been consistently associated with Alzheimer's disease (AD) though the exact mechanisms by which it influences cognition are still elusive and subject of current research. Adiponectin, the most abundant adipokine in circulation, is inversely correlated with adipose tissue dysfunction and seems to be a central player in this association. In fact, different signalling pathways are shared by adiponectin and proteins involved in AD pathophysiology and considerable amount of evidence supports its direct and indirect influence on β-amyloid and tau aggregates formation. In this paper we present a critical review of cellular, animal and clinical studies which have contributed to a more thorough understanding of the extent to which adiponectin influences the risk of developing AD as well as its progression. Finally, the effect of acetylcholinesterase inhibitors on circulating adiponectin levels, possible therapeutic applications and future research strategies are also discussed.

Associations of cord blood leptin and adiponectin with children's cognitive abilities

Background Adipocytokines may play a role in fetal programming of neurodevelopment. We aimed to investigate the associations between cord blood adipocytokine concentrations and children's intelligence test scores. Methods We used data from two ongoing pregnancy cohorts in North America: the Maternal-Infant Research on Environmental Chemicals (MIREC, n = 429) and Health Outcomes and Measures of the Environment (HOME, n = 183) Studies. Umbilical cord blood adipocytokine concentrations were measured using enzyme-linked immunosorbent assays. We assessed children's Intelligence Quotient (IQ) and its components using the Wechsler Preschool and Primary Scales of Intelligence-III or Wechsler Intelligence Scale for Children-IV. We used linear regression and linear mixed models to estimate associations between log₂-transformed adipocytokine concentrations and children's IQ after adjusting for sociodemographic, perinatal, and child factors. Results After adjusting for covariates, cord blood adiponectin was positively associated with children's full-scale IQ scores at age 3 years in the MIREC Study (β = 1.4, 95% confidence interval [CI]: 0.2, 2.5) and at ages 5 and 8 years in the HOME Study (β = 1.7, CI: -0.1, 3.5). Adiponectin was positively associated with performance IQ in both studies (MIREC: β = 2.0, CI: 0.7, 3.3; HOME: β = 2.2, CI: 0.5, 3.9). Adiponectin was positively associated with working memory composite scores at age 8 in the HOME Study (β = 3.1, CI: 1.0, 5.2). Leptin was not associated with children's IQ in either study. Conclusions Cord blood adiponectin was associated with higher full-scale and performance IQ and working memory composite scores in children. Future studies are needed to explore the mechanisms underlying these associations.

Activating Adiponectin Signaling with Exogenous AdipoRon Reduces Myelin Lipid Accumulation and Suppresses Macrophage Recruitment after Spinal Cord Injury

Myelin-laden macrophages (mye-MΦ), resulting primarily from internalization of myelin debris by infiltrating bone marrow-derived macrophages in spinal cord injury (SCI), trigger inflammatory responses that largely contribute to secondary injury. Adiponectin, which is secreted from adipose tissue, is an important hormone that modulates macrophage inflammation. In the present study, we examined the role of adiponectin on macrophage-mediated neuroinflammation after SCI. We found that in vitro activation of adiponectin receptors (AdipoRs) by their agonist AdipoRon suppressed myelin lipid accumulation in mye-MΦ through APPL1/PPARγ/LXRα/ABCA1-mediated lipid efflux, subsequently inhibiting inflammation and restoring normal function to mye-MΦ. In vivo data further confirmed that intravenous administration of AdipoRon after SCI dampened recruitment of macrophages and reduced myelin lipid accumulation. Accordingly, AdipoRon treatment ameliorated post-SCI tissue damage and astrogliosis, resulting in improved motor function. Although there was no significant pathological exacerbation in adiponectin-null mice subjected to SCI, our work reveals a functional link between adiponectin and hematogenous macrophages in the context of SCI, suggesting that activation of adiponectin signaling is a promising therapeutic approach to mitigate mye-MΦ-mediated neuroinflammation in neurological disorders involving demyelination.

Comparison of cytokines and prooxidants/antioxidants markers among adults with refractory versus well-controlled epilepsy: A cross-sectional study

PURPOSE

This study aims to investigate the serum adiponectin, interleukin (IL)-6 and oxidative stress in epilepsy patients who are refractory or non-refractory to treatments.

METHOD

The study comprised 31 refractory epilepsy, 29 well-controlled epilepsy patients and control group including 29 healthy individuals. The serum adiponectin, IL-6, total antioxidant status (TAS), total oxidant status levels (TOS) and oxidative stress index (OSİ) were determined.

RESULTS

The mean serum adiponectin and TAS levels were significantly lower in the refractory epilepsy patients than in the healty controls, and mean IL-6, TOS and OSİ levels were significantly higher. The serum adiponectin, IL-6, TAS, TOS and OSI levels were not significantly different between the well-controlled epilepsy patients and the healthy controls.

CONCLUSIONS

The mean serum IL-6 and oxidative stress levels in refractory epilepsy patients were higher and the serum adiponectin level was lower than the healthy control group. These findings may be associated with an increased risk of seizures, atherosclerosis and cardiovascular disease in refractory epilepsy patients.

Distribution of Adiponectin Receptors 1 and 2 in the Rat Olfactory Bulb and the Effect of Adiponectin Injection on Insulin Receptor Expression

BACKGROUND

Adiponectin (APN) is an adipocyte-derived hormone that has peripheral beneficial effects. Although its receptors AdipoR1 and AdipoR2 are expressed in the brain, their function in neurons is poorly understood. The aims of this work were to describe the distribution of APN receptors in the olfactory bulb (OB) as well as the possible effects of APN injection on the insulin receptor (InsR) content and Akt kinase.

METHOD

We performed the double immunofluorescence technique to describe the distribution of AdipoRs and the cellular type they were expressing. mRNA transcript and protein content were assessed by RT-PCR and Western blot, respectively. APN injection was performed to analyze its possible effect on the insulin pathway.

RESULTS

We found that AdipoRs were localized in all cell layers and in both neurons and astrocytes. We observed the presence of mRNA transcripts and immunoblot analysis confirmed the protein on the intact OB; APN injection in the OB resulted in a slight decrease of the total InsR and Akt phosphorylation and a reduction of phopho-InsR content.

CONCLUSIONS

These data demonstrated that AdipoRs are expressed in OB regions, and APN injection could act as an insulin pathway modulator in the OB and thus possibly contribute to olfaction physiology.

Globular Adiponectin Limits Microglia Pro-Inflammatory Phenotype through an AdipoR1/NF-κB Signaling Pathway

We recently reported that increased levels of Adiponectin (ApN) in the brain led to microglia phenotype and activation state regulation, thus reducing both global brain inflammation and depressive-like behaviors in mice. Apart from this, little is known on ApN molecular effects on microglia, although these cells are crucial in both physiological and pathological processes. Here we fill this gap by studying the effects and targets of ApN toward neuroinflammation. Our findings suggest that ApN deficiency in mice leads to a higher sensitivity of mice to neuroinflammation that is due to enhanced microglia responsiveness to a pro-inflammatory challenge. Moreover, we show that globular ApN (gApN) exerts direct in vivo anti-inflammatory actions on microglia by reducing IL-1β, IL-6, and TNFα synthesis. In vitro, gApN anti-inflammatory properties are confirmed in brain-sorted microglia, primary cultured and microglia cell line (BV2), but are not observed on astrocytes. Our results also show that gApN blocks LPS-induced nitrosative and oxidative stress in microglia. Finally, we demonstrate for the first time that these anti-inflammatory and anti-oxidant actions of gApN on microglia are mediated through an AdipoR1/NF-κB signaling pathway.

Adiponectin Attenuates Streptozotocin-Induced Tau Hyperphosphorylation and Cognitive Deficits by Rescuing PI3K/Akt/GSK-3β Pathway

Clinical studies have demonstrated that decreased adiponectin is associated with the development of Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD). We focused on determining the neuroprotective effect offered by adiponectin against streptozotocin-induced brain damage in ICV-STZ rat model. We found that adiponectin supplements significantly restored the cognitive deficits in ICV-STZ rat model including shorter escape latency, more crossing times and increased time spent in the target quadrant. Adiponectin supplements also increased number of dendritic branches and mushroom percentage. In addition, adiponectin supplements attenuated tau hyperphosphorylation at multiple AD-related sites through activation of protein Ser9-phosphorylated glycogen synthase kinase-3β (Ser9-GSK-3β) with increased the Akt and PI3K activity. Our data suggest that adiponectin supplements have neuroprotective effects on the ICV-STZ rat model, which may be mediated by the activation of the PI3K/Akt/GSK-3β signaling pathway.

Adiponectin controls the apoptosis and the expression of tight junction proteins in brain endothelial cells through AdipoR1 under beta amyloid toxicity

Alzheimer’s disease (AD) is the most common neurodegenerative disease, characterized by excessive beta amyloid (Aβ) deposition in brain, leading to blood–brain barrier (BBB) disruption. The mechanisms of BBB disruption in AD are still unclear, despite considerable research. The adipokine adiponectin is known to regulate various metabolic functions and reduce inflammation. Though adiponectin receptors have been reported in the brain, its role in the central nervous system has not been fully characterized. In the present study, we investigate whether adiponectin contributes to the tight junction integrity and cell death of brain endothelial cells under Aβ-induced toxicity conditions. We measured the expression of adiponectin receptors (AdipoR1 and AdipoR2) and the alteration of tight junction proteins in in vivo 5xFAD mouse brain. Moreover, we examined the production of reactive oxygen species (ROS) and the loss of tight junction proteins such as Claudin 5, ZO-1, and inflammatory signaling in in vitro brain endothelial cells (bEnd.3 cells) under Aβ toxicity. Our results showed that Acrp30 (a globular form of adiponectin) reduces the expression of proinflammatory cytokines and the expression of RAGE as Aβ transporters into brain. Moreover, we found that Acrp 30 attenuated the apoptosis and the tight junction disruption through AdipoR1-mediated NF-κB pathway in Aβ-exposed bEnd.3 cells. Thus, we suggest that adiponectin is an attractive therapeutic target for treating BBB breakdown in AD brain.

Importance of adiponectin activity in the pathogenesis of Alzheimer's disease

A recent study suggested that insulin resistance may play a central role in the pathogenesis of Alzheimer's disease (AD). In this regard, it is of note that upregulation of plasma adiponectin (APN), a benign adipokine that sensitizes the insulin receptor signaling pathway and suppresses inflammation, has recently been associated with the severities of amyloid deposits and cognitive deficits in the elderly, suggesting that APN may enhance the risk of AD. These results are unanticipated because AD has been linked to type II diabetes and other metabolic disorders in which hypoadiponectinemia has been firmly established, and because APN ameliorated neuropathological features in a mouse model of neurodegeneration. Therefore, the objective of this study is to discuss the possible mechanisms underlying the biological actions of APN in the context of AD. Given that insulin receptor signaling is required for normal function of the nervous system, we predict that APN may be upregulated to compensate for compromised activity of the insulin receptor signaling pathway. However, increased APN might be sequestered by tau in the brain, leading to neurotoxic protein aggregation in AD. Alternatively, misfolding of APN may result in downregulation of the insulin/APN signal transduction network, leading to decreased neuroprotective and neurotrophic activities. Thus, it is possible that both ‘gain of function’ and ‘loss of function’ of APN may underlie synaptic dysfunction and neuronal cell death in AD. Such a unique biological mechanism underlying APN function in AD may require a novel therapeutic strategy that is distinct from previous treatment for metabolic disorders.

The behavioral deficits and cognitive impairment are correlated with decreased IGF-II and ERK in depressed mice induced by chronic unpredictable stress

AIM

To investigate the behavioral deficits, cognitive impairment and possible mechanisms induced by chronic unpredictable stress (CUS) in mice of different ages.

METHODS

The behaviors and cognition were tested using the open field test, tail suspension test and the Morris water maze. The changes in the insulin-like growth factor II (IGF-II) and the extracellular signal-regulated kinase (ERK) and phosphorylation (p-ERK) in the hippocampus (HP) and prefrontal cortex (PFC) were evaluated by immunohistochemistry.

RESULTS

The 15-month-old mice revealed a significant decline in spontaneous behavior and the learning-memory function and showed a decrease in IGF-II and p-ERK expression levels in HP and PFC. Four weeks of CUS exposure induced significant anxiety- and depression-like behavior and learning-memory function impairment in 3- to 15-month-old mice, and reduced IGF-II and p-ERK expression levels in HP and PFC, compared with control group mice, respectively.

CONCLUSIONS

The behavioral deficits and cognitive impairment induced by CUS and aging in mice could be associated with the down-regulated expression of IGF-II and p-ERK in HP and PFC. This role seems to be dependent on the intracellular ERK pathway.

The effects of aging in the hippocampus and cognitive decline

Aging is a natural process that is associated with cognitive decline as well as functional and social impairments. One structure of particular interest when considering aging and cognitive decline is the hippocampus, a brain region known to play an important role in learning and memory consolidation as well as in affective behaviours and mood regulation, and where both functional and structural plasticity (e.g., neurogenesis) occur well into adulthood. Neurobiological alterations seen in the aging hippocampus including increased oxidative stress and neuroinflammation, altered intracellular signalling and gene expression, as well as reduced neurogenesis and synaptic plasticity, are thought to be associated with age-related cognitive decline. Non-invasive strategies such as caloric restriction, physical exercise, and environmental enrichment have been shown to counteract many of the age-induced alterations in hippocampal signalling, structure, and function. Thus, such approaches may have therapeutic value in counteracting the deleterious effects of aging and protecting the brain against age-associated neurodegenerative processes.

Intracerebroventricular administration of adiponectin attenuates streptozotocin-induced memory impairment in rats

Alzheimer’s disease (AD) has been reported to be linked with diabetes mellitus and insulin resistance. Adiponectin (ADN), an adipocytokine secreted from adipose tissue, is involved in the regulation of insulin sensitivity, energy homeostasis, and mitochondrial dysfunction. In this study, we examined the effect of ADN on passive avoidance memory in animal model of sporadic AD (sAD). On days 1 and 3 after cannulation, rats received intracerebroventricular (icv) injection of streptozotocin (STZ) (3 mg/kg). Thirty minutes before the learning process, animals received saline or ADN in different doses (6, 60, and 600 µg). The step-through latency (STL) and total time spent in the dark compartment (TDC) were recorded and analyzed. In STZ-treated rats, STL was significantly decreased, whereas TDC showed a dramatic increase. In ADN-treated rats, STL was significantly increased (P < 0.01) in all treatment doses. The number of entries was decreased in all applied doses; however, TDC was reduced only by the application of 6 ng of ADN (P < 0.05). It can be concluded that ADN is useful to improve the STZ-induced memory impairment. This study showed, for the first time, that icv administration of ADN could improve the memory acquisition in animal model of sAD.

Diagnosis and body mass index effects on hippocampal volumes and neurochemistry in bipolar disorder

We previously reported that higher body mass index (BMI) was associated with greater hippocampal glutamate+glutamine in people with bipolar disorder (BD), but not in non-BD healthy comparator subjects (HSs). In the current report, we extend these findings by examining the impact of BD diagnosis and BMI on hippocampal volumes and the concentrations of several additional neurochemicals in 57 early-stage BD patients and 31 HSs. Using 3-T magnetic resonance imaging and magnetic resonance spectroscopy, we measured bilateral hippocampal volumes and the hippocampal concentrations of four neurochemicals relevant to BD: N-acetylaspartate+N-acteylaspartylglutamate (tNAA), creatine+phosphocreatine (Cre), myoinositol (Ins) and glycerophosphocholine+phosphatidylcholine (Cho). We used multivariate factorial analysis of covariance to investigate the impact of diagnosis (patient vs HS) and BMI category (normal weight vs overweight/obese) on these variables. We found a main effect of diagnosis on hippocampal volumes, with patients having smaller hippocampi than HSs. There was no association between BMI and hippocampal volumes. We found diagnosis and BMI effects on hippocampal neurochemistry, with patients having lower Cre, Ins and Cho, and overweight/obese subjects having higher levels of these chemicals. In patient-only models that controlled for clinical and treatment variables, we detected an additional association between higher BMI and lower tNAA that was absent in HSs. To our knowledge, this was the first study to investigate the relative contributions of BD diagnosis and BMI to hippocampal volumes, and only the second to investigate their contributions to hippocampal chemistry. It provides further evidence that diagnosis and elevated BMI both impact limbic brain areas relevant to BD.

The role of adiponectin receptors in the regulation of synaptic transmission in the hippocampus

In the last two decades adiponectin, member of the adipokines family, gained attention because of its unique antidiabetic effects. However, the presence in the brain of adiponectin receptors and adiponectin itself raised interest because of the possible association with neuropsychiatric diseases. Indeed, clinical studies found altered concentration of adiponectin both in plasma and cerebrospinal fluid in several pathologies including depression, multiple sclerosis, Alzheimer's disease and stroke. Moreover, recent preclinical studies also suggest its involvement in different physiological functions. Despite this evidence very few studies attempted to elucidate the functional role of adiponectin at the synapse. To address this question, here we investigated the effect of Adiporon, an agonist of both adiponectin receptors on synaptic transmission and LTP at Schaffer-collateral CA1 pathway. Surprisingly, increasing concentration of Adiporon correlated with lower CA1-LTP levels and paired-pulse ratio, whereas basal transmission was always preserved. Collectively, our data show that the adiponectin system, beyond its involvement in metabolic diseases, plays also a critical role in synaptic activity thereby representing a putative target for the treatment of synaptic pathologies.

Caloric restriction increases brain mitochondrial calcium retention capacity and protects against excitotoxicity

Caloric restriction (CR) protects against many cerebral pathological conditions that are associated with excitotoxic damage and calcium overload, although the mechanisms are still poorly understood. Here we show that CR strongly protects against excitotoxic insults in vitro and in vivo in a manner associated with significant changes in mitochondrial function. CR increases electron transport chain activity, enhances antioxidant defenses, and favors mitochondrial calcium retention capacity in the brain. These changes are accompanied by a decrease in cyclophilin D activity and acetylation and an increase in Sirt3 expression. This suggests that Sirt3-mediated deacetylation and inhibition of cyclophilin D in CR promote the inhibition of mitochondrial permeability transition, resulting in enhanced mitochondrial calcium retention. Altogether, our results indicate that enhanced mitochondrial calcium retention capacity underlies the beneficial effects of CR against excitotoxic conditions. This protection may explain the many beneficial effects of CR in the aging brain.

The Influence of Adipose Tissue on Brain Development, Cognition, and Risk of Neurodegenerative Disorders

The brain is a highly metabolic organ and thus especially vulnerable to changes in peripheral metabolism, including those induced by obesity-associated adipose tissue dysfunction. In this context, it is likely that the development and maturation of neurocognitive circuits may also be affected and modulated by metabolic environmental factors, beginning in utero. It is currently recognized that maternal obesity, either pre-gestational or gestational, negatively influences fetal brain development and elevates the risk of cognitive impairment and neuropsychiatric disorders in the offspring. During infancy and adolescence, obesity remains a limiting factor for healthy neurodevelopment, especially affecting executive functions but also attention, visuospatial ability, and motor skills. In middle age, obesity seems to induce an accelerated brain aging and thus may increase the risk of age-related neurodegenerative diseases such as Alzheimer's disease. In this chapter we review and discuss experimental and clinical evidence focusing on the influence of adipose tissue dysfunction on neurodevelopment and cognition across lifespan, as well as some possible mechanistic links, namely the role of the most well studied adipokines.

CSF and plasma adipokines after tonic-clonic seizures

PURPOSE

Adipokines, especially leptin and adiponectin, have gained increasing importance in pathophysiology of various neurological diseases including epilepsy. There are experimental data suggesting a role for leptin in the genesis of seizures and neuroprotection related to seizures. However there are no clinical studies on the effects of epileptic seizures on adipokines.

METHODS

We measured cerebrospinal fluid (CSF) and plasma levels of leptin, adiponectin and adipsin after provoked or unprovoked primary or secondarily generalized tonic-clonic seizures in 13 female patients and seven controls. The samples were taken within 24h after the seizure onset.

RESULTS

Leptin plasma levels correlated negatively with the time to sample withdrawal, i.e. the longer the time interval between the seizure and the sample the lower the leptin levels in the patients. Interestingly, plasma adiponectin levels were significantly increased after the seizure episode.

CONCLUSION

This study provides further evidence that there are seizure-induced acute changes in adipokine metabolism. Leptin concentrations seem to decrease during the first 24h after the seizure whereas adiponectin levels increase. The meaning of this response is far from clear, but it might be an endogenous attempt to prevent harmful effects of epileptic seizures in the central nervous system.

Adiponectin, leptin and IL-1 β in elderly diabetic patients with mild cognitive impairment

The aim of the study was to determine the serum levels of adiponectin, leptin and IL-1 β in elderly diabetic patients with and without mild cognitive impairment (MCI) and to examine the associations of these markers with clinical and cognitive parameters. A biochemical evaluation was performed of 62 seniors with type 2 diabetes (T2DM) and MCI, and 132 seniors with T2DM but without MCI (controls). Serum leptin and IL-1 β levels were higher and adiponectin concentration was lower in MCI patients than controls. In MCI subjects, adiponectin level was negatively correlated with leptin, IL-1 β levels and BMI. Leptin concentration was correlated with IL-1 β level. Univariate logistic regression models revealed that the factors which increased the likelihood of diagnosis of MCI in elderly patients with T2DM were higher levels of HbA1c, leptin, IL-1 β and triglycerides, as well as lower levels of adiponectin and HDL cholesterol. Similarly, previous CVD, hypertension, hyperlipidemia, retinopathy, nephropathy, hypoglycemia, longer duration of diabetes, increased number of co-morbidities, older age, fewer years of formal education were found to be associated with MCI. The multivariable model indicated fewer years of formal education, previous CVD, hypertension, increased number of co-morbidities, higher HbA1c and IL-1 β levels and lower adiponectin level. Elderly diabetic patients with MCI have higher levels of leptin and IL-1 β and lower levels of adiponectin. Further prospective studies are needed to determine the role of these markers in the progression to dementia.

Effects of postnatal alcohol exposure on hippocampal gene expression and learning in adult mice

Fetal alcohol syndrome (FAS) is a condition resulting from excessive drinking by pregnant women. Symptoms of FAS include abnormal facial features, stunted growth, intellectual deficits and attentional dysfunction. Many studies have investigated FAS, but its underlying mechanisms remain unknown. This study evaluated the relationship between alcohol exposure during the synaptogenesis period in postnatal mice and subsequent cognitive function in adult mice. We delivered two injections, separated by 2 h, of ethanol (3 g/kg, ethanol/saline, 20% v/v) to ICR mice on postnatal day 7. After 10 weeks, we conducted a behavioral test, sacrificed the animals, harvested brain tissue and analyzed hippocampal gene expression using a microarray. In ethanol-treated mice, there was a reduction in brain size and decreased neuronal cell number in the cortex, and also cognitive impairment. cDNA microarray results indicated that 1,548 genes showed a > 2-fold decrease in expression relative to control, whereas 974 genes showed a > 2-fold increase in expression relative to control. Many of these genes were related to signal transduction, synaptogenesis and cell membrane formation, which are highlighted in our findings.

Alzheimer's like brain changes correlate with low adiponectin plasma levels in type 2 diabetic patients

AIM

To study the association between adiponectin plasma levels, and gray matter brain volume and cerebral glucose metabolism in a group of type 2 diabetes patients.

METHODS

We studied 25 type 2 diabetes patients and 25 age- and gender-matched healthy control participants. Biochemical analysis and structural cerebral magnetic resonance imaging, including voxel-based morphometry and (18)-fluorodeoxyglucose positron emission tomography, were performed. The gray matter volumes and metabolism changes were analyzed using statistical parametric mapping (SPM8).

RESULTS

Lower levels of adiponectin correlated with a lower gray matter volume in temporal regions and with reduced cerebral glucose metabolism in temporal regions (p<0.001), adjusted for age, gender, education, and the presence of at least one epsilon 4 allele for the apolipoprotein E (APOEε4 genotype).

CONCLUSIONS

Positive correlations between adiponectin plasma levels and both gray matter volume and cerebral glucose metabolism were found, predominantly in temporal regions, as in Alzheimer's disease. Adiponectin might be a biomarker for the cognitive decline associated with type 2 diabetic patients.

High-fat diet-induced obesity exacerbates kainic acid-induced hippocampal cell death

BACKGROUND

Obesity has deleterious effects on the brain, and metabolic dysfunction may exacerbate the outcomes of seizures and brain injuries. However, it is unclear whether obesity affects excitotoxicity-induced neuronal cell death. The purpose of this study was to investigate the effects of a high-fat diet (HFD) on neuroinflammation and oxidative stress in the hippocampus of kainic acid (KA)-treated mice.

RESULTS

Mice were fed with a HFD or normal diet for 8 weeks and then received a systemic injection of KA. HFD-fed mice showed hypercholesterolemia, insulin resistance, and hepatic steatosis. HFD-fed mice showed greater susceptibility to KA-induced seizures, an increased number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, neuroinflammation, and oxidative stress. Furthermore, we found that KA treatment increased HFD-induced calpain1, nuclear factor E2-related factor 2, and heme oxygenase-1 expression in the hippocampus.

CONCLUSIONS

These findings imply that complex mechanisms affected by obesity-induced systemic inflammation, neuroinflammation, ER stress, calcium overload, and oxidative stress may contribute to neuronal death after brain injury.

Relationship between Adiponectin Gene Polymorphisms and Late-Onset Alzheimer's Disease

In recent years, researchers have found that adiponectin (ANP) plays an important role in the pathogenesis of Alzheimer's disease (AD), and low serum concentrations of ANP are associated with AD. Higher plasma ANP level have a protective effect against the development of cognitive decline, suggesting that ANP may affect AD onset. Meanwhile, accumulating evidence supports the crucial role of ANP in the pathogenesis of AD. To study the relationship between ANP gene polymorphisms (rs266729, -11377C>G and rs1501299, G276T) and late-onset AD (LOAD), we carried out a case-control study that included 201 LOAD patients and 257 healthy control subjects. Statistically significant differences were detected in the genotype and allelotype frequency distributions of rs266729 and rs1501299 between the LOAD group and the control group, with a noticeable increase in the G and T allelotype frequency distributions in the LOAD group (P < 0.05). Logistic regression analysis using recessive model and additive model revealed that the rs266729 GG and rs1501299 TT genotypes are associated with a greater risk of LOAD. Haplotype analysis identified four haplotypes: CG, CT, GG, and GT. The frequencies of the CT and GG haplotypes were not significantly different (P > 0.05) between the LOAD group and control group, whereas the CG and GT haplotypes were significantly different (P < 0.05), suggesting a negative correlation between the CG haplotype and LOAD onset (OR = 0.74, 95% CI = 0.57–0.96, P = 0.022), and a positive correlation between the GT haplotype and LOAD onset (OR = 2.29, 95% CI = 1.42–3.68, P = 0.005). Therefore, we speculated that the rs266729 and rs1501299 of ANP gene polymorphisms and the GT and CG haplotypes were associated with LOAD.

Adiponectin and interleukin-6, but not adipose tissue, are associated with worse neurocognitive function in HIV-infected men

BACKGROUND

Generalized obesity has been associated with cognitive decline, a process potentially mediated by adipocytokines. The effects of regional adipose tissue (AT) on cognition, however, are not well understood. We explored cross-sectional relationships between regional AT, adipocytokines, inflammatory markers and neuropsychological (NP) test scores among HIV+ and HIV- men enrolled in the Multicenter AIDS Cohort Study.

METHODS

Visceral, subcutaneous abdominal and subcutaneous thigh AT areas were quantified by computed tomography (CT). NP tests (Trail Making Test parts A and B, and Symbol-Digit Modalities) obtained within 2 years of CT screened for psychomotor speed and executive function. Adiponectin, leptin, interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hs-CRP) were measured.

RESULTS

Of 509 HIV+ and 271 HIV- participants, HIV+ men (98% on antiretroviral therapy, 81% HIV-1 RNA<50 copies/ml) had lower median subcutaneous AT and adiponectin levels and higher hs-CRP levels, but visceral AT, body mass index, IL-6 and NP scores did not vary by HIV serostatus. In multivariable analysis, older age, ≤ high school education and African American race, but not AT area or site, were associated with worse NP test scores among all participants. In HIV+ only, higher adiponectin and IL-6 were associated with worse cognitive function independent of AT area. No HIV-specific factors were associated with NP test scores.

CONCLUSIONS

Demographic factors were associated with NP test performance, but regional adiposity was not. In HIV+ only, higher adiponectin and IL-6 were associated with worse NP test scores, supporting a role for chronic inflammation and adipocytokine imbalance in neurocognitive decline in HIV+ persons.

Serum adiponectin, leptin, and interleukin 6 levels as adipocytokines in children with febrile seizures: The role of adipose tissue in febrile seizures

Proinflammatory and anti-inflammatory cytokines have an important role in the pathogenesis of febrile seizures (FS). Adipocytokines like interleukin 6 (IL-6), leptin, and adiponectin released from adipose tissue play a role in inflammation. This study aimed to assess the probable role of adipose tissue in children with FS. We measured serum IL-6, leptin, and adiponectin levels and evaluated clinical and laboratory findings in children with FS (n = 32) and compared the results with the values of children of the same age with febrile illness without seizures (febrile control, FC; n = 26) and healthy control group (HC; n = 29). The serum levels of white blood cells, C-reactive protein, IL-6, leptin, and adiponectin were found to be significantly higher, while serum hemoglobin (Hb) levels were found to be significantly lower in FS and FC groups than in the HC group (p < 0.001). When we compared the FS with the FC group, the serum Hb levels were significantly lower in the FS group than those in the FC group (p = 0.001). There was no significant difference between the FS and FC group with regard to the serum levels of these adipocytokines (p > 0.05). Our data showed that elevated levels of these adipocytokines as acute phase reactants in FS and FC groups did not contribute to the development of FS.

Obesity and dementia: adipokines interact with the brain

Obesity is a pandemic and a serious global health concern. Obesity is a risk factor for multiple conditions and contributes to multi-morbidities, resulting in increased health costs and millions of deaths each year. Obesity has been associated with changes in brain structure, cognitive deficits, dementia and Alzheimer׳s disease. Adipokines, defined as hormones, cytokines and peptides secreted by adipose tissue, may have more widespread influence and functionality in the brain than previously thought. In this review, six adipokines, and their actions in the obese and non-obese conditions will be discussed. Included are: plasminogen activator inhibitor-1 (PAI-1), interleukin-6 (IL-6), tumor necrosis factors alpha (TNF-α), angiotensinogen (AGT), adiponectin and leptin. Their functionality in the periphery, their ability to cross the blood brain barrier (BBB) and their influence on dementia processes within the brain will be discussed.

Physical exercise-induced hippocampal neurogenesis and antidepressant effects are mediated by the adipocyte hormone adiponectin

Adiponectin (ADN) is an adipocyte-secreted protein with insulin-sensitizing, antidiabetic, antiinflammatory, and antiatherogenic properties. Evidence is also accumulating that ADN has neuroprotective activities, yet the underlying mechanism remains elusive. Here we show that ADN could pass through the blood-brain barrier, and elevating its levels in the brain increased cell proliferation and decreased depression-like behaviors. ADN deficiency did not reduce the basal hippocampal neurogenesis or neuronal differentiation but diminished the effectiveness of exercise in increasing hippocampal neurogenesis. Furthermore, exercise-induced reduction in depression-like behaviors was abrogated in ADN-deficient mice, and this impairment in ADN-deficient mice was accompanied by defective running-induced phosphorylation of AMP-activated protein kinase (AMPK) in the hippocampal tissue. In vitro analyses indicated that ADN itself could increase cell proliferation of both hippocampal progenitor cells and Neuro2a neuroblastoma cells. The neurogenic effects of ADN were mediated by the ADN receptor 1 (ADNR1), because siRNA targeting ADNR1, but not ADNR2, inhibited the capacity of ADN to enhance cell proliferation. These data suggest that adiponectin may play a significant role in mediating the effects of exercise on hippocampal neurogenesis and depression, possibly by activation of the ADNR1/AMPK signaling pathways, and also raise the possibility that adiponectin and its agonists may represent a promising therapeutic treatment for depression.

Obesity as a risk factor for Alzheimer's disease: the role of adipocytokines

Alzheimer's disease is the leading cause of dementia and the most prevalent neurodegenerative disease. It is an aging-related multi-factorial disorder and growing evidence support the contribution of metabolic factors to what was formerly thought to be a centrally mediated process. Obesity has already been recognized as an important player in the pathogenesis of this type of dementia, independently of insulin resistance or other vascular risk factors. Although the exact underlying mechanisms are still unknown, adipocyte dysfunction and concomitant alteration in adipocyte-derived protein secretion seem to be involved, since these adipocytokines can cross the blood-brain barrier and influence cognitive-related structures. Very few studies have assessed the role of adipocytokines dysfunction on cognitive impaired patients and yielded contradictory results. Interestingly, extensive research on the central effects of leptin in Alzheimer's disease-transgenic mice has demonstrated its capacity to enhance synaptic plasticity and strength, as well as to prevent beta-amyloid deposition and tau phosphorylation. In addition, adiponectin, the most abundant adipocytokine whose levels are inversely correlated to adiposity, has shown to be neuroprotective to hippocampal cells. Many other adipose-derived cytokines have mainly pro-inflammatory properties, being able to trigger and/or enhance central inflammatory cascades and also to influence the secretion of other adipocytokines involved in cognition. This paper pretends to review the existing evidence on the contribution of adipocytokines dysfunction to the increased risk of dementia associated with mid-life obesity, unraveling its insulin-independent effects on cognition.

Histamine H3 receptor antagonism by ABT-239 attenuates kainic acid induced excitotoxicity in mice

The multifaceted pathogenesis of temporal lobe epilepsy (TLE) offers a number of adjunctive therapeutic prospects. One such therapeutic strategy could be targeting H3 receptor (H3R) by selective H3R antagonists which are perceived to have antiepileptic and neuroprotective potential. Kainic acid (KA) induced seizure, a reliable model of TLE, triggers epileptogenic events resulting from initial neuronal death and ensuing recurring seizures. The present study aimed to determine whether pre-treatment with ABT-239, a novel H3R antagonist, and its combinations with sodium valproate (SVP) and TDZD-8 (glycogen synthase kinase-3β (GSK3β) inhibitor) can prevent the excitotoxic events in mice exposed to KA (10 mg/kg i.p.). ABT-239 (1 and 3 mg/kg i.p.) significantly attenuated KA-mediated behavioural and excitotoxic anomalies and restored altered expression of Bax, cleaved caspase-3, phospho-Akt (Ser473) and cAMP response element binding protein (CREB). Surprisingly, restoration of Bcl2 and phospho-GSK3β (Ser9) by ABT-239 did not reach the level of statistical significance. Co-administration of ABT-239 (1 and 3 mg/kg) with a sub-effective dose of SVP (150 mg/kg i.p.) yielded improved efficacy than when given alone. Similarly, low and high dose combinations of ABT-239 (1 and 3 mg/kg) with TDZD-8 (5 and 10 mg/kg i.p.) produced greater neuroprotection than any other treatment group. Our findings suggests a neuroprotective potential of ABT-239 and its combinations with SVP and TDZD-8 against KA-induced neurotoxicity, possibly mediated through in part each by modulating Akt/GSK3β and CREB pathways. The use of H3R antagonists as adjuvant in the treatment of human TLE might find potential utility, and can be pursued further.

Neuroactive peptides as putative mediators of antiepileptic ketogenic diets

Various ketogenic diet (KD) therapies, including classic KD, medium chain triglyceride administration, low glycemic index treatment, and a modified Atkins diet, have been suggested as useful in patients affected by pharmacoresistant epilepsy. A common goal of these approaches is to achieve an adequate decrease in the plasma glucose level combined with ketogenesis, in order to mimic the metabolic state of fasting. Although several metabolic hypotheses have been advanced to explain the anticonvulsant effect of KDs, including changes in the plasma levels of ketone bodies, polyunsaturated fatty acids, and brain pH, direct modulation of neurotransmitter release, especially purinergic (i.e., adenosine) and γ-aminobutyric acidergic neurotransmission, was also postulated. Neuropeptides and peptide hormones are potent modulators of synaptic activity, and their levels are regulated by metabolic states. This is the case for neuroactive peptides such as neuropeptide Y, galanin, cholecystokinin, and peptide hormones such as leptin, adiponectin, and growth hormone-releasing peptides (GHRPs). In particular, the GHRP ghrelin and its related peptide des-acyl ghrelin are well-known controllers of energy homeostasis, food intake, and lipid metabolism. Notably, ghrelin has also been shown to regulate the neuronal excitability and epileptic activation of neuronal networks. Several lines of evidence suggest that GHRPs are upregulated in response to starvation and, particularly, in patients affected by anorexia and cachexia, all conditions in which also ketone bodies are upregulated. Moreover, starvation and anorexia nervosa are accompanied by changes in other peptide hormones such as adiponectin, which has received less attention. Adipocytokines such as adiponectin have also been involved in modulating epileptic activity. Thus, neuroactive peptides whose plasma levels and activity change in the presence of ketogenesis might be potential candidates for elucidating the neurohormonal mechanisms involved in the beneficial effects of KDs. In this review, we summarize the current evidence for altered regulation of the synthesis of neuropeptides and peripheral hormones in response to KDs, and we try to define a possible role for specific neuroactive peptides in mediating the antiepileptic properties of diet-induced ketogenesis.

Neuroprotective effect of osmotin against ethanol-induced apoptotic neurodegeneration in the developing rat brain

Fetal alcohol syndrome is a neurological and developmental disorder caused by exposure of developing brain to ethanol. Administration of osmotin to rat pups reduced ethanol-induced apoptosis in cortical and hippocampal neurons. Osmotin, a plant protein, mitigated the ethanol-induced increases in cytochrome c, cleaved caspase-3, and PARP-1. Osmotin and ethanol reduced ethanol neurotoxicity both in vivo and in vitro by reducing the protein levels of cleaved caspase-3, intracellular [Ca²⁺]_cyt, and mitochondrial transmembrane potential collapse, and also upregulated antiapoptotic Bcl-2 protein. Osmotin is a homolog of adiponectin, and it controls energy metabolism via phosphorylation. Adiponectin can protect hippocampal neurons against ethanol-induced apoptosis. Abrogation of signaling via receptors AdipoR1 or AdipoR2, by transfection with siRNAs, reduced the ability of osmotin and adiponectin to protect neurons against ethanol-induced neurodegeneration. Metformin, an activator of AMPK (adenosine monophosphate-activated protein kinase), increased whereas Compound C, an inhibitor of AMPK pathway, reduced the ability of osmotin and adiponectin to protect against ethanol-induced apoptosis. Osmotin exerted its neuroprotection via Bcl-2 family proteins and activation of AMPK signaling pathway. Modulation of AMPK pathways by osmotin, adiponectin, and metformin hold promise as a preventive therapy for fetal alcohol syndrome.

Tonicity-responsive enhancer binding protein haplodeficiency attenuates seizure severity and NF-κB-mediated neuroinflammation in kainic acid-induced seizures

Kainic acid (KA)-induced seizures followed by neuronal death are associated with neuroinflammation and blood-brain barrier (BBB) leakage. Tonicity-responsive enhancer binding protein (TonEBP) is known as a transcriptional factor activating osmoprotective genes, and in brain, it is expressed in neuronal nuclei. Thus dysregulation of TonEBP may be involved in the pathology of KA-induced seizures. Here we used TonEBP heterozygote (+/-) mice to study the roles of TonEBP. Electroencephalographic study showed that TonEBP (+/-) mice reduced seizure frequency and severity compared with wild type during KA-induced status epilepticus. Immunohistochemistry and western blotting analysis showed that KA-induced neuroinflammation and BBB leakage were dramatically reduced in TonEBP (+/-) mice. Similarly, TonEBP-specific siRNA reduced glutamate-induced death in HT22 hippocampal neuronal cells. TonEBP haplodeficiency prevented KA-induced nuclear translocation of NF-κB p65 and attenuated inflammation. Our findings identify TonEBP as a critical regulator of neuroinflammation and BBB leakage in KA-induced seizures, which suggests TonEBP as a good therapeutic target.