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 (i) free amino acids shortened lifespan even more than proteins; (ii) the higher the amino acid-to-carbohydrate ratio, the shorter ants lived and the lower their lipid reserves; (iii) for the same amino acid-to-carbohydrate ratio, ants eating free amino acids had more lipid reserves than those eating whole proteins; and (iv) 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.

高蛋白饮食在诸多生物中均会缩短其寿命。其背后的机制究竟是蛋白质消化过程的能量消耗过高，还是其最终代谢产物——氨基酸具有毒性？为规避繁殖与寿命之间的生活史权衡，我们为不育工蚁提供基于完整蛋白质或游离氨基酸的饮食方案。实验结果如下：① 游离氨基酸相较于完整蛋白质，对寿命的缩短作用更为显著；② 氨基酸与碳水化合物的比值越高，工蚁的寿命越短，其脂质储备也越低；③ 在相同的氨基酸-碳水化合物比值下，饲喂游离氨基酸的工蚁相较于饲喂完整蛋白质的个体，脂质储备水平更高；④ 饲喂完整蛋白质饮食时，工蚁似乎通过优先摄取糖分来调节食物摄入；而饲喂游离氨基酸饮食时，它们则优先选择氨基酸。
为验证氨基酸组成的影响，我们设置了与工蚁外显子组（exome）氨基酸比例完全匹配的饮食方案；令人意外的是，该调整并未对工蚁寿命产生影响。
我们进一步设置了除单种氨基酸外其余氨基酸均供给不足的饮食方案，结果发现甲硫氨酸、丝氨酸、苏氨酸与苯丙氨酸的毒性尤为显著。综合所有实验结果，我们证实部分氨基酸是高蛋白饮食缩短寿命的关键调控因子。