Plasma Amino Acids as Correlates of Serum Insulin-Like Growth Factor 1, Linear Growth, and Fat-Free Mass: A Cross-Sectional Study among Ugandan Children with Stunting

Abstract

Background: Stunting is widespread in low-income settings because of inferior quality diets and infections, which downregulate serum concentration of insulin-like growth factor-1 (serum IGF-1). Associations among plasma concentrations of amino acids (plasma AA), serum IGF-1, and growth remain underexplored in humans. Objectives: The aim of this study was to assess the role of plasma AA as a correlate of serum IGF-1, linear growth, and fat-free mass (FFM) among stunted children. Methods: In a cross-sectional study nested in a nutrition intervention trial among 750 Ugandan children, aged 12–59 mo, with stunting, we assessed anthropometry, recent intake of animal-source foods (ASFs), fasting time, and body composition. Serum IGF-1, serum concentrations of the inflammatory markers C-reactive protein and α1-acid glycoprotein, and 21 plasma AA were measured. Results: Mean (standard deviation) age and height-for-age z-score (HAZ) were 32.0 (11.7) mo and −3.02 (0.74). Plasma AA data were available for 711−730 (95%–97%) children. For 18 AA, plasma concentrations were lower among children with elevated inflammatory markers. ASF intake within 24 h was associated with few AA; meat intake was associated with higher plasma methionine, whereas cow milk and egg intake were not associated with plasma concentration of any essential AA (EAA). Nearly all plasma AA, including all EAA, were positively associated with serum IGF-1, after adjusting for fasting and markers of inflammation. Only a few plasma AA, including methionine, threonine, and valine, were associated with FFM or FFM index. Only plasma tyrosine and taurine were associated with HAZ. Conclusions: Among stunted children, most plasma AA were positive correlates of serum IGF-1, but few correlated with HAZ or FFM. Further research is needed to clarify the role of plasma AA in the complex mechanisms underlying growth faltering in malnourished children.