Expression profile of hepatic genes related to lipid homeostasis in LSR heterozygous mice contributes to their increased response to high-fat diet.

Perturbations of lipid homeostasis manifest as dyslipidemias and obesity, which are significant risk factors for atherosclerosis and diabetes. Lipoprotein receptors in the liver are key players in the regulation of lipid homeostasis, among which the hepatic lipolysis stimulated lipoprotein receptor, LSR, was recently shown to play an important role in the removal of lipoproteins from the circulation during the postprandial phase. Since heterozygous LSR+/- mice demonstrate moderate dyslipidemia and develop higher body weight gain in response to high-fat diet compared with littermate LSR+/+ controls, we questioned if LSR heterozygosity could affect genes related to hepatic lipid metabolism. A target-specific qPCR array for 84 genes related to lipid metabolism was performed on mRNA isolated from livers of 6 mo old female LSR+/- mice and LSR+/+ littermates following a 6 wk period on a standard (STD) or high-fat diet (60% kcal, HFD). Of the 84 genes studied, 32 were significantly downregulated in STD-LSR+/- mice compared with STD-LSR+/+, a majority of which were PPARα target genes involved in lipid metabolism and transport, and insulin and adipokine-signaling pathways. Of these 32 genes, 80% were also modified in HFD-LSR+/+, suggesting that STD-LSR+/- mice demonstrated a predisposition towards a "high-fat"-like profile, which could reflect dysregulation of liver lipid homeostasis. Since similar profiles of genes were affected by either LSR heterozygosity or by high-fat diet, this would suggest that LSR is a key receptor in regulating hepatic lipid homeostasis, and whose downregulation combined with a Western-type diet may increase predisposition to diet-induced obesity.

No prognostic value of routine cerebrospinal fluid biomarkers in a population-based cohort of 407 multiple sclerosis patients.

BACKGROUND: We aimed to determine the association of clinical and routine cerebrospinal fluid biochemical markers (total protein, IgG index and oligoclonal bands) with disability in multiple sclerosis and whether these biomarkers assessed at diagnosis add prognostic value. METHODS: We followed a cohort of patients included in the Multiple Sclerosis Lorraine Register (eastern France) who had a diagnosis of multiple sclerosis for at least 5 years, as well as biological markers values and MRI findings (Barkhof's criteria). In a Cox regression model, endpoint was time to score of 4 on the Expanded Disability Status Scale (EDSS) (i.e., limited time walking without aid or rest for more than 500 m). RESULTS: For 407 patients included, the median time from multiple sclerosis onset to EDSS score 4 was 4.5 years [2.2-7.2]. Cerebrospinal fluid total protein factor < 500 mg/L was associated with EDSS score 4 on bivariate analysis (hazard ratio 0.66, 95% confidence interval 0.46-0.95, p = 0.02). On multivariate analysis, older age at disease onset (≥50 years) and initial primary progressive course of MS but not biological markers predicted worse prognosis. CONCLUSION: Routine cerebrospinal fluid biological markers at diagnosis were not prognostic factors of multiple sclerosis progression.

Ciliary neurotrophic factor cell-based delivery prevents synaptic impairment and improves memory in mouse models of Alzheimer's disease.

The development of novel therapeutic strategies for Alzheimer's disease (AD) represents one of the biggest unmet medical needs today. Application of neurotrophic factors able to modulate neuronal survival and synaptic connectivity is a promising therapeutic approach for AD. We aimed to determine whether the loco-regional delivery of ciliary neurotrophic factor (CNTF) could prevent amyloid-beta (Abeta) oligomer-induced synaptic damages and associated cognitive impairments that typify AD. To ensure long-term administration of CNTF in the brain, we used recombinant cells secreting CNTF encapsulated in alginate polymers. The implantation of these bioreactors in the brain of Abeta oligomer-infused mice led to a continuous secretion of recombinant CNTF and was associated with the robust improvement of cognitive performances. Most importantly, CNTF led to full recovery of cognitive functions associated with the stabilization of synaptic protein levels in the Tg2576 AD mouse model. In vitro as well as in vivo, CNTF activated a Janus kinase/signal transducer and activator of transcription-mediated survival pathway that prevented synaptic and neuronal degeneration. These preclinical studies suggest that CNTF and/or CNTF receptor-associated pathways may have AD-modifying activity through protection against progressive Abeta-related memory deficits. Our data also encourage additional exploration of ex vivo gene transfer for the prevention and/or treatment of AD.

Up-regulation of hepatic lipolysis stimulated lipoprotein receptor by leptin: a potential lever for controlling lipid clearance during the postprandial phase.

As a hepatic receptor for triglyceride-rich lipoproteins, the lipolysis-stimulated lipoprotein receptor (LSR) may be involved in the dynamics of lipid distribution between the liver and peripheral tissues. Here, we explore the potential role of leptin in regulating LSR. At physiological concentrations (1-10 ng/ml), leptin increased LSR protein and mRNA levels in Hepa1-6 cells through an ERK1/2-dependent and α-amanitin-sensitive pathway. In vivo, leptin treatment of C57BL6/Rj mice (1 µg 2×/d, 8 d) led to a significant increase in hepatic LSR mRNA and protein, decreased liver triglycerides and increased VLDL secretion as compared to controls. LSR(+/-) mice with elevated postprandial lipemia placed on a high-fat (60% kcal) diet exhibited accelerated weight gain and increased fat mass as compared to controls. While plasma leptin levels were increased 3-fold, hepatic leptin receptor protein levels and phosphorylation of ERK1/2 were significantly reduced. Therefore, leptin is an important regulator of LSR protein levels providing the means for the control of hepatic uptake of lipids during the postprandial phase. However, this may no longer be functional in LSR(+/-) mice placed under a chronic dietary fat load, suggesting that this animal model could be useful for the study of molecular mechanisms involved in peripheral leptin resistance.

Fertility in McCune Albright syndrome female: A case study focusing on AMH as a marker of ovarian dysfunction and a literature review.

BACKGROUND: The molecular basis of McCune Albright syndrome (MAS) is a recurrent GNAS Postzygotic gain of function sporadic mutation, resulting in a mosaic disease. Most of girls present precocious puberty, caused by the development of recurrent ovarian cysts with autonomous Hyperestrogenic stimulation. After menarche, the majority of patients with ovarian GNAS mutation have menstrual disturbances and infertility. OBJECTIVES: We wanted to focus on the fertility of MAS females and propose an appropriate management, by a detailed case report and an exhaustive review of the literature on fertility and pregnancy in MAS females. RESULTS: We present the case of a 29-year-old MAS female, who had previously undergone a unilateral ovariectomy and was managed by in vitro fertilization (IVF). Eight oocytes with many morphological abnormalities were retrieved. The GNAS mutation was found at a low frequency in follicular cells. The ovarian histopathological examination showed developing follicles of all stages, strongly expressing AMH by immunohistochemistry. In addition, AMH was high (45.5 pmol/L) and the AMH / AFC ratio (5.69 pmol/L per follicle) was much higher than in PCOS and control groups (2.16, and 1.34 respectively). CONCLUSIONS: Ovarian and endometrial involvement can be responsible for infertility in MAS women. IVF and oophorectomy may be useful in management. The genetic characterization of the different tissues may have a prognostic utility. Moreover, we suggest that the AMH could be a marker of the ovarian activity in MAS. Further studies are needed to clarify the potential oocyte abnormalities and the risk of miscarriages in order to guide genetic counseling.

Assessment of 18F-Florbetaben Amyloid PET Imaging in Patients with Suspected Alzheimer's Disease and Isolated Increase in Cerebrospinal Fluid Tau Proteins.

BACKGROUND/OBJECTIVE: The aim of this study was to assess, in routine, the rates with which an amyloid deposition was documented by 18F-florbetaben PET in patients with suspected Alzheimer's disease (AD) but with isolated increases in cerebrospinal fluid (CSF) tau-protein concentrations, and the subsequent impact of these PET results on medical management. METHODS: This prospective study included 34 patients with mild neurocognitive disorders (MND) and suspected AD (73±9 years, 16 women) and with abnormal CSF concentrations in total-tau (T-tau) and/or phosphorylated-tau (P-tau) proteins but normal Aß42 concentration and Aß42/Aß40 ratio. These patients were referred to 8F-florbetaben PET from which the PET-related changes in the confidence for AD diagnosis (low, intermediate, or high) and treatments were reported. RESULTS: The PET examinations were positive for amyloid deposition (brain amyloid plaque load, BAPL score >1) in none of the 9 patients with an increase in only T-tau proteins and in 8 among the 25 (32%) with an increase in P-tau proteins (one BAPL score of 2 and seven BAPL scores of 3). Knowledge of the PET results was associated with subsequent changes in diagnostic confidence in 44% of patients (15/34) and in the intention-to-treat with a cholinesterase inhibitor drug in 18% (6/34). CONCLUSION: In patients with suspected AD and isolated increase in CSF tau protein concentrations, an amyloid deposition is documented by 18F-florbetaben PET in as much as one third of cases when the concentration of P-tau is abnormal, and PET results are associated with significant further changes in medical management.

Towards a nutritional approach for prevention of Alzheimer's disease: biochemical and cellular aspects.

Alzheimer's disease (AD) is a major public health concern in all countries. Although the precise cause of AD is still unknown, a growing body of evidence supports the notion that soluble amyloid beta-peptide (Abeta) may be the proximate cause of synaptic injuries and neuronal death early in the disease. AD patients display lower levels of docosahexaenoic acid (DHA, C22:6 ; n-3) in plasma and brain tissues as compared to age-matched controls. Furthermore, epidemiological studies suggest that high DHA intake might have protective properties against neurodegenerative diseases. These observations are supported by in vivo studies showing that DHA-rich diets limits the synaptic loss and cognitive defects induced by Abeta peptide. Although the molecular basis of these neuroprotective effects remains unknown, several mechanisms have been proposed such as (i) regulation of the expression of potentially protective genes, (ii) activation of anti-inflammatory pathways, (iii) modulation of functional properties of the synaptic membranes along with changes in their physicochemical and structural features.

Cerebrospinal Fluid Aß42/Aß40 as a Means to Limiting Tube- and Storage-Dependent Pre-Analytical Variability in Clinical Setting.

BACKGROUND: Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers have recently been included in the criteria for AD diagnosis. Unfortunately, their wider use in routine and interpretation require more standardization, particularly for the pre-analytical steps. In particular, amyloid-ß (Aß)42 peptide measurement is strongly influenced by the type of collection tube and by repeated freeze/thaw cycles. OBJECTIVE: The objectives of this study were to compare, in clinical setting, the impact of collection tubes and the repetition of freeze/thaw cycles on Aß42 and Aß40 concentrations and consequently determine if the Aß42/Aß40 ratio could resolve the diagnosis difficulties related to these pre-analytical parameters. METHODS: CSF from 35 patients was collected in different polypropylene (PP) and stored at - 80°C after sampling. For CSF collected in the reference tube, three successive freeze-thaw cycles were done. Aß42 and Aß40 concentrations were determined in each condition in order to calculate the Aß42/Aß40 ratio. RESULTS: Our results showed that CSF Aß42 and Aß40 values were significantly different according to the type of collection tube and the number of freeze/thaw cycles. Although the calculation of the Aß42/Aß40 ratio eliminated the effect of PP tube-dependent variation, this was not the case for freeze-thaw cycle-associated variation. CONCLUSION: The use of Aß42/Aß40 ratio rather than Aß42 alone could contribute toward pre-analytical standardization, thus allowing the general use of CSF AD biomarkers in routine practice.

Maintenance of membrane organization in the aging mouse brain as the determining factor for preventing receptor dysfunction and for improving response to anti-Alzheimer treatments.

Although a major risk factor for Alzheimer's disease (AD), the "aging" parameter is not systematically considered in preclinical validation of anti-AD drugs. To explore how aging affects neuronal reactivity to anti-AD agents, the ciliary neurotrophic factor (CNTF)-associated pathway was chosen as a model. Comparison of the neuroprotective properties of CNTF in 6- and 18-month old mice revealed that CNTF resistance in the older animals is associated with the exclusion of the CNTF-receptor subunits from rafts and their subsequent dispersion to non-raft cortical membrane domains. This age-dependent membrane remodeling prevented both the formation of active CNTF-receptor complexes and the activation of prosurvival STAT3 and ERK1/2 pathways, demonstrating that age-altered membranes impaired the reactivity of potential therapeutic targets. CNTF-receptor distribution and CNTF signaling responses were improved in older mice receiving dietary docosahexaenoic acid, with CNTF-receptor functionality being similar to those of younger mice, pointing toward dietary intervention as a promising adjuvant strategy to maintain functional neuronal membranes, thus allowing the associated receptors to respond appropriately to anti-AD agents.

Cytosolic phospholipase A2 mediates neuronal apoptosis induced by soluble oligomers of the amyloid-beta peptide.

Recent data have revealed that soluble oligomeric forms of amyloid peptide (Abeta) may be the proximate effectors of the neuronal injury and death occurring in Alzheimer's disease (AD). However, the molecular mechanisms associated with the neuronal cell death induced by the nonfibrillar Abeta remain to be elucidated. In this study, we investigated the role of the cytosolic Ca2+-dependent phospholipase A2 (cPLA2), and its associated metabolic pathway, i.e., the arachidonic acid (AA) cascade, in the apoptotic cell death induced by soluble oligomers of Abeta. The treatment of rat cortical neurons with low concentrations of soluble Abeta(1-40) or Abeta(1-42) peptide resulted in an early calcium-dependent release of AA associated with a transient relocalization of cPLA2. Both cPLA2 antisense oligonucleotides and a selective inhibitor of cPLA2 activity abolished the release of AA from neurons and also protected cells against apoptosis induced by Abeta. Furthermore, inhibitors of the PKC, p38, and MEK/ERK pathways that are involved in cPLA2 phosphorylation and activation reduced Abeta-induced cell death. Finally, we demonstrate that inhibitors of cyclooxygenase-2 reduced the Abeta-induced cell death by 55%. Our studies suggest a novel neuronal response of soluble oligomers of Abeta, which occurs through a cPLA2 signaling cascade and an AA-dependent death pathway. This may prove to be crucial in AD processes and could provide important targets for drug development.

Improved Neuroprotection Provided by Drug Combination in Neurons Exposed to Cell-Derived Soluble Amyloid-ß Peptide.

Oligomeric amyloid-ß (Aß) peptide contributes to impaired synaptic connections and neurodegenerative processes, and as such, represents a primary therapeutic target for Alzheimer's disease (AD)-modifying approaches. However, the lack of efficacy of drugs that inhibit production of Aß demonstrates the need for a better characterization of its toxic effects, both on synaptic and neuronal function. Here, we used conditioned medium obtained from recombinant HEK-AßPP cells expressing the human amyloid-ß protein precursor (Aß-CM), to investigate Aß-induced neurotoxic and synaptotoxic effects. Characterization of Aß-CM revealed that it contained picomolar amounts of cell-secreted Aß in its soluble form. Incubation of primary cortical neurons with Aß-CM led to significant decreases in synaptic protein levels as compared to controls. This effect was no longer observed in neurons incubated with conditioned medium obtained from HEK-AßPP cells grown in presence of the γ-secretase inhibitor, Semagacestat or LY450139 (LY-CM). However, neurotoxic and pro-apoptotic effects of Aß-CM were only partially prevented using LY-CM, which could be explained by other deleterious compounds related to chronic oxidative stress that were released by HEK-AßPP cells. Indeed, full neuroprotection was observed in cells exposed to LY-CM by additional treatment with the antioxidant resveratrol, or with the pluripotent n-3 polyunsaturated fatty acid docosahexaenoic acid. Inhibition of Aß production appeared necessary but insufficient to prevent neurodegenerative effects associated with AD due to other neurotoxic compounds that could exert additional deleterious effects on neuronal function and survival. Therefore, association of various types of protective agents needs to be considered when developing strategies for AD treatment.

Membrane raft domains and remodeling in aging brain.

Lipids are the fundamental structural components of biological membranes. For a long time considered as simple barriers segregating aqueous compartments, membranes are now viewed as dynamic interfaces providing a molecular environment favorable to the activity of membrane-associated proteins. Interestingly, variations in membrane lipid composition, whether quantitative or qualitative, play a crucial role in regulation of membrane protein functionalities. Indeed, a variety of alterations in brain lipid composition have been associated with the processes of normal and pathological aging. Although not establishing a direct cause-and-effect relationship between these complex modifications in cerebral membranes and the process of cognitive decline, evidence shows that alterations in membrane lipid composition affect important physicochemical properties notably impacting the lateral organization of membranes, and thus microdomains. It has been suggested that preservation of microdomain functionality may represent an effective strategy for preventing or decelerating neuronal dysfunction and cerebral vulnerability, processes that are both aggravated by aging. The working hypothesis developed in this review proposes that preservation of membrane organization, for example, through nutritional supplementation of docosahexaenoic acid, could prevent disturbances in and preserve effective cerebral function.

Effect of acute and chronic psychostimulant drugs on redox status, AP-1 activation and pro-enkephalin mRNA in the human astrocyte-like U373 MG cells.

In order to approach the astroglial implication of addictive and neurotoxic processes associated with psychostimulant drug abuse, the effects of amphetamine or cocaine (1-100 microM) on redox status, AP-1 transcription factor and pro-enkephalin, an AP-1 target gene, were investigated in the human astrocyte-like U373 MG cells. We demonstrated an early increase in the generation of radical oxygen species and in the formation of 4-hydroxynonenal-adducts reflecting the pro-oxidant action of both substances. After 1 h or 96 h of treatment, Fos and Jun protein levels were altered and the DNA-binding activity of AP-1 was increased in response to both substances. Using supershift experiments, we observed that the composition of AP-1 dimer differed according to the substance and the duration of treatment. FRA-2 protein represented the main component of the chronic amphetamine- or cocaine-activated complexes, which suggests its relevance in the long-term effects of psychostimulant drugs. Concomitantly, the pro-enkephalin gene was differently regulated by either 6 h or 96 h of treatment. Because astrocytes interact extensively with the neurons in the brain, our data led us to conclude that oxidation-regulated AP-1 target genes may represent one of the molecular mechanisms underlying neuronal adaptation associated with psychostimulant dependence.

Increased susceptibility of dyslipidemic LSR+/- mice to amyloid stress is associated with changes in cortical cholesterol levels.

Alzheimer's disease (AD) is a neurodegenerative disease that has been linked to changes in cholesterol metabolism. Neuronal cholesterol content significantly influences the pro-apoptotic effect of amyloid-ß peptide42 (Aß42), which plays a key role in AD development. We previously reported that aged mice with reduced expression of the lipolysis stimulated lipoprotein receptor (LSR+/-), demonstrate membrane cholesterol accumulation and decreased intracellular lipid droplets in several brain regions, suggesting a potential role of LSR in brain cholesterol distribution. We questioned if these changes rendered the LSR+/- mouse more susceptible to Aß42-induced cognitive and biochemical changes. Results revealed that intracerebroventricular injection of oligomeric Aß42 in male 15-month old LSR+/+ and LSR+/- mice led to impairment in learning and long-term memory and decreased cortical cholesterol content of both groups; these effects were significantly amplified in the Aß42-injected LSR+/- group. Total latency of the Morris test was significantly and negatively correlated with cortical cholesterol content of the LSR+/- mice, but not of controls. Significantly lower cortical PSD95 and SNAP-25 levels were detected in Aß42-injected LSR+/- mice as compared to Aß42-injected LSR+/+ mice. In addition, 24S-hydroxy cholesterol metabolite levels were significantly higher in the cortex of LSR+/- mice. Taken together, these results suggest that changes in cortex cholesterol regulation as a result of the LSR+/- genotype were linked to increased susceptibility to amyloid stress, and we would therefore propose the aged LSR+/- mouse as a new model for understanding the link between modified cholesterol regulation as a risk factor for AD.

Oxidative stress impairs glutamate uptake in fibroblasts from patients with Alzheimer's disease.

Oxidative stress has been demonstrated in Alzheimer's disease (AD) brain and may affect glutamate transport (GT), thereby leading to excitotoxic neuronal death. Since oxidative stress markers have been shown also in peripheral tissues, we investigated possible GT alterations in fibroblast cultures obtained from 18 patients with AD and 15 control patients and analyzed the effects of the lipoperoxidation product 4-hydroxynonenal (4-HNE) and antioxidants. Basal GT was decreased by 60% in fibroblasts from patients with AD versus control patients. Exposure to HNE did not affect GT in control patients, but it reduced GT by 50% in patients with AD, without any concomitant change in cell viability; conversely, HNE exposure induced a larger increase in ROS intracellular levels in AD than in control fibroblasts. Glutathione and N-acetylcysteine completely blocked 4-HNE effects and also increased basal uptake in AD cells. Moreover, inhibition of glutathione synthesis in control fibroblasts by pretreatment with buthionine sulfoximine resulted in GT reduction (40%) and an increase in ROS levels after exposure to 4-HNE. Nevertheless, since there are no differences between GSH basal level in controls and patients with AD, the alteration of other antioxidant systems cannot be excluded. Our study supports the hypothesis of a systemic impairment of GT in AD, possibly linked to oxidative stress and to reduced antioxidant defenses, which may be partially reversed by antioxidant treatment. Therefore, we suggest fibroblast cultures as a tool for exploring pathogenetic mechanisms and possible therapeutic strategies in patients with AD.

Additional use of Aß42/Aß40 ratio with cerebrospinal fluid biomarkers P-tau and Aß42 increases the level of evidence of Alzheimer's disease pathophysiological process in routine practice.

BACKGROUND: Cerebrospinal fluid (CSF) biomarkers have recently been included in the criteria for the diagnosis of Alzheimer's disease (AD). Since interpretation of CSF profile requires the combination of three parameters, biological data are not always conclusive and isolated elevation of phosphorylated tau (P-tau) or reduction of amyloid-ß (Aß)42 alone can be observed. In these cases, Aß42/Aß40 ratio could be more relevant than Aß42 absolute values by considering inter-individual variations in the total amyloid load. OBJECTIVE: The objective of this study was to assess the use of Aß42/Aß40 ratio to improve the accuracy of biological conclusions in the diagnosis of patients with ambiguous CSF Aß42 or tau results. METHODS: Among 386 lumbar punctures analyzed in the lab in 2 years, 122 showed ambiguous biological data that were completed by CSF Aß40 quantification and Aß42/Aß40 ratio calculation. A biological conclusion was then made using 0.05 as the Aß42/Aß40 ratio cut-off. RESULTS: Our results showed that one-third of the biological profiles of patients with atypical dementia were ambiguous. The addition of Aß42/Aß40 ratio increased the proportion of interpretable biological profiles from 69% to 87%, without changing the conclusion when usual biomarkers (Aß42 and P-tau) were concordant. CONCLUSION: Our results support the use of the Aß42/Aß40 ratio in addition to the usual CSF AD biomarkers for patients with ambiguous biological profiles. This method could be specifically directed to this population in order to improve the level of certainty for clinical routine practice.

Critical role of cPLA2 in Aß oligomer-induced neurodegeneration and memory deficit.

Soluble beta-amyloid (Aß) oligomers are considered to putatively play a critical role in the early synapse loss and cognitive impairment observed in Alzheimer's disease. We previously demonstrated that Aß oligomers activate cytosolic phospholipase A(2) (cPLA(2)), which specifically releases arachidonic acid from membrane phospholipids. We here observed that cPLA(2) gene inactivation prevented the alterations of cognitive abilities and the reduction of hippocampal synaptic markers levels noticed upon a single intracerebroventricular injection of Aß oligomers in wild type mice. We further demonstrated that the Aß oligomer-induced sphingomyelinase activation was suppressed and that phosphorylation of Akt/protein kinase B (PKB) was preserved in neuronal cells isolated from cPLA(2)(-/-) mice. Interestingly, expression of the Aß precursor protein (APP) was reduced in hippocampus homogenates and neuronal cells from cPLA(2)(-/-) mice, but the relationship with the resistance of these mice to the Aß oligomer toxicity requires further investigation. These results therefore show that cPLA(2) plays a key role in the Aß oligomer-associated neurodegeneration, and as such represents a potential therapeutic target for the treatment of Alzheimer's disease.

The essential role of lipids in Alzheimer's disease.

In the absence of efficient diagnostic and therapeutic tools, Alzheimer's disease (AD) is a major public health concern due to longer life expectancy in the Western countries. Although the precise cause of AD is still unknown, soluble beta-amyloid (Abeta) oligomers are considered the proximate effectors of the synaptic injury and neuronal death occurring in the early stages of AD. Abeta oligomers may directly interact with the synaptic membrane, leading to impairment of synaptic functions and subsequent signalling pathways triggering neurodegeneration. Therefore, membrane structure and lipid status should be considered determinant factors in Abeta-oligomer-induced synaptic and cell injuries, and therefore AD progression. Numerous epidemiological studies have highlighted close relationships between AD incidence and dietary patterns. Among the nutritional factors involved, lipids significantly influence AD pathogenesis. It is likely that maintenance of adequate membrane lipid content could prevent the production of Abeta peptide as well as its deleterious effects upon its interaction with synaptic membrane, thereby protecting neurons from Abeta-induced neurodegeneration. As major constituents of neuronal lipids, n-3 polyunsaturated fatty acids are of particular interest in the prevention of AD valuable diet ingredients whose neuroprotective properties could be essential for designing preventive nutrition-based strategies. In this review, we discuss the functional relevance of neuronal membrane features with respect to susceptibility to Abeta oligomers and AD pathogenesis, as well as the prospective capacities of lipids to prevent or to delay the disease.

N-truncated amyloid-beta oligomers induce learning impairment and neuronal apoptosis.

N-terminal-truncated forms of amyloid-beta (A beta) peptide have been recently suggested to play a pivotal role early in Alzheimer's disease (AD). Among them, A beta 3(pE)-42 peptide, starting with pyroglutamyl at residue Glu-3, is considered as the predominant A beta species in AD plaques and pre-amyloid lesions. Its abundance is reported to be directly proportional to the severity of the clinical phenotype. The present study investigates the effects of soluble oligomeric A beta 3(pE)-42 after intracerebroventricular injection on mice learning ability and the molecular mechanisms of its in vitro neurotoxicity. Mice injected with soluble A beta 3(pE)-42 or A beta(l-42) displayed impaired spatial working memory and delayed memory acquisition in Y-maze and Morris water maze tests, while those injected with soluble A beta(42-1) showed no effect. These cognitive alterations were associated with free radical overproduction in the hippocampus and olfactory bulbs, but not in the cerebral cortex or cerebellum. In vitro, A beta 3(pE)-42 oligomers induced a redox-sensitive neuronal apoptosis involving caspase activation and an arachidonic acid-dependent pro-inflammatory pathway. These data suggest that A beta 3(pE)-42 could mediate the neurodegenerative process and subsequent cognitive alteration occurring in preclinical AD stages.

Docosahexaenoic acid prevents neuronal apoptosis induced by soluble amyloid-beta oligomers.

A growing body of evidence supports the notion that soluble oligomers of amyloid-beta (Abeta) peptide interact with the neuronal plasma membrane, leading to cell injury and inducing death-signalling pathways that could account for the increased neurodegeneration occurring in Alzheimer's disease (AD). Docosahexaenoic acid (DHA, C22:6, n-3) is an essential polyunsaturated fatty acid in the CNS and has been shown in several epidemiological and in vivo studies to have protective effects against AD and cognitive alterations. However, the molecular mechanisms involved remain unknown. We hypothesized that DHA enrichment of plasma membranes could protect neurones from apoptosis induced by soluble Abeta oligomers. DHA pre-treatment was observed to significantly increase neuronal survival upon Abeta treatment by preventing cytoskeleton perturbations, caspase activation and apoptosis, as well as by promoting extracellular signal-related kinase (ERK)-related survival pathways. These data suggest that DHA enrichment probably induces changes in neuronal membrane properties with functional outcomes, thereby increasing protection from soluble Abeta oligomers. Such neuroprotective effects could be of major interest in the prevention of AD and other neurodegenerative diseases.