Objective: The aim of this study was to investigate the levels of fasting maternal plasma amino acids in normal pregnant women and compare them with those in gestational diabetes controlled by diet only. We also wished to delineate the alterations occurring in intermediate metabolic pathways in gestational diabetes.
Study design: Forty-six (64.7%) pregnant women with uncomplicated pregnancy (NP group) and 25 (35.2%) women with gestational diabetes mellitus (GDM group) at 30-33 weeks of gestation participated in the study. Fasting maternal plasma carnitine (total, free, and acyl-carnitine), beta-hydroxybutyrate, free fatty acids, glycosylated hemoglobin, and 21 amino acids were assayed.
Results: Fasting carnitine esters exhibited lower levels in the GDM group (P = .03). Higher levels of fasting beta-hydroxybutyrate and free fatty acids (P < .001 and .02, respectively) were observed in the GDM group. Of the 21 amino acids, only methionine, glycine, alanine, citrulline, and ornithine levels were found at significantly higher levels in the NP group (P = .03, P < .001, P = .01, P < .001, and P < .001, respectively).
Conclusion: In gestational diabetes, ketogenic amino acids and the branched-chain amino acid isoleucine are released at low rates from skeletal muscle and are mostly catabolized in the liver rather than in peripheral tissues. In contrast, in normal pregnancy proteinolysis is enhanced, and the ketogenic amino acids along with branched-chain amino acids are catabolized in both the liver and peripheral tissues. As a result, ketogenic amino acids are fully oxidized and gluconeogenesis becomes more efficient, whereas urea cycle operates at a higher rate.