- Email: [email protected]
The role of ANGPTL3 in human lipoprotein metabolism
Abstracts / Atherosclerosis 252 (2016) e1ee196
deficiency and pharmacological inhibition of DGAT1 in mice alters cholesterol metabolism. Methods: Cholesterol absorption, as assessed by acute cholesterol uptake, was significantly decreased in the small intestine and liver upon DGAT1 deficiency/inhibition. Ablation of DGAT1 in the intestine (I-DGAT1/) alone is sufficient to cause these effects. Consequences of I-DGAT1 deficiency phenocopy findings in whole-body DGAT1/ and DGAT1 inhibitortreated mice. Results: We show that deficiency/inhibition of DGAT1 affects cholesterol metabolism via reduced chylomicron size and increased trans-intestinal cholesterol excretion. These effects are independent of cholesterol uptake at the apical surface of enterocytes but mediated through altered dietary fatty acid metabolism. Conclusions: Our findings provide insight into a novel role of DGAT1 and identify a pathway by which intestinal DGAT1 deficiency affects wholebody cholesterol homeostasis in mice. Targeting intestinal DGAT1 may represent a novel approach for the treatment of hypercholesterolemia. EAS16-0556, LIPOPROTEINS AND LIPID METABOLISM: APOB CONTAINING LIPOPROTEINS. THE ROLE OF ANGPTL3 IN HUMAN LIPOPROTEIN METABOLISM A. Tikka, J. Metso, M. jauhiainen. National Institute for Health and Welfare, Genomics & Biomarkers, Helsinki, Finland Objectives: ANGPTL3-deficiency causes familial combined hypolipidemia (OMIM#605019), a rare phenotype with a low VLDL, LDL and HDL levels in plasma. Absence of ANGPTL3 in plasma contributes to hypolipidemia by enhancing TG-clearance via lipoprotein lipase (LPL) but whether ANGPTL3 edeficiency would affect lipoprotein production in the liver or in the small intestine has not been addressed in detail. Plasma concentration of ANGPTL3 is linked to TG and LDL-C levels in genome wide linkage studies, however, it is unclear, whether ANGPTL3 sequence variation can predict combined low TG and low cholesterol phenotype in humans. Methods: We investigated whether silencing of ANGPTL3 would affect lipoprotein metabolism in human enterocytes (CACO-2) and human hepatocytes (IHH). We measured secretion rates of apoB, TG, cholesterol and phospholipids in the presence of glucose, fatty acids or in combination. We analyzed plasma ANGPTL3 concentration in two subsamples of Finnish (FINRISK study) subjects with either very low or high combined TG and cholesterol levels in plasma and in subjects with rare sequence variants in ANGPTL3 gene. Results: Silencing of ANGPTL3 affects energy substrate utilization in hepatocytes by enhancing uptake of glucose and its use as a substrate for TGformation. Hepatic fatty acid uptake and use in TG-lipogenesis or VLDL -lipoprotein secretion did not differ between silenced or control cells. Our preliminary results suggest that no major differences in TG -secretion were detected between ANGPTL3 silenced and non-silenced enterocytes. Conclusions: Silencing of ANGPTL3 affects majorily hepatic glucose and lipid metabolism with non-existent or milder effects on enterocytederived lipid metabolism. EAS16-0669, LIPOPROTEINS AND LIPID METABOLISM: APOB CONTAINING LIPOPROTEINS. ASSOCIATION OF THE POSTPRANDIAL CHYLOMICRON TRIGLYCERIDE/ APOB INDEX AND CARDIOVASCULAR EVENTS €rz 1, U. H. Scharnagl 1, C. Werner 2, T. Stojakovic 1, W. Ma €t Graz, Klinisches Institut für Medizinische Laufs 3. 1 Medizinische Universita und Chemische Labordiagnostik, Graz, Austria; 2 Univ Saarland, Internal Medicine III - Cardiology- Angiology and Internal Medicine ICU, Homburg/ €tsklinikum des Saarlandes, Klinik für Innere Saar, Germany; 3 Universita Medizin III - Kardiologie- Angiologie und Internistische Intensivmedizin, Homburg/Saar, Germany Objectives: The association of triglyceride (TG) concentrations and cardiovascular events has not been fully clarified. The aim of this study was to characterize postprandial regulation of chylomicrons in correlation with event-free survival in patients with coronary artery disease (CAD).
e99
Methods: A standardized oral triglyceride tolerance test (OTT) was performed in 58 patients with CAD on statin treatment who were followed up for 4 years. Fasting and 5 hours postprandial plasma was subjected to serial ultracentrifugation to differentiate lipoprotein subclasses and to determine TG, cholesterol, phospholipids and apolipoproteins in each fraction. Results: TG concentrations markedly increased from 141 ± 10 to 249 ± 24mg/dl after the OTT, while cholesterol parameters and apolipoproteins remained unchanged. OTT-induced changes in TG concentrations were mostly attributable to the increase of chylomicron- and VLDL-TG. The TG/apoB ratio is a marker of particle size and density. Following the OTT, the chylomicron TG/apoB index increased from 3.9 to 10.5 after 5 hours. CAD patients with a cardiovascular event in the clinical follow-up (death, myocardial infarction, unplanned revascularization), were characterized by a higher TG/apoB ratio in the postprandial chylomicron fraction (no event: 7.8; event: 13.3; p ¼ 0.015). Importantly, the TG/apoB index was an independent risk predictor in regression analyses (per unit: HR 1.03 (CI 1.01e1.06), p ¼ 0.022; per SD, log-values: HR 1.64 (CI 1.05e2.56), p ¼ 0.029; adjusted for age, gender, medication, smoking, diabetes, BMI, LDL-C, HDL-C, fasting TG). Conclusions: The detailed lipid characterization in this study on CAD patients reveals a specific postprandial dysfunction of the TG-rich chylomicrons and suggests a novel link between postprandial TG metabolism and cardiovascular risk. EAS16-0676, LIPOPROTEINS AND LIPID METABOLISM: APOB CONTAINING LIPOPROTEINS. SYSTEMATIC ASSAY OF LIPOPROTEIN LIPASE ACTIVITY AND MASS IN COHORT OF PATIENTS WITH HISTORY OF TYPE V HYPERLIPIDEMIA O. Marmontel 1, M. di Filippo 1, S. Nony 1, C. Marcais 2, C. Caussy 3, S. ^pital Louis Pradel, Biochemestry, Charriere 3, A. Sassolas 1, P. Moulin 3. 1 Ho Lyon, France; 2 Centre Hospitalier Lyon Sud, Biochemestry, Lyon, France; 3 ^ Hopital Louis Pradel, Endocrinology, Lyon, France Objectives: To decipher the functionality of Lipoprotein Lipase in type V dyslipidemia. Methods: Lipid profiles, preheparin LPL concentration and postheparin (50 UI/Kg; 10 minutes) LPL concentration and activity (PHLA) were obtained from 25 patients with documented history of type V dyslipidemia without homozygous mutation of genes involved in LPL regulation (TVHTG) and 20 control subjects (CTRL). Results: No patient had PHLA deficiency (<10 mmol/L/min). PreheparinLPL concentration was 47% lower in TVHTG patients, however it was found within the normal range in 36% of TVHTG patients. PostheparinLPL concentration was increased 10 times in TVHTG and only 5 times in CTRL, leading to similar postheparinLPL concentration in both groups. Conversely, PHLA and LPL specific activity were similar in both groups. In TVHTG and CTRL, preheparinLPL mass and PHLA were not correlated with plasma triglycerides. Normal LPL mass and activity suggesting over production and/or alteration in remnant uptake was found in 32% while low preheparinLPL mass with normal PHLA suggesting a defect in LPL availability was found in 48% of TVHTG. No TVHTG patient had specific LPL activity lower than CTRL.
TVHTG
Controls
p
n (femme/homme)
25 (5/20)
20 (9/11)
NS
Age
42 ± 2
52 ± 3.7
NS
LPL mass T0 ng/L
25.9 ± 2,2
49.0 ± 4.6
<0.001
LPL mass T10 ng/L
263.3 ± 20.8
268.6 ± 12.1
NS
LPL activity T10 mmcl/L/min
35.9 ± 2.3
34.8 ± 2.9
NS
LPL Specific activity mmol/g/min
138.3 ± 7.9
128.1 ± 7.5
NS
Mean ± SEM
deficiency and pharmacological inhibition of DGAT1 in mice alters cholesterol metabolism. Methods: Cholesterol absorption, as assessed by acute cholesterol uptake, was significantly decreased in the small intestine and liver upon DGAT1 deficiency/inhibition. Ablation of DGAT1 in the intestine (I-DGAT1/) alone is sufficient to cause these effects. Consequences of I-DGAT1 deficiency phenocopy findings in whole-body DGAT1/ and DGAT1 inhibitortreated mice. Results: We show that deficiency/inhibition of DGAT1 affects cholesterol metabolism via reduced chylomicron size and increased trans-intestinal cholesterol excretion. These effects are independent of cholesterol uptake at the apical surface of enterocytes but mediated through altered dietary fatty acid metabolism. Conclusions: Our findings provide insight into a novel role of DGAT1 and identify a pathway by which intestinal DGAT1 deficiency affects wholebody cholesterol homeostasis in mice. Targeting intestinal DGAT1 may represent a novel approach for the treatment of hypercholesterolemia. EAS16-0556, LIPOPROTEINS AND LIPID METABOLISM: APOB CONTAINING LIPOPROTEINS. THE ROLE OF ANGPTL3 IN HUMAN LIPOPROTEIN METABOLISM A. Tikka, J. Metso, M. jauhiainen. National Institute for Health and Welfare, Genomics & Biomarkers, Helsinki, Finland Objectives: ANGPTL3-deficiency causes familial combined hypolipidemia (OMIM#605019), a rare phenotype with a low VLDL, LDL and HDL levels in plasma. Absence of ANGPTL3 in plasma contributes to hypolipidemia by enhancing TG-clearance via lipoprotein lipase (LPL) but whether ANGPTL3 edeficiency would affect lipoprotein production in the liver or in the small intestine has not been addressed in detail. Plasma concentration of ANGPTL3 is linked to TG and LDL-C levels in genome wide linkage studies, however, it is unclear, whether ANGPTL3 sequence variation can predict combined low TG and low cholesterol phenotype in humans. Methods: We investigated whether silencing of ANGPTL3 would affect lipoprotein metabolism in human enterocytes (CACO-2) and human hepatocytes (IHH). We measured secretion rates of apoB, TG, cholesterol and phospholipids in the presence of glucose, fatty acids or in combination. We analyzed plasma ANGPTL3 concentration in two subsamples of Finnish (FINRISK study) subjects with either very low or high combined TG and cholesterol levels in plasma and in subjects with rare sequence variants in ANGPTL3 gene. Results: Silencing of ANGPTL3 affects energy substrate utilization in hepatocytes by enhancing uptake of glucose and its use as a substrate for TGformation. Hepatic fatty acid uptake and use in TG-lipogenesis or VLDL -lipoprotein secretion did not differ between silenced or control cells. Our preliminary results suggest that no major differences in TG -secretion were detected between ANGPTL3 silenced and non-silenced enterocytes. Conclusions: Silencing of ANGPTL3 affects majorily hepatic glucose and lipid metabolism with non-existent or milder effects on enterocytederived lipid metabolism. EAS16-0669, LIPOPROTEINS AND LIPID METABOLISM: APOB CONTAINING LIPOPROTEINS. ASSOCIATION OF THE POSTPRANDIAL CHYLOMICRON TRIGLYCERIDE/ APOB INDEX AND CARDIOVASCULAR EVENTS €rz 1, U. H. Scharnagl 1, C. Werner 2, T. Stojakovic 1, W. Ma €t Graz, Klinisches Institut für Medizinische Laufs 3. 1 Medizinische Universita und Chemische Labordiagnostik, Graz, Austria; 2 Univ Saarland, Internal Medicine III - Cardiology- Angiology and Internal Medicine ICU, Homburg/ €tsklinikum des Saarlandes, Klinik für Innere Saar, Germany; 3 Universita Medizin III - Kardiologie- Angiologie und Internistische Intensivmedizin, Homburg/Saar, Germany Objectives: The association of triglyceride (TG) concentrations and cardiovascular events has not been fully clarified. The aim of this study was to characterize postprandial regulation of chylomicrons in correlation with event-free survival in patients with coronary artery disease (CAD).
e99
Methods: A standardized oral triglyceride tolerance test (OTT) was performed in 58 patients with CAD on statin treatment who were followed up for 4 years. Fasting and 5 hours postprandial plasma was subjected to serial ultracentrifugation to differentiate lipoprotein subclasses and to determine TG, cholesterol, phospholipids and apolipoproteins in each fraction. Results: TG concentrations markedly increased from 141 ± 10 to 249 ± 24mg/dl after the OTT, while cholesterol parameters and apolipoproteins remained unchanged. OTT-induced changes in TG concentrations were mostly attributable to the increase of chylomicron- and VLDL-TG. The TG/apoB ratio is a marker of particle size and density. Following the OTT, the chylomicron TG/apoB index increased from 3.9 to 10.5 after 5 hours. CAD patients with a cardiovascular event in the clinical follow-up (death, myocardial infarction, unplanned revascularization), were characterized by a higher TG/apoB ratio in the postprandial chylomicron fraction (no event: 7.8; event: 13.3; p ¼ 0.015). Importantly, the TG/apoB index was an independent risk predictor in regression analyses (per unit: HR 1.03 (CI 1.01e1.06), p ¼ 0.022; per SD, log-values: HR 1.64 (CI 1.05e2.56), p ¼ 0.029; adjusted for age, gender, medication, smoking, diabetes, BMI, LDL-C, HDL-C, fasting TG). Conclusions: The detailed lipid characterization in this study on CAD patients reveals a specific postprandial dysfunction of the TG-rich chylomicrons and suggests a novel link between postprandial TG metabolism and cardiovascular risk. EAS16-0676, LIPOPROTEINS AND LIPID METABOLISM: APOB CONTAINING LIPOPROTEINS. SYSTEMATIC ASSAY OF LIPOPROTEIN LIPASE ACTIVITY AND MASS IN COHORT OF PATIENTS WITH HISTORY OF TYPE V HYPERLIPIDEMIA O. Marmontel 1, M. di Filippo 1, S. Nony 1, C. Marcais 2, C. Caussy 3, S. ^pital Louis Pradel, Biochemestry, Charriere 3, A. Sassolas 1, P. Moulin 3. 1 Ho Lyon, France; 2 Centre Hospitalier Lyon Sud, Biochemestry, Lyon, France; 3 ^ Hopital Louis Pradel, Endocrinology, Lyon, France Objectives: To decipher the functionality of Lipoprotein Lipase in type V dyslipidemia. Methods: Lipid profiles, preheparin LPL concentration and postheparin (50 UI/Kg; 10 minutes) LPL concentration and activity (PHLA) were obtained from 25 patients with documented history of type V dyslipidemia without homozygous mutation of genes involved in LPL regulation (TVHTG) and 20 control subjects (CTRL). Results: No patient had PHLA deficiency (<10 mmol/L/min). PreheparinLPL concentration was 47% lower in TVHTG patients, however it was found within the normal range in 36% of TVHTG patients. PostheparinLPL concentration was increased 10 times in TVHTG and only 5 times in CTRL, leading to similar postheparinLPL concentration in both groups. Conversely, PHLA and LPL specific activity were similar in both groups. In TVHTG and CTRL, preheparinLPL mass and PHLA were not correlated with plasma triglycerides. Normal LPL mass and activity suggesting over production and/or alteration in remnant uptake was found in 32% while low preheparinLPL mass with normal PHLA suggesting a defect in LPL availability was found in 48% of TVHTG. No TVHTG patient had specific LPL activity lower than CTRL.
TVHTG
Controls
p
n (femme/homme)
25 (5/20)
20 (9/11)
NS
Age
42 ± 2
52 ± 3.7
NS
LPL mass T0 ng/L
25.9 ± 2,2
49.0 ± 4.6
<0.001
LPL mass T10 ng/L
263.3 ± 20.8
268.6 ± 12.1
NS
LPL activity T10 mmcl/L/min
35.9 ± 2.3
34.8 ± 2.9
NS
LPL Specific activity mmol/g/min
138.3 ± 7.9
128.1 ± 7.5
NS
Mean ± SEM