| 1. |
- Pirazzi, Carlo, et al.
(author)
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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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In: Journal of Hepatology. - : Elsevier BV. - 0168-8278 .- 1600-0641. ; 57:6, s. 1276-1282
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Journal article (peer-reviewed)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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| 2. |
- Fagman, Johan Bourghardt, 1980, et al.
(author)
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The androgen receptor confers protection against diet-induced atherosclerosis, obesity, and dyslipidemia in female mice.
- 2015
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In: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - : Wiley. - 1530-6860 .- 0892-6638. ; 29:4, s. 1540-1550
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Journal article (peer-reviewed)abstract
- Androgens have important cardiometabolic actions in males, but their metabolic role in females is unclear. To determine the physiologic androgen receptor (AR)-dependent actions of androgens on atherogenesis in female mice, we generated female AR-knockout (ARKO) mice on an atherosclerosis-prone apolipoprotein E (apoE)-deficient background. After 8 weeks on a high-fat diet, but not on a normal chow diet, atherosclerosis in aorta was increased in ARKO females (+59% vs. control apoE-deficient mice with intact AR gene). They also displayed increased body weight (+18%), body fat percentage (+62%), and hepatic triglyceride levels, reduced insulin sensitivity, and a marked atherogenic dyslipidemia (serum cholesterol, +52%). Differences in atherosclerosis, body weight, and lipid levels between ARKO and control mice were abolished in mice that were ovariectomized before puberty, consistent with a protective action of ovarian androgens mediated via the AR. Furthermore, the AR agonist dihydrotestosterone reduced atherosclerosis (-41%; thoracic aorta), subcutaneous fat mass (-44%), and cholesterol levels (-35%) in ovariectomized mice, reduced hepatocyte lipid accumulation in hepatoma cells in vitro, and regulated mRNA expression of hepatic genes pivotal for lipid homeostasis. In conclusion, we demonstrate that the AR protects against diet-induced atherosclerosis in female mice and propose that this is mediated by modulation of body composition and lipid metabolism.-Fagman, J. B., Wilhelmson, A. S., Motta, B. M., Pirazzi, C., Alexanderson, C., De Gendt, K., Verhoeven, G., Holmäng, A., Anesten, F., Jansson, J. -O., Levin, M., Borén, J., Ohlsson, C., Krettek, A., Romeo, S., Tivesten, A. The androgen receptor confers protection against diet-induced atherosclerosis, obesity, and dyslipidemia in female mice.
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| 3. |
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| 4. |
- Hiukka, A, et al.
(author)
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ApoCIII-Enriched LDL in Type 2 Diabetes Displays Altered Lipid Composition, Increased Susceptibility for Sphingomyelinase and Increased binding to Biglycan.
- 2009
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In: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 58:9, s. 2018-2026
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Journal article (peer-reviewed)abstract
- Objective- Apolipoprotein CIII (apoCIII) is an independent risk factor for cardiovascular disease, but the molecular mechanisms involved are poorly understood. Here, we investigated potential proatherogenic properties of apoCIII-containing LDL from hypertriglyceridemic patients with type 2 diabetes. Research design and methods - LDL was isolated from controls and subjects with type 2 diabetes, and from apoB transgenic mice. LDL-biglycan binding was analyzed with a solid-phase assay using immunoplates coated with biglycan. Lipid composition was analyzed with mass spectrometry. Hydrolysis of LDL by sphingomyelinase was analyzed after labeling plasma LDL with [(3)H]sphingomyelin. ApoCIII isoforms were quantified after isoelectric focusing. Human aortic endothelial cells were incubated with desialylated apoCIII or with LDL enriched with specific apoCIII isoforms. Results- We showed that enriching LDL with apoCIII only induced a small increase in LDL-proteoglycan binding, and this effect was dependent on a functional Site A in apoB100. Our findings indicated that intrinsic characteristics of the diabetic LDL other than apoCIII per se are responsible for further increased proteoglycan binding of diabetic LDL with high endogenous apoCIII, and we showed alterations in the lipid composition of diabetic LDL with high apoCIII. We also demonstrated that high apoCIII increased susceptibility of LDL to hydrolysis and aggregation by SMase. In addition, we demonstrated that sialylation of apoCIII increased with increasing apoCIII content, and that sialylation of apoCIII was essential for its proinflammatory properties. Conclusions- We have demonstrated a number of features of apoCIII-containing LDL from hypertriglyceridemic patients with type 2 diabetes that could explain the proatherogenic role of apoCIII.
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| 5. |
- Lantero Rodriguez, Marta, et al.
(author)
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Testosterone reduces metabolic brown fat activity in male mice
- 2021
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In: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 251:1, s. 83-96
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Journal article (peer-reviewed)abstract
- Brown adipose tissue (BAT) burns substantial amounts of mainly lipids to produce heat. Some studies indicate that BAT activity and core body temperature are lower in males than females. Here we investigated the role of testosterone and its receptor (the androgen receptor; AR) in metabolic BAT activity in male mice. Castration, which renders mice testosterone deficient, slightly promoted the expression of thermogenic markers in BAT, decreased BAT lipid content, and increased basal lipolysis in isolated brown adipocytes. Further, castration increased the core body temperature. Triglyceride-derived fatty acid uptake, a proxy for metabolic BAT activity in vivo, was strongly increased in BAT from castrated mice ( 4.5-fold increase vs sham-castrated mice) and testosterone replacement reversed the castration-induced increase in metabolic BAT activity. BAT-specific AR deficiency did not mimic the castration effects in vivo and AR agonist treatment did not diminish the activity of cultured brown adipocytes in vitro, suggesting that androgens do not modulate BAT activity via a direct, AR-mediated pathway. In conclusion, testosterone is a negative regulator of metabolic BAT activity in male mice. Our findings provide new insight into the metabolic actions of testosterone.
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| 6. |
- Leppanen, Olli, et al.
(author)
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ATP depletion in macrophages in the core of advanced rabbit atherosclerotic plaques in vivo
- 2006
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In: Atherosclerosis. ; 188:2, s. 323-30
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Journal article (peer-reviewed)abstract
- The cores of rabbit plaques in vivo are hypoxic, suggesting that ATP depletion due to an insufficient supply of oxygen and nutrients could contribute to macrophage death in atherosclerotic plaques. During hypoxia, however, macrophages maintain ATP levels by anaerobic glycolysis. To directly assess ATP and glucose metabolites in plaques in vivo, we used bioluminescence imaging to map the concentrations of ATP, glucose, glycogen, and lactate in normal and atherosclerotic rabbit aortas in vivo. Hypoxia was assessed with NITP (7-(4'-(2-nitroimidazol-1-yl)-butyl)-theophylline). Normal aortas and plaques <500 microm thick were not hypoxic and had homogenous concentrations of energy metabolites. In plaques >500 microm thick, however, the cores were characterized by ATP depletion, low concentrations of glucose and glycogen, and a high concentration of lactate. A majority of ATP-depleted macrophages within the core were viable but severely hypoxic and glucose depleted. Hyperoxia in vitro reversed the ATP depletion in macrophages in viable areas of the core. Our findings suggest that ATP depletion contributes to the death of macrophages in atherosclerotic lesions and to the formation of a necrotic core.
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| 7. |
- Levin, Jan-Olov, et al.
(author)
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Delprogrammet cancerframkallande ämnen i tätortsluft, personlig exponering och bakgrundsmätningar. : Utveckling av metoder för personburen mätning av PAH.
- 2007
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Reports (other academic/artistic)abstract
- I denna studie har olika metoder för analys av partikulära polycykliska aromatiska kolväten (PAH) efter provtagning på filter utvärderats. Två metoder för ultraljudsextraktion, ett traditionellt ultraljudsvattenbad samt en ultraljudsextraktor specialdesignad för PAH-extraktion (Sonicator) samt två olika analysmetoder gaskromatografi-masspektrometri (GC/MS) och vätskekromatografi med fluorescensdetaktion (LC/Fluo) har studerats. För testerna användes bl.a certifierade referensmaterial av typen Urban Dust och Fly Ash. Sonicatorn gav för Urban Dust en avvikelse på mellan 5-35 % med GC/MS-analys och med LC/Fluo-analys var avvikelsen endast 3 % från det certifierade värdet. För extraktion av Fly Ash med Sonicatorn var avvikeslen <10 % med GC/MS-metoden medan LC/Fluo-metoden endast var ca 30 % av det certifierade värdet, vilket inte är acceptabelt. Extraktion med traditionellt ultraljudsvattenbad följt av LC/Fluo-analys gav för Urban Dust en avvikelse på ca 32%. Filterprover tagna i stadsmiljö analyserade med bägge metoderna gav likvärdiga resultat för B[a]P oberoende av analysmetod. Studien visar att båda analysmetoderna är användbara för mätningar där dammet är av typen Urban Dust, dvs. från utomhus- och tätortsmiljöer. I denna studie har fokus legat på analys av högmolekylära, partikulära PAH-komponenter och då framför allt B[a]P. Förutom B[a]P kan flertalet andra PAH-komponenter analyseras med bägge metoderna, dock har i detta projekt endast B[a]P studerats med LC-fluo-metoden eftersom detta ämne är prioriterat i EU-direktiven. En stor fördel med LC/Fluo-metoden är att den inte kräver lika omfattande provupparbetning före analys. LC/Fluo-metoden har något bättre känslighet, men bägge metoderna är tillräckligt känsliga för dessa analyser. Det är viktigt att påpeka att PAH i allmänluften domineras av PAH med 3-4 ringar dvs PAH som finns i gasfas. PAH-komponenterna fenantren, pyren och fluoranten är till 80-90% i gas fas vid 20°C. Vill man mäta sanna halter av PAH i både gasfas och partikelfas måste någon form av denuder eller motsvarande provtagningsmetod användas. För att få en bra uppfattning om totala mängden gas + partiklar och en ungefärlig uppfattning om fördelning gas/partiklar kan en enkel uppsättning av 13-mm-filter av glasfiber i kombination med adsorbentrör med XAD-2 användas [9-10]. Denna provtagningsutrustning är lättanvänd för personburna mätningar där man inte specifikt behöver mäta PM2,5 och kan användas både för GC-MS-analys och LC-Fluo-analys [9-10]. Ett intressant alternativ för att mäta gasfas-PAH är passiva provtagningstekniker som PUF (polyurethane foam disks) och SPMDs (semipermeable membrane devices) som idag används som tidsintegrerade (2-6 veckor) semikvantitativa provtagare i olika miljöövervakningsprogram för gasfas PAH både i Europa och globalt [11-13]. Det är därför viktigt att också utveckla och validera enkla och billiga metoder och gärna diffusionsprovtagare för att kunna mäta gasfas-PAH både stationärt och personburet. Lagring av prover testades inte i denna studie. Vid långtidslagring kan det vara viktigt att lagra filtren i kylskåp. PAH-föreningar med 5 eller 6 ringar anses dock vara stabila även vid lagring i rumstemperatur [7]. Sammanfattningsvis har utvärderingen visat att det är möjligt att analysera 8 av de 16 PAH-föreningar som EPA anger på personburna teflonfilter provtagna med PM2.5cykloner. Inom HÄMI-luft programmet kan man därmed vid samma provtagningstillfälle få svar på partikelmassekoncentrationen och koncentrationen av ett flertal svårflyktiga PAH-föreningar, däribland benso(a)pyren.
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| 8. |
- Magnusson, Lisa U., 1975, et al.
(author)
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Arachidonate 15-Lipoxygenase Type B Knockdown Leads to Reduced Lipid Accumulation and Inflammation in Atherosclerosis
- 2012
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In: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 7:8
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Journal article (peer-reviewed)abstract
- Inflammation in the vascular wall is important for development of atherosclerosis. We have shown previously that arachidonate 15-lipoxygenase type B (ALOX15B) is more highly expressed in human atherosclerotic lesions than in healthy arteries. This enzyme oxidizes fatty acids to substances that promote local inflammation and is expressed in lipid-loaded macrophages (foam cells) present in the atherosclerotic lesions. Here, we investigated the role of ALOX15B in foam cell formation in human primary macrophages and found that silencing of human ALOX15B decreased cellular lipid accumulation as well as proinflammatory cytokine secretion from macrophages. To investigate the role of ALOX15B in promoting the development of atherosclerosis in vivo, we used lentiviral shRNA silencing and bone marrow transplantation to knockdown mouse Alox15b gene expression in LDL-receptor-deficient (Ldlr(-/-)) mice. Knockdown of mouse Alox15b in vivo decreased plaque lipid content and markers of inflammation. In summary, we have shown that ALOX15B influences progression of atherosclerosis, indicating that this enzyme has an active proatherogenic role.
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| 9. |
- Pirazzi, Carlo, et al.
(author)
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PNPLA3 has retinyl-palmitate lipase activity in human hepatic stellate cells
- 2014
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In: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 23:15, s. 4077-4085
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Journal article (peer-reviewed)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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