Amino acids, microbiota-related metabolites, and the risk of incident diabetes among normoglycemic Chinese adults: Findings from the 4C study

Although previous studies suggest that amino acids (AAs) and microbiota-related metabolites (MRMs) are associated with type 2 diabetes mellitus (T2DM), the results remain unclear among normoglycemic populations. We test 28 serum AAs and 22 MRMs in 3,414 subjects with incident diabetes and matched normoglycemic controls from the China Cardiometabolic Disease and Cancer Cohort (4C) Study. In fully adjusted logistic regression models, per SD increment of branched-chain AAs, aromatic AAs, asparagine, alanine, glutamic acid, homoserine, 2-aminoadipic acid, histidine, methionine, and proline are positively associated with incident T2DM. In the MRM panel, serum carnitines, N-acetyltryptophan, and uric acid are positively associated with incident T2DM. Causal mediation analyses indicate 34 significant causal mediation linkages, with 88.2% through obesity and lipids. Variances explained in the serum metabolites are modestly limited in the comprehensive catalog of risk factor–metabolite–diabetes associations. These findings reveal that systematic AAs and MRMs change profile before T2DM onset and support a potential role of metabolic alterations in the pathogenesis of diabetes.