Olfactory marker protein regulates adipogenesis via the cAMP–IκBα pathway

Olfactory marker protein (OMP) regulates olfactory transduction and is also expressed in adipose tissue. Since it serves as a regulatory buffer for cyclic AMP (cAMP) levels, we hypothesized that it plays a role in modulating adipocyte differentiation. To determine the role of OMP in adipogenesis, we examined the differences in body weight, adipose tissue mass, and adipogenic or thermogenic gene expression between high-fat diet-fed control and Omp-knockout (KO) mice. cAMP production, adipogenic gene expression, and cAMP response element binding protein (CREB) phosphorylation were measured during the differentiation of 3T3-L1 preadipocytes and mouse embryonic fibroblasts (MEFs). RNA sequencing was performed to determine the gene expression patterns responsible for the reduction in adipogenesis when Omp was deleted. Body weight, adipose tissue mass, and adipocyte size decreased in Omp-KO mice. Furthermore, cAMP production and CREB phosphorylation reduced during adipogenesis induced in Omp^-/- MEFs, and the Nuclear factor kappa B was activated due to significantly reduced expression of its inhibitor. Collectively, our results suggest that loss of OMP function inhibits adipogenesis by affecting adipocyte differentiation.