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Olfactory receptor 544 (Olfr544) is expressed in extra-nasal tissues and has been shown to reduce adiposity and shift fuel preference to fats. Here, we investigated whether Olfr544 regulates feeding behavior. Azelaic acid increased cholecystokinin (CCK) secretion ex vivo and in vivo by Olfr544 dependently. In a two-food choice study, oral administration of azelaic acid reduced high fat diet (HFD) intake and increased normal diet (ND) intake, which was abolished in Olfr544-knockout mice. In a two-bottle preference test, the oral administration of azelaic acid reduced the intake of linoleic acid solution while increasing the intake of control solution (xanthan gum) and the effect of azelaic acid disappeared in Olfr544-knockout mice. Intraperitoneal injection of proglumide, a CCK-1/2 receptor antagonist, negated the effect of azelaic acid in reducing fat preference. Collectively, our findings suggested that Olfr544 activation by azelaic acid reduced calorie-rich high-fat food intake mediated, at least in part, by CCK secretion.

Olfactory receptors are ectopically expressed in extra-nasal tissues. The gut is constantly exposed to high levels of odorants where ectopic olfactory receptors may play critical roles. Activation of ectopic olfactory receptor 544 (Olfr544) by azelaic acid (AzA), an Olfr544 ligand, reduces adiposity in mice fed a high-fat diet (HFD) by regulating fuel preference to fats. Herein, we investigated the novel function of Olfr544 in the gut. In GLUTag cells, AzA induces the cAMP-PKA-CREB signaling axis and increases the secretion of GLP-1, an enteroendocrine hormone with anti-obesity effects. In wild-type (WT) mice injected AzA, GLP-1 plasma levels were elevated. The induction of GLP-1 secretion was negated in cells with Olfr544 gene knockdown and in Olfr544-deficient mice. Gut microbiome analysis revealed that AzA increased the levels of Bacteroides acidifaciens and microbiota associated with antioxidant pathways. In fecal metabolomics analysis, the levels of succinate and trehalose, metabolites correlated with a lean phenotype, were elevated by AzA. The function of Olfr544 in gut inflammation, a key feature in obesity, was further investigated. In RNA sequencing analysis, AzA suppressed LPS-induced activation of inflammatory pathways and reduced TNF-α and IL-6 expression, thereby improving intestinal permeability. The effects of AzA on the gut metabolome, microbiome, and colon inflammation were abrogated in Olfr544-KO mice. These results collectively demonstrated that activation of Olfr544 by AzA in the gut exerts multiple effects by regulating GLP-1 secretion, gut microbiome and metabolites, and colonic inflammation in anti-obesogenic phenotypes and, thus, may be applied for obesity therapeutics.