Zhang Ji-Ying, Zhao Xiao-Ya, Wen Jing, Tan Song, Zhao Zhi-Jun
College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
J Exp Biol. 2016 May 1;219(Pt 9):1327-36. doi: 10.1242/jeb.138396. Epub 2016 Mar 4.
In small mammals, marked phenotypic plasticity of digestive physiology has been shown to make it easier for them to cope with energetically stressful periods, such as lactation. It has been proposed that the capacity of the gut to digest and absorb food is not the limiting factor to sustained energy intake (SusEI) during peak lactation. In this study, plasticity in energy intake and gastrointestinal morphology was examined in striped hamsters at different stages of reproduction and when raising litters of different sizes. Mechanisms associated with digestive enzymes and neuroendocrine hormones underpinning the plasticity were also examined. Females significantly increased energy intake, digestibility, digestive tract mass and the activity of stomach pepsin and small intestine maltase, sucrase and aminopeptidase in peak lactation compared with the non-productive and post-lactating periods. Further, females raising large litters significantly increased energy intake, digestibility, gastrointestinal mass and activity of digestive enzymes, and weaned heavier offspring compared with those nursing small and medium litters, indicating that the significant plasticity of digestive physiology increased reproductive performance. Agouti-related protein (AgRP) mRNA expression in the hypothalamus was up-regulated significantly in females raising large litters relative to those raising small litters. Serum leptin levels, and mRNA expression of hypothalamus neuropeptide Y (NPY) and the anorexigenic neuropeptides pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) did not differ among females raising small, medium and large litters. Leptin levels in lactation may only reflect a state of energy balance rather than being the prime driver of hyperphagia. Some hypothalamic neuropeptides, such as NPY, POMC and CART, may be involved in the limits to the SusEI during lactation.
在小型哺乳动物中，消化生理学具有显著的表型可塑性，这使其更易于应对能量紧张的时期，如哺乳期。有人提出，肠道消化和吸收食物的能力并非哺乳期能量摄入峰值期间持续能量摄入（SusEI）的限制因素。在本研究中，我们检测了不同繁殖阶段以及哺育不同窝数幼崽的条纹仓鼠的能量摄入和胃肠道形态的可塑性。我们还研究了与消化酶和神经内分泌激素相关的机制，这些机制支撑着这种可塑性。与非繁殖期和哺乳期后相比，雌性条纹仓鼠在哺乳期能量摄入、消化率、消化道质量以及胃蛋白酶、小肠麦芽糖酶、蔗糖酶和氨肽酶的活性均显著增加。此外，与哺育中小窝数幼崽的雌性相比，哺育大窝数幼崽的雌性能量摄入、消化率、胃肠道质量和消化酶活性显著增加，断奶后代体重更重，这表明消化生理学的显著可塑性提高了繁殖性能。与哺育小窝数幼崽的雌性相比，哺育大窝数幼崽的雌性下丘脑刺鼠相关蛋白（AgRP）mRNA表达显著上调。哺育小、中、大窝数幼崽的雌性血清瘦素水平以及下丘脑神经肽Y（NPY）、厌食性神经肽阿黑皮素原（POMC）和可卡因及苯丙胺调节转录物（CART）的mRNA表达没有差异。哺乳期的瘦素水平可能仅反映能量平衡状态，而非贪食的主要驱动因素。一些下丘脑神经肽，如NPY、POMC和CART，可能参与了哺乳期SusEI所受的限制。
