Effect of gemfibrozil on biliary lipid metabolism in normolipemic subjects

Managing hyperlipidaemia in patients with COVID-19 and during its pandemic: An expert panel position statement from HEART UK

The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which causes Coronavirus Disease 2019 (COVID-19) has resulted in a pandemic. SARS-CoV-2 is highly contagious and its severity highly variable. The fatality rate is unpredictable but is amplified by several factors including advancing age, atherosclerotic cardiovascular disease, diabetes mellitus, hypertension and obesity. A large proportion of patients with these conditions are treated with lipid lowering medication and questions regarding the safety of continuing lipid-lowering medication in patients infected with COVID-19 have arisen. Some have suggested they may exacerbate their condition. It is important to consider known interactions with lipid-lowering agents and with specific therapies for COVID-19. This statement aims to collate current evidence surrounding the safety of lipid-lowering medications in patients who have COVID-19. We offer a consensus view based on current knowledge and we rated the strength and level of evidence for these recommendations. Pubmed, Google scholar and Web of Science were searched extensively for articles using search terms: SARS-CoV-2, COVID-19, coronavirus, Lipids, Statin, Fibrates, Ezetimibe, PCSK9 monoclonal antibodies, nicotinic acid, bile acid sequestrants, nutraceuticals, red yeast rice, Omega-3-Fatty acids, Lomitapide, hypercholesterolaemia, dyslipidaemia and Volanesorsen. There is no evidence currently that lipid lowering therapy is unsafe in patients with COVID-19 infection. Lipid-lowering therapy should not be interrupted because of the pandemic or in patients at increased risk of COVID-19 infection. In patients with confirmed COVID-19, care should be taken to avoid drug interactions, between lipid-lowering medications and drugs that may be used to treat COVID-19, especially in patients with abnormalities in liver function tests.

Gemfibrozil, stretching arms beyond lipid lowering

Gemfibrozil is long known for its ability to reduce the level of triglycerides in the blood circulation and to decrease the risk of hyperlipidemia. However, a number of recent studies reveal that apart from its lipid-lowering effects, gemfibrozil can also regulate many other signaling pathways responsible for inflammation, switching of T-helper cells, cell-to-cell contact, migration, and oxidative stress. In this review, we have made an honest attempt to analyze various biological activities of gemfibrozil and associated mechanisms that may help to consider this drug for different human disorders as primary or adjunct therapy.

Regulation of bile acid and cholesterol metabolism by PPARs

Bile acids are amphipathic molecules synthesized from cholesterol in the liver. Bile acid synthesis is a major pathway for hepatic cholesterol catabolism. Bile acid synthesis generates bile flow which is important for biliary secretion of free cholesterol, endogenous metabolites, and xenobiotics. Bile acids are biological detergents that facilitate intestinal absorption of lipids and fat-soluble vitamins. Recent studies suggest that bile acids are important metabolic regulators of lipid, glucose, and energy homeostasis. Agonists of peroxisome proliferator-activated receptors (PPARα, PPARγ, PPARδ) regulate lipoprotein metabolism, fatty acid oxidation, glucose homeostasis and inflammation, and therefore are used as anti-diabetic drugs for treatment of dyslipidemia and insulin insistence. Recent studies have shown that activation of PPARα alters bile acid synthesis, conjugation, and transport, and also cholesterol synthesis, absorption and reverse cholesterol transport. This review will focus on the roles of PPARs in the regulation of pathways in bile acid and cholesterol homeostasis, and the therapeutic implications of using PPAR agonists for the treatment of metabolic syndrome.

Therapeutic effects of fibrates in postprandial lipemia

Hypertriglyceridemia is observed in many metabolic diseases such as the metabolic syndrome, diabetes mellitus, or mixed dyslipidemia frequently leading to premature coronary heart disease (CHD). Additionally, several studies have shown that postprandial hypertriglyceridemia is pronounced in patients with CHD, metabolic syndrome, hypertension, and other pathologic conditions. The triglyceride-rich lipoprotein remnants accumulating in the postprandial state seem to be involved in atherogenesis and in events leading to thrombosis. Since abnormal postprandial lipemia is associated with pathologic conditions, its treatment is of clinical importance.Fibrates are of significant help in managing hypertriglyceridemia. This review summarizes the effect of fibric acid derivatives on postprandial lipemia. Fibrates decrease the production of and enhance the catabolism of triglyceride-rich lipoproteins through the activation of peroxisome proliferator-activated receptor-alpha. Results of clinical studies with fibrates have confirmed their action in decreasing postprandial triglyceride levels by increasing lipoprotein lipase activity, decreasing apolipoprotein CIII production, and by increasing fatty acid oxidation in the liver.It is concluded that fibrates are effective agents in lowering the postprandial increase in remnant lipoprotein particles and retinyl palmitate. Furthermore, fibrates can also affect the postprandial lipid profile by increasing hepatic lipase levels and in some cases, by reducing cholesterol ester transfer protein activity. The main target of fibrate therapy is to improve fasting hypertriglyceridemia, which is an essential component associated with improving postprandial lipemia. Fibrates are well tolerated by patients and adverse effects have been reported rarely after their administration.

Safety considerations with fibrate therapy

Fibrates are an important class of drugs for the management of dyslipidemia. This class of drugs is generally well tolerated but is infrequently associated with several safety issues. Fibrates, most likely by an effect mediated by peroxisome proliferator-activated receptor-alpha, may reversibly increase creatinine and homocysteine but are not associated with an increased risk for renal failure in clinical trials. Fibrates are associated with a slightly increased risk (<1.0%) for myopathy, cholelithiasis, and venous thrombosis. In clinical trials, patients without elevated triglycerides and/or low high-density lipoprotein cholesterol (HDL) levels, fibrates are associated with an increase in noncardiovascular mortality. In combination with statins, gemfibrozil generally should be avoided. The preferred option is fenofibrate, which is not associated with an inhibition of statin metabolism. Clinicians are advised to measure serum creatinine before fibrate use and adjust the dose accordingly for renal impairment. Routine monitoring of creatinine is not required, but if a patient has a clinically important increase in creatinine, and other potential causes of creatinine increase have been excluded, consideration should be given to discontinuing fibrate therapy or reducing the dose.

Body weight, plasma insulin, and coronary events with gemfibrozil in the Veterans Affairs High-Density Lipoprotein Intervention Trial (VA-HIT)

BACKGROUND

The Veterans Affairs High-Density Lipoprotein Intervention Trial (VA-HIT) showed that gemfibrozil significantly reduced major coronary events in men with known coronary heart disease (CHD). To better understand why therapy was especially effective with obesity, diabetes, and hyperinsulinemia, changes in body weight and plasma insulin were determined after 1 year of gemfibrozil or placebo therapy and related to changes in lipids and CHD events.

RESULTS

With gemfibrozil significantly more subjects lost weight (51.7% versus 38.6%, P<0.0001) and significantly fewer subjects gained weight (42.5% versus 54.0%, P<0.0001) than with placebo. Both a greater loss and smaller gain in weight with gemfibrozil were age-related and significant in subjects > or =66 years (median age), but not in younger subjects. Weight change was paralleled by changes in insulin. With gemfibrozil, CHD events were significantly reduced with weight loss (hazard ratio [HR], 0.61; 95% CI, 0.44-0.84; P=0.002) and, particularly, with diabetes or hyperinsulinemia (HR, 0.53; 95% CI, 0.34-0.83; P=0.006). In contrast, CHD events were not significantly reduced without weight loss (HR, 0.83; 95% CI, 0.62-1.12; P=0.22).

CONCLUSIONS

In VA-HIT, gemfibrozil resulted in weight loss associated with reductions in insulin. With weight loss gemfibrozil produced a significant reduction in CHD events that did not occur in the absence of weight loss.

Effects of gemfibrozil treatment on vascular reactivity of streptozotocin-diabetic rat aorta

The effects of gemfibrozil treatment on plasma lipids, lipid peroxides and vascular reactivity of aorta were investigated in diabetic rats. Rats were divided randomly into two groups: control and diabetic. Diabetes was induced by a single intraperitoneal injection of streptozotocin (45 mg kg(-1)). Twelve weeks after the induction of diabetes, some of the control and diabetic rats were started treatment with gemfibrozil (100 mg kg(-1) daily; gavage) for 2 weeks. Blood glucose, plasma triglyceride, cholesterol, low-density lipoprotein (LDL) cholesterol and thiobarbituric acid reactive substances (TBARS) levels were markedly increased and gemfibrozil treatment restored these parameters in diabetic rats. However high-density lipoprotein (HDL) cholesterol levels did not differ in all experimental groups. In diabetic rats, the endothelium-dependent relaxations to acetylcholine were decreased when compared with control rats. Gemfibrozil treatment restored the endothelium-dependent responses to acetylcholine in diabetic rats. The endothelium-independent relaxation responses to sodium nitroprusside were not altered in all groups. These findings suggest that gemfibrozil treatment has beneficial effects against cardiovascular and metabolic complications of diabetes via its hypolipidaemic and antioxidant properties.

How well tolerated are lipid-lowering drugs?

It has been clearly established that lipid-lowering treatments [such as 3-hydroxyl-3-methylglutamyl coenzyme A reductase inhibitors ('statins') or fibrates] can reduce cardiovascular events, and with one of the statins even total mortality, in high-risk populations. Intervention studies have not included the very old, but it is generally assumed that this patient group would benefit from these treatments to an extent similar to younger patients. Worries about the associations seen in observational studies between low cholesterol levels and cancer, cerebral haemorrhage or mood and behaviour change have been largely overcome by findings from the latest large drug intervention trials, which do not show any increase in these conditions with statin or fibrate treatments. The common adverse effects associated with these drugs are relatively mild and often transient in nature. Potentially more serious adverse effects, which are more clearly related to drug treatment and are probably dose-dependent, include elevations in hepatic transaminase levels and myopathy; however, these effects are uncommon and generally resolve rapidly when treatment is stopped. The risk of myopathy with fibrate treatment is increased in patients with renal impairment, and the risk of myopathy with statin treatment increases with co-administration of drugs that inhibit statin metabolism or transport. Other adverse effects are related to specific drugs, for example, clofibrate is associated with an increased risk of gallstones. Studies in elderly patients have not shown an increased risk of adverse effects with lipid-lowering drugs compared with younger patients, but in clinical practice there may be some increased risk, particularly with regards to drug interactions. Therefore, lipid-lowering drugs should be administered with extra caution to elderly patients.

Differences in hypolipidaemic effects of two statins on Hep G2 cells or human hepatocytes in primary culture

1. The objective of this study was to compare in cultured human hepatocytes or Hep G2 cells, changes in the fate of unesterified low density lipoprotein (LDL)-cholesterol induced by crilvastatin, a new cholesterol lowering drug and a reference statin, simvastatin. 2. The experiments were carried out for 20 h, each well contained 4.2 x 10(5)/cm2 Hep G2 cells or 0.5 x 10(5)/Cm2 human hepatocytes, 130 microM ursodeoxycholate, 0.68 microCi or 1.59 microCi unesterified human [14C]-LDL-cholesterol, crilvastatin or simvastatin at 0 or 50 microM (both cell types) or 300 microM (Hep-G2 cells). Incubation with the two drugs resulted in increased amounts of unesterified [14C]-LDL-cholesterol taken by the two cell types, compared to control. 3. Crilvastatin 50 microM led to significantly higher quantities of [14C]-glyco-tauro-conjugated bile salts, compared to simvastatin. Statins reduced the apo B100 level secreted by the two cell types (simvastatin) or human hepatocytes (crilvastatin). Crilvastatin enhanced both the level of apo A1 secreted by the Hep G2 cells and the level of APF, a high density lipoprotein (HDL) and biliary apoprotein. 4. Crilvastatin not only acts by stimulating LDL-cholesterol uptake by hepatocytes, but also by enhancing the catabolism of LDL-cholesterol in bile salts and probably by stimulating HDL and/or bile component secretion. Such a mechanism was not previously described for HMG CoA reductase inhibitors. Our results on APF show that this apoprotein could be considered also as an indicator of changes in bile and/or HDL compartments. 5. The human hepatocyte model appeared to be a suitable and relevant model in the pharmacological-metabolic experiments carried out in this study. It led to more consistent data than those obtained with Hep G2 cells.

Cholesterol synthesis inhibitors in cholesterol gallstone disease

Cholesterol synthesis inhibitors (HMG-CoA Reductase Inhibitors) are reported to decrease cholesterol saturation index of duodenal bile in hypercholesterolaemic subjects. The dissolution of gallstones in animals on treatment with these drugs created expectations of a therapeutical role for these drugs in cholesterol gallstone disease. However, in prospective studies with these drugs in humans, no effect on number and size of cholesterol gallstones was observed. This is likely the result of the fact that not just biliary secretion of cholesterol is decreased during treatment with these drugs in cholesterol gallstone disease, but phospholipids and bile salts as well. As a consequence, nucleation time of cholesterol crystals in gallbladder bile is not influenced by these drugs. Another important determinant in cholesterol gallstone disease, e.g. gallbladder motility, is not influenced by HMG-CoA reductase inhibitors. Although these drugs and their metabolites are secreted into the bile, they do not influence biliary lithogenicity. In conclusion, there seems to be no therapeutic role for HMG-CoA reductase inhibitors in the treatment of cholesterol gallstone disease, although no negative effects on determinants of cholesterol gallstone formation during treatment with these drugs are observed either.

Effects of simvastatin and cholestyramine on bile lipid composition and gall bladder motility in patients with hypercholesterolaemia

Although the effects of 3-hydroxy, 3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors and bile acid sequestrants on bile lipid composition have been studied separately, no data are available on combination therapy of these drugs. Moreover, the effects of prolonged (four weeks) administration of these drugs on gall bladder motility, an important determinant of cholesterol gall stone formation, have not been studied so far. A prospective study was therefore performed with eight patients who had hypercholesterolaemia (age 53 (5) (SEM), body mass index 27.4 (1.1) kg m-2, low density lipoprotein cholesterol 5.9 (0.3) mmol/l). They received treatment during three periods of four weeks with simvastatin 20 mg/day, cholestyramine 4 g twice daily, and a combination of both in random order, each treatment period separated by a two week wash out period. Before treatment and after each treatment period, postprandial gall bladder motility was studied with ultrasound, followed by duodenal bile sampling. Serum cholesterol decreased in all subjects in any treatment period illustrating good compliance. Molar percentages in duodenal bile of cholesterol, phospholipids, and bile salts were unchanged during simvastatin and cholestyramine treatment. During combined therapy percentage bile salts was lower (72.5 (2.9)% v 77.8 (1.7)% at baseline, p < 0.05) whereas phospholipids were higher (21.2 (2.4)% v 16.4 (1.3)% at baseline, p < 0.05). As a result cholesterol saturation index (CSI) did not change in any treatment period. No cholesterol crystals were detected in any bile sample, taken at baseline and after each treatment period. Bile salt hydrophobicity index during cholestyramine (0.19 (0.02)) and combined treatment (0.22 (0.01)) decreased strongly compared with baseline (0.34 (0.01), p < 0.001, p < 0.01, respectively), resulting from increased proportions of glycocholate (59.4 (3.9)% (cholestyramine), 55.6 (2.4)% (combination), and 28.2 (2.2) (baseline), p < 0.001)) and decreased proportions of deoxycholic acid and chenodeoxycholic acid. Fasting gall bladder volume was increased during simvastatin (28.7 (2.8) ml) v baseline (23.2 (2.3) ml, p < 0.01) whereas, residual volume did not differ (5.7 (0.9) ml (simvastatin) v 5.9 (0.7) (baseline). During cholestyramine and combined treatment, no significant differences in gall bladder motility were seen. In conclusion, this study suggests that HMG-CoA reductase inhibitors alone and combined with cholestyramine do not affect major determinants of cholesterol gall stone formation, for example, CSI and gall bladder emptying. In addition cholestyramine alone and combined with simvastatin leads to a strong decrease of bile salt hydrophobicity, which may be beneficial in the prevention of nucleation of cholesterol crystals.

Effects of different phenotypes of hyperlipoproteinemia and of treatment with fibric acid derivatives on the rates of cholesterol 7 alpha-hydroxylation in humans

Little is known about the relationships between hyperlipidemia and bile acid metabolism. However, hypolipidemic treatment with fibric acid derivatives has been shown to increase biliary cholesterol secretion, presumably by reducing bile acid synthesis. To clarify such relationships, we investigated the effects of different hyperlipoproteinemic conditions and of treatment with fibric acid derivatives on the rates of cholesterol 7 alpha-hydroxylation (the limiting step of bile acid synthesis) in humans. We studied 10 patients (aged 36 to 68 years) with lipoprotein phenotype IIa and with a clinical diagnosis of heterozygous familial hypercholesterolemia, a condition of reduced activity of LDL receptors, and 11 patients (aged 48 to 70 years) with lipoprotein phenotype IIb or IV and clinical diagnosis of familial combined hyperlipidemia, a condition probably related to increased hepatic lipoprotein synthesis. Cholesterol 7 alpha-hydroxylation rates were assayed in vivo by tritium release assay after an intravenous injection of [7 alpha-3H]cholesterol. The results were compared by ANOVA to the values obtained in a group of 28 normolipidemic patients (aged 34 to 83 years), with age as the covariate. Six patients were also studied after treatment with gemfibrozil (900 to 1200 mg/d for 6 to 8 weeks) and 5 patients were studied after treatment with bezafibrate (400 mg/d for 6 to 8 weeks). Hydroxylation rates were 0.82 +/- 0.22 mmol/d in the familial hypercholesterolemia group and 1.30 +/- 0.47 mmol/d in the familial combined hyperlipidemia group (P < .05 between the two groups and between patients with familial combined hyperlipidemia and control subjects; P = NS between patients with familial hypercholesterolemia and control subjects, as determined by ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol absorption and synthesis during pravastatin, gemfibrozil and their combination

The study evaluates cholesterol metabolism off and on treatment with pravastatin (P), gemfibrozil (G) and their combination (PG) in 38 middle-age hyperlipidemic primary care patients with serum cholesterol > 6 mmol/l and serum triglycerides < 4 mmol/l after a low-fat low-cholesterol diet. The subjects were randomized to P (40 mg/g), G (1200 mg/day), PG (40 + 1200 mg/day) or placebo for 12 weeks. We analyzed serum lipids, apolipoproteins A-I, B and E, serum cholesterol precursors (markers of cholesterol synthesis), serum plant sterols and cholestanol (markers of cholesterol absorption) and cholesterol metabolism by the sterol balance technique and cholesterol absorption efficiency. P alone or in combination with G lowered apoprotein E concentration, and serum cholesterol levels by inhibiting cholesterol synthesis measured by the precursor/cholesterol proportions with inconsistent change in fecal output of cholesterol. G alone decreased bile acid synthesis and increased biliary cholesterol secretion which were associated with reduced cholesterol absorption efficiency and the serum plant sterol and cholestanol proportions, and increased synthesis of cholesterol as measured both by the sterol balance technique and the precursor sterol proportions. A combination of PG also lowered LDL cholesterol similarly but triglyceride-rich lipoproteins significantly more than P alone, and otherwise inhibited the changes caused by G in cholesterol metabolism except that the precursor sterol proportions still indicated reduced cholesterol synthesis. Overall, the changes of the cholesterol precursor proportions were negatively related to that of cholesterol absorption efficiency and positively to that of cholesterol synthesis. The respective plant sterol and cholestanol values correlated oppositely to cholesterol absorption efficiency and synthesis. Serum precursor sterols reflected changes in cholesterol synthesis more sensitively than the sterol balance technique, even though only the latter method can quantitate cholesterol synthesis.

The effects of the 3-hydroxy, 3-methylglutaryl coenzyme A reductase inhibitor pravastatin on bile composition and nucleation of cholesterol crystals in cholesterol gallstone disease

3-hydroxy,3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors reduce biliary cholesterol saturation index (CSI) in duodenal bile in hypercholesterolemic patients and might be useful for gallstone dissolution. However, preliminary data suggest that these drugs are not effective in this respect. We therefore studied 33 patients with radiolucent gallstones in an opacifying gallbladder who were scheduled for elective cholecystectomy. Patients were treated with 40 mg pravastatin day-1 or placebo during the 3 weeks before surgery. Six patients could not be evaluated. Baseline characteristics (age, sex, body mass index, serum cholesterol, and the solitary/multiple gallstone ratio) were similar in both groups. Serum cholesterol fell by 39% in the pravastatin group (P < .001) and remained unchanged in the placebo group. Biliary cholesterol (9.5 +/- 1.3 vs. 14.3 +/- 1.5 mmol/L, P = .026), and phospholipid concentrations (24.8 +/- 3.9 vs. 36.7 +/- 3.9 mmol/L, P = .043) were lower in the pravastatin group. Although bile salt concentrations were lower in the pravastatin group (114 +/- 21 vs. 152 +/- 15 mmol/L), this difference was not significant. CSI was not different between both groups (142 +/- 27% [pravastatin] vs. 113 +/- 6% [placebo], P = NS). Cholesterol crystals were present in fresh bile in 7 of 13 patients in the pravastatin group and in 11 of 14 controls (P = NS). Nucleation time was comparable between the 2 groups (13 +/- 3 vs. 9 +/- 3 days, P = NS). Bile salt species and molecular species of phospholipids determined with high-performance liquid chromatography did not differ either between both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of gemfibrozil on lipid biosynthesis from acetyl-CoA derived from peroxisomal beta-oxidation

The effect of gemfibrozil, a peroxisome proliferator, on lipid biosynthesis from acetyl-CoA derived from peroxisomal beta-oxidation was studied. The specific activity of the peroxisomal fatty acyl-CoA beta-oxidation system of rats fed a chow containing 0.2% gemfibrozil for 2 weeks was approximately five times higher than that of control rats. When [1-14C]lignoceric acid, a very-long-chain fatty acid which is degraded exclusively by the peroxisomal beta-oxidation system at first, was injected into rats treated with gemfibrozil, radioactivity and content of bile acid in the bile were enhanced to approximately 2.2 and 3.5 times the control, respectively. Gemfibrozil increased the radioactivity and content of chenodeoxycholic acid more than that of cholic acid. The incorporation of radioactivity into cholesterol in the bile was as much as 4.5 times greater than the control, and content was 2.6 times greater. In the liver, incorporation of [14C]lignoceric acid into the simple lipids phosphatidylethanolamine and phosphatidylcholine was unaffected by gemfibrozil. The radioactivity and content of cholesterol separated from the simple lipids were also virtually unaffected. However, the specific activities of 3-hydroxy-3-methylglutararyl-CoA reductase (rate-limiting enzyme of cholesterol synthesis) of peroxisomes and microsomes were remarkably stimulated by gemfibrozil treatment. These results suggest that biosyntheses of cholesterol and bile acid from acetyl-CoA derived from peroxisomal beta-oxidation are stimulated by gemfibrozil, due at least in part to activation of the peroxisomal beta-oxidation system and 3-hydroxy-3-methylglutaryl-CoA reductase of peroxisomes and/or microsomes. Most peroxisomal proliferators (e.g. clofibrate) have been known to inhibit 3-hydroxy-3-methylglutaryl-CoA reductase activity. Therefore, gemfibrozil is expected to be a very useful tool for elucidating the relationship between peroxisomes and the biosyntheses of cholesterol and bile acid.

Effect of etofibrate on bile production in the normolipidemic rat

1. The effect of etofibrate, the ethandiol-1,2 diester of nicotinic and clofibric acids on bile production was studied in male rats that received a daily dose of 300 mg of etofibrate/kg body weight by stomach tube for 10 days and were compared with control rats receiving the medium. 2. The bile duct was cannulated, animals were intravenously given 1 microCi (4-14C)-cholesterol/100 b.w. and bile was collected at different intervals for a total of 4 hr. 3. Etofibrate treatment decreased plasma cholesterol and triglyceride concentrations and increased the bile flow. The cummulative amount of both bile volume and total bile radioactivity secreted increased linearly in all the animals; the respective slopes being higher in etofibrate treated rats than in controls. 4. The main labelled component found in the bile was always bile acids rather than cholesterol and the proportion of each of these compounds was similar in both groups. Neither was any difference between the groups found in the concentration of bile acids, cholesterol and phospholipids nor in the cholesterol/(bile+phospholipid) ratio. 5. Besides other factors, the present results indicate that an increase in bile flow and biliary cholesterol excretion in its free form and after its conversion into bile acids should contribute to the hypocholesterolemic effect of etofibrate.

Effect of crilvastatin, a new cholesterol lowering agent, on unesterified LDL-cholesterol metabolism into bile salts by rat isolated hepatocytes

1. The aim of these experiments was to determine the effect of crilvastatin, a new cholesterol lowering agent, on the metabolism of unesterified low density lipoprotein (LDL)-cholesterol by rat freshly isolated hepatocytes. This preclinical model was developed as an alternative to in vivo experiments, to mimic the metabolic effects of a molecule on its target cells and to define optimal conditions for future experimentation on human hepatocytes. 2. Cells were obtained from normolipidaemic or hypercholesterolaemic rats, hypercholesterolaemia was nutritionally induced. Incubations were performed in a medium containing 600 microM taurocholate and 50 microM or 300 microM crilvastatin. 3. This molecule was shown in vitro to be carried by physiological transporters, i.e., albumin-bile salt micellar associations and LDL. Crilvastatin induced a significance increase in the synthesis and secretion by hepatocytes of bile salts resulting from the metabolism of unesterified LDL-cholesterol in both normolipidaemic and hypercholesterolaemic rats. Stimulation involved non-conjugated as well as tauro- and glyco-conjugated bile salts. These findings corroborate preliminary studies showing in vivo that crilvastatin enhances the secretion of bile acids by stimulating the uptake and incorporation of LDL-cholesterol by the liver.

A multi-centre study of the efficacy and safety of pravastatin in hypercholesterolaemic patients with non-insulin-dependent diabetes mellitus

A multi-centre, non-randomized clinical study of 12-months' duration was performed in 112 patients with hyperlipidaemia associated with non-insulin-dependent diabetes mellitus to evaluate the clinical efficacy and tolerability of pravastatin and to assess its effect on glycaemic control. Patients were eligible for this trial if they fulfilled the following criteria; a high plasma total cholesterol level greater than 220 mg/dl associated with stable glycaemic control for at least 3-months' observation period. On entry, patients received 10 mg pravastatin per day (5 mg twice daily) for 12 months. Clinical efficacy was evaluated in 108 patients. The results showed that pravastatin induced a significant decrease in serum cholesterol level mainly with LDL-cholesterol. Total cholesterol levels were decreased significantly from 275 +/- 3 mg/dl to 222 +/- 4 mg/dl within 3 months of the start of treatment, and LDL-cholesterol decreased from 192 +/- 4 mg/dl to 137 +/- 4 mg/dl. After 12 months' treatment, total cholesterol and LDL-cholesterol levels were 216 +/- 4 mg/dl (p < 0.001) and 137 +/- 5 mg/dl (p < 0.001), respectively. HDL-cholesterol levels were increased from 51 +/- 2 mg/dl to 56 +/- 2 mg/dl at 3 months (p < 0.001) and 55 +/- 2 mg/dl at 12 months (p < 0.01). Triglyceride concentrations were also decreased from 173 +/- 11 mg/dl to 156 +/- 13 mg/dl at 3 months and 137 +/- 10 mg/dl at 12 months (p < 0.01). Fasting plasma glucose and glycated haemoglobin levels were not affected by pravastatin. Adverse events observed in 5 cases were always mild and reversible. These results indicate a clinical usefulness of pravastatin with high compliance in patients with hyperlipidaemia associated with non-insulin-dependent diabetes mellitus.

The effect of bezafibrate treatment on serum alkaline phosphatase isoenzyme activities

A reduction in serum total alkaline phosphatase (ALP) activity is a well-documented side effect of treatment with bezafibrate and other fibric acid derivatives. To evaluate the effect of bezafibrate treatment on individual ALP isoenzyme activities, 10 patients were studied on two separate occasions, first, after a 6-week period on no drug treatment, and second, after 6 weeks of bezafibrate therapy. On each occasion, serum total ALP and ALP isoenzyme activities and serum gamma-glutamyltransferase (GGT) activity were measured both after fasting and following the ingestion of a standardized high-fat meal rich in long-chain fatty acid triglycerides, as intestinal ALP activity is known to be influenced by dietary fat intake. Plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were measured on fasting samples. In the fasting state, bezafibrate treatment resulted in a 25% reduction (P < .01) in serum total ALP activity; liver ALP activity was reduced by 40% (P < .01), and biliary ALP activity was reduced in those patients in whom it was initially detectable, while bone and intestinal ALP activities were unchanged. There was also a 15% reduction (P < .05) in serum GGT activity, but no change in plasma AST or ALT activities. Serum intestinal ALP activity increased significantly (P < .01) by 1 hour following ingestion of the high-fat meal, but treatment with bezafibrate did not change the magnitude of this response. There was no change in the activity of any other ALP isoenzyme following fat ingestion. This study demonstrates that the effect of bezafibrate on serum ALP activity is confined to the liver and biliary isoenzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of action in the liver of crilvastatin, a new hydroxymethylglutaryl-coenzyme A reductase inhibitor

Crilvastatin is a drug from the pyrrolidone family that had been shown to induce non-competitive inhibition of rat hydroxymethylglutaryl-coenzyme A reductase activity in vitro. The aim of this study was to evaluate the activity of crilvastatin on the hepatic metabolism of cholesterol in rats. Crilvastatin increased low density lipoprotein (LDL)-cholesterol uptake by the liver more than high density lipoprotein (HDL) uptake, thus increasing by up 30% the clearance of excess plasma cholesterol. In normolipidemic rats, crilvastatin significantly enhanced acyl coenzyme A:cholesterol acyl transferase and cholesterol 7 alpha-hydroxylase activity. In rats with a previous high cholesterolemia, crilvastatin also enhanced cholesterol 7 alpha-hydroxylase activity and did not increase liver acyl coenzyme A:cholesterol acyl transferase activity. These findings suggest that a drug such as crilvastatin could have a hypocholesterolemic effect by a mechanism other than the sole inhibition of cholesterol synthesis, possibly by stimulating cholesterol and bile salt secretion via the biliary tract in previously hypercholesterolemic rats.

An enzymatic explanation of the differential effects of oleate and gemfibrozil on cultured hepatocyte triacylglycerol and phosphatidylcholine biosynthesis and secretion

Incubation (1-4 h) of primary cultures of adult rat hepatocytes with gemfibrozil (0.1-1.0 mM) significantly decreased the: (1) incorporation of [1,3-14C]glycerol into cellular triacylglycerol (30%); (2) secretion of labeled (VLDL) triacylglycerol (4-fold); and (3) oleate-induced rise in triacylglycerol biosynthesis and secretion. Gemfibrozil also increased the: (1) incorporation of labeled glycerol into cellular phosphatidylcholine (2-fold); and (2) secretion of labeled (HDL) phosphatidylcholine (10-fold). The gemfibrozil-dependent increase in the flux of labeled diacylglycerol into phosphatidylcholine is rapid (15 min) and associated with a 2-fold increase in membrane-bound phosphocholine cytidylyltransferase activity. A phosphocholine cytidylyltransferase-mediated rise in cellular CDP choline content may explain the gemfibrozil-dependent rise in phosphatidylcholine biosynthesis since homogenates of monolayers incubated with CDP choline preferentially incorporate labeled diacylglycerol into phosphatidylcholine rather than triacylglycerol. Therefore, the triacylglycerol-lowering potential of gemfibrozil may be due in part to its ability to shunt liver cell diacylglycerol into phosphatidylcholine rather than triacylglycerol. These results suggest that CDP choline may be a key regulator of the diacylglycerol branchpoint, since diacylglycerol is primarily incorporated into phosphatidylcholine or triacylglycerol depending on whether CDP choline is or is not available.

Tolerability of fibric acids. Comparative data and biochemical bases

Fibric acids are an established class of drugs for the treatment of hyperlipoproteinaemias. Although they have been in use for 30 years or longer, some doubts remain as to their relative tolerability, both as a class and as single agents. Some side effects, e.g. lithogenicity, may be related to their mode of action, while others, e.g. the acute muscular syndrome, may be linked to the spatial conformation of the molecule. These disadvantages should, however, be weighed against the additional, potentially therapeutic properties shown by these compounds. In particular, effects on maturity onset diabetes and hyperuricaemia, as well as a very interesting fibrinolytic potential, have been described for some of them. A painstaking comparative analysis of the major literature data pertaining to the clinical toxicological profile of these agents allow to conclude that, while belonging to a chemical class, fibric acids show dramatic differences from one another, in terms of side effects and of additional pharmacodynamic activities. Moreover, in the case of lithogenicity for example, considerable differences exist between normo- and hyperlipidaemic subjects. Overall, newer molecules of more sophisticated design have a significantly improved tolerability profile vs the old clofibrate.

Successful dissolution of cholesterol gallstone during treatment with pravastatin

This case report describes a 51-year-old hypercholesterolemic male patient who had a large solitary cholesterol gallstone. The patient was treated with the 3-hydroxy 3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor pravastatin, 40 mg/day. After 3 months of therapy, serum cholesterol level normalized (7.7 mmol/L before and 5.2 mmol/L during treatment), and biliary cholesterol saturation index decreased from 1.3 before to 0.8 during treatment. Repeatedly performed ultrasonography showed complete gallstone dissolution. Pravastatin may be valuable in the nonsurgical treatment of cholesterol gallstone disease particularly when there is an additional indication for HMG-CoA reductase inhibitors because of hypercholesterolemia.

Drug-induced gallbladder disease. Incidence, aetiology and management

A great variety of drugs is reported to induce gallbladder disease by various pathogenetic mechanisms. Early epidemiological studies indicated a doubled risk of gallbladder disease in women taking oral contraceptives. More recent studies, however, have failed to confirm those findings; these conflicting results might be explained by the different methods used to define gallbladder disease. It was shown that the lithogenic index of the bile is increased during intake of oral contraceptives. Estrogens cause hypersecretion of cholesterol in bile, due to increase in lipoprotein uptake by the hepatocyte. Progesterone inhibits acyl coenzyme A-cholesterol acyl transferase (ACAT) activity, causing delayed conversion of cholesterol to cholesterol esters. Of the lipid lowering drugs, only clofibrate has been shown to increase the risk for gallstone formation. The other fibric acid derivatives have similar properties, but clinical experience is not as extensive. They seem to be inhibitors of the ACAT enzyme system, thereby rendering bile more lithogenic. Conflicting epidemiological data exist regarding the induction of acute cholecystitis by thiazide diuretics. Ceftriaxone, a third-generation cephalosporin, is reported to induce biliary sludge in 25 to 45% of patients, an effect which is reversible after discontinuing the drug. The sludge is occasionally a clinical problem. It was clearly demonstrated that this sludge is caused by precipitation of the calcium salt of ceftriaxone excreted in the bile. Long term use of octreotide is complicated by gallstone formation in approximately 50% of patients after 1 year of therapy, due to gallbladder stasis. Hepatic artery infusion chemotherapy by implanted pump is shown to be associated with a very high risk of chemically induced cholecystitis. Prophylactic cholecystectomy at the time of pump implantation is therefore advocated. Some drugs, such as erythromcyin or ampicillin, are reported to cause hypersensitivity-induced cholecystitis. Furthermore, there are reports on the influence of cyclosporin, dapsone, anticoagulant treatment, and narcotic and anticholinergic medication in causing gallbladder disease.

Gemfibrozil in familial combined hyperlipidaemia: effect of added low-dose cholestyramine on plasma and biliary lipids

Gemfibrozil is frequently used for lipid-lowering in familial combined hyperlipidaemia (FCHL) and in other forms of combined hyperlipidaemia. This therapy increases biliary cholesterol saturation, enhancing the risk for gallstone formation. Furthermore, in hypertriglyceridaemia, LDL cholesterol levels often tend to rise. We have explored the possibility that addition of a low dose of cholestyramine to gemfibrozil therapy obliterates these phenomena. Eighteen gallstone-free patients with definite (n = 5) or probable (n = 10) FCHL, or combined hyperlipoproteinaemia (n = 3) were randomized to a 6 week treatment with gemfibrozil, 600 mg b.i.d., or gemfibrozil 600 mg b.i.d. plus 4 g cholestyramine o.d. After 6 weeks the patients were crossed over to the alternative treatment. Plasma lipoproteins and biliary lipids were determined at baseline and at the end of each period. Institution of gemfibrozil treatment resulted in a decrease in plasma cholesterol by 15% (P less than 0.05) and in plasma triglycerides by 47% (P less than 0.05); HDL cholesterol increased by 18% (P less than 0.05). Addition of cholestyramine further decreased plasma and LDL total cholesterol by 9% (P less than 0.05). Total triglycerides and HDL cholesterol did not change. Gemfibrozil treatment was associated with a rise in the relative biliary concentration of cholesterol from 5.6 +/- 0.4 to 6.9 +/- 0.5 molar percent (P less than 0.01), and a parallel decrease in the relative concentration of bile acids, resulting in an increased cholesterol saturation of the bile, from 77 +/- 5 to 90 +/- 6% (P less than 0.05). This change was not observed during the combined therapy (mean cholesterol saturation, 82 +/- 4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of gemfibrozil administration on biliary lipid secretion in hyperlipidemic patients. A crossover study with clofibrate

Gemfibrozil, like clofibrate, is effective in lowering both serum cholesterol and triglycerides and in increasing high-density lipoproteins. The information available about its effects on biliary lipids is still limited, and conflicting results have been reported. In this study we evaluated the effect of gemfibrozil (1.2 g/day) and clofibrate (2.0 g/day), in a single-blind crossover design for 6 weeks with a 4-week washout period, on the biliary cholesterol saturation index (SI) in stimulated hepatic bile and on the hepatic secretion rate of biliary lipids in patients with hyperlipidemia. Clofibrate increased cholesterol SI (from 1.70 +/- 0.14 to 2.05 +/- 0.24), whereas gemfibrozil decreased it (from 1.70 +/- 0.14 to 1.54 +/- 0.16). The results were not statistically significant. The hepatic secretion rate of cholesterol was significantly (p less than 0.04) increased by clofibrate therapy, whereas it was significantly (p less than 0.04) decreased after gemfibrozil; a significant (p less than 0.04) decrease in the hepatic secretion rate of bile acids, bile acid pool size, and bile acid fecal excretion (p less than 0.04) was also found after gemfibrozil administration. Gemfibrozil interferes extensively with bile acid metabolism, but it does not increase biliary cholesterol secretion, as clofibrate does. These results suggest that gemfibrozil does not seem to increase the risk of gallstone formation in patients with hyperlipidemia.

Effect of pravastatin on biliary lipid composition and bile acid synthesis in familial hypercholesterolaemia

Nine patients with heterozygous familial hypercholesterolaemia were treated for eight weeks with either 40 mg pravastatin or placebo under double blind conditions. Six patients received pravastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. Treatment with pravastatin resulted in a significant decrease in plasma cholesterol caused by a decrease in low density lipoprotein cholesterol (LDL-c) of 30% (p less than 0.005). We determined the effect of this medication on the lithogenicity of bile. Cholesterol saturation index of fasting gall bladder bile decreased with 23% (p less than 0.01) from 1.06 to 0.75 during treatment with pravastatin. A reduction of 24% (p less than 0.01) in molar percentage of biliary cholesterol was seen. After treatment the total bile acid excretion in faeces and the molar percentage of biliary bile acids were not significantly changed, suggesting that pravastatin does not influence bile acid biosynthesis to a significant extent. These findings indicate that treatment with pravastatin can decrease the incidence and complications of cholesterol gall stones.

The effect of etofibrate on cholesterol and bile acid metabolism in the hamster

Hamsters were given etofibrate at a dose of 300 mg/kg body wt, by gavage for 5 days, while being fed a chow diet. After treatment, serum cholesterol levels were 27% lower compared to those of the control animals. A similar trend was observed for triglyceride levels. Hepatic lipid levels were unchanged by the treatment. HMG-CoA reductase and acylCoA cholesterol acyltransferase were decreased while cholesterol 7 alpha-hydroxylase was not significantly modified by etofibrate. A choleretic effect and an increase of cholesterol excretion into hepatic bile was observed in treated animals. Nevertheless, composition and cholesterol saturation index of gallbladder bile were similar in control and treated animals. With respect to controls, hepatic bile of treated hamsters contained a lesser amount of cholic and deoxycholic acid and a greater amount of ursodeoxycholic acid.

Simvastatin, a competitive inhibitor of HMG-CoA reductase, lowers cholesterol saturation index of gallbladder bile

We tested the possibility that simvastatin, a competitive inhibitor of HMG-CoA reductase related to mevinolin, might alter cholesterol saturation of gallbladder bile. Ten patients with Type IIa or IIb hypercholesterolemia underwent bile sampling before, and again after, treatment with 20 or 40 mg per day simvastatin for 7 to 13 weeks. Mean cholesterol saturation index of gallbladder bile fell from 1.01 to 0.77 during simvastatin treatment (p less than 0.01). This finding strongly suggests that treatment with HMG-CoA reductase inhibitors will not predispose to development of cholesterol gallstones. Indeed, it raises the possibility that such inhibitors might have a future role to play in treatment of gallstones.

Helsinki Heart Study: primary-prevention trial with gemfibrozil in middle-aged men with dyslipidemia. Safety of treatment, changes in risk factors, and incidence of coronary heart disease

In a randomized, double-blind five-year trial, we tested the efficacy of simultaneously elevating serum levels of high-density lipoprotein (HDL) cholesterol and lowering levels of non-HDL cholesterol with gemfibrozil in reducing the risk of coronary heart disease in 4081 asymptomatic middle-aged men (40 to 55 years of age) with primary dyslipidemia (non-HDL cholesterol greater than or equal to 200 mg per deciliter [5.2 mmol per liter] in two consecutive pretreatment measurements). One group (2051 men) received 600 mg of gemfibrozil twice daily, and the other (2030 men) received placebo. Gemfibrozil caused a marked increase in HDL cholesterol and persistent reductions in serum levels of total, low-density lipoprotein (LDL), and non-HDL cholesterol and triglycerides. There were minimal changes in serum lipid levels in the placebo group. The cumulative rate of cardiac end points at five years was 27.3 per 1,000 in the gemfibrozil group and 41.4 per 1,000 in the placebo group--a reduction of 34.0 percent in the incidence of coronary heart disease (95 percent confidence interval, 8.2 to 52.6; P less than 0.02; two-tailed test). The decline in incidence in the gemfibrozil group became evident in the second year and continued throughout the study. There was no difference between the groups in the total death rate, nor did the treatment influence the cancer rates. The results are in accord with two previous trials with different pharmacologic agents and indicate that modification of lipoprotein levels with gemfibrozil reduces the incidence of coronary heart disease in men with dyslipidemia.

Adverse effects of hypolipidaemic drugs

Cholestyramine, colestipol, clofibrate, gemfibrozil, nicotinic acid (niacin), probucol, neomycin, and dextrothyroxine are the most commonly used drugs in the treatment of hyperlipoproteinaemic disorders. While adverse reaction data are available for all of them, definitive data regarding the frequency and severity of potential adverse effects from well-controlled trials using large numbers of patients (greater than 1000) are available only for cholestyramine, clofibrate, nicotinic acid and dextrothyroxine. In adult patients treated with cholestyramine, gastrointestinal complaints, especially constipation, abdominal pain and unpalatability are most frequently observed. Continued administration along with dietary manipulation (e.g. addition of dietary fibre) and/or stool softeners results in diminished complaints during long term therapy. Large doses of cholestyramine (greater than 32 g/day) may be associated with malabsorption of fat-soluble vitamins. Most significantly, osteomalacia and, on rare occasions, haemorrhagic diathesis are reported with cholestyramine impairment of vitamin D and vitamin K absorption, respectively. Paediatric patients have been reported to experience hyperchloraemic metabolic acidosis or gastrointestinal obstruction. Concurrent administration of acidic drugs may result in their reduced bioavailability. Serious adverse reactions to clofibrate will probably limit its role in the future. Of particular concern are ventricular arrhythmias, induction of cholelithiasis and cholecystitis, and the potential for promoting gastrointestinal malignancy which far outweigh the reported benefits in preventing new or recurrent myocardial infarction, cardiovascular death and overall death. Patients with renal disease are particularly prone to myositis, secondary to alterations in protein binding and impaired renal excretion of clofibrate. Drug interactions with coumarin anticoagulants and sulphonylurea compounds may produce bleeding episodes and hypoglycaemia, respectively. Nicotinic acid produces frequent adverse effects, but they are usually not serious, tend to decrease with time, and can be managed easily. Dermal and gastrointestinal reactions are most common. Truncal and facial flushing are reported in 90 to 100% of treated patients in large clinical trials. Significant elevations of liver enzymes, serum glucose, and serum uric acid are occasionally seen with nicotinic acid therapy. Liver enzyme elevations are more common in patients given large dosage increases over short periods of time, and in patients treated with sustained release formulations.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of gemfibrozil on lipids, apoproteins, and postheparin lipolytic activities in normolipidemic subjects

The lipid lowering agent Gemfibrozil was tested in 8 normolipidemic subjects during a three-month intake. Plasma triglycerides decreased by 41% and Very Low Density Lipoprotein (VLDL) triglycerides decreased by 54%. The reduction of plasma cholesterol, less marked (by 10%), was due to a decrease of Low Density Lipoprotein by 20% while High Density Lipoprotein (HDL) increased up to 30%. The separation of HDL demonstrated that only HDL3 were increased. The determination of the apoproteins in plasma and lipoprotein fractions showed similar results with a decrease of apo B (by 20%) and an increase of apo A-I and apo A-II, mainly in the HDL3 fraction. Plasma postheparin lipolytic activities (PHLA) were not influenced by the therapy and no correlation was found between these activities and any of the plasma or lipoprotein lipids. The apo C-III/apo C-II ratio in VLDL decreased by 30%; however, no correlation was found between this ratio in plasma as well as VLDL and triglycerides. In addition, the Intra Venous Fat Tolerance Test did not demonstrate any improvement of the clearance of exogenous fat. The lipid lowering efficacy of Gemfibrozil, its collateral effects, and the possible mechanisms of action are discussed.

Comparison of biliary lipid secretion in non-obese cholesterol gallstone patients with normal, young, male volunteers

Measurements of biliary lipid secretion rates were performed in 14 non-obese patients with radiolucent gallstones (9 females, 5 males; mean age 48 years; mean body weight 65 kg) and in 14 healthy male volunteers (mean age 26 years, mean body weight 74 kg). The results in the gallstone patients differ in several respect from those obtained in the volunteers. Molar percentage of cholesterol was higher (5.8 versus 5.0 mol%; P less than 0.05) and molar percentage of bile acids lower (73.8 versus 76.9 mol%; P less than 0.05) in the gallstone patients. However, these changes were not followed by notable differences in cholesterol saturation of bile (94% vs 88%). Generally, hepatic secretion rates of cholesterol were significantly elevated in the gallstone patients (55 vs 46 mg/h; P less than 0.05) whereas outputs of bile acids and phospholipids did not differ between the two groups. Although patients with cholesterol gallstones tended to have a lower percentage of chenodeoxycholic acid (38 versus 42 mol%) and increased deoxycholic acid (23 versus 16 mol%) in their bile, these differences were not significant. Nevertheless, in patients with cholesterol gallstones a significant positive correlation between deoxycholic acid secretion and cholesterol output was observed. For the whole group of patients and volunteers a positive correlation between age and cholesterol secretion could be demonstrated. The higher hepatic cholesterol secretion in gallstone patients seems not be due to differences in body weight, but rather to the older age of the patients. These results suggest that age itself or age-related changes in deoxycholic acid metabolism contributes to biliary cholesterol output in non-obese patients with cholesterol gallstones.