Adipose tissue-liver axis in alcoholic liver disease

Alcoholic liver disease(ALD) remains an important health problem worldwide. The disease spectrum is featured by early steatosis, steatohepatitis(steatosis with inflammatory cells infiltration and necrosis), with some individuals ultimately progressing to fibrosis/cirrhosis. Although the disease progression is well characterized, no effective therapies are currently available for the treatment in humans. The mechanisms underlying the initiation and progression of ALD are multifactorial and complex. Emerging evidence supports that adipose tissue dysfunction contributes to the pathogenesis of ALD. In the first part of this review, we discuss the mechanisms whereby chronic alcohol exposure contributed to adipose tissue dysfunction, including cell death, inflammation and insulin resistance. It has been long known that aberrant hepatic methionine metabolism is a major metabolic abnormality induced by chronic alcohol exposure and plays an etiological role in the pathogenesis of ALD. The recent studies in our group documented the similar metabolic effect of chronic alcohol drinking on methionine in adipose tissue. In the second part of this review, we also briefly discuss the recent research progress in the field with a focus on how abnormal methionine metabolism in adipose tissue contributes to adipose tissue dysfunction and liver damage.     

Dietary Betaine Promotes Generation of Hepatic S-Adenosylmethionine and Protects the Liver from Ethanol-Induced Fatty Infiltration

Previous studies have shown that ethanol feeding to rats alters methionine metabolism by decreasing the activity of methionine synthetase. This is the enzyme that converts homocysteine in the presence of vitamin B₁₂ and N⁵-methyltetrahydrofolate to methionine. The action of the ethanol results in an increase in the hepatic level of the substrate N⁵-methyltetrahydrofolate but as an adaptive mechanism, betaine homocysteine methyltransferase, is induced in order to maintain hepatic S-adenosylmethionine at normal levels. Continued ethanol feeding, beyond 2 months, however, produces depressed levels of hepatic S-adenosylmethionine. Because betaine homocysteine methyltransferase is induced in the livers of ethanolfed rats, this study was conducted to determine what effect the feeding of betaine, a substrate of betaine homocysteine methyltransferase, has on methionine metabolism in control and ethanol-fed animals. Control and ethanol-fed rats were given both betainelacking and betaine-containing liquid diets for 4 weeks, and parameters of methionine metabolism were measured. These measurements demonstrated that betaine administration doubled the hepatic levels of S-adenosylmethionine in control animals and increased by 4-fold the levels of hepatic S-adenosylmethionine in the ethanol-fed rats. The ethanol-induced infiltration of triglycerides in the liver was also reduced by the feeding of betaine to the ethanol-fed animals. These results indicate that betaine administration has the capacity to elevate hepatic S-adenosylmethionine and to prevent the ethanol-induced fatty liver.     

The detection of cysteine-homocysteine mixed disulphide in plasma of normal fasting man.

Cysteine-homocysteine mixed disulphide, formed in the degradation of methionine, is detected routinely in the plasma of fasting patients homozygous for homocystinuria and in some obligate heteroxygotes. It has not hitherto been identified in the plasma of normal fasting man. Using a highly cross-linked resin with lithium citrate buffers on a JEOL. Amino Acid Analyser, we have detected the mixed disulphide in every one of the plasma samples from twenty normal fasting subjects. The mean concentration was 3.25 mumol/l (SD 0.85, N = 20), with a range of from 1.68 to 4.85 mumol/l. The other neutral and acidic amino acids were within the accepted normal range. The study shows that circulating homocysteine is normally not immediately transformed to cystathionine or remethylated to methionine; some combines with cysteine to form measurable amounts of mixed disulphide. Since homocysteine may produce endothelial damage, the present findings could be relevant to an understanding of the pathogenesis of vascular disease.     

Selection of two lines of mice based on latency to onset of methionine sulfoximine seizures

Purpose:  In various animals methionine sulfoximine (MSO) induces tonic–clonic seizures resembling the most striking form of human epilepsies. The aim of the present study was to select two lines of mice based upon differences in their latency to MSO-dependent seizures, in order to characterize them.
Methods:  Random crosses involving eight inbred mice strains were used to generate the starting population in which the first MSO challenge (75 mg/kg, i.p.) was performed. Two groups of 16 breeding pairs were established by mating mice having the shortest (MSO-Fast) and the longest (MSO-Slow) convulsion latencies. Mating and selection by latency to MSO (75 mg/kg, i.p.) was carried out over six generations.
Results:  MSO-Fast mice presented a significantly shorter MSO latency, and were more susceptible to MSO than MSO-Slow ones were. Electroencephalography (EEG) alterations were observed during the preconvulsive period when MSO-Fast mice were submitted to 75 mg/kg of MSO, and MSO-Slow ones to 200 mg/kg. Using another convulsant, kainic acid, the latency to convulse of MSO-Fast mice was significantly shorter than that of the MSO-Slow ones, whereas no difference was observed in response to pentylenetetrazole (PTZ). MSO-dependent convulsions were completely antagonized by MK-801, and partially by valproic acid, suggesting a preferential involvement of glutamatergic pathways.
Discussion:  The model that we have developed for MSO "sensitive" and "resistant" mice could allow for a better understanding of MSO mechanisms of epileptogenesis, and it may also constitute a useful approach for therapeutic actions of drugs.     

The relationship between gene polymorphism of MTRR A66G and lower extremity deep venous thrombosis

ABSTRACT

Objective: To investigate the relationship between gene polymorphism of MTRR A66G and lower extremity deep venous thrombosis (DVT).

Methods: Two hundred and two patients with DVT as experimental group and 240 normal adults (control group) were enrolled in this study and white blood cells were collected, respectively. Polymorphism of the 66 loci in MTRR gene was detected by polymerase chain reaction-sequence-specific primers (PCR-SSP) in two groups. The frequency of genotype and allele distribution of each group was compared.

Results: The frequency of AA, AG and GG genotypes in 66 sites of MTRR gene were 26.76%, 4 3.66% and 29.58% in DVT group and 43.57%, 44.28% and 12.14% in control group, respectively. There was no significant difference in the distribution frequency between two groups (χ?=?3.2, P?>?.5).

Conclusions: The gene polymorphism of MTRR A66G may not be an independent genetic risk factor in DVT in China.     

蛋氨酸脑啡肽联合5-氟尿嘧啶对肝癌细胞HepG2的增殖和凋亡的影响

目的 探讨蛋氨酸脑啡肽(methionine enkephalin,MENK)及蛋氨酸脑啡肽联合5-氟尿嘧啶对肝癌细胞HepG2的增殖和凋亡的影响.方法 采用MTS法检测细胞生长的抑制作用;Hoechst33258荧光染色法观察用MENK及MENK联合5-氟尿嘧啶处理后的HepG2细胞的形态变化;流式细胞仪检测细胞凋亡率.结果 MENK(5 mmol/L)及MENK联合5-氟尿嘧啶(5 mmol/L+0.05 mmol/L)在用药24h后,对肝癌HepG2细胞具有显著的生长抑制作用(t=14.58、40.37,P＜0.05),在用药48 h后,抑制作用也非常明显(t=13.14、29.85,P＜0.05);Hoechst33258荧光染色后,MENK及MENK联合5-氟尿嘧啶处理组的细胞出现典型的凋亡形态学变化;流式细胞仪检测结果显示,与空白组比较,MENK组细胞凋亡率为15.6％(t=3.942,P＜0.05),MENK联合5-氟尿嘧啶处理组的细胞凋亡率为47.7％(t=17.19,P＜0.05).结论 MENK及MENK联合5-氟尿嘧啶对人肝癌细胞HepG2的生长具有抑制作用,并诱导细胞凋亡,且联合用药组的抑制作用强于单独用药组.     

Methionine as a double-edged sword in health and disease: Current perspective and future challenges

Methionine is one of the essential amino acids and plays a vital role in various cellular processes. Reports advocate that methionine restriction and supplementation provide promising outcomes, and its regulation is critical for maintaining a healthy life. Dietary methionine restriction in houseflies and rodents has been proven to extend lifespan. Contrary to these findings, long-term dietary restriction of methionine leads to adverse events such as bone-related disorders, stunted growth, and hyperhomocysteinemia. Conversely, dietary supplementation of methionine improves hepatic steatosis, insulin resistance, inflammation, fibrosis, and bone health. However, a high level of methionine intake shows adverse effects such as hyperhomocysteinemia, reduced body weight, and increased cholesterol levels. Therefore, dietary methionine in a safe dose could have medicinal values. Hence, this review is aimed to provide a snapshot of the dietary role and regulation of methionine in the modulation of health and age-related diseases.     

贵阳市育龄女性MTHFR和MTRR基因多态性与自然流产的相关性分析

目的分析贵阳市育龄女性亚甲基四氢叶酸还原酶(MTHFR)、甲硫氨酸合成酶还原酶(MTRR)基因多态性与自然流产的相关性,降低贵阳市育龄女性自然流产发生率。方法选取2016—2019年在贵阳市妇幼保健院进行孕前优生咨询的525例育龄女性为研究对象,按照有无自然流产史分为两组,病例组175例女性,对照组350例女性。比较两组育龄女性MTHFR C677T、A1298C及MTRR A66G基因型和等位基因分布。结果病例组MTHFR C677T野生基因型CC型69例(39.4%),杂合突变CT型76例(43.4%),纯合突变TT型30例(17.1%),对照组MTHFR C677T野生基因型CC型154例(44.0%),杂合突变CT型164例(46.9%),纯合突变TT型32例(9.1%),两组比较差异具有统计学意义(χ²=7.20,P<0.05);病例组的T等位基因频率为38.9%,较对照组T等位基因频率(32.6%)明显升高,差异有统计学意义(χ²=4.07,P<0.05)。两组MTHFR A1298C基因型分布比较差异无统计学意义(P...     

高效液相色谱法测定甲硫氨酸维生素B1注射液中甲硫氨酸和维生素B1的含量

目的建立一种快速,准确的高效液相色谱法同时测定甲硫氨酸维生素B1注射液中甲硫氨酸和维生素B1的含量.方法采用C18柱 5μm(4.6 ×250mm),流动相为乙腈–0.5mol·L-1庚烷磺酸钠(20 80),检测波长为25nm.结果甲硫氨酸的线性范围是162.1～648.3μg·mL-1,r=0.9999,平均回收率为99.83%, RSD=0.485;维生素B1的线性范围是16.96～67.84μg·mL-1, r=0.9998,平均回收率为 99.17%,RSD=1.42.结论本方法可快速准确地检测甲硫氨酸维生素B1注射液中甲硫氨酸和维生素B1的含量