外源性胰岛素对斑马鱼血糖及其转运的影响

斑马鱼（Danio rerio）在糖负荷状态下表现出持续高血糖现象。与对照组（仅腹腔注射灭菌去离子水）相比,葡萄糖组（仅腹腔注射葡萄糖）血浆胰岛素水平无显著差异,胰岛素基因表达显著上调,肝胰脏葡萄糖转运蛋白（glucose transporters,GLUTs）基因表达无显著差异,说明斑马鱼自身胰岛素分泌不足和葡萄糖转运迟缓是导致其在糖负荷状态下持续高血糖的原因。为了观察外源性胰岛素对斑马鱼血糖及其在体内转运的影响,设计低（1.25 IU/kg）、中（12.5 IU/kg）、高（125 IU/kg）3个浓度的胰岛素,分别与葡萄糖溶液（0.1 g/mL）共注射斑马鱼并观察其血糖变化。结果表明,低剂量胰岛素能有效促进斑马鱼血糖的降低,且能直观反映糖负荷后血糖的变化情况,为最适注射浓度。此外,研究显示斑马鱼血糖变化不受性别影响。在胰岛素最适注射浓度下,与葡萄糖组相比,胰岛素组（葡萄糖与胰岛素共注射）可以显著减少斑马鱼血糖恢复到正常水平的时间,进一步分析发现,斑马鱼血浆胰岛素水平增加,肝胰脏葡萄糖转运蛋白基因表达显著上调,但胰岛素基因表达却被显著抑制。综上所述,胰岛素分泌不足和葡萄糖转运迟缓是造成斑马鱼持续高血糖的原因;外源性胰岛素能够促进糖负荷状态下斑马鱼血糖的降低,但是具有反馈抑制斑马鱼肝胰脏胰岛素基因表达的作用。     

禁食与胰岛素处理对鳜血糖和leptin-A基因表达的影响

为研究硬骨鱼类leptin基因表达与血糖之间的关系, 研究在禁食与胰岛素处理后, 检测鳜血糖和肝脏、肠道和脂肪组织leptin-A基因表达水平。在禁食实验中, 鳜被禁食10d, 并分别于禁食后0、4h、2d、6d和10d取样。禁食后6d鳜血糖开始降低, 禁食后10d鳜血糖显著降低。同时, 禁食后6d鳜肝脏leptin-A基因mRNA表达水平显著升高, 禁食后4h鳜肠道和脂肪组织leptin-A基因mRNA表达水平均显著升高。在胰岛素处理实验中, 分别于注射后12h和36h取样。腹腔注射胰岛素后12h, 鳜血糖显著降低, 而鳜肝脏、肠道和脂肪组织leptin-A基因mRNA表达水平无明显变化。腹腔注射insulin后36h, 鳜肠道leptin-A基因mRNA表达水平显著升高。研究结果表明, 长期禁食或胰岛素处理均能够降低鳜血糖水平, 且影响消化器官和脂肪储存器官leptin-A基因表达。     

禁食与胰岛素处理对鳜血糖和leptin-A基因表达的影响（英文）

为研究硬骨鱼类leptin基因表达与血糖之间的关系,研究在禁食与胰岛素处理后,检测鳜血糖和肝脏、肠道和脂肪组织leptin-A基因表达水平。在禁食实验中,鳜被禁食10d,并分别于禁食后0、4h、2d、6d和10d取样。禁食后6d鳜血糖开始降低,禁食后10d鳜血糖显著降低。同时,禁食后6d鳜肝脏leptin-A基因mRNA表达水平显著升高,禁食后4h鳜肠道和脂肪组织leptin-A基因mRNA表达水平均显著升高。在胰岛素处理实验中,分别于注射后12h和36h取样。腹腔注射胰岛素后12h,鳜血糖显著降低,而鳜肝脏、肠道和脂肪组织leptin-A基因mRNA表达水平无明显变化。腹腔注射insulin后36h,鳜肠道leptin-A基因mRNA表达水平显著升高。研究结果表明,长期禁食或胰岛素处理均能够降低鳜血糖水平,且影响消化器官和脂肪储存器官leptin-A基因表达。     

生长激素释放肽-6对小鼠下丘脑摄食相关核团c-fos表达时间依从性影响北大核心CSCD

本研究旨在探讨外周注射ghrelin受体激动剂生长激素释放肽-6(growth hormone releasing peptide-6,GHRP-6)对NMRI小鼠摄食的影响以及摄食相关核团(弓状核、视上核和室旁核)的激活情况及其有效作用时间。腹腔注射GHRP-6 1,3,6 h后观察小鼠累计摄食量,同时用免疫组织化学方法检测GHRP-6对自由饮食小鼠和禁食小鼠下丘脑摄食相关核团c-fos表达影响,并观察GHRP-6作用的时间依从性。结果显示,腹腔注射了GHRP-6的小鼠摄食量明显大于生理盐水注射鼠,且在注射后3 h时观察到的摄食量的增加尤为显著,但注射后6 h内总的累计摄食量无显著变化;同时,GHRP-6能够在不依赖于摄食的情况下促进弓状核和室旁核中c-fos的表达,且c-fos的表达在注射后1 h时达到峰值,随后逐渐下降。以上结果提示,外源性注入GHRP-6可显著增加动物在给药后1、3 h的累积摄食量,该作用至少部分是通过上调弓状核和室旁核中的c-fos蛋白表达起作用的,而且具有时间依从性。本研究结果可为临床ghrelin受体激动剂的使用间隔提供理论依据。     

生长激素释放肽-6对小鼠下丘脑摄食相关核团c-fos表达时间依从性影响

本研究旨在探讨外周注射ghrelin受体激动剂生长激素释放肽-6(growth hormone releasing peptide-6,GHRP-6)对NMRI小鼠摄食的影响以及摄食相关核团(弓状核、视上核和室旁核)的激活情况及其有效作用时间。腹腔注射GHRP-6 1,3,6 h后观察小鼠累计摄食量,同时用免疫组织化学方法检测GHRP-6对自由饮食小鼠和禁食小鼠下丘脑摄食相关核团c-fos表达影响,并观察GHRP-6作用的时间依从性。结果显示,腹腔注射了GHRP-6的小鼠摄食量明显大于生理盐水注射鼠,且在注射后3 h时观察到的摄食量的增加尤为显著,但注射后6 h内总的累计摄食量无显著变化;同时,GHRP-6能够在不依赖于摄食的情况下促进弓状核和室旁核中c-fos的表达,且c-fos的表达在注射后1 h时达到峰值,随后逐渐下降。以上结果提示,外源性注入GHRP-6可显著增加动物在给药后1、3 h的累积摄食量,该作用至少部分是通过上调弓状核和室旁核中的c-fos蛋白表达起作用的,而且具有时间依从性。本研究结果可为临床ghrelin受体激动剂的使用间隔提供理论依据。     

CFTR基因在小鼠肠道组织中的差异表达

目的研究肠道组织CFTR基因表达与分泌性腹泻发生的关系。方法选取KM小鼠24只,雌雄各半,随机分为3组（每组8只）：对照组经小鼠腹腔注射0.2 mL生理盐水,实验组小鼠经腹腔注射LPS[6 mg/（kg·bw）]分别作用1 h、8 h,于注射后通过小鼠精神状态、肠道组织形态学判定分泌性腹泻模型的建立,利用荧光定量PCR法检测各段肠道组织CFTR基因的表达。结果 LPS成功诱导小鼠发生了分泌性腹泻;CFTR基因在小鼠十二指肠、空肠、回肠和结肠组织中均有不同的表达丰度,以结肠最高,但各段肠道间差异不显著;与对照组相比,LPS上调了十二指肠、空肠和回肠CFTR基因的转录,下调了结肠CFTR基因的转录。结论提示肠道组织CFTR基因转录水平的上调与LPS诱导分泌性腹泻的发生密切相关,且在各肠段发挥的作用不同,其中空肠在氯离子（Cl-）分泌中发挥主要作用,结肠的作用最弱。     

斑马鱼脑细胞凋亡基因对束丝藻毒素致毒的响应

水华束丝藻是淡水湖泊中常见的水华蓝藻,是我国滇池冬春季节常见的优势种群,因其产生麻痹性贝类毒素,损伤人和动物的神经系统而倍受关注。但有关该毒素对动物神经系统损伤的研究较少,特别是对水生脊椎动物中枢神经系统损伤的研究尚无报道,为此本研究通过腹腔注射5.3μg STXeq/kg bw束丝藻毒素,研究了24h内该藻毒素对斑马鱼脑组织超微结构损伤及脑细胞凋亡基因表达的影响,以揭示该毒素对脑组织的损伤及其脑细胞在基因水平对该毒素的响应机理。研究表明,束丝藻毒素引起斑马鱼脑组织超微结构损伤,出现细胞膜发泡和形成凋亡小体等典型的细胞凋亡结构;从分子水平进一步分析显示,该毒素引起脑细胞p53、bax、caspase-3和c-jun等凋亡相关基因的表达上调,其上调量分别是对照组表达上调量的1.92、1.55、1.63和1.55倍,且具有时间-效应关系。这说明该毒素能通过引起脑细胞凋亡基因的表达异常,使脑细胞出现凋亡性形态损伤而导致脑细胞死亡;斑马鱼脑细胞可通过启动p53→bax→caspase-3线粒体径路实现其对该毒素的响应机制;束丝藻毒素具有损伤鱼类脑的神经毒性;这是束丝藻毒素引起脑细胞凋亡基因表达异常及超微结构损伤的直接证据,也是脑细胞在基因水平对束丝藻毒素积极响应分子机理的首次报道。     

斑马鱼HO1基因的表达特征及功能研究

实验对血红素加氧酶1（HO1）在斑马鱼发育中的功能进行了研究。多重序列比对结果显示,斑马鱼HO1与哺乳类、鸟类及其他鱼类的HO1氨基酸序列的总体相似性为44.1%86.8%,血红素结合标签相似性为87.5%95.8%。对斑马鱼早期胚胎和成鱼各组织进行RT-PCR检测,结果显示HO1转录本母源存在,HO1 mRNA的表达水平在尾芽期前较低,到咽囊期迅速上升并稳定在较高水平。HO1基因在斑马鱼成鱼多个组织中均有表达,在肝脏、脾、鳃、肾中的表达量较高。WISH结果显示,HO1基因在斑马鱼胚胎的卵黄合胞层、眼和血液中的表达量较高。利用超表达和基因敲降技术发现,注射HO1 mRNA使HO1基因过表达对斑马鱼早期胚胎发育无明显影响。注射HO1 MO使HO1基因表达抑制可导致斑马鱼胚胎出现发育迟缓、围心腔水肿、尾部消失等不同程度的畸形。HO1 MO导致的斑马鱼胚胎发育异常可被HO1 mRNA回复。利用Real-Time PCR研究发现,HO1基因表达抑制可导致IGF1表达量显著下降,IGFBP1表达量显著升高。这些结果表明斑马鱼HO1基因可通过调节IGF信号途径调控胚胎的正常发育。       

γ-氨基丁酸对鳜摄食和食欲的影响

为阐明γ-氨基丁酸(GABA)对鳜(Siniperca chuatsi)摄食和食欲的影响, 对鳜脑室注射生理盐水和不同剂量的GABA(50、125、500和2000 μg)。结果显示, 注射125 μg GABA组的鳜在2h内摄食量显著升高。实时荧光定量PCR (RT-qPCR)结果显示, 注射125 μg GABA 0.5h后, 鳜鱼脑中AgRP和NPY mRNA表达量上调, CART和POMC mRNA表达量下调, 都和鳜摄食量增加相一致。相比于对照组, 注射GABA后Leptin-R的mRNA表达量在0.5h和2h都有显著下降。这些结果表明GABA可能通过leptin的信号通路来影响食欲, 进而影响摄食量。研究结果可以为GABA在水产饲料中的应用提供理论依据。     

γ-氨基丁酸对鳜摄食和食欲的影响(英)

为阐明γ-氨基丁酸(GABA)对鳜(Siniperca chuatsi)摄食和食欲的影响,对鳜脑室注射生理盐水和不同剂量的GABA(50、125、500和2000μg)。结果显示,注射125μg GABA组的鳜在2h内摄食量显著升高。实时荧光定量PCR(RT-q PCR)结果显示,注射125μg GABA 0.5h后,鳜鱼脑中Ag RP和NPY m RNA表达量上调,CART和POMC m RNA表达量下调,都和鳜摄食量增加相一致。相比于对照组,注射GABA后Leptin-R的m RNA表达量在0.5h和2h都有显著下降。这些结果表明GABA可能通过leptin的信号通路来影响食欲,进而影响摄食量。研究结果可以为GABA在水产饲料中的应用提供理论依据。     

Influence of VIP on the number of enterochromaffin and mucosal mast cells in the colon of the rat.

The possibility that VIP (Vasoactive intestinal peptide) could influence the enterochromaffin (EC) cell secretion of serotonin (5HT) and the action of VIP on the mast cell population of lamina propria were investigated in Wistar rat colon infused with a short chain fatty acid solution (sodium acetate), during a 1 h period. Under the action of an intravenous injection of synthetic porcine VIP, 14 micrograms/kg/h), the number of EC cells diminished significantly in the cecum and left colon, when compared to non-injected animals, both infused with a sodium acetate solution. At the same time, the number of mucosal mast cells in the crypts and lamina propria decreased significantly in the cecum. The postulate we put forward is that these VIP-induced changes are exerted through the stimulation of 5HT released from EC cells not only under normal physiological conditions but probably also under pathological conditions.     

DNA microarray analyses of the long-term adaptive response of Escherichia coli to acetate and propionate

In its natural environment, Escherichia coli is exposed to short-chain fatty acids, such as acetic acid or propionic acid, which can be utilized as carbon sources but which inhibit growth at higher concentrations. DNA microarray experiments revealed expression changes during exponential growth on complex medium due to the presence of sodium acetate or sodium propionate at a neutral external pH. The adaptive responses to acetate and propionate were similar and involved genes in three categories. First, the RNA levels for chemotaxis and flagellum genes increased. Accordingly, the expression of chromosomal fliC'-'lacZ and flhDC'-'lacZ fusions and swimming motility increased after adaptation to acetate or propionate. Second, the expression of many genes that are involved in the uptake and utilization of carbon sources decreased, indicating some kind of catabolite repression by acetate and propionate. Third, the expression of some genes of the general stress response increased, but the increases were more pronounced after short-term exposure for this response than for the adaptive response. Adaptation to propionate but not to acetate involved increased expression of threonine and isoleucine biosynthetic genes. The gene expression changes after adaptation to acetate or propionate were not caused solely by uncoupling or osmotic effects but represented specific characteristics of the long-term response of E. coli to either compound.     

Concomitant changes in progesterone catabolic enzymes, cytochrome P450 2C and 3A, with plasma insulin concentrations in ewes supplemented with sodium acetate or sodium propionate

Progesterone is essential for maintaining pregnancy, and several authors have suggested that low peripheral concentrations of progesterone may be responsible for high rates of embryonic loss. The primary organ involved in the catabolism of progesterone is the liver, and cytochrome P450 2C and 3A sub-families account for a large proportion of this catabolism. Elucidating a mechanism to decrease progesterone catabolism, thereby increasing embryonic and uterine exposure to progesterone, seems a logical approach to ameliorate high rates of embryonic loss. The objectives of the current experiment were to determine the pattern of insulin secretion after supplementing feed with either sodium acetate or sodium propionate and to determine any association between the differential patterns of insulin secretion with the hepatic activity of cytochrome P450 2C and 3A and progesterone clearance. Sixteen ovariectomized ewes were fed 3 kg/day for 10 days of a diet consisting of 50% corn silage, 38% triticale haylage, 12% soybean meal and 600 ml of 3.5 M sodium acetate (energy control; n = 8) or 2.0 M sodium propionate (gluconeogenic substrate; n = 8). Equal portions of the ration (1 kg as-fed basis along with 200 ml of 3.5 M sodium acetate or 2.0 M sodium propionate) were offered three times daily at 0600, 1400 and 2200 h. Concentrations of insulin in plasma were determined immediately before feeding and at 15, 30, 60, 90, 120, 180, 240 and 300 min after feeding. Progesterone clearance from peripheral circulation (ng/ml per min) was measured by giving a 5 mg injection of progesterone into the left jugular vein and collecting blood via the right jugular vein at 0, 2, 4, 6, 8, 10, 15, 20 and 30 min afterwards. Liver biopsies were taken 1 h after feeding to determine cytochrome P450 2C and 3A activities. Insulin concentrations in ewes supplemented with sodium propionate were elevated at 15, 30 and 60 min after feeding compared to the sodium acetate group. Cytochrome P450 2C and 3A activities were decreased 1 h after feeding in the sodium propionate-treated ewes relative to sodium acetate. Insulin appears to down-regulate cytochrome P450 activity, which could be used to decrease the catabolism of progesterone during early gestation, thereby increasing peripheral concentrations of progesterone and, consequently, embryonic exposure to progesterone.     

Regulation of peroxisome proliferator-activated receptor gamma on milk fat synthesis in dairy cow mammary epithelial cells

Peroxisome proliferator-activated receptor gamma (PPARγ) participates in lipogenesis in rats, goats, and humans. However, the exact mechanism of PPARγ regulation on milk fat synthesis in dairy cow mammary epithelial cells (DCMECs) remains largely unexplored. The aim of this study was to investigate the role of PPARγ regarding milk fat synthesis in DCMECs and to ascertain whether milk fat precursor acetic acid and palmitic acid could interact with PPARγ signaling to regulate milk fat synthesis. For this study, we examined the effects of PPARγ overexpression and gene silencing on cell growth, triacylglycerol synthesis, and the messenger RNA (mRNA) and protein expression levels of genes involved in milk fat synthesis in DCMECs. In addition, we investigated the influences of acetic acid and palmitic acid on the mRNA and protein levels of milk lipogenic genes and triacylglycerol synthesis in DCMECs transfected with PPARγ small interfering RNA (siRNA) and PPARγ expression vector. The results showed that when PPARγ was silenced, cell viability, proliferation, and triacylglycerol secretion were obviously reduced. Gene silencing of PPARγ significantly downregulated the expression levels of milk fat synthesis-related genes in DCMECs. PPARγ overexpression improved cell viability, proliferation, and triacylglycerol secretion. The expression levels of milk lipogenic genes were significantly increased when PPARγ was overexpressed. Acetic acid and palmitic acid could markedly improve triacylglycerol synthesis and upregulate the expression levels of PPARγ and other lipogenic genes in DCMECs. These results suggest that PPARγ is a positive regulator of milk fat synthesis in DCMECs and that acetic acid and palmitic acid could partly regulate milk fat synthesis in DCMECs via PPARγ signaling.     

DNA Microarray Analyses of the Long-Term Adaptive Response of Escherichia coli to Acetate and Propionate

In its natural environment, Escherichia coli is exposed to short-chain fatty acids, such as acetic acid or propionic acid, which can be utilized as carbon sources but which inhibit growth at higher concentrations. DNA microarray experiments revealed expression changes during exponential growth on complex medium due to the presence of sodium acetate or sodium propionate at a neutral external pH. The adaptive responses to acetate and propionate were similar and involved genes in three categories. First, the RNA levels for chemotaxis and flagellum genes increased. Accordingly, the expression of chromosomal fliC′-′lacZ and flhDC′-′lacZ fusions and swimming motility increased after adaptation to acetate or propionate. Second, the expression of many genes that are involved in the uptake and utilization of carbon sources decreased, indicating some kind of catabolite repression by acetate and propionate. Third, the expression of some genes of the general stress response increased, but the increases were more pronounced after short-term exposure for this response than for the adaptive response. Adaptation to propionate but not to acetate involved increased expression of threonine and isoleucine biosynthetic genes. The gene expression changes after adaptation to acetate or propionate were not caused solely by uncoupling or osmotic effects but represented specific characteristics of the long-term response of E. coli to either compound.     

Alteration of the apparent Ki of carnitine palmitoyltransferase for malonyl-CoA by the diabetic state and reversal by insulin

The effects of streptozotocin-induced diabetes and the subsequent treatment of diabetic animals with insulin were studied using a dose of streptozotocin that produces highly ketotic animals 48 h after injection. Carnitine palmitoyltransferase of diabetic animals had apparent Ki values for malonyl-CoA that were approximately 10 times greater than control animals, indicating a greatly decreased affinity for malonyl-CoA in the diabetic state. Subsequent treatment of diabetic animals with insulin for 5 days produced non-ketotic animals with normal blood glucose, and the affinity of carnitine palmitoyltransferase for malonyl-CoA was increased to the control level. Treatment of other groups of ketotic diabetic animals with insulin produced substantial changes in the carnitine palmitoyltransferase apparent Ki value for malonyl-CoA within 4 h. These results suggest that insulin modulates the ketotic state, at least in part, by increasing the affinity of carnitine palmitoyltransferase for malonyl-CoA to bring about inhibition of fatty acid oxidation and ketogenesis.     

Elucidation of Growth Inhibition and Acetic Acid Production by Clostridium thermoaceticum

The production of acetic acid by Clostridium thermoaceticum was studied by using batch fermentations. In a pH-controlled fermentation with sodium hydroxide (pH 6.9), this organism was able to produce 56 g of acetic acid per liter. On the other hand, when the pH was not controlled and was decreased during fermentation to 5.4, the maximum attainable acetic acid concentration was only 15.3 g/liter. To obtain a better understanding of the end product inhibition, various salts were tested to determine their effect on the growth rate of C. thermoaceticum. An inverse linear relationship between the growth rate and the final cell concentration to the sodium acetate concentration was found. By using different concentrations of externally added sodium salts, the relative growth inhibition caused by the anion was found to be in the order of acetate > chloride > sulfate. Various externally added cations of acetate were also examined with respect to their inhibitory effects on growth. The relative magnitude of inhibition on the growth rate was found to be ammonium > potassium > sodium. The combined results have shown that the undissociated acetic acid was much more inhibitory than the ionized acetate ion. Complete growth inhibition resulted when the undissociated acetic acid concentration was between 0.04 and 0.05 M and when the ionized acetate concentration was 0.8 M. Therefore, at low pH (below 6.0), undissociated acetic acid is responsible for growth inhibition, and at high pH (above 6.0), ionized acetate ion is responsible for growth inhibition.