Akiko Ishii

Asymmetric dimethylarginine is closely associated with the development and progression of nephropathy in patients with type 2 diabetes

BACKGROUND Nitric oxide (NO) is thought to play an important role in the pathogenesis of diabetic nephropathy. We conducted a prospective, observational cohort study to explore the relationship between plasma levels of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase, and the development and progression of nephropathy in patients with type 2 diabetes. METHODS This was a hospital-based observational cohort study in Japanese type 2 diabetic patients with normoalbuminuria [urinary albumin-to-creatinine ratio (ACR) <30 mg/g creatinine] or microalbuminuria (30 < or = ACR <300 mg/g creatinine). The primary endpoint was the development or progression of diabetic nephropathy, based on transition from any given stage to a more advanced stage of albuminuria. RESULTS We studied 225 diabetic patients, 81 women and 144 men, with a mean (+/-SD) age of 64 +/- 10 years. The majority (183) of patients were normoalbuminuric, with the remainder microalbuminuric (42). During the median follow-up period of 5.2 years, 27 normoalbuminuric and 10 microalbuminuric patients reached the primary endpoint. When patients were separated according to the median ADMA level (0.46 mumol/l), patients with higher ADMA levels had a greater incidence of reaching the endpoint (P = 0.014 by the log-rank test). In the multivariate Cox proportional hazard model, the hazard ratio for reaching the endpoint for patients with higher versus lower ADMA levels was 2.72 (95% confidence interval 1.25-5.95; P = 0.012). CONCLUSIONS Higher plasma levels of ADMA may be a novel and potent predictor of the progression of nephropathy in adult Japanese type 2 diabetic patients.

Molecular characterization of human tensin.

Tensin is a focal-adhesion molecule that binds to actin filaments and interacts with phosphotyrosine-containing proteins. To analyse tensins function in mammals, we have cloned tensin cDNAs from human and cow. The isolated approx. 7.7-kb human cDNA contains an open reading frame encoding 1735 amino acid residues. The amino acid sequence of human tensin shares 60% identity with chicken tensin, and contains all the structural features described previously in chicken tensin. This includes the actin-binding domains, the Src homology domain 2, and the region similar to a tumour suppressor, PTEN. Two major differences between human and chicken tensin are (i) the lack of the first 54 residues present in chicken tensin, and (ii) the addition of 34- and 38-residue inserts in human and bovine tensin. In addition, our interspecies sequencing data have uncovered the presence of a glutamine/CAG repeat that appears to have expanded in the course of evolution. Northern-blot analysis reveals a 10-kb message in most of the human tissues examined. An additional 9-kb message is detected in heart and skeletal muscles. The molecular mass predicted from the human cDNA is 185 kDa, although both endogenous and recombinant human tensin migrate as 220-kDa proteins on SDS/PAGE. The discrepancy is due to the unusually low electrophoretic mobility of the central region of the tensin polypeptide (residues 306-981). A survey of human prostate and breast cancer cell lines by Western-blot analysis shows a lack of tensin expression in most cancer cell lines, whereas these lines express considerable amounts of focal-adhesion molecules such as talin and focal-adhesion kinase. Finally, tensin is rapidly cleaved by a focal-adhesion protease, calpain II. Incubation of cells with a calpain inhibitor, MDL, prevented tensin cleavage and induced morphological change in these cells, suggesting that cleavage of tensin and other focal-adhesion constituents by calpain disrupts maintenance of normal cell shape.

Arterial Stiffness Is Associated With Incident Albuminuria and Decreased Glomerular Filtration Rate in Type 2 Diabetic Patients

OBJECTIVE To investigate the association between aortic stiffness and incident albuminuria and the decline in estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS We investigated 461 Japanese type 2 diabetic patients, comprising 199 women and 262 men, with a mean age of 59 ± 11 years. Patients were divided into two groups according to the median value of carotid-femoral pulse wave velocity (cf-PWV), which was used to evaluate aortic stiffness. The end point was defined as the transition from normo- to microalbuminuria or micro- to macroalbuminuria. The Cox proportional hazard model was used to calculate the hazard ratio (HR) and 95% CI. The correlation between cf-PWV and rate of change in eGFR was also determined by linear regression analysis. RESULTS The baseline mean (± SD) cf-PWV was 9.6 ± 2.4 m/s. During a median follow-up period of 5.9 years (range 0.3–8.6), progression of albuminuria was observed in 85 patients. The 5-year cumulative incidence of the end point in patients with cf-PWV below and above the median was 8.5 and 19.4%, respectively (P = 0.002, log-rank test). cf-PWV was significantly associated with incident albuminuria (HR 1.23, 95% CI 1.13–1.33, P < 0.001) by multivariate Cox regression analysis. A significant association between cf-PWV and annual change in eGFR was also suggested by multiple linear regression analysis (standardized estimate −0.095, P = 0.031). CONCLUSIONS Aortic stiffness is associated with incident albuminuria and the rate of decline in glomerular filtration rate in type 2 diabetic patients.

Growth differentiation factor 15 as a useful biomarker for mitochondrial disorders

The diagnosis of mitochondrial disorders (MDs) is occasionally difficult because patients often present with solitary, or a combination of, symptoms caused by each organ insufficiency, which may be the result of respiratory chain enzyme deficiency. Growth differentiation factor 15 (GDF‐15) has been reported to be elevated in serum of patients with MDs. In this study, we investigated whether GDF‐15 is a more useful biomarker for MDs than several conventional biomarkers.

Wernicke’s Encephalopathy Induced by Hyperemesis gravidarum, Associated with Bilateral Caudate Lesions on Computed Tomography and Magnetic Resonance Imaging

The case of an 18-year-old woman with Wernickes encephalopathy induced by hyperemesis gravidarum is reported. She had severe vomiting and received antiemetic therapy and intravenous administration of glucose and low-dose insulin solution without thiamine. She developed coma, nystagmus, ataxia and polyneuropathy. CT and MR imaging showed bilateral caudate lesions as well as symmetrical periventricular lesions of the thalamus and hypothalamus and periaqueductal gray matter. Caudate lesions are quite rare in Wernickes encephalopathy.

Association between plasma oxidized low-density lipoprotein and diabetic nephropathy

To investigate the association of oxidized low-density lipoprotein (ox-LDL) with the development of diabetic nephropathy, plasma levels of ox-LDL were measured in 70 patients with type 2 diabetes mellitus. A sandwich enzyme-linked immunoadsorbent assay (ELISA) using the mouse monoclonal antibody FOH1a/DLH3, which specifically recognizes oxidized phosphatidylcholine, and a horseradish peroxidase (HRP)-labeled goat anti-human apolipoprotein B IgG was used to measure ox-LDL levels. The mean age of the patients was 57.0+/-1 3.4 years, and the mean duration of diabetes was 13.4+/-8.5 years. Plasma ox-LDL levels were similar in patients with normoalbuminuria (13.7+/-3.9 U/ml), patients with microalbuminuria (12.8+/-3.9 U/ml), and normal controls (12.5+/-4.2 U/ml). However, the plasma ox-LDL level in patients with macroalbuminuria (16.8+/-7.5 U/ml) was significantly higher than those in the other groups (P<0.05). Hemoglobin A1c (HbA1c) levels were similar in diabetic patients with normoalbuminuria (8.2+/-2.2%), microalbuminuria (7.8+/-1.3%), or macroalbuminuria (7.2+/-1.4%). There was no significant correlation between the ox-LDL level and the HbA1c level. The significantly elevated plasma ox-LDL levels in patients with macroalbuminuria suggest that ox-LDL may play an important role in the progression of diabetic nephropathy.

Content of mutant mitochondrial DNA and organ dysfunction in a patient with a MELAS subgroup of mitochondrial encephalomyopathies

A point mutation of mitochondrial tRNALeu(UUR) gene is responsible for a MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) subgroup of mitochondrial encephalomyopathies. In most cases, the mutant mitochondrial DNA (mtDNA) coexists with normal mtDNA in a heteroplasmic manner. In order to quantify the content of mutant mtDNA, we developed a quantitative method of PCR. Using this method, the distribution of the mutant mtDNA was examined in 32 different tissues among 18 autopsied organs from a patient with MELAS, who had shown hypophyseal dysfunction. The percentage of the mutant mtDNA at nucleotide number 3243 in each tissue was ranged between 22% and 95%. The content of the mutant mtDNA was at the highest (95%) in the hypophysis and higher in the cerebral cortex than in the white matter. This study shows a possible correlation of tissue dysfunction with accumulation of the mutant mtDNA within the brain.

Effective adenovirus-mediated gene expression in adult murine skeletal muscle

We established an efficient method for obtaining expression of a foreign marker gene transferred in vitro into myoblasts and in vivo into adult mouse skeletal muscles using adenovirus vector. After infection of the C2 myoblasts with the adenovirus vector containing the β‐actin promoter with cytomegalovirus (CMV) enhancer (CAG promoter) AxCALacZ, significantly greater number of cells express β‐galactosidase when compared with the adenovirus vector expressing the lacZ gene under the control of the SRα viral terminal repeat promoter (AxSRLacZL) or the myosin heavy chain (MHC) IIB promoter (AxMHCLacZ). We also injected AxCALacZ into the skeletal muscles of 5‐ to 6‐week‐old C57BL/10 mice and determined that more than 60% of their muscle fibers expressed the lacZ gene 7 days after injection. The CAG promoter may have application in the development of gene therapy for Duchenne muscular dystrophy (DMD) using adenovirus vector.

Association of albuminuria and reduced estimated glomerular filtration rate with incident stroke and coronary artery disease in patients with type 2 diabetes

It is unclear whether albuminuria and reduced glomerular filtration rate (GFR) independently increase the risk of incident stroke and coronary artery disease (CAD) in Japanese patients with diabetes. We investigated the independent effects of albuminuria and estimated GFR (eGFR) on the first occurrence of stroke and CAD in patients with type 2 diabetes mellitus (T2DM). We studied 1002 T2DM patients with eGFR (ml min−1 per 1.73 m2) ⩾15 and had no previous cardiovascular disease (CVD) history. GFR was estimated using the modified three-variable equation for the Japanese. Patients were divided into four eGFR categories: ⩾90, 60–89, 30–59 and 15–29. The end point was an incident stroke and CAD events. The Cox proportional hazard model was used to calculate hazard ratio and 95% confidence interval. During a mean follow-up period of 5.2±2.1 years, 72 episodes of stroke and 90 of CAD were observed. Multivariate Cox analysis revealed no significant association between the eGFR category and incident stroke. The stroke hazard ratio (95% confidence interval) in reference to patients with an eGFR ⩾90 was 0.78 (0.40–1.56) for patients with an eGFR of 60–89, 1.47 (0.70–3.10) for patients with an eGFR of 30–59 and 1.14 (0.39–3.35) for patients with an eGFR of 15–29. Reduced eGFR was a significant risk factor for CAD, with hazard ratios (95% confidence interval) for patients with an eGFRs of 60–89, 30–59 and 15–29 at 1.81 (1.01–3.57), 2.03 (1.04–4.40) and 3.01 (1.13–8.02), respectively. Reduced eGFR is independently associated with incident CAD but not stroke in Japanese patients with T2DM.

A role of tensin in skeletal-muscle regeneration

Regeneration of skeletal muscle requires the activation, proliferation, differentiation and fusion of satellite cells to generate new muscle fibres. This study was designed to determine the role of tensin in this process. Cardiotoxin was used to induce regeneration in the anterior tibial muscles of tensin-knockout and wild-type mice. From histological analysis, we found that the regeneration process lasted longer in knockout than in wild-type mice. To investigate the mechanism involved in this delay, we examined each regeneration step in animals and cultured primary cells. We found fewer proliferating myogenic cells identified by bromodeoxyuridine and desmin double labelling in knockout mice on the first 2 days after injury. Expression of myosin, paxillin, dystrophin and dystrophin-associated proteins were delayed in knockout mice. Withdrawal from the cell cycle was less efficient in isolated knockout myoblasts, and the fusion capacity was reduced in these cells as well. These defects in regeneration most likely contributed to the 9-fold increase of centrally nucleated fibres occurring in the non-injected knockout mice. Our results demonstrated clearly that tensin plays a role in skeletal-muscle regeneration.