A concept of dietary dipeptides: A step to resolve the problem of amino acid availability in the early life of vertebrates
A concept of dietary dipeptides: A step to resolve the problem of amino acid availability in the early life of vertebrates
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DOI：
10.1242/jeb.01689
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发表时间：
2005-08-01
影响因子：
2.8
通讯作者：
Lee, KJ
中科院分区：
文献类型：
--
作者：
Dabrowski, K;Terjesen, BF;Lee, KJ
当以游离、二肽或蛋白质分子形式提供膳食氨基酸时，研究人员通过检测肌肉游离氨基酸（FAA）池和酶活性与生长反应的关系，验证了膳食二肽方法将提高对增长最快的脊椎动物——硬骨鱼对氨基酸利用的理解。我们在鱼类中提出了第一个证据，在对合成二肽饮食的反应中，肌肉FAA随着生长速度和特定肽的氨基酸可用性而变化。我们发现，与蛋白质饲料相比，二肽饲料显著减少了虹鳟鱼肌肉中必需的FAA（3-10倍）。以二肽为基础的饮食不含脯氨酸，导致肌肉游离脯氨酸和羟脯氨酸减少10-27倍。饲喂以faa为基础的饲粮或以多肽为基础的饲粮可指示胶原蛋白周转（Hyp/Pro比），且饲粮处理之间存在显著差异。检测到吡啶-5-羧酸还原酶（P5C）活性，表明P5C可能改善脯氨酸缺乏，但谷氨酸合成不能维持肌肉中游离脯氨酸水平。这一发现将推动对脯氨酸是否像哺乳动物和鸟类一样在幼鱼中有条件地不可或缺的测试。本研究表明，完全以二肽形式给予的氨基酸可以维持鱼类的生长，产生与饲料水平一致的肌肉FAA和酶反应，并识别出限制生长的氨基酸。对这些因素的理解需要一种饮食配方，这种配方将提高确定脊椎动物早期生命阶段氨基酸需求的准确性。
The premise that a dietary dipeptide approach will improve the understanding of amino acid utilization in the fastest-growing vertebrate, the teleost fish, was tested by examining the muscle free amino acid (FAA) pool and enzyme activities, in concert with growth response, when dietary amino acids were provided in free, dipeptide or protein molecular forms. We present the first evidence in fish that, in response to a synthetic dipeptide diet, muscle FAA varies as a result of both growth rate and amino acid availability of specific peptides. We demonstrate significantly diminished muscle indispensable FAA (3-10-fold) in rainbow trout alevins fed a dipeptide-based diet compared with a protein-based diet. The dipeptide-based diet did not contain proline, resulting in 10-27-fold less muscle free proline and hydroxyproline in alevins. The response of alevins fed FAA-based or peptide-based diets can be indicative of collagen turnover (Hyp/Pro ratio) and showed significant differences between dietary treatments. Pyrroline-5-carboxylate (P5C) reductase activity was detected, suggesting that P5C may ameliorate proline deficiency, but synthesis from glutamate could not maintain free proline levels in muscle. This finding will provide an impetus to test whether proline is conditionally indispensable in young fish, as in mammals and birds. This study shows that amino acids given entirely as dipeptides can sustain fish growth, result in muscle FAA and enzyme responses in line with dietary levels and identify growth-limiting amino acids. The understanding of these factors necessitates a diet formulation that will improve the accuracy of determining amino acid requirements in the early life stages of vertebrates.