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PubMed1996

Results of intensive long-term treatment of familial hypercholesterolemia.

Fifty-seven patients with familial hypercholesterolemia (FH) with mean age of 48 years (range 30 to 69), participated in a follow-up examination 5.5 years after the completion of a 1-year trial with lovastatin, cholestyramine, probucol, or omega-3 fatty acids. The goals were to record quality of life, compliance to treatment, adverse effects, and clinical outcome. The quality of life was similar to that in a Norwegian reference population. The factors causing most distress to patients were keeping a diet low in saturated fats, taking medication, and fear of death. The medication was mostly prescribed in maximum dosages. At follow-up, the reduction in total cholesterol was 36% (p < 0.05), low-density lipoprotein (LDL) cholesterol 38% (p < 0.05), triglycerides 20% (p < 0.05) compared with being on diet therapy only. High-density lipoprotein (HDL) cholesterol increased 8% (p < 0.05). Intake of saturated and monounsaturated fat increased 1.5% and 1.7% (p < 0.05), respectively; polyunsaturated fat was unchanged. Three patients experienced myocardial infarction, of whom 2 died and 1 developed angina pectoris. Before the start of lovastatin treatment, 27 coronary events occurred per 1,000 patient-years in this group compared with 12 events per 1,000 patient-years thereafter. Of 28 patients reporting adverse events, 4 discontinued lovastatin and 3 discontinued cholestyramine. Several practical and psychological difficulties were associated with FH. Long-term intensive lipid-lowering therapy was possible in FH outpatients without loss of effect and with good compliance to therapy. Intensive therapy, today is, however, not sufficient for many FH patients to reach a therapeutic goal of LDL cholesterol < 4.0 mmol/L. More potent lipid-lowering agents are needed.

Adult↗

PubMed1998

Cerivastatin in the treatment of mixed hyperlipidemia: the RIGHT study. The Cerivastatin Study Group. Cerivastatin Gemfibrozil Hyperlipidemia Treatment.

The Cerivastatin Gemfibrozil Hyperlipidemia Treatment (RIGHT) study--a multicenter, randomized, double-blind, placebo-controlled study--compared the lipid-lowering effects of cerivastatin, once daily at doses of 0.1, 0.2, and 0.3 mg with those of twice-daily gemfibrozil 600 mg in 751 patients with primary mixed hyperlipidemia. Randomization to the first 16 weeks of treatment followed an initial 4-week washout period and subsequent 6-week diet-controlled, placebo run-in phase. Patients continued to receive study medication for a further 36 weeks, with those previously on placebo switched to 0.1 mg/day cerivastatin at the end of week 16. Additional cholestyramine therapy was permitted at week 36 in patients with uncontrolled low-density lipoprotein (LDL) cholesterol levels. Cerivastatin achieved significant dose-dependent reductions in LDL cholesterol of 15-24% after 16 weeks of treatment, compared with reductions of 7.5% with gemfibrozil. Over this period both cerivastatin (0.3 mg) and gemfibrozil (1,200 mg) significantly decreased levels of triglycerides (20.3% vs 50.3%, respectively) and very low-density lipoprotein (VLDL) cholesterol (30.8% vs 47.1%, respectively), as well as increasing high-density lipoprotein (HDL) cholesterol (11.3% vs 13.3%, respectively). The reductions in LDL cholesterol and other atherogenic lipids and lipoproteins at 16 weeks were sustained in the subsequent 36-week double-blind continuation phase, during which time <10% of patients received additional cholestyramine therapy. Both study drugs were well tolerated, with the incidence of adverse events similar to that of placebo treatment. Clinically significant increases in hepatic transaminases and creatine phosphokinase occurred at a similar low frequency of around 1%. This study demonstrated that cerivastatin is a safe, well-tolerated, and effective treatment for lowering elevated LDL cholesterol and triglycerides in patients with mixed hyperlipidemia.

Adolescent↗

PubMed1989

Efficacy and tolerability of simvastatin (MK-733).

The efficacy of simvastatin, a new inhibitor of cholesterol biosynthesis, was studied in patients with familial hypercholesterolemia. A mean reduction in low-density lipoprotein cholesterol of 38 percent was observed after eight weeks of treatment with 20 mg of simvastatin; a 42 percent reduction was seen after the next 16 weeks with 40 mg. There was no difference in response whether the drug was taken in one or two doses. In another study, simvastatin (40 mg per day) was compared with cholestyramine (8 to 16 g per day). After 12 weeks, low-density lipoprotein cholesterol was reduced 43 percent by simvastatin and 29 percent by cholestyramine. Combination therapy caused a reduction in low-density lipoprotein cholesterol of 54 percent. Simvastatin appeared also to be a potent hypolipidemic drug in 10 patients with familial dysbetalipoproteinemia. The drug was well tolerated. Adverse effects were primarily composed of increases in serum transaminases and creatine phosphokinase. No effects of simvastatin on the production of steroid hormones were observed.

Adrenal Cortex↗

PubMed1998

The level of 7-dehydrocholesterol in plasma reflects the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase in the human liver.

Plasma levels of the cholesterol precursor 7-dehydrocholesterol (7-DHC) were compared with activities of the rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase assayed in liver biopsies from patients undergoing cholecystectomy. Some patients were treated with cholestyramine, deoxycholic acid or chenodeoxycholic acid prior to surgery in order to alter the activity of the enzyme. The median level of 7-DHC and the activity of HMG-CoA reductase in the untreated group were 55 ng/ml and 98 pmol/min/mg protein, respectively. The sterol levels and enzyme activities were increased in patients treated with cholestyramine (85 ng/ml and 439 pmol/min/mg protein) and deoxycholic acid (86 ng/ml and 173 pmol/min/mg protein) and decreased in patients treated with chenodeoxycholic acid (38 ng/ml and 51 pmol/min/mg protein). There was a strong positive correlation (rs=0.75, P<0.0005) between the plasma levels of 7-DHC and the activities of hepatic HMG-CoA reductase in these patients. This correlation was further improved when the plasma levels of 7-DHC were expressed relative to those of cholesterol (rs=0.90, P<0.0001). The results show that the level of 7-DHC in plasma reflects the activity of HMG-CoA reductase in the liver.

Adult↗

PubMed1999

Modulation of cholesterol 7alpha-hydroxylase and sterol 27-hydroxylase activities by steroids and physiological conditions in hamster.

Our purpose was to examine the in vitro modulation of liver mitochondrial sterol 27-hydroxylase (S27OHase) and microsomal cholesterol 7alpha-hydroxylase (CH7alphaOHase) activities by certain drugs, sterols, oxysterols and bile acids, and to compare the influence of sex, age, diet and cholestyramine on these activities, in the hamster. In vitro, 7beta-hydroxycholesterol and 5alpha-cholestan-3beta-ol (cholestanol) were strong inhibitors (at 2 microM) of both enzyme activities, while 5beta-cholestan-3alpha-ol (epicoprostanol, 2 microM) and cyclosporin A (20 microM) inhibited S27OHase, but not CH7alphaOHase. These data suggest that a hydroxyl group at the 7alpha position is not required to inhibit CH7alphaOHase and that the presence of an aliphatic CH2-CH-(CH3)2 chain appears to be structurally important for S27OHase activity. Both enzyme activities remained unchanged by hyodeoxycholic acid (40 or 80 microM) while epicoprostanol inhibited only S27OHase and chenodeoxycholic acid only CH7alphaOHase. Adult (9-week old) male or female hamsters displayed similar S27OHase activity but the CH7alphaOHase activity was lower in females than in males, suggesting that the neutral bile acid pathway has a less important role in females. In male hamsters, S27OHase activity did not change with age, while CH7alphaOHase activity significantly increased (one-year vs 9-week old). A semi-purified sucrose-rich (lithogenic) diet significantly lowered both enzyme activities compared to the commercial diet. Cholestyramine induced a stimulation of both enzymes, slightly more vigorously however for the key enzyme involved in the neutral pathway. Taken together, these data indicate that the two enzymes are separately regulated and that certain drugs or steroid compounds can be useful for specifically inhibiting or stimulating the neutral or acidic bile acid pathway.

Age Factors↗

PubMed1977

Intestinal absorption of 25-hydroxyvitamin D and osteomalacia in primary biliary cirrhosis.

Bone histology and intestinal absorption of 25-hydroxyvitamin D3 (25-OHD) were investigated in 11 patients with primary biliary cirrhosis (P.B.C.). 4 patients had osteomalacia, and all these had received long-term cholestyramine. Plasma-25-hydroxyvitamin-D (25-OHD) concentrations after an oral dose of 25-OHD3 were significantly lower in the patients with P.B.C. (especially those with osteomalacia) than in normal controls. Serum calcium and urinary calcium excretion were lower, and serum-alkaline-phosphatase higher, in patients with osteomalacia. It is suggested that absorption of 25-OHD undergoing enterohepatic circulation and of dietary vitamin D is reduced in patients with P.B.C. Absorption of 25-OHD is further decreased by cholestyramine and the development of osteomalacia is thus hastened.

Aged↗

PubMed1978

Value of bile-acid binding agents in post-vagotomy diarrhoea.

Cholecystectomy increases the incidence of post-vagotomy diarrhoea. The effect of agents which either bind bile acids or prevent their action on the colonic mucosa has been studied in 31 patients with post-vagotomy diarrhoea--15 had had vagotomy and pyloroplasty alone and 16 vagotomy and pyloroplasty and cholecystectomy. Cholestyramine was particularly useful after the combined operation. Aluminium hydroxide in large doses has a similar mechanism of action to cholestyramine and is cheaper and more palatable, but propranolol was of no value. This study suggests that the excretion and chemical composition of bile and the handling of bile acids by the small intestine is of fundamental importance in the pathogenesis of post-vagotomy diarrhoea.

Aluminum Hydroxide↗

PubMed2002

The role of transhepatic bile salt flux in the control of hepatic secretion of triacylglycerol-rich lipoproteins in vivo in rodents.

Bile salts (BS) have been shown to suppress the secretion of very-low-density lipoprotein-triglyceride (VLDL-TG) in rat and human hepatocytes in vitro. In the present study, we investigated whether the transhepatic BS flux affects VLDL-TG concentration and hepatic VLDL-TG secretion in vivo. In rats, the transhepatic BS flux was quantitatively manipulated by 1-week chronic bile diversion (BD), followed by intraduodenal infusion with taurocholate (TC) or saline for 6 h. In mice, the transhepatic BS flux was manipulated by a 3-week dietary supplementation with TC (0.5 wt.%) or cholestyramine (2 wt.%). In rats, BD followed by saline or TC infusion did not affect plasma triacylglycerol (TG) concentration, hepatic TG production rate or VLDL lipid composition, compared to control rats. In mice supplemented for 3 weeks with TC or cholestyramine, the transhepatic BS flux was increased by 335% and decreased by 48%, respectively, compared to controls. Among the three experimental groups of mice, an inverse relationship between transhepatic BS flux and either plasma TG concentration (R(2)=0.89) or VLDL-TG production rate (R(2)=0.87) was observed, but differences were relatively small. Present data support the concept that BS can reduce VLDL-TG concentration and inhibit hepatic TG secretion in vivo; however, this occurs only at supraphysiological transhepatic BS fluxes in mice.

Animals↗

PubMed1989

Disposition of lorazepam in human beings: enterohepatic recirculation and first-pass effect.

The effects of neomycin and cholestyramine on the disposition of lorazepam was examined in seven healthy drug-free men. Half-life as determined for the oral route was, in all subjects, 15% to 35% less than that determined for the intravenous route. Free oral clearance was slightly but not significantly less than free systemic clearance, but the ratio of the AUC of lorazepam glucuronide corrected for dose was twofold greater by the oral route. Urinary recoveries also differed (71.6% and 50.4%, oral versus intravenous). Neomycin and cholestyramine treatment resulted in a 19% to 26% reduction in half-life attendant on a 34% increase in free oral clearance and a 24% increase in free systemic clearance. This suggests that lorazepam undergoes significant enterohepatic recirculation in human beings and that there exists an extrahepatic pathway, at least for the intravenous route. Since pharmacokinetic measurements do not take these physiologic processes into account, the drug cannot properly be used as a marker of conjugative metabolism.

Administration, Oral↗

PubMed2003

YM-53601, a novel squalene synthase inhibitor, suppresses lipogenic biosynthesis and lipid secretion in rodents.

1. To better understand how it decreases plasma cholesterol and triglyceride levels, we evaluated the effect of (E)-2-[2-fluoro-2-(quinuclidin-3-ylidene)ethoxy]-9H-carbazole monohydrochloride(YM-53601) on lipogenic biosynthesis in the liver and lipid secretion from the liver in rats and hamsters. 2. Single administration of YM-53601 in cholestyramine-treated rats inhibited triglyceride and free fatty acid (FFA) biosynthesis at a similar dose range to that at which it inhibited cholesterol biosynthesis. YM-53601 inhibited both triglyceride and FFA biosynthesis in hamsters treated with cholestyramine. 3. YM-53601 by single oral administration decreased the enhanced plasma triglyceride levels in hamsters induced by an injection of protamine sulfate, which inhibits lipoprotein lipase (LPL) and consequently increases plasma very low-density lipoprotein (VLDL) triglyceride levels. YM-53601 also decreased the enhanced plasma triglyceride and cholesterol levels in hamsters treated with Triton WR1339, which also inhibits the degradation of VLDL. Plasma cholesterol was significantly decreased as soon as 1 h after single administration of YM-53601 in hamsters fed a normal diet. 4. This is the first report that a squalene synthase inhibitor suppresses lipogenic biosynthesis in the liver and cholesterol and triglyceride secretion from the liver in vivo. We therefore suggest that the mechanism by which YM-53601 decreases plasma triglyceride might include these effects. The finding that YM-53601 rapidly decreased plasma cholesterol suggests that this compound may be effective in decreasing plasma cholesterol levels early in the course of treatment of hypercholesterolemia in humans.

Animals↗

PubMed1976

Studies on the response of cholesterol biogenesis in feeding in rats: evidence against the existence of diurnal rhythms.

1. The biosynthesis of cholesterol was studied, by using various precursors, in rats subjected to several dietary regimes. 2. The use of 3H2O as a substrate to demonstrate differences in cholesterogenesis under various conditions was validated by using rats fed on cholesterol or cholestyramine. Cholesterol feeding resulted in decreased cholesterogenesis, whereas cholestyramine caused an increase. 3. With acetate as precursor, the biosynthesis of both digitonin-precipitable sterol and fatty acids was increased in vitro in response to a meal. 4. In rats fed ad libitum, hepatic cholesterogenesis was increased at midnight relative to mid-morning as measured by using acetate precursor in vitro. However, no such difference was found by using 3H2O in vivo. 5. The lipogenic response was measured in meal-fed rats by using 3H2O or octanoate in vivo. In contrast with findings with acetate in vitro, no postprandial stimulation of cholesterogenesis was seen with either 3H2O or octanoate as precursor, whereas fatty acid biosynthesis from either substrate was increased. 6. These findings are discussed with respect to current theories about the circadian rhythm of cholesterogenesis. Such theories are based on experiments using isolated enzyme measurements or non-physiological precursors such as acetate. 7. It is considered that results obtained with 3H2O give an accurate representation of cholesterogenesis under various conditions, and it is therefore suggested that hepatic cholesterogenesis in rats is not subjected to the same degree of diurnal rhythm as has previously been believed.

Acetates↗

PubMed1986

Regulation of low-density-lipoprotein metabolism in the rat.

The mechanism of regulation of plasma low-density-lipoprotein (LDL) metabolism in the rat was studied under a number of experimental conditions. LDL clearance and uptake in the liver was measured after intravenous pulse injection of [14C]sucrose-labelled LDL alone or in combination with reductively methylated [3H]sucrose-labelled LDL. Hyperthyroid rats showed a significant increase in fractional catabolic rate (FCR) and the proportion of LDL degraded in the liver, whereas the synthetic rate of LDL increased by 50%. Receptor-mediated clearance increased 2-fold. Hypothyroid rats showed a significant increase in LDL concentration. The FCR and proportion of LDL degraded in the liver were decreased significantly. Receptor-mediated clearance was also reduced. Cholesterol feeding increased chylomicron, very-low-density-and intermediate-density-lipoprotein cholesterol concentrations, but there was no change in the LDL concentration, FCR or the synthetic rate of LDL. Cholestyramine feeding did not induce changes in the kinetic parameters. These results indicate that, in the rat, the hepatic LDL-receptor pathway is under hormonal control, whereas cholesterol and cholestyramine feeding have no demonstrated effect on LDL metabolism.

Animals↗

PubMed1989

Regulation of mevalonate 5-pyrophosphate decarboxylase in isolated cells from chick intestinal epithelium.

The present studies were undertaken to determine whether mevalonate 5-pyrophosphate decarboxylase (EC 4.1.1.33) is subject to physiological regulation in the intestinal mucosa. Activity was determined in epithelial cells isolated in a villus-to-crypt gradient from chicks fed on different diets in order to vary the sterol flux across the intestinal epithelium. When animals were fed on cholesterol, decarboxylase activity was decreased in all the cell fractions studied, although percentages of inhibition were maximum in crypts of jejunum and ileum. In contrast, decreased sterol flux as a consequence of cholestyramine feeding stimulated decarboxylase activity, especially in villi of the duodenum, where values increased 3-fold with respect to controls. On the other hand, the total cellular sterol content was significantly increased by the cholesterol diet. In duodenum and jejunum, 20-30% of the total cholesterol was in the esterified form under these conditions. However, dietary cholestyramine did not significantly affect amounts of total cellular cholesterol in any of the cell fractions. These results demonstrate that mevalonate 5-pyrophosphate decarboxylase activity changes considerably under different dietary situations and that the existence of secondary sites in the physiological regulation of sterol synthesis in the intestinal mucosa should be considered.

Animals↗

PubMed2002

Preparation for radioactive iodine administration in differentiated thyroid cancer patients.

OBJECTIVE: Because in recent years the practice of TSH suppression has changed, and thyroxine doses have been reduced significantly in the treatment of patients with low-risk differentiated thyroid cancer, the goal of this study was to determine the time needed to attain a target TSH level (of 30 mIU/l) following levothyroxine withdrawal in patients treated with thyroxine according to current guidelines, in anticipation of radioactive iodine (RAI) administration. DESIGN: Observational study. PATIENTS: Thirteen consecutive patients with differentiated thyroid cancer on suppressive doses of levothyroxine planned for RAI administration. Five of the patients received cholestyramine in an attempt to facilitate TSH recovery. MEASUREMENTS: Serum TSH, free-T3 and free-T4, at 3-4-day intervals. RESULTS: In 13 patients on suppressive doses of thyroxine, on 15 separate occasions, baseline TSH levels were between 0.01 and 0.4 mIU/l. The mean interval required to reach the target TSH concentration of at least 30 mIU/l was 17 days (95% CI 15-19; range 11-28 days). Cholestyramine had no effect on the rate of TSH recovery. Once TSH concentration became detectable, it increased exponentially; and once it reached the upper limit of normal, it rarely took more than 10 days to attain target level. CONCLUSIONS: Attaining target TSH level before radioactive iodine administration requires a considerably shorter time than is currently recommended. Reducing preparation time might improve patients' acceptance of the procedure.

Adult↗

PubMed1996

Regulation of bile acid synthesis by estradiol and progesterone in primary cultures of rat hepatocytes.

We have used primary monolayer cultures of hepatocytes from rats fed standard and cholestyramine-diet to study the effects of 17 beta-estradiol and progesterone on the activity of cholesterol 7 alpha-hydroxylase (EC 1.14.13.17) and bile acid synthesis. Cholesterol 7 alpha-hydroxylase activity in hepatocytes freshly isolated from rats fed either diet mentioned above declined gradually during attachment and the first day of culture. Exposure of cell monolayers to 1 or 10 microM estradiol or progesterone resulted in rapid and transient increases in cholesterol 7 alpha-hydroxylase activity, the maximal stimulation of enzyme activity being observed after a 6 h culture period. Bile acid synthesis in standard cells was markedly activated by both hormones, but in cholestyramine cells only the effect caused by 10 microM progesterone was significant. The cellular content of total bile acids was not significantly altered by the presence of the hormones, except by 10 microM progesterone, which provoked an initial cellular depletion of bile acids that was rapidly restored. Bile acid output was enhanced by treating primary cultures with 10 microM estradiol or progesterone, but whereas the increases caused by progesterone were marked and sustained, those caused by estradiol were minor and transient. We conclude that progesterone and 17 beta-estradiol, in this order of potency, enhance short-term bile acid synthesis in rat hepatocyte monolayers.

Animals↗

PubMed1984

Hydroxymethylglutaryl-coenzyme A reductase-containing hepatocytes are distributed periportally in normal and mevinolin-treated rat livers.

Mevinolin is a potent inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.34), an enzyme that catalyzes the rate-limiting step in cholesterol biosynthesis. We have been studying the hepatic distribution of reductase with immunofluorescence microscopy and liver ultrastructure with electron microscopy in normal and drug-treated rats. In control animals, only about 20% of the hepatocytes were reductase positive. These cells were localized in the periportal lobular zones. The numbers of positive hepatocytes in animals given mevinolin or cholestyramine (or both) were directly proportional to the activities of the HMG-CoA reductase determined biochemically. This induction of HMG-CoA reductase immunofluorescence was centered periportally. Rats given 0.075% mevinolin alone had a homogeneous distribution of reductase staining in their hepatocyte cytoplasm, whereas a combination of 0.25% mevinolin and 3% cholestyramine caused a 150-fold increase in enzyme activity and induced prominent juxtanuclear immunofluorescent globules of HMG-CoA reductase in all hepatocytes. With electron microscopy, these bodies were composed of tightly packed stacks of smooth endoplasmic reticulum cysternae and aggregates of branched smooth endoplasmic reticulum tubules. Our data suggest that a subpopulation of periportal rat hepatocytes may be uniquely specialized for cholesterol synthesis.

Animals↗

PubMed2004

In vitro studies on the evaluation of mycotoxin detoxifying agents for their efficacy on deoxynivalenol and zearalenone.

A simple in vitro system was developed to study the efficacy of commercially available mycotoxin detoxifying agents and adsorbing substances as feed additives to detoxify deoxynivalenol (DON) and zearalenone (ZON) in situ. The in vitro model simulates the conditions (pH, temperature and transit time) of the porcine gastrointestinal tract, as pigs react most sensitively to these mycotoxins. The commercially available products were not effective in detoxifying DON and ZON under the applied conditions, while activated carbon was able to bind both toxins and cholestyramine, and a modified aluminosilicate showed good adsorption abilities for ZON. Data obtained in dose dependency studies showed an estimated adsorption capacity of cholestyramine and the modified aluminosilicate of 11.7 and 5.7 g ZON/kg detoxifying agent. The in vitro system deployed in the present study was demonstrated to be a simple, helpful tool in screening substances for their ability to detoxify DON and ZON under the simulated conditions of the porcine gastrointestinal tract. Nonetheless in vivo experiments are indispensable to proof the efficacy.

Adsorption↗

PubMed1986

In vitro binding of steroid hormones by natural and purified fibers.

The in vitro binding of estrone, estradiol-17 beta, estriol, testosterone, dihydrotestosterone, and estrone-3-glucuronide by wheat, oat, and corn brans, oat hulls, cellulose, lignin, and cholestyramine resin was measured. The extent of steroid sequestration was characteristic and reproducible for each hormone. Cholestyramine bound an average of 90% of all the steroids tested, whereas cellulose bound the least (12%). Of the other substances tested, each bound the following percentage of unconjugated hormones: lignin, 87%; wheat and oat brans, 45% each; corn bran 44%; and oat hulls, 32%. The conjugated steroid was less likely to bind than the unconjugated steroids. Lignin appeared to be an important component in the interaction with steroid hormones. The results support the hydrophobic nature of adsorption and suggest that the components of fiber in diet should be considered separately when evaluating in vivo metabolic effects.

Adsorption↗