Impact of Aldh1l1 Knockout On Metabolic Phenotype in Mouse Liver

Abstract

ALDH1L1 (10‐formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism, is highly expressed in liver. This enzyme metabolizes 10‐formyltetrahydrofolate to produce tetrahydrofolate (THF) and is involved in the regulation of reduced folate pools, de novo purine biosynthesis, and the flux of folate‐bound methyl groups. The goal of this study was to survey the metabolic impact of the Aldh1l1 gene loss in mouse liver. Aldh1l1−/− (KO) mice were generated using gene‐targeted ES cell clone (C57BL/6N background) from KOMP repository. KO mice were viable and did not show obvious phenotypic differences from the wild type animals. Flash frozen hepatic tissues from 12–14 weeks old Aldh1l1+/+and Aldh1l1−/− mice were profiled to identify metabolite changes and define associated pathways. In this study, mice were kept on standard AIN‐93 diet with 2.2 ppm of folic acid. Global metabolomic analysis was performed by Metabolon Inc. (Durham, NC) using Ultrahigh Performance Liquid Chromatography‐Tandem Mass Spectroscopy (UPLC‐MS/MS) for five samples from each group. This analysis has identified 628 known metabolites and principal component analysis demonstrated good segregation between the two genotypes. The difference for 91 metabolites was statistically significant between the two groups, with 31 compounds being decreased and 60 being elevated in Aldh1l1−/− compared to the Aldh1l1+/+ mice. This analysis indicated that KO mice might experience functional folate deficiency. Specifically, the intermediate of the histidine degradation pathway serving as a marker of folate deficiency, formiminoglutamate, was increased more than 15‐fold in KO mice. Furthermore, tissue folic acid and dihydrofolate were strongly depleted (more than 2‐fold and 5‐fold, respectively) in these animals, which would be in agreement with folate deficiency. In addition, a 2‐fold decrease in glycine was detected in KO mice. Strong drop in several glycine conjugates was also observed in the KO genotype, which is apparently associated with the deficiency of glycine. The depletion of glycine was likely caused by the decrease of the THF‐dependent synthesis of glycine from serine, with the underlying basis for this phenomenon being the decrease of the THF pool observed in Aldh1l1−/− mice. The depletion of glycine and/or folate could be the cause of several secondary effects on metabolism including the decrease in glutathione, lower availability of ascorbate, impaired mitochondrial lipid metabolism, oxidative stress, and less efficient remediation of toxic products. Our data also imply a compromised liver function in the KO mice and associated changes in gut microbiome activity. Overall, our study indicated significant metabolic perturbations caused by the Aldh1l1 gene knockout.Support or Funding InformationNIH R01DK 54388This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.