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  • 1
    Online Resource
    Online Resource
    Multiparametric magnetic resonance imaging: A robust tool to test pathogenesis and pathophysiology behind nephropathy in humans
    Wiley ; 2023
    In:  Clinical Physiology and Functional Imaging Vol. 43, No. 4 ( 2023-07), p. 207-210
    Details
    In: Clinical Physiology and Functional Imaging, Wiley, Vol. 43, No. 4 ( 2023-07), p. 207-210
    Abstract: Chronic kidney disease (CKD) is a major population disease. In diabetes as well as hypertension, kidney disease is one of the most serious complications. Recent research has demonstrated that chronic hypoxia is a key actor in the pathogenesis of CKD. In this review, we focus on how functional magnetic resonance imaging (fMRI) techniques can shed light on pathogenetic mechanisms and monitor new treatments aimed at preventing or ameliorating the disease. Multiparametric MRI techniques can measure changes in renal artery flow, tissue perfusion, and oxygenation repetitively over short time periods, enabling high time resolution. Furthermore, renal fibrosis can be quantified noninvasively by MRI diffusion tensor imaging, and techniques are upcoming to measure renal oxygen consumption. These techniques are all radiation and contrast‐free. We briefly present data, demonstrating that fMRI techniques can play a major role in future research in CKD, and possibly also in daily clinical practice.
    Type of Medium: Online Resource
    ISSN: 1475-0961 , 1475-097X
    URL: Issue
    URL: Article
    DOI: 10.1111/cpf.v43.4
    DOI: 10.1111/cpf.12818
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2004626-1
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  • 2
    Online Resource
    Online Resource
    Assessment of Perfusion and Oxygenation of the Human Renal Cortex and Medulla by Quantitative MRI during Handgrip Exercise
    Ovid Technologies (Wolters Kluwer Health) ; 2018
    In:  Journal of the American Society of Nephrology Vol. 29, No. 10 ( 2018-10), p. 2510-2517
    Details
    In: Journal of the American Society of Nephrology, Ovid Technologies (Wolters Kluwer Health), Vol. 29, No. 10 ( 2018-10), p. 2510-2517
    Abstract: Renal flow abnormalities are believed to play a central role in the pathogenesis of nephropathy and in primary and secondary hypertension, but are difficult to measure in humans. Handgrip exercise is known to reduce renal arterial flow (RAF) by means of increased renal sympathetic nerve activity. Methods To monitor medullary and cortical oxygenation under handgrip exercise–reduced perfusion, we used contrast- and radiation-free magnetic resonance imaging (MRI) to measure regional changes in renal perfusion and blood oxygenation in ten healthy normotensive individuals during handgrip exercise. We used phase-contrast MRI to measure RAF, arterial spin labeling to measure perfusion, and both changes in transverse relaxation time (T 2 *) and dynamic blood oxygenation level–dependent imaging to measure blood oxygenation. Results Handgrip exercise induced a significant decrease in RAF. In the renal medulla, this was accompanied by an increase of oxygenation (reflected by an increase in T 2 *) despite a significant drop in medullary perfusion; the renal cortex showed a significant decrease in both perfusion and oxygenation. We also found a significant correlation ( R 2 =0.8) between resting systolic BP and the decrease in RAF during handgrip exercise. Conclusions Renal MRI measurements in response to handgrip exercise were consistent with a sympathetically mediated decrease in RAF. In the renal medulla, oxygenation increased despite a reduction in perfusion, which we interpreted as the result of decreased GFR and a subsequently reduced reabsorptive workload. Our results further indicate that the renal flow response’s sensitivity to sympathetic activation is correlated with resting BP, even within a normotensive range.
    Type of Medium: Online Resource
    ISSN: 1046-6673 , 1533-3450
    URL: Article
    DOI: 10.1681/ASN.2018030272
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2018
    detail.hit.zdb_id: 2029124-3
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  • 3
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    Online Resource
    Human renal response to furosemide: Simultaneous oxygenation and perfusion measurements in cortex and medulla
    Wiley ; 2019
    In:  Acta Physiologica Vol. 227, No. 1 ( 2019-09)
    Details
    In: Acta Physiologica, Wiley, Vol. 227, No. 1 ( 2019-09)
    Abstract: Disturbances of renal medullary perfusion and metabolism have been implicated in the pathogenesis of kidney disease and hypertension. Furosemide, a loop diuretic, is widely used to prevent renal medullary hypoxia in acute kidney disease by uncoupling sodium metabolism, but its effects on medullary perfusion in humans are unknown. We performed quantitative imaging of both renal perfusion and oxygenation using Magnetic Resonance Imaging (MRI) before and during furosemide. Based on the literature, we hypothesized that furosemide would increase medullary oxygenation, decrease medullary perfusion, but cause minor changes ( 〈 10%) in renal artery flow (RAF). Methods Interleaved measurements of RAF, oxygenation ( T 2 *) and perfusion by arterial spin labelling in the renal cortex and medulla of 9 healthy subjects were acquired before and after an injection of 20 mg furosemide. They were preceded by measurements made during isometric exercise (5 minutes handgrip bouts), which are known to induce changes in renal hemodynamics, that served as a control for the sensitivity of the hemodynamic MRI measurements. Experiments were repeated on a second day to establish that the measurements and the induced changes were reproducible. Results After furosemide, T 2 * values in the medulla increased by 53% ( P   〈  0.01) while RAF and perfusion remained constant. After hand‐grip exercise, T 2 * values in renal medulla increased by 22% ± 9% despite a drop in medullary perfusion of 7.2% ± 4.7% and a decrease in renal arterial flow of 17.5% ± 1.7% ( P   〈  0.05). Mean coefficients of variation between repeated measurements for all parameters were 7%. Conclusion Furosemide induced the anticipated increase in renal medullary oxygenation, attributable exclusively to a decrease in renal oxygen consumption, since no change of RAF, cortical or medullary perfusion could be demonstrated. All measures and the induced changes were reproducible.
    Type of Medium: Online Resource
    ISSN: 1748-1708 , 1748-1716
    URL: Issue
    URL: Article
    DOI: 10.1111/apha.v227.1
    DOI: 10.1111/apha.13292
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2617148-X
    detail.hit.zdb_id: 2219379-0
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    GLP−1 Promotes Cortical and Medullary Perfusion in the Human Kidney and Maintains Renal Oxygenation During NaCl Loading
    Ovid Technologies (Wolters Kluwer Health) ; 2023
    In:  Journal of the American Heart Association Vol. 12, No. 3 ( 2023-02-07)
    Details
    In: Journal of the American Heart Association, Ovid Technologies (Wolters Kluwer Health), Vol. 12, No. 3 ( 2023-02-07)
    Abstract: GLP‐1 (glucagon‐like peptide‐1) receptor agonists exert beneficial long‐term effects on cardiovascular and renal outcomes. In humans, the natriuretic effect of GLP‐1 depends on GLP‐1 receptor interaction, is accompanied by suppression of angiotensin II, and is independent of changes in renal plasma flow. In rodents, angiotensin II constricts vasa recta and lowers medullary perfusion. The current randomized, controlled, crossover study was designed to test the hypothesis that GLP‐1 increases renal medullary perfusion in healthy humans. Methods and Results Healthy male participants (n=10, aged 27±4 years) ingested a fixed sodium intake for 4 days and were examined twice during a 1‐hour infusion of either GLP‐1 (1.5 pmol/kg per minute) or placebo together with infusion of 0.9% NaCl (750 mL/h). Interleaved measurements of renal arterial blood flow, oxygenation (R 2 *), and perfusion were acquired in the renal cortex and medulla during infusions, using magnetic resonance imaging. GLP‐1 infusion increased medullary perfusion (32±7%, P 〈 0.001) and cortical perfusion (13±4%, P 〈 0.001) compared with placebo. Here, NaCl infusion decreased medullary perfusion (−5±2%, P =0.007), whereas cortical perfusion remained unchanged. R 2 * values increased by 3±2% ( P =0.025) in the medulla and 4±1% ( P =0.008) in the cortex during placebo, indicative of decreased oxygenation, but remained unchanged during GLP‐1. Blood flow in the renal artery was not altered significantly by either intervention. Conclusions GLP‐1 increases predominantly medullary but also cortical perfusion in the healthy human kidney and maintains renal oxygenation during NaCl loading. In perspective, suppression of angiotensin II by GLP‐1 may account for the increase in regional perfusion. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04337268.
    Type of Medium: Online Resource
    ISSN: 2047-9980
    URL: Article
    DOI: 10.1161/JAHA.122.027712
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2023
    detail.hit.zdb_id: 2653953-6
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