Prevention by Methionine of Enhancement of Hepatocarcinogenesis by Coadministration of a Choline-deficient L-Amino Acid-defined Diet and Ethionine in Rats

The effects of methionine on hepatocarcinogenesis induced by Coadministration of a choline-deflcient L-amino acid-defined (CDAA) diet and ethionine were examined. F344 male rats were divided into 4 experimental groups. Groups 1 and 2 received the CDAA diet and a choline-supplemented L-amino acid-defined (CSAA) diet, respectively. Group 3 received the CDAA diet containing 0.05% ethionine, and group 4 the CDAA diet containing 0.05% ethionine and 0.47% methionine. Animals were killed after 12 weeks of treatment. Histologically, the CDAA diet induced intracellular fat accumulation and foci. In contrast, ethionine caused not only foci, but also hyperplastic nodules, cholangiofibrosis and the proliferation of oval cells without such fat accumulation. Methionine abolished the development of all of the liver lesions induced by Coadministration of the CDAA diet and ethionine. To investigate the effects of methionine on induction of c- myc and c-Ha- ras expression, as well as generation of 8-hydroxyguanine (8-OHGua) and 2-thiobarbituric acid-reacting substances (TBARS), by Coadministration of the CDAA diet and ethionine, subgroups of 3 to 5 animals were killed at 2, 4, 8 or 11 days after the beginning of the experiment. Coadministration of the CDAA diet and ethionine markedly enhanced the level of expression of c- myc and c-Ha- ras , 8-OHGua formation and TBARS generation as compared with the CDAA or CSAA diet within 11 days, and methionine blocked these actions. These results indicate that addition of methionine prevents the induction of c- myc and c-Ha- ras expression, 8-OHGua formation and TBARS generation, as well as hepatocellular lesions, by Coadministration of the CDAA diet and ethionine in rats, and suggest a possible involvement of oxidative stress and gene expression in hepatocarcinogenesis by these agents.     

地域差异与蛋氨酸合成酶基因多态性分布的相关性

目的比较青海省与其他地区正常女性蛋氨酸合成酶基因的分布特点。方法采用PCR-RFLP技术对125例正常人蛋氨酸合成酶基因进行扩增及图谱分析,结合既往发表的文献进行不同地区间的比较。结果青海省正常女性中MS基因型以A/A最多见,A/G次之。A/A基因型频率为0.5760、A/G为0.4160、G/G为0.0080。与其他地区相比较,MS基因型在青海省正常女性中的分布与国内其他地区人群中的分布差异显著。结论蛋氨酸合成酶基因多态性在不同地区间的分布存在明显差异。*     

Tyrosinose

Zusammenfassung Die biochemischen und klinischen Veränderungen eines Patienten mit Tyrosinose wurden über 2 Jahre verfolgt. Die Reduktion der Phenylalanin- und Tyrosinaufnahme führte zur Heilung der Rachitis sowie zur Normalisierung der Hypophosphatämie, der tubulären Phosphatreabsorption und der Methioninämie. Dieser Effekt war bei Auslaßversuchen reproduzierbar. Die Störungen im Methioninabbau besserten sich jedoch auch später unabhängig von der Tyrosinämie. Diese spontane Besserung, eher unabhängig von der Therapie und im Verlauf der Erkrankung oder mit zunehmendem Alter erfolgend, ließ sich gleichfalls an anderen Symptomen, wie der Thrombocytopenie, den Gerinnungsstörungen und dem verzögerten Phenylalaninabbau beobachten. Der fehlende oder nicht reproduzierbare Einfluß des normalisierten Tyrosinstoffwechsels auf diese Symptome spricht dafür, daß sie eher unabhängig neben der Tyrosinämie bestehen und nicht durch diese bedingt sind. Das Ausmaß der Tyrosinämie war in allen Krankheitsphasen abhängig von der Menge des aufgenommenen Phenylalanin und Tyrosin, die Belastungen mit Phenylalanin ergeben unabhängig vom Alter etwa gleiche Konzentrationskurven für Tyrosin. Die Störungen im Glucosestoffwechsel scheinen durch die Methioninämie verursacht, da Hypoglykämie und fehlender Anstieg des Blutzuckers nach Glukagoninjektion nur bei erhöhten Methioninserumkonzentrationen auftraten, bei isolierter Tyrosinerhöhung hingegen nicht gefunden wurden und beides durch eine Methioninbelastung provoziert werden konnte.

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TyrosinosisPrimary and secondary metabolic disturbances

A child with so-called tyrosinosis was treated with a reduced phenylalanine and tyrosine intake (100 mg/kg/day) for two periods of 2 and 9 months each. Healing of rickets, normalization of phosphate in the serum and increased tubular reabsorption of phosphate occurred during treatment achieving normal tyrosine levels, whilst these parameters, worsened when the tyrosine in the palsma rose. Methioninemia disappeared and reappeared together with tyrosinemia during and after the first period of treatment (methionine intake was unchanged). Later on these symptoms were no longer correlated, and high levels of methionine were only found during a period of vomiting, loss of weight, failure to grow and normal blood tyrosine levels. Thus the delayed methionine degradation seems be influenced by age, rate of protein synthesis and tyrosinemia. Thrombocytopenia, disturbed liver functions and other symptoms also improved with advancing age or during the natural course of the disease and did not seem to be directly related to dietary treatment. By contrast, the degree of tyrosinemia remained unchanged, depending on the amount of phenylalanine and tyrosine in the food. Hypoglycemia and methioninemia were correlated, the difference in blood sugar between periods with and without methioninemia being statistically significant. Furthermore, there was no rise in the glucose level after glucagon injection when the methionine level was elevated, whilst the results of the glucagon tests were approximately normal at low methionine levels. These findings indicate that hypoglycemia and rickets are secondary symptoms, whereas the other abnormalities seem be more independent of the disturbed tyrosine metabolism.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft     

Beta-catenin and adenomatous polyposis coli (APC) mutations in adenomas from hereditary non-polyposis colorectal cancer patients

It is known that cisplatin (CDDP) potentiates the cytotoxicity of 5-fluorouracil (5-FU), and that the biochemical mechanism is an increase in the intracellular reduced folate levels in the tumor cells. We investigated the effect of consecutive administration with lower-dose CDDP on intracellular accumulation of reduced folate and the activity of methionine synthase, a key enzyme in intracellular methionine synthesis. When CDDP (1 mg/kg) was administered i.p. to ascitic Yoshida sarcoma-bearing rats for 4 consecutive days, both the reduced folate levels and methionine synthase activity in the cells significantly increased, as the same as a single 5 mg/kg dose of CDDP. Furthermore, when Yoshida sarcoma-bearing rats were pre-treated with 1 mg/kg CDDP for 5 consecutive days, [14C]L-methionine incorporation into the isolated ascitic cells was significantly inhibited as compared to that in non-treated cells, suggesting that consecutive administration of lower-dose CDDP is capable of inducing the intracellular modulation of reduced folate levels and methionine synthase activity via inhibition of cellular uptake of methionine. In addition, 5-day administration of lower-dose (1 mg/kg) CDDP potentiated the antitumor effect of 5 mg/kg S-1, a new oral preparation of tegafur, given for 7 consecutive days, and this combined effect was almost similar to the antitumor effect of a combination of S-1 and a single conventional dose (5 mg/kg) of CDDP. Consecutive lower-dose CDDP also may be concluded to act as an important modulator of the enhancement of 5-FU cytotoxicity in experimental tumors.     

Regional coupling of blood flow and methionine uptake in an experimental tumor assessed with autoradiography

Regional distribution of L-[methyl-¹⁴C] methionine (¹⁴C-MET) and 4-[¹⁸F] fluoro-antipyrine was compared using experimental rat tumors (AH109A) and a computerized autoradiogram image processor. Tissue distributions of the two tracers were found to be inhomogeneous in the tumor with nearly identical image patterns. Analysis of tissue radioactivities revealed that 82% of ¹⁴C-MET was derived from the acid insoluble fraction at 60 min after injection. The present study showed that ¹⁴C-MET uptake closely relates to tissue blood flow and may depend on its blood to tissue transport. Rapid incorporation of MET in the acid insoluble fraction implies that it is rapidly metabolized after transport into tumor tissue.     

Pharmacokinetics of glutathione and its metabolites in normal subjects

To determine the loading and maintenance dosage of glutathione (GSH) for patients suffering from reactive oxygen species (ROS) injury such as acute paraquat intoxication, a kinetic study of reduced GSH was performed in synchrony with that of cysteine (Cys), cystine (Cys2), and methionine (Met). Human subject's porticipitation was voluntary. The effective dose of Cys, Cys2, and Met against ROS in fibroblast cells generated by paraquat was assessed using laser scanning confocal microscopy. Both Cys and Met suppressed ROS in a dose-dependent manner at concentrations of 1-1,000 microM; the concentration required to suppress ROS by 50% was 10 microM for Cys and 50 microM for Met. Using metabolite kinetics with the assumption that Cys and Met are the metabolites of GSH, expected concentrations of Cys and Met of above 20 and 50 microM were estimated when GSH was administered at 50 mg/kg body weights every 205.4 min for Cys and 427.4 min for Met.     

Inherited factor VII deficiency: identification of two novel mutations (A191V and T239P) in the catalytic domain

We describe here five F7 mutations found in four patients without bleeding history, despite constitutional coagulation Factor VII (FVII) deficiency. All five mutations are missense and affect the catalytic domain of FVII (A191T, A191V, T239P, R224Q and M298I). The A191V and T239P mutations are novel and were found in homozygous patients with no clinical bleeding tendency. The patient diagnosed with the A191V mutation had a phenotype corresponding to a moderate type 1 FVII deficiency (FVII:C 4%, FVII:Ag 5%). The T239P mutation was found in a patient with mild type 2 FVII deficiency (FVII:C 25%, FVII:Ag 95%). Novel mutations are both in close vicinity to the charge-stabilizing system of FVII. Modeling studies allow understanding in part the molecular basis for the loss of function.     

Applications of positron emission tomography in neuro-oncology: A clinical approach

The field of neuro-oncology is concerned with some of the most challenging and difficult to treat conditions in medicine. Despite modern therapies patients diagnosed with primary brain tumours often have a poor prognosis. Imaging can play an important role in evaluating the disease status of such patients. In addition to the structural information derived from MRI and CT scans, positron emission tomography (PET) provides important quantitative metabolic assessment of brain tumours. This review describes the use of PET with radiolabelled glucose and amino acid analogues to aid in the diagnosis of tumours, differentiate between recurrent tumour and radiation necrosis and guide biopsy or treatment. [¹⁸F]Fluorodeoxyglucose (FDG) is the tracer that has been used most widely because it has a 2 h half life and can be transported to imaging centres remote from the cyclotron and radiochemistry facilities which synthesise the tracers. The high uptake of FDG in normal grey matter however limits its use in some low grade tumours which may not be visualised. [¹¹C] methionine (MET) is an amino acid tracer with low accumulation in normal brain which can detect low grade gliomas, but its short 20 min half life has limited its use to imaging sites with their own cyclotron. The emergence of new fluorinated amino acid tracers like [¹⁸F]Fluoroethyl-l-tyrosine (FET) will likely increase the availability and utility of PET for patients with primary brain tumours. PET can, further, characterise brain tumours by investigating other metabolic processes such as DNA synthesis or thymidine kinase activity, phospholipid membrane biosynthesis, hypoxia, receptor binding and oxygen metabolism and blood flow, which will be important in the future assessment of targeted therapy.     

中青年脑梗死患者蛋氨酸合成酶还原酶基因多态性研究

目的 探讨蛋氨酸合成酶还原酶(MTRR)基因多态性与中青年脑梗死的关系. 方法 采用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)分析技术检测105例中青年脑梗死患者(郑州大学第一附属医院神经内科自2008年5月至2009年10月收治)和116例对照者MTRRA66G的基因型,应用高效液相色谱荧光法检测2组对象血浆同型半胱氨酸(Hey)水平. 结果 脑梗死组和对照组MTRRA 66G基因型及等位基因频率比较差异无统计学意义(P＞0.05).将脑梗死组按是否合并高血压、糖尿病和冠心病进行分层分析,发现脑梗死无合并症组GG基因型及G等位基因频率明显高于对照组(36.4％ vs 23.3％,62.1％ vs 52.2％),但差异无统计学意义(P＞0.05);脑梗死合并疾病组基因型及等位基因频率与对照组相比差异亦无统计学意义(P＞0.05).脑梗死合并疾病组、脑梗死无合并症组及对照组GG基因型血浆Hcy水平均明显高于从基因型,差异均有统计学意义(P＜0.05). 结论 MTRR A66G基因多态性与中青年脑梗死发病无关,但MTRR A66G基因纯合子突变可引起血浆Hcy水平明显升高.