Post-Heparin LPL Activity Measurement Using VLDL As a Substrate: A New Robust Method for Routine Assessment of Plasma Triglyceride Lipolysis Defects

Filippo, Mathilde Di; Marçais, Christophe; Charrière, Sybil; Marmontel, Oriane; Broyer, M.; Delay, Mireille; Merlin, Micheline; Nollace, Axel; Valéro, René; Lagarde, Michel; Pruneta-Deloche, Valérie; Moulin, Philippe; Sassolas, Agnès

doi:10.1371/journal.pone.0096482

Cited by 25 publications

(9 citation statements)

References 39 publications

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“…Heparin facilitates the release of LPL tethered to the endothelium into the blood stream for an in vitro activity assay 6 . Absent or greatly reduced LPL enzyme activity in the post-heparin plasma is diagnostic for LPL or apoC-II deficiency after excluding hepatic lipase deficiency 110 . Then, apoC-II deficiency is apparent when LPL activity is restored on adding apoC-II protein or “normal” plasma in vitro 111 .…”

Section: Clinical Presentation Of Apolipoprotein C-ii Deficiencymentioning

confidence: 99%

Apolipoprotein C-II: New findings related to genetics, biochemistry, and role in triglyceride metabolism

et al. 2017

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Apolipoprotein C-II (apoC-II) is a small exchangeable apolipoprotein found on triglyceride-rich lipoproteins (TRL), such as chylomicrons (CM) and very low-density lipoproteins (VLDL), and on high-density lipoproteins (HDL), particularly during fasting. ApoC-II plays a critical role in TRL metabolism by acting as a cofactor of lipoprotein lipase (LPL), the main enzyme that hydrolyses plasma triglycerides (TG) on TRL. Here, we present an overview of the role of apoC-II in TG metabolism, emphasizing recent novel findings regarding its transcriptional regulation and biochemistry. We also review the 24 genetic mutations in the APOC2 gene reported to date that cause hypertriglyceridemia (HTG). Finally, we describe the clinical presentation of apoC-II deficiency and assess the current therapeutic approaches, as well as potential novel emerging therapies.

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Section: Clinical Presentation Of Apolipoprotein C-ii Deficiencymentioning

confidence: 99%

Apolipoprotein C-II: New findings related to genetics, biochemistry, and role in triglyceride metabolism

et al. 2017

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“…The ITC assay is an alternative to assays that use radiolabeled (40) or fluorogenic substrates (41,42), or directly measure released fatty acids by NEFA kits (43). Because plasma contains free fatty acids at high concentrations, [0.3-1 mM (44)], the NEFA kit is applicable only when significant amounts of fatty acids have been produced by the added LPL.…”

Section: Figmentioning

confidence: 99%

Lipoprotein lipase activity and interactions studied in human plasma by isothermal titration calorimetry

Reimund

Kovrov

Olivecrona

et al. 2017

Journal of Lipid Research

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LPL is produced and secreted from parenchymal cells like adipocytes and myocytes for transport to the luminal side of the endothelium via interaction with the glycosylphosphatidylinositol-anchored high density lipoprotein binding protein 1 (GPIHBP1) (8). Several plasma components have been shown to directly or indirectly modulate the activity of LPL. apoC-II and apoA-V increase the activity of LPL, while apoC-I, apoC-III, angiopoietin-like protein (ANGPTL)3, ANGPTL4, and ANGPTL8 decrease the activity (1, 9). The expression of each of these proteins depends on nutritional and hormonal factors, so that lipid uptake in tissues to a large extent is regulated by posttranslational effects on LPL (1, 9). It is possible that the macromolecular environment in plasma itself may be an influence on the interaction of LPL with its ligands. The protein concentration of plasma (80 g/l) has been shown to cause significant crowding effects (10). It is also possible that some plasma regulators of LPL activity have not been identified yet.LPL activity can be measured in vitro by using artificial, usually emulsified, systems of radiolabeled, fluorogenic, or chromogenic substrates, or isolated triglyceride-rich lipoproteins (TRLs). The reaction products are detected at certain time points by chemical quantification or by determination of radioactivity or fluorescence. These methods have been used to unravel important aspects of the action of LPL and also to quantitate the levels of LPL activity in cells and tissues. Only small amounts of LPL activity are normally present in the circulating blood (11). Therefore, intravenous injections of heparin are made to release LPL from its endothelial binding sites. Determination of LPL activity in postheparin plasma, using artificial substrate systems, is considered to give an estimation of the amount of active LPL at the vascular endothelium (12).Lack of a suitable technique for continuous monitoring of triglyceride hydrolysis in plasma has hampered the understanding of the action of LPL under physiological Abstract LPL hydrolyzes triglycerides in plasma lipoproteins. Due to the complex regulation mechanism, it has been difficult to mimic the physiological conditions under which LPL acts in vitro. We demonstrate that isothermal titration calorimetry (ITC), using human plasma as substrate, overcomes several limitations of previously used techniques. The high sensitivity of ITC allows continuous recording of the heat released during hydrolysis. Both initial rates and kinetics for complete hydrolysis of plasma lipids can be studied. The hydrolytic breakdown of plasma triglycerides by LPL at the capillary endothelium is a crucial event that contributes to control of the levels of triglycerides in plasma (1, 2). Many recent studies support the view that an elevated level of triglycerides in plasma is an independent risk factor for development of atherosclerosis (3-5). Therefore, the LPL system is considered to be an interesting target for drug design (6, 7). Education and Research Grant IUT 19-9,...

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“…8,9 Fasting venous blood samples were taken 10 minutes preintravenous and postintravenous infusion of heparin (50 U/kg), and total postheparin lipolytic activity was determined as described. 10,11 A subset of markers was also examined 4 hours after liquid-formulated high-fat test meal (4800 kJ, 130 g of fat, 17 g of protein and 21 g of carbohydrate).…”

Section: Clinical and Biochemical Assessmentsmentioning

confidence: 99%

Clinical and Biochemical Features of Different Molecular Etiologies of Familial Chylomicronemia

Hegele¹,

Ban²,

Wang³

et al. 2017

Journal of Clinical Lipidology

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BACKGROUND: Familial chylomicronemia syndrome (FCS) is an ultra-rare phenotype that is usually caused by biallelic mutations in the LPL gene encoding lipoprotein lipase, or less often in APOC2, APOA5, LMF1, or GPIHBP1 genes encoding cofactors or interacting proteins.OBJECTIVES: We evaluated baseline phenotypes among FCS participants in a phase 3 randomized placebo-controlled trial of volanesorsen (NCT02211209).METHODS: Baseline clinical, fasting, and postfat load metabolic markers were assessed. Targeted next-generation DNA sequencing plus custom bioinformatics was used to genotype subjects.RESULTS: Among 52 FCS individuals, 41 had biallelic LPL gene mutations (LPL-FCS patients): 82%, 7%, and 11% were missense, nonsense, and splicing variants, respectively. Eleven individuals had non-LPL-FCS; 2 had mutations in APOA5, 5 in GPIHBP1, and 1 each in LMF1 and APOC2 genes, respectively. Two other individuals were double heterozygotes, each with 1 normal LPL allele. All subjects had extremely high triglycerides (TGs) and chylomicrons, but very low levels of other lipoproteins.

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Post-Heparin LPL Activity Measurement Using VLDL As a Substrate: A New Robust Method for Routine Assessment of Plasma Triglyceride Lipolysis Defects

Cited by 25 publications

References 39 publications

Apolipoprotein C-II: New findings related to genetics, biochemistry, and role in triglyceride metabolism

Apolipoprotein C-II: New findings related to genetics, biochemistry, and role in triglyceride metabolism

Lipoprotein lipase activity and interactions studied in human plasma by isothermal titration calorimetry

Clinical and Biochemical Features of Different Molecular Etiologies of Familial Chylomicronemia

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