The cellular biochemistry of cholesterol and statins: insights into the pathophysiology and therapy of Alzheimer's disease

Effect of the SIRT3-AMPK/PPAR pathway on invasion and migration of cervical cancer cells

SIRT3 is a mitochondrial deacetylation protein that can promote the invasion and migration of cancer cells. We explored the effects of SIRT3 regulation of the AMPK/PPAR signaling pathway on triglycerides and the invasion and metastasis of cervical cancer cells. Immunohistochemical methods were used to detect SIRT3. The expression of AMPK and PPAR proteins in different cervical lesions was analyzed in combination with clinicopathological parameters. qRT-PCR and western blotting were used to determine the expression levels of SIRT3 in the C33a and SiHa cervical cancer cell lines. To observe the effects of altering SIRT3 levels by lentivirus transfection and the consequent changes in AMPK and PPAR protein expression, oil red O staining was used to determine intracellular triglycerides, and scratch assays and Transwell chamber experiments were performed to evaluate cervical cancer cell migration and invasion. Our data indicate that SIRT3, AMPK, and PPAR protein expression levels show an increasing trend with cervical lesion severity and are related to the degree of lymph node metastasis and differentiation; moreover, increased expression of SIRT3 can promote the expression of AMPK and PPAR proteins, is beneficial to the formation of intracellular neutral fat, and enhances the ability of cells to metastasize and invade. Our results suggest that SIRT3 activates AMPK/PPAR signaling pathways involved in cancer lipid metabolism and promotes metastasis and cell invasion.

Involvement of Lipids in Alzheimer's Disease Pathology and Potential Therapies

Lipids constitute the bulk of the dry mass of the brain and have been associated with healthy function as well as the most common pathological conditions of the brain. Demographic factors, genetics, and lifestyles are the major factors that influence lipid metabolism and are also the key components of lipid disruption in Alzheimer's disease (AD). Additionally, the most common genetic risk factor of AD, APOE ϵ4 genotype, is involved in lipid transport and metabolism. We propose that lipids are at the center of Alzheimer's disease pathology based on their involvement in the blood-brain barrier function, amyloid precursor protein (APP) processing, myelination, membrane remodeling, receptor signaling, inflammation, oxidation, and energy balance. Under healthy conditions, lipid homeostasis bestows a balanced cellular environment that enables the proper functioning of brain cells. However, under pathological conditions, dyshomeostasis of brain lipid composition can result in disturbed BBB, abnormal processing of APP, dysfunction in endocytosis/exocytosis/autophagocytosis, altered myelination, disturbed signaling, unbalanced energy metabolism, and enhanced inflammation. These lipid disturbances may contribute to abnormalities in brain function that are the hallmark of AD. The wide variance of lipid disturbances associated with brain function suggest that AD pathology may present as a complex interaction between several metabolic pathways that are augmented by risk factors such as age, genetics, and lifestyles. Herewith, we examine factors that influence brain lipid composition, review the association of lipids with all known facets of AD pathology, and offer pointers for potential therapies that target lipid pathways.

Statin use associated with lower risk of epilepsy after intracranial haemorrhage: A population-based cohort study

AIMS

To examine the association between statin use before and after intracranial haemorrhage (ICH) and the risk of poststroke epilepsy (PSE).

METHODS

Patients with new-onset ICH between 2004 and 2012 were identified from the Taiwan National Health Insurance Research Database. The main outcome was the occurrence of epilepsy after stroke. Multivariable Cox regression modelling was used to estimate the association between statin use and the risk of PSE, with poststroke medication exposures being treated as time-dependent variables.

RESULTS

A total of 7435 patients with ICH were enrolled with a median follow-up of 17.6 months. Within the study cohort, 709 patients developed PSE. Poststroke, but not prestroke, stain use was associated with a reduced risk of PSE (adjusted hazard ratio 0.62, 95% confidence interval 0.42-0.90, P = 0.01). In subanalyses, a trend of a dose-response relationship was observed. A significant PSE risk reduction was correlated with a higher cumulative statin dose. Moreover, the risk of PSE was lower in patients receiving moderate-to-high-intensity statin therapy (adjusted hazard ratio 0.37, 95% confidence interval 0.18-0.75, P = 0.01). Lipophilic and hydrophilic statins were similar with regard to their associations with the reduced risk of PSE.

CONCLUSIONS

Statin therapy may reduce the risk of PSE after ICH, especially with moderate-to-high therapy intensity. Further research is needed to understand the mechanisms underlying the potential protective effects of statins against PSE in this patient population.

Overnutrition Determines LPS Regulation of Mycotoxin Induced Neurotoxicity in Neurodegenerative Diseases

Chronic neurodegenerative diseases are now associated with obesity and diabetes and linked to the developing and developed world. Interests in healthy diets have escalated that may prevent neurodegenerative diseases such as Parkinson's and Alzheimer's disease. The global metabolic syndrome involves lipoprotein abnormalities and insulin resistance and is the major disorder for induction of neurological disease. The effects of bacterial lipopolysaccharides (LPS) on dyslipidemia and NAFLD indicate that the clearance and metabolism of fungal mycotoxins are linked to hypercholesterolemia and amyloid beta oligomers. LPS and mycotoxins are associated with membrane lipid disturbances with effects on cholesterol interacting proteins, lipoprotein metabolism, and membrane apo E/amyloid beta interactions relevant to hypercholesterolemia with close connections to neurological diseases. The influence of diet on mycotoxin metabolism has accelerated with the close association between mycotoxin contamination from agricultural products such as apple juice, grains, alcohol, and coffee. Cholesterol efflux in lipoproteins and membrane cholesterol are determined by LPS with involvement of mycotoxin on amyloid beta metabolism. Nutritional interventions such as diets low in fat/carbohydrate/cholesterol have become of interest with relevance to low absorption of lipophilic LPS and mycotoxin into lipoproteins with rapid metabolism of mycotoxin to the liver with the prevention of neurodegeneration.

Plasma 24S-hydroxycholesterol levels in elderly subjects with late onset Alzheimer's disease or vascular dementia: a case-control study

BACKGROUND

In central nervous system cholesterol cannot be degraded but is secreted into circulation predominantly in the form of its polar metabolite 24(S)-hydroxycholesterol (24S-OH-Chol). Some studies suggested an association between 24S-OH-Chol metabolism and different neurological diseases including dementia. A possible decrease in 24S-OH-Chol plasma levels has been reported late onset Alzheimer's disease (LOAD) and vascular dementia (VD), but results of previous studies are partially contradictory.

METHODS

By high-speed liquid chromatography/tandem mass spectrometry we evaluated the plasma levels of 24S-OH-Chol in a sample of 160 older individuals: 60 patients with LOAD, 35 patients with VD, 25 subjects affected by cognitive impairment no-dementia (CIND), and 40 (144 for genetics study) cognitively normal Controls. We also investigated the possible association between PPARgamma Pro12Ala polymorphism and dementia or 24S-OH-Chol levels.

RESULTS

Compared with Controls, plasma 24S-OH-Chol levels were higher in LOAD and lower in VD; a slight not-significant increase in CIND was observed (ANOVA p: 0.001). A positive correlation between 24S-OH-Chol/TC ratio and plasma C reactive protein (CRP) levels was found in the whole sample, independent of possible confounders (multiple regression p: 0.04; r2: 0.10). This correlation was strong in LOAD (r: 0.39), still present in CIND (r: 0.20), but was absent in VD patients (r: 0.08). The PPARgamma Pro12Ala polymorphism was not associated with the diagnosis of LOAD, VD, or CIND; no correlation emerged between the Ala allele and 24S-OH-Chol plasma levels.

CONCLUSIONS

Our results suggest that plasma 24S-OH-Chol levels might be increased in the first stages of LOAD, and this phenomenon might be related with systemic inflammation. The finding of lower 24S-OH-Chol concentrations in VD might be related with a more advanced stage of VD compared with LOAD in our sample, and/or to different pathogenetic mechanisms and evolution of these two forms of dementia.

Intracranial atherosclerosis as a contributing factor to Alzheimer's disease dementia

BACKGROUND

A substantial body of evidence collected from epidemiologic, correlative, and experimental studies strongly associates atherosclerotic vascular disease (AVD) with Alzheimer's disease (AD). Depending on the precise interrelationship between AVD and AD, systematic application of interventions used to maintain vascular health and function as a component of standard AD therapy offers the prospect of mitigating the presently inexorable course of dementia. To assess this hypothesis, it is vital to rigorously establish the measures of AVD that are most strongly associated with an AD diagnosis.

METHODS

A precise neuropathological diagnosis was established for all subjects, using a battery of genetic, clinical, and histological methods. The severity of atherosclerosis in the circle of Willis was quantified by direct digitized measurement of arterial occlusion in postmortem specimens and was compared between AD and nondemented control groups by calculating a corresponding index of occlusion.

RESULTS

Atherosclerotic occlusion of the circle of Willis arteries was more extensive in the AD group than in the nondemented control group. Statistically significant differences were also observed between control and AD groups with regard to Braak stage, total plaque score, total neurofibrillary tangle score, total white matter rarefaction score, brain weight, Mini-Mental State Examination scores, and apolipoprotein E allelic frequencies.

CONCLUSIONS

Our results, combined with a consideration of the multifaceted effects of impaired cerebral circulation, suggest an immediate need for prospective clinical trials to assess the efficacy of AD prevention using antiatherosclerotic agents.

Cardiovascular dementia - a different perspective

The number of dementia patients has been growing in recent years and dementia represents a significant threat to aging people all over the world. Recent research has shown that the number of people affected by Alzheimer's disease (AD) and dementia is growing at an epidemic pace. The rapidly increasing financial and personal costs will affect the world's economies, health care systems, and many families. Researchers are now exploring a possible connection among AD, vascular dementia (VD), diabetes mellitus (type 2, T2DM) and cardiovascular diseases (CD). This correlation may be due to a strong association of cardiovascular risk factors with AD and VD, suggesting that these diseases share some biologic pathways. Since heart failure is associated with an increased risk of AD and VD, keeping the heart healthy may prove to keep the brain healthy as well. The risk for dementia is especially high when diabetes mellitus is comorbid with severe systolic hypertension or heart disease. In addition, the degree of coronary artery disease (CAD) is independently associated with cardinal neuropathological lesions of AD. Thus, the contribution of T2DM and CD to AD and VD implies that cardiovascular therapies may prove useful in preventing AD and dementia.

Liver X receptor activation restores memory in aged AD mice without reducing amyloid

Alterations in cerebral cholesterol metabolism are thought to play a role in the progression of Alzheimer's disease (AD). Liver X receptors (LXRs) are key regulators of cholesterol metabolism. The synthetic LXR activator, T0901317 has been reported to improve memory functions in animal models for AD and to reduce amyloid-β (Aβ) deposition in the brain. Here we provide evidence that long-term administration of T0901317 to aged, 21-month-old APPSLxPS1mut mice restores impaired memory. Cerebral cholesterol turnover was enhanced as indicated by the increased levels of brain cholesterol precursors and the upregulation of LXR-target genes Abca1, Abcg1, and Apoe. Unexpectedly, the improved memory functions in the APPSLxPS1mut mice after T0901317 treatment were not accompanied by a decrease in Aβ plaque load in the cortex or hippocampus DG, CA1 or CA3. T0901317 administration also enhanced cerebral cholesterol turnover in aged C57BL/6NCrl mice, but did not further improve their memory functions. In conclusion, long-term activation of the LXR-pathway restored memory functions in aged APPSLxPS1mut mice with advanced Aβ deposition. However the beneficial effects of T0901317 on memory in the APPSLxPS1mut mice were independent of the Aβ plaque load in the hippocampus, but were associated with enhanced brain cholesterol turnover.

The natural products beauveriolide I and III: a new class of beta-amyloid-lowering compounds

Attacking Alzheimer's by ACAT: The aggregation of beta-amyloid peptides, especially Abeta(42), into senile plaques is a hallmark of Alzheimer's disease (AD). We show that the fungal natural products beauveriolides I and III can potently decrease Abeta secretion from cells expressing human amyloid precursor protein; this offers a potential new scaffold for the development of compounds with proven bioavailability for the treatment of AD.

Potential mechanisms linking cholesterol to Alzheimer's disease-like pathology in rabbit brain, hippocampal organotypic slices, and skeletal muscle

Epidemiological, animal, and cellular studies suggest that abnormalities in cholesterol metabolism are important in the pathogenesis of Alzheimer's disease (AD), potentially by increasing amyloid-beta (Abeta) peptide levels. Accumulation of Abeta in the brain is suggested to play a key role in the neurodegenerative processes by triggering the hyperphosphorylation of tau and the neuronal death that develop in the course of AD. However, the mechanisms by which cholesterol increases Abeta levels are still ill-defined. Previous and ongoing work from our laboratory indicates that hypercholesterolemia leads to the increased neuronal content of cholesterol and increased levels and processing of the amyloid-beta protein precursor (AbetaPP). We also have found that the oxidized cholesterol metabolite, 27-hydroxycholesterol, increases Abeta levels in both organotypic hippocampal slices and in neuronal preparations cultured from adult rabbits. This cholesterol metabolite is predominantly formed in the circulation and, in contrast to cholesterol, has the ability to cross into the brain. These results may indicate that 27-hydroxycholesterol is the link between circulating cholesterol and AD-like pathology in the brain. We also have found pathological hallmarks in the skeletal muscle of cholesterol-fed rabbits that are suggestive of inclusion body myositis, a disease that shares some pathological similarities with AD.

Alzheimer's disease

Alzheimer's disease is the most prevalent form of dementia. There are significant efforts underway to elucidate the pathogenesis of this disease and to find ways to lessen the impact of the symptoms. This paper summarizes current knowledge regarding the diagnosis and treatment of the disorder.

Cytochrome P450s and cholesterol homeostasis

By participating in pathways of cholesterol biosynthesis and elimination, different cytochrome P450 (P450 or CYP) enzymes play an important role in maintenance of cholesterol homeostasis. CYP51 is involved in cholesterol biosynthesis, whereas CYP 7A1, 27A1, 46A1, 7B1, 39A1, and 8B1 are the key enzymes in cholesterol catabolism to bile acids, the major route of cholesterol elimination in mammals. Cholesterol transformations to steroid hormones are also initiated by the P450 enzyme CYP11A1. Finally, one of the major drug-metabolizing P450s CYP3A4 seems to contribute to bile acid biosynthesis as well. The 9 P450s will be the focus of this review and assessed as drug targets for cholesterol lowering.

"Skittish" Abca2 knockout mice display tremor, hyperactivity, and abnormal myelin ultrastructure in the central nervous system

The ATP-binding cassette transporter 2 (ABCA2) is an endolysosomal protein most highly expressed in the central and peripheral nervous system tissues and macrophages. Previous studies indicated its role in cholesterol/steroid (estramustine, estradiol, and progesterone) trafficking/sequestration, oxidative stress response, and Alzheimer's disease. Developmental studies have shown its expression during macrophage and oligodendrocyte differentiation, processes requiring membrane growth. To determine the in vivo function(s) of this transporter, we generated a knockout mouse from a gene-targeted disruption of the murine ABCA2 gene. Knockout males and females are viable and fertile. However, a non-Mendelian inheritance pattern was shown among male progeny of heterozygous crosses. Compared to wild-type and heterozygous littermates, knockout mice displayed a tremor without ataxia, hyperactivity, and reduced body weight; the latter two phenotypes were more marked in females than in males. This sexual disparity suggests a role for ABCA2 in hormone-dependent neurological and/or developmental pathways. Myelin sheath thickness in the spinal cords of knockout mice was greatly increased compared to that in wild-type mice, while a significant reduction in myelin membrane periodicity (compaction) was observed in both spinal cords and cerebra of knockout mice. Loss of ABCA2 function in vivo resulted in abnormal myelin compaction in spinal cord and cerebrum, an ultrastructural defect that we propose to be the cause of the phenotypic tremor.

Apolipoprotein E, cholesterol metabolism, diabetes, and the convergence of risk factors for Alzheimer's disease and cardiovascular disease

High fat diets and sedentary lifestyles are becoming major concerns for Western countries. They have led to a growing incidence of obesity, dyslipidemia, high blood pressure, and a condition known as the insulin-resistance syndrome or metabolic syndrome. These health conditions are well known to develop along with, or be precursors to atherosclerosis, cardiovascular disease, and diabetes. Recent studies have found that most of these disorders can also be linked to an increased risk of Alzheimer's disease (AD). To complicate matters, possession of one or more apolipoprotein E epsilon4 (APOE epsilon4) alleles further increases the risk or severity of many of these conditions, including AD. ApoE has roles in cholesterol metabolism and Abeta clearance, both of which are thought to be significant in AD pathogenesis. The apparent inadequacies of ApoE epsilon4 in these roles may explain the increased risk of AD in subjects carrying one or more APOE epsilon4 alleles. This review describes some of the physiological and biochemical changes that the above conditions cause, and how they are related to the risk of AD. A diversity of topics is covered, including cholesterol metabolism, glucose regulation, diabetes, insulin, ApoE function, amyloid precursor protein metabolism, and in particular their relevance to AD. It can be seen that abnormal lipid, cholesterol and glucose metabolism are consistently indicated as central in the pathophysiology, and possibly the pathogenesis of AD. As diagnosis of mild cognitive impairment and early AD are becoming more reliable, and as evidence is accumulating that health conditions such as diabetes, obesity, and coronary artery disease are risk factors for AD, appropriate changes to diets and lifestyles will likely reduce AD risk, and also improve the prognosis for people already suffering from such conditions.

Non-targeted profiling of lipids during kainate-induced neuronal injury

Kainate is a glutamate analog that has been widely used in pharmacological studies of neuronal injury related to ischemic conditions and epilepsy. While altered lipid metabolism has been implicated in kainate action, no study has yet investigated the associated changes in lipid metabolites on a systems scale. Here we describe a mass spectrometry-based approach for profiling of lipid mixtures in a nontargeted fashion. Combined with tandem mass spectrometry, this method aims to identify lipids that are altered between two conditions, the kainate-treated and the control hippocampal tissues. In addition to reductions in major phospholipids with mainly polyunsaturated fatty acyl chains, we find elevated levels of ions that correspond to acylated forms of phosphatidylethanolamines and ceramides. Acylated phosphatidylethanolamines are neuroprotective lipids and precursors for anandamide, which signals via cannabinoid receptors. Quantitative analysis of ceramides shows that many molecular species with different acyl compositions are increased during kainate treatment. This increase is mainly restricted to neurons rather than other brain cells in the hippocampus as revealed by immunohistochemistry of brain slices.

Is the LDL receptor involved in cortical amyloid protein clearance?

This article puts forward the hypothesis that the Low Density Lipid Receptor (LDLR) is one of the molecules that is involved in the clearance of amyloid proteins in the brain and that it may play a role in Alzheimer's Disease (AD) via its up-regulation by statins. The hypothesis is built on the following observations: a-statins (which have been shown to increase LDLR in astrocytes, see below) have a beneficial role in AD, b-defects in the LDL receptor gene are found in AD, c-molecules with similar structure to the LDLR have been shown to clear amyloid protein from the brain.

Characterization of the putative cholesterol transport protein metastatic lymph node 64 in the brain

Intracellular management of cholesterol is a critical process in the brain. Deficits with cholesterol transport and storage are linked to neurodegenerative disorders such as Neimann-Pick disease type C and Alzheimer's disease. One protein putatively involved in cholesterol transport is metastatic lymph node 64 (MLN64). MLN64 localizes to late endosomes which are part of the cholesterol internalization pathway. However, a detailed pattern of MLN64 expression in the brain is unclear. Using immunocytochemical and immunoblot analyses, we demonstrated the presence of MLN64 in several tissue types and various regions within the brain. MLN64 immunostaining in the CNS was heterogeneous, indicating selective expression in discrete specific cell populations and regions. MLN64 immunoreactivity was detected in glia and neurons, which displayed intracellular labeling consistent with an endosomal localization. Although previous studies suggested that MLN64 may promote steroid production in the brain, MLN64 immunoreactivity did not colocalize with steroidogenic cells in the CNS. These results demonstrate that MLN64 is produced in the mouse and human CNS in a restricted pattern of expression, suggesting that MLN64 serves a cell-specific function in cholesterol transport.

24(S)-hydroxycholesterol participates in a liver X receptor-controlled pathway in astrocytes that regulates apolipoprotein E-mediated cholesterol efflux

Both apolipoprotein E (apoE) and 24(S)-hydroxycholesterol are involved in the pathogenesis of Alzheimer disease (AD). It has been hypothesized that apoE affects AD development via isoform-specific effects on lipid trafficking between astrocytes and neurons. However, the regulation of the cholesterol supply of neurons via apoE-containing high density lipoproteins remains to be clarified. We show for the first time that the brain-specific metabolite of cholesterol produced by neurons, i.e. 24(S)-hydroxycholesterol, induces apoE transcription, protein synthesis, and secretion in a dose- and time-dependent manner in cells of astrocytic but not of neuronal origin. Moreover, 24(S)-hydroxycholesterol primes astrocytoma, but not neuroblastoma cells, to mediate cholesterol efflux to apoE. Similar results were obtained using the synthetic liver X receptor (LXR) agonist GW683965A, suggesting involvement of an LXR-controlled signaling pathway. A 10-20-fold higher basal LXRalpha and -beta expression level in astrocytoma compared with neuroblastoma cells may underlie these differential effects. Furthermore, apoE-mediated cholesterol efflux from astrocytoma cells may be controlled by the ATP binding cassette transporters ABCA1 and ABCG1, since their expression was also up-regulated by both compounds. In contrast, ABCG4 seems not to be involved, because its expression was induced only in neuronal cells. The expression of sterol regulatory element-binding protein (SREBP-2), low density lipoprotein receptor, 3-hydroxy-3-methylglutaryl-CoA reductase, and SREBP-1c was transiently up-regulated by GW683965A in astrocytes but down-regulated by 24(S)-hydroxycholesterol, suggesting that cholesterol efflux and synthesis are regulated independently. In conclusion, evidence is provided that 24(S)-hydroxycholesterol induces apoE-mediated efflux of cholesterol in astrocytes via an LXR-controlled pathway, which may be relevant for chronic and acute neurological diseases.

Potential role of acyl-coenzyme A:cholesterol transferase (ACAT) Inhibitors as hypolipidemic and antiatherosclerosis drugs

Acyl-coenzyme A:cholesterol transferase (ACAT) is an integral membrane protein localized in the endoplasmic reticulum. ACAT catalyzes the formation of cholesteryl esters from cholesterol and fatty acyl coenzyme A. The cholesteryl esters are stored as cytoplasmic lipid droplets inside the cell. This process is very important to the organism as high cholesterol levels have been associated with cardiovascular disease. In mammals, two ACAT genes have been identified, ACAT1 and ACAT2. ACAT1 is ubiquitous and is responsible for cholesteryl ester formation in brain, adrenal glands, macrophages, and kidneys. ACAT2 is expressed in the liver and intestine. The inhibition of ACAT activity has been associated with decreased plasma cholesterol levels by suppressing cholesterol absorption and by diminishing the assembly and secretion of apolipoprotein B-containing lipoproteins such as very low density lipoprotein (VLDL). ACAT inhibition also prevents the conversion of macrophages into foam cells in the arterial walls, a critical event in the development of atherosclerosis. This review paper will focus on the role of ACAT in cholesterol metabolism, in particular as a target to develop novel therapeutic agents to control hypercholesterolemia, atherosclerosis, and Alzheimer's disease.

Nanoparticle and other metal chelation therapeutics in Alzheimer disease

Current therapies for Alzheimer disease (AD) such as the anticholinesterase inhibitors and the latest NMDA receptor inhibitor, Namenda, provide moderate symptomatic delay at various stages of disease, but do not arrest disease progression or supply meaningful remission. As such, new approaches to disease management are urgently needed. Although the etiology of AD is largely unknown, oxidative damage mediated by metals is likely a significant contributor since metals such as iron, aluminum, zinc, and copper are dysregulated and/or increased in AD brain tissue and create a pro-oxidative environment. This role of metal ion-induced free radical formation in AD makes chelation therapy an attractive means of dampening the oxidative stress burden in neurons. The chelator desferioxamine, FDA approved for iron overload, has shown some benefit in AD, but like many chelators, it has a host of adverse effects and substantial obstacles for tissue-specific targeting. Other chelators are under development and have shown various strengths and weaknesses. In this review, we propose a novel system of chelation therapy through the use of nanoparticles. Nanoparticles conjugated to chelators show a unique ability to cross the blood-brain barrier (BBB), chelate metals, and exit through the BBB with their corresponding complexed metal ions. This method may prove to be a safe and effective means of reducing the metal load in neural tissue thus staving off the harmful effects of oxidative damage and its sequelae.

Cholesterol and apolipoprotein E in Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia in North America and Europe. The incidence of the disease rises dramatically with age. AD is a complex multifactorial disorder that involves numerous susceptibility genes, but the exact pathogenesis and biochemical basis of AD is not well understood Cholesterol is receiving a great deal of attention as a potentially crucial factor in the etiology of AD. Almost all cholesterol in the brain is synthesized in the brain. Cholesterol exits the brain through the blood-brain barrier (BBB) in the form of apolipoprotein E (ApoE) or by first being converted to a more polar compound, 24(S)-hydroxycholesterol, which is elevated in individuals with AD. The key event leading to AD appears to be the formation and aggregation in the brain of amyloid beta (Abeta) peptide, a proteolytically derived product of amyloid precursor protein (APP). Cholesterol has been demonstrated to modulate processing of APP to Abeta. High levels of cholesterol are associated with increased risk of AD. Patients taking cholesterol-lowering statins have a lower prevalence of AD. ApoE, which transports cholesterol throughout the brain, exhibits an isoform-specific association with AD such that the E4 isoform, by unknown mechanisms, shifts the onset curve toward an earlier age.

Statins, cholesterol, Co-enzyme Q10, and Parkinson's disease

'Statins', drugs that lower cholesterol are widely used. Statins block cholesterol in the body and brain by inhibiting HMG-Co-A reductase. This pathway is shared by CoQ-10. An unintended consequence of the statins is lowering of CoQ-10. As CoQ-10 may play a role in PD, its possible statins may worsen PD. Such a report has appeared. Statins came into wide use in 1997-1998, 6 years before our study began. Thus 74% of our patients on a statin had a PD duration of 1-6 years versus 56% of our patients not on a statin. A direct comparison of patients on a statin and not on a statin would bias the study in favor of the statins: patients on a statin would have a shorter disease duration and less advanced PD. Therefore we divided the patients into two groups. Group I consisted of 128 patients on a statin, and 252 not on a statin who had PD for 1-6 years. In this group, disease severity (Hoehn & Yahr Stage), levodopa dose, Co-enzyme Q10 use, prevalence of 'wearing off', dyskinesia and dementia were similar. Group II consisted of 45 patients on a statin and 200 patients not on a statin who had PD for 7-22 years. In this group disease severity, levodopa dose, Co-enzyme Q10 use, prevalence of wearing off, dyskinesia and dementia were similar. Statins although they may affect Co-enzyme Q10 levels in the body and the brain, do not worsen PD at least as assessed by stage, and prevalence of wearing-off, dyskinesia, and dementia.

Apolipoprotein Abeta: black sheep in a good family

Amyloid-beta (Abeta) has for a long time been thought to play a central role in the pathogenesis of Alzheimer disease (AD). Analysis of available data indicates that Abeta possesses properties of a metal-binding apolipoprotein influencing lipid transport and metabolism. Protection of lipoproteins from oxidation by transition metals, synaptic activity and role in the acute phase response represent plausible physiological functions of Abeta. However, these important biochemical qualities which may critically influence the development of AD, have been largely ignored by mainstream AD researchers, making Abeta appear to be a "black sheep" in a "good apolipoprotein" family. New studies are needed to shed further light on the physiological role of Abeta in lipid metabolism in the brain.