3.3 | Pathway enrichment analysis for variable
metabolites in DCDA-C and DCDA-D twins.
The majority of metabolic pathways in amino acid, translation, and
cofactor/vitamin metabolism were downregulated in both comparison 1
(DCDA-D-L/DCDA-C) and comparison 2 (DCDA-D-S/DCDA-C) (Figure
3A ). This included cysteine and methionine metabolism, glutathione
metabolism, glycine, serine, and threonine metabolism, taurine and
hypotaurine metabolism; one translation pathway was aminoacyl-tRNA
biosynthesis; and three cofactor/vitamin metabolism included nicotinate
and nicotinamide metabolism, pantothenate and CoA biosynthesis and
thiamine metabolism. Intriguingly, two pathways associated with
carbohydrate metabolism showed specific downregulation in DCDA-D-S twins
compared to the DCDA-C twins (Figure 3A , comparison 2). No
significant metabolic pathway change was detected in comparison 3
(DCDA-D-S/DCDA-D-L). The shortlisted pathways were linked to their
shared metabolites and reconstructed into an in silico metabolic
network (Figure 3B ). Cysteine, leucine, and threonine were
directly linked to the aminoacyl-tRNA-related metabolites including
cysteinyl-tRNA, leucyl-tRNA, and threonine tRNA respectively. The
network showed that cysteine was converted into antioxidant glutathione
through gamma-glutamyl-L-cysteine. Nicotinamide could lead to the
production of coenzymes such as NADP+ and
NAD+. Moreover, the network illustrated that aconitate
hydratase catalyzes the isomerization of citrate to isocitrate through
cis-aconitate in the TCA cycle (Figure 3B ). Notably, cysteine
was the most interconnected metabolite that participated in seven
significant pathways of glutathione metabolism, cofactors and vitamin
metabolism, and four different amino acid metabolisms (Figure
3C ).