Loss of Intestine-Specific FFA3 Has Protective Effects Against Diet-Induced Obesity and Hyperglycemia in Mice on a Western Diet

Free fatty acid receptor 3 (FFA3) is a recently-deorphaned G protein-coupled receptor belonging to the free fatty acid receptor family. Its ligands are short-chain fatty acids (SCFAs), which are key nutrients that play a diverse role in physiological function, including the regulation of metabolic homeostasis and glycemic control. FFA3 is broadly expressed in a multitude of tissues including the intestine, pancreas, and central nervous system, and is thought to contribute to metabolic homeostasis via a summation of its tissue-specific effects. Consequently, FFA3 has been identified as a potential drug target for metabolic diseases including obesity and type-2 diabetes. FFA3 is highly expressed in enteroendocrine cells (EECs) within the intestinal epithelium - the major site of SCFA generation - and is hypothesized to play a role in the secretion of postprandial incretin hormones, which are a group of specialized gut peptides that regulate a variety of metabolic and digestive functions following a meal. However, due to a paucity of data, the role of FFA3 within the intestine and its effects on physiology and metabolism is largely unclear. Previous in vivo studies involving this receptor have largely relied on global knockout mouse models, making it difficult to isolate its effects in EECs. To overcome this challenge, we have generated a novel intestine-specific knockout mouse model for FFA3, utilizing Cre-mediated recombination under the expression of the villin promoter. Here, we report the first in vivo characterization of FFA3 in the intestine and reveal novel insights into receptor function. Following model validation, we conducted a general metabolic assessment of male Villin-Cre-FFA3 mice on normal chow and observed no major congenital or time-dependent defects. Because dietary changes are known to alter gut microbial composition, and thereby SCFA production, a pilot study was performed on male Villin-Cre-FFA3 mice and their littermate controls to probe for a phenotype on a high-fat, high-sugar “western diet.” Mice were placed on either normal chow (NC) or western diet (WD) at 10 weeks of age and metabolically profiled for 25 weeks. Our data reveals that Villin-Cre-FFA3 mice on WD, but not NC, were protected from diet-induced metabolic dysfunction, and displayed significantly lower levels of fat mass as well as modestly improved glycemic control. Our findings suggest a novel role of FFA3 in mediating the metabolic consequences of a western diet - a state of high inflammation, dysbiosis and metabolic stress. Moreover, these data support an intestine-specific role of FFA3 in both glucose and lipid metabolism, and further suggest the receptor’s role in whole-body metabolic homeostasis and in the development of adiposity and hyperglycemia.