蛋氨酸限制提高内源性H2S活性延缓衰老的机制研究进展

蛋氨酸限制(Methionine restriction,MetR)作为饮食限制的方法之一,能够改善多种无脊椎动物、啮齿类动物及包括人类灵长类动物的衰老及其相关疾病。但MetR对衰老的具体调节作用机制尚未完全明确,目前除了与饮食限制的共有机制以外,越来越多的研究表明内源性硫化氢(Endogenous hydrogen sulfide,H2S)可能是其发挥效应的主要机制。硫化氢作为水溶性和脂溶性的小分子气体,在延缓衰老进程和改善衰老相关疾病中具有重要意义。本文阐述了MetR通过提高内源性H2S的活性延缓衰老的机制及相关研究。     

Amino acids levels and lipid peroxidation in maple syrup urine disease patients

Objective

In the present study we correlated the amino acids, branched-chain α-keto acids and α-hydroxy acids levels with the thiobarbituric acid-reactive species (TBARS) measurement, a lipid peroxidation parameter, in plasma from treated MSUD patients in order to examine whether these accumulated metabolites could be associated to the oxidative stress present in MSUD.

Design and methods

TBARS, amino acids, branched-chain α-keto acids and α-hydroxy acids concentrations were measured in plasma samples from treated MSUD patients.

Results

We verified that plasma TBARS was increased, whereas tryptophan and methionine concentrations were significantly reduced. Furthermore TBARS measurement was inversely correlated to methionine and tryptophan levels.

Conclusions

Considering that methionine and tryptophan have antioxidant activities, the data suggest that the imbalance of these amino acids may be involved with lipid peroxidation in MSUD.     

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.     

Lack of significant effects of methionine loading on endothelial function in elderly volunteers

OBJECTIVE: To test the hypothesis that an acute increase in plasma homocysteine concentration (Hcy) produced by methionine loading is associated with an acute decrease in brachial artery blood flow measured by flow-mediated dilatation (FMD) using forearm plesthysmography. DESIGN: A double-blind, cross-over, placebo controlled design was used and FMD of the brachial artery, plasma Hcy, plasma methionine, total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, plasma triglyceride, oxidised LDL, apolipoproteins (Apo) A1 and B and C reactive protein (CRP) were measured between 12 and 20 hours after methionine loading or placebo. RESULTS: Between 12 and 20 hours, after a methionine loading test, acute hyperhomocysteinaemia had no significant effect on mean FMD compared to placebo (57.08+/-6.18ml/100ml/min versus 63.46+/-5.87ml/100ml/min, p<0.5). The mean age of the eight subjects was 71.5+/-6.9 years. Twelve hours after methionine, mean triglyceride concentration was significantly increased by 23.0% compared to placebo (1.51+/-0.47mmol/l versus 1.23+/-0.44mmol/l, p<0.02). CONCLUSION: In elderly volunteers, acute hyperhomocysteinaemia induced by methionine loading resulted in no significant late impairment of endothelial function although further investigation is recommended. Acute hyperhomocysteinaemia resulted in a significant increase in plasma triglyceride concentration.     

Cutting back on the essentials: Can manipulating intake of specific amino acids modulate health and lifespan?

With few exceptions, nutritional and dietary interventions generally impact upon both old-age quality of life and longevity. The life prolonging effects, commonly observed with dietary restriction reportedly are linked to alterations in protein intake and specifically limiting the dietary intake of certain essential amino acids. There is however a paucity of data methodically evaluating the various essential amino acids on health- and lifespan and the mechanisms involved. Rodent diets containing either lower methionine content, or tryptophan, than that found in commercially available chow, appear to elicit beneficial effects. It is unclear whether all of these favorable effects associated with restricted intake of methionine and tryptophan are due to their specific unique properties or if restriction of other essential amino acids, or proteins in general, may produce similar results. Considerably more work remains to be done to elucidate the mechanisms by which limiting these vital molecules may delay the onset of age-associated diseases and improve quality of life at older ages.     

Arachidyl amido cholanoic acid improves liver glucose and lipid homeostasis in nonalcoholic steatohepatitis via AMPK and mTOR regulation

BACKGROUND Arachidyl amido cholanoic acid(Aramchol) is a potent downregulator of hepatic stearoyl-CoA desaturase 1(SCD1) protein expression that reduces liver triglycerides and fibrosis in animal models of steatohepatitis. In a phase IIb clinical trial in patients with nonalcoholic steatohepatitis(NASH), 52 wk of treatment with Aramchol reduced blood levels of glycated hemoglobin A1c, an indicator of glycemic control.AIM To assess lipid and glucose metabolism in mouse hepatocytes and in a NASH mouse model [induced with a 0.1% methionine and choline deficient diet(0.1 MCD)] after treatment with Aramchol.METHODS Isolated primary mouse hepatocytes were incubated with 20 μmol/L Aramchol or vehicle for 48 h. Subsequently, analyses were performed including Western blot, proteomics by mass spectrometry, and fluxomic analysis with ~(13)C-uniformly labeled glucose. For the in vivo part of the study, male C57 BL/6 J mice were randomly fed a control or 0.1 MCD for 4 wk and received 1 or 5 mg/kg/d Aramchol or vehicle by intragastric gavage for the last 2 wk. Liver metabolomics were assessed using ultra-high-performance liquid chromatography-time of flight-MS for the determination of glucose metabolism-related metabolites.RESULTS Combination of proteomics and Western blot analyses showed increased AMPK activity while the activity of nutrient sensor mTORC1 was decreased by Aramchol in hepatocytes. This translated into changes in the content of their downstream targets including proteins involved in fatty acid(FA) synthesis and oxidation [PACCα/β(S79), SCD1, CPT1A/B, HADHA, and HADHB], oxidative phosphorylation(NDUFA9, NDUFB11, NDUFS1, NDUFV1, ETFDH, and UQCRC2), tricarboxylic acid(TCA) cycle(MDH2, SUCLA2, and SUCLG2), and ribosome(P-p70S6K[T389] and P-S6[S235/S236]). Flux experiments with ~(13)C uniformely labeled glucose showed that TCA cycle cataplerosis was reduced by Aramchol in hepatocytes, as indicated by the increase in the number of rounds that malate remained in the TCA cycle. Finally, liver metabolomic analysis showed that glucose homeostasis was improved by Aramchol in 0.1 MCD fed mice in a dose-dependent manner, showing normalization of glucose, G6P, F6P, UDP-glucose, and Rbl5 P/Xyl5 P.CONCLUSION Aramchol exerts its effect on glucose and lipid metabolism in NASH through activation of AMPK and inhibition of mTORC1, which in turn activate FA β-oxidation and oxidative phosphorylation.     

L-甲硫氨酸通过调节脊髓DNA甲基化水平减轻甲醛溶液所致急性炎性痛机制研究

背景　甲硫氨酸能够促进DNA甲基化的发生,DNA甲基化参与疼痛的发生发展和维持。急性炎性痛是临床常见症状,控制不及时会转化成慢性炎性痛,外源性补充甲硫氨酸可能通过调节DNA甲基化参与调节急性炎性痛,改善患者疼痛症状。目的　本研究采用甲醛溶液诱导急性炎性痛模型大鼠,观察注射L-甲硫氨酸（L-MET）是否会减轻大鼠足底急性炎性痛并探讨其机制,以期为寻找新的疼痛生物标志物和开发理想的镇痛新药提供理论依据。方法　2017年7月-2018年12月,将24只健康成年清洁级雄性Sprague-Dawley（SD）大鼠按照随机数字表法分为A组（0.9%氯化钠溶液+0.9%氯化钠溶液组）、B组（L-MET+0.9%氯化钠溶液组）、C组（0.9%氯化钠溶液+2 g/L甲醛溶液组）、D组（L-MET+2 g/L甲醛溶液组）,每组6只。B组、D组腹腔注射L-MET,2次/d,总量不超过0.18 mg/kg,连续注射3 d;A组、C组注射等量0.9%氯化钠溶液。C组、D组左后足足跖部皮下注射2 g/L甲醛溶液20 μl,制作甲醛溶液所致急性炎性痛模型,大鼠足部肿胀并会出现相应的抬足舔足行为视为模型制作成功;A组、B组注射等量0.9%氯化钠溶液。全程记录给药后60 min大鼠行为学,并记录疼痛次数,每隔3 min为1个观察时段,共分20个观察时段。行为学检测结束后,将大鼠处死,取脊髓L4~L6之间脊髓组织,检测大鼠脊髓全基因组DNA甲基化水平及大鼠脊髓DNA甲基化转移酶（DNMT）1、DNMT2、DNMT3a、DNMT3b RNA水平。结果　A组、B组大鼠无明显不适异常反应;C组、D组大鼠出现躁动不安、注射足抬起不着地、舔咬或抖动注射足等反应,其疼痛行为反应呈典型的双相变化,从注射后即刻开始,持续3~5 min的急性疼痛时相（第一时相）,5~10 min的静息期,随后出现可持续0~45 min的继发性疼痛时相（第二时相）。C组、D组大鼠各时间点疼痛次数均多于A组、B组（P<0.05）;D组大鼠6~39 min疼痛次数少于C组（P<0.05）。B组、D组大鼠脊髓全基因组DNA甲基化水平高于A组（P<0.05）;C组、D组大鼠脊髓全基因组DNA甲基化水平低于B组（P<0.05）;D组大鼠脊髓全基因组DNA甲基化水平高于C组（P<0.05）。C组、D组大鼠脊髓DNMT3a、DNMT3b RNA水平高于A组、B组（P<0.05）;D组大鼠脊髓DNMT3a RNA水平低于C组,DNMT3b RNA水平高于C组（P<0.05）。结论　L-MET对于甲醛溶液所致急性炎性痛模型大鼠具有明显镇痛作用,其机制与脊髓全基因组DNA甲基化水平以及DNMT水平的变化有关。     

Sulfur-containing amino acids attenuate the development of liver fibrosis in rats through down-regulation of stellate cell activation

BACKGROUND/AIMS: We tested the pharmacological action of sulfur-containing amino acids on the development of liver fibrosis in rats and on the function of cultured stellate cells. METHODS: Liver fibrosis was induced in rats by thioacetamide administration or by ligating the common bile duct. DNA synthesis of cultured stellate cells was evaluated by BrdU incorporation. The expression of proteins and phospho-proteins was determined by western blot analysis. mRNA expression was evaluated by RT-PCR. RESULTS: Oral administration of l-cysteine or l-methionine attenuated the deposition of collagen in liver tissues in the two fibrotic models, accompanying a reduction in the expression of smooth muscle alpha-actin and platelet-derived growth factor receptor beta and mRNAs of collagens, transforming growth factor-betas and tissue inhibitors of matrix metalloproteinase. In cultured stellate cells, l-cysteine and l-methionine suppressed the DNA synthesis and the expression of growth factor receptors, smooth muscle alpha-actin and type I collagen. They hampered the phosphorylation of p44/42 MAPK and Akt under platelet-derived growth factor-BB stimulation. Stellate cells were found to express methionine adenosyltransferase 2A. CONCLUSIONS: l-Cysteine and l-methionine regulate the activation of stellate cells. Their oral supply aids the suppression of the progression of liver fibrosis.     

Effect of insulin-sensitizing agents in combination with ezetimibe, and valsartan in rats with non-alcoholic fatty liver disease

AIM: To assess whether treatment with insulin-sensitizing agents (ISAs) in combination with ezetimibe and valsartan have greater effect on hepatic fat content and lipid peroxidation compared to monotherapy in the methionine choline-deficient diet (MCDD) rat model of non-alcoholic fatty liver disease (NAFLD). METHODS: Rats (n = 6 per group) were treated with different drugs, including MCDD only, MCDD diet with either metformin (200 mg/kg), rosiglitazone (3 mg/kg), metformin plus rosiglitazone (M R), ezetimibe (2 mg/ kg), valsartan (2 mg/kg), or combination of all drugs for a total of 15 wk. Liver histology, lipids, parameters of oxidative stress and TNF-alpha were measured. RESULTS: Fatty liver (FL) rats demonstrated severe hepatic fatty infiltration (> 91% fat), with an increase in hepatic TG ( 1263%, P < 0.001), hepatic cholesterol ( 245%, P < 0.03), hepatic MDA levels ( 225%, P < 0.001), serum TNF-alpha (17.8±10 vs 7.8±0.0, P < 0.001), but a decrease in hepatic alpha tocopherol (-74%, P < 0.001) as compared to the control rats. Combination therapy with all drugs produced a significant decrease in liver steatosis (-54%), hepatic TG (-64%), hepatic cholesterol (-31%) and hepatic MDA (-70%), but increased hepatic alpha tocopherol ( 443%) as compared to FL rats. Combination therapy with ISA alone produced a smaller decrease in liver steatosis (-32% vs -54%, P < 0.001) and in hepatic MDA levels (-55% vs -70%, P < 0.01), but a similar decrease in hepatic lipids when compared with the all drugs combination. TNF-alpha levels decreased significantly in all treatment groups except in ISA group. CONCLUSION: Combination therapies have a greater effect on liver fat content as compared to monotherapy. Rosiglitazone appears to improve hepatic steatosis to a greater extent than metformin.     

同型半胱氨酸代谢相关酶基因多态性与心肌梗死关系的研究

目的研究同型半胱氨酸代谢相关酶亚甲基四氢叶酸还原酶(MTHFR)、胱硫醚-β-合成酶(CBS)及蛋氨酸合成酶(MS)基因多态性与心肌梗死(MI)相关性。方法应用聚合酶链反应-限制性内切酶片段长度多态性(PCR-RFLP)和聚合酶链反应(PCR)产物直接电泳技术,检测121例MI患者(患者组)和500例健康人(正常对照组)的MTHFR C677T、CBS 844 ins68和MS A2756G基因多态性。结果MTHFR C677T基因型分别为:CC野生型、CT杂合型、TT突变型。其在患者组分布频率分别为14.0%、46.3%、39.7%,T等位基因频率为62.85%,C等位基因频率为37.15%;正常对照组中为35.6%、44.0%2、0.4%,T等位基因频率为42.4%,C等位基因频率为57.6%。两组间各基因频率及等位基因频率比较差异均具有统计学意义(P<0.05)。而CBS 844ins 68和MSA2756G的基因型频率分布,两组间差异均无统计学意义(P>0.05)。结论MTHFR基因TT基因型,T等位基因与MI具有相关性;而CBS 844 ins68及MS A2756G基因多态性可能与MI发生无直接相关性。