The Experts below are selected from a list of 4893 Experts worldwide ranked by ideXlab platform

Sander Kersten - One of the best experts on this subject based on the ideXlab platform.

  • fasting induces ANGPTL4 and reduces lpl activity in human adipose tissue
    Molecular metabolism, 2020
    Co-Authors: Philip M M Ruppert, Gunilla Olivecrona, Charlotte C J R Michielsen, Eric J Hazebroek, Ali Pirayesh, Lydia A Afman, Sander Kersten
    Abstract:

    Abstract Objective Studies in mice have shown that the decrease in lipoprotein lipase (LPL) activity in adipose tissue upon fasting is mediated by induction of the inhibitor ANGPTL4. Here, we aimed to validate this concept in humans by determining the effect of a prolonged fast on ANGPTL4 and LPL gene and protein expression in human subcutaneous adipose tissue. Methods Twenty-three volunteers ate a standardized meal at 18.00 h and fasted until 20.00 h the next day. Blood was drawn and periumbilical adipose tissue biopsies were collected 2 h and 26 h after the meal. Results Consistent with previous mouse data, LPL activity in human adipose tissue was significantly decreased by fasting (−60%), concurrent with increased ANGPTL4 mRNA (+90%) and decreased ANGPTL8 mRNA (−94%). ANGPTL4 protein levels in adipose tissue were also significantly increased by fasting (+46%), whereas LPL mRNA and protein levels remained unchanged. In agreement with the adipose tissue data, plasma ANGPTL4 levels increased upon fasting (+100%), whereas plasma ANGPTL8 decreased (−79%). Insulin, levels of which significantly decreased upon fasting, downregulated ANGPTL4 mRNA and protein in primary human adipocytes. By contrast, cortisol, levels of which significantly increased upon fasting, upregulated ANGPTL4 mRNA and protein in primary human adipocytes as did fatty acids. Conclusion ANGPTL4 levels in human adipose tissue are increased by fasting, likely via increased plasma cortisol and free fatty acids and decreased plasma insulin, resulting in decreased LPL activity. This clinical trial was registered with identifier NCT03757767.

  • ANGPTL4 promotes bile acid absorption during taurocholic acid supplementation via a mechanism dependent on the gut microbiota
    Biochimica et Biophysica Acta, 2017
    Co-Authors: Aafke W F Janssen, Wieneke Dijk, Jos Boekhorst, Folkert Kuipers, Albert K Groen, Sabina Lukovac, Guido J E J Hooiveld, Sander Kersten
    Abstract:

    Abstract Angiopoietin-like 4 (ANGPTL4) raises plasma triglyceride levels by inhibiting lipoprotein lipase. A set of compounds that are able to reduce plasma triglyceride levels are bile acids (BA). Because BA have been shown to decrease ANGPTL4 secretion by intestinal cells, we hypothesized that BA lower plasma triglycerides (partly) via ANGPTL4. To test that hypothesis, wild-type and ANGPTL4−/− mice were fed chow supplemented with taurocholic acid (TCA) for seven days. TCA supplementation effectively lowered plasma triglycerides in wild-type and ANGPTL4−/− mice, indicating that ANGPTL4 is not required for plasma triglyceride-lowering by BA. Intriguingly, however, plasma and hepatic BA concentrations were significantly lower in TCA-supplemented ANGPTL4−/− mice than in TCA-supplemented wild-type mice. These changes in the ANGPTL4−/− mice were accompanied by lower BA levels in ileal scrapings and decreased expression of FXR-target genes in the ileum, including the BA transporter Slc10a2. By contrast, faecal excretion of specifically primary BA was higher in the ANGPTL4−/− mice, suggesting that loss of ANGPTL4 impairs intestinal BA absorption. Since the gut microbiota converts primary BA into secondary BA, elevated excretion of primary BA in ANGPTL4−/− mice may reflect differences in gut microbial composition and/or functionality. Indeed, colonic microbial composition was markedly different between ANGPTL4−/− and wild-type mice. Suppression of the gut bacteria using antibiotics abolished differences in plasma, hepatic, and faecal BA levels between TCA-supplemented ANGPTL4−/− and wild-type mice. In conclusion, 1) ANGPTL4 is not involved in the triglyceride-lowering effect of BA; 2) ANGPTL4 promotes BA absorption during TCA supplementation via a mechanism dependent on the gut microbiota.

  • angiopoietin like 4 promotes intracellular degradation of lipoprotein lipase in adipocytes
    Journal of Lipid Research, 2016
    Co-Authors: Wieneke Dijk, Stephen G Young, Sander Kersten, Mikael Larsson, Anne P Beigneux, Andre Bensadoun
    Abstract:

    LPL hydrolyzes triglycerides in triglyceride-rich lipoproteins along the capillaries of heart, skeletal muscle, and adipose tissue. The activity of LPL is repressed by angiopoietin-like 4 (ANGPTL4) but the underlying mechanisms have not been fully elucidated. Our objective was to study the cellular location and mechanism for LPL inhibition by ANGPTL4. We performed studies in transfected cells, ex vivo studies, and in vivo studies with ANGPTL4(-/-) mice. Cotransfection of CHO pgsA-745 cells with ANGPTL4 and LPL reduced intracellular LPL protein levels, suggesting that ANGPTL4 promotes LPL degradation. This conclusion was supported by studies of primary adipocytes and adipose tissue explants from wild-type and ANGPTL4(-/-) mice. Absence of ANGPTL4 resulted in accumulation of the mature-glycosylated form of LPL and increased secretion of LPL. Blocking endoplasmic reticulum (ER)-Golgi transport abolished differences in LPL abundance between wild-type and ANGPTL4(-/-) adipocytes, suggesting that ANGPTL4 acts upon LPL after LPL processing in the ER. Finally, physiological changes in adipose tissue ANGPTL4 expression during fasting and cold resulted in inverse changes in the amount of mature-glycosylated LPL in wild-type mice, but not ANGPTL4(-/-) mice. We conclude that ANGPTL4 promotes loss of intracellular LPL by stimulating LPL degradation after LPL processing in the ER.

  • physiological regulation of lipoprotein lipase
    Biochimica et Biophysica Acta, 2014
    Co-Authors: Sander Kersten
    Abstract:

    The enzyme lipoprotein lipase (LPL), originally identified as the clearing factor lipase, hydrolyzes triglycerides present in the triglyceride-rich lipoproteins VLDL and chylomicrons. LPL is primarily expressed in tissues that oxidize or store fatty acids in large quantities such as the heart, skeletal muscle, brown adipose tissue and white adipose tissue. Upon production by the underlying parenchymal cells, LPL is transported and attached to the capillary endothelium by the protein GPIHBP1. Because LPL is rate limiting for plasma triglyceride clearance and tissue uptake of fatty acids, the activity of LPL is carefully controlled to adjust fatty acid uptake to the requirements of the underlying tissue via multiple mechanisms at the transcriptional and post-translational level. Although various stimuli influence LPL gene transcription, it is now evident that most of the physiological variation in LPL activity, such as during fasting and exercise, appears to be driven via post-translational mechanisms by extracellular proteins. These proteins can be divided into two main groups: the liver-derived apolipoproteins APOC1, APOC2, APOC3, APOA5, and APOE, and the angiopoietin-like proteins ANGPTL3, ANGPTL4 and ANGPTL8, which have a broader expression profile. This review will summarize the available literature on the regulation of LPL activity in various tissues, with an emphasis on the response to diverse physiological stimuli.

  • regulation of triglyceride metabolism by angiopoietin like proteins
    Biochimica et Biophysica Acta, 2012
    Co-Authors: Frits Mattijssen, Sander Kersten
    Abstract:

    Plasma triglyceride concentrations are determined by the balance between production of the triglyceride-rich lipoproteins VLDL and chylomicrons in liver and intestine, and their lipoprotein lipase-mediated clearance in peripheral tissues. In the last decade, the group of Angiopoietin-like proteins has emerged as important regulators of circulating triglyceride (TG) levels. Specifically, ANGPTL3 and ANGPTL4 impair TG clearance by inhibiting lipoprotein lipase (LPL). Whereas ANGPTL4 irreversibly inactivates LPL by promoting conversion of active LPL dimers into inactive monomers, ANGPTL3 reversibly inhibits LPL activity. Studies using transgenic or knockout mice have clearly demonstrated the stimulatory effect of Angptl3 and ANGPTL4 on plasma TG, which is further supported by human genetic data including genome wide association studies. Whereas ANGPTL3 is mainly active in the fed state, ANGPTL4 is elevated by fasting and mediates fasting-induced changes in plasma TG and free fatty acid metabolism. Both proteins undergo oligomerization and are subject to proteolytic cleavage to generate N- and C-terminal fragments with highly divergent biological activities. Expression of ANGPTL3 is exclusive to liver and governed by the liver X receptor (LXR). In contrast, ANGPTL4 is expressed ubiquitously and under sensitive control of the Peroxisome proliferator-activated receptor (PPAR) family and fatty acids. Induction of ANGPTL4 gene expression by fatty acids and via PPARs is part of a feedback mechanism aimed at protecting cells against lipotoxicity. So far there is very little evidence that other ANGPTLs directly impact plasma lipoprotein metabolism. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.

William Yk Hwang - One of the best experts on this subject based on the ideXlab platform.

Gunilla Olivecrona - One of the best experts on this subject based on the ideXlab platform.

  • fasting induces ANGPTL4 and reduces lpl activity in human adipose tissue
    Molecular metabolism, 2020
    Co-Authors: Philip M M Ruppert, Gunilla Olivecrona, Charlotte C J R Michielsen, Eric J Hazebroek, Ali Pirayesh, Lydia A Afman, Sander Kersten
    Abstract:

    Abstract Objective Studies in mice have shown that the decrease in lipoprotein lipase (LPL) activity in adipose tissue upon fasting is mediated by induction of the inhibitor ANGPTL4. Here, we aimed to validate this concept in humans by determining the effect of a prolonged fast on ANGPTL4 and LPL gene and protein expression in human subcutaneous adipose tissue. Methods Twenty-three volunteers ate a standardized meal at 18.00 h and fasted until 20.00 h the next day. Blood was drawn and periumbilical adipose tissue biopsies were collected 2 h and 26 h after the meal. Results Consistent with previous mouse data, LPL activity in human adipose tissue was significantly decreased by fasting (−60%), concurrent with increased ANGPTL4 mRNA (+90%) and decreased ANGPTL8 mRNA (−94%). ANGPTL4 protein levels in adipose tissue were also significantly increased by fasting (+46%), whereas LPL mRNA and protein levels remained unchanged. In agreement with the adipose tissue data, plasma ANGPTL4 levels increased upon fasting (+100%), whereas plasma ANGPTL8 decreased (−79%). Insulin, levels of which significantly decreased upon fasting, downregulated ANGPTL4 mRNA and protein in primary human adipocytes. By contrast, cortisol, levels of which significantly increased upon fasting, upregulated ANGPTL4 mRNA and protein in primary human adipocytes as did fatty acids. Conclusion ANGPTL4 levels in human adipose tissue are increased by fasting, likely via increased plasma cortisol and free fatty acids and decreased plasma insulin, resulting in decreased LPL activity. This clinical trial was registered with identifier NCT03757767.

  • unfolding of monomeric lipoprotein lipase by ANGPTL4 insight into the regulation of plasma triglyceride metabolism
    Proceedings of the National Academy of Sciences of the United States of America, 2020
    Co-Authors: Gabriel Birrane, Kristian Kolby Kristensen, Haydyn D T Mertens, Gunilla Olivecrona, Muthuraman Meiyappan, Katrine Zinck Lethespensen, Thomas J D Jorgensen
    Abstract:

    The binding of lipoprotein lipase (LPL) to GPIHBP1 focuses the intravascular hydrolysis of triglyceride-rich lipoproteins on the surface of capillary endothelial cells. This process provides essential lipid nutrients for vital tissues (e.g., heart, skeletal muscle, and adipose tissue). Deficiencies in either LPL or GPIHBP1 impair triglyceride hydrolysis, resulting in severe hypertriglyceridemia. The activity of LPL in tissues is regulated by angiopoietin-like proteins 3, 4, and 8 (ANGPTL). Dogma has held that these ANGPTLs inactivate LPL by converting LPL homodimers into monomers, rendering them highly susceptible to spontaneous unfolding and loss of enzymatic activity. Here, we show that binding of an LPL-specific monoclonal antibody (5D2) to the tryptophan-rich lipid-binding loop in the carboxyl terminus of LPL prevents homodimer formation and forces LPL into a monomeric state. Of note, 5D2-bound LPL monomers are as stable as LPL homodimers (i.e., they are not more prone to unfolding), but they remain highly susceptible to ANGPTL4-catalyzed unfolding and inactivation. Binding of GPIHBP1 to LPL alone or to 5D2-bound LPL counteracts ANGPTL4-mediated unfolding of LPL. In conclusion, ANGPTL4-mediated inactivation of LPL, accomplished by catalyzing the unfolding of LPL, does not require the conversion of LPL homodimers into monomers. Thus, our findings necessitate changes to long-standing dogma on mechanisms for LPL inactivation by ANGPTL proteins. At the same time, our findings align well with insights into LPL function from the recent crystal structure of the LPL•GPIHBP1 complex.

  • characterization of ANGPTL4 function in macrophages and adipocytes using ANGPTL4 knockout and ANGPTL4 hypomorphic mice
    Journal of Lipid Research, 2019
    Co-Authors: Antwi Boasiako Oteng, Gunilla Olivecrona, Philip M M Ruppert, Lily Boutens, Wieneke Dijk, Xanthe A M H Van Dierendonck, Rinke Stienstra
    Abstract:

    Angiopoietin-like protein (ANGPTL)4 regulates plasma lipids, making it an attractive target for correcting dyslipidemia. However, ANGPTL4 inactivation in mice fed a high fat diet causes chylous ascites, an acute-phase response, and mesenteric lymphadenopathy. Here, we studied the role of ANGPTL4 in lipid uptake in macrophages and in the above-mentioned pathologies using ANGPTL4-hypomorphic and ANGPTL4−/− mice. ANGPTL4 expression in peritoneal and bone marrow-derived macrophages was highly induced by lipids. Recombinant ANGPTL4 decreased lipid uptake in macrophages, whereas deficiency of ANGPTL4 increased lipid uptake, upregulated lipid-induced genes, and increased respiration. ANGPTL4 deficiency did not alter LPL protein levels in macrophages. ANGPTL4-hypomorphic mice with partial expression of a truncated N-terminal ANGPTL4 exhibited reduced fasting plasma triglyceride, cholesterol, and NEFAs, strongly resembling ANGPTL4−/− mice. However, during high fat feeding, ANGPTL4-hypomorphic mice showed markedly delayed and attenuated elevation in plasma serum amyloid A and much milder chylous ascites than ANGPTL4−/− mice, despite similar abundance of lipid-laden giant cells in mesenteric lymph nodes. In conclusion, ANGPTL4 deficiency increases lipid uptake and respiration in macrophages without affecting LPL protein levels. Compared with the absence of ANGPTL4, low levels of N-terminal ANGPTL4 mitigate the development of chylous ascites and an acute-phase response in mice.

  • on the mechanism of angiopoietin like protein 8 for control of lipoprotein lipase activity
    Journal of Lipid Research, 2019
    Co-Authors: Oleg Kovrov, Kristian Kolby Kristensen, Erika Larsson, Michael Ploug, Gunilla Olivecrona
    Abstract:

    Angiopoietin-like (ANGPTL) 8 is a secreted inhibitor of LPL, a key enzyme in plasma triglyceride metabolism. It was previously reported that ANGPTL8 requires another member of the ANGPTL family, ANGPTL3, to act on LPL. ANGPTL3, much like ANGPTL4, is a physiologically relevant regulator of LPL activity, which causes irreversible inactivation of the enzyme. Here, we show that ANGPTL8 can form complexes with either ANGPTL3 or ANGPTL4 when the proteins are refolded together from their denatured states. In contrast to the augmented inhibitory effect of the ANGPTL3/ANGPTL8 complex on LPL activity, the ANGPTL4/ANGPTL8 complex is less active compared with ANGPTL4 alone. In our experiments, all three members of the ANGPTL family use the same mechanism to inactivate LPL, which involves dissociation of active dimeric LPL to monomers. This inactivation can be counteracted by the presence of glycosylphosphatidylinositol-anchored HDL binding protein 1, the endothelial LPL transport protein previously known to protect LPL from spontaneous and ANGPTL4-catalyzed inactivation. Our data demonstrate that ANGPTL8 may function as an important metabolic switch, by forming complexes with ANGPTL3, or with ANGPTL4, in order to direct the flow of energy from triglycerides in blood according to the needs of the body.

  • triacylglycerol rich lipoproteins protect lipoprotein lipase from inactivation by angptl3 and ANGPTL4
    Biochimica et Biophysica Acta, 2012
    Co-Authors: Stefan K Nilsson, Fredrick Anderson, Madelene Ericsson, Mikael Larsson, Elena Makoveichuk, Aivar Lookene, Joerg Heeren, Gunilla Olivecrona
    Abstract:

    Lipoprotein lipase (LPL) is important for clearance of triacylglycerols (TG) from plasma both as an enzyme and as a bridging factor between lipoproteins and receptors for endocytosis. The amount of LPL at the luminal side of the capillary endothelium determines to what extent lipids are taken up. Mechanisms to control both the activity of LPL and its transport to the endothelial sites are regulated, but poorly understood. Angiopoietin-like proteins (ANGPTLs) 3 and 4 are potential control proteins for LPL, but plasma concentrations of ANGPTLs do not correlate with plasma TG levels. We investigated the effects of recombinant human N-terminal (NT) ANGPTLs3 and 4 on LPL-mediated bridging of TG-rich lipoproteins to primary mouse hepatocytes and found that the NT-ANGPTLs, in concentrations sufficient to cause inactivation of LPL in vitro, were unable to prevent LPL-mediated lipoprotein uptake. We therefore investigated the effects of lipoproteins (chylomicrons, VLDL and LDL) on the inactivation of LPL in vitro by NT-ANGPTLs3 and 4 and found that LPL activity was protected by TG-rich lipoproteins. In vivo, postprandial TG protected LPL from inactivation by recombinant NT-ANGPTL4 injected to mice. We conclude that lipoprotein-bound LPL is stabilized against inactivation by ANGPTLs. The levels of ANGPTLs found in blood may not be sufficient to overcome this stabilization. Therefore it is likely that the prime site of action of ANGPTLs on LPL is in subendothelial compartments where TG-rich lipoprotein concentration is lower than in blood. This could explain why the plasma levels of TG and ANGPTLs do not correlate.

Kristian Kolby Kristensen - One of the best experts on this subject based on the ideXlab platform.

  • the intrinsic instability of the hydrolase domain of lipoprotein lipase facilitates its inactivation by ANGPTL4 catalyzed unfolding
    Proceedings of the National Academy of Sciences of the United States of America, 2021
    Co-Authors: Katrine Zinck Lethespensen, Kristian Kolby Kristensen, Anni Kumari, Annemarie Lund Winther, Stephen G Young
    Abstract:

    The complex between lipoprotein lipase (LPL) and its endothelial receptor (GPIHBP1) is responsible for the lipolytic processing of triglyceride-rich lipoproteins (TRLs) along the capillary lumen, a physiologic process that releases lipid nutrients for vital organs such as heart and skeletal muscle. LPL activity is regulated in a tissue-specific manner by endogenous inhibitors (angiopoietin-like [ANGPTL] proteins 3, 4, and 8), but the molecular mechanisms are incompletely understood. ANGPTL4 catalyzes the inactivation of LPL monomers by triggering the irreversible unfolding of LPL's α/β-hydrolase domain. Here, we show that this unfolding is initiated by the binding of ANGPTL4 to sequences near LPL's catalytic site, including β2, β3-α3, and the lid. Using pulse-labeling hydrogen‒deuterium exchange mass spectrometry, we found that ANGPTL4 binding initiates conformational changes that are nucleated on β3-α3 and progress to β5 and β4-α4, ultimately leading to the irreversible unfolding of regions that form LPL's catalytic pocket. LPL unfolding is context dependent and varies with the thermal stability of LPL's α/β-hydrolase domain (T m of 34.8 °C). GPIHBP1 binding dramatically increases LPL stability (T m of 57.6 °C), while ANGPTL4 lowers the onset of LPL unfolding by ∼20 °C, both for LPL and LPL•GPIHBP1 complexes. These observations explain why the binding of GPIHBP1 to LPL retards the kinetics of ANGPTL4-mediated LPL inactivation at 37 °C but does not fully suppress inactivation. The allosteric mechanism by which ANGPTL4 catalyzes the irreversible unfolding and inactivation of LPL is an unprecedented pathway for regulating intravascular lipid metabolism.

  • gpihbp1 and ANGPTL4 utilize protein disorder to orchestrate order in plasma triglyceride metabolism and regulate compartmentalization of lpl activity
    Frontiers in Cell and Developmental Biology, 2021
    Co-Authors: Kristian Kolby Kristensen, Katrine Zinck Lethespensen, Anni Kumari, Anne Louise Gronnemose, Annemarie Lundwinther
    Abstract:

    Intravascular processing of triglyceride-rich lipoproteins (TRLs) is crucial for delivery of dietary lipids fueling energy metabolism in heart and skeletal muscle and for storage in white adipose tissue. During the last decade, mechanisms underlying focal lipolytic processing of TRLs along the luminal surface of capillaries have been clarified by fresh insights into the functions of lipoprotein lipase (LPL); LPL's dedicated transporter protein, glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1); and its endogenous inhibitors, angiopoietin-like (ANGPTL) proteins 3, 4, and 8. Key discoveries in LPL biology include solving the crystal structure of LPL, showing LPL is catalytically active as a monomer rather than as a homodimer, and that the borderline stability of LPL's hydrolase domain is crucial for the regulation of LPL activity. Another key discovery was understanding how ANGPTL4 regulates LPL activity. The binding of ANGPTL4 to LPL sequences adjacent to the catalytic cavity triggers cooperative and sequential unfolding of LPL's hydrolase domain resulting in irreversible collapse of the catalytic cavity and loss of LPL activity. Recent studies have highlighted the importance of the ANGPTL3-ANGPTL8 complex for endocrine regulation of LPL activity in oxidative organs (e.g., heart, skeletal muscle, brown adipose tissue), but the molecular mechanisms have not been fully defined. New insights have also been gained into LPL-GPIHBP1 interactions and how GPIHBP1 moves LPL to its site of action in the capillary lumen. GPIHBP1 is an atypical member of the LU (Ly6/uPAR) domain protein superfamily, containing an intrinsically disordered and highly acidic N-terminal extension and a disulfide bond-rich three-fingered LU domain. Both the disordered acidic domain and the folded LU domain are crucial for the stability and transport of LPL, and for modulating its susceptibility to ANGPTL4-mediated unfolding. This review focuses on recent advances in the biology and biochemistry of crucial proteins for intravascular lipolysis.

  • unfolding of monomeric lipoprotein lipase by ANGPTL4 insight into the regulation of plasma triglyceride metabolism
    Proceedings of the National Academy of Sciences of the United States of America, 2020
    Co-Authors: Gabriel Birrane, Kristian Kolby Kristensen, Haydyn D T Mertens, Gunilla Olivecrona, Muthuraman Meiyappan, Katrine Zinck Lethespensen, Thomas J D Jorgensen
    Abstract:

    The binding of lipoprotein lipase (LPL) to GPIHBP1 focuses the intravascular hydrolysis of triglyceride-rich lipoproteins on the surface of capillary endothelial cells. This process provides essential lipid nutrients for vital tissues (e.g., heart, skeletal muscle, and adipose tissue). Deficiencies in either LPL or GPIHBP1 impair triglyceride hydrolysis, resulting in severe hypertriglyceridemia. The activity of LPL in tissues is regulated by angiopoietin-like proteins 3, 4, and 8 (ANGPTL). Dogma has held that these ANGPTLs inactivate LPL by converting LPL homodimers into monomers, rendering them highly susceptible to spontaneous unfolding and loss of enzymatic activity. Here, we show that binding of an LPL-specific monoclonal antibody (5D2) to the tryptophan-rich lipid-binding loop in the carboxyl terminus of LPL prevents homodimer formation and forces LPL into a monomeric state. Of note, 5D2-bound LPL monomers are as stable as LPL homodimers (i.e., they are not more prone to unfolding), but they remain highly susceptible to ANGPTL4-catalyzed unfolding and inactivation. Binding of GPIHBP1 to LPL alone or to 5D2-bound LPL counteracts ANGPTL4-mediated unfolding of LPL. In conclusion, ANGPTL4-mediated inactivation of LPL, accomplished by catalyzing the unfolding of LPL, does not require the conversion of LPL homodimers into monomers. Thus, our findings necessitate changes to long-standing dogma on mechanisms for LPL inactivation by ANGPTL proteins. At the same time, our findings align well with insights into LPL function from the recent crystal structure of the LPL•GPIHBP1 complex.

  • on the mechanism of angiopoietin like protein 8 for control of lipoprotein lipase activity
    Journal of Lipid Research, 2019
    Co-Authors: Oleg Kovrov, Kristian Kolby Kristensen, Erika Larsson, Michael Ploug, Gunilla Olivecrona
    Abstract:

    Angiopoietin-like (ANGPTL) 8 is a secreted inhibitor of LPL, a key enzyme in plasma triglyceride metabolism. It was previously reported that ANGPTL8 requires another member of the ANGPTL family, ANGPTL3, to act on LPL. ANGPTL3, much like ANGPTL4, is a physiologically relevant regulator of LPL activity, which causes irreversible inactivation of the enzyme. Here, we show that ANGPTL8 can form complexes with either ANGPTL3 or ANGPTL4 when the proteins are refolded together from their denatured states. In contrast to the augmented inhibitory effect of the ANGPTL3/ANGPTL8 complex on LPL activity, the ANGPTL4/ANGPTL8 complex is less active compared with ANGPTL4 alone. In our experiments, all three members of the ANGPTL family use the same mechanism to inactivate LPL, which involves dissociation of active dimeric LPL to monomers. This inactivation can be counteracted by the presence of glycosylphosphatidylinositol-anchored HDL binding protein 1, the endothelial LPL transport protein previously known to protect LPL from spontaneous and ANGPTL4-catalyzed inactivation. Our data demonstrate that ANGPTL8 may function as an important metabolic switch, by forming complexes with ANGPTL3, or with ANGPTL4, in order to direct the flow of energy from triglycerides in blood according to the needs of the body.

Xiubo Fan - One of the best experts on this subject based on the ideXlab platform.

  • low dose insulin like growth factor binding proteins 1 and 2 and angiopoietin like protein 3 coordinately stimulate ex vivo expansion of human umbilical cord blood hematopoietic stem cells as assayed in nod scid gamma null mice
    Stem Cell Research & Therapy, 2014
    Co-Authors: Xiubo Fan, Francesca Wi Lim, Justina Ml Ang, Pat Py Chu, Sudipto Bari, William Yk Hwang
    Abstract:

    Introduction Insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs) and angiopoietin-like proteins (ANGPTLs) can enhance the ex vivo expansion of hematopoietic stem cells (HSCs) when used with a standard cytokine cocktail of stem cell factor (SCF), thrombopoietin (TPO) and FLT3 ligand (FL). In order to determine the optimal dose and combination of IGFs, IGFBPs and ANGPTLs, serial dilution and full permutation of IGFBP1, IGFBP2, IGF2 and ANGPTL3 were applied on a cryopreserved umbilical cord blood mononuclear cell (UCB-MNC) ex vivo expansion system.

  • low dose igfbp1 igfbp2 and angptl3 coordinately stimulate ex vivo expansion of human umbilical cord blood ucb hematopoietic stem cells hscs
    Blood, 2010
    Co-Authors: Xiubo Fan, Sudipto Bari, Pak Yan Chu, Justina May Lynn Ang, Sai Kiang Lim, William Hwang
    Abstract:

    Abstract 1546 Ex vivo expansion of umbilical cord blood (UCB) hematopoietic stem cells (HSCs) may overcome the obstacle of low cell dose for UCB transplantation in adults. Insulin like growth factors (IGFs), IGF binding proteins (IGFBPs) and angiopoietin like proteins (ANGPTLs) can further enhance the ex vivo expansion of HSCs when used with a standard cytokine cocktail of stem cell factor (SCF), thrombopoietin (TPO) and FLT3-ligand (FL). Current doses of IGFBPs and ANGPTLs are in the range of 100∼500ng/ml, but these concentrations may not be optimal and high concentrations could be costly for clinical use. In order to determine the optimal dosage of IGFs, IGFBPs and ANGPTLs, 4×10 5 cells/mL of cryopreserved clinical UCB was inoculated in serum-free Stemspan® medium supplied with standard basal cytokine combination of 100ng/ml SCF, 50ng/ml FL and 100ng/ml TPO on an MSCs stromal layer and with individually varied doses of IGFBP1, IGFBP2, IGF2 and ANGPTL3 in the range of 0∼200ng/ml. In order to determine optimal cytokine combination, complete permutation was carried out after establishing the optimal dosage of each cytokine. On day 7, the same amount of Stemspan® medium with the indicated cytokine combination was replenished to the culture system. Cord blood cells were harvested after 12 days ex vivo culture and assayed for total cell count, cell surface phenotype (viability determined by CD45/AnnV/7AAD staining, primitive progenitor determined by CD45/CD34/CD38/CD90 staining) and functional studies (Colony-forming unit-granulocyte and macrophage (CFU-GM) was determined by methylcellulose colony culture). Paradoxically, the highest expansion of CD34 + CD38 - CD90 + primitive progenitor was at a low dose of 20ng/ml for IGFBP1, IGFBP2, IGF2 and ANGPTL3 when concentrations of 0, 20, 50, 100 and 200 ng/ml were studied (Fig. 1A). Based on this results the cytokine dosage range was narrowed down to 0∼50ng/ml and experiments (Fig. 1B) showed that the optimal cytokines dosages were 20ng/ml of IGFBP2 and ANGPTL3, 15ng/ml IGFBP1 and 10ng/ml IGF2, which could stimulate 13.0±1.1 fold, 13.3±2.4 fold, 11.0±0.8 fold and 14.3±2.1 fold expansion of CD34 + CD38 - CD90 + primitive progenitor compared to 6.8±0.2 fold with standard cytokine control (p =0.01). Studying multiple permutations, combination “ABD” comprising 15ng/ml IGFBP1, 20ng/ml IGFBP2 and 20ng/ml ANGPTL3 had the highest expansion of CD34 + CD38 - CD90 + primitive progenitor (27.7±2.2 fold compared to 8.5±1.1 fold with standard cytokines, p =0.01), was found to be superior to all other combinations, including combinations “A”, “B”, “BC”, “BD”, “CD” and “ABCD”, which could stimulate over 2 fold expansion of primitive progenitor compare to control (Figure 1C). Interestingly, despite expansion of primitive CD34+CD38-CD90+ cells, there was no further enhancement of the expansion of total cells and general progenitors compare to control (data not shown), suggesting that the cyokine cocktail enhanced only the earliest progenitors. In conclusion, IGFBP1, IGFBP2, IGF2 and ANGPTL3 can stimulate the expansion of CD34 + CD38 - CD90 + primitive progenitor at low dosage, and the optimal combination comprises IGFBP1, IGFBP2 and ANGPTL3. Further in vivo experimentation is in progress to verify the effect of our optimized cytokine combination culture system on ex vivo expansion of cryopreserved unselected clinical UCB HSCs. Disclosures: No relevant conflicts of interest to declare.

  • low dose igfbp1 igfbp2 and angptl3 coordinately stimulate ex vivo expansion of human umbilical cord blood ucb hematopoietic stem cells hscs
    Blood, 2010
    Co-Authors: Xiubo Fan, Sudipto Bari, Pak Yan Chu, Justina May Lynn Ang, Sai Kiang Lim, William Hwang
    Abstract:

    Abstract Abstract 1546 Ex vivo expansion of umbilical cord blood (UCB) hematopoietic stem cells (HSCs) may overcome the obstacle of low cell dose for UCB transplantation in adults. Insulin like growth factors (IGFs), IGF binding proteins (IGFBPs) and angiopoietin like proteins (ANGPTLs) can further enhance the ex vivo expansion of HSCs when used with a standard cytokine cocktail of stem cell factor (SCF), thrombopoietin (TPO) and FLT3-ligand (FL). Current doses of IGFBPs and ANGPTLs are in the range of 100∼500ng/ml, but these concentrations may not be optimal and high concentrations could be costly for clinical use. In order to determine the optimal dosage of IGFs, IGFBPs and ANGPTLs, 4×105cells/mL of cryopreserved clinical UCB was inoculated in serum-free Stemspan® medium supplied with standard basal cytokine combination of 100ng/ml SCF, 50ng/ml FL and 100ng/ml TPO on an MSCs stromal layer and with individually varied doses of IGFBP1, IGFBP2, IGF2 and ANGPTL3 in the range of 0∼200ng/ml. In order to determine optimal cytokine combination, complete permutation was carried out after establishing the optimal dosage of each cytokine. On day 7, the same amount of Stemspan® medium with the indicated cytokine combination was replenished to the culture system. Cord blood cells were harvested after 12 days ex vivo culture and assayed for total cell count, cell surface phenotype (viability determined by CD45/AnnV/7AAD staining, primitive progenitor determined by CD45/CD34/CD38/CD90 staining) and functional studies (Colony-forming unit-granulocyte and macrophage (CFU-GM) was determined by methylcellulose colony culture). Paradoxically, the highest expansion of CD34+CD38-CD90+ primitive progenitor was at a low dose of 20ng/ml for IGFBP1, IGFBP2, IGF2 and ANGPTL3 when concentrations of 0, 20, 50, 100 and 200 ng/ml were studied (Fig. 1A). Based on this results the cytokine dosage range was narrowed down to 0∼50ng/ml and experiments (Fig. 1B) showed that the optimal cytokines dosages were 20ng/ml of IGFBP2 and ANGPTL3, 15ng/ml IGFBP1 and 10ng/ml IGF2, which could stimulate 13.0±1.1 fold, 13.3±2.4 fold, 11.0±0.8 fold and 14.3±2.1 fold expansion of CD34+CD38-CD90+ primitive progenitor compared to 6.8±0.2 fold with standard cytokine control (p =0.01). Studying multiple permutations, combination “ABD” comprising 15ng/ml IGFBP1, 20ng/ml IGFBP2 and 20ng/ml ANGPTL3 had the highest expansion of CD34+CD38-CD90+ primitive progenitor (27.7±2.2 fold compared to 8.5±1.1 fold with standard cytokines, p =0.01), was found to be superior to all other combinations, including combinations “A”, “B”, “BC”, “BD”, “CD” and “ABCD”, which could stimulate over 2 fold expansion of primitive progenitor compare to control (Figure 1C). Interestingly, despite expansion of primitive CD34+CD38-CD90+ cells, there was no further enhancement of the expansion of total cells and general progenitors compare to control (data not shown), suggesting that the cyokine cocktail enhanced only the earliest progenitors. In conclusion, IGFBP1, IGFBP2, IGF2 and ANGPTL3 can stimulate the expansion of CD34+CD38-CD90+ primitive progenitor at low dosage, and the optimal combination comprises IGFBP1, IGFBP2 and ANGPTL3. Further in vivo experimentation is in progress to verify the effect of our optimized cytokine combination culture system on ex vivo expansion of cryopreserved unselected clinical UCB HSCs. Download : Download high-res image (289KB) Download : Download full-size image Disclosures: No relevant conflicts of interest to declare.