At young age Pcyt2+/− has no clinical symptoms of steatosis or insulin resistance (Fig. 1), yet the pathway analysis (Fig. 2A-a, Supplementary Table 2) of the 2-mo Pcyt2+/− downregulated genes (714 genes at p < 0.05) established that the most enriched pathways are for hepatic steatosis, abnormal liver physiology/morphology, increased triglyceride and ammonia, and abnormal amino-acid levels. This evidence concerns the gene PCYT2 and fatty liver disease.