Identification of metabolic phenotypes in childhood obesity by 1H NMR metabolomics of blood plasma

Abstract

Aim: To identify the plasma metabolic profile associated with childhood obesity and its metabolic phenotypes.

Materials & methods: The plasma metabolic profile of 65 obese and 37 normal-weight children was obtained using proton NMR spectroscopy. NMR spectra were rationally divided into 110 integration regions, which reflect relative metabolite concentrations, and were used as statistical variables.

Results: Obese children show increased levels of lipids, N-acetyl glycoproteins, and lactate, and decreased levels of several amino acids, α-ketoglutarate, glucose, citrate, and cholinated phospholipids as compared with normal-weight children. Metabolically healthy children show lower levels of lipids and lactate, and higher levels of several amino acids and cholinated phospholipids, as compared with unhealthy children.

Conclusion: This study reveals new valuable findings in the field of metabolomics and childhood obesity. Although validation should be performed, the proof of principle looks promising and justifies a deeper investigation of the diagnostic possibilities of proton NMR metabolomics in follow-up studies. Trial registration: NCT03014856. Registered January 9, 2017.

Keywords: N-acetyl glycoproteins; NMR spectroscopy; amino acids; childhood obesity; metabolic syndrome; metabolically healthy obesity; metabolomics; multivariate analysis; obesity; phospholipids.

Conflict of interest statement

Financial & competing interests disclosure This study is part of the Limburg Clinical Research Program (LCRP), supported by the foundation Limburg Sterk Merk, province of Limburg, Flemish government, Hasselt University, Ziekenhuis Oost-Limburg and Jessa Hospital. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.

Figures

Figure 1.. Discrimination between OB and NW based on the 1H-NMR-derived metabolic phenotype of blood plasma.

OPLS-DA score plot (A) and S-line plot (B) obtained for the OB (▴) and NW (○) children and adolescents. Each participant is represented by its metabolic profile and visualized as a single symbol of which the location is determined by the contributions of the 110 variables in the 1H NMR spectrum. The OPLS-DA score plot (LV = 3) shows the first predictive component (t[1]P: 26.1%), explaining the variation between the groups, versus the first orthogonal component (t[1]O: 53.4%) that explains the variation within the groups. The OPLS-DA S-line plot visualizes differences between OB patients (positive) and NW controls (negative). The left y-axis represents p(ctr)[1], the covariance between a variable and the classification score. It indicates if an increase or decrease of a variable is correlated to the classification score. The magnitude of the covariance is however difficult to interpret since covariance is scale dependent. This means that a high value for the covariance does not necessary imply a strong correlation, as the covariance is also influenced by the intensity of the signal with respect to the noise level. Therefore this measure will likely indicate variables with large signal intensities. On the right y-axis, p(corr)[1] is the correlation coefficient between a variable and the classification score, for example, the normalized covariance. It gives a linear indication of the strength of the correlation. As the correlation is independent of the intensity of the variable, it will be a better measure for the reliability of the variable in the classification process. In Figure 1B, the red color stands for the highest absolute value of the correlation coefficient. Strongly discriminating variables have a large intensity and large reliability. NW: Normal-weight; OB: Overweight or obese; OPLS-DA: Orthogonal partial least square discriminant analysis.

Figure 2.. Discrimination between MHO and MUO based on the 1H-NMR-derived metabolic phenotype of blood plasma.

OPLS-DA score plot (A) and S-line plot (B) obtained for the MHO (△) and MUO (•) children and adolescents. Each participant is represented by its metabolic profile and visualized as a single symbol of which the location is determined by the contributions of the 110 variables in the 1H NMR spectrum. The OPLS-DA score plot (LV = 2) shows the first predictive component (t[1]P: 38.3%), explaining the variation between the groups, versus the first orthogonal component (t[1]O: 49.4%) that explains the variation within the groups. The OPLS-DA S-line plot visualizes differences between MHO (negative) and MUO (positive) subjects. The left y-axis represents p(ctr)[1], the covariance between a variable and the classification score. The right y-axis presents p(corr)[1], the correlation coefficient between a variable and the classification score, giving a linear indication of the strength of the correlation. The red color stands for the highest absolute value of the correlation coefficient. Strongly discriminating variables have a large intensity and large reliability. MHO: Metabolically healthy obese; MUO: Metabolically unhealthy obese; OPLS-DA: Orthogonal partial least square discriminant analysis.