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.
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.
|Mandel, Abigail L; Breslin, Paul A S (2012) High endogenous salivary amylase activity is associated with improved glycemic homeostasis following starch ingestion in adults. J Nutr 142:853-8|