Genetic Variation of an Odorant Receptor OR7D4 and Sensory Perception of Cooked Meat Containing Androstenone

Although odour perception impacts food preferences, the effect of genotypic variation of odorant receptors (ORs) on the sensory perception of food is unclear. Human OR7D4 responds to androstenone, and genotypic variation in OR7D4 predicts variation in the perception of androstenone. Since androstenone is naturally present in meat derived from male pigs, we asked whether OR7D4 genotype correlates with either the ability to detect androstenone or the evaluation of cooked pork tainted with varying levels of androstenone within the naturally-occurring range. Consistent with previous findings, subjects with two copies of the functional OR7D4 RT variant were more sensitive to androstenone than subjects carrying a non-functional OR7D4 WM variant. When pork containing varying levels of androstenone was cooked and tested by sniffing and tasting, subjects with two copies of the RT variant tended to rate the androstenone-containing meat as less favourable than subjects carrying the WM variant. Our data is consistent with the idea that OR7D4 genotype predicts the sensory perception of meat containing androstenone and that genetic variation in an odorant receptor can alter food preferences

Prevalence and correlates of parosmia and phantosmia among smell disorders

Among those many individuals who suffer from a reduced odor sensitivity (hyposmia/anosmia) some individuals also experience disorders that lead to odor distortion, such as parosmia (i.e., distorted odor with a known source), or odor phantoms (i.e., odor sensation without an odor source). We surveyed a large population with at least one olfactory disorder (N = 2031) and found that odor distortions were common (46%), with respondents reporting either parosmia (19%), phantosmia (11%), or both (16%). In comparison to respondents with hyposmia or anosmia, respondents with parosmia were more likely to be female, young, and suffering from post-viral olfactory loss (p < 0.001), while respondents with phantosmia were more likely to be middle-aged (p < 0.01) and experiencing symptoms caused by head trauma (p < 0.01). In addition, parosmia, compared to phantosmia or anosmia/hyposmia, was most prevalent 3 months to a year after olfactory symptom onset (p < 0.001), which coincides with the timeline of physiological recovery. Finally, we observed that the frequency and duration of distortions negatively affects quality of life, with parosmia showing a higher range of severity than phantosmia (p < 0.001). Previous research often grouped these distortions together, but our results show that they have distinct patterns of demographics, medical history, and loss in quality of life

Identifying Treatments for Taste and Smell Disorders: Gaps and Opportunities.

The chemical senses of taste and smell play a vital role in conveying information about ourselves and our environment. Tastes and smells can warn against danger and also contribute to the daily enjoyment of food, friends and family, and our surroundings. Over 12% of the US population is estimated to experience taste and smell (chemosensory) dysfunction. Yet, despite this high prevalence, long-term, effective treatments for these disorders have been largely elusive. Clinical successes in other sensory systems, including hearing and vision, have led to new hope for developments in the treatment of chemosensory disorders. To accelerate cures, we convened the Identifying Treatments for Taste and Smell Disorders conference, bringing together basic and translational sensory scientists, health care professionals, and patients to identify gaps in our current understanding of chemosensory dysfunction and next steps in a broad-based research strategy. Their suggestions for high-yield next steps were focused in 3 areas: increasing awareness and research capacity (e.g., patient advocacy), developing and enhancing clinical measures of taste and smell, and supporting new avenues of research into cellular and therapeutic approaches (e.g., developing human chemosensory cell lines, stem cells, and gene therapy approaches). These long-term strategies led to specific suggestions for immediate research priorities that focus on expanding our understanding of specific responses of chemosensory cells and developing valuable assays to identify and document cell development, regeneration, and function. Addressing these high-priority areas should accelerate the development of novel and effective treatments for taste and smell disorders

A transcriptomic atlas of mammalian olfactory mucosae reveals an evolutionary influence on food odor detection in humans.

The mammalian olfactory system displays species-specific adaptations to different ecological niches. To investigate the evolutionary dynamics of olfactory sensory neuron (OSN) subtypes across mammalian evolution, we applied RNA sequencing of whole olfactory mucosa samples from mouse, rat, dog, marmoset, macaque, and human. We find that OSN subtypes, representative of all known mouse chemosensory receptor gene families, are present in all analyzed species. Further, we show that OSN subtypes expressing canonical olfactory receptors are distributed across a large dynamic range and that homologous subtypes can be either highly abundant across all species or species/order specific. Highly abundant mouse and human OSN subtypes detect odorants with similar sensory profiles and sense ecologically relevant odorants, such as mouse semiochemicals or human key food odorants. Together, our results allow for a better understanding of the evolution of mammalian olfaction in mammals and provide insights into the possible functions of highly abundant OSN subtypes

Cell surface expression does not predict function of ORs.

<p>(A) Primate OR2W1 orthologs and 2W subfamily members to allyl phenyl acetate. (B) Quantification of live cell-surface expression of each receptor. ** p<0.01 when compared to hOR2W1. Y-axis denotes the average Cy3 intensity in arbitrary units (a.u.) (n = 3, ± S.E.M.). S6 is positive control and Rho-pCI is negative control. (C) Representative image of live cell-surface staining for each receptor. For additional live-cell surface staining, see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002821#pgen.1002821.s013" target="_blank">Figure S13</a>, <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002821#pgen.1002821.s020" target="_blank">Table S7</a>.</p

Response of OR orthologs to 42 chemically diverse odors.

<p>(A) Tuning curves of human, chimp and macaque OR2W1 orthologs tested against 42 odors using a cAMP-mediated luciferase assay <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002821#pgen.1002821-Zhuang3" target="_blank">[26]</a>. Odorants are ordered along the x-axis according to the response elicited from the human OR2W1, with the best ligands closer to the center. Y-axis represents the luciferase response to an odor at 100 µM (n = 3, ± S.E.). Negative values on the y-axis indicate the odor elicited an inhibitory response on OR signaling. See <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002821#pgen.1002821.s006" target="_blank">Figure S6</a> for additional tuning curves. (B) Response of chimp and macaque OR2W1 orthologs (variant responses) plotted against the human OR2W1 response using the data from (A). X-axis and y-axis are response in luciferase assay at 100 µM (n = 3, ± S.E.). The black line represents the unit-slope line. Odor abbreviations in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002821#pgen.1002821.s016" target="_blank">Table S3</a>.</p