Within the type 1 diabetes population of the present study, the same bisecting GlcNAc-transferase MGAT3 SNPs influenced FA2G2S2 (IGP23; core fucosylated digalactosylated disialylated glycan) and FA2BG2S2 (IGP24) glycan proportions in opposite directions, suggesting that bisecting GlcNAc may be added after the addition of sialic acid. Here, MGAT3 is linked to type 1 diabetes mellitus.