Serum Amylase Levels in Relation to Islet β Cell Function in Patients with Early Type 2 Diabetes

OBJECTIVE The insulin-pancreatic acinar axis may play a major role in pancreatic function. Amylase is an exocrine enzyme that is produced by pancreatic acinar cells, and low serum amylase levels may be associated with endocrine diseases, such as metabolic syndrome and diabetes. We hypothesized that low serum amylase levels may be associated with impaired islet β cell function in type 2 diabetes. Therefore, we investigated the relationship between the serum amylase levels and islet β cell function in patients with early type 2 diabetes. METHODS The cross-sectional study recruited 2327 patients with a mean of 1.71±1.62 years since their diagnosis of type 2 diabetes, and all participants were treated with lifestyle intervention alone. Serum amylase levels, the 75-g oral glucose tolerance test (OGTT) and metabolic risk factors were examined in all participants. The insulin sensitivity index (Matsuda index, ISIMatsuda) and insulin secretion index (ratio of total area-under-the-insulin-curve to glucose-curve, AUCins/glu) were derived from the OGTT. Integrated islet β cell function was assessed by the Insulin Secretion-Sensitivity Index-2 (ISSI-2) (ISIMatsuda multiplied by AUCins/glu). RESULTS Serum amylase levels in the normal range were significantly correlated with ISIMatsuda, AUCins/glu and ISSI-2 (r = 0.203, 0.246 and 0.413, respectively, p<0.001). The association of the serum amylase levels with ISSI-2 (adjusted r = 0.363, p<0.001) was closer than the association with ISIMatsuda (adjusted r = 0.191, p<0.001) and AUCins/glu (adjusted r = 0.174, p<0.001) after adjusting for the anthropometric indices, time since the diagnosis of diabetes, lipid profiles, uric acid levels, estimated glomerular filtration rate, HbA1c levels, smoking and drinking using the partial correlation test. After adjusting for these metabolic risk factors in the multivariate regression analysis with the amylase levels as the dependent variable, ISSI-2 was the major independent contributor to the serum amylase levels (β = 0.416, t = 21.72, p<0.001). Meanwhile, in a comparison of the groups with the highest and lowest quartiles of serum amylase levels, the mean difference in logISSI-2 was 0.902 (95% CI 0.823 to 0.982), and after adjusting for metabolic risk factors, the mean difference in logISSI-2 was 0.610 (0.537 to 0.683). CONCLUSIONS Serum amylase levels in the normal range are positively associated with integrated islet β cell function in patients with early type 2 diabetes, as assessed by ISSI-2.