RESEARCH ARTICLE Effects of Central Administration of Glutamine and Alanine on Feed Intake and Hypothalamic Expression of Orexigenic and Anorexigenic Neuropetides in Broiler Chicks

Different amino acids have been shown to affect feed intake when injected directly into the central nervous system of birds. In the present study, we investigated the effects of L-glutamine and L-alanine on feed intake and the mRNA expression levels of hypothalamic neuropeptides involved in feed intake regulation in broiler chicks. L-Glutamine or Lalanine was intra-cerebroventricularly (ICV) administered to 4-d-old broiler chicks and the feed intake were recorded at various time points. Quantitative PCR was performed to determine the hypothalamic mRNA expression levels of neuropeptide Y (NPY), agouti related protein (AgRP), pro-opiomelanocortin (POMC), melanocortin receptor 4 (MC4R) and corticotropin releasing factor (CRF). Our results showed that ICV administration of L-glutamine (0.55 or 5.5 μmol) significantly increased feed intake up to 2 h post-administration period and the hypothalamic NPY mRNA expression levels, while it markedly decreased hypothalamic POMC and CRF mRNA expression levels. In contrast, ICV administration of L-alanine (4 μmol) significantly decreased feed intake for the first 0.5 h post-administration period, and reduced the hypothalamic AgRP mRNA expression levels, while it remarkablely enhanced the mRNA expression levels of MC4R and CRF. These findings suggested that L-glutamine and L-alanine could act within the hypothalamus to influence feed intake in broiler chicks, and that both orexigenic and anorexigenic neuropeptide genes might contribute directly to these effects.     

Hypothalamic mTOR signaling regulates food intake

The mammalian Target of Rapamycin (mTOR) protein is a serine-threonine kinase that regulates cell-cycle progression and growth by sensing changes in energy status. We demonstrated that mTOR signaling plays a role in the brain mechanisms that respond to nutrient availability, regulating energy balance. In the rat, mTOR signaling is controlled by energy status in specific regions of the hypothalamus and colocalizes with neuropeptide Y and proopiomelanocortin neurons in the arcuate nucleus. Central administration of leucine increases hypothalamic mTOR signaling and decreases food intake and body weight. The hormone leptin increases hypothalamic mTOR activity, and the inhibition of mTOR signaling blunts leptin's anorectic effect. Thus, mTOR is a cellular fuel sensor whose hypothalamic activity is directly tied to the regulation of energy intake.     

钙敏感受体和胆囊收缩素-1受体介导大豆蛋白水解物对小鼠食欲的影响

[目的]探究大豆蛋白水解物(soy protein hydrolysate,SPH)对小鼠食欲的影响及其机制,以期从营养角度为猪采食调控技术的研究提供新思路.[方法]利用胃蛋白酶水解大豆蛋白产生SPH.首先探究灌胃不同浓度SPH对小鼠短期采食量及十二指肠肽钙敏感受体(Calcium sensing receptor,C...     

北京鸭MC4R基因的克隆及其组织表达的差异

黑素皮质素受体-4(melanocortin receptor-4,MC4R)是黑素皮质素受体家族5个亚型(MCR1-5)之一,在控制食欲、体质量、能量平衡中有重要作用。本研究采用RT-PCR技术从北京鸭脑组织中克隆出鸭MC4R基因的编码区序列,分析其基因结构并进行功能预测,利用实时荧光定量进行组织差异表达研究。结果表明,鸭MC4R基因编码区全长996 bp,编码332个氨基酸,包括起始密码子ATG和终止密码子TAG;与鹅、鸡、小鼠、人的相似性分别为97%、95%、78%、80%;推导的氨基酸序列显示,鸭MC4R蛋白具有G蛋白耦联受体家族结构域;实时定量结果表明,MC4R基因在北京鸭各组织相对表达水平存在差异,其中在脑组织中表达最高,脾脏、心脏、腿肌、腹脂、肾脏次之,而在肝脏和肺脏中表达量最低。本试验为进一步研究鸭MC4R基因的生物学功能奠定了基础。     

饮用水中添加脂多糖对小鼠能量代谢及行为的影响

【目的】研究长期饮水添加不同细菌来源脂多糖对小鼠采食、能量代谢以及行为变化的影响。【方法】选用48只5周龄C57/BL小鼠,随机分为8组,腹腔注射不同浓度脂多糖,观察采食量。进一步选用24只5周龄C57/BL小鼠,随机分为3组,分别饮用水中添加5μg·mL~(–1)大肠埃希菌Escherichia coil O128:B12脂多糖组、5μg·mL~(–1)大肠埃希菌O55:B5脂多糖组和不添加的对照组,试验周期为12周。试验结束前采用旷场和高空十字迷宫分析小鼠的运动和焦虑行为。试验结束后测定体组成,并采集皮下脂肪和脑核团样本分析相关基因表达。【结果】腹腔注射高剂量脂多糖抑制了小鼠采食,而饮用水中添加5μg·mL~(–1)不同细菌脂多糖均显著提高了小鼠采食量(P0.05),且上调了下丘脑弓状核中AgRP的mRNA表达量,而对POMC的mRNA的表达量无影响;饮用水中添加5μg·mL~(–1)不同细菌脂多糖显著降低了小鼠饲料利用率和体脂沉积水平,同时显著促进了褐色脂肪UCP-1和PGC-1ɑ的表达;饮用水中添加5μg·mL~(–1)脂多糖对小鼠焦虑行为无影响,但显著促进了小鼠的自发运动。脂多糖显著促进了海马体中c-fos和DRD2 mRNA的表达。【结论】饮用水中添加大肠埃希菌脂多糖能提高小鼠食欲、促进脂肪代谢和自主运动,这可能与海马体多巴胺神经元系统活性增强有关。     

运动对高脂饮食大鼠下丘脑SOCS-3和BDNF以及瘦素抵抗的影响

目的：观察运动对高脂饮食大鼠血清和下丘脑瘦素（Leptin）以及下丘脑 瘦素长型受体（OB-Rb） 、促黑皮素受体4（MC4R）、细胞因子信号转导抑制因子-3（SOCS-3） mRNA表达和脑源性神经营养因子（ BDNF）的影响,探讨适宜运动对高脂饮食大鼠预防肥胖的部分中枢机制。方法：雄性SD鼠24只,随机分为 正常对照组（C组）,高脂模型组（H组）和高脂 60min 运动组（HE组）,每组8只。高脂模型组和高脂 60min 运动组大鼠喂饲高脂饲料,高脂饮食运动组大鼠进行60min的无负重游泳运动。持续10周。结果： 10周运动后,高脂模型组大鼠较正常对照组大鼠体重、Lee''S指数、体脂、脂体比均显著增高(p<0.05), 血清瘦素水平显著升高(p<0.05),下丘脑内OB-Rb、MC4R mRNA表达量显著降低(p<0.05),SOCS-3 mRNA表 达量显著升高(p<0.05),下丘脑BDNF含量显著降低(p<0.05);高脂60min运动组较高脂模型组大鼠体重显 著降低(p<0.01),Lee''S指数、体脂、脂体比均显著降低(p<0.05),血清瘦素水平显著升高(p<0.05),下 丘脑OB-Rb、MC4R、leptin mRNA表达量显著升高(p<0.05),下丘脑SOCS-3 mRNA表达量显著降低(p<0.05) ,下丘脑BDNF含量显著升高(p<0.05)。结论：长期适宜的运动可通过降低下丘脑SOCS-3的表达,增加下丘 脑Leptin 与受体OB-Rb的结合,降低了瘦素抵抗,激活下丘脑含 MC4R 受体的神经元,从而刺激 BDNF 的 释放,从而起到预防高脂饮食引起肥胖的作用。     

Leptin regulates striatal regions and human eating behavior

Studies of the fat-derived hormone leptin have provided key insights into the molecular and neural components of feeding behavior and body weight regulation. An important challenge lies in understanding how the rewarding properties of food interact with, and can override, physiological satiety signals and promote overeating. We used functional magnetic resonance imaging to measure brain responses in two human patients with congenital leptin deficiency who were shown images of food before and after 7 days of leptin replacement therapy. Leptin was found to modulate neural activation in key striatal regions, suggesting that the hormone acts on neural circuits governing food intake to diminish the perception of food reward while enhancing the response to satiety signals generated during food consumption.     

Rapid rewiring of arcuate nucleus feeding circuits by leptin

The fat-derived hormone leptin regulates energy balance in part by modulating the activity of neuropeptide Y and proopiomelanocortin neurons in the hypothalamic arcuate nucleus. To study the intrinsic activity of these neurons and their responses to leptin, we generated mice that express distinct green fluorescent proteins in these two neuronal types. Leptin-deficient (ob/ob) mice differed from wild-type mice in the numbers of excitatory and inhibitory synapses and postsynaptic currents onto neuropeptide Y and proopiomelanocortin neurons. When leptin was delivered systemically to ob/ob mice, the synaptic density rapidly normalized, an effect detectable within 6 hours, several hours before leptin's effect on food intake. These data suggest that leptin-mediated plasticity in the ob/ob hypothalamus may underlie some of the hormone's behavioral effects.     

Postponement of satiety by blockade of brain cholecystokinin (CCK-B) receptors

Exogenous cholecystokinin (CCK) decreases food intake and causes satiety in animals and man. However, it has not been established that endogenous CCK causes satiety or whether the response is mediated by peripheral-type (CCK-A) or brain-type (CCK-B) receptors. The development of potent and selective antagonists for CCK-A (MK-329) and CCK-B (L-365,260) receptors now allows these issues to be addressed. The CCK-A antagonist MK-329 and the CCK-B antagonist L-365,260 increased food intake in partially satiated rats and postponed the onset of satiety; however, L-365,260 was 100 times more potent than MK-329 in increasing feeding and preventing satiety. These results suggest that endogenous CCK causes satiety by an agonist action on CCK-B receptors in the brain.     

Trophic action of leptin on hypothalamic neurons that regulate feeding

In adult mammals, the adipocyte-derived hormone leptin acts on the brain to reduce food intake by regulating the activity of neurons in the arcuate nucleus of the hypothalamus (ARH). Here, we report that neural projection pathways from the ARH are permanently disrupted in leptin-deficient (Lepob/Lepob) mice and leptin treatment in adulthood does not reverse these neuroanatomical defects. However, treatment of Lepob/Lepob neonates with exogenous leptin rescues the development of ARH projections, and leptin promotes neurite outgrowth from ARH neurons in vitro. These results suggest that leptin plays a neurotrophic role during the development of the hypothalamus and that this activity is restricted to a neonatal critical period that precedes leptin's acute regulation of food intake in adults.     

Oxytocin secretion in response to cholecystokinin and food: differentiation of nausea from satiety

Administration of cholecystokinin (CCK) to rats caused a dose-dependent increase in plasma levels of the neurohypophyseal hormone oxytocin (OT). The OT secretion was comparable to that found in response to nausea-producing chemical agents that cause learned taste aversions. The effect of CCK on OT secretion was blunted after gastric vagotomy, as was the inhibition of food intake induced by CCK. Food ingestion also led to elevated plasma OT in rats, but CCK and aversive agents caused even greater OT stimulation. Thus, after administration of large doses of CCK, vagally mediated activation of central nausea pathways seems to be predominantly responsible for the subsequent decrease in food intake. Despite their dissimilar affective states, both nausea and satiety may activate a common hypothalamic oxytocinergic pathway that controls the inhibition of ingestion.     

cGhrelin对黄羽肉鸡体重与腹脂率的影响

本研究旨在观察cGhrelin对黄羽肉鸡体重与腹脂率的调节作用。选择24只14日龄的黄羽肉鸡按体重随机分为试验组和对照组,试验组每天定时腹腔注射0.5 nmol/100 g cGhrelin,对照组注射相应体积的生理盐水;注射前称重,记录摄食量;第6天屠宰检测腹脂率。结果表明:cGhrelin试验组的采食量于2 d后显著低于对照组(P0.05);3 d后试验组体重比对照组降低11.25%(P0.05);在第6天试验结束时,试验组公鸡腹脂率显著低于对照组(P0.05),而母鸡差异不显著(P0.05)。结果提示,cGhrelin具有降低黄羽肉鸡的食欲与采食量,减少脂肪沉积与体重增加。     

Modulation of brain reward circuitry by leptin

Leptin, a hormone secreted by fat cells, suppresses food intake and promotes weight loss. To assess the action of this hormone on brain reward circuitry, changes in the rewarding effect of lateral hypothalamic stimulation were measured after leptin administration. At five stimulation sites near the fornix, the effectiveness of the rewarding electrical stimulation was enhanced by chronic food restriction and attenuated by intracerebroventricular infusion of leptin. In contrast, the rewarding effect of stimulating neighboring sites was insensitive to chronic food restriction and was enhanced by leptin in three of four cases. These opposing effects of leptin may mirror complementary changes in the rewarding effects of feeding and of competing behaviors.     

Activation of central melanocortin pathways by fenfluramine

D-fenfluramine (d-FEN) was once widely prescribed and was among the most effective weight loss drugs, but was withdrawn from clinical use because of reports of cardiac complications in a subset of patients. Discerning the neurobiology underlying the anorexic action of d-FEN may facilitate the development of new drugs to prevent and treat obesity. Through a combination of functional neuroanatomy, feeding, and electrophysiology studies in rodents, we show that d-FEN-induced anorexia requires activation of central nervous system melanocortin pathways. These results provide a mechanistic explanation of d-FEN's anorexic actions and indicate that drugs targeting these downstream melanocortin pathways may prove to be effective and more selective anti-obesity treatments.     

猪黑素皮质素受体4基因的单倍型检测与分析

黑素皮质素受体4（melanocortin 4receptor,MC4R）是G蛋白耦联受体超家族的一个成员,在人和许多动物的体重、能量稳态和采食量的调控中发挥重要作用。现采用直接克隆测序的方法对23头长白猪、25头大白猪、19头民猪和7头野猪的MC4R基因进行了测序与分型。共检测到SNP位点72个,其中发生频率在2次以上的SNP位点有6个,有3个为错义突变,引起了多肽链氨基酸的替代;6个SNP位点共组成了14种单倍型,其中H1、H3、H5、H6、H7、H9、H11和H14为首次发现的单倍型。     

初生肉仔鸡血清和下丘脑摄食调节相关激素的发育规律与品种特点

 【目的】研究初生肉仔鸡血清和下丘脑摄食调节相关激素的发育规律并进行品种间比较。【方法】观测了北京油鸡和AA鸡在孵出后0、1、3、5、7、9和11 d的采食量,血清和下丘脑的胰岛素和瘦素及下丘脑NPY和α-MSH水平的变化。【结果】北京油鸡和AA鸡的生长规律基本一致,但前者的ADFI和ADG极显著低于后者（P＜0.01）。北京油鸡血清胰岛素随日龄的波动较大,而AA鸡除0 d外,其它日龄维持在7.5 μIU•ml-1左右。北京油鸡血清瘦素在各个日龄间无明显差异,而AA鸡1和3 d血清瘦素显著高于0 d（P≤0.03）。北京油鸡下丘脑瘦素随日龄增长呈下降趋势,而AA鸡1 d下丘脑瘦素高于0 d（P＜0.01）,而后有所降低。2个品种的下丘脑胰岛素和NPY随日龄的变化趋势一致。下丘脑胰岛素在出壳后前5 d的水平较高,而后有所下降。下丘脑NPY随日龄增长而上升,其中7 d最高。北京油鸡下丘脑α-MSH在出壳后前7 d的水平较低,而后有所升高,而AA鸡下丘脑α-MSH随日龄增长而降低,达5 d最低,而后又上升。相关分析表明,血清瘦素、下丘脑胰岛素、瘦素和NPY与ADFI的相关性较强,而血清胰岛素和下丘脑α-MSH与ADFI的相关性不强。【结论】血清和下丘脑的摄食相关激素的发育规律因品种和指标不同而异,胰岛素、瘦素、NPY和α-MSH在雏鸡开食过程中可能发挥着一定作用,但其具体调节机制仍需进一步研究。     

Relationship between feeding and satiation centers of the hypothalamus

Electrodes were implanted in the hypothalamus of five goats in which an alimentary instrumental conditioned reflex had been previously established. Electrical stimulation of the ventromedial hypothalamus inhibited the conditioned movements and food intake in hungry goats. This also occurred in those satiated goats in which eating and conditioned movements were elicited by stimulation of the lateral hypothalamic area. Withdrawal of the stimulation of the medial hypothalamus evoked a short aftereffect in the form of a recovery or increase in the trained movements and food intake.     

糖皮质激素及灌注色氨酸对肉仔鸡下丘脑代谢物变化的影响

【目的】利用皮下注射人工合成糖皮质激素的方式模拟应激,通过核磁共振(NMR)技术研究应激及色氨酸对肉仔鸡下丘脑代谢状况的影响,为探明下丘脑食欲调控机制提供依据。【方法】10日龄AA肉仔鸡32只随机分为4组,早6:00禁食3h后,以2.0mg·kg-1BW剂量皮下注射地塞米松,同时灌注色氨酸(生理盐水溶解,500mg·kg-1BW),对照组分别皮下注射、灌服生理盐水,3h后取血浆及下丘脑。下丘脑用高氯酸萃取后进行核磁共振研究。【结果】通过1HNMR谱,发现应激改变了肉鸡下丘脑乳酸,葡萄糖,ATP,肌醇,3-羟基丁酸的相对含量;未检测到色氨酸信号的改变。【结论】NMR技术能够检测到应激状态下下丘脑代谢物的改变;应激状态下,ATP、葡萄糖和其它能量底物信号的改变可能参与了下丘脑对食欲的调控作用。     

鸭leptin基因在大肠杆菌中的融合表达及生物学活性分析

 【目的】研究鸭leptin在体外高效表达特点，探讨表达产物的生物学活性及其功能。【方法】构建重组鸭leptin基因原核表达菌株，重组菌株经不同浓度IPTG和不同时间诱导后，对表达蛋白进行提取、纯化、复性和浓缩，经注射昆明小鼠后，对小鼠的体重﹑采食量和体脂含量进行分析。【结果】鸭leptin在大肠杆菌中实现了高效特异性融合表达，融合蛋白分子量约为20 kD，其中16 kD为鸭leptin基因表达产物，目的蛋白在0.2 mmol•L-1 IPTG的诱导下，表达量最高约占菌体总蛋白的57%。重组蛋白纯化﹑复性﹑浓缩后，能够明显降低小鼠摄食量、体重和体脂含量。【结论】鸭leptin基因在大肠杆菌中进行了高效融合表达，表达产物具有明显的生物学活性。