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The Relationship Between Single Nucleotide Polymorphisms in Taste

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The Relationship Between Single Nucleotide Polymorphisms in Taste The Relationship Between Single Nucleotide Polymorphisms in Taste Receptor Genes, Taste Perception and Dietary Intake by Elie Chamoun A Thesis presented to The University of Guelph In partial fulfillment of requirements for the degree of Doctor of Philosophy in Human Health and Nutritional Sciences Guelph, Ontario, Canada © Elie Chamoun, August 2018 i ABSTRACT THE RELATIONSHIP BETWEEN SINGLE NUCLEOTIDE POLYMORPHISMS IN TASTE RECEPTOR GENES, TASTE PERCEPTION AND DIETARY INTAKE Elie Chamoun Advisor: University of Guelph, 2018 Dr. David W.L. Ma Food preferences and dietary habits are heavily influenced by taste perception, and there is growing interest in characterizing taste preferences based on genetic variation. Genetic differences in the ability to perceive key tastes may impact eating patterns. Therefore, increased understanding of taste genetics may lead to new personalized strategies, which may influence the trajectory of chronic disease risk. Recent advances show that single nucleotide polymorphisms (SNPs) in taste receptor genes are associated with changes in psychophysical measures of taste as well as eating patterns. The current understanding of how genetic variation impacts taste function and dietary habits for sweet, fat, salt, sour, and umami taste is limited and warranted due to the role of these types of taste in detecting nutrients that pose health risks when overconsumed. Results from this thesis demonstrated that specific SNPs are associated with taste sensitivity, taste preference and eating patterns. In adults, associations between SNPs and psychophysical measures of taste were observed between rs4790151 (TRPV1) and salt sensitivity, rs2499729 (GRM4) and umami sensitivity, rs713598 (TAS2R38) and bitter sensitivity, and rs236514 (KCNJ2) and sour preference. In children, associations were observed between rs4790522 (TRPV1) and salt preference, and rs173135 (KCNJ2) and sour preference. The rs9701796 (TAS1R2) sweet taste receptor SNP was significantly associated with both sweet preference and dietary intake of added sugar in children, while calories from sugar in snacks among children were associated with the rs35874116 (TAS1R2) sweet taste receptor SNP. Work from this thesis also demonstrates that higher sensitivities to salt, sweet, and umami taste are associated with decreases in the preferences for these tastes. Overall, SNPs in taste receptor genes have been demonstrated in this thesis to associate with psychophysical ii measures of taste and, in some instances, affect food preferences and eating patterns. This emerging and active field of taste research shows great promise to enhance our fundamental understanding of how taste receptor SNPs contribute to the genetic basis of eating patterns, health and disease. Results from this thesis provide important new insights into the relationship between SNPs in taste receptor genes, taste perception and dietary intake in both children and adults. iii ACKNOWLEDGEMENTS Firstly, I would like to thank my advisor Dr. David Ma for his mentorship both during my Master’s and PhD research projects. You have played a fundamental role in my personal and professional growth over the past few years. You’ve always had my best interest in mind, and this is why I have reached the end of my PhD carrying with me a wealth of truly enriching lessons and experiences. Your professionalism and thoughtfulness have had an immeasurable impact on the way I carry myself as a student, a colleague, but also as a human being. Thank you for having such enormous confidence in me because it helped me gain confidence in my own abilities and helped me to excel as an independent thinker. As a direct result of your trust in me, I have been allowed to take on responsibilities that have honed my skills as a writer, communicator, teacher, mentor, but most of all as a leader. I wish you all of the best with your research program and believe whole-heartedly that the Guelph Family Health Study will flourish under your direction. Next, I would like to thank my Advisory Committee members Dr. Jess Haines, Dr. Alison Duncan, Dr. David Mutch, and Dr. Lisa Duizer. Jess, thank you for your support from the very start of my Master’s when the Guelph Family Health Study was still just an idea. Your expertise was immensely helpful to me, especially during my Qualifying Exam when I was able to learn a great deal from you. Alison, thank you for being such an excellent role model from the very beginning of my Master’s program. I am very fortunate to have a professor like you on my side because you care so much about the quality of my experience as a graduate student. I also deeply appreciate your mentorship in preparation for the Qualifying Exam. David, thank you for your support in the development of the genetics program of the Guelph Family Health Study. Your careful and meticulous review of my work was instrumental to my development as a scientist and your passion for nutrigenomics is not only evident, but infectious as well. Lisa, I’m going to miss our chats in the hallways of Food Science. I’m clearly not a sensory scientist, but you challenged me to push myself and encouraged me to think very deeply about my study design and methodology. I also want to thank you for your support as I prepared for the Qualifying Exam. iv I would also like to acknowledge Dr. Nina Jones who served on my Qualifying Exam committee. Thank you to Dr. Bill Bettger and Dr. Iwona Rudkowska for serving as examiners for my thesis defense, your expertise in evaluating the thesis is truly appreciated. Thanks to Jonathan Guss for playing a pioneering role in forming the GFHS and for being such a great mentor. Next, I would like to thank Lyn Hillyer and Angela Annis. Lyn, around the time that we met, I never anticipated what a great friendship we would have. I’ll always cherish our lovely chats over coffee and my palate thanks you for having an almost constant supply of chocolate in the lab. I have learned so much from you both academically and personally. Over the years, I have admired your quiet confidence and unbelievably kind heart. You have taught me so much about perseverance and your strength has inspired me more than you know. I wish you peace, love, and all the golf that your heart desires. Angela, where do I begin? You were the first person who made me feel like I was in the right place when I started graduate school, and I cannot thank you enough for that. Besides professors, you and I were the first members of the GFHS team. From those humble beginnings to the vibrant and successful GFHS that we now know, I will never forget all of the experiences we shared. Your patience, professionalism, and incredible work ethic shaped the person I am today and helped me to succeed in executing my own human research studies. As my Guelph mom, you were always there to hear me out when I was discouraged and made me feel more positive. Your friendship has meant so much to me and will continue to for years to come. I would like to acknowledge past and present members of the Ma lab for all of their direct or indirect support for my graduate work. A special thanks to Jessie Burns for being the best lab mate I have ever had and for dealing with all of my horrible dad jokes. Your future will be so bright in every way imaginable. Thank you to the GFHS team past and present members. In particular, I would like to thank research assistants Charlotte Jones, Jessica Watterworth, Tory Ambrose, Sarah Wedde and Sabrina Douglas. I would also like to thank students who processed dietary intake data including Laurie Matthews, Julia Mirotta, Dee Muszynski and Robyn Lightfoot. A very special thank you to Angel Liu and v Nicholas Carroll for being the best study assistants I could have asked for—I could not have run my studies without you two. Thank you also to the GFHS investigator team for supporting me in a variety of ways throughout my graduate career. I would also like to thank Dr. Gerarda Darlington, Dr. Zeny Feng and Annetta Qi for all of their help with statistical analysis. A final thanks to Kaity Roke for helping me develop protocols for my genetics work and for being a brilliant role model. I would be remiss not to thank the HHNS department for providing such an excellent place to go to work. Thank you to the A team for your administrative support and Becki for keeping our work areas clean. I have made some unforgettable friendships in the department over the years. Thank you to everyone who crossed paths with me for being there through all of the laughs and the tougher times. In particular, I would like to thank Adrian Taylor, Shannon Klingel, and Willem Peppler. I am so fortunate to have met you three. Not only can I laugh my face off with you, but you have always been there to talk through all the bumps in the road that is graduate school. Each of you have qualities that I am lucky to have picked up throughout our friendship such as excellent work ethic, incredible perseverance, and remarkable compassion. It would be difficult to imagine my graduate career without you. I have the deepest appreciation for my family and all of the support they have provided me all throughout my life. To my siblings Sandra and Joe, thank you for always making your little brother believe he can do anything he sets his mind to. To my parents Jeanne and Toni, your love and encouragement is seemingly limitless. Everything I have achieved is a result of your unwavering support and of raising me to be who I am today.
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