Perirenal fat associated with microalbuminuria in obese rats

Dysregulation of lipid metabolism in chronic kidney disease and the role of natural products

Dysregulation of lipid metabolism plays a key role in the onset and progression of CKD, and a thorough understanding of its regulatory mechanisms is essential for the development of effective treatments. In recent years, an increasing number of studies have focused on the pharmacological activities of natural products and their application in the treatment of chronic diseases. Natural products, including plant extracts and bioactive compounds, have been shown to exert anti-inflammatory, antioxidant, antifibrosis, and anti-apoptotic effects through various signaling pathways in the treatment of CKD. Many natural products have been shown to target dysregulated lipid metabolism through various signaling pathways. This review summarizes the key regulatory factors and signaling pathways involved in the dysregulation of lipid metabolism in chronic kidney disease (CKD), highlighting their importance as potential therapeutic targets. Recently published research on the potential therapeutic benefits of natural products for the treatment of CKD was described. These studies have revealed the multi-target role of natural products in the regulation of lipid metabolism. Natural products show great potential in targeting lipid metabolism-related pathways, offering a novel research direction for the treatment of CKD while providing a scientific basis and experimental support for the development of new treatment strategies.

Relationships of Thickness of Perirenal Fat with Urinary Levels of MCP-1 and NGAL in Patients with Hypertension

Background

We conducted a study to determine the relationships between perirenal fat (PRF) thickness and urinary levels of monocyte chemoattractant protein-1 (MCP-1) and neutrophil gelatinase-associated lipocalin (NGAL) in patients with hypertension (HTN).

Methods

In 338 HTN patients (aged 63.5±12.3 years on average), MCP-1 and NGAL levels were studied using enzyme-linked immunosorbent assay (ELISA). To measure PRF thickness, all patients underwent CT scans.

Results

We considered PRF thickness ≥1.91 cm as the diagnostic threshold for perirenal obesity. Patients with excessive PRF thickness exhibited significantly lower levels of MCP-1 and NGAL compared with those with PRF thickness ≥1.91 cm: 0.98 pg/mL (interquartile range [IQR], 0.21 to 2.05) vs. 2.35 pg/mL (IQR, 0.37 to 5.22) for MCP-1 and 50.0 pg/mL (IQR, 48.9 to 67.8) vs. 98.3 pg/mL (IQR, 68.4 to 187.1) for NGAL. We found a relationship of PRF thickness with both MCP-1 (r=0.46, P<0.05) and NGAL (r=0.53, P<0.05), the levels of which were significantly different in patients with first- and third-stage chronic kidney disease: 0.33 pg/mL (IQR, 0.21 to 1.35) vs. 4.47 pg/mL (IQR, 0.23 to 10.81); 50.0 pg/mL (IQR, 49.4 to 85.5) vs. 126.45 pg/mL (IQR, 57.5 to 205.15), respectively (P=0.04). Patients with metabolically healthy obesity (MHO) had significantly lower MCP-1 levels than those with metabolically unhealthy obesity (MUO): 0.65 pg/mL (IQR, 0.21 to 2.15) vs. 3.28 pg/mL (IQR, 2.05 to 5.22) (P=0.014). MHO patients showed significantly lower NGAL levels than MUO patients: 50.0 pg/mL (IQR, 49.4 to 62.2) vs. 98.3 pg/mL (IQR, 50.0 to 174.8) (P=0.04). Multiple linear regression analysis revealed significant relationships of MCP-1 with PRF thickness (β±standard error, 0.41±0.15; P<0.001) and smoking (0.26±0.13; P=0.01) and of NGAL with age (0.45±0.16; P<0.01) and PRF thickness (0.49±0.15; P<0.001).

Conclusion

We identified higher concentrations of renal fibrosis markers in patients with perirenal and MUO as well as a link between PRF thickness and MCP-1 and NGAL levels in urine.

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.

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.

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.

Perirenal Fat Thickness Is Associated With Contrast-Induced Nephropathy in Type 2 Diabetic Patients Undergoing Coronary Catheterization

Background: Deposition of adipose tissue may have a promoting role in the development of diabetic complications. This study is aimed at investigating the relationship between adipose tissue thickness and risk of contrast-induced nephropathy (CIN) in patients with Type 2 diabetes mellitus (T2DM). Methods: A total of 603 T2DM patients undergoing percutaneous coronary angiography or angioplasty with suspicious or confirmed stable coronary artery disease were enrolled in this study. The thicknesses of perirenal fat (PRF), subcutaneous fat (SCF), intraperitoneal fat (IPF), and epicardial fat (ECF) were measured by color Doppler ultrasound, respectively. The association of various adipose tissues with CIN was analyzed. Results: Seventy-seven patients (12.8%) developed CIN in this cohort. Patients who developed CIN had significantly thicker PRF (13.7 ± 4.0 mm vs. 8.9 ± 3.6 mm, p < 0.001), slightly thicker IPF (p = 0.046), and similar thicknesses of SCF (p = 0.782) and ECF (p = 0.749) compared to those who did not develop CIN. Correlation analysis showed that only PRF was positively associated with postoperation maximal serum creatinine (sCr) (r = 0.18, p = 0.012), maximal absolute change in sCr (r = 0.33, p < 0.001), and maximal percentage of change in sCr (r = 0.36, p < 0.001). In receiver operating characteristic (ROC) analysis, the area under the curve (AUC) of PRF (0.809) for CIN was significantly higher than those of SCF (0.490), IPF (0.594), and ECF (0.512). Multivariate logistic regression analysis further confirmed that thickness of PRF, rather than other adipose tissues, was independently associated with the development of CIN after adjusted for confounding factors (odds ratio (OR) = 1.53, 95% CI: 1.38-1.71, p < 0.001). Conclusions: PRF is independently associated with the development of CIN in T2DM patients undergoing coronary catheterization.

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.

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.

Kidney-Protective Effects of SGLT2 Inhibitors

The sodium-glucose cotransporter 2 (SGLT2) inhibitors have become an integral part of clinical practice guidelines to slow the progression of CKD in patients with and without diabetes mellitus. Although initially developed as antihyperglycemic drugs, their effect on the kidney is multifactorial resulting from profuse glycosuria and natriuresis consequent to their primary site of action. Hemodynamic and metabolic changes ensue that mediate kidney-protective effects, including ( 1 ) decreased workload of proximal tubular cells and prevention of aberrant increases in glycolysis, contributing to a decreased risk of AKI; ( 2 ) lowering of intraglomerular pressure by activating tubular glomerular feedback and reductions in BP and tissue sodium content; ( 3 ) initiation of nutrient-sensing pathways reminiscent of starvation activating ketogenesis, increased autophagy, and restoration of carbon flow through the mitochondria without production of reactive oxygen species; ( 4 ) body weight loss without a reduction in basal metabolic rate due to increases in nonshivering thermogenesis; and ( 5 ) favorable changes in quantity and characteristics of perirenal fat leading to decreased release of adipokines, which adversely affect the glomerular capillary and signal increased sympathetic outflow. Additionally, these drugs stimulate phosphate and magnesium reabsorption and increase uric acid excretion. Familiarity with kidney-specific mechanisms of action, potential changes in kidney function, and/or alterations in electrolytes and volume status, which are induced by these widely prescribed drugs, will facilitate usage in the patients for whom they are indicated.

Effect of Melatonin on Redox Enzymes Daily Gene Expression in Perirenal and Subcutaneous Adipose Tissue of a Diet Induced Obesity Model

Increased adiposity is related to oxidative stress, inflammation and metabolic disorders. Our group has shown that melatonin totally or partially prevents the alterations that obesity causes in some neuroendocrine and inflammatory parameters indicative of oxidative stress. This study analyzes the effects of HFD on the relative gene expression of several redox balance enzymes on adult male Wistar rats subcutaneous (SAT) and perirenal adipose tissue (PRAT) and the possible preventive role of melatonin. Three experimental groups were established: control, high fat diet (HFD) and HFD plus 25 μg/mL melatonin in tap water. After 11 weeks, animals were sacrificed at 09:00 a.m. and 01:00 a.m. and PRAT and SAT were collected for selected redox enzymes qRT-PCR. Differential expression of redox enzyme genes, except for SOD^Mn, GPx and catalase, was observed in the control group as a function of fat depot. HFD causes the disappearance of the temporal changes in the expression of the genes studied in the two fat depots analyzed. PRAT seems to be more sensitive than SAT to increased oxidative stress induced by obesity. Melatonin combined with a HFD intake, partially prevents the effects of the HFD on the gene expression of the redox enzymes. According to our results, melatonin selectively prevents changes in the relative gene expression of redox enzymes in PRAT and SAT of animals fed an HFD.

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.

The perirenal fat thickness was independently associated with serum uric acid level in patients with type 2 diabetes mellitus

BACKGROUND

Obesity is an important risk factor for hyperuricemia. We aimed to explore the relationship between perirenal fat thickness (PrFT) and paranephric fat thickness (PnFT) and serum uric acid (SUA) in patients with type 2 diabetes mellitus (T2DM).

METHODS

This was a cross-sectional study involving 257 patients with T2DM recruited from Beijing Luhe Hospital from September 2019 to May 2020. The basic and clinical information such as age, gender, duration of diabetes was collected through the medical records. All patients underwent a physical examination including height, weight, waist circumference, hip circumference, systolic blood pressures and diastolic blood pressure. The venous blood and urine samples were collected to measure SUA, fasting blood glucose, total cholesterol, triglyceride, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, serum creatinine, blood urea nitrogen and glycosylated hemoglobin. PrFT and PnFT were measured via ultrasonography. Pearson correlation test and linear regression analysis were used to analyze the association between PrFT and PnFT and SUA.

RESULTS

We found that PrFT and PnFT increased according to the tertiles of SUA level (P = 0.001 and P = 0.009, respectively). In addition, the PrFT and PnFT were positively associated with SUA level (r = 0.25, P < 0.001, r = 0.23, P < 0.001, respectively). Moreover, this association was stronger in males, non-obesity patients and patients with normal renal function. In the multivariate analysis, the PrFT was independently associated with SUA level after adjusting confounding factors.

CONCLUSIONS

The PrFT was independently associated with SUA level in patients with T2DM.

High Perirenal Fat Volume Affect Negatively Renal Function in Living Renal Transplantation

OBJECTIVE

We aimed to investigate the effect of perirenal fat volume (PFV) on graft functions by calculating the PFV of donor kidney with routine computed tomography before renal transplantation.

METHODS

From May 2019 to December 2020, a total of 54 living donors and recipients who met the criteria for kidney donor were included in the study. Left donor nephrectomy was performed to all donors. Data of age, sex, body mass index (BMI), PFV of the donors, estimated glomerular filtration rate (eGFR), and serum creatinine measurement data of the recipients were recorded. Serum creatinine and eGFR of the recipients were recorded at the 12th month controls. The patients were sorted into 2 groups (G) according to their GFR values. G1, GFR <60 mL/min/1.73 m²; G2, GFR ≥ 60 mL/min/1.73 m².

RESULTS

There was no difference in terms of recipient sex, recipient age, donor sex, recipient BMI, and donor BMI between the 2 groups. The mean of PFV was higher in G1 and was statistically significant (P= 0.01). The ability of the donor BMI and PFV to predict G2 was evaluated by receiver operating characteristic curve analysis. It was determined that PFV predicted G2 to be statistically significant. In the multivariate logistic regression analysis, PFV (odds ratio = 0.988, 95% GA = 0.977-0.999, P = 0.03) was found as an independent predictor of G2.

CONCLUSIONS

In conclusion, our study showed PFV as an independent risk factor for low eGFR, revealing that the previously documented relevance of increased BMI with a low eGFR can be partially explained by PFV.

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.

Perirenal Fat as a New Independent Prognostic Factor in Patients With Surgically Treated Clear Cell Renal Cell Carcinoma

INTRODUCTION

Recently increasing evidence has suggested that obesity is associated with the development and prognosis of renal cell carcinoma. The aim of the study was to investigate the association between different obesity measurements and overall survival in patients with surgically treated clear cell renal cell carcinoma.

PATIENTS AND METHODS

The data of 342 consecutive patients who underwent radical or partial nephrectomy at Peking University People's Hospital from January 2009 to November 2014 were retrospectively reviewed. Median follow-up was 82 months. The association between different obesity measurements and overall survival was evaluated using the Kaplan-Meier method and Cox regression models.

RESULTS

In univariate Cox regression analyses, perirenal fat accumulation was significantly associated with overall survival (HR: 2.271; 95% CI: 1.311-3.935; P = .003), as well as age, sex, clinical manifestation, surgical option, tumor size, and grade. The other obesity measurements, including body mass index, waist circumference, total adipose tissue, visceral adipose tissue, and percentage of visceral adipose tissue, were not assessed as prognostic indicators of overall survival in this study (P > .05). After adjusting for age, sex, clinical manifestation, surgical option, tumor size, T stage, and tumor grade, perirenal fat accumulation was still identified as an independent predictor of overall survival (HR: 2.264; 95% CI: 1.305-3.926; P == .004). The results of Kaplan-Meier model also revealing that patients with higher percentage of perirenal fat showed poorer overall survival (P == .003).

CONCLUSION

Higher percentage of perirenal adipose tissue is independently associated with increased mortality risk in surgically treated clear cell renal cell carcinoma.

Ipragliflozin Ameliorates Diabetic Nephropathy Associated with Perirenal Adipose Expansion in Mice

Sodium glucose cotransporter-2 (SGLT2) inhibitors inhibit the development of diabetic nephropathy (DN). We determined whether changes in perirenal fat (PRAT) by a SGLT2 inhibitor ipragliflozin (Ipra) contribute to the suppression of DN development. High-fat diet (HFD)-fed mice were used as a DN model and were treated with or without Ipra for 6 weeks. Ipra treatment reduced urinary albumin excretion (UAE) and glomerular hypertrophy in HFD-fed mice. In the PRAT of Ipra-treated mice, adipocyte size was increased, and inflammation, fibrosis, and adipocyte death were suppressed. In conditioned medium made from PRAT (PRAT-CM) of Ipra-treated mice, the concentration of leptin was significantly lower than PRAT-CM of mice without Ipra treatment. Serum leptin concentration in renal vein positively correlated with UAE. PRAT-CM from HFD-fed mice showed greater cell proliferation signaling in mouse glomerular endothelial cells (GECs) than PRAT-CM from standard diet-fed mice via p38MAPK and leptin-dependent pathways, whose effects were significantly attenuated in PRAT-CM from Ipra-treated mice. These findings suggest that Ipra-induced PRAT expansion may play an important role in the improvement of DN in HFD-fed mice. In vitro experiments suggest that reduced PRAT-derived leptin by Ipra could inhibit GECs proliferation, possibly contributing to the suppression of DN development.

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.

Peri-renal adipose inflammation contributes to renal dysfunction in a non-obese prediabetic rat model: Role of anti-diabetic drugs

Diabetic nephropathy is a major health challenge with considerable economic burden and significant impact on patients' quality of life. Despite recent advances in diabetic patient care, current clinical practice guidelines fall short of halting the progression of diabetic nephropathy to end-stage renal disease. Moreover, prior literature reported manifestations of renal dysfunction in early stages of metabolic impairment prior to the development of hyperglycemia indicating the involvement of alternative pathological mechanisms apart from those typically triggered by high blood glucose. Here, we extend our prior research work implicating localized inflammation in specific adipose depots in initiating cardiovascular dysfunction in early stages of metabolic impairment. Non-obese prediabetic rats showed elevated glomerular filtration rates and mild proteinuria in absence of hyperglycemia, hypertension, and signs of systemic inflammation. Isolated perfused kidneys from these rats showed impaired renovascular endothelial feedback in response to vasopressors and increased flow. While endothelium dependent dilation remained functional, renovascular relaxation in prediabetic rats was not mediated by nitric oxide and prostaglandins as in control tissues, but rather an upregulation of the function of epoxy eicosatrienoic acids was observed. This was coupled with signs of peri-renal adipose tissue (PRAT) inflammation and renal structural damage. A two-week treatment with non-hypoglycemic doses of metformin or pioglitazone, shown previously to ameliorate adipose inflammation, not only reversed PRAT inflammation in prediabetic rats, but also reversed the observed functional, renovascular, and structural renal abnormalities. The present results suggest that peri-renal adipose inflammation triggers renal dysfunction early in the course of metabolic disease.

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.

Liraglutide improves obesity-induced renal injury by alleviating uncoupling of the glomerular VEGF-NO axis in obese mice

Obesity-related kidney disease is associated with generalized endothelial dysfunction. Liraglutide, a glucagon-like peptide-1 agonist, has cardiovascular-renal protective effects in patients with diabetes. In this study, the ability of liraglutide to reduce urinary albumin excretion by alleviating glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis uncoupling was assessed in high fat diet-induced obese mice. C57BL/6J mice were divided into control and obesity groups, treated with or without liraglutide (200 μg/kg/day). Blood biochemistry and urinary albumin excretion were measured. Glomerular VEGF and the AMPK-endothelial nitric oxide synthase (eNOS) pathway were assayed by western blotting. Glomerular NO, renal haeme oxygenase-1 activity, and malondialdehyde levels were also measured. Treatment of obese mice with liraglutide led to significant reductions in body weight gain (46 ± 1 g vs 55 ± 1 g, P < .0001), visceral fat (8.9 ± 0.6 g vs 14.5 ± 0.6 g, P < .0001), perirenal fat (2.9 ± 0.2 g vs 5.4 ± 0.3 g, P < .0001), and free fatty acid (1.71 ± 0.12 mmol/L vs 1.02 ± 0.08 mmol/L, P < .0001). Liraglutide significantly improved glucose homeostasis, which was impaired in obese mice. Liraglutide reduced urinary albumin excretion and glomerular hypertrophy in obese mice. Additionally, liraglutide significantly decreased VEGF and increased glomerular NO production in glomeruli, indicating restoration of the glomerular VEGF-NO axis. Furthermore, liraglutide activated the glomerular AMPK-eNOS pathway in obese mice, upregulated renal haeme oxygenase-1 activity, and reduced the renal malondialdehyde levels in obese mice. In conclusion, liraglutide reduced microalbuminuria and ameliorated renal injury by alleviating the uncoupling of the glomerular VEGF-NO axis.

Genome-Wide DNA Methylation Changes of Perirenal Adipose Tissue in Rabbits Fed a High-Fat Diet

DNA methylation is an epigenetic mechanism that plays an important role in gene regulation without an altered DNA sequence. Previous studies have demonstrated that diet affects obesity by partially mediating DNA methylation. Our study investigated the genome-wide DNA methylation of perirenal adipose tissue in rabbits to identify the epigenetic changes of high-fat diet-mediated obesity. Two libraries were constructed pooling DNA of rabbits fed a standard normal diet (SND) and DNA of rabbits fed a high-fat diet (HFD). Differentially methylated regions (DMRs) were identified using the option of the sliding window method, and online software DAVID Bioinformatics Resources 6.7 was used to perform Gene Ontology (GO) terms and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis of DMRs-associated genes. A total of 12,230 DMRs were obtained, of which 2305 (1207 up-regulated, 1098 down-regulated) and 601 (368 up-regulated, 233 down-regulated) of identified DMRs were observed in the gene body and promoter regions, respectively. GO analysis revealed that the DMRs-associated genes were involved in developmental process (GO:0032502), cell differentiation (GO:0030154), and lipid binding (GO:0008289), and KEGG pathway enrichment analysis revealed the DMRs-associated genes were enriched in linoleic acid metabolism (KO00591), DNA replication (KO03030), and MAPK signaling pathway (KO04010). Our study further elucidates the possible functions of DMRs-associated genes in rabbit adipogenesis, contributing to the understanding of HFD-mediated obesity.

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.

Enhanced Therapeutic Potency of Nanoemulsified Garlic Oil Blend Towards Renal Abnormalities in Pre-diabetic Rats

The therapeutic potency of ultrasonic nanoemulsified garlic oil blend using a non-ionic surfactant (Tween 80) was assessed on pre-diabetic Wistar rats with microalbuminuria. The pre-diabetic condition was induced in male albino Wistar rats by supplementing high-fat diet. The prolonged period of the pre-diabetic state caused renal dysfunctioning, which was indicated by microalbuminuria. Treatment of pre-diabetic rats with nanoemulsified garlic oil blend significantly ameliorated the lipid profile (p < 0.001), urinary albumin (p < 0.01), microprotein (p < 0.001), urinary triglycerides (p < 0.01), serum triglycerides (p < 0.01), serum albumin (p < 0.05), and protein levels (p < 0.01) in comparison to treatment of pre-diabetic rats with garlic oil blend or atorvastatin. Similarly, histopathological investigations indicated a remarkable attenuation in the mesangial expansion and proliferation, glomerular and tubular basement membrane thickening, and the tubular lipid deposits on administering nanoemulsified garlic oil blend than garlic oil blend or atorvastatin. Moreover, nanoemulsified garlic oil blend significantly promoted renal podocin gene expression by 3.98-fold (p < 0.001) and attenuated increased urinary podocin level by 2.92-fold (p < 0.01). Thus, our study affirms that the efficacy of garlic oil blend was augmented upon nanoemulsification, which substantially ameliorated the renal abnormalities observed in the pre-diabetic condition than garlic oil blend or atorvastatin.

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.

Calycosin directly improves perivascular adipose tissue dysfunction by upregulating the adiponectin/AMPK/eNOS pathway in obese mice

Perivascular adipose tissue (PVAT) loses its anti-contractile activity in obesity. Calycosin, the major bioactive isoflavonoid, was shown to protect endothelial function. However, effects of calycosin on PVAT function in obesity remain unclear. We aimed to investigate the effects of calycosin on the anti-contractile activity of PVAT in obese mice and its potential mechanisms. Obesity in mice was induced with a high-fat diet, with or without calycosin treatment. Thoracic aorta responses to phenylephrine were determined. AMP protein kinase (AMPK) and endothelial nitric oxide synthase (eNOS) levels were analyzed by western blotting. Adiponectin, TNF-α levels and superoxide production were measured in the PVAT. Calycosin treatment significantly increased the anti-contractile response of PVAT, which was impaired in obese mice. This beneficial effect of calycosin was eliminated by treatments of blocking adiponectin, AMPK or eNOS. Similar results were observed for calycosin treatment ex vivo. Treatment of obese mice with calycosin significantly increased adiponectin levels, activated AMPK and eNOS phosphorylation and reduced superoxide production and TNF-α levels in PVAT. Our results indicated that calycosin restored PVAT induced anti-contractile activity and affected PVAT function through the adiponectin/AMPK/eNOS pathway in obese mice.

Renal outcomes with sodium glucose cotransporter 2 (SGLT2) inhibitor, dapagliflozin, in obese insulin-resistant model

A growing body of evidence indicates that obesity and insulin resistance contribute to the progression of renal disease. This study was performed to determine the effects of dapagliflozin, a novel sodium glucose cotransporter 2 (SGLT2) inhibitor, on renal and renal organic anion transporter 3 (Oat3) functions in high-fat diet fed rats, a model of obese insulin-resistance. Twenty-four male Wistar rats were divided into two groups, and received either a normal diet (ND) (n = 6) or a high-fat diet (HFD) (n = 18) for 16 weeks. At week 17, the HFD-fed rats were subdivided into three subgroups (n = 6/subgroup) and received either a vehicle (HFD), dapagliflozin (HFDAP; 1.0 mg/kg/day) or metformin (HFMET; 30 mg/kg/day), by oral gavage for four weeks. Metabolic parameters, renal function, renal Oat3 function, renal oxidative stress, and renal morphology were determined. The results showed that obese insulin-resistant rats induced by HFD feeding had impaired renal function and renal Oat3 function together with increased renal oxidative injury. Dapagliflozin or metformin treatment decreased insulin resistance, hypercholesterolemia, creatinine clearance and renal oxidative stress leading to improved renal function. However, dapagliflozin treatment decreased blood pressure, serum creatinine, urinary microalbumin and increased glucose excretions, and showed a greater ability to ameliorate impaired renal insulin signaling and glomerular barrier damage than metformin. These data suggest that dapagliflozin had greater efficacy than metformin for attenuating renal dysfunction and improving renal Oat3 function, at least in part by reducing renal oxidative stress and modulating renal insulin signaling pathways, and hence ameliorating renal injury.

Three-dimensional evaluation of perirenal fat volume in patients with nephrolithiasis

The concept of adipose tissue as an organ unto itself represents a new medical construct; already differences in the volume of perirenal fat around a tumor-bearing kidney have been described. We hypothesized that renal calculi may have similar impact on perirenal fat or alternatively abnormalities in urinary metabolites may be the result of perirenal fat affecting renal metabolism and subsequent stone formation. Accordingly, we conducted a study utilizing three-dimensional imaging software to evaluate perirenal fat volume (PFV) in patients with nephrolithiasis. Among 40 patients with a history of unilateral nephrolithiasis who underwent percutaneous nephrolithotomy between 2010 and 2016, the following data were acquired: body mass index, past medical history, stone characteristics and composition (i.e., calcium oxalate, calcium phosphate, uric acid, and struvite calculi). In addition, patients were stratified by dominant stone composition (≥ 50% fraction). Bilateral PFV measurements were obtained using the preoperative computed tomography scan and specialized three-dimensional imaging software. The PFV of stone-bearing kidneys was significantly greater than non-stone-bearing kidneys (397.3 and 323 cc, respectively; p = 0.004), with the PFV difference in patients with CO-dominant stone-bearing kidneys reaching statistical significance (p = 0.003). Subgroup analysis showed greater PFV surrounding the stone-bearing kidney irrespective of gender (p = 0.03), with male patients possessing significantly greater stone-bearing (p = 0.01) and bilateral PFV (p = 0.01) compared to females. No significant correlations were found between PFV and stone volume or stone density. The PFV of calcium oxalate stone-bearing kidneys is significantly greater than non-stone-bearing kidneys for both male and female patients with nephrolithiasis.

Irisin improves endothelial function in obese mice through the AMPK-eNOS pathway

Irisin is a novel hormone secreted by myocytes. Lower levels of irisin are independently associated with endothelial dysfunction in obese subjects. The objective of this study was to explore whether irisin exerts a direct vascular protective effect on endothelial function in high-fat-diet-induced obese mice. Male C57BL/6 mice were given chow or a high-fat diet with or without treatment with irisin. Aortic endothelial function was determined by measuring endothelium-dependent vasodilatation (EDV). Nitric oxide (NO) in the aorta was determined. The effect of irisin on the levels of AMP-activated protein kinase (AMPK), Akt, and endothelial NO synthase (eNOS) phosphorylation in endothelial cells was determined. Human umbilical vein endothelial cells were used to study the role of irisin in the AMPK-eNOS pathway. Acetylcholine-stimulated EDV was significantly lower in obese mice compared with control mice. Treatment of obese mice with irisin significantly enhanced EDV and improved endothelial function. This beneficial effect of irisin was partly attenuated in the presence of inhibitors of AMPK, Akt, and eNOS. Treatment of obese mice with irisin enhanced NO production and phosphorylation of AMPK, Akt, and eNOS in endothelial cells. These factors were also enhanced by irisin in human umbilical vein endothelial cells in vitro. Suppression of AMPK expression by small interfering RNA blocked irisin-induced eNOS and Akt phosphorylation and NO production. We have provided the first evidence that irisin improves endothelial function in aortas of high-fat-diet-induced obese mice. The mechanism for this protective effect is related to the activation of the AMPK-eNOS signaling pathway.

The relationship between circulating irisin levels and endothelial function in lean and obese subjects

OBJECTIVE

Irisin has been shown to turn white adipocytes into brown-like adipocytes, which is emerging as an appealing therapeutic target for obesity. The objective of the study was to determine whether circulating irisin levels are related to endothelial dysfunction in obese subjects.

DESIGN

A total of 41 nonhypertensive, nondiabetic obese subjects and 40 age- and sex-matched lean healthy control were involved in this study. Clinical characteristics, blood biochemistry, circulating irisin and adiponectin of the subjects were measured. Endothelium-dependent vasodilation (EDV) and endothelial-independent vasodilation (EIV) were determined using high-resolution ultrasound.

RESULTS

Circulating irisin and adiponectin were significantly lower in obese subjects compared with lean healthy control (P < 0·05). Endothelial function was impaired in obese subjects (maximum EDV: 8·95 ± 3·46% vs 14·56 ± 3·90%, P < 0·05). Bivariate correlation analysis revealed that circulating irisin was positively correlated with EDV(r = 0·388, P < 0·01) and negatively correlated with BMI (r = -0·281, P < 0·05), waist circumference (r = -0·298, P < 0·01), free fatty acid (FFA) (r = -0·289, P < 0·01), high-sensitivity C-reactive protein (hs-CRP) (r = -0·244, P < 0·05) and malondialdehyde (r = -0·258, P < 0·05). Multiple regression analysis revealed that circulating irisin, adiponectin, FFA and BMI were independently associated with EDV after adjusting for covariates (R(2) = 0·457, F = 8·766, P = 0·000).

CONCLUSIONS

Circulating irisin level was decreased in nonhypertensive, nondiabetic obese subjects compared with lean healthy control. Lower levels of irisin are independently associated with endothelial dysfunction. Therefore, irisin may be involved in the regulation of endothelial function in obesity.

Effect of 3,4-dihydroxyacetophenone on endothelial dysfunction in obese rats

CONTEXT

3,4-Dihydroxyacetophenone (DHAP) has been reported to possess cardiovascular pharmacological effects.

OBJECTIVE

This study was designed to determine whether DHAP could improve endothelial function in obese rats.

MATERIALS AND METHODS

Wistar rats were randomly divided into control, obesity, and DHAP groups and fed a normal, high-fat, and high-fat plus DHAP (10 mg kg(-1) d(-1)) diet, respectively, for 8 weeks. Endothelial-dependent vasodilatation was assessed. Endothelial nitric oxide synthase (eNOS) activity and nitric oxide (NO) production in endothelial cells were determined. Nuclear transcription factor kappa B (NF-κB) expression and superoxide production in aorta were evaluated.

RESULTS

DHAP treatment significantly decreased plasma triglycerides (0.94 ± 0.31 mmol/l versus 1.36 ± 0.29 mmol/l, p < 0.05) and free fatty acids (0.53 ± 0.15 mmol/l versus 0.99 ± 0.24 mmol/l, p < 0.05), reduced serum tumor necrosis factor α (35.56 ± 9.28 pg/ml versus 68.3 ± 10.24 pg/ml, p < 0.05) and malondialdehyde (2.94 ± 0.58 pg/ml versus 6.45 ± 0.70 pg/ml, p < 0.05), and increased serum adiponectin levels (164.5 ± 34.5 μg/l versus 84.5 ± 20.4 μg/l, p < 0.05). DHAP enhanced endothelial-dependent vasodilatation and improved endothelial function in obese rats (p < 0.05). eNOS activity and NO production in endothelial cells significantly decreased and NF-κB activation and superoxide production in aorta significantly increased in obese rats compared with the control group (p < 0.05). However, DHAP treatment significantly up-regulated the eNOS-NO pathway and decreased NF-κB activation and superoxide production (p < 0.05).

CONCLUSION

DHAP improved endothelial function in obese rats. This beneficial effect may be associated with up-regulation of the eNOS-NO pathway by improving lipid metabolism and reducing oxidative stress and inflammation activity.

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.

Protective effects of adiponectin on uncoupling of glomerular VEGF-NO axis in early streptozotocin-induced type 2 diabetic rats

PURPOSE

To determine whether adiponectin could reduce microalbuminuria and provide renal protective effects by improving endothelial dysfunction and uncoupling of the glomerular vascular endothelial growth factor (VEGF)-nitric oxide (NO) axis in streptozotocin-induced type 2 diabetic rats.

METHODS

Wistar rats were randomly divided into normal control group, diabetic nephropathy (DN) group induced by high-fat feeding and streptozotocin, diabetic rats injected with adenovirus-expressed adiponectin (AD-AdipoQ), and diabetic rats injected with AD-IRES-EGFP as control. Blood and urine samples were collected. Endothelium-dependent vasodilatation (EDV) of the aorta was measured. Renal tissues were collected for CD34 immunohistochemistry. Glomerular NO and VEGF levels were measured by the Griess reaction and Western blot testing, respectively.

RESULTS

Injections of AD-AdipoQ significantly increased serum adiponectin levels and reduced the urinary albumin-to-creatinine ratio in diabetic rats (P < 0.05). The levels of plasma glucose, serum insulin, high-sensitivity C-reactive protein, and malondialdehyde were significantly reduced in diabetic rats after injections of AD-AdipoQ (P < 0.05). Severe EDV impairment was observed in the DN group, which was improved by AD-AdipoQ. CD34 expression in the glomeruli was also higher in diabetic rats, indicating increased proliferation of glomerular endothelial cells. However, AD-AdipoQ improved the increased proliferation of endothelial cells in the glomeruli. Diabetic rats showed increased glomerular VEGF levels and reduced NO levels. This uncoupling of the VEGF-NO axis was partially improved by AD-AdipoQ.

CONCLUSION

Adiponectin reduces the degree of microalbuminuria and has renal protective effects by improving endothelial dysfunction and uncoupling of the glomerular VEGF-NO axis in early diabetic nephropathy.