ARG1 and metabolic dysfunction-associated steatotic liver disease: We also examined these pathways in patients with mild (fibrosis stage 0–1) and severe NAFLD (fibrosis stage 3–4), and found that patients with severe NAFLD showed decreased ARG1 and increased SMS mRNA levels, which may cause decreased spermidine synthesis and increased conversion of spermidine to spermine (Fig. S1).