TABLE 2.

Metabolic pathways significantly altered in chronic obstructive pulmonary disease (COPD)^#

Pathway name(s)	Number of metabolites in pathway	Smokers versus COPD
		Both sexes		Female		Male
		Hits	p-value (FDR¶)	Hits	p-value (FDR¶)	Hits	p-value (FDR¶)
Alterations in both sexes
Citrate (tricarboxylic acid) cycle		3	0.0009 (0.005)	3	0.0006 (0.005)	2	0.005 (0.01)
Glycerophospholipid metabolism	52	3	0.002 (0.009)	3	0.002 (0.007)	4	<0.0001 (0.0001)
Pyruvate metabolism	31	2	0.03 (0.05)	2	0.03 (0.04)	2	0.01 (0.02)
Sex-enhanced: female COPD
Fatty acid biosynthesis	50	3	0.0002 (0.002)	2	0.006 (0.01)	0	1.0 (1.0)+
Sphingolipid metabolism	25	2	0.02 (0.05)	2	0.02 (0.03)	0	1.0 (1.0)+
Sex-enhanced: male COPD
cAMP signalling pathway	40	2	0.03 (0.05)	2	0.02 (0.03)	2	0.009 (0.02)
Retrograde endocannabinoid signalling	19	2	0.02 (0.04)	2	0.01 (0.02)	2	0.005 (0.02)
Tryptophan metabolism	80	2	0.5 (1.0)+	0	1.0 (1.0)+	2	0.04 (0.05)

FDR: false discovery rate. ^#: pathway analysis was performed using integrated pathway-level analysis [24]; ^¶: calculated using Benjamini–Hochberg method with a cut-off value of p<0.3; ⁺: pathways did not pass the FDR cut-off value.