VIP and constipation disorder: The statistical analyses showed that 108 metabolites were enriched, while 150 metabolites were reduced in constipated subjects compared with those in the non-constipation group (Supplementary Table 1), and they included 49 significantly increased and 9 significantly reduced metabolites in constipation group according to the parameters of VIP > 1 and p < 0.1 (Figure 3C).