THE INFLUENCE OF ETHANOL ON HEPATIC TRANSMETHYLATION

One of the most important biochemical pathways in the organismis the biosynthesis of methionine from the methylation of homocysteine.Two different reactions are responsible for this methylation,one utilizing N⁵-methyltetra-hydrofolate as a methylating agentand the other using betaine as the methyl donor. This paperreviews some recent findings in this laboratory, which demonstratethat ethanol-feeding to rats impairs the folate-induced reaction.Our findings also show that this impairment is compensated forthrough the adaptive increase in the enzyme using betaine inthe biosynthesis of methionine. Further studies indicate thatthe mechanism of action in the impairment may occur thioughthe formation of individual adducts between the folate-inducedenzyme (methionine synthetase), its essential cofactors andacetaldehyde, a meta-bolic product of ethanol. These findingssuggest a basis for why rats are more resistant to alcoholicliver injury than humans and may offer a means of protectingagainst alcoholic liver injury in man.     

THE UTILIZATION OF THE METHYL GROUP OF METHIONINE IN THE BIOLOGICAL SYNTHESIS OF CHOLINE AND CREATINE

The transfer of methyl groups from methionine to choline and creatine has been demonstrated by the isolation of deuteriocholine and deuteriocreatine from the tissues, and of deutriocreatinine from the urine, or rats fed methionine containg a deuteriomethyl group. It was found from the deuterium ocntents of the isolated compounds that at the end of a given experimental period, each of the isolated compounds had derived approximately the same percentage of methyl groups from the deuteriomethionine of the diet. All the deuterium in the isolated choline was shown to be in the methyl grops. The concentraion of deuterium in the methyl gorups of the choline and creatine from the tissues as well as of the urinary creatinine rose to 85 per cent of that of the deuterio-methionine fed over a period of 14 weeks, strongly indicating that there was no other precursor of methyl groups in the diet employed.
The transfer of methyl groups from choline to creatime has been demonstrated by the isolation of deuteriocreatime from the tissues and of deuteriocreattnine from the urine of rats maintained on a diet containing deuteriocholine and homocystine.
Thus direct proof has been afforded to substantiate the hypothesis previously presentd that methionine may be a precursor of choline in so far as the methyl groups are concerned. The significance of these findings with regard to the prevention of fatty infiltraton of the liver and to the prevention of hemorrhagic kidneys resulting from a choline-deficient diet has been pointed out. The data support the hypothesis that the body is incapable of generationg methyl groups for certain methlations and that methyl groups must be supplied in the diet in a biologically labile from such as occurs in methionine and choline.     

THE TOXIC EFFECT OF METHIONINE

When an excessive amount of methionine is added to the diets of rats, it has been found that there is a marked inhibition of growth. This appears to be due to a combination of a reduced total food intake and a toxic effect produced by the methionine.     

托幼儿童身长体重及营养素摄入水平的研究:四年系统观察

1979～1983连续四年观察了两个全托托儿所和一个全托幼儿园儿童的身长、体重及膳食营养状况。结果表明,到1982年时,儿童身长、体重在标准均值以上的人数均超过50％,托儿所儿童能量及蛋白质的摄入量加上零食中的含量能达到供给量标准。各类食物摄入量也能达到或超过北京市推荐的托儿所儿童参考食物量标准。幼儿园儿童营养素的摄入量与供给量比较都偏低,但其生长发育良好,故对该年龄组儿童的营养素供给量应再进行研究。     

中国城乡居民膳食营养素摄入状况及变化趋势

目的:描述中国城乡居民膳食营养素摄入状况及变化趋势。方法:采用连续3d24h回顾法的食物记录数据及“称重法”记录的家庭调味品消费量数据,分析居民营养素摄入量。结果:全国23470户,68962人的膳食调查结果显示:我国居民每标准人日能量平均摄入量为9.42MJ(2250.5kcal),蛋白质65.9g,脂肪76.2g,视黄醇当量469.2μg,核黄素0.8mg,抗坏血酸88.4mg,钙388.8mg,铁23.2mg,锌11.3mg。结论:我国城乡居民理论得到保障,膳食质量有所提高,钙、视黄醇、抗坏血酸等营养素摄入不足仍是膳食中的主要问题。城乡差别明显,农村居民膳食质量亟待提高。     

膳食营养摄入与糖尿病、脑卒中和冠心病发病率的关系

目的通过了解居民膳食营养摄入,探讨膳食营养状况与糖尿病、脑卒中和冠心病之间的关系。方法根据不同经济水平、不同饮食习惯及地理分布,2008年选择浙江省内8个市、县(区),采用3 d 24 h回顾法进行食物摄入量调查;通过浙江省疾病控制中心慢性病监测系统获得8个市、县糖尿病、脑卒中和冠心病年度发病率。分析8个市、县居民膳食营养摄入与糖尿病、脑卒中和冠心病发病率的关系。结果 8个市、县(区)居民能量、蛋白质和碳水化合物摄入满足要求;脂肪供能占总体供能的比例超过WHO推荐的上限值;油脂和食盐摄入量高于推荐值;多数市、县(区)蔬菜、水果、奶制品和微量元素摄入不足。多变量线性回归分析表明:水果是糖尿病发生的保护因素;过量植物油是脑卒中发生的危险因素,水果是其保护因素。结论膳食营养因素(水果、植物油)可能与糖尿病、脑卒中的发生有一定的关系。     

甲状腺机能减退症住院率与全民食盐加碘

目的 :研究食盐加碘 (U SI)后甲状腺机能减退症状住院率的变化 ,为策略调整提供参考。方法 :甲状腺机能减退症住院率用回顾性调查方法。结果 :甲状腺机能减退症住院率在 USI后上升到原来的 2倍 ,AR百分比 4 9.4 % ,女性住院率增加高于男性 ,年龄组住院率变化不大。结论 :碘来源不同的社区应当考虑有不同加碘剂量标准     

叶酸、蛋氨酸摄入量,MTR、TS基因多态与结直肠癌关系的巢式病例对照研究

目的:研究蛋氨酸合酶(methioninesynthase,MTR)、胸苷酸合酶(thymidylatesynthase,TS)基因多态性,叶酸、蛋氨酸摄入量与结直肠癌易感性的关系。方法:采用巢式病例对照研究设计(病例140例和对照343例),通过非条件Logistic回归模型分析各多态与结直肠癌易感性的关系,及其与叶酸、蛋氨酸摄入量之间的联合作用。结果:MTR2756G等位基因携带者患结直肠癌的风险显著增高(OR=2.04,95%CI,1.22～3.39)。TS5’-UTR多态与叶酸摄入量之间的联合作用与结直肠易感性的关系有统计学意义(P=0.01)。结论:MTR2756G等位基因是结直肠癌的危险因素,TS5’-UTR多态与叶酸摄入量之间可能存在交互作用。     

DIETARY INTAKE IN A GROUP OF INSTITUTIONALISED ELDERLY AND THE EFFECT OF A FIBRE SUPPLEMENTATION PROGRAMME ON NUTRIENT INTAKE AND WEIGHT GAIN

As part of a long-term study of the effects of a dietary fibre supplementation programme on bowel function in a group of institutionalised elderly, various aspects of nutritional status were assessed before, and three, six and twelve months after introducing a fibre supplementation programme. Mean dietary intakes were satisfactory throughout the programme, although some individuals had intakes well below recommended levels for certain nutrients. The fibre supplementation programme not only improved bowel function, but also improved the nutrient density of the diet. Despite a slight increase in total energy intake, supplementation did not increase mean body weights in the group. Trace element status was not adversely affected by the supplementation programme.     

THE EFFECT OF PROTEIN INTAKE ON PLASMA AMINO ACID CONCENTRATIONS, ENZYMATIC ACTIVITY, AND FOOD INTAKE OF RATS

Feeding a high protein diet results in food intake depression, and an increase in concentration of plasma amino acids and the activity of threonine dehydratase. Food intake later increases following a decrease in plasma amino acid concentrations.     

FOOD INTAKE, SATIETY AND PEPTIDE HORMONES OF THE BRAIN-GUT AXIS

Cholecystokinin relays satiety signals to the central nervous system in addition to its well-known actions of stimulating pancreas exocrine secretion and gallbladder contraction. Its possible usefulness as an appetite depressant in obesity is reviewed.     

最大摄氧量与士兵体能评价

对５５００名战士的体能进行调查研究和分析。测定指标包括：ＶＯ２ｍａｘ、３０００ｍ跑、引体向上、立定跳远和１００ｍ跑等。结果表明，ＶＯ２ｍａｘ与３０００ｍ跑步时间和引体向上成绩明显相关，而与１００ｍ跑步时间和立定跳远距离不相关；老兵的有氧能力和肌力低于新兵，特种兵的有氧能力、肌力、速度均低于步兵。提示：ＶＯ２ｍａｘ是评价士兵体能的较好指标；部队应加强老兵和技术兵种的体能训练。     

THIAMINE INTAKE AND URINARY EXCRETION OF THIAMINE METABOLITES BY THE RAT

Thiamine tras not excreted in the ine until the tissue levels were 75 per cent saturated. However, the excrction of several metabolites of thiamine reflected dietary intake and may be useful as on index of tissue thiamine levels.     

PROTEIN SAVING ACTION OF LYSINE AND METHIONINE

Pigs fed vegetable diets with added lysine and methionine retained more nitrogen, grew as well, and showed equally normal economy of food conversion into weight gain as animals fed similar diets supplemented with animal protein.     

老年人膳食维生素K1摄入量及其主要来源

目的 :了解老年人膳食中维生素 K1 的摄入量和主要来源。方法 :对 113名 6 0岁以上老年人进行 7d膳食记录。用国内文献发表的食物中维生素 K1 含量资料和英国食物中维生素 K1 含量资料计算膳食中维生素 K1 摄入量。对所有食物按绿叶蔬菜、其它蔬菜、水果、油脂类、粮谷类、奶及蛋类、鱼肉类及其它食物进行分类 ,分别统计得出每类食物的维生素 K1含量。结果 :该人群膳食维生素 K1 摄入量为 347± 182 μg/天 ,膳食中维生素 K1 的主要来源是绿叶蔬菜占 82 % ,食用油脂占11%。菠菜、韭菜和大白菜是绿叶蔬菜中提供维生素 K1 的主要来源 ,占绿叶蔬菜提供维生素 K1 的 82 %。结论 :本研究中的老年人膳食维生素 K1 摄入量较高。多食绿叶蔬菜和植物油可提高人群膳食维生素 K1 摄入量。     

深圳市常住居民膳食结构与营养素摄入状况评价

目的了解深圳市居民的膳食结构、营养素摄入现状,为制定卫生政策和指导居民合理膳食提供科学依据。方法采用多阶段分层与人口成比例的整群随机抽样的方法,2011年2月到7月在深圳市8个区中按人口比例抽取12个社区,在每个被抽取的社区随机抽取75户居民(居住5年及以上),再将每个家庭中15岁及以上家庭成员作为调查对象参与一般问卷调查和膳食调查。结果深圳市居民谷类薯类及杂豆、蔬菜类、蛋类的摄入量分别为每标准人日257.8、336.7、31.3 g,符合中国居民平衡膳食宝塔推荐值要求;水果类、鱼虾类、奶类及其制品、大豆类及坚果的摄入量分别为标准人日97.9、59.9、43.3、15.5 g,未达膳食宝塔推荐值要求;畜禽肉类、油脂、盐的摄入量分别为每标准人日159.8、41.8、10.9 g,远远超过膳食宝塔推荐值。深圳市居民能量每标准人日摄入量为8.55 MJ(2043.7 kcal),蛋白质、脂肪、碳水化合物摄入量分别为71.2、88.3、239.3g,提供的能量比(%)分别为13.9、39.2、46.9;谷类、动物性食物、豆类提供的能量分别占35.4%、23.0%、4.0%。烟酸和维生素E平均每标准人日摄入量充足,维生素A、硫胺素、核黄素的平均每标准人日摄入量相对不足;磷、钠、铁、锰的摄入量充足,硒和钾的摄入量稍微低于RNIs,钙、镁、锌、铜的摄入量较低。结论深圳市居民膳食结构较往年有所改善,但水果类、鱼虾类、奶类及其制品、大豆类及坚果的摄入量未达推荐摄入量,畜禽肉类、油脂、盐的摄入量仍远高于推荐摄入量;三大营养物质供能比不平衡。仍需加强平衡膳食知识的宣传教育,促进合理膳食习惯的形成,防止发生营养相关慢性疾病。     

METHIONINE AND THE "METHYL FOLATE TRAP"

Normal perfused liver or suspensions of normal hepatocytes metabolize histidine only to formiminoglutamate, and cannot oxidize formate to carbon dioxide. The isolated organ or cells thus behave like vitamin B₁₂ or folate-deficient tissue. This was found to be caused by a lack of methionine. The deduction was made from these results that methionine is the key factor in regulating availability of folate. Under conditions of low methionine levels, folate becomes trapped as 5-methyl-tetrahydrofolate, as in vitamin B₁₂ deficiency.