Pleiotropic Effect of Human ApoE4 on Cerebral Ceramide and Saturated Fatty Acid Levels.

BACKGROUND: Apolipoprotein E (ApoE) is known for its role in lipid trafficking and the ɛ4 allele is a risk factor for late onset Alzheimer's disease (AD). Recently, aberrant ceramide and fatty acid (FA) levels have been implicated in AD. OBJECTIVE: To determine the specific effects of human ApoE4 (hE4) on cerebral ceramide and FA content during chow or a high fat/high cholesterol (HFHC) diet. METHODS: Cerebral ceramide and FA profiles were determined by LC-MSMS in 15-month-old female wild-type (WT), ApoE-knockout (E0), and hE4-knockin mice fed chow or a HFHC diet for 3 months. mRNA levels of genes involved in ceramide and FA metabolism were determined by qPCR. RESULTS: Similar to E0, hE4 mice displayed lower cerebral total ceramide, Cer16 : 0, and Cer24 : 1 levels than WT mice on both diets. Akin to WT mice, hE4 mice had lower total and saturated FA levels on chow than E0 mice. The HFHC diet significantly increased total and saturated FA levels in hE4 mice. Chow-fed hE4 mice showed lower mRNA levels of ceramide synthase (CerS) 6, acid sphingomyelinase, and of most ceramide and FA transporters than WT and E0 mice. The HFHC diet downregulated the expression of CerSs in hE4 and WT mice, and of ceramide and FA transporters in WT mice, but not in E0 mice. CONCLUSION: hE4 reduced cerebral ceramide levels to levels observed in E0 mice independent of diet. The HFHC diet increased cerebral FA levels in hE4 mice. This was associated with alterations in the expression of ceramide and FA transporters specifically in hE4 mice.

The Effect of a High-Fat Diet on Brain Plasticity, Inflammation and Cognition in Female ApoE4-Knockin and ApoE-Knockout Mice.

Apolipoprotein E4 (ApoE4), one of three common isoforms of ApoE, is a major risk factor for late-onset Alzheimer disease (AD). ApoE-deficient mice, as well as mice expressing human ApoE4, display impaired learning and memory functions and signs of neurodegeneration. Moreover, ApoE protects against high-fat (HF) diet induced neurodegeneration by its role in the maintenance of the integrity of the blood-brain barrier. The influence of a HF diet on the progression of AD-like cognitive and neuropathological changes was assessed in wild-type (WT), human ApoE4 and ApoE-knockout (ApoE-/-) mice to evaluate the modulatory role of ApoE in this process. From 12 months of age, female WT, ApoE4, and ApoE-/- mice were fed either a standard or a HF diet (19% butter, 0.5% cholate, 1.25% cholesterol) throughout life. At 15 months of age mice performed the Morris water maze, evaluating spatial learning and memory. ApoE-/- showed increased spatial learning compared to WT mice (p = 0.009). HF diet improved spatial learning in WT mice (p = 0.045), but did not affect ApoE4 and ApoE-/- mice. Immunohistochemical analyses of the hippocampus demonstrated increased neuroinflammation (CD68) in the cornu ammonis 1 (CA1) region in ApoE4 (p = 0.001) and in ApoE-/- (p = 0.032) mice on standard diet. HF diet tended to increase CD68 in the CA1 in WT mice (p = 0.052), while it decreased in ApoE4 (p = 0.009), but ApoE-/- remained unaffected. A trend towards increased neurogenesis (DCX) was found in both ApoE4 (p = 0.052) and ApoE-/- mice (p = 0.068). In conclusion, these data suggest that HF intake induces different effects in WT mice compared to ApoE4 and ApoE-/- with respect to markers for cognition and neurodegeneration. We propose that HF intake inhibits the compensatory mechanisms of neuroinflammation and neurogenesis in aged female ApoE4 and ApoE-/- mice.

Effect of perinatally supplemented flavonoids on brain structure, circulation, cognition, and metabolism in C57BL/6J mice.

Evidence suggests that flavanol consumption can beneficially affect cognition in adults, but little is known about the effect of flavanol intake early in life. The present study aims to assess the effect of dietary flavanol intake during the gestational and postnatal period on brain structure, cerebral blood flow (CBF), cognition, and brain metabolism in C57BL/6J mice. Female wild-type C57BL/6J mice were randomly assigned to either a flavanol supplemented diet or a control diet at gestational day 0. Male offspring remained on the corresponding diets throughout life and performed cognitive and behavioral tests during puberty and adulthood assessing locomotion and exploration (Phenotyper and open field), sensorimotor integration (Rotarod and prepulse inhibition), and spatial learning and memory (Morris water maze, MWM). Magnetic resonance spectroscopy and imaging at 11.7T measured brain metabolism, CBF, and white and gray matter integrity in adult mice. Biochemical and immunohistochemical analyses evaluated inflammation, synaptic plasticity, neurogenesis, and vascular density. Cognitive and behavioral tests demonstrated increased locomotion in Phenotypers during puberty after flavanol supplementation (p = 0.041) but not in adulthood. Rotarod and prepulse inhibition demonstrated no differences in sensorimotor integration. Flavanols altered spatial learning in the MWM in adulthood (p = 0.039), while spatial memory remained unaffected. Additionally, flavanols increased diffusion coherence in the visual cortex (p = 0.014) and possibly the corpus callosum (p = 0.066) in adulthood. Mean diffusion remained unaffected, a finding that corresponds with our immunohistochemical data showing no effect on neurogenesis, synaptic plasticity, and vascular density. However, flavanols decreased CBF in the cortex (p = 0.001) and thalamus (p = 0.009) in adulthood. Brain metabolite levels and neuroinflammation remained unaffected by flavanols. These data suggest that dietary flavanols results in subtle alterations in brain structure, locomotor activity and spatial learning. Comparison of these data to published findings in aging or neurodegeneration suggests that benefits of dietary flavanols may increase with advancing age and in disease.

Impact of dietary n-3 polyunsaturated fatty acids on cognition, motor skills and hippocampal neurogenesis in developing C57BL/6J mice.

Maternal intake of omega-3 polyunsaturated fatty acids (n-3 PUFA) is critical during perinatal development of the brain. Docosahexaenoic acid (DHA) is the most abundant n-3 PUFA in the brain and influences neuronal membrane function and neuroprotection. The present study aims to assess the effect of dietary n-3 PUFA availability during the gestational and postnatal period on cognition, brain metabolism and neurohistology in C57BL/6J mice. Female wild-type C57BL/6J mice at day 0 of gestation were randomly assigned to either an n-3 PUFA deficient diet (0.05% of total fatty acids) or an n-3 PUFA adequate diet (3.83% of total fatty acids) containing preformed DHA and its precursor α-linolenic acid. Male offspring remained on diet and performed cognitive tests during puberty and adulthood. In adulthood, animals underwent (31)P magnetic resonance spectroscopy to assess brain energy metabolites. Thereafter, biochemical and immunohistochemical analyses were performed assessing inflammation, neurogenesis and synaptic plasticity. Compared to the n-3 PUFA deficient group, pubertal n-3 PUFA adequate fed mice demonstrated increased motor coordination. Adult n-3 PUFA adequate fed mice exhibited increased exploratory behavior, sensorimotor integration and spatial memory, while neurogenesis in the hippocampus was decreased. Selected brain regions of n-3 PUFA adequate fed mice contained significantly lower levels of arachidonic acid and higher levels of DHA and dihomo-γ-linolenic acid. Our data suggest that dietary n-3 PUFA can modify neural maturation and enhance brain functioning in healthy C57BL/6J mice. This indicates that availability of n-3 PUFA in infant diet during early development may have a significant impact on brain development.

Long-chain polyunsaturated fatty acids (LCPUFA) from genesis to senescence: the influence of LCPUFA on neural development, aging, and neurodegeneration.

Many clinical and animal studies demonstrate the importance of long-chain polyunsaturated fatty acids (LCPUFA) in neural development and neurodegeneration. This review will focus on involvement of LCPUFA from genesis to senescence. The LCPUFA docosahexaenoic acid and arachidonic acid are important components of neuronal membranes, while eicosapentaenoic acid, docosahexaenoic acid, and arachidonic acid also affect cardiovascular health and inflammation. In neural development, LCPUFA deficiency can lead to severe disorders like schizophrenia and attention deficit hyperactivity disorder. Perinatal LCPUFA supplementation demonstrated beneficial effects in neural development in humans and rodents resulting in improved cognition and sensorimotor integration. In normal aging, the effect of LCPUFA on prevention of cognitive impairment will be discussed. LCPUFA are important for neuronal membrane integrity and function, and also contribute in prevention of brain hypoperfusion. Cerebral perfusion can be compromised as result of obesity, cerebrovascular disease, hypertension, or diabetes mellitus type 2. Last, we will focus on the role of LCPUFA in most common neurodegenerative diseases like Alzheimer's disease and Parkinson's disease. These disorders are characterized by impaired cognition and connectivity and both clinical and animal supplementation studies have shown the potential of LCPUFA to decrease neurodegeneration and inflammation. This review shows that LCPUFA are essential throughout life.

Impact of a multi-nutrient diet on cognition, brain metabolism, hemodynamics, and plasticity in apoE4 carrier and apoE knockout mice.

Lipid metabolism and genetic background together strongly influence the development of both cardiovascular and neurodegenerative diseases like Alzheimer's disease (AD). A non-pharmacological way to prevent the genotype-induced occurrence of these pathologies is given by dietary behavior. In the present study, we tested the effects of long-term consumption of a specific multi-nutrient diet in two models for atherosclerosis and vascular risk factors in AD: the apolipoprotein ε4 (apoE4) and the apoE knockout (apoE ko) mice. This specific multi-nutrient diet was developed to support neuronal membrane synthesis and was expected to contribute to the maintenance of vascular health. At 12 months of age, both genotypes showed behavioral changes compared to control mice and we found increased neurogenesis in apoE ko mice. The specific multi-nutrient diet decreased anxiety-related behavior in the open field, influenced sterol composition in serum and brain tissue, and increased the concentration of omega-3 fatty acids in the brain. Furthermore, we found that wild-type and apoE ko mice fed with this multi-nutrient diet showed locally increased cerebral blood volume and decreased hippocampal glutamate levels. Taken together, these data suggest that a specific dietary intervention has beneficial effects on early pathological consequences of hypercholesterolemia and vascular risk factors for AD.

A longitudinal study of cognition, proton MR spectroscopy and synaptic and neuronal pathology in aging wild-type and AßPPswe-PS1dE9 mice.

Proton magnetic resonance spectroscopy ((1)H MRS) is a valuable tool in Alzheimer's disease research, investigating the functional integrity of the brain. The present longitudinal study set out to characterize the neurochemical profile of the hippocampus, measured by single voxel (1)H MRS at 7 Tesla, in the brains of AßPPSswe-PS1dE9 and wild-type mice at 8 and 12 months of age. Furthermore, we wanted to determine whether alterations in hippocampal metabolite levels coincided with behavioral changes, cognitive decline and neuropathological features, to gain a better understanding of the underlying neurodegenerative processes. Moreover, correlation analyses were performed in the 12-month-old AßPP-PS1 animals with the hippocampal amyloid-ß deposition, TBS-T soluble Aß levels and high-molecular weight Aß aggregate levels to gain a better understanding of the possible involvement of Aß in neurochemical and behavioral changes, cognitive decline and neuropathological features in AßPP-PS1 transgenic mice. Our results show that at 8 months of age AßPPswe-PS1dE9 mice display behavioral and cognitive changes compared to age-matched wild-type mice, as determined in the open field and the (reverse) Morris water maze. However, there were no variations in hippocampal metabolite levels at this age. AßPP-PS1 mice at 12 months of age display more severe behavioral and cognitive impairment, which coincided with alterations in hippocampal metabolite levels that suggest reduced neuronal integrity. Furthermore, correlation analyses suggest a possible role of Aß in inflammatory processes, synaptic dysfunction and impaired neurogenesis.

Atorvastatin does not affect ischaemia-induced phosphatidylserine exposition in humans in-vivo.

AIM: Statins can induce pharmacologic preconditioning and thereby reduce infarct size. Cellular phosphatidylserine (PS) exposition occurs in the course of ischaemia and reperfusion and has been associated with injury. In this experiment we studied the effect of atorvastatin on PS exposition after a standardised ischaemia and reperfusion challenge. METHODS: In a double-blind randomised cross-over trial 30 healthy volunteers were allocated to 3 day treatment with atorvastatin (80 mg/day) and placebo (n = 24), or placebo treatment twice (n = 6). At the end of each treatment period, volunteers underwent 10 minutes of forearm ischaemic exercise. At reperfusion radiolabeled annexin A5 was administered intravenously and Gamma camera imaging of both hands was performed 1 and 4 hours after reperfusion. RESULTS: Annexin A5 targeting was not different between atorvastatin treatment (26.1 ± 9.8% and 24.0 ± 9.5% respectively at 1 and 4 hours after reperfusion) and placebo treatment (25.6 ± 11.0% and 24.5 ± 10.7%) (p = 0.99). Our time control experiment did not reveal a carry-over effect. CONCLUSIONS: Our results show that treatment with atorvastatin 80 mg does not reduce forearm PS exposition after ischaemic exercise. This suggests that the role of PS exposure in the prevention of ischemia and reperfusion injury by short term treatment with atorvastatin is limited.

Cholesterol and synaptic compensatory mechanisms in Alzheimer's disease mice brain during aging.

Research into the development of Alzheimer's disease (AD) provides increasing evidence that vascular risk factors, including high serum cholesterol, might influence the progression of cognitive impairment and neural degeneration. In this study, we investigated the effects of high dietary cholesterol intake and the cholesterol-lowering liver X receptor-agonist T0901317 on capillary density, amyloid-ß deposition, and presynaptic boutons in the hippocampus of adult (8 months) and aged (15 months) AßPPswe-PS1dE9 and wild-type mice to elucidate how cholesterol may affect neurodegenerative processes in aging and AD. Our results show increased number of presynaptic boutons in 15-month-old AßPP-PS1 mice compared to age-matched wild-type animals, but no difference at 8 months of age. High cholesterol intake accelerated this response by increasing the amount of presynaptic boutons at 8 and 15 months of age, while T0901317 intake decreased the amount of presynaptic boutons in 15-month-old AßPP-PS1 mice. These findings suggest a synaptic compensatory response to maintain connectivity during aging. We hypothesize that high cholesterol intake may cause impaired cerebral blood flow inducing ischemia, fortifying the above mentioned hypothesis of a compensatory mechanism. Contrarily, cholesterol-lowering agents may positively influence cerebral circulation, thereby diminishing aggravation of AD-like pathology.