RFX6 and inflammatory bowel disease: Moreover, the transcriptome analysis of colon biopsies from patients with IBD who often have fiber deficiency (31) also revealed the down-regulation of transcription factors driving enteroendocrine and L cell differentiation (Neurod1, Rfx6, and Fev) and L cell–derived peptide hormones (Gcg, Pyy, and Insl5) even during disease remission (Fig. 2D).