Bromodomain Inhibition Reveals FGF15/19 As a Target of Epigenetic Regulation and Metabolic Control

Epigenetic regulation is an important factor in glucose metabolism, but underlying mechanisms remain largely unknown. Here we investigated epigenetic control of systemic metabolism by bromodomain-containing proteins (Brds), which are transcriptional regulators binding to acetylated histone, in both intestinal cells and mice treated with the bromodomain inhibitor JQ-1. In vivo treatment with JQ-1 resulted in hyperglycemia and severe glucose intolerance. Whole-body or tissue-specific insulin sensitivity was not altered by JQ-1; however, JQ-1 treatment reduced insulin secretion during both in vivo glucose tolerance testing and ex vivo incubation of isolated islets. JQ-1 also inhibited expression of fibroblast growth factor (FGF) 15 in the ileum and decreased FGF receptor 4-related signaling in the liver. These adverse metabolic effects of Brd4 inhibition were fully reversed by in vivo overexpression of FGF19, with normalization of hyperglycemia. At a cellular level, we demonstrate Brd4 binds to the promoter region of FGF19 in human intestinal cells; Brd inhibition by JQ-1 reduces FGF19 promoter binding and downregulates FGF19 expression. Thus, we identify Brd4 as a novel transcriptional regulator of intestinal FGF15/19 in ileum and FGF signaling in the liver and a contributor to the gut-liver axis and systemic glucose metabolism.