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Biomedical subjects

T Hanafusa

Publications and source records attributed to T Hanafusa.

At least 73 records · Page 4Linked to original sources
PubMed1999

Risk factors for the progression of microalbuminuria in Japanese type 2 diabetic patients--a 10 year follow-up study.

To clarify risk factors for the progression of microalbuminuria in Japanese type 2 diabetic patients, the longitudinal study for 10 years was conducted on 67 outpatients with type 2 diabetes, who had shown no overt proteinuria at baseline. The urinary albumin index (UAI) has been determined based on the mean of at least two random urine samples each year. Categories were defined as normoalbuminuria (UAI < 30.0 mg/g x Cr.), microalbuminuria (30.0 < or = UAI < 300.0), and macroalbuminuria (UAI > or = 300.0). Progression was defined as worsening of the category and/or more than doubling of the baseline UAI value. Multiple logistic regression analysis was performed using age, duration of diabetes, HbA1c, blood pressure, BMI, serum lipids, smoking habits, and alcohol consumption as independent variables and the progression of microalbuminuria as a dependent variable. Age and HbA1c were estimated as significant and independent variables. Furthermore, genetic polymorphisms of angiotensin I-converting enzyme (ACE) and angiotensinogen were analyzed to evaluate the genetic contribution. The D/D genotype of ACE was significantly more common in progressors than in non-progressors. These results suggest that glycemic control and age are important risk factors and the D/D genotype of ACE acts as a risk factor for the progression of microalbuminuria in Japanese type 2 diabetic patients.

Adult↗
PubMed1999

Increased insulin sensitivity and hypoglycaemia in mice lacking the p85 alpha subunit of phosphoinositide 3-kinase.

The hallmark of type 2 diabetes, the most common metabolic disorder, is a defect in insulin-stimulated glucose transport in peripheral tissues. Although a role for phosphoinositide-3-kinase (PI3K) activity in insulin-stimulated glucose transport and glucose transporter isoform 4 (Glut4) translocation has been suggested in vitro, its role in vivo and the molecular link between activation of PI3K and translocation has not yet been elucidated. To determine the role of PI3K in glucose homeostasis, we generated mice with a targeted disruption of the gene encoding the p85alpha regulatory subunit of PI3K (Pik3r1; refs 3-5). Pik3r1-/- mice showed increased insulin sensitivity and hypoglycaemia due to increased glucose transport in skeletal muscle and adipocytes. Insulin-stimulated PI3K activity associated with insulin receptor substrates (IRSs) was mediated via full-length p85 alpha in wild-type mice, but via the p50 alpha alternative splicing isoform of the same gene in Pik3r1-/- mice. This isoform switch was associated with an increase in insulin-induced generation of phosphatidylinositol(3,4,5)triphosphate (PtdIns(3,4,5)P3) in Pik3r1-/- adipocytes and facilitation of Glut4 translocation from the low-density microsome (LDM) fraction to the plasma membrane (PM). This mechanism seems to be responsible for the phenotype of Pik3r1-/- mice, namely increased glucose transport and hypoglycaemia. Our work provides the first direct evidence that PI3K and its regulatory subunit have a role in glucose homeostasis in vivo.

Animals↗
PubMed1999

Overexpression of the aldose reductase gene induces apoptosis in pancreatic beta-cells by causing a redox imbalance.

To determine the role of the polyol metabolizing pathway under hyperglycemic conditions, the effects of aldose reductase (AR) on the cellular functions of pancreatic beta-cells were examined. Stable transfectants of rat AR cDNA were obtained with a pancreatic beta-cell line, HIT, in which a negligible amount of AR was originally expressed. Overproduction of AR triggered DNA fragmentation, as judged with the TUNEL method and agarose gel electrophoresis. Morphological analysis by electron microscopy also clearly showed apoptosis of the AR-overexpressing HIT cells. Induction by interleukin-1beta of gene expression such as those of an inducible form of nitric oxide synthase (NOS-II) and Mn-superoxide dismutase (Mn-SOD), was much lower in the transfectants than in the control cells, while the expression of constitutively expressed genes such as those for Cu,Zn-superoxide dismutase and insulin was not changed. The susceptibility to interleukin-1beta stimulation of the expression of the NOS II and Mn-SOD genes was due to suppressed NF-kappaB activity, which is essential for the expression of these genes. In addition, the intracellular NADPH/NADP+ ratio was considerably lower in the AR-transfected cells than in control cells. Thus, the overexpression of AR in pancreatic beta-cells induced apoptosis that may be caused by a redox imbalance.

Aldehyde Reductase↗
PubMed1999

Beneficial effects of antioxidants in diabetes: possible protection of pancreatic beta-cells against glucose toxicity.

Oxidative stress is produced under diabetic conditions and possibly causes various forms of tissue damage in patients with diabetes. The aim of this study was to examine the involvement of oxidative stress in the progression of pancreatic beta-cell dysfunction in type 2 diabetes and to evaluate the potential usefulness of antioxidants in the treatment of type 2 diabetes. We used diabetic C57BL/KsJ-db/db mice, in whom antioxidant treatment (N-acetyl-L-cysteine [NAC], vitamins C plus E, or both) was started at 6 weeks of age; its effects were evaluated at 10 and 16 weeks of age. According to an intraperitoneal glucose tolerance test, the treatment with NAC retained glucose-stimulated insulin secretion and moderately decreased blood glucose levels. Vitamins C and E were not effective when used alone but slightly effective when used in combination with NAC. No effect on insulin secretion was observed when the same set of antioxidants was given to nondiabetic control mice. Histologic analyses of the pancreases revealed that the beta-cell mass was significantly larger in the diabetic mice treated with the antioxidants than in the untreated mice. As a possible cause, the antioxidant treatment suppressed apoptosis in beta-cells without changing the rate of beta-cell proliferation, supporting the hypothesis that in chronic hyperglycemia, apoptosis induced by oxidative stress causes reduction of beta-cell mass. The antioxidant treatment also preserved the amounts of insulin content and insulin mRNA, making the extent of insulin degranulation less evident. Furthermore, expression of pancreatic and duodenal homeobox factor-1 (PDX-1), a beta-cell-specific transcription factor, was more clearly visible in the nuclei of islet cells after the antioxidant treatment. In conclusion, our observations indicate that antioxidant treatment can exert beneficial effects in diabetes, with preservation of in vivo beta-cell function. This finding suggests a potential usefulness of antioxidants for treating diabetes and provides further support for the implication of oxidative stress in beta-cell dysfunction in diabetes.

Acetylcysteine↗
PubMed1999

[Mechanism of atherosclerosis in diabetes: altered cytokine network in the vascular wall].

In the diabetic vascular complication, biochemical and mechanical injuries to endothelial cells are involved not only in the process of microangiopathy, but also in diabetic atherosclerosis (or arteriosclerosis) which is so-called macroangiopathy. In the presence of diabetes or persistent hyperglycemia, many cytokines including growth factors such as PDGF, HB-EGF, IL-1 beta and TNF alpha are upregulated in intimal cells of the arterial or aortic wall. These changes alter the cytokine network in the common mechanism of atherosclerosis, "Response-to-injury hypothesis", and further accelerate the formation of atherosclerotic lesion. In addition, diabetes causes abnormal responsibility to HB-EGF, PDGF and TGF-beta in medial smooth muscle cells leading to the elevated activity to their proliferation and migration into the intima. Thus, all cell types consisting arterial or aortic wall are involved in the process of diabetic atherosclerosis.

Arteries↗
PubMed1999

In vivo effects of calcium entry blockers on human parathyroid adenoma cells with special reference to calcium sensing ability and the hormone secretion.

We evaluated the effects of calcium-entry blockers on parathyroid hormone (PTH) secretion by human parathyroid adenoma cells in vitro. Nifedipine and bamidipine inhibited PTH secretion, while diltiazem had no significant effect. Cytosolic calcium concentrations were measured by use of the calcium-sensitive fluorescent dye fluo-3 with confocal laser scanning microscopy. Nifedipine increased the cytosolic concentration of calcium, whereas diltiazem decreased it. Results suggest that, in parathyroid adenoma cells, regulation of PTH secretion with respect to intracellular calcium concentration would be maintained despite differing response of intracellular calcium concentration following exposure to calcium-entry blockers.

Adenoma↗
PubMed1998

Human erythrocyte bisphosphoglycerate mutase: inactivation by glycation in vivo and in vitro.

2,3-Bisphosphoglycerate mutase (BPGM) [EC 5.4.2.4] is a multifunctional enzyme that catalyzes both the synthesis and the degradation of 2,3-diphosphoglycerate (2,3-DPG) and contains three types of activities in that it functions as a 2,3-DPG synthetase, a phosphoglycerate mutase and a 2,3-DPG phosphatase. In humans, BPGM occurs only in erythrocytes and plays a pivotal role in the dissociation of oxygen from hemoglobin via 2,3-DPG. The present study shows that the specific activity of BPGM in erythrocytes of diabetic patients is decreased, compared to normal controls as judged by 2,3-DPG synthetase activity and immunoreactive contents. To understand the mechanism by which the enzyme is inactivated, the enzyme was purified from pooled erythrocytes from diabetic patients and subjected to a boronate affinity column. The flow through fraction was active while the bound fraction was completely inactive. The bound fraction was reactive to an anti-hexitollysine antibody, indicating that the enzyme had undergone glycation and inactivation. The primary glycated site of the enzyme was found to be Lys158 as judged by amino acid sequencing and the reactivity with an anti-hexitollysine IgG, after reverse-phase HPLC of the lysyl-endopeptidase-digested peptides. Extensive glycation of recombinant BPGM in vitro indicated that the glycation sites were Lys2, Lys4, Lys17, Lys42, Lys158, and Lys196. From these results, the loss of enzymatic activity appears to be due to the glycation of Lys158 which may be located in the vicinity of the substrate binding site.

Aged↗
PubMed1998

Retrospective study on the impact of hepatitis C virus infection on kidney transplant patients over 20 years.

BACKGROUND: The majority of chronic hepatitis is ascribable to hepatitis C virus (HCV) infection, whereas the clinical impact has not been understood in kidney transplant recipients. Our current study was carried out to assess the impact of HCV infection on kidney recipients over the long-term, and to investigate the effect and risk of interferon-alpha (IFN-alpha) therapy for chronic active hepatitis C. METHODS: Hepatitis B surface antigen (HBsAg) and antibody to HCV (HCVAb) were examined prospectively and retrospectively in 280 patients, who underwent kidney transplants in the period from 1973 to 1996. The patient survival rate, the graft survival rate, the incidence of liver dysfunction and the cause of mortality among the HCV infected and noninfected groups were analyzed. IFN-alpha therapy was performed on 10 patients with chronic active hepatitis C. RESULTS: Prevalence of the hepatitis virus was quite high at 34.3% (96/280): the frequency of the HBsAg carrier was 3.2% (9/280), that of the HCVAb carrier was 28.6% (80/280) and that of the both carriers was 2.5% (7/280). The other 184 cases (65.7%) were negative for both HBsAg and HCVAb. Liver dysfunction developed at the significantly higher incidence of 55% in HCVAb carriers compared to the 9.2% of the noninfected group (P<0.01). HCVAb carriers had a poor survival rate in the second decade compared to the noninfected group: 83.7% vs. 88.91% for 10-year survival (P=0.44) and 63.9% vs. 87.9% for 20-year survival (P<0.05). The poor survival rate was a result of the mortality from liver disorder. Five patients died of such disease in the infected groups whereas no noninfected patient died in the same period (p<0.01). As the result of IFN-alpha therapy, biochemical activity normalized or improved in eight cases, whereas the HCV-RNA titer was reduced only in three patients. Only one patient maintained normal biochemical markers and undetectable levels of HCV-RNA for 2 years after treatment. The therapy was discontinued for five patients with the adverse effects of acute rejection, deterioration of diabetes, and depression. CONCLUSIONS: HCV infection has a significant impact on kidney transplant recipients over the long term and in particular affects them in the second decade. Our pilot study revealed only partial efficacy of IFN-alpha therapy for HCV-infected recipients, but with the high risk of acute rejection.

Adult↗
PubMed1998

A 20-year case study of a kidney transplant recipient with chronic active hepatitis C: clinical course and successful treatment for late acute rejection induced by interferon therapy.

BACKGROUND: The influence of hepatitis C virus (HCV) infection has been discussed in kidney transplantation. Our case study focused on four points: the clinical course of an HCV-infected recipient; the pathogenesis of hepatic disorders in such a patient; interferon (IFN)-alpha therapy; and the risk of IFN-alpha therapy. METHOD: A patient was suspected of acquiring HCV via transfusion at kidney transplant. He was examined several times serologically, virologically, endoscopically, and pathologically during a 20-year follow-up. RESULTS: Abnormal biochemical markers were found within a month after transplantation but recovery occurred without any treatment. Within 3 years postoperatively, hepatic disorder developed including peliosis hepatis, nodular regenerative hyperplasia, and cholestasis. These pathological conditions were ascribed to immunosuppressants: cyclophosphamide and azathioprine. Abnormal chemical markers decreased to normal values for 4 consecutive years with the substitution of cyclophosphamide and azathioprine for mizoribine. During the subsequent 13 years, the patient developed chronic hepatitis with clinical and morphological features of hepatitis C infection. Anti-HCV antibody was positive from the second post-transplant year and HCV genome was detected in the 17th year. IFN-alpha therapy was initiated in the 17th year and resulted in normal transaminase activities with no effect on viremia. However, acute cellular rejection developed. The rejection was steroid resistant but responsive to OKT3. CONCLUSION: HCV might remain latent for approximately 7 years even in kidney recipients unless toxic hepatitis occurs. Hepatotoxic drugs may cause a wide spectrum of liver diseases in HCV carriers as a result of the overload of immunosuppressants on hepatocytes. IFN-alpha could induce acute cellular rejection even in the 17th year. Such acute rejection can be reversible with OKT3.

Adult↗
PubMed1998

Characteristics of cardiac hypertrophy in the juvenile visceral steatosis mouse with systemic carnitine deficiency.

The juvenile visceral steatosis (JVS) mouse exhibits hereditary systemic carnitine deficiency and develops cardiac hypertrophy. The aim of this study was to clarify the characteristics of cardiac hypertrophy in the JVS mouse. Total carnitine content in IVS mouse heart was about 10% of that of control mouse heart at 4 and 8 weeks of age. The heart weight/body weight ratio was bigger in JVS mice than that in control mice at 2 weeks of age, and this difference in ratio increased with age. The wall areas of both ventricles and septum in JVS mice were larger than those of the control mice at 2 and 8 weeks. The myocyte diameter in both ventricular walls and septum in JVS mice was longer than that of the control mice. On electron microscopy, the percent of mitochondria in the myocyte was 66% in JVS mice, and 37% in control mice. The percent of lipid fraction in JVS mice was six-fold higher than that in control mice. Total content of adenine nucleotides in JVS mouse heart was about 60% of that in control mouse heart. Adenylate energy charge in JVS mouse heart was 63 and 45% of that in the control mouse heart at 4 and 8 weeks, respectively. Overall, the cardiac enlargement observed in this animal model could be accounted for by a proportional increase in the myocyte diameter in the ventricles and septum, accompanied by an increase in mitochondria. Furthermore, this cellular growth is associated with decreases in the levels of ATP and ADP, and adenylate energy charge.

Adenosine Diphosphate↗
PubMed1998

Malignant neoplasm in kidney transplantation.

BACKGROUND: The kidney recipient is at a higher risk for cancer than is the general population, although the incidence of neoplasms in general is considered lower in Japan than in Western countries. The cause of this increased risk associated with either transplantation or geography has not yet been established. METHOD: The incidences and sites of malignant neoplasms were analyzed in 285 kidney recipients, who had been followed up for 3007 patient-years. The relationship between immunosuppressive states, the numbers of CD4-positive T lymphocytes, and the presence of malignant neoplasms was studied retrospectively. RESULTS: Eighteen malignant neoplasms were found in 17 of the 285 patients (6%). The malignancies developed in these patients an average of++ 1 26.5 months after transplantation. The incidence was only 3.9% at 10 years, increasing to 13.9% at 20 years. No difference in the time-course incidence was found between azathioprine-based and cyclosporin-based immunosuppressive regimens. The malignancies developed in the digestive organs in more than half of the patients, and were mainly in the liver, colon and rectum, and stomach, with a relatively low incidence of skin cancer and lymphoma. There was only one case of Epstein-Barr virus genome found in 5 specimens that were tested. Concerning the immunosuppressive state, CD4-positive T lymphocyte counts were not related directly with malignancies in our series. CONCLUSION: The cumulative incidence of malignancy increased markedly in the second posttransplant decade. The site of cancers in kidney recipients mirrors that of general Japanese malignancies. Our results revealed neither the cause nor predictor for malignancies in kidney transplant patients.

Adolescent↗
PubMed1998

Mutation/polymorphism scanning of glucose-6-phosphatase gene promoter in noninsulin-dependent diabetes mellitus patients.

Glucose-6-phosphatase (G6Pase) catalyzes the rate-limiting step of gluconeogenesis, and hepatic G6Pase activity is increased in diabetes. We have cloned and analyzed the human G6Pase gene promoter region and identified putative regulatory sequences for insulin, cAMP, glucocorticoid, and hepatocyte nuclear factors. The promoter region of the G6Pase gene was analyzed in 154 noninsulin-dependent diabetes mellitus patients and 90 control subjects by PCR-single strand conformation polymorphism and direct sequencing methods. Polymorphisms were not found in any subjects. The results suggested that in noninsulin-dependent diabetic patients, the major cause of the hepatic glucose overproduction was not attributed to dysregulation of the G6Pase gene due to mutation/polymorphism of its promoter region.

Adolescent↗
PubMed1998

Mutation P291fsinsC in the transcription factor hepatocyte nuclear factor-1alpha is dominant negative.

The type 3 form of maturity-onset diabetes of the young (MODY3) results from mutations in the gene encoding the transcription factor, hepatocyte nuclear factor-1alpha (HNF-1alpha). The mechanism by which mutations in only one allele of the HNF-1alpha gene impair pancreatic beta-cell function is unclear. The functional form of HNF-1alpha is a dimer--either a homodimer or a heterodimer with the structurally related protein HNF-1beta--that binds to and activates transcription of the genes whose expression it regulates. HNF-1alpha is composed of three functional domains: an amino-terminal dimerization domain (amino acids 1-32), a DNA-binding domain with POU-like and homeodomain-like motifs (amino acids 150-280), and a COOH-terminal transactivation domain (amino acids 281-631). Because the dimerization domain is intact in many of the mutant forms of HNF-1alpha found in MODY subjects, these mutant proteins may impair pancreatic beta-cell function by forming nonproductive dimers with wild-type protein, thereby inhibiting its activity; that is, they are dominant-negative mutations. This hypothesis was tested by comparing the functional properties of the frameshift mutation P291fsinsC, the most common mutation identified to date in MODY3 patients, and wild-type HNF-1alpha. P291fsinsC-HNF-1alpha showed no transcriptional transactivation activity in HeLa cells, which lack endogenous HNF-1alpha. Overexpression of P291fsinsC-HNF-1alpha in MIN6 cells, a mouse beta-cell line, resulted in an approximately 40% inhibition of the endogenous HNF-1alpha activity in a dosage-dependent manner. Furthermore, heterodimer formation between wild-type and P291fsinsC mutant proteins were observed by electrophoretic mobility shift assay. These data suggest that the P291fsinsC mutation in HNF-1alpha functions as a dominant-negative mutation. However, other mutations, such as those in the promoter region and dimerization domain, may represent loss of function mutations. Thus mutations in the HNF-1alpha gene may lead to beta-cell dysfunction by two different mechanisms.

Animals↗
PubMed1998

Molecular mechanisms of pancreatic beta-cell destruction in autoimmune diabetes: potential targets for preventive therapy.

Mononuclear cell infiltration into the islets of the pancreas (insulitis) is characteristic of autoimmune diabetes. T lymphocytes are the predominant subpopulation seen in insulitis, and are involved in the autoimmune process. Insulin-producing beta cells are thought to be destroyed by cytotoxic T cells, cytokines or nitric oxide, and beta-cell death occurs, at least partly, via apoptosis. Beta-cell death induced by cytokines is inhibited by Bcl-2, suggesting its potential as a tool for gene therapy. The Fas/Fas-ligand system plays a critical role in inducing insulitis and overt diabetes in nonobese diabetic (NOD) mice, a model of autoimmune diabetes. T-cell receptor gene usage in infiltrating T cells is not restricted in NOD mice, but there are some observations indicating relative restriction in human IDDM patients. Preventive strategies might be developed by focusing on these molecules involved in beta-cell destruction. The establishment of screening techniques for detecting prediabetic patients is also necessary to allow successful intervention.

Animals↗