Individual Differences in AMY1 Gene Copy Number, Salivary α-Amylase Levels, and the Perception of Oral Starch

Abstract

BackgroundThe digestion of dietary starch in humans is initiated by salivary α-amylase, an endo-enzyme that hydrolyzes starch into maltose, maltotriose and larger oligosaccharides. Salivary amylase accounts for 40 to 50% of protein in human saliva and rapidly alters the physical properties of starch. Importantly, the quantity and enzymatic activity of salivary amylase show significant individual variation. However, linking variation in salivary amylase levels with the oral perception of starch has proven difficult. Furthermore, the relationship between copy number variations (CNVs) in the AMY1 gene, which influence salivary amylase levels, and starch viscosity perception has not been explored.Principal FindingsHere we demonstrate that saliva containing high levels of amylase has sufficient activity to rapidly hydrolyze a viscous starch solution in vitro. Furthermore, we show with time-intensity ratings, which track the digestion of starch during oral manipulation, that individuals with high amylase levels report faster and more significant decreases in perceived starch viscosity than people with low salivary amylase levels. Finally, we demonstrate that AMY1 CNVs predict an individual's amount and activity of salivary amylase and thereby, ultimately determine their perceived rate of oral starch viscosity thinning.ConclusionsBy linking genetic variation and its consequent salivary enzymatic differences to the perceptual sequellae of these variations, we show that AMY1 copy number relates to salivary amylase concentration and enzymatic activity level, which, in turn, account for individual variation in the oral perception of starch viscosity. The profound individual differences in salivary amylase levels and salivary activity may contribute significantly to individual differences in dietary starch intake and, consequently, to overall nutritional status.

Changes in the salivary protein profile of morbidly obese women either previously subjected to bariatric surgery or not

“…Despite a direct relationship between this salivary protein and taste not having been reported, a recent study described differences between individuals with variable levels of sensitivity to oleic acid, with one protein spot being identified as salivary amylase [30]. This protein produces changes in the viscosity perception of starchy foods [25] resulting in increases in the levels of the sweet molecules maltose and glucose in the mouth [39]. We therefore put forward the hypothesis that during the consumption of starch-containing foods, lower levels and lower enzymatic activities of this salivary protein in individuals who have been subjected to bariatric surgery may result in a lower concentration of sweet compounds in the mouth as compared with group O individuals.…”

“…Another salivary protein potentially involved in ingestion is alpha-amylase. Although a link between this protein and taste perception has not been reported, it is involved in carbohydrate digestion and absorption, having also a role in the perception of starchy foods [25]. The potential interest in examining alpha-amylase in the study of obesity is increased by the known relation between this protein's concentration levels and the activity of the sympathetic nervous system [31], which is involved in energy balance and implicated in the development and maintenance of obesity [42].…”

Programmed emulsions for sodium reduction in emulsion based foods

“…The final solution had an enzyme level of 50 units per mL, human salivary α-amylase activity has been previously reported to range between 50 and 400 units per mL. 26,27 Immediately after enzyme addition a sodium ion specific electrode (Jenway, Stone, UK) was placed into the solution and conductivity recorded for 20 s to monitor the release of sodium from w 1 to w 2 . After 20 s 1 mL of 2 M HCl was added to the sample to inactivate the enzyme and 0.02% sodium azide mixed into the sample to prevent microbial spoilage.…”

Cooking clue to human dietary diversity

“…However, heat, particularly coupled with excess water as in boiling, solubilizes starch, so that salivary amylase, which humans have in variable abundance (3), can act inside 1 s rather than after many hours. Food scientists attribute many important oral sensations in humans to this enzymic activity, including the coating and decoating of the oral mucosa to produce impressions of "creaminess" and "thickness" in semisolid starchy foods (4,5). Dental researchers suspect that sticky types of cooked starch, coupled with the tendency of salivary amylase to bind to enamel surfaces (6), may result in both becoming trapped in dental plaque, leading to a maltose sugar product and potential caries (i.e., tooth decay).…”