Plasma Cholesterol In Animals Research Articles

Dietary α-cyclodextrin reduces atherosclerosis and modifies gut flora in apolipoprotein E-deficient mice.

α-Cyclodextrin (α-CD), a cyclic polymer of glucose, has been shown to lower plasma cholesterol in animals and humans; however, its effect on atherosclerosis has not been previously described. apoE-knockout mice were fed either low-fat diet (LFD; 5.2% fat, w/w), or Western high fat diet (21.2% fat) containing either no additions (WD), 1.5% α-CD (WDA); 1.5% β-CD (WDB); or 1.5% oligofructose-enriched inulin (WDI). Although plasma lipids were similar after 11 weeks on the WD vs. WDA diets, aortic atherosclerotic lesions were 65% less in mice on WDA compared to WD (P < 0.05), and similar to mice fed the LFD. No effect on atherosclerosis was observed for the other WD supplemented diets. By RNA-seq analysis of 16S rRNA, addition of α-CD to the WD resulted in significantly decreased cecal bacterial counts in genera Clostridium and Turicibacterium, and significantly increased Dehalobacteriaceae. At family level, Comamonadaceae significantly increased and Peptostreptococcaceae showed a negative trend. Several of these bacterial count changes correlated negatively with % atherosclerotic lesion and were associated with increased cecum weight and decreased plasma cholesterol levels. Addition of α-CD to the diet of apoE-knockout mice decreases atherosclerosis and is associated with changes in the gut flora.

Abstract: P444 TRANS INTESTINAL CHOLESTEROL EFFLUX PATHWAY IS NOT MEDIATED THROUGH HDL

SR-BI/apoE double knockout (dKO) mice exhibit many features of human coronary heart disease (CHD), including hypercholesterolemia, occlusive coronary atherosclerosis, cardiac hypertrophy, myocardial infarctions, cardiac dysfunction and premature death. Ezetimibe is a FDA-approved, intestinal cholesterol absorption inhibitor that lowers plasma LDL cholesterol in humans and animals and inhibits aortic root atherosclerosis in apoE KO mice, but has not been proven to reduce CHD. Three-week-ezetimibe treatment of dKO mice (0.005% (w/w) in standard chow administered from weaning) resulted in a 35% decrease in cholesterol in IDL/LDL-size lipoproteins, but not in VLDL- and HDL-size lipoproteins. Ezetimibe treatment significantly reduced aortic root (57%) and coronary arterial (68%) atherosclerosis, cardiomegaly (24%) and cardiac fibrosis (57%), and prolonged the lives of the mice (27%). This represents the first demonstration of beneficial effects of ezetimibe treatment on CHD. The dKO mice were similarly treated with SC-435 (0.01% (w/w)), an apical sodium codependent bile acid transporter (ASBT) inhibitor, that blocks intestinal absorption of bile acids, lowers plasma cholesterol in animals, and reduces aortic root atherosclerosis in apoE KO mice. The effects of SC-435 treatment were similar to those of ezetimibe: 37% decrease in ILD/LDL-size lipoprotein cholesterol and 57% prolongation in median lifespan. Thus, inhibition of intestinal absorption of either cholesterol (ezetimibe) or bile acids (SC-435) significantly reduced plasma IDL/LDL-size lipoprotein cholesterol levels and improved survival of SR-BI/apoE dKO mice. The SR-BI/apoE dKO murine model of atherosclerotic occlusive, arterial CHD appears to provide a useful system to evaluate compounds that modulate cholesterol homeostasis and atherosclerosis.

Inhibition of intestinal absorption of cholesterol by ezetimibe or bile acids by SC-435 alters lipoprotein metabolism and extends the lifespan of SR-BI/apoE double knockout mice

SR-BI/apoE double knockout (dKO) mice exhibit many features of human coronary heart disease (CHD), including hypercholesterolemia, occlusive coronary atherosclerosis, cardiac hypertrophy, myocardial infarctions, cardiac dysfunction and premature death. Ezetimibe is a FDA-approved, intestinal cholesterol absorption inhibitor that lowers plasma LDL cholesterol in humans and animals and inhibits aortic root atherosclerosis in apoE KO mice, but has not been proven to reduce CHD. Three-week-ezetimibe treatment of dKO mice (0.005% (w/w) in standard chow administered from weaning) resulted in a 35% decrease in cholesterol in IDL/LDL-size lipoproteins, but not in VLDL- and HDL-size lipoproteins. Ezetimibe treatment significantly reduced aortic root (57%) and coronary arterial (68%) atherosclerosis, cardiomegaly (24%) and cardiac fibrosis (57%), and prolonged the lives of the mice (27%). This represents the first demonstration of beneficial effects of ezetimibe treatment on CHD. The dKO mice were similarly treated with SC-435 (0.01% (w/w)), an apical sodium codependent bile acid transporter (ASBT) inhibitor, that blocks intestinal absorption of bile acids, lowers plasma cholesterol in animals, and reduces aortic root atherosclerosis in apoE KO mice. The effects of SC-435 treatment were similar to those of ezetimibe: 37% decrease in ILD/LDL-size lipoprotein cholesterol and 57% prolongation in median lifespan. Thus, inhibition of intestinal absorption of either cholesterol (ezetimibe) or bile acids (SC-435) significantly reduced plasma IDL/LDL-size lipoprotein cholesterol levels and improved survival of SR-BI/apoE dKO mice. The SR-BI/apoE dKO murine model of atherosclerotic occlusive, arterial CHD appears to provide a useful system to evaluate compounds that modulate cholesterol homeostasis and atherosclerosis.

Effect of dietary methionine on plasma and liver cholesterol concentrations in rats and expression of hepatic genes involved in cholesterol metabolism

Methionine has been shown to increase plasma cholesterol in animals. In the present study, mechanisms were investigated by which methionine could alter cholesterol metabolism. In the first experiment, forty growing rats were fed four casein-based diets differing in methionine content (2.6, 3.5, 4.5 or 6.0 g/kg) for 14 d. In the second experiment, isolated rat hepatocytes were incubated in media supplemented with 50, 100 or 200 micromol/l methionine. Dietary methionine tended to increase plasma homocysteine concentrations in the rats (P=0.058). A weak positive correlation between circulating homocysteine and plasma cholesterol was observed (R2 0.27, P<0.01). Rats fed 3.5 g/kg or more of methionine had higher concentrations of cholesterol in their plasma, in lipoprotein fractions of density (rho; kg/l) 1.006<rho<1.063 and rho>1.063, and in liver than rats fed 2.6 g/kg methionine. Rats fed 6 g/kg methionine had a higher hepatic expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol-7alpha-hydroxylase than rats fed less methionine. The phosphatidylcholine:phosphatidylethanolamine ratio in rat liver increased with rising dietary methionine concentration; the relative mRNA concentrations of phosphatidylethanolamine N-methyltransferase and cystathionine beta-synthase remained unaffected. Hepatocytes incubated in media supplemented with 100 or 200 micromol/l methionine had a higher cholesterol synthesis than hepatocytes incubated in a medium supplemented with 50 micromol/l methionine; the LDL uptake in hepatocytes was independent of the methionine concentration of the medium. In conclusion, the present study suggests that dietary methionine induces hypercholesterolaemia at least in part via an enhanced hepatic cholesterol synthesis.

Pharmacokinetics of the Acyl Coenzyme A: Cholesterol Acyl Transferase Inhibitor CP-105,191 in Dogs-The Effect of Food and Sesame Oil on Systemic Exposure following Oral Dosing

Inhibition of acyl coenzyme A:cholesterol acyl transferase (ACAT) decreases total plasma cholesterol in animals and may be an effective therapy for atherosclerosis in man. The pharmacokinetics of CP‐105, 191, a potent inhibitor of ACAT, were explored in fed and fasted dogs. Following oral administration of drug, mean apparent plasma halffile ranged from 9 to 16 h. Systemic availability of CP‐105, 191, as determined by AUC(0–∞), was approximately 3–4‐fold higher in fed dogs than in fasted dogs when 50 mg doses were administered as aqueous suspensions.Tmaxwas achieved more rapidly andCmaxwas lower in fasted dogs. When 50 mg doses, partially dissolved in 20 mL sesame oil, were administered to fed dogs, the availability of CP‐105, 191 increased by another factor of 2. A 12.5 mg dose of CP‐105, 191, completely dissolved in sesame oil, was administered to fed and fasted dogs. Plasma AUC's were similar for fed and fasted dogs following the 12.5 mg dose, indicating that the increased availability of drug when administered with food is related to the presence of lipid.

Dietary tocotrienols reduce concentrations of plasma cholesterol, apolipoprotein B, thromboxane B2, and platelet factor 4 in pigs with inherited hyperlipemias

Normolipemic and genetically hypercholesterolemic pigs of defined lipoprotein genotype were fed a standard diet supplemented with 50 micrograms/g tocotrienol-rich fraction (TRF) isolated from palm oil. Hypercholesterolemic pigs fed the TRF supplement showed a 44% decrease in total serum cholesterol, a 60% decrease in low-density-lipoprotein (LDL)-cholesterol, and significant decreases in levels of apolipoprotein B (26%), thromboxane-B2 (41%), and platelet factor 4 (PF4; 29%). The declines in thromboxane B2 and PF4 suggest that TRF has a marked protective effect on the endothelium and platelet aggregation. The effect of the lipid-lowering diet persisted only in the hypercholesterolemic swine after 8 wk feeding of the control diet. These results support observations from previous studies on lowering plasma cholesterol in animals by tocotrienols, which are naturally occurring compounds in grain and palm oils and may have some effect on lowering plasma cholesterol in humans.

Effects of blocking plasma lipid transfer protein activity in the rabbit

Plasma lipid transfer protein activity was completely blocked in rabbits for up to 48 h by infusion with goat antibody to rabbit lipid transfer protein. Lipid transfer protein activity in plasma of control animals, infused with antibody from a non-immune goat, decreased during the experiment but was never less than 50% of pre-infusion levels. During the period that lipid transfer protein activity was completely blocked, there were changes in high-density lipoprotein composition (expressed as % by weight) with a reduction in triacylglycerol from 8.4 ± 2.4% to 1.0 ± 0.2% ( P < 0.05) and an increase in esterified cholesterol from 10.7 ± 1.7% to 14.5 ± 0.3% ( P < 0.1). In conjunction with the observed changes in high-density lipoprotein composition, there was an increase in high-density lipoprotein particle size from a mean radius of 4.7 to 5.4 nm. The change in composition and particle size was not observed in high-density lipoproteins from control animals. There was a change in the distribution of plasma cholesterol in control animals, with a fall in the proportion of cholesterol in high-density lipoproteins ( P < 0.02) and consequently an increase in the proportion of cholesterol in low-density lipoproteins ( P < 0.02). However, the distribution of plasma cholesterol in animals in which lipid transfer protein activity was inhibited was maintained at original levels during the period of inhibition. Consequently, in these animals, there was a less atherogenic distribution of cholesterol during the period of lipid transfer protein inhibition when compared with control animals. The changes observed in lipoproteins, in the absence of lipid transfer protein activity, demonstrate that lipid transfer protein modifies lipoproteins in vivo and appears to contribute to a more atherogenic lipid profile.

Effects of AOMA on cholesterol metabolism in man

A new cholesterol-lowering agent, surfomer (AOMA), has been developed that blocks cholesterol absorption and lowers plasma cholesterol in animals. To evaluate AOMA in man, we studied its effects on plasma cholesterol, cholesterol absorption, fecal excretion of cholesterol and its bacterial degradation products, coprostanol and coprostanone, and percent saturation of gallbladder bile with cholesterol in 20 individuals chosen for hyperlipidemia. These patients had low density lipoprotein cholesterol (LDL-C) of 215 ± 29 mg/dl. Two dose levels of AOMA were compared (10.8 and 5.4 grams daily), each for 1 mo in a study that combined features of inpatient and outpatient investigation. AOMA was tolerated well by all volunteers. There was a statistically significant correlation between percent absorption and LDL-C in both the control and AOMA treated states. AOMA lowered mean plasma cholesterol and LDL-C by 9.1% and 12.9% at the high dose and by 6.4% and 8.3% at the low dose, respectively. Triglyceride (control = 223 ± 58 mg/dl, treatment = 232 ± 85 mg/dl), high density lipoprotein cholesterol (HDL-C: control = 50 ± 11 mg/dl, treatment = 50 ± 13 mg/dl), and other lipoprotein lipids were not affected. AOMA lowered cholesterol absorption by 25% on the high dose. For 18 20 patients there was a statistically significant ( p < 0.001) correlation ( r = 0.74) between percent LDL-C reduction and percent absorption inhibition. For these patients, presumably, variable effectiveness of the agent in inhibiting absorption was the most important predictor of individual responsiveness although individual variation in other cholesterol regulatory mechanisms also played a role. Two other patients showed marked LDL-C reduction at unusually low levels of absorption inhibition. We also had the opportunity to compare the effects of AOMA with neomycin in 8 volunteers. Neomycin was 50% more effective in lowering LDL-C than AOMA; however, it was twice as effective in inhibiting absorption as well. AOMA dramatically reduced fecal excretion of cholesterol bacterial conversion products; whereas cholesterol per se accounted for only 50% of total neutral steroid excretion in the control state, it accounted for 93% of steroid excretion when patients were administered 10.8 grams of AOMA daily. In four patients studied there was no adverse effect of AOMA on gallbladder saturation with cholesterol; in fact, the percent saturation tended to decrease with AOMA in these four patients.