| 1. |
|
|
| 2. |
- Olivecrona, Gunilla, et al.
(author)
-
Mutation of conserved cysteines in the Ly6 domain of GPIHBP1 in familial chylomicronemia
- 2010
-
In: Journal of Lipid Research. - New York : Rockefeller U.P.. - 0022-2275 .- 1539-7262. ; 51:6, s. 1535-1545
-
Journal article (peer-reviewed)abstract
- We investigated a family from northern Sweden in which three of four siblings have congenital chylomicronemia. Lipoprotein lipase (LPL) activity and mass in pre- and post-heparin plasma were low, and LPL release into plasma after heparin injection was delayed. LPL activity and mass in adipose tissue biopsies appeared normal. [35S]Methionine incorporation studies on adipose tissue showed that newly synthesized LPL was normal in size and normally glycosylated. Breast milk from the affected female subjects contained normal to elevated LPL mass and activity levels. The milk had a lower than normal milk lipid content, and the fatty acid composition was compatible with the milk lipids being derived from de novo lipogenesis, rather than from the plasma lipoproteins. Given the delayed release of LPL into the plasma after heparin, we suspected that the chylomicronemia might be caused by mutations in GPIHBP1. Indeed, all three affected siblings were compound heterozygotes for missense mutations involving highly conserved cysteines in the Ly6 domain of GPIHBP1 (C65S and C68G). The mutant GPIHBP1 proteins reached the surface of transfected CHO cells but were defective in their ability to bind LPL (as judged by both cell-based and cell-free LPL binding assays). Thus, the conserved cysteines in the Ly6 domain are crucial for GPIHBP1 function.
|
|
| 3. |
- Olivecrona, T, et al.
(author)
-
New aspects on heparin and lipoprotein metabolism.
- 1993
-
In: Haemostasis. - 0301-0147 .- 1423-0038. ; 23 Suppl 1, s. 150-60
-
Journal article (peer-reviewed)abstract
- Lipoprotein lipase (LPL) and hepatic lipase (HL) are two enzymes which participate in metabolism of plasma lipoproteins. The enzymes are located at vascular surfaces and are released from their binding sites on injection of heparin. In this paper we give a short overview of the structure of the lipases and their role in lipoprotein metabolism. Earlier studies had shown that low molecular weight (LMW) heparin preparations result in lower LPL activities in blood than do corresponding amounts of conventional heparin. Studies with organ perfusion in rats show that the two types of heparin have similar ability to release the lipases from their binding sites in extrahepatic tissues, but that LMW heparin is less effective than conventional heparin in preventing rapid uptake and degradation of LPL by the liver. After injection of heparin the metabolism of triglyceride-rich lipoproteins is initially accelerated, presumably as a result of the high levels of circulating LPL. Then follows a phase when lipoprotein metabolism is slower than normal, perhaps because endothelial LPL has been depleted by accelerated transport to and degradation in the liver.
|
|
| 4. |
- Davies, Brandon S J, et al.
(author)
-
GPIHBP1 is responsible for the entry of lipoprotein lipase into capillaries.
- 2010
-
In: Cell metabolism. - : Elsevier BV. - 1932-7420 .- 1550-4131. ; 12:1, s. 42-52
-
Journal article (peer-reviewed)abstract
- The lipolytic processing of triglyceride-rich lipoproteins by lipoprotein lipase (LPL) is the central event in plasma lipid metabolism, providing lipids for storage in adipose tissue and fuel for vital organs such as the heart. LPL is synthesized and secreted by myocytes and adipocytes, but then finds its way into the lumen of capillaries, where it hydrolyzes lipoprotein triglycerides. The mechanism by which LPL reaches the lumen of capillaries has remained an unresolved problem of plasma lipid metabolism. Here, we show that GPIHBP1 is responsible for the transport of LPL into capillaries. In Gpihbp1-deficient mice, LPL is mislocalized to the interstitial spaces surrounding myocytes and adipocytes. Also, we show that GPIHBP1 is located at the basolateral surface of capillary endothelial cells and actively transports LPL across endothelial cells. Our experiments define the function of GPIHBP1 in triglyceride metabolism and provide a mechanism for the transport of LPL into capillaries.
|
|
| 5. |
- Hultin, M, et al.
(author)
-
Effect of protamine on lipoprotein lipase and hepatic lipase in rats.
- 1994
-
In: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 304 ( Pt 3), s. 959-66
-
Journal article (peer-reviewed)abstract
- The polycation protamine impedes the catabolism of triglyceride-rich lipoproteins and this has been suggested to be due to intravascular inactivation of lipoprotein lipase. We have made intravenous injections of protamine to rats and found that both lipoprotein lipase and hepatic lipase activities were released to plasma. The effect of protamine was more short-lived than that obtained by injection of heparin. The release of hepatic lipase by protamine was as effective as the release by heparin, while the amount of lipoprotein lipase released by protamine was only about one-tenth of that released by heparin. This was not due to inactivation of lipoprotein lipase, since injection of an excess of heparin 10 min after injection of protamine released as much lipoprotein lipase activity to plasma as in controls. The results in vivo differed from those obtained in model experiments in vitro. Protamine was able to almost quantitatively release both lipoprotein lipase and hepatic lipase from columns of heparin-agarose. The displacement was dependent on the total amount of protamine that had passed over the column, indicating that it was due to occupation by protamine of all available binding sites. Our results in vivo showed that the binding sites for lipoprotein lipase were not blocked as efficiently as those for hepatic lipase, indicating that the binding structures were not identical. It was concluded that the impaired turnover of lipoproteins by protamine probably was due to prevention of binding of the lipoproteins to endothelial cell surfaces rather than to impaired lipase function.
|
|
| 6. |
- Hultin, M, et al.
(author)
-
Metabolism of emulsions containing medium- and long-chain triglycerides or interesterified triglycerides.
- 1994
-
In: Journal of Lipid Research. - 0022-2275 .- 1539-7262. ; 35:10, s. 1850-60
-
Journal article (peer-reviewed)abstract
- This study compares the clearing and metabolism of three different lipid emulsions. They had the same phospholipid emulsifier and similar particle sizes. In one (LLL) the core component was long-chain triglycerides (TG), the second (MMM/LLL) contained equal molar amounts of medium- and long-chain TG, the third (MLM) contained synthetic TG with medium-chain (M) fatty acids in the 1,3-positions and a long-chain (L) fatty acid in the 2-position. In model experiments with bovine lipoprotein lipase, the MMM component was hydrolyzed preferentially in the MMM/LLL emulsion so that the initial products were M fatty acids and M monoglycerides. The MLM emulsion, in contrast, gave M fatty acids and formation of L-MG (monoglyceride) throughout hydrolysis. For in vivo studies [3H]oleic acid was incorporated into the emulsion TG as marker for the long-chain component. After bolus injection to rats, the MMM/LLL and MLM emulsions were cleared more rapidly than the LLL emulsion. This was true at all TG loads studied (4-64 mg for a 200 g rat). The labeled oleic acid was oxidized somewhat more rapidly when administered in the MLM emulsion compared to the MMM/LLL emulsion. There were only slight differences in tissue distribution of label. Hence, differences in in vivo metabolism of the long-chain fatty acids were small compared to the marked differences in TG structure and in patterns of product release during in vitro lipolysis.
|
|
| 7. |
- Hultin, M, et al.
(author)
-
Release of lipoprotein lipase to plasma by triacylglycerol emulsions. Comparison to the effect of heparin.
- 1992
-
In: Biochimica et Biophysica Acta. - 0006-3002 .- 1878-2434. ; 1125:1, s. 97-103
-
Journal article (peer-reviewed)abstract
- It was previously known that lipoprotein lipase (LPL) activity in plasma rises after infusion of a fat emulsion. To explore the mechanism we have compared the release of LPL by emulsion to that by heparin. After bolus injections of a fat emulsion (Intralipid) to rats, plasma LPL activity gradually rose 5-fold to a maximum at 6-8 min. During the same time the concentration of injected triacylglycerols (TG) decreased by about half. Hence, the time-course for plasma LPL activity was quite different from that for plasma TG. The disappearance of injected 125I-labelled bovine LPL from circulation was retarded by emulsion. This effect was more marked 30 min than 3 min after injection of the emulsion. The data indicate that the release of LPL into plasma is not solely due to binding of the lipase to the emulsion particles as such, but involves metabolism of the particles. Emulsion increased the fraction of labelled LPL found in adipose tissue, heart and the red muscle studied, but had no significant effect on the fraction found in liver. The effects of emulsion were quite different from those of heparin, which caused an immediate release of the lipase to plasma, decreased uptake of LPL in most extrahepatic tissues by 60-95%, and increased the fraction taken up in the liver.
|
|
| 8. |
- Kristensen, Kristian K., et al.
(author)
-
A disordered acidic domain in GPIHBP1 harboring a sulfated tyrosine regulates lipoprotein lipase
- 2018
-
In: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 115:26, s. E6020-E6029
-
Journal article (peer-reviewed)abstract
- The intravascular processing of triglyceride-rich lipoproteins depends on lipoprotein lipase (LPL) and GPIHBP1, a membrane protein of endothelial cells that binds LPL within the subendothelial spaces and shuttles it to the capillary lumen. In the absence of GPIHBP1, LPL remains mislocalized within the subendothelial spaces, causing severe hypertriglyceridemia (chylomicronemia). The N-terminal domain of GPIHBP1, an intrinsically disordered region (IDR) rich in acidic residues, is important for stabilizing LPL's catalytic domain against spontaneous and ANGPTL4-catalyzed unfolding. Here, we define several important properties of GPIHBP1's IDR. First, a conserved tyrosine in the middle of the IDR is posttranslationally modified by O-sulfation; this modification increases both the affinity of GPIHBP1-LPL interactions and the ability of GPIHBP1 to protect LPL against. ANGPTL4-catalyzed unfolding. Second, the acidic IDR of GPIHBP1 increases the probability of a GPIHBP1-LPL encounter via electrostatic steering, increasing the association rate constant (k(on)) for LPL binding by >250-fold. Third, we show that LPL accumulates near capillary endothelial cells even in the absence of GPIHBP1. In wild-type mice, we expect that the accumulation of LPL in close proximity to capillaries would increase interactions with GPIHBP1. Fourth, we found that GPIHBP1's IDR is not a key factor in the pathogenicity of chylomicronemia in patients with the GPIHBP1 autoimmune syndrome. Finally, based on biophysical studies, we propose that the negatively charged IDR of GPIHBP1 traverses a vast space, facilitating capture of LPL by capillary endothelial cells and simultaneously contributing to GPIHBP1's ability to preserve LPL structure and activity.
|
|
| 9. |
- Mahmood, Dana, 1965-, et al.
(author)
-
Lipoprotein lipase responds similarly to tinzaparin as to conventional heparin during hemodialysis
- 2010
-
In: BMC Nephrology. - London : BioMed Central. - 1471-2369. ; 11
-
Journal article (peer-reviewed)abstract
- Background: Low molecular weight (LMW) heparins are used for anticoagulation during hemodialysis (HD). Studies in animals have shown that LMW-heparins release lipoprotein lipase (LPL) as efficiently as unfractionated (UF) heparin, but are less able to retard hepatic uptake of the lipase. This raises a concern that the LPL system may become exhausted by LMW-heparin in patients on HD. We have explored this in the setting of clinical HD.Methods: Twenty patients on chronic hemodialysis were switched from a primed infusion of UF-heparin to a single bolus of tinzaparin. There were long term follow up of variables for the estimation of dialysis efficacy as well as of the LPL release during dialysis and the subsequent impact on the triglycerides.Results: The LPL activity in blood was higher on tinzaparin at 40 but lower at 180 minutes during HD. These values did not change during the 6 month study period. There were significant correlations between the LPL activities in individual patients at the beginning and end of the 6 month study period and between the activities on UF-heparin and on tinzaparin, indicating that tissue LPL was not being exhausted. Triglycerides were higher during the HD-session with tinzaparin than UF-heparin. The plasma lipid/lipoprotein levels did not change during the 6 month study period, nor during a 2-year follow up after the switch from UF-heparin to tinzaparin. Urea reduction rate and Kt/V were reduced by 4 and 7% after 6 months with tinzaparin.Conclusion: Our data demonstrate that repeated HD with UF-heparin or tinzaparin does not exhaust the LPL-system.
|
|
| 10. |
- Mohammad, M. A., et al.
(author)
-
Trends in Clinical Practice and Outcomes After Percutaneous Coronary Intervention of Unprotected Left Main Coronary Artery
- 2022
-
In: Journal of the American Heart Association. - : Ovid Technologies (Wolters Kluwer Health). - 2047-9980. ; 11:7
-
Journal article (peer-reviewed)abstract
- Background The use of percutaneous coronary intervention (PCI) to treat unprotected left main coronary artery disease has expanded rapidly in the past decade. We aimed to describe nationwide trends in clinical practice and outcomes after PCI for left main coronary artery disease. Methods and Results Patients (n=4085) enrolled in the SCAAR (Swedish Coronary Angiography and Angioplasty Registry) as undergoing PCI for left main coronary artery disease from 2005 to 2017 were included. A count regression model was used to analyze time-related differences in procedural characteristics. The 3-year major adverse cardiovascular and cerebrovascular event rate defined as death, myocardial infarction, stroke, and repeat revascularization was calculated with the Kaplan-Meier estimator and Cox proportional hazard model. The number of annual PCI procedures grew from 121 in 2005 to 589 in 2017 (389%). The increase was greater for men (479%) and individuals with diabetes (500%). Periprocedural complications occurred in 7.9%, decreasing from 10% to 6% during the study period. A major adverse cardiovascular and cerebrovascular event occurred in 35.7% of patients, falling from 45.6% to 23.9% (hazard ratio, 0.56; 95% CI, 0.41-0.78; P=0.001). Radial artery access rose from 21.5% to 74.2% and intracoronary diagnostic procedures from 14.0% to 53.3%. Use of bare-metal stents and first-generation drug-eluting stents fell from 19.0% and 71.9%, respectively, to 0, with use of new-generation drug-eluting stents increasing to 95.2%. Conclusions Recent changes in clinical practice relating to PCI for left main coronary artery disease are characterized by a 4-fold rise in procedures conducted, increased use of evidence-based adjunctive treatment strategies, intracoronary diagnostics, newer stents, and more favorable outcomes.
|
|
