Binding of thyroxine and 3,5,3'-triiodothyronine to trout plasma lipoproteins

1992 ◽  
Vol 262 (5) ◽  
pp. E712-E720 ◽  
Author(s):  
P. J. Babin
Keyword(s):  
Nutritional Status ◽  
Binding Sites ◽  
Density Lipoprotein ◽  
High Density ◽  
Plasma Lipoproteins ◽  
High Density Lipoproteins ◽  
Minor Role ◽  
Very Low Density Lipoproteins

The plasma vectors of thyroid hormones (TH) in trout have been characterized. Plasma components were separated by density gradient ultracentrifugation after first labeling binding sites with trace levels of radioactive hormones, both in vivo and in vitro. Lipoproteins play only a minor role in humans but are major carriers of thyroxine (T4) and 3,5,3'-triiodothyronine (T3) in trout plasma. More than 67% of T4 and 89% of T3 were bound to lipoproteins (density less than 1.210 g/ml), predominantly to high-density lipoproteins (HDL), regardless of the nutritional status of the animals. The percentage of hormone bound to very-low-density lipoproteins, on the other hand, was proportional to their concentration and thus to nutritional status. T3 and T4 could also bind to vitellogenin, a very-high-density lipoprotein, which could transfer TH to the yolk of oocytes. Homologous ligand displacement indicated that T3 could bind to at least two classes of saturable sites in the plasma. In addition, plasma HDL were the major binding sites with low affinity (1.7 +/- 0.4 x 10(5) M-1) but with high capacity (3.1 +/- 0.3 x 10(-5) M). In conclusion, these results show that lipoproteins are the principal binding sites of TH in trout plasma.

scholarly journals Evidence for the role of high density lipoproteins in mediating the antioxidant effect of estrogens

2000 ◽  
pp. 79-83 ◽  
Author(s):  
W Abplanalp ◽  
MD Scheiber ◽  
K Moon ◽  
B Kessel ◽  
JH Liu ◽  
...  
Keyword(s):  
Density Lipoprotein ◽  
Antioxidant Effect ◽  
High Density ◽  
In Vivo Studies ◽  
Ldl Oxidation ◽  
High Density Lipoproteins ◽  
Oh Groups

Estrogens possess strong antioxidant effects in vitro, but in vivo studies in humans have yielded conflicting results. Little is known regarding factors that mediate the antioxidant effect of estrogens in vivo. In this study the potential role of high density lipoprotein (HDL) was examined. The antioxidant effect of estradiol-17beta (E2) added to low density lipoprotein (LDL) was lost after dialysis. In contrast, the antioxidant effect of E2 added to HDL was conserved after dialysis, suggesting that E2 was bound to HDL. Binding of E2 to LDL increased after esterification (especially to long chain fatty acids). In the presence of HDL, an increased amount of E2 was transferred to LDL. E2-17 ester was as potent as E2 in preventing LDL oxidation in vitro, but 3,17-diesters were not as effective (E2=E2-17 ester>E2-3 ester>E2-3,17 diester). This was also supported by experiments which showed that estrogens with masked 3-OH groups were not effective as antioxidants. These studies provide evidence that HDL could facilitate the antioxidant effect of E2 through initial association, esterification and eventual transfer of E2 esters to LDL. Therefore it is critical that HDL peroxidation parameters be evaluated in subjects receiving estrogen replacement therapy.

Differential Effects of Reconstituted High-density Lipoprotein on Coagulation, Fibrinolysis and Platelet Activation during Human Endotoxemia

1997 ◽  
Vol 77 (02) ◽  
pp. 303-307 ◽  
Author(s):  
Dasja Pajkrt ◽  
Peter G Lerch ◽  
Tom van der Poll ◽  
Marcel Levi ◽  
Marlies Illi ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Plasma Levels ◽  
Density Lipoprotein ◽  
High Density ◽  
Tissue Type ◽  
High Density Lipoproteins ◽  
Double Blind

SummaryHigh-density lipoproteins (HDL) can bind and neutralize lipopoly- saccharides (LPS) in vitro and in vivo. HDL can also affect fibrinolytic activity and can directly influence platelet function by reducing platelet aggregation. In this study, the effects of reconstituted HDL (rHDL) on LPS-induced coagulation, fibrinolysis and platelet activation in humans were investigated. In a double-blind, randomized, placebo-controlled, cross-over study, eight healthy male volunteers were injected with LPS (4 ng/kg) on two occasions, once in conjunction with rHDL (40 mg/kg, given as a 4 h infusion starting 3.5 h prior to LPS injection), and once in conjunction with placebo. rHDL significantly reduced LPS-induced activation of coagulation (plasma levels of prothrombin fragment F1+2) and fibrinolysis (plasma levels of tissue type plasminogen activator antigen, t-PA). No effect was observed on LPS-induced inhibition of the fibrinolytic pathway (PAI-1) or on the transient thrombocytopenia elicited by LPS. Furthermore, rHDL treatment significantly enhanced the inhibition of collagen-stimulated inhibition of platelet aggregation during endotoxemia, but had no such effect on arachido- nate-stimulated platelet aggregation. rHDL treatment per se also reduced collagen-induced platelet aggregation. These results indicate that rHDL modifies the procoagulant state associated with endotoxemia.

scholarly journals Transfer and Enzyme-Mediated Metabolism of Oxidized Phosphatidylcholine and Lysophosphatidylcholine between Low- and High-Density Lipoproteins

Antioxidants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1045
Author(s):  
Naoko Sawada ◽  
Takashi Obama ◽  
Mirei Mizuno ◽  
Kiyoshi Fukuhara ◽  
Sanju Iwamoto ◽  
...  
Keyword(s):  
Cholesterol Acyltransferase ◽  
Density Lipoprotein ◽  
High Density ◽  
Short Chain ◽  
High Density Lipoproteins ◽  
Dependent Manner ◽  
Atheromatous Plaques ◽  
Oxidized Phosphatidylcholine

Oxidized low-density lipoprotein (oxLDL) and oxidized high-density lipoprotein (oxHDL), known as risk factors for cardiovascular disease, have been observed in plasma and atheromatous plaques. In a previous study, the content of oxidized phosphatidylcholine (oxPC) and lysophosphatidylcholine (lysoPC) species stayed constant in isolated in vivo oxLDL but increased in copper-induced oxLDL in vitro. In this study, we prepared synthetic deuterium-labeled 1-palmitoyl lysoPC and palmitoyl-glutaroyl PC (PGPC), a short chain-oxPC to elucidate the metabolic fate of oxPC and lysoPC in oxLDL in the presence of HDL. When LDL preloaded with d13-lysoPC was mixed with HDL, d13-lysoPC was recovered in both the LDL and HDL fractions equally. d13-LysoPC decreased by 50% after 4 h of incubation, while d13-PC increased in both fractions. Diacyl-PC production was abolished by an inhibitor of lecithin-cholesterol acyltransferase (LCAT). When d13-PGPC-preloaded LDL was incubated with HDL, d13-PGPC was transferred to HDL in a dose-dependent manner when both LCAT and lipoprotein-associated phospholipase A2 (Lp-PLA2) were inhibited. Lp-PLA2 in both HDL and LDL was responsible for the hydrolysis of d13-PGPC. These results suggest that short chain-oxPC and lysoPC can transfer between lipoproteins quickly and can be enzymatically converted from oxPC to lysoPC and from lysoPC to diacyl-PC in the presence of HDL.

scholarly journals High-Density Lipoproteins and Serum Amyloid A (SAA)

2021 ◽  
Vol 23 (2) ◽  
Author(s):  
Nancy R. Webb
Keyword(s):  
Serum Amyloid A ◽  
Inflammatory Responses ◽  
Inflammatory Diseases ◽  
Density Lipoprotein ◽  
High Density ◽  
Serum Amyloid ◽  
High Density Lipoproteins ◽  
Amyloid A

Abstract Purpose of Review Serum amyloid A (SAA) is a highly sensitive acute phase reactant that has been linked to a number of chronic inflammatory diseases. During a systemic inflammatory response, liver-derived SAA is primarily found on high-density lipoprotein (HDL). The purpose of this review is to discuss recent literature addressing the pathophysiological functions of SAA and the significance of its association with HDL. Recent Findings Studies in gene-targeted mice establish that SAA contributes to atherosclerosis and some metastatic cancers. Accumulating evidence indicates that the lipidation state of SAA profoundly affects its bioactivities, with lipid-poor, but not HDL-associated, SAA capable of inducing inflammatory responses in vitro and in vivo. Factors that modulate the equilibrium between lipid-free and HDL-associated SAA have been identified. Summary HDL may serve to limit SAA’s bioactivities in vivo. Understanding the factors leading to the release of systemic SAA from HDL may provide insights into chronic disease mechanisms.

scholarly journals The effects of insulin deficiency on the plasma clearance and exchange of high-density-lipoprotein phosphatidylcholine in rats

1992 ◽  
Vol 281 (3) ◽  
pp. 851-857 ◽  
Author(s):  
I J Martins ◽  
T G Redgrave
Keyword(s):  
Plasma Clearance ◽  
Cholesterol Acyltransferase ◽  
Density Lipoprotein ◽  
Cholesteryl Oleate ◽  
High Density ◽  
Plasma Lipoproteins ◽  
High Density Lipoproteins ◽  
Phospholipid Transfer ◽  
Plasma High Density

Triolein/cholesteryl oleate/cholesterol/phosphatidylcholine emulsions designed to model the lipid composition of chylomicrons were injected intravenously into control and streptozotocin-treated insulin-deficient rats. As previously described for lymph chylomicrons, the emulsion triolein was hydrolysed and phosphatidylcholine was transferred to the plasma high-density lipoproteins (HDL). This mechanism was used to introduce a phospholipid label into HDL in vivo. The subsequent clearance of phospholipid radioactivity from the plasma of insulin-deficient rats was significantly slower than in controls (P less than 0.025). Plasma clearance was similarly slower in insulin-deficient rats after injection of HDL that was previously labelled with radioactive phospholipids. After injection, the phospholipid label redistributed rapidly between the large-particle fraction of plasma lipoproteins (very-low- and low-density lipoproteins), and the lighter and heavier fractions of HDL. Compared with control rats, in insulin-deficient rats less of the phospholipid label was distributed to the lighter HDL fraction and more to the heavier HDL fraction, and this difference was not due to changes in activity of lecithin: cholesterol acyltransferase or in the apparent activity of phospholipid transfer protein. In insulin-deficient rats the changes in HDL phospholipid clearance and exchange appeared to be secondary to the associated hypertriglyceridaemia and the related changes in distribution of phospholipids between classes of plasma lipoproteins.

scholarly journals High density lipoproteins mediate in vivo protection against staphylococcal phenol-soluble modulins

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Josefien W. Hommes ◽  
Rachel M. Kratofil ◽  
Sigrid Wahlen ◽  
Carla J. C. de Haas ◽  
Reeni B. Hildebrand ◽  
...  
Keyword(s):  
Density Lipoprotein ◽  
Bloodstream Infections ◽  
Hdl Cholesterol ◽  
High Density ◽  
High Density Lipoproteins ◽  
Dependent Manner ◽  
Biological Functions ◽  
Healthy Humans

AbstractStaphylococcus aureus virulence has been associated with the production of phenol-soluble modulins (PSMs). These PSMs have distinct virulence functions and are known to activate, attract and lyse neutrophils. These PSM-associated biological functions are inhibited by lipoproteins in vitro. We set out to address whether lipoproteins neutralize staphylococcal PSM-associated virulence in experimental animal models. Serum from both LCAT an ABCA1 knockout mice strains which are characterised by near absence of high-density lipoprotein (HDL) levels, was shown to fail to protect against PSM-induced neutrophil activation and lysis in vitro. Importantly, PSM-induced peritonitis in LCAT−/− mice resulted in increased lysis of resident peritoneal macrophages and enhanced neutrophil recruitment into the peritoneal cavity. Notably, LCAT−/− mice were more likely to succumb to staphylococcal bloodstream infections in a PSM-dependent manner. Plasma from homozygous carriers of ABCA1 variants characterized by very low HDL-cholesterol levels, was found to be less protective against PSM-mediated biological functions compared to healthy humans. Therefore, we conclude that lipoproteins present in blood can protect against staphylococcal PSMs, the key virulence factor of community-associated methicillin resistant S. aureus.

Rapid transformation of [3H]cholesteryl ester m rat high-density lipoprotein: in vivo and in vitro studies

Steroids ◽  
1990 ◽  
Vol 55 (7) ◽  
pp. 308-313
Author(s):  
I.J. Goldberg ◽  
R.S. Rosenfeld ◽  
I. Paul ◽  
L.K. Miller ◽  
M.L. Tiell
Keyword(s):  
High Density Lipoprotein ◽  
Cholesteryl Ester ◽  
Density Lipoprotein ◽  
High Density ◽  
In Vitro Studies ◽  
Rapid Transformation

Determination of high-density lipoprotein phospholipids in serum.

1980 ◽  
Vol 26 (9) ◽  
pp. 1275-1277 ◽  
Author(s):  
Y Yamaguchi
Keyword(s):  
High Density Lipoprotein ◽  
Density Lipoprotein ◽  
Mean Value ◽  
High Density ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Very Low Density Lipoproteins ◽  
Color Development ◽  
The Mean

Abstract I describe a method for measuring high-density lipoprotein phospholipids. Magnesium chloride and dextran sulfate are used to precipitate all low-density and very-low-density lipoproteins. The supernate contains only high-density lipoproteins, the phospholipid concentration of which is determined by an enzymic method. The precision of the method (CV) is 2.35% (10 repeated assays), and the mean value for HDL-phospholipids was 1006 (SD 248) mg/L for 30 apparently healthy subjects. I used electrophoresis and enzymic color development to confirm the presence of HDL-phospholipids. Results are compared with those obtained by an ultracentrifugation method.

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