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  • 1.
    Friederich, Malou
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Persson, Patrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Deletion of Uncoupling Protein-2 reduces renal mitochondrial leak respiration, intrarenal hypoxia and proteinuria in a mouse model of type 1 diabetes2018In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 223, no 4, article id e13058Article in journal (Refereed)
    Abstract [en]

    AimUncoupling protein-2 (UCP-2) can induce mitochondrial uncoupling in the diabetic kidney. Although mitochondrial uncoupling reduces oxidative stress originating from the mitochondria and can be regarded as a protective mechanism, the increased oxygen consumption occurring secondarily to increased mitochondria uncoupling, that is leak respiration, may contribute to kidney tissue hypoxia. Using UCP-2(-/-) mice, we tested the hypothesis that UCP-2-mediated leak respiration is important for the development of diabetes-induced intrarenal hypoxia and proteinuria. MethodsKidney function, invivo oxygen metabolism, urinary protein leakage and mitochondrial function were determined in wild-type and UCP-2(-/-) mice during normoglycaemia and 2weeks after diabetes induction. ResultsDiabetic wild-type mice displayed mitochondrial leak respiration, pronounced intrarenal hypoxia, proteinuria and increased urinary KIM-1 excretion. However, diabetic UCP-2(-/-) mice did not develop increased mitochondrial leak respiration and presented with normal intrarenal oxygen levels, urinary protein and KIM-1 excretion. ConclusionAlthough functioning as an antioxidant system, mitochondria uncoupling is always in co-occurrence with increased oxygen consumption, that is leak respiration; a potentially detrimental side effect as it can result in kidney tissue hypoxia; an acknowledged unifying pathway to nephropathy. Indeed, this study demonstrates a novel mechanism in which UCP-2-mediated mitochondrial leak respiration is necessary for the development of diabetes-induced intrarenal tissue hypoxia and proteinuria.

  • 2.
    Friederich-Persson, Malou
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Persson, Patrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Nangaku, Masaomi
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Renal hypoxia due to increased oxygen metabolism is an independent pathway to nephropathy2014In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 28, no 1, article id 890.6Article in journal (Other academic)
  • 3.
    Friederich-Persson, Malou
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Persson, Patrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Nordquist, Lina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Increased kidney metabolismas a pathway to kidney tissue hypoxia and damage: effects of triiodothyronine and dinitrophenol in normoglycemic rats2013In: Advances in Experimental Medicine and Biology, ISSN 0065-2598, E-ISSN 2214-8019, Vol. 789, p. 9-14Article in journal (Refereed)
    Abstract [en]

    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.

  • 4. Patinha, Daniela
    et al.
    Carvalho, Carla
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Persson, Patrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Pihl, Liselotte
    O'Neill, Julie
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Determinants of renal oxygen metabolism during low Na+ diet: effect of angiotensin AT1 and aldosterone receptor blockadeManuscript (preprint) (Other academic)
  • 5.
    Persson, Patrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Aspects of Regulation of GFR and Tubular Function in the Diabetic Kidney: Roles of Adenosine, Nitric Oxide and Oxidative Stress2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Diabetic nephropathy is the main cause for initiation of renal replacement therapy and early symptoms in patients include increased glomerular filtration rate (GFR), decreased oxygen tension and albuminuria, followed by a progressive decline in GFR and loss of kidney function. Experimental models of diabetes display increased GFR, decreased tissue oxygenation and nitric oxide bioavailability. These findings are likely to be intertwined in a mechanistic pathway to kidney damage and this thesis investigated their roles in the development of diabetic nephropathy. In vivo, diabetes-induced oxidative stress stimulates renal tubular Na+ transport and in vitro, proximal tubular cells from diabetic rats display increased transport-dependent oxygen consumption, demonstrating mechanisms contributing to decreased kidney oxygenation. In control animals, endogenous adenosine reduces vascular resistance of the efferent arteriole via adenosine A2-receptors resulting in reduced filtration fraction. However, in diabetes, adenosine A2-signalling is dysfunctional resulting in increased GFR via increased filtration fraction. This is caused by reduced adenosine A2a receptor-mediated vasodilation of efferent arterioles. The lack of adenosine-signaling in diabetes is likely due to reduced local adenosine concentration since adenosine A2a receptor activation reduced GFR only in diabetic animals by efferent arteriolar vasodilation. Furthermore, sub-optimal insulin treatment also alleviates increased filtration pressure in diabetes. However, this does not affect GFR due to a simultaneously induction of renal-blood flow dependent regulation of GFR by increasing the filtration coefficient. In diabetes, there is decreased bioavailability of nitric oxide, resulting in alterations that may contribute to diabetes-induced hyperfiltration and decreased oxygenation. Interestingly, increased plasma concentration of l-arginine, the substrate for nitric oxide production, prevents the development of increased GFR and proteinuria, but not increased oxygen consumption leading to sustained intra-renal hypoxia in diabetes. This thesis concludes that antioxidant treatment directed towards the NADPH oxidase as well maneuvers to promote nitric oxide production is beneficial in diabetic kidneys but is targeting different pathways i.e. transport-dependent oxygen consumption in the proximal tubule by NADPH oxidase inhibition and intra-renal hemodynamics after increased plasma l-arginine. Also, the involvement and importance of efferent arteriolar resistance in the development of diabetes-induced hyperfiltration via reduced adenosine A2a signaling is highlighted.

    List of papers
    1. NADPH oxidase inhibition reduces tubular sodium transport and improves kidney oxygenation in diabetes
    Open this publication in new window or tab >>NADPH oxidase inhibition reduces tubular sodium transport and improves kidney oxygenation in diabetes
    2012 (English)In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 302, no 12, p. R1443-R1449Article in journal (Refereed) Published
    Abstract [en]

    Sustained hyperglycemia is associated with increased oxidative stress resulting in decreased intrarenal oxygen tension (Po-2) due to increased oxygen consumption (Qo(2)). Chronic blockade of the main superoxide radicals producing system, the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, normalizes Qo(2) by isolated proximal tubular cells (PTC) and reduces proteinuria in diabetes. The aim was to investigate the effects of acute NADPH oxidase inhibition on tubular Na+ transport and kidney Po-2 in vivo. Glomerular filtration rate (GFR), renal blood flow (RBF), filtration fraction (FF), Na+ excretion, fractional Li+ excretion, and intrarenal Po-2 was measured in control and streptozotocin-diabetic rats during baseline and after acute NADPH oxidase inhibition using apocynin. The effects on tubular transporters were investigated using freshly isolated PTC. GFR was increased in diabetics compared with controls (2.2 +/- 0.3 vs. 1.4 +/- 0.1 ml.min (-1).kidney (-1)). RBF was similar in both groups, resulting in increased FF in diabetics. Po-2 was reduced in cortex and medulla in diabetic kidneys compared with controls (34.4 +/- 0.7 vs. 42.5 +/- 1.2 mmHg and 15.7 +/- 1.2 vs. 25.5 +/- 2.3 mmHg, respectively). Na+ excretion was increased in diabetics compared with controls (24.0 +/- 4.7 vs. 9.0 +/- 2.0 mu m.min(-1).kidney(-1)). In controls, all parameters were unaffected. However, apocynin increased Na+ excretion (+112%) and decreased fractional lithium reabsorption (-10%) in diabetics, resulting in improved cortical (+14%) and medullary (+28%) Po-2. Qo(2) was higher in PTC isolated from diabetic rats compared with control. Apocynin, dimethylamiloride, and ouabain reduced Qo(2), but the effects of combining apocynin with either dimethylamiloride or ouabain were not additive. In conclusion, NADPH oxidase inhibition reduces tubular Na+ transport and improves intrarenal Po-2 in diabetes.

    Keywords
    apocynin, dimethylamiloride, ouabain, oxygen tension, oxidative stress, proximal tubular cells, rat, streptozotocin
    National Category
    Physiology
    Identifiers
    urn:nbn:se:uu:diva-177608 (URN)10.1152/ajpregu.00502.2011 (DOI)000305424000008 ()
    Available from: 2012-07-17 Created: 2012-07-17 Last updated: 2018-01-12Bibliographically approved
    2. Insulin induces the correlation between renal blood flow and glomerular filtration rate in diabetes: implications for mechanisms causing hyperfiltration
    Open this publication in new window or tab >>Insulin induces the correlation between renal blood flow and glomerular filtration rate in diabetes: implications for mechanisms causing hyperfiltration
    Show others...
    2012 (English)In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 303, no 1, p. R39-R47Article in journal (Refereed) Published
    Abstract [en]

    Glomerular filtration rate (GFR) and renal blood flow (RBF) are normally kept constant via renal autoregulation. However, early diabetes results in increased GFR and the potential mechanisms are debated. Tubuloglomerular feedback (TGF) inactivation, with concomitantly increased RBF, is proposed but challenged by the finding of glomerular hyperfiltration in diabetic adenosine A(1) receptor-deficient mice, which lack TGF. Furthermore, we consistently find elevated GFR in diabetes with only minor changes in RBF. This may relate to the use of a lower streptozotocin dose, which produces a degree of hyperglycemia, which is manageable without supplemental suboptimal insulin administration, as has been used by other investigators. Therefore, we examined the relationship between RBF and GFR in diabetic rats with (diabetes + insulin) and without suboptimal insulin administration (untreated diabetes). As insulin can affect nitric oxide (NO) release, the role of NO was also investigated. GFR, RBF, and glomerular filtration pressures were measured. Dynamic RBF autoregulation was examined by transfer function analysis between arterial pressure and RBF. Both diabetic groups had increased GFR (+60-67%) and RBF (+20-23%) compared with controls. However, only the diabetes + insulin group displayed a correlation between GFR and RBF (R-2 = 0.81, P < 0.0001). Net filtration pressure was increased in untreated diabetes compared with both other groups. The difference between untreated and insulin-treated diabetic rats disappeared after administering N-omega-nitro-L-arginine methyl ester to inhibit NO synthase and subsequent NO release. In conclusion, mechanisms causing diabetes-induced glomerular hyperfiltration are animal model-dependent. Supplemental insulin administration results in a RBF-dependent mechanism, whereas elevated GFR in untreated diabetes is mediated primarily by a tubular event. Insulin-induced NO release partially contributes to these differences.

    Keywords
    insulin, net filtraton pressure, N-omega-nitro-L-arginine methyl ester
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:uu:diva-179030 (URN)10.1152/ajpregu.00582.2011 (DOI)000306186600005 ()
    Available from: 2012-08-06 Created: 2012-08-06 Last updated: 2017-12-07Bibliographically approved
    3. Adenosine A2 receptor-mediated regulation of renal hemodynamics and glomerular filtration rate is abolished in diabetes
    Open this publication in new window or tab >>Adenosine A2 receptor-mediated regulation of renal hemodynamics and glomerular filtration rate is abolished in diabetes
    2013 (English)In: Advances in Experimental Medicine and Biology, ISSN 0065-2598, E-ISSN 2214-8019, Vol. 765, p. 225-230Article in journal (Refereed) Published
    Abstract [en]

    Alterations in glomerular filtration rate (GFR) are one of the earliest indications of altered kidney function in diabetes. Adenosine regulates GFR through tubuloglomerular feedback mechanism acting on adenosine A1 receptor. In addition, adenosine can directly regulate vascular tone by acting on A1 and A2 receptors expressed in afferent and efferent arterioles. Opposite to A1 receptors, A2 receptors mediate vasorelaxation. This study investigates the involvement of adenosine A2 receptors in regulation of renal blood flow (RBF) and GFR in control and diabetic kidneys. GFR was measured by inulin clearance and RBF by a transonic flow probe placed around the renal artery. Measurements were performed in isoflurane-anesthetized normoglycemic and alloxan-diabetic C57BL/6 mice during baseline and after acute administration of 3,7-dimethyl-1-propargylxanthine (DMPX), a selective A2 receptor antagonist. GFR and RBF were lower in diabetic mice compared to control (258 ± 61 vs. 443 ± 33 μl min -1 and 1,083 ± 51 vs. 1,405 ± 78 μl min -1). In control animals, DMPX decreased RBF by-6%, whereas GFR increased +44%. DMPX had no effects on GFR and RBF in diabetic mice. Sodium excretion increased in diabetic mice after A2 receptor blockade (+78%). In conclusion, adenosine acting on A2 receptors mediates an efferent arteriolar dilatation which reduces filtration fraction (FF) and maintains GFR within normal range in normoglycemic mice. However, this regulation is absent in diabetic mice, which may contribute to reduced oxygen availability in the diabetic kidney.

    Place, publisher, year, edition, pages
    Springer-Verlag New York, 2013
    Keywords
    Alloxan, C57BL/6, DMPX, Renal blood flow
    National Category
    Medical and Health Sciences Basic Medicine
    Identifiers
    urn:nbn:se:uu:diva-186810 (URN)10.1007/978-1-4614-4989-8_31 (DOI)000339280100032 ()9781461447719 (ISBN)
    Available from: 2012-12-12 Created: 2012-11-29 Last updated: 2018-01-12
    4. Reduced adenosine A2a receptor–mediated efferent arteriolar vasodilation contributes to diabetes-induced glomerular hyperfiltration
    Open this publication in new window or tab >>Reduced adenosine A2a receptor–mediated efferent arteriolar vasodilation contributes to diabetes-induced glomerular hyperfiltration
    2015 (English)In: Kidney International, ISSN 0085-2538, E-ISSN 1523-1755, Vol. 87, no 1, p. 109-115Article in journal (Refereed) Published
    Abstract [en]

    Diabetes is associated with increased risk for development of kidney disease, and an increased glomerular filtration rate is an early indication of altered kidney function. Here we determine whether reduced adenosine A2a receptor-mediated vasodilation of the efferent arteriole contributes to the increased glomerular filtration rate in diabetes. The glomerular filtration rate, renal blood flow, and proximal tubular stop flow pressure were investigated in control and streptozotocin-diabetic rats during baseline and after administration of the adenosine A2a receptor antagonist ZM241385 or the adenosine A2a receptor agonist CGS21680. The diabetes-induced glomerular hyperfiltration was reduced by 24% following A2a receptor stimulation but was unaffected by A2a receptor inhibition. Contrarily, glomerular filtration rate in controls increased by 22% after A2a receptor inhibition and was unaffected by A2a stimulation. The increased glomerular filtration rate after A2a receptor inhibition in controls and decreased glomerular filtration rate after A2a receptor activation in diabetics were caused by increased and decreased stop flow pressure, respectively. None of the interventions affected renal blood flow. Thus, the normal adenosine A2a receptor-mediated tonic vasodilation of efferent arterioles is abolished in the diabetic kidney. This causes increased efferent arteriolar resistance resulting in increased filtration fraction and hyperfiltration.

    Keywords
    kidney, CGS21680, renal blood flow, glomerular filtration rate, net filtration pressure
    National Category
    Physiology
    Research subject
    Physiology; Medical Science
    Identifiers
    urn:nbn:se:uu:diva-195428 (URN)10.1038/ki.2014.219 (DOI)000346977900014 ()
    Funder
    Swedish Research Council
    Available from: 2013-02-25 Created: 2013-02-25 Last updated: 2018-01-11Bibliographically approved
    5. L-Citrulline, But Not L-Arginine, Prevents Diabetes Mellitus–Induced Glomerular Hyperfiltration and Proteinuria in Rat
    Open this publication in new window or tab >>L-Citrulline, But Not L-Arginine, Prevents Diabetes Mellitus–Induced Glomerular Hyperfiltration and Proteinuria in Rat
    Show others...
    2014 (English)In: Hypertension, ISSN 0194-911X, E-ISSN 1524-4563, Vol. 64, no 2, p. 323-329Article in journal (Refereed) Published
    Abstract [en]

    Diabetes mellitus–induced oxidative stress causes increased renal oxygen consumption and intrarenal tissue hypoxia. Nitric oxide is an important determinant of renal oxygen consumption and electrolyte transport efficiency. The present study investigates whether l-arginine or l-citrulline to promote nitric oxide production prevents the diabetes mellitus–induced kidney dysfunction. Glomerular filtration rate, renal blood flow, in vivo oxygen consumption, tissue oxygen tension, and proteinuria were investigated in control and streptozotocin-diabetic rats with and without chronic l-arginine or l-citrulline treatment for 3 weeks. Untreated and l-arginine–treated diabetic rats displayed increased glomerular filtration rate (2600±162 versus 1599±127 and 2290±171 versus 1739±138 µL/min per kidney), whereas l-citrulline prevented the increase (1227±126 versus 1375±88 µL/min per kidney). Filtration fraction was increased in untreated diabetic rats because of the increase in glomerular filtration rate but not in l-arginine– or l-citrulline–treated diabetic rats. Urinary protein excretion was increased in untreated and l-arginine–treated diabetic rats (142±25 versus 75±7 and 128±7 versus 89±7 µg/min per kidney) but not in diabetic rats administered l-citrulline (67±7 versus 61±5 µg/min per kidney). The diabetes mellitus–induced tissue hypoxia, because of elevated oxygen consumption, was unaltered by any of the treatments. l-citrulline administered to diabetic rats increases plasma l-arginine concentration, which prevents the diabetes mellitus–induced glomerular hyperfiltration, filtration fraction, and proteinuria, possibly by a vascular effect.

    National Category
    Physiology Basic Medicine
    Research subject
    Medical Science; Physiology
    Identifiers
    urn:nbn:se:uu:diva-195487 (URN)10.1161/HYPERTENSIONAHA.114.03519 (DOI)000339120700023 ()24866144 (PubMedID)
    Available from: 2013-02-25 Created: 2013-02-25 Last updated: 2018-01-11Bibliographically approved
  • 6.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Acute intrarenal angiotensin (1-7) infusion decreases diabetes-induced glomerular hyperfiltration but increases kidney oxygen consumption in the rat2019In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 226, no 1, article id e13254Article in journal (Refereed)
    Abstract [en]

    Aim: Common kidney alterations early after the onset of insulinopenic diabetes include glomerular hyperfiltration, increased oxygen consumption and tissue hypoxia. Increased activity of the renin-angiotensin-aldosterone system (RAAS) has been implicated in most of these early alterations. The RAAS peptide angiotensin (1-7) has the potential to modulate RAAS-mediated alterations in kidney function. Thus, the aim of the present study was to determine the acute effects of angiotensin (1-7) in the kidney of insulinopenic type 1 diabetic rat and the results compared to that of normoglycaemic controls.

    Methods: Renal haemodynamics and oxygen homeostasis were measured 3 weeks after administration of streptozotocin before and after acute intrarenal infusion of angiotensin (1-7) at a dose of 400 ng min(-1).

    Results: Arterial pressure and renal blood flow were similar between groups and not affected by exogenous angiotensin (1-7). Diabetics presented with glomerular hyperfiltration, increased urinary sodium excretion and elevated kidney oxygen consumption. Angiotensin (1-7) infusion normalized glomerular filtration, increased urinary sodium excretion, decreased proximal tubular reabsorption, and elevated kidney oxygen consumption even further. The latter resulting in tubular electrolyte transport inefficiency. Angiotensin (1-7) did not affect tissue oxygen tension and had no significant effects in controls on any of the measured parameters.

    Conclusion: Diabetes results in increased responsiveness to elevated levels of angiotensin (1-7) which is manifested as inhibition of tubular sodium transport and normalization of glomerular filtration. Furthermore, elevated angiotensin (1-7) levels increase kidney oxygen consumption in the diabetic kidney even further which affects tubular electrolyte transport efficiency negatively.

  • 7.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Teerlink, Tom
    Vrije Univ Amsterdam, Med Ctr, Dept Clin Chem, Amsterdam, Netherlands.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Cellular transport of L-Arginine determines renal medullary blood flow in control rats, but not in diabetic rats despite enhanced cellular uptake capacity2017In: American Journal of Physiology - Renal Physiology, ISSN 0363-6127, E-ISSN 1522-1466, Vol. 312, no 2, p. F278-F283Article in journal (Refereed)
    Abstract [en]

    Diabetes mellitus is associated with decreased nitric oxide bioavailability thereby affecting renal blood flow regulation. Previous reports have demonstrated that cellular uptake of L-arginine is rate limiting for nitric oxide production, and that plasma L-arginine concentration is decreased in diabetes. We therefore investigated if regional renal blood flow regulation is affected by cellular L-arginine uptake in streptozotocin-induced diabetic rats. Rats were anesthetized with thiobutabarbital and left kidney was exposed. Total, cortical and medullary renal blood flow was investigated before and after renal artery infusion of increasing doses of either L-homoarginine to inhibit cellular uptake of L-arginine, or L-NAME to inhibit nitric oxide synthase. L-homoarginine infusion did not affect total or cortical blood flow in any of the groups, but caused a dose-dependent reduction in medullary blood flow. L-NAME decreased total, cortical and medullary blood flow in both groups. However, the reductions in medullary blood flow in response to both L-homoarginine and L-NAME were more pronounced in the control groups compared to the diabetic groups. Isolated cortical tubular cells displayed similar L-arginine uptake capacity whereas medullary tubular cells isolated from diabetic rats had increased L-arginine uptake capacity. Diabetics had reduced L-arginine concentrations in plasma and medullary tissue but increased L-arginine concentration in cortical tissue. In conclusion, the reduced L-arginine availability in plasma and medullary tissue in diabetes results in reduced nitric oxide-mediated regulation of renal medullary hemodynamics. Cortical blood flow regulation displays less dependency on extracellular L-arginine and the upregulated cortical tissue L-arginine may protect cortical hemodynamics in diabetes.

  • 8.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Teerlink, Tom
    Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    L-Citrulline, But Not L-Arginine, Prevents Diabetes Mellitus–Induced Glomerular Hyperfiltration and Proteinuria in Rat2014In: Hypertension, ISSN 0194-911X, E-ISSN 1524-4563, Vol. 64, no 2, p. 323-329Article in journal (Refereed)
    Abstract [en]

    Diabetes mellitus–induced oxidative stress causes increased renal oxygen consumption and intrarenal tissue hypoxia. Nitric oxide is an important determinant of renal oxygen consumption and electrolyte transport efficiency. The present study investigates whether l-arginine or l-citrulline to promote nitric oxide production prevents the diabetes mellitus–induced kidney dysfunction. Glomerular filtration rate, renal blood flow, in vivo oxygen consumption, tissue oxygen tension, and proteinuria were investigated in control and streptozotocin-diabetic rats with and without chronic l-arginine or l-citrulline treatment for 3 weeks. Untreated and l-arginine–treated diabetic rats displayed increased glomerular filtration rate (2600±162 versus 1599±127 and 2290±171 versus 1739±138 µL/min per kidney), whereas l-citrulline prevented the increase (1227±126 versus 1375±88 µL/min per kidney). Filtration fraction was increased in untreated diabetic rats because of the increase in glomerular filtration rate but not in l-arginine– or l-citrulline–treated diabetic rats. Urinary protein excretion was increased in untreated and l-arginine–treated diabetic rats (142±25 versus 75±7 and 128±7 versus 89±7 µg/min per kidney) but not in diabetic rats administered l-citrulline (67±7 versus 61±5 µg/min per kidney). The diabetes mellitus–induced tissue hypoxia, because of elevated oxygen consumption, was unaltered by any of the treatments. l-citrulline administered to diabetic rats increases plasma l-arginine concentration, which prevents the diabetes mellitus–induced glomerular hyperfiltration, filtration fraction, and proteinuria, possibly by a vascular effect.

  • 9.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Teerlink, Tom
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    L-citrulline, but not L-arginine, prevents diabetes-induced glomerular hyperfiltration and proteinuria2014In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 28, no 1, article id 689.12Article in journal (Other academic)
  • 10.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Friederich-Persson, Malou
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Inagi, Reiko
    University of Tokyo Graduate School of Medicine, Tokyo, Japan.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Adenosine A2 a receptor stimulation prevents proteinuria in diabetic rats by promoting an anti-inflammatory phenotype without affecting oxidative stress2015In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 214, no 3, p. 311-318Article in journal (Refereed)
    Abstract [en]

    AIM: Diabetic patients are at increased risk for kidney disease. There is presently no clinical treatment available that effectively protects kidney function in diabetics. The present study investigates if chronic stimulation of the adenosine A2a receptor (A2a AR) protects kidney function in insulinopenic diabetic rats.

    METHODS: Streptozotocin-induced diabetic rats and corresponding controls were chronically treated with the adenosine A2a AR agonist CGS21680 throughout the four-week diabetes duration. Kidney function was thereafter investigated and urine and plasma samples were collected for analysis of protein, oxidative stress and inflammatory markers.

    RESULTS: Glomerular filtration rate, renal blood flow, filtration fraction and diabetes-induced kidney hypoxia were all unaffected by chronic A2a AR stimulation. Furthermore, diabetic rats had increased oxidative stress, which was further increased by chronic A2a AR stimulation. However, the 10-fold increased urinary protein excretion observed in the diabetic rats was completely prevented by chronic A2a AR stimulation. These beneficial effects were accompanied by reduced levels of the pro-inflammatory TNF-α and increased levels of the anti-inflammatory IL-10 as well as decreased infiltration of macrophages, glomerular damage and basement membrane thickness.

    CONCLUSION: Chronic A2a AR stimulation prevents proteinuria and glomerular damage in experimental diabetes via an anti-inflammatory mechanism independent of oxidative stress and kidney hypoxia.

  • 11.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Adenosine A2 receptor-mediated regulation of renal hemodynamics and glomerular filtration rate is abolished in diabetes2013In: Advances in Experimental Medicine and Biology, ISSN 0065-2598, E-ISSN 2214-8019, Vol. 765, p. 225-230Article in journal (Refereed)
    Abstract [en]

    Alterations in glomerular filtration rate (GFR) are one of the earliest indications of altered kidney function in diabetes. Adenosine regulates GFR through tubuloglomerular feedback mechanism acting on adenosine A1 receptor. In addition, adenosine can directly regulate vascular tone by acting on A1 and A2 receptors expressed in afferent and efferent arterioles. Opposite to A1 receptors, A2 receptors mediate vasorelaxation. This study investigates the involvement of adenosine A2 receptors in regulation of renal blood flow (RBF) and GFR in control and diabetic kidneys. GFR was measured by inulin clearance and RBF by a transonic flow probe placed around the renal artery. Measurements were performed in isoflurane-anesthetized normoglycemic and alloxan-diabetic C57BL/6 mice during baseline and after acute administration of 3,7-dimethyl-1-propargylxanthine (DMPX), a selective A2 receptor antagonist. GFR and RBF were lower in diabetic mice compared to control (258 ± 61 vs. 443 ± 33 μl min -1 and 1,083 ± 51 vs. 1,405 ± 78 μl min -1). In control animals, DMPX decreased RBF by-6%, whereas GFR increased +44%. DMPX had no effects on GFR and RBF in diabetic mice. Sodium excretion increased in diabetic mice after A2 receptor blockade (+78%). In conclusion, adenosine acting on A2 receptors mediates an efferent arteriolar dilatation which reduces filtration fraction (FF) and maintains GFR within normal range in normoglycemic mice. However, this regulation is absent in diabetic mice, which may contribute to reduced oxygen availability in the diabetic kidney.

  • 12.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    NADPH oxidase inhibition reduces tubular sodium transport and improves kidney oxygenation in diabetes2012In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 302, no 12, p. R1443-R1449Article in journal (Refereed)
    Abstract [en]

    Sustained hyperglycemia is associated with increased oxidative stress resulting in decreased intrarenal oxygen tension (Po-2) due to increased oxygen consumption (Qo(2)). Chronic blockade of the main superoxide radicals producing system, the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, normalizes Qo(2) by isolated proximal tubular cells (PTC) and reduces proteinuria in diabetes. The aim was to investigate the effects of acute NADPH oxidase inhibition on tubular Na+ transport and kidney Po-2 in vivo. Glomerular filtration rate (GFR), renal blood flow (RBF), filtration fraction (FF), Na+ excretion, fractional Li+ excretion, and intrarenal Po-2 was measured in control and streptozotocin-diabetic rats during baseline and after acute NADPH oxidase inhibition using apocynin. The effects on tubular transporters were investigated using freshly isolated PTC. GFR was increased in diabetics compared with controls (2.2 +/- 0.3 vs. 1.4 +/- 0.1 ml.min (-1).kidney (-1)). RBF was similar in both groups, resulting in increased FF in diabetics. Po-2 was reduced in cortex and medulla in diabetic kidneys compared with controls (34.4 +/- 0.7 vs. 42.5 +/- 1.2 mmHg and 15.7 +/- 1.2 vs. 25.5 +/- 2.3 mmHg, respectively). Na+ excretion was increased in diabetics compared with controls (24.0 +/- 4.7 vs. 9.0 +/- 2.0 mu m.min(-1).kidney(-1)). In controls, all parameters were unaffected. However, apocynin increased Na+ excretion (+112%) and decreased fractional lithium reabsorption (-10%) in diabetics, resulting in improved cortical (+14%) and medullary (+28%) Po-2. Qo(2) was higher in PTC isolated from diabetic rats compared with control. Apocynin, dimethylamiloride, and ouabain reduced Qo(2), but the effects of combining apocynin with either dimethylamiloride or ouabain were not additive. In conclusion, NADPH oxidase inhibition reduces tubular Na+ transport and improves intrarenal Po-2 in diabetes.

  • 13.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Reduced adenosine A2a receptor–mediated efferent arteriolar vasodilation contributes to diabetes-induced glomerular hyperfiltration2015In: Kidney International, ISSN 0085-2538, E-ISSN 1523-1755, Vol. 87, no 1, p. 109-115Article in journal (Refereed)
    Abstract [en]

    Diabetes is associated with increased risk for development of kidney disease, and an increased glomerular filtration rate is an early indication of altered kidney function. Here we determine whether reduced adenosine A2a receptor-mediated vasodilation of the efferent arteriole contributes to the increased glomerular filtration rate in diabetes. The glomerular filtration rate, renal blood flow, and proximal tubular stop flow pressure were investigated in control and streptozotocin-diabetic rats during baseline and after administration of the adenosine A2a receptor antagonist ZM241385 or the adenosine A2a receptor agonist CGS21680. The diabetes-induced glomerular hyperfiltration was reduced by 24% following A2a receptor stimulation but was unaffected by A2a receptor inhibition. Contrarily, glomerular filtration rate in controls increased by 22% after A2a receptor inhibition and was unaffected by A2a stimulation. The increased glomerular filtration rate after A2a receptor inhibition in controls and decreased glomerular filtration rate after A2a receptor activation in diabetics were caused by increased and decreased stop flow pressure, respectively. None of the interventions affected renal blood flow. Thus, the normal adenosine A2a receptor-mediated tonic vasodilation of efferent arterioles is abolished in the diabetic kidney. This causes increased efferent arteriolar resistance resulting in increased filtration fraction and hyperfiltration.

  • 14.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Tubular reabsorption and diabetes-induced glomerular hyperfiltration2010In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 200, no 1, p. 3-10Article, review/survey (Refereed)
    Abstract [en]

    Elevated glomerular filtration rate (GFR) is a common observation in early diabetes mellitus and closely correlates with the progression of diabetic nephropathy. Hyperfiltration has been explained to be the result of a reduced load of sodium and chloride passing macula densa, secondarily to an increased proximal reabsorption of glucose and sodium by the sodium-glucose co-transporters. This results in an inactivation of the tubuloglomerular feedback (TGF), leading to a reduced afferent arteriolar vasoconstriction and subsequently an increase in GFR. This hypothesis has recently been questioned due to the observation that adenosine A(1)-receptor knockout mice, previously shown to lack a functional TGF mechanism, still display a pronounced hyperfiltration when diabetes is induced. Leyssac demonstrated in the 1960s (Acta Physiol Scand58, 1963:236) that GFR and proximal reabsorption can work independently of each other. Furthermore, by the use of micropuncture technique a reduced hydrostatic pressure in Bowman's space or in the proximal tubule of diabetic rats has been observed. A reduced pressure in Bowman's space will increase the pressure gradient over the filtration barrier and can contribute to the development of diabetic hyperfiltration. When inhibiting proximal reabsorption with a carbonic anhydrase inhibitor, GFR decreases and proximal tubular pressure increases. Measuring intratubular pressure allows a sufficient time resolution to reveal that net filtration pressure decreases before TGF is activated which highlights the importance of intratubular pressure as a regulator of GFR. Taken together, these results imply that the reduced intratubular pressure observed in diabetes might be crucial for the development of glomerular hyperfiltration.

  • 15.
    Persson, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hypoxia-inducible factor activation in diabetic kidney disease.2017In: Current opinion in nephrology and hypertension, ISSN 1062-4821, E-ISSN 1473-6543, Vol. 26, no 5, p. 345-350Article, review/survey (Refereed)
    Abstract [en]

    PURPOSE OF REVIEW:

    Tissue hypoxia is present in kidneys from diabetic patients and constitutes a central pathway to diabetic kidney disease (DKD). This review summarizes regulation of hypoxia inducible factor (HIF) and interventions towards the same for treatment of DKD.

    RECENT FINDINGS:

    In the hypoxic diabetic kidney, HIF activity and the effects of HIF signaling seem to be cell-specific. In mesangial cells, elevated glucose levels induce HIF activity by a hypoxia-independent mechanism. Elevated HIF activity in glomerular cells promotes glomerulosclerosis and albuminuria, and inhibition of HIF protects glomerular integrity. However, tubular HIF activity is suppressed and HIF activation protects mitochondrial function and prevents development of diabetes-induced tissue hypoxia, tubulointerstitial fibrosis and proteinuria. No clinical treatment targeting kidney hypoxia is currently available, but development of prolyl hydroxylase inhibitors to promote HIF activity to treat renal anemia could potentially also target diabetes-induced kidney hypoxia.

    SUMMARY:

    Increasing HIF activity in the diabetic kidney may possess a novel target for treatment of DKD by improving kidney oxygen homeostasis. However, HIF-mediated glomerulosclerosis may be a concern. The kidney outcomes from the ongoing clinical trials using prolyl hydroxylase inhibitors may provide additional insights into the complex role of HIF signaling in the diabetic kidney.

  • 16.
    Pihl, Liselotte
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Persson, Patrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Fasching, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Hansell, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    DiBona, Gerald F.
    Palm, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology, Integrative Physiology.
    Insulin induces the correlation between renal blood flow and glomerular filtration rate in diabetes: implications for mechanisms causing hyperfiltration2012In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 303, no 1, p. R39-R47Article in journal (Refereed)
    Abstract [en]

    Glomerular filtration rate (GFR) and renal blood flow (RBF) are normally kept constant via renal autoregulation. However, early diabetes results in increased GFR and the potential mechanisms are debated. Tubuloglomerular feedback (TGF) inactivation, with concomitantly increased RBF, is proposed but challenged by the finding of glomerular hyperfiltration in diabetic adenosine A(1) receptor-deficient mice, which lack TGF. Furthermore, we consistently find elevated GFR in diabetes with only minor changes in RBF. This may relate to the use of a lower streptozotocin dose, which produces a degree of hyperglycemia, which is manageable without supplemental suboptimal insulin administration, as has been used by other investigators. Therefore, we examined the relationship between RBF and GFR in diabetic rats with (diabetes + insulin) and without suboptimal insulin administration (untreated diabetes). As insulin can affect nitric oxide (NO) release, the role of NO was also investigated. GFR, RBF, and glomerular filtration pressures were measured. Dynamic RBF autoregulation was examined by transfer function analysis between arterial pressure and RBF. Both diabetic groups had increased GFR (+60-67%) and RBF (+20-23%) compared with controls. However, only the diabetes + insulin group displayed a correlation between GFR and RBF (R-2 = 0.81, P < 0.0001). Net filtration pressure was increased in untreated diabetes compared with both other groups. The difference between untreated and insulin-treated diabetic rats disappeared after administering N-omega-nitro-L-arginine methyl ester to inhibit NO synthase and subsequent NO release. In conclusion, mechanisms causing diabetes-induced glomerular hyperfiltration are animal model-dependent. Supplemental insulin administration results in a RBF-dependent mechanism, whereas elevated GFR in untreated diabetes is mediated primarily by a tubular event. Insulin-induced NO release partially contributes to these differences.

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