Urinary metabolomic profiles uncover metabolic pathways in children with asthma

Figures & data

Table 1. Baseline characteristics of the 40 children.

	Asthma (n = 30)	Controls (n = 10)	95% CI	p Value
Age (years)	6.40 (5.98, 8.20)	6.90 (5.75, 8.13)	(−1.00, 1.00)	0.814
Sex
Male (n, %)	15 (50.0)	6 (60.0)	(0.16, 2.85)	0.855
Female (n, %)	15 (50.0)	4 (40.0)
Height (cm)	120.30 (116.65, 130.85)	123.90 (115.25, 131.08)	(−7.00, 7.30)	0.975
Weight (kg)	21.85 (19.98, 24.40)	23.00 (19.40, 26.58)	(−3.40, 2.20)	0.574
BMI (kg/m^2)	14.85 ± 1.40	15.25 ± 1.24	(−1.4, 0.61)	0.432
Blood routine examinations
WBC count (×10^9/L)	6.85 (6.08, 8.20)	6.80 (5.25, 7.73)	(−0.70, 1.50)	0.522
N (%)	61.16 ± 4.46	61.59 ± 5.20	(−3.86, 3.01)	0.803
NC	4.44 (3.67, 4.76)	3.89 (3.25, 4.80)	(−0.42, 1.06)	0.333
E (%)	4.40 (3.60, 5.80)	4.45 (3.50, 5.28)	(−0.80, 1.60)	0.731
EC	0.31 (0.26, 0.40)	0.25 (0.20, 0.38)	(−0.03, 0.14)	0.142
IgE (IU/mL)	173.50 (83.00, 279.75)	87.25 (60.95, 175.75)	(−21.0, 153.00)	0.174
Allergen
Dust mites (n, %)	29 (96.7)	1 (10.0)	(14.79, 4607.52)	<0.001
Cat hair (n, %)	1 (3.3)	0 (0.00)	–	1.000
Dog hair (n, %)	2 (6.7)	0 (0.00)	–	1.000
Lung-function tests
FEV1 (%)	74.00 (68.00, 78.00)	87.50 (79.00, 98.50)	(−24.00, −9.00)	<0.001
FVC (%)	91.43 ± 9.32	102.40 ± 12.27	(−18.43, −3.50)	0.005
FEV1/FVC (%)	0.79 (0.76, 0.83)	0.87 (0.85, 0.89)	(−0.11, −0.04)	<0.001
PEF (%)	83.27 ± 8.45	101.80 ± 11.88	(−25.47, −11.60)	<0.001
FEF25 (%)	81.33 ± 7.25	100.60 ± 11.30	(−25.46, −13.07)	<0.001
FEF50 (%)	75.50 (64.00, 80.00)	85.50 (72.00, 93.25)	(−22.00, −4.00)	0.006
FEF75 (%)	60.27 ± 6.51	78.30 ± 11.90	(−26.73, −9.33)	0.001

Data are presented as numbers (percentages), mean ± standard deviation or median (lower quartile, upper quartile) as required.

CI: confidence interval; BMI: body mass index; WBC: white blood cell; N: neutrophil; NC: neutrophil count; E: eosinophil; EC: eosinophil count; IgE: immunoglobulin E; FVC: forced vital capacity; FEV₁: forced expiratory volume in 1 s; PEF: peak expiratory flow; FEF: forced expiratory flow.

Figure 1. Score scatter plot of PCA model for group asthma vs. control. The x- (PC1) and y- (PC2) axes indicate the first and second principal components, respectively. The circle represents the 95% confidence interval.

Figure 2. Score scatter plot and permutation plot test of OPLS-DA model for group asthma vs. control. (a) Score scatter plot of OPLS-DA model for group asthma vs. control. The x- (t[1]P) and y- (t[1]O) axes indicate predictive and orthogonal directions, respectively. The circle represents the 95% confidence interval. (b) Permutation plot test of OPLS-DA model for group asthma vs. control. R² and Q² indicate interpretability and predictability, respectively.

Figure 3. Volcano plot for group asthma vs. control. The x-axis indicates the change in multiples of each substance in the group (taking the logarithm base 2), and the y-axis represents the p value of the Student’s t-test (taking the negative logarithm base 10). Significantly up-regulated metabolites are shown in red, significantly down-regulated metabolites are shown in blue, and non-significantly differentiated metabolites are shown in gray.

Figure 4. Heatmap of correlation analysis for group asthma vs. control. The x- and y-axes represent the differential metabolites in this group of contrasts, with red indicating a positive correlation and blue indicating a negative correlation.

Figure 5. ROC analysis for distinguishing asthma patients from healthy controls. (a) ROC analysis of dodecanedioic acid (AUC = 0.75). (b) ROC analysis of glucobrassicin (AUC = 0.74). (c) ROC analysis of traumatic acid (AUC = 0.74).

Table 2. Identification of differentially abundant metabolites in urine between asthmatic and healthy subjects.

ID	Peak	RT	MZ	Mean asthma	Mean control	VIP	p Value	q Value	Fold change	Log_fold change
Upward
641	Glucobrassicin	318.132	227.1288629	0.009093848	0.022281495	1.13	0.012	0.396	6.52	2.70
Downward
432	Dodecanedioic acid	286.505	229.1445467	0.005731273	0.016753875	1.14	0.032	0.396	0.34	−1.55
307	Traumatic acid	132.739	447.0566545	0.001480022	0.000227166	1.34	0.029	0.394	0.41	−1.29

RT: retention time; MZ: mass-to-charge ratio; VIP: variable importance in the projection.

Figure 6. Metabolic pathways. Blue represents down-regulated significantly differentiated metabolites.

Figure 7. KEGG enrichment and differential abundance score for group asthma vs. control. (a) KEGG Enrichment for group asthma vs. control. The x-axis represents the Rich Factor, and the y-axis represents the KEGG metabolic pathway name. The color indicates the size of the p value, and the smaller the p value, the redder the color. (b) Differential Abundance Score for group asthma vs. control. The x-axis represents the DA Score and the y-axis represents the KEGG metabolic pathway name. The DA Score reflects the overall change of all metabolites in the metabolic pathway, and the score −1 indicates a downward trend in the expression of all annotated differential metabolites in the pathway.

Data availability statement

Data available on request due to restrictions, e.g., privacy or ethical.