betadex and Hypercholesterolemia

Polymeric bile acid sequestrants (BAS) have recently attracted much attention as lipid-lowering agents. These non-absorbable materials specifically bind bile acids (BAs) in the intestine, preventing bile acid (BA) reabsorption into the blood through enterohepatic circulation. Therefore, it is important to understand the structure-property relationships between the polymer sequestrant and its ability to bind specific BAs molecules. In this review, we describe pleiotropic effects of bile acids, and we focus on BAS with various molecular architectures that result in different mechanisms of BA sequestration. Here, we present 1) amphiphilic polymers based on poly(meth)acrylates, poly(meth)acrylamides, polyalkylamines and polyallylamines containing quaternary ammonium groups, 2) cyclodextrins, and 3) BAS prepared via molecular imprinting methods. The synthetic approaches leading to individual BAS preparation, as well as results of their in vitro BA binding activities and in vivo lipid-lowering activities, are discussed.

Topics: Animals; Anticholesteremic Agents; Bile Acids and Salts; Binding Sites; Drug Design; Humans; Hypercholesterolemia; Molecular Structure; Polymers

Familial Alzheimer's disease (FAD)-associated presenilin 1 (PS1) serves as a catalytic subunit of γ-secretase complex, which mediates the proteolytic liberation of β-amyloid (Aβ) from β-amyloid precursor protein (APP). In addition to its proteolytic role, PS1 is involved in non-proteolytic functions such as protein trafficking and ion channel regulation. Furthermore, postmortem AD brains as well as AD patients showed dysregulation of cholesterol metabolism. Since cholesterol has been implicated in regulating Aβ production, we investigated whether the FAD PS1-associated cholesterol elevation could influence APP processing. We found that in CHO cells stably expressing FAD-associated PS1 ΔE9, total cholesterol levels are elevated compared to cells expressing wild-type PS1. We also found that localization of APP in cholesterol-enriched lipid rafts is substantially increased in the mutant cells. Reducing the cholesterol levels by either methyl-β-cyclodextrin or an inhibitor of CYP51, an enzyme mediating the elevated cholesterol in PS1 ΔE9-expressing cells, significantly reduced lipid raft-associated APP. In contrast, exogenous cholesterol increased lipid raft-associated APP. These data suggest that in the FAD PS1 ΔE9 cells, the elevated cellular cholesterol level contributes to the altered APP processing by increasing APP localized in lipid rafts.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; beta-Cyclodextrins; Brain; CHO Cells; Cholesterol; Cricetinae; Cricetulus; Humans; Hypercholesterolemia; Membrane Microdomains; Mutation; Presenilin-1

Bile acid sequestrants (BAS) represent a therapeutic approach for the management of hypercholesterolemia that relies on the cationic polymeric nature of BAS to selectively bind negatively charged bile acids. We hypothesized that the cross-linking of β-cyclodextrin (β-CD) and saccharides such as starch or dextrin with divinyl sulfone (DVS) yields homo- and hetero-polymeric materials with the ability to trap sterols. Our hypothesis was put to test by synthesizing a library of 22 polymers that were screened to evaluate their capability to sequester both cholesterol (CHOL) and cholic and deoxycholic acids (CA and DCA). Three polymers synthesized in high yield were identified as promising. Two were neutral hetero-polymers of β-CD and starch or dextrin and the third was a weakly cationic homo-polymer of starch, highlighting the importance of the cavity effect. They were tested in hypercholesterolemic male Wistar rats and their ability to regulate hypercholesterolemia was similar to that for the reference BAS cholestyramine, but with two additional advantages: (i) they normalized the TG level and (ii) they did not increase the creatinine level. Neither hepatotoxicity nor kidney injury was detected, further supporting them as therapeutical candidates to manage hypercholesterolemia.

Topics: Animals; beta-Cyclodextrins; Bile Acids and Salts; Cross-Linking Reagents; Hypercholesterolemia; In Vitro Techniques; Kidney; Liver; Male; Polymers; Rats; Rats, Wistar; Starch; Sulfones

The ability of pharmacological agents to target both "classical" risk factors and inflammation may be key for successful outcomes in the prevention and treatment of atherogenesis. Among the promising drugs interfering with cholesterol metabolism, we investigated whether methyl beta-cyclodextrin (KLEPTOSE® CRYSMEB) could positively impact on atherogenesis, lipid profile and atherosclerotic plaque inflammation in ApoE-/- mice. Eleven-week old ApoE-/- mice were fed either a normal diet (N.D.) or a high-cholesterol diet (H.D.), resulting in different levels of hypercholesterolemia. KLEPTOSE® CRYSMEB (40mg/kg) or vehicle was intraperitoneally administrated 3 times per week in the last 16weeks before euthanasia in mice under N.D. and in the last 11weeks under H.D. Treatment with KLEPTOSE® CRYSMEB reduced triglyceride serum levels in both atherogenesis mouse models. In H.D. mice, treatment with KLEPTOSE® CRYSMEB increased HDL-cholesterol levels and reduced free fatty acids and spleen weight. In both mouse models, treatment with KLEPTOSE® CRYSMEB reduced atherosclerotic plaque size in thoraco-abdominal aortas and intraplaque T lymphocyte content, but did not induce relevant improvements in other histological parameters of vulnerability (macrophage, neutrophil, MMP-9 and collagen content). Conversely and more markedly in H.D. mice, treatment with KLEPTOSE® CRYSMEB was associated with a reduction in genetic markers of Th1-mediated immune response. In vitro, KLEPTOSE® CRYSMEB dose-dependently abrogated Th1 proliferation and IFNγ release. In conclusion, treatment with KLEPTOSE® CRYSMEB reduced atherosclerotic plaque size by improving triglyceride serum levels and Th1-mediated response. These results indicate this drug as a potential tool for blocking atheroprogression associated with different severity degrees of hypercholesterolemia.

Topics: Animals; Aorta; Apolipoproteins E; Atherosclerosis; beta-Cyclodextrins; Cholesterol; Cholesterol, HDL; Disease Models, Animal; Hypercholesterolemia; Inflammation; Lipid Metabolism; Lipids; Macrophages; Mice; Mice, Inbred C57BL; Plaque, Atherosclerotic; Th1 Cells; Triglycerides

Continuous exposure of polymorphonuclear leukocytes (PMNLs) to circulatory hemodynamics points to fluid flow as a biophysical regulator of their activity. Specifically, fluid flow-derived shear stresses deactivate leukocytes via actions on the conformational activities of proteins on the cell surface. Because membrane properties affect activities of membrane-bound proteins, we hypothesized that changes in the physical properties of cell membranes influence PMNL sensitivity to fluid shear stress. For this purpose, we modified PMNL membranes and showed that the cellular mechanosensitivity to shear was impaired whether we increased, reduced, or disrupted the organization of cholesterol within the lipid bilayer. Notably, PMNLs with enriched membrane cholesterol exhibited attenuated pseudopod retraction responses to shear that were recovered by select concentrations of benzyl alcohol (a membrane fluidizer). In fact, PMNL responses to shear positively correlated (R(2) = 0.96; P < 0.0001) with cholesterol-related membrane fluidity. Moreover, in low-density lipoprotein receptor-deficient (LDLr(-/-)) mice fed a high-fat diet (a hypercholesterolemia model), PMNL shear-responses correlated (R(2) = 0.5; P < 0.01) with blood concentrations of unesterified (i.e., free) cholesterol. In this regard, the shear-responses of PMNLs gradually diminished and eventually reversed as free cholesterol levels in blood increased during 8 wk of the high-fat diet. Collectively, our results provided evidence that cholesterol is an important component of the PMNL mechanotransducing capacity and elevated membrane cholesterol impairs PMNL shear-responses at least partially through its impact on membrane fluidity. This cholesterol-linked perturbation may contribute to dysregulated PMNL activity (e.g., chronic inflammation) related to hypercholesterolemia and causal for cardiovascular pathologies (e.g., atherosclerosis).

Topics: Animals; Benzyl Alcohol; beta-Cyclodextrins; Cell Adhesion; Cell Membrane; Cell Movement; Cholesterol; Disease Models, Animal; Dose-Response Relationship, Drug; Filipin; Humans; Hypercholesterolemia; Male; Mechanotransduction, Cellular; Membrane Fluidity; Mice; Mice, Knockout; Neutrophils; Pseudopodia; Receptors, LDL; Stress, Mechanical; Time Factors; Up-Regulation

We investigated whether primary hypercholesterolaemia per se affects glucose homeostasis and insulin secretion in low-density lipoprotein receptor knockout mice (LDLR(-/-)). Glucose plasma levels were increased and insulin decreased in LDLR(-/-) compared to the wild-type mice. LDLR(-/-) mice presented impaired glucose tolerance, but normal whole body insulin sensitivity. The dose-response curve of glucose-stimulated insulin secretion was shifted to the right in LDLR(-/-) islets. Significant reductions in insulin secretion in response to l-leucine or 2-ketoisocaproic acid were also observed in LDLR(-/-). Islet morphometric parameters, total insulin and DNA content were similar in both groups. Glucose uptake and oxidation were reduced in LDLR(-/-) islets. Removal of cholesterol from LDLR(-/-) islets corrected glucose-stimulated insulin secretion. These results indicate that enhanced membrane cholesterol content due to hypercholesterolaemia leads to a lower insulin secretion and glucose intolerance without affecting body insulin sensitivity. This represents an additional risk factor for diabetes and atherosclerosis in primary hypercholesterolaemia.

Topics: Animals; beta-Cyclodextrins; Cholesterol; Dietary Fats; Female; Glucose; Glucose Tolerance Test; Homeostasis; Hypercholesterolemia; Insulin; Insulin Secretion; Islets of Langerhans; Leucine; Lipids; Male; Mice; Mice, Knockout; Obesity; Oxidation-Reduction; Receptors, LDL

We tested the hypothesis that certain membrane-intercalating agents increase the chemical activity of cholesterol by displacing it from its low activity association with phospholipids. Octanol, 1,2-dioctanoyl-sn-glycerol (a diglyceride), and N-hexanoyl-D-erythrosphingosine (a ceramide) were shown to increase both the rate of transfer and the extent of equilibrium partition of human red blood cell cholesterol to methyl-beta-cyclodextrin. These agents also promoted the interaction of the sterol with two cholesterol-specific probes, cholesterol oxidase and saponin. Expanding the pool of bilayer phospholipids with lysophosphatides countered these effects. The three intercalators also protected the red cells against lysis by cholesterol depletion as if substituting for the extracted sterol. As is the case for excess plasma membrane cholesterol, treating human fibroblasts with octanol, diglyceride, or ceramide stimulated the rapid inactivation of their hydroxymethylglutaryl-CoA reductase, presumably through an increase in the pool of endoplasmic reticulum cholesterol. These data supported the stated hypothesis and point to competition between cholesterol and endogenous and exogenous intercalators for association with membrane phospholipids. We also describe simple screens using red cells in a microtiter well format to identify intercalating agents that increase or decrease the activity of membrane cholesterol.

Topics: beta-Cyclodextrins; Binding, Competitive; Cell Membrane; Ceramides; Cholesterol; Cholesterol Oxidase; Cyclodextrins; Diglycerides; Dose-Response Relationship, Drug; Endoplasmic Reticulum; Erythrocytes; Fibroblasts; Hemolysis; Humans; Hydroxymethylglutaryl CoA Reductases; Hypercholesterolemia; Lipid Bilayers; Oxygen; Phospholipids; Saponins; Time Factors

Beta-cyclodextrin is a compound that forms inclusion complexes with a variety of molecules, specially bile acids and sterols. This study examines the effects of beta-cyclodextrin on cholesterol and bile acid metabolism in hypercholesterolaemic rats. Male Wistar rats were divided into 4 groups that received during 7 weeks: control diet, 2% cholesterol diet (A), A+2.5% beta-cyclodextrin (B) and A+5% beta-cyclodextrin (C). The cholesterol-rich diet induced hepatomegaly and fatty liver and significantly reduced cholesterol, bile acid and phospholipid secretion. Addition of beta-cyclodextrin normalised biliary lipid secretion. Moreover, when compared to A, beta-cyclodextrin significantly lowered plasma phospholipid concentration (B: -21%; C: -29%) and the liver free/total cholesterol molar ratio (B: -40%; C: -38%), increased bile acid faecal output (B: +17%; C: +62%) and enhanced cholesterol 7alpha-hydroxylase activity (B:+50%; C : +100%)and mRNA levels (B: + 14%; C: +29%). 5% beta-cyclodextrin also reduced plasma triglycerides concentration (-38%). However, ALT and AST activities were significantly increased (B: +140% and +280%; C: +72% and +135%) and there was a high incidence of cell necrosis with portal inflammatory cell infiltration. Addition of beta-cyclodextrin to a cholesterol-rich diet results in a triglyceride-lowering action, enhancement of bile acid synthesis and excretion, and normalization of biliary lipid secretion, but produces a marked hepatotoxic effect.

Topics: Alanine Transaminase; Animals; Anticholesteremic Agents; Aspartate Aminotransferases; beta-Cyclodextrins; Bile; Bile Acids and Salts; Cholesterol; Cholesterol 7-alpha-Hydroxylase; Cholesterol, Dietary; Cyclodextrins; Diet; Eating; Feces; Hypercholesterolemia; Liver; Male; Rats; Rats, Wistar; Weight Gain

In endothelial cells, nitric oxide (NO) is produced by the endothelial isoform of nitric oxide synthase (eNOS), which is localized in the cholesterol-rich plasmalemmal microdomains involved in signal transduction, known as caveolae. The present study was undertaken to evaluate the effect of hypercholesterolemia and fatty streak formation on the endothelial caveolae and on endothelial function, and attempted to determine to what extent the caveolae were involved in endothelium-derived NO production.. We first studied the effect of atheroma on endothelial NO production. Fatty streak infiltrated aorta of cholesterol-fed New Zealand White rabbits demonstrated an impairment of acetylcholine-induced relaxation and nearly normal calcium ionophore A23187-induced maximal relaxation. The abundance of caveolae in the endothelium covering the fatty streak, as well as their 'grape-like' clustering, appeared to be decreased. We therefore investigated the effect, on endothelial NO production, of the cholesterol-binding agents 2-hydroxypropyl-beta-cyclodextrin (hp-beta-CD) and filipin, known to alter caveolae structure and/or function. Treatment with either hp-beta-CD (2%) or filipin (4 microg/ml) did not affect contraction to phenylephrine or relaxant responses to A23187 or to the NO donor sodium nitroprusside. In contrast, both treatments impaired acetylcholine-induced relaxation. Cultured bovine aortic endothelial cells (BAEC) similarly treated with hp-beta-CD demonstrated a 50% decrease of total cellular cholesterol and a decreased abundance of caveolae as well as their 'grape-like' clustering. Cholesterol depletion decreased the bradykinin-induced transient peak of free intracellular calcium and subsequent receptor-stimulated NO production (assessed using reporter cells rich in soluble guanylyl cyclase), whereas that elicited by A23187 remained unaltered.. Fatty streak deposit is associated with a decrease in caveolae 'transductosomes' abundance which appears to represent a novel mechanism of endothelial dysfunction.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; Animals; Aorta, Thoracic; Aortic Diseases; Arteriosclerosis; beta-Cyclodextrins; Cell Culture Techniques; Cell Membrane; Cyclodextrins; Endothelium, Vascular; Filipin; Hypercholesterolemia; Male; Microscopy, Electron; Muscle Contraction; Nitric Oxide; Rabbits