Morphologic features of declining renal function in type 1 diabetes

Albuminuria and Rapid Kidney Function Decline as Selection Criteria for Kidney Clinical Trials in Type 1 Diabetes Mellitus

Key Points

Severely increased urinary albumin excretion rate is an effective criterion to select persons with type 1 diabetes at high risk of GFR decline for enrollment in clinical trials. A history of rapid GFR decline is less effective but can be used to extend clinical trials to person with normoalbuminuric diabetic kidney disease. These findings have immediate implications for the design of clinical trials of novel renoprotective interventions in type 1 diabetes.

Background

The optimal criteria to select individuals with type 1 diabetes mellitus and albuminuric or normoalbuminuric diabetic kidney disease, who are at risk of rapid kidney function decline, for clinical trials are unclear.

Methods

This study analyzed data from the Preventing Early Renal Loss in Diabetes clinical trial, which investigated whether allopurinol slowed kidney function decline in persons with type 1 diabetes mellitus and early-to-moderate diabetic kidney disease. Rates of iohexol GFR (iGFR) and eGFR decline during the 3-year study were compared by linear mixed effect regression between participants enrolled based on a history of moderately or severely increased albuminuria (n =394) and those enrolled based on a recent history of rapid kidney function decline (≥3 ml/min per 1.73 m2 per year) in the absence of a history of albuminuria (n =124). The association between baseline albuminuria and iGFR/eGFR decline during the trial was also evaluated.

Results

Rates of eGFR decline during the trial were higher in participants with a history of albuminuria than in those with a history of rapid kidney function decline (−3.56 [95% confidence intervals (CIs), −3.17 to −3.95] versus −2.35 [95% CI, −1.86 to −2.84] ml/min per 1.73 m2 per year, P = 0.001). The results were similar for iGFR decline, although the difference was not significant (P = 0.07). Within the history of albuminuria group, the rate of eGFR decline was −5.30 (95% CI, −4.52 to −6.08) ml/min per 1.73 m2 per year in participants with severely increased albuminuria as compared with −2.97 (95% CI, 2.44 to −3.50) and −2.32 (95% CI, −1.61 to −3.03) ml/min per 1.73 m2 per year in those with moderately increased or normal/mildly increased albuminuria at baseline (P < 0.001).

Conclusions

Severely increased albuminuria at screening is a powerful criterion for selecting persons with type 1 diabetes mellitus at high risk of kidney function decline. A history of rapid eGFR decline without a history of albuminuria is less effective for this purpose, but it can still identify individuals with type 1 diabetes mellitus who will lose kidney function more rapidly than expected from physiological aging.

Clinical Trial registry name and registration number:

NCT02017171 .

The complex pathology of diabetic nephropathy in humans

This review summarizes the pathomorphological sequences of nephron loss in human diabetic nephropathy (DN). The relevant changes may be derived from two major derangements. First, a failure in the turnover of the glomerular basement membrane (GBM) based on an increased production of GBM components by podocytes and endothelial cells leading to the thickening of the GBM and accumulation of worn-out GBM in the mesangium. This failure may account for the direct pathway to glomerular compaction and sclerosis based on the continuous deposition of undegraded GBM material in the mesangium. Second, an increased leakiness together with an increased propensity of glomerular capillaries to proliferate leads to widespread plasma exudations. Detrimental are those that produce giant insudative spaces within Bowman's capsule, spreading around the entire glomerular circumference and along the glomerulo-tubular junction onto the tubule resulting in tubular obstruction and retroactively to glomerulosclerosis. Tubular atrophy and interstitial fibrosis develop secondarily by transfer of the glomerular damage onto the tubule. Interstitial fibrosis is locally initiated and apparently stimulated by degenerating tubular epithelia. This leads to a focal distribution of interstitial fibrosis and tubular atrophy accompanied by a varying interstitial mononuclear cell infiltration. Spreading of fibrotic areas between intact nephrons, much less to the glomerulus, has not been encountered.

Genetic and epigenetic background of diabetic kidney disease

Diabetic kidney disease (DKD) is a severe diabetic complication that affects up to half of the individuals with diabetes. Elevated blood glucose levels are a key underlying cause of DKD, but DKD is a complex multifactorial disease, which takes years to develop. Family studies have shown that inherited factors also contribute to the risk of the disease. During the last decade, genome-wide association studies (GWASs) have emerged as a powerful tool to identify genetic risk factors for DKD. In recent years, the GWASs have acquired larger number of participants, leading to increased statistical power to detect more genetic risk factors. In addition, whole-exome and whole-genome sequencing studies are emerging, aiming to identify rare genetic risk factors for DKD, as well as epigenome-wide association studies, investigating DNA methylation in relation to DKD. This article aims to review the identified genetic and epigenetic risk factors for DKD.

Early renal structural changes and potential biomarkers in diabetic nephropathy

Diabetic nephropathy is one of the most serious microvascular complications of diabetes mellitus, with increasing prevalence and mortality. Currently, renal function is assessed clinically using albumin excretion rate and glomerular filtration rate. But before the appearance of micro-albumin, the glomerular structure has been severely damaged. Glomerular filtration rate based on serum creatinine is a certain underestimate of renal status. Early diagnosis of diabetic nephropathy has an important role in improving kidney function and delaying disease progression with drugs. There is an urgent need for biomarkers that can characterize the structural changes associated with the kidney. In this review, we focus on the early glomerular and tubular structural alterations, with a detailed description of the glomerular injury markers SMAD1 and Podocalyxin, and the tubular injury markers NGAL, Netrin-1, and L-FABP in the context of diabetic nephropathy. We have summarized the currently studied protein markers and performed bioprocess analysis. Also, a brief review of proteomic and scRNA-seq method in the search of diabetic nephropathy.

Effects of Creatine Supplementation on Histopathological and Biochemical Parameters in the Kidney and Pancreas of Streptozotocin-Induced Diabetic Rats

Diabetes mellitus (DM) is a worldwide health concern, and projections state that cases will reach 578 million by 2030. Adjuvant therapies that can help the standard treatment and mitigate DM effects are necessary, especially those using nutritional supplements to improve glycemic control. Previous studies suggest creatine supplementation as a possible adjuvant therapy for DM, but they lack the evaluation of potential morphological parameters alterations and tissue injury caused by this compound. The present study aimed to elucidate clinical, histomorphometric, and histopathological consequences and the cellular oxidative alterations of creatine supplementation in streptozotocin (STZ)-induced type 1 DM rats. We could estimate whether the findings are due to DM or the supplementation from a factorial experimental design. Although creatine supplementation attenuated some biochemical parameters, the morphological analyses of pancreatic and renal tissues made clear that the supplementation did not improve the STZ-induced DM1 injuries. Moreover, creatine-supplemented non-diabetic animals were diagnosed with pancreatitis and showed renal tubular necrosis. Therefore, even in the absence of clinical symptoms and unaltered biochemical parameters, creatine supplementation as adjuvant therapy for DM should be carefully evaluated.

Critical roles of microRNA-196 in normal physiology and non-malignant diseases: Diagnostic and therapeutic implications

MicroRNAs (miRNAs) have emerged as a critical component of regulatory networks that modulate and fine-tune gene expression in a post-transcriptional manner. The microRNA-196 family is encoded by three loci in the human genome, namely hsa-mir-196a-1, hsa-mir-196a-2, and hsa-mir-196b. Increasing evidence supports the roles of different components of this miRNA family in regulating key cellular processes during differentiation and development, ranging from inflammation and differentiation of stem cells to limb development and remodeling and structure of adipose tissue. This review first discusses about the genomic context and regulation of this miRNA family and then take a bird's eye view on the updated list of its target genes and their biological processes to obtain insights about various functions played by members of the microRNA-196 family. We then describe evidence supporting the involvement of the human microRNA-196 family in regulating critical cellular processes both in physiological and non-malignant inflammatory conditions, highlighting recent seminal findings that carry implications for developing novel therapeutic or diagnostic strategies.

Increased urinary miR-196a level predicts the progression of renal injury in patients with diabetic nephropathy

BACKGROUND

Recent data suggest that miR-196a is predominantly expressed in the kidney and plays an inhibitory role in the progress of renal interstitial fibrosis (IF). However, the predictive value of miR-196a in diabetic nephropathy (DN) remains unknown. We validated the role of urinary miR-196a in the progression of renal injury in a cohort of patients with type 2 diabetes mellitus.

METHODS

Our study included 209 patients with biopsy-proven DN. The mean follow-up time was 54.03 ± 32.94 months. Histological lesions were assessed using the pathological classification established by the Renal Pathology Society. Percentages of IF and tubular atrophy were assessed using the Aperio ScanScope system. We measured the correlation of urinary miR-196a with clinical and pathological parameters using the Spearman's correlation test. The influence of urinary miR-196a on renal outcomes was assessed using Cox regression analysis.

RESULTS

Urinary miR-196a levels correlated positively with proteinuria (ρ = 0.385, P < 0.001), duration of diabetes mellitus (ρ = 0.255, P < 0.001) and systolic blood pressure (ρ = 0.267, P < 0.001). The baseline estimated glomerular filtration rate (eGFR) and hemoglobin level showed a negative correlation with urinary miR-196a (ρ = -0.247, P < 0.001 and ρ = -0.236, P = 0.001, respectively). Pathologically, urinary miR-196a levels correlated with glomerular sclerosis and IF in patients with DN. Urinary miR-196a was significantly associated with progression to end-stage renal disease [hazard ratio (HR) 2.03, P < 0.001] and a 40% reduction of baseline eGFR (HR 1.75, P = 0.001), independent of age, gender, body mass index, mean arterial pressure and hemoglobinA1c level. However, urinary miR-196a did not improve predictive power to proteinuria and eGFR in DN patients.

CONCLUSIONS

Increased urinary miR-196a was significantly associated with the progression of renal injury and might be a noninvasive prognostic marker of renal fibrosis in DN patients.

Role of sodium-glucose cotransporter 2 inhibition to mitigate diabetic kidney disease risk in type 1 diabetes

Diabetic kidney disease (DKD) is a common complication of type 1 diabetes (T1D) and a major risk factor for premature death from cardiovascular disease (CVD). Current treatments, such as control of hyperglycaemia and hypertension, are beneficial, but only partially protect against DKD. Finding new, safe and effective therapies to halt nephropathy progression has proven to be challenging. Sodium-glucose cotransporter 2 (SGLT2) inhibitors have demonstrated, in addition to glycaemic lowering, impressive protection against DKD and CVD progression in people with type 2 diabetes. Although these beneficial cardiorenal effects may also apply to people with T1D, supporting data are lacking. Furthermore, the increased rates of euglycaemic diabetic ketoacidosis may limit the use of this class in people with T1D. In this review we highlight the pathophysiology of DKD in T1D and the unmet need that exists. We further detail the beneficial and adverse effects of SGLT2 inhibitors based on their mechanism of action. Finally, we balance the effects in people with T1D and indicate future lines of research.

Changes in Albuminuria But Not GFR are Associated with Early Changes in Kidney Structure in Type 2 Diabetes

BACKGROUND

In type 1 diabetes, changes in the GFR and urine albumin-to-creatinine ratio (ACR) are related to changes in kidney structure that reflect disease progression. However, such changes have not been studied in type 2 diabetes.

METHODS

Participants were American Indians with type 2 diabetes enrolled in a clinical trial of losartan versus placebo. We followed a subset who underwent kidney biopsy at the end of the 6-year trial, with annual measurements of GFR (by urinary clearance of iothalamate) and ACR. Participants had a second kidney biopsy after a mean follow-up of 9.3 years. We used quantitative morphometric analyses to evaluate both biopsy specimens.

RESULTS

Baseline measures for 48 participants (12 men and 36 women, mean age 45.6 years) who completed the study included diabetes duration (14.6 years), GFR (156 ml/min), and ACR (15 mg/g). During follow-up, glomerular basement membrane (GBM) width, mesangial fractional volume, and ACR increased, and surface density of peripheral GBM and GFR decreased. After adjustment for sex, age, ACR, and each morphometric variable at baseline, an increase in ACR during follow-up was significantly associated with increases in GBM width, mesangial fractional volume, and mean glomerular volume, and a decrease in surface density of peripheral GBM. Decline in GFR was not associated with changes in these morphometric variables after additionally adjusting for baseline GFR.

CONCLUSIONS

In American Indians with type 2 diabetes and preserved GFR at baseline, increasing ACR reflects the progression of earlier structural glomerular lesions, whereas early GFR decline may not accurately reflect such lesions.

Do sodium-glucose cotransporter-2 inhibitors affect renal hemodynamics by different mechanisms in type 1 and type 2 diabetes?

Cardiovascular and renal outcome trials demonstrate nephroprotection with sodium-glucose cotransporter-2 inhibitors in people with type 2 diabetes. Attenuation of hyperfiltration is believed to be responsible for the nephroprotection, and studies in young adults with type 1 diabetes suggest that afferent arteriolar vasoconstriction induced by a tubuloglomerular feedback mechanism may be responsible for this effect. The study by van Bommel et al. suggests that this mechanism may not hold true in older adults with type 2 diabetes, who instead attenuate elevated glomerular filtration rate via post-glomerular vasodilation.

Retinal Microcirculation in Predicting Diabetic Nephropathy in Type 2 Diabetic Patients without Retinopathy

PURPOSE

To evaluate retinal thicknesses and retinal microcirculation in healthy controls and in diabetic patients with or without microalbuminuria.

METHODS

Eighty-six diabetic patients without diabetic retinopathy (DR) (44 normoalbuminuric, 42 microalbuminuric) and 51 healthy controls were enrolled in this cross-sectional, prospective study. Optical coherence tomography (OCT) and OCT angiography (OCTA) were performed. Correlations between OCTA parameters with mean urinary albumin levels were evaluated.

RESULTS

The mean vessel densities of superficial capillary plexus (SCP), whole disc, and peripapillary area were significantly decreased in patients with microalbuminuria compared to patients with normoalbuminuria and controls (p < 0.05 for all). The mean vessel density of deep capillary plexus was significantly reduced in patients with microalbuminuria compared to controls (p < 0.05 for all). There were no significant differences in retinal thickness between groups (p > 0.05). Both duration of diabetes and urinary albumin levels were significantly and moderately correlated with mean vessel density of whole SCP in diabetic patients (r = 0.330, p = 0.021; r = 0.356, p = 0.017, respectively).

CONCLUSION

Diabetic eyes without clinically detectable DR show impaired retinal microcirculation. Microalbuminuria is associated with alterations of retinal microcirculation in diabetic patients without DR. Evaluation of retinal microcirculation is likely useful for detecting early changes related to microvascular complications in type 2 diabetic patients.

Podocyte-specific expression of Cre recombinase promotes glomerular basement membrane thickening

Conditional gene targeting using Cre recombinase has offered a powerful tool to modify gene function precisely in defined cells/tissues and at specific times. However, in mammalian cells, Cre recombinase can be genotoxic. The importance of including Cre-expressing control mice to avoid misinterpretation and to maximize the validity of the experimental results has been increasingly recognized. While studying the role of podocytes in the pathogenesis of glomerular basement membrane (GBM) thickening, we used Cre recombinase driven by the podocyte-specific podocin promoter (NPHS2-Cre) to generate a conditional knockout. By conventional structural and functional measures (histology by periodic acid-Schiff staining, albuminuria, and plasma creatinine), we did not detect significant differences between NPHS2-Cre transgenic and wild-type control mice. However, surprisingly, the group that expressed Cre transgene alone developed signs of podocyte toxicity, including marked GBM thickening, loss of normal foot process morphology, and reduced Wilms tumor 1 expression. GBM thickening was characterized by altered expression of core structural protein laminin isoform α₅β₂γ₁. RNA sequencing analysis of extracted glomeruli identified 230 genes that were significant and differentially expressed (applying a q < 0.05-fold change ≥ ±2 cutoff) in NPHS2-Cre mice compared with wild-type control mice. Many biological processes were reflected in the RNA sequencing data, including regulation of the extracellular matrix and pathways related to apoptosis and cell death. This study highlights the importance of including the appropriate controls for potential Cre-mediated toxicity in conditional gene-targeting experiments. Indeed, omitting the Cre transgene control can result in critical errors during interpretation of experimental data.

Epigenetic Risk Profile of Diabetic Kidney Disease in High-Risk Populations

PURPOSE OF REVIEW

Epigenetic variations have been shown to reveal vulnerability to diabetes and its complications. Although it has become clear that metabolic derangements, especially hyperglycemia, can impose a long-term metabolic memory that predisposes to diabetic complications, the underlying mechanisms remain to be understood. It has been suggested that epigenetics (e.g., histone modification, DNA methylation, and non-coding RNAs) help link metabolic disruption to aberrancies related to diabetic kidney disease (DKD). In this review, we discuss the key findings and advances made in the epigenetic risk profile of DKD and provide perspectives on the emerging topics that implicate epigenetics in DKD.

RECENT FINDINGS

Epigenetic profiles can be profoundly altered in patients with diabetes, in circulating blood cells as well as in renal tissues. These changes provide useful insight into the mechanisms of diabetic kidney injury and progressive kidney dysfunction. Increasing evidence supports the role of epigenetic regulation in DKD. More studies are needed to elucidate the mechanism and importance of epigenetic changes in the initiation and progression of DKD and to further explore their diagnostic and therapeutic potential in the clinical management of patients with diabetes who have a high risk for DKD.

Advances in understanding the genetic basis of diabetic kidney disease

Diabetic kidney disease (DKD) is a devastating complication of Type 1 and Type 2 diabetes and leads to increased morbidity and mortality. Earlier work in families has provided strong evidence that heredity is a major determinant of DKD. Previous linkage analyses and candidate gene studies have identified potential DKD genes; however, such approaches have largely been unsuccessful. Genome-wide association studies (GWAS) have made significant contribution in identifying SNPs associated with common complex diseases. Thanks to advanced technology, new analytical approaches, and international research collaborations, many DKD GWASs have reported unique genes, highlighted novel biological pathways and suggested new disease mechanisms. This review summarizes the current state of GWAS technology; findings from GWASs of DKD and its related traits conducted over the past 15 years and discuss the future of this field.

The relationship between the thickness of glomerular basement membrane and renal outcomes in patients with diabetic nephropathy

AIMS

Glomerular basement membrane (GBM) thickening is considered as one of the earliest detectable pathological features of diabetic nephropathy (DN). However, whether the thickness of GBM will impact the prognosis of DN remains largely unknown. Our aim was to explore the relationship between thickness of GBM and DN progression in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 118 patients with T2DM and biopsy-proven DN who received follow-up for at least 1 year were recruited. The patients were divided into two groups according to the median (787 nm) of the GBM thickness: Group 1: GBM thickness < 787 nm (n = 59), and Group 2: GBM thickness ≥ 787 nm (n = 59). The GBM width was estimated by the direct GBM measurements as recently modified by Haas. Renal outcomes were defined by progression to ESRD and/or doubling of serum creatinine (D-Cr). The influence of GBM thickness on renal outcomes was assessed using Cox regression.

RESULTS

Compared with the Group 1, patients in Group 2 had more serious renal insufficiency and glomerular lesions. During the follow-up, ESRD occurred in 39.8% of patients, and 8.5% of patients progressed to D-Cr. The univariate analysis indicated the greater width of GBM the higher risk of renal outcomes in T2DM patients with DN (HR [95% CI] = 2.180 [1.246-3.814], p = 0.006). However, the multivariate COX analysis demonstrated that the GBM thickness was not an independent risk factor for progression to ESRD or D-Cr (HR [95% CI] = 0.825 [0.404-1.685], p = 0.597) when adjusting for important clinical variables and pathological findings.

CONCLUSIONS

In conclusion, the DN patients with greater width of GBM had relatively poorer renal prognosis, although it did not emerge as an independent indicator of disease progression.

Synergistical action of the β2 adrenoceptor and fatty acid binding protein 2 polymorphisms on the loss of glomerular filtration rate in Chinese patients with type 2 diabetic nephropathy

PURPOSE

Since altered sympathetic nerve activity and insulin resistance are implicated in the pathogenesis of type 2 diabetic nephropathy, we investigated the effect of polymorphic Arg16Gly and Gln27Glu in the β2 adrenoceptor gene and Ala54Thr in the fatty acid binding protein 2 gene on the estimated glomerular filtration rate (eGFR) in Chinese patients with the above disease.

METHODS

A total of 552 diabetic subjects recruited from annual health examinations were studied. The eGFR was calculated from the Modification of Diet in Renal Disease equation for the Chinese. Plasma norepinephrine level and genotype were determined by high-performance liquid chromatography-tandem mass spectrometry and TaqMan method, respectively. Holter-derived heart rate viability (HRV) and the MRI-generated renal apparent diffusion coefficient (ADC) were evaluated.

RESULTS

The Gly16Gly and Thr54Thr homozygotes had significantly higher microalbuminuria and lower eGFR against other genotypes in their individual polymorphism. Besides, the Gly16Gly variant exhibited markedly elevated norepinephrine level, whereas indicative of insulin resistance was increased in the Thr54Thr one. Multiple linear regression analysis further confirmed the independent genetic effect on the eGFR. Moreover, multifactor dimensionality reduction method detected a gene-gene synergistic action that subjects with the Gly16Gly/Thr54Thr genotype were exposed to higher risk of eGFR loss. Finally, these findings were accompanied by lower HRV and ADC, indicating sympathetically mediated hemodynamic changes.

CONCLUSIONS

By uncovering the genetic component of the coherent interplay between the elevated sympathetic nerve activity and metabolic disorders, our observations might promote the development of novel personalized prevention and management strategies against the diabetic nephropathy, especially in the genetically susceptible individuals.

Preservation of renal function in chronic diabetes by enhancing glomerular glucose metabolism

Diabetic nephropathy (DN) affects approximately 30-40% of patients with type 1 (T1DM) and type 2 diabetes (T2DM). It is a major cause of end-stage renal disease (ESRD) for the developed world. Hyperglycemia and genetics are major causal factors for the initiation and progression of DN. Multiple abnormalities in glucose and mitochondrial metabolism induced by diabetes likely contribute to the severity of DN. Recent clinical studies in people with extreme duration of T1DM (> 50 years, Joslin Medalist Study) have supported the importance of endogenous protective factors to neutralize the toxic effects of hyperglycemia on renal and other vascular tissues. Using renal glomeruli from these patients (namely Medalists) with and without DN, we have shown the importance of increased glycolytic flux in decreasing the accumulation of glucose toxic metabolites, improving mitochondrial function, survival of glomerular podocytes, and reducing glomerular pathology. Activation of a key glycolytic enzyme, pyruvate kinase M2 (PKM2), resulted in the normalization of renal hemodynamics and mitochondrial and glomerular dysfunction, leading to the mitigation of glomerular pathologies in several mouse models of DN.

Importance of frequency and morphological characteristics of nodular diabetic glomerulosclerosis in diabetic nephropathy

The Renal Pathology Society proposed a pathological classification for diabetic nephropathy (DN) (RPS 2010). We retrospectively examined the renal structural-functional relationships using the RPS 2010 classification in 49 DN cases. We also evaluated the importance of the percentage of glomeruli with nodular diabetic glomerulosclerosis and their morphological characteristics (cellular, cellular and extracellular matrix [ECM] or ECM types) in the pathology of DN. The classes of DN (RPS 2010) were significantly correlated with the duration of diabetes mellitus (DM), degree of proteinuria, a decreased estimated glomerular filtration rate (eGFR), and the stages of Japanese clinical DM and chronic kidney disease (CKD). When the percentage of glomeruli with nodular glomerulosclerosis (IIIA <25%, IIIB 25-50%, IIIC 50-75%, and IIID >75%) was added to class III in this classification, the classes of DN had a greater correlation with the levels of proteinuria. The morphological characteristics of nodular glomerulosclerosis such as cellular, cellular and ECM, or ECM type were associated with several clinical parameters including the duration of DM, degree of proteinuria, a decreased eGFR, and/or the stages of clinical DM and CKD. Mesangial red blood cell fragments that is indicative of microvascular injury was found in cellular or cellular and ECM types of nodular glomerulosclerosis. The RPS 2010 classification is useful as a DN pathological classification that indicates a good correlation with the clinical characteristics of DN. In addition, the frequency and morphological characteristics of nodular diabetic glomerulosclerosis is important for the evaluation of the pathology in DN.

Trans-resveratrol mitigates type 1 diabetes-induced oxidative DNA damage and accumulation of advanced glycation end products in glomeruli and tubules of rat kidneys

Hyperglycemia induces the formation of advanced glycation end products (AGEs) and their receptors (RAGEs), which alter several intracellular signaling mechanisms leading to the onset and progression of diabetic nephropathy. The present study focused on, i) modulatory effects of trans-resveratrol (3,5,4'-trihydroxy-trans-stilbene) on structural changes, AGE (N^Ɛ-carboxymethyl-lysine), RAGE, oxidative stress and DNA damage, and apoptosis, and ii) localization of fibrotic changes, AGE, RAGE, 8-oxo-dG and 4-hydroxynonenal (4-HNE) in diabetic rat kidneys. Resveratrol (5mg/kg; po, administered during last 45days of 90-day-long hyperglycemic period) administration to streptozotocin-induced type 1 diabetic male Wistar rats reduced renal hypertrophy and structural changes (tubular atrophy, mesangial expansion or shrinkage, diffuse glomerulonephritis, and fibrosis), AGE accumulation, oxidative stress and DNA damage (8-oxo-dG), 4-HNE, caspase-3, and cleaved-caspase-3, but not the RAGE expression. The AGE accumulated in the mesangium, vascular endothelium, and proximal convoluted tubules and less intensely in distal convoluted tubules of diabetic rat kidneys. The RAGE expression increased in the convoluted tubules and collecting ducts of diabetic rat kidneys, but not in the mesangium. Diabetes increased the expression of 8-oxo-dG in nuclei and cytoplasm of renal cells, and 4-HNE in glomeruli, convoluted tubules, the loops of Henle and collecting ducts. Hyperglycemia-induced AGE-RAGE axis and oxidative stress in turn induced apoptosis in diabetic kidneys. Resveratrol mitigated all diabetic effects except the RAGE expression. In conclusion, Resveratrol significantly alleviates diabetes-induced glycation, oxidative damage, and apoptosis to inhibit the progression of diabetic nephropathy. Resveratrol supplementation may be useful to hinder the onset and progression of diabetic kidney diseases.

Renal pathological implications in type 2 diabetes mellitus patients with renal involvement

AIMS

To investigate the renal pathological implications in type 2 diabetes mellitus patients with renal involvement.

METHODS

A total of 328 type 2 diabetes mellitus (T2DM) patients with renal involvement who underwent a renal biopsy and received follow-up for at least one year were recruited in our study. The patients were divided into the diabetic nephropathy (DN), non-diabetic renal disease (NDRD), and NDRD superimposed on DN groups based on the pathological diagnosis. Renal outcomes were defined by the initiation of renal replacement therapy or doubling of the serum creatinine. Kaplan-Meier analysis was used to compare renal survival, and Cox proportional hazard analysis was used to determine the predictors of renal outcomes in the DN group.

RESULTS

Renal biopsy findings revealed that 188 patients (57.32%) had pure DN, 121 patients (36.89%) had NDRD alone, and 19 patients (5.79%) had NDRD superimposed on DN. The most frequent subclassification of NDRD was membranous nephropathy (MN). Compared with the NDRD and NDRD superimposed on DN groups, patients with pure DN had poorer renal function and lower renal survival rates. In the DN group, the five-year renal survival rates of glomerular classes of I, IIa, IIb, III and IV were 100%, 84.62%, 60%, 47.5% and 33.33%, respectively. Multivariate Cox proportional hazard analysis showed that the glomerular lesions, proteinuria and serum creatinine were independent risk factors for renal outcomes, while interstitial fibrosis/inflammation and arteriolar hyalinosis were not independently associated with renal outcomes in the DN group.

CONCLUSIONS

Making an accurate pathologic diagnosis by renal biopsy is crucial for diabetes mellitus (DM) patients with renal involvement. The findings of our present study indicated that patients with pure DN had poorer renal outcomes than patients with NDRD or NDRD superimposed on DN. The classification of glomerular lesions, proteinuria and serum creatinine were independent risk factors for renal outcomes in the DN group. More studies with large samples and longer time follow-up are needed to evaluate the relationship between pathological changes and clinical characteristics in T2DM patients who have renal involvement.

Rethinking glomerular basement membrane thickening in diabetic nephropathy: adaptive or pathogenic?

Diabetic nephropathy (DN) is the leading cause of chronic kidney disease in the United States and is a major cause of cardiovascular disease and death. DN develops insidiously over a span of years before clinical manifestations, including microalbuminuria and declining glomerular filtration rate (GFR), are evident. During the clinically silent period, structural lesions develop, including glomerular basement membrane (GBM) thickening, mesangial expansion, and glomerulosclerosis. Once microalbuminuria is clinically apparent, structural lesions are often considerably advanced, and GFR decline may then proceed rapidly toward end-stage kidney disease. Given the current lack of sensitive biomarkers for detecting early DN, a shift in focus toward examining the cellular and molecular basis for the earliest structural change in DN, i.e., GBM thickening, may be warranted. Observed within one to two years following the onset of diabetes, GBM thickening precedes clinically evident albuminuria. In the mature glomerulus, the podocyte is likely key in modifying the GBM, synthesizing and assembling matrix components, both in physiological and pathological states. Podocytes also secrete matrix metalloproteinases, crucial mediators in extracellular matrix turnover. Studies have shown that the critical podocyte-GBM interface is disrupted in the diabetic milieu. Just as healthy podocytes are essential for maintaining the normal GBM structure and function, injured podocytes likely have a fundamental role in upsetting the balance between the GBM's synthetic and degradative pathways. This article will explore the biological significance of GBM thickening in DN by reviewing what is known about the GBM's formation, its maintenance during health, and its disruption in DN.

Renal diffusion-weighted imaging in diabetic nephropathy: correlation with clinical stages of disease

PURPOSE

We aimed to assess the correlation between renal apparent diffusion coefficient (ADC) values measured by diffusion-weighted imaging (DWI) and the clinical stages of diabetic nephropathy.

MATERIALS AND METHODS

DWI (b value, 0 and 600 s/mm2) was performed in 78 patients with clinically confirmed diabetic nephropathy (study group) and 22 volunteers without diabetes mellitus or any renal disease (control group). The mean ADCs were calculated from multiple region-of-interest circles positioned in the renal cortex. Diabetic nephropathy was clinically categorized into five stages based on the values of urinary albumin excretion and glomerular filtration rate (GFR).

RESULTS

Mean renal ADC values of patients with stage 3 or 4 disease were significantly lower than those in patients with stage 1 or 2 disease and the control group (P < 0.001). ADC values of patients with stage 5 disease were significantly lower than those in patients with stage 4 (P = 0.003), stage 3 (P = 0.020), stages 2 and 1, and the control group (P < 0.001). Significant correlations were found between mean renal ADC values and clinical stages of diabetic nephropathy (r=-0.751, P < 0.001), between mean renal ADC values and estimated GFR values (r=0.642, P < 0.001), and between mean renal ADC values and urinary albumin excretion (r=-0.419, P < 0.001).

CONCLUSION

Renal ADC values show a significant correlation with clinical stages of diabetic nephropathy. As a relatively simple and noninvasive tool without contrast media administration, renal quantitative DWI may potentially play a role in making clinical decisions in the follow-up of diabetic patients.

Renal diffusion-weighted imaging in diabetic nephropathy: correlation with clinical stages of disease

PURPOSE

We aimed to assess the correlation between renal apparent diffusion coefficient (ADC) values measured by diffusion-weighted imaging (DWI) and the clinical stages of diabetic nephropathy.

MATERIALS AND METHODS

DWI (b value, 0 and 600 s/mm2) was performed in 78 patients with clinically confirmed diabetic nephropathy (study group) and 22 volunteers without diabetes mellitus or any renal disease (control group). The mean ADCs were calculated from multiple region-of-interest circles positioned in the renal cortex. Diabetic nephropathy was clinically categorized into five stages based on the values of urinary albumin excretion and glomerular filtration rate (GFR).

RESULTS

Mean renal ADC values of patients with stage 3 or 4 disease were significantly lower than those in patients with stage 1 or 2 disease and the control group (P < 0.001). ADC values of patients with stage 5 disease were significantly lower than those in patients with stage 4 (P = 0.003), stage 3 (P = 0.020), stages 2 and 1, and the control group (P < 0.001). Significant correlations were found between mean renal ADC values and clinical stages of diabetic nephropathy (r=-0.751, P < 0.001), between mean renal ADC values and estimated GFR values (r=0.642, P < 0.001), and between mean renal ADC values and urinary albumin excretion (r=-0.419, P < 0.001).

CONCLUSION

Renal ADC values show a significant correlation with clinical stages of diabetic nephropathy. As a relatively simple and noninvasive tool without contrast media administration, renal quantitative DWI may potentially play a role in making clinical decisions in the follow-up of diabetic patients.

Novel therapies for diabetic kidney disease

The number of people diagnosed with diabetes is rising throughout the world, which in turn drives upward the global frequency of diabetic kidney disease (DKD). Individuals with DKD are at an increased risk for premature death, cardiovascular disease, and other severe illnesses that result in frequent hospitalizations and increased health-care utilization. Current treatments concentrate on controlling hyperglycemia and hypertension with the specific use of renin-angiotensin system inhibitors. Although such measures reduce the risk of progressive kidney disease, DKD remains the leading cause of ESRD and the major risk amplifier for death in this population. Therefore, novel therapeutic approaches are urgently needed. Ideas for novel targets for therapy are founded on recent advances in understanding DKD mechanisms that are based on experimental models and human observations. The purpose of this review is to describe the epidemiology and present knowledge of DKD pathophysiology as the basis for novel therapies including inhibitors of Janus kinases (JAK), protein kinase C, fibrosis, advanced glycation end products treatments, and endothelin.

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.

Renal lesions predict progression of diabetic nephropathy in type 1 diabetes

Whether early glomerular, tubulointerstitial, vascular, and global glomerulosclerotic lesions can predict progression of diabetic nephropathy is not well defined. Here, we sought to determine whether renal structural parameters predict the development of proteinuria or ESRD after long-term follow-up. We measured several renal structures in kidney biopsies from 94 normoalbuminuric patients with longstanding type 1 diabetes using unbiased morphometric methods. Greater width of the glomerular basement membrane and higher levels of glycated hemoglobin were independent predictors of progression to diabetic nephropathy in this normoalbuminuric cohort. Moreover, none of these patients with type 1 diabetes who had glomerular basement membrane widths within the normal range developed proteinuria and/or ESRD. In conclusion, careful quantitative assessment of kidney biopsies in normoalbuminuric patients with type 1 diabetes adds substantially to the prediction of progression to clinical diabetic nephropathy.