| 1. |
- Barbu, Andreea, et al.
(författare)
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The use of hydrogen gas clearance for blood flow measurements in single endogenous and transplanted pancreatic islets
- 2015
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Ingår i: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 97, s. 124-129
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Tidskriftsartikel (refereegranskat)abstract
- The blood perfusion of pancreatic islets is regulated independently from that of the exocrine pancreas, and is of importance for multiple aspects of normal islet function, and probably also during impaired glucose tolerance. Single islet blood flow has been difficult to evaluate due to technical limitations. We therefore adapted a hydrogen gas washout technique using microelectrodes to allow such measurements. Platinum micro-electrodes monitored hydrogen gas clearance from individual endogenous and transplanted islets in the pancreas of male Lewis rats and in human and mouse islets implanted under the renal capsule of male athymic mice. Both in the rat endogenous pancreatic islets as well as in the intra-pancreatically transplanted islets, the vascular conductance and blood flow values displayed a highly heterogeneous distribution, varying by factors 6-10 within the same pancreas. The blood flow of human and mouse islet grafts transplanted in athymic mice was approximately 30% lower than that in the surrounding renal parenchyma. The present technique provides unique opportunities to study the islet vascular dysfunction seen after transplantation, but also allows for investigating the effects of genetic and environmental perturbations on islet blood flow at the single islet level in vivo. (C) 2014 The Authors. Published by Elsevier Inc.
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| 2. |
- Carlström, Mattias, et al.
(författare)
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Role of nitric oxide deficiency in the development of hypertension in hydronephrotic animals
- 2008
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Ingår i: American Journal of Physiology - Renal Physiology. - : American Physiological Society. - 0363-6127 .- 1522-1466 .- 1931-857X. ; 294:2, s. 362-370
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Tidskriftsartikel (refereegranskat)abstract
- Hydronephrotic animals develop renal injury and hypertension, which is associated with an abnormal tubuloglomerular feedback (TGF). The TGF sensitivity is coupled to nitric oxide (NO) in the macula densa. The involvement of reduced NO availability in the development of hypertension in hydronephrosis was investigated. Hydronephrosis was induced by ureteral obstruction in young rats. Blood pressure and renal excretion were measured in adulthood, under different sodium conditions, and before and after chronic administration of either N-G- nitro-L-arginine methyl ester (L-NAME) or L-arginine. Blood samples for ADMA, SDMA, and L-arginine analysis were taken and the renal tissue was used for histology and determination of NO synthase (NOS) proteins. TGF characteristics were determined by stop-flow pressure technique before and after administration of 7-nitroindazole (7-NI) or L-arginine. Hydronephrotic animals developed salt-sensitive hypertension, which was associated with pressure natriuresis and diuresis. The blood pressure response to L-NAME was attenuated and L-arginine supplementation decreased blood pressure in hydronephrotic animals, but not in the controls. Under control conditions, reactivity and sensitivity of the TGF response were greater in the hydronephrotic group. 7-NI administration increased TGF reactivity and sensitivity in control animals, whereas, in hydronephrotic animals, neuronal NOS (nNOS) inhibition had no effect. L-Arginine attenuated TGF response more in hydronephrotic kidneys than in controls. The hydronephrotic animals displayed various degrees of histopathological changes. ADMA and SDMA levels were higher and the renal expressions of nNOS and endothelial NOS proteins were lower in animals with hydronephrosis. Reduced NO availability in the diseased kidney in hydronephrosis, and subsequent resetting of the TGF mechanism, plays an important role in the development of hypertension.
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| 3. |
- Christensen, Michael, et al.
(författare)
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Metformin attenuates renal medullary hypoxia in diabetic nephropathy through inhibition uncoupling protein-2
- 2019
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Ingår i: Diabetes/Metabolism Research Reviews. - : WILEY. - 1520-7552 .- 1520-7560. ; 35:2
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Tidskriftsartikel (refereegranskat)abstract
- Background: The purpose of the study is to examine the effect of metformin on oxygen metabolism and mitochondrial function in the kidney of an animal model of insulinopenic diabetes in order to isolate any renoprotective effect from any concomitant effect on blood glucose homeostasis.Methods: Sprague-Dawley rats were injected with streptozotocin (STZ) (50 mg kg(-1)) and when stable started on metformin treatment (250 mg kg(-1)) in the drinking water. Rats were prepared for in vivo measurements 25 to 30 days after STZ injection, where renal function, including glomerular filtration rate and sodium transport, was estimated in anesthetized rats. Intrarenal oxygen tension was measured using oxygen sensors. Furthermore, mitochondrial function was assessed in mitochondria isolated from kidney cortex and medulla analysed by high-resolution respirometry, and superoxide production was evaluated using electron paramagnetic resonance.Results: Insulinopenic rats chronically treated with metformin for 4 weeks displayed improved medullary tissue oxygen tension despite of no effect of metformin on blood glucose homeostasis. Metformin reduced UCP2-dependent LEAK and differentially affected medullary mitochondrial superoxide radical production in control and diabetic rats.Conclusions: Metformin attenuates diabetes-induced renal medullary tissue hypoxia in an animal model of insulinopenic type 1 diabetes. The results suggest that the mechanistic pathway to attenuate the diabetes-induced medullary hypoxia is independent of blood glucose homeostasis and includes reduced UCP2-mediated mitochondrial proton LEAK.
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| 4. |
- Davids, Mariska, et al.
(författare)
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Simultaneous determination of asymmetric and symmetric dimethylarginine, L-monomethylarginine, L-arginine, and L-homoarginine in biological samples using stable isotope dilution liquid chromatography tandem mass spectrometry
- 2012
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 900, s. 38-47
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Tidskriftsartikel (refereegranskat)abstract
- Production of the endogenous vasodilator nitric oxide (NO) from L-arginine by NO synthase is modulated by L-homoarginine, L-monomethylargine (MMA), asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). Here we report on a stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of these metabolites in plasma, cells and tissues. After addition of the internal standards (D-7-ADMA, D-4-L-homoarginine and C-13(6)-Larginine), analytes were extracted from the samples using Waters Oasis MCX solid phase extraction cartridges. Butylated analytes were separated isocratically on a Waters XTerra MS C18 column (3.5 mu m. 3.9 mm x 100 mm) using 600 mg/L ammonium formate in water - acetonitrile (95.5:4.5, v/v) containing 0.1 vol% formic acid, and subsequently measured on an AB Sciex API 3000 triple quadrupole mass spectrometer. Multiple reaction monitoring in positive mode was used for analyte quantification. Validation was performed in plasma. Calibration lines were linear (r(2) >= 0.9979) and lower limits of quantification in plasma were 0.4 nM for ADMA and SDMA and 0.8 nM for the other analytes. Accuracy (% bias) was <3% except for MMA (<7%), intra-assay precision (expressed as CV) was <3.5%, inter-assay precision <9.6%, and recovery 92.9-103.2% for all analytes. The method showed good correlation (r(2) >= 0.9125) with our previously validated HPLC-fluorescence method for measurement in plasma, and was implemented with good performance for measurement of tissue samples. Application of the method revealed the remarkably fast (i.e. within 60 min) appearance in plasma of stable isotope-labeled ADMA, SDMA, and MMA during infusion of D-3-methyl-1-C-13-methionine in healthy volunteers.
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| 5. |
- Eckerbom, Per, 1974-, et al.
(författare)
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Intravoxel Incoherent Motion MR Imaging of the Kidney : Pilot Study
- 2013
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Ingår i: Advances in Experimental Medicine and Biology. - New York, NY : Springer New York. - 0065-2598 .- 2214-8019. ; 765, s. 55-58
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Tidskriftsartikel (refereegranskat)abstract
- MR examinations (Achieva 3 T, Philips, Best, The Netherlands) were performed at five different occasions in a healthy volunteer (male 60 years) and in one renal cancer patient (male 78 years) with normal renal function (creatinine 88 μmol/L). Intravoxel incoherent motion (IVIM) coefficients D + D* were measured using respiratory-triggered diffusion-weighted spin-echo echo-planar imaging. Perfusion data of the patient were acquired using a saturation-recovery gradient-echo sequence and with the bolus of Gd-BOPTA (Multihance). D + D* were computed by monoexponential fitting of MR signal intensity attenuation versus b for b = 0, 50, 100, 150 s/mm2. Perfusion parameters were evaluated with “NordicICE” software. The map of D + D* was compared qualitatively with the perfusion map computed from the Gd scan. D + D* values of the cortex and medulla were in the range 2.3–2.7 and 1.1–1.6 × 10-3 mm2/s, respectively. In conclusion, in this pilot study a good qualitative relation between IVIM variables D + D* and renal perfusion has been found.
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| 6. |
- Edlund, Jenny, et al.
(författare)
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Reduced oxygenation in diabetic rat kidneys measured by T2* weighted magnetic resonance micro-imaging
- 2009
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Ingår i: Advances in Experimental Medicine and Biology. - Boston, MA : Springer US. - 0065-2598 .- 2214-8019. ; 645, s. 199-204
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Tidskriftsartikel (refereegranskat)abstract
- By applying invasive techniques for direct measurements of oxygen tension, we have reported decreased kidney oxygenation in experimental diabetes in rats. However, the non-invasive MRI technique utilizing the BOLD effect provides several advantages with the possibility to perform repetitive measurements in the same animals and in human subjects. In this study, we applied a modified single gradient echo micro-imaging sequence to detect the BOLD effect in kidneys of diabetic rats and compared the results to normoglycemic controls. All measurements were performed on inactin-anaesthetized adult male Wistar Furth rats. Diabetes was induced by streptozotocin (45 mg/kg) 14 days prior to MRI-analysis. Sixteen T2*-weighted image records (B0=1.5 T) were performed using radiofrequency spoiled gradient echo sequence with 2.6 ms step increments of TE (TE1=12 ms), while TR (75 ms) and bandwidth per pixel (71.4 Hz) were kept constant. T2* maps were computed by mono-exponential fitting of the pixel intensities. Relaxation rates R2* (1/T2*) in cortex and outer stripe of the outer medulla were similar in both groups (cortex for controls 22.3 +/- 0.4 vs. diabetics 23.1 +/- 1.8 Hz and outer stripe of outer medulla for controls 24.9 +/- 0.4 vs. diabetics 26.4 +/- 1.8 Hz; n=4 in both groups), whereas R2* was increased in the inner stripe of the outer medulla in diabetic rats (diabetics 26.1 +/- 2.4 vs. controls 18.8 +/- 1.4 Hz; n=4, P<0.05). This study demonstrates that experimental diabetes in rats induces decreased oxygenation of the renal outer medulla. Furthermore, the proposed T2*-weighted MR micro-imaging technique is suitable for detection of regional changes in kidney oxygenation in experimental animal models.
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| 7. |
- Edlund, Jenny, et al.
(författare)
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The roles of NADPH-oxidase and nNOS for the increased oxidative stress and the oxygen consumption in the diabetic kidney
- 2010
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Ingår i: Diabetes/Metabolism Research Reviews. - : Wiley. - 1520-7552 .- 1520-7560. ; 26:5, s. 349-356
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Tidskriftsartikel (refereegranskat)abstract
- Background Sustained hyperglycaemia induces increased renal oxygen consumption resulting in reduced oxygen availability in the diabetic kidney. We investigated the roles of the nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase and the neuronal nitric oxide synthase (nNOS) for the increased oxygen consumption in streptozotocin-diabetic rats.MethodsOxygen consumption was measured in isolated proximal tubular cells (PTC) from streptozotocin-induced diabetic rats (n = 7-9 per group) with and without chronic treatment with apocynin, a NADPH-oxidase inhibitor, or S-methyl-L-thiocitrulline (SMTC), a selective nNOS inhibitor, or a combination of the two and the results were compared to normoglycaemic controls (n = 10). Oxidative stress was estimated from thiobarbituric acid reactive substances and protein expression measured by Western blot.ResultsProximal tubular cells from untreated diabetic rats had increased oxygen consumption compared to controls (40.6 +/- 7.9 versus 10.9 +/- 2.0 nmol/mg protein/min). All treatments reduced the diabetes-induced increase in oxygen consumption (apocynin 10.5 +/- 1.7, SMTC 19.7 +/- 3.0 and apocynin +/- SMTC 21.6 +/- 3.6 nmol/mg protein/min). Neither apocynin nor SMTC had any effect on the oxygen consumption in cells pre-incubated with ouabain, an inhibitor of active electrolyte transport. Oxidative stress was elevated in the diabetic kidney and inhibited by all treatments. The increased oxygen consumption by diabetic proximal tubular cells correlated with increased protein expressions of p47phox and nNOS and the treatments prevented these increases.ConclusionsDiabetes induces oxidative stress, which increases oxygen consumption in proximal tubular cells. Inhibition of either NADPH-oxidase or nNOS prevented the increased oxygen consumption. The effect of blocking both these enzymes was less than additive suggesting overlapping pathways which warrant further studies.
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| 8. |
- Franzen, Stephanie, et al.
(författare)
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Differences in susceptibility to develop parameters of diabetic nephropathy in four mouse strains with type 1 diabetes
- 2014
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Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1931-857X .- 1522-1466. ; 306:10, s. F1171-F1178
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Tidskriftsartikel (refereegranskat)abstract
- One-third of diabetes mellitus patients develop diabetic nephropathy, and with underlying mechanisms unknown it is imperative that diabetic animal models resemble human disease. The present study investigated the susceptibility to develop diabetic nephropathy in four commonly used and commercially available mouse strains with type 1 diabetes to determine the suitability of each strain. Type 1 diabetes was induced in C57Bl/6, NMRI, BALB/c, and 129Sv mice by alloxan, and conscious glomerular filtration rate, proteinuria, and oxidative stress levels were measured in control and diabetic animals at baseline and after 5 and 10 wk. Histological alterations were analyzed using periodic acid-Schiff staining. Diabetic C57Bl/6 displayed increased glomerular filtration rate, i.e., hyperfiltration, whereas all other parameters remained unchanged. Diabetic NMRI developed the most pronounced hyperfiltration as well as increased oxidative stress and proteinuria but without glomerular damage. Diabetic BALB/c did not develop hyperfiltration but presented with pronounced proteinuria, increased oxidative stress, and glomerular damage. Diabetic 129Sv displayed proteinuria and increased oxidative stress without glomerular hyperfiltration or damage. However, all strains displayed intras-train correlation between oxidative stress and proteinuria. In conclusion, diabetic C57Bl/6 and NMRI both developed glomerular hyperfiltration but neither presented with histological damage, although NMRI developed low-degree proteinuria. Thus these strains may be suitable when investigating the mechanism causing hyperfiltration. Neither BALB/c nor 129Sv developed hyperfiltration although both developed pronounced proteinuria. However, only BALB/c developed detectable histological damage. Thus BALB/c may be suitable when studying the roles of proteinuria and histological alterations for the progression of diabetic nephropathy.
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| 9. |
- Franzen, Stephanie, et al.
(författare)
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Endothelin type A receptor inhibition normalises intrarenal hypoxia in rats used as a model of type 1 diabetes by improving oxygen delivery
- 2015
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 58:10, s. 2435-2442
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis Intrarenal tissue hypoxia, secondary to increased oxygen consumption, has been suggested as a unifying mechanism for the development of diabetic nephropathy. Increased endothelin-1 signalling via the endothelin type A receptor (ETA-R) has been shown to contribute to the development of chronic kidney disease, but its role in kidney oxygen homeostasis is presently unknown. Methods The effects of acute ETA-R inhibition (8 nmol/l BQ-123 for 30-40 min directly into the left renal artery) on kidney function and oxygen metabolism were investigated in normoglycaemic control and insulinopenic male Sprague Dawley rats (55 mg/kg streptozotocin intravenously 2 weeks before the main experiment) used as a model of type 1 diabetes. Results Local inhibition of ETA-R in the left kidney did not affect BP in either the control or the diabetic rats. As previously reported, diabetic rats displayed increased kidney oxygen consumption resulting in tissue hypoxia in both the kidney cortex and medulla. The inhibition of ETA-Rs restored normal kidney tissue oxygen availability in the diabetic kidney by increasing renal blood flow, but did not affect oxygen consumption. Furthermore, ETA-R inhibition reduced the diabetes-induced glomerular hyperfiltration and increased the urinary sodium excretion. Kidney function in normoglycaemic control rats was largely unaffected by BQ-123 treatment, although it also increased renal blood flow and urinary sodium excretion in these animals. Conclusions/interpretation Acutely reduced intrarenal ETA-R signalling results in significantly improved oxygen availability in the diabetic kidney secondary to elevated renal perfusion. Thus, the beneficial effects of ETA-R inhibition on kidney function in diabetes may be due to improved intrarenal oxygen homeostasis.
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| 10. |
- Franzen, Stephanie, et al.
(författare)
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Pronounced kidney hypoxia precedes albuminuria in type 1 diabetic mice
- 2016
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Ingår i: AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY. - : American Physiological Society. - 1931-857X .- 1522-1466. ; 310:9, s. F807-F809
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Tidskriftsartikel (refereegranskat)abstract
- Intrarenal tissue hypoxia has been proposed as a unifying mechanism for the development of chronic kidney disease, including diabetic nephropathy. However, hypoxia has to be present before the onset of kidney disease to be the causal mechanism. To establish whether hypoxia precedes the onset of diabetic nephropathy, we implemented a minimally invasive electron paramagnetic resonance oximetry technique using implanted oxygen sensing probes for repetitive measurements of in vivo kidney tissue oxygen tensions in mice. Kidney cortex oxygen tensions were measured before and up to 15 days after the induction of insulinopenic diabetes in male mice and compared with normoglycemic controls. On day 16, urinary albumin excretions and conscious glomerular filtration rates were determined to define the temporal relationship between intrarenal hypoxia and disease development. Diabetic mice developed pronounced intrarenal hypoxia 3 days after the induction of diabetes, which persisted throughout the study period. On day 16, diabetic mice had glomerular hyperfiltration, but normal urinary albumin excretion. In conclusion, intrarenal tissue hypoxia in diabetes precedes albuminuria thereby being a plausible cause for the onset and progression of diabetic nephropathy.
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