Aspartic acid supplementation ameliorates symptoms of diabetic kidney disease in mice.

Diabetic kidney disease (DKD) is among the most common and serious complications of both type 1 and type 2 diabetes. In this study, we used KK/Ta-Ins2Akita (KK-Akita) mice as a model of DKD and KK/Ta (KK) mice as controls to identify novel factors related to the development/progression of DKD. Capillary electrophoresis coupled with mass spectrometry analysis revealed that circulating Asp (l-aspartic acid) levels in diabetic KK-Akita mice tend to be lower than those in control KK mice. Therefore, we evaluated the effect of Asp supplementation to prevent the progression of DKD in KK-Akita mice. Mice were divided into three groups: (a) untreated KK mice (Control group), (b) untreated KK-Akita mice (DKD group), and (c) treated (double-volume Asp diet) KK-Akita mice (Tx group). Kidney sections were stained with fluorescein isothiocyanate-labeled lectins, wheat germ agglutinin (WGA), and anti-endothelial nitric oxide synthase (eNOS) antibody for evaluation of endothelial surface layer (ESL) and NO synthesis. The mesangial area and glomerular size in the DKD group were significantly larger than those in the Control group; however, there was no significant difference in those between the DKD and Tx groups. Albuminuria, the ratio of foot process effacement, and thickness of glomerular basement membrane in the Tx group were significantly lower than those in the DKD group. Furthermore, the expression levels of glomerular WGA and microvascular eNOS in the Tx group improved significantly and approached the level in the Control group. In conclusion, the improvement of albuminuria in the Tx group may be caused by the reduction of oxidative stress in the kidneys, which may lead to the subsequent improvement of glomerular ESL.

Effect of Zinc Acetate Dihydrate (NobelzinR) Treatment on Anemia and Taste Disorders in Patients with Chronic Kidney Disease with Hypozincemia.

Some patients with chronic kidney disease (CKD) receiving hemodialysis develop erythropoietin-resistant anemia, possibly due to zinc deficiency. The frequency of zinc deficiency in CKD (stages 1-5 and 5D) and CKD improvement via zinc supplementation are not completely verified. Here 500 CKD patients (Stage 1/2, n=100; Stage 3, n=100; Stage 4, n=100, Stage n=5, 100; Stage 5D, n=100) will be recruited to determine the frequency of serum zinc deficiency at each CKD stage. Patients with serum zinc concentrations <80 µg/dL will be treated with zinc acetate dihydrate (NobelzinR) to evaluate its effects on hypozincemia, taste disturbances, and anemia.

The Prevalence and Management of Diabetic Nephropathy in Asia.

BACKGROUND: Diabetic nephropathy (DN), especially type 2 diabetes, is now increasing rapidly worldwide, also in Asian countries, and is one of the major long-term vascular complications. The pathogenesis of DN involves both genetic and environmental factors. Around 30-40% of type 2 diabetic patients develop DN despite strict blood glucose and/or blood pressure control. Although it is considered that the genetic background may influence the initiation and progression of DN, the candidate genes are still obscure. SUMMARY: To search for genes that are involved in the susceptibility of DN, a candidate gene approach was taken in the beginning before the development of genome-wide association studies. Although a candidate gene approach can detect rare genetic variants, in advance we need known or presumed pathophysiological knowledge of the specific gene. Investigations using spontaneous animal models are important to determine the pathogenesis and treatment of DN patients. There are many spontaneous animal models, such as the NOD and Akita mice for type 1 diabetes and the Ob/Ob, db/db, Tsumura Suzuki Obese Diabetics, and KK-A (y) mice for type 2 diabetes. Furthermore, the toxicity of persistent hyperglycemia, the activation of reactive oxygen species, systemic and/or glomerular hypertension, microinflammation, dyslipidemia, and other factors are considered to play important roles. Diabetic patients with normoalbuminuria and normal renal function showed typical histological patterns of DN. The discovery of a specific and reliable diagnostic and prognostic biomarker other than albuminuria is urgently needed and indispensable. Since large clinical trials of oral hypoglycemic drugs in renal failure are lacking, these recommendations will need to be regularly updated after results of larger randomized trials with longer follow-up durations are available. KEY MESSAGE: It is necessary to summarize the basic and clinical features of DN patients in Asia and to use these for the treatment of such patients. FACTS FROM EAST AND WEST: The prevalence of DN is increasing in Asia and Western countries alike. The deletion (D) allele of the angiotensin-converting enzyme gene is associated with progression to end-stage renal disease in Asian patients with DN, but this association is uncertain in Europeans. An association between DN and polymorphism of the gene coding for acetyl coenzyme A carboxylase ß has been reported in Asian and Western populations. Both in Japan and the US, criteria for diagnosis are a 5-year history of diabetes and persistent albuminuria. Renal biopsy should be done in patients with severe hematuria, cellular casts and - in the US - hepatitis and HIV to rule out other pathologies. Diabetic retinopathy is considered a key criterion in Japan, but the absence of it does not rule out DN in the US. Enlargement of the kidney is observed as a diagnostic criterion in Japan. The differential use of renal biopsy as diagnostic tool might account for a different prevalence between Asian countries. Some Japanese diabetic patients showed typical histological alterations for DN with a normal ACR and GFR. The clinical classification is similar between Japan and the US including five stages based on ACR and GFR. The Japanese guidelines do not include blood pressure values for the classification of DN. Guidelines for DN treatment are evolving quickly both in Asia and Western countries based on the numerous clinical trials performed worldwide. Targeting the angiotensin system for its hemodynamic and nonhemodynamic effects is a common approach. DPP-4 inhibitors are widely used in Japan and might have a higher glucose-lowering effect in Asian patients due to their specific diet. A randomized, double-blind placebo-controlled study has been launched to assess the efficacy of the Chinese herbal tea extract Shenyan Kangfu in DN.

Pleiotropic effect of pyridoxamine on diabetic complications via CD36 expression in KK-Ay/Ta mice.

AIM: Pyridoxamine inhibits the development of diabetic complications. CD36 is a receptor/transporter which binds fatty acids of lipoproteins. The objective of the present study was to examine the pleiotropic effects of pyridoxamine, especially CD36 expression in KK-A(y)/Ta mice with type 2 diabetic nephropathy. METHODS: KK-A(y)/Ta mice were divided into 2 groups as follows: pyridoxamine treatment group and a tap water group as controls. The urinary ACR, fasting serum insulin, TG and lipoprotein subclasses were measured as biochemical parameters. The renal expressions of malondialdehyde (MDA) were evaluated by immunohistochemistry. CD36 mRNA expressions in kidney and adipose tissue were also evaluated using real-time PCR. RESULTS: Pyridoxamine decreased levels of urinary ACR, serum TG, especially VLDL and fasting serum insulin. MDA accumulation in the pyridoxamine treated group was significantly lower than those in the non-treatment group. The CD36 accumulation and mRNA expressions in kidney and adipose tissue in the treatment group were significantly higher than those in the non-treatment group. CONCLUSIONS: It appears that pyridoxamine ameliorated lipid peroxidation and insulin resistance in KK-A(y)/Ta mice. This pleiotropic effect of pyridoxamine was related to CD36 expression in the kidney and adipose tissue.

Effect of pyridoxamine (K-163), an inhibitor of advanced glycation end products, on type 2 diabetic nephropathy in KK-A(y)/Ta mice.

Advanced glycation end products (AGEs) from the Maillard reaction contribute to the pathogenesis of diabetes-associated complications such as diabetic nephropathy. In therapeutic interventions for reducing AGEs, many compounds have been reported as AGE inhibitors. The objective of the present study was to examine the effect of pyridoxamine (K-163), an AGE inhibitor, in type 2 diabetic KK-A(y)/Ta mice. KK-A(y)/Ta mice were given pyridoxamine (200 or 400 mg/kg per day) starting at 8 weeks of age for 12 weeks. They were divided into 3 groups as follows: pyridoxamine 200 mg/kg per day treatment group (n = 10), pyridoxamine 400 mg/kg per day treatment group (n = 10), and a tap water group as the control group (n = 20). The urinary albumin/creatinine ratio (ACR), body weight (BW), levels of fasting and casual blood glucose, blood glycated hemoglobin (HbA(1c)), fasting serum insulin, triglyceride (TG), total cholesterol (T-Cho), and 3-deoxyglucosone (3DG), and systemic blood pressure were measured as biochemical parameters. N(epsilon)-(Carboxymethyl)lysine (CML) and nitrotyrosine accumulations in glomeruli were evaluated by immunohistochemical analyses. Transforming growth factor beta1 (TGF-beta1) and laminin-beta1 messenger RNA expressions in the kidneys were evaluated by real-time polymerase chain reaction. Pyridoxamine, especially at 400 mg/kg per day, improved the levels of urinary ACR, fasting serum TG, and 3DG. CML and nitrotyrosine accumulations in glomeruli were decreased. Furthermore, large doses of pyridoxamine prevented not only urinary ACR but also increases of BW, casual blood glucose, and HbA(1c). TGF-beta1 and laminin-beta1 messenger RNA expressions in kidneys were significantly lower than those in the controls. There were no significant changes in the levels of fasting blood glucose, serum T-Cho, and systemic blood pressure among all groups. It appears that pyridoxamine improved urinary ACR by its anti-AGE and anti-oxidant effects in the kidneys of KK-A(y)/Ta mice.

Altered mouse cholinephosphotransferase gene expression in kidneys of type 2 diabetic KK/TA mouse.

It is generally considered that genetic factors may contribute to the susceptibility of type 2 diabetic nephropathy. The purpose of the present study is to identify molecules that contribute to the development and/or progression of this disease. Differential display was performed to isolate genes in the kidney using the KK/Ta mouse model of type 2 diabetes. The differential expression of 8 randomly chosen candidate genes (DN1-8) were verified by reverse-transcriptase polymerase chain reaction (RT-PCR) or Northern blot analysis. DN1-3 (Zn-alpha2-glycoprotein, vascular endothelial growth factor receptor [VEGFR]-2, and lactate dehydrogenase [LDH]) were overexpressed and DN7-8 (peroxisome proliferator-activated receptor [PPAR]-interacting protein [PRIP], unknown) were underexpressed in the KK/Ta mouse kidney. DN4-6 (Ezrin, transcobalamin 2, aldo-ketoreductase) did not differ between KK/Ta and control (BALB/c) mice. DN8 only showed no significant sequence similarity to previously reported genes. Molecular cloning revealed that full-length DN8 shares 89% identity with human cholinephosphotransferase 1 (hCHPT1), and we designated it as "putative" mouse cholinephosphotransferase 1 (mCHPT1). The putative mCHPT1 gene was most closely mapped to the D10Mit94 locus with the highest logarithm of odds (lod) score. In situ hybridization revealed the levels of glomerular putative mCHPT1 in BALB/c mice tended to be slightly higher than those in KK/Ta mice. The altered renal mRNA expression of these genes may be involved in the development and/or progression of diabetic nephropathy.