Postnatal development of glucose transporter proteins in bovine skeletal muscle and adipose tissue.

Facilitated diffusion of glucose across the plasma membrane is mediated by a family of glucose transporter (GLUT). GLUT1 is ubiquitously present in all tissues and involved in cellular glucose uptake, while GLUT4 plays a key role in cellular glucose uptake stimulated by insulin in skeletal muscles and adipose tissue. To examine the postnatal change in the GLUTs of ruminants, the protein levels of GLUT1 and GLUT4 were measured by Western blot analysis of skeletal muscles, adipose tissue and brain of Holstein male calves aged from 0 to 12 months. Analysis of rumen short chain volatile fatty acids revealed that rumen fermentation increased around 2-3 months old. The GLUT1 level did not change in all tissues examined during the postnatal period, while the GLUT4 levels in skeletal muscle and subcutaneous adipose tissue decreased gradually, and at 12 month old, it was about 40% of those seen at 0 month old. These results are contrast to those in non-ruminant species, in which GLUT4 increases during postnatal development, and may be related to the insulin-resistance seen in adult ruminants.     

Changes in gene expression of glucose transporters in lactating and nonlactating cows

Glucose delivery and uptake by the mammary gland are a rate-limiting step in milk synthesis. It is thought that insulin-independent glucose uptake decreases in tissues, except for the mammary gland, and insulin resistance in the whole body increases following the onset of lactation. To study glucose metabolism in peak-, late-, and nonlactating cows, the expression of erythrocyte-type glucose transporter (GLUT1) and the insulin-responsive glucose transporter (GLUT4) in the mammary gland, adipose tissue, and muscle were assessed by Western blotting and real-time PCR. Our results demonstrated that the mammary gland of lactating cows expressed a large amount of GLUT1, whereas the mammary gland of nonlactating cows did not (P < 0.05). On the other hand, adipose tissue of late and nonlactating cows expressed a large amount of GLUT1, whereas the adipose tissue of peak-lactating cows did not (P < 0.05). There were no significant differences in the abundance of GLUT4 mRNA in adipose tissue and muscle, whereas GLUT4 mRNA was not detected in the mammary gland. The plasma insulin concentration was greater (P < 0.05) in nonlactating cows than in peak- and late-lactating cows. The results of the present study indicate that in lactation, GLUT1 expression in the mammary gland and adipose tissue is a major factor for insulin-independent glucose metabolism, and the expression of GLUT4 in muscle and adipose tissue is not an important factor in insulin resistance in lactation; however, the plasma insulin concentration may play a role in insulin-dependent glucose metabolism. Factors other than GLUT4 may be involved in insulin resistance.     

巨型玫瑰冠鸡H-FABP、A-FABP基因表达的发育性变化及其肌内脂肪含量研究

为探讨心脏型脂肪酸结合蛋白（heart-type fatty acid-binding protein，H-FABP）和脂肪型脂肪酸结合蛋白（adipocyte fatty acid-binding protein，A-FABP）基因与巨型玫瑰冠鸡生长发育及肌内脂肪含量（IMF）的关系，研究H-FABP、A-FABP基因对巨型玫瑰冠鸡IMF含量和腹脂沉积的作用机制，本试验采集了巨型玫瑰冠鸡与良凤花鸡在不同周龄（2、4、6、8、10、12周龄）的腹脂、心肌、胸肌、腿肌组织样品共480份，采用实时荧光定量PCR对巨型玫瑰冠鸡与良凤花鸡不同生长阶段组织中H-FABP、A-FABP基因mRNA表达量进行了检测，并采用索氏浸提法测定了两种鸡12周龄的胸肌与腿肌的IMF含量。结果表明，巨型玫瑰冠鸡与良凤花鸡的H-FABP、A-FABP基因mRNA在腹脂、心肌、胸肌和腿肌组织中均有不同程度的表达，且两种鸡H-FABP基因mRNA在心肌组织中高度表达，在脂肪组织中表达量较低，在胸肌、腿肌组织中中度表达，而A-FABP基因相反，推测H-FABP基因主要在肌肉组织中表达，而A-FABP基因主要在脂肪组织中表达。良凤花鸡生长速度高于巨型玫瑰冠鸡；巨型玫瑰冠鸡的腹脂率均低于同性别的良凤花鸡，但胸肌、腿肌的IMF均高于同性别的良凤花鸡，表明巨型玫瑰冠鸡的肉品质优于良凤花鸡。本试验结果为巨型玫瑰冠鸡H-FABP、A-FABP基因分子选育奠定了基础。     

Cloning of avian G(0)/G(1) switch gene 2 genes and developmental and nutritional regulation of G(0)/G(1) switch gene 2 in chicken adipose tissue

Adipose triglyceride lipase (ATGL), a newly identified lipase, is a rate-limiting enzyme for triglyceride hydrolysis in adipocytes. The regulatory proteins involved in ATGL-mediated lipolysis in fat tissue are not fully identified and understood. The G(0)/G(1) switch gene 2 (G0S2) is an inhibitor of ATGL activity by interacting with ATGL through the hydrophobic domain of G0S2. Here, for the first time, we have cloned the coding sequence of G0S2 cDNA for the chicken, turkey, and quail. Sequence comparisons with mammals revealed that the avian G0S2 also have a conserved hydrophobic domain. Avian G0S2 is predominantly expressed in adipose tissues relative to other tested tissues. Within the adipose tissue, G0S2 is expressed 20-fold greater in the adipocyte than in the stromal-vascular (SV) fraction (P < 0.001). Expression of G0S2 mRNA gradually increased during differentiation of chicken adipocytes in culture (P < 0.05). However, there is G0S2 expression in embryonic adipose tissue, SV fraction, and primary preadipocytes before confluence that generally have an increased capacity of cell proliferation, which indicates it has an important role in adipocyte differentiation rather than proliferation. For a better understanding of how G0S2 responds to environmental stimuli, chickens were fasted for 24 h and then refed. Expression of G0S2 in adipose tissue was dramatically decreased (P < 0.05) in the chickens and quail after a 24-h fasting period, and increased to the control level after refeeding. In contrast to G0S2 expression, ATGL expression was induced (P < 0.05) after the 24-h fasting period and rapidly returned to the control level during the refeeding period. These data indicate that changes in lipolytic activities of adipose tissue in vivo can be regulated by G0S2 expression, as an inhibitor of ATGL.     

Microanatomic features of pancreatic islets and immunolocalization of glucose transporters in tissues of llamas and alpacas

OBJECTIVE: To describe the microanatomic features of pancreatic islets and the immunohistochemical distribution of glucose transporter (GLUT) molecules in the pancreas and other tissues of New World camelids. ANIMALS: 7 healthy adult New World camelids, 2 neonatal camelids with developmental skeletal abnormalities, and 2 BALB/c mice. PROCEDURE: Samples of pancreas, liver, skeletal muscle, mammary gland, brain, and adipose tissue were collected postmortem from camelids and mice. Pancreatic tissue sections from camelids were assessed microscopically. Sections of all tissues from camelids and mice (positive control specimens) were examined after staining with antibodies against GLUT-1, -2, -3, and -4 molecules. RESULTS: In camelids, pancreatic islets were prominent and lacked connective tissue capsules. Numerous individual endocrine-type cells were visible distant from the islets. Findings in neonatal and adult tissues were similar; however, the former appeared to have more non-islet-associated endocrine cells. Via immunostaining, GLUT-2 molecules were detected on pancreatic endocrine cells and hepatocytes in camelids, GLUT-1 molecules were detected on the capillary endothelium of the CNS, GLUT-3 molecules were detected throughout the gray matter, and GLUT-4 molecules were not detected in any camelid tissues. Staining characteristics of neonatal and adult tissues were similar. CONCLUSIONS AND CLINICAL RELEVANCE: In New World camelids, microanatomic features of pancreatic islets are similar to those of other mammals. Data suggest that the poor glucose clearance and poor insulin response to hyperglycemia in adult camelids cannot be attributed to a lack of islet cells or lack of GLUT molecules on the outer membrane of those cells.     

Molecular cloning and tissue expression of chicken AdipoR1 and AdipoR2 complementary deoxyribonucleic acids

AdipoR1 and AdipoR2 belong to a novel class of transmembrane receptors that mediate the effects of adiponectin. We have cloned the chicken AdipoR1 and AdipoR2 complementary deoxyribonucleic acids (cDNA) and determined their expression in various tissues. We also investigated the effect of feed deprivation on the expression of AdipoR1 or AdipoR2 mRNA in the chicken diencephalon, liver, anterior pituitary gland, and adipose tissue. The chicken AdipoR1 and AdipoR2 cDNA sequences were 76-83% identical to the respective mammalian sequences. A hydrophobicity analysis of the deduced amino acid sequences of chicken AdipoR1/AdipoR2 revealed seven distinct hydrophobic regions representing seven transmembrane domains. By RT-PCR, we detected AdipoR1 and AdipoR2 mRNA in adipose tissue, liver, anterior pituitary gland, diencephalon, skeletal muscle, kidney, spleen, ovary, and blood. AdipoR1 or AdipoR2 mRNA expression in various tissues was quantified by real-time quantitative PCR, and AdipoR1 mRNA expression was the highest in skeletal muscle, adipose tissue and diencephalon, followed by kidney, ovary, liver, anterior pituitary gland, and spleen. AdipoR2 mRNA expression was the highest in adipose tissue followed by skeletal muscle, liver, ovary, diencephalon, anterior pituitary gland, kidney, and spleen. We also found that a 48 h feed deprivation significantly decreased AdipoR1 mRNA quantity in the chicken pituitary gland, while AdipoR2 mRNA quantity was significantly increased in adipose tissue (P<0.05). We conclude that the AdipoR1 and AdipoR2 genes are ubiquitously expressed in chicken tissues and that their expression is altered by feed deprivation in the anterior pituitary gland and adipose tissue.     

Differential expression of peroxisome proliferator-activated receptors alpha and gamma gene in various chicken tissues

The peroxisome proliferator-activated receptors (PPARs) are the members of superfamily of nuclear hormone receptors. A great number of studies in rodent and human have shown that PPARs were involved in the lipids metabolism. The goal of the current study was to investigate the expression pattern of PPAR genes in various tissues of chicken. The tissue samples (heart, liver, spleen, lung, kidney, stomach, intestine, brain, breast muscle and adipose) were collected from six Arber Acres broilers (8 weeks old, male and female birds are half and half). Semi-quantitative RT-PCR and Northern blot were used to characterize the expression of PPAR-alpha and PPAR-gamma genes in the above tissues. By semi-quantitative RT-PCR, the results showed the expression level of PPAR-alpha gene was higher in brain, lung, kidney, heart and intestine, medium in stomach, liver and adipose than in spleen, and it did not express in breast muscle. The expression level of PPAR-gamma gene was higher in adipose, medium in brain and kidney than in spleen, heart, lung, stomach and intestine, but it did not express in liver and breast muscle. Northern blot results showed that PPAR-alpha gene expressed in heart, liver, kidney and stomach, and the intensity of hybridization signal was the stronger in liver and kidney than in other tissues, however, PPAR-gamma gene only expressed in adipose and kidney tissues. The results of this study showed the profile of PPAR gene expression in the chicken was similar to that in rodent, human and pig. However the expression profile of chicken also have its own specific trait, i.e. compared with mammals, PPAR-alpha gene can not be detected in skeletal muscle and PPAR-gamma gene can be stronger expressed in kidney tissues. This work will provide some basic data for the PPAR genes expression and lipids metabolism of birds.     

金茅黑鸡miR-206表达及靶基因预测分析

为了研究miR-206的组织表达分布及其在鸡骨骼肌生长发育中的表达规律，预测其可能的作用机制，本研究采集4周龄金茅黑鸡的心脏、肝脏、脾脏、肺脏、肾脏、胸肌、腿肌和腹脂8种组织及2、6、10、14、16周龄胸肌和腿肌组织，利用实时荧光定量PCR技术检测miR-206在8种组织及不同周龄胸肌和腿肌中的表达，利用生物信息学方法预测其靶基因并进行功能注释。结果显示，miR-206在公、母鸡胸肌和腿肌中表达量均极显著高于其他组织（P < 0.01），在腹脂、心脏、肝脏、脾脏、肺脏和肾脏中低表达，为鸡骨骼肌特异性表达miRNA；miR-206均在公、母鸡腿肌和胸肌组织生长早期（2周龄）表达最高，之后表达量逐渐下降。靶基因预测和功能分析发现，miR-206共有356个靶基因，其中21个与肌肉生成相关，多个靶基因已知参与调控肌肉生成，包括配对框7（paired box 7，Pax7）、胰岛素样生长因子1（insulin-like growth factor 1，IGF1）、脑衍生神经营养因子1（brain-derived neurotrophic factor 1，BDNF1）、视黄酸受体（retinoic acid receptor beta，RARB）和卷曲类受体7（frizzled class receptor 7，FZD7）基因。此外，发现miR-206靶基因富集到多条已知参与调控骨骼肌生成的信号通路，包括MAPK、Wnt、肌动蛋白骨架调控和黏着斑激酶信号通路。结合表达数据推测，miR-206可能通过靶向调控Pax7、IGF1、BDNF1、RARB、FZD7基因和MAPK、Wnt等信号通路参与调控鸡肌肉生成。本研究揭示了金茅黑鸡miR-206的组织表达分布及其在鸡骨骼肌生长过程中的表达规律，并预测了其调控骨骼肌生成的可能作用机理，为进一步研究miR-206在鸡肌肉生长发育中的作用机理和表达调控奠定了基础。     

Differential regulation of the GLUT1 and GLUT3 glucose transporters by growth factors and pro-inflammatory cytokines in equine articular chondrocytes

Glucose serves as the major energy substrate for articular chondrocytes and as the main precursor for the synthesis of extracellular matrix glycosaminoglycans in cartilage. Chondrocytes have been shown to express several glucose transporter (GLUT) isoforms including GLUT1 and GLUT3. The aim of this investigation was to determine the effects of endocrine and cytokine factors on the capacity of equine articular chondrocytes for transporting 2-deoxy-d-[2,6-3H] glucose and on the expression levels of GLUT1 and GLUT3. Chondrocytes maintained in monolayer culture were stimulated for 24 h with TNF-alpha (100 ng mL(-1)), IL-1beta (100 ng mL(-1)), IGF-I (20 ng mL(-1)), TGF-beta (20 ng mL(-1)) and insulin (12.5 microg mL(-1)) before measuring uptake of non-metabolizable 2-deoxyglucose in the presence and absence of the glucose transport inhibitor cytochalasin B. Polyclonal antibodies to GLUT1 and GLUT were used to compare GLUT1 and GLUT3 expression in stimulated and un-stimulated alginate encapsulated chondrocytes by Western blotting. Results indicated that 2-deoxyglucose uptake was inhibited by up to 95% in the presence of cytochalasin B suggesting that glucose uptake into equine chondrocytes is GLUT-mediated. Insulin had no effect on glucose uptake, but treatment with IGF-I, TGF-beta, IL-1beta and TNF-alpha resulted in a significant increase (>65%) in 2-deoxyglucose uptake compared to control values. GLUT1 was found to be increased in chondrocytes stimulated with all the growth factors and cytokines but GLUT 3 was only upregulated by IGF-I. The data presented support a critical role for glucose in the responses of equine articular chondrocytes to pro-inflammatory cytokines and anabolic endocrine factors.     

Age-related intestinal monosaccharides transporters expression and villus surface area increase in broiler and layer chickens

In the chicken small intestine, glucose is mainly transported by the apically located sodium/glucose cotransporter 1 (SGLT1) and the basolaterally located glucose transporter 2 (GLUT2). Fructose is transported by the apically located glucose transporter 5 (GLUT5) and similarly by GLUT2. During the early post-hatching period, the intestinal villus surface area (VSA) should be considered as an important factor related to the monosaccharide absorption capacity. Our objective here was to study intestinal monosaccharide absorption by analyzing the effects of age, diet, and breed on monosaccharide transporters and the VSA. The mRNA expression patterns of SGLT1, GLUT2 and GLUT5 genes in broiler and layer chickens were measured from the day of hatching to day 28 using the absolute quantitative real-time PCR. Both the intestinal mRNA expression levels of these genes and the VSA were affected by age. The mRNA expression levels of SGLT1 and GLUT2 were significantly increased from day 1 to day 3 and then decreased from day 3 to day 28. The expression levels of GLUT5 decreased from day 1 to day 7. The broiler chickens VSAs were significantly larger than those of the layer chickens from days 7 to 28. The effect of diet on the gene expression patterns of these monosaccharide transporters and the VSA were not significant. Our results suggest that the expression levels of these monosaccharide transporters are increased rapidly at the beginning of intestinal growth to meet the demands for monosaccharides to support the fast growth of the chick before day 7. As intestinal maturation and VSA increased, the expression levels of these monosaccharide genes decreased to a certain expression level to maintain the intestinal transport capacity and the absorption balance of all other nutrients.     

Investigation of the expression and localization of glucose transporter 4 and fatty acid translocase/CD36 in equine skeletal muscle

OBJECTIVE: To investigate the expression and localization of glucose transporter 4 (GLUT4) and fatty acid translocase (FAT/CD36) in equine skeletal muscle. SAMPLE POPULATION: Muscle biopsy specimens obtained from 5 healthy Dutch Warmblood horses. PROCEDURES: Percutaneous biopsy specimens were obtained from the vastus lateralis, pectoralis descendens, and triceps brachii muscles. Cryosections were stained with combinations of GLUT4 and myosin heavy chain (MHC) specific antibodies or FAT/CD36 and MHC antibodies to assess the fiber specific expression of GLUT4 and FAT/CD36 in equine skeletal muscle via indirect immunofluorescent microscopy. RESULTS: Immunofluorescent staining revealed that GLUT4 was predominantly expressed in the cytosol of fast type 2B fibers of equine skeletal muscle, although several type 1 fibers in the vastus lateralis muscle were positive for GLUT4. In all muscle fibers examined microscopically, FAT/CD36 was strongly expressed in the sarcolemma and capillaries. Type 1 muscle fibers also expressed small intracellular amounts of FAT/CD36, but no intracellular FAT/CD36 expression was detected in type 2 fibers. CONCLUSIONS AND CLINICAL RELEVANCE: In equine skeletal muscle, GLUT4 and FAT/CD36 are expressed in a fiber type selective manner.     

Changes in the gene expression of adiponectin and glucose transporter 12 (GLUT12) in lactating and non-lactating cows

Glucose delivery and uptake by the mammary gland is a rate‐limiting step in milk synthesis. Insulin resistance is believed to increase throughout the body following the onset of lactation. To study glucose metabolism in peak‐, late‐, and non‐lactating cows we analyzed the expression of an adipokine, namely, adiponectin, decreased insulin resistance, leptin, and a novel insulin‐responsive glucose transporter (GLUT12) in the adipose tissue and mammary gland by using real‐time polymerase chain reaction. Our results demonstrated that the mRNA level of adiponectin in the adipose tissue was greater in non‐lactating cows than in peak‐lactating cows. In the adipose tissue, there were no significant differences in the abundance of GLUT12 mRNA between the peak‐, late‐, and non‐lactating cows. In contrast, in the mammary gland, the mRNA level of GLUT12 was greater in non‐lactating cows than in peak‐ and late‐lactating cows. In the adipose tissue, the mRNA level of leptin and peroxisome proliferator‐activated receptor gamma 2 (PPARγ2) was greater in non‐lactating cows than in peak‐lactating cows. The results of the present study suggest that in lactating cows adiponectin plays an important role in insulin resistance in the adipose tissue; in the mammary gland, GLUT12 expression is believed to be an important factor for insulin‐dependent glucose metabolism.     

藏山羊脂联素基因的克隆与表达分析

为研究脂联素（AdipoQ）基因在藏山羊中的表达模式及相关功能,本试验利用生物信息学和比较基因组学方法克隆得到藏山羊AdipoQ基因序列;半定量RT-PCR和qPCR方法检测AdipoQ基因在成年藏山羊11个不同组织中的表达模式及不同脂肪组织中AdipoQ基因的相对表达量。结果显示,藏山羊AdipoQ基因编码区与牛、猪、人等哺乳动物AdipoQ基因同源性较高;AdipoQ基因在脂肪组织中表达量最高,在肌肉组织和胃中表达量较低,而在其他各组织中未检测到表达;AdipoQ基因在肾周脂肪组织中的表达量高于肠系膜脂肪组织和皮下脂肪组织中的表达量,但差异不显著（P>0.05）。本研究得到藏山羊AdipoQ基因序列、组织表达模式及不同脂肪组织中的相对表达量,为进一步研究藏山羊AdipoQ基因的功能奠定基础。     

Glucose transport in the equine hoof

Reasons for performing study: Several conditions associated with laminitis in horses are also associated with insulin resistance, which represents the failure of glucose uptake via the insulin‐responsive glucose transport proteins in certain tissues. Glucose starvation is a possible mechanism of laminitis, but glucose uptake mechanisms in the hoof are not well understood. Objectives: To determine whether glucose uptake in equine lamellae is dependent on insulin, to characterise the glucose transport mechanism in lamellae from healthy horses and ponies, and to compare this with ponies with laminitis. Methods: Study 1 investigated the effects of insulin (300 µU/ml; acute and 24 h) and various concentrations of glucose up to 24 mmol/l, on 2‐deoxy‐D‐[2,6‐³H]glucose uptake in hoof lamellar explants in vitro. Study 2 measured the mRNA expression of GLUT1 and GLUT4 transport proteins by PCR analysis in coronary band and lamellar tissue from healthy horses and ponies, ponies with insulin‐induced laminitis, and ponies suffering from chronic laminitis as a result of equine Cushing's syndrome. Results: Glucose uptake was not affected by insulin. Furthermore, the relationship between glucose concentration and glucose uptake was consistent with an insulin‐independent glucose transport system. GLUT1 mRNA expression was strong in brain, coronary band and lamellar tissue, but was weak in skeletal muscle. Expression of GLUT4 mRNA was strong in skeletal muscle, but was either absent or barely detectable in coronary band and lamellar tissue. Conclusions: The results do not support a glucose deprivation model for laminitis, in which glucose uptake in the hoof is impaired by reduced insulin sensitivity. Hoof lamellae rely on a GLUT1‐mediated glucose transport system, and it is unlikely that GLUT4 proteins play a substantial role in this tissue. Potential relevance: Laminitis associated with insulin resistance is unlikely to be due to impaired glucose uptake and subsequent glucose deprivation in lamellae.     

鸡微粒体甘油三酯转运蛋白样基因生物学特性及表达调控

旨在探究鸡微粒体甘油三酯转运蛋白样基因（MTTPL）生物学特性及其表达调控机制,为进一步探讨其在鸡肝脂质代谢中的生物学功能奠定基础。本研究首先采用PCR和测序技术,克隆MTTPL cDNA序列;利用在线软件对MTTPL蛋白结构域、三维空间结构及系统进化树进行分析;构建pcDNA3.1-MTTPL-EGFP过表达载体,通过与内质网标签蛋白的表达载体DsRed-λ共转染鸡肝癌细胞系（LMH）细胞,对MTTPL进行亚细胞定位;分别采集不同周龄卢氏绿壳蛋鸡（1日龄、1周龄、10周龄、30周龄每个周龄各8只）组织样,采用荧光定量PCR分析MTTPL基因和鸡微粒体甘油三酯转运蛋白基因（MTTP）的时空表达谱;然后用0.5、1和2 mg·kg^-1体重浓度的17 β-雌二醇分别处理海兰褐鸡（每组20只）12和24 h后,分析雌激素对肝MTTPL和MTTP表达的影响;最后用1、50、和100 nmol·L^-1 17β-雌二醇及雌激素受体拮抗剂分别处理鸡胚肝原代细胞12 h （每组3个重复）,研究雌激素调控MTTPL基因表达的作用机制。结果表明,鸡MTTPL的CDS区全长为2 646 bp,可编码881个氨基酸,与人和鸡MTTP拥有共同的祖先;定位于细胞内质网;鸡MTTPL和MTTP具有与人MTTP相同的功能域,且三维结构相似度偏差较小,分别为0.090和0.064;MTTPL基因在鸡肝和肾组织中高表达,MTTP在鸡肝、肾和小肠中高表达;在肝中,MTTPL和ApoB的表达水平随周龄的增加均显著上升（P<0.05）,而MTTP的表达仅在10周前随周龄增加显著升高（P<0.05）,而在产蛋前（10周龄）和产蛋期（30周龄）无显著变化（P>0.05）;在17β-雌二醇处理鸡12和24 h时后,MTTPL及ApoB在肝中均显著上调表达（P<0.05）,而MTTP在高浓度处理时表达量显著下调（P<0.05）,在低浓度时无显著变化;与对照组相比,雌激素可显著上调鸡胚肝原代细胞中ApoB和MTTPL的表达（P<0.05）,而MTTP表达水平无显著变化;与雌激素处理组相比,雌激素及受体ERα拮抗剂MPP共处理组MTTPL基因表达水平显著降低（P<0.05）;与MPP和雌激素共处理组相比,ERα和ERβ受体拮抗剂ICI和TAM处理组MTTPL基因表达水平无显著变化。综上所述,鸡MTTPL位于内质网中,具有与人MTTP相似的功能结构域;MTTPL和MTTP均在肝中相对高表达,且MTTPL在产蛋期鸡肝的表达显著高于产蛋前期,而MTTP无显著变化。雌激素可通过与ERα受体结合调控鸡MTTPL的表达,而MTTP不受雌激素调控。表明MTTPL可能在鸡产蛋期肝脂质代谢中发挥重要作用。     

Chicken leptin: properties and actions

Chicken leptin cDNA shows a high homology to mammalian homologous, with an expression localized in the liver and adipose tissue. It is noteworthy, that the hepatic expression is most likely associated with the primary role that this organ plays in lipogenic activity in avian species. As in mammals, chicken leptin expression is regulated by hormonal and nutritional status. This regulation is tissue-specific and with a high sensitivity in the liver compared to adipose tissue. The blood leptin levels are regulated by the nutritional state with high levels in the fed state compared to the fasted state. The recombinant chicken leptin markedly inhibits food intake as reported in mammals, suggesting the presence of an hypothalamic leptin receptor. The chicken leptin receptor has been identified and all functional motifs are highly conserved compared to mammalian homologous. Chicken leptin receptor is expressed in the hypothalamus but also in other tissues such as pancreas, where leptin inhibits insulin secretion and thus may have a key role in regulating nutrient utilization in this species.