Mediation of cognitive function by high fat diet following stress and inflammation

Impact of Long-Term Dietary High Fat and Eicosapentaenoic Acid on Behavior and Hypothalamic-Pituitary-Adrenal Axis Activity in Amyloidogenic APPswe/PSEN1dE9 Mice

INTRODUCTION

Alzheimer's disease (AD) alters neurocognitive and emotional function and causes dysregulation of multiple homeostatic processes. The leading AD framework pins amyloid beta plaques and tau tangles as primary drivers of dysfunction. However, many additional variables, including diet, stress, sex, age, and pain tolerance, interact in ways that are not fully understood to impact the onset and progression of AD pathophysiology. We asked: (1) does high-fat diet, compared to low-fat diet, exacerbate AD pathophysiology and behavioral decline? And, (2) can supplementation with eicosapentaenoic (EPA)-enriched fish oil prevent high-fat-diet-induced changes?

METHODS

Male and female APPswePSdE9 mice, and their non-transgenic littermates, were randomly assigned to a diet condition (low-fat, high-fat, high-fat with EPA) and followed from 2 to 10 months of age. We assessed baseline corticosterone concentration during aging, pain tolerance, cognitive function, stress coping, and corticosterone response to a stressor.

RESULTS

Transgenic mice were consistently more active than non-transgenic mice but did not perform worse on either cognitive task, even though we recently reported that these same transgenic mice exhibited metabolic changes and had increased amyloid beta. Mice fed high-fat diet had higher baseline and post-stressor corticosterone, but diet did not impact cognition or pain tolerance. Sex had the biggest influence, as female mice were consistently more active and had higher corticosterone than males.

CONCLUSION

Overall, diet, genotype, and sex did not have consistent impacts on outcomes. We found little support for predicted interactions and correlations, suggesting diet impacts metabolic function and amyloid beta levels, but these outcomes do not translate to changes in behaviors measured here.

Donepezil Attenuates Obesity-Associated Oxidative Stress and Central Inflammation and Improves Memory Deficit in Mice Fed a High-Fat Diet

BACKGROUND/AIMS

Obesity is associated with chronic inflammation and cognitive decline, and is considered a major risk factor for neurodegeneration. Meanwhile, neuroinflammation is important in the pathogenesis and progression of neurodegenerative diseases.

METHODS

In this study, we tested the hypothesis that donepezil would attenuate central inflammation and oxidative damage and improve memory deficit in high-fat diet (HFD)-fed mice. After 16 weeks on a HFD, C57BL/6J mice were given either donepezil (3 mg/kg, i.p.) or saline for 4 weeks in parallel to a control diet (CD) group. Thereafter, the step-through test was used to assess learning and memory function.

RESULTS

In the brain of HFD-fed mice, levels of the proinflammatory cytokines interleukin 16 and tumor necrosis factor α were reduced by donepezil treatment. Similarly, HFD-induced protein levels of advanced glycation end-products and oxidative stress in the brain were significantly decreased by donepezil treatment.

CONCLUSION

Our results indicate that donepezil may reverse obesity-related central inflammation and oxidative damage and improve memory deficit in HFD-fed mice.

Membrane Lipidome Reorganization and Accumulation of Tissue DNA Lesions in Tumor-Bearing Mice: An Exploratory Study

Increased rates of reactive oxygen/nitrogen species (ROS/RNS) are involved in almost all cancer types, associated with tumor development and progression, causing damage to biomolecules such as proteins, nucleic acids and membrane lipids, in different biological compartments. We used a human tumor xenograft mouse model to evaluate for the first time in parallel the remodeling of fatty acid moieties in erythrocyte membrane phospholipids and the level of ROS-induced DNA lesions in liver and kidney tissues. Using liquid chromatography tandem mass spectrometry the 5'R and 5'S diastereoisomers of 5',8-cyclo-2'-deoxyadenosine and 5',8-cyclo-2'-deoxyguanosine, together with 8-oxo-7,8-dihydro-2'-deoxyadenosine, were determined in mice at young (4- and 5-weeks) and old (17-weeks) ages and compared with control SCID mice without tumor implantation. Tumor-bearing mice showed a higher level of ROS-damaged nucleosides in genomic DNA as the age and tumor progress, compared to controls (1.07-1.53-fold in liver and 1.1-1.4-fold in kidney, respectively). The parallel fatty acid profile of erythrocyte membranes showed a profound lipid remodeling during tumor and age progression consisting of PUFA consumption and SFA enrichment (ca 28% and 58%, respectively, in late stage tumor-bearing mice), markers of enhanced oxidative and proliferative processes, respectively. Membrane lipid remodeling and ROS-induced DNA lesions may be combined to afford an integrated scenario of cancer progression and ageing, reinforcing a holistic vision among molecular markers rather than the biomarker identification in a single compartment.

Adult obese mice suffer from chronic secondary brain injury after mild TBI

Background

A traumatic brain injury (TBI) event is a devastating injury to the brain that may result in heightened inflammation, neurodegeneration, and subsequent cognitive and mood deficits. TBI victims with co-morbidities such as heart disease, diabetes, or obesity may be more vulnerable to the secondary brain injury that follows the initial insult. Compared to lean individuals, obese subjects tend to have worse clinical outcomes and higher mortality rates after trauma.

Methods

To elucidate whether obesity predisposes individuals to worse outcomes after TBI, we subjected adult lean and obese male/female mice to a mild TBI. The injury was administered using a controlled skull impact (CSI) device. Lean or obese 6-month-old C57 BL/6 mice were subjected once to a mild TBI. Additionally, at day 30 after injury, both the lean and obese mice were tested for increased anxiety using the open field test.

Results

At day 30 after TBI, compared to the lean mice, we found heightened microglial (MG) activation in the cerebral cortex, corpus callosum, and hypothalamus. Another compelling finding was that, compared to the non-injured obese male control mice, the obese TBI mice had a decrease in the rate of weight gain and serum corticosterone levels at day 30 after injury. Additionally, the injured obese mice displayed higher levels of anxiety as determined by a significant decrease in time spent in the non-peripheral zones in the open field test. In contrast to the obese males, the obese female mice did not exhibit increases in the number of active MG in the brain, changes in weight gain/corticosterone levels, or increased anxiety at day 30 after TBI.

Conclusions

The data presented here suggests that obese mice have worse outcomes compared to lean mice after mild TBI. Also, the obese males have worse outcomes than the injured female mice. This data may explain the sequela of chronic secondary brain injury in obese adults after a single mild TBI. Also, this report may help shape how the overweight/obese populations are monitored over the days and months following a TBI.

High-fat diet consumption disrupts memory and primes elevations in hippocampal IL-1β, an effect that can be prevented with dietary reversal or IL-1 receptor antagonism

High-fat diet (HFD)-induced obesity is reaching worldwide proportions. In addition to causing obesity, HFDs also induce a variety of health disorders, which includes cognitive decline. Hippocampal function may be particularly vulnerable to the negative consequences of HFD, and it is suspected that 'primed' neuroinflammatory processes may mediate this response. To examine the link between diet, hippocampal function and neuroinflammation, male Wistar rats were fed a medium or HFD. Hippocampal memory function was measured using contextual pre-exposure fear conditioning (CPE-FC). Rats fed a HFD demonstrated impaired memory, an effect that was augmented with longer duration of HFD consumption. HFD-induced memory impairments were linked to potentiated levels of interleukin-1 beta (IL-1β) protein in the hippocampus 2h after the foot-shock that occurs during CPE-FC. Central IL-1 receptor antagonism, with intracisterna magna (ICM) administration of hIL-1RA prior to the foot-shock prevented the diet-induced memory disruption, suggesting a critical role for IL-1β in this phenomenon. Additionally, obese animals whose diet regimen was reversed from HFD back to standard chow recovered memory function and did not demonstrate a foot-shock-induced hippocampal IL-1β increase. Interestingly, dietary reversal neutralized the negative impact of HFD on memory and IL-1β, yet animals maintained physiological evidence of obesity (increased body mass and serum leptin), indicating that dietary components, not body mass, may mediate the negative effects on memory.

Advanced pharmacotherapy evidenced by pathogenesis of autism spectrum disorder

In clinical practice, pharmacological treatment is mostly focused on behavioral symptoms in everyday life. Nevertheless, persistent effort continues to develop medication for causal treatment. Recent changes in diagnostic criteria from Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision (DSM-IV-TR) to DSM-5 would affect not only diagnosing approaches, but also therapeutic approaches. Because previous pervasive developmental disorders have been integrated into a single entity, the autism spectrum disorder (ASD), we have to prepare for what medications are valuable for the ASD. In this article, we reviewed the following etiological treatment: acetylcholine and glutamate related medicine; amino acid medicine such as secretin, endogenous opioid, and oxytocin; complementary and alternative medicine such as chelating agents, vitamins, and omega-3; promising drugs related to the scope of pharmacogenetics currently under study.

Effects of dietary fish meal and soybean meal on the ovine innate and acquired immune response during pregnancy and lactation

In recent years, livestock producers have been supplementing animal diets with fish meal (FM) to produce value-added products for health conscious consumers. As components of FM have unique neuroendocrine-immunomodulatory properties, we hypothesize that livestock producers may be influencing the overall health of their animals by supplementing diets with FM. In this study, 40 pregnant ewes were supplemented with rumen protected (RP) soybean meal (SBM: control diet) or RP FM, commencing gestation day 100 (gd100), in order to evaluate the impact of FM supplementation on the innate and acquired immune response and neuroendocrine response of sheep during pregnancy and lactation. On gd135, half the ewes from each diet (n = 10 FM, n = 10 SBM) were challenged iv with lipopolysaccharide (LPS) to simulate a systemic bacterial infection and the febrile, respiratory and neuroendocrine responses were monitored over time; the other half (n = 10 FM, n = 10 SBM) of the ewes received a saline injection as control. On lactation day 20 (ld20), all ewes (n = 20 FM, n = 20 SBM) were sensitized with hen egg white lysozyme (HEWL) and the serum haptoglobin (Hp) response was measured over time. The cutaneous hypersensitivity response (CHR) to HEWL challenge was measured on ld30 (n = 20 FM, n = 20 SBM), and blood samples were collected over time to measure the primary and secondary immunoglobulin G (IgG) response to HEWL. There was an attenuated trend in the LPS-induced febrile response by the FM treatment when compared with the SBM treatment (P = 0.06), as was also true for the respiratory response (P = 0.07), but significant differences in neuroendocrine function (serum cortisol and plasma ACTH) were not observed between treatments. Basal Hp levels were significantly lower in the FM supplemented ewes when compared with the SBM supplemented ewes (P < 0.01), and the Hp response to HEWL sensitization differed significantly over time between treatments (P < 0.01). The CHR to HEWL was also significantly attenuated in the FM treatment compared with the SBM (P < 0.01); however, treatment differences in the primary and secondary IgG responses to HEWL were not observed. These results indicate that FM supplementation differentially affects the innate and acquired immune responses in pregnant and lactating sheep compared with a typical SBM diet of commercial flocks. The long-term implications of this immunomodulation warrant further investigation.

Dietary Cholesterol Concentration and Duration Degrade Long-Term Memory of Classical Conditioning of the Rabbit's Nictitating Membrane Response

A rabbit model of Alzheimer's disease based on feeding a cholesterol diet for eight weeks shows sixteen hallmarks of the disease, including learning and memory changes. Although we have shown 2% cholesterol and copper in water can retard learning, other studies show feeding dietary cholesterol before learning can improve acquisition whereas feeding cholesterol after learning can degrade long-term memory. We explored this issue by manipulating cholesterol concentration and duration following classical trace conditioning of the rabbit's nictitating membrane response and assessed conditioned responding after eight weeks on cholesterol. First, rabbits given trace classical conditioning followed by 0.5%, 1%, or 2% cholesterol for eight weeks showed body weight and serum cholesterol levels that were a function of dietary cholesterol. Although all concentrations of cholesterol showed some sign of retarding long-term memory, the level of memory retardation was correlated with serum cholesterol levels. Second, rabbits given trace conditioning followed by different durations of a 2% cholesterol diet combined with different durations of a 0% control diet for 8 weeks showed duration and timing of a 2% cholesterol diet were important in affecting recall. The data support the idea that dietary cholesterol may retard long-term memory.

The relation of dietary choline to cognitive performance and white-matter hyperintensity in the Framingham Offspring Cohort

BACKGROUND

Choline is the precursor to the neurotransmitter acetylcholine. Loss of cholinergic neurons is associated with impaired cognitive function, particularly memory loss and Alzheimer disease (AD). Brain atrophy and white-matter hyperintensity (WMH) are also associated with impaired cognitive function and AD.

OBJECTIVE

The objective was to determine whether a relation exists between dietary choline intake, cognitive function, and brain morphology in a large, nondemented community-based cohort.

DESIGN

A dementia-free cohort of 1391 subjects (744 women, 647 men; age range: 36-83 y; mean ± SD age: 60.9 ± 9.29 y) from the Framingham Offspring population completed a food-frequency questionnaire administered from 1991 to 1995 (exam 5; remote intake) and from 1998 to 2001 (exam 7; concurrent intake). Participants underwent neuropsychological evaluation and brain MRI at exam 7. Four neuropsychological factors were constructed: verbal memory (VM), visual memory (VsM), verbal learning, and executive function. MRI measures included WMH volume (WMHV).

RESULTS

Performance on the VM and VsM factors was better with higher concurrent choline intake in multivariable-adjusted models for VM (average change in neuropsychological factor per 1-unit change in choline = 0.60; 95% CI: 0.29, 0.91; P < 0.01) and VsM (0.66; 95% CI: 0.19, 1.13; P < 0.01). Remote choline intake was inversely related to log-transformed WMHV (average change in log WMHV per 1-unit change in choline = -0.05; 95% CI: -0.10, -0.01; P = 0.02). Furthermore, an inverse association was observed between remote higher choline intake and presence of large WMVH (OR: 0.56; 95% CI: 0.34, 0.92; P = 0.01).

CONCLUSION

In this community-based population of nondemented individuals, higher concurrent choline intake was related to better cognitive performance, whereas higher remote choline intake was associated with little to no WMHV.

Side chain-oxidized oxysterols regulate the brain renin-angiotensin system through a liver X receptor-dependent mechanism

Disturbances in cholesterol metabolism have been associated with hypertension and neurodegenerative disorders. Because cholesterol metabolism in the brain is efficiently separated from plasma cholesterol by the blood-brain barrier (BBB), it is an unsolved paradox how high blood cholesterol can cause an effect in the brain. Here, we discuss the possibility that cholesterol metabolites permeable to the BBB might account for these effects. We show that 27-hydroxycholesterol (27-OH) and 24S-hydroxycholesterol (24S-OH) up-regulate the renin-angiotensin system (RAS) in the brain. Brains of mice on a cholesterol-enriched diet showed up-regulated angiotensin converting enzyme (ACE), angiotensinogen (AGT), and increased JAK/STAT activity. These effects were confirmed in in vitro studies with primary neurons and astrocytes exposed to 27-OH or 24S-OH, and were partially mediated by liver X receptors. In contrast, brain RAS activity was decreased in Cyp27a1-deficient mice, a model exhibiting reduced 27-OH production from cholesterol. Moreover, in humans, normocholesterolemic patients with elevated 27-OH levels, due to a CYP7B1 mutation, had markers of activated RAS in their cerebrospinal fluid. Our results demonstrate that side chain-oxidized oxysterols are modulators of brain RAS. Considering that levels of cholesterol and 27-OH correlate in the circulation and 27-OH can pass the BBB into the brain, we suggest that this cholesterol metabolite could be a link between high plasma cholesterol levels, hypertension, and neurodegeneration.

Dietary Effects on Cognition and Pilots' Flight Performance

The purpose of this study was to investigate the effects of diet on cognition and flight performance of 45 pilots. Based on a theory of self-care, this clinical study used a repeated-measure, counterbalanced crossover design. Pilots were randomly rotated through 4-day high-carbohydrate, high-protein, high-fat, and control diets. Cognitive flight performance was evaluated using a GAT-2 full-motion flight simulator. The Sternberg short-term memory test and Vandenberg's mental rotation test were used to validate cognitive flight test results. Pilots consuming a high-protein diet had significantly poorer (p < .05) overall flight performance scores than pilots consuming high-fat and high-carbohydrate diets.

Momordica charantia (bitter melon) attenuates high-fat diet-associated oxidative stress and neuroinflammation

Background

The rising epidemic of obesity is associated with cognitive decline and is considered as one of the major risk factors for neurodegenerative diseases. Neuroinflammation is a critical component in the progression of several neurological and neurodegenerative diseases. Increased metabolic flux to the brain during overnutrition and obesity can orchestrate stress response, blood-brain barrier (BBB) disruption, recruitment of inflammatory immune cells from peripheral blood and microglial cells activation leading to neuroinflammation. The lack of an effective treatment for obesity-associated brain dysfunction may have far-reaching public health ramifications, urgently necessitating the identification of appropriate preventive and therapeutic strategies. The objective of our study was to investigate the neuroprotective effects of Momordica charantia (bitter melon) on high-fat diet (HFD)-associated BBB disruption, stress and neuroinflammatory cytokines.

Methods

C57BL/6 female mice were fed HFD with and without bitter melon (BM) for 16 weeks. BBB disruption was analyzed using Evans blue dye. Phosphate-buffered saline (PBS) perfused brains were analyzed for neuroinflammatory markers such as interleukin-22 (IL-22), IL-17R, IL-16, NF-κB1, and glial cells activation markers such as Iba1, CD11b, GFAP and S100β. Additionally, antioxidant enzymes, ER-stress proteins, and stress-resistant transcription factors, sirtuin 1 (Sirt1) and forkhead box class O transcription factor (FoxO) were analyzed using microarray, quantitative real-time RT-PCR, western immunoblotting and enzymatic assays. Systemic inflammation was analyzed using cytokine antibody array.

Results

BM ameliorated HFD-associated changes in BBB permeability as evident by reduced leakage of Evans blue dye. HFD-induced glial cells activation and expression of neuroinflammatory markers such as NF-κB1, IL-16, IL-22 as well as IL-17R were normalized in the brains of mice supplemented with BM. Similarly, HFD-induced brain oxidative stress was significantly reduced by BM supplementation with a concomitant reduction in FoxO, normalization of Sirt1 protein expression and up-regulation of Sirt3 mRNA expression. Furthermore, plasma antioxidant enzymes and pro-inflammatory cytokines were also normalized in mice fed HFD with BM as compared to HFD-fed mice.

Conclusions

Functional foods such as BM offer a unique therapeutic strategy to improve obesity-associated peripheral inflammation and neuroinflammation.

Effect of high-fat diet on stress responsiveness in borderline hypertensive rats

Stress in combination with genetic susceptibility is a factor in the development of hypertension. We used borderline hypertensive rats to investigate whether exposure to high-fat and/or junk-food diet at different stages of ontogeny has programing consequences on stress responses. Wistar dams were fed a high- or low-fat diet for 6 weeks prior to mating with spontaneously hypertensive males, and during gestation. At birth, litters were fostered either to a dam in the same or an alternative diet condition as during gestation. After weaning, male offspring were fed either a control-chow diet or an intermittent junk food fatty diet. Between postnatal days 57-61, half of the rats in each dietary group received daily social defeat sessions using a resident-intruder protocol, and the other half were unstressed controls. Blood pressure was measured indirectly both before and after each defeat session. On the final day, rats were killed for physiological measures. Socially defeated rats showed large increases in serum corticosterone concentration and adrenal hypertrophy, indicating the effectiveness of this non-adapting stressor. Serum corticosterone level was also higher in rats fed with the junk-food diet post-weaning compared with those fed with chow only, but there were no significant effects of gestational or lactational dietary history.

Dietary fat intake in relation to cognitive change in high-risk women with cardiovascular disease or vascular factors

BACKGROUND/OBJECTIVES

Dietary fat intake may influence the rate of cognitive change among those at high risk due to vascular disease or risk factors.

SUBJECTS/METHODS

Women's Antioxidant Cardiovascular Study began in 1995-1996 as a randomized trial of antioxidants and B vitamin supplementation for secondary prevention in women with cardiovascular disease or ≥3 coronary risk factors. From 1998-1999, eligible participants aged ≥65 years were administered a telephone cognitive battery including five tests of general cognition, memory and category fluency (n=2551). Tests were administered four times over 5.4 years. The primary outcome was a global composite score averaging z-scores of all tests. Multivariable generalized linear models for repeated measures were used to evaluate the difference in cognitive decline rates across tertiles of total fat and various types of fat.

RESULTS

Total fat intake or different types of fat were not related to cognitive decline. However, older age significantly modified the association: among the oldest participants, higher intakes of mono- and polyunsaturated fat were inversely related to cognitive decline (P-interaction: 0.06 and 0.04, respectively), and the rate differences between the highest and lowest tertiles were cognitively equivalent to the rate differences observed with being 4-6 years younger.

CONCLUSIONS

In women at high risk of cognitive decline due to vascular disease or risk factors, dietary fat intake was not associated with 5-year cognitive change. However, a possible protective relation of unsaturated fats with cognitive decline in the oldest women warrants further study.

Dietary cholesterol impairs memory and memory increases brain cholesterol and sulfatide levels

Cholesterol and sulfatides play many important roles in learning and memory. To date, our observations about the effects of cholesterol on learning have been assessed during response acquisition; that is, the learning of a new memory. Here, we report for the first time to our knowledge, on the effect of a cholesterol diet on a previously formed memory. Rabbits were given trace conditioning of the nictitating membrane response for 10 days, then fed a 2% cholesterol diet for 8 weeks, and then assessed for memory recall of the initially learned task. We show that dietary cholesterol had an adverse effect on memory recall. Second, we investigated whether dietary cholesterol caused an increase in brain cholesterol and sulfatide levels in four major brain structures (hippocampus, frontal lobe, brainstem, and cerebellum) using a technique for analyzing myelin and myelin-free fractions separately. Although our data confirm previous findings that dietary cholesterol does not directly affect cholesterol and establish that it does not affect sulfatide levels in the brain, these levels did increase rather significantly in the hippocampus and frontal lobe as a function of learning and memory.

High-fat diet and hydrochlorothiazide increase oxidative stress in brain of rats

This study evaluated the effect of possible synergic interaction between high fat diet (HF) and hydrochlorothiazide (HCTZ) on biochemical parameters of oxidative stress in brain. Rats were fed for 16 weeks with a control diet or with an HF, both supplemented with different doses of HCTZ (0.4, 1.0, and 4.0 g kg(-1) of diet). HF associated with HCTZ caused a significant increase in lipid peroxidation and blood glucose levels. In addition, HF ingestion was associated with an increase in cerebral lipid peroxidation, vitamin C and non-protein thiol groups (NPSH) levels. There was an increase in vitamin C as well as NPSH levels in HCTZ (1.0 and 4.0 g kg(-1) of diet) and HF plus HCTZ groups. Na(+)-K(+)-ATPase activity of HCTZ (4.0 g kg(-1) of diet) and HCTZ plus HF-fed animals was significantly inhibited. Our data indicate that chronic intake of a high dose of HCTZ (4 g kg(-1) of diet) or HF change biochemical indexes of oxidative stress in rat brain. Furthermore, high-fat diets consumption and HCTZ treatment have interactive effects on brain, showing that a long-term intake of high-fat diets can aggravate the toxicity of HCTZ.

Classical conditioning of the rabbit's nictitating membrane response is a function of the duration of dietary cholesterol

Modifying dietary cholesterol may improve learning and memory but very high cholesterol can cause pathophysiology and death. Rabbits fed 2% cholesterol for 8, 10 or 12 weeks with 0.12 ppm copper added to distilled water and rabbits fed a normal diet without copper added to distilled water (0 weeks) were given a difficult trace classical conditioning task and an easy delay conditioning task pairing tone with corneal air puff. The majority of cholesterol-fed rabbits survived the deleterious effects of the diet but survival was an inverse function of the diet duration. Compared to controls, the level of classical conditioning and conditioning-specific reflex modification were an inverted "U"-shaped function of diet duration. Highest levels of responding occurred in rabbits on cholesterol for 10 weeks and trace conditioning was negatively correlated with the number of hippocampal beta-amyloid-positive neurons. Rabbits on the diet for 12 weeks responded at levels comparable to controls. The data provide support for the idea that dietary cholesterol may facilitate learning and memory but there is an eventual trade off with pathophysiological consequences of the diet.