Table 3.

Statistical Correlations Between Plasma Metabolites and COPD Phenotypes, Represented by the Emphysema Index, FEV₁, and FVC

	Emphysema		FEV1		FVC
	Beta	*p-value	Beta	*p-value	Beta	*p-value
Ceramides (nM)
C14	0.002	0.6198	0.010	0.8677	0.024	0.5297
C16	0.001	0.7500	−0.053	0.1914	−0.031	0.2367
C18	−0.002	0.7321	−0.109	0.0203	−0.064	0.1524
C18_1	−0.001	0.7956	−0.027	0.6452	−0.005	0.8955
C20	−0.003	0.5472	−0.082	0.1990	−0.047	0.2495
C24	−0.001	0.7397	−0.081	0.1718	−0.053	0.1582
C24_1	0.001	0.8425	−0.123	0.0366	−0.035	0.3635
SM18_0	−0.004	0.2664	−0.002	0.9702	−0.006	0.8432
SM18_1	−0.002	0.5824	−0.029	0.5328	−0.013	0.6654
SM16_0	0.002	0.5882	−0.0003	0.9947	−0.007	0.7756
SM24_0	0.003	0.4815	−0.018	0.7449	−0.009	0.8063
SM24_1	0.002	0.6800	0.018	0.7221	0.016	0.6246
Amino acids (μM)
Glycine	−0.006	0.3301	0.030	0.7387	0.003	0.9533
Alanine	−0.011	0.0844	0.012	0.8900	−0.040	0.4878
Serine	−0.009	0.1411	0.006	0.9419	−0.026	0.6314
Proline	−0.012	0.0575	0.001	0.9902	−0.049	0.3957
Valine	−0.0003	0.9489	−0.020	0.7198	−0.032	0.3625
Threonine	−0.0006	0.9213	−0.048	0.5849	−0.042	0.4572
Taurine	−0.006	0.3361	−0.002	0.9784	−0.010	0.8626
t4_OH_Pro	−0.007	0.4609	−0.197	0.1306	−0.096	0.2503
Leucine	0.0001	0.9894	0.027	0.6619	−0.036	0.3639
Isoleucine	−0.004	0.4310	−0.056	0.3779	−0.064	0.1142
Asparagine	−0.009	0.1187	0.027	0.7499	−0.055	0.3062
Aspartate	−0.014	0.1304	−0.007	0.9414	0.013	0.8458
Glutamine	−0.006	0.3138	−0.027	0.7270	−0.049	0.3243
Glutamate	−0.020	0.0055	−0.094	0.3596	−0.053	0.4176
Methionine	−0.004	0.6853	0.007	0.9580	0.034	0.6779
Histidine	−0.009	0.1345	0.086	0.3097	0.017	0.7524
Alpha_AAA	−0.015	0.0451	−0.009	0.9287	−0.013	0.8516
Phenylalanine	0.005	0.1904	−0.050	0.3055	−0.024	0.4429
Arginine	−0.014	0.1398	0.095	0.3111	−0.001	0.9803
Ac_Orn	−0.003	0.7510	−0.047	0.6910	0.003	0.7163
Citrulline	−0.008	0.2555	−0.013	0.8925	−0.027	0.6699
Tyrosine	−0.008	0.1666	0.015	0.8542	−0.042	0.4336
ADMA	−0.007	0.2140	−0.088	0.2870	−0.072	0.1774
SDMA	−0.005	0.4598	−0.072	0.4255	−0.080	0.1677
Tryptophan	−0.002	0.5637	0.029	0.6168	0.013	0.7170
Kynurenine	0.001	0.8120	−0.036	0.0213	−0.035	0.4899
Ornithine	−0.003	0.5142	−0.001	0.9835	−0.003	0.9485
Met_SO	0.004	0.2383	−0.038	0.4802	−0.021	0.5487

Notes: *This p-value was used for the Student’s t-test and chi-square test for the analyses of the metabolites and COPD phenotypes followed by linear regression analysis, respectively. Here, bold values indicate a statistically significant correlation with a p-value less than 0.05. The data was adjusted for age, smoking, pack years, BMI, Gold grade, drug history, and CCI and then analyzed using log transformation.