Alzheimer's disease: clinical and pathological characteristics

The Associations of Plasma/Serum Carotenoids with Alzheimer's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Multiple lines of evidence indicate protective effects of carotenoids in Alzheimer's disease (AD). However, previous epidemiological studies reported inconsistent results regarding the associations between carotenoids levels and the risk of AD.

OBJECTIVE

Our study aims to evaluate the associations of six major members of carotenoids with the occurrence of AD by conducting a systematic review and meta-analysis.

METHODS

Following PRISMA guidelines, a comprehensive literature search of PubMed, Web of Science, Ebsco, and PsycINFO databases was conducted, and the quality of each included studies was evaluated by a validated scoring systems. Standardized mean differences (SMD) with 95% confidence intervals (CI) were determined by using a random effects model. Heterogeneity was evaluated by I2 statistics. Publication bias was detected using funnel plots and Egger's test.

RESULTS

Sixteen studies, with 10,633 participants were included. Pooled analysis showed significantly lower plasma/serum levels of lutein (SMD = -0.86, 95% CI: -1.67 to -0.05, p = 0.04) and zeaxanthin (SMD = -0.59; 95% CI: -1.12 to -0.06, p = 0.03) in patients with AD versus cognitively intact controls, while α-carotene (SMD = 0.21, 95% CI: -0.68 to 0.26, p = 0.39), β-carotene (SMD = 0.04, 95% CI: -0.57 to 0.65, p = 0.9), lycopene (SMD = -0.12, 95% CI: -0.96 to 0.72, p = 0.78), and β-cryptoxanthin (SMD = -0.09, 95% CI: -0.83 to 0.65, p = 0.81) did not achieve significant differences.

CONCLUSION

Of six major members of carotenoids, only lutein and zeaxanthin concentrations in plasma/serum were inversely related to the risk of AD. More high-quality longitudinal studies are needed to verify these findings.

Evolution of beta-amyloid induced neuropathology: magnetic resonance imaging and anatomical comparisons in the rodent hippocampus

Alzheimer's disease (AD) is characterized by the anatomical appearance of beta-amyloid (betaA) plaques and neurofibrillary tangles. These changes are also associated with cyclical inflammation, oxidative damage and, as inferred from the autopsied brains of patients, progressive injury to neurons. Here, we report the short-term effects of an intrahippocampal injection of the toxic betaA peptide fragment 25-35 in rats using quantitative magnetic resonance imaging (MRI) methods. Physiological changes within the cornu ammonis 1 (CA1) region of the hippocampus were monitored using a 1.5 T scanner at time points of 0.25, 1 and 24 h, and 7 and 14 days post injection. Spin echo T2-weighted (T2W) and diffusion weighted (DW) images were sequentially acquired. Apparent diffusion coefficients (ADC) were calculated and compared with histological alterations. A significant elevation in mean ADC values (17%) was observed in the ipsilateral CA1 at 14 days. The ADC changes were associated with disrupted pyramidal cells and nuclear lysis observed in histological sections. The contralateral CA1 exhibited a significant decrease in mean ADC of 15% at 14 days post treatment. Histological changes in the contralateral hippocampus suggested decreased neuronal density. T2W maps revealed no significant differences between the active betaA 25-35 fragment and its non-active analog, betaA 35-25. In conclusion, these results, based on changes in hippocampal ADC, demonstrate that the betaA 25-35 treatment induced pathology consistent with edema and cellular necrosis. This is the first report describing the evolution of AD-like pathology in an animal model using DW imaging.

Importance of immunological and inflammatory processes in the pathogenesis and therapy of Alzheimer's disease

The contribution of autoimmune processes or inflammatory components in the etiology and pathogenesis of Alzheimer's disease (AD) has been suspected for many years. The presence of antigen-presenting, HLA-DR-positive and other immunoregulatory cells, components of complement, inflammatory cytokines and acute phase reactants have been established in tissue of AD neuropathology. Although these data do not confirm the immune response as a primary cause of AD, they indicate involvement of immune processes at least as a secondary or tertiary reaction to the preexisting pathogen and point out its driving-force role in AD pathogenesis. These processes may contribute to systemic immune response. Thus, experimental and clinical studies indicate impairments in both humoral and cellular immunity in an animal model of AD as well as in AD patients. On the other hand, anti-inflammatory drugs applied for the treatment of some chronic inflammatory diseases have been shown to reduce risk of AD in these patients. Therefore, it seems that anti-inflammatory drugs and other substances which can control the activity of immunocompetent cells and the level of endogenous immune response can be valuable in the treatment of AD patients.

A preliminary report: a new scale to identify the pseudodementia syndrome

BACKGROUND

The literature was reviewed to abstract items which were claimed to distinguish organic dementia from pseudodementia. Their discriminating powers were tested in a prospective study. Eighteen of these items were selected to create a questionnaire which should distinguish organic dementia from pseudodementia. The gold standard was the final diagnosis given by a consultant psychiatrist 12-14 months later.

METHOD

One hundred and twenty-eight patients referred to our service with a differential diagnosis of depressive pseudodementia were screened using a checklist of 44 characteristic features (in the form of questions with 'yes' or 'no' answers) which were claimed in the literature of differentiate between organic dementia and depressive pseudodementia. This checklist covers the areas of history, clinical data, insight and performance.

RESULTS

Forty points (questions) out of the 44 in the checklist showed significant discriminating power to differentiate dementia from depressive pseudodementia (p < 0.01). A principal component and factor analysis was performed from which 18 questions were extracted. The shortened questionnaire was able to classify (43/44 cases) 98% of dementia cases and (60/63) 95% of depression correctly. A new definition has been introduced for 'pseudodementia' as a syndrome of reversible subjective or objective cognitive problems caused by non-organic disorder. Thus depressive pseudodementia may be classified into two subtypes. Type I is a group of patients who have depressive symptoms with subject complaint of dysmnesia without measurable intellectual deficits. Type II is a group of patients who have depressive symptoms and show poor cognitive performance based on poor concentration not due to organic disorder.

Age-dependent accumulation of advanced glycosylation end products in human neurons

Glucose can react nonenzymatically with free amino groups on proteins and form advanced glycosylation end-products (AGEPs), that have been previously isolated and characterised in aging human connective tissues. In this study, we used immunocytochemistry to examine the distribution of AGEPs in the aging human brain. Our findings show that the pyramidal neurons selectively accumulate AGEP-containing vesicles in an age-dependent manner. In addition, our results demonstrate that AGEPs accumulate in the same type of neuron that degenerates in Alzheimer's disease.

Regional brain activity of free radical defense enzymes in autopsy samples from patients with Alzheimer's disease and from nondemented controls

Several lines of evidence support the hypothesis that oxygen free radicals are involved in the destruction of neurons in various degenerative disorders of the central nervous system. The activities of superoxide dismutase, catalase and glutathione peroxidase, three enzymes that contribute to the cellular defenses against free radical damage, were measured in different areas of autopsy brains from patients with Alzheimer's disease and from age matched controls. All brains were removed within 24 hours of the time of death and were cut in half sagitally. One half was stored frozen at -86 degrees C and the other half was examined histologically to confirm the presence or absence of Alzheimer's disease. Samples were taken from the frozen half for the enzyme assays. In control brains, the activity of superoxide dismutase is significantly higher in the cerebellum, frontal cortex and hippocampus than it is in the temporal cortex, parietal cortex and entorhinal cortex. The activity of catalase is significantly higher in cerebellum and frontal cortex than in hippocampus, parietal cortex and entorhinal cortex. Glutathione peroxidase activity is uniform across all brain areas studied. In Alzheimer's brains, superoxide dismutase activity is not statistically different among the various brain regions studied, but it is significantly lower than control in the cerebellum (-27%), frontal cortex (-27%) and hippocampus (-35%). Catalase is significantly higher in Alzheimer's cerebellum, frontal cortex and temporal cortex than in Alzheimer's hippocampus, parietal cortex and entorhinal cortex. However, there are no significant differences in catalase activity between Alzheimer's and control samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitochondria from Alzheimer's fibroblasts show decreased uptake of calcium and increased sensitivity to free radicals

Many of the biological abnormalities seen in samples of the brain and other tissues from patients with Alzheimer's disease, are consistent with an excessive action of oxygenic free radicals. Mitochondria from fibroblasts grown in tissue culture from skin samples taken at autopsy from patients with histologically confirmed Alzheimer's disease, take up significantly less calcium than do fibroblast mitochondria from age matched non-demented controls. Following exposure to oxygenic free radicals generated by adding ferrous ions to the incubation mixture, calcium uptake is increased to a greater extent in Alzheimer's mitochondria than in controls. At the doses used, pretreatment with the lazaroid antioxidant drug U-74500A, or with the iron chelator deferoxamine, prevents the free radical induced increase in calcium uptake by control mitochondria, but provides only partial protection for Alzheimer's mitochondria. These observations suggest that Alzheimer's fibroblast mitochondria have impaired calcium transport processes and show increased sensitivity to oxygenic free radicals.

Primary or depressive dementia: mental status screening

In the course of interviewing a patient, several aspects of everyday functioning must be covered to provide a range of observations necessary to suggest a provisional diagnosis. First organized by Adolf Meyer, the mental status examination consists of several techniques which, in recent times, have been shortened, structured and standardized to cover maximal ground in minimal time. In this article, the most popular scales are reviewed psychometrically for their capacity to detect, as first-stage instruments, cognitive impairment suggestive of primary dementia in the context of varying prevalence rates and confounding factors like sensory impairments, sociodemographics and depressive states. Several of the measures are found adequate in some respects though not in others, but all of the better ones, when used as front line implements during clinical intake, regularly improve detection over base rates. An analytical method modelled on ROC procedures is then described contrasting two of them before newer instruments are considered which aim to improve sensitivity at relatively little cost to specificity.

Oxygen free radicals and brain dysfunction

Oxygen free radicals, any chemical moiety containing an oxygen atom with an unpaired electron in the outer orbital shell, are generated during many normal biochemical reactions in living tissue. The unpaired electron makes these compounds highly reactive and they can initiate disruptive peroxidation reactions with various substrates important to the survival of cells such as proteins, lipids and nucleic acids. A fairly complex defense system has evolved to protect living tissue from free radicals and to minimize the damage they might cause. Neurons are especially vulnerable to free radical attack and impaired defenses or exposure to excess free radicals can lead to neuronal death. Free radicals contribute to neuronal loss in cerebral ischemia and hemorrhage and may be involved in the degeneration of neurons in epilepsy, schizophrenia, tardive dyskinesia, normal aging, Parkinson's Disease and Alzheimer's Disease. The development of drugs that limit or prevent the attack of free radicals on neurons would be an important advance in the treatment of these conditions.

Autopsy samples of Alzheimer's cortex show increased peroxidation in vitro

The formation of thiobarbituric acid-reactive products was measured as an index of peroxidation by oxygen free radicals in homogenates of frontal cortex and cerebellum from brains taken at autopsy and verified histologically as being Alzheimer's (n = 6) or normal (n = 6). Compared with controls, basal peroxidation is significantly higher in Alzheimer's cortex, and this difference is also evident in the presence of exogenous iron. Peroxidation in cerebellum and levels of total glutathione, RNA, and DNA in cortex and cerebellum do not differ significantly between Alzheimer's brain and controls. Iron-induced peroxidation in cortex is reduced by the lazaroid U-74500A, with calculated IC50 values that are significantly higher in Alzheimer's samples (10 microM) than in controls (2.5 microM). These observations suggest that cerebral cortex from Alzheimer's patients differs from controls with respect to in vitro peroxidation.