Renal sinus fat and renal hemodynamics: a cross-sectional analysis

Renal fat deposition measured on dixon-based MRI is significantly associated with early kidney damage in obesity

PURPOSE

To investigate the renal fat deposition on Dixon-based magnetic resonance imaging (MRI) and to explore the predictive value of renal fat biomarkers of magnetic resonance (MR-RFBs) for early kidney damage in obesity.

METHODS

This prospective study included 56 obese volunteers and 47 non-obese healthy volunteers. All volunteers underwent renal magnetic resonance examinations. The differences in MR-RFBs [including renal proton density fat fraction (PDFF), renal sinus fat volume (RSFV), and perirenal fat thickness (PRFT)] measured on Dixon-based MRI between the obese and non-obese volunteers were analyzed using a general linear model, taking sex, age, diabetes, and hypertension as covariates. The relationship between estimated glomerular filtration rate (eGFR) and demographic, laboratory, and imaging parameters in obese volunteers was examined by correlation analysis.

RESULTS

Obese volunteers had higher MR-RFBs than non-obese volunteers after controlling for confounders (all p < 0.001). Renal PDFF (r = - 0.383; p = 0.004), RSFV (r = - 0.368; p = 0.005), and PRFT (r = - 0.451; p < 0.001) were significantly negatively correlated with eGFR in obesity. After adjusting for age, sex, body mass index, diabetes, hypertension, visceral adipose tissue, subcutaneous adipose tissue, renal PDFF, and RSFV, PRFT remained independently negatively associated with eGFR (β = - 0.587; p = 0.003).

CONCLUSIONS

All MR-RFBs are negatively correlated with eGFR in obesity. The MR-RFBs, especially PRFT, may have predictive value for early kidney damage in obesity.

Metabolically healthy obesity and chronic kidney disease risk: exploring the dynamics

Obesity represents a prevalent global health concern with significant implications for various diseases, including chronic kidney disease (CKD). Within this landscape, the phenomenon of metabolically healthy obesity has emerged, challenging traditional notions about the health risks associated with excess weight. While traditional CKD risk factors involve obesity, metabolic syndrome, diabetes, and hypertension, the metabolically healthy obese (MHO) subgroup disrupts these assumptions. Our main objective in this study is to integrate existing literature on CKD in MHO individuals. In this endeavor, we delve into the pathophysiological foundations, the transition between obesity phenotypes and their impact on renal health, examine the implications of their metabolic resilience on mortality within a renal context, and explore potential management strategies specifically designed for MHO individuals. Offering a comprehensive overview of the pathophysiology, we cover various factors contributing to the risk of CKD in the metabolically healthy obese setting, including inflammation, cytokines, hemodynamics, and the renin-angiotensin-aldosterone system, gastrointestinal microbiota, diet, exercise, adipose distribution, and lipotoxicity. Through this synthesis, we aim to provide a comprehensive understanding of the risk of CKD in those classified as MHO.

Visceral Adiposity and Progression of ADPKD: A Cohort Study of Patients From the TEMPO 3:4 Trial

RATIONALE & OBJECTIVE

Body mass index (BMI) is an independent predictor of kidney disease progression in individuals with autosomal dominant polycystic kidney disease (ADPKD). Adipocytes do not simply act as a fat reservoir but are active endocrine organs. We hypothesized that greater visceral abdominal adiposity would associate with more rapid kidney growth in ADPKD and influence the efficacy of tolvaptan.

STUDY DESIGN

A retrospective cohort study.

SETTING & PARTICIPANTS

1,053 patients enrolled in the TEMPO 3:4 tolvaptan trial with ADPKD and at high risk of rapid disease progression.

PREDICTOR

Estimates of visceral adiposity extracted from coronal plane magnetic resonance imaging (MRI) scans using deep learning.

OUTCOME

Annual change in total kidney volume (TKV) and effect of tolvaptan on kidney growth.

ANALYTICAL APPROACH

Multinomial logistic regression and linear mixed models.

RESULTS

In fully adjusted models, the highest tertile of visceral adiposity was associated with greater odds of annual change in TKV of≥7% versus<5% (odds ratio [OR], 4.78 [95% CI, 3.03-7.47]). The association was stronger in women than men (interaction P<0.01). In linear mixed models with an outcome of percent change in TKV per year, tolvaptan efficacy (% change in TKV) was reduced with higher visceral adiposity (3-way interaction of treatment ∗ time ∗ visceral adiposity, P=0.002). Visceral adiposity significantly improved classification performance of predicting rapid annual percent change in TKV for individuals with a normal BMI (DeLong's test z score: -2.03; P=0.04). Greater visceral adiposity was not associated with estimated glomerular filtration rate (eGFR) slope in the overall cohort; however, visceral adiposity was associated with more rapid decline in eGFR slope (below the median) in women (fully adjusted OR, 1.06 [95% CI, 1.01-1.11] per 10 unit increase in visceral adiposity) but not men (OR, 0.98 [95% CI, 0.95-1.02]).

LIMITATIONS

Retrospective; rapid progressors; computational demand of deep learning.

CONCLUSIONS

Visceral adiposity that can be quantified by MRI in the coronal plane using a deep learning segmentation model independently associates with more rapid kidney growth and improves classification of rapid progression in individuals with a normal BMI. Tolvaptan efficacy decreases with increasing visceral adiposity.

PLAIN-LANGUAGE SUMMARY

We analyzed images from a previous study with the drug tolvaptan conducted in patients with autosomal dominant polycystic kidney disease (ADPKD) to measure the amount of fat tissue surrounding the kidneys (visceral fat). We had previously shown body mass index can predict kidney growth in this population; now we determined whether visceral fat was an important factor associated with kidney growth. Using a machine learning tool to automate measurement of fat in images, we observed that visceral fat was independently associated with kidney growth, that it was a better predictor of faster kidney growth in lean patients than body mass index, and that having more visceral fat made treatment of ADPKD with tolvaptan less effective.

The role of perirenal adipose tissue deposition in chronic kidney disease progression: Mechanisms and therapeutic implications

Chronic kidney disease (CKD) represents a significant and escalating global health challenge, with morbidity and mortality rates rising steadily. Evidence increasingly implicates perirenal adipose tissue (PRAT) deposition as a contributing factor in the pathogenesis of CKD. This review explores how PRAT deposition may exert deleterious effects on renal structure and function. The anatomical proximity of PRAT to the kidneys not only potentially causes mechanical compression but also leads to the dysregulated secretion of adipokines and inflammatory mediators, such as adiponectin, leptin, visfatin, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and exosomes. Additionally, PRAT deposition may contribute to renal lipotoxicity through elevated levels of free fatty acids (FFA), triglycerides (TAG), diacylglycerol (DAG), and ceramides (Cer). PRAT deposition is also linked to the hyperactivation of the renin-angiotensin-aldosterone system (RAAS), which further exacerbates CKD progression. Recognizing PRAT deposition as an independent risk factor for CKD underscores the potential of targeting PRAT as a novel strategy for the prevention and management of CKD. This review further discusses interventions that could include measuring PRAT thickness to establish a baseline, managing metabolic risk factors that promote its deposition, and inhibiting key PRAT-induced signaling pathways.

Renal sinus adipose tissue: exploratory study of metabolic features and transcriptome compared with omental and subcutaneous adipose tissue

OBJECTIVE

The objective was to study metabolic characteristics and transcriptome of renal sinus adipose tissue (RSAT) located around renal arteries and veins.

METHODS

Adipose tissue biopsies from RSAT, omental (OAT), and subcutaneous (SAT) depots were obtained from healthy kidney donors (20 female, 20 male). Adipocyte glucose uptake rate and cell size were measured, and gene expression analyses using transcriptomics were performed.

RESULTS

RSAT adipocytes were significantly smaller, with a higher basal glucose uptake rate, than adipocytes from SAT and OAT. Transcriptomic analyses revealed 29 differentially expressed genes between RSAT and OAT (RSAT: 23 lower, 6 higher) and 1214 differentially expressed genes between RSAT and SAT (RSAT: 859 lower, 355 higher). RSAT demonstrated molecular resemblance to OAT, both exhibiting lower metabolic gene expression and higher expression of immune-related pathways, including IL-17, TNFα, and NF-κB signaling than SAT. Weighted gene coexpression network analysis associated RSAT with immune response and nucleic acid transport processes. Despite its location near the renal hilum, RSAT closely resembled OAT and there was a lack of expression in the classical brown adipose tissue genes. Gene enrichment analyses suggest an inflammatory environment in RSAT compared with SAT and, to some extent, OAT.

CONCLUSIONS

The findings suggest specific RSAT functions that could impact renal function and, possibly, the development of renal and cardiometabolic disorders.

MR Assessed Changes of Renal Sinus Fat in Response to Glucose Regulation in West European and South Asian Patients With Type 2 Diabetes

BACKGROUND

Ethnic differences in the progression and outcome of diabetic kidney disease (DKD) remain to be elucidated. MRI-quantified renal sinus fat volume could be a potential biomarker to help investigate the changes of DKD risk in response to glucose regulation.

PURPOSE

To evaluate whether the effect of glucose-lowering treatment on renal sinus fat volume differed in West Europeans (WE) compared to South Asians (SA), and whether ethnic-related difference exists regarding the effect of liraglutide on renal sinus fat.

STUDY TYPE

Retrospective.

POPULATION

Ninety-three patients with type 2 diabetes mellitus, including 47 WE (27 males) aged 59.3 ± 6.5 years, and 46 SA (19 males) aged 54.4 ± 9.8 years.

FIELD STRENGTH/SEQUENCE

3.0 T dual-echo fast gradient-echo pulse sequence using two-point Dixon technique with a phase-correction algorithm.

ASSESSMENT

Changes of renal sinus fat volume were measured by a radiologist (LL) with 4-years' experience, and were compared between the two ethnic groups, together with glycemic level, metabolic risk factors and renal function. The effects of liraglutide were assessed.

STATISTICAL TESTS

Normality of the data was visually evaluated by histograms and Q-Q plots. Within-group and between-group differences were analyzed using paired t-tests and analysis of covariance. Associations were analyzed by person's correlation and multiple linear regression models.

RESULTS

Renal sinus fat decreased in SA patients (Δ% = -7.6% ± 14.8%), but increased in WE patients (Δ% = 5.0% ± 13.1%), with a significant difference between the two ethnic groups. In the WE group, the increase of sinus fat volume was significant in the placebo subgroup (Δ% = 6.8% ± 12.5%), in contrast to the nonsignificant increase in the liraglutide subgroup (Δ% = 3.0% ± 13.8%, P = 0.444).

DATA CONCLUSION

Renal sinus fat accumulation responds differently to glucose regulation, showing a reduction in SA patients in contrast to a persistent accumulation in WE patients. A trend of less accumulation of sinus fat in WE patients receiving liraglutide has been observed.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 4.

Noninvasive Assessment of Diabetic Kidney Disease With MRI: Hype or Hope?

Owing to the increasing prevalence of diabetic mellitus, diabetic kidney disease (DKD) is presently the leading cause of chronic kidney disease and end-stage renal disease worldwide. Early identification and disease interception is of paramount clinical importance for DKD management. However, current diagnostic, disease monitoring and prognostic tools are not satisfactory, due to their low sensitivity, low specificity, or invasiveness. Magnetic resonance imaging (MRI) is noninvasive and offers a host of contrast mechanisms that are sensitive to pathophysiological changes and risk factors associated with DKD. MRI tissue characterization involves structural and functional information including renal morphology (kidney volume (TKV) and parenchyma thickness using T1- or T2-weighted MRI), renal microstructure (diffusion weighted imaging, DWI), renal tissue oxygenation (blood oxygenation level dependent MRI, BOLD), renal hemodynamics (arterial spin labeling and phase contrast MRI), fibrosis (DWI) and abdominal or perirenal fat fraction (Dixon MRI). Recent (pre)clinical studies demonstrated the feasibility and potential value of DKD evaluation with MRI. Recognizing this opportunity, this review outlines key concepts and current trends in renal MRI technology for furthering our understanding of the mechanisms underlying DKD and for supplementing clinical decision-making in DKD. Progress in preclinical MRI of DKD is surveyed, and challenges for clinical translation of renal MRI are discussed. Future directions of DKD assessment and renal tissue characterization with (multi)parametric MRI are explored. Opportunities for discovery and clinical break-through are discussed including biological validation of the MRI findings, large-scale population studies, standardization of DKD protocols, the synergistic connection with data science to advance comprehensive texture analysis, and the development of smart and automatic data analysis and data visualization tools to further the concepts of virtual biopsy and personalized DKD precision medicine. We hope that this review will convey this vision and inspire the reader to become pioneers in noninvasive assessment and management of DKD with MRI. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 2.

An Evaluation of Renal Sinus Fat Accumulation Using the Anteroposterior Diameter of the Renal Sinus on a Computed Tomography Axial Image

Backgrounds and objectives Renal sinus fat (RSF) is an indicator of obesity-related complications. However, the measurement and imaging process are complicated. For a simple measurement of RSF, we focused on the kidney's shape change caused by RSF accumulation. Thus, this study aimed to investigate whether the anteroposterior diameter of the renal sinus (APDRS) on a computed tomography (CT) axial image is useful for evaluating RSF accumulation. Materials and methods The correlation between APDRS and RSF was investigated in 98 outpatients who underwent abdominal CT. In addition, the correlation between APDRS or RSF and obesity indicators (estimated glomerular filtration rate from serum creatinine levels (eGFRcreat), body mass index (BMI), and visceral adipose tissue (VAT)) was also investigated. We classified patients based on the presence or absence of at least one underlying disease (chronic kidney disease (CKD), cardiovascular diseases (CVD), hypertension, and type 2 diabetes (T2D)) and investigated significant differences between the two groups at APDRS and RSF. The intraclass correlation coefficient (ICC) was also calculated for APDRS. Results There was a strong positive correlation between RSF and APDRS (r = 0.802, P < 0.01). The obesity indicators (eGFRcreat, BMI, and VAT) were correlated with RSF and APDRS (P < 0.01). Out of 98 outpatients, 48 had at least one underlying disease. There were statistically significant differences in APDRS and RSF between the patients with and without at least one of the underlying diseases caused by obesity (P < 0.01). The inter-reader ICC for the measurement of the APDRS was 0.98. Conclusions APDRS on a CT axial image may be useful for the evaluation of RSF accumulation.

Renal sinus fat is associated with intrarenal hemodynamic abnormalities independent of visceral fat in patients with chronic kidney disease

OBJECTIVE

Obesity is a risk factor of chronic kidney disease (CKD), contributing to the rising incidence of cardiometabolic diseases. Renal sinus fat (RSF) is an ectopic fat depot located at the renal cavity that could impair renal function and hemodynamic through compression of renal structures. The major purpose of this study was to explore the relationship between RSF accumulation and renal dysfunction in CKD patients.

METHODS

We evaluated the associations between computed tomography measured RSF volume and key clinical and histologic parameters involved in renal function and hemodynamics in 132 well-characterized CKD patients who underwent renal biopsy (median age: 62 years; 63.6% men).

RESULTS

RSF volume normalized by renal volume (RSF%) positively correlated with obesity-related traits such body mass index and visceral fat volume (VFV) (all P < 0.001) whereas it negatively correlated with estimated glomerular filtration rate (eGFR) (ρ = -0.42, P < 0.001) and 24-h urinary creatinine clearance (CCr) (ρ = -0.34, P < 0.001). Notably, we found robust positive correlations between RSF% and renal resistive index (RRI) measured by the Doppler ultrasound (ρ = 0.40, P < 0.001), and the histological severity of global glomerular sclerosis (ρ = 0.48, P < 0.001) and interstitial fibrosis and tubular atrophy (IFTA) (ρ = 0.35, P < 0.001). In the multivariate linear regression models, after accounting for potential confounders including VFV, RSF% remained significantly associated with CCr (β = -0.26, P < 0.001), RRI (β = 0.17, P = 0.022), global glomerular sclerosis (β = 0.21, P = 0.002), and IFTA (β = 0.17, P = 0.012).

CONCLUSION

RSF accumulation is associated with renal dysfunction and hemodynamic abnormalities independent of visceral adiposity. Our results suggest that RSF may have a potential unique role in the pathogenesis of CKD.

Abdominal adipose tissue and type 2 diabetic kidney disease: adipose radiology assessment, impact, and mechanisms

Diabetic kidney disease (DKD) is a significant healthcare burden worldwide that substantially increases the risk of kidney failure and cardiovascular events. To reduce the prevalence of DKD, extensive research is being conducted to determine the risk factors and consequently implement early interventions. Patients with type 2 diabetes mellitus (T2DM) are more likely to be obese. Abdominal adiposity is associated with a greater risk of kidney damage than general obesity. Abdominal adipose tissue can be divided into different fat depots according to the location and function, including visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), perirenal adipose tissue (PAT), and renal sinus adipose tissue (RSAT), which can be accurately measured by radiology techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI). Abdominal fat depots may affect the development of DKD through different mechanisms, and radiologic abdominal adipose characteristics may serve as imaging indicators of DKD risk. This review will first describe the CT/MRI-based assessment of abdominal adipose depots and subsequently describe the current studies on abdominal adipose tissue and DKD development, as well as the underlying mechanisms in patients of T2DM with DKD.

Efficacy of parsley seed-supplemented bread in improving serum osteopontin level and renal health in obese women: A nutritional intervention study

BACKGROUND

Obesity is a global epidemic and a major contributor to chronic kidney disease worldwide. This interventional study aimed to evaluate the effects of a unique parsley seed bread and a healthy balanced diet on serum osteopontin level and renal function in obese women.

METHODS

A total of 85 obese women (BMI, 35.68 ± 0.47 kg/m2) participated in an 8-week nutritional intervention comprising two phases. In the first phase, participants consumed 100 g of ground parsley seed bread along with a healthy balanced low caloric regimen for four weeks. In the second phase, Baladi bread was substituted for the supplement, providing an equal caloric intake, for another four weeks. Relevant Anthropometric measurements, blood pressure, dietary recall, and biochemical parameters (osteopontin, IL-1β, IL-10, kidney functions, and lipid parameters) were assessed before and after each intervention phase.

RESULTS

Following the initial intervention phase, there were significant improvements in all recorded mean anthropometric parameters (p ≤ 0.001). Lipid parameters and risk factors also significantly decreased (p < 0.05), while osteopontin, creatinine, and IL-1β levels decreased significantly. eGFR, creatinine clearance, IL-10 increased. However, these improved values returned to elevated levels after the omission of the supplement in the second phase. There was a significant negative correlation between osteopontin and creatinine, creatinine clearance, and IL-10.

CONCLUSION

The combined effect of the novel parsley seed-based intervention and a healthy balanced low-calorie regimen demonstrated improvements in osteopontin level associated with renal disorders, and inflammation, in addition to dyslipidemia in obese women. This suggests a promising approach for improving and protecting kidney disorders.

Association Between Renal Sinus Fat and Cardiometabolic and Renin-Angiotensin System Parameters in Primary Aldosteronism

Context

Renal sinus fat (RSF) accumulation is associated with cardiometabolic diseases, such as obesity, diabetes, hypertension, and chronic kidney disease. However, clinical implications of RSF in primary aldosteronism (PA) remain unclear.

Objective

We aimed to investigate relationships between RSF volume and key cardiometabolic and renin-angiotensin system (RAS) parameters in PA patients and clarify the differences in these relationships between unilateral and bilateral subtypes.

Methods

We analyzed data obtained from well-characterized PA patients that involved 45 unilateral (median age: 52 years; 42.2% men) and 92 bilateral patients (51 years; 42.4% men).

Results

RSF volume normalized by renal volume (RSF%) was greater in the unilateral group than in the bilateral group (P < .05). RSF% was greater in men than in women (P < .05). RSF% positively correlated with parameters related to cardiometabolic risk, including age, body mass index, visceral fat volume, creatinine, triglycerides/high-density lipoprotein cholesterol ratio, uric acid, fasting glucose, and C-reactive protein regardless of PA subtypes (all P < .05). Intriguingly, RSF% positively correlated with plasma aldosterone concentration (PAC), aldosterone-to-renin ratio, and intact parathyroid hormone (iPTH) (all P < .05) in bilateral patients but did not correlate with RAS parameters and even showed an opposite trend in unilateral patients. In subgroup analyses by sex, these distinctions became more evident in women. After adjustment for potential confounders, RSF% remained positively correlated with PAC and iPTH in bilateral patients.

Conclusion

Our results indicate that RSF accumulation is involved in cardiometabolic dysfunction associated with PA. However, there were distinct correlations between RSF volume and RAS parameters according to sex and PA subtypes.

Sex-Specific Computed Tomography Abdominal Fat and Skeletal Muscle Characteristics in Type 2 Diabetic Retinopathy Patients With/Without Comorbid Diabetic Kidney Disease

RATIONALE AND OBJECTIVES

To investigate differences in sex-specific computed tomography abdominal fat and skeletal muscle (SM) characteristics between type 2 diabetic retinopathy (DR) patients with and without diabetic kidney disease (DKD).

MATERIALS AND METHODS

This retrospective study included type 2 diabetes mellitus DR patients with/without DKD between January 2019 and July 2021. Visceral adipose tissue (VAT), subcutaneous adipose tissue, perirenal adipose tissue (PAT), intramuscular adipose tissue, and SM areas were measured. Univariate and multivariate logistic regression analyses were used to analyze risk factors for DKD. Correlation and multiple linear regression analyses were used to clarify the association between computed tomography abdominal fat, SM characteristics, and cystatin C.

RESULTS

Two hundred and forty-one patients were enrolled and divided into DR with DKD group (n = 142) and DR without DKD group (n = 99). In men, hypertension (OR: 5.21; 95%CI: 1.93-14.05; p = 0.001), diastolic pressure (OR: 1.07; 95%CI: 1.01-1.12; p = 0.011), hemoglobin (OR: 0.94; 95%CI: 0.92-0.97; p < 0.001) and PAT attenuation value (OR: 1.09; 95%CI: 1.01-1.17; p = 0.026) were independent risk factors for DKD progression in DR patients, while the VAT index (VATI) (OR: 1.03; 95%CI: 1.01-1.05; p = 0.014) was an independent risk factor for female patients. Multiple linear regression analysis revealed significant correlations between hypertension (β = 0.22, p = 0.002) and hemoglobin (β = -0.53, p < 0.001) with cystatin C in men, and a significant correlation between VATI and cystatin C (β = 0.35, p = 0.037) in women after adjustment for confounders.

CONCLUSION

Female DR patients with elevated VAT level may suffer from a higher risk of DKD than that in male patients.

The Fatty Kidney and Beyond: A Silent Epidemic

As the prevalence of obesity rises in the United States, so does the incidence of obesity-related kidney disease. Obesity itself is an independent risk factor for chronic kidney disease where the pathophysiology is complex, involving altered hemodynamics, renin-angiotensin-aldosterone system overactivation, and adipokines leading to inflammation and fibrosis. Obesity-related kidney disease comprises both obesity-related glomerulopathy and fatty kidney disease. Obesity-related glomerulopathy is a consequence of glomerular hyperfiltration and often presents clinically with subnephrotic proteinuria and pathologically with glomerulomegaly with or without focal glomerulosclerosis. Fatty kidney disease is the effect of renal ectopic fat contributing to chronic kidney disease. Whether the renal ectopic fat is a distinct clinical entity or a pathologic mechanism contributing to obesity-related glomerulopathy, the treatment paradigm of weight and proteinuria reduction remains the same. We present the pathophysiology behind obesity-related kidney disease, clinical outcomes, and treatment strategies, which include lifestyle interventions, use of renin-angiotensin-aldosterone system inhibitors, glucagon-like peptide 1 receptor agonists, sodium-glucose co-transporter-2 inhibitors, and bariatric surgery. With old and novel therapeutics, we are attempting to stave off the silent epidemic that obesity-related kidney disease is becoming.

Kidney lipid dysmetabolism and lipid droplet accumulation in chronic kidney disease

Chronic kidney disease (CKD) is a global health problem with rising incidence and prevalence. Among several pathogenetic mechanisms responsible for disease progression, lipid accumulation in the kidney parenchyma might drive inflammation and fibrosis, as has been described in fatty liver diseases. Lipids and their metabolites have several important structural and functional roles, as they are constituents of cell and organelle membranes, serve as signalling molecules and are used for energy production. However, although lipids can be stored in lipid droplets to maintain lipid homeostasis, lipid accumulation can become pathogenic. Understanding the mechanisms linking kidney parenchymal lipid accumulation to CKD of metabolic or non-metabolic origin is challenging, owing to the tremendous variety of lipid species and their functional diversity across different parenchymal cells. Nonetheless, multiple research reports have begun to emphasize the effect of dysregulated kidney lipid metabolism in CKD progression. For example, altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury. Newly developed lipid-targeting agents are being tested in clinical trials in CKD, raising expectations for further therapeutic development in this field.

Obesity-Related Kidney Disease: Current Understanding and Future Perspectives

Obesity is a serious chronic disease and an independent risk factor for the new onset and progression of chronic kidney disease (CKD). CKD prevalence is expected to increase, at least partly due to the continuous rise in the prevalence of obesity. The concept of obesity-related kidney disease (OKD) has been introduced to describe the still incompletely understood interplay between obesity, CKD, and other cardiometabolic conditions, including risk factors for OKD and cardiovascular disease, such as diabetes and hypertension. Current therapeutics target obesity and CKD individually. Non-pharmacological interventions play a major part, but the efficacy and clinical applicability of lifestyle changes and metabolic surgery remain debatable, because the strategies do not benefit everyone, and it remains questionable whether lifestyle changes can be sustained in the long term. Pharmacological interventions, such as sodium-glucose co-transporter 2 inhibitors and the non-steroidal mineralocorticoid receptor antagonist finerenone, provide kidney protection but have limited or no impact on body weight. Medicines based on glucagon-like peptide-1 (GLP-1) induce clinically relevant weight loss and may also offer kidney benefits. An urgent medical need remains for investigations to better understand the intertwined pathophysiologies in OKD, paving the way for the best possible therapeutic strategies in this increasingly prevalent disease complex.

Targeting Renal Proximal Tubule Cells in Obesity-Related Glomerulopathy

As a metabolic disorder, obesity can cause secondary kidney damage, which is called obesity-related glomerulopathy (ORG). As the incidence of obesity increases worldwide, so does the incidence of end-stage renal disease (ESRD) caused by ORGs. However, there is still a lack of effective strategies to prevent and delay the occurrence and development of ORG. Therefore, a deeper understanding and elaboration of the pathogenesis of ORG is conducive to the development of therapeutic drugs for ORG. Here, we review the characteristics of pathological lesions of ORG and describe the roles of lipid metabolism disorders and mitochondrial oxidative stress in the development of ORG. Finally, we summarize the current available drugs or compounds for the treatment of ORG and suggested that ameliorating renal lipid metabolism and mitochondrial function may be potential therapeutic targets for ORG.

Quantification of the renal sinus fat and exploration of its relationship with ectopic fat deposition in normal subjects using MRI fat fraction mapping

Purpose

To determine the renal sinus fat (RSF) volume and fat fraction (FF) in normal Chinese subjects using MRI fat fraction mapping and to explore their associations with age, gender, body mass index (BMI) and ectopic fat deposition.

Methods

A total of 126 subjects were included in the analysis. RSF volume and FF, visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) area, and hepatic and pancreatic FFs were measured for each subject. The comparisons in gender were determined using two-tailed t-tests or the nonparametric Mann-Whitney U-test for normally or non-normally distributed data for continuous variables and the chi-square test for categorical variables. Comparisons of RFS volume and FF between right and left kidneys were determined using paired sample t-tests. Multivariable logistic models were performed to confirm whether RSF differences between men and women are independent of VAT or SAT area. When parameters were normally distributed, the Pearson correlation coefficient was used; otherwise, the Spearman correlation coefficient was applied.

Results

The RSF volumes (cm3) of both kidneys in men (26.86 ± 8.81 for right and 31.62 ± 10.32 for left kidneys) were significantly bigger than those of women (21.47 ± 6.90 for right and 26.03 ± 8.55 for left kidneys) (P < 0.05). The RSF FFs (%) of both kidneys in men (28.33 ± 6.73 for right and 31.21 ± 6.29 for left kidneys) were significantly higher than those of the women (23.82 ± 7.74 for right and 27.92 ± 8.15 for left kidneys) (P < 0.05). The RSF differences between men and women are independent of SAT area and dependent of VAT area (except for right RSF volume). In addition, the RSF volumes and FFs in both kidneys in the overall subjects show significant correlations with age, BMI, VAT area, hepatic fat fraction and pancreatic fat fraction (P < 0.05). However, the patterns of these correlations varied by gender. The RSF volume and FF of left kidney were significantly larger than those of the right kidney (P < 0.05).

Conclusion

The association between renal sinus fat and ectopic fat deposition explored in this study may help establish a consensus on the normal values of RSF volume and FF for the Chinese population. This will facilitate the identification of clinicopathological changes and aid in the investigation of whether RSF volume and FF can serve as early biomarkers for metabolic diseases and renal dysfunction in future studies.

Magnetic Resonance Imaging in Clinical Trials of Diabetic Kidney Disease

Chronic kidney disease (CKD) associated with diabetes mellitus (DM) (known as diabetic kidney disease, DKD) is a serious and growing healthcare problem worldwide. In DM patients, DKD is generally diagnosed based on the presence of albuminuria and a reduced glomerular filtration rate. Diagnosis rarely includes an invasive kidney biopsy, although DKD has some characteristic histological features, and kidney fibrosis and nephron loss cause disease progression that eventually ends in kidney failure. Alternative sensitive and reliable non-invasive biomarkers are needed for DKD (and CKD in general) to improve timely diagnosis and aid disease monitoring without the need for a kidney biopsy. Such biomarkers may also serve as endpoints in clinical trials of new treatments. Non-invasive magnetic resonance imaging (MRI), particularly multiparametric MRI, may achieve these goals. In this article, we review emerging data on MRI techniques and their scientific, clinical, and economic value in DKD/CKD for diagnosis, assessment of disease pathogenesis and progression, and as potential biomarkers for clinical trial use that may also increase our understanding of the efficacy and mode(s) of action of potential DKD therapeutic interventions. We also consider how multi-site MRI studies are conducted and the challenges that should be addressed to increase wider application of MRI in DKD.

Obesity-related hypertension and chronic kidney disease: from evaluation to management

With the recent obesity pandemic, obesity-related hypertension and its complications (e.g., heart failure, coronary disease, and chronic kidney disease [CKD]) are gaining attention in clinical and research fields. Obesity-related hypertension frequently precedes the onset of CKD and aggravates its progression. In this review, we discuss the role of visceral fat in the pathophysiology of obesity-related hypertension and the potential therapeutic strategies for its prevention and management. Various factors, including the sympathetic nervous system, renin-angiotensin-aldosterone system, and inflammatory pathways, are intricately involved in the pathogenesis of obesity-related hypertension. These factors individually and jointly contribute to the development of hypertension (usually sodium-sensitive or resistant hypertension) and, ultimately, to the progression of CKD. From a clinical standpoint, a decline in renal function in advanced CKD further makes blood pressure control challenging since only a few options are available for blood pressure-lowering medications. Proactive lifestyle modification, pharmacological treatment for obesity, and bariatric surgery can be considered for obesity control and management. Furthermore, intensive blood pressure control is required to prevent and halt the development and progression of CKD.

Prognostic impact of renal sinus fat accumulation in patients with chronic kidney disease

BACKGROUND

Obesity is associated with the development and progression of chronic kidney disease (CKD). In the general population, the amount of renal sinus fat was associated with hypertension and renal impairment. However, its impact upon those with CKD remains uncertain.

METHODS

We prospectively included CKD patients who underwent renal biopsy and simultaneously measured their renal sinus fat volume. The association between the percentage of renal sinus fat volume, which was adjusted by kidney volume, and renal outcomes was investigated.

RESULTS

A total of 56 patients (median 55 years old, 35 men) were included. Among baseline characteristics, age and visceral fat volume were positively correlated with the percentage of renal sinus fat volume (p < 0.05). The percentage of renal sinus fat volume was associated with hypertension (p < 0.01) and tended to be associated with max glomerular diameter (p = 0.078) and urine angiotensinogen creatinine ratio (p = 0.064) after adjustment with several clinical factors. The percentage of renal sinus fat volume was significantly associated with a future > 50% decline in estimated glomerular filtration rate (p < 0.05).

CONCLUSIONS

Among those with CKD who required renal biopsy, the amount of renal sinus fat was associated with poor renal outcomes accompanied by systemic hypertension.

Associations of renal sinus fat with blood pressure and ectopic fat in a diverse cohort of adults

Background

Renal sinus fat (RSF) is an ectopic fat depot shown to be associated with visceral adiposity and hypertension in predominantly white populations. The purpose of this analysis is to investigate RSF and associations between RSF and blood pressure in a cohort of African American (AA) and European American (EA) adults. A secondary purpose was to explore risk factors associated with RSF.

Methods

Participants were 116 A A and EA adult men and women. Ectopic fat depots were assessed with MRI: RSF, intraabdominal adipose tissue (IAAT), intermuscular adipose tissue (IMAT), perimuscular adipose tissue (PMAT), and liver fat. Cardiovascular measures included diastolic blood pressure (DBP), systolic blood pressure (SBP), pulse pressure, mean arterial pressure, and flow mediated dilation. Matsuda index was calculated for insulin sensitivity. Pearson correlations were used to investigate associations of RSF with cardiovascular measures. Multiple linear regression was used to evaluate contributions of RSF on SBP and DBP and to explore factors associated with RSF.

Results

No difference was observed in RSF between AA and EA participants. RSF was positively associated with DBP in AA participants, but this was not independent of age and sex. Age, male sex, and total body fat were positively associated with RSF in AA participants. Insulin sensitivity was inversely and IAAT and PMAT were positively associated with RSF in EA participants.

Conclusions

Differential associations of RSF with age, insulin sensitivity, and adipose depots among AA and EA adults suggest unique pathophysiological mechanisms influence RSF deposition, which may contribute to chronic disease etiology and progression.

The Beneficial Effects of Bariatric-Surgery-Induced Weight Loss on Renal Function

Obesity represents an independent risk factor for the development of chronic kidney disease (CKD), leading to specific histopathological alterations, known as obesity-related glomerulopathy. Bariatric surgery is the most effective means of inducing and maintaining sustained weight loss. Furthermore, in the context of bariatric-surgery-induced weight loss, a reduction in the proinflammatory state and an improvement in the adipokine profile occur, which may also contribute to the improvement of renal function following bariatric surgery. However, the assessment of renal function in the context of obesity and following marked weight loss is difficult, since the formulas adopted to estimate glomerular function use biomarkers whose production is dependent on muscle mass (creatinine) or adipose tissue mass and inflammation (cystatin-c). Thus, following bariatric surgery, the extent to which reductions in plasma concentrations reflect the actual improvement in renal function is not clear. Despite this limitation, the available literature suggests that in patients with hyperfiltration at baseline, GFR is reduced following bariatric surgery, whereas GFR is increased in patients with decreased GFR at baseline. These findings are also confirmed in the few studies that have used measured rather than estimated GFR. Albuminuria is also decreased following bariatric surgery. Moreover, bariatric surgery seems superior in achieving the remission of albuminuria and early CKD than the best medical treatment. In this article, we discuss the pathophysiology of renal complications in obesity, review the mechanisms through which weight loss induces improvements in renal function, and provide an overview of the renal outcomes following bariatric surgery.

Novel Insights in the Physiopathology and Management of Obesity-Related Kidney Disease

Obesity is recognized as an independent risk factor for the development of kidney disease, which has led to the designation of obesity-related glomerulopathy (ORG). Common renal features observed in this condition include glomerular hypertrophy, glomerulosclerosis, haemodynamic changes and glomerular filtration barrier defects. Additionally, and although less studied, obesity-related kidney disease also involves alterations in renal tubules, including tubule hypertrophy, lipid deposition and tubulointerstitial fibrosis. Although not completely understood, the harmful effects of obesity on the kidney may be mediated by different mechanisms, with alterations in adipose tissue probably playing an important role. An increase in visceral adipose tissue has classically been associated with the development of kidney damage, however, recent studies point to adipose tissue surrounding the kidney, and specifically to the fat within the renal sinus, as potentially involved in the development of ORG. In addition, new strategies for the treatment of patients with obesity-related kidney disease are focusing on the management of obesity. In this regard, some non-invasive options, such as glucagon-like peptide-1 (GLP-1) receptor agonists or sodium–glucose cotransporter-2 (SGLT2) inhibitors, are being considered for application in the clinic, not only for patients with diabetic kidney disease but as a novel pharmacological strategy for patients with ORG. In addition, bariatric surgery stands as one of the most effective options, not only for weight loss but also for the improvement of kidney outcomes in obese patients with chronic kidney disease.

Sonographic Measurement of Renal Sinus Fat to Renal Cortical Thickness Ratio Is a Better Predictor of Chronic Kidney Disease Than Cortical Thickness Alone

Objective:

The aim was to determine if the renal sinus fat-to-cortical thickness ratio was a better predictor of chronic kidney disease (CKD) than cortical thickness alone.

Materials and Methods:

A total of 199 patients were included in the study. Renal fat, parenchyma, and cortical thicknesses were evaluated by sonography retrospectively. Same day serum glomerular filtration rate (GFR) values were obtained and correlated.

Results:

The study patients had an average fat-to-cortical thickness ratio <0.4 and had a 63% probability of developing renal failure. The probability increased almost linearly from 65% to 85% for patients with a ratio between 0.4 and 0.5, and then plateaued at 85% probability for a ratio >0.5. Additionally, the average fat-to-cortical thickness ratio was statistically significant ( P-value = .02) in predicting progression to renal failure, compared to a cortical thickness alone ( P-value = .12 and P-value = .39 for the left and right kidney, respectively). However, when evaluating individual kidneys for the average fat-to-cortical thickness ratio, only the left kidney showed a statistical significance ( P-value = .02 and P-value = .08 on the left and right, respectively).

Conclusion:

The renal sinus fat-to-cortical thickness ratio has a significant negative correlation to GFR, specifically for the left kidney. The probability of developing renal failure increases with higher ratios. The renal sinus fat-to-cortical thickness ratio may also be better than cortical thickness alone in predicting progression toward CKD and it acts as an internal control for differences in body size.

Renal Sinus Fat Is Expanded in Patients with Obesity and/or Hypertension and Reduced by Bariatric Surgery Associated with Hypertension Remission

Renal sinus fat is a fat depot at the renal hilum. Because of its location around the renal artery, vein, and lymphatic vessels, an expanded renal sinus fat mass may have hemodynamic and renal implications. We studied whether renal sinus fat area (RSF) associates with hypertension and whether following bariatric surgery a decrease in RSF associates with improvement of hypertension. A total of 74 severely obese and 46 lean controls were studied with whole-body magnetic resonance imaging (MRI). A total of 42 obese subjects were re-studied six months after bariatric surgery. RSF was assessed by two independent researchers using sliceOmatic. Glomerular filtration rate (eGFR) was estimated according to the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration). Patients with obesity accumulated more RSF compared to lean controls (2.3 [1.7–3.1] vs. 1.8 [1.4–2.5] cm², p = 0.03). Patients with hypertension (N = 36) had a larger RSF depot compared to normotensive subjects (2.6 [2.0–3.3] vs. 2.0 [1.4–2.5] cm², p = 0.0007) also after accounting for body mass index (BMI). In the pooled data, RSF was negatively associated with eGFR (r = −0.20, p = 0.03), whereas there was no association with systolic or diastolic blood pressure. Following bariatric surgery, RSF was reduced (1.6 [1.3–2.3] vs. 2.3 [1.7–3.1] cm², p = 0.03) along with other markers of adiposity. A total of 9/27 of patients achieved remission from hypertension. The remission was associated with a larger decrease in RSF, compared to patients who remained hypertensive (−0.68 [−0.74 to −0.44] vs. −0.28 [−0.59 to 0] cm², p = 0.009). The accumulation of RSF seems to be involved in the pathogenesis of hypertension in obesity. Following bariatric surgery, loss of RSF was associated with remission from hypertension.

Obesity-related glomerulopathy: Current approaches and future perspectives

Obesity-related glomerulopathy (ORG) is a silent comorbidity which is increasing in incidence as the obesity epidemic escalates. ORG is associated with serious health consequences including chronic kidney disease, end-stage renal disease (ESRD), and increased mortality. Although the pathogenic mechanisms involved in the development of ORG are not fully understood, glomerular hemodynamic changes, renin-angiotensin-aldosterone system (RAAS) overactivation, insulin-resistance, inflammation and ectopic lipid accumulation seem to play a major role. Despite albuminuria being commonly used for the non-invasive evaluation of ORG, promising biomarkers of early kidney injury that are emerging, as well as new approaches with proteomics and metabolomics, might permit an earlier diagnosis of this disease. In addition, the assessment of ectopic kidney fat by renal imaging could be a useful tool to detect and evaluate the progression of ORG. Weight loss interventions appear to be effective in ORG, although large-scale trials are needed. RAAS blockade has a renoprotective effect in patients with ORG, but even so, a significant proportion of patients with ORG will eventually progress to ESRD despite therapeutic efforts. It is noteworthy that certain antidiabetic agents such as sodium-glucose cotransporter 2 inhibitors (SGLT2i) or glucagon-like peptide-1 receptor agonists (GLP-1 RAs) could be useful in the treatment of ORG through different pleiotropic effects. In this article, we review current approaches and future perspectives in the care and treatment of ORG.

Fatty kidney: A possible future for chronic kidney disease research

BACKGROUND

Metabolic syndrome is a growing twenty-first century pandemic associated with multiple clinical comorbidities ranging from cardiovascular diseases, non-alcoholic fatty liver disease and polycystic ovary syndrome to kidney dysfunction. A novel area of research investigates the concept of fatty kidney in the pathogenesis of chronic kidney disease, especially in patients with diabetes mellitus or metabolic syndrome.

AIM

To review the most updated literature on fatty kidney and provide future research, diagnostic and therapeutic perspectives on a disease increasingly affecting the contemporary world.

MATERIALS AND METHOD

We performed an extensive literature search through three databases including Embase (Elsevier) and the Cochrane Central Register of Controlled Trials (Wiley) and PubMed/Medline Web of Science in November 2021 by using the following terms and their combinations: 'fatty kidney', 'ectopic fat', 'chronic kidney disease', 'cardiovascular event', 'cardio-metabolic risk', 'albuminuria' and 'metabolic syndrome'. Each study has been individually assessed by the authors.

RESULTS

Oxidative stress and inflammation, Klotho deficiency, endoplasmic reticulum stress, mitochondrial dysfunction and disruption of cellular energy balance appear to be the main pathophysiological mechanisms leading to tissue damage following fat accumulation. Despite the lack of large-scale comprehensive studies in this novel field of research, current clinical trials demonstrate fatty kidney as an independent risk factor for the development of chronic kidney disease and cardiovascular events.

CONCLUSION

The requirement for future studies investigating the pathophysiology, clinical outcomes and therapeutics of fatty kidney is clear.

Renal Compression in Heart Failure: The Renal Tamponade Hypothesis

Renal dysfunction is one of the strongest predictors of outcome in heart failure. Several studies have revealed that both reduced perfusion and increased congestion (and central venous pressure) contribute to worsening renal function in heart failure. This paper proposes a novel factor in the link between cardiac and renal dysfunction: "renal tamponade" or compression of renal structures caused by the limited space for expansion. This space can be limited either by the rigid renal capsule that encloses the renal interstitial tissue or by the layer of fat around the kidneys or by the peritoneal space exerting pressure on the retroperitoneal kidneys. Renal decapsulation in animal models of heart failure and acute renal ischemia has been shown effective in alleviating pressure-related injury within the kidney itself, thus supporting this concept and making it a potentially interesting novel treatment in heart failure.

First genome-wide association study investigating blood pressure and renal traits in domestic cats

Hypertension (HTN) and chronic kidney disease (CKD) are common in ageing cats. In humans, blood pressure (BP) and renal function are complex heritable traits. We performed the first feline genome-wide association study (GWAS) of quantitative traits systolic BP and creatinine and binary outcomes HTN and CKD, testing 1022 domestic cats with a discovery, replication and meta-analysis design. No variants reached experimental significance level in the discovery stage for any phenotype. Follow up of the top 9 variants for creatinine and 5 for systolic BP, one SNP reached experimental-wide significance for association with creatinine in the combined meta-analysis (chrD1.10258177; P = 1.34 × 10^–6). Exploratory genetic risk score (GRS) analyses were performed. Within the discovery sample, GRS of top SNPs from the BP and creatinine GWAS show strong association with HTN and CKD but did not validate in independent replication samples. A GRS including SNPs corresponding to human CKD genes was not significant in an independent subset of cats. Gene-set enrichment and pathway-based analysis (GSEA) was performed for both quantitative phenotypes, with 30 enriched pathways with creatinine. Our results support the utility of GWASs and GSEA for genetic discovery of complex traits in cats, with the caveat of our findings requiring validation.

Renal fat fraction is significantly associated with the risk of chronic kidney disease in patients with type 2 diabetes

BACKGROUNDS

Ectopic fat deposition is closely related to chronic kidney disease (CKD). Currently, there are few population studies that have been conducted to determine the relationship between renal parenchyma fat deposition and the risk of CKD among patients with type 2 diabetes mellitus (T2DM). Therefore, we employed magnetic resonance imaging (MRI) to detect renal parenchyma fat content in individuals with T2DM, expressed as renal fat fraction (FF), to explore whether renal FF is an important risk factor for CKD in patients with T2DM.

METHODS

In this cross-sectional study, 189 subjects with T2DM were enrolled. CKD was defined as the estimated glomerular filtration rate (eGFR)<60 mL/min/1.73m². Measurement of the renal FF was performed on a 3.0-T MRI (MAGNETOM Skyra, Siemens, Erlangen, Germany). Binary logistic regression was used to determine the association between tertiles of renal FF and risk of CKD. Receiver-operator characteristic (ROC) curves were constructed to evaluate the sensitivity and specificity of renal FF in detecting CKD in T2DM patients.

RESULTS

The patients were divided into three groups according to tertiles of the renal FF level (2.498 - 7.434). As renal FF increases, patients tend to be older, and more abdominally obese, with a decreased eGFR (p<0.05). After adjustment for potential confounders, patients in the highest tertile of renal FF had a significantly increased risk of CKD than those in the lowest tertile (odds ratio (OR) = 3.98, 95% confidence interval (CI) = 1.12 - 14.09, p = 0.032), and the area under the ROC curve for this model was 0.836 (0.765-0.907).

CONCLUSIONS

The renal FF is significantly independently associated with CKD in patients with T2DM.

Renal sinus fat volume in type 2 diabetes mellitus is associated with glycated hemoglobin and metabolic risk factors

AIMS

We aimed to compare renal sinus fat volume assessed by MRI between patients with type 2 diabetes and healthy volunteers, and investigate the association between renal sinus fat and metabolic traits.

METHODS

In this cross-sectional study, renal sinus fat and parenchyma volumes measured on abdominal MRI were compared between patients and controls using analysis of covariance. Associations of renal parameters with clinical characteristics were analyzed using linear regression analysis.

RESULTS

A total of 146 participants were enrolled, consisting of 95 type 2 diabetes patients (57.2±8.8years, 49.5% male) and 51 controls (54.0±9.2years, 43.1% male). Patients with diabetes demonstrated larger sinus fat volumes (15.4±7.5cm³ vs. 10.3±7.1cm³, p<0.001) and sinus fat-parenchyma ratio than controls. In the total population, renal sinus fat was positively associated with HbA1c, abdominal VAT, cholesterol and triglycerides, after adjustment for age, sex, ethnicity and type 2 diabetes. In type 2 diabetes patients, increased sinus fat volume was significantly associated with urinary albumin-to-creatinine ratio.

CONCLUSION

Renal sinus fat volume is positively associated with several metabolic risk factors including HbA1c level and urinary albumin-to-creatinine ratio in type 2 diabetes patients, indicating a potential role of renal sinus fat in the development of diabetic nephropathy. Future studies are needed to investigate whether sinus fat volume can serve as an early biomarker for diabetic nephropathy.

Donor-Recipient BSA Matching Is Prognostically Significant in Solitary and En Bloc Kidney Transplantation From Pediatric Circulatory Death Donors

Background.

As the rate of early postoperative complications decline after transplant with pediatric donation after circulatory death (DCD) kidneys, attention has shifted to the long-term consequences of donor–recipient (D-R) size disparity given the pernicious systemic effects of inadequate functional nephron mass.

Methods.

We conducted a retrospective cohort study using Organ Procurement and Transplantation Network data for all adult (aged ≥18 y) recipients of pediatric (aged 0–17 y) DCD kidneys in the United States from January 1, 2004 to March 10, 2020.

Results.

DCD pediatric allografts transplanted between D-R pairs with a body surface area (BSA) ratio of 0.10–0.70 carried an increased risk of all-cause graft failure (relative risk [RR], 1.36; 95% confidence interval [CI], 1.10–1.69) and patient death (RR, 1.32; 95% CI, 1.01–1.73) when compared with pairings with a ratio of >0.91. Conversely, similar graft and patient survivals were demonstrated among the >0.70–0.91 and >0.91 cohorts. Furthermore, we found no difference in death-censored graft survival between all groups. Survival analysis revealed improved 10-y patient survival in recipients of en bloc allografts (P = 0.02) compared with recipients of single kidneys with D-R BSA ratios of 0.10–0.70. A similar survival advantage was demonstrated in recipients of solitary allografts with D-R BSA ratios >0.70 compared with the 0.10–0.70 cohort (P = 0.02).

Conclusions.

Inferior patient survival is likely associated with systemic sequelae of insufficient renal functional capacity in size-disparate DCD kidney recipients, which can be overcome by appropriate BSA matching or en bloc transplantation. We therefore suggest that in DCD kidney transplantation, D-R BSA ratios of 0.10–0.70 serve as criteria for en bloc allocation or alternative recipient selection to optimize the D-R BSA ratio to >0.70.

Perirenal Adipose Tissue-Current Knowledge and Future Opportunities

The perirenal adipose tissue (PRAT), a component of visceral adipose tissue, has been recently recognized as an important factor that contributes to the maintenance of the cardiovascular system and kidney homeostasis. PRAT is a complex microenvironment consisting of a mixture of white adipocytes and dormant and active brown adipocytes, associated with predipocytes, sympathetic nerve endings, vascular structures, and different types of inflammatory cells. In this review, we summarize the current knowledge about PRAT and discuss its role as a major contributing factor in the pathogenesis of hypertension, obesity, chronic renal diseases, and involvement in tumor progression. The new perspectives of PRAT as an endocrine organ and recent knowledge regarding the possible activation of dormant brown adipocytes are nowadays considered as new areas of research in obesity, in close correlation with renal and cardiovascular pathology. Supplementary PRAT complex intervention in tumor progression may reveal new pathways involved in carcinogenesis and, implicitly, may identify additional targets for tailored cancer therapy.

Perirenal Adipose Tissue Inflammation: Novel Insights Linking Metabolic Dysfunction to Renal Diseases

A healthy adipose tissue (AT) is indispensable to human wellbeing. Among other roles, it contributes to energy homeostasis and provides insulation for internal organs. Adipocytes were previously thought to be a passive store of excess calories, however this view evolved to include an endocrine role. Adipose tissue was shown to synthesize and secrete adipokines that are pertinent to glucose and lipid homeostasis, as well as inflammation. Importantly, the obesity-induced adipose tissue expansion stimulates a plethora of signals capable of triggering an inflammatory response. These inflammatory manifestations of obese AT have been linked to insulin resistance, metabolic syndrome, and type 2 diabetes, and proposed to evoke obesity-induced comorbidities including cardiovascular diseases (CVDs). A growing body of evidence suggests that metabolic disorders, characterized by AT inflammation and accumulation around organs may eventually induce organ dysfunction through a direct local mechanism. Interestingly, perirenal adipose tissue (PRAT), surrounding the kidney, influences renal function and metabolism. In this regard, PRAT emerged as an independent risk factor for chronic kidney disease (CKD) and is even correlated with CVD. Here, we review the available evidence on the impact of PRAT alteration in different metabolic states on the renal and cardiovascular function. We present a broad overview of novel insights linking cardiovascular derangements and CKD with a focus on metabolic disorders affecting PRAT. We also argue that the confluence among these pathways may open several perspectives for future pharmacological therapies against CKD and CVD possibly by modulating PRAT immunometabolism.

Nephroprotective effects of GLP-1 receptor agonists: where do we stand?

Glucagon-like peptide (GLP)-1 receptor agonists are the cornerstone in the treatment of hyperglycemia in many people suffering from type 2 diabetes (T2D). These drugs have potent glucose-lowering actions and, additionally, lower body weight through satiety induction while reducing blood pressure and dyslipidemia. Partly through these actions, GLP-1 receptor agonism was shown to reduce cardiovascular disease (CVD) in people with T2D with previous CVD or at high-risk thereof. In these cardiovascular safety trials, in secondary or exploratory analyses, GLP-1 receptor agonists were also shown to reduce macro-albuminuria, an accepted surrogate marker for diabetic kidney disease (DKD), a condition that still represents a major unmet medical need. In this review we will discuss the evidence which suggests renoprotection induced by GLP-1 receptor agonists and the potential mechanisms that may be involved. These include mitigation of hyperglycemia, overweight and insulin resistance, systemic and glomerular hypertension, dyslipidemia, sodium retention, inflammation and renal hypoxia. The recently initiated large-sized FLOW trial investigating the effects of semaglutide on hard renal outcomes in patients with DKD will provide clarity whether GLP-1 receptor agonists may reduce the burden of DKD in addition to their other beneficial metabolic and cardiovascular effects.

Multiparametric Renal MRI: An Intrasubject Test-Retest Repeatability Study

Background

Renal multiparametric magnetic resonance imaging (MRI) is a promising tool for diagnosis, prognosis, and treatment monitoring in kidney disease.

Purpose

To determine intrasubject test–retest repeatability of renal MRI measurements.

Study Type

Prospective.

Population

Nineteen healthy subjects aged over 40 years.

Field Strength/Sequences

T₁ and T₂ mapping, R₂* mapping or blood oxygenation level‐dependent (BOLD) MRI, diffusion tensor imaging (DTI), and intravoxel incoherent motion (IVIM) diffusion‐weighted imaging (DWI), 2D phase contrast, arterial spin labelling (ASL), dynamic contrast enhanced (DCE) MRI, and quantitative Dixon for fat quantification at 3T.

Assessment

Subjects were scanned twice with ~1 week between visits. Total scan time was ~1 hour. Postprocessing included motion correction, semiautomated segmentation of cortex and medulla, and fitting of the appropriate signal model.

Statistical Test

To assess the repeatability, a Bland–Altman analysis was performed and coefficients of variation (CoVs), repeatability coefficients, and intraclass correlation coefficients were calculated.

Results

CoVs for relaxometry (T₁, T₂, R₂*/BOLD) were below 6.1%, with the lowest CoVs for T₂ maps and highest for R₂*/BOLD. CoVs for all diffusion analyses were below 7.2%, except for perfusion fraction (F_P), with CoVs ranging from 18–24%. The CoV for renal sinus fat volume and percentage were both around 9%. Perfusion measurements were most repeatable with ASL (cortical perfusion only) and 2D phase contrast with CoVs of 10% and 13%, respectively. DCE perfusion had a CoV of 16%, while single kidney glomerular filtration rate (GFR) had a CoV of 13%. Repeatability coefficients (RCs) ranged from 7.7–87% (lowest/highest values for medullary mean diffusivity and cortical F_P, respectively) and intraclass correlation coefficients (ICCs) ranged from −0.01 to 0.98 (lowest/highest values for cortical F_P and renal sinus fat volume, respectively).

Data Conclusion

CoVs of most MRI measures of renal function and structure (with the exception of F_P and perfusion as measured by DCE) were below 13%, which is comparable to standard clinical tests in nephrology.

Level of Evidence

2

Technical Efficacy

Stage 1

Associations of Perirenal Fat Thickness with Renal and Systemic Calcified Atherosclerosis

BACKGROUND

We investigated associations between perirenal fat thickness and atherosclerotic calcification in six different vascular beds.

METHODS

Using a community-based cohort (n=3,919), perirenal fat thickness was estimated from computed tomography scans. It was classified as Q1 (the lowest quartile) to Q4 (the highest quartile) in each sex. Calcification in the carotid arteries, coronary arteries, thoracic aorta, abdominal aorta, iliac arteries, and renal arteries was evaluated.

RESULTS

Perirenal fat thickness was associated with older age (P<0.01) and a higher prevalence of obesity, hypertension, and dyslipidemia (P<0.01 for all). Perirenal fat thickness was independently associated with renal arterial calcification even after adjustment for age, sex, body mass index, hypertension, dyslipidemia, smoking history, and family history of heart diseases in first-degree relatives (odds ratio [OR] per quartile of perirenal fat thickness, 1.25; 95% confidence interval [CI], 1.09 to 1.44). Compared to Q1, the odds of renal arterial calcification in Q4 was about two times higher (OR, 2.05; 95% CI, 1.29 to 3.25). After adjustment for renal arterial calcification and atherosclerotic risk factors, the only other vascular bed where perirenal fat thickness showed a significant association with calcification was the abdominal aorta (OR, 1.11; 95% CI, 1.00 to 1.23; P=0.045).

CONCLUSION

Perirenal fat thickness was independently associated with vascular calcification in the renal artery and abdominal aorta.

Metabolic Surgery to Treat Obesity in Diabetic Kidney Disease, Chronic Kidney Disease, and End-Stage Kidney Disease; What Are the Unanswered Questions?

Obesity is a major factor in contemporary clinical practice in nephrology. Obesity accelerates the progression of both diabetic and non-diabetic chronic kidney disease and, in renal transplantation, both recipient and donor obesity increase the risk of allograft complications. Obesity is thus a major driver of renal disease progression and a barrier to deceased and living donor kidney transplantation. Large observational studies have highlighted that metabolic surgery reduces the incidence of albuminuria, slows chronic kidney disease progression, and reduces the incidence of end-stage kidney disease over extended follow-up in people with and without type 2 diabetes. The surgical treatment of obesity and its metabolic sequelae has therefore the potential to improve management of diabetic and non-diabetic chronic kidney disease and aid in the slowing of renal decline toward end-stage kidney disease. In the context of patients with end-stage kidney disease, although complications of metabolic surgery are higher, absolute event rates are low and it remains a safe intervention in this population. Pre-transplant metabolic surgery increases access to kidney transplantation in people with obesity and end-stage kidney disease. Metabolic surgery also improves management of metabolic complications post-kidney transplantation, including new-onset diabetes. Procedure selection may be critical to mitigate the risks of oxalate nephropathy and disruption to immunosuppressant pharmacokinetics. Metabolic surgery may also have a role in the treatment of donor obesity, which could increase the living kidney donor pool with potential downstream impact on kidney paired exchange programmes. The present paper provides a comprehensive coverage of the literature concerning renal outcomes in clinical studies of metabolic surgery and integrates findings from relevant mechanistic pre-clinical studies. In so doing the key unanswered questions for the field are brought to the fore for discussion.

The Relationship between Perirenal Fat Thickness and Reduced Glomerular Filtration Rate in Patients with Type 2 Diabetes

BACKGROUND

Obesity has been considered as an important factor in the development and progression of chronic kidney diseases (CKD). Perirenal fat, which is surrounding the kidneys, has been reported to be unique in anatomy and biological functions. This study is aimed at assessing the relationship between perirenal fat thickness (PrFT) and estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes (T2DM).

METHODS

A total of 171 patients with T2DM were recruited in the study. The basic and clinical characteristics including sex, age, diabetes duration, body mass index (BMI), waist circumference (WC), visceral fat area (VFA), glycated hemoglobin (HbA1c), serum uric acid (UA), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), and high-density lipoprotein cholesterol (HDL-c) were collected. PrFT was measured via ultrasound. eGFR was calculated using the Modification of Diet in Renal Disease (MDRD) formula.

RESULTS

Patients were divided into three groups according to PrFT, and we found patients with higher PrFT had lower eGFR. PrFT was significantly correlated with eGFR in all patients (r = -0.181, P < 0.05). Subgroup analysis by sex showed that PrFT still significantly and negatively related to eGFR in men (r = -0.264, P < 0.05), but not in women (r = -0.199, P = 0.062). The association also existed in multivariate analysis after correction for the confounding factors (β = -0.203, P = 0.017).

CONCLUSIONS

This study confirmed a negative independent relationship between PrFT and eGFR in patients with T2DM, especially in men, suggesting a possible role of perirenal fat in kidney dysfunction in T2DM patients.