Role of leptin in modulating the hypothalamic-pituitary axis and luteinizing hormone secretion in the prepuberal gilt

Three experiments (EXP) were conducted to test the hypothesis that leptin modulates LH, GnRH, and neuropeptide Y (NPY) secretion. In EXP I, prepuberal gilts received intracerebroventricular (i.c.v.) leptin injections and blood samples were collected. In EXP II, anterior pituitary cells from prepuberal gilts in primary culture were challenged with 10(-14), 10(-13), 10(-12), 10(-11), 10(-10), 10(-9), 10(-8), 10(-7), or 10(-6) M leptin individually or in combinations with 10(-10), 10(-9), and 10(-8) M GnRH. In EXP III, hypothalamic-preoptic area (HYP-POA) explants were placed in perfusion system and exposed to 0 (n=5), 10(-12) M (n=4), 10(-10) M (n=4), 10(-8) M (n=4), or 10(-6) M (n=5) human recombinant leptin (LEP) for 30 min. In EXP I, serum LH concentrations were unaffected by leptin treatment. In EXP II, all doses of leptin increased LH secretion except for 10(-12) and 10(-7) M. Only 10(-7), or 10(-13) M leptin in combination with 10(-8) or 10(-9) M GnRH, respectively, suppressed LH secretion. In EXP III, prior to leptin, media GnRH concentrations were similar across treatments. Media GnRH concentrations increased after 10(-12), 10(-10), and 10(-8) M leptin compared to control. Leptin treatment failed to influence NPY secretion across treatments. These results indicate that components of the neuroendocrine axis that regulate GnRH and LH secretion are functional and leptin sensitive before the onset of puberty. Other neural peptides in addition to NPY may mediate the acute effects of leptin on the GnRH-LH system and lastly, the inability of i.c.v. leptin treatment to increase LH secretion may in part be related to stage of sexual maturation and associated change in negative feedback action of estradiol on LH secretion.     

The role of nutrients in modulating disease

The role of nutrition in the management of diseases has often centred on correcting apparent nutrient deficiencies or meeting estimated nutritional requirements of patients. Nutrition has traditionally been considered a supportive measure akin to fluid therapy and rarely it has been considered a primary means of ameliorating diseases. Recently, however, further understanding of the underlying mechanisms of various disease processes and how certain nutrients possess pharmacological properties have fuelled an interest in exploring how nutritional therapies themselves could modify the behaviour of various conditions. Nutrients such as omega-3 fatty acids, antioxidants and certain amino acids such as arginine and glutamine have all been demonstrated to have at least the potential to modulate diseases. Developments in the area of critical care nutrition have been particularly exciting as nutritional therapies utilising a combination of approaches have been shown to positively impact outcome beyond simply proving substrate for synthesis and energy. Application of certain nutrients for the modulation of diseases in veterinary patients is still in early stages, but apparent successes have already been demonstrated, and future studies are warranted to establish optimal approaches. This review describes the rationale of many of these approaches and discusses findings both in human beings and in animals, which may guide future therapy.     

The role of vitamins in modulating disease resistance

Many of the metabolic incursions resulting from stress and oxidative damage are detrimental to disease resistance. Vitamins A, E, and C and carotenoids are able to protect cells from free radical oxidation, reduce the detrimental effects of certain eicosanoids, and enhance humoral and cellular immune responses in disease. The regulation of cell differentiation by vitamin A in maintaining an epithelial barrier to pathogen entry and the differentiation of precursor cells to functional lymphocytes by 1,25-dihydroxycholecalciferol are essential to disease resistance. Nutritionists must redefine the levels of vitamins necessary to maximize health-supportive systems. The animal's metabolism must constantly be adjusting to its environmental stress or disease and may require increased vitamins.     

The role of the somatotrophic axis in the metabolism of the chicken.

As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and development of avian species. In contrast to mammals, exogenous GH administration has little, if any, potential for improving the growth rate and feed efficiency of rapidly growing broilers; it is more likely to do so in older birds. This is at least partly because of age-related changes in tissue GH-binding activity and GH-receptor mRNA expression. The effects of GH on lipid deposition depends on the age of the bird and pattern of GH administration. Pulsatile, but not continuous, GH administration to older broilers seems to reduce fat deposition. As in rats, the bioactivity of GH might also depend on the pulse-induced cyclicity in GH receptors and GH-binding proteins. In chickens, GH is also a very potent lipolytic hormone, but seems to have no diabetogenic effect, which is reported in mammalian species. Both insulin-like growth factors have apparently no growth-promoting effects in normal growing broilers, but seem to have opposite effects on fat deposition. In contrast to GH, both insulin-like growth factors have a marked hypoglycemic effect. Whether all these effects are direct effects, or are mediated by secondary mechanisms, awaits further investigations.     

The potential role of leptin and adiponectin in obesity: a comparative review

Leptin and adiponectin are adipokines produced by the white adipose tissue. The adipokines have been shown to be valuable quantitative markers of adiposity in dogs. Leptin positively correlates with body condition score (BCS) in dogs, regardless of age, sex and breed, and is influenced by feeding state, pharmacological treatment and thyroid gland activity. Conversely, adiponectin negatively correlates with body fat mass and is therefore more abundant in lean animals. The implication of leptin and adiponectin in the pathogenesis of metabolic syndrome is well established in humans, but currently lacking in dogs. Additional studies are necessary to demonstrate their potential usefulness for monitoring the progression of obesity-related diseases and response to treatment. To date, measurement of canine leptin and adiponectin has been used in experimental studies only, whereas bodyweight and BCS are considered the first-approach parameters for the routine assessment of body fat content in obese dogs.     

瘦素的生物学功能及其作用机制

<正>Ingalls等[1](1950)发现了一只近亲繁殖的小鼠食欲亢进、过度肥胖(体脂含量超过50%),并患有糖尿病和不育症。研究发现,这只小鼠的肥胖是由一个基因发生了隐性突变引起的,故将此基因称为肥胖基因(obesegene,ob基因),这只小鼠也因此被称为ob/ob     

寡糖对动物免疫功能的作用

寡糖（oligosaccharides）又称为低聚糖或寡聚糖，是由2～10个单糖单位通过糖苷键连接而成的小聚合体，介于单体单糖与高度聚合的多糖之间。寡糖是中等分子的非淀粉多糖，大分子非淀粉多糖经相应酶的不完全水解可产生寡糖。在饲料中使用适量的寡糖，可以提高动物的生产性能，改善动物的健康状况，提高免疫力，防止腹泻。大量研究表明，寡糖除能改善动物消化道微生物区系，促进消化道有益菌的生长，抑制有害微生物的繁殖外，还具有调节动物机体免疫反应，     

营养素对水生动物瘦素基因表达的影响、瘦素的作用及其机理

瘦素(leptin)是一种蛋白质激素。鱼类瘦素主要由肝合成和分泌,参与调节摄食、代谢、生长、免疫、繁殖、神经及造血细胞发育等。本文综述了瘦素的功能及作用机理、营养素对水生动物瘦素基因表达的影响,旨在进一步理解和深入探讨水生动物瘦素的作用及机理、营养素对水生动物瘦素基因表达的影响及其机制,这对理解摄食、能量代谢调控的机制具有科学理论意义;能为有计划、有目的、有效地控制水生动物体重、脂类沉积和能量代谢,根据需要生产理想、优质和健康的水产品提供基础依据,同时为调控人类肥胖、维护健康、提高生产力等提供参考。     

Gastrointestinal tract morphological alteration by unpleasant physical treatment and modulating role of Lactobacillus in broilers

1.?An experiment was conducted to determine the effects of supposedly unpleasant physical treatment on broiler performance, small intestinal development and ameliorating role of probiotics.

2.?The following treatments were applied from day one: (1) chicks exposed to normal human contact fed basal diet (control); (2) chicks were exposed to unpleasant physical treatment and fed basal diet (UPT-BD); and (3) chicks were exposed to unpleasant physical treatment and fed basal diet supplemented with Lactobacillus (UPT-BDL). Chicks were exposed to UPT from days 1 to 21. Different segments of gastrointestinal tract were sampled at 14, 28, 35 and 42 d of age.

3.?Broilers of UPT-BD had lower feed consumption compared with control group at 7 d of age. Overall, UPT-BDL birds showed higher body weight gain (BWG) and better feed conversion ratio (FCR) over the course of the experiment.

4.?Birds of UPT-BD had lower concentrations of lactic, propionic and butyric acids in the caecum as compared with other groups at 14 d of age. Acetic acid concentration was profoundly decreased in both UPT groups compared to the control.

5.?Duodenal villus height of UPT-BD broilers showed a slight reduction compared to the control and UPT-BDL birds at 14 d of age. Afterwards until day 42, UPT-BDL birds showed the highest villus height among treatments in different parts of the small intestine.

6.?The results suggested that, even though UPT did not have significant inhibitory effects on the development of the small intestine and broiler performance, it negatively affected bacterial metabolic end products in the caecum, which could be ameliorated by the addition of Lactobacillus.     

调控鸡蛋中胆固醇含量的微量营养素

调控鸡蛋中胆固醇含量的微量营养素$山东农业大学动物科技学院@赵晓芳 $中国农业科学院畜牧研究所@张宏福     

Localization of leptin and leptin receptor in the bovine adenohypophysis

The present study was carried out to detail the cellular localization of leptin (Lep) and the leptin receptor (LepR) in the bovine adenohypophysis. Lep immunoreactivity (Lep-ir) was found in about 30% of adenohypophysial cells in the gland. Immunochemistry of Lep and specific hormones using serial sections revealed that Lep-ir was present in 60.4% of somatotrophs, 15.9% of gonadotrophs, 6.5% of mammotrophs, 6.5% of thyrotrophs and 2.4% of corticotrophs. Both the common short isoform (OBRa) and the long isoform (OBRb) of LepR mRNA were expressed in the bovine adenohypophysis. LepR immunoreactivity (LepR-ir) was found in only 2.8% of the adenohypophysial cells and over 50% of LepR-ir cells were gonadotrophs, in which most of the cells were distributed in the zona tuberalis. The findings on Lep and LepR in the adenohypophysial cells indicate that Lep may regulate gonadotroph function through autocrine/paracrine pathway in the bovine adenohypophysis.     

Birth by caesarian section alters postnatal function of the hypothalamic-pituitary-adrenal axis in young pigs

Eight crossbred sows were selected for the present study (n = 4 vaginal delivery and n = 4 Caesarian section [C-section]). Gestation length did not differ between vaginal delivery and C-section pigs (113.6 +/- .1 and 113.2 +/- .3 d, respectively; P > .16). Blood and tissue samples from 38 pigs were collected at birth. All remaining pigs were sustained with vaginal-delivery sows until 2 wk of age (n = 39). At 2 wk of age, remaining pigs were catheterized for blood sample collection to assess pituitary-adrenal responsiveness to an injection of corticotropin-releasing hormone (CRH; 10 microg/kg). Blood samples were collected at -30, -15, 0, 5, 10, 20, 40, 60, and 90 min; pigs received CRH or saline at time 0. Pigs were killed and tissue samples were collected immediately following the last blood sample. Serum concentrations of ACTH and cortisol (CS) were measured. Total RNA was isolated from the pituitary and adrenal glands to evaluate gene expression for mRNA specific for pro-opiomelanocortin (POMC) and for the ACTH receptor. Centrifuged clot:blood ratio was reduced in the C-section pigs at birth (P < .001) and at 2 wk of age (P < .043), compared with the vaginally delivered pigs. Basal serum concentration of ACTH was greater in C-section than in vaginally delivered pigs at birth (P = .01) but did not differ at 2 wk of age (P = .42). Basal serum concentration of CS was not different at birth (P = .86) but was greater in C-section pigs than in vaginally delivered pigs at 2 wk of age (P < .04). Serum concentration of ACTH was not different (P > .99) between the two groups of pigs following the CRH challenge. However, serum concentration of CS was greater (P < .05) in C-section pigs following the CRH challenge. Expression of ACTH receptor mRNA tended to be greater in C-section pigs at birth (P < .063) and at 2 wk of age (P < .016). There was no difference in POMC mRNA between treatments (P > .73); however, there was a developmental increase (P < .001) from birth to 2 wk of age. These data indicate that the birth process plays an important role in postnatal function of the hypothalamic-pituitary-adrenal axis in young pigs.     

Galacto-oligosaccharides improve barrier function and relieve colonic inflammation via modulating mucosa-associated microbiota composition in lipopolysaccharides-challenged piglets

Background:Galacto-oligosaccharides(GOS)have been shown to modulate the intestinal microbiota of suckling piglets to exert beneficial effects on intestinal function.However,the modulation of intestinal microbiota and intestinal function by GOS in intestinal inflammation injury models has rarely been reported.In this study,we investigated the effects of GOS on the colonic mucosal microbiota composition,barrier function and inflammatory response of lipopolysaccharides(LPS)-challenged suckling piglets.Methods:A total of 18 newborn suckling piglets were divided into three groups,the CON group,the LPS-CON group and the LPS-GOS group.Piglets in the LPS-GOS group were orally fed with 1 g/kg body weight of GOS solution every day.On the d 14,piglets in the LPS-CON and LPS-GOS group were challenged intraperitoneally with LPS solution.All piglets were slaughtered 2 h after intraperitoneal injection and sampled.Results:We found that the colonic mucosa of LPS-challenged piglets was significantly injured and shedding,while the colonic mucosa of the LPS-GOS group piglets maintained its structure.Moreover,GOS significantly reduced the concentration of malondialdehyde(MDA)and the activity of reactive oxygen species(ROS)in the LPS-challenged suckling piglets,and significantly increased the activity of total antioxidant capacity(T-AOC).GOS significantly increased the relative abundance of norank_f_Muribaculaceae and Romboutsia,and significantly decreased the relative abundance of Alloprevotella,Campylobacter and Helicobacter in the colonic mucosa of LPS-challenged suckling piglets.In addition,GOS increased the concentrations of acetate,butyrate and total short chain fatty acids(SCFAs)in the colonic digesta of LPS-challenged suckling piglets.GOS significantly reduced the concentrations of interleukin 1β(IL-1β),interleukin 6(IL-6),tumor necrosis factor-α(TNF-α)and cluster of differentiation 14(CD14),and the relative mRNA expression of Toll-like receptor 4(TLR4)and myeloid differentiation primary response 88(MyD88)in the LPS-challenged suckling piglets.In addition,GOS significantly reduced the relative mRNA expression of mucin2(MUC2),and significantly increased the protein expression of Claudin-1 and zonula occluden-1(ZO-1)in LPS-challenged suckling piglets.Conclusions:These results suggested that GOS can modulate the colonic mucosa-associated microbiota composition and improve the intestinal function of LPS-challenged suckling piglets.     

Role of leptin in farm animals: a review

The discovery of hormone leptin has led to better understanding of the energy balance control. In addition to its effects on food intake and energy expenditure, leptin has now been implicated as a mediator of diverse physiological functions. Recently, leptin has been cloned in several domestic species. The sequence similarity suggests a common function or mechanism of this peptide hormone across species. Leptin receptors are expressed in most of tissues, which is consistent with the multiplicity of leptin functions. The main goal of this review was to summarize knowledge about effect of leptin on physiology of farm animals. Experiments point to a stimulatory action of leptin on growth hormone (GH) secretion, normal growth and development of the brain. Surprisingly, leptin is synthesized at a high rate in placenta and may function as a growth factor for fetus, signalling the nutritional status from the mother to her offspring. Maturation of reproductive system can be stimulated by leptin administration. Morphological and hormonal changes, consistent with a major role of leptin in the reproductive system, have also been described, including the stimulation of the release of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin. Leptin has a substantial effect on food intake and feeding behaviour in animals. Administration of leptin reduces food intake. Its level decrease within hours after initiation of fasting. Leptin also serves as a mediator of the adaptation to fasting, and this role may be the primary function for which was the molecule evolved.