Renal autoregulation in health and disease

Heart failure subphenotypes based on mean arterial pressure trajectory identify patients at increased risk of acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a common complication in heart failure (HF) patients. Patients with heart failure who experience renal injury tend to have a poor prognosis. The objective of this study is to examine the correlation between the occurrence of AKI in heart failure patients and different mean arterial pressure (MAP) trajectories, with the goal of improving early identification and intervention for AKI.

METHODS

A retrospective study was conducted on patients with heart failure using data from the Medical Information Mart for Intensive Care IV (MIMIC-IV). We utilized the group-based trajectory modeling (GBTM) method to classify the 24-hour MAP change trajectories in heart failure patients. The occurrence of AKI within the first 7 days of intensive care unit (ICU) admission was considered the outcome. The impact of MAP trajectories on AKI occurrence in heart failure patients was analyzed using Cox proportional hazards models, competing risk models, and doubly robust estimation methods.

RESULTS

A cohort of 8,502 HF patients was analyzed, with their 24-hour MAP trajectories categorized into five groups: Low MAP group (Class 1), Medium MAP group (Class 2), Low-medium MAP group (Class 3), High-to-low MAP group (Class 4), and High MAP group (Class 5). The results from the doubly robust analysis revealed that Class 4 exhibited a significantly increased AKI risk than Class 3 (HR 1.284, 95% CI 1.085-1.521, p = 0.003; HR 1.271, 95% CI 1.074-1.505, p = 0.005). Conversely, the risks of Class 2 were significantly lower than those of Class 3 (HR 0.846, 95% CI 0.745-0.960, p = 0.009; HR 0.879, 95% CI 0.774-0.998, p = 0.047).

CONCLUSIONS

The 24-hour MAP trajectory in HF patients influences the risk of AKI. A rapid decrease in MAP (Class 4) is associated with a higher AKI risk, while maintaining MAP at a moderate level (Class 2) significantly reduces this risk. Therefore, closely monitoring MAP changes is crucial for preventing AKI in HF.

Impact of intrarenal arterial lesions on prognosis of IgA nephropathy: insights from a retrospective cohort study

BACKGROUND

IgA nephropathy (IgAN) presents a challenging spectrum of outcomes, often complicated by intrarenal arterial/arteriolar lesions (IALs) in affected individuals. Despite their clinical relevance, existing criteria for classifying and assessing the severity of these lesions remain undefined. This study aimed to establish semi-quantitative assessment criteria for grading IALs and to evaluate their prognostic significance in patients with IgAN.

METHOD

We conducted a retrospective cohort study of 417 cases of primary IgAN in which IALs were meticulously scored in individual biopsies. Kaplan-Meier survival analysis was employed to compare the time to the renal composite endpoint between different IALs severity groups. The association between the severity of IALs and clinical outcomes was further evaluated using multivariate Cox regression models to control for potential confounders.

RESULTS

Among the 417 patients studied, 230 (55.2%) exhibited IALs. Kaplan-Meier curve analysis showed a higher cumulative incidence of the composite endpoint in patients with IALs (p < 0.001). In a compelling multivariate analysis, we identified IALs and its subclassifications, including moderate to severe intimal fibrosis and hyalinosis, as strong independent risk factors for poor prognosis (IALs: HR = 2.15, p = 0.009; moderate to severe hyalinosis: HR = 3.58, p = 0.001; moderate to severe intimal fibrosis: HR = 3.56, p = 0.001).

CONCLUSION

Our findings underscore the prognostic significance of IALs in IgAN, particularly moderate to severe intimal fibrosis and hyalinosis and highlight the urgent need for novel therapeutic strategies specifically designed to mitigate the impact of IALs in high-risk IgAN patients.

Prevention of hypertension-induced renal vascular dysfunction through a p66Shc-targeted mechanism

Renal microvascular injury occurs in most patients with hypertension-induced nephropathy (HN). We have shown that overexpression of adaptor protein p66Shc is implicated in the loss of renal microvascular reactivity in hypertensive rats. Since sulfur heteroarotinoid A2 (SHetA2) modulates p66Shc, we tested whether SHetA2 would restore renal microvascular reactivity and mitigate kidney injury in a rat HN model. Dahl salt sensitive (SS) and p66Shc knockout (p66Shc-KO) rats were used in a well-established rat model of HN, characterized by severe renal vascular dysfunction. SHetA2 was either added acutely to isolated rat afferent arterioles or chronically administrated to rats during HN development. The ability of SHetA2 treatment to restore afferent arteriolar contraction in response to increased perfusion pressure or ATP was evaluated using the perfused juxtamedullary nephron preparation. The progression of renal damage was evaluated by measuring urinary protein excretion and conducting analysis of glomerular injury. Comparison of renal microvascular responses to perfusion pressure in p66Shc-KO rats and parental SS rats, in the presence and absence of acute preincubation with SHetA2, revealed a dose-dependent ability of SHetA2 to restore renal microvascular reactivity in SS rats with little effect upon p66Shc knockouts. Moreover, chronic treatment with SHetA2 prevented loss of renal microvascular responses and decline in renal function. SHetA2 was more potent and effective in males compared with females. Targeting p66Shc with SHetA2 diminishes renal damage and restores renal afferent arteriolar reactivity caused by hypertension. These results justify further translation of these findings to develop SHetA2 for prevention and treatment of hypertension-induced kidney damage.NEW & NOTEWORTHY Acute preincubation with modulator of p66Shc signaling sulfur heteroarotinoid A2 (SHetA2) revealed dose-dependent ability of SHetA2 to restore renal microvascular reactivity in rats with hypertension-induced nephropathy. Moreover, chronic treatment with SHetA2 prevented loss of renal microvascular responses and decline in renal function. Thus, targeting p66Shc with SHetA2 diminishes renal damage and restores renal afferent arteriolar reactivity caused by hypertension.

Toward a full-scale model of renal hemodynamics using a reconstructed vascular tree

The kidney's vascular network stands out because 1) the microcirculation not only supplies the tissues with oxygen and nutrients but also supports glomerular filtration in each nephron, 2) it contains the tubuloglomerular feedback, a mechanism that contributes to renal blood flow autoregulation and is unique to the kidney, and 3) the topology of the renal arterial network influences signaling along the vessels mediating nephron-nephron interactions. We have developed a full-scale vascular model of the rat kidney based on a reconstructed vascular network combined with a nephron model that includes glomerular filtration, tubular reabsorption, and autoregulation of afferent arteriolar resistances. The model evaluates the steady-state operating conditions of approximately 30,000 nephrons in a rat kidney and the efficiency of autoregulation under normal and pathological conditions. The simulation results show how the regulated afferent arteriolar resistances stabilize blood flow in the reconstructed full-scale renal vascular network. It is concluded that by using a reconstructed renal vascular tree, it is possible to develop a realistic full-scale model of the regulation of renal hemodynamics as a first step toward creating a virtual kidney.NEW & NOTEWORTHY We have developed the first full-scale steady-state model integrating a realistic vascular network topology of the kidney and its hemodynamic regulatory mechanisms. The vascular network is combined with approximately 30,000 nephron models that include glomerular filtration, tubular reabsorption, and autoregulation of the afferent arteriolar resistances. By simulating the adaptive properties of the renal microcirculation at steady state, our approach demonstrates the feasibility of utilizing a reconstructed vascular network for comprehensive modeling of renal function.

Protocol and rationale for a randomized controlled SGLT2 inhibitor trial in paediatric and young adult populations with chronic kidney disease: DOUBLE PRO-TECT Alport

BACKGROUND

Clinical trials have demonstrated positive cardiovascular and kidney outcomes of sodium-glucose co-transporter 2 (SGLT2) inhibitors in adult patients with diabetic and other chronic kidney diseases (CKDs). Whether benefits extend to children, teenagers and young adults with early-stage CKD is unknown. For this reason, the DOUBLE PRO-TECT Alport trial (NCT05944016) will study the progression of albuminuria in young patients with Alport syndrome (AS), the most common hereditary CKD, to assess the safety and efficacy of the SGLT2 inhibitor dapagliflozin. Patients living with AS and chronically elevated albuminuria have a high risk of kidney failure before the age of 50 years.

METHODS

DOUBLE PRO-TECT Alport is a multicentre, randomized, double-blind, placebo-controlled trial. Participants (ages 10-39 years) must have a diagnosis of AS by genetic testing or kidney biopsy, be on a stable (>3 months) maximum tolerated dose of a renin-angiotensin system inhibitor and have a urinary albumin:creatinine ratio (UACR) of >300 mg/g (paediatric) or >500 mg/g (adult).Eligible participants will be randomly assigned at a 2:1 ratio to 48 weeks of treatment with dapaglifozin 10 mg/day or matched placebo. Most participants are expected to be children with a normal estimated glomerular filtration rate (eGFR). In addition to safety, the primary (change in UACR from baseline to week 48) and key secondary (eGFR change from baseline to week 52) efficacy outcomes will be analysed with a mixed model repeated measures approach. Efficacy analyses will be performed primarily in the full analysis set according to the intention-to-treat principle. A sensitivity analysis will be performed using reference-based multiple imputation.

CONCLUSION

DOUBLE PRO-TECT Alport will assess whether SGLT2 inhibitors can safely reduce the UACR change from baseline as a marker for progression of CKD in young patients living with AS.

Acute kidney injury in severe alcohol-associated hepatitis treated with anakinra plus zinc or prednisone

BACKGROUND AND AIMS

In a recent trial, patients with severe alcohol-associated hepatitis treated with anakinra plus zinc (A+Z) had lower survival and higher acute kidney injury (AKI) rates versus prednisone (PRED). We characterize the clinical factors and potential mechanisms associated with AKI development in that trial.

APPROACH AND RESULTS

Data from 147 participants in a multicenter randomized clinical trial (74 A+Z, 73 PRED) were analyzed. AKI, AKI phenotypes, and kidney injury biomarkers were compared between participants who did/did not develop AKI in the 2 treatment arms. Multivariable competing risk analyses were performed to identify baseline risk factors for incident AKI, with death treated as a competing event. Risk factors considered were age, sex, mean arterial pressure, white blood cell count, albumin, MELD, ascites, HE, and treatment arm. At baseline, no participants had AKI; 33% (n=49) developed AKI during follow-up. AKI incidence was higher in A+Z than in PRED (45% [n=33] versus 22% [n=16], p =0.001). AKI phenotypes were similar between the 2 treatment arms ( p =0.361), but peak AKI severity was greater in A+Z than PRED (stage 3 n=21 [63.6%] vs. n=8 [50.0%], p =0.035). At baseline, urine-neutrophil-gelatinase-associated lipocalin levels were similar between participants who developed AKI in both treatment arms ( p =0.319). However, day 7 and 14 urine-neutrophil-gelatinase-associated lipocalin levels were significantly elevated in participants treated with A+Z who developed AKI versus participants treated with PRED who developed AKI ( p =0.002 and 0.032, respectively). On multivariable competing risk analysis, only A+Z was independently associated with incident AKI (subdistribution hazard ratio 2.35, p =0.005).

CONCLUSIONS

AKI occurred more frequently and was more severe in participants treated with A+Z. A+Z-treated participants with AKI had higher urine-neutrophil-gelatinase-associated lipocalin, suggesting that A+Z maybe nephrotoxic in patients with severe alcohol-associated hepatitis.

Response of the Nephron Arterial Network and Its Interactions to Acute Hypertension: A Simulation

We simulated the dynamics of a group of 10 nephrons supplied from an arterial network and subjected to acute increases in blood pressure. Arterial lengths and topology were based on measurements of a vascular cast. The model builds on a previous version exercised at a single blood pressure with 2 additional features: pressure diuresis and the effect of blood pressure on efferent arteriolar vascular resistance. The new version simulates autoregulation, and reproduces tubule pressure oscillations. Individual nephron dynamics depended on mean arterial pressure and the axial pressure gradient required to cause blood flow through the arteries. Rhythmic blood withdrawal into afferent arterioles caused blood flow fluctuations in downstream vessels. Blood pressure dependent changes in nephron dynamics affected synchronization metrics. The combination of vascular pressure gradients and oscillations created a range of arterial pressures at the origins of the 10 afferent arterioles. Because arterial blood pressure in conscious animals has ${1}/{f}$ dynamics, we applied an arterial pressure pattern with such dynamics to the model. Amplitude of tubule pressure oscillations were affected by the ${1}/{f}$ blood pressure fluctuations, but the oscillation frequencies did not change. The pressure gradients required to deliver blood to all afferent arterioles impose a complexity that affects nephrons according to their locations in the network, but other interactions compensate to ensure the stability of the system. The sensitivity of nephron response to location on the network, and the constancy of the tubular oscillation frequency provide a spatial and time context.

Gliflozines use in heart failure patients. Focus on renal actions and overview of clinical experience

Use of type 2 sodium-glucose cotransporter inhibitors (SGLT2i) gliflozines have first been applied to treatment of diabetic patients. In this setting, unexpected benefits on concomitant heart failure (HF) were seen in large trials. This clinical benefit was initially traced back to their natriuretic properties and as such they were also included in the therapeutic armamentarium of HF treatment. However, further insight into their mechanism of action has clarified their complex interaction with kidney function which better explains their prompt effectiveness in ameliorating HF outcome in the long-term, independent of left ventricular ejection fraction (LVEF) phenotype and concomitant presence of diabetes and/or chronic renal disease. This mainly results from the ability of SGLT2i to counteract the HF-associated hyperactivity of the sympathetic system and neurohormonal activation by modifying the pattern of renal tubular sodium and glucose reabsorption which results in curbing the overall sodium reabsorption. Their action results in decreased kidney workload and related oxygen consumption thus indirectly reducing sympathetic activity. The complex renal functional changes associated with HF and their modifications during SGLT2i administration will be reviewed.

Simulated microgravity predisposes kidney to injury through promoting intrarenal artery remodeling

Spaceflight-induced multi-organ dysfunction affects the health of astronauts and the safety of in-orbit flight. However, the effect of microgravity on the kidney and the underlying mechanisms are unknown. In the current study, we used a hindlimb unweighting (HU) animal model to simulate microgravity and employed histological analysis, ischemia-reperfusion experiments, renal ultrasonography, bioinformatics analysis, isometric force measurement, and other molecular experimental settings to evaluate the effects of microgravity on the kidneys and the underlying mechanisms involved in this transition. Relative to controls, 31-day hindlimb unweighting had no obvious effect on serum creatinine and urea nitrogen levels as well as on renal injury scores; however, animals in the HU group showed an impaired renal recovery to ischemia-reperfusion injury. Ultrasonography showed that renal resistive index was increased, which indicated an altered renal hemodynamics induced by simulated microgravity. The enhanced vasoconstriction mediated by the Rho-kinase pathway and impaired vasodilation mediated by NO-eNOS of the intrarenal artery contributed to the altered renal hemodynamics. Simulated microgravity predisposes the kidney to ischemia-reperfusion injury. The altered renal hemodynamics induced by renal arterial remodeling may account for the increased renal injury susceptibility, providing a target for early intervention in kidney dysfunction under microgravity.

Role of the very low frequencies of the renal oxygen saturation signal in acute kidney injury in newborns with perinatal asphyxia

Objective

Renal autoregulation, hemodynamic response, and endothelial dysfunction play significant roles in acute kidney injury (AKI) during perinatal asphyxia. A third mechanism of autoregulation, involving very low-frequency oscillations, has been described. This study aimed to evaluate the relationship between the power of the very low-frequency component of the Fast Fourier Transform (FFT) and AKI during therapeutic hypothermia (TH) treatment in neonates with perinatal asphyxia.

Study design

A retrospective longitudinal study was conducted on neonates with moderate and severe perinatal asphyxia. AKI was defined as a decrease of less than 33% in the serum creatinine level by day 3. The power of the very low-frequency component in the FFT was assessed by analyzing renal oxygen saturation using near-infrared spectroscopy (NIRS), focusing on a frequency band of approximately 0.01 Hz. Bivariate analyses were performed to explore the association between the power of the very-low-frequency component and AKI. The predictive ability of this component for AKI was evaluated using a receiver operating characteristic (ROC) curve. Additionally, a generalized estimating equation (GEE) was developed to investigate whether changes in the power of the very-low-frequency component during treatment differed according to the presence of AKI.

Results

A total of 91 patients were included in the study, of whom 15 (16.5%) developed AKI. Neonates with AKI exhibited a significantly lower power of the very low-frequency component on the second day of treatment (p = 0.001). This component demonstrated good predictive ability for AKI (ROC curve 0.77, 95% CI 0.63-0.90).

Conclusion

Among neonates with perinatal asphyxia who developed AKI, a lower power of the very-low-frequency component in FFT (approximately 0.01 Hz) was observed on the second day of therapeutic hypothermia. This finding suggests that alterations in very-low-frequency oscillations may reflect endothelial dysfunction and contribute to the development of AKI, warranting further investigation in larger cohorts.

Luminal flow in the connecting tubule induces afferent arteriole vasodilation

BACKGROUND

Renal autoregulatory mechanisms modulate renal blood flow. Connecting tubule glomerular feedback (CNTGF) is a vasodilator mechanism in the connecting tubule (CNT), triggered paracrinally when high sodium levels are detected via the epithelial sodium channel (ENaC). The primary activation factor of CNTGF-whether NaCl concentration, independent luminal flow, or the combined total sodium delivery-is still unclear. We hypothesized that increasing luminal flow in the CNT induces CNTGF via O2- generation and ENaC activation.

METHODS

Rabbit afferent arterioles (Af-Arts) with adjacent CNTs were microperfused ex-vivo with variable flow rates and sodium concentrations ranging from < 1 to 80 mM and from 5 to 40 nL/min flow rates.

RESULTS

Perfusion of the CNT with 5 mM NaCl and increasing flow rates from 5 to 10, 20, and 40 nL/min caused a flow-rate-dependent dilation of the Af-Art (P < 0.001). Adding the ENaC blocker benzamil inhibited flow-induced Af-Art dilation, indicating a CNTGF response. In contrast, perfusion of the CNT with < 1 mM NaCl did not result in flow-induced CNTGF vasodilation (P > 0.05). Multiple linear regression modeling (R2 = 0.51; P < 0.001) demonstrated that tubular flow (β = 0.163 ± 0.04; P < 0.001) and sodium concentration (β = 0.14 ± 0.03; P < 0.001) are independent variables that induce afferent arteriole vasodilation. Tempol reduced flow-induced CNTGF, and L-NAME did not influence this effect.

CONCLUSION

Increased luminal flow in the CNT induces CNTGF activation via ENaC, partially due to flow-stimulated O2- production and independent of nitric oxide synthase (NOS) activity.

Higher intraoperative blood pressure does not reduce acute kidney injury in noncardiac surgery: what do the results of the POISE-3 trial tell us?

Hypotension is a common cause of acute kidney injury (AKI), with strong associations between the duration and magnitude of hypotension seen across a range of situations including major surgery. However, it is less clear whether targeting higher intraoperative MAP results in lower rates of AKI. In a prespecified analysis of the Perioperative Ischemic Evaluation-3 (POISE-3) randomized controlled trial, this question is addressed for noncardiac major surgery. Despite an increase in cessation of antihypertensive medications and higher intraoperative mean arterial blood pressure in the intervention arm, no differences were seen in the rates of postoperative AKI. This commentary discusses the strengths and weaknesses of the trial, as well as providing some interpretation of results and their relevance to clinical practice.

Randomized, Placebo-Controlled Trial on the Renal and Systemic Hemodynamic Effects of Empagliflozin

Introduction

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) improve renal outcomes in type 2 diabetes mellitus (DM2) and chronic kidney disease (CKD). A decrease in renal blood flow (RBF) with attenuation of glomerular hyperfiltration may contribute. We examined renal and systemic hemodynamic effects of SGLT2i in relevant patient categories.

Methods

Using a double-blind placebo controlled cross-over design, we randomized patients with DM2 and estimated glomerular filtration rate (eGFR) > 60 ml/min per 1.73 m2 (n = 16), patients with DM2 and eGFR from 20 to 60 ml/min per 1.73 m2 (n = 17), and patients with nondiabetic CKD and eGFR from 20 to 60 ml/min per 1.73 m2 (n = 16) to empagliflozin 10 mg daily or placebo for 4 weeks and crossed over to the opposite treatment after 2-week washout. RBF was measured with 82Rubidium-positron emission-tomography/computed-tomography, glomerular filtration rate (GFR) with 99mTechnetium-diethylene-triamine-pentaacetate-clearance. A Mobil-O-graph was used to record 24-hour blood pressure (BP) and total vascular resistance (TVR).

Results

Compared to placebo, empagliflozin reduced RBF by 6% in the DM2-CKD group (P < 0.001) with nonsignificant decreases of 4% in the DM2 group and 1% in the CKD group (P = 0.29 and 0.72, respectively). Empagliflozin reduced GFR, BP, and TVR in all groups, whereas renal vascular resistance (RVR) remained unchanged.

Conclusion

Empagliflozin reduced RBF in patients with DM2 and CKD, whereas GFR, BP, and TVR were reduced in all groups. This pattern, together with a lack of reduction in RVR, suggests SGLT2i protect the glomerulus through combined preglomerular and post glomerular effects.

Effectiveness of tolvaptan on renal replacement therapy in patients with autosomal dominant polycystic kidney disease: a retrospective cohort study from the TriNetX global collaborative network

BACKGROUND AND HYPOTHESIS

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a major genetic contributor to end-stage kidney disease (ESKD). Current evidence on tolvaptan primarily focuses on slowing estimated glomerular filtration rate (eGFR) decline and kidney volume growth. However, direct confirmation of its effectiveness in reducing the need for hemodialysis in ESKD remains limited.

METHODS

We included ADPKD patients aged ≥18 years using TriNetx data from Sep 2, 2018, to Sep 3, 2023. Propensity score matching (PSM) ensured baseline comparability (standardized mean difference (SMD) <0.1). Hazard ratios (HRs) with 95% confidence intervals (CIs) evaluated outcomes, and subgroup analyses were performed.

RESULTS

After 1:1 PSM, both groups comprised 673 patients. The average age was 45, with generally good health (3-5% diabetes, 2-3% ischemic heart disease). Baseline eGFR averaged ∼55 ml/min/1.732m2. Post-matching, all SMDs were <0.1, indicating successful matching. Tolvaptan users exhibited lower eGFR (51.45 ± 30.09 vs. 57.37 ± 33.65, p < 0.001) and higher risk of stage 4-CKD (HR: 2.436, 95% CI:1.649, 3.599) compared to non-users. However, tolvaptan users showed significantly reduced chances of initiating hemodialysis (HR:0.362, 95%CI:0.176, 0.745), experiencing urinary tract infections (HR:0.581, 95%CI:0.354, 0.956), and all-cause mortality (HR:0.355, 95% CI:0.180, 0.700). Kaplan-Meier curves for hemodialysis initiation indicated higher survival rates among tolvaptan users across age and number of medication refill subgroups.

CONCLUSIONS

This real-world study, employing precise matching, reveals tolvaptan's role in reducing hemodialysis initiation risk in ADPKD, despite initial hemodynamic-induced lower eGFR.

RBBP6-Mediated ERRα Degradation Contributes to Mitochondrial Injury in Renal Tubular Cells in Diabetic Kidney Disease

Diabetic Kidney Disease (DKD), a major precursor to end-stage renal disease, involves mitochondrial dysfunction in proximal renal tubular cells (PTCs), contributing to its pathogenesis. Estrogen-related receptor α (ERRα) is essential for mitochondrial integrity in PTCs, yet its regulation in DKD is poorly understood. This study investigates ERRα expression and its regulatory mechanisms in DKD, assessing its therapeutic potential. Using genetic, biochemical, and cellular approaches, ERRα expression Was examined in human DKD specimens and DKD mouse models. We identified the E3 ubiquitin ligase retinoblastoma binding protein 6 (RBBP6) as a regulator of ERRα, promoting its degradation through K48-linked polyubiquitination at the K100 residue. This degradation pathway significantly contributed to mitochondrial injury in PTCs of DKD models. Notably, conditional ERRα overexpression or RBBP6 inhibition markedly reduced mitochondrial damage in diabetic mice, highlighting ERRα's protective role in maintaining mitochondrial integrity. The interaction between RBBP6 and ERRα opens new therapeutic avenues, suggesting that modulating RBBP6-ERRα interactions could be a strategy for preserving mitochondrial function and slowing DKD progression.

Glomerular pressure and tubular oxygen supply: a critical dual target for renal protection

The primary treatment goal of chronic kidney disease (CKD) is preserving renal function and preventing its progression to end-stage renal disease. Glomerular hypertension and tubular hypoxia are critical risk factors in CKD progression. However, the renal hemodynamics make it difficult to avoid both factors due to the existence of peritubular capillaries that supply oxygen to the renal tubules downstream from the glomerulus through the efferent arteriole. In the treatment strategies for balancing glomerular pressure and tubular oxygen supply, afferent and efferent arterioles of the glomerulus determine glomerular filtration rate and blood flow to the peritubular capillaries. Therefore, sodium-glucose cotransporter 2 inhibitors and angiotensin receptor-neprilysin inhibitors as well as classical renin-angiotensin system inhibitors, which can change the diameter of afferent and/or efferent arterioles, are promising options for balancing this dual target and achieving renal protection. This review focuses on the clinical importance of glomerular pressure and tubular oxygen supply and proposes an effective treatment modality for this dual target.

Oxidative Stress in Kidney Injury and Hypertension

Hypertension (HTN) is a major contributor to kidney damage, leading to conditions such as nephrosclerosis and hypertensive nephropathy, significant causes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). HTN is also a risk factor for stroke and coronary heart disease. Oxidative stress, inflammation, and activation of the renin-angiotensin-aldosterone system (RAAS) play critical roles in causing kidney injury in HTN. Genetic and environmental factors influence the susceptibility to hypertensive renal damage, with African American populations having a higher tendency due to genetic variants. Managing blood pressure (BP) effectively with treatments targeting RAAS activation, oxidative stress, and inflammation is crucial in preventing renal damage and the progression of HTN-related CKD and ESRD. Interactions between genetic and environmental factors impacting kidney function abnormalities are central to HTN development. Animal studies indicate that genetic factors significantly influence BP regulation. Anti-natriuretic mechanisms can reset the pressure-natriuresis relationship, requiring a higher BP to excrete sodium matched to intake. Activation of intrarenal angiotensin II receptors contributes to sodium retention and high BP. In HTN, the gut microbiome can affect BP by influencing energy metabolism and inflammatory pathways. Animal models, such as the spontaneously hypertensive rat and the chronic angiotensin II infusion model, mirror human essential hypertension and highlight the significance of the kidney in HTN pathogenesis. Overproduction of reactive oxygen species (ROS) plays a crucial role in the development and progression of HTN, impacting renal function and BP regulation. Targeting specific NADPH oxidase (NOX) isoforms to inhibit ROS production and enhance antioxidant mechanisms may improve renal structure and function while lowering blood pressure. Therapies like SGLT2 inhibitors and mineralocorticoid receptor antagonists have shown promise in reducing oxidative stress, inflammation, and RAAS activity, offering renal and antihypertensive protection in managing HTN and CKD. This review emphasizes the critical role of NOX in the development and progression of HTN, focusing on its impact on renal function and BP regulation. Effective BP management and targeting oxidative stress, inflammation, and RAAS activation, is crucial in preventing renal damage and the progression of HTN-related CKD and ESRD.

Metabolic Syndrome, Kidney-Related Adiposity, and Kidney Microcirculation: Unraveling the Damage

Metabolic syndrome (MetS) is a cluster of interrelated risk factors, including insulin resistance, hypertension, dyslipidemia, and visceral adiposity, all of which contribute to kidney microvascular injury and the progression of chronic kidney disease (CKD). However, the specific impact of each component of MetS on kidney microcirculation remains unclear. Given the increasing prevalence of obesity, understanding how visceral fat-particularly fat surrounding the kidneys-affects kidney microcirculation is critical. This review examines the consequences of visceral obesity and other components of MetS on renal microcirculation. These kidney-related fat deposits can contribute to the mechanical compression of renal vasculature, promote inflammation and oxidative stress, and induce endothelial dysfunction, all of which accelerate kidney damage. Each factor of MetS initiates a series of hemodynamic and metabolic disturbances that impair kidney microcirculation, leading to vascular remodeling and microvascular rarefaction. The review concludes by discussing therapeutic strategies targeting the individual components of MetS, which have shown promise in alleviating inflammation and oxidative stress. Integrated approaches that address both of the components of MetS and kidney-related adiposity may improve renal outcomes and slow the progression of CKD.

Can Radiological Renal Artery Parameters Predict Acute Kidney Injury in Infective Endocarditis Surgery?-From Imaging to Outcomes

Background: Infective endocarditis (IE) poses significant challenges in cardiovascular medicine, often necessitating valvular surgery to manage severe complications. Postoperative acute kidney injury (AKI) is a notable complication affecting patient outcomes. While clinical and procedural factors have been well studied, the role of radiological renal artery parameters in AKI risk remains underexplored. Methods: This retrospective study analyzed 80 patients with IE who underwent valvular surgery from 2013 to 2021, focusing on postoperative AKI as defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Radiological parameters, including renal artery calcification, renal ostial calcification, the presence of renal infarctions, and additional arteries, were assessed using preoperative computed tomography (CT). Statistical analyses included binary logistic and linear regression models, Kaplan-Meier survival curves, and Cox proportional hazard regression to explore associations between these parameters and AKI incidence, creatinine levels, and mortality. Results: Out of 80 patients, 31 (38.8%) developed AKI. No significant differences were found in baseline characteristics or radiological parameters between the AKI+ and AKI- groups. Binary logistic and linear regression analyses revealed no substantial relationship between anatomical factors and AKI risk or creatinine levels. However, Cox regression identified "additional renal artery" as a significant predictor of 1-month mortality (HR: 1.747, 95% CI: 1.024-2.979, p = 0.041) but not for 6- or 12-month mortality. Conclusions: Radiological anatomical factors, including calcifications and additional arteries, did not significantly impact AKI risk in IE patients undergoing valvular surgery. However, the presence of additional arteries was associated with increased short-term mortality. These findings suggest the need for further research to elucidate factors contributing to AKI and mortality in this context.

Angiotensin Receptor-Neprilysin Inhibitor in Heart Failure Patients With Renal Dysfunction

Heart failure (HF) and renal dysfunction often coexist and interact in many complex and bidirectional pathways, leading to detrimental effects on patient outcomes. The treatment of HF patients with renal dysfunction presents a significant clinical challenge. Interestingly, sacubitril/valsartan, an angiotensin receptor-neprilysin inhibitor (ARNI), may have beneficial effects on cardiac and renal outcomes in patients with HF with reduced ejection fraction, particularly by slowing the rate of decrease in the estimated glomerular filtration rate compared to a single angiotensin-converting enzyme inhibitor. Recently, more reports have emphasized the renal protection of sacubitril/valsartan in patients with HF. In HF patients with renal dysfunction, however, there is no strong evidence supporting the use of sacubitril/valsartan to reduce the absolute risk of hyperkalemia and worsening renal function; therefore, the administration of ARNI requires a careful balance between the benefits and risks. Furthermore, the lack of evidence-based management highlights the importance of an individualized approach based on published experience and multidisciplinary collaborations, as well as underlines the need for in-depth studies investigating the underlying mechanisms in cardiorenal interactions with a focus on treatments.

Lupus nephritis-related chronic kidney disease

Lupus nephritis is a common complication of systemic lupus erythematosus (SLE) and a determinant of overall morbidity and mortality, as lupus nephritis-related chronic kidney disease (CKD) drives cardiovascular disease and secondary immunodeficiency. Two lines of action are required to prevent the progression of lupus nephritis-related CKD: suppression of autoimmune SLE activity, which is a risk factor for immunopathology-related irreversible kidney injury, and management of non-immune risk factors that contribute to CKD progression. As each episode or relapse of active lupus nephritis implicates CKD progression, preventing flares of lupus nephritis is a key treatment target. Non-immune risk factors of CKD mostly include causes of nephron hyperfiltration, such as obesity, hypertension, sodium- or protein-rich diets and type 2 diabetes mellitus, as well as pregnancy. Nephrotoxic agents and smoking also drive kidney cell loss. Intrinsic risk factors for CKD progression include poor nephron endowment because of prematurity at birth, nephropathic genetic variants, ageing, male sex and previous or concomitant kidney diseases. Care for lupus nephritis involves the control of all modifiable risk factors of CKD progression. In addition, remnant nephron overload can be reduced using early dual therapy with inhibitors of the renin-angiotensin system and sodium-glucose transporter-2, whereas further renoprotective drug interventions are underway. As patients with lupus nephritis are at risk of CKD progression, they would all benefit from interdisciplinary care to minimize the risk of kidney failure, cardiovascular disease and infections.

Cardiorenal interactions in heart failure: insights from recent therapeutic advances

Heart failure is a syndrome that may develop when cardiovascular disease progresses or is insufficiently treated and associated with a poor quality of life, high mortality rates, and increased healthcare expenditures. Prevention and treatment of heart failure are therefore of utmost importance. New therapies in patients with cardiovascular disease have recently been shown to be effective in the prevention and sometimes treatment of heart failure, and additional research is underway. Specifically, in high-risk patients with either (a combination of) diabetes, chronic kidney disease, and/or heart failure, three specific drug classes [sodium-glucose co-transporter 2 inhibitors (SGLT2i), glucagon-like peptide 1 receptor agonists (GLP-1-RAs), and non-steroidal mineralocorticoid receptor antagonists (MRAs)] have taken centre stage in therapeutic approach for these high cardiovascular risk patients. The commonality of these drugs is the finding that they improve cardiovascular and renal endpoints across the cardiorenal continuum and SGTL2i have already proved effective in all subtypes of heart failure, while we await data on non-steroidal MRA therapy in heart failure. The story may be different for GLP-1-RA in patients with established heart failure, but these drugs are effective in reducing cardiovascular events in patients with diabetes. Taken together, these new therapies advance the treatment and improve the associated outcomes of patients with cardiorenal disease and diabetes, with similar characteristics and effectiveness in different conditions.

Sex-Dimorphic Kidney-Brain Connectivity Map of Mice

The kidneys are essential organs that help maintain homeostasis, and their function is regulated by the neural system. Despite the anatomical multi-synaptic connection between the central autonomic nuclei and the kidneys, it remains unclear whether there are any variations in neural connections between the nervous systems and the renal cortex and medulla in male and female mice. Here, we used the pseudorabies virus to map the central innervation network of the renal cortex and medulla in both sexes. The data revealed that specific brain regions displayed either a contralateral-bias or ipsilateral-bias pattern while kidney-innervating neurons distributed symmetrically in the midbrain and hindbrain. Sex differences were observed in the distribution of neurons connected to the left kidney, as well as those connected to the renal cortex and medulla. Our findings provide a comprehensive understanding of the brain-kidney network in both males and females and may help shed light on gender differences in kidney function and disease susceptibility in humans.

Luminal Flow in the Connecting Tubule induces Afferent Arteriole Vasodilation

Background

Renal autoregulatory mechanisms modulate renal blood flow. Connecting tubule glomerular feedback (CNTGF) is a vasodilator mechanism in the connecting tubule (CNT), triggered paracrinally when high sodium levels are detected via the epithelial sodium channel (ENaC). The primary activation factor of CNTGF-whether NaCl concentration, independent luminal flow, or the combined total sodium delivery-is still unclear. We hypothesized that increasing luminal flow in the CNT induces CNTGF via O2- generation and ENaC activation.

Methods

Rabbit afferent arterioles (Af-Arts) with adjacent CNTs were microperfused ex-vivo with variable flow rates and sodium concentrations ranging from <1 mM to 80 mM and from 5 to 40 nL/min flow rates.

Results

Perfusion of the CNT with 5 mM NaCl and increasing flow rates from 5 to 10, 20, and 40 nL/min caused a flow rate-dependent dilation of the Af-Art (p<0.001). Adding the ENaC blocker benzamil inhibited flow-induced Af-Art dilation, indicating a CNTGF response. In contrast, perfusion of the CNT with <1 mM NaCl did not result in flow-induced CNTGF vasodilation (p>0.05). Multiple linear regression modeling (R2=0.51;p<0.001) demonstrated that tubular flow (β=0.163 ± 0.04;p<0.001) and sodium concentration (β=0.14 ± 0.03;p<0.001) are independent variables that induce afferent arteriole vasodilation. Tempol reduced flow-induced CNTGF, and L-NAME did not influence this effect.

Conclusion

Increased luminal flow in the CNT induces CNTGF activation via ENaC, partially due to flow-stimulated O2- production and independent of nitric oxide synthase (NOS) activity.

A pharmacovigilance study on clinical factors of active vitamin D3 analog-related acute kidney injury using the Japanese Adverse Drug Event Report Database

Acute kidney injury (AKI) due to vitamin D therapy for osteoporosis is encountered in clinical practice, but epidemiological studies are scarce. We aimed to determine the association between AKI and vitamin D therapy and to identify risk factors for AKI using the Japanese Adverse Drug Event Report database. We used reporting odds ratios (RORs) to detect signals and evaluate risk factors using multiple logistic regression analysis. Among 298,891 reports from April 2004 to September 2023, 1071 implicated active vitamin D3 analogs as suspect drugs for adverse events. There was a significant association between AKI and active vitamin D3 analogs (ROR [95% confidence interval {CI}], eldecalcitol: 16.75 [14.23-19.72], P < 0.001; alfacalcidol: 5.29 [4.07-6.87], P < 0.001; calcitriol: 4.46 [1.88-10.59], P < 0.001). The median duration of administration before AKI onset was 15.4 weeks. Multiple logistic regression analysis showed a significant association between AKI and age ≥ 70 years (odds ratio [95% CI], 1.47 [1.04-2.07]; P = 0.028), weight < 50 kg (1.55 [1.12-2.13]; P = 0.007), hypertension (1.90 [1.42-2.54]; P < 0.001), and concomitant use of nonsteroidal anti-inflammatory drugs (1.58 [1.10-2.25], P = 0.012) and magnesium oxide (1.96 [1.38-2.78]; P < 0.001). Our results suggest that active vitamin D3 analogs are associated with AKI development. Physicians prescribing these medications to patients with risk factors should consider the possibility of AKI, especially during the first 6 months.

Interpretable Machine Learning Model Based on Superb Microvascular Imaging for Non-Invasive Determination of Crescent Status of IgAN

Purpose

To assess the crescentic status of IgA nephropathy (IgAN) non-invasively using a superb microvascular imaging (SMI)-based radiomics machine learning (ML) model.

Patients and Methods

IgAN patients who underwent renal biopsy from June 2022 to October 2023, with two-dimensional ultrasound (US) and SMI examinations conducted one day prior to the renal biopsy. The patients selected were divided randomly into a training group and a test group in a 7:3 ratio. Radiomic features were extracted from US and SMI images, then radiomic features were constructed and ML models were further established using logistic regression (LR) and extreme gradient boosting (XGBoost)XGBoost to determine the crescentic status. The utility of the proposed model was evaluated using receiver operating characteristics, calibration, and decision curve analysis. The SHapley Additive exPlanations (SHAP) was utilized to explain the best-performing ML model.

Results

A total of 147 IgAN patients were included in the study, with 103 in the training group and 44 in the test group .Among them, the US-SMI based XGBoost model achieved the best results, with an the area under the curve (AUC) of 0.839 (95% CI,0.756-0.910) and an accuracy of 78.6% in the training group.In the test group, the AUC was 0.859 (95% CI,0.721-0.964), and the accuracy was 81.8%, significantly surpassing the ML model of a single modality and the clinical model established based on occult blood. Additionally, the decision curve analysis (DCA) demonstrated that the XGBoost model provided a higher overall net benefit in the both groups.

Conclusion

The SMI radiomics ML model has the capability to accurately predict the crescentic status of IgAN patients, providing effective assistance for clinical treatment decisions.

A Triple Mystery of Insidious Organ Failure: Are the Lung, Kidney and Brain All Damaged by the Ageing Pulse?

This review explores the hypothesis that dementia in several forms, chronic kidney disease and idiopathic pulmonary fibrosis have a common cause in pulse-induced capillary haemorrhage. All three conditions are age-related and characterised by insidious onset, uncertainty about their cause, exacerbation by hypertension, resistance to treatment and the relentlessness of their progression. We argue that the three conditions are the clinical outcomes of damage caused by pulse-induced haemorrhage from capillaries. The damage, first detectable in mid-life, creates first mild and then severe symptoms of cognitive, renal and pulmonary dysfunction. We also review evidence that in all three organs there has developed, by young adulthood, a reserve of tissue that enables them to function well, despite the 'heartbeat by heartbeat' damage that accumulates from early mid-life; and that it is when that reserve is exhausted, typically in late age, that symptoms of organ failure emerge and progress. If this common cause can be established, a step will have been taken towards the understanding, treatment and delay of three conditions that have their beginnings in every individual and that, in those who survive other causes of death, become lethal in late age.

Blood Pressure Management for Hypotensive Patients in Intensive Care and Perioperative Cardiovascular Settings

Blood pressure is a critical physiological parameter, particularly in the context of cardiac intensive care and perioperative settings. As a primary indicator of organ perfusion, the maintenance of adequate blood pressure is imperative for the assurance of sufficient tissue oxygen delivery. Among critically ill and major surgery patients, the continuous monitoring of blood pressure is performed as a standard practice for patients. Nonetheless, uncertainties remain regarding blood pressure goals, and there is no consensus regarding blood pressure targets. This review describes the determinants of blood pressure, examine the influence of blood pressure on organ perfusion, and synthesize the current clinical evidence from various intensive care and perioperative settings to provide a concise guidance for daily clinical practice.

Influence of angiotensin II and telmisartan on in vivo high-resolution renal arterial impedance in rats

Angiotensin II (ANG II) is known to play an important role in regulating renal hemodynamics. We sought to quantify this effect in an in vivo rat model with high-resolution renal arterial (RA) impedance. This study examines the effects of ANG II and its type 1 receptor blocker telmisartan (TELM) on RA impedance. In baroreflex-deactivated rats, we measured RA pressure (Pr) and blood flow (Fr) during random ventricular pacing to induce pressure fluctuation at three different mean Pr (60, 80, and 100 mmHg). We then estimated RA impedance as the transfer function from Fr to Pr. The RA impedance was found to align with a three-element Windkessel model consisting of proximal (Rp) and distal (Rd) resistance and compliance (C). Our study showed Rd reflected the composite characteristics of afferent and efferent arterioles. Rd increased with increasing Pr under the baseline condition with a slope of 1.03 ± 0.21 (× 10-1) min·mL-1. ANG II significantly increased the slope by 0.72 ± 0.29 (× 10-1) min·mL-1 (P < 0.05) without affecting the intercept. TELM significantly reduced the intercept by 34.49 ± 4.86 (× 10-1) mmHg·min·mL-1 (P < 0.001) from the baseline value of 37.93 ± 13.36 (× 10-1) mmHg·min·mL-1, whereas it did not affect the slope. In contrast, Rp was less sensitive than Rd to ANG II or TELM, suggesting Rp may represent the characteristics of elastic large arteries. Our findings provide valuable insights into the influence of ANG II on the dynamics of the renal vasculature.NEW & NOTEWORTHY This present method of quantifying high-resolution renal arterial impedance could contribute to elucidating the characteristics of renal vasculature influenced by physiological mechanisms, renal diseases, or pharmacological effects. The present findings help construct a lumped-parameter renal hemodynamic model that reflects the influence of angiotensin II.

Podocyte Death in Diabetic Kidney Disease: Potential Molecular Mechanisms and Therapeutic Targets

Cell deaths maintain the normal function of tissues and organs. In pathological conditions, the abnormal activation or disruption of cell death often leads to pathophysiological effects. Diabetic kidney disease (DKD), a significant microvascular complication of diabetes, is linked to high mortality and morbidity rates, imposing a substantial burden on global healthcare systems and economies. Loss and detachment of podocytes are key pathological changes in the progression of DKD. This review explores the potential mechanisms of apoptosis, necrosis, autophagy, pyroptosis, ferroptosis, cuproptosis, and podoptosis in podocytes, focusing on how different cell death modes contribute to the progression of DKD. It recognizes the limitations of current research and presents the latest basic and clinical research studies targeting podocyte death pathways in DKD. Lastly, it focuses on the future of targeting podocyte cell death to treat DKD, with the intention of inspiring further research and the development of therapeutic strategies.

Intra-patient variability of iodine quantification across different dual-energy CT platforms: assessment of normalization techniques

OBJECTIVES

To investigate intra-patient variability of iodine concentration (IC) between three different dual-energy CT (DECT) platforms and to test different normalization approaches.

METHODS

Forty-four patients who underwent portal venous phase abdominal DECT on a dual-source (dsDECT), a rapid kVp switching (rsDECT), and a dual-layer detector platform (dlDECT) during cancer follow-up were retrospectively included. IC in the liver, pancreas, and kidneys and different normalized ICs (NICPV:portal vein; NICAA:abdominal aorta; NICALL:overall iodine load) were compared between the three DECT scanners for each patient. A longitudinal mixed effects analysis was conducted to elucidate the effect of the scanner type, scan order, inter-scan time, and contrast media amount on normalized iodine concentration.

RESULTS

Variability of IC was highest in the liver (dsDECT vs. dlDECT 28.96 (14.28-46.87) %, dsDECT vs. rsDECT 29.08 (16.59-62.55) %, rsDECT vs. dlDECT 22.85 (7.52-33.49) %), and lowest in the kidneys (dsDECT vs. dlDECT 15.76 (7.03-26.1) %, dsDECT vs. rsDECT 15.67 (8.86-25.56) %, rsDECT vs. dlDECT 10.92 (4.92-22.79) %). NICALL yielded the best reduction of IC variability throughout all tissues and inter-scanner comparisons, yet did not reduce the variability between dsDECT vs. dlDECT and rsDECT, respectively, in the liver. The scanner type remained a significant determinant for NICALL in the pancreas and the liver (F-values, 12.26 and 23.78; both, p < 0.0001).

CONCLUSIONS

We found tissue-specific intra-patient variability of IC across different DECT scanner types. Normalization mitigated variability by reducing physiological fluctuations in iodine distribution. After normalization, the scanner type still had a significant effect on iodine variability in the pancreas and liver.

CLINICAL RELEVANCE STATEMENT

Differences in iodine quantification between dual-energy CT scanners can partly be mitigated by normalization, yet remain relevant for specific tissues and inter-scanner comparisons, which should be taken into account at clinical routine imaging.

KEY POINTS

• Iodine concentration showed the least variability between scanner types in the kidneys (range 10.92-15.76%) and highest variability in the liver (range 22.85-29.08%). • Normalizing tissue-specific iodine concentrations against the overall iodine load yielded the greatest reduction of variability between scanner types for 2/3 inter-scanner comparisons in the liver and for all (3/3) inter-scanner comparisons in the kidneys and pancreas, respectively. • However, even after normalization, the dual-energy CT scanner type was found to be the factor significantly influencing variability of iodine concentration in the liver and pancreas.

Linear Correlation Between Mean Arterial Pressure and Urine Output in Critically Ill Patients

OBJECTIVE

Mean arterial pressure (MAP) plays a significant role in regulating tissue perfusion and urine output (UO). The optimal MAP target in critically ill patients remains a subject of debate. We aimed to explore the relationship between MAP and UO.

DESIGN

A retrospective observational study.

SETTING

A general ICU in a tertiary medical center.

PATIENTS

All critically ill patients admitted to the ICU for more than 10 hours.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

MAP values and hourly UO were collected in 5,207 patients. MAP levels were categorized into 10 groups of 5 mm Hg (from MAP < 60 mm Hg to MAP > 100 mg Hg), and 656,423 coupled hourly mean MAP and UO measurements were analyzed. Additionally, we compared the UO of individual patients in each MAP group with or without norepinephrine (NE) support or diuretics, as well as in patients with acute kidney injury (AKI).Hourly UO rose incrementally between MAP values of 65-100 mm Hg. Among 2,226 patients treated with NE infusion, mean UO was significantly lower in the MAP less than 60 mm Hg group (53.4 mL/hr; 95% CI, 49.3-57.5) compared with all other groups (p < 0.001), but no differences were found between groups of 75 less than or equal to MAP. Among 2500 patients with AKI, there was a linear increase in average UO from the MAP less than 60 mm Hg group (57.1 mL/hr; 95% CI, 54.2-60.0) to the group with MAP greater than or equal to 100 mm Hg (89.4 mL/hr; 95% CI, 85.7-93.1). When MAP was greater than or equal to 65 mm Hg, we observed a statistically significant trend of increased UO in periods without NE infusion.

CONCLUSIONS

Our analysis revealed a linear correlation between MAP and UO within the range of 65-100 mm Hg, also observed in the subgroup of patients treated with NE or diuretics and in those with AKI. These findings highlight the importance of tissue perfusion to the maintenance of diuresis and achieving adequate fluid balance in critically ill patients.

Resting-state MRI reveals spontaneous physiological fluctuations in the kidney and tracks diabetic nephropathy in rats

The kidneys maintain fluid-electrolyte balance and excrete waste in the presence of constant fluctuations in plasma volume and systemic blood pressure. The kidneys perform these functions to control capillary perfusion and glomerular filtration by modulating the mechanisms of autoregulation. An effect of these modulations are spontaneous, natural fluctuations in glomerular perfusion. Numerous other mechanisms can lead to fluctuations in perfusion and flow. The ability to monitor these spontaneous physiological fluctuations in vivo could facilitate the early detection of kidney disease. The goal of this work was to investigate the use of resting-state magnetic resonance imaging (rsMRI) to detect spontaneous physiological fluctuations in the kidney. We performed rsMRI of rat kidneys in vivo over 10 min, applying motion correction to resolve time series in each voxel. We observed spatially variable, spontaneous fluctuations in rsMRI signal between 0 and 0.3 Hz, in frequency bands associated with autoregulatory mechanisms. We further applied rsMRI to investigate changes in these fluctuations in a rat model of diabetic nephropathy. Spectral analysis was performed on time series of rsMRI signals in the kidney cortex and medulla. The power from spectra in specific frequency bands from the cortex correlated with severity of glomerular pathology caused by diabetic nephropathy. Finally, we investigated the feasibility of using rsMRI of the human kidney in two participants, observing the presence of similar, spatially variable fluctuations. This approach may enable a range of preclinical and clinical investigations of kidney function and facilitate the development of new therapies to improve outcomes in patients with kidney disease.NEW & NOTEWORTHY This work demonstrates the development and use of resting-state MRI to detect low-frequency, spontaneous physiological fluctuations in the kidney consistent with previously observed fluctuations in perfusion and potentially due to autoregulatory function. These fluctuations are detectable in rat and human kidneys, and the power of these fluctuations is affected by diabetic nephropathy in rats.

Biomarker for cardiorenal syndrome risk in patients with liver cirrhosis and type 2 diabetes in Saudi Arabia

OBJECTIVES

To evaluate the correlation between different attributes, levels of biomarkers, and the probability of developing cardiorenal syndrome (CRS) in patients who have been diagnosed with type 2 diabetes mellitus (T2DM) and liver cirrhosis (LC). The hypothesis suggests that liver illness may be linked to renal impairment, cardiac dysfunction, and the development of cardiorenal syndrome METHODS: The current study retrospectively assessed the medical records of patients who had LC and T2DM diagnoses and were hospitalized at Al Madina Al Munwara hospitals in 2022 and 2023.

RESULTS

This research investigated T2DM patients with physician-confirmed to have LC. Poor glycemic control is indicated by high blood glucose and glycated hemoglobin (HbA1c) readings in research participants. High blood pressure, atherogenic plasma indicator (AIP), and obesity plagued most of these individuals. High creatinine, moderate estimated Glomerular Filtration Rate (eGFR) decline, and a modest urinary albumin-to-creatinine (UACR) rise were the most prevalent variables in LC and T2DM patients. Cardiorenal syndrome risk factors, including elevated blood pressure, triglyceride levels, body mass index (BMI), and high-sensitivity C-reactive protein (hs-CRP) concentrations, were identified through logistic regression. It has been demonstrated that the prevalence of these risk factors increases with age; women may be at a greater risk for developing CRS. Specific biomarker evaluations classified 108 (22.6%) LC and T2DM patients at high risk for chronic kidney disease (CKD), 100 (20%) at risk for cardiovascular disease (CVD), and 91 (18.2%) at risk for CRS.

CONCLUSION

The current assessment included 500 patients with T2DM and LC. The risk factors for CRS identified in this study included elevated cholesterol and triglyceride levels, high BMI, and elevated blood pressure, with age being a significant factor, particularly in female patients. Early identification of these characteristics in patients with LC and T2DM could aid in mitigating the progression of chronic illnesses and their associated complications.

Decoding Organelle Interactions: Unveiling Molecular Mechanisms and Disease Therapies

Organelles, substructures in the cytoplasm with specific morphological structures and functions, interact with each other via membrane fusion, membrane transport, and protein interactions, collectively termed organelle interaction. Organelle interaction is a complex biological process involving the interaction and regulation of several organelles, including the interaction between mitochondria-endoplasmic reticulum, endoplasmic reticulum-Golgi, mitochondria-lysosomes, and endoplasmic reticulum-peroxisomes. This interaction enables intracellular substance transport, metabolism, and signal transmission, and is closely related to the occurrence, development, and treatment of many diseases, such as cancer, neurodegenerative diseases, and metabolic diseases. Herein, the mechanisms and regulation of organelle interactions are reviewed, which are critical for understanding basic principles of cell biology and disease development mechanisms. The findings will help to facilitate the development of novel strategies for disease prevention, diagnosis, and treatment opportunities.

Furosemide attenuates tubulointerstitial injury and allows functional testing of porcine kidneys during normothermic machine perfusion

BACKGROUND

Normothermic machine perfusion (NMP) is a promising pretransplant kidney quality assessment platform, but it remains crucial to increase its diagnostic potential while ensuring minimal additional injury to the already damaged kidney. Interventions that alter tubular transport can influence renal function and injury during perfusion. This study aimed to determine whether furosemide and desmopressin affect renal function and injury during NMP.

METHODS

Eighteen porcine kidneys (n = 6 per group) were subjected to 30 min of warm ischemia and 4 h of oxygenated hypothermic perfusion before being subjected to 6 h of NMP. Each organ was randomized to receive no drug, furosemide (750 mg), or desmopressin (16 μg) during NMP.

RESULTS

Compared with the other groups, the addition of furosemide resulted in significantly increased urine output, fractional excretion of sodium and potassium, and urea clearance during NMP. Urinary neutrophil gelatinase-associated lipocalin levels decreased significantly with furosemide supplementation compared with the other groups. The addition of desmopressin did not result in any significantly different outcome measurements compared with the control group.

CONCLUSIONS

This study showed that the addition of furosemide affected renal function while attenuating tubulointerstitial injury during NMP. Therefore, furosemide supplementation may provide renal protection and serve as a functional test for pretransplant kidney viability assessment during NMP.

Association between CYP4A11 and EPHX2 genetic polymorphisms and chronic kidney disease progression in hypertensive patients

BACKGROUND

There are evidence indicating that some metabolites of arachidonic acid produced by cytochromes P450 (CYP) and epoxide hydroxylase (EPHX2), such as hydroxyeicosatetraenoic acids (HETEs), epoxyeicosatrienoic acids (EETs) or dihydroxyeicosatrienoic acids (DHETEs), play an important role in blood pressure regulation and they could contribute to the development of hypertension (HT) and kidney damage. Therefore, the main aim of the study was to evaluate whether the genetic polymorphisms of CYP2C8, CYP2C9, CYP2J2, CYP4F2, CYP4F11 and EPHX2, responsible for the formation of HETEs, EETs and DHETEs, are related to the progression of impaired renal function in a group of patients with hypertension.

METHODS

151HT patients from a hospital nephrology service were included in the study. Additionally, a group of 87 normotensive subjects were involved in the study as control group. For HT patients, a general biochemistry analysis, estimated glomerular filtration rate and genotyping for different CYPs and EPHX2 variant alleles was performed.

RESULTS

CYP4A11 rs3890011, rs9332982 and EPHX2 rs41507953 polymorphisms, according to the dominant model, presented a high risk of impaired kidney function, with odds ratios (OR) of 2.07 (1.00-4.32; P=0.049) 3.02 (1.11-8.23; P=0.030) and 3.59 (1.37-9.41; P=0.009), respectively, and the EPHX2 rs1042032 polymorphism a greater risk according to the recessive model (OR=6.23; 95% CI=1.50-25.95; P=0.007). However, no significant differences in allele frequencies between HT patients and in normotensive subjects for any of the SNP analysed. In addition, the patients with diagnosis of dyslipidemia (n=90) presented higher frequencies of EPHX2 K55R (rs41507953) and *35A>G (rs1042032) variants than patients without dyslipidemia, 4% vs. 14% (P=0.005) and 16 vs. 27% (P=0.02), respectively.

CONCLUSIONS

In this study has been found higher odds of impaired renal function progression associated with rs3890011 and rs9332982 (CYP4A11) and rs41507953 and rs1042032 (EPHX2) polymorphisms, which may serve as biomarkers for improve clinical interventions aimed at avoiding or delaying, in chronic kidney disease patients, progress to end-stage kidney disease needing dialysis or kidney transplant.

Risk factors for and outcomes of heatstroke-related intracerebral hemorrhage

Some patients with heatstroke also experience intracerebral hemorrhage (ICH). However, clinical case reports of heatstroke-induced ICH are rare. The risk factors for cerebral hemorrhage after heatstroke remain unknown. The present study evaluated the clinical characteristics and risk factors of patients with heatstroke-related ICH. In this retrospective observational study, we collected data on all ICHs after heatstroke occurred between 2012 and 2022. The characteristics of patients with heatstroke-induced ICH were described. The risk factors for cerebral hemorrhage after heatstroke were examined using logistic regression analysis. In total, 177 patients were included in this study, and 11 patients with ICH secondary to heatstroke were identified. Variables with P values of <.05 in univariate models, comparing the cerebral hemorrhage and control groups, included heatstroke cause, temperature, heart rate, respiratory rate, vasopressor use, mechanical ventilation use, Acute Physiology and Chronic Health Evaluation II, total bilirubin, creatinine, platelet count, prothrombin time, procalcitonin, creatine kinase, disseminated intravascular coagulation (DIC) occurrence, and DIC score. Multivariate logistic regression showed that heatstroke patients with higher DIC scores (odds ratio, 18.402, 95% confidence interval, 1.384-244.763, P = .027) and higher creatine kinase levels (odds ratio, 1.021, 95% confidence interval, 1.002-1.041, P = .033) were at a higher risk of developing ICH. The death rate was higher in the cerebral hemorrhage group than in the control group (P = .042). Heatstroke-related cerebral hemorrhage may be associated with elevated creatinine levels and DIC severity (International Society on Thrombosis and Hemostasis score) after heatstroke, and heatstroke with cerebral hemorrhage may accelerate death.

Renal sympathetic denervation improves pressure-natriuresis relationship in cardiorenal syndrome: insight from studies with Ren-2 transgenic hypertensive rats with volume overload induced using aorto-caval fistula

The aim was to evaluate the effects of renal denervation (RDN) on autoregulation of renal hemodynamics and the pressure-natriuresis relationship in Ren-2 transgenic rats (TGR) with aorto-caval fistula (ACF)-induced heart failure (HF). RDN was performed one week after creation of ACF or sham-operation. Animals were prepared for evaluation of autoregulatory capacity of renal blood flow (RBF) and glomerular filtration rate (GFR), and of the pressure-natriuresis characteristics after stepwise changes in renal arterial pressure (RAP) induced by aortic clamping. Their basal values of blood pressure and renal function were significantly lower than with innervated sham-operated TGR (p < 0.05 in all cases): mean arterial pressure (MAP) (115 ± 2 vs. 160 ± 3 mmHg), RBF (6.91 ± 0.33 vs. 10.87 ± 0.38 ml.min-1.g-1), urine flow (UF) (11.3 ± 1.79 vs. 43.17 ± 3.24 µl.min-1.g-1) and absolute sodium excretion (UNaV) (1.08 ± 0.27 vs, 6.38 ± 0.76 µmol.min-1.g-1). After denervation ACF TGR showed improved autoregulation of RBF: at lowest RAP level (80 mmHg) the value was higher than in innervated ACF TGR (6.92 ± 0.26 vs. 4.54 ± 0.22 ml.min-1.g-1, p < 0.05). Also, the pressure-natriuresis relationship was markedly improved after RDN: at the RAP of 80 mmHg UF equaled 4.31 ± 0.99 vs. 0.26 ± 0.09 µl.min-1.g-1 recorded in innervated ACF TGR, UNaV was 0.31 ± 0.05 vs. 0.04 ± 0.01 µmol min-1.g-1 (p < 0.05 in all cases). In conclusion, in our model of hypertensive rat with ACF-induced HF, RDN improved autoregulatory capacity of RBF and the pressure-natriuresis relationship when measured at the stage of HF decompensation.

Oxidative stress and the role of redox signalling in chronic kidney disease

Chronic kidney disease (CKD) is a major public health concern, underscoring a need to identify pathogenic mechanisms and potential therapeutic targets. Reactive oxygen species (ROS) are derivatives of oxygen molecules that are generated during aerobic metabolism and are involved in a variety of cellular functions that are governed by redox conditions. Low levels of ROS are required for diverse processes, including intracellular signal transduction, metabolism, immune and hypoxic responses, and transcriptional regulation. However, excess ROS can be pathological, and contribute to the development and progression of chronic diseases. Despite evidence linking elevated levels of ROS to CKD development and progression, the use of low-molecular-weight antioxidants to remove ROS has not been successful in preventing or slowing disease progression. More recent advances have enabled evaluation of the molecular interactions between specific ROS and their targets in redox signalling pathways. Such studies may pave the way for the development of sophisticated treatments that allow the selective control of specific ROS-mediated signalling pathways.

Acute Renal Failure with Severe Loin Pain and Patchy Renal Ischemia after Anaerobic Exercise in Active Duty Marines

Acute renal failure with severe loin pain and patchy renal ischemia after anaerobic exercise (ALPE) is a rare cause of exertional acute kidney injury. The proposed mechanism of injury in ALPE is renovascular spasm, in the setting of oxidative stress and muscular damage, which creates a characteristic wedge-shaped infarction pattern on delayed imaging. Patients present with nausea, vomiting, loin or abdominal pain, and fatigue within 1-2 days of anaerobic exercise, associated with an acute rise in serum creatinine, which generally plateaus within 3 days. This process is likely exacerbated by dehydration, analgesic usage, and lower baseline fitness levels. This disease process is distinct from rhabdomyolysis, in that creatine kinase levels are not significantly elevated, myoglobinuria is not seen, and aggressive fluid resuscitation is not beneficial. We present three cases of ALPE following participation in the Marine Combat Fitness Test (CFT), an anaerobic evolution. Medical workup demonstrated no additional etiology for acute renal failure. The average peak creatinine in these patients was 2.9 mg/dL, and all demonstrated return to normal renal function, without hemodialysis. One patient experienced recurrent ALPE, after short-interval CFT participation. Military medical providers should be aware of this diagnosis when evaluating service members with acute renal injury after exercise. The clinical course is benign, and affected service members are at increased risk of recurrence, with subsequent intense exercise. Service members should engage in a graduated exercise program, before intense exercise activities, and should be monitored closely for recurrent renal injury.

Ambient temperature and kidney function in primary care patients

INTRODUCTION

Exposure to high ambient temperatures is associated with a risk of acute kidney injury. However, evidence comes from emergency departments or extreme weather exposures. It is unclear whether temperature-related adverse kidney outcomes can also be detected at a community level in a temperate climate zone.

METHODS

In a 9.5-year retrospective cohort study we correlated estimated glomerular filtration rate (eGFR) values of Swiss adult primary care patients from the FIRE cohort (Family medicine Research using Electronic medical records) with same-day maximum local ambient temperature data. We investigated 5 temperature groups (< 15 °C, 15-19 °C, 20-24 °C, 25-29 °C and  ≥ 30 °C) as well as possible interactions for patients with increased kidney vulnerability (chronic heart failure, diabetes, chronic kidney disease, therapy with renin-angiotensin-aldosterone-system (RAAS) inhibitors, diuretics or non-steroidal anti-inflammatory drugs).

RESULTS

We included 18,000 primary care patients who altogether provided 132,176 creatinine measurements. In the unadjusted analysis, higher ambient temperatures were associated with lower eGFR across all age and vulnerability groups. In the adjusted models, we did not find a consistent association.The highest ambient temperature differences (> 25 or > 30 versus < 15 °C) were associated with marginally reduced kidney function only in patients with ≥ 3 risk factors for kidney vulnerability, with a maximum estimated glomerular filtration rate reduction of -2.9 ml/min/1.73m2 (SE 1.0), P 0.003.

DISCUSSION

In a large primary care cohort from a temperate climate zone, we did not find an association between ambient temperatures and kidney function. A marginal inverse association in highly vulnerable patients is of unclear clinical relevance.

Associations Between Life's Essential 8 and Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) is closely associated with cardiovascular disease. We aimed to examine the association of Life's Essential 8 (LE8), the recently updated measurement of cardiovascular health, with the prevalence of CKD among US adults.

METHODS AND RESULTS

This population-based cross-sectional study used data from the National Health and Nutrition Examination Survey from 2007 to 2018 and included adults aged ≥20 years. Multivariable logistic and restricted cubic spline models were used to assess the associations between LE8 and CKD. Among 24 960 participants, 4437 were determined to have CKD (weighted percentage, 14.11%). After the adjustment of potential confounders, higher LE8 scores were associated with reduced odds of CKD (odds ratio for each 10-point increase, 0.79 [95% CI, 0.76-0.83]), and a nonlinear dose-response relationship was observed. Similar patterns were also identified in the associations of health behavior and health factor scores with CKD. Meanwhile, higher scores for blood glucose (odds ratio, for each 10-point increase, 0.88 [95% CI, 0.87-0.90]) and blood pressure (odds ratio, for each 10-point increase, 0.92 [95% CI, 0.91-0.94]) in the LE8 component are significantly associated with a lower prevalence of CKD. The inversed association of LE8 score and CKD was significantly stronger among middle-aged, male, and coupled participants.

CONCLUSIONS

LE8 was negatively associated with the prevalence of CKD in a nonlinear fashion. Promoting adherence to optimal cardiovascular health levels may be beneficial to reduce the burden of CKD.

In vivo mapping of hemodynamic responses mediated by tubuloglomerular feedback in hypertensive kidneys

The kidney has a sophisticated vascular structure that performs the unique function of filtering blood and managing blood pressure. Tubuloglomerular feedback is an intra-nephron negative feedback mechanism stabilizing single-nephron blood flow, glomerular filtration rate, and tubular flow rate, which is exhibited as self-sustained oscillations in single-nephron blood flow. We report the application of multi-scale laser speckle imaging to monitor global blood flow changes across the kidney surface (low zoom) and local changes in individual microvessels (high zoom) in normotensive and spontaneously hypertensive rats in vivo. We reveal significant differences in the parameters of TGF-mediated hemodynamics and patterns of synchronization. Furthermore, systemic infusion of a glucagon-like-peptide-1 receptor agonist, a potential renoprotective agent, induces vasodilation in both groups but only alters the magnitude of the TGF in Sprague Dawleys, although the underlying mechanisms remain unclear.

Assessment of peripapillary retinal nerve fiber layer thickness and vessel density in newly diagnosed SLE patients without ocular symptoms

PURPOSE

This study aims to assess peripapillary retinal nerve fiber layer thickness (pRNFLT) and peripapillary vessel density (PVD) in patients with newly diagnosed active and inactive systemic lupus erythematosus (SLE) by optical coherence tomography (OCT) and OCT angiography (OCTA).

METHODS

This is a cross-sectional study, in which 77 newly diagnosed SLE patients without ocular symptoms (including 36 active SLE patients and 41 inactive SLE patients) and 72 age- and gender-matched healthy subjects were recruited. All participants underwent OCT and OCTA to evaluate pRNFLT, PVD, and radial peripapillary capillary density (RPCD), respectively. Clinical data at the time of initial diagnosis of SLE, including erythrocyte, leukocyte, platelet, albumin-globulin ratio, erythrocyte sedimentation rate, C-reactive protein, serum complement 3, serum complement 4, anti-dsDNA antibody, and 24-h proteinuria, were collected.

RESULTS

No difference was found in pRNFLT between active SLE patients, and healthy controls, average pRNFLT, superonasal RNFLT, and inferonasal pRNFLT were reduced in inactive SLE patients than in healthy controls (p≤0.008). Temporal PVD, inferotemporal PVD, and inferotemporal RPCD in active SLE patients were significantly lower than those in healthy controls (p≤0.043). There also was a trend towards lower temporal RPCD in active SLE than healthy controls (p=0.089). Average PVD, average RPCD, superonasal RPCD, inferonasal RPCD, and inferotemporal RPCD were decreased in inactive SLE patients than in healthy controls (p≤0.047). Additionally, inferotemporal RPCD in active SLE patients was positively associated with albumin-globulin ratio (p=0.041). Temporal RPCD was negatively correlated with anti-dsDNA antibody (p=0.012) and 24-h proteinuria (p=0.006).

CONCLUSIONS

PRNFL and PVD damage existed in newly diagnosed SLE patients without ocular symptoms. Temporal and inferotemporal RPCD were associated with the laboratory indicators of impaired renal function in active SLE patients, respectively.

Perioperative Acute Kidney Injury: Implications, Approach, Prevention

Acute kidney injury remains a common and significant contributor to perioperative morbidity. Acute kidney injury worsens patient outcomes, and anesthesiologists should make significant efforts to prevent, assess, and treat perioperative renal injury. The authors discuss the impact of renal injury on patient outcomes and putative underlying mechanisms, evidence underlying treatments for acute kidney injury, and practices that may prevent the development of perioperative renal injury.

Pathophysiology of Acute Kidney Frailty

Acute kidney frailty is a premorbid condition of diminished renal functional reserve that predisposes to acute kidney injury; this condition results from subclinical wear or distortion of renal homeostatic responses that protect the renal excretory function. Knowledge of its pathophysiological basis is critical for the development of diagnostic and therapeutic strategies that allow for prophylactic intervention and disease prevention.

Impact of aging on vascular ion channels: perspectives and knowledge gaps across major organ systems

Individuals aged ≥65 yr will comprise ∼20% of the global population by 2030. Cardiovascular disease remains the leading cause of death in the world with age-related endothelial "dysfunction" as a key risk factor. As an organ in and of itself, vascular endothelium courses throughout the mammalian body to coordinate blood flow to all other organs and tissues (e.g., brain, heart, lung, skeletal muscle, gut, kidney, skin) in accord with metabolic demand. In turn, emerging evidence demonstrates that vascular aging and its comorbidities (e.g., neurodegeneration, diabetes, hypertension, kidney disease, heart failure, and cancer) are "channelopathies" in large part. With an emphasis on distinct functional traits and common arrangements across major organs systems, the present literature review encompasses regulation of vascular ion channels that underlie blood flow control throughout the body. The regulation of myoendothelial coupling and local versus conducted signaling are discussed with new perspectives for aging and the development of chronic diseases. Although equipped with an awareness of knowledge gaps in the vascular aging field, a section has been included to encompass general feasibility, role of biological sex, and additional conceptual and experimental considerations (e.g., cell regression and proliferation, gene profile analyses). The ultimate goal is for the reader to see and understand major points of deterioration in vascular function while gaining the ability to think of potential mechanistic and therapeutic strategies to sustain organ perfusion and whole body health with aging.