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- Boström, Pontus, 1982, et al.
(författare)
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The SNARE protein SNAP23 and the SNARE-interacting protein Munc18c in human skeletal muscle are implicated in insulin resistance/type 2 diabetes.
- 2010
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 59:8, s. 1870-8
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Our previous studies suggest that the SNARE protein synaptosomal-associated protein of 23 kDa (SNAP23) is involved in the link between increased lipid levels and insulin resistance in cardiomyocytes. The objective was to determine whether SNAP23 may also be involved in the known association between lipid accumulation in skeletal muscle and insulin resistance/type 2 diabetes in humans, as well as to identify a potential regulator of SNAP23. RESEARCH DESIGN AND METHODS: We analyzed skeletal muscle biopsies from patients with type 2 diabetes and healthy, insulin-sensitive control subjects for expression (mRNA and protein) and intracellular localization (subcellular fractionation and immunohistochemistry) of SNAP23, and for expression of proteins known to interact with SNARE proteins. Insulin resistance was determined by a euglycemic hyperinsulinemic clamp. Potential mechanisms for regulation of SNAP23 were also investigated in the skeletal muscle cell line L6. RESULTS: We showed increased SNAP23 levels in skeletal muscle from patients with type 2 diabetes compared with that from lean control subjects. Moreover, SNAP23 was redistributed from the plasma membrane to the microsomal/cytosolic compartment in the patients with the type 2 diabetes. Expression of the SNARE-interacting protein Munc18c was higher in skeletal muscle from patients with type 2 diabetes. Studies in L6 cells showed that Munc18c promoted the expression of SNAP23. CONCLUSIONS: We have translated our previous in vitro results into humans by showing that there is a change in the distribution of SNAP23 to the interior of the cell in skeletal muscle from patients with type 2 diabetes. We also showed that Munc18c is a potential regulator of SNAP23.
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- Levin, Malin, 1973, et al.
(författare)
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Rip2 deficiency leads to increased atherosclerosis despite decreased inflammation.
- 2011
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Ingår i: Circulation research. - 1524-4571. ; 109:11, s. 1210-8
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Tidskriftsartikel (refereegranskat)abstract
- The innate immune system and in particular the pattern-recognition receptors Toll-like receptors have recently been linked to atherosclerosis. Consequently, inhibition of various signaling molecules downstream of the Toll-like receptors has been tested as a strategy to prevent progression of atherosclerosis. Receptor-interacting protein 2 (Rip2) is a serine/threonine kinase that is involved in multiple nuclear factor-κB (NFκB) activation pathways, including Toll-like receptors, and is therefore an interesting potential target for pharmaceutical intervention.
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| 5. |
- Li, Lu, 1964, et al.
(författare)
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ARF6 Regulates Neuron Differentiation through Glucosylceramide Synthase
- 2013
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- The small GTPase ADP ribosylation factor 6 (ARF6) mediates endocytosis and has in addition been shown to regulate neuron differentiation. Here we investigated whether ARF6 promotes differentiation of Neuro-2a neuronal cells by modifying the cellular lipid composition. We showed that knockdown of ARF6 by siRNA in Neuro-2a cells increased neuronal outgrowth as expected. ARF6 knockdown also resulted in increased glucosylceramide levels and decreased sphingomyelin levels, but did not affect the levels of ceramide or phospholipids. We speculated that the ARF6 knockdown-induced increase in glucosylceramide was caused by an effect on glucosylceramide synthase and, in agreement, showed that ARF6 knockdown increased the mRNA levels and activity of glucosylceramide synthase. Finally, we showed that incubation of Neuro-2a cells with the glucosylceramide synthase inhibitor D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP) normalized the increased neuronal outgrowth induced by ARF6 knockdown. Our results thus show that ARF6 regulates neuronal differentiation through an effect on glucosylceramide synthase and glucosylceramide levels.
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| 6. |
- Olofsson, Sven-Olof, 1947, et al.
(författare)
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The formation of lipid droplets: possible role in the development of insulin resistance/type 2 diabetes.
- 2011
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Ingår i: Prostaglandins, leukotrienes, and essential fatty acids. - : Elsevier BV. - 1532-2823 .- 0952-3278. ; 85:5, s. 215-8
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Tidskriftsartikel (refereegranskat)abstract
- Neutral lipids are stored in so-called lipid droplets, which are formed as small primordial droplets at microsomal membranes and increase in size by a fusion process. The fusion is catalyzed by the SNARE proteins SNAP23, syntaxin-5 and VAMP4. SNAP23 is involved in the insulin dependent translocation of GLUT4 to the plasma membrane, and has an important role in the development of insulin resistance. Thus fatty acids relocalize SNAP23 from the plasma membrane (and the translocation of GLUT 4) to the interior of the cell giving rise to insulin resistance. Moreover this relocalization is seen in skeletal muscles biopsies from patients with type 2 diabetes compared to matched control. Thus a missorting of SNAP23 is essential for the development of insulin resistance.
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| 7. |
- Pettersson, Camilla, 1978, et al.
(författare)
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LDL-associated apolipoprotein J and lysozyme are associated with atherogenic properties of LDL found in type 2 diabetes and the metabolic syndrome.
- 2011
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Ingår i: Journal of internal medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 269:3, s. 306-321
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Tidskriftsartikel (refereegranskat)abstract
- Objectives Exchangeable low-density lipoprotein (LDL)-associated proteins can affect the atherogenic properties of LDL. Our aim was to analyze the protein composition of LDL from individuals with or without type 2 diabetes and the metabolic syndrome (T2DM) in relation to other LDL-particle characteristics, to assess whether certain proteins associate more with certain subclasses of LDL typical for T2DM, such as small, apoCIII-rich LDL. Design LDL from two cohorts of 61-year-old men (n = 19 and 64) with or without T2DM was isolated using size-exclusion chromatography or deuterium oxide-based ultracentrifugation. LDL-associated proteins were identified using mass spectrometry and quantified using two-dimensional gel electrophoresis or enzyme-linked immunosorbent assay. Differently expressed LDL-associated proteins apolipoprotein (apo)J and lysozyme were also measured in serum from a third cohort of women (n = 71) with or without T2DM. Lysozyme binding to advanced glycation end product (AGE)-LDL was examined in vitro. Results ApoJ and lysozyme were increased in LDL particles with increased apoCIII content and decreased cholesterol content. When isolated with SEC, LDL from individuals with T2DM contained more apoJ and lysozyme and less apoA1 than LDL from control individuals. LDL content of apoJ correlated with a smaller LDL-particle size. Serum levels of lysozyme, but not apoJ, were increased in individuals with T2DM. In vitro, lysozyme associated more with AGE-LDL than with unmodified LDL. Conclusions Our results indicate that apoJ and lysozyme are increased in LDL with characteristics of small dense LDL in T2DM. Small dense LDL is easily glycated, and the increased affinity of lysozyme for AGE-LDL provides a possible partial explanation for an increase of lysozyme from those with type 2 diabetes.
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- Pirazzi, Carlo, et al.
(författare)
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Patatin-like phospholipase domain-containing 3 (PNPLA3) I148M (rs738409) affects hepatic VLDL secretion in humans and in vitro
- 2012
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Ingår i: Journal of Hepatology. - : Elsevier BV. - 0168-8278 .- 1600-0641. ; 57:6, s. 1276-1282
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: The robust association between non-alcoholic fatty liver disease (NAFLD) and the genetic variant I148M (rs738409) in PNPLA3 has been widely replicated. The aim of this study was to investigate the effect of the PNPLA3 I148M mutation on: (1) hepatic secretion of very low density lipoproteins (VLDL) in humans; and (2) secretion of apolipoprotein B (apoB) from McA-RH 7777 cells, which secrete VLDL-sized apoB-containing lipoproteins. Methods: VLDL kinetics was analyzed after a bolus infusion of stable isotopes in 55 overweight/obese men genotyped for the PNPLA3 I148M variant. Intracellular lipid content, apoB secretion and glycerolipid metabolism were studied in McA-RH 7777 cells overexpressing the human 1481 wild type or 148M mutant PNPLA3 protein. Results: In humans, carriers of the PNPLA3 148M allele had increased liver fat compared to 1481 homozygotes, and kinetic analysis showed a relatively lower secretion of the large, triglyceride-rich VLDL (VLDL1) in 148M carriers vs. 1481 homozygotes for the same amount of liver fat. McA-RH 7777 cells overexpressing the 148M mutant protein showed a higher intracellular triglyceride content with a lower apoB secretion and fatty acid efflux, compared to cells overexpressing the 1481 wild type protein. The responses with 148M matched those observed in cells expressing the empty vector, indicating that the mutation results in loss of function. Conclusions: We have shown that PNPLA3 affects the secretion of apoB-containing lipoproteins both in humans and in vitro and that the 148M protein is a loss-of-function mutation. We propose that PNPLA3 148M promotes intracellular lipid accumulation in the liver by reducing the lipidation of VLDL.
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| 9. |
- Pirazzi, Carlo, et al.
(författare)
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PNPLA3 has retinyl-palmitate lipase activity in human hepatic stellate cells
- 2014
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 23:15, s. 4077-4085
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Tidskriftsartikel (refereegranskat)abstract
- Retinoids are micronutrients that are stored as retinyl esters in the retina and hepatic stellate cells (HSCs). HSCs are key players in fibrogenesis in chronic liver diseases. The enzyme responsible for hydrolysis and release of retinyl esters from HSCs is unknown and the relationship between retinoid metabolism and liver disease remains unclear. We hypothesize that the patatin-like phospholipase domain-containing 3 (PNPLA3) protein is involved in retinol metabolism in HSCs. We tested our hypothesis both in primary human HSCs and in a human cohort of subjects with non-alcoholic fatty liver disease (N = 146). Here we show that PNPLA3 is highly expressed in human HSCs. Its expression is regulated by retinol availability and insulin, and increased PNPLA3 expression results in reduced lipid droplet content. PNPLA3 promotes extracellular release of retinol from HSCs in response to insulin. We also show that purified wild-type PNPLA3 hydrolyzes retinyl palmitate into retinol and palmitic acid. Conversely, this enzymatic activity is markedly reduced with purified PNPLA3 148M, a common mutation robustly associated with liver fibrosis and hepatocellular carcinoma development. We also find the PNPLA3 I148M genotype to be an independent (P = 0.009 in a multivariate analysis) determinant of circulating retinol-binding protein 4, a reliable proxy for retinol levels in humans. This study identifies PNPLA3 as a lipase responsible for retinyl-palmitate hydrolysis in HSCs in humans. Importantly, this indicates a potential novel link between HSCs, retinoid metabolism and PNPLA3 in determining the susceptibility to chronic liver disease.
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| 10. |
- Werner, Kajsa, et al.
(författare)
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Comprehensive study of the thermal decomposition of different hemicelluloses
- 2013
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Ingår i: European Biomass Conference and Exhibition Proceedings. - : ETA-Florens Renewable Energies. - 9788889407530 ; , s. 944-946
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Carbohydrates (cellulose and hemicellulose) constitute the main fraction of plant cell walls and detailed knowledge about their thermal decomposition are therefore of great importance for understanding pyrolytic degradation properties of biomass. Hemicellulose is a diverse group of non-cellulosic polysaccharides and is composed of chains of different monomeric sugar units (pentoses, hexoses and hexuronic acids). The heterogeneous structures of hemicelluloses should be considered when evaluating the decomposition behavior. Nevertheless, thermal analysis of hemicellulose often uses the commercially available xylan as a model compound of hemicelluloses. In contrast to previous work several polysaccharides (xylan arabinogalactan, galactomannan, xyloglucan, and cellulose) were thoroughly investigated in the current study by thermogravimetric analysis, differential scanning calorimetry and pyrolysis-gas chromatography/mass spectrometry during heating in inert atmosphere. The results gave new insights into hemicellulose decomposition and demonstrated that different hemicelluloses have different decompoition behavior.
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