Insulin resistance in prepubertal obese children correlates with sex-dependent early onset metabolomic alterations

Abstract

Background: Insulin resistance (IR) is usually the first metabolic alteration diagnosed in obese children and the key risk factor for development of comorbidities. The factors determining whether or not IR develops as a result of excess body mass index (BMI) are still not completely understood.

Objectives: This study aimed to elucidate the mechanisms underpinning the predisposition toward hyperinsulinemia-related complications in obese children by using a metabolomic strategy that allows a profound interpretation of metabolic profiles potentially affected by IR.

Methods: Serum from 60 prepubertal obese children (30 girls/30 boys, 50% IR and 50% non-IR in each group, but with similar BMIs) were analyzed by using liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry and capillary electrophoresis-mass spectrometry following an untargeted metabolomics approach. Validation was then performed on a group of 100 additional children with the same characteristics.

Results: When obese children with and without IR were compared, 47 metabolites out of 818 compounds (P<0.05) obtained after data pre-processing were found to be significantly different. Bile acids exhibit the greatest changes (that is, approximately a 90% increase in IR). The majority of metabolites differing between groups were lysophospholipids (15) and amino acids (17), indicating inflammation and central carbon metabolism as the most altered processes in impaired insulin signaling. Multivariate analysis (OPLS-DA models) showed subtle differences between groups that were magnified when females were analyzed alone.

Conclusions: Inflammation and central carbon metabolism, together with the contribution of the gut microbiota, are the most altered processes in obese children with impaired insulin signaling in a sex-specific fashion despite their prepubertal status.

Figure 1

Multivariate analysis results (unsupervised, principal components analysis (PCA), and supervised, OPLS-DA, models). (a) PCA plot generated from all samples (◊) and QC samples (♦). LC–MS ESI+ data (R²_(cum)=0.48, Q²_(cum)=0.23). (b) OPLS-DA plot generated from the comparison between obese children with IR (▪) and without IR (□). LC–MS ESI+ data (R²_(cum)=0.51, Q²_(cum)=0.32). (c) OPLS-DA plot generated from the comparison between obese children with IR (▴) and without IR (Δ). Only female samples are included to generate the model. LC–MS ESI+ data (R²_(cum)=0.99, Q²_(cum)=0.45). R²= coefficient for variance explained; Q²= coefficient for variance predicted.

Figure 2

Overview of the changes observed in the metabolic profile of obese children with and without IR. Inflammation and CCM, together with the activity/contribution of the gut microbiota, were found to be altered in obesity-associated hyperinsulinemia. Metabolites that showed significant differences (P< 0.05) between IR and no-IR obese children are depicted in square box. Arrow up: increase; arrow down: decrease relative to control when the whole cohort is investigated. Male (♂) and female (♀) symbols indicate the metabolites that differ significantly between groups, when boys and girls are considered separately. FAO, fatty acid oxidation; LysoPL, Lysophospholipids.