Biomedical subjects

F Milliat

Publications and source records attributed to F Milliat.

12 recordsLinked to original sources

PubMed2005

Inhibition of Rho kinase modulates radiation induced fibrogenic phenotype in intestinal smooth muscle cells through alteration of the cytoskeleton and connective tissue growth factor expression.

BACKGROUND: Late radiation enteritis in humans is associated with accumulation of extracellular matrix and increased connective tissue growth factor (CTGF) expression that may involve intestinal muscular layers. AIMS: We investigated the molecular pathways involved in maintenance of radiation induced fibrosis by gene profiling and postulated that alteration of the Rho pathway could be associated with radiation induced fibrogenic signals and CTGF sustained expression. PATIENTS AND METHODS: Ileal biopsies from individuals with and without radiation enteritis were analysed by cDNA array, and primary cultures of intestinal smooth muscle cells were established. Then, the effect of pharmacological inhibition of p160 Rho kinase, using Y-27632, was studied by real time reverse transcription-polymerase chain reaction, western blot, and electrophoretic mobility shift assay. RESULTS: Molecular profile analysis of late radiation enteritis showed alterations in expression of genes coding for the Rho proteins. To investigate further the involvement of the Rho pathway in intestinal radiation induced fibrosis, primary intestinal smooth muscle cells were isolated from radiation enteritis. They retained their fibrogenic differentiation in vitro, exhibited a typical cytoskeletal network, a high constitutive CTGF level, increased collagen secretory capacity, and altered expression of genes coding for the Rho family. Rho kinase blockade induced a simultaneous decrease in the number of actin stress fibres, alpha smooth muscle actin, and heat shock protein 27 levels. It also decreased CTGF levels, probably through nuclear factor kappaB inhibition, and caused decreased expression of the type I collagen gene. CONCLUSION: This study is the first showing involvement of the Rho/Rho kinase pathway in radiation fibrosis and intestinal smooth muscle cell fibrogenic differentiation. It suggests that specific inhibition of Rho kinase may be a promising approach for the development of antifibrotic therapies.

Actins↗

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↗

PubMed2003

'In-field' and 'out-of-field' functional impairment during subacute and chronic phases of experimental radiation enteropathy in the rat.

PURPOSE: To investigate subacute and chronic functional consequences of localized irradiation of rat small intestine on exposed and shielded segments (proximal and distal). MATERIALS AND METHODS: The surgical model of a scrotal hernia was used. The ileal loop was exposed to single doses of 18, 21 or 29.6 Gy X-irradiation. Epithelial structure and transport capacity were followed 2 and 26 weeks post-exposure. RESULTS: Irradiated segments showed mucosal ulceration followed by transmural fibrosis. Transport capacity was impaired from 2 to 26 weeks. Subacute functional impairment was noticed in the proximal segment, without either morphological alteration or neutrophil influx. At 26 weeks, both proximal and distal segments showed impaired epithelial transport capacity, with neutrophil influx in the submucosa in cases of 21-Gy exposure and in the submucosa and muscularis propria after 29.6 Gy. CONCLUSIONS: Radiation enteritis was characterized by functional impairment, within as well as outside, the irradiation field. During the subacute phase, the irradiated segment may be a source of mediators which might influence intestinal function outside the site of injury via the blood stream and/or enteric nervous system. The development of an intestinal occlusion syndrome during the chronic phase might be responsible for intestinal dysfunction but it does not rule out a possible inflammatory process developing in the shielded parts of the small intestine.

Animals↗

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

Plasma lipoprotein distribution in the turkey (Meleagris gallopavo).

The plasma lipoprotein profile has been determined in fasted 7-week-old male turkeys. Lipoprotein classes were subfractionated by density gradient ultracentrifugation. According to phospholipid concentration over the density gradient, an initial peak was visible in the usual LDL density range, whereas two peaks were detected in that of HDL. As density increased, the lipid composition of particles showed an increase in cholesteryl esters and decrease in triglycerides. VLDL were recovered in the first fraction (d<1.013) on the top of the gradient and IDL in fractions 2-5 (d=1.013-1.028 g/ml). The LDL and HDL populations in the density range 1.028-1.090 (fractions 6-12) differ from that found in the other bird species analyzed under the same experimental conditions. LDL predominated in fractions 6-8 with mostly beta-motility and apoB100 as the major protein component. HDL predominated in fractions 10-12 (d=1.055-1.090 g/ml) and corresponded to the first HDL peak (HDL-(A)), with mostly alpha-mobility and apoA-I as the major protein component. Both LDL- and HDL-like particle populations were present in fractions 6-12, making the separation between the two classes of lipoproteins difficult. The second peak in the HDL density range (HDL-(B), d=1.076-1.146 g/ml) contained only HDL-type particles above d=1.090 g/ml. This points out the specificity of the lipoprotein distribution in the turkey that is unique among animals. The density limit at d=1.048 g/ml is a good compromise for the separation of LDL from HDL; however, the presence of HDL-like particles in the LDL density range, and the existence of two, and even three HDL subclasses should be taken into account in the design of further metabolic studies.

Animals↗

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, 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

Regional cholesterol synthesis in the intestinal mucosa of the genetically hypercholesterolaemic RICO rat: kinetic study following whole-body gamma-irradiation.

PURPOSE: To investigate regional cholesterol synthesis and kinetics following whole-body gamma-irradiation in the genetically hypercholesterolaemic RICO rat. MATERIALS AND METHODS: Male RICO rats were fed a semi-purified diet for 1 month. At 10 weeks old they were exposed to gamma-irradiation (4 Gy, 1.5 Gy/min) together with controls. At intervals from 1-8 days after irradiation an intraperitoneal administration of [1-14C] acetate was given in order to estimate cholesterogenesis in mucosal cells located at different sites in the small intestine. The protein and DNA contents of the different enterocytes isolated along the crypt/villus axis in four equal parts of the intestine were also determined. RESULTS: A marked decrease of the mean quantities of cholesterol, DNA or protein in mucosa was seen 1 and 2 days after irradiation, showing the loss of 30-40% of the intestinal epithelium. An overshoot of the cell amount was observed after 4 days with a return to basal values by 8 days after irradiation. The kinetic and topological evolution of cholesterol radioactivity, which reflects in situ cholesterol synthesis, showed a typical gradient in controls and at 8 days after irradiation. Cholesterogenesis decreased from the first to the third quarter of the small intestine (duodenum to proximal ileum), and then increased in the fourth quarter (distal ileum). In all segments of the small intestine, cholesterogenesis decreased from crypt cells to villus tip. At days 1 and 2 the gradient of cholesterogenesis on the villus was abolished. A slow recovery was seen from day 4 with a strong overshoot of cholesterol synthesis in crypt cells in every part of the small intestine. CONCLUSIONS: The RICO rat is a useful model for studying the effect of irradiation on regional cholesterogenesis in intestinal mucosa. Cholesterol synthesis in crypt cells was lowered 1 and 2 days after irradiation, over-expressed after 4 days and subsequently returned to its normal level.

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↗

PubMed1998

Effects of insulin deficiency on lipoproteins and their hepatic receptors in Rico rats.

The present study was designed to examine the effect of streptozotocin (STZ)-induced diabetes on the plasma lipoprotein profile and hepatic expression of the LDL receptor and HDL binding protein (HB2) in hypercholesterolemic Rico rats. The plasma level of HDL1 (density range 1.040-1.063), which is particularly high in this rat strain, decreased (-25%) 28 d after STZ administration (50 mg/kg). In contrast, the treatment increased (+54%) the plasma concentration of HDL2 (density range 1.063-1.210). These variations in the lipoprotein concentrations were associated with inverse changes in the hepatic protein levels of the LDL receptor (+118%) and HB2 (-46%). These results suggest that the hepatic expression of HB2, a putative HDL receptor, can influence the plasma level of apo Al-rich HDL as has already been shown for the LDL receptor for apo B/E containing lipoproteins.

Animals↗

PubMedDate not supplied

Intralipid 10%: physicochemical characterization.

OBJECTIVES: Parenteral fat emulsions contain two populations of particles: artificial chylomicrons rich in triacylglycerols (TAG), and liposomes (bilayer of phospholipids [PL] enveloping an aqueous phase). Centrifugation permits isolating the liposomes in the infranatant called mesophase. The aim of the present work was to better characterize this mesophase chemically and to view the particles it contains by electron microscopy. METHODS: Electron microscopy (Philips 410) was performed after cryofracture on native 10% Intralipid, mesophase (centrifugation for 1 h at 27 000 g), and a liposome-enriched fraction (ring of density 1.010-1.030 g/l obtained after centrifuging mesophase in a KBr density gradient at 100 000 g for 24 h). The TAG and protein content of the mesophase was analyzed and the proteins partially characterized by immunodetection (Western-blot). RESULTS: This electron microscope study of 10% Intralipid gives evidence for the coexistence of artificial chylomicrons (mean diameter, 260 nm) and liposomes (43 nm), the latter being smaller than expected and containing 8% w/w TAG after purification. The solubilization of TAG in PL bilayers (reported to be < or = 3.1% w/w) might have been increased in parenteral emulsions by the manufacturing process or/and the high TAG/PL ratio. Minute amounts of proteins have also been detected and partially characterized using a specific antibody raised against the human 7 kDa Anionic Polypeptide Factor (APF), known to strongly interact with PL in bile. CONCLUSIONS: This work has shown that the size (mean diameter, 43 nm) of the liposomes present in 10% Intralipid is smaller than that usually assumed. Traces of hydrophobic proteins in the emulsion may account for certain allergic reactions sometimes observed in infused patients.

Blotting, Western↗