The aim of this study was to examine the inhibitory effect of acute oral chlorogenic acid (CGA) ingestion on increases in blood glucose levels following glucose tolerance testing. Ten healthy male adults (age: 25.9 ± 5.4 years) participated in the study. Blood samples were collected from the antecubital vein of subjects following overnight fasting. After a 120-min rest, they were administered 75 g glucose and chlorogenic acid or placebo. The amount of chlorogenic acid administered (in the form of capsules) to the subjects was 0.1g per body mass. In addition, only capsules were ingested in placebo ingestion conditions. Blood samples were collected 4 times during the 120-min rest period at intervals of 30 min. Serum insulin and plasma glucose levels were analyzed. Serum insulin levels increased significantly at 30 min after glucose ingestion, and fixed until 120 min in both conditions. Plasma glucose level increased significantly at 30 min after glucose ingestion, followed by a slow decrease. In addition, no significant difference was found between the conditions in each parameter. In conclusion, acute oral chlorogenic acid ingestion may not inhibition blood glucose increase following glucose tolerance.
Over 15 million people worldwide contract type 2 diabetes mellitus [
Because type 2 diabetes is heterogeneous in nature, current therapies are unable to modify the natural history of this disorder. Therefore, it is necessary to explore new antidiabetic therapies. Polyphenol, an antioxidant found in many plants, fruits, vegetables, coffee, red wine, and tea, has been studied widely to examine its effect in reducing oxidative stress at the cellular level, thereby inhibiting the disease [5-7]. Coffee and wine are known to have a higher polyphenol content than other foods [
This study aimed to examine the effect of acute oral CGA ingestion on the inhibition of blood glucose increase following glucose tolerance.
Ten healthy young male adults without past type 2 diabetes history participated in this study (age: 25.9 ± 5.4 years; height: 171.2 ± 6.1 cm; body mass: 70.7 ± 8.9 kg). Written informed consent was obtained from all subjects after a full explanation of the experimental purpose and protocol was provided. Moreover, the experimental protocol was approved by the Ethics Committee on Human Experimentation of Faculty of Human Science, Kanazawa University (authorization number: 2012-10).
The experimental design was a double-blind, cross-over study. Subjects received both CGA and placebo ingestion over the course of the study, with a 1-week washout period. Moreover, the test condition order was counter balanced to eliminate order effect. In addition, subjects were instructed to refrain from intensive exercise for two days before the experiment and to fast the evening before the experiment. Subjects were also instructed to refrain from consuming beverages or food containing CGA and cold remedies.
CGA was ingested at a ratio of 0.1 g/kg body weight. CGA is one of the polyphenol and their effect looks like tannin. It contains 5% - 10% within coffee beans and its content is greater than caffeine (1% - 2%). Antioxidative effect has been expected by its ability to entrap radical, and it is suggested to include the effect of delay glucose absorption. Both CGA and placebo were administered in capsules. Each capsules were administered with 75 g glucose (Partial hydrolysate of starch), which dissolved with 150 g water.
Subjects reported to the study laboratory twice during the experiment; the standard protocol for glucose tolerance testing was followed (
Blood samples collected over the 120-min rest period
were analyzed for blood glucose and insulin. This was accomplished by transferring 3 mL of blood into a blood sampling tube containing sodium fluoride to assess blood glucose concentration and 7 mL of blood into a tube for analysis of insulin. These processes were carried out within 30 s of the blood collection. The samples were immediately centrifuged, and the supernatants were placed in chilled containers and stored at −80˚C until analyzed. Plasma glucose concentrations were analyzed by enzymatically. The inter-assay and intra-assay coefficients of variation (CV) were 0.2% and 0.9%, respectively. The samples for insulin were analyzed by high performance liquid chromatography (HPLC) using the HPLC system (Shimazu and Hitachi, Japan). Sensitivity, inter-assay, and intra-assay coefficients of variation (CV) of this assay were 5.92 nmoL/L, 4.94%, and 0.00%, respectively.
Two-way repeated measures analysis of variance (ingestion condition × measurement time) was used to examine the mean difference between CGA and placebo ingestion conditions for each parameter. When showing a significant main or interaction effect, Tukey’s honestly significant difference (HSD) was used as post hoc analysis to examine specific mean differences. An alpha concentration of 0.05 was used for all experiments.