| 1. |
- Ahnström, Josefin, et al.
(författare)
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A 6-year follow-up of dosing, coagulation factor levels and bleedings in relation to joint status in the prophylactic treatment of haemophilia
- 2004
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Ingår i: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 10:6, s. 689-697
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Tidskriftsartikel (refereegranskat)abstract
- The primary aim of this study was to investigate the possible relationship between coagulation factor level and bleeding frequency during prophylactic treatment of haemophilia after stratification of the patients according to joint scores. The secondary aim was to obtain a systematic overview of the doses of coagulation factors prescribed for prophylaxis at the Malmo haemophilia treatment centre during a 6-year period. A retrospective survey of medical records for the years 1997-2002 and pharmacokinetic study results from the 1990s was complemented by collection of blood samples for coagulation factor assay when needed. Information on the dosing and plasma levels of factor VIII or factor IX, joint scores and incidence of bleedings (joint bleeds and 'other bleeds') was compiled. The patients were stratified by age (0-6, 7-12, 13-18, 19-36 and >36 years) and joint score (0, 1-6 and >6). Individual pharmacokinetic parameters of plasma coagulation factor activities (FVIII:C and FIX:C) were estimated. Trough levels during the treatment were calculated, as well as the number of hours per week of treatment during which plasma FVIII:C/FIX:C fell below a 1, 2 or 3% target level. Fifty-one patients with haemophilia A (two moderate, 49 severe) and 13 with haemophilia B (all severe) were included, yielding data for 364 patient-years of treatment. There was a wide range of dosing schedules, the most common ones being three times a week or every other day for FVIII and twice a week or every third day for FIX. The overall relationship between FVIII:C/FIX:C levels and incidence of joint bleeding was very weak, even after stratification of the patients according to joint score. There was no relationship between coagulation factor level and incidence of other bleeds. In this cohort of patients on high-dose prophylactic treatment, dosing was based more on clinical outcome in terms of bleeding frequency than on the aim to maintain a 1% target level of FVIII:C/FIX:C. Some patients did not bleed in spite of a trough level of <1% and others did in spite of trough levels >3%. The practical implication of our findings is that dosing in prophylactic treatment of haemophilia should be individualized. Thus, proposed standard regimens should be implemented only after careful clinical consideration, with a high readiness for re-assessment and individual dose tailoring.
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| 2. |
- Ahnström, Josefin, et al.
(författare)
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Activated protein C cofactor function of protein S: a novel role for a gamma-carboxyglutamic acid residue
- 2011
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 117:24, s. 6685-6693
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Tidskriftsartikel (refereegranskat)abstract
- Protein S has an important anticoagulant function by acting as a cofactor for activated protein C (APC). We recently reported that the EGF1 domain residue Asp95 is critical for APC cofactor function. In the present study, we examined whether additional interaction sites within the Gla domain of protein S might contribute to its APC cofactor function. We examined 4 residues, composing the previously reported "Face1" (N33S/P35T/E36A/Y39V) variant, as single point substitutions. Of these protein S variants, protein S E36A was found to be almost completely inactive using calibrated automated thrombography. In factor Va inactivation assays, protein S E36A had 89% reduced cofactor activity compared with wild-type protein S and was almost completely inactive in factor VIIIa inactivation; phospholipid binding was, however, normal. Glu36 lies outside the omega-loop that mediates Ca2+-dependent phospholipid binding. Using mass spectrometry, it was nevertheless confirmed that Glu36 is gamma-carboxylated. Our finding that Gla36 is important for APC cofactor function, but not for phospholipid binding, defines a novel function (other than Ca2+ coordination/phospholipid binding) for a Gla residue in vitamin K-dependent proteins. It also suggests that residues within the Gla and EGF1 domains of protein S act cooperatively for its APC cofactor function. (Blood. 2011;117(24):6685-6693)
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| 3. |
- Ahnström, Josefin
(författare)
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Apolipoprotein M – Studies of Structure and Function
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Apolipoprotein M (apoM), a 25 kDa plasma protein, is found in all major lipoprotein classes, although the majority is found in high density lipoproteins (HDL). ApoM has been suggested to be involved in the formation of and adding to the antiatherogenic functions of HDL, but its function is still not completely known. ApoM has been suggested to be a lipokalin. By studies in vitro using recombinant apoM we were able to show that apoM shares the ligand-binding abilities of lipokalins by being able to bind retinol and its two metabolites, all-trans retinoic acid and 9-cis retinoic acid. After successful crystallization trials we managed to determine the 3D structure of recombinant apoM expressed in E.coli. ApoM displays the typical lipocalin fold that was predicted, i.e. characterized by an 8-stranded antiparallel β-barrel enclosing an internal ligand-binding pocket, flanked by a α-helix. The ligand-binding pocket in apoM can be subdivided into a hydrophilic upper part, surrounded by several positively and negatively charged residues, and a hydrophobic lower part lined by numerous hydrophobic residues. ApoM was crystallized as a complex with either myristic acid or glycerol-1-myristate in the hydrophobic pocket showing that apoM can work as a fatty acid binding protein. We were also able to detect a binding of D-sphingosine and sphingosine-1-phosphate in ligand-binding studies. The physiological importance of the binding is not known. Mature apoM is circulating with a retained signal peptide. By constructing apoM with a cleavable signal peptide we were able to show that the signal peptide is necessary for the protein’s ability to associate to lipoproteins. We were also able to show that, in contrast to apoM with a cleavable signal peptide, full-length apoM was accumulated in stably transfected HEK293 cells, expressing apoM, unless serum was present. The addition of extra cellular HDL or co-expression of HDL was enough to completely restore the apoM expression. We have in a previous study found a marked positive correlation between plasma apoM and total cholesterol levels in healthy individuals. To investigate whether plasma apoM levels predict the risk of coronary heart disease, apoM was measured in plasma from subject later developing CHD and healthy controls from two prospective case-control studies, FINRISK ´92 and Copenhagen City Heart Study. In conditional logistic regression analyses, apoM was not a predictor of CHD events. We found positive correlations for apoM with both apoA-I and apoB.
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| 4. |
- Ahnström, Josefin, et al.
(författare)
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HDL Stimulates apoM Secretion.
- 2010
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Ingår i: Protein & Peptide Letters. - 0929-8665. ; Jul 1, s. 1285-1289
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein M (apoM) in human plasma is mainly associated with HDL. A retained signal peptide anchors apoM to the lipoproteins. To investigate the role of the signal peptide in the transfer of apoM from the synthesizing cell to the lipoproteins, wildtype apoM cDNA and the Q(22)A mutant, introducing a signal peptidase cleavage site, were used to stably transfect HEK293 cells, which intrinsically do not express apolipoproteins. When cultured under serum-free conditions, wildtype apoM was, in contrast to Q(22)A, poorly secreted. Addition of serum or purified HDL stimulated secretion of wildtype apoM, which was recovered in the medium incorporated in HDL. The liver cell line HepG2, which synthesizes HDL, was cultured under serum-free conditions and found to secrete apoM as part of an HDL-like particle. In conclusion, due to its retained signal peptide, apoM is poorly secreted unless HDL is either coexpressed or added to the culture medium.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Ahnström, Josefin, et al.
(författare)
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Plasma concentrations of apolipoproteins A-I, B, and M in patients with abdominal aortic aneurysms.
- 2010
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Ingår i: Clinical Biochemistry. - : Elsevier BV. - 1873-2933 .- 0009-9120. ; 43:4-5, s. 407-410
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Apolipoproteins play important roles in the development of atherosclerosis but their involvement in the pathogenesis of abdominal aortic aneurysm (AAA) is poorly understood. The aim was to investigate whether apoA-I, apoB and apoM are independently associated with AAA. Design and methods: Plasma apoA-I, apoB and apoM were measured in 343 patients with AAA and in 214 elderly apparently healthy control individuals from the background population. Results: AAA patients had lower apolipoprotein levels, as compared to healthy individuals; apoA-I, 1.62 vs. 2.08 g/l; apoB, 0.91 vs. 1.04 g/l; apoM, 0.72 vs. 0.91 mumol/l (p<0.0001 for all three). In multivariate analyses, apoA-I and apoB were associated with AAA, odds ratios (95% confidence intervals) being 0.53 (0.43-0.64) and 0.86 (0.75-0.998), respectively. Conclusions: ApoA-I, apoB and apoM levels were significantly lower in patients with AAA than in the control individuals, but only apoA-I and apoB were independently associated to AAA.
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| 8. |
- Ahnström, Josefin, et al.
(författare)
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Plasma concentrations of apolipoproteins A-I, B, and M in patients with critical limb ischemia.
- 2010
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Ingår i: Clinical Biochemistry. - : Elsevier BV. - 1873-2933 .- 0009-9120. ; 43, s. 599-603
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Apolipoproteins affect development of atherosclerosis, but their involvement in the pathogenesis of critical limb ischemia (CLI), a severe form of atherosclerosis, has not previously been examined. DESIGN AND METHODS: ApoA-I, apoB, and apoM were measured in plasma from 196 CLI subjects and 214 control individuals from the background population. RESULTS: Cases had lower levels of the apolipoproteins, as compared to controls; apoA-I, 1.23 vs. 2.08 g/L; apoB, 0.93 vs. 1.04 g/L; apoM, 0.75 vs. 0.91 mumol/L (p<0.0001 for all three). ApoA-I and apoM correlated negatively with inflammatory markers and positively to 1- and 3-year survival rates, whereas apoB did not. In multivariate analyses, apoA-I, but not apoB and apoM, was independently associated with CLI, the odds ratio being 0.015. CONCLUSIONS: In subjects with CLI, plasma concentrations of apoA-I, apoB and apoM were significantly lower than in control individuals, but only apoA-I was independently associated to CLI.
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| 9. |
- Ahnström, Josefin, et al.
(författare)
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Plasma levels of apolipoprotein M in normal and complicated pregnancy.
- 2010
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 1600-0412 .- 0001-6349. ; 89:9, s. 1214-1217
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Tidskriftsartikel (refereegranskat)abstract
- Apolipoprotein M (apoM) is mainly associated with high-density lipoprotein in human plasma. Despite several studies suggesting apoM as an anti-atherogenic, its function is not yet fully understood. Plasma apoM was measured in normal pregnancies at four different gestational ages and in the postpartum period to investigate whether the concentration of apoM changes during pregnancy. In addition, apoM was measured at 13 weeks in women who subsequently developed preeclampsia, gestational diabetes, recurrent miscarriage, or small-for-gestational age babies, and in women with uncomplicated pregnancies. The plasma concentrations of apoM increased during pregnancy to reach highest levels in the postpartum period. Thus, plasma apoM in non-pregnant women was around 0.77 micromol/l, 0.88 micromol/l at 40 gestational weeks, and 1.05 micromol/l in the postpartum period (p < 0.0001). No differences in plasma concentrations of apoM were found among the studied pregnancy complications.
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| 10. |
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