Pediatric Metabolic Unit, Pediatrics, Woman-Mother-Child Department, University of Lausanne and University Hospital of Lausanne, Switzerland.
Pediatric Metabolic Unit, Pediatrics, Woman-Mother-Child Department, University of Lausanne and University Hospital of Lausanne, Switzerland.
Mol Genet Metab. 2021 Jun;133(2):157-181. doi: 10.1016/j.ymgme.2021.03.017. Epub 2021 Apr 18.
Glutaric aciduria type I (GA-I, OMIM # 231670) is an inborn error of metabolism caused by a deficiency of glutaryl-CoA dehydrogenase (GCDH). Patients develop acute encephalopathic crises (AEC) with striatal injury most often triggered by catabolic stress. The pathophysiology of GA-I, particularly in brain, is still not fully understood. We generated the first knock-in rat model for GA-I by introduction of the mutation p.R411W, the rat sequence homologue of the most common Caucasian mutation p.R402W, into the Gcdh gene of Sprague Dawley rats by CRISPR/CAS9 technology. Homozygous Gcdh rats revealed a high excretor phenotype, but did not present any signs of AEC under normal diet (ND). Exposure to a high lysine diet (HLD, 4.7%) after weaning resulted in clinical and biochemical signs of AEC. A significant increase of plasmatic ammonium concentrations was found in Gcdh rats under HLD, accompanied by a decrease of urea concentrations and a concomitant increase of arginine excretion. This might indicate an inhibition of the urea cycle. Gcdh rats exposed to HLD showed highly diminished food intake resulting in severely decreased weight gain and moderate reduction of body mass index (BMI). This constellation suggests a loss of appetite. Under HLD, pipecolic acid increased significantly in cerebral and extra-cerebral liquids and tissues of Gcdh rats, but not in WT rats. It seems that Gcdh rats under HLD activate the pipecolate pathway for lysine degradation. Gcdh rat brains revealed depletion of free carnitine, microglial activation, astroglyosis, astrocytic death by apoptosis, increased vacuole numbers, impaired OXPHOS activities and neuronal damage. Under HLD, Gcdh rats showed imbalance of intra- and extracellular creatine concentrations and indirect signs of an intracerebral ammonium accumulation. We successfully created the first rat model for GA-I. Characterization of this Gcdh strain confirmed that it is a suitable model not only for the study of pathophysiological processes, but also for the development of new therapeutic interventions. We further brought up interesting new insights into the pathophysiology of GA-I in brain and periphery.
谷氨酸戊二酸 1 型尿症（GA-I，OMIM#231670）是一种由于戊二酰辅酶 A 脱氢酶（GCDH）缺乏引起的先天性代谢错误。患者最常因分解代谢应激而出现急性脑病危象（AEC）伴纹状体损伤。GA-I 的病理生理学，特别是在大脑中的病理生理学，尚未完全阐明。我们通过 CRISPR/CAS9 技术将最常见的白种人突变 p.R402W 的大鼠序列同源物 p.R411W 引入 Sprague Dawley 大鼠的 Gcdh 基因，从而产生了第一个 GA-I 基因敲入大鼠模型。纯合 Gcdh 大鼠表现出高排泄表型，但在正常饮食（ND）下没有出现任何 AEC 迹象。断奶后暴露于高赖氨酸饮食（HLD，4.7%）会导致 AEC 的临床和生化迹象。在 HLD 下，Gcdh 大鼠的血浆铵浓度显著升高，同时尿素浓度降低，精氨酸排泄增加。这可能表明尿素循环受到抑制。暴露于 HLD 的 Gcdh 大鼠表现出极高的摄食量减少，导致体重严重减轻和体重指数（BMI）适度降低。这种情况表明食欲减退。在 HLD 下，Gcdh 大鼠大脑和脑外液体和组织中的哌可酸显著增加，但 WT 大鼠没有增加。似乎 HLD 下的 Gcdh 大鼠激活了赖氨酸降解的哌可酸途径。在 HLD 下，Gcdh 大鼠大脑中的游离肉碱耗尽，小胶质细胞激活，星形胶质细胞增生，星形胶质细胞凋亡，空泡数量增加，OXPHOS 活性受损，神经元损伤。在 HLD 下，Gcdh 大鼠表现出细胞内和细胞外肌酸浓度失衡以及颅内氨积累的间接迹象。我们成功地创建了第一个 GA-I 大鼠模型。对这种 Gcdh 品系的特征描述证实，它不仅是研究病理生理过程的合适模型，也是开发新治疗干预措施的合适模型。我们进一步深入了解了 GA-I 在大脑和外周的病理生理学。
