Histone β-hydroxybutyrylation underlies the reno-protective effect of β-hydroxybutyrate in hypertensive Dahl Salt-Sensitive Rats [ATAC-seq]

Background: Previously, we demonstrated that the ketone body, β-hydroxybutyrate, is a potent antihypertensive and reno-protective metabolite in Dahl Salt-Sensitive rats. However, the mechanism by which β-hydroxybutyrate confers these beneficial effects is understudied. Here we focused on determining whether the reno-protective effect of β-hydroxybutyrate is due to its known ability to epigenetically remodel chromatin via histone β-hydroxybutyrylation. Methods: We used the same animal protocol previously used for the discovery of the renoprotective effect of β-hydroxybutyrate. Briefly, post-weaning, male and female Dahl Salt-Sensitive rats were split into two groups and supplemented with or without 1,3-Butanediol for 6 weeks. At euthanasia, circulating β-hydroxybutyrate was quantitated. Renal homogenates were examined for histone 3 lysine 9 β-hydroxybutyrylation, chromatin occupancy, transcriptomic and proteomic profiles with validations. Results: Rats supplemented with 1,3-butanediol had higher circulating β-hydroxybutyrate, renal histone β-hydroxybutyrylation and significant remodeling of chromatin. Notably, regions of the genome associated with lipid catabolism were predominantly in an open chromatin configuration, leading to active transcription and translation. The most highly upregulated gene actively transcribed and translated was 3-hydroxy-3-methyglutaryl CoA Synthase 2 (Hmgcs2), a gene responsible for the biosynthesis of β-hydroxybutyrate in mitochondria. In contrast, regions with more compact chromatin structures contained immune function genes, protein tyrosine phosphatase receptor type C (Ptprc) and lymphocyte cytosolic protein 1 (Lcp1), which were suppressed. Conclusions: These results reveal that renal epigenetic histone β-hydroxybutyrylation is a novel mechanism by which transcriptional regulation of both energy metabolism and immune function occur concomitantly and contribute to renoprotection in the hypertensive Dahl rat.研究背景：既往我们已证实，酮体β-羟基丁酸（β-hydroxybutyrate）在Dahl盐敏感性大鼠（Dahl Salt-Sensitive rats）中是一种强效的抗高血压及肾保护代谢物。然而，β-羟基丁酸发挥上述有益作用的具体机制仍有待深入研究。本研究旨在探讨β-羟基丁酸的肾保护作用是否与其已知的通过组蛋白β-羟基丁酰化进行染色质表观遗传重塑的能力相关。 研究方法：我们沿用了此前用于发现β-羟基丁酸肾保护作用的动物实验方案。简言之，断奶后的雄性和雌性Dahl盐敏感性大鼠被分为两组，分别补充1,3-丁二醇（1,3-Butanediol）或不补充，干预周期为6周。在安乐处死时，检测循环中β-羟基丁酸的水平。对肾脏匀浆进行组蛋白H3赖氨酸9β-羟基丁酰化、染色质占用情况、转录组和蛋白质组谱分析，并开展验证实验。 研究结果：补充1,3-丁二醇的大鼠循环中β-羟基丁酸水平更高，肾脏组蛋白β-羟基丁酰化水平也显著升高，且染色质发生明显重塑。值得注意的是，与脂质分解代谢相关的基因组区域主要处于开放染色质构象，从而实现活跃的转录与翻译过程。上调幅度最高的活跃转录翻译基因为3-羟基-3-甲基戊二酰辅酶A合酶2（3-hydroxy-3-methyglutaryl CoA Synthase 2，Hmgcs2），该基因负责线粒体中β-羟基丁酸的生物合成。与之相反，染色质结构更紧密的区域则包含免疫功能相关基因：蛋白酪氨酸磷酸酶受体类型C（protein tyrosine phosphatase receptor type C，Ptprc）和淋巴细胞胞浆蛋白1（lymphocyte cytosolic protein 1，Lcp1），这些基因的表达受到抑制。 研究结论：上述结果表明，肾脏表观遗传组蛋白β-羟基丁酰化是一种全新的机制，可同时实现能量代谢与免疫功能的转录调控，并在高血压性Dahl大鼠模型中发挥肾保护作用。