Relevance of positive selection on human salivary amylase gene

Schnorr Stephanie L, Tahlequah OK

Investigators

Abstract

This award was provided as part of NSF's Social, Behavioral and Economic Sciences Postdoctoral Research Fellowships (SPRF) program. The goal of the SPRF program is to prepare promising, early career doctoral-level scientists for scientific careers in academia, industry or private sector, and government. SPRF awards involve two years of training under the sponsorship of established scientists and encourage Postdoctoral Fellows to perform independent research. NSF seeks to promote the participation of scientists from all segments of the scientific community, including those from underrepresented groups, in its research programs and activities; the postdoctoral period is considered to be an important level of professional development in attaining this goal. Each Postdoctoral Fellow must address important scientific questions that advance their respective disciplinary fields. Under the sponsorship of Dr. Alyssa Crittenden at University of Nevada, Las Vegas, this postdoctoral fellowship award supports an early career scientist investigating the impact of positive selection for increased copy number of the salivary amylase gene (AMY1) on the ability for humans to digest starch during the oral phase of food consumption. This project tackles unanswered questions regarding the significance of salivary alpha amylase (sAA) for starch consumption. Oral activity of sAA is the first step towards digestion of starchy foods. Yet humans have removed the need for oral digestion by externalizing food degradation through cooking, which breaks down large molecules such as starch. However it is unknown whether sAA activity during chewing is relevant for humans to digest starch. Importantly, no research exists that explores rate variation of sAA activity on raw versus cooked starch. Humans uniquely possess multiple copy numbers of AMY1, signaling a shift in dietary intake of starch. Such dietary shifts impact human health as it relates to tolerance of starch-rich diets. This project will contribute towards an understanding of human sAA genetic adaptations. Furthermore, understanding the impact of AMY1 variation on nutritional acquisition among ethnically and geographically diverse human populations helps inform dietary therapeutic strategies for metabolic disease prevention. This project uses a multidisciplinary approach to answer open questions about how dietary adaptation impacts health. The proposed research has three phases - an in-vitro modeling phase, a human participant trial phase, and a field work phase. Phase I will investigate starch digestion from exposure to sAA as a function of AMY1 copy number by measuring the reducing sugar byproducts across varying short time intervals. Histological assays will show sAA activity via the morphological changes to starch. Phase II will investigate oral starch digestion in human participants over short time intervals via oral manipulation of a starch solution. The expelled solution will similarly be measured for reducing sugars. Enzyme quantity will be measured on stimulated saliva using an ELISA kit for Amylase Alpha 1, and gene copy number will be measured using digital PCR against a reference single copy gene using DNA extracted from buccal swabs. These data will be combined with medical and dietary history data to help discover factors that influence the production and activity of sAA. Phase III entails field work to quantify chewing time allocated for orally processing starchy foods. These are valuable data to contextualize chewing for humans that subsist from foods that have not undergone extensive mechanical or thermal processing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.