Clinical and Evolutionary Significance of the Taste and Oral Digestion of Starch

描述（由申请人提供）：本研究的目的是阐明由淀粉摄入量的进化差异引起的遗传变异如何影响当今西方饮食人群的淀粉味道和消化、葡萄糖吸收和血糖。为了实现这一目标，将测试唾液淀粉酶基因（AMY1）拷贝数（CNVs）的增加会增加摄入淀粉后血糖升高的速度的假设（目的1）。此外，研究人员将测试人类存在淀粉味道的假设，并确定口服淀粉暴露是否会影响唾液淀粉酶水平（目的2）。在第一阶段，研究人员将检查个体在摄入淀粉后的血糖状况。唾液样本将分析唾液淀粉酶水平和酶功能使用Western blots和酶活性测定。由淀粉酶水解产生的淀粉分解剖面将通过高效液相色谱法（HPLC）进行评估。最后，研究人员将通过定量PCR （qPCR）、纤维荧光原位杂交（FISH）和基因分型来评估AMY1的遗传变异，包括基因拷贝数和单核苷酸多态性（SNPs）。对于Aim 2，研究人员将确定受试者是否能够独立于强度（2a）区分淀粉和单糖的味道，以及口服淀粉是否比单糖更能增加唾液淀粉酶的释放（2b；口服调节）。最后，他们还将检查将受试者置于高或低淀粉饮食中的影响，以确定唾液淀粉酶水平是否根据淀粉摄入量而上调或下调（2c；口服和口服后调节）。唾液淀粉酶将按照第1部分进行评估。

DESCRIPTION (provided by applicant): The objective of the proposed work is to elucidate how genetic variations resulting from evolutionary differences in starch intake influence starch taste and digestion, glucose absorption, and blood sugar in people consuming a Western diet today. To achieve this goal, the hypothesis that increased copy number (CNVs) of the salivary amylase gene (AMY1) increases the rate at which blood glucose rises after ingesting starch will be tested (Aim 1). Furthermore, the researchers will test the hypothesis that starch taste exists in humans and determine if oral starch exposure affects salivary amylase levels (Aim 2). For Aim 1, the researchers will examine an individuals' blood glucose profile following starch ingestion. Saliva samples will be analyzed for salivary amylase levels and enzyme functionality using Western blots and enzymatic activity assays. The starch breakdown profile resulting from amylase hydrolysis will be assessed via high performance liquid chromatography (HPLC). Finally, the researchers will assess genetic variation in AMY1, including the number of gene copies and single nucleotide polymorphisms (SNPs), through quantitative PCR (qPCR), fiber fluorescence in situ hybridization (FISH), and genotyping. For Aim 2, the researchers will determine if subjects can discriminate the taste of starch from simpler sugars independent of intensity (2a) and if oral exposure to starch will increase the release of salivary amylase more so than simpler sugars (2b; oral regulation). Finally, they will also examine the effects of placing subjects on a high or low starch diet to determine if salivary amylase levels are up or down-regulated depending on starch intake (2c; oral and post-oral regulation). Salivary amylase will be assessed as in Aim 1. PUBLIC HEALTH RELEVANCE: Evolutionarily, efficient starch metabolism may have contributed to survival during bouts of malnutrition and/or intestinal malaise, which can lead to nutrient malabsorption. However, in today's state of food excess and high starch ingestion, it is possible that increased copy number of the AMY1 gene contributes to the risk of insulin resistance and non-insulin dependent diabetes (NIDDM), disorders associated with altered carbohydrate metabolism. Therefore, it may be possible to use high AMY1 gene copy number and salivary amylase levels as risk factors to identify individuals at risk for insulin resistance and diabetes.