Читать книгу Gestational Diabetes - Группа авторов - Страница 27

Amino acids can be utilized as a fuel source or as substrates for protein synthesis. During pregnancy, the fetus is reliant on amino acids to build lean body mass and on FFAs for membrane construction. By term, the fetus and placenta contain approximately 500 g of protein, while an approximately equal amount of protein has been added to uterine muscle, breasts, and maternal blood. Maternal circulating amino acid levels decrease during pregnancy, both fasting and postprandially [50]. Third trimester levels of the essential branched chain amino acids leucine and isoleucine, as well as the glucogenic amino acids methionine, phenylalanine, and tyrosine, were significantly lower than second trimester levels, when measured after at least 4 h of fasting [53]. This may be attributed to increased utilization by mother and fetus, as an energy source but mainly for anabolism, and also to an increased volume of distribution. In addition to constructing a fetus, the mother increases uterine and breast tissue, as well as lipid storage, all anabolic functions. The anabolic process is demonstrated by positive nitrogen balance, with decreased urea synthesis compared to the nonpregnant state [54]. During prolonged fasting, there is a preferential decline in gluconeogenic amino acids [41] because the gravida begins to utilize these as a fuel source, with increased liver uptake and gluconeogenesis.