Adipokines as a link between obesity and chronic kidney disease

Obesity and the kidney: mechanistic links and therapeutic advances

Obesity is strongly associated with the development of diabetes mellitus and chronic kidney disease (CKD), but there is evidence for a bidirectional relationship wherein the kidney also acts as a key regulator of body weight. In this Review, we highlight the mechanisms implicated in obesity-related CKD, and outline how the kidney might modulate feeding and body weight through a growth differentiation factor 15-dependent kidney-brain axis. The favourable effects of bariatric surgery on kidney function are discussed, and medical therapies designed for the treatment of diabetes mellitus that lower body weight and preserve kidney function independent of glycaemic lowering, including sodium-glucose cotransporter 2 inhibitors, incretin-based therapies and metformin, are also reviewed. In summary, we propose that kidney function and body weight are related in a bidirectional fashion, and that this interrelationship affects human health and disease.

Obesity-related glomerulopathy: recent advances in inflammatory mechanisms and related treatments

Obesity-related glomerulopathy, which is an obesity-triggered kidney damage, has become a significant threat to human health. Several studies have recently highlighted the critical role of inflammation in obesity-related glomerulopathy development. Additionally, excess adipose tissue and adipocytes in patients with obesity produce various inflammatory factors that cause systemic low-grade inflammation with consequent damage to vascular endothelial cells, exacerbating glomerular injury. Therefore, we conducted a comprehensive review of obesity-related glomerulopathy and addressed the critical role of obesity-induced chronic inflammation in obesity-related glomerulopathy pathogenesis and progression, which leads to tubular damage and proteinuria, ultimately impairing renal function. The relationship between obesity and obesity-related glomerulopathy is facilitated by a network of various inflammation-associated cells (including macrophages, lymphocytes, and mast cells) and a series of inflammatory mediators (such as tumor necrosis factor α, interleukin 6, leptin, adiponectin, resistin, chemokines, adhesion molecules, and plasminogen activator inhibitor 1) and their inflammatory pathways. Furthermore, we discuss a recently discovered relationship between micronutrients and obesity-related glomerulopathy inflammation and the important role of micronutrients in the body's anti-inflammatory response. Therefore, assessing these inflammatory molecules and pathways will provide a strong theoretical basis for developing therapeutic strategies based on anti-inflammatory effects to prevent or delay the onset of kidney injury.

Childhood Obesity: Insight into Kidney Involvement

This review examines the impact of childhood obesity on the kidney from an epidemiological, pathogenetic, clinical, and pathological perspective, with the aim of providing pediatricians and nephrologists with the most current data on this topic. The prevalence of childhood obesity and chronic kidney disease (CKD) is steadily increasing worldwide, reaching epidemic proportions. While the impact of obesity in children with CKD is less pronounced than in adults, recent studies suggest a similar trend in the child population. This is likely due to the significant association between obesity and the two leading causes of end-stage renal disease (ESRD): diabetes mellitus (DM) and hypertension. Obesity is a complex, systemic disease that reflects interactions between environmental and genetic factors. A key mechanism of kidney damage is related to metabolic syndrome and insulin resistance. Therefore, we can speculate about an adipose tissue-kidney axis in which neurohormonal and immunological mechanisms exacerbate complications resulting from obesity. Adipose tissue, now recognized as an endocrine organ, secretes cytokines called adipokines that may induce adaptive or maladaptive responses in renal cells, leading to kidney fibrosis. The impact of obesity on kidney transplant-related outcomes for both donors and recipients is also significant, making stringent preventive measures critical in the pre- and post-transplant phases. The challenge lies in identifying renal involvement as early as possible, as it is often completely asymptomatic and not detectable through common markers of kidney function. Ongoing research into innovative technologies, such as proteomics and metabolomics, aims to identify new biomarkers and is constantly evolving. Many aspects of pediatric disease progression in the population of children with obesity still require clarification. However, the latest scientific evidence in the field of nephrology offers glimpses into various new perspectives, such as genetic factors, comorbidities, and novel biomarkers. Investigating these aspects early could potentially improve the prognosis of these young patients through new diagnostic and therapeutic strategies. Hence, the aim of this review is to provide a comprehensive exploration of the pathogenetic mechanisms and prevalent pathological patterns of kidney damage observed in children with obesity.

Ghrelin hormone a new molecular modulator between obesity and glomerular damage

The incidence of glomerular diseases is increasing worldwide due to increased prevalence of obesity which is a major risk factor for type-2 diabetes mellitus and cardiovascular disorders.Ghrelin, an orexigenic peptide hormone, has been implicated in obesity, and its impact on the pathology and function of the kidneys was found to be significant. Ghrelin known to regulate energy homeostasis and growth hormone release, has been shown to modulate critical signaling pathways involved in the health and survival of podocytes. These derangements directly affect glomerular function and manifest as impaired glomerular filtration barrier and leakage of albumin into urine. Although the pathological features of the above-mentioned disorders are different, they interestingly lead to similar clinical features of glomerular damage. The pathological events are majorly initiated by endocrine imbalance leading to abnormal activation of downstream signaling pathways involved in the development of glomerulosclerosis. In fact, obesity increases the risk of developing chronic kidney disease by altering the secretion of pro-inflammatory cytokines and adipokines, activating the renin-angiotensin-aldosterone system (RAAS), promoting lipotoxicity, oxidative stress and fibrosis within the kidneys. Whilst these bioregulators are well described, their direct involvement in renal homeostasis is still mostly elusive. This review summarized previous and recent evidence on the endocrine properties of ghrelin and perivascular adipose tissue involved in modulating kidney physiology.

An international Delphi consensus statement on metabolic dysfunction-associated fatty liver disease and risk of chronic kidney disease

BACKGROUND

With the rising global prevalence of fatty liver disease related to metabolic dysfunction, the association of this common liver condition with chronic kidney disease (CKD) has become increasingly evident. In 2020, the more inclusive term metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed to replace the term non-alcoholic fatty liver disease (NAFLD). The observed association between MAFLD and CKD and our understanding that CKD can be a consequence of underlying metabolic dysfunction support the notion that individuals with MAFLD are at higher risk of having and developing CKD compared with those without MAFLD. However, to date, there is no appropriate guidance on CKD in individuals with MAFLD. Furthermore, there has been little attention paid to the link between MAFLD and CKD in the Nephrology community.

METHODS AND RESULTS

Using a Delphi-based approach, a multidisciplinary panel of 50 international experts from 26 countries reached a consensus on some of the open research questions regarding the link between MAFLD and CKD.

CONCLUSIONS

This Delphi-based consensus statement provided guidance on the epidemiology, mechanisms, management and treatment of MAFLD and CKD, as well as the relationship between the severity of MAFLD and risk of CKD, which establish a framework for the early prevention and management of these two common and interconnected diseases.

Association of parental cardiovascular risk factors with offspring type 1 diabetes mellitus insulin sensitivity

AIM

This study aimed to determine whether the insulin resistance (IR) and lipid profiles in Type 1 Diabetes (T1D) offspring are associated with IR and other cardiovascular risk factors in their parents.

METHODS

This study included 99 T1D patients (19.6 ± 4.0 yrs.), 85 mothers and 60 fathers. Parents' IR was assessed by HOMA-IR, and the insulin sensitivity in T1D patients was assessed by the estimated Glucose Disposal Rate (eGDR).

RESULTS

The eGDR in the T1D offspring was negatively related to age (p = 0.023), weight (p = 0.004), LDL (p = 0.026), and microalbuminuria (p = 0.019). Maternal Type 2 Diabetes (p < 0.001) and HOMA-IR (p = 0.029) were negatively related to eGDR in their T1D offspring. The maternal HOMA-IR and the proband's eGDR were positively (p = 0.012) and negatively (p = 0.042) associated with the birth weight of the T1D offspring, respectively. We didn't find an association with the fathers' profiles.

CONCLUSIONS

In a cohort of offspring with T1D the insulin sensitivity was related to the IR, lipid profile, and the presence of T2D only in their mothers. Precocious screening and treatment of these risk factors beyond glycemic control will benefit T1D with this background.

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Waist-hip ratio measured by bioelectrical impedance analysis as a valuable predictor of chronic kidney disease development

Obesity is a major health problem worldwide and is associated with chronic kidney disease (CKD). Body mass index (BMI) is a common method of diagnosing obesity, but there are concerns about its accuracy and ability to measure body composition. This study evaluated the risk of CKD development in a middle-aged population in association with various body composition metrics. From a prospective cohort of 10,030 middle-aged adults, we enrolled 6727 for whom baseline and follow-up data were available. We collected data pertaining to participants' BMI, manually measured waist-hip ratio (WHR), and various measurements of bioelectrical impedance analysis (BIA), including total body fat content, muscle content, and calculated WHR, and classified the participants into quintiles accordingly. CKD was defined as an estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m² in follow-up laboratory tests. While an increase in BMI, WHR, and total body fat were associated with an elevated risk of CKD, an increase in total body muscle decreased the risk. Among the body composition metrics, WHR measured by BIA had the highest predictive value for CKD (C-statistics: 0.615). In addition, participants who were "healthy overweight, (defined as low WHR but high BMI), exhibited a 62% lower risk of developing CKD compared to those with "normal-weight obesity," (defined as high WHR despite a normal BMI). In conclusion, we suggest that central obesity measured by BIA is a more accurate indicator than BMI for predicting the development of CKD.

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

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

Adipokines and coronary artery calcification in incident dialysis participants

PURPOSE

Adipokines have been associated with increased risk of cardiovascular disease. Our aim was to determine if adipokine levels are associated with coronary artery calcification (CAC) as well as all-cause mortality in incident dialysis patients.

METHODS

In patients new to dialysis, we prospectively investigated the association of adiponectin, leptin and resistin with coronary artery calcification measured by ECG-gated computer tomography. Participants were recruited a median of two months after starting dialysis.

RESULTS

The mean age was 50.0 (12.6) years and 31.1% were women. About 42% percent had BMI > 30. Higher adiponectin levels were inversely associated with CAC progression as change in Agatston score [-155.1 (-267.9, -42.2), p = 0.008] or change in CAC volumes between scans [-2.8 (-4.9, -0.6), p = 0.01]. Higher leptin levels were associated with CAC progression [110.4 (34.3-186.6), p = 0.005]. Decreased leptin [HR 0.5 (0.3-0.9), p = 0.05] was associated with all-cause mortality in adjusted models. There was no significant association between all-cause mortality and adiponectin [1.4 (0.6-3.4), p = 0.4] or resistin [HR 1.7 (0.5-5.0), p = 0.4].

CONCLUSION

High adiponectin protects against CAC progression, but is not associated with increased all-cause mortality. Higher leptin, as well as higher leptin to adiponectin ratio, is associated with CAC progression. Lower leptin levels were associated with all-cause mortality. The association of adipokines and cardiovascular disease in individuals on dialysis is complex and requires further study.

Metabolic Syndrome and Obesity-Related Indices Are Associated with Rapid Renal Function Decline in a Large Taiwanese Population Follow-Up Study

A rapid decline in renal function can cause many complications, and therefore it is important to detect associated risk factors. Few studies have evaluated the associations among obesity-related indices and metabolic syndrome (MetS) with renal function decline. This longitudinal study aimed to explore these relationships in a large cohort of Taiwanese participants. The studied obesity-related indices were waist-to-height ratio (WHtR), A body shape index (ABSI), visceral adiposity index (VAI), lipid accumulation product (LAP), waist-to-hip ratio (WHR), body roundness index (BRI), conicity index (CI), body mass index (BMI), body adiposity index (BAI) and abdominal volume index (AVI). We included 122,068 participants in the baseline study, of whom 27,033 were followed for a median of four years. The baseline prevalence of MetS was 17.7%. Multivariable analysis showed that the participants with MetS and high VAI, WHtR, WHR, LAP, CI, BRI, BMI, BAI, AVI, and ABSI values were significantly associated with a high baseline estimated glomerular filtration rate (eGFR) (all p < 0.001). In addition, the participants with MetS (p < 0.001), high WHtR (p = 0.007), low LAP (p < 0.001), high BRI (p = 0.002), high CI (p = 0.002), high AVI (p = 0.001), high VAI (p = 0.017), and high ABSI (p = 0.013) were significantly associated with a low △eGFR, indicating a rapid decline in renal function. These results showed associations between MetS and high values of obesity-related indices except LAP with high baseline eGFR and rapid decline in kidney function. These findings suggest that screening for MetS and obesity may help to slow the decline in renal function in high-risk populations.

Obesity-Related Chronic Kidney Disease: Principal Mechanisms and New Approaches in Nutritional Management

Obesity is the epidemic of our era and its incidence is supposed to increase by more than 30% by 2030. It is commonly defined as a chronic and metabolic disease with an excessive accumulation of body fat in relation to fat-free mass, both in terms of quantity and distribution at specific points on the body. The effects of obesity have an important impact on different clinical areas, particularly endocrinology, cardiology, and nephrology. Indeed, increased rates of obesity have been associated with increased risk of cardiovascular disease (CVD), cancer, type 2 diabetes (T2D), dyslipidemia, hypertension, renal diseases, and neurocognitive impairment. Obesity-related chronic kidney disease (CKD) has been ascribed to intrarenal fat accumulation along the proximal tubule, glomeruli, renal sinus, and around the kidney capsule, and to hemodynamic changes with hyperfiltration, albuminuria, and impaired glomerular filtration rate. In addition, hypertension, dyslipidemia, and diabetes, which arise as a consequence of overweight, contribute to amplifying renal dysfunction in both the native and transplanted kidney. Overall, several mechanisms are closely related to the onset and progression of CKD in the general population, including changes in renal hemodynamics, neurohumoral pathways, renal adiposity, local and systemic inflammation, dysbiosis of microbiota, insulin resistance, and fibrotic process. Unfortunately, there are no clinical practice guidelines for the management of patients with obesity-related CKD. Therefore, dietary management is based on the clinical practice guidelines for the nutritional care of adults with CKD, developed and published by the National Kidney Foundation, Kidney Disease Outcome Quality Initiative and common recommendations for the healthy population. Optimal nutritional management of these patients should follow the guidelines of the Mediterranean diet, which is known to be associated with a lower incidence of CVD and beneficial effects on chronic diseases such as diabetes, obesity, and cognitive health. Mediterranean-style diets are often unsuccessful in promoting efficient weight loss, especially in patients with altered glucose metabolism. For this purpose, this review also discusses the use of non-classical weight loss approaches in CKD, including intermittent fasting and ketogenic diet to contrast the onset and progression of obesity-related CKD.

Evaluation of the association of serum glypican-4 with prevalent and future kidney function

Serum glypican-4 (GPC4) has been identified as an insulin-sensitizing adipokine serving as a marker for body mass index and insulin resistance in humans. The association of circulating GPC4 with kidney function is to date largely unexplored. Therefore, we aimed to evaluate the association between serum GPC4 and prevalent as well future kidney function in a prospective cohort study. The study included 456 Caucasian coronary angiography patients. After a median follow up period of 3.4 years, data on kidney function was reassessed in all patients. Chronic kidney disease (CKD) was defined by decreased estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² or albuminuria. At baseline, serum GPC4 was significantly associated with decreased eGFR (adjusted odds ratio (OR) per standard deviation = 4.75 [2.66–8.48]; P <  0.001), albuminuria (OR = 1.49 [1.15–1.92]; P = 0.002), and, accordingly, with CKD (OR = 1.75 [1.35–2.26]; P < 0.001). GPC4 levels also significantly and independently predicted the incidence of newly diagnosed decreased eGFR (OR = 2.74 [1.82–4.14]; P < 0.001, albuminuria (OR = 1.58 [1.01–2.46]; P = 0.043, and CKD (OR = 2.16 [1.45–3.23]; P < 0.001). ROC analysis indicated an additional predictive value of GPC4 to a basic prediction model for newly diagnosed CKD and eGFR < 60 mL/min/1.73 m². Our study, therefore, indicates that high serum GPC4 is associated with decreased prevalent and future kidney function.

Diabetes Mellitus and Heart Failure With Preserved Ejection Fraction: Role of Obesity

Heart failure with preserved ejection fraction is a growing epidemic and accounts for half of all patients with heart failure. Increasing prevalence, morbidity, and clinical inertia have spurred a rethinking of the pathophysiology of heart failure with preserved ejection fraction. Unlike heart failure with reduced ejection fraction, heart failure with preserved ejection fraction has distinct clinical phenotypes. The obese-diabetic phenotype is the most often encountered phenotype in clinical practice and shares the greatest burden of morbidity and mortality. Left ventricular remodeling plays a major role in its pathophysiology. Understanding the interplay of obesity, diabetes mellitus, and inflammation in the pathophysiology of left ventricular remodeling may help in the discovery of new therapeutic targets to improve clinical outcomes in heart failure with preserved ejection fraction. Anti-diabetic agents like glucagon-like-peptide 1 analogs and sodium-glucose co-transporter 2 are promising therapeutic modalities for the obese-diabetic phenotype of heart failure with preserved ejection fraction and aggressive weight loss via lifestyle or bariatric surgery is still key to reverse adverse left ventricular remodeling. This review focuses on the obese-diabetic phenotype of heart failure with preserved ejection fraction highlighting the interaction between obesity, diabetes, and coronary microvascular dysfunction in the development and progression of left ventricular remodeling. Recent therapeutic advances are reviewed.

Tolerance to Glucose and Lipid High Metabolic Reactions After Burns in an Obese Rat Model

The goal of this study was to determine what effect obese body weight and a burn injury can have on the metabolism of glucose and lipids in rats. We used a 3 * 3 factorial model design to provide basic glucose and lipid metabolic data characterizing the interaction between different weight and burn injury groups. Two hundred Sprague Dawley rats were categorized into three weight groups (normal, overweight, obese) and then further divided into control, second-degree, and third-degree burn groups. Our model compared interactions between weight and burn injury factors according to the above groups. Blood glucose and lipid metabolism indicators were monitored on the 1st, 3rd, 7th, and 14th days after burn injury occurred, and burned skin and blood samples were collected for testing. Compared with the normal weight group, the overweight group's fast blood glucose, fast insulin, and homeostasis model assessment of insulin resistance were higher (P < .05), and FBG in the obese group was higher than the normal weight group (P < .05). Burn injuries combined with obese body weight had an interactive effect on fast blood glucose, fast insulin, and homeostasis model assessment of insulin resistance after burn injury (P < .05). Burn injury combined with obese body weight had an interaction on low-density lipoprotein cholesterol on the 3rd day after burn injury (P < .05). Burn injury combined with obese weight had no interaction on triglyceride, total cholesterol, and high-density lipoprotein cholesterol (P > .05). Rats in the overweight and obese weight groups were observed to develop an adaptation and tolerance to a higher metabolic rate after burn injuries occurred.

Chronic constant light exposure aggravates high fat diet-induced renal injury in rats

Obesity-related kidney disease is now recognized as a global health issue, with a substantial number of patients developing progressive renal failure and end-stage renal disease. Interestingly, recent studies indicate light pollution is a novel environmental risk factor for chronic kidney disease. However, the impact of light pollution on obesity-related kidney disease remains largely unknown, with its underlying mechanism insufficiently explained. Renal hypoxia induced factor 1α (HIF1α) is critical in the development of glomerulosclerosis and renal fibrosis. The present study explored effects of constant light exposure on high fat diet (HFD) -induced renal injury and its association with HIF1α signal pathway. Thirty-two male Sprague Dawley rats were divided into four groups according to diet (HFD or normal chow diet) and light cycles (light/dark or constant light). After 16 weeks treatment, rats were sacrificed and pathophysiological assessments were performed. In normal chow fed rats, constant light exposure led to glucose abnormalities and dyslipidemia. In HFD fed rats, constant light exposure exacerbated obesity, glucose abnormalities, insulin resistance, dyslipidemia, renal functional decline, proteinuria, glomerulomegaly, renal inflammation and fibrosis. And, constant light exposure caused an increase in HIF1α and a decrease in prolyl hydroxylase domain 1 (PHD1) and PHD2 expression in kidneys of HFD-fed rats. Then, we demonstrated that BMAL1 bound directly to the promoters of PHD1 in mouse podocyte clone 5 cell line (MPC5) by ChIP assays. In conclusion, chronic constant light exposure aggravates HFD-induced renal injuries in rats, and it is associated with activation of HIF1α signal pathway.

Elevated serum leptin levels are associated with lower renal function among middle-aged and elderly adults in Taiwan, a community-based, cross-sectional study

BACKGROUND

Plasma leptin is considered a risk factor for obesity and cardio-metabolic disease, but the link between serum leptin and renal function is still under evaluation. In our study, we focused on the relationship between serum leptin and renal function, and we investigated the relationship in more detail.

METHODS

The 396 middle-aged and elderly Taiwanese adults recruited for our health survey were the subject of our research. All participants agreed to participate and signed a consent form before they joined and completed our study. We divided the participants into three groups according to eGFR tertiles and analyzed the parameters between each group. Then, we used Pearson's correlation test to investigate the relationship between eGFR levels and cardio-metabolic risk factors with adjustment for age. The scatter plot indicates the trend between serum leptin levels and eGFR levels. Participants were reclassified into three subgroups according to their leptin levels and the bar chart reveals the prevalence of chronic kidney disease (CKD) in each group. Finally, we used multivariate linear regression to evaluate the relationship between serum leptin and eGFR levels with adjustment for age, sex, smoking status, drinking status, body mass index (BMI), uric acid levels, hypertension (HTN), diabetes mellitus (DM), and dyslipidemia.

RESULTS

In our study, we analyzed the data from 396 eligible participants. A total of 41.4% of the participants were male, and the average age of all participants was 64.81 years ( ± 8.78). The participants in the high eGFR group were more likely to have lower serum leptin levels. Furthermore, eGFR values were negatively correlated with serum leptin levels even after adjustment for age. The prevalence of CKD in the high serum leptin group was higher than that in the low serum leptin group. Serum leptin levels showed significant negative correlations with eGFR levels (β=-0.14, p<0.01) in the multivariate linear regression after adjusting for age, sex, smoking status, drinking status, BMI, uric acid levels, HTN, DM, and dyslipidemia.

CONCLUSION

According to our study, serum leptin levels show a negative relationship with eGFR levels in middle-aged and elderly people in Taiwan. In addition, high serum leptin levels could be an novel marker to survey kidney failure in clinical practices.

Design, synthesis and bioactive evaluation of geniposide derivatives for antihyperuricemic and nephroprotective effects

Hyperuricemia is a principal factor mediating gout and kidney damage, and xanthine oxidase (XOD) is a key enzyme in the pathogenesis of hyperuricemia. In this context, a series of geniposide derivatives were designed and synthesized, and antihyperuricemic and nephroprotective effects of all derivatives was evaluated in vitro and in vivo. Compound 2e emerged as the most potent XOD inhibitor, with an IC₅₀ value of 6.67 ± 0.46 µM. Simultaneously, cell viability, ROS generation, and SOD levels assay showed that compound 2e could repair the damage of HKC cells by inhibiting the oxidative stress response. The results of the study indicated compound 2e significantly decreased uric acid levels by inhibiting the XOD activity, and repaired kidney damage by inhibiting the expression of TLR4/TLR2/MyD88/NF-κB and NALP3/ASC/caspase-1 signaling pathways. Enzyme inhibition kinetics suggested that compound 2e functioned via reversible mixed competitive inhibition. Moreover, a molecular docking study was performed to gain insight into the binding mode of compound 2e with XOD. These results suggest that geniposide derivatives were potential to be developed into a novel medicine to reveal healthy benefits in natural prevention and reduction risk of hyperuricemia and kidney damage.

Cardiovascular Risk Factors in Children with Obesity, Preventive Diagnostics and Possible Interventions

The increasing burden of obesity plays an essential role in increased cardiovascular morbidity and mortality. The effects of obesity on the cardiovascular system have also been demonstrated in childhood, where prevention is even more important. Obesity is associated with hormonal changes and vascular dysfunction, which eventually lead to hypertension, hyperinsulinemia, chronic kidney disease, dyslipidemia and cardiac dysfunction—all associated with increased cardiovascular risk, leading to potential cardiovascular events in early adulthood. Several preventive strategies are being implemented to reduce the cardiovascular burden in children. This paper presents a comprehensive review of obesity-associated cardiovascular morbidity with the preventive diagnostic workup at our hospital and possible interventions in children.

Diabetic Nephropathy: Challenges in Pathogenesis, Diagnosis, and Treatment

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide. Chronic hyperglycemia and high blood pressure are the main risk factors for the development of DN. In general, screening for microalbuminuria should be performed annually, starting 5 years after diagnosis in type 1 diabetes and at diagnosis and annually thereafter in type 2 diabetes. Standard therapy is blood glucose and blood pressure control using the renin-angiotensin system blockade, targeting A1c < 7%, and <130/80 mmHg. Regression of albuminuria remains an important therapeutic goal. However, there are problems in diagnosis and treatment of nonproteinuric DN (NP-DN), which does not follow the classic pattern of DN. In fact, the prevalence of DN continues to increase, and additional therapy is needed to prevent or ameliorate the condition. In addition to conventional therapies, vitamin D receptor activators, incretin-related drugs, and therapies that target inflammation may also be promising for the prevention of DN progression. This review focuses on the role of inflammation and oxidative stress in the pathogenesis of DN, approaches to diagnosis in classic and NP-DN, and current and emerging therapeutic interventions.

Adipose triglyceride lipase protects renal cell endocytosis in a Drosophila dietary model of chronic kidney disease

Obesity-related renal lipotoxicity and chronic kidney disease (CKD) are prevalent pathologies with complex aetiologies. One hallmark of renal lipotoxicity is the ectopic accumulation of lipid droplets in kidney podocytes and in proximal tubule cells. Renal lipid droplets are observed in human CKD patients and in high-fat diet (HFD) rodent models, but their precise role remains unclear. Here, we establish a HFD model in Drosophila that recapitulates renal lipid droplets and several other aspects of mammalian CKD. Cell type-specific genetic manipulations show that lipid can overflow from adipose tissue and is taken up by renal cells called nephrocytes. A HFD drives nephrocyte lipid uptake via the multiligand receptor Cubilin (Cubn), leading to the ectopic accumulation of lipid droplets. These nephrocyte lipid droplets correlate with endoplasmic reticulum (ER) and mitochondrial deficits, as well as with impaired macromolecular endocytosis, a key conserved function of renal cells. Nephrocyte knockdown of diglyceride acyltransferase 1 (DGAT1), overexpression of adipose triglyceride lipase (ATGL), and epistasis tests together reveal that fatty acid flux through the lipid droplet triglyceride compartment protects the ER, mitochondria, and endocytosis of renal cells. Strikingly, boosting nephrocyte expression of the lipid droplet resident enzyme ATGL is sufficient to rescue HFD-induced defects in renal endocytosis. Moreover, endocytic rescue requires a conserved mitochondrial regulator, peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC1α). This study demonstrates that lipid droplet lipolysis counteracts the harmful effects of a HFD via a mitochondrial pathway that protects renal endocytosis. It also provides a genetic strategy for determining whether lipid droplets in different biological contexts function primarily to release beneficial or to sequester toxic lipids.

Impact of adipose tissue in chronic kidney disease development (Review)

Obesity is a worldwide pandemic health issue. Obesity is associated with the pathogenesis of type 2 diabetes, hypertension, dyslipidemia, cardiovascular diseases, cancer, and kidney diseases. This systemic disease can affect the kidneys by two mechanisms: Indirectly through diabetes mellitus (DM) and hypertension and directly through adipokines secreted by adipose tissue. Obesity is a risk factor for chronic kidney disease (CKD), which is associated with an increased risk of morbidity and mortality among the adult population. Increased visceral adipose tissue leads to renal glomerular hyperfiltration and hyperperfusion, which may lead to glomerular hypertrophy, proteinuria, and CKD development. Adipokines are hormones produced by fat tissue. They are involved in energy homeostasis, sugar and fat metabolism, reproduction, immunity, and thermogenesis control. Hormones and cytokines secreted by adipose tissue contribute to the development and progression of CKD. Decreased serum or urinary adiponectin levels are specific in diabetic and non-diabetic CKD patients, while leptin presents increased levels, and both are associated with the development of glomerulopathy. Excessive adipose tissue is associated with inflammation, oxidative stress (OS), insulin resistance and activation of the renin angiotensin-aldosterone system (RAAS). Therefore, adipose tissue dysfunction plays an important role in the development of CKD.

The Causes and Potential Injurious Effects of Elevated Serum Leptin Levels in Chronic Kidney Disease Patients

Leptin is an adipokine that regulates appetite and body mass and has many other pleiotropic functions, including regulating kidney function. Increased evidence shows that chronic kidney disease (CKD) is associated with hyperleptinemia, but the reasons for this phenomenon are not fully understood. In this review, we focused on potential causes of hyperleptinemia in patients with CKD and the effects of elevated serum leptin levels on patient kidney function and cardiovascular risk. The available data indicate that the increased concentration of leptin in the blood of CKD patients may result from both decreased leptin elimination from the circulation by the kidneys (due to renal dysfunction) and increased leptin production by the adipose tissue. The overproduction of leptin by the adipose tissue could result from: (a) hyperinsulinemia; (b) chronic inflammation; and (c) significant lipid disturbances in CKD patients. Elevated leptin in CKD patients may further deteriorate kidney function and lead to increased cardiovascular risk.

From Obesity to Chronic Kidney Disease: How Can Adipose Tissue Affect Renal Function?

Obesity is directly associated with an increased risk of developing CKD, regardless of other comorbid conditions. Although the molecular mechanisms that link both diseases are not well established, the role of adipose tissue (AT) is becoming increasingly important in obesity-associated kidney damage. In the context of obesity, lipotoxicity and the alteration of AT secretion profile promote inflammation, oxidative stress, and fibrosis in the kidney, which ultimately leads to impaired renal function. Different studies have highlighted the importance of body weight loss in the improvement of renal function markers. In this regard, bariatric surgery, rather than low-calorie diets, has been accepted as the most effective option to lose weight. In fact, a significant reduction in proteinuria and hyperfiltration has been observed in association with surgically induced weight loss. Detection of early signs of kidney dysfunction in patients with obesity has not been accomplished yet, though. Therefore, understanding the harmful effects within the adipo-renal axis is essential to prevent the progression to the irreversible renal insufficiency. MicroRNAs have recently been described as important modulators of normal kidney function. Some of these microRNAs could be potential early markers of kidney damage, which would help with the diagnosis and the prevention of CKD.

Effects of diet and exercise on adipocytokine levels in patients with moderate to severe chronic kidney disease

BACKGROUND AND AIMS

Obesity is a pro-inflammatory risk factor for progression of CKD and cardiovascular disease. We hypothesized that implementation of caloric restriction and endurance exercise would improve adipocytokine profiles in patients with moderate to severe CKD.

METHODS AND RESULTS

We enrolled patients with moderate to severe CKD through a multi-center pilot randomized trial of diet and exercise in a 4-arm design (dietary restriction of 10%-15% reduction in caloric intake, exercise three times/week, combined diet and exercise, and control) (NCT01150851). Adipocytokines (adiponectin and leptin) were measured at the beginning and end of the study period as secondary outcomes. Treatment effect was analyzed in a multivariable model adjusted for baseline outcome values, age, gender, site and diabetes. A total of 122 participants were consented, 111 were randomized (42% female, 25% diabetic, and 91% hypertensive), 104 started intervention and 92 completed the study (Figure 1). Plasma adiponectin levels increased significantly in response to diet by 23% (95% CI: 0.2%, 49.8%, p = 0.048) among participants randomized to the caloric restriction and usual activity arm but not to exercise, whereas circulating leptin did not change by either treatment.

CONCLUSION

Our data suggest that dietary caloric restriction increases plasma adiponectin levels in stage 3-4 CKD patients, with limited effect on leptin levels. These findings suggest the potential for improving the metabolic milieu of CKD with moderate calorie restriction.

Role of Fatty Acid Binding Protein 4 (FABP4) in Kidney Disease

Accumulating evidences indicated that obesity and metabolic syndrome were independent risk factors for the development and progression of kidney diseases. Apart from inflammation, lipotoxicity, and hemodynamic factors, adipokines have been proposed to play crucial roles in the relationship between kidney diseases and metabolic disorders. As one of the key adipokines, fatty acid binding protein 4 (FABP4), which is mainly expressed in adipocytes and macrophages, has recently been shown to be associated with renal dysfunction and kidney damage. Both clinical and experimental studies have proposed circulating FABP4 as a novel predictor for renal injuries, and it might also be a predictor for cardiovascular events in patients with end stage renal disease (ESRD). FABP4 has also been detected in the glomerular cells and epithelial tubular cells in mouse and human kidneys, and the expression of FABP4 in these cells has been involved in the pathogenesis of kidney diseases. In addition, experimental studies suggested that inhibition of FABP4 had protective effects on renal damage. Here, we reviewed current knowledge regarding the role of FABP4 in pathophysiological insights as well as its potential function as a predictor and therapeutic target for kidney diseases.

Kidney damage and associated risk factors in rural and urban sub-Saharan Africa (AWI-Gen): a cross-sectional population study

BACKGROUND

Rapid epidemiological health transitions occurring in vulnerable populations in Africa that have an existing burden of infectious and non-communicable diseases predict an increased risk and consequent prevalence of kidney disease. However, few studies have characterised the true burden of kidney damage and associated risk factors in Africans. We investigated the prevalence of markers for kidney damage and known risk factors in rural and urban settings in sub-Saharan Africa.

METHODS

In this cross-sectional population study (Africa Wits-International Network for the Demographic Evaluation of Populations and their Health Partnership for Genomic Studies [AWI-Gen]), we recruited unrelated adult participants aged 40-60 years from four rural community research sites (Nanoro, Burkina Faso; Navrongo, Ghana; Agincourt and Dikgale, South Africa), and two urban community research sites (Nairobi, Kenya; and Soweto, South Africa). Participants were identified and selected using random sampling frames already in use at each site. Participants completed a lifestyle and medical history questionnaire, had anthropometric and blood pressure measurements taken, and blood and urine samples were collected. Markers of kidney damage were defined as low estimated glomerular filtration rate (eGFR; <60 mL/min per 1·73 m²), presence of albuminuria (urine albumin creatinine ratio >3 mg/mmol); or chronic kidney disease (low eGFR or albuminuria, or both). We calculated age-adjusted prevalence of chronic kidney disease, low eGFR, and albuminuria by site and sex and used logistic regression models to assess risk factors of kidney damage.

FINDINGS

Between August, 2013, and August, 2016, we recruited 10 702 participants, of whom 8110 were analysable. 4120 (50·8%) of analysable participants were male, with a mean age of 49·9 years (SD 5·8). Age-standardised population prevalence was 2·4% (95% CI 2·1-2·8) for low eGFR, 9·2% (8·4-10·0) for albuminuria, and 10·7% (9·9-11·7) for chronic kidney disease, with higher prevalences in South African sites than in west African sites (14·0% [11·9-16·4] in Agincourt vs 6·6% [5·5-7·9] in Nanoro). Women had a higher prevalence of chronic kidney disease (12·0% [10·8-13·2] vs 9·5% [8·3-10·8]) and low eGFR (3·0% [2·6-3·6] vs 1·7% [1·3-2·3]) than did men, with no sex-specific differences for albuminuria (9·9% [8·8-11·0] vs 8·4% [7·3-9·7]). Risk factors for kidney damage were older age (relative risk 1·04, 95% CI 1·03-1·05; p<0·0001), hypertension (1·97, 1·68-2·30; p<0·0001), diabetes (2·22, 1·76-2·78; p<0·0001), and HIV (1·65, 1·36-1·99; p<0·0001); whereas male sex was protective (0·85, 0·73-0·98; p=0·02).

INTERPRETATION

Regional differences in prevalence and risks of chronic kidney disease in sub-Saharan Africa relate in part to varying stages of sociodemographic and epidemiological health transitions across the area. Public health policy should focus on integrated strategies for screening, prevention, and risk factor management in the broader non-communicable disease and infectious diseases framework.

FUNDING

National Human Genome Research Institute, Office of the Director, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institute of Environmental Health Sciences, the Office of AIDS Research, and National Institute of Diabetes and Digestive and Kidney Diseases, all of the National Institutes of Health, and the South African Department of Science and Technology.

Proteomic characterization of obesity-related nephropathy

Background

Nephropathy related to obesity lacks a pathophysiological understanding and definite diagnostic pathways by biomarkers.

Methods

In this study we investigated the association between urinary peptides and body mass index (BMI) and renal function in proteome data sets from 4015 individuals.

Results

A total of 365 urinary peptides were identified to be significantly associated with BMI. The majority of these peptides were collagen fragments. In addition, most of the peptides also demonstrated a significant concordant association with estimated glomerular filtration rate (eGFR) in the investigated cohort, with the presence of diabetes exhibiting no significant association. A new classifier was developed, based on 150 urinary peptides, that enabled the distinction of non-obese subjects with preserved kidney function from obese, non-diabetic subjects with eGFR >45 mL/min/1.73 m² in an independent cohort, with an area under the curve of 0.93.

Conclusions

On a molecular level, the data strongly suggest a link between obesity and fibrosis, which may be a major cause of obesity-related nephropathy.

Bariatric surgery and kidney disease outcomes in severely obese youth

Bariatric surgery, an emerging treatment for severely obese youth with and without T2D, provides marked improvement in insulin resistance, beta-cell function, and central adiposity. Further, preliminary data suggest that bariatric surgery also results in significant improvement in markers of obesity-related nephropathy and DKD, beyond that which can be achieved with current medical interventions. Yet, the mechanisms whereby bariatric surgery attenuates kidney disease remain unclear. This review summarizes the data on the effects of bariatric surgery on obesity-related nephropathy and DKD in youth with and without T2D, in addition to potential mechanisms underlying the nephroprotective effects of weight loss surgery and how these may differ in Roux-en-Y gastric bypass vs. vertical sleeve gastrectomy. Finally, we discuss potential future non-surgical therapies to mitigate kidney disease.

Kidney function in minority children and adolescents with metabolically healthy and unhealthy obesity

Metabolic syndrome and/or body mass index (BMI) ≥40 kg/m² are risk factors for kidney function decline in the general population. To compare creatinine (Cr), estimated glomerular filtration rate (eGFR) and blood urea nitrogen (BUN) between minority children and adolescents with metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO), a chart review was conducted on subjects aged 4 to 20 years with BMI ≥95^th percentile from July 2014 to April 2017. They were stratified into MHO and MUO groups. Cr, eGFR and BUN were studied. Total n = 277: MHO n = 105 vs MUO n = 172. Cr was higher and BUN was lower in MUO whereas eGFR did not differ between the groups. Using general linear model, we found that metabolic status predicted BUN (P = .009) but not Cr or eGFR. When age, sex and Tanner stage matched, BUN, Cr and eGFR were similar between the groups. Higher BUN in MHO could be due to higher dietary protein intake. Subjects were divided into BMI ≥40 vs <40 kg/m² , BUN and eGFR were not different. A trend towards higher Cr in those with BMI ≥40 kg/m² (P = .054) was found; the group being older and taller. After age and height matching, all outcomes were not different. Higher Cr was found in those with elevated blood pressures vs the MHO (P = .047). Those with diastolic blood pressure (DBP) ≥90^th percentile had higher Cr than those with systolic blood pressure ≥90^th percentile (P = .017). Children and adolescents with MUO, and those with BMI ≥40 kg/m² did not appear to have early diminished kidney function. Higher Cr, although in normal range, occurred in those with abnormal DBP.

Predictive performance of lipid accumulation product and visceral adiposity index for renal function decline in non-diabetic adults, an 8.6-year follow-up

BACKGROUND

Lipid accumulation product (LAP) and visceral adiposity index (VAI) are surrogates for visceral adiposity dysfunction. Our aim was to evaluate potential association of these two indices with the incidence of renal function decline.

METHODS

We included 6693 non-diabetic adults age ≥ 18 years, with estimated glomerular filtration rate (eGFR) ≥ 60 ml/min/1.73 m², from the Tehran Lipid and Glucose Study 2002-2005 survey. Natural logarithmic transformation (Ln) was applied for LAP and VAI measures. The incidence of renal function decline, defined as eGFR < 60 ml/min/1.73 m², was evaluated for each gender, across tertiles of Ln LAP, Ln VAI, body mass index (BMI), waist circumference (WC), waist to height ratio (WHtR) and waist to hip ratio (WHR), using Cox-proportional hazard models.

RESULTS

Over a median 8.6 years of follow-up, 1670 new cases of renal function decline were identified (incidence rate 3.2%). After multivariable adjustment, the hazard ratios (HRs) with 95% CI across second and third tertiles of Ln LAP were 1.14 (0.86-1.50) and 1.33 (1.00-1.78) in men (P trend = 0.132); and 1.16 (0.90-1.50) and 1.24 (0.96-1.61) in women (P trend = 0.263), respectively. Multivariable adjusted HRs across second and third tertiles of Ln VAI were 1.40 (1.08-1.83) and 1.35 (1.02-1.78) in men (P trend = 0.031); and 0.93 (0.75-1.15) and 1.15 (0.93-1.41) in women (P trend = 0.072), respectively. HRs across tertiles of BMI, WC, WHtR and WHR were not significant for renal function decline among both genders in any adjustment models.

CONCLUSION

Among the adiposity indices assessed in this study, VAI seems to be an independent predictor of renal function decline only in males.

Lorcaserin and Renal Outcomes in Obese and Overweight Patients in the CAMELLIA-TIMI 61 Trial

BACKGROUND

Obesity is thought to increase renal hyperfiltration, thereby increasing albuminuria and the progression of renal disease. The effect of pharmacologically mediated weight loss on renal outcomes is not well-described. Lorcaserin, a selective serotonin 2C receptor agonist that promotes appetite suppression, led to sustained weight loss without any increased risk for major adverse cardiovascular (CV) events in the CAMELLIA-TIMI 61 trial (Cardiovascular and Metabolic Effects of Lorcaserin in Overweight and Obese Patients-Thrombolysis in Myocardial Infarction 61).

METHODS

CAMELLIA-TIMI 61 randomly assigned 12 000 overweight or obese patients with or at high risk for atherosclerotic CV disease to lorcaserin or placebo on a background of lifestyle modification. The primary renal outcome was a composite of new or worsening persistent micro- or macroalbuminuria, new or worsening chronic kidney disease, doubling of serum creatinine, end-stage renal disease, renal transplant, or renal death.

RESULTS

At baseline, 23.8% of patients had an estimated glomerular filtration rate (eGFR) <60 mL·min^-1·1.73 m^-2 and 19.0% had albuminuria (urinary albumin:creatinine ratio ≥30 mg/g). Lorcaserin reduced the risk of the primary renal composite outcome (4.2% per year versus 4.9% per year; hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.79-0.96; P=0.0064). The benefit was consistent across subpopulations at increased baseline CV and renal risk. Lorcaserin improved both eGFR and urinary albumin:creatinune ratio within the first year after randomization. The effect of lorcaserin on weight, hemoglobin A1c, and systolic blood pressure was consistent regardless of baseline renal function. Likewise, there was no excess in cardiovascular events in patients assigned to lorcaserin in comparison with placebo, regardless of renal function. After adjustment for baseline characteristics, those with evidence of kidney disease were at increased risk of major CV events. Compared with patients with an eGFR ≥90 mL·min^-1·1.73 m^-2, those with an eGFR 60-90 and those <60 mL·min^-1·1.73 m-2 had HRs of 1.25 (95% CI, 1.01, 1.56) and 1.51 (95% CI, 1.17, 1.95), respectively ( P for trend 0.0015). Likewise, compared with patients with no albuminuria (<30 mg/g), those microalbuminuria and those with macroalbuminuria had HRs of 1.46 (95% CI, 1.22, 1.74) and 2.10 (95% CI, 1.58, 2.80), respectively ( P for trend <0.0001).

CONCLUSIONS

Renal dysfunction was associated with increased CV risk in overweight and obese patients. When added to diet and lifestyle, lorcaserin reduced the rate of new-onset or progressive renal impairment in comparison with placebo.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02019264.

Elevation of serum adiponectin in mildly decreased glomerular filtration rate

Background

Adiponectin secreted by adipocytes plays a key role in insulin sensitivity, anti-inflammation, and antiatherosclerosis. It is involved in several conditions including obesity, type 2 diabetes mellitus, cardiovascular disease, and chronic kidney disease (CKD). Glomerular filtration rate is monitored to indicate the kidney function and CKD progression.

Objective

To assess the serum adiponectin levels in individuals with normal and mildly decreased glomerular filtration rate, analyze the association of serum adiponectin with various physical and biological parameters, and test whether serum adiponectin is the risk factor of mildly decreased glomerular filtration rate.

Methods

This cross-sectional study was conducted in 172 individuals with 35–60 years of age. Serum samples were collected and divided into two groups, based on estimated glomerular filtration rate (eGFR): 90 with normal eGFR (G1, eGFR ≥90 mL/min/1.73 m2) and 82 with mildly decreased eGFR (G2, eGFR = 60–89 mL/min/1.73 m2). Anthropometric data were recorded. Serum adiponectin was measured by enzyme-linked immunosorbent assay.

Results

Serum adiponectin levels were significantly increased in individuals with mildly decreased eGFR (G2), compared to G1 (8.23 ± 3.26 µg/mL and 6.57 ± 3.24 µg/mL, respectively; P = 0.001). Serum adiponectin was positively associated with age and high-density lipoprotein cholesterol but negatively associated with weight, body mass index, triglyceride, and waist and hip circumferences. Univariate analysis showed that serum adiponectin was significantly correlated with mildly decreased eGFR; however, when adjusting for confounding factors, there were no correlations. Furthermore, multivariate regression analysis showed that individuals at the age of 46–55 years (4.0; 95% CI: 1.9–8.3) and > 55 years (11.4; 95% CI: 3.7–35.5) were significantly correlated with mildly decreased eGFR.

Conclusions

Serum adiponectin was significantly elevated in individuals with mildly decreased eGFR and may be a modulation factor, but was not an independent risk factor for mildly kidney damage. Further study is needed to clarify its potential benefits as monitoring biomarker for CKD progression.

Serum levels of the adipokine zinc-alpha2-glycoprotein (ZAG) predict mortality in hemodialysis patients

Wasting has been associated with increased cardiovascular and all-cause mortality in chronic kidney disease (CKD). We investigated whether serum zinc-alpha2-glycoprotein (ZAG), a potent cachectic and lipid-mobilizing factor that is increased in patients with CKD, predicts clinical outcomes in patients on chronic hemodialysis. We quantified serum ZAG at baseline in a prospective cohort of 252 patients undergoing maintenance hemodialysis. Serum ZAG concentrations were inversely associated with serum albumin, creatinine, and triglycerides and, conversely, positively associated with age. Although ZAG is strongly linked to protein energy wasting (PEW) in patients with cancer, higher ZAG concentrations were not associated with PEW in our cohort. During a mean study follow-up of 954 days, 49 patients died and 62 patients experienced a cardiovascular event. Kaplan-Meier analysis revealed a significant correlation between serum ZAG concentrations and all-cause mortality and cardiovascular events. In separate multivariable Cox regression models, serum ZAG concentrations remained significantly associated with all-cause mortality and cardiovascular events after adjustment for demographic factors (age, sex, and dialysis vintage), metabolic parameters (serum albumin, prealbumin, triglycerides, cholesterol, normalized protein catabolic rate, and body mass index), and cardiovascular risk factors (diabetes, dyslipidemia, history of cardiovascular disease, smoking, and diuretic use as a proxy of residual renal function). Thus, serum ZAG appears to be a strong and independent predictor of mortality and cardiovascular events in patients with end-stage renal disease. Further studies are necessary to confirm this association and to elucidate the underlying mechanisms.

Endocannabinoid System and the Kidneys: From Renal Physiology to Injury and Disease

Introduction: As the prevalence of kidney disease continues to rise worldwide, there is accumulating evidence that kidney injury and dysfunction, whether acute or chronic, is associated with major adverse outcomes, including mortality. Meanwhile, effective therapeutic options in the treatment of acute kidney injury (AKI) and chronic kidney disease (CKD) have been sparse. Many of the effective treatments that are routinely utilized for different pathologies in patients without kidney disease have failed to demonstrate efficacy in those with renal dysfunction. Hence, there is an urgent need for discovery of novel pathways that can be targeted for innovative and effective clinical therapies in renal disease states.

Discussion: There is now accumulating evidence that the endocannabinoid (EC) system plays a prominent role in normal renal homeostasis and function. In addition, numerous recent studies have described mechanisms through which alteration in the EC system can contribute to kidney damage and disease. These include a potential role for cannabinoid receptors in tubulo-glomerular damage and fibrosis, which are common features of AKI, interstitial nephritis, glomerulopathy, and other conditions leading to AKI and CKD.

Conclusion: These findings suggest that manipulating the EC system may be an effective therapeutic strategy for the treatment of kidney disease and injury. However, further mechanistic studies are needed to fully delineate the role of this system in various conditions affecting the kidneys. Furthermore, while most of the current literature is focused on the role of the EC system as a whole in renal pathophysiology, future studies will also need to clarify the contribution of each component of this system, including the EC mediators, in the pathogenesis of kidney disease and their potential role as part of a therapeutic strategy.

Renal-Protective Effects of the Peroxisome Proliferator-Activated Receptor-γ Agonist Pioglitazone in ob/ob Mice

Background

This study investigated the therapeutic effects of the peroxisome proliferator-activated receptor-γ (PPARγ) agonist pioglitazone in ob/ob mice with obesity-related glomerulopathy (ORG).

Material/Methods

A total of 24 mice were divided into 3 groups: wild-type C57BL/6 mice (n=8), ob/ob mice (n=8), and ob/ob mice receiving pioglitazone treatment (n=8). Body mass, blood glucose, serum adiponectin (ADP), and urine microalbumin (mALB) levels were determined. Renal histology was examined using light and electron microscopy. Wilms tumor 1 (WT1), Zonula occludens-1 (ZO-1), AMP activated protein kinase (AMPK), and NADPH oxidase-4 (NOX-4) expression were evaluated by immunohistochemistry and Western blot.

Results

Serum ADP did not alter between weeks 0 and 12 in the control group, while the ob/ob mice showed a time-dependent decrease that was prevented by pioglitazone. Urinary mALB did not alter between week 0 and 12 in the control group, but was higher in week 0 and week 12 in the ob/ob group. Pioglitazone prevented the rise in urinary mALB in week 12. Histology revealed glomerulomegaly, mesangial proliferation, focal segmental glomerulosclerosis, and foot processes fusion in the ob/ob group, which were ameliorated by pioglitazone treatment. Compared to the control group, ob/ob mice had a higher kidney index and glomerular diameter, which were reduced by pioglitazone treatment. Immunohistochemical and Western blot experiments revealed lower expression levels of WT1, ZO-1, and AMPK and higher NOX-4 expression level in the ob/ob group, which was prevented by pioglitazone treatment.

Conclusions

Pioglitazone, a PPARγ agonist, can prevent ORG, probably by reducing oxidative stress.

Purinergic 2X7 Receptor is Involved in the Podocyte Damage of Obesity-Related Glomerulopathy via Activating Nucleotide-Binding and Oligomerization Domain-Like Receptor Protein 3 Inflammasome

Background:

The nucleotide-binding and oligomerization domain-like receptor protein 3 (NLRP3) inflammasome composed of NLRP3, apoptosis-associated speck-like protein containing CARD (ASC), and caspase-1 is engaged in the inflammatory response of many kidney diseases and can be activated by purinergic 2X7 receptor (P2X7R). This study was conducted to explore whether P2X7R plays a pathogenic role in the podocyte damage of obesity-related glomerulopathy (ORG) and whether this role is mediated by the activation of NLRP3 inflammasome.

Methods:

A mouse model of ORG was established by high-fat diet feeding. The conditionally immortalized mouse podocytes were cultured with leptin or with leptin and P2X7R antagonist (KN-62 or A438079). The mRNA and protein expression of the P2X7R and NLRP3 inflammasome components including NLRP3, ASC, and caspase-1, as well as the podocyte-associated molecules including nephrin, podocin, and desmin in mouse renal cortex or cultured mouse podocytes were tested by real-time-polymerase chain reaction and Western blot analysis, respectively.

Results:

The significantly upregulated expression of P2X7R and NLRP3 inflammasome components and the NLRP3 inflammasome activation were observed in the renal cortex (in fact their location in podocytes was proved by confocal microscopy) of ORG mice in vivo, which were accompanied with the morphological changes of podocyte damage and the expression changes of podocyte-associated molecules. Similar changes in the expression of P2X7R and NLRP3 inflammasome components as well as in the expression of podocyte-associated molecules were also observed in the cultured podocyte studies treated by leptin in vitro, and all of the above changes were significantly attenuated by the P2X7R antagonist KN-62 or A438079.

Conclusions:

P2X7R could trigger the activation of NLRP3 inflammasome, and the activated P2X7R/NLRP3 inflammasome in podocytes might be involved in the podocyte damage of ORG.

Childhood Obesity and the Metabolic Syndrome

Obesity is a leading cause of chronic kidney disease. Children with severe obesity have an increased prevalence of early kidney abnormalities and are at high risk to develop kidney failure in adulthood. The pathophysiology of obesity-related kidney disease is incompletely understood, although the postulated mechanisms of kidney injury include hyperfiltration, adipokine dysregulation, and lipotoxic injury. An improved understanding of the long-term effects of obesity on kidney health is essential treat the growing epidemic of obesity-related kidney disease. The purpose of this article is to review the epidemiology, pathophysiology, clinical features, and management of obesity-related kidney disease in children and adolescents.

Oxidative stress and adipokine levels were significantly correlated in diabetic patients with hyperglycemic crises

BACKGROUND

To investigate the relationship between blood adipokine level and oxidative stress in diabetic patients with hyperglycemic crises before and after treatment.

METHODS

We measured superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, total antioxidant capacity (TAC), and levels of 8-iso-prostaglandin F2α (8-iso-PGF2α), adiponectin, leptin, and resistin in 63 diabetic patients with hyperglycemic crises.

RESULTS

Prior to treatment, patients with hyperglycemic crises had significantly lower serum SOD activity, TAC, and adiponectin and leptin levels, and higher serum levels of MDA, 8-iso-PGF2α, and resistin compared with the healthy control individuals (all at P < 0.05). After treatment, SOD, TAC, adiponectin, and leptin levels increased significantly, while MDA, 8-iso-PGF2α, and resistin levels decreased significantly (all at P < 0.05) in the patients.

CONCLUSIONS

Diabetic patients with hyperglycemic crises have increased oxidative stress, which is associated with serum adipokine abnormalities; improved oxidative stress after treatment suggests that oxidative stress may serve as target and/or indicator for the treatment of hyperglycemic crises.

Relation of multi-marker panel to incident chronic kidney disease and rapid kidney function decline in African Americans: the Jackson Heart Study

Background

Few investigations have evaluated the incremental usefulness of multiple biomarkers representing varying physiological pathways for predicting risk of renal outcomes in African Americans.

Design, setting, participants, and measurements

We related a multi-marker panel to incident chronic kidney disease (CKD) and rapid kidney function decline (RKFD) in 2813 Jackson Heart Study participants without prevalent CKD at exam 1 (2000–2004) and with complete assays at exam 1 for 9 biomarkers: adiponectin, aldosterone, B-natriuretic peptide [BNP], cortisol, high sensitivity C-reactive protein (hsCRP), endothelin, homocysteine, plasma renin activity and mass. Incident CKD was defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² at exam 3 while RKFD was defined as eGFR ≥30% loss between exams 1 and 3 (8.2 median years). We employed multiple logistic regression model to describe association between the panel and incident CKD and RKFD and used backward elimination strategy to estimate the most parsimonious biomarker model while controlling for conventional risk factors.

Results

The multi-marker panel predicted the risk for both incident CKD (odds ratios [OR], 2.72; 95% confidence intervals [CI], 1.63, 4.56; P = 0.001) and RKFD (2.61; 95% CI, 1.67, 4.08; P < 0.001). Per standard deviation increase in log biomarker concentrations were significantly (multivariable adjusted odds ratios, [95% confidence interval], p-value) associated with incident CKD: plasma adiponectin (1.24 [1.07, 1.44], p = 0.005) and leptin (1.3 [1.06, 1.61], p = 0.011), and with RKFD: plasma adiponectin (1.22 [1.06, 1.40], p = 0.006); hsCRP (1.17 [1.01, 1.36], p = 0.031) and aldosterone (0.85 [0.74, 0.96], p = 0.012). Moderate levels (3rd quartile) of aldosterone were inversely associated with incident CKD (0.54 [0.35, 0.82], p = 0.004) while leptin was associated with RKFD (1.64 [1.10, 2.44], p = 0.015). Biomarkers improved CKD risk prediction (P = 0.003) but not RKFD risk prediction (P = 0.10).

Conclusion

In this community-based sample of African Americans, a multi-marker panel added only moderate predictive improvement compared to conventional risk factors.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1026-y) contains supplementary material, which is available to authorized users.

Inhibition of pannexin-1 channel activity by adiponectin in podocytes: Role of acid ceramidase activation

The pannexin-1 (Panx1) channel has been reported to mediate the release of ATP that is involved in local tissue inflammation, obesity, and many chronic degenerative diseases. It remains unknown whether Panx1 is present in podocytes and whether this channel in podocytes mediates ATP release leading to glomerular inflammation or fibrosis. To answer these questions, we first characterized the expression of Panx channels in podocytes. Among the three known pannexins, Panx1 was the most enriched in podocytes, either cultured or native in mouse glomeruli. Using a Port-a-Patch planar patch-clamp system, we recorded a large voltage-gated outward current through podocyte membrane under the Cs⁺in/Na⁺out gradient. Substitution of gluconate or aspartate for chloride in the bath solution blocked voltage-gated outward currents and shifted the reversal potential of Panx1 currents to the right, indicating the anion permeability of this channel. Pharmacologically, the recorded voltage-gated outward currents were substantially attenuated by specific Panx1 channel inhibitors. Given the anti-inflammatory and intracellular ATP restorative effects of adiponectin, we tested whether this adipokine inhibits Panx1 channel activity to block ATP release. Adiponectin blocked Panx1 channel activity in podocytes. Mechanistically, inhibition of acid ceramidase (AC) remarkably enhanced Panx1 channel activity under control conditions and prevented the inhibition of Panx1 channel by adiponectin. Correspondingly, intracellular addition of AC products, sphingosine or sphingosine-1-phosphate (S1P), blocked Panx1 channel activity, while elevation of intracellular ceramide had no effect on Panx1 channel activity. These results suggest that adiponectin inhibits Panx1 channel activity in podocytes through activation of AC and associated elevation of intracellular S1P.

Leptin, cardiovascular diseases and type 2 diabetes mellitus

Leptin, an adipokine that is implicated in the control of food intake via appetite suppression, may also stimulate oxidative stress, inflammation, thrombosis, arterial stiffness, angiogenesis and atherogenesis. These leptin-induced effects may predispose to the development of cardiovascular diseases. In the present review we discuss the evidence linking leptin levels with the presence, severity and/or prognosis of both coronary artery disease and non-cardiac vascular diseases such as stroke, carotid artery disease, peripheral artery disease (PAD) and abdominal aortic aneurysms (AAA) as well as with chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM). Leptin levels have been positively associated with the presence, severity, extent and lesion complexity of coronary atherosclerosis as well as with the presence, severity and poor clinical outcomes of both ischemic and hemorrhagic strokes. But conflicting results also exist. Furthermore, leptin was reported to independently predict common carotid intima-media thickness and carotid plaque instability. A link between hyperleptinemia and PAD has been reported, whereas limited data were available on the potential association between leptin and AAA. Elevated leptin concentrations have also been related to CKD incidence and progression as well as with insulin resistance, T2DM, micro- and macrovascular diabetic complications. Statins and antidiabetic drugs (including sitagliptin, metformin, pioglitazone, liraglutide and empagliflozin) may affect leptin levels. Further research is needed to establish the potential use (if any) of leptin as a therapeutic target in these diseases.

Flavanols are potential anti-obesity agents, a systematic review and meta-analysis of controlled clinical trials

BACKGROUND

The anti-obesity potential of flavonoids has been shown by animal and human studies. In this meta-analysis, we systematically reviewed controlled clinical trials and quantified the effects of flavonoids and flavonoid subclasses on obesity-related anthropometric measures.

METHODS AND RESULTS

PubMed, EMBASE, Scopus, Web of Science, and ProQuest databases were searched to identify trials examining the effect of flavonoids on body mass index (BMI), waist circumference, and body fat percentage. Fifty eight trials passed the eligibility process. Analysis endpoints were calculated as the mean difference between baseline and post-treatment. Flavonoids were in subclasses of flavanols, flavonols, isoflavones, flavanones, anthocyanins, and proanthocyanidins. They were mostly in the form of supplements and dosages varying from 40 to 1300 mg/day. Among flavonoid subclasses, flavanols showed potential for decreasing BMI, in the overall population (mean difference (MD) = -0.28 kg/m², P = 0.04; n = 21) and in the subgroups of Asians (MD = -0.42 kg/m²; P = 0.046; n = 13), ages < 50 years (MD = -0.50 kg/m²; P = 0.008; n = 14), BMI ≥ 25 kg/m² (MD = -0.30 kg/m²; P = 0.049; n = 15), and at doses ≥ 500 mg/day (MD = -0.36 kg/m²; P = 0.049; n = 12). Isoflavones also decreased BMI of non-Asian populations (MD = -0.26 kg/m²; P = 0.035; n = 13) and doses ≥ 75 mg/day (MD = -0.34 kg/m²; P = 0.027; n = 8). In the overall assessment, flavanols also decreased waist circumference (MD = -0.60 cm; P = 0.02; n = 18) but had no significant effect on body fat percentage. The available trials did not reveal significant effects from flavonols, flavanones, and anthocyanins on the specified anthropometric measures.

CONCLUSIONS

Overall results of this meta-analysis showed that flavanols have potential against obesity.