Data from: Parsing the life-shortening effects of dietary protein: effects of individual amino acids

High-protein diets shorten lifespan in many organisms. Is it because protein digestion is energetically costly or because the final products (the amino acids) are harmful? To answer this question while circumventing the life-history trade-off between reproduction and longevity, we fed sterile ant workers on diets based on whole proteins or free amino acids. We found that 1) free amino acids shortened lifespan even more than proteins; 2) the higher the amino acid-to-carbohydrate ratio, the shorter ants lived and the lower their lipid reserves; 3) for the same amino acid-to-carbohydrate ratio, ants eating free amino acids had more lipid reserves than those eating whole proteins; 4) on whole protein diets, ants seem to regulate food intake by prioritizing sugar, while on free amino acid diets they seem to prioritize amino acids. To test the effect of the amino acid profile, we tested diets containing proportions of each amino acid that matched the ant’s exome; surprisingly, longevity was unaffected by this change. We further tested diets with all amino acids under-represented except one, finding that methionine, serine, threonine and phenylalanine are especially harmful. All together, our results show certain amino acids are key elements behind the high-protein diet reduction in lifespan.

高蛋白饮食在多种生物中均可缩短其寿命。该现象的成因究竟是蛋白质消化过程的能量消耗过高，还是其最终产物——氨基酸（amino acids）具有毒性？为解答该问题，同时规避繁殖与寿命之间的生活史权衡效应，我们以完整蛋白质或游离氨基酸为基础制备饲料，饲养无菌工蚁。我们发现：1）游离氨基酸相比完整蛋白质更能显著缩短蚂蚁的寿命；2）氨基酸与碳水化合物的比值越高，蚂蚁的寿命越短，其脂质储备也越低；3）在相同的氨基酸-碳水化合物比值下，饲喂游离氨基酸的蚂蚁比饲喂完整蛋白质的蚂蚁拥有更多的脂质储备；4）在饲喂完整蛋白质的饲料时，蚂蚁似乎通过优先摄取糖类来调节食物摄入量，而在饲喂游离氨基酸的饲料时，它们则优先选择氨基酸。为验证氨基酸组成的影响，我们制备了各氨基酸比例与蚂蚁外显子组（exome）匹配的饲料；令人意外的是，寿命并未因这一调整发生改变。我们进一步测试了除某一种氨基酸外其余所有氨基酸含量均不足的饲料，结果发现甲硫氨酸（methionine）、丝氨酸（serine）、苏氨酸（threonine）与苯丙氨酸（phenylalanine）具有显著的毒性。综合来看，我们的研究结果表明，部分氨基酸是高蛋白饮食缩短寿命的关键影响因子。