Identification of non-diabetic glomerular disease in renal biopsies from diabetics--a dilemma

Diabetes and kidney disease: emphasis on treatment with SGLT-2 inhibitors and GLP-1 receptor agonists

Kidney disease is a frequent microvascular complication of both type 1 and type 2 diabetes. Historic trials have demonstrated that a tight glycaemic control is the most powerful approach to decrease the chances of developing diabetic nephropathy. However, having an HbA1c < 7% does not completely suppress the risk of kidney disease. The observed residual risk is likely ascribable to two phenomena: 1- the presence of risk factors and alterations additive to and independent of glycaemia, and 2- the activation of long-lasting imbalances by periods of exposure to uncontrolled glycemia, a phenomenon referred to as metabolic memory or legacy effect. Long-lasting oxidative stress, epigenetic alterations, cellular senescence, and the resulting chronic low-grade inflammation are all candidate mechanisms explaining the development of nephropathy despite proper control of risk factors. Recently, two classes of drugs, i.e. glucagon-like peptide (GLP) 1 receptor agonists (RA) and sodium-glucose transporter 2 inhibitors (SGLT-i) have changed this scenario. Indeed, cardiovascular outcome and other trials have clearly shown a renoprotective effect for these drugs, well-beyond their glucose-lowering properties. In this review, we summarize: 1- selected key trials and mechanisms underlying the development of diabetic kidney disease and 2- the results relative to renal endpoints in clinical trials of GLP-1 RA and SGLT-2i. Then, we briefly discuss some of the hypotheses posited to explain the marked renoprotective properties of these two classes, evidencing the still existing gaps in knowledge and proposing future directions to further implement the use of these powerful, disease-modifying drugs.

Insights into the Role of Renal Biopsy in Patients with T2DM: A Literature Review of Global Renal Biopsy Results

INTRODUCTION

Renal biopsy performed in patients with type 2 diabetes mellitus (T2DM) for atypical or suspected diabetic kidney disease (DKD) reveals one of three possibilities: diabetic nephropathy (DN, pathological diagnosis of DKD), nondiabetic kidney disease (NDKD) and DN plus NDKD (mixed form). NDKD (including the mixed form) is increasingly being recognized worldwide. With the emerging concept of DKD and the complexity of routine application of renal biopsy, the identification of "clinical indicators" to differentiate DKD from NDKD has been an area of active research.

METHODS

The PubMed database was searched for relevant articles mainly according to the keyword search method. We reviewed prevalence of the three types of DKD and different pathological lesions of NDKD. We also reviewed the clinical indicators used to identify DKD and NDKD.

RESULTS

The literature search identified 40 studies (5304 data) worldwide between 1977 and 2019 that looked at global renal biopsy and pathological NDKD lesions. The overall prevalence rate of DN, NDKD and DN plus NDKD is reported to be 41.3, 40.6 and 18.1%, respectively. In Asia, Africa (specifically Morocco and Tunisia) and Europe, the most common isolated NDKD pathological type is membranous nephropathy, representing 24.1, 15.1 and 22.6% of cases, respectively. In contrast, focal segmental glomerulosclerosis is reported to be the primary pathological type in North America (specifically the USA) and Oceania (specifically New Zealand), representing 22% and 63.9% of cases, respectively. Tubulointerstitial disease accounts for a high rate in the mixed group (21.7%), with acute interstitial nephritis being the most prevalent (9.3%), followed by acute tubular necrosis (9.0%). Regarding clinical indicators to differentiate DKD from NDKD, a total of 14 indicators were identified included in 42 studies. Among these, the most commonly studied indicators included diabetic retinopathy, duration of diabetes, proteinuria and hematuria. Regrettably, indicators with high sensitivity and specificity have not yet been identified.

CONCLUSION

To date, renal biopsy is still the gold standard to diagnose diabetes complicated with renal disease, especially when T2DM patients present atypical DKD symptoms (e.g. absence of diabetic retinopathy, shorter duration of diabetes, microscopic hematuria, sub-nephrotic range proteinuria, lower glycated hemoglobin, lower fasting blood glucose). We conclude that renal biopsy as early as possible is of great significance to enable personalized treatment to T2DM patients.

Non-diabetic Renal Diseases in Patients with Diabetes Mellitus Clinicopathological Correlation

BACKGROUND AND AIMS

Non-diabetic renal diseases (NDRDs) form an important part of disease manifestations in patients with diabetes.

METHODS

This hospital-based prospective study was conducted to analyze incidence and spectrum of NDRDs in patients with diabetes with or without diabetic nephropathy (DN), effect of early specific interventions on outcome, and renal-retinal relationship in type 1 and type 2 diabetes mellitus with nephropathy. 44 Patients with T2DM with the clinical suspicion of NDRD were subjected to renal biopsy Renal biopsies were performed by using an automated biopsy gun. Tissue was processed for Light microscopy-LM and Immunofluorescence-IF. Electron Microscopy was done as and when required by reprocessing the tissue embedded in paraffin for LM. Biopsies were reported by one experienced renal pathologist.

RESULTS

Renal histopathology revealed that of 44 enrolled patients with clinically suspected NDRD, 61.4% had isolated NDRD, 13.6% had NDRD superimposed on DN, and 25% had isolated DN. The most common NDRDs were minimal change disease (19.2%) and DN + chronic pyelonephritis (33.3%) in patients with isolated NDRD, and NDRD superimposed on DN, respectively. In the DN group, no patient had proliferative diabetic retinopathy (PDR) or hypertensive retinopathy, 45.5% had nonproliferative diabetic retinopathy (NPDR) and 54.5% had no microangiopathy in retina. In the NDRD group, 9.1% each had PDR and hypertensive retinopathy, 36.4% had NPDR and 45.4% had no microangiopathy in retina. No patient in the DN group and 72.7% in the NDRD group received specific treatment. In hospital, dialysis support was provided to 27.3% and 21.2% of patients in the DN and NDRD groups, respectively. In the DN group, 72.7% of patients improved with conservative therapy, 18.2% were dependent on dialysis when discharged. One patient died during treatment. In the NDRD group, 78.8% showed recovery in the renal function and clinical improvement, 15.1% were dialysis dependent when discharged. Two patients died during treatment.

CONCLUSION

Accurate diagnosis of underlying NDRD by kidney biopsy facilitates initiation of specific therapy, which may lead to clinical improvement in significant number of patients.

Gut Microbiota-Dependent Trimethylamine-N-oxide and Serum Biomarkers in Patients with T2DM and Advanced CKD

Trimethylamine-N-oxide (TMAO) is a product of dietary, gut microbiome, and tissues metabolism. Elevated blood TMAO levels are associated with heart attack, stroke and chronic kidney disease (CKD). The purpose of our study was to investigate the gut microbiota associated with trimethylamine (TMA) production, the precursor of TMAO, and the serum levels of TMAO and inflammatory biomarkers associated with type 2 diabetes mellitus (T2DM) and CKD. Twenty adults with T2DM and advanced CKD and 20 healthy adults participated in the study. Analyses included anthropometric and metabolic parameters, characterization of TMA producing gut microbiota, and concentrations of TMAO, lipopolysaccharides (LPS) endotoxin, zonulin (Zo) gut permeability marker, and serum inflammatory and endothelial dysfunction biomarkers. Diversity of the gut microbiota was identified by amplification of V3-V4 regions of the 16S ribosomal RNA genes and DNA sequencing. TMAO was quantified by Mass Spectrometry and serum biomarkers by ELISA. The significance of measurements justified by statistical analysis. The gut microbiome in T2DM-CKD patients exhibited a higher incidence of TMA-producing bacteria than control, p < 0.05. The serum levels of TMAO in T2DM-CKD patients were significantly higher than controls, p < 0.05. TMAO showed a positive correlation with Zo and LPS, inflammatory and endothelial dysfunction biomarkers. A positive correlation was observed between Zo and LPS in T2DM-CKD subjects. An increased abundance of TMA-producing bacteria in the gut microbiota of T2DM-CKD patients together with excessive TMAO and increased gut permeability might impact their risk for cardiovascular disease through elevation of chronic inflammation and endothelial dysfunction.

Clinical predictors differentiating non-diabetic renal diseases from diabetic nephropathy in a large population of type 2 diabetes patients

AIMS

Non-diabetic renal diseases (NDRDs) are associated with better renal outcomes than diabetic nephropathy (DN). This study was conducted to determine the common clinical markers predicting NDRDs in type 2 diabetes patients.

METHODS

Patients with type 2 diabetes mellitus who underwent a renal biopsy were screened. Eligible patients were categorized into two groups: DN group and NDRD group. Patient's clinical characteristics and laboratory data were collected. Logistic regression analysis was performed to identify risk factors for NDRD development, and the diagnostic performance of these variables was evaluated.

RESULTS

The study included 248 patients, 96 (38.71%) in the DN group and 152 (61.29%) in the NDRD group. Patients in the NDRD group had a shorter duration of DM and higher hemoglobin, estimated glomerular filtration rate, and urine osmotic pressure values as well as a higher incidence of glomerular hematuria than patients in the DN group. In the NDRD patients, the most common pathological type was membranous nephropathy (55, 36.18%). Absence of retinopathy (OR, 44.696, 95% CI, 15.91-125.566), glomerular hematuria (OR, 9.587, 95% CI, 2.027-45.333), and DM history ⩽5years (OR, 4.636, 95% CI, 1.721-12.486) were significant and independent risk factors for the development of NDRD (P<0.01). Absence of retinopathy achieved the overall highest diagnostic efficiency with a sensitivity of 92.11% and specificity of 82.29%. Glomerular hematuria had the highest specificity (93.75%).

CONCLUSION

Shorter duration of diabetes (⩽5years), absence of retinopathy, and presence of glomerular hematuria were independent indicators associated with NDRDs, indicating the need for renal biopsy.

Spectrum of renal disease in diabetes

The spectrum of renal disease in patients with diabetes encompasses both diabetic kidney disease (including albuminuric and non-albuminuric phenotypes) and non-diabetic kidney disease. Diabetic kidney disease can manifest as varying degrees of renal insufficiency and albuminuria, with heterogeneity in histology reported on renal biopsy. For patients with diabetes and proteinuria, the finding of non-diabetic kidney disease alone or superimposed on the changes of diabetic nephropathy is increasingly reported. It is important to identify non-diabetic kidney disease as some forms are treatable, sometimes leading to remission. Clinical indications for a heightened suspicion of non-diabetic kidney disease and hence consideration for renal biopsy in patients with diabetes and nephropathy include absence of diabetic retinopathy, short duration of diabetes, atypical chronology, presence of haematuria or other systemic disease, and the nephrotic syndrome.

Concurrent diabetic nephropathy and C1q nephropathy in a young male patient: The first report in literature

BACKGROUND

C1q nephropathy (C1qN) is an uncommon glomerulopathy with a significant deposition of C1q in mesangium without clinical evidence of lupus.According to the best of our knowledge, there is not any report on coincidence of diabetes mellitus and C1qN.

CASE PRESENTATION

In this report, we presented a 28 years-old-patient with type 1 diabetes and nephrotic range proteinuria, glomerular hematuria and C1q glomerulopathy in renal biopsy.

CONCLUSIONS

According to the best of our knowledge, there is no previous report about the association between type 1 DM and C1qN. Prevalence of autoimmune disease is higher in type 1 DM and this may explain the relation between DM and C1qN in our patient.

Nondiabetic kidney disease in type 2 diabetic patients: A single center experience

Nondiabetic renal disease (NDRD) is seen as a cause of proteinuria and renal failure in type 2 diabetes mellitus (DM). The clinical differences between NDRD and diabetic glomerulosclerosis (DGS) are not clear. This study was done to find the spectrum of NDRD in type 2 DM patients and differences in clinical profile between NDRD and DGS patients. Data of patients with type 2 DM who underwent renal biopsy in this institute from 1990 to 2008 were analyzed retrospectively. Patients were categorized as isolated NDRD, NDRD with DGS, and isolated DGS. A total of 75 patients were included. Mean age was 45 ± 10.2 years, male to female ratio was 3.1 : 1, median duration of DM was 12 months (range, 1 year-15 years), proteinuria was 4.2 ± 3.4 g/day, and serum creatinine was 4.3 ± 3.9 mg/dl. Hypertension was observed in 63 (84%) cases and microscopic hematuria in 24 (32%) cases. Nephrotic syndrome (38.7%) was the commonest clinical presentation. Forty-eight (64%) cases had NDRD and 27 (36%) had DGS. The commonest NDRD was minimal change disease (12.5%). Three (6.3%) patients had lupus nephritis. Tubulointerstitial nephritis has been observed in 10.4% patients. No significant differences between NDRD and DGS patients were found except hypertension which was significantly high in the DGS group. Acute kidney injury and nephritic syndrome were not observed in the DGS group. In conclusion, the incidence of biopsy-proven NDRD in type 2 DM in this study was high. Kidney biopsy aided in the detection of NDRD in clinically suspected patients.

Clinical predictors of non-diabetic renal disease and role of renal biopsy in diabetic patients with renal involvement: a single centre review

BACKGROUND

Type 2 diabetes mellitus (T2DM) is reportedly the leading cause of end-stage renal disease (ESRD) worldwide. However, non-diabetic renal diseases (NDRD) are not uncommon among T2DM patients with renal involvement. Our study aimed to examine the prevalence of NDRD in T2DM and clinical markers for diabetic nephropathy (DN) and NDRD and to determine the role of renal biopsy in T2DM patients and its impact on clinical practice.

METHODS

We conducted a retrospective analysis of T2DM patients in whom renal biopsies were performed from January 2004 to March 2008 (n = 110).

RESULTS

Biopsy results were divided into three groups: group I/pure DN (62.7%), group II/isolated NDRD (18.2%), and group III/mixed lesions (19.1%). The causes of NDRD in decreasing order of frequency were acute interstitial nephritis, glomerulonephritides, hypertensive renal disease, and acute tubular necrosis. Significant clinical markers for DN are presence of diabetic retinopathy and longer duration of diabetes. For NDRD, useful clinical markers include the presence of acute renal failure and microscopic hematuria. In the DN subgroup, Indians had significantly shorter duration of diabetes on biopsy compared with Malays and Chinese.

CONCLUSIONS

NDRD is prevalent in T2DM patients, and given its potentially treatable nature, renal biopsy should be considered in T2DM patients with nephropathy, especially in those with atypical features.

Clinical indicators which necessitate renal biopsy in type 2 diabetes mellitus patients with renal disease

BACKGROUND

The diagnosis of diabetic nephropathy (DN) is always based on clinical grounds. However, the necessity for renal biopsy of type 2 diabetes mellitus (DM) patients with renal disease to establish the diagnosis remains unclear.

METHODS

We retrospectively studied 50 type 2 diabetic patients performed with renal biopsy between December 2002 and December 2006. Based on renal pathology, patients were divided into group I: DN alone, group II: non-diabetic renal disease (NDRD) superimposed on DN and group III: isolated NDRD. Factors like DM > 10 years, retinopathy, previous minimal proteinuria without sudden heavy proteinuria, no glomerular haematuria and non-small-sized kidney were collected to evaluate their sensitivity, specificity, positive predictive value and negative predictive value for prediction of DN or NDRD in type 2 diabetic patients.

RESULTS

Group I consisted of 24 patients, group II 15 patients and group III 11 patients. Acute interstitial nephritis was the most prevalent second renal disease in our study. Sensitivity and specificity for group I was poor in five features except high sensitivity in no sudden heavy proteinuria (83.3%) and non-small-sized kidney (95.8%). Comparable retinopathy, sudden heavy proteinuria and haematuria (p > 0.05) was noted between the three groups. Significant biopsy indicators included higher serum albumin, lower urinary daily protein excretion and lower 24-h creatinine clearance (C(Cr)) rate (p < 0.05).

CONCLUSION

Our study demonstrated that DM > 10 years and retinopathy did not exclude NDRD in type 2 DM patients, and need for renal biopsy. Higher serum albumin, lower urinary daily protein and 24-h C(Cr) were indicative for biopsy to exclude NDRD.

Non diabetic renal disease in type 2 diabetes mellitus

AIM

The aim of this analysis of renal biopsies in people with type 2 diabetes was to know the prevalence and nature of non-diabetic renal disease (NDRD) and to note its correlation with the duration of diabetes, extent of proteinuria and presence or absence of retinopathy.

METHODS

From January 2000 to December 2004, 160 people with type 2 diabetes with clinically suspected NDRD underwent renal biopsy reported by a single pathologist. The case records of these patients were retrospectively analysed. Based on the biopsy findings, patients were grouped as Group I, isolated NDRD; Group II, NDRD with underlying diabetic glomerulosclerosis; and Group III, isolated diabetic glomerulosclerosis. The relation of histology with clinical profile in each group was noted and statistically analysed using strata 6 software.

RESULTS

Of the 160 patients studied, 118 were males and 42 were females (2.8:1). The average age was 51.35 years (30-79). Indications for renal biopsy included: nephrotic syndrome in 55 (34.37%), acute renal failure (ARF) in 49 (30.62%), rapidly progressive renal failure (RPRF) in 24 (15%), absent retinopathy in 19 (11.87%), haematuria in 10 (6.25%) and acute on chronic renal failure (CRF) in three (1.87%) patients. Group I included 68 patients (42.50%), Group II included 48 patients (30%) and Group III included 44 patients (27.50%). The mean duration of diabetes was 5.37, 10.12 and 6.86 years in Groups I, II and III respectively. The duration of diabetes was significantly less in Group I compared with Group II and III combined (5.37 vs 8.53; P < 0.001). Diabetic retinopathy was absent in 61 (38.13%) patients, of whom 41 (67.21%) had isolated NDRD. The most common NDRD were acute interstitial nephritis (18.1%), post infectious glomerulonephritis (17.24%), membranous nephropathy (11.20%) and focal segmental glomerulosclerosis (7.75%).

CONCLUSIONS

Prevalence of NDRD (either isolated or superimposed on underlying diabetic glomerulosclerosis) is very high in appropriate clinical settings. The shorter duration of diabetes and the absence of retinopathy, especially when associated with nephrotic proteinuria, strongly predict NDRD.

Proteinuria in Diabetic Patients – Is It Always Diabetic Nephropathy?

BACKGROUND

Diabetic nephropathy (dNP) is a consequence of type 1 and type 2 diabetes, typically occurring between 5 and 15 years after diabetes has been diagnosed. The coincidence of dNP and diabetic retinopathy (dRP) is well known. In this study we correlated the histological findings of the kidney biopsy with the clinically expected diagnosis of dNP.

PATIENTS AND METHODS

Over a 4-year period with a total of 326 kidney biopsies, 85 biopsies were performed on patients with diabetes. In all of these patients we had information about duration of diabetes and ophthalmological status. Additionally, data about proteinuria, urine sediment and autoantibodies were available. The nephrologist had to give the suspected diagnosis before the biopsy was performed, using the clinical data available.

RESULTS

In 57 patients (67%) dNP was predicted clinically before biopsy. In 28 patients we expected a different kind of kidney disease. Only 43 patients had dNP histologically. In 16 out of 19 patients with dRP we also found dNP. 26 patients with dNP did not have dRP. So dRP was very specific but not sensitive to predict dNP. On the other hand, all patients without dRP but acanthocytes in urine sediment had non-diabetic kidney disease (NDKD). In the case of patients with neither dRP nor acanthocytes, it was very difficult to distinguish between dNP and NDKD. Acanthocytes and antineutrophil cytoplasmatic antibodies with positive antibodies for proteinase 3 or myeloperoxidase were found only in NDKD, but ANAs were detected in a wide titer range in dNP and NDKD. The known duration of the diabetes ranged from 1 to 40 years. There were no additional parameters to differentiate this group.

CONCLUSIONS

Diabetic patients with dRP and proteinuria frequently have dNP. In patients without typical retinal findings dNP is less likely, thus a kidney biopsy is necessary to confirm the diagnosis. Additional knowledge about urine sediment and autoantibodies is helpful, but is not sufficient to differentiate NDKD from dNP in the majority of patients.

Diabetic nephropathy and retinopathy

Diabetic nephropathy and retinopathy are arguably the two most dreaded complications of diabetes. Together they contribute to serious morbidity and mortality. As they progress to end-stage renal disease and blindness, they impose enormous medical, economic,and social costs on both the patient and the health care system. Because nephropathy and retinopathy are frequently linked in patients,this article reviews their common and individual aspects of pathophysiology, clinical features, and management.

Initial characterization of a rat model of diabetic nephropathy

The lack of an appropriate animal model that spontaneously develops diabetic nephropathy has been a significant limitation in the search for genetic factors underlying this disease and the development of new therapeutic strategies to prevent progressive renal disease in diabetes. We introgressed the mitochondria and some passenger loci from the FHH/EurMcwi rat into the genetic background of diabetic GK rats, creating a new rat strain, T2DN (T2DN/Mcwi). Despite the high degree of genetic similarity between T2DN and GK rats (97% at 681 loci), diabetes ensues earlier and progresses more severely in T2DN rats. T2DN rats exhibit proteinuria by 6 months of age, accompanied by renal histologic abnormalities such as focal glomerulosclerosis, mesangial matrix expansion, and thickening of basement membranes. These characteristics progress over time, and nearly all T2DN rats exhibit diffuse global glomerulosclerosis with nodule formation and arteriolar hyalinosis by 18 months of age. The histologic changes in the kidney of T2DN rats closely mimic the changes seen in the kidney of patients with diabetes. These results indicate that the T2DN rat is a suitable model for investigating diabetic nephropathy. Here we report the initial genetic and physiological characterization of this new rat model of diabetic nephropathy.

Causes of albuminuria in patients with type 2 diabetes without diabetic retinopathy

BACKGROUND

The causes of albuminuria in patients with type 2 diabetes are heterogeneous and are scantily investigated, particularly if the patient has a lack of diabetic retinopathy. Therefore, we evaluated the structural background of albuminuria in a large consecutive group of Caucasian patients with type 2 diabetes without retinopathy.

METHODS

Three hundred forty-seven consecutive patients with type 2 diabetes with persistent albuminuria (>300 mg/24 h) were recorded. Fundus photo (80%) and ophthalmoscopy were performed. Ninety-three (27%) had no retinopathy, and a kidney biopsy was performed in 52 (56%) of these patients. An insufficient tissue sample was obtained in one patient. The biopsies were evaluated by three masked nephropathologists.

RESULTS

The biopsies revealed diabetic glomerulopathy in 69% of the patients (28 males and 7 females), while the remaining 31% (95% CI, 18 to 44) had either nondiabetic glomerulopathies such as glomerulonephritis (N = 7, 6 males and 1 female, 13%) or normal glomerular structure (N = 9, 7 males and 2 females, 18%). No significant differences in sex, age (56 +/- 8 vs. 53 +/- 10 years, mean SD), body mass index (30 +/- 4 vs. 31 +/- 8 kg/m2), known duration of diabetes (6 +/- 6 vs. 4 +/- 3 years), GFR (95 +/- 29 vs. 89 +/- 31 mL/min/1.73 m2), albuminuria (1304 +/- 169 to 4731 vs. 1050 +/- 181 to 5176 mg/24 hours), blood pressure (150/87 +/- 16/9 vs. 145/89 +/- 16/9 mm Hg), prevalence of hypertension (89 vs. 100%), hemoglobin A1c (8.2 +/- 1.6% vs. 9.0 +/- 2.5%), and serum total cholesterol (7.1 +/- 2.4 vs. 6.3 +/- 1.6 mmol/L) were found between patients with and without diabetic glomerulopathy.

CONCLUSIONS

Albuminuric patients with type 2 diabetes without diabetic retinopathy have a prevalence of biopsies with normal glomerular structure or nondiabetic kidney diseases of approximately 30%. A separation between diabetic and nondiabetic glomerular lesions was not possible based on demographic, clinical, or laboratory data. Consequently, such patients may require further evaluation, including a kidney biopsy.

Association between diabetic retinopathy and genetic variations in α2β1 integrin, a platelet receptor for collagen

Platelets might be involved in the pathogenesis of diabetic microangiopathy. Wide interindividual variations in the density of a platelet collagen receptor (2β1 integrin or glycoprotein Ia/IIa) are reportedly associated with polymorphism(s) in the gene encoding the  subunit of the receptor, including a Bgl II polymorphism in intron 7. The aim of the present study was to determine the relationship between the Bgl II polymorphism and the susceptibility to diabetic microangiopathy. A case-control study comparing 227 patients with type II diabetes mellitus (119 with versus 108 without diabetic retinopathy) as well as 169 nondiabetic subjects demonstrated that genotypes with Bgl II (+) allele had a significant increase in the risk for retinopathy. The odds ratio for Bgl II (+/+) to Bgl II (−/−) was 3.41 (95% CI, 1.49-7.78, P = .0036) when analysis was confined to those with a disease duration of diabetes of 10 years or more. The present study suggests that the presence of a Bg II (+) allele is a genetic risk factor for diabetic retinopathy.