Method for treating alzheimer's disease

The present invention provides a method for treating or preventing the onset of Alzheimer's Disease comprising administering to a mammal in need thereof an Alzheimer's Disease-preventing or treating amount of a plasma-triglyceride level-lowering agent. Optionally, the plasma-triglyceride level-lowering agent can be co-administered with a cholesterol level-lowering agent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention comprises a new method for treating and preventing or delaying the onset of Alzheimer's Disease. It is born by the observation that risk factors for cardiovascular disease can have a profound impact on the expression of A&bgr; in AD brains. The data presented herein implicates ApoE &egr;4 status as the major determinant in the expression of A&bgr;N-40. Also independent of ApoE genotype, higher levels of plasma cholesterol in the form of LDL are related to higher concentrations of A&bgr;N-42 in the AD brain. In addition, the data show a benefit of having an elevated ratio of HDL-C relative to very low density lipoprotein cholesterol (VLDL-C), plus low density lipoprotein cholesterol (LDL-C), in reduction of AD. The data clearly establishes the participation of plasma cholesterol in the pathophysiology of AD. Other studies have shown that other neurological disorders, such as vascular dementia and stroke, are related to hypercholesterolemia and hypertension. In these latter diseases, retrospective and prospective epidemiological studies have demonstrated that the use of anti-hypertensive agents or control of plasma cholesterol levels, through diet and drugs, have decreased the morbidity and mortality caused by these diseases. Thus, regulation of cardiovascular risk factors can also offer an as yet unexplored avenue to prevent or at least delay the occurrence of Alzheimer's Disease. In view of the foregoing, therefore, in one aspect of the invention, a method of treating Alzheimer's Disease is provided, the method comprising administering to a mammal suffering from Alzheimer's Disease an Alzheimer's Disease-alleviating amount of a plasma triglyceride level-lowering agent. Numerous, triglyceride level-lowering agents are known, and include, but are not limited to, fibrates (e.g., clofibrate, gemfibrozil (CI-719), fenofibrate, ciprofibrate, and bezafibrate), niacin, carboxyalkethers, thiazolinediones, eicosapentaenoic acid (EPA) and EPA-containing compositions (e.g., Max EPA, SuperEPA) Thazolinediones useful in the present invention include, for, example, darglitazore, pioglitazone, BRL49653 (rosiglitazone), and troglitazone. Carboxyalkylethers useful in the invention are described in U.S. Pat. No. 5,648,387. Specifically, such compounds have the structure of Formula I 1 wherein n and m independently are integers from 2 to 9; R 1 , R 2 , R 3 , and R 4 independently are C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynl, and R 1 and R 2 together with the carbon to which they are attached, and R 3 and R 4 together with the carbon to which they are attached, can complete a carbocyclic ring having from 3 to 6 carbons; Y 1 and Y 2 , independently are COOH, CHO, tetrazole, and COOR 5 where R 5 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl; and where the alkyl, alkenyl, and alkynyl groups may be substituted with one or two groups selected from halo, hydroxy, C 1 -C 6 alkoxy, and phenyl. Preferred carboxyalkylethers for use in the invention have the above formula wherein n and m are the same integer, and wherein R 1 , R 2 , R 3 , and R 4 each are alkyl. Further preferred carboxyalkylethers are those in which Y 1 and Y 2 independently are COOH or COOR 5 where R 5 is alkyl. The most preferred carboxyalkylethers for use in the invention have the formula 2 wherein n and m are each an integer selected from 2, 3, 4, or 5, ideally 4or 5. An especially preferred carboxyalkylether for use in the invention is CI-1027, which has the formula 3 Another group of lipid regulators which lower triglycerides and which can be used according to this invention are inhibitors of acyl-coenzyme A:cholesterol acyltransferase (ACAT). Such ACAT inhibitors are well-known, for example, as described in U.S. Pat. No. 5,491,172. These compounds have the general structure 4 wherein X and Y are O, S, or (CR′R″) n , n is 1 to 4, R is hydrogen, alkyl or benzyl, R 1 and R 2 include aryl and cycloalkyl. One compound from within this group is especially preferred, namely 2,6-bis(1-methylethyl)phenyl&lsqb;2,4,6-tris(1-methylethyl)phenyl&rsqb;acetyl&rsqb;sulfamate, now generically known as avasimibe, and also known as CI-1011. Other commonly available plasma triglyceride-lowering agents can also be employed. One such compound is PD 69405, which a has the structure 5 In another embodiment of this aspect of the invention, a method for treating AD is provided in which the plasma triglyceride level-lowering agent is co-administered with an effective plasma cholesterol lowering amount of a plasma cholestero level-lowering agent. Many such plasma cholesterol-level-lowering agents useful in this embodiment are known and include, but are not limited to, stains (e.g. lovastatin (U.S. Pat. No, 4,231,938), mevastatin (U.S. Pat. No. 3,983,140), simvastatin (U.S. Pat. No. 4,444,784), atorvastatin, cerivastain (U.S. Pat. No. 5,502,199 and EP 617019), velostatin (U.S. Pat. Nos. 4,441;,784 and 4,450,171), flurastatin (U.S. Pat. No. 4,739,073), dalvastatin (EP Appln. Publn. No. 739510 A2), fluindostatin (EP Appln. Publn. No. 363934 A1) and pravastatin (U.S. Pat. No. 4,346,227), the bile acid sequestrants (e.g., cholestyramine and colestipol), and agents that block intestinal cholesterol absorption, e.g., &bgr;-sitosterol, SCH48461, CP-148,623 (Harris et al., Clin. Pharm. Therap., 1997;61:385), saponins, neomycin, and ACAT (acyl-CoA:cholesterol acyltransferase) inhibitors. The patent art is rich with compounds that inhibit cholesterol biosynthesis, as evidenced by U.S. Pat. Nos. 5,468,771, 5,447,717, 5,385,932, 5, 376,383, 5,369,125, 5,362,752, 5,359,096, 5,326,783, 5,322,855, 5,317,031, 5,310,949, 5,302,604, 5,294,627, 5,286,895, 5,284,758, 5,283.256, and 5,278,320. In a second aspect of the invention, a method of preventing the onset of Alzheimer's Disease is provided, the method comprising administering to a mammal an Alzheimer's Disease-preventing amount of a plasma triglyceride level-lowering agent. Such plasma triglyceride level-lowering agents are known in the art and include those recited above. In another embodiment of this aspect of the invention, a method of preventing the onset of AD is provided in which the plasma triglyceride level-lowering agent is co-administered with an effective plasma cholesterol-lowering amount of a plasma cholesterol level-lowering agent. Many such plasma cholesterol-level-lowering agents are useful in this embodiment are known and include those recited previously. In another aspect of the invention, methods of treating and preventing AD are provided, which methods comprise administering to a mammal a combination of agents that lower the mammal's blood triglyceride level and its LDL-cholesterol (LDL-C) level and raise its HDL level. Agents that reduce LDL-C levels are known and include HMG-CoA reductase (HMGR) inhibitors, especially the statins such as atorvastatin, lovastatin, simvastatin, pravastatin, rivastatin, mevastatin, fluindostatin, cerivastatin, velostatin, fluvastatin dalvastatin, as well as dihydrocompactin (U.S. Pat. No. 4,450,171), compactin (U.S. Pat. No. 4,804,770), and neomycin. Atorvastatin calcium is particularly preferred (U.S. Pat. No. 5,273,995). HDL level-increasing drugs include gemfibrozil and simvastatin, and especially the carboxyalkylethers mentioned above, for example Cl-1027. In yet another aspect of the invention, methods of treating and preventing AD are provided, which methods comprise administering to a mammal an agent that raises the mammal's HDL cholesterol level. In another aspect the HDL cholesterol (HDL-C) level-raising agent is administered in combination with an LDL-C lowering agent. Besides the agents expressly recited herein, there are many known agents useful in the various aspects of the invention, many of which are described in The Merck Index (Eleventh Edition) (Budavari et al., Eds., Merck & Co., Inc., Rahway, N.J.) and the Physician's Desk Reference (Medical Economics Data Production Co., Montvale N.J.). Pharmaceutically acceptable salts of the compounds useful in the invention can also be used. It will also be clear to those skilled in the art that more than one agent can be used for any particular purpose, as can pharmaceutically acceptable compositions comprising one or more agents. The amounts of agents suitable for use in the various aspects of the invention are readily and routinely determinable by those skilled in the art using standard, art recognized methods. For example, to determine effective and optimal amounts of triglyceride level-loitering agents useful for treating AD, several groups of patients suffering from AD should be followed. One group, the control group is to be administered a placebo. The remaining groups are administered varying amounts of a triglyceride level-lowering agent, and the cognitive skills of the individuals in each of the groups monitored to determine which group or groups manifest better cognitive skills compared to the control group. Similar routine studies can be conducted to determine effective and optimal amounts of such agents for preventing and/or delaying the onset of AD, with and without the co-administration of a cholesterol level-lowering agent. In general, however, amounts of triglyceride level-lowering agent and cholesterol level-lowering agent useful in all aspects of the invention are those that are commonly and routinely used for the treatment of vascular and cardiac disease. Relatedly, regimes for administration of the agents for use in the treatment of vascular and cardiac disease can be used in the various aspects of the present invention. Such agents typically are administered at doses of about 0.1 mg to about 1000 mg per day, and ideally at about 5 mg to about 100 mg per day. The combination to be employed can be formulated individually in their normal fashion (e.g., atorvastatin, troglitazone, rosiglitazone, gemfibrozil), or the agents can be formulated as a fixed dose combination, for example, an oral tablet containing 40 mg of atorvastatin and 200 mg of gemfibrozil or carboxyalkylether. Administration of the agents recited in each aspect of the invention can be conducted by the sane methods the agents are administered to treat vascular and cardiac disease, which are widely known and commonly used. The ability of the triglyceride level-lowering agents and the cholesterol level-lowering agents to prevent or delay the onset of AD has been established by the following detailed examples. The examples are provided for illustrative purposes only, and are not intended to be limiting in any respect. 
 EXAMPLE 1 Apolipoprotein E is a 34 kDa amphipathic pro that associates with serum triglyceride-rich and high-density lipoproteins and is involved in the transport of cholesterol between tissues. Three isoforms of the ApoE protein that differ by one or two amino acids are found in the human population. The ApoE2, E3, and E4 are respectively coded by the genes ApoE &egr;2, &egr;3, and &egr;4. Apoliprotein E &egr;4 represents a well-established risk factor for AD. Individuals with AD carrying the ApoE &egr;4 allele have more profuse deposits of A&bgr; in the cerebral cortex and vascular walls than the other ApoE alleles. This implies that ApoE4 interactions with A&bgr; or its lipid transport function or both affect the accumulation of A&bgr;. The increased risk of cardiovascular disease conferred by ApoE4 is attributed to an associated hypercholesterolemia that can promote or exacerbate atherosclerosis, hypertension, myocardial infarction and critical coronary artery disease. The following experiment investigated the relationship between AD and known risk factors for cardiovascular disease, including ApoE genotype, serum lipids, lipoproteins, and apolipoprotein levels. In addition, A&bgr; levels in the gray matter were determined. The results are discussed in terms of the implicit involvement of lipid metabolism in the pathophysiology of Alzheimer's Disease. Human Subjects and Methodology Human Tissue, Sixty-four AD and 36 non-demented control brains were obtained from Sun Health Research Institute Brain Bank (postmortem-freezing delay 1-3 hours, average 2.1 hours). The brains from the demented patients fulfilled the diagnostic criteria of AD as dictated by the Consortium to Establish a Registry or Alzheime's Disease (CERAD). The control cases had no clinical history of dementia or neurological symptoms, and on neuropathological examination did not meet the AD guidelines. Blood was collected in the immediate post-mortem by cardiac puncture from left ventricle. ApoE genotyping. ApoE genotyping was carried out using standard techniques. Crude genomic DNA, prepared from white blood cell nuclei, was submitted to 40 cycles of polymerase chain reaction, and digested with restriction enzyme PhaI prior to electrophoresis on an 8% polyacylamide gel. Quantitation of lipids. Serum total cholesterol and triglycerides were determined enzymatically by standard procedures. Serum lipoprotein cholesterol profiles and distribution among lipoproteins were determined by on-line post column analysis on Superose 6HR high performance gel filtration chromatography (HPGC). Lipoprotein cholesterol was determined by multiplying the independently determined total serum cholesterol by the percent area for each lipoprotein distinctly separated by the HPGC method. ApoA-I ApoE and ApoB levels were determined by immunoturbidometric methods using commercially available kits (Wako Chemical USA, Inc., Richmond, Va.) on a Cobus Mira Plus analyzer (Roche Diagnostics Systems, Branhburg, N.J.), Quantitation of brain cholesterol. Brain lipids were extracted by standard methods. Briefly, 0.2 g of white or grey brain tissue, plus 100 &mgr;g of 4cholesten-3-one (internal standard) was homogenized in 5 mL of chloroform/methanol (2:1, v/v) and then filtered through Whatman No. 1 filter paper. Another 2 mL of the chloroform/methanol mixture was used to re-extract the residue. Water (1.5 mL) was added to the extract and centrifuged at 2000 g for 10 minutes to distinctly separate the biphase. The lower chloroform phase containing the lipid extract was taken to dryness under nitrogen gas, and then dissolved in 1 mL of 2-propanol/hexane (1:19, v/v) for HPLC analysis. Brain cholesterol was separated by high pressure liquid chromatography (Thermo Separation Products, Freemont, Calif.), from internal standard on a 5 &mgr;m silica normal phase column (Zorbax SIL, 4.6×250 mm) at a flow rare of 1 mL/minute. The relative absorbance values at 208 nm for the internal standard, and cholesterol were considered in the final calculation of brain cholesterol. Europium immunoassay (EIA) of A&bgr;Peptides Cerebral cortex (0.8 g) from the superior frontal gyrus was minced and rinsed with buffer (20 mM Tris-HCl, pH 8.5) containing protease inhibitors. The tissue was homogenized in 3 mL of buffer, spun at 100,000 g for 1 hour at 4° C. and prepared for A&bgr; quantitation. One hundred microliters of the final diluted solution was submitted to EIA. Rabbit antibodies R163 and R165, raised against amino acids 34-40 and 36-42 of A&bgr;, respectively were coated to microliter plates. Wells were blocked with bovine serum albumin (1%) and 100 &mgr;L of the specimens or of A&bgr; standards were applied, incubated at room temperature for 2 hours, and then rinsed with 0.05% Tween 20-tris buffered saline (TTBS). Europium-labeled 4G8 antibody (against A&bgr; residue 17-24) was added to the wells, incubated for 2 hours and washed with TTBS, and rinsed with deionized water. Finally, the Eu enhancement solution (Wallac Inc., Gaithersburg, Md.) was added and the plates read in a fluorimeter using excitation and emission wavelengths of 320 and 615 nm, respectively. The values obtained from triplicated wells, were calculated based on standard curves generated on each plate. Statistical Analysis. Two-tailed Student T-Test was applied when variable means where compared between control and AD subjects. Analysis of covariance (ANCOVA) of linear regression was used to estimate the relationships between two variables. The effects of ApoE genotype were determined by analysis of variance (ANOVA). Post-hoc multiple comparisons were only applied to those significant ANOVA groups. Significant differences between genotypes were determined by Fishers Protected Lest Significant Differences (PLSD) for the comparisons of multiple means. Results Examination of the lipid profiles of AD versus control subjects reveals a significant elevation in the amount of total cholesterol (TC), primarily in higher concentration of LDL in the AD cases (Table 1). This difference can be appreciated by its frequency distribution, segmented by decile, as shown in FIG. 1 . In controls subjects, 81 percent (29 of 36 subjects) had LDL cholesterol levels below the third decile (i.e., below 112 mg/dL), with all control subjects having LDL cholesterol below the fifth decile (i.e., below 163 mg/dL). In contrast, only 53 percent of the AD subjects fell below the third decile (36 of 68 subjects), while 21 percent (14 of 69 subjects) of these subjects had cholesterol above the fifth decile. Apolipoprotein B (ApoB), which is primarily associated with serum LDL, is also significantly elevated in AD (Table 1). Other lipids, such as VLDL-cholesterol, triglycerides (TG), ApoA-I. and ApoE, showed no significant differences between the AD and control groups (Table 1). In contrast, the levels of the HDL cholesterol, as well a the ratio of the HDL cholesterol to VLDL plus LDL cholesterol, were significantly higher in the control group than in the AD population (Table 1). As expected, the levels of A&bgr;N-40 and A&bgr;N-42 in brain were substantially higher in AD than those of control group (Table 1). When compared to the control group, the amount of brain white matter cholesterol in AD patients was less, as was the brain grey matter cholesterol as shown in FIG. 2 . Large population studies show an effect of ApoE isoforms on serum total and LDL cholesterol levels. In our cohort, serum cholesterol levels were also increased in ApoE &egr;4 carriers; however, this elevation was not significant. The impact of ApoE genotype in this study is most evident on the amount of A&bgr;N-40 in AD brains ( FIG. 3A ). The highest level of A&bgr;N-40 was found in AD patients homozygous for ApoE4, the amount being 20 times and 4 times greater than in those individuals with ApoE &egr;E3/&egr;3 and E3/&egr;4, respectively ( FIG. 3A ), Any AD subjects carrying ApoE &egr;4 had approximately twice the quantity of A&bgr;N-42 when compared to those AD cases lacking, the ApoE &egr;4 allele, as well as to all ApoE genotypes in the control group ( FIG. 3B ). The sums of A&bgr;N-40 plus A&bgr;N-42 relative to each ApoE genotype are shown in FIG. 3C . In AD subjects, the total A&bgr; linearity increased with the addition of one and two ApoE &egr;4 alleles ( FIG. 3C ). In all cases, total A&bgr; was significantly higher in the AD subjects homozygous for ApoE4 than all other isoforms in either the AD or control cohorts ( FIG. 3C ). Significant associations between the levels of total serum cholesterol, LDL cholesterol and ApoB in AD subjects were seen with A&bgr;N-42 (FIGS. 4 A-C), but not A&bgr;N-40 (data not shown). The strongest correlation occurred between ApoB and A&bgr;N-42 ( FIG. 4C ), where the “r” value is the correlation factor, r&equals;1 being a perfect 1:1 correlation. These data clearly establish that those AD subjects with higher levels of total serum cholesterol, LDL cholesterol ad ApoB are more likely to have higher levels of A&bgr;N-42. In control subjects (C), virtually no correlations were seen between these serum lipid parameters and A&bgr;N-42 levels ( FIG. 4 A-C,). The amounts of HDL also failed to show an association with A&bgr; N-42 in either control or AD brains ( FIG. 4D ). These data establish that higher concentrations of total serum cholesterol leads to higher levels of &bgr;-amyloid peptide in AD brains. The above study investigated whether factors associated with cardiovascular disease, such as high levels of serum total cholesterol, LDL cholesterol and low levels of HDL cholesterol, were associated with AD. The results establish that total serum and LDL cholesterol, as well as ApoB levels, are associated with increased deposition of A&bgr;N-42 in demented individuals with neuropathological confirmed AD. The brain deposition of A&bgr;N-42 was significantly correlated with serum total and LDL cholesterol, and ApoB in the AD, but not in control subjects. There were also a disproportionate number of AD (47%) compared to control (18%) subjects with LDL cholesterol greater than 112 mg/dL (i.e., above the third decile for LDL cholesterol). It is well-recognized that ApoE4 increases amyloid load in AD brain. The present data establish that the level of A&bgr;N-40 in AD brains appears governed almost exclusively by the presence of ApoE &egr;4. A&bgr;N-40 increases from 1.2 to 6.0 to 24.1 ug/g for 0, 1 and 2 copies of the ApoE &egr;4 allele, respectively. A similar but less dramatic trend is also observed for A&bgr;N-42. Immunological techniques have revealed an association between ApoE &egr;4 and higher concentrations of A&bgr; N-40 in AD cerebral cortex, and also between ApoE &egr;4 and vascular amyloid. Since most of A&bgr;N-40 is found in the cerebrovasculature, the foregoing data show that the presence of ApoE4 affects deposition of A&bgr; in blood vessels. The cerebrovascular amyloidosis observed in AD destroys the myocytes of small arteries and arterioles and obliterates the capillary network resulting in severe damage to cerebral blood flow. This compromise leads to neuronal damage through ischemia and hypoxia. Thus, ApoE &egr;4 may increase the risk of developing AD and accelerate its age of onset through indirect consequences on vessels in the brain. Several lines of evidence have already suggested that cholesterol, or cholesterol metabolism, might influence susceptibility to AD. Two previous clinical studies showed that total serum or LDL cholesterol was elevated in patients with AD. In addition, individuals with ApoE &egr;4, a recognized risk factor for cardiovascular disease and AD, also tend to manifest hypercholesterolemia. Moreover, the incidence of AD appears to be higher in countries with high fat and caloric diets, and decreased in populations ingesting diets that decrease cardiovascular disease. Epidemiological investigations have further demonstrated that the risk for AD was greater in individuals with elevated cholesterol levels, and that the onset of AD occurred earlier in those individuals who were ApoE &egr;4 carriers with high serum cholesterol. 1 TABLE 1 Comparison Between AD and Control Subjects With Respect to Serum Lipids and Brain Tissue A&bgr; N-40 and A&bgr; N-42 AD Control (n &equals; 64) (n &equals; 36) P value* age (years) 81.6 ± 0.9 78.7 ± 1.3 0.054 TC(rr.g/dL) 176.0 ± 8.2 152.8 ± 7.1 0.061 VLDL-C (mg/dL) 18.6 ± 2.0 17.0 ± 2.0 0.619 LDL-C (mg/dL) 124.0 ± 7.0 95.5 ± 5.0 0.006 HDL-C (mg/dL) 35.0 ± 1.8 42.3 ± 3.7 0.040 HDL-C/(VLDL-C &plus; LDL-C) 0.31 ± 0.03 0.41 ± 0.04 0.048 TG (mg/dL) 225.3 ± 12.6 201.4 ± 16.0 0.249 ApoA-I (mg/dL) 100.0 ± 3.3 108.2 ± 5.1 0.162 ApoD (mg/dL) 91.8 ± 4.4 76.6 ± 31 0.018 ApoE (mg/dL) 4.8 ± 0.3 5.0 ± 0.4 0.753 A&bgr; N-40 (&mgr;g/g) 7.47 ± 2.05 1.11 ± 0.56 0.024 A&bgr; N-42 (&mgr;g/g) 18.2 ± 1.7 7.87 ± 1.68 <0.001 A&bgr; Total (&mgr;g/g) 25.7 ± 2.8 9.0 ± 1.9 <0.001 TC &equals; Total scrum cholesterol; VLDL-C &equals; Very low density lipoprotein cholesterol; LDL-C &equals; Low density lipoprotein cholesterol; HDL-C &equals; High density lipoprotein cholesterol; TG &equals; Triglycerides. *Two-tailed Student T-test probability 
 EXAMPLE 2 This experiment was designed to determine the ability of lipid regulating agents to alter the production of &bgr;-amyloid peptide (A&bgr;) in cultured cells, and their consequent activity in preventing and treating Alzheimer's Disease. Chinese hamster ovary (CHO) cells were stably transfected with a construct to enable the overexpression of the human &bgr;-amyloid precursor protein (&bgr;APP gene to cause increased production of A&bgr;. The measurement of A&bgr; synthesized by these &bgr;APP-CHO cells was done using a standard sandwich ELISA assay, employing well-characterized antibodies to the N-terminus (6E10) and middle (4G8) of A&bgr;. This assay is routinely used to measure A&bgr; in tissues, body fluids, and cell culture media. Cultures of &bgr;APP-CHO cells were grown to near confluency, and then the test compounds were added at various dose concentrations to the cell medium. FIG. 5 shows the dramatic reduction in A&bgr; caused by several statins, Mevastatin, lovastatin, and simvastatin all caused a dramatic dose-dependent reduction in A&bgr;. Pravastatin caused a dose-dependent reduction in A&bgr; as well, albeit somewhat less pronounced. Several other lipid regulating agents were evaluated in the &bgr;APP-CHO cells. Avasimibe (CI-1011) caused a substantial dose-dependent reduction in A&bgr;, as shown in FIG. 6 . PD 69405, CI-1027, and CI-719 caused only moderate changes at the concentrations tested. 
 EXAMPLE 3 The following experiment established that lipid regulating agents cause a reduction in insoluble fibrillar A&bgr;N-42 in the brains of animals. Mice aged 24 months were fed a high fat (15%) high cholesterol (1.25%) diet containing 0.5% cholic acid (High Fat) or regular rodent chow (chow) for 4 weeks. During the last 2 weeks of the study, two groups of mice were given 10 mg/kg simvastatin daily by oral gavage. Mice were then sacrificed by anesthetic overdose perfused with cold 0.9% saline via heart puncture. The saline rinsed brain was then removed from the skull and frozen over dry ice. The brain samples were stored at −80° C. until assayed for A&bgr;N-40 and A&bgr;N-42. On the day of assay, brains were thawed and the hippocampus and cortex were dissected from the rest of the brain. These samples were dounce homogenized in tris-buffered saline (TBS) containing protease inhibitor cocktail (PIC) and 0.5 mM ethylene diamine tetraacetic acid (EDTA). The samples were centrifuged at 100,000XG for 1 hour. The supernatants were drawn off, and the remaining pellet was treated with 0.2% diethylamine buffer in 50 nM saline. The pellet was re-suspended in diethylamine (DEA) by probe sonication, and the samples were centrifuged again at 100,000XG, for 1 hour. The DEA extracted supernatant samples were drawn off and neutralized to pH 8.0 by the addition of 2 M tris HCl buffer. The amount of A&bgr;N-40 and A&bgr;N-42 were measured in these samples by ELISA. In addition, a protein assay was run on each sample so that variations in sample size could be normalized by protein content. Thus, A&bgr; values are expressed in ng/mg protein. Table 7 shows that the lipid regulating agent simvastatin (S) caused a substantial reduction in A&bgr;N-42 in all animals, compared to non-treated controls (C). The animals having the High Fat diet exhibited slightly less inhibition of A&bgr; N-42 than the Chow fed animals. The compound had only marginal effect on A&bgr; N-40.