Relevance of positive selection on human salivary amylase gene

该奖项是美国国家科学基金会社会、行为和经济科学博士后研究奖学金（SPRF）计划的一部分。SPRF计划的目标是为学术界、工业界或私营部门和政府的科学事业准备有前途的早期职业博士级科学家。SPRF奖励包括在知名科学家的赞助下进行为期两年的培训，并鼓励博士后进行独立研究。美国国家科学基金会寻求促进科学界各阶层的科学家，包括那些未被充分代表的群体的科学家，参与其研究项目和活动；博士后阶段被认为是实现这一目标的一个重要的专业发展阶段。每个博士后必须解决各自学科领域的重要科学问题。在拉斯维加斯内华达大学Alyssa Crittenden博士的赞助下，该博士后奖学金支持一位早期职业科学家，研究唾液淀粉酶基因（AMY1）拷贝数增加对人类在口服食物消耗阶段消化淀粉能力的积极选择的影响。这个项目解决了关于唾液α淀粉酶（sAA）对淀粉消耗的意义的悬而未决的问题。sAA的口服活性是消化淀粉类食物的第一步。然而，人类通过烹饪使食物降解外部化，从而消除了口服消化的需要。烹饪可以分解淀粉等大分子。然而，尚不清楚咀嚼过程中sAA的活性是否与人类消化淀粉有关。重要的是，没有研究探索sAA活性在生淀粉和熟淀粉上的速率变化。人类独特地拥有AMY1的多个拷贝数，这表明饮食中淀粉摄入量的变化。这种饮食变化影响人类健康，因为它涉及到对富含淀粉的饮食的耐受性。该项目将有助于了解人类sAA基因适应。此外，了解AMY1变异对不同种族和地域人群营养获取的影响，有助于为代谢性疾病预防的饮食治疗策略提供信息。该项目采用多学科方法来回答有关饮食适应如何影响健康的开放性问题。拟议的研究有三个阶段-体外建模阶段，人体参与者试验阶段和现场工作阶段。第一阶段将通过在不同的短时间间隔内测量还原糖副产物来研究暴露于sAA的淀粉消化作为AMY1拷贝数的函数。组织学分析将显示sAA活性通过淀粉的形态变化。第二阶段将通过口服淀粉溶液在短时间间隔内研究人类参与者的口服淀粉消化。排出的溶液也将以同样的方法测定还原糖。使用淀粉酶α 1酶联免疫吸附试验（ELISA kit for淀粉酶α 1）在刺激唾液上测定酶的数量，使用从口腔拭子中提取的DNA对参考单拷贝基因使用数字PCR测定基因拷贝数。这些数据将与医疗和饮食史数据相结合，以帮助发现影响sAA产生和活性的因素。第三阶段需要实地工作来量化分配给口腔处理淀粉类食物的咀嚼时间。这些都是有价值的数据，以咀嚼为生的人类的食物，没有经过广泛的机械或热加工。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.