The evolving understanding of the contribution of lipid metabolism to diabetic kidney disease

An Exome-wide Association Study for Type 2 Diabetes-Attributed End-Stage Kidney Disease in African Americans

Introduction

Compared with European Americans, African Americans (AAs) are at higher risk for developing end-stage kidney disease (ESKD). Genome-wide association studies (GWAS) have identified >70 genetic variants associated with kidney function and chronic kidney disease (CKD) in patients with and without diabetes. However, these variants explain a small proportion of disease liability. This study examined the contribution of coding genetic variants for risk of type 2 diabetes (T2D)-attributed ESKD and advanced CKD in AAs.

Methods

Exome sequencing was performed in 456 AA T2D-ESKD cases, and 936 AA nondiabetic, non-nephropathy control individuals at the discovery stage. A mixed logistic regression model was used for association analysis. Nominal associations (P < 0.05) were replicated in an additional 2020 T2D-ESKD cases and 1121 nondiabetic, non-nephropathy control individuals. A meta-analysis combining 4533 discovery and replication samples was performed. Putative T2D-ESKD associations were tested in additional 1910 nondiabetic ESKD and 219 T2D-ESKD cases, as well as 912 AA nondiabetic non-nephropathy control individuals.

Results

A total of 11 suggestive T2D-ESKD associations (P < 1 x 10⁻⁴) from 8 loci (PLEKHN1, NADK, RAD51AP2, RREB1, PEX6, GRM8, PRX, APOL1) were apparent in the meta-analysis. Exclusion of APOL1 renal-risk genotype carriers identified 3 additional suggestive loci (OTUD7B, IFITM3, DLGAP5). Rs41302867 in RREB1 displayed consistent association with T2D-ESKD and nondiabetic ESKD (odds ratio: 0.47; P = 1.2 x 10⁻⁶ in 4605 all-cause ESKD and 2969 nondiabetic non-nephropathy control individuals).

Conclusion

Our findings suggest that coding genetic variants are implicated in predisposition to T2D-ESKD in AAs.

Mitochondrial dysfunction in diabetic kidney disease

Globally, diabetes is the leading cause of chronic kidney disease and end-stage renal disease, which are major risk factors for cardiovascular disease and death. Despite this burden, the factors that precipitate the development and progression of diabetic kidney disease (DKD) remain to be fully elucidated. Mitochondrial dysfunction is associated with kidney disease in nondiabetic contexts, and increasing evidence suggests that dysfunctional renal mitochondria are pathological mediators of DKD. These complex organelles have a broad range of functions, including the generation of ATP. The kidneys are mitochondrially rich, highly metabolic organs that require vast amounts of ATP for their normal function. The delivery of metabolic substrates for ATP production, such as fatty acids and oxygen, is altered by diabetes. Changes in metabolic fuel sources in diabetes to meet ATP demands result in increased oxygen consumption, which contributes to renal hypoxia. Inherited factors including mutations in genes that impact mitochondrial function and/or substrate delivery may also be important risk factors for DKD. Hence, we postulate that the diabetic milieu and inherited factors that underlie abnormalities in mitochondrial function synergistically drive the development and progression of DKD.

[Diabetic dyslipidemia and microvascular complications of diabetes]

Diabetic dyslipidemia is one of the main risk factors for atherosclerosis. Although its participation in diabetic microvascular complications is not that dominant, dyslipidemia may play an important role in formation and progression of these complications. Pathophysiological mechanisms by which diabetic dyslipidemia affects the etiopathogenesis of diabetic nephropathy, retinopathy, neuropathy and diabetic foot are presented. The data from clinical studies and treatment possibilities for particular microvascular complications using lipid-lowering therapy are discussed.Key words: diabetes mellitus - diabetic foot - dyslipidemia - nephropathy - neuropathy - retinopathy.

FXR/TGR5 Dual Agonist Prevents Progression of Nephropathy in Diabetes and Obesity

Bile acids are ligands for the nuclear hormone receptor farnesoid X receptor (FXR) and the G protein-coupled receptor TGR5. We have shown that FXR and TGR5 have renoprotective roles in diabetes- and obesity-related kidney disease. Here, we determined whether these effects are mediated through differential or synergistic signaling pathways. We administered the FXR/TGR5 dual agonist INT-767 to DBA/2J mice with streptozotocin-induced diabetes, db/db mice with type 2 diabetes, and C57BL/6J mice with high-fat diet-induced obesity. We also examined the individual effects of the selective FXR agonist obeticholic acid (OCA) and the TGR5 agonist INT-777 in diabetic mice. The FXR agonist OCA and the TGR5 agonist INT-777 modulated distinct renal signaling pathways involved in the pathogenesis and treatment of diabetic nephropathy. Treatment of diabetic DBA/2J and db/db mice with the dual FXR/TGR5 agonist INT-767 improved proteinuria and prevented podocyte injury, mesangial expansion, and tubulointerstitial fibrosis. INT-767 exerted coordinated effects on multiple pathways, including stimulation of a signaling cascade involving AMP-activated protein kinase, sirtuin 1, PGC-1α, sirtuin 3, estrogen-related receptor-α, and Nrf-1; inhibition of endoplasmic reticulum stress; and inhibition of enhanced renal fatty acid and cholesterol metabolism. Additionally, in mice with diet-induced obesity, INT-767 prevented mitochondrial dysfunction and oxidative stress determined by fluorescence lifetime imaging of NADH and kidney fibrosis determined by second harmonic imaging microscopy. These results identify the renal signaling pathways regulated by FXR and TGR5, which may be promising targets for the treatment of nephropathy in diabetes and obesity.

Location-Specific Oral Microbiome Possesses Features Associated With CKD

INTRODUCTION

Chronic kidney disease (CKD), a progressive loss of renal function, can lead to serious complications if underdiagnosed. Many studies suggest that the oral microbiota plays important role in the health of the host; however, little is known about the association between the oral microbiota and CKD pathogenesis.

METHODS

In this study, we surveyed the oral microbiota in saliva, the left and right molars, and the anterior mandibular lingual area from 77 participants (18 with and 59 without CKD), and tested their association with CKD to identify microbial features that may be predictive of CKD status.

RESULTS

The overall oral microbiota composition significantly differed by oral locations and was associated with CKD status in saliva and anterior mandibular lingual samples. In CKD patients, we observed a significant enrichment of Neisseria and depletion of Veillonella in both sample types and a lower prevalence of Streptococcus in saliva after adjustment for other comorbidities. Furthermore, we detected a negative association of Neisseria and Streptococcus genera with the kidney function as measured by estimated glomerular filtration rate. Neisseria abundance also correlated with plasma interleukin-18 levels.

CONCLUSION

We demonstrate the association of the oral microbiome with CKD and inflammatory kidney biomarkers, highlighting a potential role of the commensal bacteria in CKD pathogenesis. A better understanding of the interplay between the oral microbiota and CKD may help in the development of new strategies to identify at-risk individuals or to serve as a novel target for therapeutic intervention.

Shared and distinct lipid-lipid interactions in plasma and affected tissues in a diabetic mouse model

Lipids are ubiquitous metabolites with diverse functions; abnormalities in lipid metabolism appear to be related to complications from multiple diseases, including type 2 diabetes. Through technological advances, the entire lipidome has been characterized and researchers now need computational approaches to better understand lipid network perturbations in different diseases. Using a mouse model of type 2 diabetes with microvascular complications, we examined lipid levels in plasma and in renal, neural, and retinal tissues to identify shared and distinct lipid abnormalities. We used correlation analysis to construct interaction networks in each tissue, to associate changes in lipids with changes in enzymes of lipid metabolism, and to identify overlap of coregulated lipid subclasses between plasma and each tissue to define subclasses of plasma lipids to use as surrogates of tissue lipid metabolism. Lipid metabolism alterations were mostly tissue specific in the kidney, nerve, and retina; no lipid changes correlated between the plasma and all three tissue types. However, alterations in diacylglycerol and in lipids containing arachidonic acid, an inflammatory mediator, were shared among the tissue types, and the highly saturated cholesterol esters were similarly coregulated between plasma and each tissue type in the diabetic mouse. Our results identified several patterns of altered lipid metabolism that may help to identify pathogenic alterations in different tissues and could be used as biomarkers in future research into diabetic microvascular tissue damage.

Metabolomics and Gene Expression Analysis Reveal Down-regulation of the Citric Acid (TCA) Cycle in Non-diabetic CKD Patients

Chronic kidney disease (CKD) is a public health problem with very high prevalence and mortality. Yet, there is a paucity of effective treatment options, partly due to insufficient knowledge of underlying pathophysiology. We combined metabolomics (GCMS) with kidney gene expression studies to identify metabolic pathways that are altered in adults with non-diabetic stage 3-4 CKD versus healthy adults. Urinary excretion rate of 27 metabolites and plasma concentration of 33 metabolites differed significantly in CKD patients versus controls (estimate range-68% to +113%). Pathway analysis revealed that the citric acid cycle was the most significantly affected, with urinary excretion of citrate, cis-aconitate, isocitrate, 2-oxoglutarate and succinate reduced by 40-68%. Reduction of the citric acid cycle metabolites in urine was replicated in an independent cohort. Expression of genes regulating aconitate, isocitrate, 2-oxoglutarate and succinate were significantly reduced in kidney biopsies. We observed increased urine citrate excretion (+74%, p=0.00009) and plasma 2-oxoglutarate concentrations (+12%, p=0.002) in CKD patients during treatment with a vitamin-D receptor agonist in a randomized trial. In conclusion, urinary excretion of citric acid cycle metabolites and renal expression of genes regulating these metabolites were reduced in non-diabetic CKD. This supports the emerging view of CKD as a state of mitochondrial dysfunction.

Vascular complications in diabetes: old messages, new thoughts

In parallel with the growing diabetes pandemic, there is an increasing burden of micro- and macrovascular complications, occurring in the majority of patients. The identification of a number of synergistic accelerators of disease, providing therapeutic pathways, has stabilised the incidence of complications in most western nations. However, the primary instigators of diabetic complications and, thus, prevention strategies, remain elusive. This has necessitated a refocus on natural history studies, where tissue and plasma samples are sequentially taken to determine when and how disease initiates. In addition, recent Phase III trials, wherein the pleiotropic effects of compounds were arguably as beneficial as their glucose-lowering capacity in slowing the progression of complications, have identified knowledge gaps. Recently the influence of other widely recognised pathological pathways, such as mitochondrial production of reactive oxygen species, has been challenged, highlighting the need for a diverse and robust global research effort to ascertain viable therapeutic targets. Technological advances, such as -omics, high-resolution imaging and computational modelling, are providing opportunities for strengthening and re-evaluating research findings. Newer areas such as epigenetics, energetics and the increasing scrutiny of our synergistic inhabitants, the microbiota, also offer novel targets as biomarkers. Ultimately, however, this field requires concerted lobbying to support all facets of diabetes research.

Crosstalk of Hyperglycemia and Dyslipidemia in Diabetic Kidney Disease

Background

Diabetic kidney disease (DKD) is defined by the functional, structural, and clinical abnormalities of the kidney that are caused by diabetes.

Summary

One-third of both type 1 diabetes and type 2 diabetes patients suffer from DKD, which is the leading cause of end-stage renal disease, and is also associated with cardiovascular disease and high public health care costs. Serum glucose level and lipid level are key factors in the pathogenesis of DKD and are modifiable. The goal of this review is to provide an update on the roles of glucose and lipid metabolism in DKD and their crosstalk at the molecular level. We will further discuss the recent advances regarding metabolic nuclear receptors in glucose-lipid crosstalk, which may provide new potential therapeutic targets for DKD.

Key Message

AMPK, SREBP-1, and some metabolic hormone receptors including liver X receptors, farnesoid X receptors, and peroxisome proliferator-activated receptors mediate the crosstalk of hyperglycemia and dyslipidemia in diabetic kidney disease and might be potential treatment candidates.

Mitochondrial energetics in the kidney

The kidney requires a large number of mitochondria to remove waste from the blood and regulate fluid and electrolyte balance. Mitochondria provide the energy to drive these important functions and can adapt to different metabolic conditions through a number of signalling pathways (for example, mechanistic target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) pathways) that activate the transcriptional co-activator peroxisome proliferator-activated receptor-γ co-activator 1α (PGC1α), and by balancing mitochondrial dynamics and energetics to maintain mitochondrial homeostasis. Mitochondrial dysfunction leads to a decrease in ATP production, alterations in cellular functions and structure, and the loss of renal function. Persistent mitochondrial dysfunction has a role in the early stages and progression of renal diseases, such as acute kidney injury (AKI) and diabetic nephropathy, as it disrupts mitochondrial homeostasis and thus normal kidney function. Improving mitochondrial homeostasis and function has the potential to restore renal function, and administering compounds that stimulate mitochondrial biogenesis can restore mitochondrial and renal function in mouse models of AKI and diabetes mellitus. Furthermore, inhibiting the fission protein dynamin 1-like protein (DRP1) might ameliorate ischaemic renal injury by blocking mitochondrial fission.

Advances in the Understanding and Treatment of Mitochondrial Fatty Acid Oxidation Disorders

Purpose of review

This review focuses on advances made in the past three years with regards to understanding the mitochondrial fatty acid oxidation (FAO) pathway, the pathophysiological ramifications of genetic lesions in FAO enzymes, and emerging therapies for FAO disorders.

Recent findings

FAO has now been recognized to play a key energetic role in pulmonary surfactant synthesis, T-cell differentiation and memory, and the response of the proximal tubule to kidney injury. Patients with FAO disorders may face defects in these cellular systems as they age. Aspirin, statins, and nutritional supplements modulate the rate of FAO under normal conditions and could be risk factors for triggering symptoms in patients with FAO disorders. Patients have been identified with mutations in the ACAD9 and ECHS1 genes, which may represent new FAO disorders. New interventions for long-chain FAODs are in clinical trials. Finally, post-translational modifications that regulate fatty acid oxidation protein activities have been characterized that represent important new therapeutic targets.

Summary

Recent research has led to a deeper understanding of FAO. New therapeutic avenues are being pursued that may ultimately cause a paradigm shift for patient care.

Increasing the level of peroxisome proliferator-activated receptor γ coactivator-1α in podocytes results in collapsing glomerulopathy

Inherited and acquired mitochondrial defects have been associated with podocyte dysfunction and chronic kidney disease (CKD). Peroxisome proliferator-activated receptor γ coactivator-1α (PGC1α) is one of the main transcriptional regulators of mitochondrial biogenesis and function. We hypothesized that increasing PGC1α expression in podocytes could protect from CKD. We found that PGC1α and mitochondrial transcript levels are lower in podocytes of patients and mouse models with diabetic kidney disease (DKD). To increase PGC1α expression, podocyte-specific inducible PGC1α-transgenic mice were generated by crossing nephrin-rtTA mice with tetO-Ppargc1a animals. Transgene induction resulted in albuminuria and glomerulosclerosis in a dose-dependent manner. Expression of PGC1α in podocytes increased mitochondrial biogenesis and maximal respiratory capacity. PGC1α also shifted podocytes towards fatty acid usage from their baseline glucose preference. RNA sequencing analysis indicated that PGC1α induced podocyte proliferation. Histological lesions of mice with podocyte-specific PGC1α expression resembled collapsing focal segmental glomerular sclerosis. In conclusion, decreased podocyte PGC1α expression and mitochondrial content is a consistent feature of DKD, but excessive PGC1α alters mitochondrial properties and induces podocyte proliferation and dedifferentiation, indicating that there is likely a narrow therapeutic window for PGC1α levels in podocytes.

Urinary lysophopholipids are increased in diabetic patients with nephropathy

Diabetic nephropathy (DN) is a major cause of chronic kidney disease that frequently leads to end stage renal failure. Lysophosphatidic acid (LPA) and lysophosphatidylcholine (LPC) are lysophospholipid mediators shown to accumulate in kidney and to promote renal inflammation and tubulo-interstitial fibrosis in diabetic rodent models. Here we assessed whether LPA and LPC were associated to the development of nephropathy in diabetic human patients. Several molecular species of LPA and LPC were quantified by LC/MS-MS in urine and plasma from type 2 diabetic patients with (cases; n=41) or without (controls, n=41) nephropathy symptoms (micro/macro-albuminuria and eGFR<60ml/min/1.73m²). Cases and controls were matched for sex, age and diabetes duration. Six species were detected in urine for both LPA and LPC, LPA16:0, LPA20:4, LPC16:0, LPC18:0, LPC18:1, and LPC18:2 that were significantly more concentrated in cases than in controls. Total LPC and LPA (sum of detected species) were significantly and exclusively associated with albuminuria (P<0.0001 and P=0.0009 respectively) and were significantly higher in the 3rd when compared to the 1st albuminuria tertile in cases. Plasma lysophospholipids showed a different species profile urine and their concentrations were not different between cases and controls. In conclusion, urine concentration of lysophospholipids increases in diabetic patients with DN as the likely result of their co-excretion with albumin combined with possible local production by kidney. Because LPA and LPC are known to promote renal inflammation and tubulo-interstitial fibrosis, their increased production in DN could participate to the development of kidney damage associated with diabetes.

gamAID: Greedy CP tensor decomposition for supervised EHR-based disease trajectory differentiation

We propose gamAID, an exploratory, supervised nonnegative tensor factorization method that iteratively extracts phenotypes from tensors constructed from medical count data. Using data from diabetic patients who later on get diagnosed with chronic kidney disorder (CKD) as well as diabetic patients who do not receive a CKD diagnosis, we demonstrate the potential of gamAID to discover phenotypes that characterize patients who are at risk for developing a disease.

Precision Medicine Approaches to Diabetic Kidney Disease: Tissue as an Issue

PURPOSE OF REVIEW

Precision medicine approaches, that tailor medications to specific individuals has made paradigm-shifting improvements for patients with certain cancer types.

RECENT FINDINGS

Such approaches, however, have not been implemented for patients with diabetic kidney disease. Precision medicine could offer new avenues for novel diagnostic, prognostic and targeted therapeutics development. Genetic studies associated with multiscalar omics datasets from tissue and cell types of interest of well-characterized cohorts are needed to change the current paradigm. In this review, we will discuss precision medicine approaches that the nephrology community can take to analyze tissue samples to develop new therapeutics for patients with diabetic kidney disease.

High Glucose Promotes CD36 Expression by Upregulating Peroxisome Proliferator-Activated Receptor γ Levels to Exacerbate Lipid Deposition in Renal Tubular Cells

Diabetic kidney disease (DKD) appears to be closely related to lipid deposition in kidney. The aim of this study was to determine whether high glucose (HG) exacerbated lipid deposition by increasing CD36 expression via AKT-PPARγ signaling pathway. Our results showed that HG activated AKT signaling pathway, followed by an increase in PPARγ that induced CD36 overexpression, ultimately causing lipid deposition in HK-2 cells. We also found that inhibition of AKT-PPARγ signaling pathway or knockdown of CD36 could reduce HG-induced lipid accumulation in HK-2 cells. These results indicated that AKT-PPARγ signaling pathway mediated HG-induced lipid deposition by upregulating CD36 expression in HK-2 cells and that inhibition of AKT-PPARγ signaling pathway had the potential beneficial effects of reducing lipid deposition in diabetic kidney.

Glycative Stress and Its Defense Machinery Glyoxalase 1 in Renal Pathogenesis

Chronic kidney disease is a major public health problem around the world. Because the kidney plays a role in reducing glycative stress, renal dysfunction results in increased glycative stress. In turn, glycative stress, especially that due to advanced glycated end products (AGEs) and their precursors such as reactive carbonyl compounds, exacerbates chronic kidney disease and is related to premature aging in chronic kidney disease, whether caused by diabetes mellitus or otherwise. Factors which hinder a sufficient reduction in glycative stress include the inhibition of anti-glycation enzymes (e.g., GLO-1), as well as pathogenically activated endoplasmic reticulum (ER) stress and hypoxia in the kidney. Promising strategies aimed at halting the vicious cycle between chronic kidney disease and increases in glycative stress include the suppression of AGE accumulation in the body and the enhancement of GLO-1 to strengthen the host defense machinery against glycative stress.

Plasma Triglycerides and HDL-C Levels Predict the Development of Diabetic Kidney Disease in Subjects With Type 2 Diabetes: The AMD Annals Initiative

OBJECTIVE

Despite the achievement of blood glucose, blood pressure, and LDL cholesterol (LDL-C) targets, the risk for diabetic kidney disease (DKD) remains high among patients with type 2 diabetes. This observational retrospective study investigated whether diabetic dyslipidemia-that is, high triglyceride (TG) and/or low HDL cholesterol (HDL-C) levels-contributes to this high residual risk for DKD.

RESEARCH DESIGN AND METHODS

Among a total of 47,177 patients attending Italian diabetes centers, 15,362 patients with a baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m², normoalbuminuria, and LDL-C ≤130 mg/dL completing a 4-year follow-up were analyzed. The primary outcome was the incidence of DKD, defined as either low eGFR (<60 mL/min/1.73 m²) or an eGFR reduction >30% and/or albuminuria.

RESULTS

Overall, 12.8% developed low eGFR, 7.6% an eGFR reduction >30%, 23.2% albuminuria, and 4% albuminuria and either eGFR <60 mL/min/1.73 m² or an eGFR reduction >30%. TG ≥150 mg/dL increased the risk of low eGFR by 26%, of an eGFR reduction >30% by 29%, of albuminuria by 19%, and of developing one abnormality by 35%. HDL-C <40 mg/dL in men and <50 mg/dL in women were associated with a 27% higher risk of low eGFR and a 28% risk of an eGFR reduction >30%, with a 24% higher risk of developing albuminuria and a 44% risk of developing one abnormality. These associations remained significant when TG and HDL-C concentrations were examined as continuous variables and were only attenuated by multivariate adjustment for numerous confounders.

CONCLUSIONS

In a large population of outpatients with diabetes, low HDL-C and high TG levels were independent risk factors for the development of DKD over 4 years.

Thioredoxin-interacting protein regulates lipid metabolism via Akt/mTOR pathway in diabetic kidney disease

Abnormal lipid metabolism contributes to the renal lipid accumulation, which is associated with diabetic kidney disease, but its precise mechanism remains unclear. The growing evidence demonstrates that thioredoxin-interacting protein is involved in regulating cellular glucose and lipid metabolism. Here, we investigated the effects of thioredoxin-interacting protein on lipid accumulation in diabetic kidney disease. In contrast to the diabetic wild-type mice, the physical and biochemical parameters were improved in the diabetic thioredoxin-interacting protein knockout mice. The increased renal lipid accumulation, expression of acetyl-CoA carboxylase, fatty acid synthase and sterol regulatory element binding protein-1, and phosphorylated Akt and mTOR associated with diabetes in wild-type mice was attenuated in diabetic thioredoxin-interacting protein knockout mice. Furthermore, thioredoxin-interacting protein knockout significantly increased the expression of peroxisome proliferator-activated receptor-α, acyl-coenzyme A oxidase 1 and carnitine palmitoyltransferaser 1 in diabetic kidneys. In vitro experiments, using HK-2 cells, revealed that knockdown of thioredoxin-interacting protein inhibited high glucose-mediated lipid accumulation, expression of acetyl-CoA carboxylase, fatty acid synthase and sterol regulatory element binding protein-1, as well as activation of Akt and mTOR. Moreover, knockdown of thioredoxin-interacting protein reversed high glucose-induced reduction of peroxisome proliferator-activated receptor-α, acyl-coenzyme A oxidase 1 and carnitine palmitoyltransferaser 1 expression in HK-2 cells. Importantly, blockade of Akt/mTOR signaling pathway with LY294002, a specific PI3K inhibitor, replicated these effects of thioredoxin-interacting protein silencing. Taken together, these data suggest that thioredoxin-interacting protein deficiency alleviates diabetic renal lipid accumulation through regulation of Akt/mTOR pathway, thioredoxin-interacting protein may be a potential therapeutic target for diabetic kidney disease.

Effect of breviscapine injection on clinical parameters in diabetic nephropathy: A meta-analysis of randomized controlled trials

Diabetic nephropathy (DN) is currently a major public health problem worldwide. The objective of the present study was to evaluate the clinical effect of breviscapine injections in patients with DN. A meta-analysis was performed using the following databases to obtain published reports in any language: PubMed/MEDLINE, Embase, China National Knowledge Infrastructure, Chinese Evidence-Based Medicine, Wanfang Digital Periodicals, Chinese Academic Journals Full-text Database, Chinese Biological and Medical Database, China Doctoral and Masters Dissertations Full-text Database and the Chinese Proceedings of Conference Full-text Database. Two assessors independently reviewed each trial. A total of 35 randomized controlled trials, which performed studies on a total of 2,320 patients (1,188 in treatment groups and 1,132 in control groups), were included in the present meta-analysis. Data were analyzed using Stata version 11.0 for Windows. The results from the analysis demonstrated that breviscapine injections have greater therapeutic effects in patients with DN in comparison with the control group, including renal protective effects (reducing urine protein, serum creatinine and blood urea nitrogen) and adjustment for dyslipidemia (affecting levels of cholesterol, triglycerides and high density lipoproteins). These effects indicate that breviscapine injections are beneficial to patients with DN. Further studies are required to determine the mechanisms underlying the therapeutic effects of breviscapine.

Obesity-related glomerulopathy: clinical and pathologic characteristics and pathogenesis

The prevalence of obesity-related glomerulopathy is increasing in parallel with the worldwide obesity epidemic. Glomerular hypertrophy and adaptive focal segmental glomerulosclerosis define the condition pathologically. The glomerulus enlarges in response to obesity-induced increases in glomerular filtration rate, renal plasma flow, filtration fraction and tubular sodium reabsorption. Normal insulin/phosphatidylinositol 3-kinase/Akt and mTOR signalling are critical for podocyte hypertrophy and adaptation. Adipokines and ectopic lipid accumulation in the kidney promote insulin resistance of podocytes and maladaptive responses to cope with the mechanical forces of renal hyperfiltration. Although most patients have stable or slowly progressive proteinuria, up to one-third develop progressive renal failure and end-stage renal disease. Renin-angiotensin-aldosterone blockade is effective in the short-term but weight loss by hypocaloric diet or bariatric surgery has induced more consistent and dramatic antiproteinuric effects and reversal of hyperfiltration. Altered fatty acid and cholesterol metabolism are increasingly recognized as key mediators of renal lipid accumulation, inflammation, oxidative stress and fibrosis. Newer therapies directed to lipid metabolism, including SREBP antagonists, PPARα agonists, FXR and TGR5 agonists, and LXR agonists, hold therapeutic promise.

Distinct urinary lipid profile in children with focal segmental glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) accounts for the majority of new-onset end-stage renal disease (ESRD) during adolescence. FSGS treatment is a great challenge for pediatric nephrologists due to intertwined molecular pathways underlining its complex pathophysiology. There is emerging evidence showing that perturbed lipid metabolism plays a role in the pathophysiology of FSGS.

METHODS

We postulate that the nephrotic milieu in FSGS differs from minimal change disease (MCD) and that urinary lipidomics can be used as a tool for early diagnosis of FSGS. We explored the urinary lipid profile of patients with FSGS and MCD using an unbiased metabolomics approach.

RESULTS

We discovered a unique lipid signature characterized by increased concentration of fatty acid (FA) and lysophosphatidylcholines (LPC) and a decrease in urinary concentration of phosphatidylcholine (PC) in patients with FSGS. These findings indicate increased metabolism of membrane phospholipid PC by phospholipase A2 (PLA2), resulting in higher urinary concentrations of LPC and FA.

CONCLUSIONS

We propose that increased PC by-products can be used as a biomarker to diagnose FSGS and shed light on the mechanism of tubular and podocyte damage. Validation of identified urinary lipids as a biomarker in predicting the diagnosis and progression of FSGS in a larger patient population is warranted.

Adenosine monophosphate-activated protein kinase in diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease, and its pathogenesis is complex and has not yet been fully elucidated. Abnormal glucose and lipid metabolism is key to understanding the pathogenesis of DN, which can develop in both type 1 and type 2 diabetes. A hallmark of this disease is the accumulation of glucose and lipids in renal cells, resulting in oxidative and endoplasmic reticulum stress, intracellular hypoxia, and inflammation, eventually leading to glomerulosclerosis and interstitial fibrosis. There is a growing body of evidence demonstrating that dysregulation of 5′ adenosine monophosphate–activated protein kinase (AMPK), an enzyme that plays a principal role in cell growth and cellular energy homeostasis, in relevant tissues is a key component of the development of metabolic syndrome and type 2 diabetes mellitus; thus, targeting this enzyme may ameliorate some pathologic features of this disease. AMPK regulates the coordination of anabolic processes, with its activation proven to improve glucose and lipid homeostasis in insulin-resistant animal models, as well as demonstrating mitochondrial biogenesis and antitumor activity. In this review, we discuss new findings regarding the role of AMPK in the pathogenesis of DN and offer suggestions for feasible clinical use and future studies of the role of AMPK activators in this disorder.

New molecular insights in diabetic nephropathy

Diabetes mellitus represents one of the major causes of functional kidney impairment. The review highlights the most significant steps made over the last decades in understanding the molecular basis of diabetic nephropathy (DN), which may provide reliable biomarkers for early diagnosis and prognosis, along with new molecular targets for personalized medicine. There is an increased interest in developing new therapeutic strategies to slow DN progression for improving patients' quality of life and reducing all-cause morbidity and disease-associated mortality. It is highly important to have a science-based medical attitude when facing diabetic patients with associated comorbidities and risk of rapid evolution toward end-stage renal disease. The data discussed herein were mainly from MEDLINE and PubMed articles published in English from 1990 to 2015 and from up-to-date. The search term was "diabetic nephropathy and oxidative stress".

Diabetic Kidney Disease: A Syndrome Rather Than a Single Disease

The term "diabetic kidney" has recently been proposed to encompass the various lesions, involving all kidney structures that characterize protean kidney damage in patients with diabetes. While glomerular diseases may follow the stepwise progression that was described several decades ago, the tenet that proteinuria identifies diabetic nephropathy is disputed today and should be limited to glomerular lesions. Improvements in glycemic control may have contributed to a decrease in the prevalence of glomerular lesions, initially described as hallmarks of diabetic nephropathy, and revealed other types of renal damage, mainly related to vasculature and interstitium, and these types usually present with little or no proteinuria. Whilst glomerular damage is the hallmark of microvascular lesions, ischemic nephropathies, renal infarction, and cholesterol emboli syndrome are the result of macrovascular involvement, and the presence of underlying renal damage sets the stage for acute infections and drug-induced kidney injuries. Impairment of the phagocytic response can cause severe and unusual forms of acute and chronic pyelonephritis. It is thus concluded that screening for albuminuria, which is useful for detecting "glomerular diabetic nephropathy", does not identify all potential nephropathies in diabetes patients. As diabetes is a risk factor for all forms of kidney disease, diagnosis in diabetic patients should include the same combination of biochemical, clinical, and imaging tests as employed in non-diabetic subjects, but with the specific consideration that chronic kidney disease (CKD) may develop more rapidly and severely in diabetic patients.