Delphinidin-Rich Maqui Berry Extract (Delphinol®) Lowers Fasting and Postprandial Glycemia and Insulinemia in Prediabetic Individuals during Oral Glucose Tolerance Tests

Abstract

Delphinidin anthocyanins have previously been associated with the inhibition of glucose absorption. Blood glucose lowering effects have been ascribed to maqui berry (Aristotelia chilensis) extracts in humans after boiled rice consumption. In this study, we aimed to explore whether a standardized delphinidin-rich extract from maqui berry (Delphinol) affects glucose metabolism in prediabetic humans based on glycemia and insulinemia curves obtained from an oral glucose tolerance test (OGTT) after a challenge with pure glucose. Volunteers underwent four consecutive OGTTs with at least one week washout period, in which different doses of Delphinol were administered one hour before glucose intake. Delphinol significantly and dose-dependently lowered basal glycemia and insulinemia. Lower doses delayed postprandial glycemic and insulinemic peaks, while higher doses reversed this tendency. Glycemia peaks were dose-dependently lowered, while insulinemia peaks were higher for the lowest dose and lower for other doses. The total glucose available in blood was unaffected by treatments, while the total insulin availability was increased by low doses and decreased by the highest dose. Taken together, these open exploratory results suggest that Delphinol could be acting through three possible mechanisms: by inhibition of intestinal glucose transporters, by an incretin-mediated effect, or by improving insulin sensitivity.

Conflict of interest statement

Competing InterestsThis study was supported by an unconditional research grant from MNL-Chile to the Reproductive Health Research Institute, Pontificia Universidad Católica de Chile, Santiago, Chile.

Figures

Figure 1

Mean glycemia variation during OGTT for all volunteers treated with four different Delphinol doses of nil (control), 60, 120, and 180 mg, at four different occasions with several washout days in between experiments. Sixty minutes after Delphinol intake, participants presented with dose-dependent lowering of basal blood glucose. At this time, 75 g of glucose was consumed and resulting postprandial glucose levels are presented. Statistically significant (α = 0.05) altered values compared to untreated control are indicated by an asterisk.

Figure 2

Mean insulinemia variation during OGTT for all volunteers treated with four different Delphinol doses of nil (control), 60, 120, and 180 mg, at four different occasions with several washout days in between experiments. Sixty minutes after Delphinol intake, participants presented with dose-dependent lowering of basal blood glucose. At this time, 75 g of glucose was consumed and resulting postprandial glucose levels are presented. Statistically significant (α = 0.05) altered values compared to untreated control are indicated by an asterisk.

Figure 3

(a) Mean glycemia variation during OGTT for all volunteers treated with each separate Delphinol dose. Basal and postprandial glycemia levels are presented, in order to compare the tendencies observed at each time point depending on the dose administered. (b) Time normalized area under the glycemia curve for each dose with the contribution of each time segment. (c) Maximum glycemia peak for each dose, with regression line and 95% confidence intervals, slope value, and associated significance level. Statistically significant (α = 0.05) altered values compared to untreated control are indicated by an asterisk.

Figure 4

(a) Mean insulinemia variation during OGTT for all volunteers treated with each separate Delphinol dose. Basal and postprandial insulinemia levels are presented, in order to compare the tendencies observed at each time point depending on the dose administered. (b) Time normalized area under the insulinemia curve for each dose with the contribution of each time segment. (c) Maximum insulinemia peak for each dose. Statistically significant (α = 0.05) altered values compared to untreated control are indicated by an asterisk.