A new study has found that individuals with type 2 diabetes or prediabetes exhibit a stronger association between AMY1 gene copy number and salivary amylase activity compared with individuals without diabetes.
The AMY1 gene encodes salivary amylase, an enzyme that initiates starch digestion in the oral cavity. AMY1 copy number varies widely, ranging from 2 to 20 copies per diploid genome, and may influence glucose metabolism.
Investigators analyzed saliva and genetic data from 196 adults in Ithaca, New York, including 18 individuals with clinically confirmed type 2 diabetes (T2D) or prediabetes—based on medical records and oral mixed-meal tolerance testing—and 178 without. AMY1 copy number was determined using both quantitative PCR and droplet digital PCR, and salivary amylase activity was measured. A subset of 94 participants provided up to four saliva samples on different days to assess diurnal variation.
Results showed a significant positive association between AMY1 copy number and enzyme activity. In individuals with T2D or prediabetes, each additional AMY1 copy was associated with a 43% increase in salivary amylase activity, compared with a 14% increase in controls. These estimates were based on a model incorporating 285 saliva samples after excluding those with incomplete data.
Salivary amylase activity also varied by time of day, with a 19% increase per hour in the morning and 9% per hour in the afternoon. The rate of change between these time periods was not statistically significant.
Copy number estimates obtained by qPCR and ddPCR were strongly correlated (intraclass correlation coefficient, 0.95), with ddPCR showing slightly greater precision.
Although AMY1 copy number remains constant, salivary amylase activity fluctuates due to factors such as time of day, stress, and caffeine intake. These fluctuations may reflect short-term changes in starch metabolism and glucose regulation.
The elevated salivary amylase activity observed in participants with T2D or prediabetes may reflect a compensatory mechanism in response to impaired glucose homeostasis. As a cross-sectional study, however, the findings cannot determine causality.
The authors noted that prospective studies are needed to evaluate whether rising salivary amylase activity precedes the onset of diabetes or is a consequence of metabolic dysfunction. The study also supports further investigation into whether salivary amylase monitoring could aid in early detection or disease tracking.
Study data are publicly available on Zenodo. The authors reported no conflicts of interest.
Source: PLOS One