3.2 | Analysis of hair metabolome profiles in DCDA-C
and DCDA-D twins
Uniform Manifold Approximation and Projection (UMAP) of our hair samples
demonstrated distinct global metabolomic separation of DCDA-C, DCDA-D-S,
and DCDA-D-L twins (Figure 2A ). DCDA-D-S and DCDA-D-L co-twins
more resembled each other, while DCDA-C twins were separated from the
larger and smaller DCDA-D twins. In total, nine significant metabolites
discriminated DCDA-D-L twins from DCDA-C twins by logistic regression
with a p-value less than 0.05 (Figure 2B, comparison 1). This
included lower levels of 10,13-dimethyltetradecanoic acid, nicotinamide,
three amino acids, and two organic compounds. 17 significant hair
metabolites contributed to the separation of the DCDA-D-S and DCDA-C
twins (Figure 2B , comparison 2). This encompassed three amino
acids and one amino acid derivative at lower levels in DCDA-D-S twins
than in DCDA-C twins, while tryptophan, isoleucine, and most of the
organic compounds identified in comparison 2 were found at higher levels
in DCDA-D-S twins. A single metabolite, cis-aconitic acid, showed higher
levels in DCDA-D-L relative to DCDA-D-S (Figure 2B , comparison
3). To find the shared metabolic changes in both larger and smaller
DCDA-D co-twins compared to DCDA-C twins, four common differential
metabolites in both comparisons 1 and 2 were shortlisted including
cysteine, l-leucine, 2-aminobutyric acid, and threonine (Figure
2C ). Noticeably, the lower concentration of cysteine, threonine, and
leucine was detected in both DCDA-D-S and DCDA-D-L groups compared to
the DCDA-C group. Meanwhile, 2-aminobutyric acid was the only
shortlisted metabolite that displayed the lowest concentration in DCDA-C
groups compared to both DCDA-D groups.