牛SCD基因研究进展

硬脂酰辅酶A去饱和酶（SCD）是催化主要包括棕榈酰CoA（C16：0）、硬脂酰CoA（C18：0）在内的饱和脂肪酸（SFA）产生单不饱和脂肪酸（MUFA）合成的关键酶，对牛奶、脂肪组织中脂肪酸的组成以及肌肉间脂肪沉积有着重要影响。文章概述了近年来牛SCD基因相关的研究进展。     

胰岛素、胰高血糖素和神经肽Y对体外培养犊牛肝细胞硬脂酰CoA去饱和酶mRNA表达的影响

在应用实时荧光定量PCR法观察胰岛素(In)、胰高血糖素(GLN)、神经肽(NPY)对体外培养新生犊牛肝细胞硬脂酰CoA去饱和酶(Stearoyl CoA desaturase,SCD) mRNA丰度的影响.结果显示,随着培养液中In含量的升高,肝细胞中的SCD mRNA表达逐渐升高(P＜0.05),呈现明显的剂量依赖促进效应;随着培养液中GLN含量的升高,肝细胞SCD mRNA丰度表达逐渐减弱,高血糖素处理组SCD mRNA表达均极显著低于对照组(P＜0.01);而随着NPY质量浓度在0～1 000 ng/L之间逐渐上升,肝细胞SCDmRNA的表达水平不断升高,各处理组显著高于对照组,除50 ng/L处理组和500 ng/L处理组之间差异不显著外,其他处理组之间差异显著(P＜0.05).结果表明,胰岛素和神经肽Y促进SCD mRNA表达,胰高血糖素抑制SCD mRNA表达.     

SCD基因在两个奶山羊品种中的酶切多态性分析

硬脂酰辅酶A去饱和酶(SCD)是酯酰去饱和酶超家族的成员,是控制脂肪组织和乳腺中的饱和脂肪酸向不饱和脂肪酸转化的舍铁关键酶.然而,目前少见关于山羊SCD基因遗传变异方面的研究.在对两个奶山羊品种(西农萨能和关中奶山羊)的708个个体的研究中发现了SCD基因的3个碱基突变,其中一个为错义突变,并且由此构建了单倍型A、B和C,共发现了6种基因型.通过关联分析表明:CC基因型个体的体高和体长明显大于BC基因型个体(P＜0.05).     

奶牛日粮添加豆油抑制乳腺硬脂酰辅酶A去饱和酶(SCD)基因mRNA表达水平

硬脂酰辅酶A去饱和酶(SCD)是奶牛乳腺合成共轭亚油酸(CLA)的关键酶。奶牛日粮饲喂35 d豆油后,与不添加豆油的对照组相比,抑制了奶牛乳腺组织SCD基因mRNA的表达,研究结果表明,日粮亚油酸对乳腺SCD酶基因表达具有抑制作用。     

藏猪和杜洛克猪SCD、CPT1B基因表达差异及其与IMF含量相关性分析

为了揭示脂肪型的藏猪和瘦肉型的杜洛克猪肌内脂肪(IMF)沉积相关基因的表达差异,试验采用荧光定量PCR(qRT-PCR)方法检测了两猪种背最长肌中硬脂酰辅酶A去饱和酶(SCD)基因、肉碱脂酰转移酶Ⅰ(CPT1B)基因在180日龄的表达差异,分析其表达与IMF含量的相关性。结果表明:180日龄藏猪SCD mRNA表达量极显著高于杜洛克猪(P0.01),而藏猪CPT1B mRNA表达量显著高于杜洛克猪(P0.05)。相关性分析结果显示,SCD、CPT1B mRNA表达量均与IMF含量呈正相关。     

梯度敲除MSTN对SCD5表达量的影响

为了改善猪肉品质,探究肌肉抑制素(MSTN)通过硬脂酰辅酶A去饱和酶5(SCD5)调控脂质代谢的分子通路,试验采用qPCR和Western-blot方法检测MSTN野生型细胞系PK15、单等位基因敲除型细胞系PK3108及双等位基因敲除型细胞系L18中SCD5的表达量变化。结果表明:在mRNA水平,MSTN单等位基因和双等位基因敲除引起SCD5 98%和96%的下调;在蛋白质水平,MSTN单等位基因敲除对SCD5影响较小,双等位基因敲除引起SCD5大幅下调。说明在细胞水平上,失活MSTN可引起SCD5表达量下调。     

哺乳动物Acot2基因的研究进展

酰基辅酶A硫酯酶2(Acot2)是酰基辅酶A硫酯酶(Acots)家族成员之一,其将酰基辅酶A(CoA)水解成游离脂肪酸和CoA,具有维持细胞水平的游离脂肪酸和酰基CoA(游离脂肪酸的活化形式)的潜力,在脂质代谢中发挥重要作用。本文对Acot2基因的定位、结构特征、生理功能及其调控进行综述,以期对Acot2基因的进一步探究提供参考。     

猪硬脂酰辅酶A去饱和酶蛋白生物信息学分析

为了探究硬脂酰辅酶A去饱和酶(SCD)的结构和生物学功能,利用Expasy、Sopma等生物信息学软件,对猪SCD的氨基酸序列进行初步的生物信息学分析。结果表明:猪SCD基因编码359个氨基酸,平均分子质量为41.38 ku;该蛋白存在4个跨膜结构域,分别包含1个潜在的O-糖基化位点、3个N-糖基化位点和16个磷酸化位点;二级结构由α螺旋、β转角、延伸链和随机卷曲组成;该蛋白具有低复杂结构和跨膜结构两种功能结构域。     

武定鸡与大围山微型鸡脂肪酸含量及SCD基因表达差异研究

脂肪酸是重要的风味物质,影响着鸡肉品质性状,硬脂酰辅酶A去饱和酶(Stearoyl-CoA desaturase,SCD)是合成单不饱和脂肪酸的关键酶,是调节肝脏脂肪生成和脂类氧化的关键控制点。研究以90日龄武定鸡和大围山微型鸡为研究对象,检测肌肉组织中脂肪酸含量及SCD基因表达量结果显示,武定鸡肌肉中脂肪酸含量和SCD基因表达量显著高于大围山微型鸡,且在不同部位存在显著差异。研究表明,SCD基因是影响家鸡脂肪酸形成的重要候选基因。     

日粮中添加梧桐子油和罗格列酮对绵羊背最长肌中脂代谢相关酶活性的影响

为了研究日粮中添加硬脂酰辅酶A去饱和酶(SCD)的活性促进剂(罗格列酮)和抑制剂(梧桐子油)对绵羊背最长肌中的脂肪酸合成酶(FAS)、脂蛋白脂酶(LPL)、乙酰辅酶A羧化酶(ACC)以及SCD活性的影响,试验将18只美利奴×小尾寒羊杂交公羊随机分为3组,对照组饲喂基础日粮,梧桐子油组饲喂基础日粮+15 g/d梧桐子油,罗格列酮组饲喂基础日粮+8 mg/d罗格列酮,试验期为50d,其中过渡期10 d、预饲期5 d、正试期35 d,测定绵羊背最长肌中的FAS、LPL、ACC及SCD活性。结果表明:与对照组相比,梧桐子油组绵羊背最长肌中ACC和SCD酶活性显著受到抑制(P0.05),罗格列酮组绵羊背最长肌中LPL和SCD酶活性显著提高(P0.05)。     

牛科家养动物硬脂酰辅酶A脱氢酶1基因的研究进展

硬脂酰辅酶A脱氢酶1(stearoyl-CoA desaturase-1,SCD1)是哺乳动物脂肪细胞中饱和脂肪酸转换为单一不饱和脂肪酸的关键酶,对动物机体及动物产品中脂肪酸的组成和含量有重要的影响。本文对普通牛、水牛、山羊和绵羊等牛科常见家养动物的SCD1基因的结构与功能、变异类型及其与经济性状关联的研究进展进行了综述,并对该基因的未来研究进行了展望。     

利用三个基因标记选育大白核心群后备种猪初报

猪氟烷基因(RYR1)c.1843C>T突变位点是造成猪应激综合征的主效基因位点.硬脂酰辅酶A去不饱和酶基因(SCD)是控制单不饱和脂肪酸合成的关键酶,其启动子区域-233上T>C突变位点对肥胖和背膘厚有重要影响.α1岩藻糖基转移酶基因(FUT1)基因是ETEC F18受体蛋白基因,其开放阅读框M307的G>A突变位点影响仔猪断乳后水肿和腹泻的发生.该研究采用PCR-RFLP方法,检测了福建仁锋种猪有限公司大约克核心群60头后备种猪个体在这3个基因相应突变位点的基因型.结果表明,该群体已完全淘汰了应激敏感型n等位基因,建立了氟烷应激抵抗系:且保持着高频率(90.8%)的SCD基因、有利降低背膘沉积、提高瘦肉率的T等位基因;但FUT1的ECF18抗性等位基因A的频率相对较低(26.7%),易感等位基因G的频率较高(73.3%).该研究结果结合该场的性能测定结果运用于指导该大白核心群后备种猪的选种选育实践,可望提高核心群内种猪产肉量性状、抗应激能力和降低仔猪断乳后腹泻抗性发生.     

日粮脂肪酸组成对硬脂酰辅酶A去饱和酶的调控

硬脂酰辅酶A去饱和酶是体内饱和脂肪酸向单一不饱和脂肪酸转化的关键酶类,也是瘦素(Ob)基因通过信号传导发挥代谢生理调控作用的重要组分。其活性的高低关系到动物体脂肪酸的组成和瘦肉率的高低,进而影响产肉率和腌肉制品的产量,本文仅就日粮脂肪酸组成对该酶基因表达和酶活的调控进行综述。     

Effect of short‐chain fatty acids on triacylglycerol accumulation,lipid droplet formation and lipogenic gene expression in goat mammary epithelial cells

Short‐chain fatty acids (SCFAs) are the major energy sources for ruminants and are known to regulate various physiological functions in other species. However, their roles in ruminant milk fat metabolism are still unclear. In this study, goat mammary gland epithelial cells (GMECs) were treated with 3 mmol/L acetate, propionate or butyrate for 24 h to assess their effects on lipogenesis. Data revealed that the content of triacylglycerol (TAG) and lipid droplet formation were significantly stimulated by propionate and butyrate. The expression of FABP3, SCD1, PPARG, SREBP1, DGAT1, AGPAT6 and ADRP were upregulated by propionate and butyrate treatment. In contrast, the messenger RNA (mRNA) expression of FASN and LXRα was not affected by propionate, but reduced by butyrate. Acetate had no obvious effect on the content of TAG and lipid droplets but increased the mRNA expression of SCD1 and FABP3 in GMECs. Additionally, it was observed that propionate significantly increased the relative content of mono‐unsaturated fatty acids (C18:1 and C16:1) at the expense of decreased saturated fatty acids (C16:0 and C18:0). Butyrate and acetate had no significant effect on fatty acid composition. Overall, the results from this work help enhance our understanding of the regulatory role of SCFAs on goat mammary cell lipid metabolism.     

Ovine adipose tissue monounsaturated fat content is correlated to depot-specific expression of the stearoyl-CoA desaturase gene

The basis for the variation in fatty acid composition in different ovine adipose tissue depots was investigated. The proportion of stearic (C18:0) and oleic (C18:1) acids vary in a site-specific fashion; abdominal depots (omental and perirenal) contain relatively more C18:0 than C18:1, and carcass depots, especially sternum, have a markedly higher proportion of C18:1. Additionally, expression of a number of lipogenic enzyme genes (stearoyl-CoA desaturase [SCD], acetyl-CoA carboxylase-alpha [ACC-alpha], lipoprotein lipase [LPL]) and the cytoskeletal protein gene alpha-tubulin vary among depots, although the pattern of variation differs for each mRNA. When these expression data were related to the mean cell volume of adipocytes pooled from all depots, a significant pattern emerged: expression of the ACC-alpha, LPL, and alpha-tubulin genes was highly correlated with the size of adipocytes. In contrast, when the expression of SCD mRNA was assessed as a function of mean cell volume, two populations of adipocytes emerged: no significant correlation was found between the expression of SCD mRNA per adipocyte and mean cell volume for the abdominal depots, although a highly significant correlation was observed between SCD gene expression and mean cell volume for the carcass and epicardial depots. Similarly, a highly significant correlation was found for the amount of C18:1 per adipocyte and the abundance of SCD mRNA per adipocyte for the carcass and epicardial depots, whereas no significant correlation was observed for these traits for the omental and perirenal depots. Thus, the SCD gene seems to be regulated in a depot-specific fashion and in a manner distinct from that of the ACC and LPL genes.     

Influence of bovine growth hormone and growth hormone-releasing factor on messenger RNA abundance of lipoprotein lipase and stearoyl-CoA desaturase in the bovine mammary gland and adipose tissue

Our objective was to determine the influence of bovine growth hormone (bGH) and bovine growth hormone-releasing factor (bGRF) administration on the mRNA abundance of lipoprotein lipase (LpL) and stearoyl-CoA desaturase (SCD). Primiparous Holstein cows received bGH, bGRF, or no treatment from 118 to 181+/-1 d postpartum. We hypothesized that bGH and bGRF treatment would increase the mRNA abundance of both SCD and LpL in the mammary gland with a corresponding reduction in adipose tissue. Milk yield significantly increased but milk fat percentage did not change as a result of bGH or bGRF treatment. Short-, medium-, and long-chain fatty acid concentrations in milk were not affected by either bGH or bGRF treatments, with the exception of a modest, but significant, increase in C16:1 and C18:1 following bGH treatment. Analysis was conducted on the genes encoding LpL (E.C. 3.3.1.34), a key enzyme involved in the uptake of fatty acids into tissues, and SCD (E.C. 1.14.99.5), which is the enzyme responsible for introducing delta9 double bonds in fatty acids of 16 and 18 carbons in length. In adipose tissue, treatment with bGH and bGRF reduced the mRNA abundance of LpL to 14.6 and 25.7% respectively, of that observed for control animals. Similarly, these treatments reduced the SCD mRNA abundance to undetectable levels in adipose tissue. In mammary gland, bGH and bGRF had no significant impact on LpL mRNA abundance. Bovine GH did not significantly affect SCD mRNA abundance in the mammary gland, and bGRF reduced SCD mRNA abundance. From this study to examine the role of bGH and bGRF on the expression of the genes encoding these key lipogenic enzymes in cattle, we conclude that the increased substrate required for enhanced milk fatty acid yield may have been provided through redirection of nutrients to the mammary gland away from adipose tissue and through overall increased metabolism in the mammary gland.     

Negative effects of long-term feeding of high-grain diets to lactating goats on milk fat production and composition by regulating gene expression and DNA methylation in the mammary gland

Background: It is well known that feeding a high concentrate(HC) diet to lactating ruminants likely induces subacute ruminal acidosis(SARA) and leads to a decrease in milk fat production. However, the effects of feeding a HC diet for long periods on milk fatty acids composition and the mechanism behind the decline of milk fat still remains poorly understood. The aim of this study was to investigate the impact of feeding a HC diet to lactating dairy goats on milk fat yield and fatty acids composition with an emphasis on the mechanisms underlying the milk fat depression. Seventeen mid-lactating dairy goats were randomly allocated to three groups. The control treatment was fed a low-concentrate diet(35% concentrate, n = 5, LC) and there were two high-concentrate treatments(65% concentrate, HC), one fed a high concentrate diet for a long period(19 wks, n = 7, HL); one fed a high concentrate diet for a short period of time(4 wk, n = 5, HS). Milk fat production and fatty acids profiles were measured. In order to investigate the mechanisms underlying the changes in milk fat production and composition,the gene expression involved in lipid metabolism and DNA methylation in the mammary gland were also analyzed.Results: Milk production was increased by feeding the HC diet in the HS and HL groups compared with the LC diet(P 0.01), while the percentage of milk fat was lower in the HL(P 0.05) but not in the HS group. The total amount of saturated fatty acids(SFA) in the milk was not changed by feeding the HC diet, whereas the levels of unsaturated fatty acids(UFA) and monounsaturated fatty acids(MUFA) were markedly decreased in the HL group compared with the LC group(P 0.05). Among these fatty acids, the concentrations of C15:0(P 0.01), C17:0(P 0.01), C17:1(P 0.01), C18:1 n-9 c(P 0.05), C18:3 n-3 r(P 0.01) and C20:0(P 0.01) were markedly lower in the HL group, and the concentrations of C20:0(P 0.05) and C18:3 n-3 r(P 0.01) were lower in the HS group compared with the LC group. However, the concentrations of C18:2 n-6 c(P 0.05) and C20:4 n-6(P 0.05) in the milk fat were higher in the HS group. Real-time PCR results showed that the m RNA expression of the genes involved in milk fat production in the mammary gland was generally decreased in the HL and HS groups compared with the LC group. Among these genes, ACSL1, ACSS1 2, ACACA, FAS, SCD, FADS2, and SREBP1 were downregulated in the mammary gland of the HL group(P 0.05), and the expressions of ACSS2, ACACA, and FADS2 m RNA were markedly decreased in the HS goats compared with the LC group(P 0.05). In contrast to the gene expression, the level of DNA methylation in the promoter regions of the ACACA and SCD genes was increased in the HL group compared with the LC group(P 0.05). The levels of ACSL1 protein expression and FAS enzyme activity were also decreased in the mammary gland of the HL compared with the LC group(P 0.05).Conclusions: Long-term feeding of a HC diet to lactating goats induced milk fat depression and FAs profile shift with lower MUFAs but higher SFAs. A general down-regulation of the gene expression involved in the milk fat production and a higher DNA methylation in the mammary gland may contribute to the decrease in milk fat production in goats fed a HC diet for long time periods.     

Subcutaneous and intramuscular adipose tissue stearoyl-coenzyme A desaturase gene expression and fatty acid composition in calf- and yearling-fed Angus steers

We proposed that stearoyl-CoA desaturase (SCD) activity dictates fatty acid composition of adipose tissue and muscle in beef cattle, regardless of ruminal or hepatic fatty acid hydrogenation or desaturation. Twelve Angus steers were assigned to a calf-fed (CF) group and slaughtered at weaning (8 mo of age; n=4), 12 mo of age (n=4), or 16 mo of age (n=4). Twelve steers were assigned to a yearling-fed (YF) group and slaughtered at 12 mo of age (n=4), 16 mo of age (n=4), and 17.5 mo of age (n=4; 525 kg, market weight). Data were analyzed based on time on the corn-based finishing diet, with terminal age as a covariate, and orthogonal polynomial contrasts were tested on the main effects of treatment group and time on the finishing diet. Fatty acids from duodenal digesta, plasma, liver, LM, and subcutaneous and intramuscular adipose tissue were measured, and SCD gene expression was measured in intramuscular and subcutaneous adipose tissues. In duodenal digesta, palmitic and linoleic acids increased by 100% over the sampling period, α-linolenic acid decreased over the sampling period, and trans-vaccenic acid was greater in YF than in CF steers (all P < 0.01). The proportion of α-linolenic acid decreased over time in all tissues, including liver. The SCD index (ratio of SCD fatty acid products to SCD fatty acid substrates) increased over time in LM and in intramuscular and subcutaneous adipose tissues. The SCD:glyceraldehyde 3-phosphate dehydrogenase mRNA ratio was virtually undetectable at the initial sampling periods in subcutaneous adipose tissue of YF and CF steers, and it increased over time (P < 0.01). The SCD index and SCD:glyceraldehyde 3-phosphate dehydrogenase ratio were greater in intramuscular adipose tissue of CF steers than in that of YF steers. The SCD index did not change over time in liver and decreased over time in duodenal digesta. We conclude that, unlike essential fatty acids, the SFA and MUFA composition of adipose tissue is regulated by adipose tissue fatty acid desaturation, with little contribution from hepatic or duodenal fatty acids.