| 1. |
- Adiels, Martin, 1976, et al.
(författare)
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A new combined multicompartmental model for apolipoprotein B-100 and triglyceride metabolism in VLDL subfractions
- 2005
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Ingår i: J Lipid Res. - 0022-2275 .- 1539-7262. ; 46:1, s. 58-67
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Tidskriftsartikel (refereegranskat)abstract
- The use of stable isotopes in conjunction with compartmental modeling analysis has greatly facilitated studies of the metabolism of the apolipoprotein B (apoB)-containing lipoproteins in humans. The aim of this study was to develop a multicompartment model that allows us to simultaneously determine the kinetics of apoB and triglyceride (TG) in VLDL(1) and VLDL(2) after a bolus injection of [(2)H(3)]leucine and [(2)H(5)]glycerol and to follow the catabolism and transfer of the lipoprotein particles. Here, we describe the model and present the results of its application in a fasting steady-state situation in 17 subjects with lipid values representative of a Western population. Analysis of the correlations showed that plasma TG was determined by the VLDL(1) and VLDL(2) apoB and TG fractional catabolic rate. Furthermore, the model showed a linear correlation between VLDL(1) TG and apoB production. A novel observation was that VLDL TG entered the circulation within 21 min after its synthesis, whereas VLDL apoB entered the circulation after 33 min. These observations are consistent with a sequential assembly model of VLDL and suggest that the TG is added to a primordial apoB-containing particle in the liver.
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| 2. |
- Ahnström, Josefin, et al.
(författare)
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Hydrophobic ligand binding properties of the human lipocalin apolipoprotein M
- 2007
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Ingår i: Journal of Lipid Research. - 1539-7262. ; 48:8, s. 1754-1762
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein M (apoM) is a plasma protein associated mainly with HDL. ApoM is suggested to be important for the formation of pre beta-HDL, but its mechanism of action is unknown. Homology modeling has suggested apoM to be a lipocalin. Lipocalins share a structurally conserved beta-barrel, which in many lipocalins bind hydrophobic ligands. The aim of this study was to test the ability of apoM to bind different hydrophobic substances. ApoM was produced both in Escherichia coli and in HEK 293 cells. Characterization of both variants with electrophoretic and immunological methods suggested apoM from E. coli to be correctly folded. Intrinsic tryptophan fluorescence of both apoM variants revealed that retinol, all-trans-retinoic acid, and 9-cis-retinoic acid bound ( dissociation constant 5 2-3 mu M), whereas other tested substances ( e.g., cholesterol, vitamin K, and arachidonic acid) did not. The intrinsic fluorescence of two apoM mutants carrying single tryptophans was quenched by retinol and retinoic acid to the same extent as wild-type apoM, indicating that the environment of both tryptophans was affected by the binding. In conclusion, the binding of retinol and retinoic acid supports the hypothesis that apoM is a lipocalin. The physiological relevance of this binding has yet to be elucidated.
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| 3. |
- Ahnström, Josefin, et al.
(författare)
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Levels of apolipoprotein M are not associated with the risk of coronary heart disease in two independent case-control studies
- 2008
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Ingår i: Journal of Lipid Research. - 1539-7262. ; 49:9, s. 1912-1917
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein M (apoM), a 25 kDa plasma protein belonging to the lipocalin protein family, is predominantly associated with HDL. Studies in mice have suggested apoM to be important for the formation of pre-beta-HDL and to increase cholesterol efflux from macrophage foam cells. Overexpression of human apoM in LDL receptor-deficient mice reduced the atherogenic effect of a cholesterol-rich diet. The aim of the present study was to investigate whether the apoM levels in man predict the risk for coronary heart disease (CHD). ApoM was measured in samples from two separate case-control studies. FINRISK '92 consisted of 255 individuals, of whom 80 developed CHD during follow-up and 175 were controls. The Copenhagen City Heart Study included 1,865 individuals, of whom 921 developed CHD during follow-up and 944 were controls. Correlation studies of apoM concentration with several analytes showed a marked positive correlation with HDL and total cholesterol as well as with apoA-I and apoB. There was no significant difference in mean apoM level between CHD and control subjects in either study. In conditional logistic regression analyses, apoM was not a predictor of CHD events, [odds ratio (95% CI) 0.97 (0.74-1.27) and 0.92 (0.84-1.02), respectively]. In conclusion, no association between apoM and CHD could be found in this study.-Ahnstrom, J., O. Axler, M. Jauhiainen, V. Salomaa, A. S. Havulinna, C. Ehnholm, R. Frikke-Schmidt, A. Tybjaerg-Hansen, and B. Dahlback. Levels of apolipoprotein M are not associated with the risk of coronary heart disease in two independent case-control studies.
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| 4. |
- Axler, Olof, et al.
(författare)
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An ELISA for apolipoprotein M reveals a strong correlation to total cholesterol in human plasma
- 2007
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Ingår i: Journal of Lipid Research. - 1539-7262. ; 48:8, s. 1772-1780
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein M (apoM) is a 188 amino acid, 25 kDa protein belonging to the lipocalin protein superfamily. Although predominantly associated with high density lipoprotein, apoM is found in all major lipoprotein classes. To facilitate clinical studies of apoM, we have developed a sandwich ELISA for the measurement of apoM in human plasma. This method has been used to investigate normal apoM variation and to establish reference values for healthy individuals through the measurement of 598 samples from the Nordic Reference Interval Project Bio-bank and Database ( NOBIDA) biobank. For women 18-49 years old, the reference interval for apoM was 0.58-1.18 mu mol/l, whereas for women 501 years and for men, the reference range was 0.61-1.30 mu mol/l. Correlation studies of apoM with 26 common clinical chemical analytes from the NOBIDA database revealed a marked positive correlation with plasma total cholesterol (r = 0.52) and LDL and HDL cholesterol ( r = 0.43 and 0.36, respectively). There was no statistically significant correlation with HDL/total cholesterol ratio or body mass index. In conclusion, a sandwich ELISA for the measurement of apoM in human plasma shows that apoM concentration is strongly correlated to total cholesterol in healthy individuals.
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| 5. |
- Carlson, Tomas, et al.
(författare)
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Single polyprenol and dolichol isolation by semipreparative high-performance liquid chromatography technique
- 2000
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Ingår i: Journal of Lipid Research. - 0022-2275 .- 1539-7262. ; 41:7, s. 1177-1180
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Tidskriftsartikel (refereegranskat)abstract
- A new method of separation of single polyprenols (or dolichols) from a mixture of isoprenoid alcohols is described. Application of a high-performance liquid chromatography (HPLC) apparatus equipped with a semipreparative ODS column resulted in preparation of long-chain (dihydro)polyprenols of high purity (>95%). This approach substantially decreases the time scale of the conventional chromatographical preparative procedure. The method can be widely used in chemical and biochemical projects, where single polyprenols or dolichols are required.
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| 6. |
- Cheng, Yajun, et al.
(författare)
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Purification, characterization, and expression of rat intestinal alkaline sphingomyelinase.
- 2002
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Ingår i: Journal of Lipid Research. - 1539-7262. ; 43:2, s. 316-324
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Tidskriftsartikel (refereegranskat)abstract
- Intestinal alkaline sphingomyelinase (SMase) has physiological roles in the digestion of sphingomyelin (SM) and clinical implications in colonic carcinogenesis. In the present work, the enzyme from rat has been purified 1,589-fold with 11% recovery by elution of the intestine with bile salt, precipitation of the proteins by acetone, and several types of chromatographies. Its molecular mass was 58 kDa and optimal pH was 9 to 9.5. Under the optimal conditions, the V(max) was 930 micromol/h/mg and K(m) was about 1.25 mM. The enzyme could hydrolyze phosphatidylcholine at pH 7.4 in the presence of Ca2+; the rate was about 8% of that for SM. The activity against SM was dependent on bile salt. Taurine conjugated bile salts were much more effective than glycine conjugated ones, and the most effective bile salts were taurocholate and taurochenodeoxycholate. 3-[(3-Cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS) and Triton X100 (TX100) had no stimulatory effects. Unlike neutral SMase, intestinal alkaline SMase was not Mg2+ dependent, not inhibited by EDTA, and not inhibited by glutathione. The enzyme was stable during incubation with temperatures up to 50 degree C and in pHs from 7 to 10. Trypsin and chymotrypsin had no effects on its activity, and 10 mM dithiothreitol reduced its activity by 25%. A specific antibody against the enzyme was developed, and Western blot showed that the enzyme was expressed in the intestine but not in other organs. In conclusion, we purified a potentially important SMase in the intestine with several properties different from neutral SMase.
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| 7. |
- Christoffersen, Christina, et al.
(författare)
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Isolation and characterization of human apolipoprotein M-containing lipoproteins
- 2006
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Ingår i: Journal of Lipid Research. - 1539-7262. ; 47:8, s. 1833-1843
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein M (apoM) is a novel apolipoprotein with unknown function. In this study, we established a method for isolating apoM-containing lipoproteins and studied their composition and the effect of apoM on HDL function. ApoM-containing lipoproteins were isolated from human plasma with immunoaffinity chromatography and compared with lipoproteins lacking apoM. The apoM-containing lipoproteins were predominantly of HDL size; similar to 5% of the total HDL population contained apoM. Mass spectrometry showed that the apoM-containing lipoproteins also contained apoJ, apoA-I, apoA II, apoC-I, apoC-II, apoC-III, paraoxonase 1, and apoB. ApoM-containing HDL (HDLapoM+) contained significantly more free cholesterol than HDL lacking apoM (HDLapoM-) (5.9 +/- 0.7% vs. 3.2 +/- 0.5%; P < 0.005) and was heterogeneous in size with both small and large particles. HDLapoM+ inhibited Cu2+-induced oxidation of LDL and stimulated cholesterol efflux from THP-1 foam cells more efficiently than HDLapoM-. In conclusion, our results suggest that apoM is associated with a small heterogeneous subpopulation of HDL particles. Nevertheless, apoM designates a subpopulation of HDL that protects LDL against oxidation and stimulates cholesterol efflux more efficiently than HDL lacking apoM.
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| 8. |
- Cristea, Mirela, et al.
(författare)
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On the singular, dual, and multiple positional specificity of manganese lipoxygenase and its G316A mutant
- 2007
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Ingår i: Journal of Lipid Research. - 0022-2275 .- 1539-7262. ; 48:4, s. 890-903
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Tidskriftsartikel (refereegranskat)abstract
- Manganese lipoxygenase (Mn-LO) oxygenates 18:3n-3 and 18:2n-6 to bis-allylic 11S-hydroperoxy fatty acids, which are converted to 13R-hydroperoxy fatty acids. Other unsaturated C16-C22 fatty acids, except 17:3n-3, are poor substrates, possibly due to ineffective enzyme activation (MnIIMnIII) by produced hydroperoxides. Our aim was to determine whether unsaturated C16-C22 fatty acids were oxidized by MnIII-LO. MnIII-LO oxidized C16, C19, C20, and C22 n-3 and n-6 fatty acids. The carbon chain length influenced the position of hydrogen abstraction (n-8, n-5) and oxygen insertion at the terminal or the penultimate 1Z,4Z-pentadienes. Dilinoleoyl¬glycero¬phosphatidyl¬¬choline was oxidized by Mn-LO in agreement with a “tail first” model. 16:3n-3 was oxidized at the bis-allylic n-5 carbon and at positions n-3, n-7, and n-6. Long fatty acids, 19:3n-3, 20:3n-3, 20:4n-6, 22:5n-3, and 22:5n-6, were mainly oxidized at the n-6 and the bis-allylic n-8 positions (in ratios of ~3:2). The bis-allylic hydroperoxides accumulated with one exception, 13-hydroperoxyeicosatetraenoic acid (13-HPETE). MnIII-LO oxidized 20:4n-6 to 15R-HPETE (~60%) and 13-HPETE (~37%) and converted 13-HPETE to 15R-HPETE. MnIII-LO G316A mainly oxygenated 16:3n-3 at positions n-7 and n-6, 19:3n-3 at n-10, n-8, and n-6, 20:3n-3 at n-10 and n-8. We conclude that Mn-LO likely binds fatty acids “tail first” and oxygenates many C16, C18, C20 and C22 fatty acids to significant amounts of bis-allylic hydroperoxides.
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| 9. |
- Diczfalusy, Ulf, et al.
(författare)
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Marked upregulation of cholesterol 25-hydroxylase expression by lipopolysaccharide
- 2009
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Ingår i: Journal of Lipid Research. - 1539-7262 .- 0022-2275. ; 50:11, s. 2258-2264
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Tidskriftsartikel (refereegranskat)abstract
- During screening of genes upregulated by lipopolysaccharide (LPS; endotoxin) treatment of bone marrow-derived mouse macrophages, it was unexpectedly found that cholesterol 25-hydroxylase (Ch25h) was strongly upregulated. Treatment of macrophages with 10 ng/ml of LPS for 2 h resulted in a 35-fold increase in the expression of Ch25h. In contrast, LPS treatment did not increase the expression of Cyp27a1 or Cyp7b1. The increased Ch25h expression was found to be independent of Myeloid differentiation protein 88 signaling but dependent on Toll-like receptor 4 signaling. LPS treatment of macrophages caused a 6- to 7-fold increase in cellular 25-hydroxycholesterol concentration. When macrophages were treated with increasing concentrations of 25-hydroxycholesterol, a dose-dependent release of CCL5 into the culture medium was observed. Intravenous injection of LPS in eight healthy volunteers resulted in an increase in plasma 25-hydroxycholesterol concentration. The possibility is discussed that 25-hydroxycholesterol may have a role in the inflammatory response, in addition to its more established role in the regulation of cholesterol homeostasis.-Diczfalusy, U., K. E. Olofsson, A- M. Carlsson, M. Gong, D. T. Golenbock, O. Rooyackers, U. Flaring, and H. Bjorkbacka. Marked upregulation of cholesterol 25-hydroxylase expression by lipopolysaccharide. J. Lipids Res. 2009. 50: 2258-2264.
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| 10. |
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