1
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Salvador AF, Shyu CR, Parks EJ. Measurement of lipid flux to advance translational research: evolution of classic methods to the future of precision health. EXPERIMENTAL & MOLECULAR MEDICINE 2022; 54:1348-1353. [PMID: 36075949 PMCID: PMC9534914 DOI: 10.1038/s12276-022-00838-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/22/2022] [Accepted: 07/12/2022] [Indexed: 02/08/2023]
Abstract
Over the past 70 years, the study of lipid metabolism has led to important discoveries in identifying the underlying mechanisms of chronic diseases. Advances in the use of stable isotopes and mass spectrometry in humans have expanded our knowledge of target molecules that contribute to pathologies and lipid metabolic pathways. These advances have been leveraged within two research paths, leading to the ability (1) to quantitate lipid flux to understand the fundamentals of human physiology and pathology and (2) to perform untargeted analyses of human blood and tissues derived from a single timepoint to identify lipidomic patterns that predict disease. This review describes the physiological and analytical parameters that influence these measurements and how these issues will propel the coming together of the two fields of metabolic tracing and lipidomics. The potential of data science to advance these fields is also discussed. Future developments are needed to increase the precision of lipid measurements in human samples, leading to discoveries in how individuals vary in their production, storage, and use of lipids. New techniques are critical to support clinical strategies to prevent disease and to identify mechanisms by which treatments confer health benefits with the overall goal of reducing the burden of human disease. Personalized tracking of how lipid (fat) metabolism changes over time could lead to improvements in the diagnosis and treatment of several diseases. Elizabeth Parks and colleagues from the University of Missouri, Columbia, USA, discuss the ways in which researchers use stable isotope labeling to monitor the kinetics of fatty acids and other lipids in the body. Usually, lipid quantities are measured only at a single timepoint, however the tracking of lipid turnover over time provides further diagnostic information. Aided by new techniques such as high-throughput mass spectrometry and machine learning, researchers are now able to continuously map total lipid contents in individual patients. The transition of measurements of lipid flux from the research laboratory to the doctor’s office will likely play a role in a new era of precision medicine.
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Affiliation(s)
- Amadeo F Salvador
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, 65212, USA.,Department of Medicine, Division of Gastroenterology and Hepatology, School of Medicine, University of Missouri, Columbia, MO, 65212, USA.,Department of Electrical Engineering and Computer Science, Institute for Data Science and Informatics, University of Missouri, Columbia, MO, 65211, USA
| | - Chi-Ren Shyu
- Department of Electrical Engineering and Computer Science, Institute for Data Science and Informatics, University of Missouri, Columbia, MO, 65211, USA
| | - Elizabeth J Parks
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, 65212, USA. .,Department of Medicine, Division of Gastroenterology and Hepatology, School of Medicine, University of Missouri, Columbia, MO, 65212, USA.
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2
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Jansen M, Contini C. LDL retention time in plasma can be -based on causation- estimated by the lipid composition of LDL and other lipoproteins. PLoS One 2022; 17:e0272050. [PMID: 35901111 PMCID: PMC9333322 DOI: 10.1371/journal.pone.0272050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 07/12/2022] [Indexed: 11/21/2022] Open
Abstract
Introduction Information on LDL’s dynamic behaviour of LDL (i.e. production rate and fractional catabolic rate) are of interest if pathologies, lipid-lowering strategies or LDL-metabolism itself are investigated. Determination of these rates is costly and elaborate. Here we studied the interrelationship of LDL mass, its composition and other lipoproteins. Based on this data, we deducted information about LDL’s dynamic behaviour. Methods Lipoprotein profiles of n = 236 participants are evaluated. Plasma was separated by sequential ultracentrifugation into VLDL, IDL, LDL and HDL. Additionally, LDL and HDL were separated into subfractions. Stepwise multiple linear regressions were used to study LDL’s ApoB mass and lipid composition. Relying on these results and on causation, we constructed a mathematical model to estimate LDL’s retention time. Results The ApoB mass in LDL correlated best among all measured parameters (including corresponding lipid compositions but using no LDL-associated parameters) with the cholesterol ester content in IDL. TG/CE ratios in LDL’s subfractions were strongly correlated with the corresponding ratios in IDL and HDL. The constructed mathematical model links the TG/CE ratio of LDL and HDL to LDL’s ApoB concentration and enables a good estimate of LDL’s retention time in plasma. Discussion Relying on our statistic evaluations, we assume that i) the production of nascent LDL via IDL as well as ii) LDL’s prolonged retention are mapped by the TG/CE ratio in LDL subfractions. HDL’s TG/CE ratio is associated with the change in LDL’s TG/CE ratio during its retention in plasma. Our mathematical model uses this information and enables–by relying on causation- a good estimation of LDL’s retention time.
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Affiliation(s)
- Martin Jansen
- Institute of Clinical Chemistry and Laboratory Medicine, Medical Centre -University of Freiburg, Freiburg im Breisgau, Germany
- Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
- * E-mail:
| | - Christine Contini
- Institute of Clinical Chemistry and Laboratory Medicine, Medical Centre -University of Freiburg, Freiburg im Breisgau, Germany
- Faculty of Medicine, University of Freiburg, Freiburg im Breisgau, Germany
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3
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Ying Q, Chan DC, Barrett PHR, Watts GF. Unravelling lipoprotein metabolism with stable isotopes: tracing the flow. Metabolism 2021; 124:154887. [PMID: 34508741 DOI: 10.1016/j.metabol.2021.154887] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/16/2021] [Accepted: 09/01/2021] [Indexed: 12/13/2022]
Abstract
Dysregulated lipoprotein metabolism is a major cause of atherosclerotic cardiovascular disease (ASCVD). Use of stable isotope tracers and compartmental modelling have provided deeper understanding of the mechanisms underlying lipid disorders in patients at high risk of ASCVD, including familial hypercholesterolemia (FH), elevated lipoprotein(a) [Lp(a)] and metabolic syndrome (MetS). In patients with FH, deficiency in low-density lipoprotein (LDL) receptor activity not only impairs the catabolism of LDL, but also induces hepatic overproduction and decreases catabolism of triglyceride-rich lipoproteins (TRLs). Patients with elevated Lp(a) are characterized by increased hepatic secretion of Lp(a) particles. Atherogenic dyslipidemia in MetS patients relates to a combination of overproduction of very-low density lipoprotein-apolipoprotein (apo) B-100, decreased catabolism of apoB-100-containing particles, and increased catabolism of high-density lipoprotein-apoA-I particles, as well as to impaired clearance of TRLs in the postprandial state. Kinetic studies show that weight loss, fish oils, statins and fibrates have complementary modes of action that correct atherogenic dyslipidemia. Defining the kinetic mechanisms of action of proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 inhibitors on lipid and lipoprotein mechanism in dyslipidemic subjects will further our understanding of these therapies in decreasing the development of ASCVD. "Everything changes but change itself. Everything flows and nothing remains the same... You cannot step twice into the same river, for other waters and yet others go flowing ever on." Heraclitus (c.535- c. 475 BCE).
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Affiliation(s)
- Qidi Ying
- Medical School, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | - Dick C Chan
- Medical School, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | - P Hugh R Barrett
- Faculty of Medicine and Health, University of New England, Armidale, Australia
| | - Gerald F Watts
- Medical School, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia; Lipid Disorders Clinic, Departments of Cardiology and Internal Medicine, Royal Perth Hospital, Perth, Australia.
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4
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Watts GF, Chan DC, Pang J, Ma L, Ying Q, Aggarwal S, Marcovina SM, Barrett PHR. PCSK9 Inhibition with alirocumab increases the catabolism of lipoprotein(a) particles in statin-treated patients with elevated lipoprotein(a). Metabolism 2020; 107:154221. [PMID: 32240727 DOI: 10.1016/j.metabol.2020.154221] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/16/2020] [Accepted: 03/30/2020] [Indexed: 12/12/2022]
Abstract
BACKGROUND Lipoprotein(a) (Lp(a)) is a low-density lipoprotein (LDL) particle containing apolipoprotein(a) (apo(a)) covalently linked to apolipoprotein B-100 (apoB). Statin-treated patients with elevated Lp(a) have an increased risk of atherosclerotic cardiovascular disease (ASCVD). Recent trials show that proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition decreases Lp(a) and cardiovascular events, particularly in high risk patients with elevated Lp(a). We investigated the kinetic mechanism whereby alirocumab, a PCSK9 inhibitor, lowers Lp(a) in statin-treated patients with high Lp(a) and ASCVD. METHODS The effects of 12-week alirocumab treatment (150 mg every 2 weeks) on apo(a) kinetics were studied in 21 patients with elevated Lp(a) concentration (>0.5 g/L). Apo(a) fractional catabolic rate (FCR) and production rate (PR) were determined using intravenous D3-leucine administration, mass spectrometry and compartmental modelling. All patients were on long-term statin treatment. RESULTS Alirocumab significantly decreased plasma concentrations of total cholesterol (-39%), LDL-cholesterol (-67%), apoB (-56%), apo(a) (-25%) and Lp(a) (-22%) (P< 0.001 for all). Alirocumab also significantly lowered plasma apo(a) pool size (-26%, P <0.001) and increased the FCR of apo(a) (+28%, P< 0.001), but did not alter apo(a) PR, which remained significantly higher relative to a reference group of patients on statins with normal Lp(a) (P< 0.001). CONCLUSIONS In statin-treated patients, alirocumab lowers elevated plasma Lp(a) concentrations by accelerating the catabolism of Lp(a) particles. This may be consequent on marked upregulation of hepatic receptors (principally for LDL) and/or reduced competition between Lp(a) and LDL particles for these receptors; the mechanism could contribute to the benefit of PCSK9 inhibition with alirocumab on cardiovascular outcomes.
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Affiliation(s)
- Gerald F Watts
- Lipid Disorders Clinic, Department of Cardiology, Royal Perth Hospital, Perth, Australia; School of Medicine, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia.
| | - Dick C Chan
- School of Medicine, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | - Jing Pang
- School of Medicine, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | - Louis Ma
- School of Medicine, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | - Qidi Ying
- School of Medicine, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | | | - Santica M Marcovina
- Northwest Lipid Metabolism and Diabetes Research Laboratories, Division of Metabolism, Endocrinology, and Nutrition, Seattle, USA; Department of Medicine, University of Washington, Seattle, USA
| | - P Hugh R Barrett
- Faculty of Medicine and Health, University of New England, Armidale, Australia
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Croyal M, Blanchard V, Ouguerram K, Chétiveaux M, Cabioch L, Moyon T, Billon-Crossouard S, Aguesse A, Bernardeau K, Le May C, Flet L, Lambert G, Hadjadj S, Cariou B, Krempf M, Nobécourt-Dupuy E. VLDL (Very-Low-Density Lipoprotein)-Apo E (Apolipoprotein E) May Influence Lp(a) (Lipoprotein [a]) Synthesis or Assembly. Arterioscler Thromb Vasc Biol 2020; 40:819-829. [DOI: 10.1161/atvbaha.119.313877] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Objective:
To clarify the association between PCSK9 (proprotein convertase subtilisin/kexin type 9) and Lp(a) (lipoprotein [a]), we studied Lp(a) kinetics in patients with loss-of-function and gain-of-function
PCSK9
mutations and in patients in whom extended-release niacin reduced Lp(a) and PCSK9 concentrations.
Approach and Results:
Six healthy controls, 9 heterozygous patients with familial hypercholesterolemia (5 with low-density lipoprotein receptor [
LDLR
] mutations and 4 with
PCSK9
gain-of-function mutations) and 3 patients with heterozygous dominant-negative
PCSK9
loss-of-function mutations were included in the preliminary study. Eight patients were enrolled in a second study assessing the effects of 2 g/day extended-release niacin. Apolipoprotein kinetics in VLDL (very-low-density lipoprotein), LDL (low-density lipoprotein), and Lp(a) were studied using stable isotope techniques. Plasma Lp(a) concentrations were increased in
PCSK9
-gain-of-function and familial hypercholesterolemia-
LDLR
groups compared with controls and
PCSK9
-loss-of-function groups (14±12 versus 5±4 mg/dL;
P
=0.04), but no change was observed in Lp(a) fractional catabolic rate. Subjects with
PCSK9
-loss-of-function mutations displayed reduced apoE (apolipoprotein E) concentrations associated with a VLDL-apoE absolute production rate reduction. Lp(a) and VLDL-apoE absolute production rates were correlated (
r
=0.50;
P
<0.05). ApoE-to-apolipoprotein (a) molar ratios in Lp(a) increased with plasma Lp(a) (
r
=0.96;
P
<0.001) but not with PCSK9 levels. Extended-release niacin-induced reductions in Lp(a) and VLDL-apoE absolute production rate were correlated (
r
=0.83;
P
=0.015). In contrast, PCSK9 reduction (−35%;
P
=0.008) was only correlated with that of VLDL-apoE absolute production rate (
r
=0.79;
P
=0.028).
Conclusions:
VLDL-apoE production could determine Lp(a) production and/or assembly. As PCSK9 inhibitors reduce plasma apoE and Lp(a) concentrations, apoE could be the link between PCSK9 and Lp(a).
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Affiliation(s)
- Mikaël Croyal
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Valentin Blanchard
- Université de La Réunion, INSERM, UMR 1188 Diabète athérothrombose Réunion Océan Indien (DéTROI), Plateforme CYROI, Saint-Denis de La Réunion, France (V.B., G.L.)
| | - Khadija Ouguerram
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Maud Chétiveaux
- L’institut du thorax, INSERM, CNRS, University of Nantes, France (M. Chétiveaux, C.L.M.)
| | - Léa Cabioch
- Biogenouest-Corsaire platform, Saint Gilles, France (L.C.)
| | - Thomas Moyon
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Stéphanie Billon-Crossouard
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Audrey Aguesse
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
| | - Karine Bernardeau
- P2R «Production de protéines recombinantes», CRCINA, SFR-Santé, INSERM, CNRS, UNIV Nantes, CHU Nantes, France (K.B.)
| | - Cédric Le May
- L’institut du thorax, INSERM, CNRS, University of Nantes, France (M. Chétiveaux, C.L.M.)
| | - Laurent Flet
- Pharmacy Department, Nantes University Hospital, France (L.F.)
| | - Gilles Lambert
- Université de La Réunion, INSERM, UMR 1188 Diabète athérothrombose Réunion Océan Indien (DéTROI), Plateforme CYROI, Saint-Denis de La Réunion, France (V.B., G.L.)
| | - Samy Hadjadj
- L’institut du thorax, INSERM, CNRS, University of Nantes, CHU Nantes, France (S.H., B.C.)
| | - Bertrand Cariou
- L’institut du thorax, INSERM, CNRS, University of Nantes, CHU Nantes, France (S.H., B.C.)
| | - Michel Krempf
- From the NUN, INRA, CHU Nantes, UMR 1280, PhAN, IMAD, CRNH-O, France (M. Croyal, K.O., S.B.-C., A.A., M.K.)
- CRNH-O Mass Spectrometry Core Facility, F-44000 Nantes, France (M. Croyal, K.O., T.M., S.B.-C., A.A., M.K.)
- ELSAN, clinique Bretéché, Nantes, France (M.K.)
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6
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Ma L, Chan DC, Ooi EMM, Marcovina SM, Barrett PHR, Watts GF. Apolipoprotein(a) Kinetics in Statin-Treated Patients With Elevated Plasma Lipoprotein(a) Concentration. J Clin Endocrinol Metab 2019; 104:6247-6255. [PMID: 31393573 DOI: 10.1210/jc.2019-01382] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 08/02/2019] [Indexed: 02/08/2023]
Abstract
BACKGROUND Lipoprotein(a) [Lp(a)] is a low-density lipoprotein‒like particle containing apolipoprotein(a) [apo(a)]. Patients with elevated Lp(a), even when treated with statins, are at increased risk of cardiovascular disease. We investigated the kinetic basis for elevated Lp(a) in these patients. OBJECTIVES Apo(a) production rate (PR) and fractional catabolic rate (FCR) were compared between statin-treated patients with and without elevated Lp(a). METHODS The kinetics of apo(a) were investigated in 14 patients with elevated Lp(a) and 15 patients with normal Lp(a) levels matched for age, sex, and body mass index using stable isotope techniques and compartmental modeling. All 29 patients were on background statin treatment. Plasma apo(a) concentration was measured using liquid chromatography-mass spectrometry. RESULTS The plasma concentration and PR of apo(a) were significantly higher in patients with elevated Lp(a) than in patients with normal Lp(a) concentration (all P < 0.01). The FCR of apo(a) was not significantly different between the groups. In univariate analysis, plasma concentration of apo(a) was significantly associated with apo(a) PR in both patient groups (r = 0.699 and r = 0.949, respectively; all P < 0.01). There was no significant association between plasma apo(a) concentration and FCR in either of the groups (r = 0.160 and r = -0.137, respectively). CONCLUSION Elevated plasma Lp(a) concentration is a consequence of increased hepatic production of Lp(a) particles in these patients. Our findings provide a kinetic rationale for the use of therapies that target the synthesis of apo(a) and production of Lp(a) particles in patients with elevated Lp(a).
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Affiliation(s)
- Louis Ma
- School of Biomedical Sciences, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
- School of Medicine, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
| | - Dick C Chan
- School of Biomedical Sciences, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
- School of Medicine, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
| | - Esther M M Ooi
- School of Biomedical Sciences, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
| | - Santica M Marcovina
- Northwest Lipid Metabolism and Diabetes Research Laboratories, Division of Metabolism, Endocrinology, and Nutrition, Department of Medicine, University of Washington, Seattle, Washington
| | - P Hugh R Barrett
- Faculty of Medicine and Health, University of New England, Armidale, New South Wales, Australia
| | - Gerald F Watts
- School of Medicine, Faculty of Health and Medicine, University of Western Australia, Perth, Western Australia, Australia
- Lipid Disorders Clinic, Department of Cardiology, Royal Perth Hospital, Perth, Western Australia, Australia
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7
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Watts GF, Chan DC, Somaratne R, Wasserman SM, Scott R, Marcovina SM, Barrett PHR. Controlled study of the effect of proprotein convertase subtilisin-kexin type 9 inhibition with evolocumab on lipoprotein(a) particle kinetics. Eur Heart J 2018; 39:2577-2585. [DOI: 10.1093/eurheartj/ehy122] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 03/02/2018] [Indexed: 12/24/2022] Open
Affiliation(s)
- Gerald F Watts
- Lipid Disorders Clinic, Department of Cardiology, Royal Perth Hospital, Perth, WA, Australia
- Schools of Medicine and Biomedical Science, University of Western Australia, Perth, WA, Australia
| | - Dick C Chan
- Schools of Medicine and Biomedical Science, University of Western Australia, Perth, WA, Australia
| | | | | | - Rob Scott
- Formerly of Amgen, Inc., Thousand Oaks, CA, USA
| | - Santica M Marcovina
- Northwest Lipid Metabolism and Diabetes Research Laboratories, Division of Metabolism, Endocrinology, and Nutrition, Department of Medicine, University of Washington, Seattle, WA, USA
| | - P Hugh R Barrett
- Schools of Medicine and Biomedical Science, University of Western Australia, Perth, WA, Australia
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8
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Blanchard V, Ramin-Mangata S, Billon-Crossouard S, Aguesse A, Durand M, Chemello K, Nativel B, Flet L, Chétiveaux M, Jacobi D, Bard JM, Ouguerram K, Lambert G, Krempf M, Croyal M. Kinetics of plasma apolipoprotein E isoforms by LC-MS/MS: a pilot study. J Lipid Res 2018. [PMID: 29540575 DOI: 10.1194/jlr.p083576] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Human apoE exhibits three major isoforms (apoE2, apoE3, and apoE4) corresponding to polymorphism in the APOE gene. Total plasma apoE concentrations are closely related to these isoforms, but the underlying mechanisms are unknown. We aimed to describe the kinetics of apoE individual isoforms to explore the mechanisms for variable total apoE plasma concentrations. We used LC-MS/MS to discriminate between isoforms by identifying specific peptide sequences in subjects (three E2/E3, three E3/E3, and three E3/E4 phenotypes) who received a primed constant infusion of 2H3-leucine for 14 h. apoE concentrations and leucine enrichments were measured hourly in plasma. Concentrations of apoE2 were higher than apoE3, and concentrations of apoE4 were lower than apoE3. There was no difference between apoE3 and apoE4 catabolic rates and between apoE2 and apoE3 production rates (PRs), but apoE2 catabolic rates and apoE4 PRs were lower. The mechanisms leading to the difference in total plasma apoE concentrations are therefore related to contrasted kinetics of the isoforms. Production or catabolic rates are differently affected according to the specific isoforms. On these grounds, studies on the regulation of the involved biochemical pathways and the impact of pathological environments are now warranted.
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Affiliation(s)
- Valentin Blanchard
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France.,INSERM, UMR 1188 DéTROI, University of La Réunion, F-97490 Sainte Clotilde, France
| | | | - Stéphanie Billon-Crossouard
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France.,INRA, UMR 1280 PhAN, F-44000 Nantes, France
| | - Audrey Aguesse
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France.,INRA, UMR 1280 PhAN, F-44000 Nantes, France
| | - Manon Durand
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France.,L'institut du Thorax, INSERM, CNRS, UNIV Nantes, F-44000 Nantes, France
| | - Kevin Chemello
- INSERM, UMR 1188 DéTROI, University of La Réunion, F-97490 Sainte Clotilde, France
| | - Brice Nativel
- INSERM, UMR 1188 DéTROI, University of La Réunion, F-97490 Sainte Clotilde, France
| | - Laurent Flet
- Pharmacy Department, Nantes University Hospital, F-44093 Nantes, France
| | - Maud Chétiveaux
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France
| | - David Jacobi
- L'institut du Thorax, INSERM, CNRS, UNIV Nantes, F-44000 Nantes, France.,L'institut du Thorax, CHU Nantes, F-44093 Nantes, France
| | - Jean-Marie Bard
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France.,University of Nantes, Mer, Molécules, Santé (MMS) - EA 2160 and Institut Universitaire Mer et Littoral (IUML) - FR3473 CNRS, F-44000 Nantes, France, and Department of Biopathology, Institute of Cancer and Oncology, F-44800 Saint-Herblain, France
| | - Khadija Ouguerram
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France.,INRA, UMR 1280 PhAN, F-44000 Nantes, France
| | - Gilles Lambert
- INSERM, UMR 1188 DéTROI, University of La Réunion, F-97490 Sainte Clotilde, France
| | - Michel Krempf
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France.,INRA, UMR 1280 PhAN, F-44000 Nantes, France.,L'institut du Thorax, CHU Nantes, F-44093 Nantes, France
| | - Mikaël Croyal
- CRNHO, West Human Nutrition Research Center, F-44000 Nantes, France .,INRA, UMR 1280 PhAN, F-44000 Nantes, France
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9
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Croyal M, Billon-Crossouard S, Goulitquer S, Aguesse A, León L, Fall F, Chétiveaux M, Moyon T, Blanchard V, Ouguerram K, Lambert G, Nobécourt E, Krempf M. Stable Isotope Kinetic Study of ApoM (Apolipoprotein M). Arterioscler Thromb Vasc Biol 2017; 38:255-261. [PMID: 29146748 DOI: 10.1161/atvbaha.117.310208] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 10/30/2017] [Indexed: 01/31/2023]
Abstract
OBJECTIVE ApoM (apolipoprotein M) binds primarily to high-density lipoprotein before to be exchanged with apoB (apolipoprotein B)-containing lipoproteins. Low-density lipoprotein (LDL) receptor-mediated clearance of apoB-containing particles could influence plasma apoM kinetics and decrease its antiatherogenic properties. In humans, we aimed to describe the interaction of apoM kinetics with other components of lipid metabolism to better define its potential benefit on atherosclerosis. APPROACH AND RESULTS Fourteen male subjects received a primed infusion of 2H3-leucine for 14 hours, and analyses were performed by liquid chromatography-tandem mass spectrometry from the hourly plasma samples. Fractional catabolic rates and production rates within lipoproteins were calculated using compartmental models. ApoM was found not only in high-density lipoprotein (59%) and LDL (4%) but also in a non-lipoprotein-related compartment (37%). The apoM distribution was heterogeneous within LDL and non-lipoprotein-related compartments according to plasma triglycerides (r=0.86; P<0.001). The relationships between sphingosine-1-phosphate and apoM were confirmed in all compartments (r range, 0.55-0.89; P<0.05). ApoM fractional catabolic rates and production rates were 0.16±0.07 pool/d and 0.14±0.06 mg/kg per day in high-density lipoprotein and 0.56±0.10 pool/d and 0.03±0.01 mg/kg per day in LDL, respectively. Fractional catabolic rates of LDL-apoM and LDL-apoB100 were correlated (r=0.55; P=0.042). Significant correlations were found between triglycerides and production rates of LDL-apoM (r=0.73; P<0.004). CONCLUSIONS In humans, LDL kinetics play a key role in apoM turnover. Plasma triglycerides act on both apoM and sphingosine-1-phosphate distributions between lipoproteins. These results confirmed that apoM could be bound to high-density lipoprotein after secretion and then quickly exchanged with a non-lipoprotein-related compartment and to LDL to be slowly catabolized.
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Affiliation(s)
- Mikaël Croyal
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Stéphanie Billon-Crossouard
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Sophie Goulitquer
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Audrey Aguesse
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Luis León
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Fanta Fall
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Maud Chétiveaux
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Thomas Moyon
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Valentin Blanchard
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Khadija Ouguerram
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Gilles Lambert
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Estelle Nobécourt
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.)
| | - Michel Krempf
- From the INRA, UMR 1280, CHU Hôtel-Dieu, Faculty of Medicine, University of Nantes, France (M.C., S.B.-C., A.A., L.L., F.F., T.M., K.O., E.N., M.K.); CRNHO, West Human Nutrition Research Center, Nantes, France (M.C., S.B.-C., A.A., F.F., M.C., V.B., K.O., E.N., M.K.); INSERM-UBO, UMR 1078-ECLA, IBSAM, School of Medicine, University of Brest, France (S.G.); Biotechnology Program, National School of Medicine and Homeopathy, National Polytechnic Institute, Mexico City, Mexico (L.L.); INSERM UMR 1188 DéTROI, University of La Réunion, Sainte-Clotilde, France (G.L.); CHU de la Réunion, School of Medicine, University of la Réunion, Saint-Denis, France (E.N.); and Department of Endocrinology, Metabolic Diseases and Nutrition, G and R Laennec Hospital, Nantes, France (M.K.).
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10
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SRM-based measurements of proprotein convertase subtilisin/kexin type 9 and lipoprotein(a) kinetics in nonhuman primate serum. Bioanalysis 2016; 8:2551-2563. [DOI: 10.4155/bio-2016-0146] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Aim: PCSK9 and Lp(a) have been identified as potential biomarkers for cardiovascular disease. The ability to measure protein turnover rates will provide insights into the dynamic properties of these proteins and lead to better understanding of their biological roles. We aimed to implement the stable isotope-labeled tracers ([2H3]-leucine) and develop a novel LC-selected reaction monitoring (SRM) mass spectrometry (MS) method to study the kinetics of PCSK9 and Lp(a). Results: A sensitive method using immunoaffinity enrichment coupled with LC-SRM MS was developed to measure the production and degradation rates of PCSK9 and Lp(a) in naive nonhuman primate serum. Comparable results were obtained from two different routes of tracer administration. Conclusion: Immunoaffinity enrichment coupled with LC-SRM MS demonstrated success in in vivo kinetic measurements of proteins with relatively slow turnover rate (Lp[a]) or low abundance (PCSK9) in serum.
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11
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Chan DC, Barrett PHR, Watts GF. Recent explanatory trials of the mode of action of drug therapies on lipoprotein metabolism. Curr Opin Lipidol 2016; 27:550-556. [PMID: 27749370 DOI: 10.1097/mol.0000000000000348] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Dysregulated lipoprotein metabolism leads to increased plasma concentrations of atherogenic lipoproteins. We highlight the findings from recent studies of the effect of lipid-regulating therapies on apolipoprotein metabolism in humans employing endogenous labelling with stable isotopically labelled isotopomers. RECENT FINDINGS Fish oil supplementation and niacin treatment both reduce fasting and postprandial triglyceride levels by decreasing the hepatic secretion of VLDL-apoB-100 (apoB) and apoB-48-containing chylomicron particles in obese and/or type 2 diabetes. Niacin also lowers plasma LDL-apoB and Lp(a) levels by increasing catabolism of LDL-apoB and decreasing secretion of Lp(a), respectively. In subjects with hypercholesterolaemia, inhibition of cholesteryl ester transfer protein raises apoA-I and lowers apoB by decreasing and increasing the catabolism of HDL-apoA-I and LDL-apoB, respectively. Antisense oligonucleotides directed at apoB mRNA lowers plasma LDL-cholesterol and apoB chiefly by increasing the catabolism and decreasing the secretion of LDL-apoB in healthy subjects. That apoB ASO treatment does not lower hepatic secretion in humans is unexpected and merits further investigation. SUMMARY Kinetic studies provide mechanistic insight into the mode of action of lipid lowering therapies and lipoprotein disorders. Understanding the mode of action of new drugs in vivo is important to establish their effective use in clinical practice.
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Affiliation(s)
- Dick C Chan
- Metabolic Research Centre, School of Medicine and Pharmacology, University of Western Australia, Perth, Australia
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12
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Croyal M, Fall F, Ferchaud-Roucher V, Chétiveaux M, Zaïr Y, Ouguerram K, Krempf M, Nobécourt E. Multiplexed peptide analysis for kinetic measurements of major human apolipoproteins by LC/MS/MS. J Lipid Res 2016; 57:509-15. [PMID: 26773160 DOI: 10.1194/jlr.d064618] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Indexed: 11/20/2022] Open
Abstract
A multiplexed assay was developed by MS to analyze, in a single run, six major human Apos involved in lipoprotein metabolism: ApoA-I, ApoA-II, ApoB100, ApoC-II, ApoC-III, and ApoE. This method was validated in vivo in six subjects who received a 14 h constant infusion of [5,5,5-(2)H3]L-leucine at 10 μM/kg/h. Plasma lipoprotein fractions were isolated from collected blood samples and were digested with trypsin. Proteotypic peptides were subsequently analyzed by LC/MS/MS. Enrichment measurement data were compared with those obtained by the standard method using GC/MS. The required time to obtain the LC/MS/MS data was less than that needed for GC/MS. The enrichments from both methods were correlated for ApoA-I (r = 0.994; P < 0.0001) and ApoB100 (r = 0.999; P < 0.0001), and the Bland-Altman plot confirmed the similarity of the two methods. Intra- and inter-assay variability calculated for the six Apos of interest did not exceed 10.7 and 12.5%, respectively, and kinetic parameters were similar and/or in agreement with previously reported data. Therefore, LC/MS/MS can be considered as a useful tool for human Apo kinetic studies using stable isotopes.
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Affiliation(s)
- Mikaël Croyal
- INRA, UMR 1280, Physiologie des Adaptations Nutritionnelles, CHU Hôtel-Dieu, F-44000 Nantes, France CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France
| | - Fanta Fall
- INRA, UMR 1280, Physiologie des Adaptations Nutritionnelles, CHU Hôtel-Dieu, F-44000 Nantes, France CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France
| | - Véronique Ferchaud-Roucher
- INRA, UMR 1280, Physiologie des Adaptations Nutritionnelles, CHU Hôtel-Dieu, F-44000 Nantes, France CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France
| | - Maud Chétiveaux
- CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France
| | - Yassine Zaïr
- CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France
| | - Khadija Ouguerram
- INRA, UMR 1280, Physiologie des Adaptations Nutritionnelles, CHU Hôtel-Dieu, F-44000 Nantes, France CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France
| | - Michel Krempf
- INRA, UMR 1280, Physiologie des Adaptations Nutritionnelles, CHU Hôtel-Dieu, F-44000 Nantes, France CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France Department of Endocrinology, Metabolic Diseases, and Nutrition, G and R Laennec Hospital, F-44093 Nantes, France
| | - Estelle Nobécourt
- INRA, UMR 1280, Physiologie des Adaptations Nutritionnelles, CHU Hôtel-Dieu, F-44000 Nantes, France CRNHO, West Human Nutrition Research Center, CHU, F-44093 Nantes, France Department of Endocrinology, Metabolic Diseases, and Nutrition, G and R Laennec Hospital, F-44093 Nantes, France
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Adiels M, Mardinoglu A, Taskinen MR, Borén J. Kinetic Studies to Elucidate Impaired Metabolism of Triglyceride-rich Lipoproteins in Humans. Front Physiol 2015; 6:342. [PMID: 26635628 PMCID: PMC4653309 DOI: 10.3389/fphys.2015.00342] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 11/03/2015] [Indexed: 01/06/2023] Open
Abstract
To develop novel strategies for prevention and treatment of dyslipidemia, it is essential to understand the pathophysiology of dyslipoproteinemia in humans. Lipoprotein metabolism is a complex system in which abnormal concentrations of various lipoprotein particles can result from alterations in their rates of production, conversion, and/or catabolism. Traditional methods that measure plasma lipoprotein concentrations only provide static estimates of lipoprotein metabolism and hence limited mechanistic information. By contrast, the use of tracers labeled with stable isotopes and mathematical modeling, provides us with a powerful tool for probing lipid and lipoprotein kinetics in vivo and furthering our understanding of the pathogenesis of dyslipoproteinemia.
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Affiliation(s)
- Martin Adiels
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, University of Gothenburg Gothenburg, Sweden ; Health Metrics Unit, Sahlgrenska Academy, University of Gothenburg Gothenburg, Sweden
| | - Adil Mardinoglu
- Department of Biology and Biological Engineering, Chalmers University of Technology Gothenburg, Sweden ; Science for Life Laboratory, KTH - Royal Institute of Technology Stockholm, Sweden
| | - Marja-Riitta Taskinen
- Heart and Lung Centre, Helsinki University Hospital and Research Programs' Unit, Diabetes & Obesity, University of Helsinki Helsinki, Finland
| | - Jan Borén
- Department of Molecular and Clinical Medicine/Wallenberg Laboratory, University of Gothenburg Gothenburg, Sweden
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Evaluating computational models of cholesterol metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1360-76. [DOI: 10.1016/j.bbalip.2015.05.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 05/08/2015] [Accepted: 05/26/2015] [Indexed: 02/02/2023]
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15
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Berglund M, Adiels M, Taskinen MR, Borén J, Wennberg B. Improved Estimation of Human Lipoprotein Kinetics with Mixed Effects Models. PLoS One 2015; 10:e0138538. [PMID: 26422201 PMCID: PMC4589417 DOI: 10.1371/journal.pone.0138538] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 09/01/2015] [Indexed: 12/25/2022] Open
Abstract
Context Mathematical models may help the analysis of biological systems by providing estimates of otherwise un-measurable quantities such as concentrations and fluxes. The variability in such systems makes it difficult to translate individual characteristics to group behavior. Mixed effects models offer a tool to simultaneously assess individual and population behavior from experimental data. Lipoproteins and plasma lipids are key mediators for cardiovascular disease in metabolic disorders such as diabetes mellitus type 2. By the use of mathematical models and tracer experiments fluxes and production rates of lipoproteins may be estimated. Results We developed a mixed effects model to study lipoprotein kinetics in a data set of 15 healthy individuals and 15 patients with type 2 diabetes. We compare the traditional and the mixed effects approach in terms of group estimates at various sample and data set sizes. Conclusion We conclude that the mixed effects approach provided better estimates using the full data set as well as with both sparse and truncated data sets. Sample size estimates showed that to compare lipoprotein secretion the mixed effects approach needed almost half the sample size as the traditional method.
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Affiliation(s)
- Martin Berglund
- Department of Mathematical Sciences, Chalmers University of Technology and the University of Gothenburg, Göteborg, Sweden
| | - Martin Adiels
- Department of Mathematical Sciences, Chalmers University of Technology and the University of Gothenburg, Göteborg, Sweden
- Department of Molecular and Clinical Medicine, University of Gothenburg, Göteborg, Sweden
- * E-mail:
| | - Marja-Riitta Taskinen
- Department of Medicine, Cardiovascular Research Unit, Diabetes and Obesity Research Program, Heart and Lung Center, University of Helsinki, Helsinki, Finland
| | - Jan Borén
- Department of Molecular and Clinical Medicine, University of Gothenburg, Göteborg, Sweden
| | - Bernt Wennberg
- Department of Mathematical Sciences, Chalmers University of Technology and the University of Gothenburg, Göteborg, Sweden
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Desai NK, Ooi EM, Mitchell PD, Furtado J, Sacks FM. Metabolism of apolipoprotein A-II containing triglyceride rich ApoB lipoproteins in humans. Atherosclerosis 2015; 241:326-33. [PMID: 26071654 PMCID: PMC4509984 DOI: 10.1016/j.atherosclerosis.2015.05.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 04/23/2015] [Accepted: 05/11/2015] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To characterize human triglyceride-rich lipoproteins (TRL) with and without apoA-II and to study their metabolism in vivo. METHODS Plasma from 11 participants on a controlled diet given a bolus infusion of [D5]l-phenylalanine to label apoB was combined into four pools and applied to anti-apoA-II immunoaffinity columns. Fractions with and without apoA-II were separated into VLDL and IDL by ultracentrifugation; lipids and apolipoproteins were measured. For kinetic measurements, apoB was isolated and hydrolyzed to the constituent amino acids. Tracer enrichment was measured by GCMS. Metabolic rates were determined by SAAM-II. RESULTS VLDL and IDL with apoA-II comprised 7% and 9% of total VLDL and IDL apoB respectively. VLDL with apoA-II was enriched in apoC-III, apoE, and cholesterol compared to VLDL without apoA-II. Mean apoB FCR of VLDL with apoA-II was significantly lower than for VLDL without apoA-II (2.80 ± 0.96 pools/day v.s. 5.09 ± 1.69 pools/day, P = 0.009). A higher percentage of VLDL with apoA-II was converted to IDL than was cleared from circulation, compared to VLDL without apoA-II (96 ± 8% vs. 45 ± 22%; P = 0.007). The rate constants for conversion of VLDL to IDL were similar for VLDL with and without apoA-II. Thus, a very low rate constant for clearance accounted for the lower FCR of VLDL with apoA-II. CONCLUSION VLDL with apoA-II represents a small pool of VLDL particles that has a slow FCR and is predominantly converted to IDL rather than cleared from the circulation.
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Affiliation(s)
- Nirav K Desai
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, MA, USA; Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Esther M Ooi
- School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia, Australia; Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Paul D Mitchell
- Clinical Research Center, Boston Children's Hospital, Boston, MA, USA
| | - Jeremy Furtado
- Department of Nutrition, Harvard School of Public Health and Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, MA, USA
| | - Frank M Sacks
- Department of Nutrition, Harvard School of Public Health and Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, MA, USA.
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Lassman ME, McAvoy T, Lee AYH, Chappell D, Wong O, Zhou H, Reyes-Soffer G, Ginsberg HN, Millar JS, Rader DJ, Gutstein DE, Laterza O. Practical immunoaffinity-enrichment LC-MS for measuring protein kinetics of low-abundance proteins. Clin Chem 2014; 60:1217-24. [PMID: 24751376 DOI: 10.1373/clinchem.2014.222455] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND For a more complete understanding of pharmacodynamic, metabolic, and pathophysiologic effects, protein kinetics, such as production rate and fractional catabolic rate, can offer substantially more information than protein concentration alone. Kinetic experiments with stable isotope tracers typically require laborious sample preparation and are most often used for studying abundant proteins. Here we describe a practical methodology for measuring isotope enrichment into low-abundance proteins that uses an automated procedure and immunoaffinity enrichment (IA) with LC-MS. Low-abundance plasma proteins cholesteryl ester transfer protein (CETP) and proprotein convertase subtilisin/kexin type 9 (PCSK9) were studied as examples. METHODS Human participants (n = 39) were infused with [(2)H(3)]leucine, and blood samples were collected at multiple time points. Sample preparation and analysis were automated and multiplexed to increase throughput. Proteins were concentrated from plasma by use of IA and digested with trypsin to yield proteotypic peptides that were analyzed by microflow chromatography-mass spectrometry to measure isotope enrichment. RESULTS The IA procedure was optimized to provide the greatest signal intensity. Use of a gel-free method increased throughput while increasing the signal. The intra- and interassay CVs were <15% at all isotope enrichment levels studied. More than 1400 samples were analyzed in <3 weeks without the need for instrument stoppages or user interventions. CONCLUSIONS The use of automated gel-free methods to multiplex the measurement of isotope enrichment was applied to the low-abundance proteins CETP and PCSK9.
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Affiliation(s)
| | | | | | | | | | | | | | - Henry N Ginsberg
- Molecular Biomarkers and Diagnostics, Molecular Biomarkers-PPDM, and Clinical Pharmacology, Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Whitehouse Station, NJ; Columbia University Medical Center, New York, NY; Division of Translational Medicine and Human Genetics, University of Pennsylvania, Philadelphia, PA
| | - John S Millar
- Division of Translational Medicine and Human Genetics, University of Pennsylvania, Philadelphia, PA
| | - Daniel J Rader
- Division of Translational Medicine and Human Genetics, University of Pennsylvania, Philadelphia, PA
| | - David E Gutstein
- Clinical Pharmacology, Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Whitehouse Station, NJ
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18
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Lu J, Mazer NA, Hübner K. Mathematical models of lipoprotein metabolism and kinetics: current status and future perspective. ACTA ACUST UNITED AC 2013. [DOI: 10.2217/clp.13.52] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Postprandial hypertriglyceridemia and cardiovascular disease: current and future therapies. Curr Atheroscler Rep 2013; 15:309. [PMID: 23345190 DOI: 10.1007/s11883-013-0309-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Exaggerated postprandial hypertriglyceridemia is a risk factor for cardiovascular disease. This metabolic abnormality is principally due to overproduction and/or decreased catabolism of triglyceride-rich lipoproteins (TRLs) and is a consequence of pathogenic genetic variations and other coexistent medical conditions, particularly obesity and insulin resistance. Accumulation of TRL in the postprandial state promotes the formation of small, dense low-density lipoproteins, as well as oxidative stress, inflammation, and endothelial dysfunction, all of which compound the risk of cardiovascular disease. The cardiovascular benefits of lifestyle modification (weight loss and exercise) and conventional lipid-lowering therapies (statins, fibrates, niacin, ezetimibe, and n-3 fatty acid supplementation) could involve their favorable effects on TRL metabolism. New agents, such as dual peroxisome-proliferator-activated receptor α/δ agonists, diacylglycerol, inhibitors of diacylglycerol acyltransferase 1 and microsomal triglyceride transfer protein, antisense oligonucleotides for apolipoprotein B-100 and apolipoprotein C-III, and incretin-based therapies, may enhance the treatment of postprandial lipemia, but their efficacy needs to be tested in clinical end point trials. Further work is required to develop a simple clinical protocol for investigating postprandial lipemia, as well as internationally agreed management guidelines for this type of dyslipidemia.
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20
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Ooi EMM, Ng TWK, Watts GF, Barrett PHR. Dietary fatty acids and lipoprotein metabolism: new insights and updates. Curr Opin Lipidol 2013; 24:192-7. [PMID: 23619368 DOI: 10.1097/mol.0b013e3283613ba2] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
PURPOSE OF REVIEW Dyslipidemia is a powerful risk factor for cardiovascular disease (CVD). Dietary fatty acid composition regulates lipids and lipoprotein metabolism and may confer CVD benefit. This review updates understanding of the effect of dietary fatty acids on lipoprotein metabolism in humans. RECENT FINDINGS High dietary fish-derived n-3 polyunsaturated fatty acid (PUFA) consumption diminished hepatic triglyceride-rich lipoprotein (TRL) secretion and enhanced TRL to LDL conversion. n-3 PUFA also decreased TRL-apoB-48 concentration by decreasing TRL-apoB-48 secretion. High n-6 PUFA intake decreased liver fat, and plasma proprotein convertase subtilisin/kexin type 9, triglycerides, total-cholesterol and LDL-cholesterol concentrations. Intake of saturated fatty acids with increased palmitic acid at the sn-2 position was associated with decreased postprandial lipemia, which might be due to decreased triglyceride absorption. Replacing carbohydrate with monounsaturated fatty acids increased TRL catabolism. Ruminant trans-fatty acid decreased HDL cholesterol, but the mechanisms are unknown. A new role for APOE genotype in regulating lipid responses was also described. SUMMARY The major advances in understanding the effect of dietary fatty acids on lipoprotein metabolism have focused on n-3 PUFA. This knowledge provides insights into the importance of regulating lipoprotein metabolism as a mode to improve plasma lipids and potential CVD risk. Further studies are required to better understand the cardiometabolic effects of other dietary fatty acids.
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Affiliation(s)
- Esther M M Ooi
- Metabolic Research Centre, School of Medicine & Pharmacology, University of Western Australia, Perth, Western Australia, Australia
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21
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Schwaiger JP, Nakada Y, Berberich R, Ikewaki K, Dieplinger B, Zitt E, Neyer U, Salmhofer H, Kronenberg F, Koenig P, Dieplinger H. Lipoprotein kinetics in male hemodialysis patients treated with atorvastatin. Clin J Am Soc Nephrol 2013; 8:1319-26. [PMID: 23599405 DOI: 10.2215/cjn.10881012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES In vivo metabolism of atherogenic apolipoprotein B (apoB)-containing lipoproteins is severely impaired in patients undergoing hemodialysis (HD), resulting in markedly prolonged residence times of these particles. It is unclear whether treatment with statins improves LDL kinetics in HD patients as is known for the general population. Therefore, this kinetic study assessed apoB-containing lipoproteins in these patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Kinetic measures were analyzed with stable-isotope technology in six men undergoing HD before and after 3 months of daily administration of 10 mg of atorvastatin. Patients were 18-65 years of age, had LDL cholesterol levels between 90 and 200 mg/dl, and had been treated with HD for >6 months. They consumed a standardized isocaloric diet for 3 days before analysis. Fractional catabolic rates (FCRs) and production rates of very-low-density lipoprotein (VLDL)-apoB, intermediate-density lipoprotein-apoB, and LDL-apoB were determined using multicompartment modeling after plasma lipoprotein separation, precipitation of apoB, and determination of tracer-to-tracee ratios using mass spectrometry. RESULTS Plasma concentrations of VLDL- and LDL-apoB were significantly lower (mean ± SD, 7.77±2.62 versus 11.27±6.15 mg/dl, P<0.05; 56.9±23.9 versus 84.0±21.1 mg/dl, P=0.03) and their FCRs were significantly higher (7.20±3.08 versus 5.20±2.98 days(-1), P<0.05; 0.851±0.772 versus 0.446±0.232 days(-1), P<0.05) after 3 months of atorvastatin treatment. Accordingly, the residence times in plasma of VLDL- and LDL-apoB were significantly lower after treatment (0.14 versus 0.19 day and 1.2 versus 2.2 days, respectively). CONCLUSION Lower plasma concentrations and improved kinetics of atherogenic lipoproteins were observed in HD patients after administration of low-dose atorvastatin.
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Affiliation(s)
- Johannes P Schwaiger
- Division of Genetic Epidemiology, Department of Medical Genetics and Molecular Pharmacology, Innsbruck Medical University, Innsbruck, Austria
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22
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Thongtang N, Diffenderfer MR, Ooi EMM, Asztalos BF, Dolnikowski GG, Lamon-Fava S, Schaefer EJ. Linkage between C-reactive protein and triglyceride-rich lipoprotein metabolism. Metabolism 2013; 62:369-75. [PMID: 23018145 PMCID: PMC4315144 DOI: 10.1016/j.metabol.2012.08.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 08/14/2012] [Accepted: 08/15/2012] [Indexed: 01/17/2023]
Abstract
OBJECTIVE Inflammation plays an important role in atherosclerosis. Elevated C-reactive protein (CRP) levels are associated with a greater risk of cardiovascular disease. Our goal was to study CRP metabolism, and to determine its relationship with lipoprotein metabolism using stable isotope methodology. MATERIAL/METHODS Eight subjects with combined hyperlipidemia underwent a 15-h primed-constant infusion with deuterated leucine. CRP was purified from the plasma density fraction greater than 1.21g/ml by affinity chromatography. Lipoprotein fractions were separated by sequential ultracentrifugation. Isotope enrichment was determined by gas chromatography/mass spectrometry. RESULTS The subjects had mean LDL-C levels of 147.5mg/dl and mean CRP levels of 3.4mg/l. The mean CRP production rate (PR) was 0.050±0.012mg/kg/day and the mean CRP fractional catabolic rate (FCR) was 0.343±0.056 pools/day (residence time 2.92days). CRP pool size (PS) was significantly related to production (r=0.93; p<0.001), but not FCR. CRP PS was also related to body mass index (r=0.79; p=0.02). There was a significant association between CRP FCR and TRL apoB-100 FCR (r=0.74, p=0.04), as well as between CRP PS and TRL apoB-48 FCR (r=-0.90, p=0.002), indicating linkage between CRP and TRL metabolism. CONCLUSION The main determinant of plasma CRP levels was CRP production rate. Moreover a significant linkage between CRP metabolism and both TRL apoB-100 and apoB-48 catabolism was noted.
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Watts GF, Chan DC. Novel insights into the regulation of postprandial lipemia by glucagon-like peptides: significance for diabetes. Diabetes 2013; 62:336-8. [PMID: 23349538 PMCID: PMC3554347 DOI: 10.2337/db12-1098] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Gerald F Watts
- School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia.
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24
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Vergès B, Guiu B, Cercueil JP, Duvillard L, Robin I, Buffier P, Bouillet B, Aho S, Brindisi MC, Petit JM. Retinol-binding protein 4 is an independent factor associated with triglycerides and a determinant of very low-density lipoprotein-apolipoprotein B100 catabolism in type 2 diabetes mellitus. Arterioscler Thromb Vasc Biol 2012; 32:3050-7. [PMID: 23087360 DOI: 10.1161/atvbaha.112.255190] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Retinol-binding protein 4 (rbp4) is an adipokine secreted by adipocytes and liver, whose levels are elevated in type 2 diabetes mellitus (T2DM). Plasma levels of rbp4 and triglycerides are strongly correlated in T2DM. However, we do not know whether this association is direct or indirect via liver fat content, and the link between rbp4 and triglyceride metabolism remains unknown. METHODS AND RESULTS Liver fat measurement by proton spectroscopy was performed in 221 patients with T2DM, and an in vivo kinetic study with stable isotopes was carried out in 14 patients with T2DM. In multivariate analysis, triglycerides were associated positively with rbp4 (β=0.273, P<0.0001), apolipoprotein (apo) B (β=0.258, P<0.0001), and liver fat (β=0.191, P=0.002) and negatively with high-density lipoprotein cholesterol (β=-0.442, P<0.0001). rbp4 was correlated positively with apoB100 very-low-density lipoprotein (VLDL) pool (r=0.62, P=0.017) and negatively with VLDL-apoB100 total fractional catabolic rate (r=-0.66, P=0.001). In multivariate analysis, rbp4 (P=0.015), plasma triglycerides (P=0.024), and sex (P=0.026) were independently associated with VLDL-apoB100 total fractional catabolic rate. CONCLUSIONS In T2DM, plasma rbp4 level is associated with plasma triglycerides, independently of liver fat content. There is a strong independent negative correlation between plasma rbp4 and VLDL-apoB100 total fractional catabolic rate. These data suggest that rbp4 may be involved in the pathophysiology of hypertriglyceridemia in T2DM by reducing VLDL catabolism.
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Affiliation(s)
- Bruno Vergès
- Department of Endocrinology-Diabetology, University Hospital, Dijon, France.
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25
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Chan DC, Hoang A, Barrett PHR, Wong ATY, Nestel PJ, Sviridov D, Watts GF. Apolipoprotein B-100 and apoA-II kinetics as determinants of cellular cholesterol efflux. J Clin Endocrinol Metab 2012; 97:E1658-66. [PMID: 22745238 DOI: 10.1210/jc.2012-1522] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Cellular cholesterol efflux is a key step in reverse cholesterol transport and may depend on the metabolism of apolipoprotein (apo) B-100, apoA-I, and apoA-II. OBJECTIVE We examined the associations between cholesterol efflux and plasma concentrations and kinetics of very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL)-apoB-100, high-density lipoprotein (HDL)-apoA-I, and HDL-apoA-II in men. DESIGN, SUBJECTS, AND METHODS: Thirty men were recruited from the community with a wide range of body mass index. The capacity of plasma and HDL to efflux cholesterol was measured ex vivo. Apolipoprotein kinetics were measured using stable isotope techniques and multicompartmental modeling. RESULTS Cholesterol efflux to whole plasma was correlated with plasma levels of cholesterol, triglyceride, apoB-100, insulin, cholesteryl ester transfer protein, and lecithin-cholesterol acyltransferase, body mass index and waist circumference (P < 0.05 in all). Cholesterol efflux was inversely correlated with the fractional catabolic rate (FCR) of VLDL (r = -0.728), IDL (r = -0.662), and LDL-apoB-100 (r = -0.479) but positively correlated with the FCR (r = 0.438) and production rate (r = 0.468) of HDL-apoA-II. In multiple regression analysis, the concentration and FCR of VLDL-apoB-100 (β-coefficient = 0.708 and -0.518, respectively) and IDL-apoB-100 (β-coefficient = 0.354 and -0.447, respectively) were independent predictors of cholesterol efflux. The association of cholesterol efflux with apoB-100 metabolism was diminished after removal of apoB-100-containing lipoproteins from plasma prior to efflux. All associations, except for cholesteryl ester transfer protein, were lost when cholesterol efflux to isolated HDL was tested. CONCLUSIONS The plasma concentration and kinetics of apoB-100-containing lipoproteins are significant predictors of the capacity of whole plasma to effect cellular cholesterol efflux.
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Affiliation(s)
- Dick C Chan
- School of Medicine and Pharmacology, University of Western Australia, Royal Perth Hospital, G.P.O. Box X2213, Perth, Western Australia 6847, Australia
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Ramos-Roman MA, Lapidot SA, Phair RD, Parks EJ. Insulin activation of plasma nonesterified fatty acid uptake in metabolic syndrome. Arterioscler Thromb Vasc Biol 2012; 32:1799-808. [PMID: 22723441 DOI: 10.1161/atvbaha.112.250019] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Insulin control of fatty acid metabolism has long been deemed dominated by suppression of adipose lipolysis. The goal of the present study was to test the hypothesis that this single role of insulin is insufficient to explain observed fatty acid dynamics. METHODS AND RESULTS Fatty acid kinetics were measured during a meal tolerance test and insulin sensitivity assessed by intravenous glucose tolerance test in overweight human subjects (n=15; body mass index, 35.8 ± 7.1 kg/m(2)). Non-steady state tracer kinetic models were formulated and tested using ProcessDB software. Suppression of adipose fatty acid release, by itself, could not account for postprandial nonesterified fatty acid concentration changes, but adipose suppression combined with insulin activation of fatty acid uptake was consistent with the measured data. The observed insulin K(m) for nonesterified fatty acid uptake was inversely correlated with both insulin sensitivity of glucose uptake (intravenous glucose tolerance test insulin sensitivity; r=-0.626; P=0.01) and whole body fat oxidation after the meal (r=-0.538; P=0.05). CONCLUSIONS These results support insulin regulation of fatty acid turnover by both release and uptake mechanisms. Activation of fatty acid uptake is consistent with the human data, has mechanistic precedent in cell culture, and highlights a new potential target for therapies aimed at improving the control of fatty acid metabolism in insulin-resistant disease states.
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Affiliation(s)
- Maria A Ramos-Roman
- Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390-9052, USA
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Abstract
To develop novel strategies for the prevention and treatment of dyslipidaemia, it is essential to understand the pathophysiology of dyslipoproteinaemia in humans. Lipoprotein metabolism is a complex system in which abnormal concentrations of various lipoprotein particles can result from alterations in their rates of production, conversion and/or catabolism. Traditional methods that measure plasma lipoprotein concentrations only provide static estimates of lipoprotein metabolism and hence limited mechanistic information. By contrast, the use of tracers labelled with stable isotopes and mathematical modelling provides a powerful tool for probing lipid and lipoprotein kinetics in vivo and furthering understanding of the pathogenesis of dyslipoproteinaemia.
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Affiliation(s)
- J Borén
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden.
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28
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Vergès B, Duvillard L, Brindisi MC, Gautier E, Krempf M, Costet P, Cariou B. Lack of association between plasma PCSK9 and LDL-apoB100 catabolism in patients with uncontrolled type 2 diabetes. Atherosclerosis 2011; 219:342-8. [DOI: 10.1016/j.atherosclerosis.2011.07.098] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 07/04/2011] [Accepted: 07/14/2011] [Indexed: 11/26/2022]
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Ooi EMM, Watts GF, Sprecher DL, Chan DC, Barrett PHR. Mechanism of action of a peroxisome proliferator-activated receptor (PPAR)-delta agonist on lipoprotein metabolism in dyslipidemic subjects with central obesity. J Clin Endocrinol Metab 2011; 96:E1568-76. [PMID: 21816786 DOI: 10.1210/jc.2011-1131] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Dyslipidemia increases the risk of cardiovascular disease in obesity. Peroxisome proliferator-activated receptor (PPAR)-δ agonists decrease plasma triglycerides and increase high-density lipoprotein (HDL)-cholesterol in humans. OBJECTIVE The aim of the study was to examine the effect of GW501516, a PPAR-δ agonist, on lipoprotein metabolism. Design, Setting, and Intervention: We conducted a randomized, double-blind, crossover trial of 6-wk intervention periods with placebo or GW501516 (2.5 mg/d), with 2-wk placebo washout between treatment periods. PARTICIPANTS We recruited 13 dyslipidemic men with central obesity from the general community. MAIN OUTCOME MEASURES We measured the kinetics of very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein-, and low-density lipoprotein (LDL)-apolipoprotein (apo) B-100, plasma apoC-III, and high-density lipoprotein (HDL) particles (LpA-I and LpA-I:A-II). RESULTS GW501516 decreased plasma triglycerides, fatty acid, apoB-100, and apoB-48 concentrations. GW501516 decreased the concentrations of VLDL-apoB by increasing its fractional catabolism and of apoC-III by decreasing its production rate (P < 0.05). GW501516 reduced VLDL-to-LDL conversion and LDL-apoB production. GW501516 increased HDL-cholesterol, apoA-II, and LpA-I:A-II concentrations by increasing apoA-II and LpA-I:A-II production (P < 0.05). GW501516 decreased cholesteryl ester transfer protein activity, and this was paralleled by falls in the triglyceride content of VLDL, LDL, and HDL and the cholesterol content of VLDL and LDL. CONCLUSIONS GW501516 increased the hepatic removal of VLDL particles, which might have resulted from decreased apoC-III concentration. GW501516 increased apoA-II production, resulting in an increased concentration of LpA-I:A-II particles. This study elucidates the mechanism of action of this PPAR-δ agonist on lipoprotein metabolism and supports its potential use in treating dyslipidemia in obesity.
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Affiliation(s)
- Esther M M Ooi
- Metabolic Research Centre, School of Medicine and Pharmacology, University of Western Australia, GPO Box X2213, Perth, Western Australia 6847, Australia
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Ramakrishnan R, Ramakrishnan JD. A state space transformation can yield identifiable models for tracer kinetic studies with enrichment data. Bull Math Biol 2010; 72:2019-46. [PMID: 20195911 PMCID: PMC3275642 DOI: 10.1007/s11538-010-9522-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 02/09/2010] [Indexed: 10/19/2022]
Abstract
Tracer studies are analyzed almost universally by multicompartmental models where the state variables are tracer amounts or activities in the different pools. The model parameters are rate constants, defined naturally by expressing fluxes as fractions of the source pools. We consider an alternative state space with tracer enrichments or specific activities as the state variables, with the rate constants redefined by expressing fluxes as fractions of the destination pools. Although the redefinition may seem unphysiological, the commonly computed fractional synthetic rate actually expresses synthetic flux as a fraction of the product mass (destination pool). We show that, for a variety of structures, provided the structure is linear and stationary, the model in the enrichment state space has fewer parameters than that in the activities state space, and is hence better both to study identifiability and to estimate parameters. The superiority of enrichment modeling is shown for structures where activity model unidentifiability is caused by multiple exit pathways; on the other hand, with a single exit pathway but with multiple untraced entry pathways, activity modeling is shown to be superior. With the present-day emphasis on mass isotopes, the tracer in human studies is often of a precursor, labeling most or all entry pathways. It is shown that for these tracer studies, models in the activities state space are always unidentifiable when there are multiple exit pathways, even if the enrichment in every pool is observed; on the other hand, the corresponding models in the enrichment state space have fewer parameters and are more often identifiable. Our results suggest that studies with labeled precursors are modeled best with enrichments.
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Affiliation(s)
- Rajasekhar Ramakrishnan
- Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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Chan DC, Watts GF. Dyslipidaemia in the metabolic syndrome and type 2 diabetes: pathogenesis, priorities, pharmacotherapies. Expert Opin Pharmacother 2010; 12:13-30. [PMID: 20629587 DOI: 10.1517/14656566.2010.502529] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
IMPORTANCE OF THE FIELD Dyslipoproteinaemia is a cardinal feature of the metabolic syndrome that accelerates atherosclerosis. It is usually characterized by high plasma concentrations of triglyceride-rich and apolipoprotein B (apoB)-containing lipoproteins, with depressed concentrations of high-density lipoprotein (HDL). Drug interventions are essential for normalizing metabolic dyslipidaemia. AREAS COVERED IN THIS REVIEW This review discusses the mechanisms and treatment for dyslipidaemia in the metabolic syndrome and type 2 diabetes. WHAT THE READER WILL GAIN A comprehensive understanding of the pathophysiology and pharmacotherapy of dyslipidaemia in the metabolic syndrome and diabetes. TAKE HOME MESSAGE Dysregulation of lipoprotein metabolism may be due to a combination of overproduction of triglyceride-rich lipoproteins, decreased catabolism of apoB-containing particles, and increased catabolism of HDL particles. These abnormalities may be consequent on a global metabolic effect of insulin resistance and an excess of both visceral and hepatic fat. Lifestyle modifications may favourably alter lipoprotein transport in the metabolic syndrome. Patients with dyslipidaemia and established cardiovascular disease should receive a statin as first-line therapy. Combination with other lipid-regulating agents, such as ezetimibe, fibrates, niacins and fish oils may optimize the benefit of statin on atherogenic dyslipidaemia.
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Affiliation(s)
- Dick C Chan
- University of Western Australia, Metabolic Research Centre, School of Medicine and Pharmacology, GPO Box X2213, Perth, WA 6847, Australia.
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Mechanisms for therapeutic correction of dyslipidaemia in insulin resistance and diabetes. ATHEROSCLEROSIS SUPP 2010; 11:61-4. [PMID: 20452838 DOI: 10.1016/j.atherosclerosissup.2010.04.044] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 04/21/2010] [Indexed: 11/21/2022]
Abstract
Dyslipidaemia is a common cardiovascular risk factor in insulin resistant subjects with obesity, type 2 diabetes mellitus and the metabolic syndrome. Lipoprotein metabolism is complex and abnormal plasma concentrations result from alterations in the rates of production and/or catabolism of diverse lipoprotein particles. Understanding the dysregulation and therapeutic correction of lipoprotein transport in insulin resistant states has relied on the use of stable isotope tracers and modelling methods. The effects of lifestyle and therapeutic interventions on the kinetics of apolipoproteins B-100 and A-I containing lipoproteins are reviewed.
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Abstract
PURPOSE OF REVIEW We review stable isotope tracer studies of apolipoprotein B-100 (apoB) kinetics concerning genetic polymorphisms and mutations that affect human lipoprotein metabolism. RECENT FINDINGS In obese men, the allelic combination of the apoB signal peptide, SP24, and cholesteryl ester transfer protein, CETP B1B1, is independently associated with lower VLDL apoB secretion. Microsomal triglyceride transfer protein -493G/T carriers have reduced IDL apoB and LDL apoB production as compared with controls. Mutations in cholesterol transporters (ATP-binding cassette transporter G8 and Niemann-Pick C1 Like 1) are associated with reduced VLDL apoB secretion and increased LDL apoB production and catabolism. The ATP-binding cassette transporter G8 400K variant is a significant, independent predictor of VLDL apoB secretion. Mutations in lipases (lipoprotein lipase and hepatic lipase) and transfer proteins (lecithin-cholesterol acyltransferase and cholesteryl ester transfer protein) alter their functional activity, which impact on VLDL and LDL kinetics. SUMMARY Mutations in genes that regulate intrahepatic apoB assembly and lipid substrate availability to the liver impact on VLDL apoB secretion. Lipoprotein tracer studies can provide functional insight into the potential impact of genetic polymorphisms in regulating apoB metabolism in humans.
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Affiliation(s)
- Theodore W K Ng
- Metabolic Research Centre, School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia, Australia
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Therapeutic regulation of apoB100 metabolism in insulin resistance in vivo. Pharmacol Ther 2009; 123:281-91. [DOI: 10.1016/j.pharmthera.2009.04.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 04/16/2009] [Indexed: 11/16/2022]
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Abstract
PURPOSE OF REVIEW To review new data concerning HDL metabolism and cardiovascular disease, the concept of HDL 'functionality', and HDL kinetics in the metabolic syndrome. RECENT FINDINGS HDL-apoA-I and apoA-II may be better predictors of cardiovascular disease than HDL-cholesterol. Cholesteryl ester transfer protein inhibition with torcetrapib does not benefit cardiovascular disease; whether this is related to 'congestion' of HDL transport or a specific off-target vasopressor effect remains unclear. Accelerated catabolism of HDL particles in metabolic syndrome could be due to increased hepatic secretion of apoB and apoC-III, hepatic steatosis, and low plasma adiponectin. The role of serum amyloid A and homocysteine is uncertain. In metabolic syndrome, therapies that could favourably alter HDL transport include weight loss, fish oils, higher dose statins, and fibrates; 'balancing feedback' may offset reduced catabolism of HDL, fenofibrate being the only agent hitherto shown to increase apoA-I production. SUMMARY Elevating HDL-apoA-I and apoA-II may be a more important therapeutic objective than increased HDL-cholesterol. Recent studies underscore the potential value of studying HDL functionality, particularly in the metabolic syndrome. Reverse cholesterol transport can only be reliably probed at present by studying the kinetics of HDL particles or apolipoproteins; new methods are needed for investigating cellular and whole body cholesterol turnover. In metabolic syndrome, HDL-raising therapies have differential impact on HDL kinetics, the optimal endpoint being to increase transport and concentration with unchanged or accelerated catabolism.
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Affiliation(s)
- Gerald F Watts
- Metabolic Research Centre, School of Medicine and Pharmacology, University of Western Australia, Perth, Australia.
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Ramakrishnan R, Ramakrishnan JD. Using mass measurements in tracer studies--a systematic approach to efficient modeling. Metabolism 2008; 57:1078-87. [PMID: 18640385 PMCID: PMC2601710 DOI: 10.1016/j.metabol.2008.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Accepted: 03/27/2008] [Indexed: 10/24/2022]
Abstract
Tracer enrichment data are fitted by multicompartmental models to estimate rate constants and fluxes or transport rates. In apolipoprotein turnover studies, mass measurements are also available, for example, apolipoprotein B levels in very low-density lipoprotein, intermediate-density lipoprotein, and low-density lipoprotein, and are often essential to calculate some of the rate constants. The usual method to use mass measurements is to estimate pool masses along with rate constants. A systematic alternative approach is developed to use flux balances around pools to express some rate constants in terms of the other rate constants and the measured masses. The resulting reduction in the number of parameters to be estimated makes the modeling more efficient. In models that would be unidentifiable without mass measurements, the usual approach and the proposed approach yield identical results. In a simple two-pool model, the number of unknown parameters is reduced from 4 to 2. In a published five-pool model for apolipoprotein B kinetics with three mass measurements, the number of parameters is reduced from 12 to 9. With m mass measurements, the number of responses to be fitted and the number of parameters to be estimated are each reduced by m, a simplification by 1/4 to 1/3 in a typical pool model. Besides a proportionate reduction in computational effort, there is a further benefit because the dimensionality of the problem is also decreased significantly, which means ease of convergence and a smaller likelihood of suboptimal solutions. Although our approach is conceptually straightforward, the dependencies get considerably more complex with increasing model size. To generate dependency definitions automatically, a Web-accessible program is available at http://biomath.info/poolfit/constraints.
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Affiliation(s)
- Rajasekhar Ramakrishnan
- Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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37
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Computational lipidology: predicting lipoprotein density profiles in human blood plasma. PLoS Comput Biol 2008; 4:e1000079. [PMID: 18497853 PMCID: PMC2361219 DOI: 10.1371/journal.pcbi.1000079] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Accepted: 04/04/2008] [Indexed: 01/14/2023] Open
Abstract
Monitoring cholesterol levels is strongly recommended to identify patients at risk for myocardial infarction. However, clinical markers beyond "bad" and "good" cholesterol are needed to precisely predict individual lipid disorders. Our work contributes to this aim by bringing together experiment and theory. We developed a novel computer-based model of the human plasma lipoprotein metabolism in order to simulate the blood lipid levels in high resolution. Instead of focusing on a few conventionally used predefined lipoprotein density classes (LDL, HDL), we consider the entire protein and lipid composition spectrum of individual lipoprotein complexes. Subsequently, their distribution over density (which equals the lipoprotein profile) is calculated. As our main results, we (i) successfully reproduced clinically measured lipoprotein profiles of healthy subjects; (ii) assigned lipoproteins to narrow density classes, named high-resolution density sub-fractions (hrDS), revealing heterogeneous lipoprotein distributions within the major lipoprotein classes; and (iii) present model-based predictions of changes in the lipoprotein distribution elicited by disorders in underlying molecular processes. In its present state, the model offers a platform for many future applications aimed at understanding the reasons for inter-individual variability, identifying new sub-fractions of potential clinical relevance and a patient-oriented diagnosis of the potential molecular causes for individual dyslipidemia.
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38
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Abstract
The concurrence of visceral obesity, insulin resistance and dyslipidaemia comprises the concept of the metabolic syndrome. The metabolic syndrome is an escalating problem in developed and developing societies that tracks with the obesity epidemic. Dyslipidaemia in the metabolic syndrome is potently atherogenic and, hence, is a major risk factor for CVD (cardiovascular disease) in these subjects. It is globally characterized by hypertriglyceridaemia, near normal LDL (low-density lipoprotein)-cholesterol and low plasma HDL (high-density lipoprotein)-cholesterol. ApoC-III (apolipoprotein C-III), an important regulator of lipoprotein metabolism, is strongly associated with hypertriglyceridaemia and the progression of CVD. ApoC-III impairs the lipolysis of TRLs [triacylglycerol (triglyceride)-rich lipoproteins] by inhibiting lipoprotein lipase and the hepatic uptake of TRLs by remnant receptors. In the circulation, apoC-III is associated with TRLs and HDL, and freely exchanges among these lipoprotein particle systems. However, to fully understand the complex physiology and pathophysiology requires the application of tracer methodology and mathematical modelling. In addition, experimental evidence shows that apoC-III may also have a direct role in atherosclerosis. In the metabolic syndrome, increased apoC-III concentration, resulting from hepatic overproduction of VLDL (very-LDL) apoC-III, is strongly associated with delayed catabolism of triacylglycerols and TRLs. Several therapies pertinent to the metabolic syndrome, such as PPAR (peroxisome-proliferator-activated receptor) agonists and statins, can regulate apoC-III transport in the metabolic syndrome. Regulating apoC-III metabolism may be an important new therapeutic approach to managing dyslipidaemia and CVD risk in the metabolic syndrome.
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Ooi EMM, Watts GF, Nestel PJ, Sviridov D, Hoang A, Barrett PHR. Dose-dependent regulation of high-density lipoprotein metabolism with rosuvastatin in the metabolic syndrome. J Clin Endocrinol Metab 2008; 93:430-7. [PMID: 18029469 PMCID: PMC2729151 DOI: 10.1210/jc.2007-0854] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Low plasma concentration of high-density lipoprotein (HDL) cholesterol is a risk factor for cardiovascular disease and a feature of the metabolic syndrome. Rosuvastatin has been shown to increase HDL cholesterol concentration, but the mechanisms remain unclear. METHODS AND RESULTS Twelve men with the metabolic syndrome were studied in a randomized, double-blind, crossover trial of 5-wk therapeutic periods with placebo, 10 mg/d rosuvastatin, or 40 mg/d rosuvastatin, with 2-wk placebo washout between each period. Compared with placebo, there was a significant dose-dependent increase in HDL cholesterol, HDL particle size, and concentration of HDL particles that contain apolipoprotein A-I (LpA-I). The increase in LpA-I concentration was associated with significant dose-dependent reductions in triglyceride concentration and LpA-I fractional catabolic rate, with no changes in LpA-I production rate. There was a significant dose-dependent reduction in the fractional catabolic rate of HDL particles containing both apolipoprotein A-I and A-II (LpA-I:A-II), with concomitant reduction in LpA-I:A-II production rate, and hence no change in LpA-I:A-II concentration. CONCLUSIONS Rosuvastatin dose-dependently increased plasma HDL cholesterol and LpA-I concentrations in the metabolic syndrome. This could relate to reduction in plasma triglycerides with remodeling of HDL particles and reduction in LpA-I fractional catabolism. The findings contribute to understanding mechanisms for the HDL-raising effect of rosuvastatin in the metabolic syndrome with implications for reduction in cardiovascular disease.
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Affiliation(s)
- Esther M M Ooi
- Metabolic Research Centre, School of Medicine and Pharmacology, Royal Perth Hospital, University of Western Australia, Perth, Western Australia 6847, Australia
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Ramakrishnan R. Alternative equations for whole-body protein synthesis and for fractional synthetic rates of proteins. Metabolism 2007; 56:1550-60. [PMID: 17950107 PMCID: PMC2435311 DOI: 10.1016/j.metabol.2007.06.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Accepted: 06/29/2007] [Indexed: 12/01/2022]
Abstract
In a constant infusion study of a mass isotope of leucine, two alternative equations are commonly available to calculate amino acid oxidation rate and, thence, whole-body protein synthesis. One, developed by Matthews et al (Am J Physiol Endocrinol Metab. 1980;238:E473-E479), is shown here to require assuming a tracee steady state (TSS), namely, that tracee (unlabeled) amino acid concentrations and fluxes (rates of oxidation and incorporation into protein) are unaltered compared with the preinfusion state. The other, developed by Garlick and coworkers (Melville et al, Metabolism 1989;38:248-255), stems from a protein steady state (PSS) assumption, namely, that protein synthesis is unaffected by the tracer infusion. We derive here a simple expression for the relative difference in whole-body protein synthesis computed from the two assumptions, and a simple test of the validity of TSS in the form of an equality that must be satisfied by plasma measurements at all times. We also propose two experiments to discriminate between the two assumptions. Theoretical reasons and experimental evidence from the literature are offered to support PSS. The two assumptions result in different expressions for fractional synthetic rates (FSRs) of individual or organ proteins-TSS requires the use of tracer-to-tracee ratios and PSS the use of enrichments. An expression is derived here for the relative difference in FSR with TSS vs PSS. For both whole-body synthesis and for FSR, the TSS assumption consistently results in an underestimate, the relative bias roughly equal to the precursor amino acid enrichment.
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Affiliation(s)
- Rajasekhar Ramakrishnan
- Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York NY 10032, USA.
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Suckling K. Drug discovery in the metabolic syndrome: context and some recent developments. Expert Opin Ther Targets 2007; 11:801-8. [PMID: 17504017 DOI: 10.1517/14728222.11.6.801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The metabolic syndrome, encompassing the clinically distinct but related areas of dyslipidaemia, insulin resistance, obesity and vascular disease, offers a wide arena for drug discovery. There is substantial and growing unmet medical need, particularly as the worldwide epidemic of obesity continues to develop. There are also many targets and biological mechanisms that can be exploited. However, the context for clinical development is challenging because of the many ways in which the syndrome can be approached. As with most therapeutic areas, preclinical data provide only limited confidence in the potential of a novel target in humans. In this review, the author outlines the context for drug discovery in the metabolic syndrome, the clinical and biological scope and recent developments in preclinical models. Finally, existing examples of drug targets for a range of biological mechanisms are considered, outlining their biology and points relevant to lead identification and optimisation and clinical development.
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Magkos F, Patterson BW, Mittendorfer B. Reproducibility of stable isotope-labeled tracer measures of VLDL-triglyceride and VLDL-apolipoprotein B-100 kinetics. J Lipid Res 2007; 48:1204-11. [PMID: 17325388 DOI: 10.1194/jlr.d600048-jlr200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
To gain insight into the mechanisms regulating plasma lipid homeostasis, FFA, VLDL-triglyceride (TG), and VLDL-apolipoprotein B-100 (apoB-100) kinetics are commonly assessed using stable isotope-labeled tracer methods. The reproducibility of these measurements, which is critical for the experimental design, is unknown. Therefore, we investigated the repeatability of plasma FFA, VLDL-TG, and VLDL-apoB-100 kinetics in eight healthy men using stable isotope-labeled tracer techniques. There were no systematic differences in plasma FFA, VLDL-TG, and VLDL-apoB-100 concentrations and kinetics between the two studies. Intraindividual day-to-day variability for various outcome variables ranged from 15% to 25%, and almost all of this was of biological origin. The most robust outcome variables were FFA rate of appearance and hepatic VLDL-TG and VLDL-apoB-100 secretion rates; the least robust were VLDL-TG and VLDL-apoB-100 plasma clearance rates and mean residence times. Overall, physiologically meaningful differences in mean values (i.e., 25-30% in magnitude) can be obtained with a sample size of 6-10 subjects for paired studies and 12-20 subjects per group for cross-sectional studies, assuming a type I error rate of 0.05 and a type II error rate of 0.20 (i.e., 80% power). These findings will be useful for future studies investigating FFA, VLDL-TG, and VLDL-apoB-100 kinetics with the methods described.
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Affiliation(s)
- Faidon Magkos
- Washington University School of Medicine, St. Louis, MO, USA
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Ramakrishnan R. Studying apolipoprotein turnover with stable isotope tracers: correct analysis is by modeling enrichments. J Lipid Res 2006; 47:2738-53. [PMID: 16951401 PMCID: PMC3276318 DOI: 10.1194/jlr.m600302-jlr200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein kinetic parameters are determined from mass spectrometry data after administering mass isotopes of amino acids, which label proteins endogenously. The standard procedure is to model the isotopic content of the labeled precursor amino acid and of proteins of interest as tracer-to-tracee ratio (TTR). It is shown here that even though the administered tracer alters amino acid mass and turnover, apolipoprotein synthesis is unaltered and hence the apolipoprotein system is in a steady state, with the total (labeled plus unlabeled) masses and fluxes remaining constant. The correct model formulation for apolipoprotein kinetics is shown to be in terms of tracer enrichment, not of TTR. The needed mathematical equations are derived. A theoretical error analysis is carried out to calculate the magnitude of error in published results using TTR modeling. It is shown that TTR modeling leads to a consistent underestimation of the fractional synthetic rate. In constant-infusion studies, the bias error percent is shown to equal approximately the plateau enrichment, generally <10%. It is shown that, in bolus studies, the underestimation error can be larger. Thus, for mass isotope studies with endogenous tracers, apolipoproteins are in a steady state and the data should be fitted by modeling enrichments.
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Affiliation(s)
- Rajasekhar Ramakrishnan
- Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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Parhofer KG, Barrett PHR. Thematic review series: patient-oriented research. What we have learned about VLDL and LDL metabolism from human kinetics studies. J Lipid Res 2006; 47:1620-30. [PMID: 16720894 DOI: 10.1194/jlr.r600013-jlr200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein metabolism is the result of a complex network of many individual components. Abnormal lipoprotein concentrations can result from changes in the production, conversion, or catabolism of lipoprotein particles. Studies in hypolipoproteinemia and hyperlipoproteinemia have elucidated the processes that control VLDL secretion as well as VLDL and LDL catabolism. Here, we review the current knowledge regarding apolipoprotein B (apoB) metabolism, focusing on selected clinically relevant conditions. In hypobetalipoproteinemia attributable to truncations in apoB, the rate of secretion is closely linked to the length of apoB. On the other hand, in patients with the metabolic syndrome, it appears that substrate, in the form of free fatty acids, coupled to the state of insulin resistance can induce hypersecretion of VLDL-apoB. Studies in patients with familial hypercholesterolemia, familial defective apoB, and mutant forms of proprotein convertase subtilisin/kexin type 9 show that mutations in the LDL receptor, the ligand for the receptor, or an intracellular chaperone for the receptor are the most important determinants in regulating LDL catabolism. This review also demonstrates the variance of results within similar, or even the same, phenotypic conditions. This underscores the sensitivity of metabolic studies to methodological aspects and thus the importance of the inclusion of adequate controls in studies.
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