Folic acid reverses nitric oxide synthase uncoupling and prevents cardiac dysfunction in insulin resistance: Role of Ca2+/calmodulin-activated protein kinase II

Nitric oxide synthase (NOS) may be uncoupled to produce superoxide rather than nitric oxide (NO) under pathological conditions such as diabetes mellitus and insulin resistance, leading to cardiac contractile anomalies. Nonetheless, the role of NOS uncoupling in insulin resistance-induced cardiac dysfunction remains elusive. Given that folic acid may produce beneficial effects for cardiac insufficiency partially through its NOS recoupling capacity, this study was designed to evaluate the effect of folic acid on insulin resistance-induced cardiac contractile dysfunction in a sucrose-induced insulin resistance model. Mice were fed a sucrose or starch diet for 8 weeks before administration of folic acid in drinking water for an additional 4 weeks. Cardiomyocyte contractile and Ca²⁺ transient properties were evaluated and myocardial function was assessed using echocardiography. Our results revealed whole body insulin resistance after sucrose feeding associated with diminished NO production, elevated peroxynitrite (ONOO⁻) levels, and impaired echocardiographic and cardiomyocyte function along with a leaky ryanodine receptor (RYR) and intracellular Ca²⁺ handling derangement. Western blot analysis showed that insulin resistance significantly promoted Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) phosphorylation, which might be responsible for the leaky RYR and cardiac mechanical dysfunction. NOS recoupling using folic acid reversed insulin resistance-induced changes in NO and ONOO⁻, CaMKII phosphorylation, and cardiac mechanical abnormalities. Taken together, these data demonstrated that treatment with folic acid may reverse cardiac contractile and intracellular Ca²⁺ anomalies through ablation of CaMKII phosphorylation and RYR Ca²⁺ leak.     

Changes in Muscarinic Binding in Distant Brain Regions Showing Neuronal Losses After Folic Acid Injections into the Substantia Innominata

Injection of folic acid (FA) into the nucleus substantia innominata (NSI) was found to decrease [3H]quinuclidinyl benzilate ([3H]QNB) binding in the frontal cortex, pyriform cortex, amygdala, and the NSI itself without changing the KD. Binding in the thalamus, caudate nucleus, hippocampus, and substantia nigra was not affected. [3H]Flunitrazepam binding was unchanged in all eight regions studied. Previous work indicates FA injections into the NSI produce epileptiform activity and cause loss of GABAergic and possibly other neurons in the frontal and pyriform cortices, the amygdala, and thalamus. The reductions of [3H]QNB binding in the first three of these regions are interpreted as indicating that many of the neurons lost are cholinoceptive, a finding that supports the previous hypothesis that activation of cholinergic projections from the NSI is an important part of the mechanism of cell loss in these regions.     

血清同型半胱氨酸、叶酸、维生素B12水平与冠状动脉病变严重程度的相关性分析

摘要 目的：探讨血清同型半胱氨酸(homocysteine, Hcy)、叶酸、维生素B12水平与冠状动脉病变严重程度的相关性。方法：选取经冠脉造影检查确诊的稳定期冠心病患者220例为研究组,并以同期健康查体志愿者100例为对照组。检测和比较两组血清Hcy、叶酸、维生素B12和N -末端脑钠肽前体(N-terminal brain natriuretic peptide precursor,NT-proBNP)水平。研究组根据冠脉造影情况进行SYNTAX评分评价,通过心脏超声检查检测左室射血分数(left ventricular ejection fraction,LVEF),确定冠脉病变严重程度。比较研究组SYNTAX低分组(1～22分)、中分组(23～32分)和高分组(≥33分)患者上述各指标水平,并分析研究组血清Hcy、叶酸、维生素B12水平与其血清NT-proBNP 水平、SYNTAX评分和LVEF的关系。结果：与对照组比较,研究组血清Hcy和NT-proBNP水平升高而血清叶酸、维生素B12水平降低(P＜0.05)。研究组SYNTAX评分和LVEF分别为(28.76±6.58)分和(47.33±8.66)%,SYNTAX中分和高分患者血清Hcy和NT-proBNP水平高于SYNTAX低分患者而血清叶酸、维生素B12水平和LVEF则低于SYNTAX低分患者,SYNTAX高分患者血清Hcy和NT-proBNP水平高于SYNTAX中分患者而血清叶酸、维生素B12水平和LVEF则低于SYNTAX中分患者(P＜0.05)。Pearson线性相关分析结果显示研究组血清Hcy水平与其血清NT-proBNP 水平、SYNTAX评分均呈正相关(r=0.881,0.793,P＜0.05),与其LVEF则呈负相关(r=-0.876,P＜0.05);而其血清叶酸、维生素B12水平与其血清NT-proBNP 水平、SYNTAX评分均呈负相关(叶酸：r=-0.786,-0.825;维生素B12：r=-0.884,-0.818,P＜0.05),与其LVEF则呈正相关(r=0.893,0.859,P＜0.05)。结论：血清Hcy是冠心病的重要危险因素,其水平随着冠状动脉病变程度加重而升高;血清叶酸、维生素B12是冠心病的保护因素,其水平随着冠状动脉病变程度加重而降低。     

不同胃癌前病变中医证型PG、G-17、CEA和叶酸水平变化及相关性研究

目的:对不同胃癌前病变中医证型和血清胃蛋白酶原(pepsinogen,PG)、胃泌素-17(gastrin-17,G-17)、癌胚抗原(carcinoembryonic antigen,CEA)和叶酸水平变化的关系进行探讨,为胃癌前病变的诊断提供一定的依据。方法:以80例胃癌前病变(precancerous lesion of gastric cancer,PLGC)患者研究组,80例健康者为对照组,对研究组患者进行中医临床辨证分型,对两组研究对象的血清PG、G-17、CEA和叶酸进行测定比较。结果:研究组PLGC患者中医证型分布不均匀,差异显著(P<0.05),由多到少依次为湿热蕴胃并/兼脾胃虚寒证>胃络瘀阻并/兼气阴两虚证>痰湿中阻并/兼脾胃气虚证>肝胃气滞并/兼气阴两虚证>肝胃气滞并/兼脾胃虚寒证>湿热蕴胃并/兼胃阴不足证。PLGC不同中医证型患者血清PG I和PG II水平差异显著(P<0.05);与对照组比较,各证型PG I水平均显著降低,PG II水平均显著升高(P<0.05)。且湿热蕴胃并/兼脾胃虚寒证和胃络瘀阻并/兼气阴两虚证的PG I水平显著低于其他证候,血清PG II水平显著高于其他(P<0.05)。与对照组比较,研究组不同证候的G-17、CEA水平显著升高,叶酸水平显著降低(P<0.05);观察组中湿热蕴胃并/兼脾胃虚寒证和胃络瘀阻并/兼气阴两虚证G-17、CEA显著高于其他证候,叶酸水平显著低于其他证候(P<0.05)。结论:胃癌前病变不同中医证型血清PG、G-17、CEA和叶酸存在明显差异。     

Electrochemical determination of folic acid: A short review

Folic acid (FA) is an electroactive compound of biological origin. It helps our body to produce and maintain healthy cells. It can significantly reduce the occurrence of neural tube defects and also prevents change in DNA structure. FA deficiency can lead to various health risks. Therefore, a sensitive, specific, and reproducible way of FA detection is essential. A number of analytical methods are in practice for the quantification of FA. However, electroanalytical methods are attracting much attention because of their advantage over conventional methods, as they are fast, simple, sensitive, and cost effective. Moreover, modification of electrodes offers control over size and morphology which allows miniaturization for applicability in portable electrochemical devices.     

叶酸- 聚乙二醇- 阿霉素连接物及其制剂稳定性研究

目的:考察叶酸-聚乙二醇-阿霉素连接物(FA-PEG-hyd-DOX)及其制剂在不同实验条件下的稳定性,为其开发应用奠定基础。方法:参照2010版《中国药典》二部附录XIXC《原料药与药物制剂稳定性试验指导原则》,将DOX、FA-PEG-hyd-DOX连接物原料及其冻干粉制剂置于高温、高湿、强光照环境中,不同时间对样品的DOX质量百分含量、熔点、外观性状等指标进行考察分析。结果:DOX在高温、高湿、强光照环境中放置10天后,DOX质量百分含量分别为31.95%、66.36%和61.27%,熔点分别为195℃、194℃和194℃。FA-PEG-hyd-DOX连接物在高温、高湿、强光照环境中放置10天后,DOX质量百分含量分别为2.71%、3.85%和3.14%,熔点范围分别为169-175℃、170-175℃和170-175℃。FA-PEG-hyd-DOX冻干粉制剂在高温、高湿、强光照环境中放置10天后,DOX质量百分含量分别为3.80%、5.76%和4.80%。结论:FA-PEG-hyd-DOX连接物原料的稳定性高于DOX,FA-PEG-hyd-DOX甘露醇冻干粉制剂的稳定性高于其原料药。     

Tetrahydrofolate and 5-methyltetrahydrofolate are folates with high antioxidant activity. Identification of the antioxidant pharmacophore

The presumed protective effect of folic acid on the pathogenesis of cardiovascular, hematological and neurological diseases and cancer has been associated with the antioxidant activity of folic acid. Peroxynitrite (PON) scavenging activity and inhibition of lipid peroxidation (LPO) of the physiological forms of folate and of structurally related compounds were tested. It was found that the fully reduced forms of folate, i.e. tetrahydrofolate (THF) and 5-methyltetrahydrofolate (5-MTHF), had the most prominent antioxidant activity. It appeared that their protection against LPO is less pronounced than their PON scavenging activity. The antioxidant activity of these forms of folic acid resides in the pterin core, the antioxidant pharmacophore is 4-hydroxy-2,5,6-triaminopyrimidine. It is suggested that an electron donating effect of the 5-amino group is of major importance for the antioxidant activity of 4-hydroxy-2,5,6-triaminopyrimidine. A similar electron donating effect is probably important for the antioxidant activity of THF and 5-MTHF.     

Effect of Maternal Ethanol Consumption during Pregnancy and Lactation on Kinetic Parameters of Folic Acid Intestinal Transport in Suckling Rats

Ethanol ingestion is known to interfere with folate absorption and metabolism. A fostering/crossfostering analysis of maternal ethanol exposure effects on jejunum and ileum kinetic parameters in vivo of offspring rat folic acid absorption at 21 days postpartum was carried out. The rats were divided into four groups: CP, control pups; GP, pups exposed to ethanol only during gestation; LP, pups exposed to ethanol only during lactation; GLP, pups exposed to ethanol during gestation and lactation. Jejunal and ileal loop transport studies were performed using in vivo perfusion at a flow rate of 3 ml/min for 5 min. Folic acid concentrations of 0.25, 0.5, 1, 1.5 and 2.5 μm were used. Jejunal and ileal absorption values were determined by the difference between the initial and the final amounts of substrate in the perfusate and expressed as picomoles per square centimeter of intestinal surface every 5 min. The results indicated that ethanol consumption by the dams during gestation and/or lactation led to significant changes in V _max, with no significant changes in apparent K _m. These findings suggest that exposure to ethanol during gestational and suckling periods leads to a general delay in postnatal body weight and that intestinal folate absorption appears to be upregulated in suckling rats, this effect being higher in the LP group.     

Effects of folate cycle disruption by the green tea polyphenol epigallocatechin-3-gallate

We demonstrate that the tea polyphenol, epigallocatechin-3-gallate, is an efficient inhibitor of human dihydrofolate reductase. Like other antifolate compounds, epigallocatechin-3-gallate acts by disturbing folic acid metabolism in cells, causing the inhibition of DNA and RNA synthesis and altering DNA methylation. Epigallocatechin-3-gallate was seen to inhibit the growth of a human colon carcinoma cell line in a concentration and time dependent manner. Rescue experiments using leucovorin and hypoxanthine–thymine medium were the first indication that epigallocatechin-3-gallate could disturb the folate metabolism within cells. Epigallocatechin-3-gallate increased the uptake of [³H]-thymidine and showed synergy with 5-fluorouracil, while its inhibitory action was strengthened after treatment with hypoxanthine, which indicates that epigallocatechin-3-gallate decreases the cellular production of nucleotides, thus, disturbing DNA and RNA synthesis. In addition to its effects on nucleotide biosynthesis, antifolate treatment has been linked to a decrease in cellular methylation. Here, we observed that epigallocatechin-3-gallate altered the p16 methylation pattern from methylated to unmethylated as a result of folic acid deprivation. Finally, we demonstrate that epigallocatechin-3-gallate causes adenosine to be released from the cells because it disrupts the purine metabolism. By binding to its specific receptors, adenosine can modulate different signalling pathways. This proposed mechanism should help us to understand most of the molecular and cellular effects described for this tea polyphenol.     

乳酸菌合成叶酸的研究进展

叶酸普遍存在于各类食物中,但由于叶酸的不稳定性以及饮食习惯的差异性,各国叶酸缺乏现象普遍存在。叶酸是参与核酸合成及细胞分裂分化的重要物质,叶酸缺乏引起机体功能的混乱,由此引发癌症等一系列的疾病。大部分乳酸菌是叶酸缺陷型菌株,但越来越多的研究表明其很多种类都具有叶酸合成能力。本文主要概述产叶酸乳酸菌的分类,乳酸菌生物合成叶酸的机制,以及利用乳酸菌进行的叶酸基因工程研究进展。