Department of Biology, University of Bergen, Bergen High Technology Centre, Bergen, Norway.
Gen Comp Endocrinol. 2013 Mar 1;183:83-8. doi: 10.1016/j.ygcen.2012.09.027. Epub 2012 Nov 27.
Atlantic salmon was used to investigate the effect of long- and short-term dietary ration on the tissue expression levels of leptins. Compared to ad libitum fed fish (0.8-3kg), 6months of dietary restriction (60%) resulted in significantly lower body mass and adiposity, but did not produce a clear effect on the expression levels of either lepa1 or lepa2. For visceral adipose tissue, however, the long-term data indicated that season appeared to influence the levels of lepa1 expression of ad libitum fed fish, but not feed-restricted fish. By comparing the total levels of leptin mRNA expression to the tissue lipid contents, we found that only white muscle lepa1 showed the positive relation reported in mammals. The existence of a postprandial leptin response in Atlantic salmon parr was determined in fed and unfed parr over a 24h period. In contrast to other animals, lepa1 peaked in the unfed fish, initially in the white muscle at 6h, and subsequently in belly flap, liver and visceral adipose tissue at 9h. Only lepa2 in the visceral adipose tissue of fed fish showed a similar 9h peak, but at an order of magnitude lower than lepa1 in the unfed fish. These data reveal that short-term feed restriction causes a latent (6-9h) upregulation of lepa-type genes in the fatty tissues of Atlantic salmon, a finding that contrasts the mammalian response.
大西洋鲑被用来研究长期和短期饮食配比对瘦素组织表达水平的影响。与自由采食（0.8-3kg）的鱼相比，6 个月的饮食限制（60%）导致体重和肥胖率显著降低，但对 lepa1 或 lepa2 的表达水平没有明显影响。然而，对于内脏脂肪组织，长期数据表明，季节似乎影响自由采食鱼的 lepa1 表达水平，但对限制饮食的鱼没有影响。通过将瘦素 mRNA 表达的总水平与组织脂质含量进行比较，我们发现只有白色肌肉的 lepa1 表现出与哺乳动物报道的正相关关系。在 fed 和 unfed 幼鲑中，确定了大西洋鲑幼鲑餐后瘦素反应的存在，持续 24 小时。与其他动物不同，lepa1 在未喂食的鱼中达到峰值，最初在 6 小时时在白色肌肉中，随后在 9 小时时在腹部瓣、肝脏和内脏脂肪组织中达到峰值。只有 fed 鱼的内脏脂肪组织中的 lepa2 表现出类似的 9 小时峰值，但幅度低于未喂食鱼中的 lepa1。这些数据表明，短期饮食限制导致大西洋鲑脂肪组织中 lepa 型基因的潜伏（6-9 小时）上调，这与哺乳动物的反应形成对比。
