Mechanisms of dietary control of the transsulfuration pathway and increased endogenous hydrogen sulfide production

摘要 卡路里限制(CR)，或在没有营养不良的情况下强制减少食物摄入，对 多个实验生物体中的糖脂平衡、急性应激抵抗和寿命。 限制饮食中含硫氨基酸蛋氨酸和半胱氨酸，又称蛋氨酸限制(MR) 在实验中的啮齿动物中得到了大部分相同的好处，但没有强制限制卡路里，因此 可能是由不同的潜在机制造成的。 在之前的资助期间，我们发现了一种新的多效性益处的分子机制。 CR和MR的共同之处：通过增加内源硫化氢气体(H2S)的产量 进化上保守的跨硫途径(TSP)。特别是，我们发现了以下限制 半胱氨酸的摄入增加了TSP酶胱硫醚γ裂解酶(Cgl)的表达，导致 硫化氢。 直到最近，人们才开始意识到硫化氢对健康的好处。转基因CGL基因敲除小鼠 缺乏产生足够的内源性硫化氢的能力会导致高血压和易感性 神经退行性疾病，而外源性硫化氢添加可以作为血管扩张剂、免疫调节剂和 在实验啮齿动物中使用神经保护剂，甚至在低等生物中延长寿命。我们的发现是 增加内源性硫化氢对于CR的两个主要健康益处是必要和充分的，即 更强的抗压性和跨越进化边界的寿命延长，巩固了这样一种概念 增加内源性硫化氢对许多健康结果是非常有益的。我们的发现也证明了 这项建议的主要目标，即了解增加内源性 硫化氢的产生，并将这些发现应用于具有高度临床相关性的领域。 在这里，我们建议检验这样一种假设，即饮食中蛋白质含量低，尤其是硫氨基含量低 蔬菜蛋白中发现的蛋氨酸和半胱氨酸，会导致CGL表达增加和 硫化氢的产生部分是通过激活氨基酸剥夺传感器GCN2来实现的。我们还将测试 假设内源性硫化氢产生的底物来自自噬，将这个效应连接到 长寿首次给硫化氢生产带来好处。最后，我们将探讨硫化氢在保护中的新作用 抗电离辐射的造血干细胞，并测试一种增加硫化氢输送的新机制 对骨髓等组织涉及循环CGL蛋白的内分泌作用。

SUMMARY Calorie restriction (CR), or enforced reduced food intake without malnutrition, is highly beneficial on glucose and lipid homeostasis, acute stress resistance and longevity in multiple experimental organisms. Restriction of dietary sulfur amino acids methionine and cysteine, known as methionine restriction (MR), also results in most of the same benefits in experimental rodents, but without enforced calorie restriction, and thus potentially by a different underlying mechanism. In the prior funding period we discovered a novel molecular mechanism underlying pleiotropic benefits common to both CR and MR: increased production of endogenous hydrogen sulfide gas (H2S) via the evolutionarily conserved transsulfuration pathway (TSP). In particular, we found that restriction specifically of cysteine intake increased expression of the TSP enzyme cystathionine γ-lyase (CGL), resulting in increased H2S. The health benefits of H2S have only recently begun to be appreciated. Engineered CGL knockout mice lacking the ability to produce adequate endogenous H2S have high blood pressure and susceptibility to neurodegenerative disease, while exogenous H2S addition can act as a vasodilator, immunomodulator, and neuroprotectant in experimental rodents, and even increase lifespan in lower organisms. Our finding that increased endogenous H2S is necessary and sufficient for two of the major health benefits of CR, namely increased stress resistance and extended longevity across evolutionary boundaries, cements the notion that increased endogenous H2S is highly beneficial to numerous health outcomes. Our findings also justify the major goal of this proposal, namely to understand novel interventional approaches to increasing endogenous H2S production, and applying of these findings to areas of high clinical relevance. Here we propose to test the hypothesis that diets low in protein, and particular low in the sulfur amino acids methionine and cysteine as found in vegetable-derived proteins, result in increased CGL expression and H2S production in part through activation of the amino acid deprivation sensor GCN2. We will also test the hypothesis that the substrate for endogenous H2S production is derived from autophagy, linking this effector of longevity benefits to H2S production for the first time. Finally, we will explore the novel role of H2S in protection of hematopoietic stem cells against ionizing radiation, and test a novel mechanism of increasing H2S delivery to tissues such as bone marrow involving endocrine action of circulating CGL protein.