GPT and type 2 diabetes mellitus: Previous MR studies have revealed that genetically elevated fasting insulin (FI) and liability to T2D increase alanine aminotransferase (ALT) and MASLD risk [13–15], whereas some MR studies have shown higher systemic iron status and iron homeostasis biomarkers (e.g., ferritin, serum iron, or transferrin saturation (TSAT)) may increase risk of MASLD [16, 17], but with some exceptions [18, 19].