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Biomedical subjects

M Okubo

Publications and source records attributed to M Okubo.

At least 55 records · Page 3Linked to original sources
PubMed2000

A novel dominant-negative mutation of the hepatocyte nuclear factor-1alpha gene in Japanese early-onset type 2 diabetes.

We investigated the presence and the function of hepatocyte nuclear factor-1alpha (HNF-1alpha) mutations in 26 Japanese subjects with type 2 diabetes. The subjects were between 20 and 39 years of age on diagnosis and had diabetic first-degree relatives. Two different frameshift mutations were found in 2 subjects (8 %). One novel mutation, T539fsdelC (deletion of C in codon 539 for Thr), is predicted to generate a protein of normal 539 residues at the N-terminus followed by an abnormal 119 amino acid protein. The mutation, P291fsinsC (insertion of C in codon 291 for Pro) should lead to production of a truncated protein of 315 amino acids. Transfection reporter assay using MIN6 and HepG2 cells revealed both mutations to have null function in the transactivation of reporter gene expression. When transfected with wild-type gene, these mutations behaved as dominant-negative regulators in both cells. An equimolar amount of T539fsdelC reduced wild-type activity by approximately 80% in MIN6 cells, while the same concentration of P291fsinsc reduced it by 30%. The sequences responsible for the transactivation activity of HNF-1alpha are confined largely to amino acids 547-628, so that the T539fsdelC mutation, which affects this entire region, replacing amino acids 540-631 with an abnormal 119 amino acid protein, may acquire a potent dominant-negative function.

Adult↗
PubMed2000

Cloning of novel soluble gp130 and detection of its neutralizing autoantibodies in rheumatoid arthritis.

In an attempt to isolate disease-associated autoantigens in rheumatoid arthritis (RA), we cloned a new autoantigen named gp130-RAPS, which is a novel soluble form of the IL-6 signal-transducing molecule gp130. gp130-RAPS is a 50-kDa protein translated from alternatively spliced mRNA and has a truncated form of gp130 with a unique sequence, Asn-Ile-Ala-Ser-Phe (NIASF), in its COOH-terminus. We observed serum antibodies to this NIASF sequence frequently in patients with RA, but not in those with other systemic rheumatic diseases or in healthy subjects. In RA, detection of those antibodies was significantly associated with disease activity indices such as serum C-reactive protein (CRP) levels, erythrocyte sedimentation rate, blood platelet counts, and serum IL-6 concentration. In vitro experiments revealed that gp130-RAPS inhibited IL-6 activity, and this inhibition was neutralized by antibodies to the COOH-terminus of gp130-RAPS derived from patients with RA. Thus, autoantibody to gp130-RAPS may play an important role in the progression of RA by promoting IL-6 activity. Inspection of autoantibodies to gp130-RAPS may become a practical clinical test for RA. gp130-RAPS and its autoantibody provide a new clue to the complicated pathogenesis of RA.

Animals↗
PubMed2000

DiGeorge syndrome with Graves' disease: A case report.

DiGeorge syndrome (DGS) is characterized by aplasia or hypoplasia of the thymus and parathyroid glands, cardiac defects and anomaly face. This syndrome is usually associated with hypocalcemia resulting from hypoparathyroidism. In most cases the initial symptom is tetany caused by hypocalcemia within 24-48 hours after birth, with symptoms by immune abnormality appearing later. We report a woman who passed with no symptoms before age 18 and was diagnosed DiGeorge syndrome by tetany with developing auto-immune thyroid disease (Graves' disease). She had surgery for intraventricular septal defect at age 3, hypoparathyroidism, decrease of T cells in peripheral blood and the deletion of the 22nd chromosome long arm (22q11.2). It is supposed that abnormalities of immune function of this case are not complete as indicated by complicating of Graves' disease, and contributing to her long-term survival.

Adolescent↗
PubMed2000

A Japanese patient with lipoprotein lipase deficiency homozygous for the Gly188Glu mutation prevalent worldwide.

We studied the molecular basis of familial lipoprotein lipase (LPL) deficiency in a new Japanese kindred. The proband was a four-month-old infant with severe hyperchylomicronemia. In postheparin plasma, LPL activity was virtually absent, although LPL mass was detectable. Single strand conformational polymorphism (SSCP) analysis showed an abnormal band with exon 5 of the LPL gene that was amplified by PCR from the proband's genomic DNA. DNA sequence analysis of the amplified fragment demonstrated that the proband was homozygous for a G-to-A change at nucleotide position 818 resulting in the substitution of glutamic acid for glycine at codon 188. Although this is among the first Gly188Glu mutations identified in Japanese, the missense mutation has previously been reported as a prevalent cause of familial LPL deficiency worldwide and has been proposed to have a common origin. However, DNA haplotype analysis with either restriction fragment length polymorphism (RFLP) or microsatellite markers revealed that the DNA haplotype of the proband was not identical to the haplotype previously reported as common to the other patients with the Gly188Glu mutation. These results add the Gly188Glu mutation to the growing list of LPL gene mutations underlying familial LPL deficiency in Japanese and indicate that the origin of the Gly188Glu mutation is not necessarily common but would be multicentric at least in part.

Adult↗
PubMed2000

Thrombopoietin levels in serum and liver tissue in patients with chronic viral hepatitis and hepatocellular carcinoma.

Thrombocytopenia in liver diseases is considered to be due to splenic platelet pooling and accelerated destruction. Since thrombopoietin (TPO), a regulator of thrombopoiesis, is produced mainly in the liver, decreased production of TPO may account for thrombocytopenia in liver diseases. To address this issue, we measured serum TPO, using a sensitive sandwich ELISA, in 108 patients with chronic viral hepatitis, which included chronic hepatitis (CH) and liver cirrhosis (LC), and hepatocellular carcinoma (HCC), and in 29 normal controls. TPO mRNA in 78 liver samples was examined by reverse transcription (RT)-PCR. Platelet counts in CH, LC, HCC and controls were 176 +/- 15 x 10(9)/l, 81 +/- 8 x 10(9)/l, 99 +/- 7 x 10(9)/l and 234 +/- 9 x 10(9)/l respectively. Serum TPO levels in CH, LC and HCC were 2.79 +/- 0.4 fmol/ml, 1.49 +/- 0.2 fmol/ml and 1.97 +/- 0.2 fmol/ml, and were higher than those of controls. Serum TPO levels were positively correlated with prothrombin time and serum albumin (P < 0.05, in each case), and negatively correlated with Indocyanine Green test and Pugh score (P < 0.01 and P < 0.05 respectively). However, RT-PCR and immunohistochemistry showed that expression of TPO mRNA and protein were similar in the different liver diseases, suggesting that serum TPO is a reflection of the total mass of functional liver. Platelet counts were negatively correlated with spleen index, but not with serum TPO. These results suggest that thrombocytopenia in liver disease is not directly associated with serum TPO but is associated with hypersplenism.

Adult↗
PubMed1999

Glycogen storage disease type IIIa: first report of a causative missense mutation (G1448R) of the glycogen debranching enzyme gene found in a homozygous patient.

Several different mutations in the glycogen-debranching enzyme gene AGL have been found in patients with glycogen storage disease type III (GSD III) to date, but no missense mutations have been reported for GSD III, only nonsense, splicing, and deletion/insertion lesions. Here we describe a novel G1448R missense mutation in a Japanese GSD IIIa patient from a consanguineous family. Sequence analysis of cDNA from the patient' liver specimen revealed two separate nucleotide changes: a G-to-A transition at nucleotide 3737 in exon 26 (3737G>A) and a G-to-C transversion at nucleotide 4742 in exon 33 (4742G>C), both of which result in substitution of glycine by arginine (G1115R and G1448R). Because homo-zygotes for G1115R were found in healthy controls, G1115R seems to be a polymorphism. Restriction fragment length polymorphism analysis with Bsa JI showed that the patient was homozygous for G1448R and that none of the normal controls had the mutation. This missense mutation is located at a putative glycogen-binding site that is indispensable for enzyme activity. Thus, G1448R is likely to be the causative mutation in this patient. This is the first report of a missense mutation associated with GSD III.

Amino Acid Substitution↗
PubMed1999

Reduced prevalence of diabetes according to 1997 American Diabetes Association criteria.

AIMS/HYPOTHESIS: We examined the prevalence of diabetes and investigated the characteristics of subjects diagnosed by the American Diabetes Association and the World Health Organization criteria. METHODS: A total of 1235 Japanese-Americans living in Hawaii and Los Angeles was studied. Of the subjects 114 were classified as previously diagnosed as having diabetes. A 75-g glucose tolerance test was given to the rest of the subjects. RESULTS: When abnormal glucose tolerance was diagnosed by the American Diabetes Association criteria, it was possible to identify only 40 % of diabetic subjects who had not been previously diagnosed compared with the current World Health Organization criteria based on a glucose tolerance test. In addition, the subjects identified by the American Diabetes Association criteria had higher glucose concentrations and had less insulin secretory capacity and they were in need of intensive treatment for diabetes. On the other hand, the subjects not diagnosed by the American Diabetes Association criteria alone were those whose glucose tolerance would be more likely to improve with lifestyle modification. CONCLUSION/INTERPRETATION: It might be better to use the fasting plasma glucose criterion advocated by the American Diabetes Association in combination with a glucose tolerance test after taking a detailed medical history. To reduce the number of subjects requiring the glucose tolerance test, priority should be given to subjects with impaired fasting glucose (6.1 </= fasting plasma glucose < 7.0 mmol/l). [Diabetologia (1999) 42: 1168-1170]

Adult↗
PubMed1999

Association of beta3-adrenergic receptor gene polymorphism with insulin resistance in Japanese-American men.

The Trp64Arg variant of the beta3-adrenergic receptor (beta3-AR) gene is relatively common in Japanese people. We hypothesized that this variant may be associated with obesity and insulin resistance when combined with a westernized lifestyle. To test this hypothesis, we investigated the relationships between the beta3-AR gene variant and obesity and insulin resistance in Japanese-American men, who are known to have a higher prevalence of type 2 diabetes mellitus (DM). The subjects were 152 Japanese-American men living in Hawaii, 83 with normal glucose tolerance (NGT), 40 with impaired glucose tolerance (IGT), and 29 with DM. The frequency of the Trp64Arg allele of the beta3-AR gene was 0.18, almost identical to that of the mainland Japanese. The prevalence of the Trp64Arg allele was 30.1% in NGT, 35.0% in IGT, and 41.4% in DM subjects (nonsignificant). The Trp64Arg variant of the beta3-AR gene showed no significant relationship with obesity or insulin resistance in NGT subjects. However, fasting and 2-hour insulin levels and insulin resistance as determined by homeostasis model assessment (HOMA) were significantly higher in IGT subjects with the Trp64Arg variant. Although indices of obesity were the same in IGT subjects with and without the Trp64Arg variant, differences in the body mass index (BMI) and percent body fat between NGT and IGT subjects were greater for individuals with the Trp64Arg variant. Thus, there is an association between the Trp64Arg variant of the beta3-AR gene and insulin resistance in Japanese-Americans with IGT.

Adult↗
PubMed1999

Effect of probucol on hypercholesterolemia in renal transplant patients.

BACKGROUND: Hypercholesterolemia is a well-known complication in kidney transplant recipients, although its pathogenesis may be multifactorial. The therapeutic effect of probucol on post-transplant hypercholesterolemia was prospectively evaluated. METHODS: Twelve hypercholesterolemic kidney transplant patients with serum total cholesterol > or = 250 mg/dl without diabetes mellitus or hypoproteinemia were prospectively treated with probucol (250 mg, bid, for three months). Before initiating and at the end of treatment, blood was drawn after at least a 12-hour fast to measure lipids in serum and lipoprotein fractions, apoproteins (apo), lipoprotein fractions, lethicin cholesterol acyl transferase (LCAT), free fatty acids (FFAs), and cholesterol ester. The lipid profiles of 17 healthy subjects were also examined. RESULTS: After treatment with probucol, serum total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and apo AI were significantly decreased, whereas cholesterol ester increased significantly. CONCLUSIONS: Post-transplant hypercholesterolemia is featured with abnormalities in very low-density lipoprotein (VLDL) metabolism. Although HDL cholesterol decreased, probucol might have acted as an antiatherogenic by modulating HDL metabolism and stimulating reverse transfer of cholesterol from peripheral tissue.

Adult↗
PubMed1999

Inhibition of hepatocellular carcinoma by glycyrrhizin in diethylnitrosamine-treated mice.

Glycyrrhizin (GL) is widely used in Japan as a therapeutic agent for chronic active liver diseases. However, its action on hepatocarcinogenesis remains to be elucidated. To clarify its effect, mice treated with diethylnitrosamine (NDEA) with or without GL were analyzed. Five-week-old male BALB/c mice were divided into two groups, GL (n=50) and C (n=47). Mice in the GL group intramuscularly received 2 mg of GL 3 days a week, and mice in the C group received the same volume of saline in the same way. After 2 weeks, the mice were treated with an i.p. injection of 75 mg/kg body wt of NDEA weekly for 3 weeks and 100 mg/kg body wt of NDEA weekly for the following 3 weeks. Thirty additional mice that did not receive NDEA treatment were divided into two groups, GC (n=15) and SC (n=15). They received GL or saline, respectively. Mice in the 4 groups were killed every 5 weeks after the last injection of NDEA from 7 weeks to 32 weeks. Liver function tests such as AST and albumin were significantly improved in the GL group compared with the C group (P < 0.05, each). Although liver nodules appeared in the C group at 22 weeks, they were not observed until 32 weeks in the GL group. At 32 weeks, the mean number of liver tumors, composed of adenoma and hepatocellular carcinoma (HCC), in the GL group was 0.71, which was significantly decreased compared with 1.64 of the C group (P < 0.05). The mean number of HCC in the GL group was 0.29/liver, which was lower than 0.82/liver in the C group (P < 0.05). The incidence rate of HCC at 32 weeks was 64% in the C group and 21% in the GL group (P < 0.05, C versus GL group). Our results suggest that GL treatment inhibits the occurrence of HCC.

Adenoma↗
PubMed1999

Characterisation of T cell clonotypes that accumulated in multiple joints of patients with rheumatoid arthritis.

OBJECTIVE: To investigate whether identical T cell clonotypes accumulate in multiple rheumatoid joints, the clonality of T cells that had infiltrated into synovial tissue (ST) samples simultaneously obtained from multiple joints of patients with rheumatoid arthritis (RA) was analysed. METHODS: T cell receptor (TCR) beta gene transcripts, amplified by reverse transcription-polymerase chain reaction from ST and peripheral blood lymphocytes of five RA patients, were subjected to single strand conformation polymorphism analysis and DNA sequencing. RESULTS: Approximately 40% of accumulated T cell clonotypes found in one joint of a patient were found in multiple joints in the same patient. Furthermore, identical amino acid sequences were found in TCR beta junctional regions of these clonotypes from different patients with at least one HLA molecule match. CONCLUSIONS: The T cell clonotypes accumulating in multiple rheumatoid joints may be involved in the perpetuation of polyarthritis by reacting to antigens common to these multiple joints.

Amino Acid Sequence↗
PubMed1999

Effects of background color on the global and local processing of hierarchically organized stimuli.

Recent studies have shown that (1) the global precedence effects in processing the hierarchically organized stimulus can be attenuated by eliminating the low spatial frequencies contained in the stimulus and (2) the human magnocellular pathway is responsible for processing low spatial frequencies and the pathway can be attenuated by imposing a red background on the stimulus. In the present study, a reaction-time experiment was conducted to examine the effect of background color of the stimulus to the processing of the hierarchically organized stimulus. The result showed that although the control condition (a green background) produced a prototypical asymmetric global interference, a red background that was equiluminant to the green background produced a symmetrical interference. It was concluded that the human magnocellular pathway is at least partially responsible in producing the global precedence effects.

Analysis of Variance↗
PubMed1999

HLA class I deficiencies due to mutations in subunit 1 of the peptide transporter TAP1.

The transporter associated with antigen processing (TAP), which is composed of two subunits (TAP1 and TAP2) that have different biochemical and functional properties, plays a key role in peptide loading and the cell surface expression of HLA class I molecules. Three cases of HLA class I deficiency have previously been shown to result from the absence of a functional TAP2 subunit. In the present study, we analyzed two cases displaying not only the typical lung syndrome of HLA class I deficiency but also skin lesions, and found these patients to be TAP1-deficient. This defect leads to unstable HLA class I molecules and their retention in the endoplasmic reticulum. However, the absence of TAP1 is compatible with life and does not seem to result in higher susceptibility to viral infections than TAP2 deficiency. This work also reveals that vasculitis is often observed in HLA class I-deficient patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗