Consequences of Glomerular Hyperfiltration: The Role of Physical Forces in the Pathogenesis of Chronic Kidney Disease in Diabetes and Obesity

Renoprotective mechanisms of exercise training against acute and chronic renal diseases - A perspective based on experimental studies

Regular exercise training can lead to several health benefits, reduce mortality risk, and increase life expectancy. On the other hand, a sedentary lifestyle is a known risk factor for chronic diseases and increased mortality. Acute kidney injury (AKI) and chronic kidney disease (CKD) represent a significant global health problem, affecting millions of people worldwide. The progression from AKI to CKD is well-recognized in the literature, and exercise training has emerged as a potential renoprotective strategy. Thus, this article aims to review the main molecular mechanisms underlying the renoprotective actions of exercise training in the context of AKI and CKD, focusing on its antioxidative, anti-inflammatory, anti-apoptotic, anti-fibrotic, and autophagy regulatory effects. For that, bibliographical research was carried out in Medline/PubMed and Scielo databases. Although the pathophysiological mechanisms involved in renal diseases are not fully understood, experimental studies demonstrate that oxidative stress, inflammation, apoptosis, and dysregulation of fibrotic and autophagic processes play central roles in the development of tissue damage. Increasing evidence has suggested that exercise can beneficially modulate these mechanisms, potentially becoming a safe and effective non-pharmacological strategy for kidney health protection and promotion. Thus, the evidence base discussed in this review suggests that an adequate training program emerges as a valuable tool for preserving renal function in experimental animals, mainly through the production of antioxidant enzymes, nitric oxide (NO), irisin, IL-10, and IL-11. Future research can continue to explore these mechanisms to develop specific guidelines for the prescription of exercise training in different populations of patients with kidney diseases.

The New Challenge of Obesity - Obesity-Associated Nephropathy

In recent years, obesity has become one of the major diseases that affect human health and consume human health resources, especially when it causes comorbidities such as hypertension, diabetes, cardiovascular disease and kidney disease. Many studies have demonstrated that obesity is associated with the development of chronic kidney disease and can exacerbate the progression of end-stage renal disease. This review described the mechanisms associated with the development of obesity-associated nephropathy and the current relevant therapeutic modalities, with the aim of finding new therapeutic targets for obesity-associated nephropathy. The mechanisms of obesity-induced renal injury include, in addition to the traditional alterations in renal hemodynamics, the involvement of various mechanisms such as macrophage infiltration in adipose tissue, alterations in adipokines (leptin and adiponectin), and ectopic deposition of lipids. At present, there is no "point-to-point" treatment for obesity-induced kidney injury. The renin-angiotensin-aldosterone system (RAAS) inhibitors, sodium-dependent glucose transporter 2 (SGLT-2) inhibitors and bariatric surgery described in this review can reduce urinary protein to varying degrees and delay the progression of kidney disease. In addition, recent studies on the therapeutic effects of intestinal flora on obesity may reduce the incidence of obesity-related kidney disease from the perspective of primary prevention. Both of these interventions have their own advantages and disadvantages, so the continuous search for the mechanism of obesity-induced related kidney disease will be extremely helpful for the future treatment of obesity-related kidney disease.

Obesity and glomerular filtration rate

Obesity has received considerable attention in general medicine and nephrology over the last few years. This condition increases the risk of metabolic syndrome, diabetes mellitus, hypertension, and dyslipidemia, which are the main risk factors for developing chronic kidney disease (CKD). Kidney damage caused by obesity can be explained by many mechanisms, such as sympathetic nervous and renin-angiotensin-aldosterone systems activation, mechanical stress, hormonal unbalance, as well as inflammatory cytokines production. Even though creatinine-based glomerular filtration rate (GFR) equations in obese individuals have been validated (Salazar-Corcoran and CKD-MCQ), changes in body weight after bariatric surgery (BS) leads to changes in creatininemia, affecting its reliability. Thus, an average between creatine and cystatin-based GFR equations would be more appropriate in this setting. Bariatric surgery can reverse diabetes mellitus and improve hypertension, which are the main causes of CKD. Conclusion: GFR can be affected by obesity and BS, and its value should be cautiously evaluated in this setting.

Chronic Kidney Disease Diets for Kidney Failure Prevention: Insights from the IL-11 Paradigm

Nearly every fifth adult in the United States and many older adults worldwide are affected by chronic kidney disease (CKD), which can progress to kidney failure requiring invasive kidney replacement therapy. In this review, we briefly examine the pathophysiology of CKD and discuss emerging mechanisms involving the physiological resolution of kidney injury by transforming growth factor beta 1 (TGFβ1) and interleukin-11 (IL-11), as well as the pathological consequences of IL-11 overproduction, which misguides repair processes, ultimately culminating in CKD. Taking these mechanisms into account, we offer an overview of the efficacy of plant-dominant dietary patterns in preventing and managing CKD, while also addressing their limitations in terms of restoring kidney function or preventing kidney failure. In conclusion, this paper outlines novel regeneration strategies aimed at developing a reno-regenerative diet to inhibit IL-11 and promote repair mechanisms in kidneys affected by CKD.

The relation between autophagy modulation by intermittent fasting and aquaporin 2 expression in experimentally induced diabetic nephropathy in albino rat

Polyuria is an early sign of diabetic nephropathy (DN) that produces dehydration in diabetic patients. This could be caused by alteration of renal aquaporin 2 (AQP2) expression. This study aimed to describe the relation between autophagy modulation via intermittent fasting (IF) and renal AQP2 expression and polyuria in case of DN. We divided the rats into control, DN and IF groups. After 2 and 4 weeks of diabetes induction, blood glucose (BG), serum creatinine (Scr), urine volume, and 24 hours urine protein (UP) were examined. Diabetic nephropathy histopathological index (DNHI) was calculated to evaluate histopathological changes. Immunohistochemistry and real-time PCR were performed to measure the levels of AQP2 and the autophagy marker; LC3 in kidney tissue. DNHI was correlated to the PCR and immunoexpression of AQP2 and LC3. Intermittent fasting significantly decreased the BG, Scr, urine volume, 24 hours UP, and DNHI as compared diabetes. Diabetes significantly elevated the immunoreactivity and mRNA expression levels of AQP2 and LC3 as compared to the control. However, the IF decreased AQP2 and stimulated autophagy in cyclic fashion. Our data revealed significant positive correlations between AQP2 and LC3 at the level of immunoexpression and mRNA at 2nd weeks. Taken together, these data showed that autophagy stimulation didn't regulate AQP2 expression in case of diabetic nephropathy, however IF decreased polyuria through improvement of glycemic state.

Dihydropyridine Calcium Channel Blockers and Kidney Outcomes

BACKGROUND

Early trials of dihydropyridine calcium channel blockers (DCCBs) suggest a detrimental effect on intraglomerular pressure and an association with albuminuria.

OBJECTIVE

We sought to evaluate the associations of DCCB initiation with albuminuria and kidney failure with replacement therapy (KFRT) and to determine whether renin-angiotensin system (RAS) blockade modified these associations.

DESIGN

We conducted a target trial emulation study using a new user, active comparator design and electronic health record data from Geisinger Health.

PARTICIPANTS

We included patients without severe albuminuria or KFRT who were initiated on a DCCB or thiazide (active comparator) between January 1, 2004, and December 31, 2019.

MAIN MEASURES

Using inverse probability of treatment weighting, we performed doubly robust Cox proportional hazards regression to estimate the association of DCCB initiation with incident severe albuminuria (urine albumin to creatinine ratio > 300 mg/g) and KFRT, overall and stratified by RAS blocker use.

KEY RESULTS

There were 11,747 and 26,758 eligible patients initiating a DCCB and thiazide, respectively, with a weighted baseline mean age of 60 years, systolic blood pressure of 143 mm Hg, and eGFR of 86 mL/min/1.73 m2, and with a mean follow-up of 8 years. Compared with thiazides, DCCBs were significantly associated with the development of severe albuminuria (hazard ratio [HR], 1.29; 95% confidence interval [CI], 1.16-1.43), with attenuation of risk in the presence of RAS blockade (P for interaction < 0.001). The risk of KFRT was increased among patients without RAS blockade (HR, 1.66; 95% CI, 1.19-2.31), but not with RAS blockade (P for interaction = 0.005).

CONCLUSIONS

DCCBs were associated with increased risk of albuminuria and, in the absence of RAS blockade, KFRT. These findings suggest coupling DCCB therapy with RAS blockade may mitigate adverse kidney outcomes.

Pediatric kidney dimensions and risk of persistent albuminuria in Mexican adolescents

In Mexico, chronic kidney disease of unknown origin is highly prevalent. Screening studies in adolescents have shown persistent microalbuminuria (pACR), adaptive podocytopathy and decreased kidney volume (KV). Here, we sought to develop normality tables of kidney dimensions by ultrasound in the Mexican state of Aguascalientes pediatric population (0 to 18y) and evaluate the relationship between the KV and pACR among the region's adolescents in a cross-sectional study. Kidney length (KL) and KV were determined by ultrasound. Our findings were compared with those in international literature of different populations where tables and graphs of normal kidney dimensions by ultrasound were reported. We compared organ dimensions in individuals above the age of 11 without albuminuria with those in patients with pACR recruited through screening studies in adolescents in Aguascalientes. This included 1068 individuals to construct percentile tables and graphs of the KL. Kidney dimensions were significantly lower when compared with all international comparisons. From a total 14,805 screen individuals, we compared 218 adolescents with pACR and 377 individuals without significant albuminuria. The Total KV adjusted to body surface (TKVBS) was significantly associated with pACR (odds ratio 1.03, 95% confidence interval 1.02-1.03). The upper quartile of TKVBS was highly associated with pACR (7.57, 4.13-13.87), hypertension (2.53, 1.66-3.86), and hyperfiltration (26 vs 11.5%). Thus, TKVBS is directly associated with pACR while greater KV, arterial hypertension, and hyperfiltration in patients with pACR suggest that the increase in volume is secondary to kidney hypertrophy. Additionally, the adaptative podocytopathy with low fibrosis seen on kidney biopsy which was performed in a subset of patients, and the smaller kidney dimensions in our population point to prenatal oligonephronia as the primary cause of the detected kidney disease.

Crosstalk among podocytes, glomerular endothelial cells and mesangial cells in diabetic kidney disease: an updated review

Diabetic kidney disease (DKD) is a long-term and serious complication of diabetes that affects millions of people worldwide. It is characterized by proteinuria, glomerular damage, and renal fibrosis, leading to end-stage renal disease, and the pathogenesis is complex and involves multiple cellular and molecular mechanisms. Among three kinds of intraglomerular cells including podocytes, glomerular endothelial cells (GECs) and mesangial cells (MCs), the alterations in one cell type can produce changes in the others. The cell-to-cell crosstalk plays a crucial role in maintaining the glomerular filtration barrier (GFB) and homeostasis. In this review, we summarized the recent advances in understanding the pathological changes and interactions of these three types of cells in DKD and then focused on the signaling pathways and factors that mediate the crosstalk, such as angiopoietins, vascular endothelial growth factors, transforming growth factor-β, Krüppel-like factors, retinoic acid receptor response protein 1 and exosomes, etc. Furthermore, we also simply introduce the application of the latest technologies in studying cell interactions within glomerular cells and new promising mediators for cell crosstalk in DKD. In conclusion, this review provides a comprehensive and updated overview of the glomerular crosstalk in DKD and highlights its importance for the development of novel intervention approaches.

Anti-obesity pharmacotherapy in adults with chronic kidney disease

Obesity is a leading risk factor for the development and progression of kidney disease and a major barrier to optimal management of patients with chronic kidney disease. While in the past anti-obesity drugs offered only modest weight loss efficacy in exchange for various safety and tolerability risks, a wave of safer, more tolerable, and more effective treatment options is transforming the management of obesity. This review evaluates current and future pharmacologic anti-obesity therapy in adults through a kidney-oriented lens. It also explores the goals of anti-obesity treatment, describes the underlying putative mechanisms of action, and raises important scientific questions that deserve further exploration in people with chronic kidney disease.

Mitochondria-Derived Reactive Oxygen Species Contribute to Synergistic Interaction of Diabetes and Hypertension in Causing Chronic Kidney Injury

Diabetes (DM) and hypertension (HTN) are major risk factors for chronic kidney injury, together accounting for >70% of end-stage renal disease. The combination of DM and HTN significantly accelerates development of renal injury; however, the underlying mechanisms of this synergy are still poorly understood. This study assessed whether mitochondria (MT) dysfunction is essential in developing renal injury in a rat model with combined DM and HTN. Type 1 DM was induced in Wistar rats by streptozotocin (STZ). HTN was induced six weeks later by inter-renal aorta constriction between the renal arteries, so that right kidneys were exposed to HTN while left kidneys were exposed to normotension. Kidneys exposed to DM or HTN alone had only mild glomerular injury and urinary albumin excretion (UAE). In contrast, kidneys exposed to DM plus 8 weeks HTN had significantly increased UAE and glomerular structural damage with reduced glomerular filtration rate. Marked increases in MT-derived reactive oxygen species (ROS) were also observed in right kidneys exposed to HTN+DM. We further tested whether treatment with MT-targeted antioxidant (MitoTEMPO) after the onset of HTN attenuates renal injury in rats with DM+HTN. Results show that kidneys in DM+AC+MitoTEMPO rats had lower UAE, less glomerular damage, and preserved MT function compared to untreated DM+AC rats. Our studies indicate that MT-derived ROS play a major role in promoting kidney dysfunction when DM is combined with HTN. Preserving MT function might be a potential therapeutic approach to halt the development of renal injury when DM coexists with HTN.

Periconceptional Serum Creatinine and Risk of Childhood Autism Spectrum Disorder: A Research Letter

Background

Autism spectrum disorder (ASD) is a neurodevelopmental condition that manifests in early childhood, in which the maternal metabolic syndrome may be a risk factor. The kidney is a barometer of maternal metabolic syndrome duration and severity.

Objective

The main objective of this study is to determine whether periconceptional kidney function is associated with ASD in early childhood.

Design Setting and Participants

This retrospective population-based cohort study was completed in Ontario, Canada. Included were singleton children born in an Ontario hospital between April 2007 and March 2021, who were alive at age 48 months and whose mother had a recorded prepregnancy body mass index (BMI) and a measured serum creatinine (SCr) between 120 days preconception and 28 days postconception.

Measurement

The main study outcome was a diagnosis of ASD between ages 24 and 48 months.

Methods

Relative risks (RRs) of ASD in association with periconceptional SCr were generated using modified Poisson regression and adjusted for several confounders.

Results

The cohort comprised 86 054 women, who had 89 677 liveborn children surviving to at least 48 months of age. There was no significant association between periconceptional SCr and ASD (RR: 0.86; 95 % confidence interval: [0.67, 1.10]).

Limitations

Selection bias may have arisen had SCr been ordered on clinical grounds.

Conclusions

Further study is warranted to determine whether prepregnancy glomerular hyperfiltration is a marker of ASD and other behavioral conditions in childhood. To do so, a more accurate measure of hyperfiltration is needed than SCr.

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.

Sex-dependent effects of Canagliflozin on kidney protection in mice with combined hypertension-type 1 diabetes

Canagliflozin (CANA) is a sodium-glucose cotransporter 2 (SGLT2) inhibitor with blood glucose lowering effects. CANA also promotes kidney protection in patients with cardiovascular diseases and type 2 diabetes (T2D), as well as in normoglycemic patients with hypertension or heart failure. Clinical studies, although conduct in both sexes, do not report sex-dependent differences in T2DM treated with CANA. However, the impact of CANA in type 1 diabetes, as well in sex-dependent outcomes in such cohort needs further understanding. To analyze the effects of CANA in mice with combined hypertension and type 1 diabetes, diabetes was induced by STZ injection (5 days, 50mg/kg/day) in both male and female 8 weeks old genetic hypertensive mice (Lin), whereas the control (Lin) received 0.1M sodium citrate injections. 8 weeks after STZ. Mice were fed either regular or CANA-infused diet for 4 weeks. 8 weeks after STZ, hyperglycemia was present in both male and female mice. CANA reversed BG increase mice fed regular diet. Male LinSTZ mice had elevated water intake, urine output, urinary albumin to creatinine ratio (ACR), kidney lesion score, and creatinine clearance compared to the Lin control group. Kidney injury was improved in male LinSTZ + CANA group in male mice. Water intake and urine output were not statistically significantly different in female LinSTZ compared to female LinSTZ+ CANA. Moreover, CANA did not improve kidney injury in female mice, showing no effect in creatinine clearance, lesion score and fibrosis when compared to LinSTZ fed regular diet. Here we show that Canagliflozin might exert different kidney protection effects in male compared to female mice with hypertension and type 1 diabetes. Sex-dimorphisms were previously found in the pathophysiology of diabetes induced by STZ. Therefore, we highlight the importance of in-depth investigation on sex-dependent effects of CANA, taking in consideration the unique characteristics of disease progression for each sex.

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.

Modifiable kidney disease risk factors among nondiabetic adults with obesity from the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE

It is unknown whether weight change or physical fitness is associated with chronic kidney disease (CKD) risk among nondiabetic adults with obesity.

METHODS

This was a prospective, longitudinal cohort study of adults with obesity without baseline CKD or diabetes enrolled in the Multi-Ethnic Study of Atherosclerosis (MESA). Linear mixed-effects and multistate models were adjusted for demographics, time-varying covariates including blood pressure, and comorbidities these were used to examine associations of weight change and slow walking pace (<2 miles/h) with (i) rate of annual estimated glomerular filtration rate (eGFR) decline and (ii) incident CKD, defined as eGFRCr-Cys  < 60 mL/min/1.73 m2 , and tested for interaction by baseline hypertension status.

RESULTS

Among 1208 included MESA participants (median BMI 33.0 kg/m2 [interquartile range 31.2-35.9]), 15% developed CKD. Slow walking pace was associated with eGFR decline (-0.27 mL/min/1.73 m2 /year; 95% CI: -0.42 to -0.12) and CKD risk (adjusted hazard ratio 1.48; 95% CI: 1.08 to 2.01). Weight gain was associated with CKD risk (adjusted hazard ratio 1.34; 95% CI: 1.02 to 1.78 per 5 kg weight gain from baseline). There was no significant interaction by baseline hypertension status.

CONCLUSIONS

Slow walking pace and weight gain were associated with CKD risk among adults with obesity who did not have diabetes at baseline.

Podocyte injury of diabetic nephropathy: Novel mechanism discovery and therapeutic prospects

Diabetic nephropathy (DN) is a severe complication of diabetes mellitus, posing significant challenges in terms of early prevention, clinical diagnosis, and treatment. Consequently, it has emerged as a major contributor to end-stage renal disease. The glomerular filtration barrier, composed of podocytes, endothelial cells, and the glomerular basement membrane, plays a vital role in maintaining renal function. Disruptions in podocyte function, including hypertrophy, shedding, reduced density, and apoptosis, can impair the integrity of the glomerular filtration barrier, resulting in elevated proteinuria, abnormal glomerular filtration rate, and increased creatinine levels. Hence, recent research has increasingly focused on the role of podocyte injury in DN, with a growing emphasis on exploring therapeutic interventions targeting podocyte injury. Studies have revealed that factors such as lipotoxicity, hemodynamic abnormalities, oxidative stress, mitochondrial dysfunction, and impaired autophagy can contribute to podocyte injury. This review aims to summarize the underlying mechanisms of podocyte injury in DN and provide an overview of the current research status regarding experimental drugs targeting podocyte injury in DN. The findings presented herein may offer potential therapeutic targets and strategies for the management of DN associated with podocyte injury.

Cardiovascular outcomes and safety of SGLT2 inhibitors in chronic kidney disease patients

Background

Sodium-glucose co-transporter 2 (SGLT2) inhibitors provide cardiovascular protection for patients with heart failure (HF) and type 2 diabetes mellitus (T2DM). However, there is little evidence of their application in patients with chronic kidney disease (CKD). Furthermore, there are inconsistent results from studies on their uses. Therefore, to explore the cardiovascular protective effect of SGLT2 inhibitors in the CKD patient population, we conducted a systematic review and meta-analysis to evaluate the cardiovascular effectiveness and safety of SGLT2 inhibitors in this patient population.

Method

We searched the PubMed® (National Library of Medicine, Bethesda, MD, USA) and Web of Science™ (Clarivate™, Philadelphia, PA, USA) databases for randomized controlled trials (RCTs) of SGLT2 inhibitors in CKD patients and built the database starting in January 2023. In accordance with our inclusion and exclusion criteria, the literature was screened, the quality of the literature was evaluated, and the data were extracted. RevMan 5.3 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark) and Stata® 17.0 (StataCorp LP, College Station, TX, USA) were used for the statistical analyses. Hazard ratios (HRs), odds ratios (ORs), and corresponding 95% confidence intervals (CIs) were used for the analysis of the outcome indicators.

Results

Thirteen RCTs were included. In CKD patients, SGLT2 inhibitors reduced the risk of cardiovascular death (CVD) or hospitalization for heart failure (HHF) by 28%, CVD by 16%. and HHF by 35%. They also reduced the risk of all-cause death by 14% without increasing the risk of serious adverse effects (SAEs) and urinary tract infections (UTIs). However, they increased the risk of reproductive tract infections (RTIs).

Conclusion

SGLT2 inhibitors have a cardiovascular protective effect on patients with CKD, which in turn can significantly reduce the risk of CVD, HHF, and all-cause death without increasing the risk of SAEs and UTIs but increasing the risk of RTIs.

Modeling the renoprotective mechanisms of SGLT2 inhibition in hypertensive chronic kidney disease

Sodium-glucose cotransporter (SGLT)-2 inhibitors have recently been approved for chronic kidney disease (CKD) based on their ability to lower proteinuria and slow CKD progression independent of diabetes status. In diabetic renal disease, modulation of tubuloglomerular feedback (TGF) leading to lower intraglomerular pressure has been postulated as one of the mechanisms of renal protection with SGLT2 inhibition; however, this mechanism has not been sufficiently explored in non-diabetic CKD. We hypothesized that SGLT2 inhibition exerts renoprotection in CKD through increasing TGF despite normoglycemia. To test this hypothesis, we used an integrative mathematical model of human physiology, HumMod. Stage 3 CKD conditions were simulated by reducing nephron mass which was associated with hypertension, low glomerular filtration rate (GFR) (55 mL/min), hyperfiltration of remnant nephrons, elevated albuminuria (500 mg/day), and minimal levels of urinary glucose (0.02 mmol/L). SGLT2 inhibition was associated with acute reductions in GFR associated with afferent arteriolar vasoconstriction due to TGF. After 12 months, glomerular pressure, nephron damage, and chronic GFR decline were reduced with SGLT2 inhibition with additional SGLT1 inhibitory effects further enhancing these effects. This model supports the use of SGLT2 inhibitors to reduce hyperfiltration in CKD and mitigate renal disease progression, even in the absence of diabetes.

GPR56 Promotes Diabetic Kidney Disease Through eNOS Regulation in Glomerular Endothelial Cells

Although glomerular endothelial dysfunction is well recognized as contributing to the pathogenesis of diabetic kidney disease (DKD), the molecular pathways contributing to DKD pathogenesis in glomerular endothelial cells (GECs) are only partially understood. To uncover pathways that are differentially regulated in early DKD that may contribute to disease pathogenesis, we recently conducted a transcriptomic analysis of isolated GECs from diabetic NOS3-null mice. The analysis identified several potential mediators of early DKD pathogenesis, one of which encoded an adhesion G protein-coupled receptor-56 (GPR56), also known as ADGRG1. Enhanced glomerular expression of GPR56 was observed in human diabetic kidneys, which was negatively associated with kidney function. Using cultured mouse GECs, we observed that GPR56 expression was induced with exposure to advanced glycation end products, as well as in high-glucose conditions, and its overexpression resulted in decreased phosphorylation and expression of endothelial nitric oxide synthase (eNOS). This effect on eNOS by GPR56 was mediated by coupling of Gα12/13-RhoA pathway activation and Gαi-mediated cAMP/PKA pathway inhibition. The loss of GPR56 in mice led to a significant reduction in diabetes-induced albuminuria and glomerular injury, which was associated with reduced oxidative stress and restoration of eNOS expression in GECs. These findings suggest that GPR56 promotes DKD progression mediated, in part, through enhancing glomerular endothelial injury and dysfunction.

ARTICLE HIGHLIGHTS

The Fatty Kidney and Beyond: A Silent Epidemic

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

Pharmacokinetics of obese adults: Not only an increase in weight

Obesity is a pathophysiological state defined by a body mass index > 30 kg/m2 and characterized by an adipose tissue accumulation leading to an important weight increased. Several pathologies named comorbidities such as cardiovascular disease, type 2 diabetes and cancer make obesity the fifth cause of death in the world. Physiological changes impact the four main phases of pharmacokinetics of some drugs and leads to an inappropriate drug-dose. For absorption, the gastrointestinal transit is accelerated, and the gastric empty time is shortened, that can reduce the solubilization and absorption of some oral drugs. The drug distribution is probably the most impacted by the obesity-related changes because the fat mass (FM) increases at the expense of the lean body weight (LBW), leading to an important increase of the volume of distribution for lipophilic drugs and a low or moderately increase of this parameter for hydrophilic drugs. This modification of the distribution may require drug-dose adjustments. By various mechanisms, the metabolism and elimination of drugs are impacted by obesity and should be considered as similar or lower than that non-obese patients. To better understand the necessary drug-dose adjustments in obese patients, a narrative review of the literature was conducted to highlight the main elements to consider in the therapeutic management of adult obese patients.

CKD Urine Metabolomics: Modern Concepts and Approaches

One of the primary challenges regarding chronic kidney disease (CKD) diagnosis is the absence of reliable methods to detect early-stage kidney damage. A metabolomic approach is expected to broaden the current diagnostic modalities by enabling timely detection and making the prognosis more accurate. Analysis performed on urine has several advantages, such as the ease of collection using noninvasive methods and its lower protein and lipid content compared with other bodily fluids. This review highlights current trends in applied analytical methods, major discoveries concerning pathways, and investigated populations in the context of urine metabolomic research for CKD over the past five years. Also, we are presenting approaches, instrument upgrades, and sample preparation modifications that have improved the analytical parameters of methods. The onset of CKD leads to alterations in metabolism that are apparent in the molecular composition of urine. Recent works highlight the prevalence of alterations in the metabolic pathways related to the tricarboxylic acid cycle and amino acids. Including diverse patient cohorts, using numerous analytical techniques with modifications and the appropriate annotation and explanation of the discovered biomarkers will help develop effective diagnostic models for different subtypes of renal injury with clinical applications.

Inhibition of STIM1 alleviates high glucose-induced proliferation and fibrosis by inducing autophagy in mesangial cells

Diabetic nephropathy (DN) is a renal microvascular complication caused by diabetes mellitus. One of the most typical characteristics of DN is glomerular mesangial cells (GMCs) proliferation. Stromal interaction molecule 1 (STIM1), a Ca2+ channel, is involved in many diseases. In this study, we investigated the role of STIM1 in the proliferation and fibrosis in high glucose (HG)-induced HBZY-1 cells. We found that the expression of STIM1 was increased in renal tissues of diabetic rat and HBZY-1 cells stimulated by HG. Downregulation of STIM1-mediated SOCE suppressed hyperglycemic cell proliferation and fibrosis by activating autophagy. In addition, the inhibitory effect of downregulating STIM1 on cells was blocked by autophagy inhibitor Bafilomycin A1 (BafA1). Moreover, this experiment also showed that STIM1 regulated autophagy, cell proliferation and fibrosis via PI3K/AKT/mTOR signal pathway. These results clarify the role of STIM1 in HBZY-1 cells and its mechanism, and provide a new target for the treatment of DN.

Correlation Between the Variability of Different Obesity Indices and Diabetic Kidney Disease: A Retrospective Cohort Study Based on Populations in Taiwan

Purpose

To investigate the association of five obesity indices and the variability of these indices with diabetic kidney disease (DKD) in patients with type 2 diabetes and compare the predictive validity of these markers for the risk of DKD in this large longitudinal cohort study.

Patients and Methods

A total of 2659 patients with type 2 diabetes who did not have DKD were enrolled between 2006 and 2019 at Lee's United Clinic in Taiwan. Data were collected for each subject, including demographic data, personal medical history, clinical parameters and calculated Body mass index (BMI), visceral adiposity index (VAI), lipid accumulation product (LAP), body roundness index (BRI) and variability of five obesity indices. Cox regression analysis was performed to determine the relationship between different obesity indicators and DKD risk. Cox's proportional hazards model was evaluated the predictive effect of obesity indices on DKD.

Results

The risk of developing DKD increased with an increase in the BRI, LAP, VAI, WC and BMI (all P trend<0.05), and the variability of VAI was significantly associated with DKD [HR=1.132, 95% CI (1.001, 1.281)] after adjusting for corresponding variables. BRI had the strongest predictive effect on DKD. BRI had the best predictive performance, with AUC of 0.807, 0.663 and 0.673 at 1, 3 and 5 years, respectively. Cox regression analysis of risk factors for DKD in patients stratified by BRI quartiles showed that patients in the Q4 group had the highest risk of developing DKD [HR=1.356, 95% CI (1.131, 1.626)].

Conclusion

BMI, WC, VAI, LAP, BRI and VAI variability were associated with a significant increase in the risk of DKD events, and BRI was superior and alternative obesity index for predicting DKD.

Targeting Renal Proximal Tubule Cells in Obesity-Related Glomerulopathy

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

Metformin reduces insulin resistance and attenuates progressive renal injury in prepubertal obese Dahl salt-sensitive rats

Prepubertal obesity is currently an epidemic and is considered as a major risk factor for renal injury. Previous studies have demonstrated that insulin resistance contributes to renal injury in obesity, independent of diabetes. However, studies examining the relationship between insulin resistance and renal injury in obese children are lacking. Recently, we reported that progressive renal injury in Dahl salt-sensitive (SS) leptin receptor mutant (SSLepRmutant) rats was associated with insulin resistance before puberty. Therefore, the aim of the present study was to examine whether decreasing insulin resistance with metformin will reduce renal injury in SSLepRmutant rats. Four-wk-old SS and SSLepRmutant rats were separated into the following two groups: 1) vehicle and 2) metformin (300 mg/kg/day) via chow diet for 4 wk. Chronic administration of metformin markedly reduced insulin resistance and dyslipidemia in SSLepRmutant rats. We did not detect any differences in mean arterial pressure between vehicle and metformin-treated SS and SSLepRmutant rats. Proteinuria was significantly greater in SSLepRmutant rats versus SS rats throughout the study, and metformin administration significantly reduced proteinuria in SSLepRmutant rats. At the end of the protocol, metformin prevented the renal hyperfiltration observed in SSLepRmutant rats versus SS rats. Glomerular and tubular injury and renal inflammation and fibrosis were significantly higher in vehicle-treated SSLepRmutant rats versus SS rats, and metformin reduced these parameters in SSLepRmutant rats. These data suggest that reducing insulin resistance with metformin prevents renal hyperfiltration and progressive renal injury in SSLepRmutant rats before puberty and may be therapeutically useful in managing renal injury during prepubertal obesity.NEW & NOTEWORTHY Childhood/prepubertal obesity is a public health concern that is associated with early signs of proteinuria. Insulin resistance has been described in obese children. However, studies investigating the role of insulin resistance during childhood obesity-associated renal injury are limited. This study provides evidence of an early relationship between insulin resistance and renal injury in a rat model of prepubertal obesity. These data also suggest that reducing insulin resistance with metformin may be renoprotective in obese children.

Kidney Considerations in Pediatric Obesity

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Tubular and Glomerular Size by Cortex Depth as Predictor of Progressive CKD after Radical Nephrectomy for Tumor

SIGNIFICANCE STATEMENT

Glomerular size differs by cortex depth. Larger nephrons are prognostic of progressive kidney disease, but it is unknown whether this risk differs by cortex depth or by glomeruli versus proximal or distal tubule size. We studied the average minor axis diameter in oval proximal and distal tubules separately and by cortex depth in patients who had radical nephrectomy to remove a tumor from 2019 to 2020. In adjusted analyses, larger glomerular volume in the middle and deep cortex predicted progressive kidney disease. Wider proximal tubular diameter did not predict progressive kidney disease independent of glomerular volume. Wider distal tubular diameter showed a gradient of strength of prediction of progressive kidney disease in the more superficial cortex than in the deep cortex.

BACKGROUND

Larger nephrons are prognostic of progressive kidney disease, but whether this risk differs by nephron segments or by depth in the cortex is unclear.

METHODS

We studied patients who underwent radical nephrectomy for a tumor between 2000 and 2019. Large wedge kidney sections were scanned into digital images. We estimated the diameters of proximal and distal tubules by the minor axis of oval tubular profiles and estimated glomerular volume with the Weibel-Gomez stereological model. Analyses were performed separately in the superficial, middle, and deep cortex. Cox proportional hazard models assessed the risk of progressive CKD (dialysis, kidney transplantation, sustained eGFR <10 ml/min per 1.73 m 2 , or a sustained 40% decline from the postnephrectomy baseline eGFR) with glomerular volume or tubule diameters. At each cortical depth, models were unadjusted, adjusted for glomerular volume or tubular diameter, and further adjusted for clinical characteristics (age, sex, body mass index, hypertension, diabetes, postnephrectomy baseline eGFR, and proteinuria).

RESULTS

Among 1367 patients were 62 progressive CKD events during a median follow-up of 4.5 years. Glomerular volume predicted CKD outcomes at all depths, but only in the middle and deep cortex after adjusted analyses. Proximal tubular diameter also predicted progressive CKD at any depth but not after adjusted analyses. Distal tubular diameter showed a gradient of more strongly predicting progressive CKD in the superficial than deep cortex, even in adjusted analysis.

CONCLUSIONS

Larger glomeruli are independent predictors of progressive CKD in the deeper cortex, whereas in the superficial cortex, wider distal tubular diameters are an independent predictor of progressive CKD.

Preliminary Feasibility Study on Diffusion Kurtosis Imaging to Monitor the Early Functional Alterations of Kidneys in Streptozocin-Induced Diabetic Rats

RATIONALE AND OBJECTIVES

The aim of this study was to investigate the potential of diffusion kurtosis imaging (DKI) to assess the early renal functional undulation of diabetic mellitus (DM).

MATERIALS AND METHODS

Fifty-seven Sprague-Dawley (SD) rats were randomly divided into two groups and eventually 48 rats were included in this study: the normal control (CON) group and diabetic mellitus (DM) group. Weeks 0, 4, 8, and 12 after the diabetes model was successfully established, all the rats were scanned on the 3.0T MRI. The DKI derived parameters of renal parenchyma, including fractional anisotropy (FAco, FAme), mean diffusivity (MDco, MDme), and mean kurtosis (MKco, MKme) were measured. Their alteration over time was analyzed and then correlated with urine volume (UV), blood urea nitrogen (BUN), and serum creatinine (Scr) using Pearson correlation analysis. Finally, hematoxylin and eosin (H&E) staining was performed on the kidneys of the two groups.

RESULT

There was a decreasing trend in FA, MK, and MD values over time in diabetic rats. Also, the gradually worsening histological damage of kidneys was noted over time in diabetic rats. The cortical FA and MK values and medullary FA, MK and MD values of diabetic rats were significantly lower than those of controls at most time points after DM induction. In addition, negative correlations were revealed between the BUN and FAco (r = -0.43, p = 0.03) or FAme value (r = -0.49, p = 0.01). The cortical MK value was moderately correlated with UV (r = -0.46, p = 0.03) and BUN (r = -0.55, p = 0.01).

CONCLUSION

The preliminary findings suggest that DKI might be an effective and sensitive tool to assess the early changes of renal function impairment in diabetic rats. The FA values of the cortex and medulla and the MK value of the cortex are sensitive markers in detecting renal injury in diabetic rats.

Glomerular hyperfiltration and hypertrophy: an evaluation of maximum values in pathological indicators to discriminate "diseased" from "normal"

The success of sodium-glucose cotransporter 2 inhibitors and bariatric surgery in patients with chronic kidney disease has highlighted the importance of glomerular hyperfiltration and hypertrophy in the progression of kidney disease. Sustained glomerular hyperfiltration and hypertrophy can lead to glomerular injury and progressive kidney damage. This article explores the relationship between obesity and chronic kidney disease, focusing on the roles of glomerular hyperfiltration and hypertrophy as hallmarks of obesity-related kidney disease. The pathological mechanisms underlying this association include adipose tissue inflammation, dyslipidemia, insulin resistance, chronic systemic inflammation, oxidative stress, and overactivation of the sympathetic nervous system, as well as the renin-angiotensin aldosterone system. This article explains how glomerular hyperfiltration results from increased renal blood flow and intraglomerular hypertension, inducing mechanical stress on the filtration barrier and post-filtration structures. Injured glomeruli increase in size before sclerosing and collapsing. Therefore, using extreme values, such as the maximal glomerular diameter, could improve the understanding of the data distribution and allow for better kidney failure predictions. This review provides important insights into the mechanisms underlying glomerular hyperfiltration and hypertrophy and highlights the need for further research using glomerular size, including maximum glomerular profile, calculated using needle biopsy specimens.

ADAM metallopeptidase domain 10 knockdown enables podocytes to resist high glucose stimulation by inhibiting pyroptosis via MAPK pathway

Diabetic nephropathy (DN) is a common severe microvascular complication of diabetes mellitus, and podocyte damage occurs in the early stages of DN. The urine of patients with various types of glomerular disease presents increased levels of ADAM metallopeptidase domain 10 (ADAM10). The present study aimed to explore the role of ADAM10 in podocyte damage. Therefore, the expression of ADAM10 in high glucose (HG)-stimulated podocytes was measured by reverse transcription-qPCR and western blot. Moreover, the effects of ADAM10 knockdown on podocyte inflammation and apoptosis were determined by ELISA, western blot and TUNEL assay after confirming the efficacy of cell transfection. Subsequently, the effects of ADAM10 knockdown on the MAPK pathway and pyroptosis were assessed by western blot. Through performing the aforementioned experiments, the role of the MAPK pathway in the regulatory effects of ADAM10 was then investigated by pretreating podocytes with pathway agonists. ADAM10 expression was upregulated in HG-stimulated podocytes, while ADAM10 knockdown suppressed inflammation, apoptosis and pyroptosis of HG-stimulated podocytes and inhibited the activation of the MAPK signaling pathway. However, when podocytes were pretreated with pathway agonists (LM22B-10 or p79350), the aforementioned effects of ADAM10 knockdown were suppressed. The present study demonstrated that ADAM10 knockdown suppressed the inflammation, apoptosis and pyroptosis of HG-stimulated podocytes by blocking the MAPK signaling pathway.

Obesity, Preserved Ejection Fraction Heart Failure, and Left Ventricular Remodeling

Owing to the overwhelming obesity epidemic, preserved ejection fraction heart failure commonly ensues in patients with severe obesity and the obese phenotype of preserved ejection fraction heart failure is now commonplace in clinical practice. Severe obesity and preserved ejection fraction heart failure share congruent cardiovascular, immune, and renal derangements that make it difficult to ascertain whether the obese phenotype of preserved ejection fraction heart failure is the convergence of two highly prevalent conditions or severe obesity enables the development and progression of the syndrome of preserved ejection fraction heart failure. Nevertheless, the obese phenotype of preserved ejection fraction heart failure provides a unique opportunity to assess whether sustained and sizeable loss of excess body weight via metabolic bariatric surgery reverses the concentric left ventricular remodeling that patients with preserved ejection fraction heart failure commonly display.

Autosomal Dominant Polycystic Kidney Disease in Children and Adolescents: Assessing and Managing Risk of Progression

The clinical management of autosomal dominant polycystic kidney disease (ADPKD) in adults has shifted from managing complications to delaying disease progression through newly emerging therapies. Regarding pediatric management of the disease, there are still specific hurdles related to the management of children and adolescents with ADPKD and, unlike adults, there are no specific therapies for pediatric ADPKD or stratification models to identify children and young adults at risk of rapid decline in kidney function. Therefore, early identification and management of factors that may modify disease progression, such as hypertension and obesity, are of most importance for young children with ADPKD. Many of these risk factors could promote disease progression in both ADPKD and chronic kidney disease. Hence, nephroprotective measures applied early in life can represent a window of opportunity to prevent the decline of the glomerular filtration rate especially in young patients with ADPKD. In this review, we highlight current challenges in the management of patients with pediatric ADPKD, the importance of early modifying factors in disease progression as well as the gaps and future perspectives in the pediatric ADPKD research field.

The Importance of Animal Models in Biomedical Research: Current Insights and Applications

Animal research is considered a key element in advance of biomedical science. Although its use is controversial and raises ethical challenges, the contribution of animal models in medicine is essential for understanding the physiopathology and novel treatment alternatives for several animal and human diseases. Current pandemics’ pathology, such as the 2019 Coronavirus disease, has been studied in primate, rodent, and porcine models to recognize infection routes and develop therapeutic protocols. Worldwide issues such as diabetes, obesity, neurological disorders, pain, rehabilitation medicine, and surgical techniques require studying the process in different animal species before testing them on humans. Due to their relevance, this article aims to discuss the importance of animal models in diverse lines of biomedical research by analyzing the contributions of the various species utilized in science over the past five years about key topics concerning human and animal health.

The Fat Kidney

PURPOSE OF REVIEW

The purpose of this review is to summarize the current evidence on the role of obesity in the development and progression of chronic kidney disease and the current evidence on nutritional, pharmacological, and surgical strategies for the management of individuals with obesity and chronic kidney disease.

RECENT FINDINGS

Obesity can hurt the kidney via direct pathways, through the production of pro-inflammatory adipocytokines, and indirectly due to systemic complications of obesity, including type 2 diabetes mellitus and hypertension. In particular, obesity can damage the kidney through alterations in renal hemodynamics resulting in glomerular hyperfiltration, proteinuria and, finally, impairment in glomerular filtratation rate. Several strategies are available for weight loss and maintenance, such as the modification of lifestyle (diet and physical activity), anti-obesity drugs, and surgery therapy, but there are no clinical practice guidelines to manage subjects with obesity and chronic kidney disease. Obesity is an independent risk factor for the progression of chronic kidney disease. In subjects with obesity, weight loss can slow down the progression of renal failure with a significant reduction in proteinuria and improvement in glomerular filtratation rate. Specifically, in the management of subjects with obesity and chronic renal disease, it has been shown that bariatric surgery can prevent the decline in renal function, while further clinical studies are needed to evaluate the efficacy and safety on the kidney of weight reducing agents and the very low-calorie ketogenic diet.

Continuous Positive Airway Pressure Effect on Albuminuria Progression in Patients with Obstructive Sleep Apnea and Diabetic Kidney Disease: A Randomized Clinical Trial

Rationale: Obstructive sleep apnea (OSA) is associated with impaired glycemic control and a higher risk of vascular complications, such as diabetic kidney disease (DKD). However, the effect of apnea-hypopnea suppression on DKD progression is unclear. Objectives: To assess the effect of continuous positive airway pressure (CPAP) on the urinary albumin-to-creatinine ratio (UACR) in patients with DKD and OSA. Methods: In a 52-week, multicentric, open-label, parallel, and randomized clinical trial, 185 patients with OSA and DKD were randomized to CPAP and usual care (n = 93) or usual care alone (n = 92). Measurements and Main Results: UACR, estimated glomerular filtration rate, serum concentrations of creatinine and glycated hemoglobin, insulin resistance, lipid concentrations, sleepiness, and quality of life. A 52-week change in UACR from baseline did not differ significantly between the CPAP group and the usual-care group. However, in per-protocol analyses that included 125 participants who met prespecified criteria for adherence, CPAP treatment was associated with a great reduction in UACR (mean difference, -10.56% [95% confidence interval, -19.06 to -2.06]; P = 0.015). CPAP effect on UACR was higher in nonsleepy patients with more severe OSA, worse renal function, and a more recent diagnosis of DKD. CPAP treatment also improved glycemic control and insulin resistance, as well as sleepiness and health-related quality of life. Conclusions: In patients with OSA and DKD, the prescription of CPAP did not result in a statistically significant reduction in albuminuria. However, good adherence to CPAP treatment in addition to usual care may result in long-term albuminuria reduction compared with usual care alone. Clinical trial registered with www.clinicaltrials.gov (NCT02816762).

Molecular pathways that drive diabetic kidney disease

Kidney disease is a major driver of mortality among patients with diabetes and diabetic kidney disease (DKD) is responsible for close to half of all chronic kidney disease cases. DKD usually develops in a genetically susceptible individual as a result of poor metabolic (glycemic) control. Molecular and genetic studies indicate the key role of podocytes and endothelial cells in driving albuminuria and early kidney disease in diabetes. Proximal tubule changes show a strong association with the glomerular filtration rate. Hyperglycemia represents a key cellular stress in the kidney by altering cellular metabolism in endothelial cells and podocytes and by imposing an excess workload requiring energy and oxygen for proximal tubule cells. Changes in metabolism induce early adaptive cellular hypertrophy and reorganization of the actin cytoskeleton. Later, mitochondrial defects contribute to increased oxidative stress and activation of inflammatory pathways, causing progressive kidney function decline and fibrosis. Blockade of the renin-angiotensin system or the sodium-glucose cotransporter is associated with cellular protection and slowing kidney function decline. Newly identified molecular pathways could provide the basis for the development of much-needed novel therapeutics.

Is the proximal tubule the focus of tubulointerstitial fibrosis?

Tubulointerstitial fibrosis (TIF), a common end result of almost all progressive chronic kidney diseases (CKD), is also the best predictor of kidney survival. Almost all cells in the kidney are involved in the progression of TIF. Myofibroblasts, the primary producers of extracellular matrix, have previously received a great deal of attention; however, a large body of emerging evidence reveals that proximal tubule (PT) plays a central role in TIF progression. In response to injury, renal tubular epithelial cells (TECs) transform into inflammatory and fibroblastic cells, producing various bioactive molecules that drive interstitial inflammation and fibrosis. Here we reviewed the increasing evidence for the key role of the PT in promoting TIF in tubulointerstitial and glomerular injury and discussed the therapeutic targets and carrier systems involving the PT that holds particular promise for treating patients with fibrotic nephropathy.

Visceral fat and attribute-based medicine in chronic kidney disease

Visceral adipose tissue plays a central role in obesity and metabolic syndrome and is an independent risk factor for both cardiovascular and metabolic disorders. Increased visceral adipose tissue promotes adipokine dysregulation and insulin resistance, leading to several health issues, including systemic inflammation, oxidative stress, and activation of the renin-angiotensin-aldosterone system. Moreover, an increase in adipose tissue directly and indirectly affects the kidneys by increasing renal sodium reabsorption, causing glomerular hyperfiltration and hypertrophy, which leads to increased proteinuria and kidney fibrosis/dysfunction. Although the interest in the adverse effects of obesity on renal diseases has grown exponentially in recent years, the relationship between obesity and renal prognosis remains controversial. This may be attributed to the long clinical course of obesity, numerous obesity-related metabolic complications, and patients' attributes. Multiple individual attributes influencing the pathophysiology of fat accumulation make it difficult to understand obesity. In such cases, it may be effective to elucidate the pathophysiology by conducting research tailored to individual attributes from the perspective of attribute-based medicine/personalized medicine. We consider the appropriate use of clinical indicators necessary, according to attributes such as chronic kidney disease stage, level of visceral adipose tissue accumulation, age, and sex. Selecting treatments and clinical indicators based on individual attributes will allow for advancements in the clinical management of patients with obesity and chronic kidney disease. In the clinical setting of obesity-related nephropathy, it is first necessary to accumulate attribute-based studies resulting from the accurate evaluation of visceral fat accumulation to establish evidence for promoting personalized medicine.

Obesity and chronic kidney disease

The prevalence of obesity has increased dramatically during the past decades, which has been a major health problem. Since 1975, the number of people with obesity worldwide has nearly tripled. An increasing number of studies find obesity as a driver of chronic kidney disease (CKD) progression, and the mechanisms are complex and include hemodynamic changes, inflammation, oxidative stress, and activation of the renin-angiotensin-aldosterone system (RAAS). Obesity-related kidney disease is characterized by glomerulomegaly, which is often accompanied by localized and segmental glomerulosclerosis lesions. In these patients, the early symptoms are atypical, with microproteinuria being the main clinical manifestation and nephrotic syndrome being rare. Weight loss and RAAS blockers have a protective effect on obesity-related CKD, but even so, a significant proportion of patients eventually progress to end-stage renal disease despite treatment. Thus, it is critical to comprehend the mechanisms underlying obesity-related CKD to create new tactics for slowing or stopping disease progression. In this review, we summarize current knowledge on the mechanisms of obesity-related kidney disease, its pathological changes, and future perspectives on its treatment.

Association of Estimated Glomerular Filtration Rate With Progression of Albuminuria in Individuals With Type 2 Diabetes

OBJECTIVE

To elucidate the association of glomerular filtration rate (GFR) at baseline with subsequent progression of albuminuria in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This was a single-center retrospective cohort study of 6,618 Japanese adults with type 2 diabetes and urinary albumin-to-creatinine ratio of <300 mg/g, comprising 2,459 women and 4,159 men with a mean (± SD) age of 60 ± 12 years. The exposure was baseline estimated GFR (eGFR) (mL/min/1.73 m2), treated as a categorical variable and classified into five categories: ≥90, 75-90, 60-75, 45-60, and <45, as well as a continuous variable. The outcome was progression of albuminuria category (i.e., from normoalbuminuria to micro- or macroalbuminuria or from micro- to macroalbuminuria). Hazard ratios (HRs) for the outcome were estimated using the multivariable Cox proportional hazards model. In the analysis treating baseline eGFR as a continuous variable, the multivariable-adjusted restricted cubic spline model was used.

RESULTS

During the median follow-up period of 6.3 years, 1,190 individuals reached the outcome. When those with a baseline eGFR of 75-90 mL/min/1.73 m2 were considered the reference group, HRs (95% CIs) for the outcome in those with a baseline eGFR of ≥90, 60-75, 45-60, or <45 mL/min/1.73 m2 were 1.38 (1.14-1.66), 1.34 (1.14-1.58), 1.81 (1.50-2.20), or 2.37 (1.84-3.05), respectively. Furthermore, the inverse J-shaped curve was more clearly shown by the spline model.

CONCLUSIONS

This study of Japanese adults with type 2 diabetes suggests that both high and low GFRs are implicated in the pathogenesis of albuminuria progression.

Novel insights in classic versus relative glomerular hyperfiltration and implications on pharmacotherapy

PURPOSE OF REVIEW

Glomerular filtration rate (GFR) assessment and its estimation (eGFR) is a long-lasting challenge in medicine and public health. Current eGFR formulae are indexed for standardized body surface area (BSA) of 1.73 m2, ignoring persons and populations wherein the ratio of BSA or metabolic rate to nephron number might be different, due to increased BSA, increased metabolic rate or reduced nephron number. These equations are based on creatinine, cystatin C or a combination of the two, which adds another confounder to eGFR assessment. Unusually high GFR values, also known as renal hyperfiltration, have not been well defined under these equations.

RECENT FINDINGS

Special conditions such as solitary kidney in kidney donors, high dietary protein intake, obesity and diabetes are often associated with renal hyperfiltration and amenable to errors in GFR estimation. In all hyperfiltration types, there is an increased intraglomerular pressure that can be physiologic, but its persistence over time is detrimental to glomerulus leading to progressive glomerular damage and renal fibrosis. Hyperfiltration might be underdiagnosed due to BSA standardization embedded in the formula. Hence, timely intervention is delayed. Reducing intraglomerular pressure in diabetes can be achieved by SGLT2 inhibitors or low protein diet to reverse the glomerulopathy process.

SUMMARY

Accurate identification of glomerular hyperfiltration as a pre-CKD condition needs accurate estimation of GFR in the above normal range should establish a threshold for timely intervention.

Store-operated Ca2+ channel signaling: Novel mechanism for podocyte injury in kidney disease

Studies over the last decade have markedly broadened our understanding of store-operated Ca2+ channels (SOCs) and their roles in kidney diseases and podocyte dysfunction. Podocytes are terminally differentiated glomerular visceral epithelial cells which are tightly attached to the glomerular capillary basement membrane. Podocytes and their unique foot processes (pedicels) constitute the outer layer of the glomerular filtration membrane and the final barrier preventing filtration of albumin and other plasma proteins. Diabetic nephropathy and other renal diseases are associated with podocyte injury and proteinuria. Recent evidence demonstrates a pivotal role of store-operated Ca2+ entry (SOCE) in maintaining structural and functional integrity of podocytes. This article reviews the current knowledge of SOCE and its contributions to podocyte physiology. Recent studies of the contributions of SOC dysfunction to podocyte injury in both cell culture and animal models are discussed, including work in our laboratory. Several downstream signaling pathways mediating SOC function in podocytes also are examined. Understanding the pivotal roles of SOC in podocyte health and disease is essential, as SOCE-activated signaling pathways are potential treatment targets for podocyte injury-related kidney diseases.

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.

Signaling Pathways of Podocyte Injury in Diabetic Kidney Disease and the Effect of Sodium-Glucose Cotransporter 2 Inhibitors

Diabetic kidney disease (DKD) is one of the most important comorbidities for patients with diabetes, and its incidence has exceeded one tenth, with an increasing trend. Studies have shown that diabetes is associated with a decrease in the number of podocytes. Diabetes can induce apoptosis of podocytes through several apoptotic pathways or induce autophagy of podocytes through related pathways. At the same time, hyperglycemia can also directly lead to apoptosis of podocytes, and the related inflammatory reactions are all harmful to podocytes. Podocyte damage is often accompanied by the production of proteinuria and the progression of DKD. As a new therapeutic agent for diabetes, sodium-glucose cotransporter 2 inhibitors (SGLT2i) have been demonstrated to be effective in the treatment of diabetes and the improvement of terminal outcomes in many rodent experiments and clinical studies. At the same time, SGLT2i can also play a protective role in diabetes-induced podocyte injury by improving the expression of nephrotic protein defects and inhibiting podocyte cytoskeletal remodeling. Some studies have also shown that SGLT2i can play a role in inhibiting the apoptosis and autophagy of cells. However, there is no relevant study that clearly indicates whether SGLT2i can also play a role in the above pathways in podocytes. This review mainly summarizes the damage to podocyte structure and function in DKD patients and related signaling pathways, as well as the possible protective mechanism of SGLT2i on podocyte function.

Glomerular Endothelial Cell-Derived miR-200c Impairs Glomerular Homeostasis by Targeting Podocyte VEGF-A

Deciphering the pathophysiological mechanisms of primary podocytopathies that can lead to end-stage renal disease and increased mortality is an unmet need. Studying how microRNAs (miRs) interfere with various signaling pathways enables identification of pathomechanisms, novel biomarkers and potential therapeutic options. We investigated the expression of miR-200c in urine from patients with different renal diseases as a potential candidate involved in podocytopathies. The role of miR-200c for the glomerulus and its potential targets were studied in cultured human podocytes, human glomerular endothelial cells and in the zebrafish model. miR-200c was upregulated in urine from patients with minimal change disease, membranous glomerulonephritis and focal segmental glomerulosclerosis and also in transforming growth factor beta (TGF-β) stressed glomerular endothelial cells, but not in podocytes. In zebrafish, miR-200c overexpression caused proteinuria, edema, podocyte foot process effacement and glomerular endotheliosis. Although zinc finger E-Box binding homeobox 1/2 (ZEB1/2), important in epithelial to mesenchymal transition (EMT), are prominent targets of miR-200c, their downregulation did not explain our zebrafish phenotype. We detected decreased vegfaa/bb in zebrafish overexpressing miR-200c and could further prove that miR-200c decreased VEGF-A expression and secretion in cultured human podocytes. We hypothesize that miR-200c is released from glomerular endothelial cells during cell stress and acts in a paracrine, autocrine, as well as context-dependent manner in the glomerulus. MiR-200c can cause glomerular damage most likely due to the reduction of podocyte VEGF-A. In contrast, miR-200c might also influence ZEB expression and therefore EMT, which might be important in other conditions. Therefore, we propose that miR-200c-mediated effects in the glomerulus are context-sensitive.

What can we learn from kidney organoids?

The ability to generate 3-dimensional models of the developing human kidney via the directed differentiation of pluripotent stem cells-termed kidney organoids-has been hailed as a major advance in experimental nephrology. Although these provide an opportunity to interrogate human development, model-specific kidney diseases facilitate drug screening and even deliver bioengineered tissue; most of these prophetic end points remain to be realized. Indeed, at present we are still finding out what we can learn and what we cannot learn from this approach. In this review, we will summarize the approaches available to generate models of the human kidney from stem cells, the existing successful applications of kidney organoids, their limitations, and remaining challenges.

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.

Observational and clinical evidence that plant-based nutrition reduces dietary acid load

Contemporary diets in Western countries are largely acid-inducing and deficient in potassium alkali salts, resulting in low-grade metabolic acidosis. The chronic consumption of acidogenic diets abundant in animal-based foods (meats, dairy, cheese and eggs) poses a substantial challenge to the human body's buffering capacities and chronic retention of acid wherein the progressive loss of bicarbonate stores can cause cellular and tissue damage. An elevated dietary acid load (DAL) has been associated with systemic inflammation and other adverse metabolic conditions. In this narrative review, we examine DAL quantification methods and index observational and clinical evidence on the role of plant-based diets, chiefly vegetarian and vegan, in reducing DAL. Quantitation of protein and amino acid composition and of intake of alkalising organic potassium salts and magnesium show that plant-based diets are most effective at reducing DAL. Results from clinical studies and recommendations in the form of expert committee opinions suggest that for a number of common illnesses, wherein metabolic acidosis is a contributing factor, the regular inclusion of plant-based foods offers measurable benefits for disease prevention and management. Based on available evidence, dietary shifts toward plant-based nutrition effectively reduces dietary-induced, low-grade metabolic acidosis.