| 1. |
- Zhou, Qiongyu, et al.
(författare)
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Corrosion behavior of Hf0.5 Nb0.5 Ta0.5 Ti1.5 Zr refractory high-entropy in aqueous chloride solutions
- 2019
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Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 98, s. 63-68
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Tidskriftsartikel (refereegranskat)abstract
- The Hf0.5Nb0.5Ta0.5Ti1.5Zr refractory high-entropy alloy with excellent corrosion resistance in the 3.5 wt% NaCl solution is identified in this work. This refractory high-entropy alloy exhibits much better general corrosion resistance than that of the 316L stainless steel, due to its corrosion current density being about one fifth of that in the latter. Meanwhile, the pitting potential of Hf0.5Nb0.5Ta0.5Ti1.5Zr reaches an unusually high value of +8.36 V, much higher than that of reported high-entropy alloys. The superior passivity of Hf0.5Nb0.5Ta0.5Ti1.5Zr is accredited to the formation of a single-phase solid solution containing high amount of homogenously distributed passivity-promoting elements, and also the existence of metallic Ta and OH− species in the passive film, which contribute to the high immunity to passive film breakdown.
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| 2. |
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| 3. |
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| 4. |
- Cai, Demin, et al.
(författare)
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Gestational dietary betaine supplementation suppresses hepatic expression of lipogenic genes in neonatal piglets through epigenetic and glucocorticoid receptor-dependent mechanisms
- 2016
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1861:1, s. 41-50
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Tidskriftsartikel (refereegranskat)abstract
- Methyl donors play critical roles in nutritional programming through epigenetic regulation of gene expression. Here we fed gestational sows with control or betaine-supplemented diets (3 g/kg) throughout the pregnancy to explore the effects of maternal methyl-donor nutrient on neonatal expression of hepatic lipogenic genes. Betaine-exposed piglets demonstrated significantly lower liver triglyceride content associated with down-regulated hepatic expression of lipogenic genes acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD) and sterol regulatory element-binding protein-1c. Moreover, s-adenosyl methionine to s-adenosyl homocysteine ratio was elevated in the liver of betaine-exposed piglets, which was accompanied by DNA hypermethylation on FAS and SCD gene promoters and more enriched repression histone mark H31K27me3 on SCD gene promoter. Furthermore, glucocorticoid receptor (GR) binding to SCD gene promoter was diminished along with reduced serum cortisol and liver GR protein content in betaine-exposed piglets. GR-mediated SCD gene regulation was confirmed in HepG2 cells in vitro. Dexamethasone (Dex) drastically increased the luciferase activity of porcine SCD promoter, while the deletion of GR response element on SCD promoter significantly attenuated Dex-mediated SCD transactivation. In addition, miR-let-7e, miR-1285 and miR-124a, which respectively target porcine SCD, ACC and GR, were significantly up-regulated in the liver of betaine-exposed piglets, being in accordance with decreased protein content of these three genes. Taken together, our results suggest that maternal dietary betaine supplementation during gestation attenuates hepatic lipogenesis in neonatal piglets via epigenetic and GR-mediated mechanisms.
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| 5. |
- Chaudhari, Aditi, et al.
(författare)
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ARAP2 promotes GLUT1-mediated basal glucose uptake through regulation of sphingolipid metabolism
- 2016
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981. ; 1861:11, s. 1643-1651
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Tidskriftsartikel (refereegranskat)abstract
- Lipid droplet formation, which is driven by triglyceride synthesis, requires several droplet-associated proteins. We identified ARAP2 (an ADP-ribosylation factor 6 GTPase-activating protein) in the lipid droplet proteome of NIH-3T3 cells and showed that knockdown of ARAP2 resulted in decreased lipid droplet formation and triglyceride synthesis. We also showed that ARAP2 knockdown did not affect fatty acid uptake but reduced basal glucose uptake, total levels of the glucose transporter GLUT1, and GLUT1 levels in the plasma membrane and the lipid micro-domain fraction (a specialized plasma membrane domain enriched in sphingolipids). Microarray analysis showed that ARAP2 knockdown altered expression of genes involved in sphingolipid metabolism. Because sphingolipids are known to play a key role in cell signaling, we performed lipidomics to further investigate the relationship between ARAP2 and sphingolipids and potentially identify a link with glucose uptake. We found that ARAP2 knockdown increased glucosylceramide and lactosylceramide levels without affecting ceramide levels, and thus speculated that the rate-limiting enzyme in glycosphingolipid synthesis, namely glucosylceramide synthase (GCS), could be modified by ARAP2. In agreement with our hypothesis, we showed that the activity of GCS was increased by ARAP2 knockdown and reduced by ARAP2 overexpression. Furthermore, pharmacological inhibition of GCS resulted in increases in basal glucose uptake, total GLUT1 levels, triglyceride biosynthesis from glucose, and lipid droplet formation, indicating that the effects of GCS inhibition are the opposite to those resulting from ARAP2 knockdown. Taken together, our data suggest that ARAP2 promotes lipid droplet formation by modifying sphingolipid metabolism through GCS.
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| 6. |
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| 7. |
- Haj-Yasein, Nadia Nabil, et al.
(författare)
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Cysteine deprivation prevents induction of peroxisome proliferator-activated receptor gamma-2 and adipose differentiation of 3T3-L1 cells.
- 2017
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 1878-2434. ; 1862:6, s. 623-635
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Tidskriftsartikel (refereegranskat)abstract
- Plasma cysteine is strongly associated with body fat mass in human cohorts and diets low in cysteine prevents fat accumulation in mice. It is unclear if plasma cysteine affects fat development or if fat accumulation raises plasma cysteine. To determine if cysteine affects adipogenesis, we differentiated 3T3-L1 preadipocytes in medium with reduced cysteine. Cells incubated in media with 10-20μM cysteine exhibited reduced capacity to differentiate into triacylglycerol-storing mature adipocytes compared with cells incubated with 50μM cysteine. Low cysteine severely reduced expression of peroxisome proliferator-activated receptor gamma2 (Pparγ2) and its target genes perlipin1 (Plin1) and fatty acid binding protein-4 (Fabp4). Expression of stearoyl-CoA desaturase-1 (Scd1), known to be repressed with cysteine depletion, was also reduced with low cysteine. Medium depletion of the essential amino acids leucine, valine, and isoleucine had only a modest effect on adipocyte specific gene expression and differentiation. Stimulation with the PPARγ agonist BRL-49653 or addition of a hydrogen sulfide donor enhanced differentiation of 3T3-L1 cells cultured in low cysteine. This demonstrates that the ability to induce PPARγ expression is preserved when cells are cultured in low cysteine. It therefore appears that cysteine depletion inhibits adipogenesis by specifically affecting molecular pathways required for induction of PPARγ expression, rather than through a general reduction of global protein synthesis. In conclusion, we show that low extracellular cysteine reduces adipocyte differentiation by interfering with PPARγ2 and PPARγ target gene expression. Our results provide further evidence for the hypothesis that plasma cysteine is a casual determinant for body fat mass.
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| 8. |
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| 9. |
- Hyötyläinen, Tuulia, 1971-, et al.
(författare)
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Lipidomics in biomedical research-practical considerations
- 2017
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier. - 0006-3002 .- 1878-2434. ; 1862:8, s. 800-803
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Tidskriftsartikel (refereegranskat)abstract
- Lipids have many central physiological roles including as structural components of cell membranes, energy storage sources and intermediates in signaling pathways. Lipid-related disturbances are known to underlie many diseases and their co-morbidities. The emergence of lipidomics has empowered researchers to study lipid metabolism at the cellular as well as physiological levels at a greater depth than was previously possible. The key challenges ahead in the field of lipidomics in medical research lie in the development of experimental protocols and in silico techniques needed to study lipidomes at the systems level. Clinical questions where lipidomics may have an impact in healthcare settings also need to be identified, both from the health outcomes and health economics perspectives. This article is part of a Special Issue entitled: BBALIP_Lipidomics Opinion Articles edited by Sepp Kohlwein.
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| 10. |
- Idevall-Hagren, Olof, et al.
(författare)
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Detection and manipulation of phosphoinositides
- 2015
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1851:6, s. 736-745
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Forskningsöversikt (refereegranskat)abstract
- Phosphoinositides (PIs) are minor components of cell membranes, but play key roles in cell function. Recent refinements in techniques for their detection, together with imaging methods to study their distribution and changes, have greatly facilitated the study of these lipids. Such methods have been complemented by the parallel development of techniques for the acute manipulation of their levels, which in turn allow bypassing the long-term adaptive changes implicit in genetic perturbations. Collectively, these advancements have helped elucidate the role of Pis in physiology and the impact of the dysfunction of their metabolism in disease. Combining methods for detection and manipulation enables the identification of specific roles played by each of the Pis and may eventually lead to the complete deconstruction of the PI signaling network. Here, we review current techniques used for the study and manipulation of cellular Pis and also discuss advantages and disadvantages associated with the various methods. This article is part of a Special Issue entitled Phosphoinositides.
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| 11. |
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| 12. |
- Kober, Alexandra Carmen, et al.
(författare)
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Implications of cerebrovascular ATP-binding cassette transporter G1 (ABCG1) and apolipoprotein M in cholesterol transport at the blood-brain barrier
- 2017
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981. ; 1862:6, s. 573-588
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Tidskriftsartikel (refereegranskat)abstract
- Impaired cholesterol/lipoprotein metabolism is linked to neurodegenerative diseases such as Alzheimer's disease (AD). Cerebral cholesterol homeostasis is maintained by the highly efficient blood-brain barrier (BBB) and flux of the oxysterols 24(S)-hydroxycholesterol and 27-hydroxycholesterol, potent liver-X-receptor (LXR) activators. HDL and their apolipoproteins are crucial for cerebral lipid transfer, and loss of ATP binding cassette transporters (ABC)G1 and G4 results in toxic accumulation of oxysterols in the brain. The HDL-associated apolipoprotein (apo)M is positively correlated with pre-β HDL formation in plasma; its presence and function in the brain was thus far unknown. Using an in vitro model of the BBB, we examined expression, regulation, and functions of ABCG1, ABCG4, and apoM in primary porcine brain capillary endothelial cells (pBCEC). RT Q-PCR analyses and immunoblotting revealed that in addition to ABCA1 and scavenger receptor, class B, type I (SR-BI), pBCEC express high levels of ABCG1, which was up-regulated by LXR activation. Immunofluorescent staining, site-specific biotinylation and immunoprecipitation revealed that ABCG1 is localized both to early and late endosomes and on apical and basolateral plasma membranes. Using siRNA interference to silence ABCG1 (by 50%) reduced HDL-mediated [3H]-cholesterol efflux (by 50%) but did not reduce [3H]-24(S)-hydroxycholesterol efflux. In addition to apoA-I, pBCEC express and secrete apoM mainly to the basolateral (brain) compartment. HDL enhanced expression and secretion of apoM by pBCEC, apoM-enriched HDL promoted cellular cholesterol efflux more efficiently than apoM-free HDL, while apoM-silencing diminished cellular cholesterol release. We suggest that ABCG1 and apoM are centrally involved in regulation of cholesterol metabolism/turnover at the BBB.
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| 13. |
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| 14. |
- Ljunggren, Stefan A, et al.
(författare)
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Lipoprotein profiles in human heterozygote carriers of a functional mutation P297S in scavenger receptor class B1.
- 2015
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier. - 1388-1981 .- 1879-2618. ; 1851:12, s. 1587-1595
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Tidskriftsartikel (refereegranskat)abstract
- The scavenger receptor class B type 1 (SR-B1) is an important HDL receptor involved in cholesterol uptake and efflux, but its physiological role in human lipoprotein metabolism is not fully understood. Heterozygous carriers of the SR-B1P297S mutation are characterized by increased HDL cholesterol levels, impaired cholesterol efflux from macrophages and attenuated adrenal function. Here, the composition and function of lipoproteins were studied in SR-B1P297S heterozygotes.Lipoproteins from six SR-B1P297S carriers and six family controls were investigated. HDL and LDL/VLDL were isolated by ultracentrifugation and proteins were separated by two-dimensional gel electrophoresis and identified by mass spectrometry. HDL antioxidant properties, paraoxonase 1 activities, apoA-I methionine oxidations and HDL cholesterol efflux capacity were assessed.Multivariate modeling separated carriers from controls based on lipoprotein composition. Protein analyses showed a significant enrichment of apoE in LDL/VLDL and of apoL-1 in HDL from heterozygotes compared to controls. The relative distribution of plasma apoE was increased in LDL and in lipid-free form. There were no significant differences in paraoxonase 1 activities, HDL antioxidant properties or HDL cholesterol efflux capacity but heterozygotes showed a significant increase of oxidized methionines in apoA-I.The SR-B1P297S mutation affects both HDL and LDL/VLDL protein compositions. The increase of apoE in carriers suggests a compensatory mechanism for attenuated SR-B1 mediated cholesterol uptake by HDL. Increased methionine oxidation may affect HDL function by reducing apoA-I binding to its targets. The results illustrate the complexity of lipoprotein metabolism that has to be taken into account in future therapeutic strategies aiming at targeting SR-B1.
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| 15. |
- Makoveichuk, Elena, et al.
(författare)
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TNF-alpha decreases lipoprotein lipase activity in 3T3-L1 adipocytes by up-regulation of angiopoietin-like protein 4
- 2017
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier. - 1388-1981 .- 1879-2618. ; 1862:5, s. 533-540
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Tidskriftsartikel (refereegranskat)abstract
- Lipoprotein lipase (LPL) hydrolyzes lipids in plasma lipoproteins so that the fatty acids can be taken up and used by cells. The activity of LPL changes rapidly in response to changes in nutrition, physical activity and other conditions. Angiopoietin-like protein 4 (ANGPTL4) is an important controller of LPL activity. Both LPL and ANGPTL4 are produced and secreted by adipocytes. When the transcription blocker Actinomycin D was added to cultures of 3T3-L1 adipocytes, LPL activity in the medium increased several-fold. LPL mRNA decreased moderately during 5 h, while ANGPTL4 mRNA and protein declined rapidly, explaining that LPL activity was increased. TNF-alpha is known to reduce LPL activity in adipose tissue. We have shown that TNF-a increased ANGPTL4 both at the mRNA and protein level. Expression of ANGPTL4 is known to be under control of Foxol. Use of the Foxol-specific inhibitor AS1842856, or knockdown of ANGPTL4 by RNAi, resulted in increased LPL activity in the medium. Both with ActD and with the Foxol inhibitor the cells became unresponsive to TNF-a. This study shows that TNF-a, by a Foxol dependent pathway, increases the transcription of ANGPTL4 which is secreted by the cells and causes inactivation of LPL.
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| 16. |
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| 17. |
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| 18. |
- Mwinyi, Jessica, et al.
(författare)
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NAFLD is associated with methylation shifts with relevance for the expression of genes involved in lipoprotein particle composition
- 2017
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1862:3, s. 314-323
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Tidskriftsartikel (refereegranskat)abstract
- Non-alcoholic fatty liver disease (NAFLD) is characterized by the accumulation of triglycerides, cholesterol and toxic free fatty acids and is related to low vitamin D levels. In an analysis of specific gene sets we elucidate to what extent NAFLD associates to epigenetic and related transcriptional changes in gene networks regulating lipid, energy and vitamin D balance. Two gene clusters responsible for lipid homeostasis (74 genes) and vitamin D and energy balance (31 genes) were investigated with regard to average epigenetic shifts within the first 1500 bp next to the transcriptional start site. Three cohorts from two published genome wide driven studies that used a microarray approach were investigated including altogether 103 NAFLD and 75 liver healthy subjects. In the first two steps associations between NAFLD abundance, strength of fibrosis and methylation were investigated in two cohorts by multiple linear regression analyses, correcting for important clinical and demographic parameters. Methylation associated strength of transcription in genes showing significant NAFLD related methylation changes were studied in a third step using a third cohort and applying Pearson's correlation and robust linear regression analyses. 41 genes in gene cluster 1 and 14 genes in cluster 2 were significantly differentially methylated in dependency of NAFLD and hepatic fibrosis. We detect new genes significantly changed in methylation, including APO family members (lipid transport), NPC1L1, STARD (cholesterol transport) and GRHL (energy homeostasis). Our results allow novel insights into the hepatic epigenetic regulation of genes important for lipid and vitamin D balance in NAFLD.
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| 19. |
- Nedergaard, Jan, et al.
(författare)
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Cell proliferation and apoptosis inhibition : essential processes for recruitment of the full thermogenic capacity-of-brown-adipose-tissue
- 2019
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1864:1, s. 51-58
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Forskningsöversikt (refereegranskat)abstract
- In mice living under normal animal house conditions, the brown adipocytes in classical brown adipose tissue depots are already essentially fully differentiated: UCP1 mRNA and UCP1 protein levels are practically saturated. This means that any further recruitment in response to cold exposure or any other browning agent - does not result in significant augmentation of these parameters. This may easily be construed to indicate that classical brown adipose tissue cannot be further recruited. However, this is far from the case: the capacity for further recruitment instead lies in the ability of the tissue to increase the number of brown-fat cells, a remarkable and highly controlled physiological recruitment process. We have compiled here the available data concerning the unique ability of norepinephrine to increase cell proliferation and inhibit apoptosis in brown adipocytes. Adrenergically stimulated cell proliferation is fully mediated via beta(1)-adrenoceptors and occurs through activation of stem cells in the tissue; intracellular mediation of the signal involves CAMP and protein kinase A activation, but activation of Erk1/2 is not part of the pathway. Apoptosis inhibition in brown adipocytes is induced by both beta- and alpha(1)-adrenergic receptors and here the intracellular pathway includes Erk1/2 activation. This unique ability of norepinephrine to increase cell number in an apparently mitogenically dormant tissue provides possibilities to augment the metabolic capacity of brown adipose tissue, also for therapeutic purposes.
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| 20. |
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| 21. |
- Oliw, E, 1948-
(författare)
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Polyunsaturated C-18 fatty acids derivatized with Gly and Ile as an additional tool for studies of the catalytic evolution of fungal 8-and 9-dioxygenases
- 2018
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : ELSEVIER SCIENCE BV. - 1388-1981 .- 1879-2618. ; 1863:11, s. 1378-1387
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Tidskriftsartikel (refereegranskat)abstract
- The fungal linoleate diol synthase (LDS) family contains over twenty characterized 8-, 9-, and 10-dioxygenases (DOX), usually fused to catalytically competent cytochromes P450. Crystal structures are not available, but indirect evidence suggests that linoleic acid enters the active site of 8R-DOX-LDS headfirst and enters 9S-DOX-allene oxide synthase (AOS) with the omega-end (tail) first. Fatty acids derivatized with amino acids can conceivably be used to study oxidation in tail first position by enzymes, which bind natural fatty acids headfirst. The results might reveal catalytic similarities of homologous enzymes. 8R-DOX-5,8-LDS oxidize 18:2n-6-Ile and 18:2n-6-Gly in tail first position to 9S-hydroperoxy metabolites, albeit with less position and stereo specificity than 9S-DOX-AOS. The oxygenation mechanism of 9S-DOX-AOS with antarafacial hydrogen abstraction at C-11 and oxygen insertion at C-9 was also retained. Two homologues, 8R-DOX-7,8-LDS and 8R-DOX-AOS, oxidized 18:2n-6-Ile and 18:2n-6-Gly at C-9, suggesting a conserved feature of 8R-DOX domains. 9R-DOX-AOS, with 54% sequence identity to 9S-DOX-AOS, did not oxidize the derivatized C-18 fatty acids. 9Z,12Z-16:2, two carbon shorter than 18:n-6 from the omega-end, was rapidly metabolized to an alpha-ketol, but 7Z,10Z-16:2 was not a substrate. An unsaturated carbon chain from C-1 to C-8 was apparently more important than the configuration at the omega-end. 8R-DOX-LDS and 9R-DOX-AOS may thus bind 18:2n-6 in the same orientation. The oxidation of 18:2n-6 in straight or reverse head-to-tail positions illustrates evolutionary traits between 8- and 9-DOX domains. Fatty acids derivatized with amino acids provide a complementary tool for the analysis of evolution of enzymes.
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| 22. |
- Pingitore, Piero, 1986, et al.
(författare)
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The role of PNPLA3 in health and disease.
- 2019
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Ingår i: Biochimica et biophysica acta. - : Elsevier BV. - 0006-3002. ; 1864:6, s. 900-906
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Tidskriftsartikel (refereegranskat)abstract
- The human patatin-like phospholipase domain-containing 3 (PNPLA3) gene encodes for a protein of 481 amino-acids. The variant rs738409 is a cytosine to guanine substitution, encoding for the isoleucine to methionine substitution at position 148 (I148M) of the protein. This variant is strongly associated with the entire spectrum of liver disease. Although this variant is one of the best characterized and deeply studied, the mechanism behind the PNPLA3 and the liver disease is still not well defined. Functionally, it has become clear that the PNPLA3 protein is an enzyme with lipase activity towards triglycerides and retinyl esters, and acyltransferase activity on phospholipids. The aim of this review is to collect the latest data, obtained by in vitro and in vivo experiments, on the functional aspects of the PNPLA3 protein. Defining the precise role of PNPLA3 in the liver lipid metabolism, in order to develop novel therapies for the treatment of liver disease, will be the key of future research.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Sargsyan, Ernest, et al.
(författare)
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Oleate protects beta-cells from the toxic effect of palmitate by activating pro-survival pathways of the ER stress response
- 2016
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1861:9, s. 1151-1160
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Tidskriftsartikel (refereegranskat)abstract
- Long-term exposure of beta cells to saturated fatty acids impairs insulin secretion and increases apoptosis. In contrast, unsaturated fatty acids protect beta-cells from the long-term negative effects of saturated fatty acids. We aimed to identify the mechanisms underlying this protective action of unsaturated fatty acids. To address the aim, insulin-secreting MINE cells were exposed to palmitate in the absence or presence of oleate and analyzed by using nano-LC MS/MS based proteomic approach. Important findings were validated by using alternative approaches. Proteomic analysis identified 34 proteins differentially expressed in the presence of palmitate compared to control samples. These proteins play a role in insulin processing, mitochondrial function, metabolism of biomolecules, calcium homeostasis, exocytosis, receptor signaling, ER protein folding, antioxidant activity and anti-apoptotic function. When oleate was also present during culture, expression of 15 proteins was different from the expression in the presence of palmitate alone. Most of the proteins affected by oleate are targets of the ER stress response and play a pro-survival role in beta cells such as protein folding and antioxidative defence. We conclude that restoration of pro-survival pathways of the ER stress response is a major mechanism underlying the protective effect of unsaturated fatty acids in beta-cells treated with saturated fatty acids.
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| 27. |
- Sooman, Linda, et al.
(författare)
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Replacement of two amino acids of 9R-dioxygenase-allene oxide synthase of Aspergillus niger inverts the chirality of the hydroperoxide and the allene oxide
- 2016
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 1878-2434. ; 1861:2, s. 108-118
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Tidskriftsartikel (refereegranskat)abstract
- The genome of Aspergillus niger codes for a fusion protein (EHA25900), which can be aligned with ~50% sequence identity to 9S-dioxygenase (DOX)-allene oxide synthase (AOS) of Fusarium oxysporum, homologues of the Fusarium and Colletotrichum complexes and with over 62% sequence identity to homologues of Aspergilli, including (DOX)-9R-AOS of Aspergillus terreus. The aims were to characterize the enzymatic activities of EHA25900 and to identify crucial amino acids for the stereospecificity. Recombinant EHA25900 oxidized 18:2n-6 sequentially to 9R-hydroperoxy-10(E),12(Z)-octadecadienoic acid (9R-HPODE) and to a 9R(10)-allene oxide. 9S- and 9R-DOX-AOS catalyze abstraction of the pro-R hydrogen at C-11, but the direction of oxygen insertion differs. A comparison between twelve 9-DOX domains of 9S- and 9R-DOX-AOS revealed conserved amino acid differences, which could contribute to the chirality of products. The Gly616Ile replacement of 9R-DOX-AOS (A. niger) increased the biosynthesis of 9S-HPODE and the 9S(10)-allene oxide, whereas the Phe627Leu replacement led to biosynthesis of 9S-HPODE and the 9S(10)-allene oxide as main products. The double mutant (Gly616Ile, Phe627Leu) formed over 90% of the 9S stereoisomer of HPODE. 9S-HPODE was formed by antarafacial hydrogen abstraction and oxygen insertion, i.e., the original H-abstraction was retained but the product chirality was altered. We conclude that 9R-DOX-AOS can be altered to 9S-DOX-AOS by replacement of two amino acids (Gly616Ile, Phe627Leu) in the DOX domain.
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| 28. |
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| 29. |
- Surmacz, Liliana, et al.
(författare)
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Short-chain polyisoprenoids in the yeast Saccharomyces cerevisiae - New companions of the old guys
- 2015
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Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981 .- 1879-2618. ; 1851:10, s. 1296-1303
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Tidskriftsartikel (refereegranskat)abstract
- Dolichols are, among others, obligatory cofactors of protein glycosylation in eukaryotic cells. It is well known that yeast cells accumulate a family of dolichols with Dol-15/16 dominating while upon certain physiological conditions a second family with Dol-21 dominating is noted. In this report we identified the presence of additional short-chain length polyprenols - all-trans Pren-7 in three yeast strains (SS328, BY4741 and L5366), Pren-7 was accompanied by traces of putative Pren-6 and -8. Moreover, in two of these strains a single polyprenol mainly-cis-Pren-11 was synthesized at the stationary phase of growth. Identity of polyprenols was confirmed by HR-HPLC/MS, NMR and metabolic labeling. Additionally, simvastatin inhibited their biosynthesis.
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| 30. |
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| 31. |
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