[Fish by-products oil corrects dyslipidemia, improves reverse cholesterol transport and stimulates paraoxonase-1 activity in obese rat]

AIM OF THE STUDY

To valorize fish by-products oil by investigating its effects on dyslipidemia, hyperglycemia, reverse cholesterol transport and paraoxonase-1 activity in obese rat.

METHODS

Sixteen male Wistar rats were fed a high fat diet. At 400 ± 10 g, obese rats were randomly divided into two groups: the first received 20% of sardine by-products oil and the second 20% of the edible portion oil. At d28, glycemia and serum lipids concentrations were estimated. High density lipoproteins (HDL2 and HDL3) were separated and their contents and composition in lipids and apolipoproteins were analyzed. Lecithin: cholesterol acyltransferase and paraoxonase-1 activities were assessed.

RESULTS

In group which consumed sardine by-products oil, serum cholesterol and triacylglycerols were reduced (-8% and -36%, respectively). However, glycemia was similar. HDL3-phospholipids, HDL3-unesterified cholesterol and HDL3-apolipoproteins were decreased by 56%, 10% and 12%, respectively. Lecithin: cholesterol acyltransferase activity was increased by 35% and the content of HDL2-cholesteryl esters was elevated by 12%. Serum paraoxonase-1 activity was increased by 25%.

CONCLUSION

In obese rat, sardine by-products oil may have a protective effect against cardiovascular risk by improving the anti-atherogenic metabolic pathway of cholesterol and triacylglycerols. This anti-atherogenic action is particularly enhanced by the increase in paraoxonase-1 activity which protects lipoproteins from oxidation.

Cholesteryl esters associated with acyl-CoA:cholesterol acyltransferase predict coronary artery disease in patients with symptoms of acute coronary syndrome

OBJECTIVES

Identifying the likelihood of a patient having coronary artery disease (CAD) at the time of emergency department (ED) presentation with chest pain could reduce the need for stress testing or coronary imaging after myocardial infarction (MI) has been excluded. The authors aimed to determine if a novel cardiac biomarker consisting of plasma cholesteryl ester (CE) levels typically derived from the activity of the enzyme acyl-CoA:cholesterol acyltransferase (ACAT2) are predictive of CAD in a clinical model.

METHODS

A single-center prospective cohort design enrolled participants with symptoms of acute coronary syndrome (ACS) undergoing coronary computed tomography angiography (CCTA) or invasive angiography. Plasma samples were analyzed for CE composition with mass spectrometry. The primary endpoint was any CAD determined at angiography. Multivariable logistic regression analyses were used to estimate the relationship between the sum of the plasma concentrations from cholesteryl palmitoleate (16:1) and cholesteryl oleate (18:1) (defined as ACAT2-CE) and the presence of CAD. The added value of ACAT2-CE to the model was analyzed comparing the C-statistics and integrated discrimination improvement (IDI).

RESULTS

The study cohort was composed of 113 participants with a mean (± standard deviation [SD]) age of 49 (±11.7) years, 59% had CAD at angiography, and 23% had an MI within 30 days. The median (interquartile range [IQR]) plasma concentration of ACAT2-CE was 938 μmol/L (IQR = 758 to 1,099 μmol/L) in patients with CAD and 824 μmol/L (IQR = 683 to 998 μmol/L) in patients without CAD (p = 0.03). When considered with age, sex, and the number of conventional CAD risk factors, ACAT2-CE levels were associated with a 6.5% increased odds of having CAD per 10 μmol/L increase in concentration. The addition of ACAT2-CE significantly improved the C-statistic (0.89 vs. 0.95, p = 0.0035) and IDI (0.15, p < 0.001) compared to the reduced model. In the subgroup of low-risk observation unit patients, the CE model had superior discrimination compared to the Diamond-Forrester classification (IDI = 0.403, p < 0.001).

CONCLUSIONS

Plasma levels of ACAT2-CE have strong potential to predict a patient's likelihood of having CAD when considered in a clinical model but not when used alone. In turn, a clinical model containing ACAT2-CE could reduce the need for cardiac imaging after the exclusion of MI.

Studies on plasma lipid and phospholipid composition in pernicious anemia before and after specific treatment

Patients with pernicious anemia (PA) have been compared with a reference group concerning the concentration of lipids in plasma before (34 cases) and after (15 cases) treatment with vitamin B12. The lipid parameters in plasma and in postheparin plasma have been measured before and after 6 hours' incubation at 37degree C before and after specific treatment. In a limited number of cases the lecithin: cholesterol acyl transfer (LCAT) rate has been determined. In relapse, the PA cases showed increased free fatty acid (FFA) and triglyceride (TG) concentrations but decreased concentrations of total cholesterol (TC), unesterified cholesterol (UC) and all examined phospholipid fractions. After treatment, FFA remained unchanged and TG decreased, while TC and possibly also UC and the phospholipid frations were in line with reference levels. After incubations, UC and phosphatidylcholine (PC) decreased and lysolecithin (LL) increased. FFA increased and TG decreased. Incubation of postheparin plasma resulted in an augmented decrease in TG and PC and increase in FFA and LL, In relapse, the changes on incubation were less pronounced than after treatment. The LCAT was low but within the normal range before treatment in the six cases examined. After treatment, LCAT rates increased but were still normal in relation to the plasma lipid concentrations. The study showed a decreased net esterification of cholesterol and LL formation on incubation of plasma in PA cases in relapse. This finding might be explained by the low concentration of plasma substrates for the LCAT reaction and phospholipases. After treatment the concentration of lipid substrates was restored to normal, with subsequent normal LL formation and cholesterol esterification. The observations could also explain the frequent lack of stabilization of erythrocytes suspended in plasma of PA after incubation, resulting in virtually the same ESR after as before this procedure. Due to low LL formation following the insufficient substrate availability for LCAT and phospholipase, the previously reported critical level of the LL concentration is not reached and cannot achieve its normal reduction of the ESR.

Monounsaturated fatty acids and atherosclerosis: opposing views from epidemiology and experimental animal models

A substantial body of epidemiologic data has shed light on the potential protective effects of the Mediterranean diet against atherosclerosis in humans. Many believe the reason the Mediterranean diet is atheroprotective is the elevated consumption of olive oil, an oil poor in saturated fatty acids (SFA) and highly enriched in monounsaturated fatty acids (MUFA). Based on human feeding studies, the American Heart Association and the US Food and Drug Administration have advocated for the consumption of MUFA as a more healthy replacement for SFA. However, using experimental animal models in which extent of atherosclerosis can be directly measured following dietary intervention, it has been demonstrated that MUFA-enriched diets are not atheroprotective when compared with SFA-enriched diets. Hence, the current body of experimental evidence refutes the idea that MUFAs per se are atheroprotective; therefore much additional work is needed to determine which aspects of the Mediterranean diet are indeed heart healthy.

Hypocholesterolemic and antioxidant properties of 3-(4-hydroxyl)propanoic acid derivatives in high-cholesterol fed rats

The purpose of the present study was to evaluate the in vivo efficacy of two cinnamic acid synthetic derivatives (allyl 3-[4-hydroxyphenyl]propanoate; HPP304, 1-naphthyl-methyl 3-[4-hydroxyphenyl]propanoate; HPP305) in high-cholesterol fed rats and compare their actions to that of cinnamic acid. Cinnamic acid and its synthetic derivatives were supplemented with a high-cholesterol diet for 42 days at a dose of 0.135 mmol/100g of diet. The supplementation of HPP304 and HPP305 significantly lowered cholesterol and triglyceride levels in the plasma and liver with a simultaneous increase in the HDL-cholesterol concentration, whereas cinnamic acid only lowered the plasma cholesterol concentration. Cinnamic acid lowered hepatic HMG-CoA reductase activity in high-cholesterol fed rats, however, its synthetic derivatives (HPP304 and HPP305) did not affect HMG-CoA reductase activity compared to the control group. Instead, the HPP304 and HPP305 supplements significantly lowered hepatic acyl coenzyme A:cholesterol acyltransferase activity and increased the fecal bile acid. The SOD activity of the erythrocytes and liver was not different between the groups, however, the activities of CAT and GSH-Px, and the level of GSH in the erythrocytes were significantly higher in the HPP304 and HPP305 groups than in the control group. On the other hand, the activities of CAT and GSH-Px, and the level of malondialdehyde in the liver were significantly lower in the HPP304 and HPP305 groups. The antioxidant activities of these cinnamic acid synthetic derivatives were similar to the cinnamic acid in the high-cholesterol fed rats. In addition, HPP304 and HPP305 lowered amniotransferase activity in the plasma. These results suggest that two cinnamic acid synthetic derivatives (HPP304 and HPP305) exert lipid-lowering action and antioxidant properties without hepatotoxicity in high-cholesterol fed rats.

Genetic etiology of isolated low HDL syndrome: incidence and heterogeneity of efflux defects

OBJECTIVE

We have used a multitiered approach to identify genetic and cellular contributors to high-density lipoprotein (HDL) deficiency in 124 human subjects.

METHODS AND RESULTS

We resequenced 4 candidate genes for HDL regulation and identified several functional nonsynonymous mutations including 2 in apolipoprotein A-I (APOA1), 4 in lecithin:cholesterol acyltransferase (LCAT), 1 in phospholipid transfer protein (PLTP), and 7 in the ATP-binding cassette transporter ABCA1, leaving 88% (110/124) of HDL deficient subjects without a genetic diagnosis. Cholesterol efflux assays performed using cholesterol-loaded monocyte-derived macrophages from the 124 low HDL subjects and 48 control subjects revealed that 33% (41/124) of low HDL subjects had low efflux, despite the fact that the majority of these subjects (34/41) were not carriers of dysfunctional ABCA1 alleles. In contrast, only 2% of control subjects presented with low efflux (1/48). In 3 families without ABCA1 mutations, efflux defects were found to cosegregate with low HDL.

CONCLUSIONS

Efflux defects are frequent in low HDL syndromes, but the majority of HDL deficient subjects with cellular cholesterol efflux defects do not harbor ABCA1 mutations, suggesting that novel pathways contribute to this phenotype.

Acamprosate involvement in triacylglycerol hydrolysis and transacylation with cholesterol in chronically ethanol-drinking rats

Acamprosate (AC) is used as a drug for treating alcoholism. We evaluated the effect of AC on serum triacylglycerol hydrolysis (GEH, glycerol ester hydrolysis), triacylglycerol transacylation with cholesterol (GECAT, glycerol ester:cholesterol acyltransferase), and acylcholesterol hydrolysis (Cease, cholesterol ester hydrolysis) in an experimental model of alcoholism. Ethanol-preferring (PRF), non-preferring (NPF), and control (CR) male Wistar rats were treated with AC (500 mg/kg, p.o.) for 21 consecutive days. The beneficial effect of AC on lipid parameters of PRF rats included decreased triacylglycerol, total cholesterol, and LDL-cholesterol, and increased HDL-cholesterol levels. Acamprosate-compensated changes associated with ethanol consumption were observed. Acamprosate treatment decreased GECAT and increased Cease control rats, but increased GECAT and decreased CEase in PRF animals. In all groups of rats, AC treatment did not influence GEH. In conclusion, our results suggest that AC can influence triacylglycerol metabolism by its action on the balance between hydrolysis and transacylation in rats.

HMG-CoA reductase, cholesterol 7alpha-hydroxylase, LCAT, ACAT, LDL receptor, and SRB-1 in hereditary analbuminemia

BACKGROUND

Hereditary analbuminemia is associated with hypercholesterolemia, which has been shown to be primarily caused by increased extrahepatic production of cholesterol. Nagase rats with hereditary analbuminemia (NAR) have been used as a model to dissect the effect of primary hypoalbuminemia from that caused by proteinuria in nephrotic syndrome. The present study was undertaken to explore the effect of hereditary analbuminemia on protein expression of the key factors involved in cholesterol metabolism.

METHODS

Hepatic tissue protein abundance of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, cholesterol 7alpha-hydroxylase (a rate-limiting enzyme in cholesterol catabolism), low density lipoprotein (LDL) receptor, high density lipoprotein (HDL) receptor (SRB-1), acyl-coA cholesterol acyltransferase-2 (ACAT-2), and plasma concentration of lecithin cholesterol acyltransferase (LCAT), as well as HMG-CoA reductase, ACAT, and LCAT activities were determined in fasting male NAR and Sprague-Dawley control rats.

RESULTS

The NAR group exhibited significant up-regulation of HMG-CoA reductase protein abundance but normal HMG-CoA reductase enzymatic activity. This was coupled with a significant up-regulation of cholesterol 7alpha-hydroxylase and a mild up-regulation of ACAT protein abundance and activity. However, hepatic LDL receptor and HDL receptor and plasma LCAT protein concentration and activity were normal in NAR.

CONCLUSION

Hypercholesterolemia in NAR is associated with elevated hepatic HMG-CoA reductase protein abundance, but normal HMG-CoA reductase activity. These findings point to post-translational regulation of this enzyme and favor an extrahepatic origin of hypercholesterolemia in NAR. The observed up-regulation of cholesterol 7alpha-hydroxylase represents a compensatory response to the associated hypercholesterolemia. Unlike nephrotic syndrome, which causes severe LDL receptor, HDL receptor, and LCAT deficiencies, hereditary analbuminemia does not affect these proteins.

Endothelial lipase is a major genetic determinant for high-density lipoprotein concentration, structure, and metabolism

High-density lipoprotein (HDL) protects against atherosclerosis. Endothelial lipase (EL) has been postulated to be involved in lipoprotein, and possibly HDL, metabolism, yet the evidence has been scarce and conflicting. We have inactivated EL in mice by gene targeting. EL(-/-) mice have elevated plasma and HDL cholesterol, and increased apolipoproteins A-I and E. NMR analysis reveals an abundance of large HDL particles. There is down-regulation of the transcripts for phospholipid transfer protein, but up-regulation of those for hepatic lipase and lipoprotein lipase. Plasma lecithin:cholesterol acyltransferase is unchanged despite an increase in hepatic mRNA; lecithin:cholesterol acyltransferase activity toward endogenous EL(-/-) substrate is, however, reduced by 50%. HDL clearance is decreased in EL(-/-) mice; both the structure of HDL and the presence of EL are factors that determine the rate of clearance. To determine EL's role in humans, we find a significant association between a single-nucleotide polymorphism 584C/T in the EL (LIPG) gene and HDL cholesterol in a well characterized population of 372 individuals. We conclude that EL is a major determinant of HDL concentration, structure, and metabolism in mice, and a major determinant of HDL concentration in humans.

Lipid-lowering efficacy of hesperetin metabolites in high-cholesterol fed rats

BACKGROUND

Hesperetin is a naturally occurring flavonoid that has hypolipidemic properties.

METHODS

Male rats were fed a 1 g/100 g high-cholesterol diet for 5 weeks along with hesperetin (0.02%, 0.066 mmol/100 g diet) and hesperetin metabolites. The hesperetin metabolites, m-hydroxycinnamic acid (m-HC), 3,4-dihydroxyphenylpropionic acid (3,4-DHPP), and 3-methoxy-4-hydroxycinnamic acid (ferulic acid), were supplemented based on an equivalent amount of hesperetin.

RESULTS

The supplementation of hesperetin and its metabolites significantly lowered the plasma total cholesterol and triglyceride concentrations compared to the control group. The hepatic HMG-CoA reductase and acyl-CoA:cholesterol acyltransferase (ACAT) activities were significantly lower in the hesperetin and its metabolite supplemented groups than in the control group. The excretion of acidic sterol was significantly higher in the hesperetin, m-HC, 3,4-DHPP, and ferulic acid supplemented groups than in the control group.

CONCLUSIONS

These results demonstrated that the hesperetin metabolites played as potent a role as hesperetin in plasma lipid-lowering activities in vivo, and further suggest that cholesterol biosynthesis and esterification were concomitantly reduced by hesperetin and its metabolites, as indicated by the decreased HMG-CoA reductase and ACAT activities.

Gene-drug interaction: additive influence of mutant APOA1 and testosterone on plasma HDL-cholesterol

OBJECTIVES

Factors associated with decreased plasma high-density lipoprotein (HDL) cholesterol concentration, or hypoalphalipoproteinemia, include androgenic steroids and mutations in APOA1, encoding apolipoprotein (apo) A-I, the main structural protein of HDL. However, there is little information regarding the extent of plasma HDL lowering when exogenous testosterone is used in subjects with monogenic low HDL.

DESIGN AND METHODS

A man with coronary heart disease (CHD) had been receiving exogenous testosterone post-orchidectomy. He had marked hypoalphalipoproteinemia, which was not responsive to diet or medication. To identify a possible genetic contribution to his biochemical phenotype, we sequenced the LCAT and APOA1 genes.

RESULTS

There were no sequence abnormalities in LCAT, but we found that he was a heterozygote for a novel APOA1 mutation in codon 107 (AAG->TGG), which predicted the replacement of lysine by tryptophan (K107W). Serial biochemical measurements over 11 years showed that plasma HDL cholesterol on either intramuscular or oral testosterone was 0.19 +/- 0.06 mmol/L, while plasma HDL cholesterol on transdermal testosterone was significantly higher at 0.52 +/- 0.18 mmol/L (p = 0.015, unpaired t-test).

CONCLUSIONS

The findings suggest that the low plasma HDL cholesterol associated with heterozygosity for mutant APOA1 can become extremely depressed during treatment with oral or intramuscular androgens. The findings also suggest that transdermal testosterone may perturb HDL to a lesser extent than other routes of delivery in such patients.

Unique character and metabolism of high density lipoprotein (HDL) in fetus

Lipid and lipoprotein profiles, and enzymes for the lipid metabolism were compared between cord and adult blood. Consistent with previous reports, the major lipoprotein in cord blood was high-density lipoprotein (HDL), and that in adult blood was low-density lipoprotein (LDL). The level of apolipoprotein E (apo E) in cord blood was almost equivalent to that in adult blood, while other apolipoproteins and lipids were all lower than the adult level. In cord blood, apo E-rich HDL cholesterol represented more than 30% of total HDL cholesterol (around 11% in adult), and the concentration was about twice of that in adult blood. This apo E-rich HDL cholesterol was poorly esterified (E/T 56%) compared with that in adults (93%). The lecithin:cholesterol acyltransferase (LCAT) activity in cord blood was extremely low, while the activity and mass of cholesteryl ester transfer protein (CETP) were higher than those in adult blood. The apo E genotype did not show influences on total cholesterol, LDL cholesterol, total HDL cholesterol, and apo E rich HDL cholesterol levels in cord blood, as opposed to those in adult blood. The association of D442G mutation of the CETP gene with the increased HDL cholesterol in adult blood was not seen in cord blood. Rather, the mutation was associated with low total cholesterol and LDL cholesterol levels in cord blood. These results indicate that, in fetus, the character and metabolism of HDL, especially of apo E-rich HDL cholesterol, are distinct from those in adults.

Lipoprotein lipase and cholesterol transfer activities of lean and obese Zucker rats

Adult female lean and obese Zucker rats maintained under standard conditions were used for the estimation of plasma, liver and white adipose tissue (WAT) activity of lipoprotein lipase, plasma and liver hepatic lipase and plasma lecithin-cholesterol acyltransferase. No differences in plasma or tissue levels of lipoprotein lipase between lean and obese rats were detected, but the larger WAT size of the obese rats resulted in higher lipase activity per unit of rat weight. Hepatic lipase levels in plasma were higher in the obese, but in liver, the higher activity was found in lean rats. No significant differences were found for lecithin-cholesterol acyltransferase activity, except when the levels in the HDL fraction were expressed per unit of protein weight, showing lower activity in the obese rats. In conclusion, the essentially maintained enzyme activities in obese rat tissues suggest that they cannot explain the deficient lipoproteins processing of obese rats, and, consequently their dislipidaemia.

Fat infiltration in liver and activity of lecithin:cholesterol acyltransferase in serum of dry and lactating dairy cows

To study the relationship between fat infiltration in the liver and the decrease in the activity of serum lecithin:cholesterol acyltransferase (LCAT), blood and liver samples were taken from 14 multiparous (MP) and 16 primiparous (PP) dairy cows four weeks and one week before, and one, four and eight weeks after calving. During the dry period, half the animals received a protein supplement. LCAT activity decreased significantly in all groups before parturition, but returned to the initial level within 1-4 weeks after parturition. There were no differences between the feeding groups, but after calving, the LCAT activity in the MP cows was significantly lower than in the PP cows. Fat infiltration was not detected in the PP cows, and in the MP cows fat infiltration was mild and fell within the physiological range. There was no correlation between liver fat content and the activity of LCAT in serum. These results suggest that shortly before and after parturition, the activity of LCAT in serum is limited by post-transcriptional regulation, possibly by the availability of amino acid for export protein synthesis in the liver.

Net mass transfer of plasma cholesteryl esters and lipid transfer proteins in normolipidemic patients with peripheral vascular disease

The role of plasma cholesteryl ester transfer and lipid transfer proteins in atherosclerosis is unclear. Recent data suggest both antiatherogenic and atherogenic properties for cholesteryl ester transfer protein (CETP). The overall effect of CETP on atherosclerosis may thus vary depending on individual lipid metabolism. To test whether lipid transfer parameters are of importance even in patients without major lipid risk factors for atherosclerosis, CETP mass and activity, net mass transfer of cholesteryl esters between endogenous lipoproteins (CET), and phospholipid transfer protein (PLTP) activity were determined in plasma from 18 normolipidemic male patients with peripheral vascular disease and 21 controls. Furthermore, lecithin: cholesterol acyltransferase (LCAT) activity was tested. The results show that CETP mass, CETP activity, and LCAT activity are not different between patients and controls. However, specific CETP activity (CETP activity/CETP mass) is lower in the patients (P < .02). On the contrary, higher CET is observed in patients' plasma (P < .001). Increased plasma PLTP activity (P = .052) is demonstrable in the patients. If the data of all subjects are combined, CET correlates positively with triglycerides ([TG], r = .45, P < .001) and with PLTP activity (r = .32, P < .05) but negatively with specific CETP activity (r = -.37 P < .05). CET and specific CETP activity remain significantly different in TG-matched patients and controls and are more strongly interrelated (r = -.71, P < .001), suggesting a higher and selective influence of lipid transfer inhibitor(s) on CET and CETP activity in the patients. CET allows the best discrimination between patients and controls in univariate and multivariate analysis. Eighty-eight percent of the subjects are correctly classified by CET as a single parameter. The results suggest that increased CET in the patients may reflect atherogenic alterations in TG metabolism and/or in lipid transfer protein activities despite normal fasting lipoprotein levels.

Serum lecithin: cholesterol acyltransferase activity and HDL2 and HDL3 composition in small for gestational age newborns

The aim of this study was to determine serum lecithin: cholesterol acyltransferase (LCAT) activity in parallel with HDL2 and HDL3 composition in cord sera of small for gestational age (SGA) newborns, and to compare them with those obtained from appropriate for gestational age (AGA) newborns. LCAT activity was assayed by conversion of [3H]cholesterol to labelled cholesteryl ester. HDL2 and HDL3 were separated by ultracentrifugation. Serum cholesteryl ester, apolipoprotein (apo) A-I concentrations and LCAT activity were significantly lower (-47%, -18% and -56%, respectively), whereas serum triglyceride amounts were twofold higher in SGA newborns than in AGA newborns. In SGA newborns, HDL2 and HDL3 levels were low, and HDL3 and HDL2 phospholipid and HDL2-cholesteryl ester contents were diminished. HDL3-apo A-I, A-II, C-III and E values were lower in SGA newborns. In HDL2, apo A-I, A-II and E concentrations were decreased. Therefore, in SGA newborns, the reduced LCAT activity was associated with quantitative and qualitative changes in HDL2 and HDL3 particles.

Pharmacokinetic properties of YM17E, an inhibitor of acyl coenzyme A: cholesterol acyl transferase, and serum cholesterol levels in healthy volunteers

We conducted a single and repeat oral dose study of YM17E, a novel inhibitor of acyl coenzyme A (CoA): cholesterol acyltransferase, in healthy male volunteers to evaluate the pharmacokinetic profile, tolerability and effect of the drug on serum cholesterol. In the single administration study, YM17E was administered after a meal to two groups of subjects (each containing six subjects taking the drug and three taking placebo) receiving 3, 60 and 300 mg or 15, 60 and 450 mg YM17E, respectively. Plasma concentrations of unchanged drug following single oral administration at 3-300 mg after a meal increased with increasing dose. In contrast, plasma concentrations after administration of 450 mg were almost the same as after 300 mg. Unchanged YM17E was not detected in urine after single administration, suggesting that it was excreted via the bile or urine after metabolism. Five active metabolites (M1, M2-a, M2-b, M3 and M4) were observed in plasma at concentrations comparable to those of unchanged YM17E. Their plasma concentrations increased in a slightly greater than dose-dependent manner from 3 to 300 mg. The effect of food was studied in an open crossover design with a 1-week washout period. Twelve subjects received 150 mg YM17E in both the fasted and post-prandial states. The AUC and Cmax after fasting were closely similar to those after a meal, showing that bioavailability was not affected by food intake. In the repeated oral dose study, the subjects received test drug at 150 mg or 300 mg (n = 6 each) or placebo (n = 3) twice a day (after breakfast and after dinner) for 7 days. On days 1 and 7, the subjects received YM17E once a day (after breakfast) for evaluation of pharmacokinetic properties. After repeated oral administration of 150 mg b.d., plasma concentrations reached steady state by day 5 (mean Cmin 48.6 ng.ml-1). After repeated administration of 300 mg b.d., plasma concentrations prior to each daily morning dose increased up to the 5th day (mean Cmin 166.6 ng.ml-1) and then tended to decrease until the 7th day. No significant signs, symptoms or changes in serum cholesterol levels were observed during the single and repeated oral dose studies at 150 mg b.d. Although statistical analysis was not conducted because of the small number of subjects, all subjects receiving repeated oral administration of 300 mg twice daily showed a 25% decrease in serum cholesterol level on day 7, but also the simultaneous occurrence of diarrhoea.

Decreased serum lecithin:cholesterol acyltransferase activity in spontaneous cases of fatty liver in cows

Lecithin:cholesterol acyltransferase (LCAT) activity in serum was evaluated in spontaneous cases of fatty liver in cows. The enzyme activity of 631 +/- 62 U (mean +/- SEM, decrease in nmol of free cholesterol per h per ml of serum) in cows with fatty liver (n = 16) was significantly (p < 0.01) lower than that in cows without fatty liver (979 +/- 22 U; n = 16). In addition to the decrease in LCAT activity, the concentrations of phosphatidylcholine (a fatty aryl donor for esterification of free cholesterol) and of cholesteryl esters (products of the LCAT reaction) were reduced in the high-density lipoprotein fractions from cows with fatty livers. The concentrations in the serum of apolipoprotein A-I, an activator of LCAT, was also reduced in cows with fatty livers. These results suggest that the decreased LCAT activity, which may be attributable to impaired hepatic secretion or to the suppression of the activity in the plasma by reduced concentrations of phosphatidylcholine and apolipoprotein A-I, resulted in the lower concentrations of cholesteryl esters. Because cholesteryl esters are utilized in steroidogenic tissues for the synthesis of steroid hormones such as progesterone and glucocorticoids, and insufficient supply of the cholesterols may be of relevance to the reduced fertility and immune competence observed in cows with fatty livers.

Effect of treatment with simvastatin on serum cholesteryl ester transfer in patients on dialysis. PERFECT Study Collaborative Group

BACKGROUND

Plasma cholesteryl ester transfer activity is increased in patients with chronic renal failure on dialysis who have elevated levels of apolipoprotein B (apoB)-containing lipoproteins. Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitor, reduces levels of these lipoproteins but the effect of treatment on cholesteryl ester transfer activity in patients on dialysis remains to be determined.

METHODS

We measured serum newly synthesized cholesteryl ester transfer (NCET) activity, lecithin:cholesterol acyltransferase (LCAT) activity and serum lipid, lipoprotein and apolipoprotein concentrations before and immediately after 6 months treatment with simvastatin (10 mg daily, n = 24) or placebo (n = 29) in 53 patients with chronic renal failure receiving haemodialysis or continuous ambulatory peritoneal dialysis (CAPD).

RESULTS

Simvastatin therapy significantly reduced serum cholesterol, LDL cholesterol, apoB concentrations, and both NCET (P = 0.001) and LCAT (P = 0.012) rates. The decrease in NCET activity was correlated significantly with the corresponding decrease in apoB concentration (r = 0.715, P < 0.001) and LCAT activity (r = 0.715, P < 0.001) during simvastatin therapy and was no longer significant when apoB concentration (P = 0.14) or LCAT activity (P = 0.07) were controlled.

CONCLUSIONS

These data show that simvastatin therapy reduces serum NCET rates, and suggest that this may be linked to the concomitant decrease in levels of apoB-containing lipoproteins which are acceptors of transferred cholesteryl esters, and to the decrease in serum LCAT rates in patients with chronic renal failure with treatment.

Impaired suppression of plasma free fatty acids and triglycerides by acute hyperglycaemia-induced hyperinsulinaemia and alterations in high density lipoproteins in essential hypertension

OBJECTIVES

Essential hypertension may be associated with abnormalities in free fatty acids (FFA) and triglyceride metabolism, which could lead to alterations in high density lipoproteins (HDL). Lecithin: cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) are key factors in the esterification of cholesterol and the subsequent transfer of cholesteryl ester from HDL towards triglyceride-rich lipoproteins. We compared baseline plasma lipids, HDL lipids, plasma LCAT and CETP activity as well as the lowering of plasma FFA and triglycerides by acute hyperglycaemia-induced hyperinsulinaemia in patients with essential hypertension and control subjects.

SETTING

University Hospital, Groningen.

SUBJECTS AND DESIGN

Eight patients with essential hypertension and eight control subjects were studied during a 3-h hyperglycaemic glucose clamp (blood glucose, 10 mmol L-1).

MAIN OUTCOME MEASURES

Plasma insulin, FFA, triglycerides and HDL lipids, plasma LCAT and CETP.

RESULTS

Baseline plasma FFA, total cholesterol and HDL cholesterol were not different between the groups, but plasma triglycerides tended to be higher in the hypertensive patients (P < 0.10). The baseline HDL free cholesterol content and the HDL free cholesterol/cholesteryl ester ratio were lower (P < 0.05 for both) in the hypertensive than in the control group. Although baseline plasma LCAT and CETP activity were not significantly different between the groups, the plasma LCAT/CETP ratio, reflecting the amount of active LCAT compared to that of CETP, was higher in the hypertensive patients (P < 0.05). In the combined subjects and in the hypertensive group, the HDL free cholesterol content was negatively related to plasma triglycerides and to the LCAT/CETP ratio, whereas this ratio was positively correlated with plasma triglycerides (P < or = 0.01 for all correlations). During a 3-h hyperglycaemic clamp (blood glucose 10 mmol L-1) plasma FFA and triglycerides decreased to a lesser extent (P < 0.02 and P = 0.05) and remained higher (P < 0.05 for both) in the hypertensive patients, despite similar plasma insulin levels.

CONCLUSION

The action of insulin on FFA metabolism is impaired which is likely to contribute to higher plasma triglycerides in essential hypertension. In turn, higher triglycerides influence the HDL lipid composition, either directly or via an effect on the plasma LCAT/CETP ratio.

Anti-hyperlipidemic and anti-atherosclerotic actions of shosaikoto (kampo medicine)

We investigated the anti-atherosclerotic action shown by Shosaikoto, a Kampo medicine, using hypercholesterolemic mice. Oral administration of Shosaikoto significantly suppressed the elevation of serum cholesterol in C57BL/6 mice fed a 1.25% cholesterol-enriched diet for four weeks and improved the T cell ratio in peripheral blood, which decreased with the increase of the serum cholesterol level. In addition, Shosaikoto reduced the accumulation of cholesteryl oleate, which alters macrophages into foam cells, after the treatment of macrophages with oxidized or acetylated low density lipoprotein (LDL). Enzymatic study revealed that the treatment of macrophages with oxidized LDL enhanced acyl-coenzyme A: cholesterol acyltransferase (ACAT) activity and markedly reduced neutral cholesteryl ester hydrolase (NCEase) activity. Shosaikoto treatment prevented a decrease in the NCEase activity, however due to the oxidized LDL treatment, although it slightly augmented ACAT activity. Thus, Shosaikoto, which is known to modulate the immune system, improves macrophage and lymphocyte functions diminished by hypercholesterolemia, resulting in an anti-atherosclerotic action.

Functional lecithin:cholesterol acyltransferase deficiency and high density lipoprotein deficiency in transgenic mice overexpressing human apolipoprotein A-II

The concentration of high density lipoproteins (HDL) is inversely related to the risk of atherosclerosis. The two major protein components of HDL are apolipoprotein (apo) A-I and apoA-II. To study the role of apoA-II in lipoprotein metabolism and atherosclerosis, we have developed three lines of C57BL/6 transgenic mice expressing human apoA-II (lines 25.3, 21.5, and 11.1). Northern blot experiments showed that human apoA-II mRNA was present only in the liver of transgenic mice. SDS-polyacrylamide gel electrophoresis and Western blot analysis demonstrated a 17.4-kDa human apoA-II in the HDL fraction of the plasma of transgenic mice. After 3 months on a regular chow, the plasma concentrations of human apoA-II were 21 +/- 4 mg/dl in the 25.3 line, 51 +/- 6 mg/dl in the 21.5 line, and 74 +/- 4 mg/dl in the 11.1 line. The concentration of cholesterol in plasma was significantly lower in transgenic mice than in control mice because of a decrease in HDL cholesterol that was greatest in the line that expressed the most apoA-II (23 mg/dl in the 11.1 line versus 63 mg/dl in control mice). There was also a reduction in the plasma concentration of mouse apoA-I (32 +/- 2, 56 +/- 9, 91 +/- 7, and 111 +/- 2 mg/dl for lines 11.1, 21.5, 25.3, and control mice, respectively) that was inversely correlated with the amount of human apoA-II expressed. Additional changes in plasma lipid/lipoprotein profile noted in line 11.1 that expressed the highest level of human apoA-II include elevated triglyceride, increased proportion of total plasma, and HDL free cholesterol and a marked (>10-fold) reduction in mouse apoA-II. Total endogenous plasma lecithin:cholesterol acyltransferase (LCAT) activity was reduced to a level directly correlated with the degree of increased plasma human apoA-II in the transgenic lines. LCAT activity toward exogenous substrate was, however, only slightly decreased. The biochemical changes in the 11.1 line, which is markedly deficient in plasma apoA-I, an activator for LCAT, are reminiscent of those in patients with partial LCAT deficiency. Feeding the transgenic mice a high fat, high cholesterol diet maintained the mouse apoA-I concentration at a normal level (69 +/- 14 mg/dl in line 11.1 compared with 71 +/- 6 mg/dl in nontransgenic controls) and prevented the appearance of HDL deficiency. All this happened in the presence of a persistently high plasma human apoA-II (96 +/- 14 mg/dl). Paradoxical HDL elevation by high fat diets has been observed in humans and is reproduced in human apoA-II overexpressing transgenic mice but not in control mice. Finally, HDL size and morphology varied substantially in the three transgenic lines, indicating the importance of apoA-II concentration in the modulation of HDL formation. The LCAT and HDL deficiencies observed in this study indicate that apoA-II plays a dynamic role in the regulation of plasma HDL metabolism.

Sesame lignans modulate cholesterol metabolism in the stroke-prone spontaneously hypertensive rat

1. Effects of sesamin and episesamin (an epimer of sesamin) on lipid metabolism, in particular cholesterol metabolism, were examined in normocholesterolaemic and hypercholesterolaemic stroke-prone spontaneously hypertensive rats (SHRSP). 2. In normocholesterolaemic SHRSP fed a regular diet, both sesamin and episesamin significantly increased the concentration of serum total cholesterol, which was due to an increase of high density lipoprotein (HDL) subfraction rich in apoE (apoE-HDL). In addition, both substances effectively decreased serum very low density lipoprotein (VLDL). In the liver, only episesamin significantly decreased the activity of microsomal acyl-CoA:cholesterol acyltransferase. 3. In hypercholesterolaemic SHRSP fed a high-fat and high-cholesterol diet (HFC diet), only episesamin improved serum lipoprotein metabolism with an increase in apoA-I and a decrease in apoB. In the liver, both sesamin and episesamin significantly suppressed cholesterol accumulation. Interestingly, only episesamin significantly increased the activity of microsomal cholesterol 7alpha-hydroxylase. 4. These results indicate that sesamin may be effective in preventing cholesterol accumulation in the liver. In comparison with sesamin, episesamin may be effective in the regulation of cholesterol metabolism in the serum and liver.

Human plasma lecithin:cholesterol acyltransferase. On the substrate efficiency of cholest-5-ene-3 beta-thiol as a fatty acyl acceptor

Lecithin:cholesterol acyltransferase (LCAT) is a plasma enzyme which catalyses cholesteryl ester formation from lecithin and cholesterol present in the surface of plasma lipoproteins. Sterol fatty acid acceptors have previously been shown to require the presence of a trans conformation of the A/B ring and a 3 beta-OH group. Our laboratory has, however, demonstrated that two thiol sites within LCAT can become fatty acylated following lecithin cleavage although this does not appear to be essential for catalysis. In order to assess the ability of LCAT to donate a fatty acid derived from the sn-2 position of lecithin and present as an acyl enzyme intermediate (linked via an oxyester bond to Ser-181) to a sulfhydryl residue, we evaluated the ability of cholest-5-ene-3 beta-thiol to act as a substrate for cholesterol ester formation by LCAT. Thiocholesterol was a good terminal fatty acyl acceptor when incorporated into synthetic proteoliposomes containing lecithin/thiocholesterol/apo A-I in the molar ratios of 250:15:0.8. The Km for thiocholesterol was 203.6 microM with a Vmax of 5.3 nmol thiocholesteryl ester formed/h per microgram. The Km for cholesterol when substituted for thiocholesterol in the proteoliposomes was 29.5 microM with a Vmax of 8.8 nmol cholesteryl ester formed/h per microgram. Thiocholesterol and cholesterol were shown to occupy the same catalytic site in LCAT. Thus, thiocholesterol exhibits approx. 10% of the substrate efficiency of cholesterol when incubated with pure human LCAT. We conclude that LCAT can transacylate a fatty acyl moiety from the sn-2 position of lecithin to the 3 beta-SH group of thiocholesterol forming a cholesteryl thioester. Although the 3 beta-SH group is not as good a terminal acceptor as the 3 beta-OH group of cholesterol, LCAT is clearly capable of transacylating a fatty acid esterified via an oxyester linkage to one containing a thioester.

Dietary fatty acid modification of HDL phospholipid molecular species alters lecithin: cholesterol acyltransferase reactivity in cynomolgus monkeys

In the following report, cynomolgous monkeys, fed atherogenic diets containing either saturated, monounsaturated, polyunsaturated (n-6 Poly) or fish oil (n-3 Poly) fat as 35% of total calories, provide a model for the study of dietary fat effects on plasma lipoproteins and atherosclerosis. We have previously described the ability of polyunsaturated fat diets to lower plasma described the ability of polyunsaturated fat diets to lower plasma high density lipoprotein (HDL) cholesterol levels and alter HDL subpopulation distribution in the primate model. These experiments investigate possible mechanisms responsible for such modifications. Animals fed polyunsaturated fat had significantly lower plasma concentrations of HDL cholesterol, total plasma cholesterol, and apolipoprotein A-I. Such changes were reflected in the distribution of protein among HDL subfractions, with the most remarkable modification in subclass distribution being the preponderance of small HDL particles in the n-3 Poly-fed animals. Striking alterations were also observed in the distribution of phosphatidylcholine (PC) molecular species (diet effect P < 0.0001 for all major molecular species). Phosphatidylcholine isolated from lipoproteins were used to make recombinant HDL (rHDL) particles. The reaction rate of purified lecithin:cholesterol acyltransferase (LCAT) with particles made from n-3 Poly-derived PC was 50% of that determined using rHDL formed with PC from other dietary groups (P < 0.0001). When the distribution of LCAT-derived rHDL cholesteryl esters was analyzed, LCAT demonstrated little selectivity for certain PC molecular species except in n-3 Poly-derived rHDL where 18:2-containing PC was selectively utilized. These data demonstrate that differences in dietary fat intake can significantly alter HDL PC concentration and molecular species distribution. We suggest that diet-induced alterations in HDL PC molecular species modify the type of cholesteryl esters produced during the LCAT reaction thereby affecting the plasma cholesteryl ester pool. We also propose that dietary n-3 Poly affects cholesteryl ester metabolism in part via LCAT by lowering PC (LCAT substrate) availability, altering the rate of the LCAT reaction, and decreasing HDL cholesterol concentrations; however, n-6 Poly dietary fat effects on HDL concentration appear to be through some mechanism other than LCAT.

Libyan family with hypercholesterolemia and increased high-density lipoprotein cholesterol in plasma

Genetic deficiencies of cholesteryl ester transport protein (CETP) and hepatic lipase activities have been associated with hyperalpha-lipoproteinemias. Here we present a family of 11 members, of which 9, including the father, mother, 5 sons, and 2 daughters, show a marked increase in high-density lipoprotein (HDL) cholesterol alone with low plasma concentrations of triglycerides. Analyses of lecithin:cholesterol acyltransferase (LCAT) activity, cholesteryl ester transfer between HDL fractions, hepatic lipase (HL) activity, and lipoprotein lipase (LPL) activity in these cases showed that a decrease in the heparin-releasable HL activity was the possible cause of the marked increase of HDL2 fractions observed in nine of them. Such a defect in HL activity could significantly affect HDL metabolism in particular and lipoprotein metabolism in general. Evidently, a marked increase in serum total cholesterol due to abnormal metabolism of HDL cholesterol, separate from known causes of altered low-density lipoprotein cholesterol metabolism, e.g., a clearance or a receptor defect, is not uncommon. The coordinated action of HL, LCAT, LPL, and CETP may be essential for normal metabolism of plasma lipoproteins.

Role of sn-2 acyl group of phosphatidylcholine in determining the positional specificity of lecithin-cholesterol acyltransferase

Although human plasma lecithin-cholesterol acyltransferase (LCAT) is believed to be specific for the sn-2 position of phosphatidylcholine (PC), our recent studies showed that it derives a significant percent of acyl groups from the sn-1 position of certain PC species. To understand the physicochemical basis for this altered positional specificity, we determined the effect of sn-2 acyl group of PC on the enzyme activity and utilization of 16:0 from the sn-1 position by purified human and rat LCATs. Positional isomers of PC containing 16:0 at sn-2 were better substrates for human LCAT than the corresponding sn-1-16:0 isomers, whereas the reverse was true for rat LCAT. The positional specificity of human LCAT varied greatly depending on the nature of the acyl group at sn-2. The sn-1 contribution from various sn-1-16:0-2-acyl PCs for cholesteryl ester (CE) synthesis was 1.0% from 16:0-16:0, 1.4% from 16:0-20:5, 7.3% from 16:0-18:1, 47.0% from 16:0-20:3, 49.9% from 16:0-20:4, 54.9% from 16:0-22:6, and 72.3% from 16:0-18:0. There was a linear relationship between the percentage of 16:0 CE formed (from sn-1 position) and the acyl chain length at sn-2 position (r = 0.94). Rat LCAT also transferred some 16:0 from sn-1 position of 16:0-22:6, 16:0-20:3, and 16:0-18:0 PCs, but not from the other natural PCs tested. The phospholipase A activity of both LCATs in the presence of 16:0-20:4 PC showed the same positional specificity as CE synthesis, indicating that the specificity is determined at the formation of acyl-enzyme intermediate. These results show that the positional specificity of LCAT is influenced by the structure of PC, especially the chain length of the sn-2 acyl group.

Plasma lipoprotein profiles of normocholesterolemic and hypercholesterolemic homozygotes for apolipoprotein E2(Arg158-->Cys) compared

We compared plasma lipoprotein profiles of 15 individuals with normocholesterolemic (plasma cholesterol 4.81 +/- 0.90 mmol/L) familial dysbetalipoproteinemia (NFD) and 15 patients with hypercholesterolemic (plasma cholesterol 10.61 +/- 2.32 mmol/L) familial dysbetalipoproteinemia (HFD), matched for age and sex. All subjects were homozygous for apoE2(Arg158-->Cys). Compared with 15 normolipidemic controls (plasma cholesterol 5.47 +/- 0.92 mmol/L), subjects with NFD and HFD had greater cholesterol concentrations of large very-low-density lipoprotein (VLDL1), small VLDL (VLDL2), and intermediate-density lipoprotein, each of which was correlated to their plasma total cholesterol concentration. VLDL1 and VLDL2 subfractions were enriched in cholesteryl ester, and plasma cholesteryl ester transfer protein activities were increased in both NFD and HFD; however, absolute changes were larger in HFD than in NFD. Concentrations of low-density lipoprotein cholesterol were lower in HFD (1.89 +/- 0.48 mmol/L) and NFD (1.56 +/- 0.36 mmol/L) than in normolipidemic controls (3.35 +/- 0.73 mmol/L). We conclude that all subjects homozygous for apoE2(Arg158-->Cys) show features of dysbetalipoproteinemia.

Effect of adiposity on plasma lipid transfer protein activities: a possible link between insulin resistance and high density lipoprotein metabolism

The mechanisms responsible for the decreased high density lipoprotein (HDL) cholesterol levels associated with obesity and insulin resistance are not well understood. Lecithin: cholesterol acyltransferase (LCAT) and cholesterol ester transfer protein (CETP) are key factors in the esterification of cholesterol in HDL and the subsequent transfer of cholesteryl ester towards apolipoprotein B-containing lipoproteins. Phospholipid transfer protein (PLTP) may be involved in the regulation of HDL particle size. We therefore measured the activities of LCAT, CETP and PLTP using exogenous substrate assays, as well as lipids, lipoproteins, insulin and C-peptide in fasting plasma from eight healthy obese men (body mass index > 27 kg m-2) and 24 non-obese subjects. The obese men had lower levels of HDL cholesterol (P < 0.05) and higher levels of plasma triglycerides (P < 0.05), insulin (P < 0.05) and C-peptide (P < 0.01), as compared to the quartile of subjects with the lowest body mass index (BMI < 22.4 kg m-2). CETP and PLTP activities were elevated in the obese men by 35% (P < 0.01) and by 15% (P < 0.05), respectively. LCAT activity was comparable among the quartiles. Linear regression analysis showed that CETP activity was positively correlated with body mass index (P < 0.02), fasting blood glucose (P < 0.05) and plasma C-peptide (P < 0.05). PLTP activity was positively related to body mass index (P < 0.01), waist to hip circumference ratio (P < 0.001), as well as to fasting blood glucose (P < 0.05) and plasma C-peptide (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of lipoproteins with analytical capillary isotachophoresis

An analytical free flow capillary isotachophoresis procedure, with a discontinuous electrolyte system, for the detailed analysis of lipoproteins in human body fluids has been developed. The technique is based on prestaining whole serum lipoproteins with a lipophilic dye before separation. Human serum lipoproteins are separated into 14 well-characterized subfractions according to their electrophoretic mobility. High density lipoproteins (fraction 1 to 6) are separated into three major subpopulations, the fast migrating high density lipoprotein (HDL) subpopulation, containing mainly apo AI and phosphatidylcholine, the subpopulation with intermediate mobility, consisting of particles rich in apo AII, apo E, and C apolipoproteins, and the slowly migrating HDL subfraction, containing mainly particles rich in apo AI, apo AIV, and lecithin: cholesterol acyltransferase (LCAT) activity. The apo B containing lipoproteins (fraction 7 to 14) can be subdivided into four major functional groups. The first represents chylomicron derived particles and large triglyceride-rich very low density lipoproteins (VLDL). The second group consists of small VLDL and intermediate density lipoprotein (IDL) particles, anf the third and fourth group represent the low density lipoproteins. The isotachophoretic analysis of human serum samples obtained from patients with hyperlipoproteinemias is compatible with the classification according to the Frederickson phenotypes and reflects the respective biochemical abnormalities. Furthermore, several genetic disorders of lipid and lipoprotein metabolism like HDL deficiency syndromes, familial LCAT deficiency, Fish eye disease, hypobetalipoproteinemia and abetalipoproteinemia can be well characterized by analytical capillary isotachophoresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma lipid transport in the horse (Equus caballus)

1. Equine plasma contains lipoproteins corresponding to very low density (VLDL), low density (LDL) and high density lipoproteins (HDL). 2. HDL accounts for approximately 60% of plasma lipoprotein mass and consists of a single population of particles. 3. LDL is heterogeneous comprising three discrete subfractions. 4. Two proteins are found in the region of apolipoprotein (apo) B-100 in VLDL and LDL and a third similar to apoB-48 is in VLDL. 5. Lecithin:cholesterol acyl transferase is active in plasma and hepatic lipase and lipoprotein lipase are evident in post-heparin plasma. 6. There is no significant cholesteryl ester transfer protein activity.

Macrophage colony-stimulating factor regulates both activities of neutral and acidic cholesteryl ester hydrolases in human monocyte-derived macrophages

Macrophage colony-stimulating factor (M-CSF) regulates cholesterol metabolism in vivo and in vitro. We studied the effects of M-CSF on enzyme activities of acidic cholesteryl ester (CE) hydrolase, neutral CE hydrolase, and acyl-coenzyme A:cholesterol acyltransferase (ACAT), all of which are involved in cellular cholesterol metabolism in macrophages. During the differentiation of monocytes to macrophages, these enzyme activities were induced and further enhanced in response to M-CSF. M-CSF (100 ng/ml) enhanced acidic and neutral CE hydrolase and ACAT activities by 3.2-, 4-, and 2.3-fold, respectively, in the presence of acetyl LDL. The presence of acetyl LDL influenced these enzyme activities. ACAT and acidic CE hydrolase activities were increased and neutral CE hydrolase activity was decreased, indicating that these enzymes are regulated by intracellular cholesterol enrichment. M-CSF increased the ratios of acidic CE hydrolase to ACAT activity and of neutral CE hydrolase to ACAT activity. The results suggest that M-CSF enhances net hydrolysis of CE by stimulating the two CE hydrolases to a greater extent than ACAT, and M-CSF may reduce the rate of atherogenesis.

Evidence for an altered lipid metabolic state in circulating blood monocytes under conditions of hyperlipemia in swine and its implications in arterial lipid metabolism

Circulating blood monocytes were isolated from normal and hypercholesterolemic swine, and the monocyte lipid compositions and lipid biosynthesis profiles were assessed. The data indicate that monocytes freshly isolated from hyperlipemic swine have increased phospholipid and cholesterol contents and have increased biosynthetic capability for synthesizing phospholipids, triglycerides, and cholesteryl esters, but not cholesterol. The profile of the stimulated lipid synthesis capability is similar to that of the swine aortic intima undergoing atherogenic change. These studies indicate that circulating blood monocytes in hyperlipemic swine, which are known to give rise to intimal foam cells in the early fatty streak lesion, can contribute to altered vessel lipid metabolism without a requirement for in situ modification by wall factors.

ACAT activity in freshly isolated human mononuclear cell homogenates from hyperlipidemic subjects

Acyl-coenzyme A:cholesterol acyltransferase (ACAT) catalyzes the esterification of cholesterol in human mononuclear cells (MNC). In order to assess the relationship between lipid levels and ACAT activity in circulating MNC, we measured the rate of [14C]oleoyl-CoA incorporation into cholesterol ester in freshly isolated MNC homogenates from hyperlipidemic subjects. Baseline, off-treatment results obtained in 14 hypertriglyceridemic subjects (eight type IV and six type III) and seven subjects with familial hypercholesterolemia (FH) due to the same deletion of greater than 10 kb on the low-density lipoprotein (LDL)-receptor gene were compared with values determined in 12 healthy normolipidemic subjects. The rate of cholesterol esterification was 45 +/- 28 pmol/5 min/mg cell protein in healthy normolipidemic controls. This rate was significantly higher in type IV subjects (84 +/- 52 pmol/5 min/mg cell protein, P less than .05) and FH subjects (67 +/- 25 pmol/5 min/mg cell protein, P less than .05). The values were more dispersed in type III subjects; the mean value for the group (72 +/- 46 pmol/5 min/mg cell protein) was not statistically different from the control. Hypertriglyceridemic patients were then treated with 6 g/d of omega-3 fatty acids. This resulted in a significant reduction in plasma total triglycerides and very-low-density lipoprotein (VLDL)-cholesterol in both type III subjects (-57% and -51%, P less than .05) and type IV subjects (-62% and -62%, P less than .01). The reduction in VLDL concentration was associated with a significantly lower ACAT activity in MNC homogenates from type IV subjects (from 84 +/- 52 to 60 +/- 36 pmol/5 min/mg cell protein, P less than .05), but not from type III hypertriglyceridemic subjects (from 72 +/- 46 to 73 +/- 36 pmol/5 min/mg cell protein). In conclusion, we found that cholesterol esterification in human MNC is elevated in hyperlipidemic subjects and can be decreased with normalization of lipid levels. However, ACAT activity changes occurring with treatment are heterogeneous among hyperlipidemic subjects, suggesting that factors other than plasma lipid level reduction affect ACAT activity in vivo.

A mutation in the human apolipoprotein A-I gene. Dominant effect on the level and characteristics of plasma high density lipoproteins

Epidemiologic and genetic data suggest an inverse relationship between plasma high density lipoprotein (HDL) cholesterol and the incidence of premature coronary artery disease. Some of the defects leading to low levels of HDL may be a consequence of mutations in the genes coding for HDL apolipoproteins A-I and A-II or for enzymes that modify these particles. A proband with plasma apoA-I and HDL cholesterol that are below 15% of normal levels and with marked bilateral arcus senilis was shown to be heterozygous for a 45-base pair deletion in exon four of the apoA-I gene. This most likely represents a de novo mutation since neither parent carries the mutant allele. The protein product of this allele is predicted to be missing 15 (Glu146-Arg160) of the 22 amino acids comprising the third amphipathic helical domain. The HDL of the proband and his family were studied. Using anti-A-I and anti-A-II immunosorbents we found three populations of HDL particles in the proband. One contained both apoA-I and A-II, Lp(A-I w A-II); one contained apoA-I but no A-II, Lp(A-I w/o A-II); and the third (an unusual one) contained apoA-II but no A-I. Only Lp(A-I w A-II) and (A-I w/o A-II) were present in the plasma of the proband's parents and brother. Analysis of the HDL particles of the proband by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed two protein bands with a molecular mass differing by 6% in the vicinity of 28 kDa whereas the HDL particles of the family members exhibited only a single apoA-I band. The largely dominant effect of this mutant allele (designated apoA-ISeattle) on HDL levels suggests that HDL particles containing any number of mutant apoA-I polypeptides are catabolized rapidly.

Acute effects of resistance exercise on parameters of lipoprotein metabolism

Ten healthy, trained males (25.4 +/- 3.1 yr) were studied before and after 90 min of resistance exercise to determine the acute effects of high volume (HV) and low volume (LV) sessions on alterations in lipid and lipoprotein concentrations as well as the activity of lecithin: cholesterol acyltransferase (LCAT). The HV session involved the use of 8-12 repetition maximum (RM) loads performed to exhaustion with 60 s rest intervals between sets, while the LV session involved the use of 1-5RM loads with 3 min rest intervals between sets. Fasting blood samples were drawn from an antecubital vein immediately before and after exercise as well as 24, 48, and 72 h post-exercise. Following adjustment for changes in plasma volume, significant changes were only found following the HV session. These included increases in HDL-C (11%) and HDL3-C (12%) 24 h post-exercise. Modifications in HDL-C were significantly different from both the LV and control sessions. In contrast, triglycerides and LCAT were significantly depressed 24 h post-exercise following the HV session when compared with immediate post-exercise values. There were no significant changes in either total cholesterol or HDL2-C at any time. The results of this study suggest that the potential of resistance exercise to affect acute modifications in the lipoprotein profile resides in the volume of exercise performed.

Regulation of ACAT activity by a cholesterol substrate pool during the progression and regression phases of atherosclerosis: implications for drug discovery

The regulation of aortic ACAT by a cholesterol substrate pool (CSP) was investigated in a rabbit progression/regression model of dietary-induced atherosclerosis. ACAT activity increased 25-fold during the 10-week progression phase of the study. ACAT activity decreased 8-fold during the 24-week regression phase of the study, however, it was still 14-fold greater than in normal aortas. ACAT activity assayed in the absence vs. the presence of exogenous cholesterol was used as a qualitative measure of the amount of cholesterol in the CSP. The CSP was filled to 28% of capacity in normal aortas, this increased to 75% during the progression phase. By the end of the regression phase, the CSP was filled to 100% of capacity even though serum cholesterol levels had returned to normal. The data are discussed in terms of emerging concepts of intracellular cholesterol trafficking, ACAT inhibitors, and the types of atherosclerotic lesions which may be subject to amelioration by ACAT inhibitors.

Associations of lecithin: cholesterol acyltransferase (LCAT) mass concentrations with exercise, weight loss, and plasma lipoprotein subfraction concentrations in men

The relationships between plasma lecithin:cholesterol acyltransferase (LCAT) mass concentrations and lipids, apolipoprotein, and lipoprotein subfraction concentrations were studied in men assigned at random to a one-year exercise program (n = 48) and to a sedentary control condition (n = 31). Exercise training did not significantly affect mean concentrations of LCAT-mass. Moreover changes in LCAT within the exercise group were unrelated to distance run and weight loss. The baseline data and the one-year change data showed consistent positive correlations between LCAT concentrations and total cholesterol, low density lipoprotein cholesterol, very low density lipoprotein cholesterol, and apolipoprotein B concentrations, and consistently weak correlations between LCAT concentrations and high density lipoprotein (HDL)-cholesterol, HDL2, and apolipoprotein A-I concentrations. The strong correlation between LCAT and total cholesterol may account for LCAT's relationships with lipoprotein subfractions, apolipoprotein B and other lipoprotein cholesterol concentrations.

On the mechanism by which an ACAT inhibitor (CL 277,082) influences plasma lipoproteins in the rat

CL 277,082 is an inhibitor of acyl-CoA: cholesterol acyltransferase (ACAT). The effects of this drug on lipoprotein metabolism have been examined in cholesterol-fed rats. An optimal dose of drug incorporated into the diet (0.1% w/w) for 7 days reduced plasma cholesterol by 48% and plasma triglycerides by 72%. The decrease in plasma cholesterol was due to a reduction in triglyceride-rich lipoproteins and in HDL cholesterol. There was a significant 72% reduction in intestinal ACAT activity, accompanied by a 41% reduction in hepatic cholesterol content. There was a smaller 21% reduction in hepatic ACAT activity. Hepatic HMG-CoA reductase activity increased 3-fold. HDL binding activity by liver membranes was not altered significantly. The decrease in plasma cholesterol with this ACAT inhibitor is most likely due to decreased absorption of dietary cholesterol resulting from inhibition of intestinal ACAT.

Effect of a neutralizing monoclonal antibody to cholesteryl ester transfer protein on the redistribution of apolipoproteins A-IV and E among human lipoproteins

The effect of inhibiting cholesteryl ester transfer protein (CETP) on the in vitro redistribution of apolipoproteins(apo) A-IV and apoE among lipoproteins in whole plasma was studied in seven normal male subjects. Plasmas were incubated in the presence of a purified monoclonal antibody TP2 (Mab TP2) that neutralizes the activity of CETP. Mab TP2 had no effect on lecithin:cholesterol acyltransferase (LCAT) activity. Prior to and following a 6-h incubation at 37 degrees C in the presence of Mab TP2 or a control mouse myeloma immunoglobulin (IgG), plasmas were gel-filtered on Sephacryl S-300 and the distribution of apoA-IV and apoE among lipoproteins was determined by radioimmunoassay. Incubation (i.e., with active LCAT and CETP) increased the amount of apoA-IV associated with lipoproteins by 240%. When CETP activity was inhibited during incubation, the amount of apoA-IV that became lipoprotein-associated was significantly increased (315% of basal). Plasma incubation also caused a redistribution of apoE from high density lipoproteins (HDL) to larger lipoproteins (131% of basal); however, when CETP was inhibited, significantly greater amounts of apoE became associated with the larger particles (155% of basal). These effects were observed in all seven subjects. Increased movement of apoE from HDL to triglyceride-rich particles was not due to displacement by apoA-IV since loss of apoE from HDL was still observed when no movement of apoA-IV onto HDL occurred, such as during LCAT or combined LCAT and CETP inhibition. We speculate that low CETP activity (e.g., in species such as rats) may lead to an increased content of HDL apoA-IV and also to apoE enrichment of triglyceride-rich lipoproteins, augmenting their clearance.

Different cholesterol fractions, LCAT activity and lipid peroxides in the serum of children whose parents had early coronary heart disease

Children whose parents had early coronary heart disease were investigated for lipid abnormalities. In order to assess high risk parameters and the efficacy of the applied care, serum total cholesterol (TC), total triglyceride (TT), total free cholesterol (FC) high density lipoprotein cholesterol (HDLC), high density lipoprotein free cholesterol (HDLFC), lipid peroxide (LP) levels, and lecithin: cholesterol acyl transferase (LCAT) activity were measured. Compared to a group of control children, the offspring of high risk subjects had increased TC, FC, and LP levels and decreased HDLC levels. After one year of preventative care all parameters normalized except the high FC level and elevated LCAT activity. The measurement of serum FC and LP levels seems to be a useful method for the determination of true high risk. The LCAT activity may show the efficacy of the dietary treatment.

Alterations in molecular species of cholesterol esters formed via plasma lecithin-cholesterol acyltransferase in human subjects consuming fish oil

The influence of a dietary supplement of n-3 polyunsaturated fatty acids containing eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) on the molecular species of cholesteryl esters (CE) formed via the plasma lecithin (phosphatidylcholine)-cholesterol acyltransferase (LCAT; EC 2.3.1.43) reaction was evaluated. For this purpose, one group of eight subjects received an encapsulated fish lipid concentrate (MaxEPA) and another group of eight volunteers in the control group received encapsulated olive oil for 22 days. Plasma lipid profiles and fatty acid compositions of plasma phosphatidylcholine (PC) and CE were measured at day 0 and day 22 in all subjects. A decrease in plasma triglyceride (by 34%) and a moderate rise in high-density lipoprotein (HDL)-cholesterol (by 13%) was observed in the MaxEPA group. For characterization of the plasma LCAT-derived reaction products formed in vitro, [14C]cholesterol was used as the substrate and the newly formed molecular species of [14C]CE were separated by argentation thin-layer chromatography. Marked shifts were found in the abundance of the various classes of LCAT-derived products in the MaxEPA group whereas no significant changes were observed in the controls. The proportion of the [14C]CE as pentaenoic (EPA) species rose by 9-fold (from 1.5% at day 0 to 14.4% at day 22) as the dienoic (linoleate) species fell (from 50.6 to 39.2%); a moderate rise in the hexaenoic (DHA) species (from 1.7 to 2.4%) with no significant change in the tetraenoic (arachidonate) (AA) species was observed. The LCAT results were in the order of the observed shifts in the fatty acid patterns of the plasma CE.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution and localization of lecithin:cholesterol acyltransferase and cholesteryl ester transfer activity in A-I-containing lipoproteins

Two types of A-I-containing lipoproteins are found in human high density lipoproteins (HDL): particles with A-II (Lp(A-I with A-II] and particles without A-II (Lp(A-I without A-II]. We have studied the distribution of lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer (CET) activities in these particles. Lp(A-I with A-II) and Lp(A-I without A-II) particles were isolated from ten normolipidemic subjects by anti-A-I and anti-A-II immunosorbents. Most plasma LCAT mass (70 +/- 15%), LCAT (69 +/- 16%), and CET (81 +/- 15%) activities were detected in Lp(A-I without A-II). Some LCAT (mass: 16 +/- 7%, activity: 17 +/- 8%) and CET activities (7 +/- 8%) were detected in Lp(A-I with A-II). To determine the size subspecies that contain LCAT and CET activities, isolated Lp(A-I with A-II) and Lp(A-I without A-II) particles of six subjects were further fractionated by gel filtration column chromatography. In Lp(A-I without A-II), most LCAT and CET activities were associated with different size particles, with the majority of the LCAT and CET activities located in particles with hydrated Stokes diameters of 11.6 +/- 0.4 nm and 10.0 +/- 0.6 nm, respectively. In Lp(A-I with A-II), most of the LCAT and CET activities were located in particles similar in size: 11.1 +/- 0.4 nm and 10.6 +/- 0.3 nm, respectively. Ultracentrifugation of A-I-containing lipoproteins resulted in dissociation of both LCAT and CET activities from the particles. Furthermore, essentially all CET and LCAT activities were recovered in the non-B-containing plasma obtained by anti-LDL immunoaffinity chromatography. This report, therefore, provides direct evidence for the association of LCAT and CET protein with A-I-containing lipoproteins. Our conclusions pertain to fasting normolipidemic subjects and may not be applicable to hyperlipidemic or nonfasting subjects.

Identification of homozygosity for a human apolipoprotein A-I variant

An apolipoprotein (apo) A-I variant, previously described in two Norwegian families (Schamaun et al. 1983. Hum. Genet. 64: 380-383), represents a mutation in apoA-I in which a single amino acid substitution of lysine for glutamic acid has taken place at residue 136. An offspring resulting from intermarriage between the two families is genotypically homozygous for this variant. He is the first individual discovered to be homozygous for any of the apoA-I variants. Analysis of lipid data collected from these families indicates one or more lipid abnormalities. The low density lipoproteins (LDL) of subjects having this apoA-I variant demonstrate a compositional abnormality. The plasma cholesterol concentration in the homozygous subject is low because of the extremely reduced levels of LDL and apoB, a property shared by some of his first-degree relatives. However, because of the presence of apoE2 in this family, it is not possible to definitively link these lipid abnormalities to the presence of the A-I variant.

Effect of insulin on low-density-lipoprotein metabolism in human lymphocytes in vitro

The metabolism of low-density lipoproteins (LDL) in vitro in the presence of insulin was studied in freshly isolated human peripheral-blood lymphocytes. Insulin appeared to decrease the binding affinity of 125I-LDL to its cell-surface receptor, without any change in apparent Vmax or in the number of LDL receptors. As a consequence, the absolute amounts of 125I-LDL internalized and degraded were lower in the presence of insulin than in its abscence, although the fraction of internalized 125I-LDL degraded in either instance was quite similar. 3-Hydroxy-3-methylglutaryl-CoA reductase activity, and hence cholesterol synthesis, were stimulated by insulin. This effect of insulin was independent of the inhibitory effect of LDL on cholesterol synthesis. At the same time, acid cholesterol esterase and acyl-CoA: cholesterol O-acetyltransferase activities were lower in cells incubated with insulin than in controls. The net effect of these metabolic alterations seems to be that cells accumulate greater quantities of free and esterified cholesterol when treated with insulin.

Familial apolipoprotein A-I and C-III deficiency, variant II

The biochemical, clinical, and genetic features were examined in the proband (homozygote) and heterozygotes (n = 17) affected with familial apolipoprotein A-I and C-III deficiency, variant II (previously described as apolipoprotein A-I absence). The proband was a 45-year-old white female with mild corneal opacification and significant three-vessel coronary artery disease (CAD), who died shortly after bypass surgery. Autopsy findings included significant atherosclerosis in the coronary and pulmonary arteries and the abdominal aorta as well as extracellular stromal lipid deposition in the cornea. No reticuloendothelial lipid deposits in the liver, bone marrow, or spleen were noted (unlike Tangier disease). Laboratory features included marked high density lipoprotein (HDL) deficiency and undetectable plasma apolipoproteins (apo) A-I and C-III. The percentage of plasma cholesterol in the unesterified form was normal at 30%. The activity and mass of lecithin:cholesterol acyltransferase (LCAT) were 42% and 36% of normal, respectively, and the cholesterol esterification rate was 43% of normal. Deficiencies of plasma vitamin E and essential fatty acid (linoleic, C18:2) were also noted. Evaluation of plasma lipoproteins and apolipoproteins in 37 kindred members revealed 17 heterozygotes with HDL cholesterol values below the 10th percentile of normal. Of these, all had apoA-I levels more than one standard deviation below the normal mean, and 37.5% had a similar decrease in apoC-III values. Mean (+/- SD) plasma HDL cholesterol, apoA-I, and apoC-III values (mg/dl) in heterozygotes were 54.0%, 62.4%, and 79.2% of normal, respectively. No evidence of CAD was observed in 10 heterozygotes 40 years of age or less; however, CAD was detected in 3 of 7 heterozygotes over 40 years of age, one of whom died at age 56 years of complications of myocardial infarction and stroke. The inheritance pattern in this kindred was autosomal codominant. ApoA-I isolated from a heterozygote had an isoelectric focusing pattern and amino acid composition similar to normal. Utilizing DNA isolated from two obligate heterozygotes, no abnormalities in the apoA-I or apoC-III genes were detected by Southern blot analysis utilizing specific probes following restriction enzyme digestion. The data indicate that familial apolipoprotein A-I and C-III deficiency, variant II, is similar to variant I (described by Norum et al. 1982. N. Engl. J. Med. 306: 1513-1519), but differs at the clinical level (lack of xanthomas), the biochemical level (lack of detectable apoA-I, lower apoA-II level), and at the gene level.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma activities of lipoprotein lipase, hepatic lipase and lecithin: cholesterol acyltransferase in patients considered for parenteral nutrition with fat emulsion

Intralipid is a fat emulsion which is widely used for intravenous nutrition in very ill patients. In order to know more about the capacity of these patients to metabolize exogenous triglycerides, the plasma activities of lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyltransferase (LCAT), the key enzymes in the metabolism of serum lipoproteins were measured by a radioisotope technique in 23 critically ill patients and 20 patients with recent major surgery. Compared with normal volunteers, the activities were significantly decreased. On the other hand, the capacity to clear intravenously given Intralipid (0.1 g/kg), expressed as fractional removal rate (K2), was retained in patients. It is suggested that the measurement of K2 could not be useful to evaluate the capacity of Intralipid administration to satisfy the metabolic needs and also that its utilization must be reevaluated in terms of potential harmful effects.