Hepato-Neuro Laboratory, CRCHUM, Université de Montréal, Montréal, Canada.
Synlogic Inc, Cambridge, MA, USA.
Liver Int. 2021 May;41(5):1020-1032. doi: 10.1111/liv.14815. Epub 2021 Mar 1.
Hyperammonemia associated with chronic liver disease (CLD) is implicated in the pathogenesis of hepatic encephalopathy (HE). The gut is a major source of ammonia production that contributes to hyperammonemia in CLD and HE and remains the primary therapeutic target for lowering hyperammonemia. As an ammonia-lowering strategy, Escherichia coli Nissle 1917 bacterium was genetically modified to consume and convert ammonia to arginine (S-ARG). S-ARG was further modified to additionally synthesize butyrate (S-ARG + BUT). Both strains were evaluated in bile-duct ligated (BDL) rats; experimental model of CLD and HE.
One-week post-surgery, BDLs received non-modified EcN (EcN), S-ARG, S-ARG + BUT (3x10 CFU/day) or vehicle until sacrifice at 3 or 5 weeks. Plasma (ammonia/pro-inflammatory/liver function), liver fibrosis (hydroxyproline), liver mRNA (pro-inflammatory/fibrogenic/anti-apoptotic) and colon mRNA (pro-inflammatory) biomarkers were measured post-sacrifice. Memory, motor-coordination, muscle-strength and locomotion were assessed at 5 weeks.
In BDL-Veh rats, hyperammonemia developed at 3 and further increased at 5 weeks. This rise was prevented by S-ARG and S-ARG + BUT, whereas EcN was ineffective. Memory impairment was prevented only in S-ARG + BUT vs BDL-Veh. Systemic inflammation (IL-10/MCP-1/endotoxin) increased at 3 and 5 weeks in BDL-Veh. S-ARG + BUT attenuated inflammation at both timepoints (except 5-week endotoxin) vs BDL-Veh, whereas S-ARG only attenuated IP-10 and MCP-1 at 3 weeks. Circulating ALT/AST/ALP/GGT/albumin/bilirubin and gene expression of liver function markers (IL-10/IL-6/IL-1β/TGF-β/α-SMA/collagen-1α1/Bcl-2) were not normalized by either strain. Colonic mRNA (TNF-α/IL-1β/occludin) markers were attenuated by synthetic strains at both timepoints vs BDL-Veh.
S-ARG and S-ARG + BUT attenuated hyperammonemia, with S-ARG + BUT additional memory protection likely due to greater anti-inflammatory effect. These innovative strategies, particularly S-ARG + BUT, have potential to prevent HE.
慢性肝脏疾病（CLD）相关的高血氨与肝性脑病（HE）的发病机制有关。肠道是氨生成的主要来源，这导致 CLD 和 HE 中的高血氨，并仍然是降低血氨的主要治疗靶点。作为一种降低血氨的策略，大肠杆菌 Nissle 1917 菌被遗传修饰为消耗和将氨转化为精氨酸（S-ARG）。S-ARG 进一步被修饰为另外合成丁酸（S-ARG+BUT）。这两种菌株都在胆管结扎（BDL）大鼠中进行了评估；CLD 和 HE 的实验模型。
手术后一周，BDL 接受非修饰 EcN（EcN）、S-ARG、S-ARG+BUT（每天 3x10 CFU）或载体，直至 3 或 5 周时处死。牺牲后测量血浆（氨/促炎/肝功能）、肝纤维化（羟脯氨酸）、肝 mRNA（促炎/纤维形成/抗凋亡）和结肠 mRNA（促炎）生物标志物。5 周时评估记忆、运动协调、肌肉力量和运动。
在 BDL-Veh 大鼠中，3 周时出现高血氨，5 周时进一步增加。S-ARG 和 S-ARG+BUT 可预防这种增加，而 EcN 无效。只有 S-ARG+BUT 可预防 5 周时与 BDL-Veh 相比的记忆障碍。全身炎症（IL-10/MCP-1/内毒素）在 3 周和 5 周时在 BDL-Veh 中增加。S-ARG+BUT 在两个时间点均减轻炎症（除了 5 周时的内毒素）与 BDL-Veh 相比，而 S-ARG 仅在 3 周时减轻 IP-10 和 MCP-1。两种菌株均未使循环 ALT/AST/ALP/GGT/白蛋白/胆红素和肝功能标志物的基因表达（IL-10/IL-6/IL-1β/TGF-β/α-SMA/胶原-1α1/Bcl-2）正常化。与 BDL-Veh 相比，合成菌株在两个时间点均减轻结肠 mRNA（TNF-α/IL-1β/occludin）标志物。
S-ARG 和 S-ARG+BUT 减轻了高血氨，S-ARG+BUT 还具有额外的记忆保护作用，可能是由于抗炎作用更强。这些创新策略，特别是 S-ARG+BUT，具有预防 HE 的潜力。
