Pathogenesis of diabetic glomerulopathy: hemodynamic considerations

Parallelism and non-parallelism in diabetic nephropathy and diabetic retinopathy

Diabetic nephropathy (DN) and diabetic retinopathy (DR), as microvascular complications of diabetes mellitus, are currently the leading causes of end-stage renal disease (ESRD) and blindness, respectively, in the adult working population, and they are major public health problems with social and economic burdens. The parallelism between the two in the process of occurrence and development manifests in the high overlap of disease-causing risk factors and pathogenesis, high rates of comorbidity, mutually predictive effects, and partial concordance in the clinical use of medications. However, since the two organs, the eye and the kidney, have their unique internal environment and physiological processes, each with specific influencing molecules, and the target organs have non-parallelism due to different pathological changes and responses to various influencing factors, this article provides an overview of the parallelism and non-parallelism between DN and DR to further recognize the commonalities and differences between the two diseases and provide references for early diagnosis, clinical guidance on the use of medication, and the development of new drugs.

Urine Immunoglobin G Greater Than 2.45 mg/L Has a Correlation with the Onset and Progression of Diabetic Kidney Disease: A Retrospective Cohort Study

Aim: To further assess the correlation between urine immunoglobin G (IgG) greater than 2.45 mg/L and the onset and progression of diabetic kidney disease (DKD). Methods: One thousand and thirty-five patients with type 2 diabetes mellitus (T2DM) were divided into two groups based on the baseline levels of 24 h urinary albumin excretion (24 h UAE): one group with 24 h UAE < 30 mg/24 h and one with 24 h UAE ≥ 30 mg/24 h. The groups were subdivided using baseline levels of urine IgG (≤2.45 mg/L and >2.45 mg/L; hereafter, the Low and High groups, respectively). We used logistic regression to assess the risk of urine IgG and it exceeding 2.45 mg/L. Kaplan–Meier curves were used to compare the onset and progression time of DKD. The receiver operating characteristic curve was used to test the predictive value of urine IgG exceeding 2.45 mg/L. Results: Urine IgG was an independent risk factor for the onset and progression of DKD. The rate and risk of DKD onset and progression at the end of follow-up increased significantly in the High group. The onset and progression time of DKD was earlier in the High group. Urine IgG exceeding 2.45 mg/L has a certain predictive value for DKD onset. Conclusions: Urine IgG exceeding 2.45 mg/L has a correlation with the onset and progression of DKD, and it also has a certain predictive value for DKD onset.

Relation between Blood Pressure Management and Renal Effects of Sodium-Glucose Cotransporter 2 Inhibitors in Diabetic Patients with Chronic Kidney Disease

AIM

The renoprotective effect of sodium-glucose cotransporter 2 inhibitors is thought to be due, at least in part, to a decrease in blood pressure. The aim of this study was to determine the renal effects of these inhibitors in low blood pressure patients and the dependence of such effect on blood pressure management status.

METHODS

The subjects of this retrospective study were 740 patients with type 2 diabetes mellitus and chronic kidney disease who had been managed at the clinical facilities of the Kanagawa Physicians Association. Data on blood pressure management status and urinary albumin-creatinine ratio were analyzed before and after treatment.

RESULTS

Changes in the logarithmic value of urinary albumin-creatinine ratio in 327 patients with blood pressure < 130/80 mmHg at the initiation of treatment and in 413 patients with BP above 130/80 mmHg were -0.13 ± 1.05 and -0.24 ± 0.97, respectively. However, there was no significant difference between the two groups by analysis of covariance models after adjustment of the logarithmic value of urinary albumin-creatinine ratio at initiation of treatment. Changes in the logarithmic value of urinary albumin-creatinine ratio in patients with mean blood pressure of <102 mmHg (n = 537) and those with ≥102 mmHg (n = 203) at the time of the survey were -0.25 ± 1.02 and -0.03 ± 0.97, respectively, and the difference was significant in analysis of covariance models even after adjustment for the logarithmic value of urinary albumin-creatinine ratio at initiation of treatment (p < 0.001).

CONCLUSION

Our results confirmed that blood pressure management status after treatment with SGLT2 inhibitors influences the extent of change in urinary albumin-creatinine ratio. Stricter blood pressure management is needed to allow the renoprotective effects of sodium-glucose cotransporter 2 inhibitors.

SGLT2 Inhibitors as a Therapeutic Option for Diabetic Nephropathy

Diabetic nephropathy (DN) is a major cause of end-stage renal disease (ESRD) worldwide. Glycemic and blood pressure (BP) control are important but not sufficient to attenuate the incidence and progression of DN. Sodium–glucose cotransporter (SGLT) 2 inhibitors are a new class of glucose-lowering agent suggested to exert renoprotective effects in glucose lowering-dependent and independent fashions. Experimental studies have shown that SGLT2 inhibitors attenuate DN in animal models of both type 1 diabetes (T1D) and type 2 diabetes (T2D), indicating a potential renoprotective effect beyond glucose reduction. Renoprotection by SGLT2 inhibitors has been demonstrated in T2D patients with a high cardiovascular risk in randomized controlled trials (RCTs). These favorable effects of SGLT2 inhibitors are explained by several potential mechanisms, including the attenuation of glomerular hyperfiltration, inflammation and oxidative stress. In this review article, we discuss the renoprotective effects of SGLT2 inhibitors by integrating experimental findings with the available clinical data.

Evaluation of Bacillus subtilis SPB1 biosurfactant effects on hyperglycemia, angiotensin I-converting enzyme (ACE) activity and kidney function in rats fed on high-fat-high-fructose diet

This study investigated the protective and the curative effects of Bacillus subtilis SPB1 crude lipopeptide biosurfactant in alleviating induced obesity complications in rats fed on high-fat-high-fructose diet (HFFD). Male Wistar rats were divided into five groups with the following treatment schedule: normal diet-fed rats (CD), HFFD-fed rats, HFFD-fed rats supplemented with SPB1 biosurfactant from the first day of the experiment (HFFD + Bios1), rats fed on HFFD receiving standard drug (HFFD + Torva), or SPB1 biosurfactant (HFFD + Bios2) during the last 4 weeks of the study. HFFD induced hyperglycemia, manifested by a significant (p < 0.001) increase (20%) in the levels of glucose and α-amylase activity in the plasma, when compared with CD. The administration of SPB1 biosurfactant to rats fed on HFFD reverted back normal blood glucose and α-amylase activity levels. Also, the findings clearly showed that acute oral administration of SPB1 biosurfactant reduced significantly (34%) the peak of blood glucose concentration 60 min after glucose administration, as compared with untreated rats fed on HFFD. Furthermore, renal dysfunction indices such as creatinine and urea as well as the level of angiotensin I-converting enzyme (ACE) exhibited remarkable increases in serum of rats fed on HFFD by 28.35%, 46%, and 92%,. Interestingly, SPB1 lipopeptides treatments decreased the creatinine and urea levels significantly (p < 0.001) near normal values, as compared with that of the HFFD group, and also showed an improvement of the kidney cortex architecture. Moreover, SPB1 biosurfactant displayed a potent inhibition of ACE activity in vitro (CI₅₀ value=1.37 mg/mL) as well as in vivo in obese rats by 42% and 27.25% with HFFD + Bios1 and HFFD + Bios2 treatments, respectively, and comparatively with the HFFD group. Besides, SPB1 lipopeptides treatments improved some of serum electrolytes such as Na⁺, K⁺, Ca²⁺, and Mg²⁺. The results showed that SPB1 lipopeptide biosurfactant presented useful hypoglycemic and antihypertensive properties, and was able to alleviate renal lipid deposition in rats fed on a hypercaloric diet.

Differential urinary glycoproteome analysis of type 2 diabetic nephropathy using 2D-LC-MS/MS and iTRAQ quantification

Background

Diabetic nephropathy (DN) is the leading cause of chronic kidney failure and end-stage kidney disease. More accurate and non-invasive test for the diagnosis and monitoring the progression of DN is urgently needed for the better care of such patients.

Methods

In this study we utilized urinary glycoproteome to discover the differential proteins during the course of type 2 DN. The urinary glycoproteins from normal controls, normalbuminuira, microalbuminura, and macroalbuminuria patients were enriched by concanavalin A (ConA) and analyzed by 2DLC/MS/MS and isobaric tags for relative and absolute quantitation quantification.

Results

A total of 478 proteins were identified and 408 were annotated as N-linked glycoproteins. A total of 72, 107 and 123 differential proteins were identified in normalbuminuria, microalbuminuria and macroalbuminuria, respectively. By bioinformatics analysis, in normalbuminruia state, cell proliferation and cell movement were activated, which might reflect the compensatory phase during the disease development. In micro- and macro-albuminuria, cell death and apoptosis was activated, which might reflect the de-compensatory phase. Pathway analysis showed acute phase proteins, the member of high density lipoprotein and low density lipoprotein proteins were changed, indicating the role of the inflammatory response and lipid metabolism abnormality in the pathogenesis of DN. Six selected differential proteins were validated by Western Blot. Alpha-1-antitrypsin (SERPINA1) and Ceruloplasmin are the two markers with excellent area under curve values (0.929 and 1.000 respectively) to distinguish the microalbuminuria and normalbuminuria. For the first time, we found pro-epidermal growth factor and prolactin-inducible protein were decreased in macroalbuminuria stage, which might reflect the inhibition of cell viability and the activation of cell death in kidney.

Conclusions

Above data indicated that urinary glycoproteome could be useful to distinguish the differences in protein profiles in different stages in DN, which will help better individualized care of patients in DN.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0712-9) contains supplementary material, which is available to authorized users.

Renal autoregulation in health and disease

Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.

Hypertension increases urinary excretion of immunoglobulin G, ceruloplasmin and transferrin in normoalbuminuric patients with type 2 diabetes mellitus

OBJECTIVE

Increased urinary excretion of certain plasma proteins, such as immunoglobulin G (IgG), ceruloplasmin and transferrin, with different molecular radii of 55 Å or less and different isoelectric points have been reported to precede development of microalbuminuria in patients who have diabetes mellitus with hypertension. We examined how hypertension affects these urinary proteins in a diabetic state.

METHODS

Excretion of IgG, ceruloplasmin, transferrin, albumin, α2-macroglobulin with a large molecular radius of 88 Å and N-acetylglucosaminidase in first-morning urine samples were measured in normoalbuminuric patients (urinary albumin-to-creatinine ratio < 15 mg/g) with hypertension and nondiabetes mellitus (group hypertension, n = 32), type 2 diabetes mellitus and normotension (group diabetes mellitus, n = 52) and type 2 diabetes mellitus and hypertension (group Both, n =45), and in age-matched controls (n = 72).

RESULTS

Urinary IgG, ceruloplasmin, transferrin, albumin and N-acetylglucosaminidase and estimated glomerular filtration rate (eGFR) were significantly elevated in groups diabetes mellitus and Both compared with controls. Furthermore, urinary IgG, ceruloplasmin and transferrin in group Both were significantly higher than those in group diabetes mellitus. These exhibited a positive and relatively strong association with eGFR compared with controls. No significant difference in urinary albumin or N-acetylglucosaminidase was found between the two diabetic groups. In contrast, group hypertension had elevated urinary transferrin without any changes in the other compounds. Urinary α2-macroglobulin did not differ among the four groups.

CONCLUSION

These findings suggest that normoalbuminuric diabetic patients without hypertension have both glomerular hemodynamic changes such as increased intraglomerular hydraulic pressure and altered proximal tubules, and that hypertension increases intraglomerular hydraulic pressure. Increased urinary IgG, ceruloplasmin and transferrin may reflect an increase in intraglomerular hydraulic pressure.

New insights into molecular mechanisms of diabetic kidney disease

Diabetic kidney disease remains a major microvascular complication of diabetes and the most common cause of chronic kidney failure requiring dialysis in the United States. Medical advances over the past century have substantially improved the management of diabetes mellitus and thereby have increased patient survival. However, current standards of care reduce but do not eliminate the risk of diabetic kidney disease, and further studies are warranted to define new strategies for reducing the risk of diabetic kidney disease. In this review, we highlight some of the novel and established molecular mechanisms that contribute to the development of the disease and its outcomes. In particular, we discuss recent advances in our understanding of the molecular mechanisms implicated in the pathogenesis and progression of diabetic kidney disease, with special emphasis on the mitochondrial oxidative stress and microRNA targets. Additionally, candidate genes associated with susceptibility to diabetic kidney disease and alterations in various cytokines, chemokines, and growth factors are addressed briefly.

SOD1, but not SOD3, deficiency accelerates diabetic renal injury in C57BL/6-Ins2(Akita) diabetic mice

Superoxide dismutase (SOD) is a major defender against excessive superoxide generated under hyperglycemia. We have recently reported that renal SOD1 (cytosolic CuZn-SOD) and SOD3 (extracellular CuZn-SOD) isoenzymes are remarkably down-regulated in KK/Ta-Ins2(Akita) diabetic mice, which exhibit progressive diabetic nephropathy (DN), but not in DN-resistant C57BL/6- Ins2(Akita) (C57BL/6-Akita) diabetic mice. To determine the role of SOD1 and SOD3 in DN, we generated C57BL/6-Akita diabetic mice with deficiency of SOD1 and/or SOD3 and investigated their renal phenotype at the age of 20 weeks. Increased glomerular superoxide levels were observed in SOD1(-/-)SOD3(+/+) and SOD1(-/-)SOD3(-/-) C57BL/6-Akita mice but not in SOD1(+/+)SOD3(-/-) C57BL/6-Akita mice. The SOD1(-/-)SOD3(+/+) and SOD1(-/-)SOD3(-/-) C57BL/6-Akita mice exhibited higher glomerular filtration rate, increased urinary albumin levels, and advanced mesangial expansion as compared with SOD1(+/+)SOD3(+/+) C57BL/6-Akita mice, yet the severity of DN did not differ between the SOD1(-/-)SOD3(+/+) and SOD1(-/-)SOD3(-/-) C57BL/6-Akita groups. Increased renal mRNA expression of transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF), reduced glomerular nitric oxide (NO), and increased renal prostaglandin E2 (PGE2) production were noted in the SOD1(-/-)SOD3(+/+) and SOD1(-/-)SOD3(-/-) C57BL/6-Akita mice. This finding indicates that such renal changes in fibrogenic cytokines, NO, and PGE2, possibly caused by superoxide excess, would contribute to the development of overt albuminuria by promoting mesangial expansion, endothelial dysfunction, and glomerular hyperfiltration. The present results demonstrate that deficiency of SOD1, but not SOD3, increases renal superoxide in the setting of diabetes and causes overt renal injury in nephropathy-resistant diabetic mice, and that SOD3 deficiency does not provide additive effects on the severity of DN in SOD1-deficient C57BL/6-Akita mice.

Urinary markers of glomerular injury in diabetic nephropathy

Diabetic nephropathy, the leading cause of renal failure worldwide, affects approximately one-third of all people with diabetes. Microalbuminuria is considered the first sign and the best predictor of progression to renal failure and cardiovascular events. However, albuminuria has several limitations. Therefore, earlier, more sensitive and specific biomarkers with greater predictability are needed. The aim of this paper is to discuss the current literature on biomarkers of glomerular injury that have been implicated in diabetic kidney disease.

Induction of oxidative stress in kidney

Oxidative stress has a critical role in the pathophysiology of several kidney diseases, and many complications of these diseases are mediated by oxidative stress, oxidative stress-related mediators, and inflammation. Several systemic diseases such as hypertension, diabetes mellitus, and hypercholesterolemia; infection; antibiotics, chemotherapeutics, and radiocontrast agents; and environmental toxins, occupational chemicals, radiation, smoking, as well as alcohol consumption induce oxidative stress in kidney. We searched the literature using PubMed, MEDLINE, and Google scholar with “oxidative stress, reactive oxygen species, oxygen free radicals, kidney, renal injury, nephropathy, nephrotoxicity, and induction”. The literature search included only articles written in English language. Letters or case reports were excluded. Scientific relevance, for clinical studies target populations, and study design, for basic science studies full coverage of main topics, are eligibility criteria for articles used in this paper.

Differential proteome profiling using iTRAQ in microalbuminuric and normoalbuminuric type 2 diabetic patients

Diabetic nephropathy (DN) is a long-term complication of diabetes mellitus that leads to end-stage renal disease. Microalbuminuria is used for the early detection of diabetic renal damage, but such levels do not reflect the state of incipient DN precisely in type 2 diabetic patients because microalbuminuria develops in other diseases, necessitating more accurate biomarkers that detect incipient DN. Isobaric tags for relative and absolute quantification (iTRAQ) were used to identify urinary proteins that were differentially excreted in normoalbuminuric and microalbuminuric patients with type 2 diabetes where 710 and 196 proteins were identified and quantified, respectively. Some candidates were confirmed by 2-DE analysis, or validated by Western blot and multiple reaction monitoring (MRM). Specifically, some differentially expressed proteins were verified by MRM in urine from normoalbuminuric and microalbuminuric patients with type 2 diabetes, wherein alpha-1-antitrypsin, alpha-1-acid glycoprotein 1, and prostate stem cell antigen had excellent AUC values (0.849, 0.873, and 0.825, resp.). Moreover, we performed a multiplex assay using these biomarker candidates, resulting in a merged AUC value of 0.921. Although the differentially expressed proteins in this iTRAQ study require further validation in larger and categorized sample groups, they constitute baseline data on preliminary biomarker candidates that can be used to discover novel biomarkers for incipient DN.

Oxidative stress and diabetic kidney disease

The number of people with diabetic kidney disease continues to increase worldwide despite current treatments. Of the pathophysiologic mechanisms that have been identified in the development and progression of diabetic nephropathy, oxidative stress (more accurately described as increased levels of reactive oxygen species; ROS) is of major importance. The increase in ROS is due to both increased production and to decreased and/or inadequate antioxidant function. To date, human clinical trials with antioxidants have not been shown to be effective. This is likely due, at least in part, to the lack of specificity of current agents. Recent research has determined both major sources of high glucose-induced cellular ROS production as well as high glucose-induced changes in antioxidant function. Treatments targeted at one or more of the specific diabetes-induced alterations in the regulation of ROS levels will likely lead to effective treatments that prevent the development and progression of diabetic kidney disease.

A glimpse of various pathogenetic mechanisms of diabetic nephropathy

Diabetic nephropathy is a well-known complication of diabetes and is a leading cause of chronic renal failure in the Western world. It is characterized by the accumulation of extracellular matrix in the glomerular and tubulointerstitial compartments and by the thickening and hyalinization of intrarenal vasculature. The various cellular events and signaling pathways activated during diabetic nephropathy may be similar in different cell types. Such cellular events include excessive channeling of glucose intermediaries into various metabolic pathways with generation of advanced glycation products, activation of protein kinase C, increased expression of transforming growth factor β and GTP-binding proteins, and generation of reactive oxygen species. In addition to these metabolic and biochemical derangements, changes in the intraglomerular hemodynamics, modulated in part by local activation of the renin-angiotensin system, compound the hyperglycemia-induced injury. Events involving various intersecting pathways occur in most cell types of the kidney.

Effect of experimental hyperglycaemia on renal haemodynamics in prediabetic patients with and without AT1 receptor blockade

BACKGROUND AND OBJECTIVES

To prevent diabetic nephropathy, knowledge about early renal impairment caused by a disturbed glucose homoeostasis is essential. The purpose of our study was to investigate haemodynamic changes of the kidney in subjects with impaired glucose tolerance (prediabetics, IGT) during experimental hyperglycaemia and the effect of angiotensin receptor blockade.

DESIGN

In our prospective case control study, we measured renal haemodynamics in 13 non-albuminuric males with normal kidney function and IGT (diagnosed by an oral glucose tolerance test, OGTT) and in 13 matched controls with a normoglycemic response in the OGTT. Glomerular filtration rate (GFR) was assessed by determination of sinistrin clearance; renal plasma flow (RPF) by para-aminohippuric acid clearance. All measurements were performed at rest and during hyperglycaemic stress testing (clamp technique; target blood glucose approximately 170 mg dL(-1)). We examined renal effects of valsartan (4 weeks 160 mg day(-1)) at rest and during experimental hyperglycaemia. Metabolic (glycosylated haemoglobin, adiponectin) and inflammatory (high sensitive C-reactive protein) parameters were compared with and without valsartan in both groups.

RESULTS

During experimental hyperglycaemia, GFR and RPF decreased significantly more in prediabetics compared with controls. Under valsartan, the hyperglycaemia induced decrease of GFR and RPF was blunted in part by valsartan. Hs-CRP and HbA1c were significantly higher in prediabetics when compared with controls and improved both under valsartan. Adiponectin was lower in prediabetics and increased significantly under valsartan.

CONCLUSIONS

Hyperglycaemia induces impairments of renal haemodynamics as well as inflammatory and metabolic parameters in subjects with impaired glucose tolerance, which improve under valsartan.

Autoantibodies in type 2 diabetes induce stress fiber formation and apoptosis in endothelial cells

CONTEXT

Macular edema contributes to visual impairment, and albuminuria is associated with increased cardiovascular mortality in adults with type 2 diabetes mellitus. These microvascular complications result from increased capillary leakage of plasma proteins whose causation is not completely understood.

OBJECTIVE

The objective of the present study was to test whether plasma from type 2 diabetes with maculopathy/albuminuria or control subjects contains autoantibodies that can induce apoptosis or activate Rho kinase (ROCK) in endothelial cells.

DESIGN

A cohort of Veterans Affairs Diabetes Trial adults (>40 yr of age) was randomized to standard vs. intensive glycemic treatment lasting 5-7.5 yr.

SETTING

The study was conducted in outpatient clinics.

PATIENTS

Case and age-matched control subjects who differed for the baseline presence of significant diabetic maculopathy and/or progression to macro-albuminuria were included in the study.

INTERVENTION

Pharmacological and lifestyle interventions in the Veterans Affairs Diabetes Trial generally resulted in substantially improved glycemic, blood pressure, and lipid levels.

RESULTS

Autoantibodies from patients with macular edema or progression to albuminuria potently induced caspase-dependent apoptosis in endothelial cells (up to 60%), whereas IgG from age-matched normal plasma caused much less apoptosis (<10%; P < 0.0001). The active inhibitory autoantibodies triggered stress fiber formation in endothelial cells likely through the activation of Rho guanosine 5'-triphosphatase, which could be nearly completed inhibited by 10 microm Y27632, a specific ROCK inhibitor.

CONCLUSIONS

These results suggest that autoantibodies from a subset of advanced type 2 diabetes may contribute to diabetic vascular complications by activating ROCK, inducing stress fiber formation and apoptosis in endothelial cells.

Salt-resistant blood pressure and salt-sensitive renal autoregulation in chronic streptozotocin diabetes

Hyperfiltration occurs in early type 1 diabetes mellitus in both rats and humans. It results from afferent vasodilation and thus may impair stabilization of glomerular capillary pressure by autoregulation. It is inversely related to dietary salt intake, the "salt paradox." Restoration of normal glomerular filtration rate (GFR) involves increased preglomerular resistance, probably mediated by tubuloglomerular feedback (TGF). To begin to test whether the salt paradox has pathogenic significance, we compared intact vs. diabetic (streptozotocin) Long-Evans rats with normal and increased salt intake, 1 and approximately 3% by weight of food eaten, respectively. Weekly 24-h blood pressure records were acquired by telemetry before and during diabetes. Blood glucose was maintained at approximately 20 mmol/l by insulin implants. GFR was significantly elevated only in diabetic rats on normal salt intake, confirming diabetic hyperfiltration and the salt paradox. Renal blood flow dynamics show strong contributions to autoregulation by both TGF and the myogenic mechanism and were not impaired by diabetes or by increased salt intake. Separately, systolic pressure was not elevated in diabetic rats at any time during 12 wk with normal or high salt intake. Autoregulation was effective in all groups, and the diabetic-normal salt group showed significantly improved autoregulation at low perfusion pressures. Histological examination revealed very minor glomerulosclerosis and modest mesangial expansion, although neither was diagnostic of diabetes. Periodic acid-Schiff-positive droplets found in distal tubules and collecting duct segments were diagnostic of diabetic kidneys. Biologically significant effects attributable to increased salt intake were abrogation of hyperfiltration and of the left shift in autoregulation in diabetic rats.

Natriuretic peptide/natriuretic peptide receptor-A (NPR-A) system has inhibitory effects in renal fibrosis in mice

OBJECT

This study was designed to examine whether natriuretic peptide/natriuretic peptide receptor-A (NPR-A) system attenuates renal fibrosis in a unilateral ureteral obstruction (UUO) model and also examined the mechanism involved.

METHODS

Three groups were studied: untreated UUO in wild-type mice; untreated UUO in NPR-A KO mice; and ANP treated (0.05 microg/kg/min) UUO in wild-type mice. We measured histological and immunohistochemical findings (alpha-SMA and F4/80), tissue cGMP levels, various mRNA expression levels by real-time PCR analysis, and transcription factor levels (AP-1 and NF-kappaB) in renal tissue.

RESULTS

Compared with wild-type UUO mice, NPRA-KO UUO mice had abnormal morphological findings (fibrous area: +26%, alpha-SMA expression: +30%) with lower tissue cGMP levels and increases in the mRNA expression levels of TGF-beta, collagen I, collagen III, PAI-1, renin and angiotensinogen, whereas there were no differences in F4/80 positive cells or the mRNA expression levels of ICAM-1, osteopontin, or MCP-1 between the two groups. In contrast, ANP pre-treatment significantly improved morphological changes with increase of tissue cGMP levels and reduction in the mRNA expression level of TGF-beta, collagen I, collagen III, PAI-1, ICAM-1, osteopontin, MCP-1, renin, and angiotensinogen. NPRA-KO UUO mice had higher AP-1 levels than wild-type UUO mice and ANP pre-treatment reduced AP-1 and NF-kappaB activity.

CONCLUSION

The endogenous natriuretic peptide/NPR-A system may inhibit renal fibrosis partly via inhibition of the angiotensin/AP-1/TGF-beta/collagen pathway and exogenous ANP pre-treatment may inhibit it partly via both the angiotensin/AP-1/TGF-beta/collagen and NF-kappaB/inflammatory pathways.

Renal injury in streptozotocin-diabetic Ren2-transgenic rats is mainly dependent on hypertension, not on diabetes

Induction of streptozotocin (STZ) diabetes in hypertensive rats transgenic for the mouse ren-2 gene (TGR) has been described as a model of progressive diabetic nephropathy. We investigated the long-term course of STZ diabetes in TGR and appropriate Sprague-Dawley control rats (SD) and tested the role of angiotensin-dependent hypertension by treating rats with the angiotensin II type 1 receptor blocker losartan (1 mg·kg−1·day−1) via osmotic minipumps. Five weeks after STZ injection, diabetes developed in TGR and SD. Urinary albumin excretion was increased by diabetes and, to a much higher degree, by hypertension. The effects of hypertension and diabetes were not additive, and only the effects of hypertension were ameliorated by losartan. A similar pattern was observed for cell proliferation and macrophage infiltration in the kidney. In contrast, the effects of hypertension and diabetes on glomerular collagen IV accumulation were additive 5 wk after STZ injection. In a long-term study for 20 wk after STZ, survival was better in STZ-treated TGR than in normoglycemic TGR, whereas all SD survived. Impaired creatinine clearance and increased macrophage infiltration as well as glomerular and interstitial matrix deposition were prominent in TGR compared with SD, regardless of the presence or absence of diabetes. In conclusion, STZ diabetes in TGR may be useful to study glomerular and interstitial matrix deposition early in the course of diabetes. However, the long-term course of this animal model resembles severe hypertensive nephrosclerosis, rather than progressive diabetic nephropathy.

Glomerular hyperfiltration in non-proteinuric and non-hypertensive Japanese type 2 diabetic patients

Glomerular hyperfiltration (GHF) may be an important factor in the initiation of glomerular damage and in predisposing diabetic patients to the later development of diabetic nephropathy (DN). Previous reports show wide range of prevalence of GHF in type 2 diabetic patients. This cross-sectional study was designed to determine the prevalence of GHF at an early stage of DN in Japanese type 2 diabetic patients and to investigate the relationships between clinical variables and GHF. We measured the glomerular filtration rate (GFR) using the plasma clearance of iohexol in 56 control subjects and 93 type 2 diabetic patients without hypertension or overt proteinuria. We used Altman's method to calculate the age-adjusted 95% reference ranges for GFR from the data of control subjects and classified GHF in type 2 diabetics from the reference ranges. Hyperfiltrators (defined as GFR > mean GFR + 1.96 S.D. of control subjects) was found in 17% patients (16/93). Other 77 patients (83%) were normofiltrators (defined as GFR< or = mean GFR + 1.96 S.D. of control subjects). GFR values, both in hyperfiltrators and normofiltrators, were 140.5 +/- 14.6 and 98.8 +/- 14.0 ml/min/1.73 m2, respectively. Age, sex, BMI, blood pressure, albumin excretion rate, and frequency of microalbuminuria did not differ between the hyperfiltrators and normofiltrators. Fasting plasma glucose and hemoglobin A1c were significantly higher in the hyperfiltrators than the normofiltrators (P<0.001 and 0.004, respectively). GHF exists among Japanese type 2 diabetic patients with no evidence of overt proteinuria or hypertension. Glycemic control might be a significant determinant of GHF in these patients.

Characterization of susceptibility of inbred mouse strains to diabetic nephropathy

Differential susceptibility to diabetic nephropathy has been observed in humans, but it has not been well defined in inbred strains of mice. The present studies characterized the severity of diabetic nephropathy in six inbred mouse strains including C57BL/6J, DBA/2J, FVB/NJ, MRL/MpJ, A/J, and KK/HlJ mice. Diabetes mellitus was induced using low-dose streptozotocin injection. Progression of renal injury was evaluated by serial measurements of urinary albumin excretion, glomerular filtration rate (GFR), and terminal assessment of renal morphology over 25 weeks. Despite comparable levels of hyperglycemia, urinary albumin excretion and renal histopathological changes were dramatically different among strains. DBA/2J and KK/HlJ mice developed significantly more albuminuria than C57BL/6J, MRL/MpJ, and A/J mice. Severe glomerular mesangial expansion, nodular glomerulosclerosis, and arteriolar hyalinosis were observed in diabetic DBA/2J and KK/HlJ mice. Glomerular hyperfiltration was observed in all diabetic strains studied except A/J. The significant decline in GFR was not evident over the 25-week period of study, but diabetic DBA/2J mice exhibited a tendency for GFR to decline. Taken together, these results indicate that differential susceptibility to diabetic nephropathy exists in inbred mice. DBA/2J and KK/HlJ mice are more prone to diabetic nephropathy, whereas the most widely used C57BL/6J mice are relatively resistant to development of diabetic nephropathy.

Glomerular structural changes in pregnant, diabetic, and pregnant-diabetic rats

Kidneys enlarge both during pregnancy and in diabetes. The enlargement and morphology of glomeruli was studied during pregnancy and in diabetes in order to examine possible similarities, differences, and interactions in the growth in these conditions. Morphometric investigations were performed on glomeruli in pregnant rats, in rats with 2 weeks' diabetes, and in pregnant-diabetic rats. Kidneys were enlarged 22% in the midterm pregnant rats compared with controls, 74% in diabetic rats, and a further 21% in pregnant-diabetic rats. Glomerular volume was enlarged by 26% during midterm pregnancy in normal animals. Diabetes induced an enlargement in glomerular volume of 58% and a further 18% in midterm diabetic animals due to pregnancy. Within the glomerulus, pregnancy in normal animals induced minor non-significant changes. Diabetes induced significant increase in several parameters: mesangial volume and cell volume, capillary and glomerular basement membrane volume, capillary wall surface area, foot process width, filtration slit length, and nuclear number. Pregnancy in diabetic animals induced no significant additional changes. In conclusion, kidney enlargement in pregnancy shows very few glomerular changes in either normal or diabetic animals. Enlargement of glomeruli in diabetes involves hypertrophy and hyperplasia concurrent with several morphological changes within the glomerulus.

Urinary excretion of transferrin and orosomucoid are increased after acute protein loading in healthy subjects

BACKGROUND/AIMS

The aim of this study was to elucidate what kind of plasma proteins would change their urinary excretions when the glomerular filtration rate (GFR) was increased.

METHODS

We measured urinary excretions of three plasma proteins with different molecular radii (MR) and isoelectric points (pI): albumin, orosomucoid (OM) and transferrin (Tf), after acute protein loading in healthy subjects.

RESULTS

Urinary excretion of OM with more anioic charge and smaller MR than albumin, and Tf with more cationic charge and slightly larger molecular weight than albumin, significantly increased in parallel with increased creatinine clearances after acute protein loading. These renal responses returned to basal levels 9 h after protein ingestion. In contrast, increases in urinary excretion of albumin were not observed.

CONCLUSION

Because these findings could not be explained by changes in either size or charge selectivity of shunt pores in the glomerular capillary wall, it is suggested that urinary excretion of albumin may have a special property that distinguishes it from other plasma proteins and may be a less sensitive marker to reflect changes in renal hemodynamics than the other plasma proteins.

Parallel increase in urinary excretion rates of immunoglobulin G, ceruloplasmin, transferrin, and orosomucoid in normoalbuminuric type 2 diabetic patients

OBJECTIVE

Increased urinary excretions of several plasma proteins with different molecular radii <55 A and different isoelectric points (pI), such as IgG, ceruloplasmin, transferrin, and orosomucoid, have been independently reported to precede the development of microalbuminuria in diabetic patients. We examined whether increases in urinary excretions of these proteins would be in parallel in the same patient.

RESEARCH DESIGN AND METHODS

Urinary excretion rates of proteins mentioned above in timed overnight urine samples were evaluated in 61 normoalbuminuric type 2 diabetic patients (group D) aged 40-60 years and in 17 age-matched control subjects (group C).

RESULTS

The excretion rates of these proteins were significantly higher in group D than in group C. These exhibited a strong linear correlation with each other and had a weak correlation with the excretion rate of N-acethylglucosaminidase. The excretion rate of alpha2-macroglobulin with large molecular radii of 88 A was not different between groups C and D, nor did they have any correlations with the excretion rates of the other proteins. Creatinine clearance and blood pressure levels in group D were significantly higher than those in group C.

CONCLUSIONS

In normoalbuminuric diabetic patients, excretion rates of plasma proteins with molecular radii <55 A increased in parallel with each other. In view of our previous finding that urinary excretions of these plasma proteins selectively increased in parallel with enhanced glomerular filtration rate after acute protein loading, the present finding may be explained by renal hemodynamic changes, such as increased intraglomerular hydraulic pressure.

Impact of renin angiotensin system blockade on renal function in health and disease: an end or a beginning?

Substantial reduction of functioning nephrons from any origin is followed by a relentless progression to chronic renal failure. This progression continues long after the acute nephropathy and its initiating events have subsided. Glomerular hypertension and hyperfiltration are the major contributors to this progressive nephron loss. Studies on the adverse effects of hemodynamic changes and attempts to define the modalities that slow the rate of progression of renal disease have been among the dominant trends in modern nephrology. Numerous animal studies as well as recent clinical trials indicate that blockade of the renin angiotensin system effectively retards progression of nephropathy from diverse origins.

Altered electromechanical coupling in the renal microvasculature during the early stage of diabetes mellitus

1. The early stage of type 1 diabetes mellitus (DM) is characterized by renal hyperfiltration, which promotes the eventual development of diabetic nephropathy. The hyperfiltration state is associated with afferent arteriolar dilation and diminished responsiveness of this vascular segment to a variety of vasoconstrictor stimuli, whereas efferent arteriolar diameter and vasoconstrictor responsiveness are typically unaltered. 2. The contractile status of preglomerular vascular smooth muscle appears to be tightly coupled to membrane potential (E(m)) and its influence on Ca(2+) influx through voltage-gated channels. Efferent arteriolar tone is largely independent of electromechanical events. Hence, defective electromechanical mechanisms in vascular smooth muscle should engender selective changes in preglomerular microvascular function, such as those evident during the early stage of DM. 3. Afferent arteriolar contractile responses to K(+)-induced depolarization and BAYK8644 are diminished 2 weeks after onset of DM in the rat. Similarly, depolarization-induced Ca(2+) influx and the resulting increase in intracellular [Ca(2+)] are abated in the preglomerular microvasculature of diabetic rats. The intracellular [Ca(2+)] response to depolarization is rapidly restored by normalization of extracellular glucose levels. These observations suggest that hyperglycaemia in DM impairs regulation of afferent arteriolar voltage-gated Ca(2+) channels. 4. Dysregulation of E(m) may also contribute to afferent arteriolar dilation in DM. Vasodilator responses to pharmacological opening of ATP-sensitive K(+) channels are exaggerated in afferent arterioles from diabetic rats. Moreover, blockade of these channels normalizes afferent arteriolar diameter in kidneys from diabetic rats. These observations suggest that increased functional availability and basal activation of ATP-sensitive K(+) channels promote afferent arteriolar dilation in DM. 5. We propose that dysregulation of E(m) (involving ATP- sensitive K(+) channels) and a diminished Ca(2+) influx response to depolarization (involving voltage-gated Ca(2+) channels) may act synergistically to promote preglomerular vasodilation during the early stage of DM.

Renal vascular responses to captopril and to candesartan in patients with type 1 diabetes mellitus

BACKGROUND

Enhanced renal vasodilator responses to angiotensin-converting enzyme (ACE) inhibition in diabetes mellitus despite a normal or low plasma renin activity level have suggested intrarenal activation of the renin-angiotensin system in this disease. There is, however, a continuing debate as to the mediators of the renal hemodynamic response to ACE inhibition-reduced angiotensin II formation or pathways involving kinins, prostaglandins, and nitric oxide.

METHODS

Twelve patients with type 1 diabetes mellitus of 18 +/- 3.2 (SEM) years of duration (7 females and 5 males, ages 17 to 50, 32 +/- 4.0 years) who were free of sustained microalbuminuria and on a high-salt diet were given the ACE inhibitor captopril (25 mg orally) on one day and the AT1 receptor blocker candesartan (16 mg orally) on another day. Renal plasma flow (RPF) and glomerular filtration rate were measured before and for four hours after administration.

RESULTS

Both drugs caused a significant increase in RPF (captopril 574 +/- 26 to 625 +/- 37 mL/min/1.73 m2, P = 0.008; candesartan 577 +/- 26 to 643 +/- 37, P = 0.004). There was a highly significant correlation between the responses to captopril and to candesartan (r = 0.86, P < 0.001). Seven subjects had an RPF response to captopril that was accentuated (90 +/- 13 mL/min/1.73 m2), while five had a response that was normal (-4 +/- 9). There was no significant change in glomerular filtration rate on either drug.

CONCLUSION

The remarkable rise in RPF in response to captopril and candesartan despite high-salt balance suggests the intrarenal activation of the renin-angiotensin system in diabetes that is not reflected in plasma renin levels. The high correlation between the renal hemodynamic response to captopril and to candesartan indicates that reduced angiotensin II formation is the main mechanism of action of the ACE inhibitor.

Exaggerated impact of ATP-sensitive K(+) channels on afferent arteriolar diameter in diabetes mellitus

Experiments were performed to determine the involvement of ATP-sensitive K(+) channels (K(ATP) channels) in the renal afferent arteriolar dilation that occurs during the hyperfiltration stage of insulin-dependent diabetes mellitus (IDDM). IDDM was induced in rats by streptozotocin (STZ) injection, and adequate insulin was provided to maintain moderate hyperglycemia. Sham rats received vehicle treatments. Two weeks later, afferent arteriolar function was assessed using the in vitro blood-perfused juxtamedullary nephron technique. Baseline afferent arteriolar lumen diameter was greater in STZ rats (25.9 +/- 1.1 microm) than in sham rats (20.8 +/- 1.0 microm). Glibenclamide (3 to 300 microM) had virtually no effect on afferent arterioles from sham rats; however, this K(ATP) antagonist caused concentration-dependent afferent arteriolar constriction in kidneys from STZ-treated rats, restoring lumen diameter to 20.6 +/- 1.7 microm (P > 0.05 versus sham baseline). In both groups of rats, pinacidil (a cyanoguanidine K(ATP) agonist; 0.3 to 300 microM) evoked concentration-dependent afferent arteriolar dilation, indicating the functional expression of K(ATP) channels; however, lumen diameter was increased by 73% in STZ kidneys but only by 48% in sham kidneys. The gliben-clamide-sensitive afferent arteriolar dilator response to 1 microM PCO-400 (a benzopyran K(ATP) agonist) was also accentuated in STZ kidneys. These observations suggest that increases in both the functional availability and basal activation of K(ATP) channels promote afferent arteriolar vasodilation during the early stage of IDDM, changes that likely contribute to the etiology of diabetic hyperfiltration.

Octreotide administration in diabetic rats: effects on renal function and morphology

The effects of synthetic somatostatin analogue, octreotide, on fractional kidney weight (FKW), urinary protein excretion (UPE), creatinine clearance (Cl(cre)) and renal morphological changes were studied in alloxan-diabetic and non-diabetic rats comparatively. Diabetic rats were treated with twice daily s.c. injections of octreotide (2x2.5 microg) for 90 days. Untreated diabetic and non-diabetic animals were used as reference. The body weights and blood glucose levels of the animals were followed-up throughout the study period. After 90 days, FKW and renal morphology were evaluated. When compared to octreotide-treated diabetic group (O-D: 1.96+/-0. 23), normal control rats (NC: 1.24+/-0.05) showed a lower FKW (P<0. 05) and the FKW value of non-treated diabetic controls (DC: 2.74+/-0. 17) were significantly higher (P<0.05). Cl(cre) values were calculated at 45th and 90th days. At the 45th day, Cl(cre) values (ml/min) of O-D group (0.75+/-0.06) and NC group (0.56+/-0.09) were significantly lower than non-treated DC group (1.05+/-0.1) (P<0.05). However, at the 90th day no significant difference in Cl(cre) was observed. At the 45th day, UPE (mg/dl/day) was significantly higher in non-treated DC group (1000.45+/-392.38) when compared to NC group (236+/-36.59) (P<0.005) and UPE levels of O-D group were only slightly lower than that of non-treated diabetic group. At the 90th day, no significant beneficial effect of octreotide on UPE was observed. Octreotide did not prevent the histopathological changes related to diabetes. In conclusion, 5 microg/day octreotide administrations to diabetic rats for 90 days prevented renal weight increase but this treatment were insufficient to decrease the histopathological changes, UPE and increased Cl(cre).

Lack of association between the heparan sulfate proteoglycan gene polymorphism and diabetic nephropathy in Japanese NIDDM with proliferative diabetic retinopathy

The development of diabetic nephropathy shows remarkable variation among individuals. Therefore, not only hyperglycemia but also genetic factors may contribute to the development of diabetic nephropathy Heparan sulfate proteoglycan (HSPG) is thought to play an important role as a component of the charge selectivity barrier in the glomerular basement membrane. Recently, a BamHI restriction fragment length polymorphism (RFLP) in the HSPG gene (HSPG2) was reported to be associated with diabetic nephropathy in Caucasian insulin-dependent diabetes mellitus (IDDM). The aim of the present study was to examine the contribution of the BamHI HSPG2 polymorphism to the development of diabetic nephropathy in Japanese non-insulin-dependent diabetes mellitus (NIDDM). For this purpose, we recruited 102 patients with diabetic nephropathy and 64 age-matched patients without diabetic nephropathy from Japanese NIDDM patients. Since all the subjects had proliferative diabetic retinopathy, it seems likely that they would be exposed to hyperglycemia for a long time. In the present study, the BamHI HSPG2 genotype and allele frequencies were not significantly different between the patients with nephropathy and the patients without nephropathy. Therefore, we conclude that the BamHI HSPG2 polymorphism is not associated with the development of diabetic nephropathy in Japanese NIDDM.

Urinary excretion of ceruloplasmin is elevated in the subjects with "borderline glucose tolerance test"

To examine whether or not there are any renal alterations in subjects with borderline glucose tolerance and in patients with non-insulin dependent diabetes mellitus (NIDDM) classified by the criteria of Japan Diabetic Association, urinary excretions of plasma proteins including albumin, ceruloplasmin (Cerulo) and IgG were measured in timed overnight urine samples. Eighty middle-aged, non-obese, normotensive, untreated men with urinary albumin excretion rates below 20 microg/minutes, beta2-microglobulin excretion rates below 140 microg/minutes and creatinine clearance values exceeding 80 ml x min(-1) x (1.73 m2)(-1) were included in this study. Three groups were defined according to the results of 75 g oral glucose tolerance test (OGTT) as follows: D group, 10 subjects with NIDDM; B group, 40 subjects with "borderline glucose tolerance test" and N group, 30 subjects with normal glucose tolerance. The fractional clearance (theta) of Cerulo, but not albumin and IgG, was elevated in 37. 5% of the B group compared with the upper limit of that of the N group. Furthermore, theta-Cerulo and theta-IgG increased in the D group compared with those of the N and the B groups. Recently, we found that theta-Cerulo and theta-IgG increased in healthy volunteers when GFR was elevated by acute protein loading and that increase in theta-Cerulo is remarkable than increase in theta-IgG. The present result, taken together with our recent finding mentioned above, suggests that increases in theta-Cerulo and theta-IgG may not be due to an impairment of charge selectivity in the glomerular basement membrane, but due to an increase of intraglomerular hydraulic pressure.

Diabetes, microalbuminuria and hypertension

Diabetes is a chronic condition which poses a risk for three major complications. They are diabetic retinopathy, nephropathy and neuropathy. Almost one third of diabetic patients (IDDM or NIDDM) develop diabetic nephropathy in their life time. Because of increased vascular permeability in chronic conditions increased urinary albumin excretion in the range of 30-200 mg/L (microalbuminuria) gives an early signal of incipient diabetic nephropathy. The prevalence of microalbuminuria was found to be 41% in diabetic patients with duration of more than 5 years. Seventy percent of diabetic patients with microalbuminuria were hypertensive. ACE inhibitors are shown to have significant effects on microalbuminuria and hypertension. We conclude that microalbuminuria is an early feature of excessive capillary leakage and its assessment in diabetic patients with duration of more than 5 years provides a simple non-invasive method of early diagnosis of incipient diabetic nephropathy. An early intervention may retard the progression to end-stage renal disease (ESRD).

d-alpha-tocopherol treatment prevents glomerular dysfunctions in diabetic rats through inhibition of protein kinase C-diacylglycerol pathway

Since diabetes now accounts for 35% of all new cases of end-stage renal disease in the United States, it is really important to prevent the onset of diabetic nephropathy. Activation of protein kinase C (PKC) is implicated to be one of the causal factors in the development of renal dysfunctions in diabetes. In this study, we have demonstrated that total diacylglycerol (DAG) contents and PKC activity in glomeruli were significantly increased in diabetic rats as compared to control rats, but intraperitoneal injection of d-alpha-tocopherol prevented these biochemical abnormalities in parallel with normalization of glomerular dysfunction such as increased glomerular filtration rate (GFR) in diabetic rats. Albuminuria in diabetic rats was also significantly increased as compared to control rats, whereas d-alpha-tocopherol treatment again ameriolated increased albuminuria in parallel with the inhibition of glomerular PKC activation by diabetes. Moreover, we have observed that the activity of DAG kinase, which metabolizes DAG to phosphatidic acid and acts as an attenuator for the DAG-PKC pathway, was enhanced by d-alpha-tocopherol treatment. These results suggest that the increase in the DAG-PKC pathway might play an important role for the development of glomerular dysfunctions in diabetes and d-alpha-tocopherol treatment could be helpful in diabetic nephropathy.

The angiotensin I-converting enzyme (ACE) locus is strongly associated with age and duration of diabetes in patients with type I diabetes

We have investigated the frequency of the angiotensin I-converting enzyme (ACE) insertion/ deletion (I/D) polymorphism in 249 patients with type I diabetes and 162 normal healthy controls. There was no significant difference in the frequency of ACE genotypes between those patients with diabetic nephropathy (n = 72) (nephropaths) compared to those with no proteinuria after 20 years duration of diabetes (n = 86) (normoalbuminurics). There was, however, a significant difference in the frequency of ACE genotypes between the short-duration and long-term normoalbuminuric group (chi = 11.5, p = 0.001). Analysis of the ACE genotypes with respect to age and duration of diabetes showed that homozygosity for the insertion (I/I) genotype was significantly decreased with longer duration of diabetes (r2 = 92.7%, p < 0.009). No association was found with age in the normal controls. In conclusion, these results suggest that the ACE locus may be associated with longevity and survival in patients with type I diabetes rather than diabetic nephropathy or microvascular disease per se.

The acute effect of smoking on systemic haemodynamics, kidney and endothelial functions in insulin-dependent diabetic patients with microalbuminuria

The acute effect of smoking upon arterial blood pressure, urinary albumin excretion rate, glomerular filtration rate and transcapillary escape rate of albumin were investigated in nine normotensive insulin-dependent diabetic patients with microalbuminuria, who had been smoking for 19 (range 4-30) years. In a prospective, open randomized cross-over design, patients were investigated with and without smoking three cigarettes per hour during a 5.5-h period. A rise in systolic blood pressure and heart rate (Takeda TM2420, median (range)) was observed during the smoking day (10(-11 to 14) mmHg and 8 (-1 to 19) beats min-1), compared to the non-smoking day (1 mmHg (-7 to 13) (p = 0.05) and 0 beats min-1 (-2 to 4) (p < 0.01)). Urinary albumin excretion rate (ELISA), glomerular filtration rate (plasma clearance of 51Cr-EDTA) and transcapillary escape rate of albumin (125I-albumin) remained the same with or without smoking. Our study suggests that heavy smoking induces an abrupt rise in systolic blood pressure and heart rate, while vascular leakage of albumin and glomerular filtration rate remain unaltered in normotensive insulin-dependent diabetic patients with microalbuminuria who had been smoking for several years.

Angiotensin converting enzyme gene polymorphism and renal artery resistance in patients with insulin dependent diabetes mellitus

The present study was carried out to elucidate whether renal hemodynamic changes are associated with angiotensin converting enzyme (ACE) gene polymorphism in patients with insulin dependent diabetes mellitus (IDDM). We studied 32 Japanese patients with IDDM (aged 15 +/- 3 years in mean +/- SD) without renal failure or retinopathy. Renal hemodynamics were examined by duplex Doppler sonography and arterial resistance index was calculated. ACE genotypes were determined by polymerase chain reaction amplification. Resistance index (RI) of arcuate arteries in IDDM patients with DD genotype was significantly elevated, being 0.64 +/- 0.04, 0.66 +/- 0.05, and 0.71 +/- 0.05 for II, ID and DD genotype groups, respectively (II vs. DD, p < 0.02). In patients with DD genotype with normoalbuminuria (n = 27), it was also significantly elevated in DD genotype patients (II vs. DD, p < 0.02). In addition, multiple regression analysis with a forward elimination procedure showed that only the ACE genotype was associated with RI of arcuate arteries (R2 = 0.24, p < 0.01) among the parameters of sex, age, IDDM duration, body mass index, HbA1c, plasma glucose levels, serum levels of total cholesterol and creatinine, urinary albumin excretion index, mean blood pressure and ACE genotype. The present study demonstrated that renal arterial resistance is elevated in IDDM patients with DD genotype. ACE gene polymorphism which could be linked to intrarenal circulatory disturbance may be associated with the initiation and progression of diabetic nephropathy.

Acute effect of calcium blocker on renal hemodynamics in diabetic spontaneously hypertensive rat

This study was done to examine the acute effect of a calcium channel blocker on renal hemodynamics in the diabetic spontaneously hypertensive rat (SHR). Streptozotocin was used to induce diabetes, and barnidipine (B) was used as a calcium blocker. Renal blood flow (RBF) and glomerular filtration rate (GFR) were measured by a clearance method with paraaminohypurate (PAH) and inulin, respectively. Rats were divided into two groups: nondiabetic SHR, N-SHR; diabetic SHR, DM-SHR. B increased RBF in N-SHR (7.44 +/- 1.99 versus 8.50 +/- 1.97 mL/min/g.kw) while there was no change in DM-SHR. B reduced renovascular resistance (RVR) in DM-SHR and N-SHR. B increased GFR in N-SHR (1.15 +/- 0.24 versus 1.34 +/- 0.25 mL/min/g.kw), in spite of no changes in DM-SHR. B did not modify filtration fraction (FF) in both groups. These results indicate (1) in SHR, B exerts beneficial effects on hypertensive renal damage by reducing mean arterial pressure (MAP), RVR, RBF, and GFR; (2) in diabetic SHR, B is less effective in restoring renal hyperfiltration in spite of reducing RVR.

The characteristics of renal hemodynamics in diabetic spontaneously hypertensive rats in comparison with diabetic Wistar-Kyoto rats

Diabetic Sprague-Dawley (SD) rats are known to exhibit renal hyperfiltration and hyperperfusion accompanied by renal hypertrophy. We examined whether such characteristics of renal hemodynamics in diabetic SD rats are also observed in diabetic spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. SHR and WKY rats were divided into four groups: D-S, diabetic SHR; N-S, nondiabetic SHR; D-W, diabetic WKY rats; and N-W, nondiabetic WKY rats. Streptozotocin (STZ), 90 mg, was intraperitoneally injected to induce diabetes. Renal blood flow (RBF) and glomerular filtration rate (GFR) were measured by a clearance method with paraaminohypurate and insulin, respectively, 7-12 days after diabetes induction. In D-S and D-W, there was no increase in the kidney weight and RBF, in spite of significant increases in GFR and fasting blood sugar levels. These results indicate that, in both WKY and SHR, diabetes does not always produce renal hypertrophy and does not result in an increase in RBF.

Type II diabetic nephropathy in perspective

The magnitude of type II diabetic nephropathy dilemma is observable in the growing number of diabetic patients with end-stage renal lesion receiving various modalities of treatment. Progressive glomerulopathy associated with proteinuria and hypertension is strongly causative of renal failure and mortality in diabetic patients. Besides hypertension, diabetes exceeds all other glomerulopathies in causing end-stage renal failure. Alterations in glomerular structure and function observed in diabetic patients are implicated in the development and progression of renal derangement. Diabetic glomerulosclerosis, an aggregate of structural and functional perturbations of the kidney, is indicated by alterations in the accumulation of extracellular matrix components, The pathology, epidemiology, risk factors, and other dependent variables may throw some light in the pathogenetic mechanisms and the prevention, treatment, and management modalities of type II diabetic nephropathy.

Angiotensin II in cell growth and matrix production

Glomerular mesangial cells and cardiac fibroblasts have been called "myofibroblasts" because of their phenotypic characteristics (resembling both the fibroblast and muscle cells). Thus, it is not surprising that AII would have similar effects on both cell types, which play critical roles in target organ stress response and wound healing, ultimately leading to remodeling changes. These effects are primarily mediated by the AT1 receptor and include: 1) growth: hyperplasia in cardiac fibroblasts and hypertrophy in normal adult mesangial cells and 2) matrix production: there appears to be an early upregulation of fibronectin message which is later followed by an increase in collagens. It is likely that elevated production of fibronectin may activate signal transduction pathways which lead to increased expression of collagen genes, and which may be critical for the organization and laying down of collagens. Thus, an overall theme that emerges is the impact of AII on both growth and wound repair. Other potential important cellular effects of AII in these systems include: 1) stimulation of growth factors, cytokines, and arachidonic acid products that could have autocrine or paracrine effects, 2) regulation of cell migration and adhesion, 3) alteration of responses to neurohormones, 4) development and maintenance of a differentiated phenotype, and others. Molecular techniques including subtraction hybridization, differential display, antisense knockout, and development of transgenic and embryonic stem cell models will be important in defining the specific role of AII in cardiovascular and renal disease.

Acute and chronic effects of thromboxane A2 inhibition on the renal hemodynamics in streptozotocin-induced diabetic rats

We examined acute and chronic effects of thromboxane (TX) A2 inhibition on the renal hemodynamics at early and late stage of untreated streptozotocin (STZ)-induced diabetic rats. Two weeks and 28 weeks after the induction of diabetes, renal blood flow (RBF) under anesthesia was measured with an electromagnetic flowmeter before and after TXA2 inhibition. In two-week-old diabetic rats, a specific TXA2 synthetase inhibitor, OKY-046, or a specific TXA2 receptor antagonist, Sulotroban, increased renal vascular resistance (RVR) and ameliorated the hyperperfusion. The renal vasoconstrictive effect of OKY-046 was blunted by an angiotensin converting enzyme (ACE) inhibitor, MK422, or an angiotensin II receptor antagonist, Saralasin. On the contrary, OKY-046 ameliorated the renal hypoperfusion by decreasing RVR in 28-week-old diabetic rats. Chronic oral administration of OKY-046 ameliorated not only the renal hyperperfusion but increased urinary albumin excretion (UAE) at two weeks, but also the renal hypoperfusion, filtration fraction and UAE at 24 weeks. It is suggested that TXA2 might, at least in part, play important roles in the hyperperfusion by modulating activity of the renin-angiotensin system at an early stage of untreated diabetic rats and in the hypoperfusion at the late stage of untreated diabetic rats, and that TXA2 is also involved in the increase of UAE. These results support roles for TXA2 in the progression of renal injury in STZ-induced diabetic rats.

Glomerular size- and charge selectivity in type 2 (non-insulin-dependent) diabetic patients with diabetic nephropathy

In an attempt to evaluate the mechanisms of proteinuria in diabetic kidney disease, we measured the renal clearances of albumin, total IgG, and IgG4 in 20 male Type 2 (non-insulin-dependent) diabetic patients with diabetic glomerulosclerosis (biopsy proven), in 10 male Type 2 diabetic patients without nephropathy (urinary albumin excretion rate < or = 30 mg/24 h), and in 10 healthy male subjects. The fractional clearance of albumin was increased in patients with nephropathy: 659 (42-4355) x 10(-6) (median (range)), compared to 2.6 (0.2-14.2) x 10(-6) in patients without nephropathy, and 2.3 (0.4-4.2) x 10(-6) in healthy subjects. The fractional clearance of total IgG (neutral) and of IgG4 (anionic) was 40-50 times higher in patients with nephropathy compared to the two other groups. The IgG/IgG4 selectivity index was not significantly different in the three groups, being: 1.12 (0.06-5.65), 1.16 (0.45-3.72) and 1.35 (0.65-3.34) in patients with nephropathy, patients without nephropathy, and healthy subjects, respectively. The IgG/albumin selectivity index was decreased in patients with nephropathy: 0.27 (0.01-1.26) compared to 1.29 (0.07-2.67) (p < 0.05) and 1.23 (0.76-7.84) (p < 0.001) in patients without nephropathy and healthy subjects, respectively. No significant change in IgG/albumin selectivity index was observed between patients without nephropathy and healthy subjects. The systolic blood pressure was elevated in the patients with nephropathy: 164 +/- 21 mm Hg (mean +/- SD) compared to patients without nephropathy: 145 +/- 20 mm Hg (p < 0.05) and to healthy subjects: 133 +/- 19 mm Hg (p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)