Ghrelin对采食和分泌调节作用的研究进展

Ghrelin是从鼠和人的胃中分离得到的一种生长激素释放激素受体天然的内源性配体,它由28个氨基酸残基组成,且氮端第三位丝氨酸发生了辛酰基化,Ghrelin具有广泛的生物学功能,包括调控动物采食、调节生长激素释放、调节胃肠功能及调节能量平衡等,对Ghrelin的研究具有重要的理论意义和广阔的应用前景,文中综述了Ghrelin对采食及对其分泌调节作用的研究进展。     

Hormonal regulation of leptin receptor expression in primary cultures of porcine hepatocytes

A study was conducted to elucidate hormonal control of leptin receptor gene expression in primary cultures of porcine hepatocytes. Hepatocytes were isolated from pigs (52 kg) and seeded into collagen-coated T-25 flasks. Monolayer cultures were established in medium containing fetal bovine serum for 1 day and switched to a serum-free medium for the remainder of the 3-day culture period. To establish basal conditions hepatocytes were maintained in serum-free William's E medium containing 10 nM dexamethasone and 1 ng/ml insulin. For the final 24 h, insulin (1 or 100 ng/ml) or glucagon (100 ng/ml), were added in the presence or absence of 100 nM triiodothyronine (T3). RNA was extracted and quantitative RT-PCR was performed with primers specific for the long form and total porcine leptin receptors. Leptin receptor expression was calculated relative to co-amplified 18S rRNA. Expression of the long form of the leptin receptor was confirmed under basal conditions. Insulin, glucagon and synthetic human proteins (ghrelin and GLP-1) at 100 ng/ml had no influence on leptin receptor expression; the addition of T3 was associated with a marked increase (P < 0.001) in expression of total and long forms of the leptin receptor by 1.6 and 2.4-fold, respectively. Addition of leptin to cells which were pre-treated with T3 for 24 h (to up-regulate leptin receptor expression), confirmed the lack of a direct effect of leptin on glucagon-induced glycogen turnover and cAMP production. These data suggest that porcine hepatocytes may be insensitive to leptin stimulation even when leptin receptor expression is enhanced by T3.     

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.     

日粮膳食纤维与猪肠道健康调控

日粮纤维目前基本认定为第七大营养素,在猪体内中虽然消化率不高,甚至会影响其他营养素消化吸收,但能发酵产生短链脂肪酸,具有改善肠道微生物环境、调控母猪生理行为、调控猪肠道健康等作用。文章综述了日粮纤维在猪体内的营养特性和对肠道的调控作用,为日粮纤维在猪生产中的应用提供参考。     

Serum leptin and ghrelin levels in response to methylprednisolone injection in healthy dogs

The aim of this study was to investigate the effects of methylprednisolone treatment on serum leptin and ghrelin levels in healthy dogs (n=40). After 14 h of fasting, the dogs were injected intramuscularly with saline (control group) or methylprednisolone (1, 5 or 10mg/kg). Blood samples were collected prior to (baseline) and 2, 3, 4, 8, 12 and 24h subsequent to the treatments. Serum leptin and ghrelin were measured by radioimmunoassay. The mean baseline serum leptin and ghrelin were 2.5+/-0.1 ng/mL (n=40) and 35.0+/-2.1 pg/mL (n=40), respectively. In the control dogs, serum leptin, but not ghrelin levels showed a significant fluctuation during the 24h observation period. Serum leptin increased significantly (p<0.05-0.01) between 2 and 12h after 1mg/kg of methylprednisolone. Serum leptin levels showed biphasic response to 5mg/kg of methylprednisolone: its level decreased to 1.9+/-0.1 ng/mL (p<0.01) at 2h and increased at 12h (2.6+/-0.1 ng/mL) (p<0.01). In response to 10mg/kg of methylprednisolone, serum leptin levels decreased significantly (p<0.01) for 24h. Serum ghrelin levels decreased to 19+/-5 pg/mL at 2-3h (p<0.01) or increased to 87+/-18 pg/mL at 3-8h (p<0.05-0.01) after 1mg/kg of methylprednisolone or 10mg/kg of methylprednisolone, respectively. Serum ghrelin levels did not change at any time point during 24h observation period after 5mg/kg of methylprednisolone. There was a significant (p<0.001) inverse correlation (r=-0.635) between serum leptin and ghrelin levels. In conclusion, we found that methylprednisolone increases or decreases serum leptin and ghrelin levels depending upon its dose and there is a negative correlation between serum leptin and ghrelin levels after methylprednisolone administration.     

Exercise-induced alterations in plasma concentrations of ghrelin, adiponectin, leptin, glucose, insulin, and cortisol in horses

Six Standardbred (STB) mares (11+/-2 years, 521+/-77 kg; means+/-SD) performed an exercise trial (EX) where they underwent an incremental exercise test (GXT) as well as a parallel control trial (CON) to test the hypothesis that short-term, high intensity exercise would alter plasma concentrations of glucose, leptin, adiponectin, ghrelin, insulin and cortisol. Plasma samples were taken before (0 min), during (last 10s at 6, 8m/s, and the velocity eliciting VO(2max)), and after exercise (2, 10, 30, 60 min; 12 and 24h post-GXT). A second set of blood samples was collected before and after an afternoon meal given at 1515 h (at 1500, 1514, 1530, and 1545 h). Data were analyzed using ANOVA for repeated measures and Tukey's test. During the GXT, there were no changes (P>0.05) in the plasma concentrations of glucose, leptin, adiponectin or ghrelin. However, there was a 29% increase (P<0.05) in mean plasma cortisol concentration and a 35% decrease (P<0.05) in mean plasma insulin concentration. Substantial increases (P<0.05) in the mean plasma concentrations of glucose and cortisol of 36% and 102%, respectively, were seen in the EX trial during the first 60 min post-GXT. Plasma leptin concentration, measured at the 24h post-GXT time point, was 20% lower (P<0.05) during the EX trial compared with the parallel time point in the standing control (CON) trial. Plasma ghrelin concentration was 37% lower (P<0.05) in the EX trial compared with CON before and after the afternoon meal, but was 43% higher (P<0.05) 12h post-GXT. There were no differences between EX and CON for plasma concentrations of insulin or adiponectin during recovery. It was concluded that short-term high intensity exercise alters plasma leptin and ghrelin concentrations in STB mares post-exercise, which may signal the exercised animals to alter energy intake.     

Leptin and Ghrelin and the Indices of Lipid Metabolism as Related to Sex Steroid Hormones in Trotters

This study examined the influence of sex steroid hormones on lipid metabolism in horses. The group of 34 clinically healthy Standardbred trotters aged 2 to 4 years was studied during an exercise test. The horses were divided into groups according to their sex. These groups were: 11 stallions, 16 mares, and seven geldings. Concentrations of testosterone, 17-β-estradiol, leptin, ghrelin, glycerol, free fatty acids (FFA), and triacylglycerols (TG) were measured in plasma obtained from blood samples taken at rest and after the end of the exercise. At rest, plasma ghrelin concentration was significantly higher in geldings than in stallions and mares (1,541 ± 206 vs 1,280 ± 288 and 1,310 ± 267 pg/mL, respectively; P = .012). Leptin was lower in geldings than in mares (2.65 ± 0.93 vs 4.70 ± 2.31 ng/mL; P = .036). The post-exercise rise in plasma ghrelin and TG concentrations was significantly higher in mares than in geldings (+220 ± 330 vs -25 ± 206 pg/mL; P = .049 and 0.31 ± 0.14 vs 0.13 ± 0.15 mmol/L; P = .016, respectively). The increase in plasma FFA level was higher in geldings than in stallions (535 ± 178 vs 334 ± 191 μmol/L, P = .046). In conclusion, lipolysis rate in geldings is higher than in noncastrated trotters.     

不同饲喂次数对猪生产性能的影响

本试验研究不同饲喂次数对育肥猪生长性能的影响。试验结果表明,生长肥育母猪(平均初始体重60kg)日饲喂2次较为合理。     

Effects of cysteamine supplementation on the intestinal expression of amino acid and peptide transporters and intestinal health in finishing pigs

This study aimed to evaluate the effects of cysteamine supplementation on the expression of jejunal amino acid and peptide transporters and intestinal health in finishing pigs. Sixty barrows were allocated into two experimental diets consisting of a basal control diet supplemented with 0 or 142 mg/kg cysteamine. After 41 days, 10 pigs per treatment were slaughtered. The results showed that cysteamine supplementation increased the apparent digestibility of crude protein (CP) (P < 0.05) and the trypsin activity in jejunal digesta (P < 0.01). Cysteamine supplementation also increased the messenger RNA abundance of SLC7A7, SLC7A9 and SLC15A1, occludin, claudin‐1 and zonula occludens protein‐1 (P < 0.001) in the jejunum mucosa. Increased glutathione content (P < 0.01) and glutathione peroxidase activity (P < 0.05) and decreased malondialdehyde content (P < 0.01) were observed in pigs receiving cysteamine. Additionally, cysteamine supplementation increased the concentrations of secretory immunoglobulin A (IgA) (P < 0.05), IgM (P < 0.001) and IgG (P < 0.001) in the jejunal mucosa. It is concluded that cysteamine supplementation could influence protein digestion and absorption via increasing trypsin activity, enhancing the digestibility of CP, and promoting the expression of jejunal amino acid and peptide transporters. Moreover, cysteamine improved intestinal integrity, antioxidant capacity and immune function in the jejunum, which were beneficial for intestinal health.     

Chronic intestinal inflammation and intestinal disease in dogs

Normal individuals maintain tolerance to the endogenous bacterial flora residing within their alimentary tract, a phenomenon mediated by the gastrointestinal lymphoid tissue. Loss of this tolerance is a key factor in the development of chronic intestinal inflammation. Manifestations of such uncontrolled inflammation in humans include inflammatory bowel disease and celiac disease. Dogs may similarly be affected, and although the etiopathogenesis is likely similar, the lesions differ. This review includes discussion of the factors involved in breakdown of mucosal tolerance, the immunologic basis of canine enteropathies, and the use of novel immunotherapies for these diseases.     

日粮纤维调节猪肠道微生物和肠黏膜屏障功能的研究进展

仔猪腹泻难题制约生猪养殖水平的提高。随着高铜、高锌、抗生素的限用禁用,仔猪腹泻亟需"绿色"替代方案。日粮纤维作为第六大营养素,具有维持肠道健康的生理功能。日粮纤维可以通过优化肠道菌群结构,调节黏膜屏障等作用促进猪肠道的健康发育与完整功能实现。文章就日粮纤维对猪肠道微生物以及黏膜屏障功能的可能作用途径以及相关作用机制进行综述,以促进日粮纤维在猪日粮生产上应用,尤其是仔猪日粮生产上的合理广泛利用。     

Effects of feeding pattern on ghrelin and insulin secretion in pigs

Ghrelin is a peptide hormone that has been implicated in the regulation of feed intake, but little is known about its secretion in pigs. Hence, the effect of feeding pattern on the regulation of ghrelin secretion was tested. In experiment 1, barrows were allotted randomly into 1 of 2 groups, (1) ad libitum fed (CONT) and (2) limited access to feed (once per day, MEAL). Blood samples were taken through jugular catheters every 15 min for 6 h after 7 d on the experimental feeding regimen. Plasma concentrations of ghrelin and insulin were determined by radioimmunoassay. Ghrelin concentrations in the MEAL pigs were elevated before feeding and declined after feeding (P < 0.01). No pattern in plasma ghrelin concentrations was observed in the CONT pigs, but ghrelin concentrations were lower than in the MEAL group. Insulin concentrations were greater in CONT pigs (P < 0.01) during most of the sampling and increased after feeding in the MEAL pigs (P < 0.01). In experiment 2, the treatments were the same as in experiment 1; however, the amount of feed was increased in the MEAL group so that their daily intake was similar to the CONT pigs. Ghrelin concentrations in the MEAL group were again elevated before the meal and declined afterward (P < 0.01). Insulin but not glucose concentrations were negatively correlated with ghrelin. Once-per-day feeding resulted in increased plasma concentrations of ghrelin, which decreased after feeding. Ghrelin may be involved in the regulation of feed intake in pigs.     

Review of a histological intestinal approach to assessing the intestinal function in chickens and pigs

The general histological features of the small intestine are well known. However, histological intestinal alterations induced by ingested feeds have not been established. To demonstrate such a relationship; (i) the post‐hatching development of intestinal villi in chickens was observed; (ii) histological intestinal differences were compared in White Leghorns and broilers; and (iii) histological intestinal alteration was investigated in fasting and refeeding treatments, using chickens and piglets. Histological intestinal recovery responses; (iv) to luminal nutrient absorption, intraluminal physical stimulation, or intravenous parenteral alimentation in fasted chickens, as well as; (v) to particle size and nutritional level of refed diets in fasted chickens and piglets were also compared. To induce compensatory enlargement of ileal villi; (vi) the jejunum was surgically resected. To reconfirm the histological intestinal alterations induced artificially; (vii) conventional feeding experiments were enforced in chickens and piglets. These fundamental investigations demonstrate that the high values of villus height, cell area and cell mitosis numbers as well as protuberated epithelial cells are hypertrophied by ingested feeds . Finally, as examples of practical use in the animal production field; (viii) useful feed resources to improve the growth performance by activating the intestinal function in chickens and piglets; and (ix) an effective forced molting method are introduced. Based on the histological intestinal alterations related with growth performance in chickens and piglets, this article reviews progress in the establishment of a histological intestinal index to assess the intestinal function.     

Peripartum changes in orexigenic and anorexigenic hormones in relation to back fat thickness and feeding strategy of sows

Highly prolific sows often experience peripartum hypophagia, resulting in decreased production rate. Leptin, ghrelin, and resistin are known as feed intake–regulating hormones in many species, but it is yet unknown how feeding strategy and body condition will affect these hormones around parturition in sows. In the present study, a total of 63 sows, parity 2 to 7 were divided over 2 treatment groups which were fed either restricted (RESTRICT) or ad libitum (ADLIB) during the peripartum period (day 106 of gestation until day 7 of lactation). Within each treatment group, sows were assigned to 1 of 3 body condition groups based on back fat thickness at day 106 of gestation: <18 mm (LEAN), between 18 and 22 mm (MODERATE), and >22 mm (FAT). Postprandial blood samples were taken on days 107, 109, and 112 of gestation and on days 1, 3, and 5 of lactation. With RIA, leptin, ghrelin, and resistin of each sample were analyzed. For both leptin and resistin, the hormonal profile gradually increased throughout the peripartum period (P < 0.001), whereas ghrelin peaked on day 109 of gestation compared with day 107 of gestation and day 1 of lactation. Other time points were intermediate between those two (P < 0.001). The peripartum profile of leptin was significantly higher for FAT sows than for the 2 other condition groups. No effect of body condition on ghrelin and resistin concentrations was observed. None of the 3 measured hormones were affected by feeding strategy. In conclusion, during the peripartum period feed intake of sows did not affect leptin, ghrelin, or resistin profiles. Leptin was the only hormone investigated that reflected body condition. Although body condition and late gestation feed intake have been previously described as risk factors for peripartum hypophagia, they did not induce hypophagia in any of the sows or affect the profile of the observed feed intake–regulating hormones during the peripartum period.     

肠道黏膜屏障机能及其调控研究进展

肠道不仅仅是机体消化、吸收营养物质的主要场所,也是机体的一道防御屏障。肠道黏膜屏障包括黏膜生物屏障、机械屏障、化学屏障和免疫屏障,不论是哪一种肠道黏膜屏障受到损伤,都会导致机体不同程度的伤害,与一些疾病的发生密切相关。本文就肠道黏膜屏障机能及其调控研究进展进行综述,为进一步认识肠道黏膜屏障及治疗由其损伤引起的疾病提供参考和帮助。     

抗菌肽对断奶仔猪生长性能、养分消化率、肠道微生物含量及绒毛结构的影响

文章旨在研究日粮添加不同水平抗菌肽替代抗生素对断奶仔猪生长性能、养分消化率、肠道微生物含量及绒毛结构的影响。试验选择平均体重为(5.76±0.02)kg的21 d断奶的杜×长×大仔猪672头,根据个体大小随机分为4组,每组4个重复,每个重复42头。试验分为1～14 d和15～28 d两个阶段,对照组饲喂基础日粮+60 mg/kg盐霉素,抗菌肽组饲喂基础日粮+0、50或100 mg/kg抗菌肽。试验进行28 d。对照组较抗菌肽组显著提高了断奶仔猪28 d体重(P <0.05),1～14 d和1～28 d日增重(P <0.05),1～14 d、15～28 d、1～28 d采食量,显著降低了1～28 d料重比(P <0.05)。随着日粮抗菌肽添加水平的升高,28 d体重、1～14 d、15～28 d及1～28 d日增重显著升高(P <0.05)。对照组较抗菌肽组显著提高了断奶仔猪14和28 d干物质、14 d粗蛋白质表观消化系数(P <0.05)。对照组较抗菌肽组显著降低了14和28 d粪中大肠杆菌含量(P <0.05),且总厌氧菌、梭菌和大肠杆菌含量随抗菌肽添加水平的升高而显著降低(P <0.05);与抗菌肽组相比,对照组显著降低了回肠总厌氧菌含量(P <0.05)。饲喂对照组日粮的断奶仔猪较抗菌肽组显著降低了空肠隐窝深度(P <0.05),显著提高了空肠绒毛高度与隐窝深度的比值(P <0.05)。根据试验结果推断,日粮添加抗菌肽可以作为抗生素替代品,具有提高断奶仔猪生长性能、干物质和粗蛋白质的表观消化率、绒毛形态及降低粪中有害菌含量的作用。     

Effects of orexigenic peptides and leptin on melatonin secretion during different photoperiods in seasonal breeding ewes: an in vitro study

The pineal gland (PG) acts as a neuroendocrine transducer of daily and seasonal time through the nocturnal release of melatonin. Here, we examined the interaction of season, orexin, ghrelin, and leptin on melatonin secretion by pineal explants in short-term culture. Glands were collected after sunset from 12 ewes during long days (LD; April and May) and from an additional 12 ewes during short days (SD; October and November). Glands were transected sagittally into strips, with each equilibrated in 2.5 mL of Dulbecco's modified Eagle's medium for 60 min, followed by a 2-h incubation in control medium or medium containing orexin B (10 and 100 ng/mL), ghrelin (10 and 100 ng/mL), or 50 ng/mL of leptin. After a 3-h incubation, some PG explants treated previously with lower doses of orexin or ghrelin were challenged with 50 ng/mL of leptin and those treated with both doses of orexin were challenged with 300 nM of the β-agonist isoproterenol. One milliliter of medium was harvested and replaced from each well every 30 min. Treatment with the low dose of orexin during LD increased melatonin secretion about 110% (P<0.01); treatment with a high dose increased melatonin secretion about 47% (P<0.001). During the SD period, leptin stimulated (P < 0.05) melatonin secretion slightly compared with mean melatonin concentration in controls. However, together, orexin and leptin depressed (P<0.01) melatonin secretion. Both doses of ghrelin reduced (P < 0.01) melatonin concentration during the SD season compared with control culture. Addition of ghrelin and leptin to culture medium increased (P<0.01) melatonin concentration compared with ghrelin-treated culture and decreased melatonin concentration (P<0.01) compared with leptin-treated culture during SD. Isoproterenol stimulated (P<0.01) melatonin secretion compared with values observed during the pretreatment period. We conclude that orexigenic peptides (orexin B and ghrelin) and an anorectic peptide (leptin) affect PG directly. The responses of PG to those hormones depend on day length. Moreover, secretion of melatonin from the ovine PG is under an adrenergic regulation.     

Effects of immune-mediated enteroluminal neltrophil emigration on intestinal function in pigs.

Intestinal function was assessed in cannulated loops of porcine proximal jejunum during immune-mediated emigration of neutrophils into the intestine. Net water, net sodium, net chloride, undirectional sodium and unidirectional chloride fluxes were measured before and after intestinal exposure to an antigen in both sensitized and nonsensitized pigs. Neutrophil emigration was assessed histologically. The results indicate that fluid and electrolyte movements in the intestine are not significantly altered during immune-mediated enteroluminal neutrophil emigration suggesting that the neutrophil response does not interfere with intestinal function.     

Lactulose as a marker of intestinal barrier function in pigs after weaning

Intestinal barrier function in pigs after weaning is almost exclusively determined in terminal experiments with Ussing chambers. Alternatively, the recovery in urine of orally administered lactulose can be used to assess intestinal permeability in living animals. This experiment was designed to study the barrier function of the small intestine of pigs over time after weaning. The aim was to relate paracellular barrier function (measured by lactulose recovery in the urine) with macromolecular transport [measured by horseradish peroxidase (HRP) using Ussing chambers] and bacterial translocation to assess whether lactulose recovery is related to possible causes of infection and disease. Forty gonadectomized male pigs (6.7 ± 0.6 kg) were weaned (d 0) at a mean age of 19 d, fitted with urine collection bags, and individually housed. Pigs were dosed by oral gavage with a marker solution containing lactulose (disaccharide) and the monosaccharides l-rhamnose, 3-O-methylglucose, and d-xylose at 2 h and at 4, 8, and 12 d after weaning. The recovery of sugars in the urine was determined over 18 h after each oral gavage. The day after each permeability test, the intestines of 10 pigs were dissected to determine bacterial translocation to the mesenteric lymph nodes and jejunal permeability for HRP in Ussing chambers. Recovery of l-rhamnose in urine was affected by feed intake and by the time after weaning (P ≤ 0.05). Recovery of lactulose from the urine was greater (P ≤ 0.05) at 4, 8, and 12 d after weaning compared with the first day after weaning and was negatively correlated with feed intake (r = -0.63, P ≤ 0.001). The mean translocation of aerobic bacteria to the mesenteric lymph nodes was greater at 5 and 13 d after weaning compared with d 1 (P ≤ 0.05). Lactulose recovery showed no correlation with permeability for HRP nor with bacterial translocation (P > 0.05). Although both lactulose recovery and bacterial translocation increased over time after weaning, lactulose recovery did not correlate with the permeability for HRP nor bacterial translocation within a pig (P > 0.05). Therefore, we conclude that lactulose recovery in the urine of pigs after weaning is not associated with risk factors for infections. However, it appears to be possible to measure paracellular barrier function with orally administered lactulose in pigs shortly after weaning. Further studies will reveal whether this variable is relevant for the long-term performance or health of pigs after weaning.