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4.P.285 Inhibition of cholesterogenesis decreases hepatic secretion of apolipoprotein B-100 in normolipidaemic subjects
356 4 .P.284
Thursday 9 October 1997: Posters Lipoprotein metabolism The long term effect of captopril on liver and serum lipid composition in rat
E . Tvrzicka t , O . Nov'dkova 2 , F. Novak t , B . Jiraskovat, B . Staiikova2 , F. Novak2 . 1 1st Faculty of Medicine; 2 Faculty of Sciences, Charles University, Prague, Czech Republic Captopril, an angiotensin converting enzyme inhibitor (ACEI) is widely used drug in the treatment of arterial hypertension and cardiac failure . Major effect of ACEIs is blockade of angiotensin II synthesis from angiotensin I, which causes vasodilatation . There has been little evidence that ACEI administration causes a quantitative changes in serum lipids but ACEI were shown to have benefitial effects on levels of antiatherogenic apolipoproteins Apo Al and Apo A2 . There have been reports that long term administration of captopril have no effect on serum lipid levels . The aim of this study was to investigate whether long term administration of captopril influence phospholipid (PL) composition and lipid fatty acyl (FA) pattern of liver tissue and serum in rat . The male Wistar rats (initial weight 510-520 g) were randomized to control group (CON) and captopril group (CAP) receiving 0.44 mg of drug daily . The animals were sacrificed after 53 days . Lipids were separated by thin layer chromatography . FA patterns were determined by gas chromatography . In liver there was no change in concentration of individual PL except of phophatidylinositol decrease in CAP (2 .9 f 0 .08 vs . 2 .7 f 0 .06) . We also observed increased content of palmitic acid (16 :0) and decreased content of n-6 and n-3 polyunsaturated FA (PUFA) in triacylgylcerols (TG) in CAP . There was increase of 16 :0 and n-3 PUFA in phosphatidylcholine (PC) and phosphatidylethynolamine (PE) and decrease of n-6 PUFA in PE and diphosphatidylglycerol in CAP. In serum there was increased content of stearic acid (18 :0) in TG and PC. We observed decrease of palmitoleic (18 :1 n-9) and vaccenic (18 :1 n-7) acids in cholesterol esters in CAP. We conclude that long term administration of captopril results in remodelling of FA profile in individual lipid classes of both liver and serum in rat.
4 .P.285
Inhibition of cholesterogenesis decreases hepatic secretion of apolipoprotein B-100 in normolipidaemic subjects
G .F. Watts, R .P. Naoumovat , J .M. Kelly, F.M . Riches, K.D . Croft, G .R. Thompson' . University Department of Medicine and Western Australia Heart Research Institute, University of Western Australia, Royal Perth Hospital, Perth, Western Australia ; I Lipoprotein Team, MRC Clinical Sciences Centre, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK We examined the effect of Simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl CoenzymeA redutase, on the kinetics of very-low-density lipoprotein apolipoprotein B-100 (VLDL apoB) in 13 normolipidaemic men in a randomized, placebo-controlled, cross-over study. Simvastatin significantly decreased the plasma concentrations of low-density-lipoprotein (LDL) cholesterol by 36%, triglycerides by 26%, mevalonic acid by 34% and lathosterol by 32% . Hepatic secretion rate of VLDL apoB was measured directly using a primed, constant intravenous infusion of [1- 13 C]-leucine with monitoring of isotopic enrichment of apoB by gas chromatography/mass spectrometry ; fractional turnover rate was derived using a monoexponential function . Simvastatin decreased VLDL apoB pool size by 53% and hepatic secretion rate of VLDL apoB by 46%, but did not significantly influence the fractional catabolic rate of VLDL apoB . The change in hepatic VLDL apoB secretion was significantly and independently correlated with changes in plasma mevalonic acid and lathosterol concentrations and lathosterol :cholesterol ratio . The data supports the hypothesis that the rate of de novo cholesterol synthesis directly regulates the hepatic secretion of VLDL apoB in normal subjects .
4 . P 286
Inhibition of microsomal triglyceride transfer protein (MTP) decreases secretion of oleate-induced triglyceride-rich very low density lipoproteins (VLDL) from hepatoma cells
Z . Yao, R. S . McLeod, Y Wang . University of Ottawa Heart Institute, Ottawa, KI Y 4E9, Canada In humans, hepatic VLDL are the main precursor of plasma low density lipoproteins (LDL) and have been recognized as potentially atherogenic lipoproteins . We studied the effect of MTP inhibition on secretion of TG-rich VLDL using rat hepatoma McA-RH7777 cells transfected with recombinant human apoB. In these cells, secretion of B100-VLDL or B48-VLDL could be induced by exogenous oleate, and MTP activity could be reduced by 65-70% using the photoaffinity inhibitor BMS-192951 . Two protocols were used to
determine the effect of MTP inhibition on the assembly of TG and apoBs into VLDL. Cell protein and lipid were labeled with radioactive amino acids and oleate either before or after MTP inhibition, and secretion of labeled apoB and TG on BI00-VLDL or B48-VLDL were monitored after oleate supplement . Under both conditions, MTP inhibition decreased (by 80%) incorporation of both labeled TG and B48 into B48-VLDL but had little effect on B48-HDL secretion . In addition, MTP inhibition decreased incorporation of de novo synthesized TG (by 50%) and B100 (by 90%) into B100-VLDL. MTP inhibition did not appear to affect the synthesis or turnover of TG . These data together indicate that inhibition of MTP activity is a potent means to supress the oleate-induced secretion of hepatic TG-rich VLDL .
4 .P.287
Mode of action of pantethine in increasing HDL-C in hyperlipidemic patients with low HDL-C
J.R . Zhu, Q.Q . Han, B . Chen . Dept. of Int. Med., Zhong Shan Hospital, Shanghai Med. University, Shanghai, China ; Tomikawa M., Daiichi Pharmaceutical Co., Ltd. Tokyo, Japan Pantethine, an intermediate precursor of CoenzymeA has been shown to markedly increase HDL-C together with decrease in serum lipids in hyperlipidemic patients with low HDL-C . A clinical study has been carried out to elucidate it's mechanism of increasing HDL-C in hyperlipidemic patients with low HDL-C (<0.8 m mol/L) or normal HDL-C (0 .8^-L6 m mol/L) . Fourteen male hyperlipidemic patients (Type fib or IV) were treated with pantethine 400 mg tid for 12 weeks after a run-in period of 4 weeks with placebo . The enzyme activities of LPL, HTGL and CETP were determined in plasma pre- and post-heparin injection before and after 12 weeks treatment with pantethine. LPL mass in plasma was also assayed according to the method of Sandwich EIA. Results : Pantethine 400 mg tid increased HDL-C by 44 .9% in hyperlipidemic patients with low HDL-C in comparison with increase in HDL-C by 6% in hyperlipidemic patients with nomal HDL-C. In studying the changes in LPL, HTGL and CETP activities between responders who have shown increase in HDL-C and non-responders groups, it was shown that responders had a significant increase in activity of LPL while no significant changes in activities of HTGL and CETP. Some of responders also showed increase in LPL mass . Conclusion : Pantethine increases HDL-C through enhancement of LPL activity in hyperlipidemic patients with low HDL-C .
4 .R288
The metabolic basis of a new form of recessive hypercholesterolemia : The "FH-like" hypercholesterolemia
G. Zuliani, M. Arca t , G . Bader, A . Pacifico2 , A . Signore3 , F. Campagnat , A. Montalil, M . Chianelli3 , G. RicciI, M . Maioli2 , R . Fellin . 2nd Department of Internal Medicine, University of Ferrara ; tlnstitute of Terapia Medica Sistematica, University of Rome "La Sapienza " ; 2 lnstitute of Clinica Medica, University of Sassari, Italy; 3lnstitute of Clinica Medica II, University of Rome "La Sapienza" We described a pedigree from Sardinia (Italy) with several cases of severe primary hypercholesterolemia and/or premature sudden death (Zuliani et al 1995 Eur J Clin Invest 25 : 322-331) . Familial hypercholesterolemia (FH), familial defective apo B (FDB), and fl-sitosterolemia were excluded by haplotype segregation analysis, and in vitro studies. Bimodal distribution of plasma cholesterol levels, absence of vertical trasmission, reduction of reproductive fitness in affected individuals, and consanguinity, were consistent with an autosomal recessive trait . We identified a second Sardinian kindred with similar characteristics ; the 2 probands have severe hypercholesterolemia, while parents and grandparents are normal . FH, FDB, i-sitosterolemia were ruled out by in vitro studies . We investigated the metabolic basis of this lipid disorder by studying the in vivo LDL metabolism in 3 probands from these 2 families. LDL turnover study was conducted as previously described (Arca et al 1994 JAMA 271 : 453-549) by injecting autologus 12 1-LDL ; 5 normal controls were included. A severe reduction of LDLApo B fractional catabolic rate was found in the 3 probands (0 .18, 0 .20 and 0 .22 pools/day respectively VS 0 .33 f 0 .01 pools/day in controls) . We then studied the in vivo organspecific LDL uptake in the 3 probands, 5 controls, and 1 FH homozygote by injecting 99 Tc-labeled LDL, and measuring the LDL uptake by y-camera ; the 3 probands showed a marked, selective reduction of LDL uptake by the liver, comparable with that observed in the FE homozygous . Conclusions are : 1) In these two Sardinian kindreds, recessive hypercholesterolemia is due to a marked reduction of the in vivo catabolism of LDL, caused by a selective reduction of LDL uptake by the liver ; 2) We advance that in this new lipid
11th International Symposium on Atherosclerosis, Paris, October 1997
Thursday 9 October 1997: Posters Lipoprotein metabolism The long term effect of captopril on liver and serum lipid composition in rat
E . Tvrzicka t , O . Nov'dkova 2 , F. Novak t , B . Jiraskovat, B . Staiikova2 , F. Novak2 . 1 1st Faculty of Medicine; 2 Faculty of Sciences, Charles University, Prague, Czech Republic Captopril, an angiotensin converting enzyme inhibitor (ACEI) is widely used drug in the treatment of arterial hypertension and cardiac failure . Major effect of ACEIs is blockade of angiotensin II synthesis from angiotensin I, which causes vasodilatation . There has been little evidence that ACEI administration causes a quantitative changes in serum lipids but ACEI were shown to have benefitial effects on levels of antiatherogenic apolipoproteins Apo Al and Apo A2 . There have been reports that long term administration of captopril have no effect on serum lipid levels . The aim of this study was to investigate whether long term administration of captopril influence phospholipid (PL) composition and lipid fatty acyl (FA) pattern of liver tissue and serum in rat . The male Wistar rats (initial weight 510-520 g) were randomized to control group (CON) and captopril group (CAP) receiving 0.44 mg of drug daily . The animals were sacrificed after 53 days . Lipids were separated by thin layer chromatography . FA patterns were determined by gas chromatography . In liver there was no change in concentration of individual PL except of phophatidylinositol decrease in CAP (2 .9 f 0 .08 vs . 2 .7 f 0 .06) . We also observed increased content of palmitic acid (16 :0) and decreased content of n-6 and n-3 polyunsaturated FA (PUFA) in triacylgylcerols (TG) in CAP . There was increase of 16 :0 and n-3 PUFA in phosphatidylcholine (PC) and phosphatidylethynolamine (PE) and decrease of n-6 PUFA in PE and diphosphatidylglycerol in CAP. In serum there was increased content of stearic acid (18 :0) in TG and PC. We observed decrease of palmitoleic (18 :1 n-9) and vaccenic (18 :1 n-7) acids in cholesterol esters in CAP. We conclude that long term administration of captopril results in remodelling of FA profile in individual lipid classes of both liver and serum in rat.
4 .P.285
Inhibition of cholesterogenesis decreases hepatic secretion of apolipoprotein B-100 in normolipidaemic subjects
G .F. Watts, R .P. Naoumovat , J .M. Kelly, F.M . Riches, K.D . Croft, G .R. Thompson' . University Department of Medicine and Western Australia Heart Research Institute, University of Western Australia, Royal Perth Hospital, Perth, Western Australia ; I Lipoprotein Team, MRC Clinical Sciences Centre, Royal Postgraduate Medical School, Hammersmith Hospital, London, UK We examined the effect of Simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl CoenzymeA redutase, on the kinetics of very-low-density lipoprotein apolipoprotein B-100 (VLDL apoB) in 13 normolipidaemic men in a randomized, placebo-controlled, cross-over study. Simvastatin significantly decreased the plasma concentrations of low-density-lipoprotein (LDL) cholesterol by 36%, triglycerides by 26%, mevalonic acid by 34% and lathosterol by 32% . Hepatic secretion rate of VLDL apoB was measured directly using a primed, constant intravenous infusion of [1- 13 C]-leucine with monitoring of isotopic enrichment of apoB by gas chromatography/mass spectrometry ; fractional turnover rate was derived using a monoexponential function . Simvastatin decreased VLDL apoB pool size by 53% and hepatic secretion rate of VLDL apoB by 46%, but did not significantly influence the fractional catabolic rate of VLDL apoB . The change in hepatic VLDL apoB secretion was significantly and independently correlated with changes in plasma mevalonic acid and lathosterol concentrations and lathosterol :cholesterol ratio . The data supports the hypothesis that the rate of de novo cholesterol synthesis directly regulates the hepatic secretion of VLDL apoB in normal subjects .
4 . P 286
Inhibition of microsomal triglyceride transfer protein (MTP) decreases secretion of oleate-induced triglyceride-rich very low density lipoproteins (VLDL) from hepatoma cells
Z . Yao, R. S . McLeod, Y Wang . University of Ottawa Heart Institute, Ottawa, KI Y 4E9, Canada In humans, hepatic VLDL are the main precursor of plasma low density lipoproteins (LDL) and have been recognized as potentially atherogenic lipoproteins . We studied the effect of MTP inhibition on secretion of TG-rich VLDL using rat hepatoma McA-RH7777 cells transfected with recombinant human apoB. In these cells, secretion of B100-VLDL or B48-VLDL could be induced by exogenous oleate, and MTP activity could be reduced by 65-70% using the photoaffinity inhibitor BMS-192951 . Two protocols were used to
determine the effect of MTP inhibition on the assembly of TG and apoBs into VLDL. Cell protein and lipid were labeled with radioactive amino acids and oleate either before or after MTP inhibition, and secretion of labeled apoB and TG on BI00-VLDL or B48-VLDL were monitored after oleate supplement . Under both conditions, MTP inhibition decreased (by 80%) incorporation of both labeled TG and B48 into B48-VLDL but had little effect on B48-HDL secretion . In addition, MTP inhibition decreased incorporation of de novo synthesized TG (by 50%) and B100 (by 90%) into B100-VLDL. MTP inhibition did not appear to affect the synthesis or turnover of TG . These data together indicate that inhibition of MTP activity is a potent means to supress the oleate-induced secretion of hepatic TG-rich VLDL .
4 .P.287
Mode of action of pantethine in increasing HDL-C in hyperlipidemic patients with low HDL-C
J.R . Zhu, Q.Q . Han, B . Chen . Dept. of Int. Med., Zhong Shan Hospital, Shanghai Med. University, Shanghai, China ; Tomikawa M., Daiichi Pharmaceutical Co., Ltd. Tokyo, Japan Pantethine, an intermediate precursor of CoenzymeA has been shown to markedly increase HDL-C together with decrease in serum lipids in hyperlipidemic patients with low HDL-C . A clinical study has been carried out to elucidate it's mechanism of increasing HDL-C in hyperlipidemic patients with low HDL-C (<0.8 m mol/L) or normal HDL-C (0 .8^-L6 m mol/L) . Fourteen male hyperlipidemic patients (Type fib or IV) were treated with pantethine 400 mg tid for 12 weeks after a run-in period of 4 weeks with placebo . The enzyme activities of LPL, HTGL and CETP were determined in plasma pre- and post-heparin injection before and after 12 weeks treatment with pantethine. LPL mass in plasma was also assayed according to the method of Sandwich EIA. Results : Pantethine 400 mg tid increased HDL-C by 44 .9% in hyperlipidemic patients with low HDL-C in comparison with increase in HDL-C by 6% in hyperlipidemic patients with nomal HDL-C. In studying the changes in LPL, HTGL and CETP activities between responders who have shown increase in HDL-C and non-responders groups, it was shown that responders had a significant increase in activity of LPL while no significant changes in activities of HTGL and CETP. Some of responders also showed increase in LPL mass . Conclusion : Pantethine increases HDL-C through enhancement of LPL activity in hyperlipidemic patients with low HDL-C .
4 .R288
The metabolic basis of a new form of recessive hypercholesterolemia : The "FH-like" hypercholesterolemia
G. Zuliani, M. Arca t , G . Bader, A . Pacifico2 , A . Signore3 , F. Campagnat , A. Montalil, M . Chianelli3 , G. RicciI, M . Maioli2 , R . Fellin . 2nd Department of Internal Medicine, University of Ferrara ; tlnstitute of Terapia Medica Sistematica, University of Rome "La Sapienza " ; 2 lnstitute of Clinica Medica, University of Sassari, Italy; 3lnstitute of Clinica Medica II, University of Rome "La Sapienza" We described a pedigree from Sardinia (Italy) with several cases of severe primary hypercholesterolemia and/or premature sudden death (Zuliani et al 1995 Eur J Clin Invest 25 : 322-331) . Familial hypercholesterolemia (FH), familial defective apo B (FDB), and fl-sitosterolemia were excluded by haplotype segregation analysis, and in vitro studies. Bimodal distribution of plasma cholesterol levels, absence of vertical trasmission, reduction of reproductive fitness in affected individuals, and consanguinity, were consistent with an autosomal recessive trait . We identified a second Sardinian kindred with similar characteristics ; the 2 probands have severe hypercholesterolemia, while parents and grandparents are normal . FH, FDB, i-sitosterolemia were ruled out by in vitro studies . We investigated the metabolic basis of this lipid disorder by studying the in vivo LDL metabolism in 3 probands from these 2 families. LDL turnover study was conducted as previously described (Arca et al 1994 JAMA 271 : 453-549) by injecting autologus 12 1-LDL ; 5 normal controls were included. A severe reduction of LDLApo B fractional catabolic rate was found in the 3 probands (0 .18, 0 .20 and 0 .22 pools/day respectively VS 0 .33 f 0 .01 pools/day in controls) . We then studied the in vivo organspecific LDL uptake in the 3 probands, 5 controls, and 1 FH homozygote by injecting 99 Tc-labeled LDL, and measuring the LDL uptake by y-camera ; the 3 probands showed a marked, selective reduction of LDL uptake by the liver, comparable with that observed in the FE homozygous . Conclusions are : 1) In these two Sardinian kindreds, recessive hypercholesterolemia is due to a marked reduction of the in vivo catabolism of LDL, caused by a selective reduction of LDL uptake by the liver ; 2) We advance that in this new lipid
11th International Symposium on Atherosclerosis, Paris, October 1997