腺苷蛋氨酸对酒精性脂肪肝大鼠治疗效果及机制的研究

目的观察腺苷蛋氨酸（SAM）对酒精性肝损伤的防治作用及机制。方法将48只SD大鼠随机分为对照组（Ⅰ组）、模型组（Ⅱ组）及SAM低剂量组（Ⅲ组）、SAM高剂量组（Ⅳ组）,每组12只。除对照组外,其余三组给予酒精、鱼油灌胃配合高脂饮食诱导酒精性肝损伤,4周后Ⅰ、Ⅱ组腹腔注射生理盐水,Ⅲ、Ⅳ组分别腹腔注射SAMl00mg／kg、200mg／kg,第8周均处死。测定血浆总同型半胱氨酸（tHcy）浓度、血清丙氨酸转移酶（ALT）、天冬氨酸转移酶（AST）浓度;测定肝匀浆丙二醛（MDA）、超氧化物歧化酶（SOD）和还原型谷胱甘肽（GSH）含量,行肝脏病理组织学检查。结果与Ⅰ组比较,Ⅱ组肝损伤明显,表现为ALT、AST、tHcy水平升高,肝脂肪变性,MDA含量增加,SOD和GSH水平下降;Ⅲ、Ⅳ组MDA降低、GSH升高,但tHcy水平和肝组织SOD含量无显著变化,Ⅲ、Ⅳ组间无明显差别。结论SAM可防治大鼠酒精性肝损伤,其机制可能与调节肝脏内氧化抗氧化系统的平衡有关;SAM对血浆tHcy水平无明显影响。     

S-adenosylhomocysteine is associated with subclinical atherosclerosis and renal function in a cardiovascular low-risk population

Objective

Although homocysteine has been proposed as a cardiovascular risk factor, interventional trials lowering homocysteine have not consistently demonstrated clinical benefit. Recent evidence proposed the homocysteine metabolite S-adenosylhomocysteine (SAH) rather than homocysteine itself as the real culprit in cardiovascular disease. Of note, SAH is predominantly excreted by the kidneys, and cannot be lowered by vitamin supplementation. Due to its cumbersome measurement, data from large studies on the association between SAH, kidney function and cardiovascular disease are not available.

Methods

We recruited 420 apparently healthy subjects into our I Like HOMe FU study. Among all study participants, we assessed parameters of C1 metabolism (homocysteine, SAH and S-adenosylmethionine), renal function (estimated glomerular filtration rate [eGFR]) and subclinical atherosclerosis (common carotid intima-media-thickness [IMT]). eGFR was estimated by the CKD-EPI_creat-cys equation.

Results

Traditional cardiovascular risk factors and subclinical atherosclerosis were associated with SAH, but not with homocysteine (IMT vs SAH: r = 0.129; p = 0.010; IMT vs homocysteine: r = 0.009; p = 0.853). Moreover, renal function was more closely correlated with SAH than with homocysteine (eGFR vs SAH: r = −0.335; p < 0.001; eGFR vs homocysteine: r = −0.250; p < 0.001). The association between eGFR and SAH remained significant after adjustment for traditional cardiovascular risk factors.

Conclusion

In summary, cardiovascular risk factors, subclinical atherosclerosis and eGFR are more strongly associated with SAH than with homocysteine in apparently healthy subjects. Thus, SAH might represent a more promising target to prevent cardiovascular disease than homocysteine.     

SAMe treatment prevents the ethanol-induced epigenetic alterations of genes in the Toll-like receptor pathway

Prior studies showed that Toll-like receptor (TLR) signaling pathway genes were upregulated in the liver of rats fed ethanol, but not in rats fed ethanol plus S-adenosylmethionine (SAMe). These results were obtained using a PCR microplate array analysis for TLRs and associated proteins such as proinflammatory cytokines and chemokine mRNA levels. A large number of genes were upregulated by the ethanol diet, but not the ethanol plus SAMe diet. In the present study, using the same experimental rat livers, DNA methylation analysis was done by using an Epitect Methyl DNA Restriction Kit (Qiagen, 335451) (24 genes). The results of all the genes combined show a highly significant increase in methylation in the ethanol-fed group of rats, but not in the dextrose-fed, SAMe-fed or ethanol plus SAMe-fed groups of rats. There was also an increase in DNA methylation in rats with high blood alcohol levels compared to a rat with a low blood alcohol level. The individual genes that were upregulated as indicated by the increased mRNA measured by qPCR correlated positively with the increased methylation of the DNA of the corresponding genes as follows: Cd14, Hspa1a, Irf1, Irak1, Irak2, Map3k7, Myd88, Pparα, Ripk2, Tollip and Traf6.     

Thiopurines: Factors influencing toxicity and response

Thiopurines are the backbone of current anti-leukemia regimens and have also been effective immunosuppressive agents for the past half a century. Extensive research on their mechanism of action has been undertaken, yet many issues remain to be addressed to resolve unexplained cases of thiopurine toxicity or treatment failure. The aim of this review is to summarize current knowledge of the mechanism of thiopurine action in experimental models and put into context with clinical observations. Clear understanding of their metabolism will contribute to maximizing efficacy and minimizing toxicity by individually tailoring therapy according to the expression profile of relevant factors involved in thiopurine activation pathway.     

SAMe prevents the induction of the immunoproteasome and preserves the 26S proteasome in the DDC-induced MDB mouse model

Mallory–Denk bodies (MDBs) form in the liver of alcoholic patients. This occurs because of the accumulation and aggregation of ubiquitinated cytokeratins, which hypothetically is due to the ubiquitin–proteasome pathway's (UPP) failure to degrade the cytokeratins. The experimental model of MDB formation was used in which MDBs were induced by refeeding DDC to drug-primed mice. The gene expression and protein levels of LMP2, LMP7 and MECL-1, the catalytic subunits in the immunoproteasome, as well as FAT10, were increased in the liver cells forming MDBs but not in the intervening normal hepatocytes. Chymotrypsin-like activity of the UPP was decreased by DDC refeeding, indicating that a switch from the UPP to the immunoproteasome had occurred at the expense of the 26S proteasome. The failure of the UPP to digest cytokeratins would explain MDB aggregate formation. SAMe prevented the decrease in UPP activity, the increase in LMP2, LMP7, and MECL-1 protein levels and MDB formation induced by DDC. DDC refeeding also induced the TNFα and IFNγ receptors. SAMe prevented the increase in the TNFα and IFNγ receptors, supporting the idea that TNFα and IFNγ were responsible for the up regulation of LMP2, LPM7, and FAT10. These results support the conclusion that MDBs form in FAT10 over-expressing hepatocytes where the up regulation of the immunoproteasome occurs at the expense of the 26S proteasome.     

Age-associated decline of hepatic handling of cholephilic anions in humans is reverted by S-adenosylmethionine (SAMe)

Decreased fluidity of hepatocyte plasma membrane may contribute to the age-associated changes of liver function. This study aimed at investigating whether the hepatic clearance of organic anions declines with age and whether S-adenosylmethionine (SAMe), a substance proven to be effective in reversing the age-related decrease of membrane fluidity, might influence this process. Nicotinic acid (NA) half-life and serum bilirubin pharmacokinetics after NA load (5.9 umol/kg body weight i.v.) were studied in 10 healthy young males (YM) aged 14-28 years and in 10 healthy elderly males (EM) aged 65-81 years, before and after SAMe administration (800 mg/day intravenously for 10 days). At baseline, EM showed serum total bilirubin (STB) levels significantly higher than YM. Similarly, the bilirubinaemic mean curves, STB peak and STB time curve concentration after NA load, expressed as area under the curve (AUC), were significantly higher in EM than in YM (p<0.01). NA half-life was also significantly prolonged in the aged group (p<0.001). SAMe treatment was followed by a significant decrease of basal STB, STB peak and AUC of STB after NA load in EM (p<0.01 vs pre-treatment values) while NA half-life was significantly shortened in both groups (p<0.001). As NA and bilirubin share a common carrier protein for hepatic uptake, bilitranslocase, the changes observed in EM may be attributed to the reduced lateral mobility of hepatocyte plasma membrane proteins occurring with age. SAMe, by improving membrane fluidity, may increase the diffusion coefficient of bilitranslocase restoring the hepatic handling of organic anions.     

Methylation metabolism in sepsis and systemic inflammatory response syndrome

Abstract

We have recently shown that sepsis leads to alterations of methylation metabolism in a rodent model. In this study we analyzed methylation metabolism and DNA methylation in human sepsis. Patients treated in one of the Intensive Care Units (ICU) at the University Hospital Bonn diagnosed with sepsis or systemic inflammatory response syndrome (n = 12) and patients who were treated due to traumatic brain injury, or stroke without clinical or laboratory signs of sepsis or major inflammation (n = 22) were included. Blood samples were taken two times a week, until ICU treatment was discontinued. Deproteinized plasma was used for simultaneous determination of the ubiquitous methyl-group donor S-adenosylmethionine (SAM) and its demethylated residue, S-adenosylhomocysteine (SAH), by using stable isotope dilution tandem mass spectrometry. Homocysteine (Hcys), hydrolyzation product of SAH, was determined by fully automated particle-enhanced immunonephelometry, and global DNA-methylation was measured by liquid chromatography tandem mass spectrometry. SAM (p < 0.001) and SAH (p < 0.001) plasma levels were higher in septic patients suggesting an increased cellular release of SAM and SAH in septic patients. The SAM/SAH ratio was decreased in septic patients (p = 0.002). There were no differences in homocysteine plasma levels (p = 0.32) or global leukocyte DNA methylation between septic and non-septic patients (p = 0.21) suggesting that sepsis-induced changes in methylation metabolism do not affect homocysteine plasma levels or the availability of SAM-derived methyl groups for DNA methylation. Sepsis and systemic inflammatory response syndrome induce considerable changes of methylation metabolism without apparent functional consequences on homocysteine plasma levels or DNA methylation. Further studies may explore the clinical relevance of the observed changes.     

腺苷蛋氨酸对原发性肝癌切除术后肝功能的保护作用

目的探讨腺苷蛋氨酸在原发性肝癌肝切除术后的肝功能的保护作用。方法 40例原发性肝癌行肝切除术患者随机分为两组,试验组术后单一予腺苷蛋氨酸连续应用,对照组予硫普罗宁和还原型谷胱甘肽联合应用,分析比较两组术后第1、3、7天肝功能水平变化。结果除术后第7天,试验组血清TBIL和DBIL明显低于对照组外(P<0.05),其余两组术后第1、3、7天肝功能均无统计学差异。结论腺苷蛋氨酸可在多重机制上起到保护肝功能的作用,适合原发性肝癌患者的围手术期应用。     

S-腺苷甲硫氨酸抑制大肠癌细胞生长的实验研究

目的探讨S-腺苷甲硫氨酸(SAM)对人大肠癌细胞生长的抑制作用及抑癌机制。方法用SAM对大肠癌细胞系HT-29进行处理,使其癌基因c-myc和H-ras启动子区域甲基化。用噻唑蓝(MTT)法检测肿瘤细胞生长状态;甲基化特异性聚合酶链反应(PCR)(MSP)法检测c-myc和H-ras启动子区域甲基化状态;细胞免疫荧光染色检测C-MYC和H-RAS蛋白的表达情况。结果大肠癌细胞系HT-29经SAM处理后,癌基因c-myc和H-ras启动子区域重新出现甲基化。经SAM处理的大肠癌细胞组与对照组相比,细胞生长受到明显抑制,差异有统计学意义(P<0.05);C-MYC和H-RAS蛋白表达明显降低,差异有统计学意义(P<0.05)。结论 SAM能使HT-29中癌基因c-myc和H-ras启动子区域重新甲基化,降低C-MYC和H-RAS蛋白的表达水平,且有效抑制了肿瘤细胞的生长,从而为肿瘤治疗提供了新的靶点。