Reduced salivary amylase activity in metabolic syndrome patients with obesity could be improved by treatment with a dipeptidyl peptidase IV inhibitor

High Blood Glucose After Starch Loading in Young Women With Small Increase in Salivary Amylase: Another Crucial Role of Postprandial Salivary Amylase

BACKGROUND

Salivary α-amylase plays a crucial role in the glucose metabolism. However, postprandial salivary α-amylase activity (SAA) and its relationship with blood glucose (BG) are poorly understood. Therefore, we investigated SAA and BG after starch loading in healthy young women.

METHODS

In 60 healthy non-obese young women, we investigated SAA, BG, and blood 3-hydroxybutyrate (3HB) after the consumption of 150 g rice (starch 48.8 g). Participants were classified into two groups based on the changes (Δ) in SAA from baseline at 60 min: small- and large-increase in ΔSAA groups (SI-ΔSAA and LI-ΔSAA).

RESULTS

BG levels were significantly higher at 60, 90, and 120 min in participants with SI-ΔSAA (n = 31) than LI-ΔSAA (n = 29). Baseline 3HB concentration was also higher in participants with SI-ΔSAA. ΔSAA at 60 min was most closely and inversely correlated with BG and ΔBG at 90 min (r = -0.53 and -0.50, both P < 0.0001). Generalized linear model analysis also indicated that ΔSAA at 60 min was the most predictive of ΔBG at 90 min.

CONCLUSIONS

Higher levels of BG and ΔBG were observed after starch loading in healthy young women with smaller increase in salivary amylase, suggesting another crucial role of postprandial salivary amylase for the postprandial glucose metabolism.

Fructose and methylglyoxal-induced glycation alters structural and functional properties of salivary proteins, albumin and lysozyme

Glycation process refers to reactions between reduction sugars and amino acids that can lead to formation of advanced glycation end products (AGEs) which are related to changes in chemical and functional properties of biological structures that accumulate during aging and diseases. The aim of this study was to perform and analyze in vitro glycation by fructose and methylglyoxal (MGO) using salivary fluid, albumin, lysozyme, and salivary α-amylase (sAA). Glycation effect was analyzed by biochemical and spectroscopic methods. The results were obtained by fluorescence analysis, infrared spectroscopy (total attenuated reflection-Fourier transform, ATR-FTIR) followed by multivariate analysis of principal components (PCA), protein profile, immunodetection, enzymatic activity and oxidative damage to proteins. Fluorescence increased in all glycated samples, except in saliva with fructose. The ATR-FTIR spectra and PCA analysis showed structural changes related to the vibrational mode of glycation of albumin, lysozyme, and salivary proteins. Glycation increased the relative molecular mass (Mr) in protein profile of albumin and lysozyme. Saliva showed a decrease in band intensity when glycated. The analysis of sAA immunoblotting indicated a relative reduction in intensity of its correspondent Mr after sAA glycation; and a decrease in its enzymatic activity was observed. Carbonylation levels increased in all glycated samples, except for saliva with fructose. Thiol content decreased only for glycated lysozyme and saliva with MGO. Therefore, glycation of salivary fluid and sAA may have the potential to identify products derived by glycation process. This opens perspectives for further studies on the use of saliva, an easy and non-invasive collection fluid, to monitor glycated proteins in the aging process and evolution of diseases.