Salivary Amylase: Digestion and Metabolic Syndrome

Abstract

Salivary amylase is a glucose-polymer cleavage enzyme that is produced by the salivary glands. It comprises a small portion of the total amylase excreted, which is mostly made by the pancreas. Amylases digest starch into smaller molecules, ultimately yielding maltose, which in turn is cleaved into two glucose molecules by maltase. Starch comprises a significant portion of the typical human diet for most nationalities. Given that salivary amylase is such a small portion of total amylase, it is unclear why it exists and whether it conveys an evolutionary advantage when ingesting starch. This review will consider the impact of salivary amylase on oral perception, nutrient signaling, anticipatory metabolic reflexes, blood sugar, and its clinical implications for preventing metabolic syndrome and obesity.

Starch Digestion–Related Amylase Genetic Variant Affects 2-Year Changes in Adiposity in Response to Weight-Loss Diets: The POUNDS Lost Trial

“…Growing evidence suggests the important implications of amylase gene and copy number variation in obesity and metabolic diseases (30,41), and we show that amylase genetic regulation might have a substantial impact on improving obesity. Limitations of this study were unavailability of data on glucose tolerance tests and that we did not measure AMY1-AMY2 copy numbers, serum, or salivary amylase concentrations, which limited our ability to explore potential underlying mechanisms.…”

“…Previous studies show that copy numbers of AMY1 and AMY2A (6) as well as serum levels of the two enzymes (5) are significantly correlated and that salivary and pancreatic amylase proportions are approximately equal in serum (5). In addition, production of pancreatic amylase is regulated by insulin (29,30), and obese individuals with insulin resistance may have reduced pancreatic amylase levels (5). Because the SNP rs11185098 is located in the AMY1 , AMY2A , and AMY2B gene region, we could not distinguish between salivary and pancreatic gene effects or whether both genes account for the observations.…”

Human amylase gene copy number variation as a determinant of metabolic state

“…A clue originates from the observation of a positive correlation between CNV within AMY1 and the concentration and activity of salivary amylase in humans: increased copies of AMY1 presumably result in increased production and activity of salivary amylase, thereby facilitating initiation of amylase digestion within the saliva [14,15,18,21,25,[28][29][30][31]. Although pancreatic amylase accounts for most of digestion of starch within the diet, the role of salivary amylase in starch digestion should not be under-estimated [32].…”

“…First of all, studies have shown that humans and rodents both obtained the expression of salivary amylase independently by a retroviral insertion into the amylase gene region; the fact that it has persisted in both evolutionary lines suggests that the expression of salivary amylase confers a selective advantage [14,35,36]. Next, obligate carnivores do not produce salivary amylase [14,37], whereas animals which feed on starch-rich plant matter, such as fruits and seeds, display salivary amylase activity [14]. Although domesticated dogs do not produce salivary amylase [14,38,39,40], they do display CNV of AMY2B, which is correlated with serum amylase activity [40].…”

“…One region of particular interest that displays such multi-allelic complexity is the genetic sequence coding for the amylase enzymes [10]. In humans, the amylase enzyme occurs in two distinct forms: i) salivary (produced by the salivary glands), and; ii) pancreatic (produced by the exocrine pancreas) [13,14]. These enzymes play a key role in the digestion of starch.…”