Renal Blood Flow Research Articles

FRI153 Genetic Variant In Armadillo Repeat Containing 5 Gene (ARMC5) Associates With Salt Sensitivity Of Blood Pressure And Aldosterone In A Caucasian Cohort

Abstract Disclosure: W.W. Parksook: None. M. Heydarpour: None. L. Pojoga: None. A. Gaye: None. G.H. Gibbons: None. G.H. Williams: Advisory Board Member; Self; Cereno. Consulting Fee; Self; Alnylam, Crinetics, Damian, KBP bioscience, Paxel, Relapsa, Unicycive. Grant Recipient; Self; NIH 2 grants. J.S. Williams: Advisory Board Member; Self; Mellicell, Inc. Background: Genetic alterations of ARMC5 have been reported in various adrenal disorders, particularly in primary bilateral macronodular adrenal hyperplasia. Increasing evidence shows that polymorphic variants in ARMC5 are also associated with blood pressure (BP), hypertension, and the renin-angiotensin-aldosterone-system (RAAS) in individuals of African descent; however, little is known about these relationships in Caucasians. Herein, we conducted a deep phenotyping study to assess the association of ARMC5 variants with BP, salt sensitivity of BP (SSBP), and components of the RAAS in Caucasians. Methods: Normotensive and hypertensive, non-diabetic, non-chronic kidney disease, Caucasian participants underwent two dietary interventions at 5-7 days apart (200 mmol/day and 10 mmol/day sodium) to assess SSBP and other hormonal parameters. All participants were genotyped using a Multi-Ethnic-Genotyping-Array. Association analysis and the quality control of the genomic data were assessed by PLINK. Participants with complete data for SSBP and hormonal parameters, who were in salt balance, were included in the analysis (n= 306). Multiple linear regression models were used to assess the association between the genetic variant and outcome parameters. Results: There were 5 single nucleotide polymorphisms in the ARMC5 region. rs4889660 was significantly associated with SSBP in additive and dominant models when adjusted by Bonferroni correction. In a candidate gene analysis, rs4889660 risk allele carriers had greater SSBP than non-risk allele homozygotes (β= 4 mmHg, P= 0.03). Following dietary sodium restriction, rs4889660 risk allele carriers had lower serum aldosterone levels in an upright position (β= -6.9 ng/dl, P= 0.04) and serum aldosterone levels after angiotensin II stimulation (β= -3.0 ng/dl, P= 0.02). There were no differences between plasma renin activity, serum and urinary cortisol levels, and renal plasma flows between genotypes. Conclusions: There was an association between the ARMC5 rs4889660 variant and SSBP in Caucasians. With dietary sodium restriction, aldosterone responses to both upright posture and angiotensin II infusion were lower in the risk allele carriers. The reduced aldosterone responses suggest that an alteration in the RAAS system is not the cause of the SSBP, but is in response to a defect in another sodium-mediated homeostatic mechanism. Presentation: Friday, June 16, 2023

Organ blood flow assessment with the ModulHeart cardiorenal support device.

ModulHeart (Puzzle Medical Devices Inc) is a novel percutaneous flow entrainment pump anchored in the descending aorta. The current study evaluates the hemodynamic effect of ModulHeart support and its impact on cerebral, myocardial, and renal blood flow. ModulHeart was implanted in the descending aorta of four healthy calves. A ramp protocol (2000 RPM increments) was performed with the pump operating at five different speeds from 14 000 to 22 000 RPM. For each speed, pressures proximal and distal to the pump, and right heart catheterization measurements were recorded. Stable-isotope labeled microspheres were injected in the left ventricle to evaluate organ perfusion. Thermodilution cardiac output increased by 23% at 22 000 RPM. Greater pump speeds resulted in greater pump gradients, up to 10 mm Hg in mean arterial pressure at 22 000 RPM, without significant reduction of proximal perfusion pressures. Arterial pulse pressure remained stable at all speeds. ModulHeart was not associated with a reduction in cerebral or myocardial blood flow at any speed. Renal cortical and medullary blood flow increased by up to 50% and 40%, respectively. The ModulHeart device implanted in the descending aorta of healthy calves resulted in significant arterial pressure gradients and preserved pulse pressure. Greater pump speeds translated into greater increases in renal blood flow, with no decrease in cerebral or myocardial perfusion.

Enhanced external counterpulsation, focusing on its effect on kidney function, and utilization in patients with kidney diseases: a systematic review.

Enhanced external counterpulsation (EECP) is provided by a noninvasive device positively affecting cardiovascular function via mechanisms called diastolic augmentation and systolic unloading. The renal aspects of EECP therapy have not been extensively investigated. To assess the effect of EECP on renal function and to determine the application in patients with kidney disease. MEDLINE, EMBASE, SCOPUS, and Cochrane CENTRAL databases were searched for all studies involving EECP treatments. The title and abstract of all searched literatures were screened, and those focusing on renal outcome or conducting in kidney disease patients were selected. Eight studies were included in the qualitative analysis. EECP increases stroke volume, mean arterial pressure, renal artery blood flow, renal plasma flow, glomerular filtration rate (GFR), plasma atrial natriuretic peptide, urine volume, and urinary sodium chloride excretion, but reduces the plasma concentration of renin and endothelin-1 in healthy subjects. A single session of EECP after radioactive contrast exposure could provide increased contrast clearance, and this reduces contrast-induced kidney injury in patients, irrespective of previous kidney function. Thirty-five-hour sessions of EECP treatment were illustrated to increase long-term estimated GFR in patients with chronic angina and heart failure. In cirrhotic patients, EECP fails to improve GFR and renal vascular resistance. EECP device could maintain blood pressure, decrease angina symptoms, and increase cardiac perfusion in hemodialysis patients. EECP treatment potentially increases renal perfusion and prevents kidney injury in several conditions. EECP possibly provides beneficial effects on hemodynamics and cardiac function in hemodialysis patients.

Change in renal blood flow in response to intrarenal pressure alterations induced by ureteroscopy in an in-vivo porcine model.

High irrigation rates are commonly used during ureteroscopy and can increase intrarenal pressure (IRP) substantially. Concerns have been raised that elevated IRP may diminish renal blood flow (RBF) and perfusion of the kidney. Our objective was to investigate the real-time changes in RBF while increasing IRP during Ureteroscopy (URS) in an in-vivo porcine model. Four renal units in two porcine subjects were used in this study, three experimental units and one control. For the experimental units, RBF was measured by placing an ultrasonic flow cuff around the renal artery, while performing ureteroscopy in the same kidney using a prototype ureteroscope with a pressure sensor at its tip. Irrigation was cycled between two rates to achieve targeted IRPs of 30mmHg and 100mmHg. A control data set was obtained by placing the ultrasonic flow cuff on the contralateral renal artery while performing ipsilateral URS. At high IRP, RBF was reduced in all three experimental trials by 10-20% but not in the control trial. The percentage change in RBF due to alteration in IRP was internally consistent in each porcine renal unit and independent of slower systemic variation in RBF encountered in both the experimental and control units. RBF decreased 10-20% when IRP was increased from 30 to 100mmHg during ureteroscopy in an in-vivo porcine model. While this reduction in RBF is unlikely to have an appreciable effect on tissue oxygenation, it may impact heat-sink capacity in vulnerable regions of the kidney.

Dynamic volume status assessment with the VExUS score after heart valve surgery complicated by acute kidney injury: a case series

Background: Fluid overload is an independent risk factor for acute kidney injury after cardiac surgery. An objective volume status assessment remains an unsolved clinical problem.Objective: To analyze the relationship between the dynamic changes in splanchnic blood flow patterns (portal, hepatic, and interlobar renal veins), reflecting the venous congestion severity, and severity of renal dysfunction in the studied patients.Methods: From February to May 2023, 3 patients after open heart surgery developed acute kidney injury in the postoperative period: 2 of them required renal replacement therapy. In the perioperative period, all patients underwent Doppler ultrasonographic assessment of the splanchnic blood flow according to the venous excess ultrasound (VExUS) score.Results: The most distinct changes in blood flow patterns were observed in portal and interlobar renal veins. Two anuric patients requiring renal replacement therapy had a pulsatile portal venous flow with systolic flow reversal that indicated severe venous congestion and biphasic renal venous flow. After restoration of urine output in 1 patient, the blood flow pattern in the portal vein returned to the normal pattern. In another patient, the blood flow remained pulsatile, which manifested itself by persisting clinical signs of overhydration. In the third patient, the portal blood flow also was pulsatile but had no systolic flow reversal. The renal blood flow was biphasic, although it was initially continuous. After restoration of urine output and overhydration improvement, the blood flow pattern returned to the preoperative pattern.Conclusion: In the studied patients, the dynamic assessment of splanchnic blood flow using the VExUS score allowed to objectively assess the venous congestion severity and served as an additional criterion for initiating renal replacement therapy in case of acute kidney injury progression. Further research could validate this type of monitoring because its interpretation requires a comprehensive assessment due to moderate specificity. Received 21 June 2023. Revised 17 July 2023. Accepted 24 July 2023. Informed consent: The patients’ informed consent to use the records for medical purposes is obtained. Funding: The study did not have sponsorship. Conflict of interest: The authors declare no conflicts of interests. Contribution of the authors: The authors contributed equally to this article.

MRI-based quantification of whole-organ renal metabolic rate of oxygen.

During the early stages of diabetes, kidney oxygen utilization increases. The mismatch between oxygen demand and supply contributes to tissue hypoxia, a key driver of chronic kidney disease. Thus, whole-organ renal metabolic rate of oxygen (rMRO2 ) is a potentially valuable biomarkerof kidney function. The key parameters required to determine rMRO2 include the renal blood flow rate (RBF) in the feeding artery and oxygen saturation in the draining renal vein (SvO2 ). However, there is currently no noninvasive method to quantify rMRO2 in absolute physiologic units. Here, a new MRI pulse sequence, Kidney Metabolism of Oxygen via T2 and Interleaved Velocity Encoding (K-MOTIVE), is described, along with evaluation of its performance in the human kidney in vivo. K-MOTIVE interleaves a phase-contrast module before a background-suppressed T2 -prepared balanced steady-state-free-precession (bSSFP) readout to measure RBF and SvO2 in a single breath-hold period of 22 s, yielding rMRO2 via Fick's principle. Variants of K-MOTIVE to evaluate alternative bSSFP readout strategies were studied. Kidney mass was manually determined from multislice gradient recalled echo images. Healthy subjects were recruited to quantify rMRO2 of the left kidney at 3-T field strength (N= 15). Assessments of repeat reproducibility and comparisons with individual measurements of RBF and SvO2 were performed, and the method's sensitivity was evaluated with a high-protein meal challenge (N= 8). K-MOTIVE yielded the following metabolic parameters: T2 = 157 ± 19 ms; SvO2 = 92% ± 6%; RBF = 400 ± 110 mL/min; and rMRO2 = 114 ± 117(μmol O2 /min)/100 g tissue. Reproducibility studies of T2 and RBF (parameters directly measured by K-MOTIVE) resulted in coefficients of variation less than 10% and intraclass correlation coefficients more than 0.75. The high-protein meal elicited an increase in rMRO2 , which was corroborated by serum biomarkers. The K-MOTIVE sequence measures SvO2 and RBF, the parameters necessary to quantify whole-organ rMRO2 , in a single breath-hold. The present work demonstrates that rMRO2 quantification is feasible with good reproducibility. rMRO2 is a potentially valuable physiological biomarker.

Incidence, associated factors, and outcomes of acute kidney injury following placement of antibiotic bone cement spacers in two-stage exchange for periprosthetic joint infection: a comprehensive study.

Two-stage exchange with placement of antibiotic cement spacer (ACS) is the gold standard for the treatment of chronic periprosthetic joint infection (PJI), but it could cause a high prevalence of acute kidney injury (AKI). However, the results of the current evidence on this topic are too mixed to effectively guide clinical practice. We retrospectively identified 340 chronic PJI patients who underwent the first-stage exchange with placement of ACS. The Kidney Disease Improving Global Outcomes guideline was used to define postoperative AKI. Multivariate logistic analysis was performed to determine the potential factors associated with AKI. Furthermore, a systematic review and meta-analysis on this topic were conducted to summarize the knowledge in the current literature further. In our cohort, the incidence of AKI following first-stage exchange was 12.1%. Older age (per 10 years, OR= 1.509) and preoperative hypoalbuminemia (OR= 3.593) were independent predictors for postoperative AKI. Eight AKI patients progressed to chronic kidney disease after 90 days. A meta-analysis including a total of 2525 PJI patients showed the incidence of AKI was 16.6%, and AKI requiring acute dialysis was 1.4%. Besides, host characteristics, poor baseline liver function, factors contributing to acute renal blood flow injury, and the use of nephrotoxic drugs may be associated with the development of AKI. However, only a few studies supported an association between antibiotic dose and AKI. AKI occurs in approximately one out of every six PJI patients undergoing first-stage exchange. The pathogenesis of AKI is multifactorial, with hypoalbuminemia could be an overlooked associated factor. Although the need for acute dialysis is uncommon, the fact that some AKI patients will develop CKD still needs to be taken into consideration.

Maternal dexamethasone exposure does not affect glucose tolerance but alters renal haemodynamics in F1 rats in a sex-dependent manner.

Prenatal programming with dexamethasone increases the risk of the development of hyperglycaemia and insulin resistance, leading to diabetes in adulthood. Dexamethasone also causes a decline in renal glomerular filtration in the adult offspring. Sodium-glucose cotransporter-2 (SGLT2) plays a significant role in regulating blood glucose and renal haemodynamics in diabetic patients. However, the role of SGLT2 in dexamethasone-induced programming and the putative sex-dependent effects on the changes named earlier is unknown. Therefore, this study aimed to investigate the impact of maternal dexamethasone treatment on glucose tolerance, insulin sensitivity, renal perfusion and renal function in adult male and female offspring and the possible contribution of SGLT2 to these changes. Pregnant Sprague Dawley rats (F0 ) were treated with either vehicle or dexamethasone (0.2 mg/kg ip) from gestation Day 15 to 20. F1 males and F1 females were randomly selected from each mother at 4 months of age. There was no change in serum Na+ , Na+ excretion rate, glucose tolerance or insulin sensitivity in F1 male or female rats. However, dexamethasone caused significant glomerular hypertrophy and decreases in CSinistrin and CPAH indicating decreased glomerular filtration rate and renal plasma flow, respectively, in dexamethasone-treated F1 male but not female rats. Dexamethasone did not affect SGLT2 mRNA or protein expression in F1 males or females. We conclude that dexamethasone-mediated prenatal programming of glomerular volume, renal function and haemodynamics is sex-dependent, occurring only in adult male offspring.

Effects of liraglutide on extraglycemic inflammatory markers and renal hemodynamic parameters in diabetic kidney disease (DKD).

Diabetic kidney disease (DKD) was the leading cause of kidney disease, which has been a crucial public health. Liraglutide is a drug, widely used for DKD treatment globally. However, the extraglycemic inflammatory markers and renal hemodynamic parameters of DKD patients treated with liraglutide has been not reported. In this study, 160 patients with early DKD were enrolled, 80 cases in the control group and 80 cases in the treatment group, respectively. The individuals in the control group were treated with metformin, while the individuals in the treatment group were treated with liraglutide and metformin for 3 months. The urinary microalbumin and urinary creatinine was measured to calculate the ratio (UACR), while the Doppler ultrasound were measured before and after treatment. After 3 months of treatment, body mass index (BMI), waist circumference (WC) and low-density lipoprotein cholesterol (LDL) in the treatment group were significantly decreased compared with before and after treatment in the control group; the levels of cystatin and UACR in treatment group were lower than before treatment and control group; The end-diastolic blood flow velocity (EDV) of renal artery and segment artery in treatment group was significantly higher than that before treatment and control group; The levels of CRP, TNF-α and IL-6 in the treatment group after treatment were lower than those before treatment and those in the control group. After 3 months of treatment, blood cystatin in the treatment group decreased significantly compared with before treatment and after treatment in the control group, with statistical significance After 3 months of treatment, the EDV of renal artery and renal segment in treatment group was significantly higher than that before treatment and control group, the peak systolic blood flow velocity (PSV) and EDV of renal interlobar artery in treatment group were significantly higher than those before treatment and control group. The resistance index (RI) was significantly lower than that before treatment and control group. Liraglutide can reduce inflammatory indicators, renal artery blood flow and renal function indicators in early DKD patients.

Efficacy of Dynamics-based Features for Machine Learning Classification of Renal Hemodynamics.

Different machine learning approaches for analyzing renal hemodynamics using time series of arterial blood pressure and renal blood flow rate measurements in conscious rats are developed and compared. Particular emphasis is placed on features used for machine learning. The test scenario involves binary classification of Sprague-Dawley rats obtained from two different suppliers, with the suppliers' rat colonies having drifted slightly apart in hemodynamic characteristics. Models used for the classification include deep neural network (DNN), random forest, support vector machine, multilayer perceptron. While the DNN uses raw pressure/flow measurements as features, the latter three use a feature vector of parameters of a nonlinear dynamic system fitted to the pressure/flow data, thereby restricting the classification basis to the hemodynamics. Although the performance in these cases is slightly reduced in comparison to that of the DNN, they still show promise for machine learning (ML) application. The pioneering contribution of this work is the establishment that even with features limited to hemodynamics-based information, the ML models can successfully achieve classification with reasonably high accuracy.

Feasibility of Simultaneous Quantification of Myocardial and Renal Perfusion With Cardiac Positron Emission Tomography.

Given the central importance of cardiorenal interactions, mechanistic tools for evaluating cardiorenal physiology are needed. In the heart and kidneys, shared pathways of neurohormonal activation, hypertension, and vascular and interstitial fibrosis implicate the relevance of systemic vascular health. The availability of a long axial field of view positron emission tomography (PET)/computed tomography (CT) system enables simultaneous evaluation of cardiac and renal blood flow. This study evaluated the feasibility of quantification of renal blood flow using data acquired during routine, clinically indicated 13N-ammonia myocardial perfusion PET/CT. Dynamic PET image data were used to calculate renal blood flow. Reproducibility was assessed by the intraclass correlation coefficient among 3 independent readers. PET-derived renal blood flow was correlated with imaging and clinical parameters in the overall cohort and with histopathology in a small companion study of patients with a native kidney biopsy. Among 386 consecutive patients with myocardial perfusion PET/CT, 296 (76.7%) had evaluable images to quantify renal perfusion. PET quantification of renal blood flow was highly reproducible (intraclass correlation coefficient 0.98 [95% CI, 0.93-0.99]) and was correlated with the estimated glomerular filtration rate (r=0.64; P<0.001). Compared across vascular beds, resting renal blood flow was correlated with maximal stress myocardial blood flow and myocardial flow reserve (stress/rest myocardial blood flow), an integrated marker of endothelial health. In patients with kidney biopsy (n=12), resting PET renal blood flow was strongly negatively correlated with histological interstitial fibrosis (r=-0.85; P<0.001). Renal blood flow can be reliably measured from cardiac 13N-ammonia PET/CT and allows for simultaneous assessment of myocardial and renal perfusion, opening a potential novel avenue to interrogate the mechanisms of emerging therapies with overlapping cardiac and renal benefits.

Abstract 040: Evidence Of Increased Glycolysis In Renal Cortex Of High Salt Fed Sprague Dawley Rats

To determine whole kidney O 2 and substance metabolism in an unanesthetized state, arterial (A), renal venous (Vr) blood and urine (U) were analyzed together with measurements of renal blood flow (RBF), blood pressure (BP) and GFR in conscious freely moving male SD rats. RBF and BP were measured continuously (24/7) via chronically implanted ultrasonic flow probe and A-line respectively. A and Vr blood through chronically implanted catheters and urine (U) were sampled intermittently when rats were fed a 0.4% NaCl (LS) diet and on days 7, 14, and 21 after switching to a 4.0% NaCl (HS) diet (HS7, HS14, HS21). A and Vr O 2 contents were determined by radiometer and a global metabolomic analysis was performed at the JAX Laboratory (LC-MS-MS). GFR was determined in another group of rats by transcutaneous detection of the attenuation of i.v. injected FITC sinistrin. Cortical (Cx) and outer medullary (OM) tissues were obtained from the other group of rats and underwent metabolomic and mRNAseq analyses (Novogene). From another group of rats, glomeruli (Glo), proximal tubules (PT) and non-PT were isolated for RT-PCR. BP and RBF slightly increased by HS3 (P&lt;0.05) and were sustained at these levels. O 2 extraction rose progressively from 0.10 ± 0.01 at LS to 0.14 ± 0.01 at HS21 (P&lt;0.05). GFR increased from 0.64 to 0.83 mL/min/100 g (P&lt;0.05) at HS7 and sustained. Na + reabsorption and O 2 consumption were positively correlated. Clear distinctions were observed in a sparse partial least squares discriminant analysis of tissue metabolomics among LS, HS14, and HS21. The mRNAseq analysis found that the HS diet resulted in the activation of immune system-related genes in both Cx and OM and the downregulation of genes related to the TCA cycle and metabolism of amino acids and fatty acids in Cx only. In contrast, glycolysis-related genes including hexokinase ( Hk ) and pyruvate kinase ( Pkm ) were upregulated in Cx. Metabolic fluxes (A-Vr-U) showed the increased release of lactate and pyruvate from the kidney when fed HS. Increased mRNA expression of Hk and Pkm in HS21 was observed only in PT but not in Glo and non-PT. In summary, SD rats fed a HS diet underwent changes in RBF, O 2 extraction, and utilization of substrates with evidence of increased glycolysis.

Abstract P214: Impact Of NADPH Oxidase 4 Knockout On Renal O 2 Consumption In Dahl Salt-sensitive Rats

It has been generally thought that in normal Sprague-Dawley (SD) rats, a high salt diet has minimal impact on blood pressure and kidney function. However, as we have recently reported, the kidneys of SD rats fed a 4.0% NaCl diet (HS) exhibit enhanced O 2 consumption (VO 2 ) and marked changes in the metabolic pathways responsible for the generation of ATP and reactive oxygen species (ROS). In the current study, we examined the level of renal VO 2 in Dahl salt-sensitive (SS) rats and those in which the NADPH Oxidase 4 (NOX4) gene was globally knocked out (SS Nox4 -/- ). Male SS (n=9) and SS Nox4 -/- (n=10) rats were fed a 0.4% NaCl (LS) diet. At 7-8 weeks of age, the rats were implanted with a renal artery ultrasonic flow probe (Transonic) together with a femoral arterial catheter and a renal venous catheter. Renal blood flow (RBF) and mean arterial pressure (MAP) were measured continuously (24/7) and arterial (A) and renal venous (Vr) blood was sampled intermittently when rats were fed a LS and on days 7, 14, and 21 after switching to a HS diet. Blood O 2 content was immediately measured by a radiometer. The average 24-hour MAP of SS rats rose after switching to a HS diet from 122 ± 2 on the LS to 140 ± 2 on HS7, and to 164 ± 5 by HS21. In contrast, MAP in SS Nox4 -/- rats increased from 121 ± 2 mmHg at LS to 132 ± 1 mmHg at HS7 and 152 ± 3 mmHg at HS21 (p&lt;0.05). RBF was not significantly changed but tended to progressively rise in both strains of rats with 24-hr flows averaging 7.8 ± 0.7 ml/min when fed LS and 8.9 ± 1.0 ml/min at HS21, and SS Nox4 -/- from 6.9 ± 0.7 to 8.2 ± 0.9. Normalized by changes of kidney weights obtained in another group of SS and SS Nox4 -/- rats, RBF was significantly reduced over the 3 weeks of the HS diet given the increase of kidney weights (SS LS 7.0 ± 0.6, HS7 5.7 ± 0.5, HS21 4.9 ± 0.6; SS Nox4 -/- LS 6.4 ± 0.7, HS7 6.2 ± 0.7, HS21 5.4 ± 0.7). Most importantly, the O 2 extraction ratio at LS was lower in SS Nox4 -/- (10.5 ± 1.0%) compared to SS (14.6 ± 1.0%) (p&lt;0.05). When switched to the HS diet, this was further reduced in the SS Nox4 -/- rats reaching 7.6 ± 0.9% at HS21 (p&lt;0.05), while it did not change significantly in SS (13.3 ± 1.4%) at HS21. We conclude that the elevated levels of renal O 2 consumption observed in SS rats are at least in part a consequence of increased oxidative stress associated with NOX4.

Abstract P174: Determining The Effect Of Diet And Short-term Voluntary Exercise On Renal Function And RAS mRNA Expression In Male C57Bl/6 Mice: A Pilot Study

Poor dietary quality and exercise are key risk factors for kidney and cardiovascular diseases. Dietary quality is not considered in most preclinical animal studies and has likely hindered overall progress in biomedical research. We developed a novel diet to model the nutritional inadequacies of Americans and our data suggest poor dietary quality influences kidney function. Therefore, the goal of the current study is to determine how diet and exercise impact kidney and cardiovascular health in mice. Male C57Bl/6 mice were assigned to 1 of 3 diets: chow, synthetic AIN93G, or our novel Americanized diet (AD). Mice were assigned to exercise or control groups, with exercise being free access to an exercise wheel for 16 hours 3 times a week. After 4 weeks, systolic blood pressure (SBP) and renal blood flow (RBF) were quantified in a subset of each group. Renal mRNA expression of RAS genes was determined by RT-PCR in the remaining animals. Data were analyzed using General Linear Model Procedures in SPSS, with significance determined at P &lt;0.05 and a tendency indicated at P &lt;0.1. Neither diet ( P =0.6) nor exercise ( P= 0.5) significantly influenced SBP or RBF, however, a significant diet*exercise interaction occurred ( P =0.03). AIN-fed mice with exercise had a significantly lower (94±8 mmHg, p=0.009) blood pressure as compared to the AIN control group (116±4 mmHg). Similarly, exercise also tended ( P =0.09) to reduce RBF in mice fed AIN. Exercise, regardless of diet, resulted in a doubling (p=0.03) in renal angiotensinogen expression as compared to control mice. This effect was most apparent in mice fed chow. Diet also mediated the significant effect of exercise on renal Mme expression ( P =0.04), with exercise lowering Mme expression in mice fed AIN and AD (50% reduction) and increasing its expression (3-times greater) in mice fed chow. A similar trend was observed with Agtr1a ( P =0.07). Regardless of diet, exercise also tended to upregulate Ace1 (p=0.054) compared to control mice. Results of this pilot study suggest that diet significantly influences the physiological response to exercise, particularly renal physiology and the control of blood pressure. Additional studies are needed to confirm these preliminary results and identify the molecular mechanisms responsible.

Daytime Variation in Kidney Perfusion, Oxygenation, and Sodium Concentration Assessed by Multiparametric MRI in Healthy Volunteers.

MRI can provide information on kidney structure, perfusion, and oxygenation. Furthermore, it allows for the assessment of kidney sodium concentrations and handling, allowing multiparametric evaluation of kidney physiology. Multiparametric MRI is promising for establishing prognosis and monitoring treatment responses in kidney diseases, but its intraindividual variation during the day is unresolved. To investigate the variation in multiparametric MRI measurements from the morning to the evening. Prospective. Ten healthy volunteers, aged 29 ± 5 without history of kidney disease. 3 T/T1 mapping, blood-oxygen level dependent imaging, arterial spin labeling perfusion imaging, diffusion weighted imaging, and sodium imaging. A multiparametric MRI protocol, yielding T1, R2*, ADC, renal blood flow and renal sodium levels, was acquired in the morning, noon, and evening. The participants were fasting prior to the first examination. Urine biochemical analyses were performed to complement MRI data. The cortex and medulla were analyzed separately in a semi-automatic fashion, and gradients of total sodium concentration (TSC) and R2* gradients were calculated from outer cortex to inner medulla. Analyses of variance and mixed-effects models to estimate differences from time of day. Coefficients of variation to assess variability within and between participants. A P-value <0.05 was considered statistically significant. The coefficients of variation varied from 5% to 18% for proton-based parametric sequences, while it was 38% for TSC over a day. Multiparametric MRI is stable over the day. The coefficients of variation over a day were lower for proton multiparametric MRI, but higher for sodium MRI. 2 TECHNICAL EFFICACY: Stage 2.

Abstract P399: High Salt Induced Mitochondrial Uncoupling And Enhanced Respiratory Activity In Isolated Proximal Tubules From Dahl Salt-sensitive Rats

The nephron actively reabsorbs ~99% of the Na + from the glomerular filtrate to maintain fluid and solute homeostasis, ~70% of which occurs in the proximal tubules (PT), where mitochondria consume a great amount of O 2 for ATP production to meet the energy demand. However, the effect of a high salt diet upon the PT energy metabolism and respiratory activity is not well-known. To determine this, the PT of Dahl salt-sensitive (SS) rats were isolated with the rats fed either 0.4% NaCl (LS) or 7, 14 and 21 days after feeding a 4.0% NaCl (HS) diet. Changes in O 2 consumption rate (OCR) of the PT were determined using a high-throughput Agilent Seahorse XF96 Extracellular Flux Analyzer and Mitochondrial Stress Test Protocol. Basal OCRs were assessed with only amino acids used as fuel for oxidative phosphorylation (OxPhos). Under these conditions, by day 7 of the HS diet, OCR increased from 9.2±0.5 to 17.2±0.8 pmol/min/μg, (p&lt;0.05), which rose to 20.2±1.0 and 18.9±0.7 pmol/min/μg (p&lt;0.05 vs LS), respectively, at HS day 14 and HS day 21. The Seahorse protocol was also modified to determine the OCR responses to representative circulating substrates. The OCR responses from baseline to glucose or pyruvate were unchanged by the HS diet compared to the PT of LS fed rats. However, a sustained increase in the proton leak OCR was observed for glucose (LS: 2.5±0.5 vs HS day 7: 7.3±1.1; p&lt;0.05) and for pyruvate (LS: 2.3±0.3 vs HS day 7: 7.9±0.2; p&lt;0.05). These high levels of proton leak were maintained throughout the 21 days of the HS diet. Since it is known that uncoupling proteins (UCP) and ADP/ATP translocase (ANT) enhance proton leak, gene expression was quantified from the isolated PT segments. Increased Ucp2 expression was found (p&lt;0.05) in response to the HS diet (days 7, 14, and 21) compared to LS fed rats but no changes were observed in the expression of Slc25A4 (ANT1) or Slc25A5 (ANT2). In summary, the HS diet resulted in increased PT O 2 consumption and proton leak in SS rats which was associated with an increase of Ucp2 gene expression. Given recent evidence that this is associated with a decrease in renal blood flow (RBF/kidney wt), we propose that increases in the PT O 2 consumption contribute to the onset of regional chronic ischemia and exacerbates renal damage and hypertension.

Abstract P397: Preservation Of Renal Microvascular Function In Ischemia-reperfusion Induced Kidney Injury In Rats

Proper renal blood flow and glomerular filtration rate are critical for maintaining normal kidney function by precisely adjusting preglomerular microvascular resistance. Renal ischemia-reperfusion (IR) insult markedly increased mRNA expression of the inflammatory chemokine (C-C motif) Ligand 2 (CCL2) in rat kidney tissues. We hypothesized that depletion of macrophages prevented IR-induced renal autoregulatory impairment via reduction of CCL2 in preglomerular microvessels (PGMV). IR was induced in male rats by 60-minute bilateral renal artery occlusion followed by reperfusion. Some IR rats were treated with the selective macrophage inhibitor, Liposome-encapsulated clodronate (LC) following reperfusion and repeated 72 hours post-IR. Afferent arteriolar autoregulatory reactivity was assessed using the in vitro blood-perfused juxtamedullary nephron preparation in sham, IR, and IR+LC rats on day 7. Afferent arterioles from sham-operated rats exhibited pressure-dependent vasoresponsiveness. The baseline arteriolar diameter averaged 13.4 ± 0.5 μm at renal perfusion pressure (RPP) of 100 mmHg. Diameter increased to 117 ± 4% of baseline at RPP of 65 mmHg and decreased to 69 ± 2% at 170 mmHg, respectively. In contrast, afferent arterioles from IR rats only increased to 104 ± 2% and decreased to 91 ± 5% of baseline at 65 and 170 mmHg, respectively (P &lt; 0.05 vs sham), indicating the impaired autoregulatory capacity in IR rats. LC-treated IR rats, however, markedly improved the pressure-dependent vasoresponsiveness. A decrease in RPP to 65 mmHg resulted in a 124 ± 17% increase in the baseline diameter, whereas increasing RPP to 170 mmHg led to a 74 ± 7% decrease in diameter. Additionally, IR markedly increased CCL2 mRNA expression in isolated PGMV by 10-fold 7 days post-IR. IR also elevated NADPH oxidase subunits (gp91 phox , P67 phox , and P47 phox ). Significantly, LC treatment suppressed mRNA expression of CCL2, gp91 phox , P67 phox , and P47 phox in IR-PGMV. In conclusion, depletion of macrophages preserves afferent arteriolar autoregulatory capacity and reduces PGMV CCL2 mRNA expression in IR rats, suggesting a critical role of macrophages in mediating renal microvascular autoregulatory impairment in IR-induced kidney injury via the increase of CCL2 in PGMV.

Reduced tubuloglomerular feedback activity and absence of its synchronization in a connexin40 knockout rat.

Introduction: Tubuloglomerular feedback (TGF) is the negative feedback component of renal blood flow (RBF) autoregulation. Neighbouring nephrons often exhibit spontaneous TGF oscillation and synchronization mediated by endothelial communication, largely via connexin40 (Cx40). Methods: We had a knockout (KO) rat made that lacks Cx40. One base pair was altered to create a stop codon in exon 1 of Gja5, the gene that encodes Cx40 (the strain is WKY-Gja55em1Mcwi). Blood pressure (BP)-RBF transfer functions probed RBF dynamics and laser speckle imaging interrogated the dynamics of multiple efferent arterioles that reach the surface (star vessels). Results: The distribution of wild type (WT), heterozygote, and KO pups at weaning approximated the Mendelian ratio of 1:2:1; growth did not differ among the three strains. The KO rats were hypertensive. BP-RBF transfer functions showed low gain of the myogenic mechanism and a smaller TGF resonance peak in KO than in WT rats. Laser speckle imaging showed that myogenic mechanism had higher frequency in KO than in WT rats, but similar maximum spectral power. In contrast, the TGF frequency was similar while peak power of its oscillation was much smaller in KO than in WT rats. In WT rats, plots of instantaneous TGF phase revealed BP-independent TGF synchronization among star vessels. The synchronization could be both prolonged and widespread. In KO rats TGF synchronization was not seen, although BP transients could elicit short-lived TGF entrainment. Discussion: Despite the reduced TGF spectral power in KO rats, there was sufficient TGF gain to induce oscillations and therefore enough gain to be effective locally. We conclude that failure to synchronize is dependent, at least in part, on impaired conducted vasomotor responses.

QUALITATIVE ASSESSMENT OF RENAL BLOOD PRESSURE USING NANOTECHNOLOGY INTERVENTION

The renal system is one of the major organ systems present in the human body, it is responsible for maintaining electrolyte balance, secreting important hormones, and maintaining homeostasis in the body. Every individual has 2 kidneys which are located behind the peritoneum at the level of L2-L3 from the vertebral column. Broadly kidneys function to filter blood, purify it, and eliminate toxic waste. We propose a diagnostic test that evaluates the renal blood flow rate in the kidneys and assesses their functioning based on their hemodynamics in the given time frame. Here we aim to explore the application of nanoparticles to assess localized blood pressure in the kidney based on the illumination intensity/radioactivity. Connexin40(Cx40) is a transmembrane protein present in juxtaglomerular apparatus, Cx40 gold antibodies prepared can be conjugated with nanoparticles and introduced in renal circulation. Imaging technologies such as fluorescence/computed tomography can be used to detect these nanoparticles. Once injected they can be assessed and information on renal blood flow can be obtained. The intensity generated on screening can be used for the assessment of renal blood pressure. This information will be valuable for the assessment of kidney function.

Effect of left renal vein compression stenosis on functional status of left kidney in patients with pelvic venous disorders

ObjectiveWe evaluated the effect of left renal vein (LRV) compression stenosis on the functional state of the left kidney in patients with pelvic venous disorders (PeVDs). MethodsWe examined 162 female patients with PeVD and diagnosed LVR compression stenosis using duplex ultrasound (DUS) in 40. Patients with clinical manifestations of PeVD (n = 26) had symptoms and signs of pelvic venous congestion but without pain in the left flank of the abdomen, typical for nutcracker syndrome (NS). The remaining patients were asymptomatic (n = 14). The parameters measured with DUS included the angle of the superior mesenteric artery (SMA) with the aorta, the LRV diameter (Dhilum/Dstenosis) ratio, and LRV velocity (Vstenosis/Vhilum) ratio. All the patients underwent laboratory testing (complete blood count, urinalysis, and biochemical blood testing) and dynamic renal scintigraphy to assess the secretory and evacuation functions of the renal tubular system. ResultsThe laboratory tests revealed no abnormalities, including no hematuria or proteinuria, in either group. The Dhilum/Dstenosis and Vstenosis/Vhilum ratios varied from 2.8 to 5.2 and from 2.9 to 8.3, respectively, and did not differ between the symptomatic and asymptomatic patients. All 40 patients with LRV compression stenosis were diagnosed with left gonadal vein reflux with a mean duration of 4.7 ± 0.6 seconds and 2.2 ± 0.6 seconds in the symptomatic and asymptomatic patients, respectively (P = .005). Eight patients had signs of NS on DUS, including five in the symptomatic group (SMA angle, 34.8° ± 2.7°; Dhilum/Dstenosis ratio, 5.2 ± 0.2; and Vstenosis/Vhilum ratio, 5.7 ± 0.4) and three in the asymptomatic group (SMA angle, 35° ± 2.8°; Dhilum/Dstenosis ratio, 5; and Vstenosis/Vhilum ratio, 5 ± 0.5). The groups did not differ significantly in the DUS parameters. Scintigraphy did not reveal any cases of secretory or evacuation dysfunction of the left kidney, including in the patients with DUS signs of NS. The maximum uptake time, elimination half-life, and effective renal plasma flow were within the normal ranges. ConclusionsLRV compression stenosis without hematuria has no significant effects on the functional state of the left kidney, irrespective of the disease severity. In patients with PeVDs, dynamic renal scintigraphy provides an objective assessment of left kidney function.