Sonographic evaluation of para- and perirenal fat thickness is an independent predictor of early kidney damage in obese patients

Ultrasound innovations in abdominal radiology: techniques and clinical applications in pediatric imaging

Contrast-enhanced ultrasound, microvascular imaging, elastography, and fat quantification have varying degrees of utility, with some applications in the pediatric setting mirroring that in adults and having unique uses when applied to children in others. This review will present novel ultrasound technologies and the clinical context in which they are applied to the pediatric abdomen. New ultrasound technologies have a broad range of applications in clinical practice and represent a powerful diagnostic tool with the potential to replace other imaging modalities, such as magnetic resonance imaging and computed tomography, in specific cases.

Comprehensive assessment of distinct abdominal fat compartments beyond liver content in overweight/obese patients using MRI and ultrasound imaging

BACKGROUND

Ectopic fat deposition, involving lipid infiltration within organs and fat accumulating surrounding organs, plays a crucial role in the development of metabolic abnormalities in obesity. Current imaging measurements of obesity primarily focus on lipid infiltration within liver, neglecting fat deposition in other areas. This study aims to explore the methods of measuring and correlating different types of abdominal ectopic fat deposition in obese patients using magnetic resonance imaging (MRI) and ultrasound techniques, and to investigate the relationship between these fat parameters and obesity-related metabolic markers.

METHODS

Abdominal ectopic fat deposition including liver fat content, mesenteric fat thickness (MFT), perirenal fat thickness (PrFT) and preperitoneal fat thickness (PFT) were measured in 220 overweight/obese patients using both MRI and ultrasound techniques. Correlation analysis validated the concordance of fat parameters at specific sites between the two imaging methods and identified the cutoff values of hepatic attenuation coefficient (AC) for diagnosis of liver steatosis. Additionally, we investigated the correlation between fat parameters by both methods and obesity-related metabolic markers.

RESULTS

Ultrasonic measurement of PrFT and hepatic AC both had high correlation with PrFT (r = 0.829, p < 0.001) and hepatic Proton-density fat fraction (PDFF, r = 0.822, p < 0.001) measured via MR. Hepatic AC cutoff values for diagnosing mild, moderate, and severe fatty liver were 0.705 dB/cm/MHz (AUC = 0.922), 0.755 dB/cm/MHz (AUC = 0.923), and 0.875 dB/cm/MHz (AUC = 0.890) respectively. Hepatic AC correlated significantly with AST and ALT (r = 0.477 ~ 0.533, p < 0.001). MFT measured by ultrasound were positively associated with glycated hemoglobin (r = 0.324 ~ 0.371, p < 0.001) and serum triglyceride levels (r = 0.303 ~ 0.353, p < 0.001). PrFT measured by both methods showed significant positive correlations with serum creatinine levels (r = 0.305 ~ 0.308, p < 0.001).

CONCLUSIONS

Both MRI and ultrasound demonstrate metabolic correlations in quantifying mesenteric, hepatic, and perirenal fat. In addition to assessment of liver fat content, the measurements of ectopic fat deposition by MRI or ultrasound are a simple and crucial way for comprehensive fat evaluation in individuals with overweight/obesity.

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.

Transcriptome analysis reveals selectively high expression of beige adipocyte marker genes in mouse perinephric fat

To reveal the differences in the properties of visceral adipose tissue in healthy unstimulated mice, we performed transcriptome analysis using RNA sequencing. Among visceral adipose tissues, perinephric adipose tissue was found to exclusively express beige adipocyte markers while expressing white adipocyte markers. These results imply potential specific roles of perinephric adipose tissue in both physiological and pathological conditions.

Perirenal Adipose Tissue: Clinical Implication and Therapeutic Interventions

Perirenal adipose tissue (PRAT) has been identified as an important factor in local and general homeostasis of the human body and is especially important in regulating renal and cardiovascular functions. It has also been identified as a crucial risk factor to consider in cardiovascular and renal disorders, malignancies, and various other diseases. Having a concrete idea of the effects of therapeutic interventions on the size and metabolism of the PRAT could prove highly beneficial. This review summarizes what is known about the PRAT and provides a collection of studies on the effects of therapeutic interventions on PRAT and its related diseases. We used papers written on a variety of subjects, mainly concerning adipose tissue and the effects of therapeutic procedures on it. Our main challenge was to excerpt the information specifically related to the PRAT in these papers. These effects vary greatly, from an increase or decrease in mass or size of the PRAT to changes in metabolism and drug residue accumulation. The current studies often fail to consider PRAT as an individual subject of research and only examine the adipose tissue of the entire body as a whole. This leads us to believe this field could benefit greatly from further research.

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.

New Perspectives on Obesity-Associated Nephropathy from Pathophysiology to Therapeutics: Revealing the Promise of GLP-1 RA Therapy

Obesity represents a substantial risk factor for a multitude of metabolic disorders, which seriously threatens human life and health. As the global obesity epidemic intensifies, obesity-related nephropathy (ORN) has attracted great attention. ORN arises from both physical/mechanical and non-physical insults to the glomerular and tubular structures precipitated by obesity, culminating in structural impairments and functional aberrations within the kidneys. Physical injury factors include changes in renal hemodynamics, renal compression, and mechanical stretching of podocytes. Non-physical injury factors include overactivation of the RAAS system, insulin resistance, lipotoxicity, inflammation, and dysregulation of bile acid metabolism. Exploring molecules that target modulation of physical or nonphysical injury factors is a potential approach to ORN treatment. ORN is characterized clinically by microproteinuria and pathologically by glomerulomegaly, which is atypical and makes early diagnosis difficult. Investigating early diagnostic markers for ORN thus emerges as a critical direction for future research. Additionally, there is no specific drug for ORN in clinical treatment, which mainly focuses on weight reduction, mitigating proteinuria, and preserving renal function. In our review, we delineate a progressive therapeutic approach involving enhancements in lifestyle, pharmacotherapy, and bariatric surgery. Our emphasis underscores glucagon-like peptide-1 receptor agonists (GLP-1 RAs) as poised to emerge as pivotal therapeutic modalities for ORN in forthcoming clinical avenues.

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.

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.

The potential mechanisms underlying the modulating effect of perirenal adipose tissue on hypertension: Physical compression, paracrine, and neurogenic regulation

Hypertension, a prevalent global cardiovascular disease, affects approximately 45.4 % of adults worldwide. Despite advances in therapy, hypertension continues to pose a significant health risk due to inadequate management. It has been established that excessive adiposity contributes majorly to hypertension, accounting for 65 to 75 % of primary cases. Fat depots can be categorised into subcutaneous and visceral adipose tissue based on anatomical and physiological characteristics. The metabolic impact and the risk of hypertension are determined more significantly by visceral fat. Perirenal adipose tissue (PRAT), a viscera enveloping the kidney, is known for its superior vascularisation and abundant innervation. Although traditionally deemed as a mechanical support tissue, recent studies have indicated its contributing potential to hypertension. Hypertensive patients tend to have increased PRAT thickness compared to those without, and there is a positive correlation between PRAT thickness and elevated systolic blood pressure. This review encapsulates the anatomical characteristics and biogenesis of PRAT. We provide an overview of the potential mechanisms where PRAT may modulate blood pressure, including physical compression, paracrine effects, and neurogenic regulation. PRAT has become a promising target for hypertension management, and continuous effort is required to further explore the underlying mechanisms.

The role of irisin in kidney diseases

Irisin is a hormone that is produced mainly by skeletal muscles in response to exercise. It has been found to have a close correlation with obesity and diabetes mellitus for its energy expenditure and metabolic properties. Recent research has revealed that irisin also possesses anti-inflammatory, anti-oxidative and anti-apoptotic properties, which make it associated with major chronic diseases, such as chronic kidney disease (CKD), liver diseases, osteoporosis, atherosclerosis and Alzheimer s disease. The identification of irisin has not only opened up new possibilities for monitoring metabolic and non-metabolic diseases but also presents a promising therapeutic target due to its multiple biological functions. Studies have shown that circulating irisin levels are lower in CKD patients than in non-CKD patients and decrease with increasing CKD stage. Furthermore, irisin also plays a role in many CKD-related complications like protein energy wasting (PEW), cardiovascular disease (CVD) and chronic kidney disease-mineral and bone disorder (CKD-MBD). In this review, we present the current knowledge on the role of irisin in kidney diseases and their complications.

Finerenone protects against progression of kidney and cardiovascular damage in a model of type 1 diabetes through modulation of proinflammatory and osteogenic factors

The non-steroidal mineralocorticoid receptor antagonist (MRA) finerenone (FIN) improves kidney and cardiovascular outcomes in patients with chronic kidney disease (CKD) in type 2 diabetes (T2D). We explored the effect of FIN in a novel model of type 1 diabetic Munich Wistar Frömter (MWF) rat (D) induced by injection of streptozotocin (15 mg/kg) and additional exposure to a high-fat/high-sucrose diet. Oral treatment with FIN (10 mg/kg/day in rat chow) in diabetic animals (D-FIN) was compared to a group of D rats receiving no treatment and a group of non-diabetic untreated MWF rats (C) (n = 7-10 animals per group). After 6 weeks, D and D-FIN exhibited significantly elevated blood glucose levels (271.7 ± 67.1 mg/dl and 266.3 ± 46.8 mg/dl) as compared to C (110.3 ± 4.4 mg/dl; p < 0.05). D showed a 10-fold increase of kidney damage markers Kim-1 and Ngal which was significantly suppressed in D-FIN. Blood pressure, pulse wave velocity (PWV) and arterial collagen deposition were lower in D-FIN, associated to an improvement in endothelial function due to a reduction in pro-contractile prostaglandins, as well as reactive oxygen species (ROS) and inflammatory cytokines (IL-1, IL-6, TNFα and TGFβ) in perivascular and perirenal adipose tissue (PVAT and PRAT, respectively). In addition, FIN restored the imbalance observed in CKD between the procalcifying BMP-2 and the nephroprotective BMP-7 in plasma, kidney, PVAT, and PRAT. Our data show that treatment with FIN improves kidney and vascular damage in a new rat model of DKD with T1D associated with a reduction in inflammation, fibrosis and osteogenic factors independently from changes in glucose homeostasis.

Upregulation in Inflammation and Collagen Expression in Perirenal but Not in Mesenteric Adipose Tissue from Diabetic Munich Wistar Frömter Rats

Perirenal adipose tissue (PRAT) surrounding the kidney is emerging as a player and novel independent risk factor in diabetic kidney disease (DKD); DKD is a complication of diabetes and is a major cause of increased cardiovascular (CV) risk and CV mortality in affected patients. We determined the effect of diabetes induction on (i) kidney and CV damage and (ii) on the expression of proinflammatory and profibrotic factors in both the PRAT and the mesenteric adipose tissue (MAT) of Munich Wistar Frömter (MWF) rats. The 16-week-old male MWF rats (n = 10 rats/group) were fed standard chow (MWF-C) or a high-fat/high-sucrose diet for 6 weeks together with low-dose streptozotocin (15 mg/kg i.p.) at the start of dietary exposure (MWF-D). Phenotyping was performed at the end of treatment through determining water intake, urine excretion, and oral glucose tolerance; use of the homeostatic model assessment-insulin resistance index (HOMA-IR) evidenced the development of overt diabetes manifestation in MWF-D rats. The kidney damage markers Kim-1 and Ngal were significantly higher in MWF-D rats, as were the amounts of PRAT and MAT. A diabetes-induced upregulation in IL-1, IL-6, Tnf-α, and Tgf-β was observed in both the PRAT and the MAT. Col1A1 was increased in the PRAT but not in the MAT of MWF-D, whereas IL-10 was lower and higher in the PRAT and the MAT, respectively. Urinary albumin excretion and blood pressure were not further increased by diabetes induction, while heart weight was higher in the MWF-D. In conclusion, our results show a proinflammatory and profibrotic in vivo environment in PRAT induced by diabetes which might be associated with kidney damage progression in the MWF strain.

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.

Clinical and Imaging Parameters Associated With Impaired Kidney Function in Patients With Acute Decompensated Heart Failure With Reduced Ejection Fraction

BACKGROUND

Acute worsening of cardiac function frequently leads to kidney dysfunction. This study aimed to identify clinical and imaging parameters associated with impaired kidney function in patients with acute decompensated heart failure with reduced ejection fraction (HFrEF).

METHODS

Data from 131 patients hospitalized with acute decompensated HFrEF (left ventricular ejection fraction, < 40%) were analyzed. Patients were divided into two groups according to the glomerular filtration rate (GFR) at admission (those with preserved kidney function [GFR ≥ 60 mL/min/1.73 m²] and those with reduced kidney function [GFR < 60 mL/min/1.73 m²]). Various echocardiographic parameters and perirenal fat thicknesses were assessed by computed tomography.

RESULTS

There were 71 patients with preserved kidney function and 60 patients with reduced kidney function. Increased age (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.04-1.12; p = 0.005), increased log N-terminal pro b-type natriuretic peptide (OR, 1.74; 95% CI, 1.14-2.66; p = 0.010), and increased perirenal fat thickness (OR, 1.19; 95% CI, 1.10-1.29; p < 0.001) were independently associated with reduced kidney function, even after adjusting for variable clinical and echocardiographic parameters. The optimal average perirenal fat thickness cut-off value of > 12 mm had a sensitivity of 55% and specificity of 83% for kidney dysfunction prediction.

CONCLUSIONS

Thick perirenal fat was independently associated with impaired kidney function in patients hospitalized for acute decompensated HFrEF. Measurement of perirenal fat thickness may be a promising imaging marker for the detection of HFrEF patients who are more susceptible to kidney dysfunction.

Kidney Considerations in Pediatric Obesity

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is a common condition and a major cause of morbidity and mortality in adults, but children and adolescents are also at risk for early kidney injury and development of CKD. Obesity contributes both directly and indirectly to the development of CKD. The purpose of this review is to describe obesity-related kidney disease (ORKD) and diabetic kidney disease (DKD) and their impact in the pediatric population.

RECENT FINDINGS

Although obesity-related CKD in childhood and adolescence is uncommon, nascent kidney damage may magnify the lifetime risk of CKD. Glomerular hyperfiltration is an early phenotype of both ORKD and DKD and typically manifests prior to albuminuria and progressive decline in GFR. Novel treatments for obesity and type 2 diabetes exerting protective effects on the kidneys are being investigated for use in the pediatric population. It is important to understand the impact of obesity on the kidneys more fully in the pediatric population to help detect injury earlier and intervene prior to the onset of irreversible progression of disease and to guide future research in this area.

Role of dysfunctional peri-organ adipose tissue in metabolic disease

Metabolic disease is a complex disorder defined by a group with interrelated factors. There is growing evidence that obesity can lead to a variety of metabolic diseases, including diabetes and cardiovascular disease. Excessive adipose tissue (AT) deposition and ectopic accumulation can lead to increased peri-organ AT thickness. Dysregulation of peri-organ (perivascular, perirenal, and epicardial) AT is strongly associated with metabolic disease and its complications. The mechanisms include secretion of cytokines, activation of immunocytes, infiltration of inflammatory cells, involvement of stromal cells, and abnormal miRNA expression. This review discusses the associations and mechanisms by which various types of peri-organ AT affect metabolic diseases while addressing it as a potential future treatment strategy.

Folate Deficiency Enhanced Inflammation and Exacerbated Renal Fibrosis in High-Fat High-Fructose Diet-Fed Mice

The prevalence of obesity and chronic kidney disease (CKD) is increasing simultaneously and rapidly worldwide. Our previous study showed that folate deficiency increased lipid accumulation and leptin production of adipocytes. Whether folate plays a role in CKD, particularly obesity-related nephropathy remains unclear. To investigate the effects of folate deficiency on CKD in diet-induced obese mice, four groups of male C57BL/6 mice were fed either a normal-fat diet (NF) with folate (NF+f); NF without folate (NF-f); high-fat high-fructose diet (HFF) with folate (HFF+f); or HFF without folate (HFF-f) for 12 months during the study. The results showed that HFF increased not only body weight, fasting blood glucose, total cholesterol (TC), low-density lipoprotein (LDL)-cholesterol, and blood pressure, but also cytokines levels, such as interleukin (IL)-2, interferon (IFN)-γ, IL-17A/F, IL-6, monocyte chemoattractant protein (MCP)-1, and transforming growth factor (TGF)-β1. The indicators of kidney failure including urinary protein, neutrophil gelatinase-associated lipocalin (NGAL), renal type I and IV collagen deposits and leptin content, and serum creatinine were also increased by HFF. Folate-deficient diets further elevated serum TC, LDL-cholesterol, IL-6, tumor necrosis factor (TNF)-α, MCP-1, TGF-β1, and leptin, but decreased IL-10 level, and thus exacerbated renal fibrosis. To investigate the possible mechanisms of folate deficiency on renal injury, phosphorylation of pro-fibrosis signaling molecules, including signal transducer and activator of transcription (STAT)3 and small mothers against decapentaplegic (Smad)2/3, were assayed. Both HFF and folate deficiency significantly increased the phosphorylation of STAT3 and Smad2/3, suggesting synergistic effects of HFF-f on chronic renal inflammation and fibrosis. In conclusion, the results demonstrated that folate deficiency might aggravate inflammatory status and enhance renal fibrosis.

Diagnostic performance of hypoechoic perinephric fat as a predictor of prediabetes and diabetes

PURPOSE

To evaluate prevalence and predictive value of hypoechoic perinephric fat (HPF) in patients with prediabetes and diabetes compared to non-diabetics.

METHODS

Of 240 patients with renal ultrasound and hemoglobin A1c (HbA1c) measurements, 114 patients had either prediabetes (HbA1c 5.7-6.4%) or diabetes (HbA1c ≥ 6.5%), and 126 patients did not. Two radiologists (blinded to diagnosis) reviewed images and discrepancies were resolved by a third. Inter-reader agreement was compared using free-marginal kappa and intraclass correlation coefficient. Fisher's exact test, Mann-Whitney test, multivariable logistic regression, and Spearman's rank correlation test with two-tailed p < 0.05 were used to determine statistical significance.

RESULTS

HPF was exclusively identified in prediabetic and diabetic patients with a prevalence of 23% (vs 0%; p < 0.001). Identification of HPF had almost perfect inter-reader agreement (k = 0.94) and was statistically significant (p = 0.034) while controlling for body mass index (BMI) and estimated glomerular filtration rate in multivariable analysis. HPF had extremely high specificity and positive predictive value (100% for both) in patients with prediabetes and diabetes although it was not a sensitive finding (23% sensitivity). In patients with prediabetes and diabetes, those with HPF were statistically significantly more likely to have chronic kidney disease (CKD) (p = 0.003). There was no statistically significant difference in BMI, stages of CKD, and types of diabetes.

CONCLUSION

Hypoechoic perirenal fat has almost perfect inter-reader agreement and is highly specific for and predictive of prediabetes and diabetes. Its presence may also help identify those with chronic kidney disease among prediabetic and diabetic patients.

Irisin protects against obesity-related chronic kidney disease by regulating perirenal adipose tissue function in obese mice

BACKGROUND

Compared with typical visceral fat deposits in obesity and metabolic syndrome, perirenal adipose tissue (PRAT) dysfunction is more closely linked to obesity-related chronic kidney disease (OB-CKD). The myokine irisin reportedly promotes positive outcomes in metabolic disease. This study investigated whether irisin could reduce urinary albumin excretion and demonstrate renoprotective effects through the regulation of PRAT function in obese mice.

METHODS

C57BL/6 J mice received a high-fat diet (HFD) with or without concurrent administration of irisin. Glucose tolerance, plasma levels of free fatty acids, and urinary albumin excretion were assessed, along with renal morphology. The vascular endothelial growth factor and nitric oxide in glomeruli were also analyzed, in addition to PRAT function-associated proteins.

RESULTS

Irisin administration significantly reduced the final body weight, fat mass, and free fatty acids, without reducing PRAT mass, in HFD mice. Furthermore, irisin decreased urinary albumin excretion and attenuated both renal fibrosis and lipid accumulation. Irisin administration led to increases in PRAT function-associated proteins, including sirtuin1, uncoupling protein-1, and heme-oxygenase-1. Ex vivo treatment of PRAT and glomeruli with irisin also restored PRAT function. Finally, irisin treatment restored the vascular endothelial growth factor-nitric oxide axis.

CONCLUSIONS

Irisin attenuated metabolic disorders and protected against OB-CKD by normalizing the PRAT-kidney axis. These results suggest that agents targeting PRAT activation might be useful for treatment of OB-CKD.

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.

Pararenal Fat and Renal Dysfunction in Patients without Significant Cardiovascular Disease

INTRODUCTION

Accumulation of fat tissue around the kidneys is considered to be a risk factor for chronic kidney disease (CKD). The objective of the study was to investigate the association of pararenal fat tissue (PRFT) and renal dysfunction in patients without clinically significant cardiovascular diseases (CVDs).

METHODS

The study included 320 patients without CVDs (mean age 63.8 ± 13.9 years). All patients underwent anthropometric measurements, standard biochemical blood tests, including a lipid panel and uric acid concentration. Glomerular filtration rate (GFR) was calculated using the CKD-EPI formula. All patients underwent computed tomography of the abdomen with measurement of the PRFT thickness. The research results were processed using StatSoftStatistica 10.0 software.

RESULTS

The average PRFT thickness was 1.45 cm [0.9; 2.0]. It was significantly higher in obese individuals when compared with patients with normal body weight (1.9 cm [1.3; 2.6] vs. 1.0 cm [0.6; 1.7]) and overweight people (1.9 cm [1.3; 2.6] vs. 1.1 cm [0.8; 1.6]) (p < 0.001). GFR was significantly higher in subjects with normal body weight when compared with obese patients (72 mL/min/1.73 m2 [59; 83] vs. 61 mL/min/1.73 m2 [51; 70]) and overweight patients (72 mL/min/1.73 m2 [59; 83] vs. 61 mL/min/1.73 m2 [54; 72]) (p < 0.001). PRFT thickness was significantly higher in patients with stage 3 CKD when compared with those with stage 1 CKD (2.2 cm [1.6; 3.3] vs. 0.9 cm [0.9; 1.0]) and with stage 2 CKD (2.2 cm [1.6; 3.3] vs. 1.3 cm [0.9; 1.8]) (p < 0.001). A significant correlation was found between PRFT thickness and body mass index (r = 0.49, p < 0.05), waist circumference (r = 0.55, p < 0.05), GFR (r = -0.47, p < 0.05), and uric acid level (r = 0.46, p < 0.05). Multiple linear regression analysis revealed a significant relationship between GFR and age (β ± SE -0.43 ± 0.15, p = 0.01), PRFT thickness (β ± SE -0.38 ± 0.14, p = 0.01) and with the level of low-density lipoprotein cholesterol (β ± SE -0.32 ± 0.12, p = 0.01). Logistic regression analysis showed that the risk of renal dysfunction development was associated with PRFT thickness (OR = 6.198; 95% CI: 1.958-19.617; p < 0.05). ROC analysis determined the threshold values of PRFT thickness (>1.68 cm, AUC = 0.875), above which the development of renal dysfunction can be predicted (sensitivity 63.2%, specificity 93.4%).

CONCLUSION

The results of our study indicate the relationship between PRFT and visceral obesity and renal dysfunction in patients without clinically significant CVDs.

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.

Metabolism Score for Visceral Fat (METS-VF): A New Predictive Surrogate for CKD Risk

PURPOSE

Metabolic disorders are closely related to the occurrence and development of chronic kidney disease (CKD). We explored the prospective association between the Metabolic Score for Visceral Fat (METS-VF) and CKD in a 5-year follow-up study.

PATIENTS AND METHODS

In this cohort study, 631 adults not suffering from CKD from Wanzhai Town, in China in 2012 were included at baseline and followed up in 2017 and 2018. Multivariable logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between METS-VF and CKD risk. Area under the receiver operating characteristic curve (AUC) analyses were used to evaluate the ability of METS-VF, waist-to-height ratio (WhtR), visceral adiposity index (VAI), homeostatic model assessment of insulin resistance (HOMA-IR), body mass index (BMI) to predict CKD risk.

RESULTS

We identified 103 CKD cases during follow-up. After adjustment for confounding factors, comparing the lowest quartile of METS-VF, the OR (95% CI) of CKD risk in the highest quartile was 3.04 (1.39-6.64). The per Standard deviation (SD) increase in METS-VF was positively correlated with CKD risk. The AUC of METS-VF for predicting CKD risk was, in general, higher than that for WhtR, VAI, HOMA-IR, and BMI.

CONCLUSION

METS-VF may be an indicator for predicting CKD risk.

Perirenal Fat Volume Is Positively Associated With Serum Uric Acid Levels in Chinese Adults

BACKGROUND

Visceral fat has been considered an important risk factor of elevated serum uric acid (SUA). Perirenal fat is a unique visceral fat around the kidneys that has special morphological and physiological features while its relationship with SUA remains incompletely elucidated. This study aimed to assess the association between perirenal fat volume (PrFV) and SUA.

METHODS

A cross-sectional study was conducted in 102 subjects aged ≥ 18 years old recruited from Nanjing,China. The clinical characteristics including age, sex, drinking behavior, history of hypertension, body mass index, waist circumference, total cholesterol, fast plasma glucose, urea, serum creatinine, C-reactive protein, and SUA were recorded. PrFV was measured by ultrasonography. Multivariate linear models and the restricted cubic spline were used to investigate the association between PrFV and SUA.

RESULTS

The median age of this study population was 52.5 (42.0-60.0) years and 56.9% were female. The median value of SUA was 5.73 mg/dL (4.58-6.80 mg/dL). The subjects were divided by PrFV tertiles and we found that the subjects in the highest PrFV tertile had a higher level of SUA compared to those in the lowest tertile (β=1.86, 95%CI 1.23-2.48, P for trend <0.001).The positive association also remained after adjustment for potential covariates (tertile3 versus tertile1: β=0.99, 95%CI 0.35-1.63, P for trend =0.005). There was an increase of approximately 0.53 mg/dL in SUA per 1-fold increase in PrFV (β=0.53, 95%CI 0.02-1.04, P for nonlinearity = 0.637).

CONCLUSION

Our results confirmed a positive independent relationship between PrFV and SUA in Chinese adults. This study suggested that perirenal fat might constitute a potential risk factor for elevated serum uric acid levels.

The Utility of Perirenal Fat in Determining the Risk of Onset and Progression of Diabetic Kidney Disease

BACKGROUND

Perirenal fat (PRF) has multiple effects on the kidney through its physical structure and adipocytokine-secreting ability. The present study explored the relationship between PRF thickness and the onset and progression of albuminuria in patients with diabetes.

METHODS

In the cross-sectional analysis, we screened 959 patients from 8764 subjects with type 2 diabetes mellitus (T2DM) who met the inclusion criteria and measured their perirenal fat thickness (PFT) using color Doppler ultrasound. A group of laboratory indexes were included in the analysis models. In a longitudinal study, a total of 218 patients with a baseline UACR <30 mg/g were included in the follow-up study.

RESULTS

In a cross-sectional analysis, patients with diabetes and higher PFT presented with higher albuminuria. Multiple logistic regression analysis indicated that PFT was an independent risk factor for the degree of albuminuria in patients with T2DM (odds ratio = 4.186, 95%CI: 2.290-7.653, P < 0.001). In a longitudinal study, 218 albuminuria-free patients with T2DM at the baseline were followed up for a mean of 12.3 months. Based on the cutoff value from the ROC diagnostic test in the cross-sectional study, patients were divided into two groups: higher PFT (H-PFT) and lower PFT (L-PFT). Kaplan-Meier survival curve analysis showed that H-PFT was associated with a higher incidence of albuminuria than L-PFT (log-rank test, χ2 = 4.522, P = 0.033). Cox regression analysis showed that PFT was a risk factor for the earlier onset of albuminuria (hazard ratio 2.83, 95% CI: 1.34-4.88, P < 0.001).

CONCLUSIONS

PRF evaluated by color Doppler ultrasound is an easy and reliable tool for predicting the onset and progression of albuminuria in patients with T2DM.

Cardiorenal Fat: A Cardiovascular Risk Factor With Implications in Chronic Kidney Disease

There is a growing interest in the potential role of adipose tissues in cardiac and renal pathophysiology, and determining the mechanisms by which fat compartments around the heart and kidneys influence cardiovascular disease is of clinical importance in both general and high-risk populations. Epicardial fat and perirenal fat have been associated with adverse outcomes in chronic kidney disease (CKD) patients. Epicardial fat is a rich source of free fatty acids and is capable of secreting inflammatory and pro-atherogenic cytokines that promote atherosclerosis through a local paracrine effect. Recent evidence has demonstrated that perirenal fat has a closer correlation with kidney diseases than other visceral fat deposits in obesity or metabolic disturbances. Moreover, perirenal fat has been reported as an independent risk factor for CKD progression and even associated with cardiorenal dysfunction. Accordingly, these forms of organ-specific fat deposits may act as a connecter between vascular and cardiorenal disease. This review explores the possible links between epicardial and perirenal fat and its significant role as a modulator of cardiorenal dysfunction in CKD patients.

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.

Non-alcoholic fatty kidney disease (NAFKD): A novel disease that explains the etiology of hyperuricemia and gout in metabolic syndrome

Gout is the most common inflammatory arthritis in adults. It is causally associated with intraarticular deposition of monosodium urate crystals in hyperuricemia. The commonest pathogenesis is renal under-excretion of urate in metabolic syndrome. Despite being the commonest type, the exact etiology of hyperuricemia in metabolic syndrome remains unclear. Historically, common gout was found at increased rates in affluent men, earning its name the 'disease of kings'. It is also rare in premenopausal women. The authors hypothesize that the etiology of common gout is a novel condition termed non-alcoholic fatty kidney disease (NAFKD). The hypothesis offers an explanation of the two prerequisites necessary for the development of NAFKD (that leads to hyperuricemia and gout) as follows: 1) sustained positive energy balance and 2) male sex hormone predominance state. The hypothesis presented herein could guide the prevention and early detection of hyperuricemia and support curative modalities.

Distinct associations of intraperitoneal and retroperitoneal visceral adipose tissues with metabolic syndrome and its components

BACKGROUND & AIMS

Metabolic syndrome (MS) is associated with adverse outcomes, and visceral adipose tissue (VAT) is associated with MS. Recently, VAT has been classified into intraperitoneal VAT (IVAT) and retroperitoneal VAT (RVAT). This study aimed to evaluate the association of IVAT and RVAT with the prevalence of MS or its components.

METHODS

In our cross-sectional study, the prevalence of MS or its components was analyzed in 803 middle-aged Japanese participants. The cross-sectional area of the abdominal adipose tissue was evaluated from an unenhanced computed tomography scan at the third lumbar vertebra, and IVAT or RVAT was analyzed using a specialized software. The areas were normalized for the square of the participants' height in meters and described as the IVAT or RVAT area index.

RESULTS

In age, sex, and BMI adjusted model, the IVAT, or RVAT area index was independently associated with the prevalence of MS. After simultaneous inclusion of IVAT, RVAT, and deep and superficial subcutaneous adipose tissue area indices for multivariate logistic regression analysis, the IVAT area index was found to be independently associated with the prevalence of MS (adjusted odds ratio [OR], 1.03; 95% confidence intervals [CI], 1.02-1.08) and its components, including waist circumference (OR, 1.07; 95% CI, 1.03-1.10), glucose (1.03; 1.01-1.05), triglycerides (1.03; 1.00-1.05), and high-density lipoprotein cholesterol (1.03; 1.00-1.05), whereas the RVAT area index was not. The RVAT area index was independently associated with the prevalence of component-blood pressure (1.06; 1.02-1.11), whereas the IVAT area index was not.

CONCLUSIONS

IVAT and RVAT are associated differently with the prevalence of MS and its components.

Identification of distinct transcriptome signatures of human adipose tissue from fifteen depots

The functional and metabolic characteristics of specific adipose tissue (AT) depots seem to be determined by intrinsic mechanisms. We performed a comprehensive transcriptome profiling of human AT from distinct fat depots to unravel their unique features potentially explaining molecular mechanisms underlying AT distribution and their contribution to health and disease. Post-mortem AT samples of five body donors from 15 anatomical locations were collected. Global mRNA expression was measured by Illumina® Human HT-12 v4 Expression BeadChips. Data were validated using qPCR and Western Blot in a subset of ATs from seven additional body donors. Buccal and heel AT clearly separated from the “classical” subcutaneous AT depots, and perirenal and epicardial AT were distinct from visceral depots. Gene-set enrichment analyses pointed to an inflammatory environment and insulin resistance particularly in the carotid sheath AT depot. Moreover, the epicardial fat transcriptome was enriched for genes involved in extracellular matrix remodeling, inflammation, immune signaling, coagulation, thrombosis, beigeing, and apoptosis. Interestingly, a striking downregulation of the expression of leptin receptor was found in AT from heel compared with all other AT depots. The distinct gene expression patterns are likely to define fat depot specific AT functions in metabolism, energy storage, immunity, body insulation or as cushions. Improved knowledge of the gene expression profiles of various fat depots may strongly benefit studies aimed at better understanding of the genetics and the pathophysiology of obesity and adverse body fat composition.

Peri-renal fat thickness is positively associated with the urine albumin excretion rate in patients with type 2 diabetes

BACKGROUNDS

Albuminuria, the earliest clinical manifestation of diabetic kidney disease (DKD), is a major prognostic indicator of renal progression. Obesity itself is associated with the development of DKD and accelerates its progression. Accumulation of peri-renal fat on the kidneys can damage kidney function. Measuring the perirenal fat thickness (PFT) by ultrasound is a non-invasive method to measure ectopic fat deposition on the kidney. In this study, we aim to obtain the association between albuminuria and PFT.

METHODS

Eighty-nine subjects with type 2 diabetes mellitus (T2DM) were enrolled. Albuminuria was defined as a urine albumin-to-creatinine ratio (UACR) ≧30 mg/g. Measurement of the PFT was performed by B-mode ultrasound (Toshiba SSA-680A) and determined from the surface of the abdominal musculature to the surface of kidney. Pearson correlation coefficients were determined to test the significant independent relationship between the PFT and demographic, anthropometric and laboratory parameters.

RESULTS

Patients were divided into those with (n = 66) and without (n = 23) albuminuria. PFT (odds ratio [OR], 19.3; 95% CI, 2.25-165.00; p = 0.01) was significantly correlated with albuminuria based on multiple logistic regression analysis. Additionally, linear regression confirmed that degree of albuminuria has a positive association with the PFT (r = 0.233; p = 0.03).

CONCLUSIONS

Our study showed that an increased PFT is positively associated with the albuminuria among patients with T2DM. Our findings suggest that measurement of the PFT may represent a helpful tool to assess the risk of developing albuminuria in patients with T2DM.

Novel insight into perirenal adipose tissue: A neglected adipose depot linking cardiovascular and chronic kidney disease

Obesity is associated with adverse metabolic diseases including cardiovascular disease (CVD) and chronic kidney disease (CKD). These obesity-related diseases are highly associated with excess fat accumulation in adipose tissue. However, emerging evidence indicates that visceral adiposity associates more with metabolic and cardiovascular risk factors. Perirenal adipose tissue, surrounding the kidney, is originally thought to provides only mechanical support for kidney. However, more studies demonstrated perirenal adipose tissue have a closer association with renal disease than other visceral fat deposits in obesity. Additionally, perirenal adipose tissue is also an independent risk factor for CKD and even associated more with CVD. Thus, perirenal adipose tissue may be a connection of CVD with CKD. Here, we will provide an overview of the perirenal adipose tissue, a neglected visceral adipose tissue, and the roles of perirenal adipose tissue linking with CVD and CKD and highlight the perirenal adipose tissue as a potential strategy for future therapeutics against obesity-related disease.

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.

Perirenal fat thickness is associated with metabolic risk factors in patients with chronic kidney disease

Background

Adipose tissue accumulation in specific body compartments has been associated with diabetes, hypertension and dyslipidemia. Perirenal fat (PRF) may lead to have direct lipotoxic effects on renal function and intrarenal hydrostatic pressure. This study was undertaken to explore the association of PRF with cardiovascular risk factors and different stages of chronic kidney disease (CKD).

Methods

We studied 103 patients with CKD of different stages (1 to 5). PRF was measured by B-mode renal ultrasonography in the distal third between the cortex and the hepatic border and/or spleen.

Results

The PRF thickness was greater in CKD patients with impaired fasting glucose than in those with normal glucose levels (1.10 ± 0.40 cm vs. 0.85 ± 0.39 cm, P < 0.01). Patients in CKD stages 4 and 5 (glomerular filtration rate [GFR] < 30 mL/min/1.73 m²) had the highest PRF thickness. Serum triglyceride levels correlated positively with the PRF thickness; the PRF thickness was greater in patients with triglyceride levels ≥ 150 mg/dL (1.09 ± 0.40 cm vs. 0.86 ± 0.36 cm, P < 0.01). In patients with a GFR < 60 mL/min/1.73 m², uric acid levels correlated positively with the PRF thickness (P < 0.05).

Conclusion

In CKD patients, the PRF thickness correlated significantly with metabolic risk factors that could affect kidney function.

The Effect of Lipotoxicity on Renal Dysfunction in a Nonobese Rat Model of Metabolic Syndrome: A Urinary Proteomic Approach

INTRODUCTION

The development of metabolic syndrome-associated renal dysfunction is exacerbated by a number of factors including dyslipidemia, ectopic deposition of lipids and their toxic metabolites, impairment of lipid metabolism, and insulin resistance. Renal dysfunction is also affected by the production of proinflammatory and profibrotic factors secreted from adipose tissue, which can in turn directly impair kidney cells and potentiate insulin resistance. In this study, we investigated the manifestation of renal lipid accumulation and its effect on renal dysfunction in a model of metabolic syndrome-the hereditary hypertriglyceridemic rat (HHTg)-by assessing microalbuminuria and targeted urinary proteomics. Male Wistar control rats and HHTg rats were fed a standard diet and observed over the course of ageing at 3, 12, and 20 months of age.

RESULTS

Chronically elevated levels of triglycerides in HHTg rats were associated with increased levels of NEFA during OGTT and over a period of 24 hours (+80%, P < 0.01). HHTg animals exhibited qualitative changes in NEFA fatty acid composition, represented by an increased proportion of saturated fatty acids (P < 0.05) and a decreased proportion of n-3 PUFA (P < 0.01). Ectopic lipid deposition in the kidneys of HHTg rats-triglycerides (+30%) and cholesterol (+10%)-was associated with markedly elevated microalbuminuria as ageing increased, despite the absence of microalbuminuria at the young age of 3 months in these animals. According to targeted proteomic analysis, 3-month-old HHTg rats (in comparison to age-matched controls) exhibited increased urinary secretion of proinflammatory parameters (MCP-1, IL-6, IL-8, P < 0.01) and decreased urinary secretion of epidermal growth factor (EGF, P < 0.01) before manifestation of microalbuminuria. Elevation in the urinary secretion of inflammatory cytokines can be affected by increased relative expression of MCP-1 in the renal cortex (P < 0.05).

CONCLUSIONS

Our results confirm dyslipidemia and ectopic lipid accumulation to be key contributors in the development of metabolic syndrome-associated renal dysfunction. Assessing urinary secretion of proinflammatory cytokines and epidermal growth factor can help in detecting early development of metabolic syndrome-associated renal dysfunction.

Para-perirenal distribution of body fat is associated with reduced glomerular filtration rate regardless of other indices of adiposity in hypertensive patients

Obesity is a well-known risk factor for the development and progression of chronic kidney disease. Recently, para-perirenal ultrasonographic fat thickness (PUFT) has shown to correlate with both total and visceral fat better than body mass index (BMI), waist circumference (WC), and other indices of obesity. Moreover, a local paracrine and mechanical action of the PUFT on kidney has been described in recent studies. Aim of our study was to assess the relationship between glomerular filtration rate (GFR) and PUFT in comparison with other anthropometric and ultrasonographic indices of adiposity. Two hundred and ninety-six hypertensive patients were enrolled. PUFT, cutis-rectis thickness and rectis-aorta thickness were obtained by ultrasonography. Anthropometric measures of adiposity were also measured. Estimated GFR was calculated using the CKD-EPI equation. Higher PUFT values were observed in patients with impaired renal function (P < 0.001), whereas no differences in BMI and WC were shown between groups divided by GFR. PUFT significantly correlated with GFR in all patients (r = -0.284; P < 0.001), with no differences in groups divided by sex, diabetes, or BMI. This association held in multivariate analyses also after correction for confounding factors, including other adiposity indices (P < 0.001). When receiver operating characteristic curves were built to detect a eGFR < 60 mL/minutes per 1.73 m² , a PUFT value ≤3.725 cm showed a negative predictive value of 94.0%, with the largest area under the curve (AUC: 0.700) among the variables considered. In conclusion, the relationship between PUFT and GFR seems to be more accurate and less influenced by the bias affecting traditional indices of adiposity.

High perirenal fat thickness predicts a poor progression-free survival in patients with localized clear cell renal cell carcinoma

OBJECTIVES

The aim of the study was to assess the association between the progression-free survival (PFS) and perirenal fat thickness (PFT) in a population of histopathologically confirmed, localized clear cell renal cell carcinoma (ccRCC) patients.

METHODS

We retrospectively enrolled 174 patients with localized ccRCC at our center between December 2009 and December 2015. The preoperative visceral fat area (VFA), PFT, and subcutaneous fat area (SFA) were evaluated. Kaplan-Meier curves were used to assess the differences in PFS between the high and the low PFT groups within sexes. Potential independent prognostic factors of PFS were identified by univariable and multivariable Cox analyses.

RESULTS

During the follow-up period (median, 38 months), 27 patients (21 with high PFT and 6 with low PFT) experienced tumor progression. Kaplan-Meier curves revealed that high PFT was associated with a worse PFS than low PFT (P = 0.005). In the univariable Cox analyses, high VFA, high PFT, T stage, and the presence of sarcomatoid differentiation were significantly associated with a poor PFS. Moreover, both high PFT and VFA retained significance in the multivariable analysis.

CONCLUSION

We first report the evidence that high PFT presents as an independent risk factor of tumor progression in localized ccRCC. We suggest that this noninvasive and readily available preoperative parameter may help in the risk stratification of ccRCC patients before surgery.

Mayo Adhesive Probability Score Is an Independent Computed Tomography Scan Predictor of Adherent Perinephric Fat in Open Partial Nephrectomy

OBJECTIVE

To evaluate predictive radiological elements for adherent perinephric fat (APF) and the Mayo adhesive probability (MAP) score in the setting of open partial nephrectomy, and to assess their reproducibility.

PATIENTS AND METHODS

We performed a retrospective case-control study involving 86 patients who had open partial nephrectomies performed by a single surgeon between January 1, 2009 and April 1, 2015. Radiological elements were assessed by 4 readers blinded to patient APF status. Univariate and multivariate analyses were performed for all radiological and clinical factors. Reproducibility was analyzed using agreement coefficients.

RESULTS

On univariate analysis for radiological findings, lateral and posterior fat thickness (odds ratio [OR]: 1.084 [1.033, 1.138], P < .001), stranding (OR: 2.179 [1.431, 3.318], P < .001), -80 HU fat area, and the MAP score (OR: 1.797 [1.332, 2.424], P < .001) were predictive of APF. On multivariate analysis, only age and the MAP score remained statistically significant (OR: 1.060 [1.005, 1.118], P = .03; and OR: 1.560 [1.137, 2.139], P = .0058, respectively). The reproducibility of the MAP score was fair (AC1 = 0.367 and kappa F = 0.353), as was that of stranding (AC1 = 0.499, kappa F = 0.376). The agreement was important if we defined a "low" (0 to 3) or "high" (4 or 5) score (AC1 = 0.706 and kappa F = 0.681).

CONCLUSION

The MAP score was the element that best predicted APF in our study, although its reproducibility among our readers was only fair. The agreement becomes important if we defined "low or high" score.

Perirenal Fat Promotes Renal Arterial Endothelial Dysfunction in Obese Swine through Tumor Necrosis Factor-α

PURPOSE

Perirenal fat is associated with poor blood pressure control and chronic kidney disease but the underlying mechanisms remain elusive. We tested the hypothesis that perirenal fat impairs renal arterial endothelial function in pigs with obesity-metabolic derangements.

MATERIALS AND METHODS

We studied 14 domestic pigs after 16 weeks of a high fat/high fructose diet (obesity-metabolic derangement group) or standard chow (lean group). Renal blood flow, glomerular filtration rate and visceral fat volumes were studied in vivo by computerized tomography. Renal arterial endothelial function was also studied ex vivo in organ baths.

RESULTS

Pigs with obesity-metabolic derangements demonstrated increased body weight, blood pressure, cholesterol and intra-abdominal fat compared to lean pigs and perirenal fat volume was significantly larger. Renal blood flow and glomerular filtration rate were markedly elevated while urinary protein level was preserved. Ex vivo acetylcholine induced, endothelium dependent vasodilation of renal artery rings was substantially impaired in pigs with obesity-metabolic derangements compared to lean pigs. Endothelial function was further blunted in obesity-metabolic derangement and lean arterial rings by incubation with perirenal fat harvested from pigs with obesity-metabolic derangements but not from lean pigs. It was restored by inhibiting tumor necrosis factor-α. Perirenal fat from pigs with obesity-metabolic derangements also showed increased pro-inflammatory macrophage infiltration and tumor necrosis factor-α expression.

CONCLUSIONS

In pigs with obesity-metabolic derangements perirenal fat directly causes renal artery endothelial dysfunction, which is partly mediated by tumor necrosis factor-α.

Renal protective effects of induction of haem oxygenase-1 combined with increased adiponectin on the glomerular vascular endothelial growth factor-nitric oxide axis in obese rats

What is the central question of this study? This study aimed to investigate whether induction of haem oxygenase-1 (HO-1) can protect the kidneys of obese rats by regulating the glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis by increasing the adiponectin concentrations. What is the main finding and its importance? Induction of HO-1 reduces the degree of microalbuminuria and has renal protective effects by improving endothelial function and regulating the uncoupled glomerular VEGF-NO axis in diet-induced obese rats. The mechanism may be related to increased activation of the HO-1-adiponectin axis. The glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis plays a critical role in maintenance of normal kidney function in obesity. Induction of haem oxygenase-1 (HO-1) may result in a parallel increase in adiponectin secretion. The aim of this study was to investigate whether induction of HO-1 could protect the kidneys of obese rats by regulating the glomerular VEGF-NO axis by increasing adiponectin levels. Rats received high-fat diets and were injected with either cobalt protoporphyrin to induce HO-1 or stannous protoporphyrin to inhibit HO-1. Blood and urine samples were collected. Endothelial function was determined by measuring the endothelium-dependent vasodilatation of the aorta. Renal tissues were collected for CD34 immunohistochemistry. The glomerular VEGF-NO axis and the AMP kinase-phosphoinositide 3-kinase (PI3K)/Akt-endothelial nitric oxide synthase pathway were measured. Induction of HO-1 by cobalt protoporphyrin decreased microalbuminuria, plasma free fatty acids, serum high-sensitivity C-reactive protein and malondialdehyde levels and increased serum adiponectin levels compared with the untreated obese rats. Severe impairment of endothelium-dependent vasodilatation was observed in the obese rats, which was improved to some extent by HO-1 induction. Induction of HO-1 reduced glomerular CD34 expression and production of reactive oxygen species in obese rats. Obese rats showed increased glomerular VEGF expression and reduced NO levels. This uncoupling of the glomerular VEGF-NO axis was improved to some extent by induction of HO-1, with enhancement of p-AMP kinase, p-Akt and phospho-endothelial nitric oxide synthase in obese rats. These results indicate that induction of HO-1 with cobalt protoporphyrin reduces the degree of microalbuminuria and has renal protective effects by improving endothelial dysfunction and regulating the glomerular VEGF-NO axis in diet-induced obese rats by increasing adiponectin levels.

Perirenal fat associated with microalbuminuria in obese rats

PURPOSE

To determine whether perirenal fat is associated with increased urinary albumin excretion and whether perirenal fat affects renal vascular endothelial function in obese rats.

METHODS

Wistar rats were randomly divided into normal and obesity group, which were fed with normal and high-fat diet, respectively. Blood and urine samples were collected. Endothelial function of the aorta was determined by measuring endothelium-dependent vasodilatation. Renal tissues were collected for CD34 immunohistochemistry and free fatty acids (FFA) measurement. Levels of glomerular nitric oxide (NO) and reactive oxygen species (ROS) were measured.

RESULTS

After 24 weeks, plasma FFA, high-sensitivity C-reactive protein, and malondialdehyde levels were elevated and were significantly higher in renal venous blood than in jugular venous blood in obese rats. Urinary albumin/creatinine ratio, glomerular CD34 expression, glomerular ROS level, and renal cortex FFA levels were higher in obese rats. Endothelial dysfunction was more severe in the infra-renal aorta than in the thoracic aorta in obese rats. Plasma adiponectin and glomerular NO levels were lower in obese rats.

CONCLUSION

Perirenal fat is associated with increased urinary albumin excretion in obese rats. The mechanism may be renal vascular endothelial dysfunction caused by increased oxidative stress and activation of inflammatory molecular pathways due to elevated FFA and low adiponectin levels.