APOB and systemic lupus erythematosus: Some serum metabolites were shared exclusively across two age groups, such as increased lactate and phenylalanine in SLE patients in both Group 2 and 3, compared with reduced acetoacetate and increased ApoB : ApoA1 ratio in both Group 1 and 2, supporting a more conserved signature across consecutive age groups in SLE for some serum metabolites.