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寿命。其背后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——氨基酸本身具有毒性？为解答该问题并规避繁殖与寿命间的生活史权衡，我们为不育工蚁饲喂以完整蛋白质或游离氨基酸为基础的日粮。研究结果显示：(1) 游离氨基酸相较完整蛋白质更能缩短工蚁寿命；(2) 氨基酸与碳水化合物的比值越高，工蚁寿命越短，其脂质储备也越低；(3) 在相同的氨基酸与碳水化合物比值条件下，饲喂游离氨基酸的工蚁相较于饲喂完整蛋白质的工蚁，拥有更高的脂质储备；(4) 饲喂完整蛋白质日粮时，工蚁似乎通过优先摄取糖分来调控食物摄入；而饲喂游离氨基酸日粮时，工蚁则优先选择摄取氨基酸。为探究氨基酸谱的影响，我们设置了氨基酸组成与工蚁外显子组匹配的日粮进行测试；令人意外的是，寿命并未受该配比变化的影响。我们进一步设置了除单种氨基酸外其余氨基酸均占比不足的日粮进行测试，发现甲硫氨酸、丝氨酸、苏氨酸与苯丙氨酸具有格外显著的毒性。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影响因子。