Department of Physiology and Immunology, Faculty of Biology, University of Barcelona, Barcelona 08028, Spain.
Fish Endocrinology Laboratory, Department of Biological and Environmental Sciences, University of Gothenburg, 40590 Gothenburg, Sweden.
Gen Comp Endocrinol. 2015 Jan 1;210:114-23. doi: 10.1016/j.ygcen.2014.10.016. Epub 2014 Nov 8.
As leptin has a key role on appetite, knowledge about leptin regulation is important in order to understand the control of energy balance. We aimed to explore the modulatory effects of adiposity on plasma leptin levels in vivo and the role of potential regulators on leptin expression and secretion in rainbow trout adipocytes in vitro. Fish were fed a regular diet twice daily ad libitum or a high-energy diet once daily at two ration levels; satiation (SA group) or restricted (RE group) to 25% of satiation, for 8weeks. RE fish had significantly reduced growth (p<0.001) and adipose tissue weight (p<0.001), and higher plasma leptin levels (p=0.022) compared with SA fish. Moreover, plasma leptin levels negatively correlated with mesenteric fat index (p=0.009). Adipocytes isolated from the different fish were treated with insulin, ghrelin, leucine, eicosapentaenoic acid or left untreated (control). In adipocytes from fish fed regular diet, insulin and ghrelin increased leptin secretion dose-dependently (p=0.002; p=0.033, respectively). Leptin secretion in control adipocytes was significantly higher in RE than in SA fish (p=0.022) in agreement with the in vivo findings, indicating that adipose tissue may contribute to the circulating leptin levels. No treatment effects were observed in adipocytes from the high-energy diet groups, neither in leptin expression nor secretion, except that leptin secretion was significantly reduced by leucine in RE fish adipocytes (p=0.025). Overall, these data show that the regulation of leptin in rainbow trout adipocytes by hormones and nutrients seems to be on secretion, rather than at the transcriptional level.
瘦素在食欲中起着关键作用，因此了解瘦素的调节对于理解能量平衡的控制非常重要。我们旨在探索肥胖对体内血浆瘦素水平的调节作用，并研究潜在调节因子对虹鳟鱼脂肪细胞中瘦素表达和分泌的体外作用。鱼被喂食正常饮食，每日两次自由进食或高能饮食，每日一次，分为两种喂养水平；饱食（SA 组）或限制（RE 组）到饱食的 25%，持续 8 周。与 SA 鱼相比，RE 鱼的生长速度显著降低（p<0.001），脂肪组织重量降低（p<0.001），血浆瘦素水平升高（p=0.022）。此外，血浆瘦素水平与肠系膜脂肪指数呈负相关（p=0.009）。从不同鱼中分离的脂肪细胞用胰岛素、胃饥饿素、亮氨酸、二十碳五烯酸或未处理（对照）处理。在正常饮食喂养的鱼的脂肪细胞中，胰岛素和胃饥饿素剂量依赖性地增加瘦素分泌（p=0.002；p=0.033）。对照脂肪细胞中，RE 鱼的瘦素分泌显著高于 SA 鱼（p=0.022），这与体内发现一致，表明脂肪组织可能有助于循环瘦素水平。在高能饮食组的脂肪细胞中，除了亮氨酸可显著降低 RE 鱼脂肪细胞的瘦素分泌（p=0.025）外，没有观察到激素和营养素对脂肪细胞中瘦素表达和分泌的治疗作用。总体而言，这些数据表明，激素和营养素对虹鳟鱼脂肪细胞中瘦素的调节似乎是在分泌水平上，而不是在转录水平上。
