pharmaceutics Review Ectopic Odorant Receptor Responding to Flavor Compounds: Versatile Roles in Health and Disease Tao Tong 1,* , Yanan Wang 1, Seong-Gook Kang 2 and Kunlun Huang 1,3,4,* 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China;
[email protected] 2 Department of Food Engineering, Mokpo National University, Muangun 58554, Korea;
[email protected] 3 Key Laboratory of Safety Assessment of Genetically Modified Organism (Food Safety), Ministry of Agriculture, Beijing 100083, China 4 Beijing Laboratory for Food Quality and Safety, Beijing 100083, China * Correspondence:
[email protected] (T.T.);
[email protected] (K.H.); Tel.: +86-10-6273-7244 (T.T.); +86-10-6273-7786 (K.H.) Abstract: Prompted by the ground-breaking discovery of the rodent odorant receptor (OR) gene family within the olfactory epithelium nearly 30 years ago, followed by that of OR genes in cells of the mammalian germ line, and potentiated by the identification of ORs throughout the body, our appreciation for ORs as general chemoreceptors responding to odorant compounds in the regulation of physiological or pathophysiological processes continues to expand. Ectopic ORs are now activated by a diversity of flavor compounds and are involved in diverse physiological phenomena varying from adipogenesis to myogenesis to hepatic lipid accumulation to serotonin secretion. In this review, we outline the key biological functions of the ectopic ORs responding to flavor compounds and the underlying molecular mechanisms. We also discuss research opportunities for utilizing ectopic ORs as therapeutic strategies in the treatment of human disease as well as challenges to be overcome in the Citation: Tong, T.; Wang, Y.; Kang, future.