COL1A1 and Hepatic fibrosis: Twenty weeks of Western diet feeding resulted in liver fibrosis in microbiome-humanized mice, as determined by increased hepatic mRNA expression of genes involved in fibrosis, including transforming growth factor-beta 1 (Tgfb1), tissue inhibitor of metalloproteinase-1 (Timp1), and collagen type I alpha 1 (Col1a1) (Fig. 3A–C).