Soluble polysaccharides reduce binding and inhibitory activity of tea polyphenols against porcine pancreatic α-amylase

The effects of three soluble polysaccharides on the inhibitory activity of tea polyphenols against porcine pancreatic α-amylase (PPA) were studied through PPA inhibition, half inhibition concentration (IC50), inhibition kinetics and fluorescence quenching. The results show that citrus pectin, wheat arabinoxylan and oat β-glucan could each increase the IC50 values and competitive inhibition constants (Kic), and decrease the fluorescence quenching constants (KFQ) of tea polyphenols interacting with PPA. The data show a competitive interaction equilibrium among polysaccharides, polyphenols and PPA. For individual polyphenols, there were negative linear correlations between both the values of 1/Kic and KFQ and that of IC50 with and without polysaccharides, indicating that the decreased inhibitory activity of polyphenols induced by the polysaccharides was caused by the reduced binding of polyphenols with PPA. Additionally, the slopes of the linear relationship between IC50 and Kic and that between KFQ and 1/Kic remained stable with and without polysaccharides, suggesting that these constants may be combined to characterize the effects of soluble polysaccharides on the PPA inhibition by polyphenols

A narrowing range of bone scan in newly diagnosed prostate cancer patients: A retrospective comparative study

Objectives: The objective of the following study is to clarify a suitable group whereby a bone scan could be spared at the initial staging of prostate cancer, we wished to identify the possible relationship between bone metastasis and clinical and pathological parameters including serum total prostate specific antigen (PSA) concentration, alkaline phosphatase (ALP), biopsy Gleason Score (GS), and percentage of pathological cores. Materials and Methods: We reviewed the results of 220 bone scintigraphies, which were done between January 1, 2011 and June 30, 2013 in patients with newly diagnosed prostate cancer. These parameters were evaluated together with standard clinicopathological data to determine the prediction ability of the bone scan by univariate and multivariate analyses. Results: Bone metastases were seen in 44 patients of all 220 patients (20%, 95% confidence interval, 17-24%). In univariate analysis, PSA and biopsy GS were useful in predicting the bone scan result, but ALP and percentage of pathological cores was not. In multivariate analysis, the single most useful parameter in predicting the bone scan result was PSA (P < 0.001). Conclusions: A bone scan seems to be impractical in newly diagnosed prostate cancer patients with serum PSA level <20 ng/ml and GS up to seven and pre-treatment PSA is the best predictor of the need for the bone scan according to results of this study

The Mechanisms of Alpha-Amylase Inhibition by Flavan-3-Ols and the Possible Impacts of Drinking Green Tea on Starch Digestion

International audienceMany studies have shown that flavan-3-ols inhibit mammalian alpha-amylases but the published IC 50 and K i values vary up to a thousand times. We therefore tested the effects of 6 pure flavan-3-ols-abundant in green tea-on the activity of pure porcine pancreatic alpha-amylase (PPA) under steady-state kinetic conditions. We used both amylose and maltopentaose as substrates, along with spectrophotometry and chromatography as analytical tools, respectively. A Docking approach was also used to probe the interaction between PPA and each flavan-3-ol. The results showed that the 6 flavan-3-ols inhibit amylose hydrolysis with K i comprised between 7 and 34 μM, according to a mixed inhibition profile for gallocatechin gallate, and a competitive inhibition profile for the 5 other flavanols. Only the galloyl-containing flavan-3-ols inhibited the maltopentaose hydrolysis with a K i of about 30 μM according to a noncompetitive profile. We conclude that dietary flavan-3-ols could inhibit starch digestion nonnegligibly. The results of the docking trials were concordant with the kinetic data and have noticeably revealed that the cis-flavan-3-ols epigallocatechin gallate and epicatechin gallate bind similarly to PPA, involving π-stacking with Trp59