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PLTP activity and cholesteryl ester transfer are elevated and closely linked to insulin resistance in hypertriglyceridemia: reversal upon bezafibrate therapy
Posters 20. Triglycerides ~
POSTPRANDIAL HYPERTRIGLYCERIDEMIA IN FIRST DEGREE RELATIVES OF PATIENTS WITH PREMATURE ATHEROSCLEROSIS IS LIMITED TO INSULIN RESISTANT SUBJECTS
C.A. Geluk, C.J.M. Halkes, D.W. Erkelens, M. Castro Cabezas. Dpt. Vasc. Med. UMCU, PO Box 85500, G02.402, 3508 GA Utrecht, the Netherlands Background: Postprandial hypertriglyceridemia in normolipidemic patients with coronary artery disease (CAD) is associated to insulin resistance and may be genetically determined. We studied postprandial lipemia and insulin sensitivity in patients with premature CAD and their first degree relatives. Methods: Twenty-seven normolipidemic patients with premature CAD, 56 first degree relatives without CAD and 102 unrelated healthy volunteers measured capillary triglycerides (TG) on 6 fixed time points on 3 different days. Total area under the mean capillary TG curve (TGc-AUC) represents diurnal triglyceridemia and correlates with results from standardized oral fat loads. Subjects were subdivided based on insulin sensitivity using guidelines from the European Group for the Study of Insulin Resistance. Results: Fasting plasma cholesterol and TG in CAD patients (5.54-0.7 and 1.644-0.99 mmol/L, respectively) and relatives (5.44-1.0 and 1.22+0.53 mmol/L) were significantly higher compared to healthy controls (4.6+1.0 and 0.934-0.48 mmoFL). TGc-AUC was highest in CAD patients (30.74-13.6 mmol.h/L), intermediate in relatives (24.44-9.4 mmol.h/L) and lowest in controls (20.34-7.3 mmol.h/L). When CAD patients were subdivided into insulin resistant (IR; n = 6) and insulin sensitive (n = 21) subjects, both had higher TGc-AUC (39.44-18.1 and 28.24-11.4 mmol.h/L, respectively) than healthy controls (p < 0.01). TGc-AUC in IR relatives (n = 9; 31.14-12.9 mmol.h/L) was similar to CAD patients. Insulin sensitive relatives (n = 47; 23.14-8.1 mmol.h/L) and controls had similar diurnal triglyceridemia. Conclusion: Postprandial hypertriglyceridemia is present in both insulin resistant and sensitive normolipidemic CAD patients. Postprandial hypertriglyceridemia in first degree relatives of these patients is limited to insulin resistant subjects. ~-~
CONCURRENTLY INCREASED CHOLESTEROL SYNTHESIS AND DECREASED CHOLESTEROL ABSORPTION IN HYPERTRIGLYCERIDEMIA. EFFECTS OF BEZAFIBRATE THERAPY
I.J.A.M. Jonkers 1, H.M.G. Princen2, R. Buytenhek2, EH. O'Neill 3, G.R. Thompson3, A.H.M. Smelt 1. 1Leiden University Medical Center,
Leiden," 2TNO-PG, Gaubius Laboratory, Leiden, The Netherlands; 3Imperial School of Medicine, Hammersmith Hospital, London, UK Hypertriglyceridemia (HTG) is a disorder in the VLDL-metabolism. To date it is unclear whether disturbed cholesterol synthesis and/or cholesterol absorption contribute to the expression of HTG. In addition, it is not fully understood whether the lipid-lowering effects of bezafibrate therapy are achieved through effects on cholesterol synthesis and/or cholesterol absorption. Therefore, we compared cholesterol synthesis and cholesterol absorption between 9 patients with endogenous hypertriglyceridemia and 9 age-, sex and body mass index matched normolipidemic controls. Secondary, we investigated the effects of bezafibrate (400 mg/day, 7 weeks) on these parameters in these 9 HTG patients. Cholesterol synthesis was determined by measurement of both fasting plasma levels of mevalonic acid (MVA) and the serum ratio of lathosterol to cholesterol. Cholesterol absorption was assayed using serum ratios of [3-sitosterol, campesterol and cholestanol to cholesterol. Patients with HTG had 14-fold higher serum TG than controls, whereas body mass index was similar in both groups (27.6-4-2.7 vs. 27.8+1.9 kg/m 2 for controls and HTG patients respectively). Lathosterol to cholesterol ratio was higher in HTG patients than in controls (2.80-4-1.14 vs. 1.314-0.55, p < 0.01), whereas MVA levels tended to be higher in HTG patients than in controls as well (+17%, p = 0.09). MVA levels correlated with the ratio of lathosterol to cholesterol (r = 0.802, p < 0.01). Ratios of both I$-sitosterol and cholestanol to cholesterol were lower in HTG patients than in controls (-38%, p = 0.019 and -75%, p = 0.03 respectively), whereas no significant differences were observed in the ratio of campesterol to cholesterol between HTG patients and controls. Bezafibrate therapy significantly reduced serum TG and cholesterol (-69 and -27% respectively, both p < 0.04). Cholesterol synthesis was inhibited by bezafibrate, as represented by reductions in lathosterol to cholesterol ratio (-25%, p = 0.03) and a tendency towards reduction in plasma MVA levels (-21%, p = 0.09). Cholesterol absorption was not affected by bezafibrate therapy. Conclusion: These data demonstrate the presence of increased cholesterol synthesis as well as decreased cholesterol absorption in hypertriglyc-
139
eridemia. In addition, the lipid-lowering effects of bezafibrate therapy can at least partly be explained by a reduction in cholesterol synthesis.
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PLTP ACTIVITY AND CHOLESTERYL ESTER TRANSFER ARE ELEVATED AND CLOSELY LINKED TO INSULIN RESISTANCE IN HYPERTRIGLYCERIDEMIA: REVERSAL UPON BEZAFIBRATE THERAPY
I.J.A.M. Jonkers 1. A.H.M. Smelt 1, L.M. Scheek2, T. van Gent2, EH.A.E de Man 1, A. van der Laarse 1, A. van Tol2. 1Leiden University Medical Center,
Albinasdreef 2, 2300 RC, Leiden; 2Cardiovascular Research Institute (COEUR), Erasmus University, Rotterdam, The Netherlands Hypertriglyceridemia (HTG) is associated with insulin resistance, increased cholesteryl ester transfer (CET) and low HDL-cholesterol (HDL-C) levels. The recently identified phospholipid transfer protein (PLTP) may be involved in these relationships. Therefore the associations between CET, lipoprotein profile, insulin resistance and transfer protein activities (CETP and PLTP) were investigated in 18 endogenous HTG patients and 20 normolipidemic controls. In addition, the effects of 6 week-treatment with bezafibrate were studied on these parameters in HTG patients in a double-blind, placebocontrolled, cross-over trial. HTG patients had 13.2 fold higher serum triglycerides, 0.5 fold lower HDL-C, 5.7 fold higher insulin resistance %, 1.9 fold higher FFA levels and 2.4 fold higher CET in conjunction with higher CETP and PLTP activity levels compared to controls (+20% and +48% respectively, all p < 0.01). Bezafibrate therapy reduced serum triglycerides, CET, insulin resistance %, FFA levels, CETP-, and PLTP activity (-69%, -37%, -53%, -48%, -12%, and -8%, respectively) and increased HDL-C (+27%, all p < 0.05). After adjustment for the disorder HTG, regression analysis showed no relationship between PLTP activity and both CET and HDL-C, whereas insulin resistance did contribute to PLTP activity levels (p < 0.01). Similarly, CET was predicted by serum TG, CETP activity, insulin and FFA levels (all p < 0.04). Bezafibrate-induced reduction in CET and increase in HDL-C levels correlated with the reduction in CETP activity and FFA levels (all p < 0.02), but not with the reduction in PLTP activity (both p > 0.27). Bezafibrateinduced change in PLTP activity tended to correlated with the reduction in FFA levels (r = 0.455, p = 0.058). Conclusion: We propose that PLTP activity is increased in HTG as a result of the presence of insulin resistance. Bezafibrate-induced amelioration of the insulin resistance is associated with a reduction of both CET and PLTP towards normal levels.
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SUSCEPTIBILITY OF VLDL SUBFRACTIONS TO OXIDATION IN PATIENTS WITH TYPE 2 DIABETES MELLITUS AND THEIR EFFECTS ON VASCULAR CELL ADHESION MOLECULE EXPRESSOIN IN ENDOTHELIAL CELLS
K.C.B. Tan, S.W.M. Shiu. Department of Medicine, University of Hong
Kong, Hong Kong Hypertriglyceridaemia is an independent cardiovascular risk factor in patients with type 2 diabetes mellitus and is mainly due to an increased in VLDL. The aims of this study were to determine whether VLDL subfractions from patients with type 2 diabetes mellitus were more susceptible to oxidation and to investigate the effects of VLDL subfractions on cytokineinduced vascular cell adhesion molecules (VCAM) expression in human endothelial cells. VLDL1 and VLDL2 were isolated by density gradient ultracentrifugation. The susceptibility of individual VLDL subfraction to oxidation was determined by measuring the kinetics of conjugated diene formation during copper-mediated oxidation. To investigate VCAM expression, human aortic endothelial cells were pre-incubated with VLDL subfractions and VCAM expression determined by flow cytometry after addition of tumour necrosis factor a. VLDL 1 and VLDL2 were isolated from 23 patients with type 2 diabetes mellitus and 11 non-diabetic controls. There were no significant differences in the lag time of VLDL1 to oxidation but the lag time of VLDL2 was significantly shorter in diabetic patients than controls (88.24-37.9 minutes vs 115.2+30.0 respectively, p < 0.05). VLDL2 from diabetic patients induced a greater degree of VCAM expression than controls (2.90+0.82 fluorescence units vs 2.24-4-0.42, p < 0.05). In conclusion, small dense VLDL2 in patients with type 2 diabetes mellitus is potentially atherogenic. It is more prone to oxidation and causes a greater degree of augmentation of cytokine-activated VCAM expression in endothelial cells.
72nd EAS Congress
POSTPRANDIAL HYPERTRIGLYCERIDEMIA IN FIRST DEGREE RELATIVES OF PATIENTS WITH PREMATURE ATHEROSCLEROSIS IS LIMITED TO INSULIN RESISTANT SUBJECTS
C.A. Geluk, C.J.M. Halkes, D.W. Erkelens, M. Castro Cabezas. Dpt. Vasc. Med. UMCU, PO Box 85500, G02.402, 3508 GA Utrecht, the Netherlands Background: Postprandial hypertriglyceridemia in normolipidemic patients with coronary artery disease (CAD) is associated to insulin resistance and may be genetically determined. We studied postprandial lipemia and insulin sensitivity in patients with premature CAD and their first degree relatives. Methods: Twenty-seven normolipidemic patients with premature CAD, 56 first degree relatives without CAD and 102 unrelated healthy volunteers measured capillary triglycerides (TG) on 6 fixed time points on 3 different days. Total area under the mean capillary TG curve (TGc-AUC) represents diurnal triglyceridemia and correlates with results from standardized oral fat loads. Subjects were subdivided based on insulin sensitivity using guidelines from the European Group for the Study of Insulin Resistance. Results: Fasting plasma cholesterol and TG in CAD patients (5.54-0.7 and 1.644-0.99 mmol/L, respectively) and relatives (5.44-1.0 and 1.22+0.53 mmol/L) were significantly higher compared to healthy controls (4.6+1.0 and 0.934-0.48 mmoFL). TGc-AUC was highest in CAD patients (30.74-13.6 mmol.h/L), intermediate in relatives (24.44-9.4 mmol.h/L) and lowest in controls (20.34-7.3 mmol.h/L). When CAD patients were subdivided into insulin resistant (IR; n = 6) and insulin sensitive (n = 21) subjects, both had higher TGc-AUC (39.44-18.1 and 28.24-11.4 mmol.h/L, respectively) than healthy controls (p < 0.01). TGc-AUC in IR relatives (n = 9; 31.14-12.9 mmol.h/L) was similar to CAD patients. Insulin sensitive relatives (n = 47; 23.14-8.1 mmol.h/L) and controls had similar diurnal triglyceridemia. Conclusion: Postprandial hypertriglyceridemia is present in both insulin resistant and sensitive normolipidemic CAD patients. Postprandial hypertriglyceridemia in first degree relatives of these patients is limited to insulin resistant subjects. ~-~
CONCURRENTLY INCREASED CHOLESTEROL SYNTHESIS AND DECREASED CHOLESTEROL ABSORPTION IN HYPERTRIGLYCERIDEMIA. EFFECTS OF BEZAFIBRATE THERAPY
I.J.A.M. Jonkers 1, H.M.G. Princen2, R. Buytenhek2, EH. O'Neill 3, G.R. Thompson3, A.H.M. Smelt 1. 1Leiden University Medical Center,
Leiden," 2TNO-PG, Gaubius Laboratory, Leiden, The Netherlands; 3Imperial School of Medicine, Hammersmith Hospital, London, UK Hypertriglyceridemia (HTG) is a disorder in the VLDL-metabolism. To date it is unclear whether disturbed cholesterol synthesis and/or cholesterol absorption contribute to the expression of HTG. In addition, it is not fully understood whether the lipid-lowering effects of bezafibrate therapy are achieved through effects on cholesterol synthesis and/or cholesterol absorption. Therefore, we compared cholesterol synthesis and cholesterol absorption between 9 patients with endogenous hypertriglyceridemia and 9 age-, sex and body mass index matched normolipidemic controls. Secondary, we investigated the effects of bezafibrate (400 mg/day, 7 weeks) on these parameters in these 9 HTG patients. Cholesterol synthesis was determined by measurement of both fasting plasma levels of mevalonic acid (MVA) and the serum ratio of lathosterol to cholesterol. Cholesterol absorption was assayed using serum ratios of [3-sitosterol, campesterol and cholestanol to cholesterol. Patients with HTG had 14-fold higher serum TG than controls, whereas body mass index was similar in both groups (27.6-4-2.7 vs. 27.8+1.9 kg/m 2 for controls and HTG patients respectively). Lathosterol to cholesterol ratio was higher in HTG patients than in controls (2.80-4-1.14 vs. 1.314-0.55, p < 0.01), whereas MVA levels tended to be higher in HTG patients than in controls as well (+17%, p = 0.09). MVA levels correlated with the ratio of lathosterol to cholesterol (r = 0.802, p < 0.01). Ratios of both I$-sitosterol and cholestanol to cholesterol were lower in HTG patients than in controls (-38%, p = 0.019 and -75%, p = 0.03 respectively), whereas no significant differences were observed in the ratio of campesterol to cholesterol between HTG patients and controls. Bezafibrate therapy significantly reduced serum TG and cholesterol (-69 and -27% respectively, both p < 0.04). Cholesterol synthesis was inhibited by bezafibrate, as represented by reductions in lathosterol to cholesterol ratio (-25%, p = 0.03) and a tendency towards reduction in plasma MVA levels (-21%, p = 0.09). Cholesterol absorption was not affected by bezafibrate therapy. Conclusion: These data demonstrate the presence of increased cholesterol synthesis as well as decreased cholesterol absorption in hypertriglyc-
139
eridemia. In addition, the lipid-lowering effects of bezafibrate therapy can at least partly be explained by a reduction in cholesterol synthesis.
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PLTP ACTIVITY AND CHOLESTERYL ESTER TRANSFER ARE ELEVATED AND CLOSELY LINKED TO INSULIN RESISTANCE IN HYPERTRIGLYCERIDEMIA: REVERSAL UPON BEZAFIBRATE THERAPY
I.J.A.M. Jonkers 1. A.H.M. Smelt 1, L.M. Scheek2, T. van Gent2, EH.A.E de Man 1, A. van der Laarse 1, A. van Tol2. 1Leiden University Medical Center,
Albinasdreef 2, 2300 RC, Leiden; 2Cardiovascular Research Institute (COEUR), Erasmus University, Rotterdam, The Netherlands Hypertriglyceridemia (HTG) is associated with insulin resistance, increased cholesteryl ester transfer (CET) and low HDL-cholesterol (HDL-C) levels. The recently identified phospholipid transfer protein (PLTP) may be involved in these relationships. Therefore the associations between CET, lipoprotein profile, insulin resistance and transfer protein activities (CETP and PLTP) were investigated in 18 endogenous HTG patients and 20 normolipidemic controls. In addition, the effects of 6 week-treatment with bezafibrate were studied on these parameters in HTG patients in a double-blind, placebocontrolled, cross-over trial. HTG patients had 13.2 fold higher serum triglycerides, 0.5 fold lower HDL-C, 5.7 fold higher insulin resistance %, 1.9 fold higher FFA levels and 2.4 fold higher CET in conjunction with higher CETP and PLTP activity levels compared to controls (+20% and +48% respectively, all p < 0.01). Bezafibrate therapy reduced serum triglycerides, CET, insulin resistance %, FFA levels, CETP-, and PLTP activity (-69%, -37%, -53%, -48%, -12%, and -8%, respectively) and increased HDL-C (+27%, all p < 0.05). After adjustment for the disorder HTG, regression analysis showed no relationship between PLTP activity and both CET and HDL-C, whereas insulin resistance did contribute to PLTP activity levels (p < 0.01). Similarly, CET was predicted by serum TG, CETP activity, insulin and FFA levels (all p < 0.04). Bezafibrate-induced reduction in CET and increase in HDL-C levels correlated with the reduction in CETP activity and FFA levels (all p < 0.02), but not with the reduction in PLTP activity (both p > 0.27). Bezafibrateinduced change in PLTP activity tended to correlated with the reduction in FFA levels (r = 0.455, p = 0.058). Conclusion: We propose that PLTP activity is increased in HTG as a result of the presence of insulin resistance. Bezafibrate-induced amelioration of the insulin resistance is associated with a reduction of both CET and PLTP towards normal levels.
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SUSCEPTIBILITY OF VLDL SUBFRACTIONS TO OXIDATION IN PATIENTS WITH TYPE 2 DIABETES MELLITUS AND THEIR EFFECTS ON VASCULAR CELL ADHESION MOLECULE EXPRESSOIN IN ENDOTHELIAL CELLS
K.C.B. Tan, S.W.M. Shiu. Department of Medicine, University of Hong
Kong, Hong Kong Hypertriglyceridaemia is an independent cardiovascular risk factor in patients with type 2 diabetes mellitus and is mainly due to an increased in VLDL. The aims of this study were to determine whether VLDL subfractions from patients with type 2 diabetes mellitus were more susceptible to oxidation and to investigate the effects of VLDL subfractions on cytokineinduced vascular cell adhesion molecules (VCAM) expression in human endothelial cells. VLDL1 and VLDL2 were isolated by density gradient ultracentrifugation. The susceptibility of individual VLDL subfraction to oxidation was determined by measuring the kinetics of conjugated diene formation during copper-mediated oxidation. To investigate VCAM expression, human aortic endothelial cells were pre-incubated with VLDL subfractions and VCAM expression determined by flow cytometry after addition of tumour necrosis factor a. VLDL 1 and VLDL2 were isolated from 23 patients with type 2 diabetes mellitus and 11 non-diabetic controls. There were no significant differences in the lag time of VLDL1 to oxidation but the lag time of VLDL2 was significantly shorter in diabetic patients than controls (88.24-37.9 minutes vs 115.2+30.0 respectively, p < 0.05). VLDL2 from diabetic patients induced a greater degree of VCAM expression than controls (2.90+0.82 fluorescence units vs 2.24-4-0.42, p < 0.05). In conclusion, small dense VLDL2 in patients with type 2 diabetes mellitus is potentially atherogenic. It is more prone to oxidation and causes a greater degree of augmentation of cytokine-activated VCAM expression in endothelial cells.
72nd EAS Congress