Gnmt, or glycine N-methyltransferase, is a key enzyme in one-carbon metabolism. It catalyzes the production of methylglycine (sarcosine) by taking a methyl group from S-adenosyl-L-methionine and methylating glycine, thus clearing methionine from the body [1,2]. This process is crucial in regulating methyl group availability in mammalian cells and is associated with pathways like autophagy, as well as cholesterol intracellular trafficking and mTOR signaling pathway [1,2].

Genetic models, especially knockout mouse models, have been instrumental in understanding Gnmt's role. Gnmt knockout mice develop liver injury, fibrosis, and hepatocellular carcinoma, indicating its importance in maintaining liver health [4]. In pancreatic cancer, Gnmt is markedly downregulated, suggesting its potential as a biomarker and therapeutic target [3]. In bladder cancer, higher Gnmt expression is associated with muscle invasion and metastasis, with urinary sarcosine levels potentially serving as a marker for muscle invasion [5]. In non-alcoholic fatty liver disease, miR-873-5p downregulates Gnmt, disrupting mitochondrial functionality [6].

In conclusion, Gnmt is essential in multiple biological processes, especially in maintaining liver homeostasis. Its role in diseases such as liver cancer, pancreatic cancer, and bladder cancer, as well as non-alcoholic fatty liver disease, has been revealed through gene knockout mouse models. These findings provide important insights into disease mechanisms and potential therapeutic targets related to Gnmt.