Pathologic classification of diabetic nephropathy

Urinary excretion of high molecular weight adiponectin is an independent predictor of decline of renal function in type 2 diabetes

Adiponectin and urinary adiponectin excretions have been ascribed a function in glomerular physiology and seem to indicate vascular disease in diabetes. The aim of this study was to compare the urinary excretion of albumin and adiponectin as predictors for decline of renal function in patients with type 2 diabetes and early kidney disease. Over 141 patients were screened for renal function (estimated GFR, ml/min*1.73 m(2)), albumin excretion rate (AER, mg/24 h), total as well as high molecular weight (HMW) urinary adiponectin excretion (ng/mol u-creatinine). AER and adiponectin excretion were studied as predictors of renal function after 1 year. After 1 year, 36 patients were in the upper quartile of eGFR decline and defined as progressors (delta eGFR = - 12.3 ± 6.3) while the remaining 105 patients were defined as non-progressors (delta eGFR = 1.4 ± 6.0). At baseline, HMW-adiponectin excretion was positively correlated with HbA1c (p < 0.001) and negatively with eGFR (p < 0.001), but not with AER (p = 0.14). Progressors showed increased urinary HMW-adiponectin at baseline (158[IQR41/479] vs. 65[24/168] ng/mol; p < 0.01), while total adiponectin (182[101/1534] vs. 345[118/1361] ng/mol) and AER (48[23/109] vs. 46[25/108] mg/24 h) excretion showed no differences between the groups. Multivariate logistic regression showed that HMW-adiponectin excretion was an independent predictor of renal progression in all patients (OR 1.86 [95 % CI 1.34-2.59]; p < 0.01), especially in those (n = 45) with normal AER at baseline (OR 2.16 [95 % CI 1.1-4.56]; p < 0.05). Urinary HMW-adiponectin but not AER improved the prediction of progressors in ROC analysis (AUC 0.72 [95 % CI 0.63-0.81] vs. 0.80 [95 % CI 0.71-0.90], p < 0.05). In conclusion, urinary HMW-adiponectin excretion may identify diabetes patients at increased risk for progression of kidney disease.

Altered renal lipid metabolism and renal lipid accumulation in human diabetic nephropathy

Animal models link ectopic lipid accumulation to renal dysfunction, but whether this process occurs in the human kidney is uncertain. To this end, we investigated whether altered renal TG and cholesterol metabolism results in lipid accumulation in human diabetic nephropathy (DN). Lipid staining and the expression of lipid metabolism genes were studied in kidney biopsies of patients with diagnosed DN (n = 34), and compared with normal kidneys (n = 12). We observed heavy lipid deposition and increased intracellular lipid droplets. Lipid deposition was associated with dysregulation of lipid metabolism genes. Fatty acid β-oxidation pathways including PPAR-α, carnitine palmitoyltransferase 1, acyl-CoA oxidase, and L-FABP were downregulated. Downregulation of renal lipoprotein lipase, which hydrolyzes circulating TGs, was associated with increased expression of angiopoietin-like protein 4. Cholesterol uptake receptor expression, including LDL receptors, oxidized LDL receptors, and acetylated LDL receptors, was significantly increased, while there was downregulation of genes effecting cholesterol efflux, including ABCA1, ABCG1, and apoE. There was a highly significant correlation between glomerular filtration rate, inflammation, and lipid metabolism genes, supporting a possible role of abnormal lipid metabolism in the pathogenesis of DN. These data suggest that renal lipid metabolism may serve as a target for specific therapies aimed at slowing the progression of glomerulosclerosis.

Diabetic kidney disease and the cardiorenal syndrome: old disease, new perspectives

In this article, the literature is reviewed regarding the role of blood pressure variability and nocturnal nondipping of blood pressure as well as the presence of diabetic kidney disease (DKD), in the absence of albuminuria, as risk predictors for progressive DKD. The importance of glycemic and blood pressure control in patients with diabetes and chronic kidney disease, and the use of oral hypoglycemic agents and antihypertensive agents in this patient cohort, are also discussed.

Diabetic nephropathy: diagnosis and treatment

Nephropathy remains a major cause of morbidity and a key determinant of mortality in patients with type 1 or type 2 diabetes mellitus. Research is ongoing to identify biomarkers that in addition to albuminuria and glomerular filtration rate assist in the prediction and monitoring of renal disease in diabetes mellitus. Current strategies to treat this condition focus on intensification of glycaemic control and excellent control of blood pressure using regimens based on blockade of the renin-angiotensin system. Other approaches to control blood pressure and afford renoprotection are under active clinical investigation, including renal denervation and endothelin receptor antagonism. With increasing understanding of the underlying pathophysiological processes implicated in diabetic nephropathy, new specific renoprotective treatment strategies are anticipated to become available over the next few years.

Renal histologic parameters influencing postoperative renal function in renal cell carcinoma patients

BACKGROUND

Pre-existing non-neoplastic renal diseases or lesions may influence patient renal function after tumor removal. However, its description is often neglected or omitted in pathologic reports. To determine the incidence and clinical significance of non-neoplastic lesions, we retrospectively examined renal tissues obtained during 85 radical nephrectomies for renal cell carcinoma.

METHODS

One paraffin-embedded tissue block from each case containing a sufficient amount of non-tumorous renal parenchyma was cut and processed with hematoxylin and eosin and periodic acid-Schiff methods. Non-neoplastic lesions of each histological compartment were semi-quantitatively and quantitatively evaluated.

RESULTS

Among the various histologic lesions found, tubular atrophy, arterial intimal thickening, and glomerulosclerosis were the most common (94.1%, 91.8%, and 88.2%, respectively). Glomerulosclerosis correlated with estimated glomerular filtration rate at the time of surgery, as well as at 1- and 5-years post-surgery (p=.0071), but tubulointerstitial fibrosis or arterial fibrous intimal thickening did not. Post-hoc analysis revealed that glomerulosclerosis of more than 20% predicted post-operative renal function. However, its significance disappeared when gender and age were considered.

CONCLUSIONS

In conclusion, non-neoplastic lesions, especially with regard to glomerulosclerosis percentage, should be described in pathology reports to provide additional information on renal function decline.

Renal structure in normoalbuminuric and albuminuric patients with type 2 diabetes and impaired renal function

OBJECTIVE

The structural basis of normoalbuminuric renal insufficiency in patients with type 2 diabetes remains to be elucidated. We compared renal biopsy findings in patients with type 2 diabetes and estimated glomerular filtration rate (eGFR) and measured GFR of <60 mL/min/1.73 m2, associated with either normo-, micro-, or macroalbuminuria.

RESEARCH DESIGN AND METHODS

In patients with normo- (n = 8) or microalbuminuria (n = 6), renal biopsies were performed according to a research protocol. In patients with macroalbuminuria (n = 17), biopsies were performed according to clinical indication. Findings were categorized according to the Fioretto classification: category 1 (C1), normal/near normal; category 2 (C2), typical diabetic nephropathy (DN) with predominantly glomerular changes; and category 3 (C3), atypical with disproportionately severe interstitial/tubular/vascular damage and with no/mild diabetic glomerular changes.

RESULTS

In our study population (mean eGFR 35 mL/min/1.73 m2), typical glomerular changes (C2) of DN were observed in 22 of 23 subjects with micro- or macroalbuminuria compared with 3 of 8 subjects with normoalbuminuria (P = 0.002). By contrast, predominantly interstitial or vascular changes (C3) were seen in only 1 of 23 subjects with micro- or macroalbuminuria compared with 3 of 8 normoalbuminuric subjects (P = 0.08). Mesangial area increased progressively from normal controls to patients with type 2 diabetes and normo-, micro-, and macroalbuminuria. Varying degrees of arteriosclerosis, although not necessarily the predominant pattern, were seen in seven of eight subjects with normoalbuminuria.

CONCLUSIONS

Typical renal structural changes of DN were observed in patients with type 2 diabetes and elevated albuminuria. By contrast, in normoalbuminuric renal insufficiency, these changes were seen less frequently, likely reflecting greater contributions from aging, hypertension, and arteriosclerosis.

Long-term outcomes of Japanese type 2 diabetic patients with biopsy-proven diabetic nephropathy

OBJECTIVE

We evaluated the structural-functional relationships and the prognostic factors for renal events, cardiovascular events, and all-cause mortality in type 2 diabetic patients with biopsy-proven diabetic nephropathy.

RESEARCH DESIGN AND METHODS

Japanese type 2 diabetic patients with biopsy-proven diabetic nephropathy (n = 260) were enrolled. Patients were stratified by albuminuria (proteinuria) and estimated glomerular filtration rate (eGFR) at the time of renal biopsy. The outcomes were the first occurrence of renal events (requirement of dialysis or a 50% decline in eGFR from baseline), cardiovascular events (cardiovascular death, nonfatal myocardial infarction, coronary interventions, or nonfatal stroke), and all-cause mortality.

RESULTS

The factors associated with albuminuria (proteinuria) regardless of eGFR were hematuria, diabetic retinopathy, low hemoglobin, and glomerular lesions. The factors associated with low eGFR regardless of albuminuria (proteinuria) were age and diffuse, nodular, tubulointerstitial, and vascular lesions. The glomerular, tubulointerstitial, and vascular lesions in patients with normoalbuminuria (normal proteinuria) and low eGFR were more advanced compared to those in patients with normoalbuminuria (normal proteinuria) and maintained eGFR. In addition, compared to patients with micro-/macroalbuminuria (mild/severe proteinuria) and low eGFR, their tubulointerstitial and vascular lesions were similar or more advanced in contrast to glomerular lesions. The mean follow-up period was 8.1 years. There were 118 renal events, 62 cardiovascular events, and 45 deaths. The pathological determinants were glomerular lesions, interstitial fibrosis and tubular atrophy (IFTA), and arteriosclerosis for renal events, arteriosclerosis for cardiovascular events, and IFTA for all-cause mortality. The major clinical determinant for renal events and all-cause mortality was macroalbuminuria (severe proteinuria).

CONCLUSIONS

Our study suggests that the characteristic pathological lesions as well as macroalbuminuria (severe proteinuria) were closely related to the long-term outcomes of biopsy-proven diabetic nephropathy in type 2 diabetes.

Renal prognosis a long time after renal biopsy on patients with diabetic nephropathy

BACKGROUND

A new classification of diabetic nephropathy was reported by Tervaert et al., but the association between pathological findings and the clinical outcomes remains unclear.

METHODS

Among 310 patients with diabetes mellitus who underwent renal biopsy from March 1985 to January 2010 and were confirmed to have diabetic nephropathy according to the Tervaert's classification, 205 patients were enrolled in this study. Cox proportional hazard regression analysis was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) for death-censored renal death. Each regression analysis employed two levels of multivariate adjustment.

RESULTS

After adjustment for age, gender, estimated glomerular filtration rate, type of diabetes, urinary protein excretion, systolic blood pressure, body mass index, HbA1c, diabetic retinopathy and red blood cells in urinary sediment at the time of renal biopsy, compared with glomerular class IIA, the HRs for death-censored renal death of glomerular classes I, IIB, III and IV were 0.21 (95% CI: 0.04-1.25), 2.12 (0.89-5.04), 4.23 (1.80-9.90), and 3.27 (1.32-8.10), respectively. Also, compared with an interstitial fibrosis and tubular atrophy score 1 group, HRs for score 0 group, score 2 group and score 3 group were 0.08 (0.01-0.57), 2.17 (0.96-4.91), 4.78 (1.96-11.68), respectively.

CONCLUSIONS

The progression of glomerular, tubulointerstitial and vascular lesions was associated with higher HRs for renal death. These results suggest the clinical utility of Tervaert's pathological classification.

Receptor for advanced glycation end-products promotes premature senescence of proximal tubular epithelial cells via activation of endoplasmic reticulum stress-dependent p21 signaling

Premature senescence is a key process in the progression of diabetic nephropathy (DN). In our study, we hypothesized that receptors for advanced glycation end-products (RAGE) mediate endoplasmic reticulum (ER) stress to induce premature senescence via p21 signaling activation in diabetic nephropathy. Here, we demonstrated that elevated expression of RAGE, ER stress marker glucose-regulated protein 78 (GRP78), and cell-cycle regulator p21 was all positively correlated with enhanced senescence-associated-β-galactosidase (SA-β-gal) activity in DN patients. In addition, the fraction of SA-β-gal or cells in the G0G1 phase were enhanced in cultured mouse proximal tubular epithelial cells (PTECs) and the expression of RAGE, GRP78 and p21 was up-regulated by advanced glycation end-products (AGEs) in a dose- and time-dependent manner. Interestingly, ER stress inducers or RAGE overexpression mimicked AGEs induced-premature senescence, and this was significantly suppressed by p21 gene silencing. However, RAGE blocking successfully attenuated AGEs-induced ER stress and p21 expression, as well as premature senescence. Moreover, ER stress inducers directly caused p21 activation, premature senescence, and also enhanced RAGE expression by positive feedback. These observations suggest that RAGE promotes premature senescence of PTECs by activation of ER stress-dependent p21 signaling.

Histologic classification of glomerular diseases: clinicopathologic correlations, limitations exposed by validation studies, and suggestions for modification

The value of classification systems applied to the examination of renal biopsies is based on several factors: first, on the ability to provide efficient communication between pathologists and between pathologists and clinicians; second, on the possibility to implement diagnostic information with prognostic indication. Even more important, the practical value of a classification is proved by the ability of providing elements that guide therapeutic decisions and can be used in the follow-up of the patient. With these aims, new histologic classification systems have been proposed in the last decade for lupus nephritis and IgA nephropathy under the leadership of the Renal Pathology Society and the International Society of Nephrology. These classifications have gained a significant level of worldwide acceptance and have been the subject of multiple single-center and multicenter validation studies, which have underpinned their clinical benefits and limitations and served to highlight remaining questions and difficulties of interpretation of the biopsy sample. More recently, a classification system has also been proposed for ANCA-associated crescentic glomerulonephritis (ANCA-GN), although the validation process for this is still in an early stage. In this review, we examine in some detail the ISN/RPS classification for lupus nephritis and the Oxford classification for IgA nephropathy, with emphasis on clinicopathologic correlations, their value for and evolving impact on clinical studies and clinical practice, and their significant limitations in this regard as exposed by validation studies. We also suggest possible ways by which these classifications might be modified to make them more applicable to clinical practice. Finally, we more briefly discuss the newly proposed classification for ANCA-GN.

A story of microalbuminuria and diabetic nephropathy

CONTEXT

It is estimated that more than 346 million people worldwide have diabetes mellitus . By the year 2030, it is predicted that diabetes will become the seventh leading cause of death in the world. Development of chronic kidney disease (CKD) in patients with diabetes adds significantly to the morbidity and mortality and significantly increases health care costs, even before the development of end stage renal disease (ESRD). Evidence  acquisitions: Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched.

RESULTS

Diabetic nephropathy (DN) is increasing rapidly worldwide. It is the leading cause of new cases of ESRD in the USA.  Interestingly, although DN is the most common cause of ESRD in diabetic patients, diabetes mellitus is also an independent and strong risk factor for ESRD ascribed to causes other than DN (e.g. hypertensive nephropathy).

CONCLUSIONS

It is important to be aware of the pitfalls of using the urine albumin level in predicting development and progression of diabetic nephropathy in order to treat and advise the patients accurately.  Research into finding new markers is rapidly evolving but current progress makes it likely we will be using the urine albumin level for some years into the future.

Collapsing glomerulopathy superimposed on diabetic nephropathy: insights into etiology of an under-recognized, severe pattern of glomerular injury

BACKGROUND

Collapsing glomerulopathy (CG) represents severe podocyte injury with massive proteinuria, rapid progression and relative resistance to therapy. It is associated with multiple etiologies, including obliterative arteriopathy in transplants. However, its association with diabetic nephropathy (DN) has not been reported.

METHODS

Renal biopsies performed in diabetic patients for either increasing proteinuria or deteriorating renal function, or both, were retrospectively reviewed. The clinicopathologic features and immunohistochemical staining of podocytes were analyzed.

RESULTS

Of 534 patients with DN, 26 human immunodeficiency virus (HIV)-negative patients were found to have CG superimposed on DN (5% DN cases). At the time of biopsy, their mean serum creatinine was 3.8 mg/dL and proteinuria was 9.8 g/24 h. Renal biopsy showed CG in 2-30% (mean 16% of glomeruli), with segmental (2%) and global (33%) glomerulosclerosis. DN classification was Class IV-12, III-8, IIb-4 and IIa-2. Vascular sclerosis was moderate (44%) and severe (56%). Extensive arteriolar hyalinosis with >50% luminal stenosis was seen in 85% of cases. Markers of podocyte differentiation were lost, consistent with other types of CG. Cytokeratin was focally positive in 70% and VEGF overexpressed in 43%. Follow-up on 17 patients: 13 developed end-stage renal disease (ESRD) in 7 months from the time of biopsy. The development to ESRD in these patients was more rapid than diabetic controls without CG (P=0.005). The remaining four, 5-24 months follow-up, had an increase in creatinine with stable proteinuria.

CONCLUSIONS

CG contributes to an increased level or new onset of proteinuria in DN which may be intractable. CG in DN with advanced vascular hyalinosis is presumably due to ischemic podocyte injury and is of prognostic significance.

The purinergic 2X7 receptor participates in renal inflammation and injury induced by high-fat diet: possible role of NLRP3 inflammasome activation

Renal disease associated with type 2 diabetes and the metabolic syndrome is characterized by a distinct inflammatory phenotype. The purinergic 2X7 receptor (P2X7 R) and the nucleotide-binding and oligomerization domain-like receptor containing a pyrin domain 3 (NLRP3) inflammasome have been separately shown to play a role in two models of non-metabolic chronic kidney disease. Moreover, the NLRP3 inflammasome has been implicated in chronic low-grade sterile inflammation characterizing metabolic disorders, though the mechanism(s) involved in inflammasome activation under these conditions are still unknown. We investigated the role of P2X7 R (through activation of the NLRP3 inflammasome) in renal inflammation and injury induced by a high-fat diet, an established model of the metabolic syndrome. On a high-fat diet, mice lacking P2X7 R developed attenuated renal functional and structural alterations as well as reduced inflammation, fibrosis, and oxidative/carbonyl stress, as compared with wild-type animals, in the absence of significant differences in metabolic parameters. This was associated with blunted up-regulation of the NLRP3 inflammasome components NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), pro-caspase 1, pro-interleukin (IL)-1β, and pro-IL-18, as well as reduced inflammasome activation, as evidenced by decreased formation of mature caspase 1, whereas mature IL-1β and IL-18 were not detected. Up-regulated expression of NLRP3 and pro-caspase 1, post-translational processing of pro-caspase-1, and release of IL-18 in response to lipopolysaccharide + 2'(3')-O-(4-benzoylbenzoyl)ATP were attenuated by P2X7 R silencing in cultured mouse podocytes. Protein and mRNA expression of P2X7 R, NLRP3, and ASC were also increased in kidneys from subjects with type 2 diabetes and the metabolic syndrome, showing histologically documented renal disease. These data provide evidence of a major role for the purinergic system, at least in part through activation of the NLRP3 inflammasome, in the process driving 'metabolic' renal inflammation and injury and identify P2X7 R and NLRP3 as novel therapeutic targets.

Associations between structural and functional changes to the kidney in diabetic humans and mice

Type 1 and Type 2 diabetic patients are at high risk of developing diabetic nephropathy (DN). Renal functional decline is gradual and there is high variability between patients, though the reason for the variability is unknown. Enough diabetic patients progress to end stage renal disease to make diabetes the leading cause of renal failure. The first symptoms of DN do not appear for years or decades after the onset of diabetes. During and after the asymptomatic period structural changes develop in the diabetic kidney. Typically, but not always, the first symptom of DN is albuminuria. Loss of renal filtration rate develops later. This review examines the structural abnormalities of diabetic kidneys that are associated with and possibly the basis for advancing albuminuria and declining GFR. Mouse models of diabetes and genetic manipulations of these models have become central to research into mechanisms underlying DN. This article also looks at the value of these mouse models to understanding human DN as well as potential pitfalls in translating the mouse results to humans.

Temporal profile of diabetic nephropathy pathologic changes

Diabetic nephropathy, by far, is the most common cause of end stage renal disease in the US and many other countries. In type 1 diabetes, the natural history of diabetic nephropathy is tightly linked to evolution of classic lesions of the disease, namely glomerular basement membrane thickening, increased mesangial matrix, and reduced glomerular filtration surface density. These lesions progress in parallel and correlate with increased albumin excretion rate and reduced glomerular filtration rate across a wide range of renal function. In fact, the vast majority of the variances of albumin excretion and glomerular filtration rates can be explained by these glomerular lesions alone in type 1 diabetic patients. Although, classic lesions of diabetic nephropathy, indistinguishable from those of type 1 diabetes, also occur in type 2 diabetes, renal lesions are more heterogeneous in type 2 diabetic patients with some patients developing more advanced vascular or chronic tubulointerstitial lesions than diabetic glomerulopathy. More research biopsy longitudinal studies, especially in type 2 diabetic patients, are needed to better understand various pathways of renal injury in diabetic nephropathy.

Structural renal changes in obesity and diabetes

Overweight, obesity, and associated diseases represent an emerging problem, not only in Western countries but also in the developing world. They are now characterized as epidemic diseases. Obesity is particularly serious because its incidence in children and adolescents increased dramatically: it is estimated that in the United States every eighth adolescent suffers from obesity, which in the long run may reduce life expectancy in the population. Apart from cardiovascular disease (ie, blood pressure, stroke, and coronary heart disease), kidney diseases also have been shown to be associated with obesity. Epidemiologic studies have indicated that obesity can be a risk factor of chronic kidney disease irrespective of the presence or absence of diabetes, arterial hypertension, and other comorbidities. More evidence is accumulated on the link between chronic kidney disease in obesity and abnormalities in adipokine secretion (hyperleptinemia, lack of adiponectin), activation of the renin-angiotensin system, chronic inflammation, endothelial dysfunction, lipid accumulation, impaired renal hemodynamics, and diminished nephron number related to body mass. In general, obesity is known to aggravate the course of many primary renal diseases such as glomerulonephritides, but also impairs renal function after kidney transplantation. Microalbuminuria, proteinuria, hyperfiltration, and impaired renal function are associated with obesity. Histologically, secondary focal segmental sclerosis has been shown to be caused particularly by obesity. Of practical purpose for clinical nephrology, loss of body weight either by lifestyle modification or bariatric surgery improves albuminuria and hyperfiltration in obese patients, making renal disease in obesity accessible for prevention programs. This review specifically addresses the pathogenesis and morphology of renal functional and particularly structural changes in obesity and associated renal disease such as diabetic nephropathy.

Nonneoplastic renal cortical scarring at tumor nephrectomy predicts decline in kidney function

CONTEXT

Evaluating nontumor portions of tumor nephrectomies is useful to diagnose nonneoplastic renal disease.

OBJECTIVE

To determine the medical renal disease frequency and to assess the prognostic significance of the various renal pathologic variables with long-term follow-up in tumor nephrectomy patients.

DESIGN

We reviewed nonneoplastic kidney sections of 456 consecutive cases from 1998 to 2008. Seventy-five cases were excluded (19 tumor compression, 25 no nonneoplastic tissue, 22 embolized kidneys, 9 end stage). Special staining, immunofluorescence, and/or electron microscopy was performed where appropriate. Vascular sclerosis was scored from mild to severe; interstitial fibrosis/tubular atrophy and global glomerulosclerosis (GS) were expressed as percentages. Follow-up, minimum 12 months, was evaluated in 156 cases. All renal pathologic variables were compared with regard to change in creatinine level from preoperative assessment to follow-up.

RESULTS

Of 381 cases, 57 had additional medical renal disease (15%), most frequently diabetic nephropathy (28) and hypertensive nephropathy (11). Postoperative creatinine levels increased significantly in patients with severe arteriosclerosis or arteriolosclerosis, >5% GS, and >10% interstitial fibrosis/tubular atrophy. Seventy-four percent of cases with additional nonneoplastic diagnoses showed severe arteriolosclerosis. Higher corresponding GS was seen in the more affected vascular cases: mean, 5.56% GS for mild versus 23% GS for severe. Three patients progressed to renal failure 1 to 4 years after nephrectomy, 2 with hypertensive nephrosclerosis and 1 with diabetic nephropathy.

CONCLUSIONS

Medical renal disease was identified in 15% of tumor nephrectomy specimens. The degrees of vascular sclerosis, GS, and interstitial fibrosis/tubular atrophy are predictive of elevated creatinine levels in postnephrectomy patients. Prognostic implications of the nontumor pathology are important in nephrectomized patients.

Fractalkine and its receptor mediate extracellular matrix accumulation in diabetic nephropathy in mice

AIMS/HYPOTHESIS

Fractalkine (FKN) is a unique chemokine that works as a chemoattractant and an adhesion molecule. Previous studies have demonstrated that FKN plays a role in ischaemic and protein-overload renal injury via its cognate receptor chemokine (C-X3-C motif) receptor 1 (CX3CR1). However, involvement of the FKN/CX3CR1 system in diabetic nephropathy remains unclear. We examined the role of FKN/CX3CR1 in diabetic mice and mouse mesangial cells (MMCs).

METHODS

Streptozotocin (50 mg kg(-1) day(-1)) was intraperitoneally administered for 5 days to male Cx3cr1-knockout (KO) mice and wild-type (WT) mice. MMCs transfected with Fkn (also known as Cx3cl1) or Cx3cr1 siRNA, respectively, were used to elucidate the role of FKN/CX3CR1 in extracellular matrix (ECM) synthesis.

RESULTS

At 12 weeks, diabetic Cx3cr1 KO mice showed no significant changes in plasma glucose, but markers of renal inflammation, fibrosis and ECM, such as the fractional mesangial area, fibronectin and collagen, were significantly lower in diabetic Cx3cr1 KO mice compared with diabetic WT mice. High glucose, oleic acid and TGF-β1 stimulated FKN and CX3CR1 expression, together with the expression of ECM proteins in MMCs, but the effects were significantly attenuated by Fkn or Cx3cr1 siRNA. More importantly, FKN itself increased mesangial ECM through CX3CR1 and subsequent activation of reactive oxygen species and mitogen-activated protein kinases. A neutralising TGF-β antibody inhibited FKN/CX3CR1 in MMCs treated with diabetic stimuli and decreased FKN-induced ECM accumulation.

CONCLUSIONS/INTERPRETATION

These results demonstrate that FKN/CX3CR1 may play an important role in diabetic renal injury through upregulation of ECM synthesis and could therefore be a therapeutic target for preventing diabetic nephropathy.

Antioxidant and renoprotective effects of Spirogyra neglecta (Hassall) Kützing extract in experimental type 2 diabetic rats

Spirogyra neglecta extract (SNE) has shown antihyperglycemia and antihyperlipidemia in type 2 diabetic mellitus (T2DM) rats. This study investigated the antioxidant and renoprotective effects of SNE in T2DM rats induced by high-fat diet with low-single dose streptozotocin. T2DM rats were fed daily with SNE (0.25, 0.5, and 1 g/kg BW) for 12 weeks. Renal morphology, malondialdehyde levels, qPCR, and western blotting were analyzed. Renal cortical slices were used to determine renal transport of organic anions, which are estrone sulfate and para-aminohippurate, mediated through organic anion transporter 3-Oat3. Insulin and PKCζ were known to activate Oat3 function while it was inhibited by PKCα. Compared to T2DM, plasma glucose, triglyceride, insulin resistance, renal morphology, and malondialdehyde levels were significantly improved by SNE supplementation. Reduced glutathione peroxidase and nuclear factor κB expressions were related to antioxidant effect of SNE. Oat3 mRNA and protein were not different among groups, but insulin-stimulated rOat3 followed by anion uptakes was abolished in T2DM. This was restored in the slices from SNE treatment. The mechanism of SNE-improved Oat3 was associated with PKCα and PKCζ expressions and activities. These findings indicate that SNE has beneficial effects on renal transport through antioxidant enzymes and PKCs in T2DM rats.

Reversibility of structural and functional damage in a model of advanced diabetic nephropathy

The reversibility of diabetic nephropathy remains controversial. Here, we tested whether replacing leptin could reverse the advanced diabetic nephropathy modeled by the leptin-deficient BTBR ob/ob mouse. Leptin replacement, but not inhibition of the renin-angiotensin-aldosterone system (RAAS), resulted in near-complete reversal of both structural (mesangial matrix expansion, mesangiolysis, basement membrane thickening, podocyte loss) and functional (proteinuria, accumulation of reactive oxygen species) measures of advanced diabetic nephropathy. Immunohistochemical labeling with the podocyte markers Wilms tumor 1 and p57 identified parietal epithelial cells as a possible source of regenerating podocytes. Thus, the leptin-deficient BTBR ob/ob mouse provides a model of advanced but reversible diabetic nephropathy for further study. These results also suggest that restoration of lost podocytes is possible but is not induced by RAAS inhibition, possibly explaining the limited efficacy of RAAS inhibitors in promoting repair of diabetic nephropathy.

VEGF and podocytes in diabetic nephropathy

Vascular endothelial growth factor-A (VEGF-A) is a protein secreted by podocytes that is necessary for survival of endothelial cells, podocytes, and mesangial cells. VEGF-A regulates slit-diaphragm signaling and podocyte shape via VEGF-receptor 2-nephrin-nck-actin interactions. Chronic hyperglycemia-induced excess podocyte VEGF-A and low endothelial nitric oxide drive the development and the progression of diabetic nephropathy. The abnormal cross-talk between VEGF-A and nitric oxide pathways is fueled by the diabetic milieu, resulting in increased oxidative stress. Recent findings on these pathogenic molecular mechanisms provide new potential targets for therapy for diabetic renal disease.

Effect of PACAP treatment on kidney morphology and cytokine expression in rat diabetic nephropathy

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide, exerting diverse effects. One of its frequently examined functions is cell protection, which is achieved mainly via inhibiting apoptotic, inflammatory and oxidative processes. All its three receptors (PAC1, VPAC1, VPAC2) are expressed in the kidney and PACAP has been shown to have protective effects against different renal pathologies. Diabetic nephropathy is the leading cause of end stage renal disease. The aim of the present study was to investigate the possible ameliorative effect of PACAP in streptozotocin-induced diabetic nephropathy and to evaluate its anti-inflammatory effect in this model. Diabetes was induced by a single intravenous injection of streptozotocin (65 mg/kg) in male Wistar rats. PACAP-treated animals were administered ip. 20 μg PACAP every second day, while untreated animals were given vehicle. Kidneys were removed after 8-weeks survival. Besides the complex histological analysis (glomerular PAS positive area/glomerulus area, tubular damage, arteriolar hyalinosis), expression of several cytokines was evaluated by cytokine array and Luminex assay. Histological analysis revealed severe diabetic changes in kidneys of control diabetic animals (glomerular PAS-positive area expansion, tubular damage, Armanni-Ebstein phenomenon). PACAP treatment significantly diminished the damage. Diabetic kidneys showed significant cytokine activation compared to their healthy controls. PACAP was effective in downregulation of several cytokines including CINC-1, TIMP-1, LIX, MIG, s-ICAM. To conclude, PACAP is effective in ameliorating diabetic nephropathy at least partly through its well-known anti-inflammatory effect. These results raise the opportunity for the use of PACAP as a possible therapeutic or preventive method in treating the complications of diabetes.

Nephropathy in diabetes

The most common cause of end stage renal disease (ESRD) requiring dialysis is diabetes. Both environmental and genetic factors have been postulated as the risk factors of Diabetic Nephropathy (DN). Hyperglycemia-induced metabolic and hemodynamic pathways are recognized to be mediators of kidney injury. Multiple biochemical pathways have been postulated that explain how hyperglycemia causes tissue damage: Non-enzymatic glycation that generates advanced glycation end products, activation of protein kinase C, acceleration of the polyol pathway and oxidative stress. Three major histologic pathological changes occur in DN: Mesangial expansion, GBM thickening, and glomerular sclerosis. It now seems clear in targeting a therapeutic regimen to achieve blood glucose, blood pressure and proteunuric goals, dietary protein and salt restriction, weight reduction, aggressive lipid lowering, smoking cessation and exercise. Multiple intensive interventions reduce cardiovascular events as well as nephropathy by about half when compared with conventional multifactorial treatment.

Prevalence of diabetic nephropathy complicating non-diabetic renal disease among Chinese patients with type 2 diabetes mellitus

Background

The incidence of diabetes mellitus (DM) and diabetic nephropathy (DN) have risen rapidly in the past few decades and have become an economic burden to the healthcare system in China. DN is a major complication of DM and is a leading cause of end-stage renal disease (ESRD). The occurrence of non-diabetic renal disease (NDRD) in diabetic patients has been increasingly recognized in recent years. It is generally believed that it is difficult to reverse DN, whereas some cases of NDRD are readily treatable and remittable. However, DN is known to co-exist with NDRD in a poorly defined population of patients with type 2 diabetes mellitus (T2DM). This study estimated the prevalence of co-existing DN and NDRD in Chinese patients.

Methods

Data were retrospectively analyzed from 244 patients with T2DM who had undergone a renal biopsy between January 2003 and December 2011 at the Nephrology Department, China-Japan Friendship Hospital, China. Male patients numbered 151 (61.9%) of the study population. The biopsies were performed because urinary abnormalities or renal function were atypical of a diagnosis of DN. Biopsy samples were examined using light, immunofluorescence (IF) and electron microscopy (EM). Clinical parameters were recorded for each patient at the time of biopsy.

Results

Nineteen of 244 diabetic patients (7.8%) had co-existing DN and NDRD. These patients showed clinical features and pathologic characteristics of DN, including a high prevalence of diabetic retinopathy (89.5%), a long duration of diabetes, increased thickness of the glomerular basement membrane (GBM) and mesangial expansion. However, they also presented with clinical findings which were inconsistent with DN, such as hematuria, rapidly progressive renal failure and marked proteinuria. Immunoglobulin A (IgA) nephropathy was apparent in 10 out of the 19 patients (52.6%), tubulointerstitial lesions were found in four patients (21.1%), membrano-proliferative glomerulonephritis (MPGN) in three patients (15.8%) and membranous nephropathy (MN) in two patients (10.5%).

Conclusion

Retrospective analysis of biopsy data suggests that approximately 8% of Chinese patients with T2DM may have co-existing DN and NDRD. The most common histological diagnosis in our small series was IgA nephropathy.

Digital pathology evaluation in the multicenter Nephrotic Syndrome Study Network (NEPTUNE)

Pathology consensus review for clinical trials and disease classification has historically been performed by manual light microscopy with sequential section review by study pathologists, or multi-headed microscope review. Limitations of this approach include high intra- and inter-reader variability, costs, and delays for slide mailing and consensus reviews. To improve this, the Nephrotic Syndrome Study Network (NEPTUNE) is systematically applying digital pathology review in a multicenter study using renal biopsy whole slide imaging (WSI) for observation-based data collection. Study pathology materials are acquired, scanned, uploaded, and stored in a web-based information system that is accessed through a web-browser interface. Quality control includes metadata and image quality review. Initially, digital slides are annotated, with each glomerulus identified, given a unique number, and maintained in all levels until the glomerulus disappears or sections end. The software allows viewing and annotation of multiple slide sections concurrently. Analysis utilizes "descriptors" for patterns of injury, rather than diagnoses, in renal parenchymal compartments. This multidimensional representation via WSI, allows more accurate glomerular counting and identification of all lesions in each glomerulus, with data available in a searchable database. The use of WSI brings about efficiency critical to pathology review in a clinical trial setting, including independent review by multiple pathologists, improved intraobserver and interobserver reproducibility, efficiencies and risk reduction in slide circulation and mailing, centralized management of data integrity and slide images for current or future studies, and web-based consensus meetings. The overall effect is improved incorporation of pathology review in a budget neutral approach.

Effects of SGLT2 inhibition in human kidney proximal tubular cells--renoprotection in diabetic nephropathy?

Sodium/glucose cotransporter 2 (SGLT2) inhibitors are oral hypoglycemic agents used to treat patients with diabetes mellitus. SGLT2 inhibitors block reabsorption of filtered glucose by inhibiting SGLT2, the primary glucose transporter in the proximal tubular cell (PTC), leading to glycosuria and lowering of serum glucose. We examined the renoprotective effects of the SGLT2 inhibitor empagliflozin to determine whether blocking glucose entry into the kidney PTCs reduced the inflammatory and fibrotic responses of the cell to high glucose. We used an in vitro model of human PTCs. HK2 cells (human kidney PTC line) were exposed to control 5 mM, high glucose (HG) 30 mM or the profibrotic cytokine transforming growth factor beta (TGFβ1; 0.5 ng/ml) in the presence and absence of empagliflozin for up to 72 h. SGLT1 and 2 expression and various inflammatory/fibrotic markers were assessed. A chromatin immunoprecipitation assay was used to determine the binding of phosphorylated smad3 to the promoter region of the SGLT2 gene. Our data showed that TGFβ1 but not HG increased SGLT2 expression and this occurred via phosphorylated smad3. HG induced expression of Toll-like receptor-4, increased nuclear deoxyribonucleic acid binding for nuclear factor kappa B (NF-κB) and activator protein 1, induced collagen IV expression as well as interleukin-6 secretion all of which were attenuated with empagliflozin. Empagliflozin did not reduce high mobility group box protein 1 induced NF-κB suggesting that its effect is specifically related to a reduction in glycotoxicity. SGLT1 and GLUT2 expression was not significantly altered with HG or empagliflozin. In conclusion, empagliflozin reduces HG induced inflammatory and fibrotic markers by blocking glucose transport and did not induce a compensatory increase in SGLT1/GLUT2 expression. Although HG itself does not regulate SGLT2 expression in our model, TGFβ increases SGLT2 expression through phosphorylated smad3.

Glomerulopathy in the KK.Cg-A(y) /J mouse reflects the pathology of diabetic nephropathy

The KK.Cg-A (y) /J (KK-A (y) ) mouse strain is a previously described model of type 2 diabetes with renal impairment. In the present study, female KK-A (y) mice received an elevated fat content diet (24% of calories), and a cohort was uninephrectomized (Unx) to drive renal disease severity. Compared to KK-a/a controls, 26-week-old KK-A (y) mice had elevated HbA1c, insulin, leptin, triglycerides, and cholesterol, and Unx further elevated these markers of metabolic dysregulation. Unx KK-A (y) mice also exhibited elevated serum BUN and reduced glomerular filtration, indicating that reduction in renal mass leads to more severe impairment in renal function. Glomerular hypertrophy and hypercellularity, mesangial matrix expansion, podocyte effacement, and basement membrane thickening were present in both binephric and uninephrectomized cohorts. Glomerular size was increased in both groups, but podocyte density was reduced only in the Unx animals. Consistent with functional and histological evidence of increased injury, fibrotic (fibronectin 1, MMP9, and TGF β 1) and inflammatory (IL-6, CD68) genes were markedly upregulated in Unx KK-A (y) mice, while podocyte markers (nephrin and podocin) were significantly decreased. These data suggest podocyte injury developing into glomerulopathy in KK-A (y) mice. The addition of uninephrectomy enhances renal injury in this model, resulting in a disease which more closely resembles human diabetic nephropathy.

Null mutations at the p66 and bradykinin 2 receptor loci induce divergent phenotypes in the diabetic kidney

Candidate genes have been identified that confer increased risk for diabetic glomerulosclerosis (DG). Mice heterozygous for the Akita (Ins2(+/C96Y)) diabetogenic mutation with a second mutation introduced at the bradykinin 2 receptor (B2R(-/-)) locus express a disease phenotype that approximates human DG. Src homology 2 domain transforming protein 1 (p66) controls mitochondrial metabolism and cellular responses to oxidative stress, aging, and apoptosis. We generated p66-null Akita mice to test whether inactivating mutations at the p66 locus will rescue kidneys of Akita mice from disease-causing mutations at the Ins2 and B2R loci. Here we show null mutations at the p66 and B2R loci interact with the Akita (Ins2(+/C96Y)) mutation, independently and in combination, inducing divergent phenotypes in the kidney. The B2R(-/-) mutation induces detrimental phenotypes, as judged by increased systemic and renal levels of oxidative stress, histology, and urine albumin excretion, whereas the p66-null mutation confers a powerful protection phenotype. To elucidate the mechanism(s) of the protection phenotype, we turned to our in vitro system. Experiments with cultured podocytes revealed previously unrecognized cross talk between p66 and the redox-sensitive transcription factor p53 that controls hyperglycemia-induced ROS metabolism, transcription of p53 target genes (angiotensinogen, angiotensin II type-1 receptor, and bax), angiotensin II generation, and apoptosis. RNA-interference targeting p66 inhibits all of the above. Finally, protein levels of p53 target genes were upregulated in kidneys of Akita mice but unchanged in p66-null Akita mice. Taken together, p66 is a potential molecular target for therapeutic intervention in DG.

Hypothyroidism complicating nephropathy in a diabetes patient

We describe a patient with type 2 diabetes mellitus and autoimmune hypothyroidism who presented with elevated serum creatinine possibly due to subclinical rhabdomyolysis induced by hypolipidemic drug therapy in the background of diabetic nephropathy. Both hypothyroidism and rhabdomyolysis were asymptomatic in this case as evidenced by lack of classical clinical features of hypothyroidism despite elevated serum TSH and absent pigment cast in renal biopsy. The combination of diabetes mellitus and hypothyroidism is common in the general population and should not be forgotten in patients with diabetes and kidney disease.

Spectrum of nontumoral renal pathologies in tumor nephrectomies: nontumoral renal parenchyma changes

Non-neoplastic changes are not rarely seen in renal parenchyma of nephrectomy specimens removed for primary renal neoplasms. These changes often involve both kidneys, thus causing impairment of renal function, reducing patient's quality of life and sometimes threatening it. Renal tissue accompanying the tumor provides an opportunity in order to evaluate these changes. However, the clinician should make available clinical and laboratory findings involving renal functions of the patient to the pathologist. It is also important that the pathologist must have appropriate knowledge and experience in nephropathology. In this study, we aimed to correlate these changes with the clinical data and make inquiries regarding our experience with nonneoplastic kidney pathology. Consecutive 403 nephrectomy specimens with primary renal neoplasms submitted to our department between 2003 and 2009 were re-examined. Twenty-three nephrectomy materials from 21 patients had non-neoplastic changes, 2 of which were bilateral. Patient follow-up data were obtained from electronic medical records. Of all cases, eight had diabetic nephropathy; 2, amyloidosis; 5, segmental proliferative and/or sclerotic glomerulonephritis; and 6, cystic renal changes. These findings were seen in 5% of nephrectomy specimens diagnosed as clear cell renal cell carcinoma (RCC), chromophobe cell RCC and oncocytoma, whereas this rate was two times higher in nephrectomy specimens with papillary RCC. Most patients with renal failure who were diagnosed with clear cell carcinoma died within the first two years. Despite limited number of cases in our series, prognosis of cases with clear cell RCC were poorer. Consequently, we think that non-neoplastic changes should be reported along with the details regarding the tumor in order to achieve best treatment planning.

Vegfa protects the glomerular microvasculature in diabetes

Vascular endothelial growth factor A (VEGFA) expression is increased in glomeruli in the context of diabetes. Here, we tested the hypothesis that this upregulation of VEGFA protects the glomerular microvasculature in diabetes and that therefore inhibition of VEGFA will accelerate nephropathy. To determine the role of glomerular Vegfa in the development and progression of diabetic nephropathy, we used an inducible Cre-loxP gene-targeting system that enabled genetic deletion of Vegfa selectively from glomerular podocytes of wild-type or diabetic mice. Type 1 diabetes was induced in mice using streptozotocin (STZ). We then assessed the extent of glomerular dysfunction by measuring proteinuria, glomerular pathology, and glomerular cell apoptosis. Vegfa expression increased in podocytes in the STZ model of diabetes. After 7 weeks of diabetes, diabetic mice lacking Vegfa in podocytes exhibited significantly greater proteinuria with profound glomerular scarring and increased apoptosis compared with control mice with diabetes or Vegfa deletion without diabetes. Reduced local production of glomerular Vegfa in a mouse model of type 1 diabetes promotes endothelial injury accelerating the progression of glomerular injury. These results suggest that upregulation of VEGFA in diabetic kidneys protects the microvasculature from injury and that reduction of VEGFA in diabetes may be harmful.

Diabetic nephropathy and extracellular matrix

Diabetic nephropathy (DN) is a serious complication in diabetes. Major typical morphological changes are the result of changes in the extracellular matrix (ECM). Thus, basement membranes are thickened and the glomerular mesangial matrix and the tubulointerstitial space are expanded, due to increased amounts of ECM. One important ECM component, the proteoglycans (PGs), shows a more complex pattern of changes in DN. PGs in basement membranes are decreased but increased in the mesangium and the tubulointerstitial space. The amounts and structures of heparan sulfate chains are changed, and such changes affect levels of growth factors regulating cell proliferation and ECM synthesis, with cell attachment affecting endothelial cells and podocytes. Enzymes modulating heparan sulfate structures, such as heparanase and sulfatases, are implicated in DN. Other enzyme classes also modulate ECM proteins and PGs, such as matrix metalloproteinases (MMPs) and serine proteases, such as plasminogen activator, as well as their corresponding inhibitors. The levels of these enzymes and inhibitors are changed in plasma and in the kidneys in DN. Several growth factors, signaling pathways, and hyperglycemia per se affect ECM synthesis and turnover in DN. Whether ECM components can be used as markers for early kidney changes is an important research topic, whereas at present, the clinical use remains to be established.

Renoprotective effects of a novel Nox1/4 inhibitor in a mouse model of Type 2 diabetes

Nox (NADPH oxidase)-derived ROS (reactive oxygen species) have been implicated in the development of diabetic nephropathy. Of the Nox isoforms in the kidney, Nox4 is important because of its renal abundance. In the present study, we tested the hypothesis that GKT136901, a Nox1/4 inhibitor, prevents the development of nephropathy in db/db (diabetic) mice. Six groups of male mice (8-week-old) were studied: (i) untreated control db/m, (ii) low-dose GKT136901-treated db/m (30 mg/kg of body weight per day), (iii) high-dose GKT136901-treated db/m (90 mg/kg of body weight per day), (iv) untreated db/db; (v) low dose GKT136901-treated db/db; and (vi) high-dose GKT136901-treated db/db. GKT136901, in chow, was administered for 16 weeks. db/db mice developed diabetes and nephropathy as evidenced by hyperglycaemia, albuminuria and renal injury (mesangial expansion, tubular dystrophy and glomerulosclerosis). GKT136901 treatment had no effect on plasma glucose or BP (blood pressure) in any of the groups. Plasma and urine TBARSs (thiobarbituric acid-reacting substances) levels, markers of systemic and renal oxidative stress, respectively, were increased in diabetic mice. Renal mRNA expression of Nox4, but not of Nox2, increased, Nox1 was barely detectable in db/db. Expression of the antioxidant enzyme SOD-1 (superoxide dismutase 1) decreased in db/db mice. Renal content of fibronectin, pro-collagen, TGFβ (transforming growth factor β) and VCAM-1 (vascular cell adhesion molecule 1) and phosphorylation of ERK1/2 (extracellular-signal-regulated kinase 1/2) were augmented in db/db kidneys, with no change in p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase). Treatment reduced albuminuria, TBARS and renal ERK1/2 phosphorylation and preserved renal structure in diabetic mice. Our findings suggest a renoprotective effect of the Nox1/4 inhibitor, possibly through reduced oxidative damage and decreased ERK1/2 activation. These phenomena occur independently of improved glucose control, suggesting GKT136901-sensitive targets are involved in complications of diabetes rather than in the disease process.

Beneficial effects of an alternating high- fat dietary regimen on systemic insulin resistance, hepatic and renal inflammation and renal function

Background

An Alternating high- cholesterol dietary regimen has proven to be beneficial when compared to daily high- cholesterol feeding. In the current study we explored whether the same strategy is applicable to a high- fat dietary regimen.

Objective

To investigate whether an alternating high- fat dietary regimen can effectively diminish insulin resistance, hepatic and renal inflammation and renal dysfunction as compared to a continuous high- fat diet.

Design

Four groups of male ApoE*3Leiden mice (n = 15) were exposed to different diet regimens for 20 weeks as follows: Group 1: low- fat diet (10 kcal% fat); Group 2: intermediate- fat diet (25 kcal% fat); Group 3: high- fat diet (45 kcal% fat) and Group 4: alternating- fat diet (10 kcal% fat for 4 days and 45 kcal% fat for 3 days in a week).

Results

Compared to high fat diet feeding, the alternating and intermediate- fat diet groups had reduced body weight gain and did not develop insulin resistance or albuminuria. In addition, in the alternating and intermediate- fat diet groups, parameters of tissue inflammation were markedly reduced compared to high fat diet fed mice.

Conclusion

Both alternating and intermediate- fat feeding were beneficial in terms of reducing body weight gain, insulin resistance, hepatic and renal inflammation and renal dysfunction. Thus beneficial effects of alternating feeding regimens on cardiometabolic risk factors are not only applicable for cholesterol containing diets but can be extended to diets high in fat content.

Clinical implications of pathologic diagnosis and classification for diabetic nephropathy

AIM

The usefulness of renal pathologic diagnosis in type II DM (diabetes mellitus) remains debate.

METHODS

We grouped the pathologic diagnoses as pure DN (diabetic nephropathy), NDRD (non-diabetic renal disease), and NDRD mixed with DN (Mixed). We classified pure DN as the criteria suggested by Tervaert. We compared the accuracy of clinical parameters to predict DN and usefulness of pathology to predict renal prognosis.

RESULTS

Among 126 enrolled patients, there were 50 pure DN, 65 NDRN, and 11 Mixed. The sensitivity and specificity for predicting DN with the presence of retinopathy were 77.8-73.6% and, with a cut-off value of 7.5 years of diabetic duration, the sensitivity and specificity were 64.5-67.2%. ESRD (end stage renal disease) occurred in 44.0% of DN, 18.2% of Mixed, and 12.3% of NDRD (p<0.001). Among pure DN, Class IV showed the lowest estimated glomerular filtration rate (eGFR). We estimated the 5-year renal survival rate as 100.0% in Classes I and IIa, 75.0% in Class IIb, 66.7% in Class III, and 38.1% in Class IV (p=0.002).

CONCLUSIONS

Nephropathy of type II DM was diverse and could not be completely predicted by clinical parameters. The renal pathologic diagnosis was a good predictor for renal prognosis in type II DM.

Safety and complications of percutaneous kidney biopsies in 715 children and 8573 adults in Norway 1988-2010

BACKGROUND AND OBJECTIVES

Skepticism about performing renal biopsies is often because of uncertainty regarding risk of complications. The aim of this study was to evaluate safety and relevant complications of renal biopsies in pediatric and adult patients in a large national registry study.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Kidney biopsies reported in the Norwegian Kidney Biopsy Registry from 1988 to 2010 were included. Risk factors for major complications (blood transfusion and/or surgical or catheter intervention) were analyzed using logistic regression statistics.

RESULTS

Of the 9288 biopsies included, 715 were from children, and 8573 were from adults (≥18 years). Median age was 49 years (range=2 weeks to 94 years). Gross hematuria appeared after biopsy in 1.9% of the patients; 0.9% of patients needed blood transfusion, and 0.2% of patients needed surgical intervention/catheterization. The frequencies were 1.9%, 0.9%, and 0.2% in adults and 1.7%, 0.1% and 0.1% in children, respectively; 97.9% of the biopsies were without complications. In unadjusted analyses, risk factors for major complications were age>60 years, estimated GFR<60 ml/min per 1.73 m(2), systolic hypertension, acute renal failure, and smaller clinical center size (<30 biopsies/yr). Adjusted analyses (adjusted for age and/or estimated GFR) showed higher odds ratios (OR) only for smaller clinical center (OR=1.60 [1.02-2.50]) and low estimated GFR (estimated GFR=30-59 ml/min per 1.73 m(2) [OR=4.90 (1.60-14.00)] and estimated GFR<30 ml/min per 1.73 m(2) [OR 15.50 (5.60-43.00)]).

CONCLUSIONS

Percutaneous renal biopsy is a low-risk procedure in all ages. Reduced estimated GFR and smaller center size are associated with an increased risk of major complications.

A position paper on standardizing the nonneoplastic kidney biopsy report

The biopsy report for nonneoplastic kidney diseases represents a complex integration of clinical data with light, immunofluorescence, and electron microscopic findings. Practice guidelines for the handling and processing of the renal biopsy have previously been created. However, specific guidelines for essential pathologic parameters that should be included in these pathology reports do not exist. The Renal Pathology Society has coordinated an effort through the formation of an ad hoc committee to enumerate the essential elements and pathologic parameters that should be reported for every biopsy specimen. This endeavor aims to establish a minimum reporting standard and to improve communication between pathologists and other physicians. This document represents the collective effort and consensus opinions of this ad hoc committee of the Renal Pathology Society.

Association between urinary IgG and relative risk for factors affecting proteinuria in type 2 diabetic patients

Abnormal glomerular permeability is the primary step towards the glomerulosclerosis. The progression rate of glomerulosclerosis is proportionate to abundance and severity of lesions created at incipient stage, which is reflected as proteinuria even though eGFR remains in the normal range. Therefore, there is a current need to find out the association between relative risks for the factors leading to proteinuria. The relations could be more informative, if it is with respect to the macromolecules like "IgG" excretion in urine. Type 2 diabetic patients were selected for this study with eGFR > 75 ml/min/1.73 m(2) and grouped into four quartiles based on UIgGCR. The markers of key factors affecting progression of proteinuria were estimated through biochemical tests. The impact of these markers on proteinuria was accessed by applying multinomial logistic regression. The adjusted odds ratio for the UGAGCR was 1.186 (95 % CI: 1.061-1.327) P < 0.003 in highest quartiles of UIgGCR, followed by odds ratio for markers of collagen catabolism 1.051 (95 % CI: 1.025-1.079) P < 0.001, and USACR 1.044 (95 % CI: 1.013-1.077) P < 0.006 respectively. The marker of glycation, i.e., glycated hemoglobin showed the highest odds ratio 5.449 (95 % CI: 1.132-26.236) P < 0.035. In addition, odds for the systolic blood pressure was observed 1.387 (95 % CI: 1.124-1.712) P < 0.002. The higher odds inform and could help to discriminate the diabetic patients with fast progressive diabetic nephropathy. The study describes critical relationship between the urinary excretion of IgG and factors leading to proteinuria in type 2 diabetic patients.

The emerging concept of chronic kidney disease without clinical proteinuria in diabetic patients

The natural history of diabetic nephropathy was defined in the 1980s on the basis of longitudinal studies undertaken in patients with type 1 and type 2 diabetes. However, an increasing number of studies have indicated that certain diabetic patients do not present with the same evolution as was then defined: for example, some often have significant initial deterioration of glomerular filtration rate whereas, in others, microalbuminuria is reduced spontaneously. Chronic kidney disease (CKD) may be accompanied, rather than preceded, by macroalbuminuria, or it may develop in patients with microalbuminuria or even in those with albuminuria levels that revert to normal. CKD can also develop in patients whose albuminuria levels remain normal. Progression to macroalbuminuria is, in fact, less frequent than regression to normoalbuminuria or no change in microalbuminuria status in diabetic patients with microalbuminuria, especially in type 1 diabetes. Some experience progressive deterioration of renal function due to diabetes without developing significant proteinuria: this is seen fairly frequently and can affect 50% of patients with renal insufficiency. Such cases are more often older patients treated with renin-angiotensin system blockers who usually have a history of cardiovascular disease. Evolution to end-stage renal disease is slower in this subgroup of patients, although histological analyses may show surprisingly advanced glomerular lesions. The main parameters of surveillance remain regular monitoring of glycaemia, and control of blood pressure and the evolution of initial albuminuria levels. Nevertheless, why some patients exhibit conventional diabetic nephropathy while others have slower declines in renal function associated with normal albuminuria levels or microalbuminuria is unclear. It is hoped that the new pathological classification of diabetic nephropathy will help in our understanding of these discrepancies.

Mass spectrometry for diabetic nephropathy monitoring: new effective tools for physicians

The main aim of diabetic nephropathy monitoring is to identify molecular markers, that is, to find changes occurring at metabolome and proteome levels indicative of the disease's development. The mass spectrometry methods available today have been successfully applied to this field. This paper provides a short description of the basic aspects of the mass spectrometric methods used for diabetic nephropathy monitoring, reporting and discussing the results obtained using different approaches.

Histological predictors for renal prognosis in diabetic nephropathy in diabetes mellitus type 2 patients with overt proteinuria

AIM

Although several clinical risk factors for end-stage renal disease in diabetic nephropathy are known, the pathological findings that may help predict renal prognosis have not yet been defined.

METHODS

We enrolled 69 diabetes mellitus type 2 patients with overt proteinuria and biopsy-confirmed diabetic nephropathy with mesangial expansion, and retrospectively examined the association of histological and clinical findings with renal outcome. The median follow-up duration was 52 months. Histological scoring was made according to that of Tervaert et al. Patients were divided into four groups according to glomerular classification (class 2a, mild mesangial expansion, n=11; class 2b, severe mesangial expansion without nodular sclerosis, n=15; class 3, nodular sclerosis, n=36; class 4, global glomerulosclerosis observed in more than 50% of glomeruli, n=7). Interstitial and vascular lesions were scored for each patient. A renal event was defined as a condition requiring the initiation of chronic dialysis or doubling of the serum creatinine level.

RESULTS

Cox proportional hazard analysis showed that the glomerular classes were not significant variables, while interstitial fibrosis, tubular atrophy and interstitial inflammation were independent variables associated with renal end-point (HR: 3.36 (95% confidence interval: 1.21-9.32), 4.74 (1.26-17.91)). There were no significant differences in the renal survival rates between the glomerular classes 2a and 2b combined group and the glomerular class 3 group (P=0.17, log-rank test).

CONCLUSION

Interstitial lesions but not glomerular lesions were a significant predictor for renal prognosis in diabetic nephropathy in type 2 diabetes patients with overt proteinuria.

Comparative safety and efficiency of five percutaneous kidney biopsy approaches of native kidneys: a multicenter study

BACKGROUND

Renal biopsy (RB) is necessary for the diagnosis, prognosis, and therapy guidance of native kidney diseases. Few studies have compared outcomes of RB procedures. We retrospectively compared the safety and efficiency of five biopsy procedures.

METHODS

The number of glomeruli on light microscopy (LM) and on immunofluorescence (IF) and serious adverse events following RB performed in five nephrology units (C1-C5) were collected. C1 performed ultrasound (US) assessment before RB and used a 14-gauge core-cutting needle biopsy gun, C2 US guidance and a 14-gauge needle, C3 tomodensitometry guidance and a 14-gauge needle, C4 US guidance and a 16-gauge needle, and C5 tomodensitometry guidance and a 16-gauge needle.

RESULTS

RB was performed in 943 adults between January 2006 and July 2010. Serious adverse events occurred in 1.5% of biopsies. The complication rate was not different between nephrology units. The mean number of glomeruli on biopsy was 14.2 ± 8.6 with LM and 4.4 ± 3.3 on IF. It was different according to the nephrology unit for LM (p = 0.01) and for IF (p < 0.001). The number of failed biopsies was influenced by the nephrology unit and radiological guidance technique, favoring real-time US guidance. Failed biopsies using US or tomodensitometry assessment before RB was certainly due to kidney imprecise localization since it was often non-renal tissue sampling. At least 10 glomeruli were found in 69% of biopsies on LM. This rate varied according to the nephrology unit (p = 0.004) and was higher when 14-gauge needles were used in comparison with 16-gauge needles.

CONCLUSION

RB is safe regardless of the technical procedure, but radiological guidance and needle size influence the efficiency of biopsies.