SIRT1 Controls Enteroendocrine Progenitor Cell Proliferation in High-Fat Diet-Fed Mice

Abstract

Background & aims: We aimed to investigate how sirtuin 1 (SIRT1), a conserved mammalian Nicotinamide adenine dinucleotide⁺-dependent protein deacetylase, regulates the number of enteroendocrine cells (EECs). EECs benefit metabolism, and their increase potentially could treat type 2 diabetes and obesity.

Methods: We used mice with specific Sirt1 disruption in the intestinal epithelium (VilKO, villin-Cre⁺, and Sirt1^flox/flox mice) or enteroendocrine progenitor cells (EEPCs) (NgnKO, neurogenin 3-Cre⁺, Sirt1^flox/flox mice) and mice with increased SIRT1 activity owing to overexpression (Sir2d mice) or 24-hour fasting. Mice were fed a high-fat diet (HFD), and blood glucagon-like peptide 1 (GLP-1) and glucose levels were measured. Intestinal tissues, EECs, and formed organoids were analyzed using quantitative polymerase chain reaction, immunoblotting, and immunohistochemistry.

Results: In HFD-fed VilKO and NgnKO mice, an increase in EECs (42.3% and 37.2%), GLP-1- or GLP-2-producing L cells (93.0% and 61.4%), and GLP-1 (85.7% and 109.6%) was observed after glucose loading, explaining the improved metabolic phenotype of HFD-VilKO mice. These increases were associated with up-regulated expression of neurogenin 3 (EEPC marker) in crypts of HFD-VilKO and HFD-NgnKO mice, respectively. Conversely, Sir2d or 24-hour fasted mice showed a decrease in EECs (21.6%), L cells (41.6%), and proliferative progenitor cells. SIRT1 overexpression- or knockdown-mediated change in the progenitor cell proliferation was associated with Wnt/β-catenin activity changes. Notably, Wnt/β-catenin inhibitor completely suppressed EEC and L-cell increases in HFD-VilKO mice or organoids from HFD-VilKO and HFD-NgnKO mice.

Conclusions: Intestinal SIRT1 in EECs modulates the EEPC cycle by regulating β-catenin activity and can control the number of EECs in HFD-fed mice, which is a previously unknown role.

Keywords: Cell Cycle; GLP-1; Type 2 Diabetes.