APOA1 and systemic lupus erythematosus: Twenty-four of these metabolites were significantly reduced in SLE compared with HCs at all ages, dominated by total, small and medium HDL metabolites and HDL-bound peptide ApoA1, representing 68% of the 25 age-common metabolites (Fig. 1B and C; Supplementary Table S4, available at Rheumatology online).