Department of Biological Sciences, Fort Hays State University, 600 Park Street, Hays, KS 67601, USA.
Gen Comp Endocrinol. 2011 Sep 15;173(3):411-8. doi: 10.1016/j.ygcen.2011.06.011. Epub 2011 Jun 28.
Leptin is a key pleiotropic cytokine involved in regulation of energy homeostasis and immunity in mammals. In channel catfish, the presence of a partial messenger RNA sequence that encodes a leptin-like peptide (LLP) has been identified and investigated. The objectives of the present studies were to clone and characterize full-length catfish LLP gene, examine tissue expression of LLP mRNA, and determine effects of prolonged fasting and exposure to Edwardsiella ictaluri (E. ictaluri), the bacteria that causes enteric septicemia in catfish, on LLP mRNA expression. Full-length catfish LLP gene was sequenced by genome walking and by 5'- and 3'-RACE. Catfish LLP gene contained three exons with the coding region located in exons 2 and 3. The amino acid sequence of the channel catfish LLP shared very low sequence similarities with leptin of other fish species or the mammalian leptin (24-49%). Using real-time polymerase chain reaction, LLP mRNA expression was detected in various tissues including brain, stomach, spleen, heart, liver, and trunk kidney and was especially high in the liver and trunk kidney. Expression of LLP mRNA in liver and brain was similar between fish that were fasted for 30days and those that received feed daily for 30days (P>0.10). Expression of LLP mRNA was increased in liver, spleen, and trunk kidney within 48h post-exposure to E. ictaluri compared to unexposed fish (P<0.05). Based on the results of the current studies, amino acid sequence of catfish LLP is highly dissimilar to mammalian and fish leptin. Unlike in most mammals, catfish LLP expression is independent of energy status. However, the expression of catfish LLP is increased after exposure to pathogenic bacteria, which is similar to mammals. Further investigations are required to clearly define the biological function and regulation of catfish LLP.
瘦素是一种关键的多功能细胞因子，参与哺乳动物能量稳态和免疫的调节。在斑点叉尾鮰中，已经鉴定并研究了存在编码瘦素样肽（LLP）的部分信使 RNA 序列。本研究的目的是克隆和表征全长鮰鱼 LLP 基因，检测 LLP mRNA 的组织表达，并确定长时间禁食和暴露于爱德华氏菌（导致鮰鱼败血病的细菌）对 LLP mRNA 表达的影响。通过基因组步移和 5'-和 3'-RACE 对全长鮰鱼 LLP 基因进行测序。鮰鱼 LLP 基因包含三个外显子，编码区位于外显子 2 和 3。斑点叉尾鮰 LLP 的氨基酸序列与其他鱼类或哺乳动物瘦素的序列相似性非常低（24-49%）。使用实时聚合酶链反应，在包括脑、胃、脾、心、肝和躯干肾在内的各种组织中检测到 LLP mRNA 的表达，并且在肝和躯干肾中表达水平特别高。在禁食 30 天和每天喂食 30 天的鱼之间，肝和脑中的 LLP mRNA 表达相似（P>0.10）。与未暴露于鱼的鱼相比，暴露于爱德华氏菌后 48 小时内，肝、脾和躯干肾中的 LLP mRNA 表达增加（P<0.05）。根据目前的研究结果，鱼 LLP 的氨基酸序列与哺乳动物和鱼类瘦素高度不同。与大多数哺乳动物不同，鱼 LLP 的表达不依赖于能量状态。然而，在暴露于致病性细菌后，鱼 LLP 的表达增加，这与哺乳动物相似。需要进一步研究以明确定义鱼 LLP 的生物学功能和调节。
