| 1. |
- Amrutkar, Manoj, et al.
(författare)
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Genetic Disruption of Protein Kinase STK25 Ameliorates Metabolic Defects in a Diet-Induced Type 2 Diabetes Model
- 2015
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 64:8, s. 2791-2804
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the molecular networks controlling ectopic lipid deposition, glucose tolerance, and insulin sensitivity is essential to identifying new pharmacological approaches to treat type 2 diabetes. We recently identified serine/threonine protein kinase 25 (STK25) as a negative regulator of glucose and insulin homeostasis based on observations in myoblasts with acute depletion of STK25 and in STK25-overexpressing transgenic mice. Here, we challenged Stk25 knockout mice and wild-type littermates with a high-fat diet and showed that STK25 deficiency suppressed development of hyperglycemia and hyperinsulinemia, improved systemic glucose tolerance, reduced hepatic gluconeogenesis, and increased insulin sensitivity. Stk25(-/-) mice were protected from diet-induced liver steatosis accompanied by decreased protein levels of acetyl-CoA carboxylase, a key regulator of both lipid oxidation and synthesis. Lipid accumulation in Stk25(-/-) skeletal muscle was reduced, and expression of enzymes controlling the muscle oxidative capacity (Cpt1, Acox1, Cs, Cycs, Ucp3) and glucose metabolism (Glut1, Glut4, Hk2) was increased. These data are consistent with our previous study of STK25 knockdown in myoblasts and reciprocal to the metabolic phenotype of Stk25 transgenic mice, reinforcing the validity of the results. The findings suggest that STK25 deficiency protects against the metabolic consequences of chronic exposure to dietary lipids and highlight the potential of STK25 antagonists for the treatment of type 2 diabetes.
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| 2. |
- Asplund, Annika, 1979, et al.
(författare)
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Macrophages exposed to hypoxia secrete proteoglycans for which LDL has higher affinity
- 2011
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Ingår i: ATHEROSCLEROSIS. - 0021-9150. ; 215:1, s. 77-81
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Tidskriftsartikel (refereegranskat)abstract
- Macrophages are prominent in hypoxic areas of atherosclerotic lesions. Their secreted proteoglycans (PG) can modulate the retention of lipoproteins as well as the activity of enzymes, cytokines, and growth factors involved in atherogenesis. Versican appears to be one of the main extracellular matrix components binding LDL in the arterial intima. We have recently shown that hypoxia increases versican and perlecan expression in macrophages, and that this increase was regulated by the hypoxia inducible factor (HIF). Here we report effects of hypoxia on human monocyte-derived macrophage (HMDM) secreted glycosaminoglycans (GAG), and its interaction with LDL. After 24 h exposure to 0.5% O2 (hypoxia), metabolically labeled GAG of secreted PG had higher affinity for LDL compared to 21% O2 (control cells). GAG secreted by HMDM in hypoxia were found to be more sulfated and longer which might be responsible for the increased affinity of LDL for these GAG chains. These results indicate that hypoxia induced changes in macrophage GAG biosynthesis have important consequences for the interaction with LDL. If present in vivo, an augmented association of GAG with LDL might contribute to the development of atherosclerosis in hypoxic intima.
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| 3. |
- Fridén, Vincent, 1975, et al.
(författare)
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Clearance of cardiac troponin T with and without kidney function
- 2017
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Ingår i: Clinical Biochemistry. - : Elsevier BV. - 0009-9120. ; 50:9, s. 468-474
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The extent of kidney-dependent clearance of the cardiac damage biomarker cardiac troponin T (cTnT) is not known. Methods and results: We examined clearance of cTnT after injection of heart extracts in rats with or without clamped kidney vessels. The extent of degradation of cTnT to fragments able to pass the glomerular membrane and the kidney extraction index of cTnT was examined in human subjects. After a bolus injection of rat cardiac extract, simulating a large myocardial infarction, there was no significant difference in clearance of cTnT with or without kidney function. However, a slower clearance was observed late in the clearance process, when cTnT levels were low. When low levels of rat cardiac extract were infused at a constant rate to steady state, clamping of the renal vessels resulted in significant 2-fold reduction in clearance of cTnT. Over 60% of the measured cTnT in human subjects had a molecular weight below 17 kDa, expected to have a relatively free passage over the glomerular membrane. The extraction index of cTnT in three heart failure patients undergoing renal vein catheterization was 8-19%. Kidney function adjusted cTnT levels increased the area under the ROC curve for diagnosis of myocardial infarction of the cTnT analysis in an emergency room cohort. Conclusions: At high concentrations, often found after a large myocardial infarction, extrarenal clearance of cTnT dominates. At low levels of cTnT, often found in patients with stable cTnT elevations, renal clearance also contribute to the clearance of cTnT. This potentially explains why stable cTnT levels tend to be higher in patients with low kidney function. (C) 2017 Published by Elsevier Inc. on behalf of The Canadian Society of Clinical Chemists.
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| 4. |
- Fridén, Vincent, 1975
(författare)
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Properties of the glomerular endothelial cell surface layer in vitro and in vivo.
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A healthy kidney produces final urine that is practically devoid of proteins and other physiologically important solutes. Tremendous amounts of fluid are filtered every day through the glomerular filtration barrier which is the actual sieving site in the kidney. Failure of the filtering function leads to proteinuria, which is a feature common to nearly all kidney disease. In spite of this pivotal role, the central mechanisms behind proteinuria are still unexplained. The filtration barrier is a complex biological membrane composed of four different structures: the podocytes (epithelial cells), the glomerular basement membrane, the glomerular endothelium and the glomerular endothelial cell surface layer (ESL). During the last decade the focus for understanding the regulation of this selective sieve has rested heavily on the study of the podocytes, whereas the glomerular endothelium and the glomerular ESL has been more or less neglected as contributors to the permselectivity of the barrier. However, it is of fundamental importance to investigate all components of the filtration barrier in order to understand the pathophysiology of proteinuric kidney disease. The molecular structure of the glomerular ESL is largely unexplored, and available data about its constituents so far is only based on in vitro studies. The aim of this thesis was to identify molecules located in the glomerular ESL with a functional significance for normal glomerular filtration in vivo, and to examine whether a disease-emulating milieu damages major structural glomerular ESL components and thus increases the glomerular permeability to proteins. We have developed a method for qualitative and quantitative assessment of the glomerular ESL in rats, which includes a brief injection of hypertonic sodium chloride into the renal artery. This displaces and elutes non-covalently bound components of the glomerular ESL which are then subsequently collected for further characterization with liquid chromatography-mass spectrometry. Morphological as well as functional effects have been characterized by electron microscopy and by universal methods analyzing charge- and size selectivity of biological membranes. A conditionally immortalized human glomerular endothelial cell line was used to study the effects of hyperglycemia on glomerular ESL proteoglycans. Functional alterations were analyzed in terms of protein restriction by measuring the passage of albumin across a human glomerular endothelial cell monolayer. In conclusion, we have identified molecules from the glomerular ESL in rats that are essential for maintaining a normal glomerular barrier function. Further, we found that hyperglycemia was associated with an alteration of glomerular ESL proteoglycans which lead to an increased permeability for albumin. Overall, the observations in this thesis emphasize the importance of the glomerular ESL for the restriction of proteins in the glomerular filtration barrier.
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| 5. |
- Fridén, Vincent, 1975, et al.
(författare)
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The glomerular endothelial cell coat is essential for glomerular filtration
- 2011
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Ingår i: Kidney international. - : Elsevier BV. - 1523-1755 .- 0085-2538. ; 79:12, s. 1322-1330
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Tidskriftsartikel (refereegranskat)abstract
- The endothelial cell surface layer (ESL) is believed to contribute to the glomerular barrier, and the nature of its molecular structure is still largely unknown. The ESL consists of the membrane-bound glycocalyx and the loosely attached endothelial cell coat (ECC). A brief injection of hypertonic sodium chloride into the left renal artery was used to displace, elute, and collect non-covalently bound components of the renal ESL in rats. This procedure increased the fractional clearance of albumin 12-fold without detectable morphological changes as assessed by electron microscopy compared with the control group injected with isotonic saline. Mathematical modeling suggested a reduced glomerular charge density. Mass spectrometry of the renal eluate identified 17 non-covalently bound proteins normally present in the ECC. One of these proteins, orosomucoid, has previously been shown to be important for capillary permselectivity. Another protein, lumican, is expressed by glomerular endothelial cells and likely contributes to maintaining an intact barrier. Thus, the absence of one or more of these proteins causes proteinuria and illustrates the importance of the ECC in glomerular permselectivity.Kidney International advance online publication, 16 March 2011; doi:10.1038/ki.2011.58.
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| 6. |
- Gustafsson, Maria, 1976, et al.
(författare)
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Retention of Low-Density Lipoprotein in Atherosclerotic Lesions of the Mouse. Evidence for a Role of Lipoprotein Lipase
- 2007
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Ingår i: Circ Res. - 1524-4571. ; 101:8, s. 777-783
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Tidskriftsartikel (refereegranskat)abstract
- Direct binding of apolipoprotein (apo)B-containing lipoproteins to proteoglycans is the initiating event in atherosclerosis, but the processes involved at later stages of development are unclear. Here, we investigated the importance of the apoB-proteoglycan interaction in the development of atherosclerosis over time and investigated the role of lipoprotein lipase (LPL) to facilitate low-density lipoprotein (LDL) retention at later stages of development. Atherosclerosis was analyzed in apoB transgenic mice expressing LDL with normal (control LDL) or reduced proteoglycan-binding (RK3359-3369SA LDL) activity after an atherogenic diet for 0 to 40 weeks. The initiation of atherosclerosis was delayed in mice expressing RK3359-3369SA LDL, but they eventually developed the same level of atherosclerosis as mice expressing control LDL. Retention studies in vivo showed that although higher levels of (131)I-tyramine cellobiose-labeled control LDL ((131)I-TC-LDL) were retained in nonatherosclerotic aortae compared with RK3359-3369SA (131)I-TC-LDL, the retention was significantly higher and there was no difference between the groups in atherosclerotic aortae. Lower levels of control (125)I-TC-LDL and RK3359-3369SA (125)I-TC-LDL were retained in atherosclerotic aortae from ldlr(-/-) mice transplanted with lpl(-/-) compared with lpl(+/+) bone marrow. Uptake of control LDL or RK3359-3369SA LDL into macrophages with specific expression of human catalytically active or inactive LPL was increased compared with control macrophages. Furthermore, transgenic mice expressing catalytically active or inactive LPL developed the same extent of atherosclerosis. Thus, retention of LDL in the artery wall is initiated by direct LDL-proteoglycan binding but shifts to indirect binding with bridging molecules such as LPL.
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| 7. |
- Khramova, Alina, 1989, et al.
(författare)
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Proteoglycans contribute to the functional integrity of the glomerular endothelial cell surface layer and are regulated in diabetic kidney disease
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- All capillary endothelia, including those of the glomeruli, have a luminal cell surface layer (ESL) consisting of glycoproteins, glycolipids, proteoglycans (PGs) and glycosaminoglycans. Previous results have demonstrated that an intact ESL is necessary for a normal filtration barrier and damage to the ESL coupled to proteinuria is seen for example in diabetic kidney disease (DKD). We used the principles of ion exchange chromatography in vivo to elute the highly negatively charged components of the ESL with a 1M NaCl solution in rats. Ultrastructural morphology and renal function were analyzed and 17 PGs and hyaluronan were identified in the ESL. The high salt solution reduced the glomerular ESL thickness, led to albuminuria and reduced GFR. To assess the relevance of ESL in renal disease the expression of PGs in glomeruli from DKD patients in a next generation sequencing cohort was investigated. We found that seven of the homologues of the PGs identified in the ESL from rats were differently regulated in patients with DKD compared to healthy subjects. The results show that proteoglycans and glycosaminoglycans are essential components of the ESL, maintaining the permselective properties of the glomerular barrier and thus preventing proteinuria. © 2021, The Author(s).
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| 8. |
- Morelli, Paula I, et al.
(författare)
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IFNgamma regulates PDGF-receptor alpha expression in macrophages, THP-1 cells, and arterial smooth muscle cells.
- 2006
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Ingår i: Atherosclerosis. - : Elsevier BV. - 0021-9150 .- 1879-1484. ; 184:1, s. 39-47
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Tidskriftsartikel (refereegranskat)abstract
- The recruitment of monocyte-derived macrophages (MDMs) and arterial smooth muscle cells (ASMCs) contributes to inflammation and development of intimal hyperplasia during atherosclerosis. Platelet-derived growth factor (PDGF) is a potent mitogen for SMC, signalling through PDGF-receptor subunits alpha (Ralpha) and beta (Rbeta). We have previously found that interferon gamma (IFNgamma) upregulates PDGF-Ralpha mRNA expression in human MDM (hMDM) which causes an increased migration towards PDGF. In the present study, we found that IFNgamma mediated an upregulation of PDGF-Ralpha mRNA also in THP-1 cells. The induction of PDGF-Ralpha in both hMDM and THP-1 cells was caused by STAT1 binding to the PDGF-Ralpha promoter. In human ASMCs, IFNgamma again stimulated a transient STAT1-binding to the PDGF-Ralpha promoter. However, this was not followed by an upregulation of PDGF-Ralpha mRNA. IFNgamma-stimulation resulted in augmented expression of PDGF-Ralpha protein in differentiated hMDM. Early hMDM only expressed an immature and not fully glycosylated form of the PDGF-Ralpha protein. In contrast, THP-1 cells did not synthesize PDGF-Ralpha protein, implying further posttranscriptional inhibition. Our results contribute to a better understanding of the complex regulation of PDGF-Ralpha expression and how proinflammatory factors may contribute to PDGF-related hyperplasia in vascular diseases.
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| 9. |
- Muslimovic, Aida, et al.
(författare)
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The Liver and Kidneys mediate clearance of cardiac troponin in the rat
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Cardiac-specific troponins (cTn), troponin T (cTnT) and troponin I (cTnI) are diagnostic biomarkers when myocardial infarction is suspected. Despite its clinical importance it is still not known how cTn is cleared once it is released from damaged cardiac cells. The aim of this study was to examine the clearance of cTn in the rat. A cTn preparation from pig heart was labeled with fluorescent dye or fluorine 18 (18 F). The accumulation of the fluorescence signal using organ extracts, or the 18 F signal using positron emission tomography (PET) was examined after a tail vein injection. The endocytosis of fluorescently labeled cTn was studied using a mouse hepatoma cell line. Close to 99% of the cTnT and cTnI measured with clinical immunoassays were cleared from the circulation two hours after a tail vein injection. The fluorescence signal from the fluorescently labeled cTn preparation and the radioactivity from the 18F-labeled cTn preparation mainly accumulated in the liver and kidneys. The fluorescently labeled cTn preparation was efficiently endocytosed by mouse hepatoma cells. In conclusion, we find that the liver and the kidneys are responsible for the clearance of cTn from plasma in the rat.
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| 10. |
- Singh, A., et al.
(författare)
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High glucose causes dysfunction of the human glomerular endothelial glycocalyx
- 2011
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Ingår i: American journal of physiology. Renal physiology. - : American Physiological Society. - 1522-1466 .- 1931-857X. ; 300:1
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Tidskriftsartikel (refereegranskat)abstract
- The endothelial glycocalyx is a gel-like layer which covers the luminal side of blood vessels. The glomerular endothelial cell (GEnC) glycocalyx is composed of proteoglycan core proteins, glycosaminoglycan (GAG) chains, and sialoglycoproteins and has been shown to contribute to the selective sieving action of the glomerular capillary wall. Damage to the systemic endothelial glycocalyx has recently been associated with the onset of albuminuria in diabetics. In this study, we analyze the effects of high glucose on the biochemical structure of the GEnC glycocalyx and quantify functional changes in its protein-restrictive action. We used conditionally immortalized human GEnC. Proteoglycans were analyzed by Western blotting and indirect immunofluorescence. Biosynthesis of GAG was analyzed by radiolabeling and quantified by anion exchange chromatography. FITC-albumin was used to analyze macromolecular passage across GEnC monolayers using an established in vitro model. We observed a marked reduction in the biosynthesis of GAG by the GEnC under high-glucose conditions. Further analysis confirmed specific reduction in heparan sulfate GAG. Expression of proteoglycan core proteins remained unchanged. There was also a significant increase in the passage of albumin across GEnC monolayers under high-glucose conditions without affecting interendothelial junctions. These results reproduce changes in GEnC barrier properties caused by enzymatic removal of heparan sulfate from the GEnC glycocalyx. They provide direct evidence of high glucose-induced alterations in the GEnC glycocalyx and demonstrate changes to its function as a protein-restrictive layer, thus implicating glycocalyx damage in the pathogenesis of proteinuria in diabetes.
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