Dalmolin Camila, Almeida Daniela Volcan, Figueiredo Marcio Azevedo, Marins Luis Fernando
Laboratório de Biologia Molecular, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande - FURG, Av. Itália km 8, Rio Grande, RS, 96203-900, Brazil.
Fish Physiol Biochem. 2015 Oct;41(5):1131-41. doi: 10.1007/s10695-015-0074-5. Epub 2015 May 20.
The biological actions of growth hormone (GH) are pleiotropic, including growth promotion, energy mobilization, gonadal development, appetite, and social behavior. The regulatory network for GH is complex and includes many central and peripheral endocrine factors as well as that from the environment. It is known that GH transgenesis results in increased growth, food intake, and consequent metabolic rates in fishes. However, the manner in which GH transgenesis alters the energetic metabolism in fishes has not been well explored. In order to elucidate these consequences, we examined the effect of GH overexpression on appetite control mechanisms in a transgenic zebrafish (Danio rerio) model. To this, we analyzed feeding behavior and the expression of the main appetite-related genes in two different feeding periods (fed and fasting) in non-transgenic (NT) and transgenic (T) zebrafish as well as glycaemic parameters of them. Our initial results have shown that NT males and females present the same feeding behavior and expression of main appetite-controlling genes; therefore, the data of both sexes were properly grouped. Following grouped data analyses, we compared the same parameters in NT and T animals. Feeding behavior results have shown that T animals eat significantly more and faster than NT siblings. Gene expression results pointed out that gastrointestinal (GT) cholecystokinin has a substantial contribution to the communication between peripheral and central control of food intake. Brain genes expression analyses revealed that T animals have a down-regulation of two strong and opposite peptides related to food intake: the anorexigenic proopiomelanocortin (pomc) and the orexigenic neuropeptide Y (npy). The down-regulation of pomc in T when compared with NT is an expected result, since the decrease in an anorexigenic factor might keep the transgenic fish hungry. The down-regulation of npy seemed to be contradictory at first, but if we consider the GH's capacity to elevate blood glucose, and that NPY is able to respond to humoral factors like glucose, this down-regulation makes sense. In fact, our last experiment showed that transgenics presented elevated blood glucose levels, confirming that npy might responded to this humoral factor. In conclusion, we have shown that GT responds to feeding status without interference of transgenesis, whereas brain responds to GH transgenesis without any effect of treatment. It is clear that transgenic zebrafish eat more and faster, and it seems that it occurs due to pomc down-regulation, since npy might be under regulation of the humoral factor glucose.
生长激素（GH）的生物学作用具有多效性，包括促进生长、动员能量、性腺发育、调节食欲以及影响社会行为。GH的调控网络复杂，涉及许多中枢和外周内分泌因子以及环境因素。已知GH转基因会导致鱼类生长加快、食物摄入量增加以及代谢率随之提高。然而，GH转基因改变鱼类能量代谢的方式尚未得到充分研究。为了阐明这些影响，我们在转基因斑马鱼（Danio rerio）模型中研究了GH过表达对食欲控制机制的影响。为此，我们分析了非转基因（NT）和转基因（T）斑马鱼在两个不同摄食期（喂食和禁食）的摄食行为、主要食欲相关基因的表达以及它们的血糖参数。我们的初步结果表明，NT雄性和雌性具有相同的摄食行为和主要食欲控制基因的表达；因此，将两性的数据进行了合理分组。在对分组数据进行分析后，我们比较了NT和T动物的相同参数。摄食行为结果表明，T动物比NT同胞吃得更多、更快。基因表达结果指出，胃肠道（GT）胆囊收缩素在食物摄入的外周和中枢控制之间的通讯中起重要作用。脑基因表达分析显示，T动物中与食物摄入相关的两种作用强烈且相反的肽出现下调：厌食性的促肾上腺皮质激素原（pomc）和食欲神经性肽Y（npy）。与NT相比，T中pomc的下调是预期结果，因为厌食因子的减少可能使转基因鱼保持饥饿状态。npy的下调起初似乎相互矛盾，但如果考虑到GH升高血糖的能力，并且NPY能够对葡萄糖等体液因子做出反应，那么这种下调就有意义了。事实上，我们的最后一项实验表明转基因鱼的血糖水平升高，证实npy可能对这种体液因子做出了反应。总之，我们已经表明，GT对摄食状态做出反应而不受转基因的干扰，而脑对GH转基因做出反应而不受处理的任何影响。很明显，转基因斑马鱼吃得更多、更快，似乎这是由于pomc下调所致，因为npy可能受体液因子葡萄糖的调节。
