Hippocampal Gene Expression Research Articles

Chaihu-shugan-san alleviates depression-like behavior in mice exposed to chronic unpredictable stress by altering the gut microbiota and levels of the bile acids hyocholic acid and 7-ketoDCA.

Chaihu-Shugan-San (CSS) is a traditional botanical drug formula often prescribed to treat depression in oriental countries, but its pharmacotherapeutic mechanism remains unknown. It was recently reported that CSS alters the composition of intestinal microflora and related metabolites such as bile acids (BAs). Since the intestinal microflora affects physiological functions of the brain through the gut-microbiota-brain axis, herein we investigated whether CSS altered BA levels, gut microflora, and depression-like symptoms in chronic unpredictable mild stress (CUMS) mice, a well-established mouse model of depression. Furthermore, we determined whether BA manipulation and fecal microbiota transplantation altered CSS antidepressant actions. We found that the BA chelator cholestyramine impaired the antidepressant effects of CSS, which was partially rescued by dietary cholic acid. CSS increased the relative abundance of Parabacteroides distasonis in the colon of CUMS mice, and increased serum levels of various BAs including hyocholic acid (HCA) and 7-ketodeoxycholic acid (7-ketoDCA). Furthermore, gut bacteria transplantation from CSS-treated mice into untreated or cholestyramine-treated CUMS mice restored serum levels of HCA and 7-ketoDCA, alleviating depression-like symptoms. In the hippocampus, CSS-treated mice had decreased expression of genes associated with BA transport (Bsep and Fxr) and increased expression of brain-derived neurotrophic factor and its receptor, TrkB. Overall, CSS increases intestinal P. distasonis abundance, leading to elevated levels of secondary BAs in the circulation and altered expression of hippocampal genes implicated in BA transport and neurotrophic signaling. Our data strongly suggest that the gut microbiota-brain axis contributes to the potent antidepressant action of CSS by modulating BA metabolism.

Prenatal Dexamethasone Exposure in Male Rats Alters Gene Expression Patterns of Epigenetic Enzymes in Hippocampus and Cortex

Objective: This study aimed to examine the effects of prenatal stress (PS) induced by dexamethasone exposure on gene expression levels of epigenetic enzymes in hippocampus and cerebral cortex of male rats through relative mRNA levels of histone acetyltransferases (activating transcription factor 2, P300), histone deacetylases (HDAC1, HDAC2), and DNA methyltransferases (DNMT1, DNMT3a, DNMT3b). Methods: Pregnant rats were daily injected subcutaneously with dexamethasone (0.2 mg/kg) or saline during the third week of gestation. After birth, male rats were killed at 90 days of age (n = 5 for control and dexamethasone groups). Hippocampal and cortical tissues were used for gene expression analyses. The effects of dexamethasone on epigenetic mechanisms were investigated by real-time polymerase chain reaction through relative mRNA levels of DNMT1, DNMT3a, DNMT3b, activating transcription factor 2, P300, HDAC1, and HDAC2. Statistical comparisons were performed with Student’s t-test. Results: Prenatal dexamethasone exposure (PDE) caused increased DNMT1, DNMT3a, DNMT3b, activating transcription factor 2 and decreased P300 mRNA levels in hippocampus while increased DNMT3a, DNMT3b, activating transcription factor 2, P300, HDAC1, and HDAC2 mRNA levels were achieved in cortex. Furthermore, no significant differences were obtained in cortical DNMT1 and hippocampal HDAC1 and HDAC2 gene expression levels between control and prenatally stressed rats. Conclusion: Our results emphasize the effect of prenatal dexamethasone exposure on gene expression levels of epigenetic enzymes involved in histone acety latio n/dea cetyl ation and DNA methylation in male rats and suggest that prenatal stress may lead to epigenetic dysregulation through alterations in hippocampal and cortical gene expression patterns of DNMT1, DNMT3a, DNMT3b, activating transcription factor 2, P300, HDAC1, and HDAC2.

The Zinc-sensing Receptor (GPR39) Modulates Declarative Memory and Age-related Hippocampal Gene Expression in Male Mice

As a neuromodulator, zinc regulates synaptic plasticity, learning and memory. Synaptic zinc is also a crucial factor in the development of toxic forms of amyloid beta protein and, subsequently, of Alzheimer’s dementia (AD). Therefore, efforts to pinpoint mechanisms underlying zinc-dependent cognitive functions might aid AD research, by providing potential novel targets for drugs. One of the most understudied proteins in this regard is a zinc-sensing metabotropic receptor: GPR39. In this study we investigated the impact of GPR39 knock-out (KO) on age-related memory decline in mice of both sexes, by comparing them to age-matched wild-type (WT) littermates. We also tested the effects of a GPR39 agonist (TC-G 1008) on declarative memory of old animals, and its disruption in adult mice. We observed episodic-like memory (ELM) and spatial memory (SM) deficits in male GPR39 KO mice, as well as intact procedural memory in GPR39 KO mice regardless of age and sex. ELM was also absent in old WT male mice, and all female mice regardless of their genotype. Acute application of TC-G 1008 (10 mg/kg) reversed a deficit in two of three ELM components in old WT male mice, and had no promnesic effect on consolidation interference of ELM in adult WT mice. We discuss the possible neurobiological mechanisms and the translational value of these results for potential add-on pharmacotherapy of AD aimed at the zinc-sensing receptor.

Zinc Ameliorates Nogo-A Receptor and Osteocalcin Gene Expression in Memory-Sensitive Rat Hippocampus Impaired by Intracerebroventricular Injection of Streptozotocin.

Metabolic dysfunction is a critical step in the etiopathogenesis of Alzheimer's disease. In this progressive neurological disorder, impaired zinc homeostasis has a key role that needs to be clarified. The aim of this study was to investigate the effect of zinc deficiency and administration on hippocampal Nogo-A receptor and osteocalcin gene expression in rats injected with intracerebroventricular streptozotocin (icv-STZ). Forty male Wistar rats were divided into 5 groups in equal numbers: Sham 1 group received icv artificial cerebrospinal fluid (aCSF); Sham 2 group received icv a CSF and i.p. saline; STZ group received 3mg/kg icv STZ; STZ-Zn-deficient group received 3mg/kg icv STZ and fed a zinc-deprived diet; STZ-Zn-supplemented group received 3mg/kg icv STZ and i.p. zinc sulfate (5mg/kg/day). Hippocampus tissue samples were taken following the cervical dislocation of the animals under general anesthesia. Nogo-A receptor and osteocalcin gene expression levels were determined by real-time-PCR method. Zinc supplementation attenuated the increase in hippocampal Nogo-A receptor gene expression, which was significantly increased in zinc deficiency. Again, zinc supplementation upregulated the intrinsic protective mechanisms of the brain by activating osteocalcin-expressing cells in the brain. The results of the study show that zinc has critical effects on Nogo-A receptor gene expression and hippocampal osteocalcin gene expression levels in the memory-sensitive rat hippocampus that is impaired by icv-STZ injection. These results are the first to examine the effect of zinc deficiency and supplementation on hippocampal Nogo-A receptor and osteocalcin gene expression in icv-STZ injection in rats.

Exploring the key ferroptosis-related gene in the peripheral blood of patients with Alzheimer’s disease and its clinical significance

IntroductionAlzheimer’s disease (AD) is the most common type of dementia, and there is growing evidence suggesting that ferroptosis is involved in its pathogenesis. In this study, we aimed to investigate the key ferroptosis-related genes in AD and identify a novel ferroptosis-related gene diagnosis model for patients with AD.Materials and methodsWe extracted the human blood and hippocampus gene expression data of five datasets (GSE63060, GSE63061, GSE97760, GSE48350, and GSE5281) in the Gene Expression Omnibus database as well as the ferroptosis-related genes from FerrDb. Differentially expressed ferroptosis-related genes were screened by random forest classifier, and were further used to construct a diagnostic model of AD using an artificial neural network. The patterns of immune infiltration in the peripheral immune system of AD were also investigated using the CIBERSORT algorithm.ResultsWe first screened and identified 12 ferroptosis-related genes (ATG3, BNIP3, DDIT3, FH, GABARAPL1, MAPK14, SOCS1, SP1, STAT3, TNFAIP3, UBC, and ULK) via a random forest classifier, which was differentially expressed between the AD and normal control groups. Based on the 12 hub genes, we successfully constructed a satisfactory diagnostic model for differentiating AD patients from normal controls using an artificial neural network and validated its diagnostic efficacy in several external datasets. Further, the key ferroptosis-related genes were found to be strongly correlated to immune cells infiltration in AD.ConclusionWe successfully identified 12 ferroptosis-related genes and established a novel diagnostic model of significant predictive value for AD. These results may help understand the role of ferroptosis in AD pathogenesis and provide promising therapeutic strategies for patients with AD.

Investigation of the effects of pinacidil and glibenclamide administration on HCN1, KCNT1, Kir 6.1, SUR1 gene expressions in hippocampus and cortex regions in epileptic rats

The purpose of this study was to look into the effects of pinacidil and glibenclamide on HCN1, KCNT1, Kir 6.1, and SUR1 gene expression in epileptic rats hippocampus and cortex. Male Wistar-Albino rats were used in this study. The drugs pinacidil and glibenclamide were utilized. Control, Epilepsy, Epilepsy-O, and Epilepsy-B were the five groups formed. The epileptic focus was created by intracortical administration of penicillin at a dose of 500 IU/2 μl. Hippocampus and Cortex are removed from all animals and Kir 6.1, SUR1, HCN1, and KCNT1 gene expression levels were determined by qPCR. The SPSS 21 program was used for statistics. HCN1 gene expression level is equal in the hippocampus and cortex (p<0.05). KCNT1, SUR1, and KIR6.1 are more expressed in the hippocampus than in the cortex (p<0.05). In epilepsy groups, HCN1 gene expression level was found to be higher than KCNT1, SUR1, and KIR6.1 gene expression levels (p<0.05). KIR6.1, SUR1, gene expression levels decreased with the application of pinacidil and glibenclamide (p<0.05). SUR1 and KIR6.1 gene expression levels were considerably lower in the epilepsy pinacidil group compared to the other groups. The gene expression levels in the hippocampus were found to be considerably higher than in the cortex group, according to this study. The fact that HCN1 gene expression levels are significantly greater in both the brain and the hippocampus 24 hours following the commencement of epileptic convulsions suggests that preventive medication may be possible.

Contrasting effects of sleep fragmentation and angiotensin-II treatment upon pro-inflammatory responses of mice

Disordered sleep promotes inflammation in brain and peripheral tissues, but the mechanisms that regulate these responses are poorly understood. One hypothesis is that activation of the sympathetic nervous system (SNS) from sleep loss elevates blood pressure to promote vascular sheer stress leading to inflammation. As catecholamines produced from SNS activation can directly regulate inflammation, we pharmacologically altered blood pressure using an alternative approach-manipulation of the renin-angiotensin system (RAS). Male C57BL6/J mice were treated with angiotensin or captopril to elevate and reduce blood pressure, respectively and then exposed to 24-h of sleep fragmentation (SF) or allowed to sleep (control). Pro- and anti-inflammatory cytokine gene expression and as endothelial adhesion gene expression as well as serum glucocorticoids (corticosterone) were measured. RAS manipulation elevated cytokines and endothelial adhesion expression in heart and aorta while SF increased cytokine expression in peripheral tissues, but not brain. However, there were interactive effects of angiotensin-II and SF upon cytokine gene expression in hippocampus and hypothalamus, but not prefrontal cortex. SF, but not RAS manipulation, elevated serum corticosterone concentration. These findings highlight the contrasting effects of RAS manipulation and SF, implying that inflammation from SF is acting on different pathways that are largely independent of RAS manipulation.

The effects of ruminant milk treatments on hippocampal, striatal, and prefrontal cortex gene expression in pigs as a model for the human infant.

While infant formula is usually bovine milk-based, interest in other ruminant milk-based formulas is growing. However, whether different ruminant milk treatments with varying nutrient compositions influence the infant’s brain development remains unknown. The aim was to determine the effects of consuming bovine, caprine, or ovine milk on brain gene expression in the early postnatal period using a pig model of the human infant. Starting at postnatal day 7 or 8, pigs were exclusively fed bovine, ovine, or caprine milk for 15 days. The mRNA abundance of 77 genes in the prefrontal cortex, hippocampus, and striatum regions was measured at postnatal day 21 or 22 using NanoString. The expression level of two hippocampal and nine striatal genes was most affected by milk treatments, particularly ovine milk. These modulatory genes are involved in glutamate, gamma-aminobutyric acid, serotonin, adrenaline and neurotrophin signaling and the synaptic vesicle cycle. The expression level of genes involved in gamma-aminobutyric acid signaling was associated with pigs’ lactose intake. In contrast, milk treatments did not affect the mRNA abundance of the genes in the prefrontal cortex. This study provides the first evidence of the association of different ruminant milk treatments with brain gene expression related to cognitive function in the first 3 months of postnatal life.

Triiodothyronine Treatment reverses Depression-Like Behavior in a triple-transgenic animal model of Alzheimer's Disease.

Alzheimer disease's (AD) is a neurodegenerative disorder characterized by cognitive and behavioral impairment. The central nervous system is an important target of thyroid hormones (TH). An inverse association between serum triiodothyronine (T3) levels and the risk of AD symptoms and progression has been reported. We investigated the effects of T3 treatment on the depression-like behavior in male transgenic 3xTg-AD mice. Animals were divided into 2 groups treated with daily intraperitoneal injections of 20 ng/g of body weight (b.w.) L-T3 (T3 group) or saline (vehicle, control group). The experimental protocol lasted 21 days, and behavioral tests were conducted on days 18-20. At the end of the experiment, the TH profile and hippocampal gene expression were evaluated. The T3-treated group significantly increased serum T3 and decreased thyroxine (T4) levels. When compared to control hippocampal samples, the T3 group exhibited attenuated glycogen synthase kinase-3 (GSK3), metalloproteinase 10 (ADAM10), amyloid-beta precursor-protein (APP), serotonin transporter (SERT), 5HT1A receptor, monocarboxylate transporter 8 (MCT8) and bone morphogenetic protein 7 (BMP-7) gene expression, whereas augmented superoxide dismutase 2 (SOD2) and Hairless gene expression. T3-treated animals also displayed reduced immobility time in both the tail suspension and forced swim tests, and in the latter presented a higher latency time compared to the control group. Therefore, our findings suggest that in an AD mouse model, T3 supplementation promotes improvements in depression-like behavior, through the modulation of the serotonergic related genes involved in the transmission mediated by 5HT1A receptors and serotonin reuptake, and attenuated disease progression.

Targeting acetyl-CoA metabolism attenuates the formation of fear memories through reduced activity-dependent histone acetylation

Histone acetylation is a key component in the consolidation of long-term fear memories. Histone acetylation is fueled by acetyl-coenzyme A (acetyl-CoA), and recently, nuclear-localized metabolic enzymes that produce this metabolite have emerged as direct and local regulators of chromatin. In particular, acetyl-CoA synthetase 2 (ACSS2) mediates histone acetylation in the mouse hippocampus. However, whether ACSS2 regulates long-term fear memory remains to be determined. Here, we show that Acss2 knockout is well tolerated in mice, yet the Acss2-null mouse exhibits reduced acquisition of long-term fear memory. Loss of Acss2 leads to reductions in both histone acetylation and expression of critical learning and memory-related genes in the dorsal hippocampus, specifically following fear conditioning. Furthermore, systemic administration of blood-brain barrier-permeable Acss2 inhibitors during the consolidation window reduces fear-memory formation in mice and rats and reduces anxiety in a predator-scent stress paradigm. Our findings suggest that nuclear acetyl-CoA metabolism via ACSS2 plays a critical, previously unappreciated, role in the formation of fear memories.

Infusion of etoposide in the CA1 disrupts hippocampal immediate early gene expression and hippocampus-dependent learning

Tight regulation of immediate early gene (IEG) expression is important for synaptic plasticity, learning, and memory. Recent work has suggested that DNA double strand breaks (DSBs) may have an adaptive role in post-mitotic cells to induce IEG expression. Physiological activity in cultured neurons as well as behavioral training leads to increased DSBs and subsequent IEG expression. Additionally, infusion of etoposide—a common cancer treatment that induces DSBs—impairs trace fear memory. Here, we assessed the effects of hippocampal infusion of 60 ng of etoposide on IEG expression, learning, and memory in 3–4 month-old C57Bl/6J mice. Etoposide altered expression of the immediate early genes cFos and Arc in the hippocampus and impaired hippocampus-dependent contextual fear memory. These data add to the growing evidence that DSBs play an important role in IEG expression, learning, and memory, opening avenues for developing novel treatment strategies for memory-related disorders.

Altered genome-wide hippocampal gene expression profiles following early life lead exposure and their potential for reversal by environmental enrichment

Early life lead (Pb) exposure is detrimental to neurobehavioral development. The quality of the environment can modify negative influences from Pb exposure, impacting the developmental trajectory following Pb exposure. Little is known about the molecular underpinnings in the brain of the interaction between Pb and the quality of the environment. We examined relationships between early life Pb exposure and living in an enriched versus a non-enriched postnatal environment on genome-wide transcription profiles in hippocampus CA1. RNA-seq identified differences in the transcriptome of enriched vs. non-enriched Pb-exposed animals. Most of the gene expression changes associated with Pb exposure were reversed by enrichment. This was also true for changes in upstream regulators, splicing events and long noncoding RNAs. Non-enriched rats also had memory impairments; enriched rats had no deficits. The results demonstrate that an enriched environment has a profound impact on behavior and the Pb-modified CA1 transcriptome. These findings show the potential for interactions between Pb exposure and the environment to result in significant transcriptional changes in the brain and, to the extent that this may occur in Pb-exposed children, could influence neuropsychological/educational outcomes, underscoring the importance for early intervention and environmental enrichment for Pb-exposed children.

Muscarinic Acetylcholine Receptors-Mediated Activation of PKC Restores the Hippocampal Immediate Early Gene Expression and CREB Phosphorylation in Scopolamine-Induced Amnesic Mice

Amnesia is the inability to store new information and recall old memories. After the postulation of cholinergic hypothesis of geriatric memory dysfunction, the cholinergic signaling became a popular target to understand the underlying molecular mechanism of amnesia and its recovery. Scopolamine is a non-selective cholinergic receptor antagonist and induces amnesia through downregulation of synaptic plasticity genes including immediate early genes (IEGs). Scopolamine-induced amnesic mouse model is widely used to study the memory impairment that mimics the pathophysiology of aging, neurodegenerative, and neuropsychiatric disorders. However, a detailed understanding of cholinergic signaling-mediated regulation of plasticity-related gene expression remains elusive. Therefore, we have investigated the role of muscarinic acetylcholine receptors (mAChRs) and their downstream mediator protein kinase C (PKC) in the regulation of IEGs expression in amnesic mice hippocampus. Pilocarpine, a mAChRs agonist, was used to activate the cholinergic signaling in scopolamine-induced amnesia. Further, a PKC activator bryostatin 1 was used to understand the sole involvement of PKC as a downstream mediator of mAChRs-mediated signaling. Pilocarpine treatment significantly restored the scopolamine-induced impaired recognition memory and downregulated hippocampal IEGs expression and phosphorylation of ERK1/2 (extracellular signal-regulated kinase 1/2) and CREB (cAMP response element-binding protein). On the other hand, the bryostatin 1-mediated activation of PKC in scopolamine-induced amnesia selectively restored the hippocampal IEGs expression, recognition memory, and phosphorylation of ERK1/2 and CREB. Taken together, our findings suggest that mAChRs and their downstream mediator PKC regulate the hippocampal IEGs expression and ERK1/2-mediated CREB phosphorylation in scopolamine-induced amnesic mice.

Early Life Stress-Induced Epigenetic Programming of Hippocampal NPY-Y2 Receptor Gene Expression Changes in Response to Adult Stress

Early Life Stress (ELS) can critically influence brain development and future stress responses and thus represents an important risk factor for mental health and disease. Neuropeptide Y (NPY) is discussed to be a key mediator of resilient vs. vulnerable adaptations and specifically, the NPY-Y2 receptor (Y2R) may be involved in the pathophysiology of depression due to its negative regulation of NPY-release. The present study addressed the hypotheses that ELS and adult stress (AS) affect the expression of hippocampal Y2R and that exposure to ELS induces an epigenetically mediated programming effect towards a consecutive stress exposure in adulthood. The specific aims were to investigate if (i) ELS or AS as single stressors induce changes in Y2 receptor gene expression in the hippocampus, (ii) the predicted Y2R changes are epigenetically mediated via promoter-specific DNA-methylation, (iii) the ELS-induced epigenetic changes exert a programming effect on Y2R gene expression changes in response to AS, and finally (iv) if the predicted alterations are sex-specific. Animals were assigned to the following experimental groups: (1) non-stressed controls (CON), (2) only ELS exposure (ELS), (3) only adult stress exposure (CON+AS), and (4) exposure to ELS followed by AS (ELS+AS). Using repeated maternal separation in mice as an ELS and swim stress as an AS we found that both stressors affected Y2R gene expression in the hippocampus of male mice but not in females. Specifically, upregulated expression was found in the CON+AS group. In addition, exposure to both stressors ELS+AS significantly reduced Y2R gene expression when compared to CON+AS. The changes in Y2R expression were paralleled by altered DNA-methylation patterns at the Y2R promoter, specifically, a decrease in mean DNA-methylation in the CON+AS males compared to the non-AS exposed groups and an increase in the ELS+AS males compared to the CON+AS males. Also, a strong negative correlation of mean DNA-methylation with Y2R expression was found. Detailed CpG-site-specific analysis of DNA-methylation revealed that ELS induced increased DNA-methylation only at specific CpG-sites within the Y2R promoter. It is tempting to speculate that these ELS-induced CpG-site-specific changes represent a “buffering” programming effect against elevations of Y2R expression induced by AS.

The liver X receptors agonist GW3965 attenuates depressive-like behaviors and suppresses microglial activation and neuroinflammation in hippocampal subregions in a mouse depression model.

Liver X receptors (LXRs) have recently been reported to be novel and potential targets for the reversal of depressive-like behaviors, but the mechanism remains unclear. Hippocampal neuroinflammation and impairment of the normal structure and function of microglia are closely associated with depression. To investigate the effects of LXRs agonist (GW3965) on neuroinflammation and microglia in the hippocampal formation of mice with chronic unpredictable stress (CUS)-induced depression, depressive-like behaviors were evaluated by behavioral tests, hippocampal LXRs gene expression were evaluated by qRT-PCR, the protein expression levels of interleukin-1β, tumor necrosis factor-α, inducible nitric oxide synthase, nuclear factor kappa B, and cluster of differentiation 206 were estimated by western blotting, modern stereological methods were used to precisely quantify the total number of microglia in each hippocampal subregion, and immunofluorescence was used to detect the density of activated microglia and the morphology of microglia. We found that GW3965 alleviated the depressive-like behavior induced by CUS, reversed the decrease in hippocampal LXRα and LXRβ induced by CUS, increased the protein expression of pro-inflammatory factors, and decreased the protein expression of antiinflammatory factors induced by CUS. Moreover, CUS intervention significantly increased the number of microglia in the CA1 region, CA2/3 region, and dentate gyrus and the density of activated microglia in the CA2/3 region and dentate gyrus and significantly decreased the endpoints of microglial branches and process length of microglia in the dentate gyrus, while 4weeks of injections with GW3965 reversed these changes. These findings suggest that regulating the number, activated state, and morphology of microglia in hippocampal subregions might be an important basis for the antidepressant effects of LXRs.

Constant light in early life induces fear-related behavior in chickens with suppressed melatonin secretion and disrupted hippocampal expression of clock- and BDNF-associated genes

BackgroundLight management plays an important role in the growth and behavior of broiler chickens. Constant light in early post hatch stage has been a common practice in broiler industry for improving growth performance, while whether and how constant light in early life affects the behavior of broiler chickens is rarely reported.ResultsIn this study, newly hatched chicks were kept in either constant (24 L:0 D, LL) or (12 L:12 D, LD) photoperiod for 7 d and then maintained in 12 L:12 D thereafter until 21 days of age. Constant light increased the average daily feed intake but not the body weight, which led to higher feed conversion ratio. Chickens in LL group exhibited fear-related behaviors, which was associated with higher corticosterone, lower melatonin and 5-HT levels. Concurrently, constant light exposure increased the mRNA expression of clock-related genes and suppressed the expression of antioxidative genes in the hippocampus. Moreover, brain derived neurotrophic factor/extracellular signal-regulated kinase (BDNF/ERK) pathway was suppressed in the hippocampus of chickens exposed to constant light in the first week post hatching.ConclusionsThese findings indicate that constant light exposure in early life suppress melatonin secretion and disrupts hippocampal expression of genes involved in circadian clock and BDNF/ERK pathway, thereby contributing to fear-related behaviors in the chicken.

Fenofibrate Improves Cognitive Impairment Induced by High-Fat High-Fructose Diet: A Possible Role of Irisin and Heat Shock Proteins.

A high-fat, high-fructose diet (HFFD) impairs cognitive functions and increases susceptibility to neurodegenerative disorders. Irisin and heat shock protein 70 (HSP70) are well known for their role in neuroprotection. The possible neuroprotective effects of fenofibrate on HFFD-induced cognitive dysfunction and the involvement of irisin and HSP70 in these effects were investigated in this study. Rats were divided into normal control, HFFD, dimethylsulfoxide+HFFD, and fenofibrate+HFFD groups. At the end of the experiment, fenofibrate treatment restored hippocampus histological characteristics to almost normal and improved HFFD-induced cognitive deficit. It reduced body weight gain and had hypolipidemic effects by significantly lowering total cholesterol, triglycerides, and low-density lipoprotein cholesterol levels while increasing high-density lipoprotein cholesterol levels. It has antioxidant and anti-inflammatory effects as it significantly reduced the hippocampal malondialdehyde, interleukin-6, and tumor necrosis factor-alpha levels, while significantly increasing the reduced glutathione level. It prevented HFFD-induced hypoxia by significantly lowering hippocampal vascular endothelial growth factor and hypoxia-inducible factor-1 alpha levels. It significantly activated the hippocampal peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α)/irisin/brain-derived neurotrophic factor pathway. It significantly increased hippocampal HSP70 while decreasing the HSP90 levels. It enhanced synaptic plasticity by significantly upregulating the hippocampal relative GluR1 gene expression. Furthermore, hippocampal irisin levels in the HFFD group were found to be positively correlated with cognitive function, hippocampal HSP70, and relative GluR1 gene expression levels, while negatively correlated with hippocampal HSP90 and HIF1α levels. Therefore, fenofibrate may be used as a potential medication to treat HFFD-induced neurodegenerative disorders.

Effects of a High Glycemic Diet and Soluble Epoxide Hydrolase Inhibitor on Hippocampal Microvascular Function, and Multigenomic Modifications

ObjectivesDiet is a modifiable risk factor for cardiovascular disease (CVD) and dementia, yet relatively little is known about the effect of a high glycemic diet (HGD) on the brain microvasculature. The objective of our study was to determine the multigenomic effects of a HGD on hippocampal microvessels, and to determine if a soluble epoxide hydrolase (sEH) inhibitor (sEHI), known to be vasculoprotective and anti-inflammatory, modulates these effects.MethodsWild type male and female mice were fed a low glycemic diet (LGD, 12% sucrose/weight) or a HGD (34% sucrose/weight) with/without the sEHI, trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB), for 12 wks. Brain hippocampal microvascular gene expression was assessed by microarray and data analyzed using a multiomic approach for differential expression of protein and non-protein coding genes, gene networks, functional pathways, and transcription factors.ResultsGlobal hippocampal microvascular gene expression was fundamentally different for mice fed the HGD vs the LGD. The HGD modulated expression of genes involved in cell signaling, neurodegeneration, metabolism, and cell adhesion/inflammation/oxidation effects reversible by t-AUCB and hence sEH inhibitor correlated with protection against Alzheimer's dementia. However, in female, HGD had very minor genomic modifications, while sEHI presented significant effect in female mice on LGD.ConclusionsOurs is the first study to demonstrate that high dietary glycemia contributes to brain hippocampal microvascular inflammation, through sEH, effects that were sex-dependant.Funding SourcesThis work was supported by an award from the Richard A. and Nora Eccles Foundation (A20-0111), the Richard A. and Nora Eccles Harrison Endowed Chair in Diabetes Research (J.C.R.), and the Frances Lazda Endowed Chair in Women's Cardiovascular Medicine (A.C.V).

1306-P: In Vivo Downregulation of Pancreatic Amylin in Diabetic Mice Improves Recognition Memory

Hypersecretion of amylin, a β-cell hormone that regulates satiation, is common in individuals with prediabetes and is associated with pancreatic amyloid deposition and type-2 diabetes. Evidence has emerged that increased circulating levels of amyloid-forming human amylin may potentially impair brain function. Because mouse amylin is non-amyloidogenic, we generated transgenic mice with conditional pancreatic expression of amyloid-forming human amylin to study how in vivo knockdown of human amylin expression influences brain function during the development of type-2 diabetes. Males and females were fed a high-fat diet starting at 3 months of age to induce amylin hypersecretion and glucose dysregulation. Males developed hyperglycemia at 5 months of age, whereas females showed glucose dysregulation 3-4 months later. At 5 months of age, human amylin-expressing male mice were randomly assigned to either amylin downregulation (by peritoneal tamoxifen injection) or control (maintained amylin expression) groups (n = 10/group) . Two months later, we assessed brain function with a novel object recognition test and performed comparative non-targeted metabolomics and global RNA-seq analyses of hippocampal tissue. Mice with downregulated human amylin showed enhanced recognition memory index (p < 0.001) and lower blood glucose levels (p < 0.001) compared to those that continued to express human amylin. This was associated with increased hippocampal levels of glycolysis metabolites, including lactic acid (p < 0.01) , glucose-6-phosphate (p = 0.06) , and fructose (p = 0.07) . Hippocampal gene-expression patterns between the two mouse groups revealed extensive compensatory changes in gene expression related to glucose metabolism. In conclusion, amylin downregulation in diabetic mice improves systemic glucose homeostasis and memory. Molecular processes associated with improved memory involve increased hippocampal glycolytic fluxes and compensatory gene expression. Disclosure V.Gopal viswanathan: None. M.Muehlbauer: None. J.R.Bain: Other Relationship; CardioEphEx, LLC. F.Despa: None. N.Verma: None. E.D.Winford: None. D.Kotiya: None. L.E.Radulescu: None. N.Leibold: None. K.C.Chen: None. S.Despa: None. D.A.Hill: None. Funding National Institutes of Health NS116058, AG057290, AG053999

α-Tocopherol Restriction Exacerbated Lipopolysaccharide-Induced Inflammatory Response in α-Tocopherol Transfer Protein-Null Mice

ObjectivesThe α-tocopherol transfer protein-null (Ttpa−/−) mouse model is a valuable tool for studying the molecular and functional consequences of vitamin E (α-tocopherol, αT) deficiency. Our objective was to assess how dietary αT restriction, followed by lipopolysaccharide (LPS) exposure affected the inflammatory response in Ttpa−/− and wild-type (Ttpa+/+) mice.MethodsAfter weaning (3 weeks of age), male Ttpa+/+ and Ttpa−/− littermates (n = 36/genotype) were fed an αT deficient diet ad libitum for 4 weeks. At 7 weeks of age, mice were injected with LPS (1 or 10 µg/mouse) or saline (control) intraperitoneally and sacrificed 4 hours post-injection. Brain and heart IL-6 levels, a marker of inflammatory response, and serum and tissue αT concentrations were measured via ELISA and HPLC-PDA, respectively. Hippocampal Il6, Tnf, and Gpx1 expression, markers of inflammatory and oxidative stress response, were measured via RT-qPCR, and blood immune cell profiles were measured via a hematology analyzer.ResultsαT concentrations in serum and most analyzed tissues were below the limit of detection in Ttpa−/− mice but not Ttpa+/+ mice. Circulating white blood cell levels, particularly lymphocytes, were lower in all LPS groups compared to controls (P < 0.01). The 10 µg LPS groups had elevated IL-6 in the cerebellum and heart compared to controls, confirming an acute inflammatory response (P < 0.01). Hippocampal Il6 and Tnf expression were significantly increased in Ttpa−/− mice that received 10 µg LPS compared to those that received saline (∼20- and ∼3-fold higher, respectively) (P < 0.01). Comparing expression patterns by genotype, the 10 µg LPS-Ttpa−/− mice had ∼2-fold lower Gpx1 and ∼2-fold higher Il6 expression than the 10 µg LPS-Ttpa+/+ mice. Hippocampal Il6 expression was increased by LPS in a dose-dependent manner (P < 0.05).ConclusionsLPS, especially at the higher dose, altered inflammatory markers in the brain, heart, and serum. αT restriction further exacerbated the expression of select hippocampal genes.Funding SourcesAbbott Nutrition via the Center for Nutrition, Learning and Memory, University of Illinois, Urbana-Champaign; Division of Nutritional Sciences Vision 20/20 and Margin of Excellence Research grants.