Corepressors NCOR1 and SMRT regulate metabolism via intestinal regulation of carbohydrate transport

Objective: Nuclear receptor action is mediated in part by the nuclear receptor corepressor 1 (NCOR1) and the silencing mediator of retinoic acid and thyroid hormone receptor (SMRT; also known as NCOR2). NCOR1 and SMRT regulate metabolic pathways that govern body mass, insulin sensitivity and energy expenditure and represent an understudied area in the realm of metabolic health and disease. Previously, we found that NCOR1 and SMRT are essential for maintaining metabolic homeostasis and their knockout (KO) leads to rapid weight loss and hypoglycemia, which is not survivable. Because of a potential defect in glucose absorption, we sought to determine the role of NCOR1 and SMRT specifically in intestinal epithelial cells (IECs). Methods: We used a post-natal strategy to disrupt NCOR1 and SMRT throughout IECs in adult mice. These mice were characterized metabolically by assessing body weight, glucose levels and subjecting the mice to metabolic phenotyping, body composition analysis and glucose tolerance testing. IECs were isolated from the jejunum of the small intestine and profiled by bulk RNA sequencing. Results: We found that the post-natal KO of NCOR1 and SMRT from IECs leads to rapid weight loss and hypoglycemia with a significant reduction in survival. This was accompanied by alterations in glucose metabolism and activation of fatty acid oxidation in IECs. Metabolic phenotyping confirmed a reduction in body mass driven by a loss of body fat without any difference in food intake. This appeared to be driven by a reduction of key intestinal carbohydrate transporters, including SGLT1, GLUT2 and GLUT5. Conclusions: Intestinal NCOR1 and SMRT act in tandem to regulate glucose levels and body weight. This in part may be mediated by regulation of intestinal carbohydrate transporters.