静脉灌注丙酸钠和乙酸钠对新生犊牛血糖及某些代谢激素含量的影响

三头装有暂时性颈静脉血管瘘的黑白花品种新生公犊,通过静脉灌注丙酸钠和乙酸钠溶液(1.0mol,PH7.4,37C)50ml,观察灌注前后血浆葡萄糖及某些代谢激素含量的变化。结果表明:灌注丙酸钠15分钟后,血糖和血浆胰岛素浓度明显升高;皮质醇含量有升高趋势而甲状腺素呈下降趋势,但差异不明显;三碘甲腺原氨酸则一直在基础水平上下波动。灌注乙酸钠对血糖和上述激素浓度均无显著的规律性影响。说明乙酸钠和丙酸钠在新生犊牛体内表现了不同的营养和代谢作用。     

围产期绵羊血浆胰岛素样生长因子-1水平的动态变化及胆酸负荷对其的影响

:6只成年考力代妊娠母羊 ,经 2周适应饲养后随机分为两组。在安装颈静脉血管瘘后 ,一组通过颈静脉瘘管灌注胆酸 ( 2mg/kg) ,另一组同步灌注等量的生理盐水。间隔 1 4天灌注 1次 ,直至分娩。在灌注前和灌注后每天定时采取血样 ,测定血浆IGF -1水平 ,研究绵羊围产期血浆IGF -1的动态变化及胆酸负荷对其的影响。结果表明 ,围产期母羊血浆IGF -1正常水平在 572 .1 0± 2 0 7.1 5ng/ml～ 787.1 2±4 2 .33ng/ml之间 ,没有明显的动态变化规律。但分娩后的IGF -1平均水平显著低于分娩前平均值 ,分别是 639.54± 56.37ng/ml和 70 5.2 1± 52 .2 4ng/ml(P <0 .0 5)。胆酸灌注组母羊妊娠后期血浆IGF -1水平平均为 62 5.2 8± 85.56ng/ml,比对照母羊低 (P <0 .0 5)。本研究提示妊娠后期绵羊母体血浆高水平的IGF -1可能与胎儿生长发育有关 ;胆酸负荷可能影响了妊娠母体的肝功能或胎盘的调节作用     

胆酸负荷对妊娠后期绵羊母体和胎儿血浆IGF—2及其代谢物水平的影响

以绵羊及其胎儿为试验对象，研究了胆酸负荷对妊娠后期母体和胎儿血浆胰岛素样生长因子－2(in-sulin-like growth factor-2,IGF-2）及其代谢物水平的影响。将7只确知妊娠时间的绵羊分为试验组5只和对照组2只，试验前装置颈静脉瘘，在妊娠90h和104d2闪给试验组静脉灌注胆酸盐1．1mg/kg，给对照组静脉灌注等量生理盐水，妊娠120d时手术安装胎儿后肢胫前动脉血管瘘。每天采胎儿和母体的血样，分离血浆，测定血浆IGF－2和主要代谢物水平。同时测定胎儿出生时生长发育指标。结果表明：（1）试验组母羊IGF－2水平低于对照组，相反其胎儿IGF－2水平却高于对照组（P＜0．05）；（2）试验组母羊的总蛋白和乳酸水平分别比对照组35．64％；（3）试验组胎儿出生重比对照组小29．00％，胎龄短7．50d。因此认为，胆酸重复灌注可引起妊娠绵羊早产和胎儿出生重降低，而这可能与IGF－2和主要代谢物水平变化有关。     

十二指肠灌注亮氨酸对奶牛胰腺淀粉酶分泌的影响

本试验旨在研究十二指肠灌注亮氨酸对奶牛胰腺淀粉酶分泌的影响。以4头周岁荷斯坦母牛[(215±7)kg]为试验动物,手术安装十二指肠胰液收集袋、灌注管和回流管以及颈静脉插管,采用4×4拉丁方试验设计,进行十二指肠亮氨酸灌注试验[(灌注水平分别为0、29.5、59.1和88.6μmol/(kg.h)]。结果表明,随亮氨酸灌注水平升高,血浆胰岛素和胆囊收缩素浓度升高(P<0.05),胰腺α-淀粉酶合成速率(U/h)呈先升高后降低趋势(P<0.01),在29.5μmol/(kg.h)灌注水平时最大。十二指肠灌注亮氨酸也极显著影响了胰腺α-淀粉酶分泌浓度(U/L,P<0.01;U/g prot,P<0.01)。结果表明,亮氨酸可能通过刺激胰岛素和胆囊收缩素释放,调控青年奶牛胰腺淀粉酶分泌功能,二者存在剂量效应。     

免疫应激对断奶仔猪免疫和神经内分泌激素的影响

试验研究了免疫应激对断奶仔猪免疫和神经内分泌激素的影响。选用 6头体重为 (7.6± 0 .3)kg的(2 8± 3)d的达兰断奶仔猪 ,绝食 12h后 ,随机选取 4头猪从腹膜注射 2 0 0 μg/kg(BW)的脂多糖 (LPS) ,另 2头注射等量生理盐水作对照。于注射后 0、1、2和 3h ,分别采血测定血浆白细胞介素 1β(IL 1β)、前列腺素E2 (PGE2 )、皮质醇、生长激素 (GH)和类胰岛素生长因子 I(IGF I)的含量。结果表明 :(1)注射LPS激活了应激轴 :与对照组相比 ,LPS提高了注射后 1h(P <0 .10 )、2h(P <0 .0 1)和 3h(P <0 .0 1)的IL 1β水平 ,提高了注射后 1h(P <0 .0 5 )和 3h(P <0 .0 1)的皮质醇和PGE2 水平 ;(2 )注射LPS抑制了生长轴 :LPS降低了注射后 3h的GH水平 (P <0 .10 ) ,降低了注射后 2h (P <0 .0 5 )和 3h(P <0 .0 1)的IGF I水平。结果显示 ,免疫应激激活了仔猪应激轴 ,而抑制了生长轴 ,在一定程度上揭示了免疫应激抑制生长的机制     

瘤胃乙酸、丙酸比例对绵羊体内氧化代谢和血浆胰岛素水平动态变化的影响

本研究以全胃营养灌注绵羊为试验动物 ,用物质代谢区室分析方法和同位素示踪技术研究了瘤胃乙酸、丙酸比例对体内氧化代谢和血浆胰岛素水平动态变化的影响。不同试验处理间营养灌注液能量、蛋白质水平相同 ,而瘤胃灌注混合挥发性脂肪酸的乙酸、丙酸比例不同。三种混合挥发性脂肪酸的乙酸、丙酸比例分别为75 :15(VFA1)、65 :25(VFA2)、45 :45(VFA3)。由测定引入 14C -乙酸后血液二氧化碳放射比强度—时间曲线上升段斜率(k值)反映体内氧化代谢强度。试验结果为 ,瘤胃灌注VFA1 时的k值显著高于灌注VFA2 和VFA3 时的k值(P<0.05) ,而VFA2 和VFA3 两处理间的差异不显著(P>0.05) ,说明瘤胃灌注VFA1 时绵羊体内氧化代谢强度增加。向停止灌注24小时的绵羊瘤胃内灌注VFA1,血浆胰岛素水平在恢复灌注后缓慢上升。将瘤胃灌注混合挥发性脂肪酸由VFA1 换为VFA2 后 ,血浆胰岛素水平迅速上升 ,之后迅速下降 ,而由VFA2 换为VFA3 后未出现血浆胰岛素水平的明显变化 ,说明血浆胰岛素水平的变化与体内糖代谢调节状态有关 ,而瘤胃灌注VFA1 时的体内糖代谢调节状态与灌注VFA2 和VFA3 时明显不同。     

口饲胰岛素对新生仔猪血浆胰岛素水平及糖代谢的影响

分别给新生正常和子宫内发育迟缓（IUGR）仔猪口饲胰岛素,研究仔猪血浆中胰岛素水平的变化,以及外源性胰岛素对新生仔猪体内糖代谢的影响。结果证实：人工饲喂3d后,血浆中胰岛素浓度极显著提高（P〈0．01）;肝糖原含量极显著降低（P〈0．01）;血浆中胰岛素水平,正常仔猪Ⅰ组显著高于M组（P〈0．05）;LDH活性,M组和Ⅰ组显著高于N组（P〈0．05）,Ⅰ组低于M组（P〉0．05）;MDH活性和血浆中葡萄糖浓度没有显著变化（P〉0．05）。上述结果证明：仔猪出生0～3d,糖代谢发生剧烈变化,口饲胰岛素使正常仔猪血浆中胰岛素水平显著提高,但对仔猪糖代谢影响不显著。     

静脉注射挥发性脂肪酸钠盐溶液对绵羊瘤胃运动的影响

实验以颈静脉分别注射乙酸、丙酸、丁酸的钠盐溶液模拟反刍动物采食后血液中挥发性脂肪酸(VFA,下同)升高的状况;以瘤胃平滑肌电为瘤胃消化运动的指标,研究了绵羊血液中VFA对瘤胃消化运动的影响。结果表明:0.2M的乙酸钠50ml,丙酸钠5ml或丁酸钠2.5ml可增强瘤胃运动的频率和强度:而1M的乙酸钠50ml、丙酸钠5ml或丁酸钠2.5ml对瘤胃运动的频率和强度有抑制作用。三种VFA钠盐的作用强弱顺序是:丁酸钠>丙酸钠>乙酸钠。     

二花脸猪乳中生长因子的动态分析及其与大约克猪的比较

通过 2个系列实验 ,分析了二花脸猪乳中生长因子 (IGF Ⅰ、EGF和胰岛素 )在泌乳早期 (1～ 2 1d)的含量及其变化规律 ,并与大约克猪进行了比较研究。结果表明 ,二花脸和大约克猪乳中IGF Ⅰ在初乳中浓度很高 ,分娩 1周后迅速下降 ,泌乳第 7～ 2 1天变化不大。在泌乳第 1～ 7天 ,二花脸猪乳中IGF Ⅰ低于大约克猪 ,泌乳第 7天以后又高于大约克 ,但 2种猪的差别不显著 (P >0 0 5)。猪乳中的EGF变化规律基本上和IGF Ⅰ相同。在泌乳第 1天 ,二花脸猪乳中的EGF显著低于大约克猪 (P <0 0 5) ,第 1天以后 2种猪没有明显差异。二花脸和大约克猪乳中的胰岛素在初乳很高 ,产后 4d迅速下降 ,4d以后变化幅度不大。二花脸猪乳中的胰岛素在泌乳早期 (1～ 2 1d)全都低于大约克猪 ,其中在泌乳第 1天、第 6～ 7天、第 8～10天和第 11～ 14天这 4个阶段显著低于大约克猪 (P <0 0 5)。     

日粮脂肪水平对湖羊双胞胎公羔生长性能及血清指标的影响

旨在研究日粮不同脂肪水平对早期断奶双胞胎湖羊公羔生长发育、体尺指标、断奶前腹泻率及血清指标的影响。选择7日龄体重相近、健康的湖羊双胞胎公羔30对,采用配对试验设计,分为正常脂肪组(NF)和高脂肪组(HF),一对双胞胎随机分到两个组中。7日龄断母乳,NF组开始饲喂脂肪含量为15%的代乳品和2.8%的开食料,HF组开始饲喂脂肪含量27%的代乳品及5.0%的开食料,饲喂至60日龄断液体饲料(代乳品)。60~120日龄统一饲喂开食料(US)。所有羔羊定期晨饲前称重,记录每日采食量及腹泻情况;在60、90及120日龄晨饲前颈静脉采血,用于测定血清学常规指标。结果表明:1)在30、50、90及120日龄时,HF组羔羊体重显著高于NF组(P0.05),而断代乳品时,HF组羔羊体重有显著高于NF组的趋势(0.05P0.10)。在7~60日龄阶段,HF组代乳品平均采食量显著高于NF组(P0.05),但开食料采食量、平均日增重及饲料转化率在两组间差异不显著(P0.05);在60~90日龄阶段,HF组平均日增重及开食料采食量显著高于NF组(P0.05),而饲料转化率HF组显著低于NF组(P0.05);在90~120日龄期间,HF组羔羊采食量显著高于NF组(P0.05),而饲料转化率有显著高于NF组的趋势(0.05P0.10)。在整个试验期,HF组总平均采食量显著高于NF组(P0.05),平均日增重及饲料转化率在两组间差异不显著(P0.05)。2)试验期内HF组羔羊断奶前腹泻率有显著低于NF组的趋势(0.05P0.10)。试验期间两组羔羊体尺指标基本上无显著差异(P0.05)。断奶前饲喂高脂肪日粮可以在一定程度上提高湖羊双胞胎公羔断奶前后的生长性能;高脂肪日粮可以降低断代乳品前腹泻率;且本试验条件下高脂肪日粮对羔羊血液指标的影响在其自身调节的范围内。     

Propionate is not an important regulator of plasma leptin concentration in dairy cattle

Propionate was recently shown to increase leptin synthesis in rodents. To determine if a similar effect occurs in ruminants, propionate was administered to lactating dairy cows. In experiment 1, 31 cows were given an intrajugular Na propionate bolus (1,040 micromol/kg body weight), increasing plasma propionate from 160 to 5,680 microM and plasma insulin from 6.8 to 77.8 microIU/mL. Plasma leptin concentration decreased from 2.11 ng/mL before bolus to 1.99 ng/mL after dosing (P<0.05) with no differences in leptin concentrations at 20, 50, and 100 min post-bolus (P>0.10). In experiment 2, 12 cows were used in a duplicated 6 x 6 Latin square experiment to assess the dose-response effect of ruminal propionate infusion on plasma leptin concentration. Sodium propionate was infused at rates of 0, 260, 520, 780, 1040, or 1,300 mmol/h, while total short-chain fatty acid infusion rate was held constant at 1,300 mmol/h by addition of Na acetate to the infusate. Coccygeal blood was sampled following 18 h of infusion. Increasing the rate of propionate infusion linearly increased plasma propionate concentration from 180 to 330 microM (P<0.001) and plasma insulin concentration from 6.7 to 9.1 microIU/mL (P<0.05). There was a quadratic response in plasma leptin concentration (P=0.04) with a maximum at 780 mmol/h propionate, but leptin concentrations increased by no more than 8% relative to the 0 mmol/h propionate infusion. Leptin concentrations were correlated with insulin concentrations but not with propionate concentrations in plasma. Propionate is not a physiological regulator of leptin secretion in lactating dairy cows.     

Effects of isoenergetic infusions of propionate and glucose on portal-drained visceral nutrient flux and concentrations of hormones in lambs maintained by total intragastric infusion

Three lambs were used in a repeated Latin square design to determine the influence of isoenergetic infusions of propionate or glucose on portal-drained visceral flux (PDV) of nutrients and concentrations of insulin, glucagon, growth hormone and prolactin. Lambs were fitted with appropriate catheters for blood sampling and maintained on total intragastric infusion of nutrients. Basal VFA, casein, mineral and vitamin infusions (isocaloric and isonitrogenous) were supplemented with an additional 22 +/- .5 kcal/h from propionate, glucose or a combination of propionate plus glucose. Ruminal fluid proportion and arterial blood concentration and PDV flux of propionate increased (P less than .10) by 17 mol/100 mol, .02 mM and 40 mmol/h, respectively, with infusion of an additional 61 mmol/h of propionate. Regression equations predicted that, on a net basis, 67% of ruminally infused propionate and 43% of abomasally infused glucose appeared in portal blood. Arterial L-lactate, beta-hydroxybutyrate and acetate concentrations, and beta-hydroxybutyrate flux were increased (P less than .10) by .34 mM, .20 mM, .50 mM and 4.2 mmol/h, respectively, with infusion of 33 mmol/h of added glucose. Net utilization of glucose by the PDV was approximately 4.4 mmol/h when no glucose was infused. Increased infusion of propionate resulted in a 22.2-micrograms/h increase in PDV flux of insulin (P less than .08) but had no effect on arterial insulin, glucagon and prolactin concentrations (P greater than .10). Arterial growth hormone increased by 3.8 ng/ml with increasing glucose infusion (P less than .08).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of propionate infusion and dietary energy on dry matter intake in sheep

Four nonlactating, nonpregnant, mature ewes equipped with multiple venous and arterial catheters were used to evaluate the influence of propionate as a satiety signal in ruminants. Our experiment was a 4 x 4 Latin square with portal infusion (physiological saline [Sa] or sodium propionate [Pr]) and DE intake (Lo, 63% of maintenance requirement, or Hi, 200% of maintenance requirement) as factors. One 240-min infusion of Pr (1 mmol/min) or Sa into the portal vein began at approximately 0800 on d 8 of each 8-d period. Feed intake was measured and hepatic blood was sampled every 30 min during infusion. Intake of DM and digestible energy (DEI) during infusion were not affected by infusion or diet and were most rapid at 30 min postfeeding. Average 30-min DMI and DEI were 539 g and 1,484 kcal, respectively, at 240 min. Cumulative DMI and DEI were unaffected by infusion but tended to be greater with Lo. After 30 min, animals tended to consume Lo at a greater rate than Hi, suggesting that satiety was delayed. Insulin concentration was increased (P less than .02) when animals consumed Hi (36.1 mU/liter) vs Lo (16.8 mU/liter) and was elevated (P less than .01) at 30 and 60 min postfeeding when animals were infused with Pr. Plasma acetate tended to be reduced with Pr infusion. Plasma Pr tended to increase with Pr infusion, especially when sheep were fed Lo. Satiety, DMI, and DEI were not affected by Pr infusion in this study.     

Rumen microbial sequestration of [2-(13)C]acetate in cattle

To investigate the impact of rumen microbial sequestration of VFA carbon on estimates of acetate availability based on intraruminal infusion of [2-(13)C] acetate, three nonlactating or low-yielding dairy cows were continuously intraruminally infused with [2-(13)C]acetate for 26 h. The 13C content of ruminal VFA, duodenal carbon, and fatty acids (FA) and AA isolated from liquid-associated ruminal microbes and duodenal DM was measured by an isotope ratio mass spectrometer interfaced to an elemental analyzer or a gas-liquid chromatograph. The ruminal gross production of acetate was 38 +/- 4 mol/d and could account for about 38% of the DE intake. Of the intraruminally infused 13C in [2-(13)C]acetate, 7.6 +/- 0.9% was recovered at the duodenum. The 13C content of ruminal propionate, butyrate, and valerate increased (P < 0.05) with intraruminal infusion of [2-(13)C]acetate. It was estimated that about 28% of the 13C intraruminally infused in [2-(13)C]acetate could be accounted for by duodenal 13C flow and absorption of non-acetate VFA. A number of FA isolated from liquid-associated ruminal microbes (C6, C12, C14, anteiso C15, and iso C15) were enriched with 13C (P < 0.05) at a level comparable to the enrichment of ruminal butyrate. Any absorption of these FA from the rumen would further contribute to non-acetate 13C uptake. A maximum of 72% of the ruminal gross production of acetate represented acetate absorption from the rumen in the present study. Consequently, previously used models using intraruminal isotope dilution techniques seem not to be appropriate for measuring acetate availability in ruminants. The number of metabolites exchanging carbon with acetate was found to be so high that assessments of the entire range of inter conversions seem to be practically impossible. Portal absorption studies are discussed as an alternative method of estimating VFA availability to the metabolism in ruminants.     

Propionate absorbed from the colon acts as gluconeogenic substrate in a strict carnivore, the domestic cat (Felis catus)

In six normal‐weight and six obese cats, the metabolic effect of propionate absorbed from the colon was assessed. Two colonic infusions were tested in a crossover design with intervals of 4 weeks. The test solution contained 4 mmol sodium propionate per kg ideal body weight in a 0.2% NaCl solution. Normal saline was given as control solution. Solutions were infused into the hindgut over 30 min. Blood samples were obtained prior to and at various time points after starting the infusion. As body condition did not affect evaluated parameters, all data were pooled. Plasma glucose concentrations showed differences neither over time nor during or after infusion with propionate or control. Plasma amino acid concentrations rose over time (p < 0.001), but were similar for both infusions. Plasma propionylcarnitine rose markedly towards the end of the propionate infusion and decreased afterwards (p < 0.001), whereas 3‐hydroxy‐3‐methylglutarylcarnitine was lower 30 (p = 0.005) and 60 min (p = 0.032) after ending propionate infusions and acetylcarnitine tended to fall at the same time points (p = 0.079; p = 0.080), suggesting inhibition of gluconeogenesis from pyruvate and amino acids, but initiation of propionate‐induced gluconeogenesis. In conclusion, propionate absorbed from the colon is hypothesized to act as gluconeogenic substrate, regardless of the cat’s body condition.     

Coordinate regulation of ovine adipose tissue gene expression by propionate

The current study examined the acute effects of intravenous propionate infusion on plasma hormones and metabolites and the expression of adipose tissue lipogenic genes. Four yearling rams were assigned to one oftwo groups (saline or propionate infusion) in a crossover design. All sheep were cannulated in both jugular veins and infused with 1.2 M propionate at a rate of 64 micromol x mix(-1) x kg BW(-1) for 30 min. Blood samples were collected at -10, 0, 5, 10, 20, 30, 60, and 120 min after initiation of infusion. Subcutaneous adipose tissue biopsies were obtained from the tailhead at 0 and 2 h after propionate infusion and analyzed for gene expressions of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor gamma, leptin, and uncoupling protein-2 using a nonisotopic ribonuclease protection assay. The partial cDNA of the enoyl reductase region of ovine fatty acid synthase was cloned and sequenced from s.c. adipose tissue of sheep. The deduced amino acid sequence (210 amino acids) was 86% identical to human, 88% identical to rat, 88% identical to mouse, and 72% identical to chicken. Plasma glucose and insulin concentrations abruptly increased 5 min after beginning propionate infusion and further increased up until 30 min but were unaffected in saline-infused sheep (P < 0.05). Plasma concentration of NEFA decreased (P < 0.05) during propionate infusion, whereas IGF-I levels were unaltered. The amounts of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor gamma, and leptin mRNA increased (P < 0.05) in s.c. adipose tissue of propionate-infused sheep compared with those of saline-infused sheep. However, uncoupling protein-2 mRNA decreased (P < 0.05) in propionate-infused sheep. This study demonstrates that an acute nutrient challenge, in the form of i.v. propionate, can stimulate or inhibit the expression of various adipose tissue genes involved with lipogenesis and adipose tissue metabolism.     

Effects of short- or long-term infusions of acetate or propionate on luteinizing hormone, insulin, and metabolite concentrations in beef heifers

Two trials were conducted to evaluate the effects of short- (Trial 1) or long-term (Trial 2) intraruminal isocaloric infusions of acetate or propionate on secretion of LH, insulin, and selected metabolites in short- or long-term energy-restricted beef heifers. In Trial 1, 16 Angus heifers were assigned on d 6 to 12 of a synchronized estrous cycle (estrus = d 0) to a body weight-maintenance (BWM; n = 4) or an energy-restricted, body weight-loss (BWL; n = 12) treatment. On d 12 of a synchronized estrous cycle, heifers received PGF2alpha to synchronize estrus, and 12 h later BWL heifers received intraruminal, isocaloric infusions of acetate, propionate, or vehicle for 6 h and BWM heifers received vehicle concurrently. Mean plasma LH and LH pulse frequencies and amplitudes were not affected by treatment (P > .05). In contrast, infusion of propionate increased plasma insulin (P < .05) and reduced plasma concentration of NEFA (P < .05). In Trial 2, six ovariectomized Angus heifers were energy-restricted for 30 d. On d 14 and 26 of restriction, heifers began receiving intraruminal isocaloric infusions of acetate or propionate for 96 h in a switchback approach. Intraruminal infusions of vehicle for 6 h preceded infusions of acetate or propionate. Jugular blood was collected at 12-min intervals during infusions of vehicle and during the last 6 h of infusion of acetate or propionate. Mean concentration of LH and amplitude of pulses of LH were lower during acetate vs propionate or vehicle infusion (P < .05). Infusion of propionate increased insulin relative to acetate or vehicle infusion (P < .05). Plasma NEFA were reduced by infusion of propionate (P < .05) and increased by infusion of acetate (P < .05).     

Tryptophan enhances ghrelin expression and secretion associated with increased food intake and weight gain in weanling pigs

These studies were conducted to determine whether ghrelin, a 28-amino acid peptide produced mainly by the stomach, was involved in tryptophan-mediated appetite stimulation in swine. In experiment 1, 36 crossbred (Long WhitexLarge White) barrows were used in a 2x3 factorial design to determine the effects of food intake (ad libitum versus limit fed) and tryptophan level (0.12%, 0.19% and 0.26%) on growth performance as well as ghrelin expression, plasma insulin, ghrelin and leptin levels. Ad libitum fed pigs gained more weight, but had poorer feed conversion than limit fed pigs. Weight gain, food intake and feed conversion all improved with increased ingestion of dietary tryptophan. Ad libitum feeding increased plasma insulin. Plasma insulin was unaffected by the level of dietary tryptophan. However, plasma leptin was significantly lower in pigs fed 0.19% tryptophan compared to those fed 0.12% tryptophan. Plasma ghrelin levels and ghrelin mRNA level in gastric fundus and duodenun was significantly higher in pigs fed 0.19% and 0.26% tryptophan diet compared with pigs fed 0.12%. In the second experiment, 18 crossbred barrows were divided into three treatments involving oral infusion of saline, tryptophan (40mg/kg BW) or 5-hydroxytryptophan (40mg/kg BW). Plasma ghrelin levels at 20, 40 and 60min after infusion of tryptophan were higher than after saline and 5-hydroxytryptophan infusion, 5-hydroxytryptophan infusion induced lower food intake than saline infusion, and tryptophan infusion increased food intake 2, 8 and 24h after infusion. In conclusion, oral tryptophan ingestion increased ghrelin expression in gastric fundus and plasma ghrelin level.     

Effect of volatile fatty acid infusion on blood plasma free amino acid profiles in growing lambs.

Five ram lambs (average body mass: 25 kg) were given, through a catheter inserted into the left ruminal vein, a total of 28.8 mM sodium acetate, 14.4 mM sodium propionate and 4.8 mM sodium butyrate per kg body mass as a 2-hour infusion. During and at 0, 1, 2, 4, 6, 10 and 24 h after the infusion blood samples were taken from the jugular vein and the blood plasma was assayed for free amino acid (FAA) and immunoreactive insulin (IRI) concentrations. Volatile fatty acid (VFA) infusion significantly decreased the blood plasma concentrations of all FAA but cystine. The lowest FAA concentrations were measured in plasma samples taken at the end of the 2-h infusion. Subsequently the level of all amino acids rose and by 24 h after the infusion the blood plasma concentration of all FAA came close to the preinfusion value. The largest differences were observed in the concentration of glutamate, glycine, leucine and isoleucine. In contrast to FAA, IRI concentration was increased significantly (almost fivefold) by VFA infusion. By 10 h after the infusion IRI concentration returned to the initial level. The results reported here indicate that energy supply given in the form of VFA infusion significantly affects blood plasma FAA profiles, supposedly as a result of changes induced in protein synthesis in tissues. Insulin presumably plays a role in the regulation of these changes.     

Dietary fatty acids modulate hormone repsonses in lactating cows: Mechanistic role for 5′-deiodinase activity in tissue

Supplemental dietary fat provides excess fatty acids (FA), which can alter circulating concentrations of several hormones. To test the effects of fatty acid isomer type and possible sites of regulation, we abomasally infused fat mixtures high in cis-C_18:1 FA (iTRS) or no infusion (NI) and performed intravenous arginine (ARG) and intramuscular thyrotropin-releasing hormone (TRH) challenges. The experimental design was a replicated 3 × 3 Latin square. Challenges were conducted on Days 10 (ARG) and 12 (TRH) after initiation of fat infusion on each of three 4-wk experimental periods. Plasma concentrations of IGF-I were lower (P < 0.01) when cows received iCIS or iTRS compared with NI. Plasma insulin concentrations increased with ARG but responses were not affected by FA. Plasma growth hormone (GH) was unchanged after ARG. Peak plasma GH and thyroid-stimulating hormone (TSH) responses to TRH were blunted (P < 0.05 and P < 0.1, respectively), whereas thyroxine (T₄) and triiodothyronine (T3) responses were augmented post-TRH (P < 0.01) when cows received either FA isomer. Prolactin responses to TRH were not different between infusion treatments, although basal plasma concentrations before TRH were higher in cows infused with iTRS (P < 0.05). To focus on fat regulation of the thyroid axis, we tested directly in vitro the ability of fatty acids dissolved with sodium taurocholate to affect Type-I 5'-deiodinase (5'D) activity in bovine liver homogenates. Homogenate 5'D was not affected by C_2:0---C10:0 fatty acids, but decreased linearly (P < 0.01) with increasing concentrations of C_12:0---C_16:0 and C_18:1 isomers. CisC_18:1 decreased 5′D more than the trans-isomer (P < 0.01), the difference was only apparent at concentrations greater than 0.25 mM. The data suggest that various aspects of pituitary hormone regulation are differentially affected by FA composition. Fatty acid infusion may accentuate end organ responses in the thyroid axis and decrease IGF-I in the somatotropic axis. The data also suggest that FA isomer may alter patterns of extrathyroidal generation of thyroid hormones via direct influences on 5′D.