Background Plasma-free amino acid profiles have been reported to correlate with obesity and glucose metabolism, and have been studied as potentially useful biomarkers of lifestyle-related diseases affecting metabolism in adulthood. However, knowledge of these relationships is lacking in children, despite the growing public health problem posed by childhood obesity. The aim of this study was to assess whether plasma-free amino acid profiles can serve as useful biomarkers of lifestyle-related diseases in children with obesity. Methods This retrospective study used the medical records of 26 patients (15 male, 11 female) aged 9 or 10 years presenting with moderate to severe obesity and hyperlipidemia between April 2015 and March 2017. A degree of obesity of 30% or more was defined as moderate or severe. Amino acid levels were compared between obese children with and without impaired glucose tolerance using a t-test or Mann–Whitney U test. In addition, the influence of factors such as intima media thickness, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, amino acids, and homeostasis model assessment-insulin resistance (HOMA-IR) were analyzed pairwise using Pearson’s correlation or Spearman’s rank correlation. Results HOMA-IR was positively correlated with valine, leucine (Leu), isoleucine, phenylalanine, tryptophan, methionine, threonine, lysine, alanine, tyrosine, glutamate (Glu), proline, arginine, ornithine, total free amino acids (all P < 0.01), and aspartate ( P = 0.010). Moreover, blood uric acid levels were positively correlated with Leu ( P = 0.005) and Glu ( P = 0.019), and negatively correlated with serine, glycine, and asparagine ( P = 0.007, P = 0.003, and P = 0.013, respectively). Conclusions Amino acid profile reflects impaired glucose tolerance and hyperuricemia at an early stage of obesity. It is therefore a useful marker to inform early intervention in children with obesity, as in adults. Electronic supplementary material The online version of this article (10.1186/s12887-019-1647-8) contains supplementary material, which is available to authorized users.

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HepG2 cells are widely used as a human hepatocytes model, but their functions, including drug metabolism, are inferior to primary hepatocytes. We previously reported that the hepatic gene expressions in HepG2 cells were upregulated by treatment with zebularine, which is an inhibitor of DNA methylation, through the inhibition of both DNA methyltransferase 1 (DNMT1) and double-stranded RNA-dependent protein kinase (PKR). In this study, we established a new HepG2 cell subline, HepG2-DP cells, by stable double knockdown of DNMT1 and PKR and evaluated its function. Albumin production, expression of CYP1A2 genes, and accumulation of lipid droplets were increased in HepG2-DP cells compared with the original HepG2 cells. Comprehensive gene expression analysis of transcription factors revealed that the expression of important genes for hepatic function, such as HNF1β, HNF4α, ONECUT1, FOXA1, FOXA2, FOXA3, and various nuclear receptors, was upregulated in HepG2-DP cells. These results indicate that the newly established HepG2-DP cells are a highly functional hepatocyte cell line. In addition, we investigated whether HepG2-DP cells are able to mature by differentiation induction, since HepG2 cells are derived from hepatoblastoma. The gene expression of major CYPs and Phase II, III drug-metabolizing enzyme genes was significantly increased in HepG2-DP cells cultured in differentiation induction medium. These results suggest that HepG2-DP cells can be further matured by the induction of differentiation and could therefore be applied to studies of drug metabolism and pharmacokinetics.