Biomedical subjects

J Férézou

Publications and source records attributed to J Férézou.

At least 19 recordsLinked to original sources

PubMed2004

Plasma lipids, lipoprotein composition and profile during induction and treatment of hepatic lipidosis in cats and the metabolic effect of one daily meal in healthy cats.

Anorexia in obese cats may result in feline hepatic lipidosis (FHL). This study was designed to determine plasma lipids and lipoprotein profiles in queens at different stages during experimental induction of FHL (lean, obese, FHL), and after 10 weeks of treatment. Results were compared with those obtained from lean queens of same age fed the same diet but at a maintenance level, once a day. Hepatic lipidosis led to an increase in plasma triacylglycerol (TG), very low density lipoprotein (VLDL) and low density lipoprotein (LDL), and an enrichment of LDL with TG and of high density lipoprotein (HDL) with cholesterol, suggesting that VLDL secretion is enhanced, VLDL and LDL catabolism is lowered, and lipoprotein exchanges are impaired in FHL. This study also showed that cholesterolaemia is increased in cats fed at a dietary rhythm of one meal per day compared to ad libitum feeding.

Animal Feed↗

PubMed2001

Overexpression of SR-BI in hamsters treated with a novel ACAT inhibitor (F12511).

The effect of a novel acyl-coenzyme A: cholesterol acyltransferase (ACAT) inhibitor on cholesterol metabolism was studied in hamsters. Oral administration of F12511 (10 mg/kg/d) for 4 weeks produced a decrease in dietary cholesterol absorption (-18%) and in the liver concentration of esterified cholesterol (-75%), as compared with control values in untreated hamsters. While the hepatic expression of LDLr was unchanged by the treatment, that of SR-BI was increased (+142%), which suggests that the hepatic expression of SR-BI could be upregulated by a depletion of the cholesterol stores, due to ACAT inhibition. This SR-BI overexpression, however, did not induce a fall in plasma HDL-cholesterol concentration, in contrast with previous reports in transgenic mice overexpressing SR-BI at a higher extent.

Administration, Oral↗

PubMed2001

Hamsters predisposed to sucrose-induced cholesterol gallstones (LPN strain) are more resistant to excess dietary cholesterol than hamsters that are not sensitive to cholelithiasis induction.

We compared the effects of cholesterol feeding in male hamsters from two strains with different propensities to sucrose-induced cholelithiasis; Laboratoire de Physiologie de la Nutrition (LPN) hamsters are predisposed to developing biliary cholesterol gallstones, whereas Janvier (JAN) hamsters are not. When fed a basal control diet, LPN hamsters had a lower cholesterolemia (-21%, P = 0.01) than JAN hamsters, and a higher activity of 3-hydroxy-3-methyl glutaryl coenzyme A reductase in liver (+148%, P = 0.018) and intestine (+281%, P < 0.0001). After feeding the same diet enriched with 0.3% cholesterol for 5 wk, cholesterolemia increased more dramatically in JAN hamsters (+235%, P < 0.001) than in LPN hamsters (+108%, P < 0.001), as did the liver concentration of cholesterol, which reached 152.30 +/- 13.00 and 44.41 +/- 9.06 micromol/g, respectively. Only JAN hamsters displayed hepatomegaly, with an increased cholesterol saturation index of the gallbladder bile (+100%, P < 0.01), due to the cholesterol challenge. In liver, cholesterol feeding reduced cholesterol 7alpha-hydroxylase activity and mRNA level, and stimulated sterol 27-hydroxylase and oxysterol 7alpha-hydroxylase activities. Hepatic levels of LDL receptor decreased by approximately 60% in both strains, whereas HDL receptor scavenger class B type 1 (SR-BI) levels were unaffected by dietary cholesterol. The greater resistance of LPN hamsters to the hypercholesterolemic diet can be explained by a lower capacity to store cholesterol in the liver and greater efficiency in reducing the activity of 3-hydroxy-3-methyl glutaryl coenzyme A reductase in response to cholesterol feeding [from 11263 to 261 pmol/(min x organ) in LPN hamsters and from 4530 to 694 pmol/(min x organ) in JAN hamsters]. These results highlight the usefulness of this two-strain model, which offers some analogy with the inverse association between the predisposition to cholelithiasis and the risk of atherosclerosis in humans.

Animals↗

PubMed2000

Short and long-term effects of streptozotocin on dietary cholesterol absorption, plasma lipoproteins and liver lipoprotein receptors in RICO rats.

Adult male genetically hypercholesterolemic RICO rats were studied 6 and 28 days after streptozotocin (STZ) administration together with untreated RICO controls. The absorption coefficient of dietary cholesterol was determined using dual-isotope blood ratio method. Plasma lipoproteins as well as fecal neutral sterols and bile acids were analysed at both experimental times. Liver lipid parameters were measured and lipoprotein receptors (LDLr, SR-BI and HB2) were assayed by immunodetection. Six days after STZ administration, dietary cholesterol absorption was more efficient (+49%) in treated rats than in controls, and stayed higher (+68%) in the diabetic rats sacrificed at day 28. Fecal neutral sterol elimination decreased soon after STZ administration (by 35% at day 6), due to a higher cholesterol absorption coefficient, then increased to control level at day 28, due to installed diabetes-induced hyperphagia. Comparison of the lipoprotein profiles indicated that the concentration of HDL1. which is typically high in control Rico rats, fell significantly in diabetic rats at both experimental times, whereas that of HDL2 increased only at day 28. In diabetic rats, an early and strong enhancement of the hepatic expression of SR-BI appeared at day 6 (+415%) and persisted at day 28, but at a lesser extent (+85%). The expression of LDLr and HB2 was unchanged at day 6, but was significantly modified at day 28 (+140% for LDLr and -50% for HB2). These data show that streptozotocin-induced diabetes in Rico rats results in modifications of the expression of liver lipoprotein receptors which can contribute to alterations of the lipoprotein profile.

Animals↗

PubMed2000

Cholesterol crystallization in gall-bladder bile of pigs given cholesterol-beta-cyclodextrin-enriched diets with either casein or soyabean concentrate as protein sources.

Cholesterol precipitation from supersaturated bile is the earliest and determinant step in the formation of cholesterol gallstones, which is thought to be diet-dependent. Bile composition, appearance and growth of cholesterol crystals were studied in fresh gall-bladder biles from pigs adapted to four different protein-containing diets over 3 weeks: 160 g dietary protein/kg as casein (C16; n 6), or as soyabean-protein concentrate (S16; n 6), or a mixture of both protein sources (casein-soyabean protein, 70:30, w/w) (CS16; n 6), or 320 g of the mixed protein/kg (CS32; n 6). Moreover, all four diets contained 3 g cholesterol/kg and 50 g beta-cyclodextrin/kg as modifiers of bile composition towards cholesterol pro-crystallization. Cholesterol precipitation was most active after the high-protein diet, CS32, and the casein diet, C16, and lowest after the soyabean-protein diet, S16. It was intermediate after the mixed diet, CS16, but still much lower than in the former two groups. These diet-induced variations were suggested to be mediated through modifications in the biliary profile of bile acids, whereas all other biliary constituents studied were essentially unchanged. The fasting level of plasma cholesterol was lowest in both 160 g protein/kg diets containing soyabean protein (S16 and CS16), highest for the high-protein diet CS32, and intermediate for the C16 diet. These results should encourage clinical studies on the effect of soyabean protein, or other vegetable proteins, for primary or recurrence prevention of cholelithiasis at its earliest stage.

Animals↗

PubMed2000

Cholesterol, bile acid, and lipoprotein metabolism in two strains of hamster, one resistant, the other sensitive (LPN) to sucrose-induced cholelithiasis.

A comprehensive study of cholesterol, bile acid, and lipoprotein metabolism was undertaken in two strains of hamster that differed markedly in their response to a sucrose-rich/low fat diet. Under basal conditions, hamsters from the LPN strain differed from Janvier hamsters by a lower cholesterolemia, a higher postprandial insulinemia, a more active cholesterogenesis in both liver [3- to 4-fold higher 3-hydroxy 3-methylglutaryl coenzyme A reductase (HMG-CoAR) activity and mRNA] and small intestine, and a lower hepatic acyl-coenzyme A:cholesterol acyltransferase activity. Cholesterol saturation indices in the gallbladder bile were similar for both strains, but the lipid concentration was 2-fold higher in LPN than in Janvier hamsters. LPN hamsters had a lower capacity to transform cholesterol into bile acids, shown by the smaller fraction of endogenous cholesterol converted into bile acids prior to fecal excretion (0.34 vs. 0.77). In LPN hamsters, the activities of cholesterol 7alpha-hydroxylase (C7OHase) and sterol 27-hydroxylase (S27OHase), the two rate-limiting enzymes of bile acid synthesis, were disproportionably lower (by 2-fold) to that of HMG-CoAR. When fed a sucrose-rich diet, plasma lipids increased, dietary cholesterol absorption improved, hepatic activities of HMG-CoA reductase, C7Ohase, and S27OHase were reduced, and intestinal S27OHase was inhibited in both strains. Despite a similar increase in the biliary hydrophobicity index due to the bile acid enrichment in chenodeoxycholic acid and derivatives, only LPN hamsters had an increased lithogenic index and developed cholesterol gallstones (75% incidence), whereas Janvier hamsters formed pigment gallstones (79% incidence). These studies indicate that LPN hamsters have a genetic predisposition to sucrose-induced cholesterol gallstone formation related to differences in cholesterol and bile acid metabolism.

Animals↗

PubMed1999

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

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

Age Factors↗

PubMed1999

Catabolism of HDL1 cholesteryl ester in the rat. Effect of ethinyl estradiol treatment.

The present study was performed in control and ethinyl estradiol-treated rats in order to determine the mechanisms involved in the catabolism of HDL1 cholesteryl ester. Ligand blottings on liver membranes showed that purified HDL1, containing about 70% apolipoprotein E and 10% apolipoprotein AI, bind to the LDL receptor (130 kDa) and not to HB2 (100 kDa) or SR-BI (82 kDa), candidate HDL receptors. Immunoblots showed that the treatment increased the hepatic level of the LDL receptor five- to ten-fold, strongly decreased that of SRBI and did not change that of HB2. An in vivo kinetic study showed that the turnover of HDL1 cholesteryl ester is more rapid in treated than control rats. The liver participation (60%) in this clearance was not modified by the treatment. Therefore, it can be concluded that the catabolism of HDL1 cholesteryl ester, in control as in treated rats, is essentially ensured by the uptake of entire particles in the hepatocytes via LDL receptors.

Adrenal Glands↗

PubMed1999

Ionizing radiation alters hepatic cholesterol metabolism and plasma lipoproteins in Syrian hamster.

PURPOSE: The investigation of the effects of ionizing radiation on hepatic cholesterol metabolism and the concentration and composition of plasma lipoproteins in the male Syrian hamster. MATERIALS AND METHODS: After sublethal whole-body 60Co gamma-irradiation (8 Gy, 1 Gy/min), plasma lipoproteins were separated by density-gradient ultracentrifugation. Activities of hydroxymethylglutarylCoA (HMGCoA) reductase and of cholesterol 7alpha-hydroxylase were measured in hepatic microsomes and the low-density lipoprotein (LDL) receptor mass was determined in hepatic total membranes. Lipid peroxidation in LDL was assessed in vitro as the formation of conjugated dienes at 234 nm. A group of pair-fed animals served as controls as the food intake was markedly decreased with exposure to radiation. RESULTS: Plasma lipid concentrations decreased 2 days post-irradiation and then markedly increased by day 6 post-irradiation; plasma cholesterol was increased by 77% and triglycerides by +207%. LDL accumulated in plasma while high-density lipoprotein (HDL) levels decreased. HDL contained significant amounts of apo SAA, the acute phase apolipoprotein. The activities of hepatic HMGCoA reductase, the rate-limiting enzyme for cholesterol synthesis, increased (+125%, p=0.06); hepatic cholesterol 7alpha-hydroxylase, the rate-limiting enzyme for bile acid synthesis, decreased (-85%); and the hepatic LDL receptor mass also decreased (-44%). The susceptibility of LDL to oxidation was also increased when animals were exposed to radiation. CONCLUSIONS: Lipoprotein modifications that appeared following radiation exposure may result from an induced inflammatory state and may further contribute to vascular damage.

Animals↗

PubMed1999

Antilithiasic effect of beta-cyclodextrin in LPN hamster: comparison with cholestyramine.

Beta-Cyclodextrin (BCD), a cyclic oligosaccharide that binds cholesterol and bile acids in vitro, has been previously shown to be an effective plasma cholesterol lowering agent in hamsters and domestic pigs. This study examined the effects of BCD as compared with cholestyramine on cholesterol and bile acid metabolism in the LPN hamster model model for cholesterol gallstones. The incidence of cholesterol gallstones was 65% in LPN hamsters fed the lithogenic diet, but decreased linearly with increasing amounts of BCD in the diet to be nil at a dose of 10% BCD. In gallbladder bile, cholesterol, phospholipid and chenodeoxycholate concentrations, hydrophobic and lithogenic indices were all significantly decreased by 10% BCD. Increases in bile acid synthesis (+110%), sterol 27-hydroxylase activity (+106%), and biliary cholate secretion (+140%) were also observed, whereas the biliary secretion of chenodeoxycholate decreased (-43%). The fecal output of chenodeoxycholate and cholate (plus derivatives) was increased by +147 and +64%, respectively, suggesting that BCD reduced the chenodeoxycholate intestinal absorption preferentially. Dietary cholestyramine decreased biliary bile acid concentration and secretion, but dramatically increased the fecal excretion of chenodeoxycholate and cholate plus their derivatives (+328 and +1940%, respectively). In contrast to BCD, the resin increased the lithogenic index in bile, induced black gallstones in 34% of hamsters, and stimulated markedly the activities of HMG-CoA reductase (+670%), sterol 27-hydroxylase (+310%), and cholesterol 7alpha-hydroxylase (+390%). Thus, beta-cyclodextrin (BCD) prevented cholesterol gallstone formation by decreasing specifically the reabsorption of chenodeoxycholate, stimulating its biosynthesis and favoring its fecal elimination. BCD had a milder effect on lipid metabolism than cholestyramine and does not predispose animals to black gallstones as cholestyramine does in this animal model.

Animals↗

PubMed1997

Reduced cholesterol absorption in hamsters by crilvastatin, a new 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor.

Crilvastatin, a new drug from the pyrrolidone family, has been previously shown to inhibit the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, in vitro and in vivo, to reduce the absorption of dietary cholesterol and to stimulate the activity of cholesterol 7 alpha-hydroxylase in the rat. The aim of this study was to evaluate the effects of crilvastatin on cholesterol and bile acid metabolism in the hamster. In hamsters fed on a lithogenic diet for 8 weeks, crilvastatin treatment (200 mg/day per kg body weight) did not change plasma lipid levels, failed to improve bile parameters and did not prevent gallstone formation. In hamsters fed on a basal cholesterol-rich (0.2%) diet for 8 weeks, crilvastatin at the same dose reduced the cholesterol level in the plasma by 20%, with a decrease of both low-density and high-density lipoprotein cholesterol. The drug did not significantly stimulate the biliary secretion of bile acids but significantly decreased the activity of acyl coenzyme A:cholesterol acyltransferase in the small intestine by 64%. This effect was enhanced when cholestyramine, a bile acid-sequestering resin, was given in combination with crilvastatin. Crilvastatin alone did not change the activity of cholesterol 7 alpha-hydroxylase in the liver, despite the marked reduction in both hepatic cholesterogenesis and intestinal absorption of dietary cholesterol (the absorption coefficient was 44 +/- 2% in treated hamsters vs. 61 +/- 7% in controls).

Animals↗

PubMed1997

Hypocholesterolemic action of beta-cyclodextrin and its effects on cholesterol metabolism in pigs fed a cholesterol-enriched diet.

To examine the effects of beta-cyclodextrin (BCD), a non-absorbable carbohydrate, on lipid metabolism, growing pigs were fed a 0.3% cholesterol-enriched diet for 4 weeks or this diet containing 5% or 10% BCD. Pigs fed a basal diet without added cholesterol or BCD were used as controls. The cholesterol-rich diet induced hypercholesterolemia (1.75 vs. 0.84 g/l plasma) due to increased LDL concentration, delayed the plasma clearance of vitamin A, enhanced liver cholesterol storage, lowered the hepatic activities of LDL-receptors (by 47%) and HMG-CoA reductase (by 62%), stimulated cholesterol 7alpha-hydroxylase (x3), and accelerated the fecal output of neutral sterols (x4). Addition of BCD to the cholesterol-rich diet prevented the elevation of plasma cholesterol due to dietary cholesterol excess. Moreover, BCD produced a dose-dependent effect in reducing liver cholesterol storage, stimulating hepatic cholesterogenesis, increasing the proportion of primary bile acids in bile and in feces, and the fecal loss of neutral sterols and bile acids. Pigs receiving 10% BCD thus differed markedly from controls, especially for HMG-CoA reductase and cholesterol 7alpha-hydroxylase hepatic activities (x5), and fecal output of total bile acids (x3) and hyocholic acid (x20), and their overall cholesterol synthesis was higher (+50%), despite the abundant dietary cholesterol. Owing to the property of BCD to bind cholesterol and bile acids in vitro, these results suggest that this resistant carbohydrate accelerates body cholesterol turnover by reducing cholesterol absorption, increasing cholesterol and bile acid synthesis, and altering the action of the intestinal microflora.

Animals↗

PubMed1996

Phospholipid-rich particles in commercial parenteral fat emulsions. An overview.

In parenteral nutrition, the infusion of a fat EMU supplies both concentrated energy and covers the essential fatty acid requirements, the basic objective being to mimic as well as possible the input of chylomicrons into the blood. This objective is well met by the TAGRP of the EMU, which behave as true chylomicrons. However, commercial EMU also contain an excess of emulsifier in the form of PLRP. The number of these PLRP depends directly on the PL/TAG ratio of the EMU. They differ from the TAGRP by their composition (PL vs TAG and PL), their structure (PL in bilayer versus monolayer), and their granulometry (mean diameter 70-100 nm for PL vs 200-500 nm). The metabolic fate of the PLRP is similar in several ways to that of the TAGRP: exchanges of PL with the PL of the different cellular membranes and of the lipoproteins; captation of free CH from these same structures; and enrichment in apolipoproteins. However, because the TAGRP are the preferred substrates of the lipolytic enzymes, their clearance is much more rapid (half-life < 1 h) than that of the PLRP. As the infusion is continued, the PLRP end up accumulating and being transformed into LP-X (free CH/PL = 1; half-life of several days). As soon as the EMU is infused, the PLRP enter into competition with the TAGRP, in the lipolysis process as well as for sites of binding and for catabolism. The sites for catabolism of the two types of PAR are not the same: adipose tissues and muscles utilize the fatty acids and monoacylglycerols released by the lipolysis of the TAGRP; hepatocytes take up their remnants; the RES and the hepatocytes participate in the catabolism of the PLRP and the LP-X. Thus, prolonged infusion of EMU rich in PLRP leads to a hypercholesterolemia, or at least a dyslipoproteinemia, due to elevated LP-X, associated with a depletion of cells in CH, stimulating thus tissue cholesterogenesis. However, parenteral nutrition has evolved towards the utilization of EMU with a low PL/TAG ratio (availability of 30% formula) and less rapid delivery. For these reasons, the hypercholesterolemias that used to be observed with the 10% EMU have become much less spectacular or have even disappeared. It is interesting to note that patients on prolonged TPN, in particular those with a short small intestine, have weak cholesterolemia, reflecting a lowering of HDL and LDL not masked by elevated LP-X. At present, it seems difficult to produce sufficiently stable parenteral EMU devoid of PLRP. Notwithstanding, all the observations made since the introduction of the EMU in TPN are in favour of the use of PLRP-poor EMU. It is clear that the 10% formulas, and generally those with a PL/TAG ratio of 12/100, are ill-advised, especially in patients with a retarded clearance of circulating lipids.

Cholesterol↗

PubMed1995

Crilvastatin, a new 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor, inhibits cholesterol absorption in genetically hypercholesterolemic rats.

Crilvastatin is a new drug from the pyrrolidone family, which acts as a non-competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase. The long-term effects of oral crilvastatin treatment (200 mg per day per kg body weight for 4 and 10 weeks) were investigated on in vivo cholesterogenesis in male adult normocholesterolemic (SW) and genetically hypercholesterolemic (RICO) rats. In both strains of rats, the treatment had no effect on the plasma cholesterol level, but efficiently inhibited cholesterol synthesis in liver and intestine, as shown by the decreased incorporation of exogenous [14C]acetate into hepatic (3.5-fold in SW, 1.7-fold in RICO rats) and intestinal (2.5-fold in SW, 3.3-fold in RICO rats) sterols. In RICO rats in which the dietary cholesterol absorption coefficient was two-fold lower in treated (38%) than in untreated (78%) rats, this drug reduced intestinal cholesterol absorption. As a result, the total plasma cholesterol input (absorption + synthesis), measured by isotope analysis in RICO rats, was markedly lower in treated (11.3 mg per day) than in untreated animals (28.8 mg per day).

Absorption↗

PubMed1995

Total parenteral nutrition stimulates hepatic cholesterol synthesis in the rat.

Cholesterol synthesis was studied in parenterally fed rats, as compared to orally fed rats with or without saline infusion. Conditions of total parenteral nutrition (TPN) involved the intravenous infusion of a nutritive mixture containing 20% Intralipid as the lipid source (50% of non-protein energy) at the continuous rate of 2 ml per h, for five days. In rats maintained in isotopic steady state by daily injections of [3H]cholesterol, isotope dilution indicated that the endogenous plasma cholesterol input was significantly higher (+15%, P < 0.05) in TPN than in orally fed rats, which suggested a slight stimulation of whole body cholesterogenesis. Cholesterol synthesis was assessed in TPN and orally fed rats by the in vivo incorporation of [1,2-13C]- and [1-14C]acetate into hepatic and intestinal sterols, and by the activity of HMG-CoA reductase in microsomes isolated from liver and small intestine. Both methods demonstrated that TPN markedly stimulated the hepatic cholesterol synthesis, since the radioactivity of liver sterols was 6- to 10-fold higher, and the activity of HMG-CoA reductase 5-fold higher, in TPN than in orally fed rats. Despite the weight reduction of the small intestine, by about 20% after TPN, the incorporation of exogenous [14C]acetate into intestinal sterols was similar in TPN and orally fed rats. As the liver and intestine are the main organs responsible for the appearance of endogenous cholesterol in plasma, it may be concluded that the increased endogenous plasma cholesterol input was mainly due to a strong stimulation of hepatic cholesterol synthesis in TPN rats.

Animals↗

PubMed1995

Effects of hyodeoxycholic acid and alpha-hyocholic acid, two 6 alpha-hydroxylated bile acids, on cholesterol and bile acid metabolism in the hamster.

The effects of hyodeoxycholic (HDCA) and alpha-hyocholic acids (alpha-HCA), on cholesterol, bile acid and lipoprotein metabolism, were studied in hamsters. The animals were fed a low cholesterol control diet supplemented with 0.1% HDCA or alpha-HCA for 3 weeks. In both treated groups, the LDL-cholesterol concentration was significantly lowered and was associated with a global hypocholesterolemic effect. Moreover, hepatic cholesterol ester storage was reduced and HMGCoA reductase activity was respectively enhanced 13.5-times and 7.7-times in HDCA and alpha-HCA groups compared to controls. In contrast, cholesterol 7 alpha-hydroxylase activity and LDL-receptor activity and mass were not modified. In bile, the cholesterol saturation index was increased 5-fold (HDCA group) and 2-fold (alpha-HCA group) as a consequence of an enlarged proportion of biliary cholesterol. The two 6-hydroxylated bile acids induced an enhanced fecal excretion of neutral sterols (HDCA group: 11.6-times, alpha-HCA group: 3.2-times versus controls) which was consistent with a 59% decrease in intestinal cholesterol absorption in the HDCA group. The major effects due to bile acid treatments were a decrease in LDL-cholesterol concentration, a strong stimulation of hepatic cholesterol biosynthesis and an excessive loss of cholesterol in feces. These perturbations might be the result of the enrichment of bile with hydrophilic bile acids, leading to a limited return of endogenous cholesterol from the intestine to the liver.

Animals↗

PubMed1995

Hepatic lipase gene expression is upregulated by a cystine-rich diet in male but not in female rats.

Male and female rats fed a cystine-rich diet (5% L-cystine) became hypercholesterolemic after 2 months, with 2-fold higher cholesterol levels carried mainly by the HDL1 and HDL2 lipoprotein fractions. Post-heparin lipoprotein lipase activity was increased in male rats only (60%, P < 0.01), while hepatic lipase (HL) activity was increased in both males and females (48%, P < 0.001 and 27%, P < 0.01, respectively). In the liver, HL activity and mRNA levels were increased in males (30%, P < 0.01, and 70%, P < 0.001, respectively), but not in females. A higher correlation between HDL1-cholesterol and liver HL activity was found in male rats than in female rats. In the latter, although the cystine diet induced a virtually identical increase in HDL1-cholesterol, HL gene expression was not promoted. It is suggested that HL gene expression may be triggered by the uptake of HDL1-cholesterol in male rats, while oestrogens in female rats would counteract this effect.

Animals↗

PubMed1995

Hepatic apolipoprotein and LDL receptor gene expression in the genetically hypercholesterolemic (RICO) rat.

The present study was designed to examine apolipoprotein and LDL receptor gene expression in genetically hypercholesterolemic RICO rats. In the plasma of RICO rats as compared to SW (control) rats, the hypercholesterolemia (+41%) was associated with a significant increase in plasma apo B (+23%) and apo E (+68%) concentrations. Study of apolipoprotein synthesis in the liver has shown that this increase in plasma apo B and apo E concentrations was not associated with modification in their synthesis and mRNA levels. Study of apo E mRNA level in various tissues has shown only the modification in adrenals in RICO as compared to SW rats (2.7-fold increase). Study of LDL binding, LDL receptor mass and LDL receptor mRNA level in the liver of RICO and SW rats has shown no significant differences between these two strains. EDTA-resistant binding of rat LDL was lower in RICO than in SW rats suggesting that binding sites others than the LDL receptor are present in lesser amount in this hypercholesterolemic strain.

Adrenal Glands↗