| 1. |
- Burmakin, Mikhail, et al.
(författare)
-
Pharmacological HIF-PHD inhibition reduces renovascular resistance and increases glomerular filtration by stimulating nitric oxide generation
- 2021
-
Ingår i: Acta Physiologica. - : John Wiley & Sons. - 1748-1708 .- 1748-1716. ; 233:1
-
Tidskriftsartikel (refereegranskat)abstract
- AIM: Hypoxia-inducible factors (HIFs) are O2 -sensitive transcription factors that regulate multiple biological processes which are essential for cellular adaptation to hypoxia. Small molecule inhibitors of HIF-prolyl hydroxylase domain (PHD) dioxygenases (HIF-PHIs) activate HIF-dependent transcriptional programs and have broad clinical potential. HIF-PHIs are currently in global late-stage clinical development for the treatment of anaemia associated with chronic kidney disease. Although the effects of hypoxia on renal haemodynamics and function have been studied in animal models and in humans living at high altitude, the effects of pharmacological HIF activation on renal haemodynamics, O2 metabolism and metabolic efficiency are not well understood.METHODS: Using a cross-sectional study design, we investigated renal haemodynamics, O2 metabolism, gene expression and NO production in healthy rats treated with different doses of HIF-PHIs roxadustat or molidustat compared to vehicle control.RESULTS: Systemic administration of roxadustat or molidustat resulted in a dose-dependent reduction in renovascular resistance (RVR). This was associated with increased glomerular filtration rate (GFR), urine flow and tubular sodium transport rate (TNa ). Although both total O2 delivery and TNa were increased, more O2 was extracted per transported sodium in rats treated with high-doses of HIF-PHIs, suggesting a reduction in metabolic efficiency. Changes in RVR and GFR were associated with increased nitric oxide (NO) generation and substantially suppressed by pharmacological inhibition of NO synthesis.CONCLUSIONS: Our data provide mechanistic insights into dose-dependent effects of short-term pharmacological HIF activation on renal haemodynamics, glomerular filtration and O2 metabolism and identify NO as a major mediator of these effects.
|
|
| 2. |
- Edlund, Jenny, et al.
(författare)
-
Reduced oxygenation in diabetic rat kidneys measured by T2* weighted magnetic resonance micro-imaging
- 2009
-
Ingår i: Advances in Experimental Medicine and Biology. - Boston, MA : Springer US. - 0065-2598 .- 2214-8019. ; 645, s. 199-204
-
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.
|
|
| 3. |
- Edlund, Jenny, et al.
(författare)
-
The roles of NADPH-oxidase and nNOS for the increased oxidative stress and the oxygen consumption in the diabetic kidney
- 2010
-
Ingår i: Diabetes/Metabolism Research Reviews. - : Wiley. - 1520-7552 .- 1520-7560. ; 26:5, s. 349-356
-
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.
|
|
| 4. |
- Franzen, Stephanie, et al.
(författare)
-
Differences in susceptibility to develop parameters of diabetic nephropathy in four mouse strains with type 1 diabetes
- 2014
-
Ingår i: American Journal of Physiology-Renal Physiology. - : American Physiological Society. - 1931-857X .- 1522-1466. ; 306:10, s. F1171-F1178
-
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.
|
|
| 5. |
|
|
| 6. |
- Franzén, Stephanie, et al.
(författare)
-
Intrarenal activation of endothelin type B receptors improves kidney oxygenation in type 1 diabetic rats
- 2018
-
Ingår i: American Journal of Physiology - Renal Physiology. - : AMER PHYSIOLOGICAL SOC. - 1931-857X .- 1522-1466. ; 314:3, s. F439-F444
-
Tidskriftsartikel (refereegranskat)abstract
- About one-third of patients with type 1 diabetes develops kidney disease. The mechanism is largely unknown, but intrarenal hypoxia has been proposed as a unifying mechanism for chronic kidney disease, including diabetic nephropathy. The endothelin system has recently been demonstrated to regulate oxygen availability in the diabetic kidney via a pathway involving endothelin type A receptors (ETA-R). These receptors mainly mediate vasoconstriction and tubular sodium retention, and inhibition of ETA-R improves intrarenal oxygenation in the diabetic kidney. Endothelin type B receptors (ETB-R) can induce vasodilation of the renal vasculature and also regulate tubular sodium handling. However, the role of ETB-R in kidney oxygen homeostasis is unknown. The effects of acute intrarenal ETB-R activation (sarafotoxin 6c for 30-40 min; 0.78 pmol/h directly into the renal artery) on kidney function and oxygen metabolism were investigated in normoglycemic controls and insulinopenic male Sprague-Dawley rats administered streptozotocin (55 mg/kg) 2 wk before the acute experiments. Intrarenal activation of ETB-R improved oxygenation in the hypoxic diabetic kidney. However, the effects on diabetes-induced increased kidney oxygen consumption could not explain the improved oxygenation. Rather, the improved kidney oxygenation was due to hemodynamic effects increasing oxygen delivery without increasing glomerular filtration or tubular sodium load. In conclusion, increased ETB-R signaling in the diabetic kidney improves intrarenal tissue oxygenation due to increased oxygen delivery secondary to increased renal blood flow.
|
|
| 7. |
- Friederich, Malou, et al.
(författare)
-
Diabetes-induced up-regulation of uncoupling protein-2 results in increased mitochondrial uncoupling in kidney proximal tubular cells
- 2008
-
Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 1878-2434 .- 0005-2728. ; 1777:7-8, s. 935-940
-
Tidskriftsartikel (refereegranskat)abstract
- We have previously reported increased O(2) consumption unrelated to active transport by tubular cells and up-regulated mitochondrial uncoupling protein (UCP)-2 expressions in diabetic kidneys. It is presently unknown if the increased UCP-2 levels in the diabetic kidney results in mitochondrial uncoupling and increased O(2) consumption, which we therefore investigated in this study. The presence of UCP-2 in proximal tubular cells was confirmed by immunohistochemistry and found to be increased (western blot) in homogenized tissue and isolated mitochondria from kidney cortex of diabetic rats. Isolated proximal tubular cells had increased total and ouabain-insensitive O(2) consumption compared to controls. Isolated mitochondria from diabetic animals displayed increased glutamate-stimulated O(2) consumption (in the absence of ADP and during inhibition of the ATP-synthase by oligomycin) compared to controls. Guanosine diphosphate, an UCP inhibitor, and bovine serum albumin which removes fatty acids that are essential for UCP-2 uncoupling activity, independently prevented the increased glutamate-stimulated O(2) consumption in mitochondria from diabetic animals. In conclusion, diabetic rats have increased mitochondrial UCP-2 expression in renal proximal tubular cells, which results in mitochondrial uncoupling and increased O(2) consumption. This mechanism may be protective against diabetes-induced oxidative stress, but will increase O(2) usage. The subsequently reduced O(2) availability may contribute to diabetes-induced progressive kidney damage.
|
|
| 8. |
- Friederich, Malou, et al.
(författare)
-
Uncoupling protein-2 in diabetic kidneys : increased protein expression correlates to increased non-transport related oxygen consumption
- 2008
-
Ingår i: Advances in Experimental Medicine and Biology. - Boston, MA : Springer Berlin/Heidelberg. - 0065-2598 .- 2214-8019. ; 614, s. 37-43, s. 37-43
-
Tidskriftsartikel (refereegranskat)abstract
- Diabetic patients have an elevated risk to develop renal dysfunction and it has been postulated that altered energy metabolism is involved. We have previously shown that diabetic rats have markedly decreased oxygen availability in the kidney, resulting from increased oxygen consumption. A substantial part of the increased oxygen consumption is unrelated to tubular transport, suggesting decreased mitochondrial efficiency. In this study, we investigated the protein expression of mitochondrial uncoupling protein (UCP)-2 in kidney tissue from control and streptozotocin (STZ)-induced diabetic rats. Protein levels of UCP-2 were measured in adult male control and STZ-diabetic Wistar Furth as well as Sprague Dawley rats in both the kidney cortex and medulla by Western blot technique. Two weeks of hyperglycemia resulted in increased protein levels of UCP-2 in kidneys from both Wistar Furth and Sprague Dawley rats. Both cortical and medullary UCP-2 levels were elevated 2-3 fold above control levels. We conclude that sustained STZ-induced hyperglycemia increases the kidney levels of mitochondrial UCP-2, which could explain the previously reported increase in non-transport related oxygen consumption in diabetic kidneys. The elevated UCP-2 levels may represent an effort to reduce the increased production of superoxide radicals which is evident during diabetes.
|
|
| 9. |
- Friederich-Persson, Malou, et al.
(författare)
-
Increased kidney metabolism as a pathway to kidney tissue hypoxia and damage : effects of triiodothyronine and dinitrophenol in normoglycemic rats.
- 2013
-
Ingår i: Advances in Experimental Medicine and Biology. - New York, NY : Springer-Verlag New York. - 0065-2598 .- 2214-8019. - 9781461474111 - 9781461472568 ; 789, s. 9-14
-
Tidskriftsartikel (refereegranskat)abstract
- Intrarenal tissue hypoxia is an acknowledged common pathway to end-stage renal disease in clinically common conditions associated with development of chronic kidney disease, such as diabetes and hypertension. In diabetic kidneys, increased oxygen metabolism mediated by mitochondrial uncoupling results in decreased kidney oxygen tension (PO2) and contributes to the development of diabetic nephropathy. The present study investigated whether increased intrarenal oxygen metabolism per se can cause intrarenal tissue hypoxia and kidney damage, independently of confounding factors such as hyperglycemia and oxidative stress. Male Sprague-Dawley rats were untreated or treated with either triiodothyronine (T3, 10 g/kg bw/day, subcutaneously for 10 days) or the mitochondria uncoupler dinitrophenol (DNP, 30 mg/kg bw/day, oral gavage for 14 days), after which in vivo kidney function was evaluated in terms of glomerular filtration rate (GFR, inulin clearance), renal blood flow (RBF, Transonic, PAH clearance), cortical PO2 (Clark-type electrodes), kidney oxygen consumption (QO2), and proteinuria. Administration of both T3 and DNP increased kidney QO2 and decreased PO2 which resulted in proteinuria. However, GFR and RBF were unaltered by either treatment. The present study demonstrates that increased kidney metabolism per se can cause intrarenal tissue hypoxia which results in proteinuria. Increased kidney QO2 and concomitantly reduced PO2 may therefore be a mechanism for the development of chronic kidney disease and progression to end-stage renal disease.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
- Liss, Per, et al.
(författare)
-
Iodinated contrast media decrease renomedullary blood flow. A possible cause of contrast media-induced nephropathy
- 2009
-
Ingår i: Advances in Experimental Medicine and Biology. - Boston, MA : Springer US. - 0065-2598 .- 2214-8019. ; 645, s. 213-218
-
Tidskriftsartikel (refereegranskat)abstract
- The renal medulla has been implicated as a key target for contrast media-induced nephropathy (CIN). Although the effects of contrast media (CM) on whole kidney blood flow are well characterized, the effect of CM on renal medullary blood flow has been controversial. It has been reported that an extremely high dose of a high osmolar CM (iothalamate; 2900 mg I/kg bw) injected rapidly increased the renal outer medullary blood flow (OMBF). However, more clinical relevant doses consistently result in a sustained decrease in medullary blood flow. Furthermore, simultaneous measurements using both laser-Doppler flowmetry and hydrogen washout yield similar results of a decrease in OMBF after CM administration. CM induced a transient 28% decrease in the laser-Doppler signal from the outer medulla, while the hydrogen washout rate in the same region was reduced by approximately 50%. Furthermore, CM administration consistently results in decreased medullary oxygen tension (PO2). The renal medulla works already during normal physiological conditions at the verge of hypoxia, and the majority of the studies published so far are in agreement with the hypothesis that CIN may have its origin in a further reduction in blood flow and/or oxygen availability of this region of the kidney.
|
|
| 14. |
- Liss, Per, et al.
(författare)
-
Iodinated contrast media inhibit oxygen consumption in freshly isolated proximal tubular cells from elderly humans and diabetic rats : Influence of nitric oxide.
- 2016
-
Ingår i: Upsala Journal of Medical Sciences. - : Uppsala Medical Society. - 0300-9734 .- 2000-1967. ; 121:1, s. 12-16
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives Mechanisms underlying contrast medium (CM)-induced nephropathy remain elusive, but recent attention has been directed to oxygen availability. The purpose of this study was to evaluate the effect of the low-osmolar CM iopromide and the iso-osmolar CM iodixanol on oxygen consumption (QO2) in freshly isolated proximal tubular cells (PTC) from kidneys ablated from elderly humans undergoing nephrectomy for renal carcinomas and from normoglycemic or streptozotocin-diabetic rats. Materials PTC were isolated from human kidneys, or kidneys of normoglycemic or streptozotocin-diabetic rats. QO2 was measured with Clark-type microelectrodes in a gas-tight chamber with and without each CM (10 mg I/mL medium). L-NAME was used to inhibit nitric oxide (NO) production caused by nitric oxide synthase. Results Both CM reduced QO2 in human PTC (about -35%) which was prevented by L-NAME. PTC from normoglycemic rats were unaffected by iopromide, whereas iodixanol decreased QO2 (-34%). Both CM decreased QO2 in PTC from diabetic rats (-38% and -36%, respectively). L-NAME only prevented the effect of iopromide in the diabetic rat PTC. Conclusions These observations demonstrate that CM can induce NO release from isolated PTC in vitro, which affects QO2. Our results suggest that the induction of NO release and subsequent effect on the cellular oxygen metabolism are dependent on several factors, including CM type and pre-existing risk factors for the development of CM-induced nephropathy.
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
- Nordquist, Lina, et al.
(författare)
-
Activation of Hypoxia-Inducible Factors Prevents Diabetic Nephropathy
- 2015
-
Ingår i: Journal of the American Society of Nephrology. - : American Society of Nephrology. - 1046-6673 .- 1533-3450. ; 26:2, s. 328-338
-
Tidskriftsartikel (refereegranskat)abstract
- Hyperglycemia results in increased oxygen consumption and decreased oxygen tension in the kidney. We tested the hypothesis that activation of hypoxia-inducible factors (HIFs) protects against diabetes-induced alterations in oxygen metabolism and kidney function. Experimental groups consisted of control and streptozotocin-induced diabetic rats treated with or without chronic cobalt chloride to activate HIFs. We elucidated the involvement of oxidative stress by studying the effects of acute administration of the superoxide dismutase mimetic tempol. Compared with controls, diabetic rats displayed tissue hypoxia throughout the kidney, glonnerular hyperfiltration, increased oxygen consumption, increased total mitochondrial leak respiration, and decreased tubular sodium transport efficiency. Diabetic kidneys showed proteinuria and tubulointerstitial damage. Cobalt chloride activated HIFs, prevented the diabetes-induced alterations in oxygen metabolism, mitochondrial leak respiration, and kidney function, and reduced proteinuria and tubulointerstitial damage. The beneficial effects of tempol were less pronounced after activation of HIFs, indicating improved oxidative stress status. In conclusion, activation of HIFs prevents diabetes-induced alteration in kidney oxygen metabolism by normalizing glomerular filtration, which reduces tubular electrolyte load, preventing mitochondrial leak respiration and improving tubular transport efficiency. These improvements could be related to reduced oxidative stress and account for the reduced proteinuria and tubulointerstitial damage. Thus, pharnnacologic activation of the HIF system may prevent development of diabetic nephropathy.
|
|
| 18. |
- Nordquist, Lina, et al.
(författare)
-
Hypoxia in the diabetic kidney is independent of advanced glycation end-products.
- 2013
-
Ingår i: Advances in Experimental Medicine and Biology. - New York, NY : Kluwer Academic Publishers. - 0065-2598 .- 2214-8019. ; 765, s. 185-193
-
Tidskriftsartikel (refereegranskat)abstract
- Sustained hyperglycemia is closely associated with increased risk to develop nephropathy. We have previously reported alterations in the intrarenal oxygen metabolism already after the early onset of diabetes. Furthermore, formation of advanced glycation end-products (AGE) is postulated as a major contributor to diabetic nephropathy. We therefore investigated the possible relationship between altered oxygen metabolism and AGE in diabetic kidneys.Normoglycemic and streptozotocin-diabetic rats with and without chronic treatment with aminoguanidine (AGE inhibitor; 600 mg/kg bw/24 h in drinking water) or L-N(6)-(1-Iminoethyl)lysine (L-NIL, iNOS inhibitor, 1 mg/kg bw/24 h in drinking water) were studied 2 weeks after induction of diabetes. Glomerular filtration rate (GFR) was estimated by inulin clearance, oxygen tension (pO(2)) and interstitial pH by microelectrodes and regional renal blood flow (RBF) by laser-Doppler. Histological changes were evaluated on fixed tissue.Glomerular hyperfiltration was unaffected by aminoguanidine, whereas L-NIL normalized GFR in diabetic rats. pO(2) and interstitial pH, but not RBF, were lower in both kidney cortex and medulla compared to control rats, but was unaffected by both chronic treatments. Urinary protein excretion was higher in diabetic rats and unaffected by L-NIL, whereas aminoguanidine paradoxically increased this parameter. Damage scores were similar in all groups.In conclusion, diabetes-induced alterations in intrarenal oxygen metabolism are independent of the AGE pathway, and precede any morphological changes. These findings highlight the early stage of diabetes as being a metabolic disorder also in the kidney.
|
|
| 19. |
- Nordquist, Lina, et al.
(författare)
-
Proinsulin C-peptide reduces diabetes-induced glomerular hyperfiltration via efferent arteriole dilation and inhibition of tubular sodium reabsorption
- 2009
-
Ingår i: American Journal of Physiology - Renal Physiology. - : American Physiological Society. - 0363-6127 .- 1522-1466 .- 1931-857X. ; 297:5, s. F1265-F1272
-
Tidskriftsartikel (refereegranskat)abstract
- C-peptide reduces diabetes-induced glomerular hyperfiltration in diabetic patients and experimental animal models. However, the mechanisms mediating the beneficial effect of C-peptide remain unclear. We investigated whether altered renal afferent-efferent arteriole tonus or alterations in tubular Na+ transport (T(Na)) in response to C-peptide administration mediate the reduction of diabetes-induced glomerular hyperfiltration. Glomerular filtration rate, filtration fraction, total and cortical renal blood flow, total kidney O2 consumption (QO2), T(Na), fractional Na+ and Li+ excretions, and tubular free-flow and stop-flow pressures were measured in anesthetized adult male normoglycemic and streptozotocin-diabetic Sprague-Dawley rats. The specific effect of C-peptide on transport-dependent QO2 was investigated in vitro in freshly isolated proximal tubular cells. C-peptide reduced glomerular filtration rate (-24%), stop-flow pressure (-8%), and filtration fraction (-17%) exclusively in diabetic rats without altering renal blood flow. Diabetic rats had higher baseline T(Na) (+40%), which was reduced by C-peptide. Similarly, C-peptide increased fractional Na+ (+80%) and Li+ (+47%) excretions only in the diabetic rats. None of these parameters was affected by vehicle treatments in either group. Baseline QO2 was 37% higher in proximal tubular cells from diabetic rats than controls and was normalized by C-peptide. C-peptide had no effect on ouabain-pretreated diabetic cells from diabetic rats. C-peptide reduced diabetes-induced hyperfiltration via a net dilation of the efferent arteriole and inhibition of tubular Na+ reabsorption, both potent regulators of the glomerular net filtration pressure. These findings provide new mechanistic insight into the beneficial effects of C-peptide on diabetic kidney function.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
- O'Neill, Julie, et al.
(författare)
-
Acute SGLT inhibition normalizes O-2 tension in the renal cortex but causes hypoxia in the renal medulla in anaesthetized control and diabetic rats
- 2015
-
Ingår i: American Journal of Physiology - Renal Physiology. - : American Physiological Society. - 0363-6127 .- 1522-1466 .- 1931-857X. ; 309:3, s. F227-F234
-
Tidskriftsartikel (refereegranskat)abstract
- Early stage diabetic nephropathy is characterized by glomerular hyperfiltration and reduced renal tissue PO2. Recent observations have indicated that increased tubular Na+-glucose linked transport (SGLT) plays a role in the development of diabetes-induced hyperfiltration. The aim of the present study was to determine how inhibition of SLGT impacts upon PO2 in the diabetic rat kidney. Diabetes was induced by streptozotocin in Sprague-Dawley rats 2 wk before experimentation. Renal hemodynamics, excretory function, and renal O-2 homeostasis were measured in anesthetized control and diabetic rats during baseline and after acute SGLT inhibition using phlorizin (200 mg/kg ip). Baseline arterial pressure was similar in both groups and unaffected by SGLT inhibition. Diabetic animals displayed reduced baseline PO2 in both the cortex and medulla. SGLT inhibition improved cortical PO2 in the diabetic kidney, whereas it reduced medullary PO2 in both groups. SGLT inhibition reduced Na+ transport efficiency [tubular Na+ transport (TNa)/renal O-2 consumption (QO(2))] in the control kidney, whereas the already reduced TNa/QO(2) in the diabetic kidney was unaffected by SGLT inhibition. In conclusion, these data demonstrate that when SGLT is inhibited, renal cortex PO2 in the diabetic rat kidney is normalized, which implies that increased proximal tubule transport contributes to the development of hypoxia in the diabetic kidney. The reduction in medullary PO2 in both control and diabetic kidneys during the inhibition of proximal Na+ reabsorption suggests the redistribution of active Na+ transport to less efficient nephron segments, such as the medullary thick ascending limb, which results in medullary hypoxia.
|
|
| 23. |
- Palm, Fredrik, et al.
(författare)
-
Diabetes-induced decrease in renal oxygen tension : effects of an altered metabolism
- 2006
-
Ingår i: Advances in Experimental Medicine and Biology. - 0065-2598 .- 2214-8019. ; 578, s. 161-166
-
Tidskriftsartikel (refereegranskat)abstract
- During conditions with experimental diabetes mellitus, it is evident that several alterations in renal oxygen metabolism occur, including increased mitochondrial respiration and increased lactate accumulation in the renal tissue. Consequently, these alterations will contribute to decrease the interstitial pO2, preferentially in the renal medulla of animals with sustained long-term hyperglycemia.
|
|
| 24. |
- Palm, Fredrik, et al.
(författare)
-
Effects of the contrast medium iopromide on renal hemodynamics and oxygen tension in the diabetic rat kidney
- 2003
-
Ingår i: Advances in Experimental Medicine and Biology. - 0065-2598 .- 2214-8019. ; 530, s. 653-659
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated the effects of the contrast medium (CM) iopromide on regional renal blood flow and oxygen tension (pO2) in the streptozotocin (STZ)-induced diabetic Wistar Furth rats. RESULTS: In normoglycemic rats, CM injection induced a transient decrease followed by an increase in renal cortical blood flow (CBF), whereas CBF increased directly in the diabetic animals. Renal outer medullary blood flow (OMBF) increased in controls, while it decreased in the diabetic animals following CM injection. In control rats a marked initial decrease in OM pO2 following injection of CM was observed. In animals diabetic for 4 weeks only a slight decrease was seen, whereas in 9-week diabetic animals a persistent increase was recorded. CONCLUSIONS: An altered oxygen tension and hemodynamic response to CM was found in diabetic rats. If these disturbances may contribute to the development of renal dysfunction by CM in the diabetic rat kidney remains to be elucidated.
|
|
| 25. |
- Palm, Fredrik, et al.
(författare)
-
Nitric oxide originating from NOS1 controls oxygen utilization and electrolyte transport efficiency in the diabetic kidney
- 2010
-
Ingår i: American Journal of Physiology - Renal Physiology. - : American Physiological Society. - 0363-6127 .- 1522-1466 .- 1931-857X. ; 298:2, s. F416-F420
-
Tidskriftsartikel (refereegranskat)abstract
- Palm F, Fasching A, Hansell P, K llskog. Nitric oxide originating from NOS1 controls oxygen utilization and electrolyte transport efficiency in the diabetic kidney. Am J Physiol Renal Physiol 298: F416-F420, 2010. First published November 18, 2009; doi: 10.1152/ajprenal.00229.2009.-Nitric oxide (NO) is a potent regulator of both vascular tone and cellular oxygen consumption (QO(2)). Diabetic kidneys have reduced NO availability and increased QO(2). However, the exact nitric oxide synthase (NOS) isoform regulating QO(2), hemodynamics, and excretory function in the diabetic kidney remains unclear. We therefore investigated the effects of both selective neuronal NOS (NOS1) inhibition and nonselective NOS inhibition. Oxygen utilization, electrolyte transport efficiency [tubular Na+ transport (T-Na)/QO(2)], renal blood flow (RBF), glomerular filtration rate (GFR), and mean arterial pressure (MAP) were measured in vivo in control and streptozotocin-diabetic rats before and after administration of the selective NOS1 inhibitor S-methyl-L-thiocitrulline (SMTC) or the nonselective NOS inhibitor N-G-nitro-L-arginine methyl ester (L-NAME). Diabetic rats had higher baseline QO(2) and GFR than control rats, although RBF was similar in the groups. SMTC and L-NAME increased QO(2) and reduced T-Na/QO(2) only in the diabetic animals, whereas both inhibitors increased MAP and reduced RBF in both groups. GFR was reduced by L-NAME, but SMTC had no effect in either group. Carbachol increased RBF and decreased MAP in SMTC-treated rats, whereas it had no effect in L-NAME-treated rats, indicating that SMTC selectively inhibited NOS1. In conclusion, NO regulates RBF and GFR similarly in both control and diabetic rats. However, selective NOS1 inhibition increased QO(2) and reduced T-Na/QO(2) in the diabetic rat kidney, indicating a pivotal role of NO produced by NOS1 in maintaining control of QO(2) and tissue oxygenation in these kidneys.
|
|
