Methylphenidate prevents high-fat diet (HFD)-induced learning/memory impairment in juvenile mice

Influence of High-Fat Diets Consumed During the Juvenile Period on Hippocampal Morphology and Function

The negative impact of obesity on neurocognitive functioning is an issue of increasing clinical interest. Over the last decade, a number of studies have analyzed the influence of high-fat diets (HFDs) on cognitive performance, particularly in adolescent individuals. Different approaches, including behavioral, neurochemical, electrophysiological and morphological studies, have been developed to address the effect of HFDs on neural processes interfering with learning and memory skills in rodents. Many of the studies have focused on learning and memory related to the hippocampus and the mechanisms underlying these processes. The goal of the current review article is to highlight the relationship between hippocampal learning/memory deficits and nutritional/endocrine inputs derived from HFDs consumption, with a special emphasis on research showing the effect of HFDs intake during the juvenile period. We have also reviewed recent research regarding the effect of HFDs on hippocampal neurotransmission. An overview of research suggesting the involvement of fatty acid (FA) receptor-mediated signaling pathways in memory deficits triggered by HFDs is also provided. Finally, the role of leptin and HFD-evoked hyperleptinemia is discussed.

TLR4 inhibitor TAK-242 attenuates the adverse neural effects of diet-induced obesity

BACKGROUND

Obesity exerts negative effects on brain health, including decreased neurogenesis, impaired learning and memory, and increased risk for Alzheimer's disease and related dementias. Because obesity promotes glial activation, chronic neuroinflammation, and neural injury, microglia are implicated in the deleterious effects of obesity. One pathway that is particularly important in mediating the effects of obesity in peripheral tissues is toll-like receptor 4 (TLR4) signaling. The potential contribution of TLR4 pathways in mediating adverse neural outcomes of obesity has not been well addressed. To investigate this possibility, we examined how pharmacological inhibition of TLR4 affects the peripheral and neural outcomes of diet-induced obesity.

METHODS

Male C57BL6/J mice were maintained on either a control or high-fat diet for 12 weeks in the presence or absence of the specific TLR4 signaling inhibitor TAK-242. Outcomes examined included metabolic indices, a range of behavioral assessments, microglial activation, systemic and neuroinflammation, and neural health endpoints.

RESULTS

Peripherally, TAK-242 treatment was associated with partial inhibition of inflammation in the adipose tissue but exerted no significant effects on body weight, adiposity, and a range of metabolic measures. In the brain, obese mice treated with TAK-242 exhibited a significant reduction in microglial activation, improved levels of neurogenesis, and inhibition of Alzheimer-related amyloidogenic pathways. High-fat diet and TAK-242 were associated with only very modest effects on a range of behavioral measures.

CONCLUSIONS

These results demonstrate a significant protective effect of TLR4 inhibition on neural consequences of obesity, findings that further define the role of microglia in obesity-mediated outcomes and identify a strategy for improving brain health in obese individuals.

Licorice root components mimic estrogens in an object location task but not an object recognition task

This study investigated the efficacy of components of licorice root to alter performance on two different recognition tasks, a hippocampus-sensitive metric change in object location (MCOL) task and a striatum-sensitive double object recognition (DOR) task. Isoliquiritigenin (ISL), licorice root extract (LRE), and whole licorice root powder (LRP) were assessed. Young adult female rats were ovariectomized (OVX) and exposed to ISL, LRE or LRP at 0.075%, 0.5% or 5% respectively in the diet. An estradiol group was included as a positive control based on our prior findings. Rats were allowed to explore two objects for three 5-min study trials (separated by 3-min intervals) before a fourth 5-min test trial where the objects were moved closer together (MCOL task) or replaced with two new objects (DOR task). Rats typically habituate to the objects across the three study trials. An increase in object exploration time in the test trial suggests the rat detected the change. Estradiol improved MCOL performance and impaired DOR performance, similar to previously shown effects of estradiol and other estrogens, which tend to improve learning and memory on hippocampus-sensitive tasks and impair striatum-sensitive cognition. LRP had no effect on recognition while exposure to ISL and LRE improved MCOL performance. Exposure to ISL, LRE and LRP failed to attenuate DOR, contrary to effects of estradiol shown here and to previous reports in young-adult OVX rats. These findings suggest components of licorice root may prove to be effective therapies targeting memory enhancement without unintended deleterious cognitive effects.

Sustained high-fat diet modulates inflammation, insulin signalling and cognition in mice and a modified xenin peptide ameliorates neuropathology in a chronic high-fat model

AIMS

To demarcate pathological events in the brain as a result of short-term to chronic high-fat-diet (HFD) feeding, which leads to cognitive impairment and neuroinflammation, and to assess the efficacy of Xenin-25[Lys(13)PAL] in chronic HFD-fed mice.

METHODS

C57BL/6 mice were fed an HFD or a normal diet for 18 days, 34 days, 10 and 21 weeks. Cognition was assessed using novel object recognition and the Morris water maze. Markers of insulin signalling and inflammation were measured in brain and plasma using immunohistochemistry, quantitative PCR and multi-array technology. Xenin-25[Lys(13)PAL] was also administered for 5 weeks in chronic HFD-fed mice to assess therapeutic potential at a pathological stage.

RESULTS

Recognition memory was consistently impaired in HFD-fed mice and spatial learning was impaired in 18-day and 21-week HFD-fed mice. Gliosis, oxidative stress and IRS-1 pSer⁶¹⁶ were increased in the brain on day 18 in HFD-fed mice and were reduced by Xenin-25[Lys(13)PAL] in 21-week HFD-fed mice. In plasma, HFD feeding elevated interleukin (IL)-6 and chemokine (C-X-C motif) ligand 1 at day 34 and IL-5 at week 10. In the brain, HFD feeding reduced extracellular signal-regulated kinase 2 (ERK2), mechanistic target of rapamycin (mTOR), NF-κB1, protein kinase C (PKC)θ and Toll-like receptor 4 (TLR4) mRNA at week 10 and increased expression of glucacon-like peptide-1 receptor, inhibitor of NF-κB kinase β, ERK2, mTOR, NF-κB1, PKCθ and TLR4 at week 21, elevations that were abrogated by Xenin-25[Lys(13)PAL].

CONCLUSIONS

HFD feeding modulates cognitive function, synapse density, inflammation and insulin resistance in the brain. Xenin-25[Lys(13)PAL] ameliorated markers of inflammation and insulin signalling dysregulation and may have therapeutic potential in the treatment of diseases associated with neuroinflammation or perturbed insulin signalling in the brain.

Mental health problems in relation to eating behavior patterns, nutrient intakes and health related quality of life among Iranian female adolescents

Aims

To identify the association between mental health problems, eating behavior patterns, nutrient intakes and health related quality of life (HRQoL) among Iranian female adolescents.

Materials and methods

The current cross-sectional study conducted among three high-schools randomly selected from 10-day-public high schools in the selected sub-county from Tabriz city-Iran between December 2015 through March 2016. Participants were a sample of 107 adolescent girls aged 15–17 years old. Anthropometric parameters were measured and assessments of HRQoL, mental health problems and eating behavioral patterns were performed by Short Form 36 (SF-36), Strengths and Difficulties Questionnaires (SDQ) and Eating Behavioral Pattern Questionnaire (EBPQ) respectively. Dietary intake was assessed using a semi-quantitative Food-Frequency Questionnaire (FFQ) adapted for the Iranian society. Quality of life was measured with HRQoL questionnaire. Quantitative analysis using independent sample t test was performed for comparison of continuous variables between two subgroups (unlikely, possible/probable) of each category of mental health problem. Multiple logistic regression was used to measure the potential predictors (e.g. eating patterns and HRQoL) of mental health problems in two models of crude and adjusted for age and body mass index (BMI). P values less than 0.05 were considered as statistically significant.

Results

Indicators of conduct problems and hyperactivity disorders were the most prevalent mental health problems among female adolescents (25.2% and 18.6% respectively). The prevalence of hyperactivity disorders among female adolescents was 35.5%. Female adolescents in high scores of ‘snacking and convenience’, ‘planning ahead’ and ‘meal skipping’ eating patterns were more likely to have indicators of emotional disorders (P < 0.05). Also, being in the high tertile of ‘low fat eating’ pattern made adolescents less likely to have hyperactivity disorders (P < 0.05). Moreover, according to our finding, high scores of vitality and mental health components of HRQoL were associated with reduced likelihood of emotional disorders, conduct disorders and hyperactivity disorders. No significant difference in terms of BMI and nutrient intakes in different categories of mental health problems according to SDQ scoring was identified.

Conclusions

In the current study unhealthy eating patterns including ‘snacking and convenience’, ‘planning ahead’ and ‘meal skipping’ eating patterns were positive predictors of “emotional disorders” while “low fat” eating pattern was negative predictor of hyperactivity disorders.

Extinction and reinstatement of an operant responding maintained by food in different models of obesity

A major problem in treating obesity is the high rate of relapse to abnormal food-taking habits after maintaining an energy balanced diet. Alterations of eating behavior such as compulsive-like behavior and lack of self-control over food intake play a critical role in relapse. In this study, we used an operant paradigm of food-seeking behavior on two different diet-induced obesity models, a free-choice chocolate-mixture diet and a high-fat diet with face validity for a rapid development of obesity or for unhealthy food regularly consumed in our societies. A reduced operant performance and motivation for the hedonic value of palatable chocolate pellets was revealed in both obesity mouse models. However, only mice exposed to high-fat diet showed an increased compulsive-like behavior in the absence of the reinforcer further characterized by impaired operant learning, enhanced impulsivity and intensified inflexibility. We used principal component analysis to globally identify the specific behaviors responsible for the differences among diet groups. Learning impairment and inflexible behaviors contributed to a first principal component, explaining the largest proportion of the variance in the high-fat diet mice phenotype. Reinforcement, impulsion and compulsion were the main contributors to the second principal component explaining the differences in the chocolate-mixture mice behavioral phenotype. These behaviors were not exclusive of chocolate group because some high-fat individuals showed similar values on this component. These data indicate that extended access to hypercaloric diets differentially modifies operant behavior learning, behavioral flexibility, impulsive-like and compulsive-like behavior, and these effects were dependent on the exposure to each specific diet.

Normal diet Vs High fat diet - A comparative study: Behavioral and neuroimmunological changes in adolescent male mice

Recent evidence has established that consumption of High-fat diet (HFD)-induced obesity is associated with deficits in hippocampus-dependent memory/learning and mood states. Nevertheless the link between obesity and emotional disorders still remains to be elucidated. This issue is of particular interest during adolescence, which is important period for shaping learning/memory and mood regulation that can be sensitive to the detrimental effects of HFD. Our present study is focused to investigate behavioral and metabolic influences of short-term HFD intake in adolescent C57BL/6 mice. HFD caused weight gain, impaired glucose tolerance (IGT) and depression-like behavior as early as after 3 weeks which was clearly proved by a decrease in number of groomings in the open field test (OFT) and an increase in immobility time in the tail suspension test (TST). In the 4th week HFD induced obese model was fully developed and above behavioral symptoms were more dominant (decrease in number of crossings and groomings and increase in immobility time in both FST and TST). At the end of 6th week hippocampal analysis revealed the differences in morphology (reduced Nissl positive neurons and decreased the 5-HT_1A receptor expression), neuronal survival (increased cleaved caspase-3 expression), synaptic plasticity (down regulation of p-CREB and BDNF), and inflammatory responses (increase in expression of pro-inflammatory cytokines and decrease in expression of anti-inflammatory cyokines) in HFD mice. Our results demonstrate that, high-fat feeding of adolescent mice could provoke "depression-like" behavior as early as 3 weeks and modulate structure, neuron survival and neuroinflammation in hippocampus as early as 6 weeks proving that adolescent age is much prone to adverse effects of HFD, which causes obesity, behavioral differences, memory and learning deficiencies.

IDO chronic immune activation and tryptophan metabolic pathway: A potential pathophysiological link between depression and obesity

Obesity and depression are among the most pressing health problems in the contemporary world. Obesity and depression share a bidirectional relationship, whereby each condition increases the risk of the other. By inference, shared pathways may underpin the comorbidity between obesity and depression. Activation of cell-mediated immunity (CMI) is a key factor in the pathophysiology of depression. CMI cytokines, including IFN-γ, TNFα and IL-1β, induce the catabolism of tryptophan (TRY) by stimulating indoleamine 2,3-dioxygenase (IDO) resulting in the synthesis of kynurenine (KYN) and other tryptophan catabolites (TRYCATs). In the CNS, TRYCATs have been related to oxidative damage, inflammation, mitochondrial dysfunction, cytotoxicity, excitotoxicity, neurotoxicity and lowered neuroplasticity. The pathophysiology of obesity is also associated with a state of aberrant inflammation that activates aryl hydrocarbon receptor (AHR), a pathway involved in the detection of intracellular or environmental changes as well as with increases in the production of TRYCATs, being KYN an agonists of AHR. Both AHR and TRYCATS are involved in obesity and related metabolic disorders. These changes in the TRYCAT pathway may contribute to the onset of neuropsychiatric symptoms in obesity. This paper reviews the role of immune activation, IDO stimulation and increased TRYCAT production in the pathophysiology of depression and obesity. Here we suggest that increased synthesis of detrimental TRYCATs is implicated in comorbid obesity and depression and is a new drug target to treat both diseases.

Cognitive impairment and gene expression alterations in a rodent model of binge eating disorder

Binge eating disorder (BED) is defined as recurrent, distressing over-consumption of palatable food (PF) in a short time period. Clinical studies suggest that individuals with BED may have impairments in cognitive processes, executive functioning, impulse control, and decision-making, which may play a role in sustaining binge eating behavior. These clinical reports, however, are limited and often conflicting. In this study, we used a limited access rat model of binge-like behavior in order to further explore the effects of binge eating on cognition. In binge eating prone (BEP) rats, we found novel object recognition (NOR) as well as Barnes maze reversal learning (BM-RL) deficits. Aberrant gene expression of brain derived neurotrophic factor (Bdnf) and tropomyosin receptor kinase B (TrkB) in the hippocampus (HPC)-prefrontal cortex (PFC) network was observed in BEP rats. Additionally, the NOR deficits were correlated with reductions in the expression of TrkB and insulin receptor (Ir) in the CA3 region of the hippocampus. Furthermore, up-regulation of serotonin-2C (5-HT_2C) receptors in the orbitoprefrontal cortex (OFC) was associated with BM-RL deficit. Finally, in the nucleus accumbens (NAc), we found decreased dopamine receptor 2 (Drd2) expression among BEP rats. Taken together, these data suggest that binge eating vegetable shortening may induce contextual and reversal learning deficits which may be mediated, at least in part, by the altered expression of genes in the CA3-OFC-NAc neural network.

Autism-Like Behaviours and Memory Deficits Result from a Western Diet in Mice

Nonalcoholic fatty liver disease, induced by a Western diet (WD), evokes central and peripheral inflammation that is accompanied by altered emotionality. These changes can be associated with abnormalities in social behaviour, hippocampus-dependent cognitive functions, and metabolism. Female C57BL/6J mice were fed with a regular chow or with a WD containing 0.2% of cholesterol and 21% of saturated fat for three weeks. WD-treated mice exhibited increased social avoidance, crawl-over and digging behaviours, decreased body-body contacts, and hyperlocomotion. The WD-fed group also displayed deficits in hippocampal-dependent performance such as contextual memory in a fear conditioning and pellet displacement paradigms. A reduction in glucose tolerance and elevated levels of serum cholesterol and leptin were also associated with the WD. The peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1a) mRNA, a marker of mitochondrial activity, was decreased in the prefrontal cortex, hippocampus, hypothalamus, and dorsal raphe, suggesting suppressed brain mitochondrial functions, but not in the liver. This is the first report to show that a WD can profoundly suppress social interactions and induce dominant-like behaviours in naïve adult mice. The spectrum of behaviours that were found to be induced are reminiscent of symptoms associated with autism, and, if paralleled in humans, suggest that a WD might exacerbate autism spectrum disorder.

Acute fasting inhibits central caspase-1 activity reducing anxiety-like behavior and increasing novel object and object location recognition

BACKGROUND

Inflammation within the central nervous system (CNS) is frequently comorbid with anxiety. Importantly, the pro-inflammatory cytokine most commonly associated with anxiety is IL-1β. The bioavailability and activity of IL-1β are regulated by caspase-1-dependent proteolysis vis-a-vis the inflammasome. Thus, interventions regulating the activation or activity of caspase-1 should reduce anxiety especially in states that foster IL-1β maturation.

METHODS

Male C57BL/6j, C57BL/6j mice treated with the capase-1 inhibitor biotin-YVAD-cmk, caspase-1 knockout (KO) mice and IL-1R1 KO mice were fasted for 24h or allowed ad libitum access to food. Immediately after fasting, caspase-1 activity was measured in brain region homogenates while activated caspase-1 was localized in the brain by immunohistochemistry. Mouse anxiety-like behavior and cognition were tested using the elevated zero maze and novel object/object location tasks, respectively.

RESULTS

A 24h fast in mice reduced the activity of caspase-1 in whole brain and in the prefrontal cortex, amygdala, hippocampus, and hypothalamus by 35%, 25%, 40%, 40%, and 40% respectively. A 24h fast also reduced anxiety-like behavior by 40% and increased novel object and object location recognition by 21% and 31%, respectively. IL-1β protein, however, was not reduced in the brain by fasting. ICV administration of YVAD decreased caspase-1 activity in the prefrontal cortex and amygdala by 55%, respectively leading to a 64% reduction in anxiety like behavior. Importantly, when caspase-1 KO or IL1-R1 KO mice are fasted, no fasting-dependent reduction in anxiety-like behavior was observed.

CONCLUSIONS

Results indicate that fasting decrease anxiety-like behavior and improves memory by a mechanism tied to reducing caspase-1 activity throughout the brain.

Simvastatin and Bezafibrate ameliorate Emotional disorder Induced by High fat diet in C57BL/6 mice

High fat diet (HFD)-induced metabolic disorders may lead to emotional disorders. This study aimed to explore the effect of simvastatin (SMV) and bezafibrate (BZ) on improving HFD-induced emotional changes, and tried to identify their different mechanisms. The intraperitoneal glucose tolerance test (IPGTT) was used to evaluate glucose control ability; and behavior tests including open field tests (OFT), forced swimming tests (FST), tail suspension tests (TST) and sucrose preference (SPT), were then performed to evaluate emotional changes. Serum samples were collected for the LC-MS based metabolomics analysis to explore the emotional-related differential compounds; we then evaluated the effect of the drugs. The abnormal serum metabolic profiling and emotional changes caused by HFD in mice was alleviated by SMV treatment, whereas BZ only affected the emotional disorder. The improvement of cannabinoid analogues and then produced influences on the endocannabinoid system, which may be a potential mechanism SMV action. BZ promoted tryptophan-serotonin pathway and inhibited tryptophan-kynurenine pathway, which may be its mechanism of action. Here, we proposed a shed light on the biological mechanisms underlying the observed effects, and identified an important drug candidate for the treatment of emotional disorders induced by HFD.

The Relationship between Fatty Acids and Different Depression-Related Brain Regions, and Their Potential Role as Biomarkers of Response to Antidepressants

Depression is a complex disorder influenced by a variety of biological and environmental factors. Due to significant heterogeneity, there are remarkable differences in how patients respond to treatment. A primary objective of psychiatric research is to identify biological markers that could be used to better predict and enhance responses to antidepressant treatments. Diet impacts various aspects of health, including depression. The fatty acid composition of the Western diet, which has a high ratio of n-6:n-3 polyunsaturated fatty acids, is associated with increased incidence of depression. The brain is rich in lipids, and dietary fatty acids act within specific brain regions to regulate processes that impact emotional behavior. This manuscript reviews existing evidence demonstrating brain region-specific fatty acid profiles, and posits that specific fatty acids may serve as predictive biomarkers of response to antidepressants. Furthermore, increasing blood levels of certain fats, such as n-3s, via dietary intervention may serve as an adjunct to improve the efficacy of antidepressants. Notably, most of the existing research regarding fats and depression-related brain regions has focused on n-3s, as compared to n-6s, monounsaturated, and saturated fats. This review article will help guide future work investigating the relationships between fatty acids, brain regions, and antidepressant efficacy.

Z-Guggulsterone Produces Antidepressant-Like Effects in Mice through Activation of the BDNF Signaling Pathway

BACKGROUND

Z-guggulsterone, an active compound extracted from the gum resin of the tree Commiphora mukul, has been shown to improve animal memory deficits via activating the brain-derived neurotrophic factor signaling pathway. Here, we investigated the antidepressant-like effect of Z-guggulsterone in a chronic unpredictable stress mouse model of depression.

METHODS

The effects of Z-guggulsterone were assessed in mice with the tail suspension test and forced swimming test. Z-guggulsterone was also investigated in the chronic unpredictable stress model of depression with fluoxetine as the positive control. Changes in hippocampal neurogenesis as well as the brain-derived neurotrophic factor signaling pathway after chronic unpredictable stress/Z-guggulsterone treatment were investigated. The tryptophan hydroxylase inhibitor and the tyrosine kinase B inhibitor were also used to explore the antidepressant-like mechanisms of Z-guggulsterone.

RESULTS

Z-guggulsterone (10, 30 mg/kg) administration protected the mice against the chronic unpredictable stress-induced increases in the immobile time in the tail suspension test and forced swimming test and also reversed the reduction in sucrose intake in sucrose preference experiment. Z-guggulsterone (10, 30 mg/kg) administration prevented the reductions in brain-derived neurotrophic factor protein expression levels as well as the phosphorylation levels of cAMP response element binding protein, extracellular signal-regulated kinase 1/2, and protein kinase B in the hippocampus and cortex induced by chronic unpredictable stress. Z-guggulsterone (10, 30 mg/kg) treatment also improved hippocampal neurogenesis in chronic unpredictable stress-treated mice. Blockade of the brain-derived neurotrophic factor signal, but not the monoaminergic system, attenuated the antidepressant-like effects of Z-guggulsterone.

CONCLUSIONS

Z-guggulsterone exhibits antidepressant activity via activation of the brain-derived neurotrophic factor signaling pathway and upregulation of hippocampal neurogenesis.

BDNF concentrations and daily fluctuations differ among ADHD children and respond differently to methylphenidate with no relationship with depressive symptomatology

RATIONALE

Brain-derived neurotrophic factor (BDNF) enhances the growth and maintenance of several monoamine neuronal systems, serves as a neurotransmitter modulator and participates in the mechanisms of neuronal plasticity. Therefore, BDNF is a good candidate for interventions in the pathogenesis and/or treatment response of attention deficit hyperactivity disorder (ADHD).

OBJECTIVE

We quantified the basal concentration and daily fluctuation of serum BDNF, as well as changes after methylphenidate treatment.

METHOD

A total of 148 children, 4-5 years old, were classified into groups as follows: ADHD group (n = 107, DSM-IV-TR criteria) and a control group (CG, n = 41). Blood samples were drawn at 2000 and 0900 hours from both groups, and after 4.63 ± 2.3 months of treatment, blood was drawn only from the ADHD group for BDNF measurements. Factorial analysis was performed (Stata software, version 12.0).

RESULTS

Morning BDNF (36.36 ± 11.62 ng/ml) in the CG was very similar to that in the predominantly inattentive children (PAD), although the evening concentration in the CG was higher (CG 31.78 ± 11.92 vs PAD 26.41 ± 11.55 ng/ml). The hyperactive-impulsive group, including patients with comorbid conduct disorder (PHI/CD), had lower concentrations. Methylphenidate (MPH) did not modify the concentration or the absence of daily BDNF fluctuations in the PHI/CD children; however, MPH induced a significant decrease in BDNF in PAD and basal day/night fluctuations disappeared in this ADHD subtype. This profile was not altered by the presence of depressive symptoms.

CONCLUSIONS

Our data support a reduction in BDNF in untreated ADHD due to the lower concentrations in PHI/CD children, which is similar to other psychopathologic and cognitive disorders. MPH decreased BDNF only in the PAD group, which might indicate that BDNF is not directly implicated in the methylphenidate-induced amelioration of the neuropsychological and organic immaturity of ADHD patients.

Comparison of the behavioral effects of exercise and high fat diet on cognitive function in adolescent rats

Adolescence is a critical period for neurodevelopment, neuronal plasticity, and cognitive function. Experiences of adolescence can be exerted positive and negative effects on brain development. Physical exercise has a positive effect on brain function, which is characterized by improving memory function and increased neural plasticity. High fat diet (HFD)-induced obesity has a negative effect on brain function, which is characterized by insulin resistance and neuroinflammation and reduced microvessel constructure. Although the positive effect of exercise and negative effect of obesity on cognitive function have been documented, it has not been well whether comparison of the effects of exercise and obesity on cognitive function in adolescent rats. In the present study, we evaluated the behavioral changes related to cognitive function induced by exercise and obesity in adolescent rats. Male Wistar rats were randomly divided into three groups: the control group (CON), the exercise group (Ex), the high fat diet group (HFD). The HFD containing fat 60% was freely provided. The present results showed that spatial learning ability and short-term memory did not show significant effect exercise as compared to the control group. The present results showed that spatial learning ability and short-term memory was significantly decreased HFD-induced obesity group as compared to the control group. These results suggest that positive effect of physical exercise in adolescence rats may be exerted no significant effect on cognitive function. But, negative effect of HFD-induced obesity might induce cognitive impairment. HFD-induced obesity in adolescent rats may be used as an animal model of neurodevelopmental disorders.

GPR40/FFAR1 deficient mice increase noradrenaline levels in the brain and exhibit abnormal behavior

The free fatty acid receptor 1 (GPR40/FFAR1) is a G protein-coupled receptor, which is activated by long chain fatty acids. We have previously demonstrated that activation of brain GPR40/FFAR1 exerts an antinociceptive effect that is mediated by the modulation of the descending pain control system. However, it is unclear whether brain GPR40/FFAR1 contributes to emotional function. In this study, we investigated the involvement of GPR40/FFAR1 in emotional behavior using GPR40/FFAR1 deficient (knockout, KO) mice. The emotional behavior in wild and KO male mice was evaluated at 9-10 weeks of age by the elevated plus-maze test, open field test, social interaction test, and sucrose preference test. Brain monoamines levels were measured using LC-MS/MS. The elevated plus-maze test and open field tests revealed that the KO mice reduced anxiety-like behavior. There were no differences in locomotor activity or social behavior between the wild and KO mice. In the sucrose preference test, the KO mice showed reduction in sucrose preference and intake. The level of noradrenaline was higher in the hippocampus, medulla oblongata, hypothalamus and midbrain of KO mice. Therefore, these results suggest that brain GPR40/FFAR1 is associated with anxiety- and depression-related behavior regulated by the increment of noradrenaline in the brain.

Pifithrin-μ Prevents Cisplatin-Induced Chemobrain by Preserving Neuronal Mitochondrial Function

Cognitive impairment, termed chemobrain, is a common neurotoxicity associated with chemotherapy treatment, affecting an estimated 78% of patients. Prompted by the hypothesis that neuronal mitochondrial dysfunction underlies chemotherapy-induced cognitive impairment (CICI), we explored the efficacy of administering the small-molecule pifithrin (PFT)-μ, an inhibitor of mitochondrial p53 accumulation, in preventing CICI. Male C57BL/6J mice injected with cisplatin ± PFT-μ for two 5-day cycles were assessed for cognitive function using novel object/place recognition and alternation in a Y-maze. Cisplatin impaired performance in the novel object/place recognition and Y-maze tests. PFT-μ treatment prevented CICI and associated cisplatin-induced changes in coherency of myelin basic protein fibers in the cingular cortex and loss of doublecortin⁺ cells in the subventricular zone and hippocampal dentate gyrus. Mechanistically, cisplatin decreased spare respirator capacity of brain synaptosomes and caused abnormal mitochondrial morphology, which was counteracted by PFT-μ administration. Notably, increased mitochondrial p53 did not lead to cerebral caspase-3 activation or cytochrome-c release. Furthermore, PFT-μ administration did not impair the anticancer efficacy of cisplatin and radiotherapy in tumor-bearing mice. Our results supported the hypothesis that neuronal mitochondrial dysfunction induced by mitochondrial p53 accumulation is an underlying cause of CICI and that PFT-μ may offer a tractable therapeutic strategy to limit this common side-effect of many types of chemotherapy. Cancer Res; 77(3); 742-52. ©2016 AACR.

Behavioral changes in male mice fed a high-fat diet are associated with IL-1β expression in specific brain regions

High-fat diet (HFD)-induced obesity is associated with not only increased risk of metabolic and cardiovascular diseases, but cognitive deficit, depression and anxiety disorders. Obesity also leads to low-grade peripheral inflammation, which plays a major role in the development of metabolic alterations. Previous studies suggest that obesity-associated central inflammation may underlie the development of neuropsychiatric deficits, but further research is needed to clarify this relationship. We used 48 male C57BL/6J mice to investigate whether chronic consumption of a high-fat diet leads to increased expression of interleukin-1β (IL-1β) in the hippocampus, amygdala and frontal cortex. We also determined whether IL-1β expression in those brain regions correlates with changes in the Y-maze, open field, elevated zero maze and forced swim tests. After 16weeks on dietary treatments, HFD mice showed cognitive impairment on the Y-maze test, greater anxiety-like behavior during the open field and elevated zero maze tests, and increased depressive-like behavior in the forced swim test. Hippocampal and amygdalar expression of IL-1β were significantly higher in HFD mice than in control mice fed a standard diet (SD). Additionally, hippocampal GFAP and Iba1 immunoreactivity were increased in HFD mice when compared to SD controls. Cognitive performance negatively correlated with level of IL-1β in the hippocampus and amygdala whereas an observed increase in anxiety-like behavior was positively correlated with higher expression of IL-1β in the amygdala. However, we observed no association between depressive-like behavior and IL-1β expression in any of the brain regions investigated. Together our data provide evidence that mice fed a HFD exhibit cognitive deficits, anxiety and depressive-like behaviors. Our results also suggest that increased expression of IL-1β in the hippocampus and amygdala may be associated with the development of cognitive deficits and anxiety-like behavior, respectively.

The Effects of High-fat-diet Combined with Chronic Unpredictable Mild Stress on Depression-like Behavior and Leptin/LepRb in Male Rats

Leptin plays a key role in the pathogenesis of obesity and depression via the long form of leptin receptor (LepRb). An animal model of comorbid obesity and depression induced by high-fat diet (HFD) combined with chronic unpredictable mild stress (CUMS) was developed to study the relationship between depression/anxiety-like behavior, levels of plasma leptin and LepRb in the brains between four groups of rats, the combined obesity and CUMS (Co) group, the obese (Ob) group, the CUMS group and controls. Our results revealed that the Co group exhibited most severe depression-like behavior in the open field test (OFT), anxiety-like behavior in elevated plus maze test (EMT) and cognitive impairment in the Morris water maze (MWM). The Ob group had the highest weight and plasma leptin levels while the Co group had the lowest levels of protein of LepRb in the hypothalamus and hippocampus. Furthermore, depressive and anxiety-like behaviors as well as cognitive impairment were positively correlated with levels of LepRb protein and mRNA in the hippocampus and hypothalamus. The down-regulation of leptin/LepRb signaling might be associated with depressive-like behavior and cognitive impairment in obese rats facing chronic mild stress.

Adolescent Maturational Transitions in the Prefrontal Cortex and Dopamine Signaling as a Risk Factor for the Development of Obesity and High Fat/High Sugar Diet Induced Cognitive Deficits

Adolescence poses as both a transitional period in neurodevelopment and lifestyle practices. In particular, the developmental trajectory of the prefrontal cortex (PFC), a critical region for behavioral control and self-regulation, is enduring, not reaching functional maturity until the early 20 s in humans. Furthermore, the neurotransmitter dopamine is particularly abundant during adolescence, tuning the brain to rapidly learn about rewards and regulating aspects of neuroplasticity. Thus, adolescence is proposed to represent a period of vulnerability towards reward-driven behaviors such as the consumption of palatable high fat and high sugar diets. This is reflected in the increasing prevalence of obesity in children and adolescents as they are the greatest consumers of “junk foods”. Excessive consumption of diets laden in saturated fat and refined sugars not only leads to weight gain and the development of obesity, but experimental studies with rodents indicate they evoke cognitive deficits in learning and memory process by disrupting neuroplasticity and altering reward processing neurocircuitry. Consumption of these high fat and high sugar diets have been reported to have a particularly pronounced impact on cognition when consumed during adolescence, demonstrating a susceptibility of the adolescent brain to enduring cognitive deficits. The adolescent brain, with heightened reward sensitivity and diminished behavioral control compared to the mature adult brain, appears to be a risk for aberrant eating behaviors that may underpin the development of obesity. This review explores the neurodevelopmental changes in the PFC and mesocortical dopamine signaling that occur during adolescence, and how these potentially underpin the overconsumption of palatable food and development of obesogenic diet-induced cognitive deficits.

Diet-induced obesity prolongs neuroinflammation and recruits CCR2(+) monocytes to the brain following herpes simplex virus (HSV)-1 latency in mice

Herpes simplex virus (HSV)-1 is a ubiquitous human infection, with increased prevalence in obese populations. Obesity has been linked to increased inflammation, susceptibility to infection, and higher rates of anxiety disorder and cognitive impairment. To determine how obesity alters neuroinflammation and behavior following infection, we infected weanling C57BL/6 or CCR2(RFP/+)/CX3CR1(GFP/+) mice with a very low dose of HSV-1. Following viral latency (14days post infection (d p.i.)), mice were randomly assigned to remain on the low fat (LF) diet or switched to a 45% high fat (HF) diet. Eight weeks post diet shift, latently infected mice on the HF diet (HSV-HF) had greater microglial activation and infiltration of inflammatory CCR2(+) monocytes in the hypothalamus and dentate gyrus, in comparison to both HSV-LF mice and uninfected mice on LF and HF diets. VCAM staining was present in hypothalamus and hippocampus of the HSV-HF mice in the areas of monocyte infiltration. Infiltrating monocytes also produced proinflammatory cytokines demonstrating that, along with activated microglia, monocytes contribute to sustained neuroinflammation in latently infected obese mice. Utilizing a light-dark preference test, we found that HSV-HF mice had increased anxiety-like behavior. In the marble-burying test, HF diet and HSV infection resulted in increased numbers of buried marbles. Together, these mice provide a useful, testable model to study the biobehavioral effects of obesity and latent HSV-1 infection in regards to anxiety and may provide a tool for studying diet intervention programs in the future.

Z-Guggulsterone Improves the Scopolamine-Induced Memory Impairments Through Enhancement of the BDNF Signal in C57BL/6J Mice

Memory impairment is a common symptom in patients with neurodegenerative disorders, and its suppression could be beneficial to improve the quality of life of those patients. Z-guggulsterone, a compound extracted from the resin of plant Commiphora whighitii, exhibits numerous pharmacological effects in clinical practice, such as treatment of inflammation, arthritis, obesity and lipid metabolism disorders. However, the role and possible mechanism of Z-guggulsterone on brain-associated memory impairments are largely unknown. This issue was addressed in the present study in a memory impairment model induced by scopolamine, a muscarinic acetylcholine receptor antagonist, using the passive avoidance, Y-maze and Morris water maze tests. Results showed that scopolamine significantly decreased the step-through latency and spontaneous alternation of C57BL/6J mice in passive avoidance and Y-maze test, whereas increased the mean escape latency and decreased the swimming time in target quadrant in Morris water maze test. Pretreatment of mice with Z-guggulsterone at doses of 30 and 60 mg/kg effectively reversed the scopolamine-induced memory impairments. Mechanistic studies revealed that Z-guggulsterone pretreatment reversed the scopolamine-induced increase in acetylcholinesterase (AchE) activity, as well as decreases in brain-derived neurotrophic factor (BDNF) protein expression and cAMP response element-binding protein (CREB), extracellular regulated kinase 1/2 (ERK1/2) and protein kinase B (Akt) phosphorylation levels in the hippocampus and cortex. Inhibition of the BDNF signal, however, blocked the memory-enhancing effect of Z-guggulsterone. Therefore, these findings demonstrate that Z-guggulsterone attenuates the scopolamine-induced memory impairments mainly through activation of the CREB-BDNF signaling pathway, thereby exhibiting memory-improving effects.

Behavioral consequences of exposure to a high fat diet during the post-weaning period in rats

We explored the impact of exposure to an obesogenic diet (High Fat-High Sucrose; HFS) during the post-weaning period on sweet preference and behaviors linked to reward and anxiety. All rats were fed chow. In addition a HFS-transient group had access to this diet for 10days from post-natal (PN) day 22 and a HFS-continuous group continued access until adult. Behavioral tests were conducted immediately after PN 32 (adolescence) or after PN 60 (adult) and included: the condition place preference (CPP) test for chocolate, sugar and saccharin preference (anhedonia), the elevated plus maze (anxiety-like behavior) and the locomotor response to quinpirole in the open field. Behavior was unaltered in adult rats in the HFS-transient group, suggesting that a short exposure to this obesogenic food does not induce long-term effects in food preferences, reward perception and value of palatable food, anxiety or locomotor activity. Nevertheless, rats that continued to have access to HFS ate less chocolate during CPP training and consumed less saccharin and sucrose when tested in adolescence, effects that were attenuated when these rats became adult. Moreover, behavioral effects linked to transient HFS exposure in adolescence were not sustained if the rats did not remain on that diet until adult. Collectively our data demonstrate that exposure to fat and sucrose in adolescence can induce immediate reward hypofunction after only 10days on the diet. Moreover, this effect is attenuated when the diet is extended until the adult period, and completely reversed when the HFS diet is removed.

Short-Term High-Fat Diet (HFD) Induced Anxiety-Like Behaviors and Cognitive Impairment Are Improved with Treatment by Glyburide

Obesity-associated comorbidities such as cognitive impairment and anxiety are increasing public health burdens that have gained prevalence in children. To better understand the impact of childhood obesity on brain function, mice were fed with a high-fat diet (HFD) from weaning for 1, 3 or 6 weeks. When compared to low-fat diet (LFD)-fed mice (LFD-mice), HFD-fed mice (HFD-mice) had impaired novel object recognition (NOR) after 1 week. After 3 weeks, HFD-mice had impaired NOR and object location recognition (OLR). Additionally, these mice displayed anxiety-like behavior by measure of both the open-field and elevated zero maze (EZM) testing. At 6 weeks, HFD-mice were comparable to LFD-mice in NOR, open-field and EZM performance but they remained impaired during OLR testing. Glyburide, a second-generation sulfonylurea for the treatment of type 2 diabetes, was chosen as a countermeasure based on previous data exhibiting its potential as an anxiolytic. Interestingly, a single dose of glyburide corrected deficiencies in NOR and mitigated anxiety-like behaviors in mice fed with HFD-diet for 3-weeks. Taken together these results indicate that a HFD negatively impacts a subset of hippocampal-independent behaviors relatively rapidly, but such behaviors normalize with age. In contrast, impairment of hippocampal-sensitive memory takes longer to develop but persists. Since single-dose glyburide restores brain function in 3-week-old HFD-mice, drugs that block ATP-sensitive K(+) (KATP) channels may be of clinical relevance in the treatment of obesity-associated childhood cognitive issues and psychopathologies.

Early life exposure to obesogenic diets and learning and memory dysfunction

Obesogenic dietary factors, such as simple sugars and saturated fatty acids, have been linked to memory impairments and hippocampal dysfunction. Recent evidence suggests that the brain may be particularly vulnerable to the effects of obesogenic diets during early life periods of rapid growth, maturation, and brain development. Investigations utilizing rodent models indicate that early life exposure to "high fat diets" (40-65% kcal derived from fat) or simple sugars (sucrose or high fructose corn syrup) can impair hippocampus-dependent learning and memory processes. In some cases, these deficits occur independent of obesity and metabolic derangement and can persist into adulthood despite dietary intervention. Various neurobiological mechanisms have been identified that may link early life consumption of obesogenic dietary factors with hippocampal dysfunction, including increased neuroinflammation and reduced neurotrophin mediated regulation of neurogenesis and synaptic plasticity. Age, duration of exposure, and dietary composition are key variables contributing to the interaction between early life diet and cognitive dysfunction, however, more research is needed to unravel the precise critical windows of development and causal dietary factors.

Neuroprotective effects of metformin against Aβ-mediated inhibition of long-term potentiation in rats fed a high-fat diet

Metformin (Met) is used to treat neurodegenerative disorders such as Alzheimer's disease (AD). Conversely, high-fat diets (HFD) have been shown to increase AD risk. In this study, we investigated the neuroprotective effects of Met on β-amyloid (Aβ)-induced impairments in hippocampal synaptic plasticity in AD model rats that were fed a HFD. In this study, 32 adult male Wistar rats were randomly assigned to four groups: group I (control group, regular diet); group II (HFD+vehicle); group III (HFD+Aβ); or group IV (Met+HFD+Aβ). Rats fed a HFD were injected with Aβ to induce AD, allowed to recover, and treated with Met for 8 weeks. The rats were then anesthetized with intraperitoneal injections of urethane and placed in a stereotaxic apparatus for surgery, electrode implantation, and field potential recording. In vivo electrophysiological recordings were then performed to measure population spike (PS) amplitude and excitatory postsynaptic potential (EPSP) slope in the hippocampal dentate gyrus. Long-term potentiation (LTP) was induced by high-frequency stimulation of the perforant pathway. Blood samples were then collected to measure plasma levels of triglycerides, low-density lipoproteins, very low-density lipoprotein, and cholesterol. After induction of LTP, PS amplitude and EPSP slope were significantly decreased in Aβ-injected rats fed a HFD compared to vehicle-injected animals or untreated animals that were fed a normal diet. Met treatment of Aβ-injected rats significantly attenuated these decreases, suggesting that Met decreased the effects of Aβ on LTP. These findings suggest that Met treatment is neuroprotective against the detrimental effects of Aβ and HFDs on hippocampal synaptic plasticity.

Dopaminergic Receptors and Tyrosine Hydroxylase Expression in Peripheral Blood Mononuclear Cells: A Distinct Pattern in Central Obesity

Background

Dopamine (DA) may be involved in central obesity (CO), an inflammatory condition, through its role in the central nervous system and in periphery, where it may affect immune cell function through five different DA receptors (DR). Whether dopaminergic pathways in peripheral immune cells are implicated in the inflammatory condition linked to CO is however unknown.

Methods

In a cohort of blood donors with and without CO, categorized by waist circumference (WC) (CO: WC ≥0.80 m in women and ≥0.94 m in men), we studied the expression of DR and tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of DA, in peripheral blood mononuclear cells (PBMCs) and their relation with anthropometric and metabolic/endocrine and inflammatory parameters. DR D_1-5 and TH expression was assessed by semi quantitative real-time PCR. As inflammatory markers we investigated the immunophenotype of monocyte subsets by flow cytometry, staining for CD14, CD16, CD11b and CD36.

Results

CO individuals showed higher plasma levels of leptin and higher inflammatory pattern of monocytes compared with non-CO. PBMC expression of DR D₂, DR D₄ and DR D₅ as well as of TH were lower in CO in comparison with non-CO. DR D₂, and DR D₅ expression correlated with lower WC and weight, and with lower inflammatory pattern of monocytes, and TH expression correlated with lower WC. DR D₄ expression correlated with lower plasma levels of glycosylated hemoglobin, and DR D₂ expression correlated with lower CO.

Conclusions

Results show that CO is associated with peripheral inflammation and downregulation of dopaminergic pathways in PBMCs, possibly suggesting DR expressed on immune cells as pharmacological targets in obesity for better metabolic outcome.

Effects of high-fat diet exposure on learning & memory

The associations between consumption of a high-fat or 'Western' diet and metabolic disorders such as obesity, diabetes, and cardiovascular disease have long been recognized and a great deal of evidence now suggests that diets high in fat can also have a profound impact on the brain, behavior, and cognition. Here, we will review the techniques most often used to assess learning and memory in rodent models and discuss findings from studies assessing the cognitive effects of high-fat diet consumption. The review will then consider potential underlying mechanisms in the brain and conclude by reviewing emerging literature suggesting that maternal consumption of a high-fat diet may have effects on the learning and memory of offspring.

Oleuropein-Rich Diet Attenuates Hyperglycemia and Impaired Glucose Tolerance in Type 2 Diabetes Model Mouse

Oleuropein, a phenolic compound found in abundance in olive leaves, has beneficial effects on various diseases. However, it is unknown whether an oleuropein-rich diet is efficacious against type 2 diabetic phenotypes. In this study, we investigated the effects of the oleuropein-containing supplement OPIACE, whose oleuropein content exceeds 35% (w/w), on the diabetic phenotypes in type 2 diabetes model Tsumura Suzuki Obese Diabetes (TSOD) mouse. TSOD mice were fed OPIACE at 4 weeks of age, i.e., before the TSOD mice exhibited diabetic phenotypes. We revealed that OPIACE attenuated hyperglycemia and impaired glucose tolerance in TSOD mice over the long-term (from 10 to 24 weeks of age) but had no effect on obesity. Furthermore, we demonstrated that OPIACE mildly reduced oxidative stress in TSOD mice by 26.2% and attenuated anxiety-like behavioral abnormality in aged TSOD mice. The results suggest that oleuropein suppresses the progression of type 2 diabetes and diabetes-related behavioral abnormality over the long-term.

Molecular targets of the multifunctional iron-chelating drug, M30, in the brains of mouse models of type 2 diabetes mellitus

BACKGROUND AND PURPOSE

Neurodegenerative diseases are now recognized to be multifunctional, whereby a heterogeneous set of reactions acts independently or cooperatively, leading eventually to the demise of neurons. This has led our group to design and synthesize the multifunctional, nontoxic, brain-permeable, iron chelator compound M30 with a range of pharmacological properties. Here, we have characterized the molecular targets of M30 in the brains of animal models of type 2 diabetes mellitus (T2DM).

EXPERIMENTAL APPROACH

Effects of M30 on molecular mechanisms associated with neuroprotection in the CNS were investigated-in the high-fat diet (HFD) and ob/ob transgenic mouse models of T2DM, using real-time PCR and Western blotting analyses. Brain monoamine oxidase (MAO) activity and catecholamine levels, and peripheral glucose tolerance were assayed after treatment in vivo.

KEY RESULTS

M30 increased cerebral levels of insulin and insulin receptor and phosphorylated-GSK-3β in HFD mice, compared with vehicle-treated HFD mice. In both T2DM mice models, M30 treatment significantly up-regulated cerebral hypoxia-inducible factor (HIF)-1α protein levels and induced the expression of several HIF-1 target genes involved in neuroprotection, glycolysis, neurogenesis, oxidative stress and anti-inflammation. Additionally, M30 inhibited MAO-A and -B activities in the cerebellum. Accordingly, M30 administration significantly reduced brain levels of dopamine metabolites and increased levels of 5-HT and noradrenaline. Glucose tolerance was also improved after M30 treatment in both models of T2DM.

CONCLUSIONS AND IMPLICATIONS

In the brain of HFD and ob/ob transgenic mice, M30 exerted a variety of beneficial neuroprotective regulatory effects that may act synergistically to delay or prevent neurodegenerative processes associated with T2DM.

IL-4 Knock Out Mice Display Anxiety-Like Behavior

Inflammation is a recognized antecedent and coincident factor when examining the biology of anxiety. Little is known, however, about how reductions in endogenous anti-inflammatory mediators impact anxiety. Therefore, mood- cognition- and anxiety-associated/like behaviors were examined in IL-4 knock out (KO) mice and wild-type (WT) mice. In comparison to WT mice, IL-4 KO mice demonstrated decreased burrowing and increased social exploration. No differences were seen in forced swim or saccharine preference testing. IL-4 KO mice had similar performance to WT mice in the Morris water maze and during object location and novel object recognition. In the elevated zero-maze, IL-4 KO mice, in comparison to WT mice, demonstrated anxiety-like behavior. Anxiety-like behavior in IL-4 KO mice was not observed, however, during open-field testing. Taken together, these data indicate that IL-4 KO mice display state, but not trait, anxiety suggesting that reductions in endogenous anti-inflammatory bioactives can engender subtypes of anxiety.

Amyloid β Enhances Typical Rodent Behavior While It Impairs Contextual Memory Consolidation

Alzheimer's disease (AD) is associated with an early hippocampal dysfunction, which is likely induced by an increase in soluble amyloid beta peptide (Aβ). This hippocampal failure contributes to the initial memory deficits observed both in patients and in AD animal models and possibly to the deterioration in activities of daily living (ADL). One typical rodent behavior that has been proposed as a hippocampus-dependent assessment model of ADL in mice and rats is burrowing. Despite the fact that AD transgenic mice show some evidence of reduced burrowing, it has not been yet determined whether or not Aβ can affect this typical rodent behavior and whether this alteration correlates with the well-known Aβ-induced memory impairment. Thus, the purpose of this study was to test whether or not Aβ affects burrowing while inducing hippocampus-dependent memory impairment. Surprisingly, our results show that intrahippocampal application of Aβ increases burrowing while inducing memory impairment. We consider that this Aβ-induced increase in burrowing might be associated with a mild anxiety state, which was revealed by increased freezing behavior in the open field, and conclude that Aβ-induced hippocampal dysfunction is reflected in the impairment of ADL and memory, through mechanisms yet to be determined.

Genetic variability to diet-induced hippocampal dysfunction in BXD recombinant inbred (RI) mouse strains

Evidence has emerged suggesting that diet-induced obesity can have a negative effect on cognitive function. Here, we exploited a mouse genetic reference population to look for the linkage between these two processes on a genome-wide scale. The focus of this report is to determine whether the various BXD RI strains exhibited different behavioral performance and hippocampal function under high fat dietary (HFD) condition. We quantified genetic variation in body weight gain and consequent influences on behavioral tests in a cohort of 14 BXD strains of mice (8-12 mice/strain, n = 153), for which we have matched data on gene expression and neuroanatomical changes in the hippocampus. It showed that BXD66 was the most susceptible, whereas BXD77 was the least susceptible strain to dietary influences. The performance of spatial reference memory tasks was strongly correlated with body weight gain (P < 0.05). The obesity-prone strains displayed more pronounced spatial memory defects compared to the obesity-resistant strains. These abnormalities were associated with neuroinflammation, synaptic dysfunction, and neuronal loss in the hippocampus. The biological relevance of DSCAM gene polymorphism was assessed using the trait correlation analysis tool in Genenetwork. Furthermore, a significant strain-dependent gene expression difference of DSCAM was detected in the hippocampus of obese BXD strains by real-time quantitative PCR. In conclusion, a variety of across-strain hippocampal alterations and genetic predispositions to diet-induced obesity were found in a set of BXD strains. The obesity-prone and obesity-resistant lines we have identified should be highly useful to study the molecular genetics of diet-induced cognitive decline.

Brain and behavioral perturbations in rats following Western diet access

Energy dense "Western" diets (WD) are known to cause obesity as well as learning and memory impairments, blood-brain barrier damage, and psychological disturbances. Impaired glucose (GLUT1) and monocarboxylate (MCT1) transport may play a role in diet-induced dementia development. In contrast, ketogenic diets (KD) have been shown to be neuroprotective. We assessed the effect of 10, 40 and 90 days WD, KD and Chow maintenance on spontaneous alternation (SA) and vicarious trial and error (VTE) behaviors in male rats, then analyzed blood glucose, insulin, and ketone levels; and hippocampal GLUT1 and MCT1 mRNA. Compared to Chow and KD, rats fed WD had increased 90 day insulin levels. SA was decreased in WD rats at 10, but not 40 or 90 days. VTE was perturbed in WD-fed rats, particularly at 10 and 90 days, indicating hippocampal deficits. WD rats had lower hippocampal GLUT1 and MCT1 expression compared to Chow and KD, and KD rats had increased 90 day MCT1 expression compared to Chow and WD. These data suggest that WD reduces glucose and monocarboxylate transport at the hippocampus, which may result in learning and memory deficits. Further, KD consumption may be useful for MCT1 transporter recovery, which may benefit cognition.

Mori folium and mori fructus mixture attenuates high-fat diet-induced cognitive deficits in mice

Obesity has become a global health problem, contributing to various diseases including diabetes, hypertension, cancer, and dementia. Increasing evidence suggests that obesity can also cause neuronal damage, long-term memory loss, and cognitive impairment. The leaves and the fruits of Morus alba L., containing active phytochemicals, have been shown to possess antiobesity and hypolipidemic properties. Thus, in the present study, we assessed their effects on cognitive functioning in mice fed a high-fat diet by performing immunohistochemistry, using antibodies against c-Fos, synaptophysin, and postsynaptic density protein 95 and a behavioral test. C57BL/6 mice fed a high-fat diet for 21 weeks exhibited increased body weight, but mice coadministered an optimized Mori Folium and Mori Fructus extract mixture (2 : 1; MFE) for the final 12 weeks exhibited significant body weight loss. Additionally, obese mice exhibited not only reduced neural activity, but also decreased presynaptic and postsynaptic activities, while MFE-treated mice exhibited recovery of these activities. Finally, cognitive deficits induced by the high-fat diet were recovered by cotreatment with MFE in the novel object recognition test. Our findings suggest that the antiobesity effects of MFE resulted in recovery of the cognitive deficits induced by the high-fat diet by regulation of neural and synaptic activities.

Neurochemical and electrophysiological deficits in the ventral hippocampus and selective behavioral alterations caused by high-fat diet in female C57BL/6 mice

Mounting experimental evidence, predominantly from male rodents, demonstrates that high-fat diet (HFD) consumption and ensuing obesity are detrimental to the brain. To shed additional light on the neurological consequences of HFD consumption in female rodents and to determine the relatively early impact of HFD in the likely continuum of neurological dysfunction in the context of chronic HFD intake, this study investigated effects of HFD feeding for up to 12weeks on selected behavioral, neurochemical, and electrophysiological parameters in adult female C57BL/6 mice; particular focus was placed on the ventral hippocampus (vHIP). Selected locomotor, emotional and cognitive functions were evaluated using behavioral tests after 5weeks on HFD or control (low-fat diet) diets. One week later, mice were sacrificed and brain regional neurochemical (monoamine) analysis was performed. Behaviorally naïve mice were maintained on their respective diets for an additional 5-6weeks at which time synaptic plasticity was determined in ex vivo slices from the vHIP. HFD-fed female mice exhibited increased: (i) locomotor activity in the open field testing, (ii) mean turn time on the pole test, (iii) swimming time in the forced swim test, and (iv) number of marbles buried in the marble burying test. In contrast, the novel object recognition memory was unaffected. Mice on HFD also had decreased norepinephrine and dopamine turnover, respectively, in the prefrontal cortex and the vHIP. HFD consumption for a total of 11-12weeks altered vHIP synaptic plasticity, evidenced by significant reductions in the paired-pulse ratio and long-term potentiation (LTP) magnitude. In summary, in female mice, HFD intake for several weeks induced multiple behavioral alterations of mainly anxiety-like nature and impaired monoamine pathways in a brain region-specific manner, suggesting that in the female, certain behavioral domains (anxiety) and associated brain regions, i.e., the vHIP, are preferentially targeted by HFD.

The impact of discontinuing methylphenidate on weight and eating behavior

Chronic administration of the amphetamine-derivative methylphenidate (MPH) may induce appetite reduction and weight loss. By contrast, the effects that stopping chronic MPH may exert on eating behavior and body weight are poorly known. We report the case of a male patient with childhood attention deficit/hyperactivity disorder (ADHD), who discontinued MPH treatment at the age of 11 years and was lost to follow-up until the age of 16. The patient's body mass index increased by five points within 1 year of MPH cessation while the symptoms of ADHD were re-emerging. The patient secondarily developed DSM-5 criteria for eating disorders. Discontinuing chronic MPH can significantly affect weight and eating behavior. Such risks should warrant further studies, as they could be particularly increased in patients with ADHD, who share common vulnerability factors with both obesity and eating disorders.

The saturated fatty acid, palmitic acid, induces anxiety-like behavior in mice

OBJECTIVES

Excess fat in the diet can impact neuropsychiatric functions by negatively affecting cognition, mood and anxiety. We sought to show that the free fatty acid (FFA), palmitic acid, can cause adverse biobehaviors in mice that last beyond an acute elevation in plasma FFAs.

METHODS

Mice were administered palmitic acid or vehicle as a single intraperitoneal (IP) injection. Biobehaviors were profiled 2 and 24 h after palmitic acid treatment. Quantification of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their major metabolites was performed in cortex, hippocampus and amygdala. FFA concentration was determined in plasma. Relative fold change in mRNA expression of unfolded protein response (UPR)-associated genes was determined in brain regions.

RESULTS

In a dose-dependent fashion, palmitic acid rapidly reduced mouse locomotor activity by a mechanism that did not rely on TLR4, MyD88, IL-1, IL-6 or TNFα but was dependent on fatty acid chain length. Twenty-four hours after palmitic acid administration mice exhibited anxiety-like behavior without impairment in locomotion, food intake, depressive-like behavior or spatial memory. Additionally, the serotonin metabolite 5-HIAA was increased by 33% in the amygdala 24h after palmitic acid treatment.

CONCLUSIONS

Palmitic acid induces anxiety-like behavior in mice while increasing amygdala-based serotonin metabolism. These effects occur at a time point when plasma FFA levels are no longer elevated.

Effect of dietary restriction on peripheral monoamines and anxiety symptoms in obese subjects with metabolic syndrome

Reduced circulating monoamines may have a role in the development of the metabolic syndrome (MetS), which is becoming a major health problem worldwide. Moreover, an association between anxiety disorder and MetS has been reported; however, it is not clear whether weight loss can diminish anxiety. This investigation is aimed to examine the effects of a weight loss intervention on peripheral monoamines levels and anxiety symptoms in subjects with metabolic syndrome (MetS). The study population encompassed subjects with MetS (age: 50±10 y.o. and BMI: 35.8±4.3 kg/m2) selected from the RESMENA study after they had completed the 6-month weight loss intervention (-30% energy). Anthropometric measurements, dietary records, anxiety symptoms, and blood monoamines levels were analysed before and after the intervention. Dopamine (DA) (+18.2%; 95% confidence interval (CI): -51.2 to -0.5) and serotonin (5-HT) (+16.1%; 95% CI: -26.3 to -2.2) blood levels were significantly increased after the intervention. Higher DA blood concentrations at the end of the study were inversely related with the carbohydrate intake during the study (B=-3.3; 95% CI: -8.4 to -0.4) and basal DA levels predicted a greater decrease in body weight and anthropometric parameters. Subjects with higher 5-HT concentrations after the weight loss intervention also showed a lower energy intake during the intervention (B=-0.04; 95% CI: -0.07 to -0.01). Additionally, anxiety symptoms decreased after the weight loss treatment (-28.3%; 95% CI: 6.2-20.4), which was parallel to a greater decrease in body weight and anthropometric markers, being related to lower 5-HT basal levels. Dietary restriction in patients with MetS may help in reducing anxiety symptoms, and also in increasing 5-HT and DA blood levels. These results provide further insights regarding emotional and neurological factors behind weight loss.

Fasting Induces IL-1 Resistance and Free-Fatty Acid-Mediated Up-Regulation of IL-1R2 and IL-1RA

OBJECTIVE

Weight-loss is a near societal obsession and many diet programs use significant calorie restriction including fasting/short term starvation to generate rapid effects. Fasting is also a well-recognized cause of immunosuppression especially within the innate immune system. In this study, we sought to determine if the IL-1 arm of the neuroimmune system was down-regulated by a 24 h fast and how fasting might generate this effect.

DESIGN

Mice were allowed ad libitum access to food or had food withheld for 24 h. Expression of the endogenous IL-1 antagonists, IL-1 receptor type 2 (IL-1R2), and IL-1 receptor antagonist (IL-1RA) was determined as were sickness behaviors before and after IL-1β administration.

RESULTS

Fasting markedly increased gene expression of IL-1R2 (83-fold in adipose tissue, 9.5-fold in liver) and IL-1RA (68-fold in liver). Fasted mice were protected from IL-1β-induced weight-loss, hypoglycemia, loss of locomotor, and social anxiety. These protections were coupled to a large positive interaction of fasting and IL-1β on IL-1R2 gene expression in adipose tissue and liver (2.6- and 1.6-fold, respectively). Fasting not only increased IL-1RA and IL-1R2 protein 2.5- and 3.2-fold, respectively, in liver but also increased IL-1R2 1.8-fold in adipose tissue. Fasting, in turn, triggered a 2.4-fold increase in plasma free-fatty acids (FFAs) and a 2.1-fold increase in plasma corticosterone. Inhibition, of glucocorticoid action with mifepristone did not impact fasting-dependent IL-1R2 or IL-1RA gene expression. Administration of the FFA, palmitate, to mice increased liver IL-1R2 and IL-1RA gene expression by 14- and 11-fold, respectively.

CONCLUSION

These findings indicate that fasting augments expression of endogenous IL-1 antagonists inducing IL-1 resistance. Fasting-induced increases in plasma FFAs appears to be a signal that drives immunosuppression during fasting/short term starvation.

Depression-like behaviors in mice subjected to co-treatment of high-fat diet and corticosterone are ameliorated by AICAR and exercise

Major depressive disorder (MDD) and type II diabetes mellitus (T2DM) are highly co-morbid, and there may be a bi-directional connection between the two. Herein, we have described a mouse model of a depression-like and insulin-resistant (DIR) state induced by the co-treatment of high-fat diet (HFD) and corticosterone (CORT). 5-Aminoimidazole-4-carboxamide-1-β-d- ribofuranoside (AICAR), a pharmacological activator of AMP-activated protein kinase (AMPK), was originally used to improve insulin resistance (IR). Interestingly, our results show a clear potential for AICAR as a putative antidepressant with a chronic action on the DIR mice. In contrast to the traditional antidepressants, AICAR as a promising antidepressant avoids reducing insulin actions of skeletal muscle in the context of long-term HFD. Exercise also produced antidepressant effects. Our data suggest that the effects of AICAR and exercise on DIR may further increase our understanding on the link between depression and diabetes.

The role of brain-derived neurotrophic factor in comorbid depression: possible linkage with steroid hormones, cytokines, and nutrition

Increasing evidence demonstrates a connection between growth factor function (including brain-derived neurotrophic factor, BDNF), glucocorticoid levels (one of the steroid hormones), and the pathophysiology of depressive disorders. Because both BDNF and glucocorticoids regulate synaptic function in the central nervous system, their functional interaction is of major concern. Interestingly, alterations in levels of estrogen, another steroid hormone, may play a role in depressive-like behavior in postpartum females with fluctuations of BDNF-related molecules in the brain. BDNF and cytokines, which are protein regulators of inflammation, stimulate multiple intracellular signaling cascades involved in neuropsychiatric illness. Pro-inflammatory cytokines may increase vulnerability to depressive symptoms, such as the increased risk observed in patients with cancer and/or autoimmune diseases. In this review, we discuss the possible relationship between inflammation and depression, in addition to the cross-talk among cytokines, BDNF, and steroids. Further, since nutritional status has been shown to affect critical pathways involved in depression through both BDNF function and the monoamine system, we also review current evidence surrounding diet and supplementation (e.g., flavonoids) on BDNF-mediated brain functions.