Mari Inoue

Kochi University, Kōchi-shi, Kochi-ken, Japan

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Publications (14)39.16 Total impact

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    ABSTRACT: α-Klotho was first identified as an aging gene and was later shown to be a regulator of phosphate metabolism. Fibroblast growth factor 23 (FGF23) is the key regulator of phosphate metabolism. Serum levels of soluble α-Klotho in chronic kidney disease (CKD) patients have not previously been determined, especially in relation with FGF23 and creatinine levels. This study was designed to investigate whether serum soluble α-Klotho levels are modulated by renal function, age, and FGF23 level in CKD patients. This study is the first report on the utility of measuring soluble α-Klotho levels in human CKD. A total of 292 CKD patients were enrolled. Serum samples were collected, and FGF23 and soluble α-Klotho levels were measured using enzyme-linked immunosorbent assay kits. In addition, serum creatinine, hemoglobin, albumin, calcium, and phosphate levels were measured. Serum soluble α-Klotho levels were associated positively with estimated glomerular filtration rate (eGFR) (P < 0.0001) and inversely with serum creatinine level (P < 0.01). Interestingly, α-Klotho levels were significantly decreased in stage 2 CKD compared with stage 1 (P = 0.0001). Serum FGF23 levels were associated positively with serum creatinine and negatively with eGFR. FGF23 levels were significantly increased in stage 5 compared with stage 1 CKD. Soluble α-Klotho was associated inversely with log-transformed FGF23 level (P < 0.01). Our data indicate that soluble α-Klotho levels are significantly decreased in stage 2 CKD compared to stage 1, and not only in the advanced stages of the disease. Soluble α-Klotho may thus represent a new biomarker for the diagnosis of CKD, especially in the early stage.
    Clinical and Experimental Nephrology 03/2012; 16(5):722-9. · 1.25 Impact Factor
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    ABSTRACT: Fetuin-A, also known as alpha2-Heremans Schmid glycoprotein, is an abundant plasma protein synthesized predominantly in the liver. Fetuin-A inhibits insulin receptor autophosphorylation, which is mediated by its intrinsic tyrosine kinase activity. In this study, we examined the association between the serum fetuin-A level and insulin resistance in Japanese men. We recruited 300 unrelated Japanese men without known chronic diseases, such as diabetes mellitus, or a history of regular drug use, and who underwent health examinations. From a 75-g oral glucose tolerance test, the study population included 194 individuals with normal glucose tolerance, 91 with impaired glucose tolerance and/or impaired fasting glucose, and 15 with diabetes mellitus. Serum fetuin-A concentrations were measured using an ELISA kit. Serum fetuin-A concentrations were positively correlated with fasting insulin levels (r = 0.269, p<0.001), HOMA-IR (r = 0.274, p<0.001) and LDL-cholesterol (r = 0.172, p<0.01), and negatively correlated with HDL-cholesterol concentrations (r = -0.191, p<0.001). Fetuin-A concentrations were also positively correlated with serum leptin (r = 0.150, p<0.01) and negatively with adiponectin concentrations (r = -0.208, p<0.001). Stepwise regression analyses confirmed that the fetuin-A concentration was independently associated with the fasting insulin level and HOMA-IR, as were body mass index, triglyceride, LDL-cholesterol, leptin and adiponectin concentrations. Our data suggest that increased serum fetuin-A levels constitute an independent marker of insulin resistance and an atherogenic lipid profile in Japanese men.
    Journal of atherosclerosis and thrombosis 09/2010; 17(9):925-33. · 2.93 Impact Factor
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    ABSTRACT: We have demonstrated that pitavastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, enhanced human serum paraoxonase (PON1) gene promoter activity and that protein kinase C (PKC) activated PON1 expression through Sp1 in cultured HepG2 cells. We investigated whether PKC was involved in pitavastatin-induced PON1 expression. PON1 gene promoter activity was assessed by a reporter gene assay using cultured Huh7 cells. PON1 protein expression and PKC activation were measured by Western blotting. The binding activity of Sp1 to the PON1 gene upstream was analyzed by electrophoretic mobility shift assay. Both PON1 gene promoter activity and PON1 protein expression were elevated by pitavastatin stimulation. The effects of pitavastatin on PON1 promoter activity and PON1 protein expression were attenuated by both bisindolylmaleimide IX (Ro-31-8220) and bisindolylmaleimide I. Electrophoretic mobility shift assay showed that pitavastatin increased the Sp1-PON1 DNA binding, and this effect was attenuated by Ro-31-8220. Pitavastatin activated atypical PKC, but never conventional or novel PKC. Myristoylated pseudosubstrate peptide inhibitor of PKCzeta abolished the pitavastatin-increased PON1 promoter activity; however, calphostin C and Gö6976 (PKC inhibitors except for PKCzeta) did not influence the promoter activity. In addition, an overexpression of dominant negative form of PKCzeta expression vector obviously decreased pitavastatin-induced PON1 promoter activation. These observations suggest that pitavastatin activates PKC, especially PKCzeta isoform, which increases the binding intensity of Sp1 to PON1 DNA promoter responsible for enhanced transcription of PON1 gene and increased PON1 protein expression in Huh7 cells.
    Metabolism: clinical and experimental 09/2010; 59(9):1287-93. · 3.10 Impact Factor
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    ABSTRACT: A 55-year-old woman with signs of acromegaly was referred to our hospital. Endocrinological examinations showed that she had high levels of growth hormone (GH; 5.54 ng ml(-1); normal range: 0.66-3.68 ng ml(-1)) and insulin-like growth factor-I (IGF-I; 508 ng ml(-1); normal range: 37-266 ng ml(-1)) levels, incomplete suppression of serum GH following a 75-gram oral glucose tolerance test (oGTT; trough GH 3.66 ng ml(-1)), and paradoxical GH responses to a TRH provocation test (peak GH 38.9 ng ml(-1)). Dynamic magnetic resonance imaging (MRI) suggested the presence of an intrasellar mass lesion (5.9 x 2.8 mm) in the left part of her pituitary gland (Fig. 1a, upper panel). F-18 fluorodeoxyglucose (FDG) positron emission tomographic (PET) imaging clearly showed focal but remarkable FDG uptake (Fig. 1a, lower panel), consistent with the localization of the tumor suspected on MRI. The tumor was removed by transsphenoidal surgery. Subsequent histological analysis confirmed the diagnosis of a GH-producing pituitary adenoma. After removal, serum IGF-I levels decreased to a normal range (178 ng ml(-1)), and serum GH was appropriately suppressed during oGTT (trough GH 0.30 ng ml(-1)), suggesting that complete resection was obtained [1]. While postsurgical changes made it difficult to detect any residual lesion on MRI (Fig. 1b, upper panel), abnormal FDG uptake was not seen on FDG-PET after surgery (Fig. 1b, lower panel). PET scans are reported to be a valuable tool for the detection of pituitary adenomas [2-4]. This case clearly showed that FDG-PET is also useful for re-evaluation of the disease after surgery. PET scans are recommended for patients with equivocal pituitary mass lesions on conventional MRI, and for follow-up examinations after surgery.
    Pituitary 11/2009; 13(1):78-9. · 2.67 Impact Factor
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    ABSTRACT: Alpha2-Heremans Schmid glycoprotein (AHSG), also known as fetuin-A, is secreted from the liver and inhibits tyrosine kinase activity of the insulin receptor. Hyperglycemia in type 2 diabetes is not only a secondary manifestation of insulin resistance, but could also be responsible for directly inducing insulin resistance in target tissues. In this study, we examined the effect of high glucose (HG) on AHSG gene transcription in the human hepatoma cell line HepG2. AHSG transcriptional activity and protein expression were evaluated using reporter gene assays and Western blot analysis, respectively. D-glucose, but not L-glucose or mannitol, dose-dependently enhanced AHSG promoter activity. HG (25 mM) also increased AHSG protein expression. No protein kinase C inhibitors (bisindolylmaleimide, Ro-31-8220), an inhibitor of hexosamine biosynthesis pathway (6-diazo-5-oxo-L-norleucine), or a superoxide radical scavenger (tempol) affected HG-induced transactivation. MAPK/ERK kinase inhibitors (PD98059, U0126), but not the JNK inhibitor (SP600125) or p38 inhibitor (SB203580), significantly inhibited promoter activation by HG. Our data suggest that HG enhances AHSG transcription through activation of the ERK1/2 signaling pathway. Increased AHSG expression in the liver may be a cause of glucose toxicity in the diabetic state.
    Journal of atherosclerosis and thrombosis 09/2009; 16(4):448-56. · 2.93 Impact Factor
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    ABSTRACT: Human serum paraoxonase (PON1) is associated with HDL and inhibits oxidative modification of LDL. PON1 enzymatic activity has been shown to decrease in diabetic patients; however, the effect of PON1 status on long-term outcome has not been reported. In this study, we examined the association between baseline PON1 status and the development of cardiovascular disease (CVD) during 10 years of follow-up in 88 type 2 diabetic patients whose enzymatic activities, concentrations, and genetic polymorphisms of PON1 had been determined. A total of 20 CVD events were recorded during the follow-up period. Using Kaplan-Meier survival curves, we found a significantly increased incidence of CVD in patients with a lower concentration or paraoxonase activity of PON1 than each median value (log-rank 7.460; P < 0.01, and log-rank 4.187; P < 0.05, respectively). By Cox regression analysis, both concentration and paraoxonase activity were significantly associated with the development of CVD, even after correction for gender, age, and preexisting CVD (P < 0.05). Low concentration and enzymatic activity of PON1 may be an independent predictor of cardiovascular events in diabetic patients.
    Acta Diabetologica 10/2008; 46(3):239-42. · 4.63 Impact Factor
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    ABSTRACT: It has been shown that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors have pleiotropic effects and that human serum paraoxonase (PON1) inhibits the oxidative modification of low-density lipoprotein. We investigated the effects of pitavastatin on PON1 gene promoter activity and PON1 protein expression through the activation of mitogen-activated protein (MAP) kinase signaling cascades in cultured Huh7 cells. Both PON1 gene promoter activity and PON1 protein expression were elevated by pitavastatin stimulation. Pitavastatin phosphorylated p44/42 MAP kinase. The effects of pitavastatin on PON1 promoter activity and PON1 protein expression were attenuated by PD98059. The cotransfection of Sp1 expression vector increased PON1 promoter activity, and mithramycin suppressed pitavastatin-enhanced PON1 promoter activity. The latter activity was attenuated by cotransfection with the expression vector of sterol regulatory element-binding protein-2 (SREBP-2) with mutated p44/42 MAP kinase specific phosphorylation sites. Pitavastatin increased the Sp1-PON1 DNA complex and this effect was attenuated by PD98059. These observations suggest that pitavastatin phosphorylates p44/42 MAP kinase and then activates the transcription of PON1 gene and increases the PON1 protein expression in Huh7 cells. Furthermore, we speculate that pitavastatin affects both the phosphorylation of SREBP-2 and the Sp1 binding to PON1 DNA through the activation of p44/42 MAP kinase signaling cascade.
    Atherosclerosis 06/2008; 202(2):439-45. · 3.71 Impact Factor
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    ABSTRACT: alpha2-Heremans Schmid glycoprotein (AHSG), also designated fetuin-A, is an abundant plasma protein that is expressed in hepatocytes. AHSG/fetuin-A has diverse biological functions including regulation of calcium homeostasis and inhibition of insulin receptor tyrosine kinase activity. The aim of this study was to detect single nucleotide polymorphisms (SNPs) of the AHSG gene that can be involved in regulation of AHSG/fetuin-A expression. By a cycle sequencing method, two common SNPs in the promoter region of AHSG gene, -799A/T (rs2248690, dbSNP ID) and -425G/T (rs2077119), were identified. A reporter gene assay using HepG2 cells showed that the -799A allele had significantly higher promoter activity compared with the -799T allele. The overexpression of c-Fos/c-Jun significantly repressed transcriptional activity and a gel shift assay showed that the -799T DNA fragment had a greater affinity for transcription factor AP-1 than the -799A. In 40 unrelated healthy subjects, serum AHSG/fetuin-A levels increased with the following order of genotypes: -799TT<-799AT<-799AA (mean+/-S.E.M.; 222.1+/-11.0, 291.8+/-8.1, and 349.0+/-13.0 microg/ml, respectively, P<0.001). In conclusion, SNP rs2248690 in the promoter region of the AHSG gene affects the AHSG gene transcription, possibly by producing different association with AP-1.
    Diabetes research and clinical practice 01/2008; 79(1):164-70. · 2.74 Impact Factor
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    ABSTRACT: The oxidative modification of low-density lipoproteins (LDL) plays a central role in the initiation and acceleration of atherosclerosis. Iron plays a part in the formation of highly toxic free radicals such as hydroxide and superoxide anions, which can induce lipid peroxidation. We investigated whether serum iron status was associated with circulating oxidized LDL (oxLDL) levels in type 2 diabetic patients, in whom oxidative stress and susceptibility to lipid oxidation were supposedly increased. Serum ferritin levels were significantly correlated with plasma oxLDL concentrations in both male and female patients (p<0.02 and p<0.05, respectively). No correlation was detected between ferritin and LDL-cholesterol (LDL-C) concentrations despite the close correlation between LDL-C and oxLDL concentrations (p<0.0001). Stepwise regression analysis showed that ferritin concentration was an independent positive determinant of oxLDL level, in addition to triglyceride concentration, body mass index and sex. This is the first report to show that serum ferritin is associated with circulating oxLDL levels in patients with type 2 diabetes. Further work is required to establish a causative link between iron excess and the development of diabetic vascular complications.
    Endocrine Journal 11/2006; 53(5):665-70. · 2.23 Impact Factor
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    ABSTRACT: The insertion/deletion (I/D) polymorphism in intron 16 of the angiotensin-converting enzyme (ACE) gene is involved in the development of cardiovascular diseases. We compared the ACE mRNA expression originating from the allele with a deletion (D allele) and that from the allele with an insertion (I allele) in human white blood cells from ID heterozygotes. We identified the mRNA from the I allele by using the G2215A polymorphism that lies in exon 15 and that was linked to the I/D polymorphism. RNA samples were obtained from 12 healthy heterozygotes of both I/D and G2215A, and every insertion was shown to be linked to 2215G. ACE mRNA was amplified by the reverse transcription/polymerase chain reaction (RT-PCR) method with an end-labeled antisense primer. The PCR products were digested with HaeII and separated by electrophoresis, and the relative radioactivities of the 2215A and 2215G bands were measured on an auto-image analyzer. The results showed that, in every cases, the intensity of the 2215A product (D allele origin) was higher than that of the 2215G product (I allele origin). The mean ratio of 2215A to 2215G was 1.79 (1.11-2.62). Thus, the D allele leads to higher expression of the ACE mRNA and may affect the renin-angiotensin system in local regions.
    Human Genetics 08/2004; 115(2):91-6. · 4.63 Impact Factor
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    ABSTRACT: A 77-year-old Japanese woman with massive painless ascites caused by chronic lupus peritonitis is reported. Peritoneal effusion had been resistant to the administration of steroids during the whole treatment period. It was characteristic that the titers of anti-DNA antibodies and the level of immune complex were elevated in the peritoneal fluid with suppressed levels of complements in ascites, although serum immunological markers reflecting the activity of SLE presented improvement after initiation of the treatment. Fifteen patients with chronic lupus peritonitis were reported previously. We reviewed the literature and suggest that chronic lupus peritonitis at elderly onset may demonstrate a poor response to the glucocorticoid therapy because of persistent inflammation in the peritoneum and the presence of impaired vascular circulation in addition to immunological mechanisms.
    Internal Medicine 12/2002; 41(11):1056-61. · 0.97 Impact Factor
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    ABSTRACT: The expression of paraoxonase1 (PON1) during inflammation has been investigated in vitro. The alteration of steady state PON1 mRNA in HepG2 cells by interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), was investigated relative to acute-phase serum amyloid A (A-SAA) mRNA. PON1 mRNA expression by HepG2 cells was decreased within three hours of stimulation by IL-1beta or TNF-alpha. Relative to PON1 mRNA expression, the pattern of steady state A-SAA mRNA expression was altered reciprocally and inversely by IL-1beta. These findings suggested that the decrease in serum PON activity after abdominal surgery in our previous clinical study may be ascribed to a decrease in steady state PON1 mRNA expression by liver with proinflammatory cytokines.
    Amyloid 10/2002; 9(3):160-4. · 4.44 Impact Factor
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    ABSTRACT: Cardiac death from atherosclerosis is common in patients undergoing hemodialysis. Although the enzymic activity of human serum paraoxonase (PON1) has been reported to be decreased in such patients, serum PON1 concentrations have not been measured. We investigated serum PON1 concentrations in 81 patients undergoing hemodialysis and 103 age-matched healthy subjects using an enzyme immunoassay. The PON1 concentration was significantly lower in the patient group than the control group (mean +/- SD: 6.78 +/- 3.56 vs 18.01 +/- 4.55 U/ml, respectively. p < 0.0001). There were no significant relationships between serum PON1 concentrations and the PON1 genetic polymorphisms, 55Leu/Met (L/M) and 192Gln/Arg (Q/R). The concentration adjusted for HDL-cholesterol or apolipoprotein A-I was also lower in the patient group. However, the specific activities (enzyme activity divided by the PON1 concentration) of paraoxonase and arylesterase were increased in the patient group compared with the control group. In the male patients, but not the female patients, PON1 concentrations were significantly lower in subjects with than without coronary heart disease (CHD) (mean +/- SD: 4.48 +/- 2.77 vs 7.34 +/- 3.22 U/ml, respectively. p < 0.01). In conclusion, the serum PON1 concentration in hemodialyzed patients was significantly decreased, resulting in an attenuation of PON1 enzymic activity. This decrease may be in part involved in the development of cardiovascular disease.
    Journal of atherosclerosis and thrombosis 01/2002; 9(3):133-8. · 2.93 Impact Factor
  • Diabetes Research and Clinical Practice - DIABETES RES CLIN PRACT. 01/2000; 50:96-96.