Absorption and metabolism of short‐chain fatty acids in ruminants

Short‐chain fatty acids (SCFA), viz. acetate, propionate and butyrate are quantitatively important substrates in ruminant energy metabolism. In the reviewed literature, 16–44% of ME intake was recovered as portal appearance of SCFA. This is considerably lower than expected when related to the estimated intra‐gastric flux of SCFA. The discrepancy is caused by portal drained viscera metabolism of arterially abundant metabolites e.g., acetate and the metabolism of acetate and butyrate to acetoacetate and D‐3‐hydroxybu‐tyrate in the absorptive epithelia. Even though considerable variations between experiments on acetate and propionate appearance are found, there seems to be a great deal of evidence that the proportion of gastroin‐testinally produced acetate and propionate absorbed to the portal blood is 50–75%. The portal recovery of butyrate has been found to be between 10 and 36% dependent on intraruminal infusion rate.

It is concluded that major parts of acetate and propionate are directly absorbed to the portal vein. The true absorption rate of acetate can only be estimated by taking the portal drained viscera metabolism of arterial actetate into account. Butyrate is generally found to have a low recovery in the portal vein, but the production of D‐3‐hydroxybutyrate seems to be underestimated in major parts of the literature. It is therefore necessary to measure portal appearance as well as portal drained viscera metabolism to assess the quantitative as well as the qualitative contribution of SCFA and SCFA metabolites to whole animal metabolism.     

Entamoeba invadens: restriction of ploidy by colonic short chain fatty acids

The DNA content of Entamoeba parasites appears to be regulated by an unusual mechanism. This conclusion, however, was based on experiments that examined parasites grown in media that did not contain short chain fatty acids (SCFAs) normally found in the colonic lumen. Since one of these SCFAs, butyrate, is known to affect DNA replication in eukaryotic cells, we examined the effect of SCFAs on Entamoeba trophozoite DNA content. Similar to reports from others, we found that Entamoeba invadens trophozoite cultures grown in conventional medium (TYI-S-33) contained cells with 2N, 4N, 8N, and 16N amounts of DNA. In contrast, cultures grown in TYI medium containing colonic SCFAs added in place of glucose contained a minor population with 2N, a major population with 4N, and very few cells with higher amounts of DNA. SCFAs also prevented the normal increase in the number of nuclei per cell in trophozoites that were induced to encyst. These results suggest that E. invadens trophozoite stage parasites growing in the intestine in the presence of high amounts of SCFAs have a ploidy range restricted to 2N/4N. Axenic growth of trophozoites in the absence of SCFAs, however, appears to allow trophozoites to increase the amount of DNA per cell, which they must do during the normal encystment process.     

鸡肠道菌群和短链脂肪酸相互关系的研究进展

肠道是动物机体重要的消化和营养吸收器官。肠道菌群决定肠道健康,进而影响机体健康。近来关于肠道菌群的研究越来越多,且肠道菌群酵解底物产生的短链脂肪酸也备受人们关注。短链脂肪酸主要包括乙酸、丙酸、丁酸等及其盐类。在对肠道功效方面,短链脂肪酸发挥着重要作用,如氧化供能、维持水电解质平衡、调节免疫、抗病原微生物及抗炎、调节肠道菌群平衡、改善肠道功能等。因此,本文根据近年来国内外相关研究报道,综述了鸡肠道不同种类、含量的菌群对短链脂肪酸来源和吸收的影响;不同种类、含量和制剂形态的短链脂肪酸对肠道菌群影响的研究进展,为更好地了解鸡肠道菌群和短链脂肪酸的相互关系和提高禽类养殖水平提供理论指导。     

短链脂肪酸调控人髓母细胞瘤UW228 3细胞增殖、凋亡和侵袭作用的研究

目的 研究菌群代谢产物短链脂肪酸——丙酸、丁酸对人髓母细胞瘤UW228 3细胞增殖、凋亡和侵袭的影响。 方法 分别用10 μmol/L丙酸和5 μmol/L丁酸处理UW228 3细胞,通过HE染色观察细胞形态,MTT法测定细胞活力,流式细胞术检测细胞凋亡,细胞划痕检测细胞侵袭,PCR和Western Blot检测凋亡相关基因和蛋白的表达。 结果 10 μmol/L丙酸和5 μmol/L丁酸能够有效抑制UW228 3细胞增殖能力,增加细胞凋亡率,并显著抑制UW228 3细胞侵袭能力,提高Caspase 3基因以及蛋白表达,降低c Myc、Bcl 2、Survivin基因以及蛋白的表达。 结论 菌群代谢产物丙酸、丁酸能够抑制人髓母细胞瘤UW228 3细胞增殖和侵袭,并促进细胞凋亡,具有治疗髓母细胞瘤的潜在价值。     

Selectivity of lipases and esterases towards phenol esters

The selectivity of 28 lipases and esterases in the hydrolysis of butanoates of o-, m- or p-substituted phenols was investigated in a microtiterplate format. The phenols released during enzyme-catalyzed hydrolysis were converted in situ with Gibbs’ reagent to form a blue indophenol complex, which was quantified spectrophotometrically at 600 nm. Substantial differences in rates were found, which exhibits that the type and position of the substituent at the alkyl group has a strong influence on the selectivity of the enzymes. For various enzymes, the p-nitro derivative was the best substrate, whereas for other enzymes the m-Cl-derivative was preferentially hydrolyzed. Analysis of the data using the Hammett equation showed that sometimes the observed changes followed a predictable trend, but in several cases the result is very unexpected.     

肠道菌群代谢产物短链脂肪酸在慢性肾脏病中的研究进展

近年来研究发现肾脏与肠道微生态间存在密切的联系,称为“肠-肾轴”。慢性肾脏病患者(CKD)由于各种因素往往导致肠道生态失调,表现为肠道菌群种类的相对丰度、组成及其代谢产物发生改变。肠道菌群代谢产物短链脂肪酸(SCFAs)是联系宿主和肠道菌群的重要中介物质,具有生物学效应。研究发现SCFAs主要通过与G蛋白偶联受体结合,抑制组蛋白去乙酰化酶调节RAS系统、炎症反应和细胞自噬等,起到延缓肾脏炎症和纤维化的作用。基于SCFAs与肾脏之间的紧密联系,SCFAs可能成为慢性肾脏病治疗的新靶点。外源性补充SCFAs能延缓CKD发生和发展的作用逐渐受到认可。因此,进一步研究SCFAs在肾脏方面的具体作用机制尤为重要。     

短链脂肪酸在宿主能量代谢方面的调节作用

肠道菌群数量庞大,对宿主多种生理活动具有重要调节作用。现有研究发现,肠道菌群主要通过调节其产生的不同代谢产物,参与宿主物质代谢反应,改变能量代谢水平,影响机体炎症反应。在诸多代谢产物中,短链脂肪酸（醋酸盐、丙酸盐、丁酸盐等）具有重要调节作用,对机体代谢功能方面具有深远影响。本文结合国内外相关研究文献,综述了短链脂肪酸在调节机体能量代谢方面的相关研究,以期为进一步阐明其在机体能量代谢方面的作用提供科学依据。     

Release of fatty acid-binding protein and long chain fatty acids from isolated rat heart after ischemia and subsequent calcium paradox

To obtain insight into the relation between the release of heart-type fatty acid-binding protein (H-FABP_c) and of long-chain fatty acids (FA) from injured cardiac tissue, rat hearts were Langendorff perfused according to the following scheme: 30 min normoxia, 60 min ischemia, 30 min reperfusion, 10 min Ca²⁺ free perfusion and finally 10 min Ca²⁺ repletion. During this protocol right ventricular (Q _rv ) and interstitial effluent samples (Q _i ) were collected at regular intervals. During reperfusion a total of 0.8±0.1 nmol H-FABP_c but no FA were detected in the effluents. However, during Ca²⁺ readmission, 45±4 nmol H-FABP_c (80–90% of total tissue content) was released with an initial (first 3 min) simultaneous release of FA (FA/H-FABP_c ratio 0.90±0.07 mol/mol). Thereafter, FA release continued at 10–15 nmol per min mainly inQ _rv while the rate of H-FABP_c release decreased. During Ca²⁺ repletion, tissue FA content raised rapidly from 168±20 to 1918±107 nmol/g dry weight. These findings suggest that after severe cardiac damage initially FA is released bound to H-FABP_c, whereas further FA release occurs in a non-protein bound manner.     

Effect of ciprofibrate on the activation and oxidation of very long chain fatty acids

The effect of ciprofibrate, a hypolipidemic drug, was examined in the metabolism of palmitic (C_16:0) and lignoceric (C_24:0) acids in rat liver. Ciprofibrate is a peroxisomal proliferating drug which increases the number of peroxisomes. The palmitoyl-CoA ligase activity in peroxisomes, mitochondria and microsomes from ciprofibrate treated liver was 3.2, 1.9 and 1.5-fold higher respectively and the activity for oxidation of palmitic acid in peroxisomes and mitochondria was 8.5 and 2.3-fold higher respectively. Similarly, ciprofibrate had a higher effect on the metabolism of lignoceric acid. Treatment with ciprofibrate increased lignoceroyl-CoA ligase activity in peroxisomes, mitochondria and microsomes by 5.3, 3.3 and 2.3-fold respectively and that of oxidation of lignoceric acid was increased in peroxisomes and mitochondria by 13.4 and 2.3-fold respectively. The peroxisomal rates of oxidation of palmitic acid (8.5-fold) and lignoceric acid (13.4-fold) were increased to a different degree by ciprofibrate treatment. This differential effect of ciprofibrate suggests that different enzymes may be responsible for the oxidation of fatty acids of different chain length, at least at one or more step(s) of the peroxisomal fatty acid -oxidation pathway.     

A multisubstrate assay for lipases/esterases: Assessing acyl chain length selectivity by reverse-phase high-performance liquid chromatography

Lipases and esterases are hydrolytic enzymes and are known to hydrolyze esters with unique substrate specificity and acyl chain length selectivity. We have developed a simple competitive multiple substrate assay for determination of acyl chain length selectivity of lipases/esterases using RP-HPLC with UV detection. A method for separation and quantification of 4-nitrophenyl fatty acid esters (C₄–C₁₈) was developed and validated. The chain length selectivity of five lipases and two esterases was determined in a multisubstrate reaction system containing equimolar concentrations of 4-nitrophenyl esters (C₄–C₁₈). This assay is simple, reproducible, and a useful tool for determining chain length selectivity of lipases/esterases.     

野牦牛和家牦牛粪便菌群与短链脂肪酸关系的研究

短链脂肪酸(SCFA)是反刍动物吸收饲草、饲料中营养物质的重要形式。肠道菌群能够降解食物生成SCFA并影响其比例。本文通过16S r DNA测序和气相色谱质谱联用仪,分别测定了野牦牛(Bos mutus)和家牦牛(Bos grunniens)粪便菌群组成及SCFA含量,通过比较分析两种牦牛肠道菌群与SCFA的关系,筛选出野牦牛肠道中与SCFA高浓度有正相关关系的菌群。结果显示,野牦牛粪便菌群主要有厚壁菌门(Firmicutes)(66. 47%)、拟杆菌门(Bacteroidetes)(26. 00%)和变形菌门(Proteobacteria)(3. 48%),主要的科有瘤胃球菌科(Ruminococcaceae)(55. 18%)、拟杆菌科(Bacteroidaceae)(8. 75%)和毛螺菌科(Lachnospiraceae)(7. 57%),家牦牛的菌群结构和组成与野牦牛相似。野牦牛粪便中SCFA以乙酸和丙酸为主,乙酸、丙酸、异丁酸、正丁酸和正戊酸的含量均显著高于家牦牛(P <0. 01)。Spearman相关分析显示,野牦牛粪便菌群中紫单胞菌科(Porphyromonadaceae)、拟杆菌科(Bacteroidaceae)、普雷沃氏菌科(Paraprevotellaceae)、理研菌科(Rikenellaceae)和韦荣球菌科(Erysipelotrichaceae)与SCFA具有较强相关性(r> 0. 4),而家牦牛仅有弱相关性(r <0. 3)。说明牦牛后肠道具有丰富的能够促进SCFA生成的益生菌群,进而提高食物的转化效率。     

Effects of short chain fatty acids on seedlings

Abstract. Primary roots of lettuce show no appreciable diminution of sensitivity of SCFA between 24 and 72 h, so it is likely that all actively growing primary roots are susceptible to inhibition by SCFA. While roots do not recover from long exposures to high concentrations of SCFA, partial recovery is seen following exposure to intermediate levels.
SCFA inhibit elongation of lettuce and turnip hypocotyls as well as roots. However, higher concentrations are required to produce a given inhibition of hypocotyl. In contrast with the inhibition of roots, inhibition of shoots is markedly dependent on the chain length of the fatty acid. Thus, either access to sites of action or action at the sites differs between shoots and roots of the same seedling plants.     

平台化学品短链支链脂肪酸和短链支链醇的微生物代谢工程

短链支链脂肪酸和短链支链醇均为重要的平台化学品,是合成多种高附加值产品的前体物质,市场需求巨大。目前两者的生产主要是利用基于石化原料的化学合成法。化学合成法存在着严重依赖化石燃料、反应效率低以及极易造成环境污染等缺点。微生物代谢工程的快速发展为这些平台化学品的生产提供了一条极具潜力的生物合成路线。利用微生物代谢工程技术构建生产这些平台化学品的微生物细胞工厂具有绿色清洁、可持续发展和经济效益好等独特优势。本文系统综述了近年来微生物代谢工程技术在短链支链脂肪酸和短链支链醇合成方面的研究进展,包括所涉及的宿主菌株、关键酶、代谢途径及其改造等,并探讨了未来的发展前景。     

Short chain fatty acids but not lactate or succinate stimulate mucus release in the rat colon

Background: Short chain fatty acids (SCFAs) affect various intestinal functions. Mucus is an important physiological component of the intestinal mucosal barrier. However, the effect of SCFAs or other organic acids on the intestinal mucus release is poorly understood. The aim of this study was to investigate whether lumen SCFA stimulates mucus release into the rat colon. Methods: A solution of SCFA, lactate or succinate was infused into the colon of anesthetized rats, and we then measured the hexose content of the effluent. We also examined the influence of cholinergic antagonists on the effects of SCFA. Results: A SCFA mixture (75 mM acetate, 35 mM propionate and 20 mM butyrate) or individual SCFAs (130 mM) increased the mucus release into the colon in a similar manner. The individual SCFAs, but not lactate or succinate, stimulated colonic mucus secretion in similar concentration-dependent manners. Butyrate stimulated colonic mucus secretion at 20 mM, but acetate, propionate, lactate and succinate at this concentration did not. Pretreatment with an anti-cholinergic agent diminished the stimulatory effects of SCFAs on mucus secretion. Conclusions: Lumen SCFAs, but not lactate or succinate, stimulate mucus release from the rat colon via a cholinergic nerve mechanism.     

Isotopomer enrichment assay for very short chain fatty acids and its metabolic applications

The present work illustrated an accurate GC/MS measurement for the low isotopomer enrichment assay of formic acid, acetic acid, propionic aicd, butyric acid, and pentanoic acid. The pentafluorobenzyl bromide derivatives of these very short chain fatty acids have high sensitivity of isotopoic enrichment due to their low natural isotopomer distribution in negative chemical ionization mass spectrometric mode. Pentafluorobenzyl bromide derivatization reaction was optimized in terms of pH, temperature, reaction time, and the amount of pentafluorobenzyl bromide versus sample. The precision, stability, and accuracy of this method for the isotopomer analysis were validated. This method was applied to measure the enrichments of formic acid, acetic acid, and propionic acid in the perfusate from rat liver exposed to Krebs–Ringer bicarbonate buffer only, 0–1 mM [3,4-¹³C₂]-4-hydroxynonanoate, and 0–2 mM [5,6,7-¹³C₃]heptanoate. The enrichments of acetic acid and propionic acid in the perfusate are comparable to the labeling pattern of acetyl-CoA and propionyl-CoA in the rat liver tissues. The enrichment of the acetic acid assay is much more sensitive and precise than the enrichment of acetyl-CoA by LC-MS/MS. The reversibility of propionyl-CoA from succinyl-CoA was confirmed by the low labeling of M1 and M2 of propionic acid from [5,6,7-¹³C₃]heptanoate perfusates.     

基于气相色谱法分析T2DM患者粪便中SCFAs水平与HbA1c的相关性

目的 研究2型糖尿病患者粪便中6种短链脂肪酸水平与糖化血红蛋白的相关性。 方法 采用气相色谱法检测粪便中短链脂肪酸的含量,并对方法学进行考察。选取2018年在本院查体的2型糖尿病患者57例,根据糖化血红蛋白水平将其分为高糖化组(糖化血红蛋白>7.0,28例)与低糖化组(糖化血红蛋白≤7.0,29例)。应用气相色谱法检测两组患者粪便中6种短链脂肪酸水平,并分析6种短链脂肪酸水平与糖化血红蛋白的相关性。 结果 低糖化组患者粪便中乙酸、丙酸、丁酸、戊酸水平显著高于高糖化组(均P0.05)。Pearson相关性分析结果表明:在2型糖尿病患者中,糖化血红蛋白与粪便中乙酸呈负相关(r=-0.540 1,P结论 2型糖尿病患者粪便中短链脂肪酸水平与糖化血红蛋白存在一定的相关性,短链脂肪酸水平的下降可能是影响血糖控制不佳的主要原因。     

Production of dicarboxylic acids from novel unsaturated fatty acids by laccase-catalyzed oxidative cleavage

The establishment of renewable biofuel and chemical production is desirable because of global warming and the exhaustion of petroleum reserves. Sebacic acid (decanedioic acid), the material of 6,10-nylon, is produced from ricinoleic acid, a carbon-neutral material, but the process is not eco-friendly because of its energy requirements. Laccase-catalyzing oxidative cleavage of fatty acid was applied to the production of dicarboxylic acids using hydroxy and oxo fatty acids involved in the saturation metabolism of unsaturated fatty acids in Lactobacillus plantarum as substrates. Hydroxy or oxo fatty acids with a functional group near the carbon–carbon double bond were cleaved at the carbon–carbon double bond, hydroxy group, or carbonyl group by laccase and transformed into dicarboxylic acids. After 8 h, 0.58 mM of sebacic acid was produced from 1.6 mM of 10-oxo-cis-12,cis-15-octadecadienoic acid (αKetoA) with a conversion rate of 35% (mol/mol). This laccase-catalyzed enzymatic process is a promising method to produce dicarboxylic acids from biomass-derived fatty acids.