ESPE Abstracts

Background/Objectives: Blood amino acid (AA) and acylcarnitine (AC) concentrations are informative on physiological and disease-associated changes in human metabolic pathways. Previously, AAs and ACs were examined as potential biomarkers or predictors of complex metabolic diseases in adults and children. However, there is still a lack of studies examining physiological AA and AC blood levels in healthy paediatric populations. We aimed to assess the intra-person variability of AA and AC concentrations and associations with anthropometric parameters related to body fat.

Methods: Concentrations of 23 AAs, 6 ACs and free carnitine of 2213 children between 3 months and 19 years from the Leipzig LIFE Child Study were analyzed using liquid chromatography/tandem mass spectrometry. The stability of metabolites was assessed using the coefficient of determination. Associations with different body fat indices were determined by Pearson correlation and linear regression.

Results: We found substantial yearly fluctuations in blood metabolite concentrations in the same person during childhood and adolescence. Most metabolites had a positive correlation with anthropometric parameters, e.g. alanine and proline showed a strong association with waist circumference in females (alanine ß=0.107, P <0.01, proline ß=0.115, P <0.001). Waist circumference generally correlated stronger than waist to hip ratio (WHR) with metabolite concentrations. As an exception, glycine showed negative associations with skinfold thickness measurements, BMI-SDS and waist circumference, especially in normal weight girls. We noted a considerable influence of sex and pubertal status, e.g. the negative association between glycine and the anthropometric indices was stronger during puberty than before puberty in boys, whereas for girls the negative association existed before and during puberty. In males, the short-chain ACs acetylcarnitine (C2) and propionylcarnitine (C3) showed strongest correlations to various parameters for body fat distribution (e.g. for biceps skinfold thickness C2: ß= 0.084, P = 0.005; C3 ß=0.095, P = 0.002). We also observed weight group specific differences: in girls, the overweight/obese group showed stronger positive correlations between metabolites and weight and body fat related measures than the normal weight group, most prominently for free carnitine.

Conclusion: Integrating blood metabolite profiling with anthropometric parameters like skinfold thicknesses and waist circumference supports current research regarding body fat distribution, obesity and metabolic diseases. We showed that metabolite concentrations in children undergo significant changes during childhood and adolescence and identified differences related to sex, weight and pubertal status in the associations between amino acid and acylcarnitine metabolite concentrations and anthropometric parameters associated with body fat.