Is hemochromatosis a risk factor for Alzheimer's disease?

Excess iron accumulation in the brain is a consistent observation in Alzheimer's Disease. Iron affects amyloid precursor protein (AbetaPP) processing and promotes deposition of Abeta. Iron is also among the most potent biological toxins because of its ability to react with oxygen to form reactive oxygen species. Consequently, elucidation of the mechanisms associated with maintaining brain iron homeostasis is fundamentally important to understanding the underlying pathogenesis in AD. The iron overload disorder, Hemochromatosis, is the most common genetic disorder (1:200) so a significant percentage of AD patients can be expected to carry this mutation. Heterozygotes for this mutation also have an increased, but sub-clinical iron burden. Given the high percentage of the population who are at significant risk for iron overload, we propose that the hemochromatosis mutation be considered as a confounding factor when evaluating the contribution of genetic associations with AD and treatment strategies and efficacy. Two recent papers and new evidence presented here that the protein associated with hemochromatosis is expressed on blood vessels, choroid plexus and the ependymal cells in the brain are offered as support for this proposal.     

Is cholesterol a culprit in Alzheimer's disease?

A pivotal role for cholesterol influence on production of the putative AD toxin, amyloid beta (Abeta), has been amply demonstrated. More importantly, this relationship has consistently been identified in both in vivo and in vitro studies. Lowering cholesterol levels has been shown to cause a beneficial effect on Abeta levels in animal models, and epidemiological data indicate a beneficial effect on the risk of AD with prior statin use. Blinded, placebo-controlled clinical investigations assessing the benefit of statins on cognitive indices in mild to moderate AD are ongoing and one will be reported on soon. A prospective study assessing the effect of statin use on the risk of AD is under way as an observational component of a placebo-controlled primary prevention trial testing anti-inflammatory agents. Nevertheless, the foregoing suggests that routine monitoring and intervention for elevated cholesterol levels among the elderly could promote more than a healthy heart.     

Alzheimer's disease: cholesterol a menace?

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease manifested by cognitive and memory deterioration, culminating in a spectrum of neuropsychiatric disturbances and the impairment of daily activities. AD is a multifactorial disease with a range of contributing factors which includes genes and diet. The magnitude of AD is reflected in the loss of individuality of the affected person and in the terminal course through which the disease develops. In this review, we aim to provide a background on AD and the contribution of cholesterol in the etiology of Alzheimer's. Cholesterol seems to be intimately linked with the generation of amyloid plaques, which is central to the pathogenesis of AD. Although there are conflicting reports on the role of cholesterol in AD, majority of the studies point out the positive association of cholesterol with AD.     

Cholesterol levels in mood disorders: high or low?

Objectives: To assess cholesterol levels in patients with mood disorders.

Methods: All consecutively admitted patients meeting inclusion criteria (n=50) who were hospitalized in an affective disorders unit received assessments of cholesterol levels. Correlations were made with diagnosis using DSM-IV criteria, current mood states, and other clinical and demographic features of illness. Exclusion criteria included current alcohol abuse, medical illnesses that could influence cholesterol levels, eating disorders, and age greater than 70 years.

Results: Cholesterol levels did not differ based on diagnostic status of unipolar depression or bipolar disorder. In the total sample, cholesterol levels were lower in patients with current manic (170.2±38.9, p=0.05) and depressive (182.0±42.0) than in mixed (226.4±43.3) episodes (p=0.05). In subgroups of patients with bipolar disorder, manic episodes (169.9±38.8, n=9) were associated with lower cholesterol levels than depressive (201.0±49.4) or mixed (226.4±44.4) episodes (p=0.02 for comparison of manic and mixed episodes). Body mass index (BMI), age, alcohol use, and gender did not account for these findings.

Conclusions: Cholesterol levels were lower in manic and depressive than in mixed episodes. No differences were found between diagnoses of unipolar or bipolar mood disorders. Cholesterol may be a state rather than a trait function, and may be influenced by the acute mood state.     

Is MTHFR polymorphism a risk factor for Alzheimer's disease like APOE?

BACKGROUND: The role of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms as risk factors for the occurrence of Alzheimer's disease (AD) is still controversial. OBJECTIVE: To verify the association between MTHFR and apolipoprotein E (APOE) polymorphisms and Alzheimer's disease. METHOD: This work was conducted as a case-control study. Cases included thirty patients with probable AD. Controls were constituted by 29 individuals without dementia according to neuropsychological tests paired to age, sex, race and educational level. DNA was isolated from peripheral leukocytes of anticoagulated venous blood. Genotyping of APOE and MTHFR were performed by DNA amplification and digestion. The frequences of APOE and MTHFR genotypes were submitted by chi-square test corrected by Fisher test; the APOE genotypes, to chi-square linear tendency test and the frequences of MTHFR mutant and AD, by stratificated analysis adjust by Mantel-Haenszel method. RESULTS: There was significant difference about APOE4 and APOE2 in the groups. (p=0.002) The odds ratio increased exponentially with the increased number of E4 allele (chi2 linear tendency test). No significant difference was detected on MTHFR genotypes in both case and control groups. CONCLUSION: The APOE4 is a risk factor and demonstrated a dose-dependent effect while APOE2 allele conferred a protection to AD. The MTHFR mutation had no correlation with AD.     

Cholesterol and Alzheimer's disease: is there a link?

The Abeta-amyloid peptide (Abeta), the main component of amyloid plaques, is derived by proteolytic cleavage from the amyloid precursor protein (APP). Epidemiologic and biochemical data suggest a link between cholesterol, APP processing, Abeta, and Alzheimer's disease. Two recent epidemiologic studies indicate that there is a decreased prevalence of AD associated with the use of cholesterol-lowering drugs that inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase inhibitors or statins). Experiments in cell culture and in vivo demonstrate that treatment with statins reduces production of Abeta. The authors discuss how cholesterol might modulate Abeta deposit formation. As neurons receive only small amounts of exogenous cholesterol, statins that efficiently cross the blood-brain barrier may reduce the amount of neuronal cholesterol below a critical level. Decreased neuronal cholesterol levels inhibit the Abeta-forming amyloidogenic pathway possibly by removing APP from cholesterol- and sphingolipid-enriched membrane microdomains. In addition, depletion of cellular cholesterol levels reduces the ability of Abeta to act as a seed for further fibril formation. These intriguing relationships raise the hopes that cholesterol-lowering strategies may influence the progression of AD.     

Advanced parental age: a risk factor for Alzheimer's disease or depression in the elderly?

BACKGROUND: Advanced parental age has been suggested as a risk factor for Alzheimer's disease (AD) as well as for other psychiatric disorders. In the present investigation, a sample of gerontopsychiatric patients was examined for a possible parental age effect. STUDY POPULATION AND METHODS: Eighty-three patients with AD, 154 elderly patients with depressive episodes, and 48 comorbid patients (AD and depressive episode) as well as 107 age-matched healthy control subjects from the general population were included in the investigation. Information on the years of birth of the parents was derived from personal or family history information. RESULTS: The mean maternal and paternal ages at the time of birth of the index subject were not significantly different for the different diagnostic subgroups or for the control sample. CONCLUSION: There was no evidence in our sample that advanced parental age increases the risk of AD or depression in the elderly.     

Is plasma amyloid-beta a reliable biomarker for Alzheimer's disease?

Over the past decade, a tremendous amount of consistent data have accumulated showing reduced levels of the 42 amino acid isoform of amyloid-beta (Abeta(42)) in cerebrospinal fluid (CSF) from patients with mature as well as incipient Alzheimer's disease (AD). However, as CSF analyses necessitate a spinal tap, which some consider hard to implement in the clinical routine and in clinical trials, there is a strong interest in the possible association of Abeta levels in plasma with AD. This review provides an update on the current status of research on plasma Abeta as a biomarker for AD in the context of recent patents in the field.     

Is Alzheimer's disease a synaptic disorder?

BACKGROUND: In Alzheimer's disease (AD), the common symptom is loss of memory. Learning and memory are associated with amoeboid movements of synaptic endings. Docosahexaenoic acid (DHA) is a major lipid constituent of synaptic end sites. Minor changes in the fluidity of phospholipidic membranes have a dramatic impact on the function of synapses, where membrane fluidity may influence the neurotransmitter receptor activity. METHOD: Studies pertaining to the role of DHA as a neuroprotective agent was reviewed. RESULTS: Here we will show a conceptual framework for the role of DHA in the prevention of AD. The DHA content has been shown to be decreased in the brain and plasma of patients affected by AD. Aspirin triggers the generation of DHA-derived mediators that are themselves neuroprotective. CONCLUSION: Adequate dietary intakes of the neuroprotective DHA (and aspirin?) may slow down the progression of AD. An essential reserve of synapses from early development is needed.     

Is functional decline necessary for a diagnosis of Alzheimer's disease?

BACKGROUND: The purpose of this study is to examine baseline differences and annualized cognitive and functional change scores in mild Alzheimer's disease (AD) patients with and without impaired activities of daily living (ADL). METHODS: We recruited 267 mild probable AD patients with at least 1 year of follow-up (NINCDS-ADRDA criteria, MMSE>or=20). Based on initial ADL scores, they were divided into 2 groups: unimpaired (n=40) and impaired (n=227). We compared the differences in annualized change scores on MMSE, Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog), ADL and Clinical Dementia Rating sum of box score (CDR-SB) for patients with and without functional impairment at baseline. RESULTS: The group with unimpaired ADL at baseline had a significantly shorter symptom duration (p=0.01) and better neuropsychological test scores at baseline (p<0.001) than those with impaired ADL. The annualized cognitive and functional change of each group from baseline to 1-year follow-up was not significantly different on the MMSE, ADAS-cog, CDR-SB, Physical Self-Maintenance Scale and Instrumental Activities of Daily Living. After 1 year, 56% of the initially unimpaired group and 6% of the initially impaired group reported no ADL impairment. CONCLUSIONS: Our study suggests that functional decline should not be required for the diagnosis of mild AD.     

Preventative medicine and Alzheimer's disease:is Alzheimer's disease risk reduction achievable?

正Alzheimer 's disease(AD) has a multifactorial etiology that has eluded scientists and clinicians for decades. This incomplete understanding of the causal factors likely contributes to the dearth of effective therapeutics available to treat this growing pandemic. Cholinesterase inhibitors such as galantamine, rivastigmine and donepezil are considered frontline treatments but these medications merely treat some of the symptoms associated with AD,     

Asymptomatic Alzheimer's disease: a prodrome or a state of resilience?

Neuritic plaques and neurofibrillary tangles, the neuropathological hallmarks of AD, are not limited to individuals with dementia. These pathologic changes can also be present in the brains of cognitively normal older adults - a condition we defined as Asymptomatic AD (ASYMAD). Although it remains unclear whether these individuals would remain clinically normal with longer survival, they seem to be able to compensate for or delay the appearance of dementia symptoms. Here, we provide a historical background and highlight the combined clinical, pathologic and morphometric evidence related to ASYMAD. Understanding the nature of changes during this apparently asymptomatic state may shed light on the mechanisms that forestall the progression of the disease and allow for maintenance of cognitive health, an important area of research that has been understudied relative to the identification of risks and pathways to negative health outcomes.