Research Article Details

Article ID: A06259
PMID: 32951289
Source: Physiol Rep
Title: Targeted and untargeted metabolomics provide insight into the consequences of glycine-N-methyltransferase deficiency including the novel finding of defective immune function.
Abstract: Fatty liver disease is increasing along with the prevalence of obesity and type-2 diabetes. Hepatic fibrosis is a major health complication for which there are no efficacious treatment options available. A better understanding of the fundamental mechanisms that contribute to the accumulation of fibrosis is needed. Glycine-N-methyltransferase (GNMT) is a critical enzyme in one-carbon metabolism that serves to regulate methylation and remethylation reactions. GNMT knockout (GNMT-/- ) mice display spontaneous hepatic fibrosis and later develop hepatocellular carcinoma. Previous literature supports the idea that hypermethylation as a consequence of GNMT deletion contributes to the hepatic phenotype observed. However, limited metabolomic information is available and the underlying mechanisms that contribute to hepatic fibrogenesis in GNMT-/- mice are still incomplete. Therefore, our goals were to use dietary intervention to determine whether increased lipid load exacerbates steatosis and hepatic fibrosis in this model and to employ both targeted and untargeted metabolomics to further understand the metabolic consequences of GNMT deletion. We find that GNMT mice fed high-fat diet do not accumulate more lipid or fibrosis in the liver and are in fact resistant to weight gain. Metabolomics analysis confirmed that pan-hypermethylation occurs in GNMT mice resulting in a depletion of nicotinamide intermediate metabolites. Further, there is a disruption in tryptophan catabolism that prevents adequate immune cell activation in the liver. The chronic cellular damage cannot be appropriately cleared due to a lack of immune checkpoint activation. This mouse model is an excellent example of how a disruption in small molecule metabolism can significantly impact immune function.
DOI: 10.14814/phy2.14576

Strategy ID Therapy Strategy Synonyms Therapy Targets Therapy Drugs
S02 Enhance lipid metabolism triglyceride-lowering; lipid tolerance; lipid metabolism 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) inhibitor; Decreases intestinal cholesterol absorption; FXR agonist; ACC inhibitor; FAS inhibitor; DGAT2 inhibitor; SCD-1 inhibitor Atorvastatin; Ezetimibe; Obeticholic Acid; GS-9674; GS-0976; TVB-2640; IONIS-DGAT2rx; Aramchol; Details
S03 Anti-fibrosis fibrosis Angiotensin Receptor Blocker (ARB); CCR2/CCR5 antagonist; Thyroid receptor β agonist; PEGylated human FGF21 analogue; Monoclonal antibody to lysyl oxidase-like 2 (LOXL2); Galectin-3 inhibitor; FGF19 variant Losartan; Cenicriviroc; VK-2809; MGL-3196; Pegbelfermin; Simtuzumab; GR-MD-02; NGM282 Details

Target ID Target Name GENE Action Class UniProtKB ID Entry Name
T10 Caspase-1 CASP1 inhibitor Enzyme P29466 CASP1_HUMAN Details
T18 Acetyl-CoA carboxylase 1 ACACA inhibitor Enzyme Q13085 ACACA_HUMAN Details

Diseases ID DO ID Disease Name Definition Class
I14 9970 Obesity An overnutrition that is characterized by excess body fat, traditionally defined as an elevated ratio of weight to height (specifically 30 kilograms per meter squared), has_material_basis_in a multifactorial etiology related to excess nutrition intake, decreased caloric utilization, and genetic susceptibility, and possibly medications and certain disorders of metabolism, endocrine function, and mental illness. https://en.wikipedia.org/wiki/Obesity disease of metabolism/acquired metabolic disease/ nutrition disease/overnutrition Details

Drug ID Drug Name Type DrugBank ID Targets Category Latest Progress
D240 Nicotinamide Chemical drug DB02701 PARP inhibitor Metabolic disorder drug Under clinical trials Details
D248 Obeticholic Acid Chemical drug DB05990 NR1H4 activator; NR1H4 agonist; FXR agonist Enhance lipid metabolism Approval rejected Details
D328 Serine Chemical drug DB00133 SRR Improve insulin resistance Under clinical trials Details