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Biomedical subjects

Yoshinao Kobayashi

Publications and source records attributed to Yoshinao Kobayashi.

At least 19 recordsLinked to original sources
PubMed2006

Hepatic oxidative DNA damage correlates with iron overload in chronic hepatitis C patients.

Hepatic oxidative stress occurs in chronic hepatitis C (CH-C), but little is known about its producing mechanisms and precise role in the pathogenesis of the disease. To determine the relevance of hepatic oxidatively generated DNA damage in CH-C, 8-hydroxy-2'-deoxyguanosine (8-OHdG) adducts were quantified in liver biopsy specimens by immunohistochemical staining, and its relationship with clinical, biochemical, and histological parameters, and treatment response was assessed in 40 CH-C patients. Hepatic 8-OHdG counts were significantly correlated with serum transaminase levels (r=0.560, p=0.0005) and histological grading activity (p=0.0013). Remarkably, 8-OHdG levels were also significantly related to body and hepatic iron storage markers (vs serum ferritin, r=0.565, p=0.0004; vs hepatic total iron score, r=0.403, p=0.0119; vs hepatic hepcidin messenger RNA, r=0.516, p=0.0013). Baseline hepatic oxidative stress was more prominent in nonsustained virological responder (non-SVR) than in SVR to interferon (IFN)/ribavirin treatment (50.8 vs 32.7 cells/10(5) microm2, p=0.0086). After phlebotomy, hepatic 8-OHdG levels were significantly reduced from 53.4 to 21.1 cells/10(5) microm2 (p=0.0125) with concomitant reductions of serum transaminase and iron-related markers in CH-C patients. In conclusion, this study showed that hepatic oxidatively generated DNA damage frequently occurs and is strongly associated with increased iron deposition and hepatic inflammation in CH-C patients, suggesting that iron overload is an important mediator of hepatic oxidative stress and disease progression in chronic HCV infection.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2006

Lactoferrin inhibits lipid peroxidation in patients with chronic hepatitis C.

Lactoferrin is a milk protein with inhibitory effect on lipid peroxidation induced by oxidative stress. Oxidative stress plays an important role in the pathogenesis of chronic hepatitis C (CHC). The aim of this study was to evaluate the effect of bovine lactoferrin (bLF) monotherapy on lipid peroxidation, hepatic inflammation and iron metabolism in patients with CHC. Ninety Japanese patients with CHC were randomly assigned to two groups: bLF group (n=47) treated with bLF at a dose of 3.6g/day and a control group (n=43) that remained untreated. Plasma 8-isoprostane levels and clinical laboratory data including iron metabolism parameters were measured. Plasma 8-isoprostatne level was significantly decreased from 8.6+/-3.7 to 6.9+/-2.1pg/ml in the bLF group (P<0.05). Plasma levels of 8-isoprostane did not significantly change in the control group. The decline in plasma 8-isoprostane levels was positively correlated with improvement in the level of ALT in the bLF group. No significant change in serum HCV RNA levels or iron metabolism markers was found after bLF treatment. Therapy with bLF was associated with improvement in lipid peroxidation and ALT levels in CHC. Administration of bLF is a promising therapeutic approach for suppressing oxidative stress in non-responders to antiviral therapy.

Journal Article↗
PubMed2006

Physicochemical and pharmacokinetic characterization of highly potent recombinant L-methionine gamma-lyase conjugated with polyethylene glycol as an antitumor agent.

A highly potent recombinant L-methionine gamma-lyase (METase) conjugated with polyethylene glycol (PEG) was characterized physicochemically and pharmacokinetically in vivo and in vitro. Pegylated METase (PEG-METase), which contains pyridoxal 5'-phosphate (PLP) as a cofactor in the molecule, is a potent anticancer agent that can deplete L-methionine from plasma. Although pegylation decreased its specific activity, dithiothreitol (DTT) treatment increased it over three times with the detachment of one PEG moiety modified with a cysteine residue. We can produce DTT-treated PEG-METase on a large scale in sufficient quality for therapeutic use. The superiority of DTT-treated PEG-METase was confirmed by the enhancement of L-methionine depletion and amelioration of pharmacokinetics in mice. The holoenzyme of DTT-treated PEG-METase gave a several times larger area under the plasma concentration curve than that of DTT-untreated PEG-METase, not because of an increase of the half-life but because of high specific activity. Conversely, simultaneous PLP infusion led to a greatly increased half-life of the holoenzyme. DTT-treated PEG-METase administration with PLP infusion was the most useful combination for maximizing the potency of the enzyme. We showed that serum albumin interfered with holoenzyme activity in vitro. The decrease of holoenzyme activity was dependent on the type of serum albumin. We concluded that PLP was released from PEG-METase by serum albumin in vivo and in vitro. The deleterious effect of PLP dissociation from PEG-METase could be improved by supplementing PLP and oleic acid. Their synergistic effect in preventing a decrease of the holoenzyme activity was also observed.

Animals↗
PubMed2006

Role of transferrin receptor 2 in hepatic accumulation of iron in patients with chronic hepatitis C.

BACKGROUND AND AIM: Iron deposition in the liver is a common finding in patients with chronic hepatitis C (CH-C). The mechanism of this hepatic accumulation of iron is not completely understood. This study assessed if the protein expression of transferrin receptor 2 (TfR2) is upregulated in the liver of patients with CH-C and if TfR2 protein mediates iron accumulation during hepatitis C virus (HCV) infection. METHOD: Liver specimens from patients with CH-C that underwent interferon (IFN) therapy (n=23) and from patients with CH-B (n=18) were evaluated. Hepatic expression of TfR2 protein was analyzed by immunohistochemistry. Total hepatic iron score (THIS) was evaluated by Prussian blue staining. RESULTS: TfR2 protein was expressed in the cell membrane and cytosol of hepatocytes. Cytosol TfR2 protein was found to co-localize with Tf. THIS (P=0.0198) and hepatic TfR2 (P=0.0047) expression were significantly higher in CH-C than in CH-B. The change in THIS values (rho=0.580, P=0.0079) and the grade of histological activity (rho=0.444, P=0.0373) were significantly correlated with changes in TfR2 expression after IFN therapy. CONCLUSIONS: The protein expression of TfR2 is significantly associated with iron deposition in the liver in patients with CH-C. HCV infection may affect the hepatic expression of TfR2, leading to iron accumulation in the liver.

Adult↗
PubMed2006

Increased lipid peroxidation in patients with non-alcoholic fatty liver disease and chronic hepatitis C as measured by the plasma level of 8-isoprostane.

BACKGROUND: Oxidative stress plays an important role in the pathogenesis of chronic liver diseases. The plasma level of 8-isoprostane, a product of lipid peroxidation, is a marker of oxidative stress in vivo. The aim of the present study was to clarify whether the degree of lipid peroxidation, as measured by the plasma level of 8-isoprostane, influences the progression of chronic liver diseases and hepatocarcinogenesis. METHODS: Plasma 8-isoprostane levels were investigated in 14 patients with non-alcoholic fatty liver disease (NAFLD), 75 with chronic hepatitis C (CH-C), 14 with cured CH-C, 14 with HCV-positive hepatocellular carcinoma (HCC-C) and 38 healthy volunteers. 8-Isoprostane was measured by enzyme immunoassay after affinity column purification. RESULTS: Plasma 8-isoprostane was significantly elevated in NAFLD (11.9 [3.8-56.8] pg/mL), CH-C (10.1 [4.2-134.5] pg/mL) as compared to controls (6.3 [3.6-11.1] pg/mL). Plasma 8-isoprostane values were positively correlated with body mass index in NAFLD (P < 0.05) and with total cholesterol in cured CH-C (P < 0.01). 8-Isoprostane levels were not significantly related to sex, age, biochemical data or iron metabolism markers in all liver diseases. In addition, after the administration of peg-interferon, the values of 8-isoprostane improved in almost all patients, reaching values of healthy subjects. CONCLUSIONS: 8-Isoprostane values are elevated in patients with NAFLD and CH-C as compared to healthy controls. Oxidative stress caused by increased lipid peroxidation is involved in the pathogenesis of NAFLD and CH-C.

Adolescent↗
PubMed2006

Morphological identification of hepatitis C virus E1 and E2 envelope glycoproteins on the virion surface using immunogold electron microscopy.

It is known that hepatitis C virus (HCV) particles are spherical, 55-65 nm particles with fine surface projections of about 6 nm in length and with a 30-35 nm inner core. We have reported that free HCV particles labeled with gold particles specific to the HCV E1 glycoprotein are located in 1.14-1.16 g/ml fractions from plasma samples with high HCV RNA titers after sucrose density gradient centrifugation. However, the morphology of the HCV E2 glycoprotein on the virion has not yet been elucidated. To visualize HCV E2 localization on the virion, we used the same plasma samples where HCV particles were clearly shown. An indirect immunogold electron microscopic study was carried out using monoclonal and polyclonal anti-HCV E2 antibodies. HCV-like particles specifically reacted with the anti-HCV E2 antibodies. Moreover, to evaluate the localization of the HCV E1 and E2 glycoproteins on the virion surface, an immunogold electron microscopic study using double labeling with anti-HCV E1 antibodies and anti-HCV E2 antibodies was also performed. These particles also specifically reacted with both anti-E1 and E2 antibodies. This is the first report showing the presence of both HCV E1 and E2 glycoproteins on HCV virion surface in human plasma samples.

Hepacivirus↗
PubMed2006

Linkage disequilibrium of UGT1A1 *6 and UGT1A1 *28 in relation to UGT1A6 and UGT1A7 polymorphisms.

UDP-glucuronosyltransferase (UGT) enzymes are responsible for the glucuronidation and detoxification of many endogenous or exogenous xenobiotics. Gilbert's syndrome (GS) and Crigler Najjar syndrome type 2 (CNS-II) are characterized by unconjugated hyperbilirubinemia due to reduced enzymatic activity of UGT1A1. Recent studies have demonstrated the frequent co-existence of UGT1A1 *28 (-53 [TA]6>7) with other polymorphisms of UGT1A6 and UGT1A7. This finding suggests the occurrence of linkage disequilibrium (LD) among UGT1A1, UGT1A6 and UGT1A7 polymorphisms. UGT1A1 *6 (211G>A, G71R) and UGT1A1 *28 are common in Asian populations. In the present study, we investigated the LD of UGT1A1 *6 and UGT1A1 *28 in relation to UGT1A6 and UGT1A7 polymorphisms. Exon 1 of UGT1A1, UGT1A6 and UGT1A7 was sequenced using genomic DNA isolated from peripheral leukocytes of 390 Japanese subjects. LD and haplotypes were analyzed using SNPAlyze ver. 5.0 software. UGT1A1 *6 had a strong LD in relation to UGT1A6 variants including 541A>G and 552A>C (D'=0.846-0.848, r(2)=0.413-0.438) and UGT1A7 variants including 387T>G, 391C>A, 392G>A and 622T>C (D'=0.667-0.858, r(2)=0.207-0.413). UGT1A1 *28 had a lower degree of LD than UGT1A1 *6 in relation to these variants (D'=0.245-0.401, r(2)=0.025-0.063). All the haplotypes with G71R lacked -53[TA]6>7. The present study showed for the first time that the LD of UGT1A1 *6 in relation to UGT1A6 and 1A7 polymorphisms is far stronger than UGT1A1 *28. The UGT1A1 *6 allele appears to be independent of the UGT1A1 *28 allele. Although patients with GS and CNS-II are believed to have good prognosis, a subgroup of GS or CNS-II patients with the UGT1A1 *6 polymorphism might be at risk of abnormal drug metabolism and of developing malignant disease.

Adult↗
PubMed2005

Improvement of regional cerebral blood flow after oral intake of branched-chain amino acids in patients with cirrhosis.

AIM: To evaluate the effect of oral intake of branched-chain amino acids (BCAA) on brain perfusion in patients with liver cirrhosis. METHODS: Single photon emission computed tomography scans were performed in 43 patients with cirrhosis and in 15 age-matched healthy subjects. Twenty-nine out of forty-three patients were randomly treated with either BCAA granules or placebo, and single photon emission computed tomography was performed before and after the treatment. We measured the regional cerebral blood flow values using a three-dimensional stereotaxic region of interest template. RESULTS: Cirrhotic patients had regions of significant hypoperfusion in the bilateral central (right P=0.039, P<0.05; left P=0.006 P<0.01), parietal (right P=0.018, P<0.05; left P=0.009, P<0.01), angular (right P=0.039, P<0.05; left P 0.008, P<0.01), and left pericallosal segments (P=0.038 P<0.05) as compared with healthy subjects. A significant increase in cerebral perfusion was observed 70 min after the oral intake of BCAA in the angular (right P=0.012, P<0.05; left P=0.049, P<0.05), temporal (right P=0.012, P<0.05; left P=0.038, P<0.05), pericallosal segments (right P=0.025, P<0.05; left P=0.049, P<0.05) and left precentral (P=0.044, P<0.05), parietal (P=0.040, P<0.05) and thalamus (P=0.033, P<0.05). No significant change in perfusion was observed in the placebo group. CONCLUSION: Administration of BCAA rapidly improves cerebral perfusion.

Administration, Oral↗
PubMed2005

Polymorphism of UDP-glucuronosyltransferase 1A7 gene: a possible new risk factor for lung cancer.

UDP-glucuronosyltransferase (UGT) 1A7 detoxifies hydroxylated benzo-(alpha)-pyrenes and 2-hydroxyamino-1-methyl-6-phenylimidazo (4,5-beta) pyridine. The purpose of this study was to evaluate whether UGT1A7 polymorphisms are risk factors for lung cancer. A total of 113 Japanese patients with lung cancer and 178 healthy individuals were enrolled in this study. Genomic DNA was isolated from leukocytes. Exon 1 of UGT1A7 was sequenced. Homozygous UGT1A7*3/3 was observed in 17 (15%) of patients with lung cancer, and this incidence was significantly increased compared with the control group (4.5%, P=0.0036). Multivariate logistic regression analysis demonstrated a significant association of lung cancer with Brinkmann index (odds ratio=4.577, P=0.0004) and homozygous UGT1A7*3 (odds ratio=4.020, P=0.0037). The presence of UGT1A7 polymorphisms was associated with lung cancer. Homozygous UGT1A7*3 is a possible risk factor for lung cancer, at least in the Japanese population. Thus, determination of UGT1A7 polymorphisms may provide an important clue to preventive measures against lung cancer.

Adult↗
PubMed2005

Accumulation of 8-nitroguanine in the liver of patients with chronic hepatitis C.

BACKGROUND/AIMS: Nucleic acid damage by reactive nitrogen and oxygen species may contribute to inflammation-related carcinogenesis. To investigate the extent of nucleic acid damage in hepatitis C virus infection and its change after interferon treatment, we measured 8-nitroguanine and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the liver of patients with chronic hepatitis C (CHC) before and after interferon therapy. METHODS: Hepatic accumulation of 8-nitroguanine and 8-OHdG was immunohistochemically evaluated in 20 CHC patients and 7 control patients with non-alcoholic fatty liver. RESULTS: Immunoreactivities of 8-nitroguanine and 8-OHdG were strongly detected in the liver from patients with CHC, but not in control livers. 8-Nitroguanine accumulation was found not only in infiltrating inflammatory cells, but also hepatocytes particularly in the periportal area. The accumulation of 8-nitroguanine and 8-OHdG increased with inflammatory grade (8-nitroguanine; P = 0.0019, 8-OHdG; P = 0.0009). In the sustained virological responder group after interferon therapy, 8-nitroguanine and 8-OHdG accumulation were markedly decreased in the liver (8-nitroguanine; P = 0.018, 8-OHdG; P = 0.018). CONCLUSIONS: In this study, we demonstrated for the first time that 8-nitroguanine accumulated in the liver of patients with CHC. 8-Nitroguanine is a useful biomarker to evaluate the severity of HCV-induced chronic inflammation in relation to hepatocellular carcinoma.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2005

Upregulation of transferrin receptor 2 and ferroportin 1 mRNA in the liver of patients with chronic hepatitis C.

BACKGROUND: Iron accumulation has been reported to be associated with progression of liver injury. The mechanism of iron accumulation in the liver is not known. In the present study, hepatic messenger RNA (mRNA) expression of transferrin receptor (TfR)1, TfR2, and ferroportin (FP)1 was measured in patients with chronic hepatitis (CH). METHODS: Eleven patients with CH-B and 43 patients with CH-C were enrolled. All patients underwent liver biopsy. Hepatic expression of TfR1, TfR2 and FP1 mRNA was analyzed using a real-time polymerase chain reaction. Total hepatic iron score (THIS) was evaluated by Prussian blue staining. RESULTS: Serum ferritin concentration is significantly higher in CH-C than in CH-B. Values of THIS of >/=5 were observed only in CH-C patients (44% of CH-C patients). The expression level of TfR2 mRNA was 10-26-fold higher than the TfR1 mRNA expression level. The TfR2 and FP1 mRNA expression was significantly higher in CH-C than in CH-B patients. Hepatic expression of TfR2 and FP1 mRNA was well correlated with THIS. CONCLUSIONS: Hepatic iron accumulation is more severe in patients with CH-C. Upregulation of hepatic iron transporters may contribute to the hepatic iron accumulation in CH-C.

Adult↗