In non-pregnant adults, plasma branched chain amino acid (BCAA; LEU: leucine; ISO: isoleucine; VAL: valine) concentrations are often correlated with insulin resistance, but the etiology of this association remains unclear. The purpose of this study was to describe the changes in BCAA concentrations from early to late pregnancy and determine if changes are associated with insulin resistance.


Plasma samples from overnight-fasted participants from the ongoing study called the Expecting study from the Arkansas Children’s Nutrition Center were used to measure BCAA (EZ:faast, Torrance, CA), and glucose and insulin (both on Randox Daytona Clinical Analyzer, Crumlin, UK) concentrations at early (EP: ~10 weeks) and late (LP: ~30 weeks) pregnancy (n=53). The homeostatic model assessment of insulin resistance (HOMA2-IR) was calculated. Total gestational weight gain (GWG, kg) was measured between EP and LP. The best fit model was created using stepwise multiple linear regression analyses where change in HOMA2-IR (HOMA2-IRLP–HOMA2-IREP) was the dependent variable and change in BCAA plasma concentrations, BMI at enrollment, and GWG were the independent variables.


Although both BMI and insulin resistance increased during pregnancy, LEU (combined groups at EP: 100.3±2.2; LP: 90.1±2.4 nmol/ml, p=0.001), ISO (EP: 69.3±1.7; LP: 65.2±2.4 nmol/ml, p=0.02), and VAL (EP: 241.7±6.3; LP: 221.0±5.6 nmol/ml, p<0.001) concentrations decreased significantly from EP to LP. Further, change in LEU was negatively associated with change in HOMA2-IR (β=-0.041, p=0.002) when adjusting for BMI at enrollment and GWG.


BCAA concentration decreased from EP to LP. Unlike results often reported in non-pregnant adults, our data indicate the opposite relationship between LEU concentration and insulin resistance in pregnant women.