Effects of gestational diabetes on diurnal profiles of plasma glucose, lipids, and individual amino acids

To assess the effects of gestational diabetes mellitus (GDM) on intermediary metabolism in late pregnancy, circulating levels of glucose, FFA, triglycerides, cholesterol, and individual amino acids were monitored for 24 h while subjects received a liquid formula diet (containing 2110 cal and 275 g carbohydrate) in three equal feedings at 0800, 1300, and 1800. Attempts were made to distinguish between varying degrees of severity of gestational diabetes by subdividing the population into those with fasting plasma glucose within the normal range for pregnancy, i.e., below 105 mg/dl (GDM < 105), and those with fasting plasma glucose of 105 mg/dl or greater (GDM ≥ 105). Both groups were compared with pregnant women with normal carbohydrate metabolism (NM). The diurnal profiles indicated that premeal, postprandial averages, and integrated 24-h values for plasma glucose were consistently higher in GDM ≥ 105 than in GDM < 105; both GDM groups uniformly exceeded the values in NM. Plasma FFA tended to be higher in all GDM, with maximal increments occurring in the early hours before breakfast and assuming greatest significance in GDM ≥ 105. The elevations in circulating cholesterol that occur in pregnancy were not significantly different at any time point in NM, GDM < 105, and GDM ≥ 105. However, the increases in plasma triglycerides were greater in GDM < 105 and GDM ≥ 105 than in NM and most marked in GDM ≥ 105. Diurnal profiles for a number of individual amino acids (phenylalanine, tyrosine, alanine, serine, proline) were not affected by gestational diabetes. However, certain other amino acids, particularly the branched chain (leucine, isoleucine, valine) tended to be elevated in subjects with GDM and to the most significant extent in GDM ≥ 105. Although the GDM subjects tended to be heavier than the NM, the progressively more pronounced metabolic abnormalities in GDM ≥ 105 than in GDM < 105 would suggest that relative insulinopenia rather than obesity contributed to the differences. Our findings indicate that gestational diabetes is attended by disturbances of varying degrees in all major classes of insulin-dependent foodstuffs and must be viewed as a disorder of multiple fuels.