1.P.77 Correction of hypoalphalipoproteinemia in LDL receptor deficiency by lecithin: cholesterol acyltransferase (LCAT)

Monday 6 October 1997: Posters Transgenic animal models

32

I1 .P 73

Weight reduction improves cholesterol absorption and svnthesis in relation to imuroved ah~cose metabolism of obese GIDDM patients -

P. Simonen’, H. Gylling’ , A.N. Howard2, Medicine, University of Helsinki, Finland;

T.A. Miettinen’. ‘Department of 2 University of Cambridge, UK

Weight reduction is recommended to obese NIDDM subjects, but its long term effects on cholesterol (C) metabolism are poorly known. We studied the effects of a very low calorie diet (VLCD) followed by dietary counselling for 2 years in 10 randomly selected and in 6 diet control only (R) overweight diabetics (BMI > 30 kg/m2) without insulin therapy on C absorption efficiency (CAE), serum cholestanol and plant sterol (PS) proportions to C, and C synthesis with measuring serum precursor sterol proportions and fecal neutral sterols (NS) and bile acids (BA), and LDL and HDL kinetics. At baseline, CAE and fecal NS or BA were correlated with variables of glucose metabolism; serum insulin (IRI) vs NS r = 0.738, blood glucose (BG) vs NS+BA r = 0.659, CAE vs steroid hormone binding globulin (SHBG) r = 0.575. After 2 years, in combined VLCD and R, serum C was unchanged (increased in VLCD; P < O.OS), HDL-C was increased (P < 0.05) and triglycerides decreased (P < O.OS), body weight (BW) was decreased by 6 kg (P < 0.01) and BG by - 1.2 mmol/l (P < O.Ol), SHBG increased and IRI decreased (ns), CAE increased by 8% (P < O.Ol), NS decreased by 16% (P < O.Ol), NS+BA tended to decrease (8%) cholestanol, PS tended to increase (elevated by 20-39% in VLCD; P < 0.05) and those of precursor sterols decreased (ns). FCR for LDL apoB and HDL apoA1 decreased by about 40% (P < 0.05 for both). At 2 years, SHBG was related to cholestanol, PS and CAE (r = 0.404 to 0.778) and BG to cholestanol (r = 0.665). The change in BW was related to those of cholestanol, PS and CAE (r = -0.343 to -0.641) and the change in CAE to those of BG, SHBG and IRI (r = 0.291 to 0.543). In conclusion, variables reflecting insulin resistance are related to variables reflecting cholesterol absorption and synthesis in NIDDM. Weight reduction improves not only insulin resistance but also cholesterol absorption and synthesis.

rl1 P 74

High sensitivity of a new cholesterol 7a hydroxylase assay in hamster liver, with 2.hydroxypropyl-B-Cyclodextrin (HPBCD) as a vehicle for solubiig radiolabeled cholesterol

M. Souidi, M. Parquet, C. Lutton. Laboratoire (INRA), Universite’ Paris&d, Orsay, France

Physiologic

de la Nutrition

2-hydroxypropyl+cyclodextrin (HPBCD), a 7-pyranose-unit molecule very soluble in water, possesses an hydrophobic core that accommodates cholesterol or other hydrophobic molecules. Its use for cholesterol 7a-hydroxylase (key-enzyme for bile acid synthesis) assay caused more than a ten-fold increase in apparent specific activity in hepatic microsomes of Hamster. With short incubation time (6 min), microsomes from hamster liver (5 and 9 weeks old) fed with a ground diet yielded rates of 7o-hydroxycholesterol formation of 115 & 10 and 150 f 16 pmohmin per mg protein, respectively, whereas microsomes from hamsters fed with a lithogenic sucrose-rich diet (5 weeks old) yielded rates of 7o-hydroxycholesterol of 77 f 7 pmol/min per mg protein, significantly lower (-33%) than that of corresponding control hamsters.

TRANSGENIC ANIMAL MODELS 1 .P

75

I A. Boullier’, 3254nstitut

Paraoxonase activity in human apolipoprotein A-I transgenic rabbits P. Duriez’ , J.C. Fruchart’, N. Duverges, Pasteur-Lille; 2Rh6ne Poulenc Rarer-Wry

G.R. Castro’. ‘Inserm sur Seine, France

Paraoxonase (PON) is a high density lipoprotein associate enzyme able to hydrolyse lipid peroxides. Thus it might protect LDL from oxidation, a potentially important antiatherogenic role. Recently, it has been shown that cholesterol-fed human apolipoprotein A-I transgenic rabbits (Tg A-I) are protected from the development of aortic fatty-streak lesions. The aim of our study was to determine if there is a relationship between PON activity and the reduction of lesions development observed in the Tg A-I rabbits and to determine the influence of the cholesterol rich diet on PON activity. 46 Tg A-I and 50 control rabbits were maintained for 14 weeks on an atherogenic diet containing 0.5% cholesterol. 11th International

Symposium

PON activity (U/ml) was significantly higher in Tg A-I than in controls (4006 i 717 vs 3078 f 623 nmol/min/ml; p < 0.0001) at week 0. Moreover, in the control group, mean values of PON activity in female were significantly higher than in male rabbits (3249 f 710 vs 2894 f 460: p < 0.05). This difference was not significant in the Tg group. During the cholesterol rich diet, PON activity progressively decreased in both groups: 47 and 50% of the initial values of controls and Tg A-I respectively at week 14, in spite of the mean aortic lesion area measured was significantly less in TgA-I (n = 12) than in controls (n = 18). The rest of animals were kept on the cholesterol diet or changed to a regular diet for 16 additional weeks, PGN activity decreased 20% or increased 20% over the 14 week value for both groups of animals on cholesterol rich or regular diet respectively. In conclusion our results indicate that: 1) the protection from atherosclerosis observed in TgA-I rabbits is not related to PON activity, 2) PON activity is highly modified by diet.

IIII76 1 .P

Evolution of immunological markers of LDL oxidation in cholesterol-fed human apolipoprotein AI transgenic rabbits

A. Boullier’, N. Hennuyer’, N. Duverge’?, F. Emmanue12, A. Tailleux’ , C. Fievet’ , P. Denefle*, J.C. Fruchart’ , G.R. Castro’, P. Dmiez’. ‘INSERM (1325, Institut Pasteur, Lille; 2RMne-Poulenc Rarer Gencell Division, Wry-Alfortville, France In Human apolipoprotein AI transgenic rabbits (H apoA1 Tg), atheroprotection is mediated by an increase in reverse cholesterol transport (Duverger N, Circulation, 1996, 94: 713: 717) but HDL have been reported to reduce LDL oxidation because of their paraoxonase content. In this study, we have investigated if there are relationships between LDL oxidation markers (antioxidized and anti malondialdehyde LDL autoantibodies (ox-LDL-Ab and MDA-LDL-Ab, respectively), LDL-immune complexes (LDL-IC) and anticardiolipin autoantibodies (AC-Ab)) and atherosclerosis development in 13 H apoA1 Tg rabbits and 18 non transgenic littermates (C) submitted to a cholesterol rich diet (0.4%) for 14 weeks. Mean values of total cholesterol, non HDL cholesterol, HDL-cholesterol and triglycerides increased significantly (p < 0.05) in the H apoA1 Tg group. The aortic atheroma area was reduced in the H apoA1 Tg group (25 -+ 10% vs 32 f 8%. p < 0.05). During cholesterol feeding, ox-LDL-Ab, LDL-IC and AC-Ab increased uromessivelv in both group; At week 10, AC-Ab were higher in the H apoAI Tggroup