Interaction of haemodynamic and metabolic pathways in the genesis of diabetic nephropathy

Bibliometric Analysis and Visualization of Research Progress in the Diabetic Nephropathy Field from 2001 to 2021

Methods

The PubMed database was searched to identify all studies related to DN that were published from 2001 to 2021, with these studies being separated into four time-based groups. The characteristics of these studies were analyzed and extracted using BICOMB. Biclustering analyses for each of these groups were then performed using gCLUTO, with these results then being analyzed and GraphPad Prism 5 being used to construct strategy diagrams. The social network analyses (SNAs) for each group of studies were conducted using NetDraw and UCINET.

Results

In total, 18,889 DN-associated studies published from 2001 to 2021 and included in the PubMed database were incorporated into the present bibliometric analysis. Biclustering analysis and strategy diagrams revealed that active areas of research interest in the DN field include studies of the drug-based treatment, diagnosis, etiology, pathology, physiopathology, and epidemiology of DN. The specific research topics associated with these individual areas, however, have evolved over time in a dynamic manner. Strategy diagrams and SNA results revealed podocyte metabolism as an emerging research hotspot in the DN research field from 2010 to 2015, while DN-related microRNAs, signal transduction, and mesangial cell metabolism have emerged as more recent research hotspots in the interval from 2016 to 2021.

Conclusion

Through analyses of PubMed-indexed studies pertaining to DN published since 2001, the results of this bibliometric analysis offer a knowledge framework and insight into active and historical research hotspots in the DN research space, enabling investigators to readily understand the dynamic evolution of this field over the past two decades. Importantly, these analyses also enable the prediction of future DN-related research hotspots, thereby potentially guiding more focused and impactful research efforts.

Research Progress on the Positive and Negative Regulatory Effects of Rhein on the Kidney: A Review of Its Molecular Targets

Currently, both acute kidney injury (AKI) and chronic kidney disease (CKD) are considered to be the leading public health problems with gradually increasing incidence rates around the world. Rhein is a monomeric component of anthraquinone isolated from rhubarb, a traditional Chinese medicine. It has anti-inflammation, anti-oxidation, anti-apoptosis, anti-bacterial and other pharmacological activities, as well as a renal protective effects. Rhein exerts its nephroprotective effects mainly through decreasing hypoglycemic and hypolipidemic, playing anti-inflammatory, antioxidant and anti-fibrotic effects and regulating drug-transporters. However, the latest studies show that rhein also has potential kidney toxicity in case of large dosages and long use times. The present review highlights rhein's molecular targets and its different effects on the kidney based on the available literature and clarifies that rhein regulates the function of the kidney in a positive and negative way. It will be helpful to conduct further studies on how to make full use of rhein in the kidney and to avoid kidney damage so as to make it an effective kidney protection drug.

Obesity and Diabetic Complications: A Study from the Nationwide Diabetes Report of the National Program for Prevention and Control of Diabetes (NPPCD-2021) Implications for Action on Multiple Scales

BACKGROUND

Obesity plays a major role in the pathogenesis and development of macro- and microvascular complications of type 2 diabetes (T2D) and type 1 diabetes (T1D). We aimed to assess the association between obesity and macrovascular and microvascular complications of diabetes.

METHODS

This study consisted of 111,830 patients (age range: 1-106) with diabetes including 10,641 T1D (3187 obese [38.2% men] and 7454 non-obese [45.5% men]) and 101,189 T2D (51,873 obese [27.5% men] and 49,316 non-obese [33.4% men]) from the National Program for Prevention and Control of Diabetes (NPPCD-2021) in Iran, who attended academic tertiary care outpatient clinics from February 2016 to April 2021. A pooled logistic regression model was used to examine the association between obesity and diabetic complications.

RESULTS

Among patients with T1D, a significant association was found between obesity and cardiovascular disease (CVD), neuropathy, nephropathy and retinopathy (OR= 1.75, 1.56, 1.80 and 1.92, P-value= 0.001, 0.004, 0.001 and <0.001, respectively). In T2D, a statistically significant association was found between obesity and CVD, neuropathy and nephropathy (OR= 1.63, 1.98, 1.21, respectively, P-values <0.001).

CONCLUSION

Obesity was independently associated with CVD, neuropathy and nephropathy in patients with T1D and T2D and with retinopathy only in T1D, to different degrees. The association between obesity and retinopathy and neuropathy was the strongest among T1D and T2D, respectively. Findings from this study suggest that obesity affects diabetic complications differently among the two types of diabetes, in terms of epidemiology and pathophysiology. This signifies the importance of different preventive and therapeutic approaches to obesity in T1D compared to T2D, on a national and global scale.

Advances in The Study of RNA-binding Proteins in Diabetic Complications

Background

It has been reported that diabetes mellitus affects 435 million people globally as a primary health care problem. Despite many therapies available, many diabetes remains uncontrolled, giving rise to irreversible diabetic complications that pose significant risks to patients’ wellbeing and survival.

Scope of Review

In recent years, as much effort is put into elucidating the posttranscriptional gene regulation network of diabetes and diabetic complications; RNA binding proteins (RBPs) are found to be vital. RBPs regulate gene expression through various post-transcriptional mechanisms, including alternative splicing, RNA export, messenger RNA translation, RNA degradation, and RNA stabilization.

Major Conclusions

Here, we summarized recent studies on the roles and mechanisms of RBPs in mediating abnormal gene expression in diabetes and its complications. Moreover, we discussed the potential and theoretical basis of RBPs to treat diabetes and its complications.

• Mechanisms of action of RBPs involved in diabetic complications are summarized and elucidated.

• We discuss the theoretical basis and potential of RBPs for the treatment of diabetes and its complications.

• We summarize the possible effective drugs for diabetes based on RBPs promoting the development of future therapeutic drugs.

Green tea peptides ameliorate diabetic nephropathy by inhibiting the TGF-β/Smad signaling pathway in mice

Diabetic nephropathy (DN) is the most important cause of middle and late-stage chronic kidney disease. Green tea polypeptides are extracted from tea pomace, and exhibit various pharmacological effects. In this study, we analyzed the reno-protective effects of green tea peptides in diabetic db/db mice, and explored the underlying mechanisms. Peptide treatment for 5 weeks significantly reduced the blood glucose levels and other indices of diabetes, and alleviated renal injury measured in terms of blood creatinine, urea nitrogen and urinary albumin/urinary creatinine levels. Mechanistically, the green tea peptides downregulated p-Smad2/3, α-SMA, ZO-1 and vimentin proteins in the kidney tissues, and elevated Smad7. Thus, green tea peptides inhibited the deposition of ECM proteins by suppressing excessive activation of the TGF-β/Smad signaling pathway and reducing fibronectin levels. On the other hand, tea peptides ameliorated renal injury by inhibiting the production of inflammatory factors (iNOS and TNF-α) by suppressing the NF-κB signaling pathway. In addition, we confirmed the inhibitory effect of green tea peptides on the TGF-β/Smad signaling pathway in TGF-β1-stimulated HK-2 cells. Therefore, tea peptides can be considered as an effective candidate for alleviating DN.

Toxicological effect of Artemisinin-Based Combination Therapies plus Paracetamol in malaria patients

BACKGROUND

Following the paucity of safety reports in the use of Artemisinin-Based Combination Therapies (ACTs) plus paracetamol, the study assessed safety potential of artemether-lumefantrine (ALP), artesunate-amodiaquine (AAP), artesunate-mefloquine (AMP), artesunate-sulphadoxine-pyrimethamine (ASPP) and dihydroartemisinin-piperaquine (DHPP) combination with paracetamol in malaria patients.

METHODS

ACTs and paracetamol were administered concomitantly in conventional doses/regimen to randomly selected patients. Blood samples were collected from the ante-cubital vein before and after completion of therapies. Toxicity markers such as weights, glucose, lipids, renal electrolytes, liver enzymes and haematological indices were assessed using standard protocols.

RESULTS

The total numbers of participants were 57 patients. Male to female ratio was 1:1.1. Mean body weight and ages were 59.19 ± 1.39 kg and 42.86 ± 1.32 years respectively. The mean temperatures prior to and after therapy were 37.49 ± 1.02 °C and 37.50 ± 0.17 °C respectively. Mean parasitaemia before the commencement of therapy was 6282 ± 21.01 parasites/μl. Out of thirty-seven toxicological indices evaluated, twenty-four were significantly altered by ACTs plus paracetamol (P < 0.05). Increased serum toxicity markers due to the drug combinations were glucose (AAP, AMP), urea (ALP, ASPP), bicarbonate ion (ALP, AAP, AMP, ASPP), chloride ion (ALP, AAP, AMP), creatinine (ALP, AAP, AMP, ASPP), alkaline phosphatase (ALP, AAP), aspartate aminotransferase and alanine aminotransferase (ALP, AAP, AMP, ASPP, DHPP), total protein (AMP, DHPP) and albumin (AMP, DHPP). Decreased serum toxicity markers due to the drugs were glucose (ALP, ASPP, DHPP), urea (AMP), bicarbonate ion (DHPP), chloride ion (ASPP, DHPP), creatinine (DHPP), alkaline phosphatase (AMP, ASPP, DHPP), total protein (ALP, AAP, and ASPP) and albumin (ALP, AAP, ASPP). Altered haematological indices were white blood cells, red blood cells, mean cell haemoglobin and platelets.

CONCLUSION

Since ACTs plus paracetamol altered human system, discrete selection is essential in managing uncomplicated malaria most especially in patients with co-morbid conditions.

GLP-1 Receptor Agonists in Diabetic Kidney Disease: From Physiology to Clinical Outcomes

Diabetic kidney disease (DKD) is one of the most common complications in type 2 diabetes mellitus (T2D) and a major cause of morbidity and mortality in diabetes. Despite the widespread use of nephroprotective treatment of T2D, the incidence of DKD is increasing, and it is expected to become the fifth cause of death worldwide within 20 years. Previous studies have demonstrated that GLP-1 receptor agonists (GLP-1 RA) have improved macrovascular and microvascular outcomes independent of glycemic differences, including DKD. GLP-1Ras’ improvement on kidney physiology is mediated by natriuresis, reduction in hyperfiltration and renin-angiotensin-aldosterone system (RAAS) activity and anti-inflammatory properties. These findings translate into improved clinical outcomes such as an enhanced urine albumin-to-creatinine ratio (UACR) and a reduction in renal impairment and the need for renal replacement therapies (RRT). In this article, we review the role of GLP-1RAs on the mechanisms and effect in DKD and their clinical efficacy.

A Review on Cellular and Molecular Mechanisms Linked to the Development of Diabetes Complications

Modern lifestyle, changing eating habits and reduced physical work have been known to culminate into making diabetes a global pandemic. Hyperglycemia during the course of diabetes is an important causative factor for the development of both microvascular (retinopathy, nephropathy and neuropathy) and macrovascular (coronary artery disease, stroke and peripheral artery disease) complications. In this article, we summarize several mechanisms accountable for the development of both microvascular and macrovascular complications of diabetes. Several metabolic and cellular events are linked to the augmentation of oxidative stress like the activation of advanced glycation end products (AGE) pathway, polyol pathway, Protein Kinase C (PKC) pathway, Poly-ADP Ribose Polymerase (PARP) and hexosamine pathway. Oxidative stress also leads to the production of reactive oxygen species (ROS) like hydroxyl radical, superoxide anion and peroxides. Enhanced levels of ROS rescind the anti-oxidant defence mechanisms associated with superoxide dismutase, glutathione and ascorbic acid. Moreover, ROS triggers oxidative damages at the level of DNA, protein and lipids, which eventually cause cell necrosis or apoptosis. These physiological insults may be related to the microvascular complications of diabetes by negatively impacting the eyes, kidneys and the brain. While underlying pathomechanism of the macrovascular complications is quite complex, hyperglycemia associated atherosclerotic abnormalities like changes in the coagulation system, thrombin formation, fibrinolysis, platelet and endothelial function and vascular smooth muscle are well proven. Since hyperglycemia also modulates the vascular inflammation, cytokines, macrophage activation and gene expression of growth factors, elevated blood glucose level may play a central role in the development of macrovascular complications of diabetes. Taken collectively, chronic hyperglycemia and increased production of ROS are the miscreants for the development of microvascular and macrovascular complications of diabetes.

Dietary restriction regimens for fighting kidney disease: Insights from rodent studies

This review critically discusses the research findings on the effects of various dietary restriction regimens in rodent models of kidney disease. Long-term caloric restriction executed at both early and progressive stages of kidney disease was found to exert beneficial effects in rodents. Moreover, some studies have also demonstrated the efficacy of short-term caloric restriction in treating the kidney disease of variable aetiologies possibly by improving mitochondrial dysfunction, autophagy process and suppression of inflammation. However, the mechanisms underlying these short-term caloric restriction mediated protective effects in rodent models of kidney disease are not completely understood. Importantly, few available evidences have also suggested that carbohydrate restriction can exert beneficial effects in aging and experimentally induced renal injury models, but the mechanisms are not explored yet. Interestingly, the benefits of low protein diet in kidney disease models are extensively reported in literature. However, in most of these studies implementation of the low protein dietary regimen was found to associated with increased high carbohydrate and caloric intake (non-isocaloric). Thus, testing the effects of low protein diet under isocaloric conditions might further help to particularly understand the role of dietary protein content in pathology of kidney disease. Moreover, the direct evidences comparing the efficacy of various dietary restriction regimens in rodent models of kidney diseases are also scarce at present.

Effect of Lercanidipine on Kidney Microanatomy in Cohen-Rosenthal Diabetic Hypertensive Rats

The study was undertaken to determine the effect of treatment with the dihydropyridine-type calcium antagonist lercanidipine on the renal vasculature in Cohen-Rosenthal diabetic hypertensive rats, a genetic model of hypertension associated with type 2 diabetes mellitus. Eight animals were given a daily oral dose of 3 mg/kg lercanidipine in drinking water for 8 weeks, and 6 control animals received no treatment. The effects on blood pressure, glucose level, and kidney microanatomy were evaluated. Lercanidipine reduced systolic blood pressure and glucose level. In the control group small arteries and glomerular arterioles exhibited wall thickening and luminal narrowing. Lercanidipine administration prevented the changes in small-sized arteries and glomerular arterioles. The glomerular changes observed in the untreated Cohen-Rosenthal diabetic hypertensive rats were not seen in the lercanidipine-treated animals. Lercanidipine also had beneficial effects on the renal vasculature, suggesting that the compound may be considered for treating hypertension associated with diabetes.

Elevated serum monocyte chemoattractant protein-1 levels and its genetic polymorphism is associated with diabetic retinopathy in Chinese patients with Type 2 diabetes

AIM

Previous studies have reported that monocyte chemoattractant protein-1 (MCP-1) is involved in inflammatory and metabolic diseases. The purpose of this study is to investigate the role of MCP-1 in the pathogenesis of diabetic retinopathy (DR) in Han Chinese patients with Type 2 diabetes.

METHODS

Serum levels of MCP-1 protein in patients classified as diabetic without retinopathy (DWR) and DR, including NPDR and PDR, were assayed by enzyme-linked immunosorbent assay. Genomic DNA from 198 DWR patients, 176 NPDR patients and 143 PDR patients were genotyped by using a PCR restriction fragment length polymorphism (PCR-RFLP) assay.

RESULTS

MCP-1 serum levels were significantly higher in NPDR and PDR patients than in the DWR patients. The frequencies of the GG genotype and G allele of the single nucleotide polymorphism (SNP) were significantly increased in DR patients compared with DWR patients. Further subgroup analysis was performed to test whether there was an association between the PDR or NPDR and DWR groups. Significantly higher frequencies of the GG genotype and G allele were observed in PDR and NPDR patients compared with DWR patients. Furthermore, the 25 patients with PDR were divided into three groups according to the genotype of the tested SNP. The expression of the MCP-1 gene was higher in the GG genotype group compared with the other two groups.

CONCLUSIONS

The results suggested that the -2518 GG genotype and G allele of MCP-1 are associated with an increased risk of PDR in the Chinese Han population. This polymorphism may influence the expression of the MCP-1 gene, which may play an important role in the pathogenesis of DR.

Oxidative stress-related genes in type 2 diabetes: association analysis and their clinical impact

Worldwide prevalence of diabetes mellitus motivates a number of association studies to be conducted throughout the world. Eleven polymorphisms from nine candidate genes in oxidative stress pathway have been analyzed in eastern Indian type 2 diabetic patients (n = 145) and healthy controls (n = 100). Different biochemical parameters were also analyzed for their association with the disease. Significant associations were observed for rs2070424 A>G SOD1 (OR 3.91, 95% CI 2.265-8.142, P < 0.001), rs854573 A>G PON1 (OR 3.415, 95% CI 2.116-5.512, P < 0.001), rs6954345 G>C PON2 (OR 3.208, 95% CI 2.071-4.969, P < 0.001), RAGE rs1800624 -374 T>A (OR 3.58, 95% CI 2.218-5.766, P < 0.001), and NOS3 -786 T>C (OR 3.75, 95% CI 2.225-6.666, P < 0.001). Haplotype containing two risk alleles of PON1 and PON2 genes was significantly associated with disease (OR 8.34, 95% CI 1.554-44.804, P < 0.002). Our results suggest that carriers of major and efficient alleles of oxidative stress genes are more likely to survive the comorbid complications and single copy of risk allele is sufficient for developing the disease.

Obesity and diabetic kidney disease

Obesity and diabetes are major causes of CKD and ESRD, and are thus enormous health concerns worldwide. Both obesity and diabetes, along with other elements of the metabolic syndrome including hypertension, are highly interrelated and contribute to the development and progression of renal disease. Studies show that multiple factors act in concert to initially cause renal vasodilation, glomerular hyperfiltration, and albuminuria, leading to the development of glomerulopathy. The coexistence of hypertension contributes to the disease progression, which, if not treated, may lead to ESRD. Although early intervention and management of body weight, hyperglycemia, and hypertension are imperative, novel therapeutic approaches are also necessary to reduce the high morbidity and mortality associated with both obesity-related and diabetes-related renal disease.

Renal interstitial hyaluronan: functional aspects during normal and pathological conditions

The glycosaminoglycan (GAG) hyaluronan (HA) is recognized as an important structural component of the extracellular matrix, but it also interacts with cells during embryonic development, wound healing, inflammation, and cancer; i.e., important features in normal and pathological conditions. The specific physicochemical properties of HA enable a unique hydration capacity, and in the last decade it was revealed that in the interstitium of the renal medulla, where the HA content is very high, it changes rapidly depending on the body hydration status while the HA content of the cortex remains unchanged at very low amounts. The kidney, which regulates fluid balance, uses HA dynamically for the regulation of whole body fluid homeostasis. Renomedullary HA elevation occurs in response to hydration and during dehydration the opposite occurs. The HA-induced alterations in the physicochemical characteristics of the interstitial space affects fluid flux; i.e., reabsorption. Antidiuretic hormone, nitric oxide, angiotensin II, and prostaglandins are classical hormones/compounds involved in renal fluid handling and are important regulators of HA turnover during variations in hydration status. One major producer of HA in the kidney is the renomedullary interstitial cell, which displays receptors and/or synthesis enzymes for the hormones mentioned above. During several kidney disease states, such as ischemia-reperfusion injury, tubulointerstitial inflammation, renal transplant rejection, diabetes, and kidney stone formation, HA is upregulated, which contributes to an abnormal phenotype. In these situations, cytokines and other growth factors are important stimulators. The immunosuppressant agent cyclosporine A is nephrotoxic and induces HA accumulation, which could be involved in graft rejection and edema formation. The use of hyaluronidase to reduce pathologically overexpressed levels of tissue HA is a potential therapeutic tool since diuretics are less efficient in removing water bound to HA in the interstitium. Although the majority of data describing the role of HA originate from animal and cell studies, the available data from humans demonstrate that an upregulation of HA also occurs in diabetic kidneys, in transplant-rejected kidneys, and during acute tubular necrosis. This review summarizes the current knowledge regarding interstitial HA in the role of regulating kidney function during normal and pathological conditions. It encompasses mechanistic insights into the background of the heterogeneous intrarenal distribution of HA; i.e., late nephrogenesis, its regulation during variations in hydration status, and its involvement during several pathological conditions. Changes in hyaluronan synthases, hyaluronidases, and binding receptor expression are discussed in parallel.

Evaluation of renal hypoxia in diabetic mice by BOLD MRI

OBJECTIVE

Renal hypoxia has been proposed to be a pathophysiologic feature of diabetic kidney disease but it has been difficult to demonstrate in vivo, particularly in mouse models of diabetes. The objective of this work was to examine the sensitivity of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) to assess renal oxygenation in vivo in a mouse model of diabetic kidney disease, the db/db mice.

RESEARCH DESIGN AND METHODS

Kidney BOLD MRI studies were performed on a 3.0 T scanner using multiple gradient echo sequence with a custom-designed surface coil to acquire T2*-weighted images. Studies were performed in 10-week-old db/db mice (n = 7) and db/m controls (n = 6).

RESULTS

R2* is a measure of the tissue deoxyhemoglobin concentration and higher values of R2* are associated with hypoxia. The db/db mice had higher medullary (43.1 ± 5.1 s⁻¹ vs. 32.3 ± 3.7⁻¹ s, P = 0.001) and cortical R2* (31.7 ± 3.1 s⁻¹ vs. 27.1 ± 4.1 s⁻¹, P = 0.04) values. Using pimonidazole staining as a marker of kidney hypoxia, in kidney sections from 10-week-old db/db mice neither cortex nor medulla had significant differences as compared with 10-week-old db/m mice (cortex: db/db 2.14 ± 0.05 vs. db/m 2.02 ± 0.28, medulla: db/db 2.81 ± 0.08 vs. db/m 2.6 ± 0.08). The db/db mice demonstrated further increased cortical and medullary hypoxia when scanned again at 15 weeks of age.

CONCLUSIONS

The report shows that renal BOLD MRI is a sensitive method for the in vivo evaluation of renal hypoxia in a mouse model of diabetic kidney disease where progressive renal hypoxia can be documented over time. BOLD MRI may be useful to monitor therapeutic interventions that may improve tissue hypoxia in the diabetic kidney.

Obesity, metabolic syndrome and diabetic nephropathy

Diabetic nephropathy is becoming an increasingly important cause of morbidity and mortality worldwide owing to the increasing prevalence of type 2 diabetes, largely driven by increasing obesity. There is considerable evidence that obesity, hypertension and other elements of the metabolic syndrome also contribute to the progression of renal disease independent of diabetes. How they interact and contribute to diabetic nephropathy, however, is not completely understood. Clinical diabetic nephropathy is preceded by an increase in glomerular filtration rate, microalbuminuria and glomerular hypertrophy. Poor glycemic control and elevated systolic blood pressure exacerbate proteinuria and renal injury that may culminate in end-stage renal disease. A similar sequence of events may lead to obesity-related renal disease even in the absence of diabetes. This chapter compares and contrasts factors involved in the development of glomerular hemodynamic and kidney pathological processes associated with diabetes and obesity.

Renal injury in angiotensin II+L-NAME-induced hypertensive rats is independent of elevated blood pressure

The balance between angiotensin II (ANG II) and nitric oxide plays an important role in renal function and is thought to contribute to the progression of renal injury in experimental hypertension. In the present study, we investigated the extent of blood pressure (BP)-dependent and BP-independent pathways of renal injury following 2 wk of hypertension produced by intravenous infusion of ANG II (5 ng·kg⁻¹·min⁻¹)+N(ω)-nitro-l-arginine methyl ester (l-NAME; 1.4 μg·kg⁻¹·min⁻¹) in male Sprague-Dawley rats. An aortic balloon occluder was positioned between the renal arteries to maintain (24 h/day) BP to the left kidney (servo-controlled) at baseline levels, whereas the right kidney (uncontrolled) was chronically exposed to elevated BP. Over the 14-day experimental protocol, the average BP to uncontrolled kidneys (152.7 ± 1.8 mmHg) was significantly elevated compared with servo-controlled (113.0 ± 0.2 mmHg) kidneys and kidneys from sham rats (108.3 ± 0.1 mmHg). ANG II+l-NAME infusion led to renal injury that was focal in nature and mainly confined to the outer medulla. Despite the differences in BP between servo-controlled and uncontrolled kidneys, there was a similar ~3.5-fold increase in renal outer medullary tubular injury, ~2-fold increase in outer medullary interstitial fibrosis, ~2-fold increase in outer medullary macrophage infiltration, and a significant increase in renal oxidative stress, all of which are indicative of BP-independent mediated pathways. The results of this study have important implications regarding the pathogenesis of renal injury in various experimental models of hypertension and provide novel insights regarding the variable association observed between hypertension and renal injury in some human populations.

Role of angiotensin II in the development of nephropathy and podocytopathy of diabetes

Diabetic kidney disease is the leading cause of end-stage renal disease worldwide. Podocytes are highly differentiated, pericyte-like cells that are essential for normal function of the kidney filter. Loss of podocytes is a hallmark of progressive kidney diseases including diabetic nephropathy. Podocytes are a direct target for angiotensin II - mediated injury by altered expression and distribution of podocyte proteins. Additionally, angiotensin II promotes podocyte injury indirectly by increasing calcium influx and production of reactive oxygen species. Notwithstanding the convincing rationale for angiotensin II blockade as a treatment modality, the incidence of diabetes-related end stage renal disease has increased steadily despite widespread use of angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs). Recently published clinical trials have rekindled a debate on the safety and efficacy of dual blockade of the renin-angiotensin system (RAS). This review summarizes the rationale for blockade of angiotensin II as a therapeutic target in treating diabetic kidney disease, including the critical role played by podocytes. Recent relevant clinical trials on the role of RAS blockade in the treatment of diabetic kidney disease are discussed.

Oxidative stress pathway genes and chronic renal insufficiency in Asian Indians with Type 2 diabetes

BACKGROUND

There are significant regional variations in prevalence of diabetes and diabetic chronic renal insufficiency (CRI) in India. Oxidative stress plays an important role in the development of diabetic complications. To determine the importance of the polymorphisms in the genes involved in maintenance of cellular redox balance, we performed a case control study in subjects from south and north India.

METHODS

Successive cases presenting to the study centers with Type 2 diabetes of >2 years duration and moderate CRI (n=194, south India 104, north India 90) diagnosed by serum creatinine >or=2 mg/dl after exclusion of nondiabetic causes of CRI were compared with diabetes subjects with no evidence of renal disease (n=224, south India 149, north India 75). Twenty-six polymorphisms from 13 genes from the oxidative stress pathway were analyzed using polymerase chain reaction-restriction fragment length polymorphism. Genes included were superoxide dismutases (SOD1, 2, 3), uncoupling proteins (UCP1, 2), endothelial nitric oxide synthase (NOS3), glutathione-S-transferases (GST) (M1, T1, P1), vascular endothelial growth factor (VEGF), paraoxonase (PON) 1 and 2, and nicotinamide adenine dinucleotide phosphate reduced, oxidase p22(phox). Genes were tested for their association with CRI using chi(2) test.

RESULTS

In south Indian (SI) subjects there was significant allelic and genotypic association of the wild-type allele in SOD2 (Ala9Val; P=.002 and P=.013, respectively), UCP1 (-112 T>G, P=.012 and P=.009; Ala64Thr, P=.015 and P=.004), NOS3 (Glu298Asp, P=.002 and P=.009) and GSTP1 (Ile105Val, P=.003 and P=.004) genes with development of CRI. None of these observations were replicated in the north Indian (NI) subjects. A genotypic but not allelic association was observed for two markers, VEGF (-460 T>C) and PON1 (Arg192Gly) among NI diabetic CRI subjects.

CONCLUSION

The nonreplication of association suggests differential genetic susceptibility of the two populations to diabetic chronic renal insufficiency. In the SI diabetic subjects, oxidative stress pathway genes might be an important predictor for the development of diabetic complications. Further, the association of wild-type alleles may suggest that they confer greater survival ability to comorbid complications and may be nephroprotective.

Angiotensin mediates renal fibrosis in the nephropathy of glycogen storage disease type Ia

Patients with glycogen storage disease type Ia (GSD-Ia) develop renal disease of unknown etiology despite intensive dietary therapies. This renal disease shares many clinical and pathological similarities to diabetic nephropathy. We studied the expression of angiotensinogen, angiotensin type 1 receptor, transforming growth factor-beta1, and connective tissue growth factor in mice with GSD-Ia and found them to be elevated compared to controls. While increased renal expression of angiotensinogen was evident in 2-week-old mice with GSD-Ia, the renal expression of transforming growth factor-beta and connective tissue growth factor did not increase for another week; consistent with upregulation of these factors by angiotensin II. The expression of fibronectin and collagens I, III, and IV was also elevated in the kidneys of mice with GSD-Ia, compared to controls. Renal fibrosis was characterized by a marked increase in the synthesis and deposition of extracellular matrix proteins in the renal cortex and histological abnormalities including tubular basement membrane thickening, tubular atrophy, tubular dilation, and multifocal interstitial fibrosis. Our results suggest that activation of the angiotensin system has an important role in the pathophysiology of renal disease in patients with GSD-Ia.

Association of TGFbeta1, TNFalpha, CCR2 and CCR5 gene polymorphisms in type-2 diabetes and renal insufficiency among Asian Indians

Background

Cytokines play an important role in the development of diabetic chronic renal insufficiency (CRI). Transforming growth factor β1 (TGF β1) induces renal hypertrophy and fibrosis, and cytokines like tumor necrosis factor-alpha (TNFα), chemoattractant protein-1 (MCP-1), and regulated upon activation and normal T cell expressed and secreted (RANTES) mediate macrophage infiltration into kidney. Over expression of these chemokines leads to glomerulosclerosis and interstitial fibrosis. The effect of MCP-1 and RANTES on kidney is conferred by their receptors i.e., chemokine receptor (CCR)-2 and CCR-5 respectively. We tested association of nine single nucleotide polymorphisms (SNPs) from TGFβ1, TNFα, CCR2 and CCR5 genes among individuals with type-2 diabetes with and without renal insufficiency.

Methods

Type-2 diabetes subjects with chronic renal insufficiency (serum creatinine ≥ 3.0 mg/dl) constituted the cases, and matched individuals with diabetes of duration ≥ 10 years and normoalbuminuria were evaluated as controls from four centres in India. Allelic and genotypic contributions of nine SNPs from TGFβ1, TNFα, CCR2 and CCR5 genes to diabetic CRI were tested by computing odds ratio (OR) and 95% confidence intervals (CI). Sub-analysis of CRI cases diabetic retinopathy status as dependent variable and SNP genotypes as independent variable in a univariate logistic regression was also performed.

Results

SNPs Tyr81His and Thr263Ile in TGF β1 gene were monomorphic, and Arg25Pro in TGF β1 gene and Δ32 polymorphism in CCR5 gene were minor variants (minor allele frequency <0.05) and therefore were not considered for case-control analysis. A significant allelic association of 59029G>A SNP of CCR5 gene has been observed and the allele 59029A seems to confer predisposition to development of diabetic CRI (OR 1.39; CI 1.04–1.84). In CRI subjects a compound group of genotypes "GA and AA" of SNP G>A -800 was found to confer predisposition for proliferative retinopathy (OR 3.03; CI 1.08–8.50, p = 0.035).

Conclusion

Of the various cytokine gene polymorphisms tested, allele 59029A of CCR5 gene is significantly associated with diabetic renal insufficiency among Asian Indians. Result obtained for 59029G>A SNP of CCR5 gene is in conformity with reports from a Japanese population but due to sub-optimal power of the sample, replication in larger sample set is warranted.

A metabolomic comparison of urinary changes in type 2 diabetes in mouse, rat, and human

Type 2 diabetes mellitus is the result of a combination of impaired insulin secretion with reduced insulin sensitivity of target tissues. There are an estimated 150 million affected individuals worldwide, of whom a large proportion remains undiagnosed because of a lack of specific symptoms early in this disorder and inadequate diagnostics. In this study, NMR-based metabolomic analysis in conjunction with multivariate statistics was applied to examine the urinary metabolic changes in two rodent models of type 2 diabetes mellitus as well as unmedicated human sufferers. The db/db mouse and obese Zucker (fa/fa) rat have autosomal recessive defects in the leptin receptor gene, causing type 2 diabetes. 1H-NMR spectra of urine were used in conjunction with uni- and multivariate statistics to identify disease-related metabolic changes in these two animal models and human sufferers. This study demonstrates metabolic similarities between the three species examined, including metabolic responses associated with general systemic stress, changes in the TCA cycle, and perturbations in nucleotide metabolism and in methylamine metabolism. All three species demonstrated profound changes in nucleotide metabolism, including that of N-methylnicotinamide and N-methyl-2-pyridone-5-carboxamide, which may provide unique biomarkers for following type 2 diabetes mellitus progression.

Imaging the renin-angiotensin system: an important target of anti-hypertensive therapy

Multiphoton fluorescence microscopy allows visualization, manipulation, and quantification of the structure-function relationships between pharmacological interventions and their physiological effects. The application of these methods to live animals permits direct observation of acute physical responses that lack chemically detectable signals in the blood or urine and would otherwise remain unknown. With the use of special fluorescent dyes, chemical/hormonal responses may also be detected. The delivery and site-specific effects of drugs can be monitored in real-time. The capacity to simultaneously visualize both proximal and distal segments of the nephron permits observation of the dynamic processes within the living kidney and a quantitative assessment of the various operations. Consequently, a clinically valuable and pending application for multi-photon microscopy will be to provide real-time, quantitative imaging of basic organ functions and their responses to therapeutic intervention. Imaging of the intra-renal renin content and enzymatic activity of renin in situ and in real-time is a new, more informative measure of RAS activity. Direct visualization of the molecular and cellular components of renin release signals and the interactions between the vascular endothelium, tubular epithelium, local mediators, and the renin producing cells provides great insight for drug development. Examples of how the effects of various RAS inhibitors can be visualized in the intact kidney are provided: including angiotensin converting enzyme inhibition (captopril), angiotensin II type 1 receptor blockade (olmesartan), and renin inhibition (aliskiren). The site-specific actions of diuretics, like furosemide, have also been visualized. Quantitative imaging of basic renal functions in health and disease can provide key information to assess the delivery and effects of pharmaceutical interventions.