Karen Tan

Context Due to the essential role of carnitine as an intermediary in amino acid, carbohydrate and lipid metabolism, a detailed characterization of circulating and urinary carnitine concentrations will aid in elucidating the molecular basis of impaired maternal metabolic flexibility and facilitating timely intervention for expectant mothers. Objective To investigate the association of maternal plasma and urinary free carnitine and acylcarnitines with cardiometabolic risk factors. Methods LC-MS/MS-based quantification of free carnitine and acylcarnitines (C2-C18) was performed on 765 plasma and 702 urine samples collected at preconception, 26-28 weeks’ pregnancy, and three months postpartum in the Singapore PREconception Study of long-Term maternal and child Outcomes (S-PRESTO) cohort study. Results Plasma concentrations of free carnitine and acylcarnitines decreased coupled with increased renal clearance in pregnancy compared to preconception and postpartum. Renal clearance of carnitine increased with an increase in pre-pregnancy body mass index (ppBMI) and gestational weight gain. Plasma short-chain acylcarnitines were positively associated with ppBMI, irrespective of the physiological state, while medium- and long-chain acylcarnitines were negatively associated with ppBMI at preconception and postpartum but showed a positive association in pregnancy. Similarly, plasma short-chain acylcarnitines were positively associated with HOMA-IR whereas medium- and long-chain acylcarnitines were negatively associated with HOMA-IR at preconception and in pregnancy. Mothers who developed gestational diabetes mellitus during pregnancy had ∼10% higher plasma propionylcarnitine concentration and ∼18% higher urine tiglylcarnitine concentration compared to mothers with normal glucose metabolism at preconception. Conclusions This study provides the metabolic and physiological basis of maternal carnitine homeostasis, which can be used in assessment of maternal cardiometabolic health at preconception to improve pregnancy outcomes.