Antioxidant and Antidiabetic Properties of a Thinned-Nectarine-Based Nanoformulation in a Pancreatic β-Cell Line

Abstract

Pancreatic β-cells play a crucial role in maintaining glucose homeostasis, although they are susceptible to oxidative damage, which can ultimately impair their functionality. Thinned nectarines (TNs) have gained increasing interest due to their high polyphenol and abscisic acid (ABA) content, both of which possess antidiabetic properties. Nevertheless, the efficacy of these bioactive compounds may be compromised by limited stability and bioavailability in vivo. This study aimed to develop nanoformulations (NFs) containing pure ABA or a TN extract (TNE) at an equivalent ABA concentration. Subsequently, the insulinotropic and antioxidant potential of the NFs and their unformulated (free) forms were compared in MIN-6 pancreatic cells exposed to varying glucose (5.5 mM and 20 mM) and iron (100 µM) concentrations. NF-TNE treatment exhibited enhanced antioxidant activity compared to free TNE, while ABA-based groups showed no significant antioxidant activity. Moreover, MIN6 cells incubated with both high glucose and iron levels demonstrated significantly higher insulin AUC levels after treatment with all samples, with NF-TNE displaying the most pronounced effect. In conclusion, these results highlight the additional beneficial potential of TNE due to the synergistic combination of bioactive compounds and demonstrate the significant advantage of using a nanoformulation approach to further increase the benefits of this and similar phytobioactive molecules.

Keywords: abscisic acid; agro-food waste products; bioactive compounds; nanoformulations; pancreatic β-cells; polyphenols.

Figure 1

MTT analysis on MIN6 cell viability at 24, 48, and 72 h. (A) Cells treated with free ABA and free TNE; (B) cells treated with NF-ABA (ascorbyl palmitate/DSPE-PEG nanoformulated abscisic acid) and NF-TNE (ascorbyl palmitate/DSPE-PEG nanoformulated thinned nectarine extract); values are presented as means ± S.D. of 4 replicates. Cells incubated with MEM were regarded as the control in the analysis; data were analyzed with a one-way ANOVA followed by Dunnett’s post hoc test; * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001, **** p < 0.0001, significantly different from the control group. ABA, abscisic acid; Ctrl, control; TNE, thinned nectarine extract.

Figure 2

MTT results of 24, 48, and 72 h pre-treatment with (A) DSPE-PEG/ascorbyl palmitate nanoformulated ABA and free ABA, (B) DSPE-PEG/ascorbyl palmitate nanoformulated TNE and free TNE on MIN6 cells; values are presented as means ± SEM of 4 replicates. Cells incubated with MEM were regarded as the control in the analysis; data were analyzed with two-way ANOVA followed by Sidak’s post hoc test; * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001 vs. not nanoformulated sample at the same treatment concentrations; ABA, abscisic acid; Ctrl, control; TNE, thinned nectarine extract; DSPE-PEG, 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-(polyethylene glycol-2000).

Figure 3

Cellular antioxidant activity (CAA) assay results of nanoformulated and unformulated TNE. Values are presented as the mean ± S.D. of 6 replicates; data were analyzed with a two-tailed Student’s t-test; **** p < 0.0001, significantly different from non-nanoformulated samples at the same treatment concentration (ABA 0.05 µM); NF-TNE, ascorbyl palmitate/DSPE-PEG nanoformulated TNE; TNE, thinned nectarine extract.

Figure 4

Effects of iron (100 μM) preincubation in MIN6 cells. The data represent mean ± SEM, n = 4. Data were analyzed with one-way ANOVA followed by Sidak’s post hoc test; * p ≤ 0.05, ** p ≤ 0.01, **** p ≤ 0.0001 significantly different from samples incubated without iron at the same glucose concentration. Abbreviations: Glu, glucose; NF-ABA, ascorbyl palmitate/DSPE-PEG nanoformulated abscisic acid; NF-TNE, ascorbyl palmitate/DSPE-PEG nanoformulated thinned nectarine extract.

Figure 5

Effects of iron (100 μM) preincubation in MIN6 cells. The data represent the mean ± SEM, n = 4. Data were analyzed with one-way ANOVA followed by Sidak’s post hoc test; * p ≤ 0.05, *** p ≤ 0.001, **** p ≤ 0.0001 significantly different from samples incubated without iron at the same glucose concentration. Abbreviations: ABA, abscisic acid; Ctrl, control (MEM); TNE, thinned nectarine extract.

Figure 6

The effect of treatment with two different concentrations of glucose (5 mM and 20 mM) w/wo iron (100 µM) on MIN6 cells insulin secretion. The data represent the mean ± SEM, n = 4. Data were analyzed with one-way ANOVA followed by Tukey’s multiple comparison test; **** p ≤ 0.0001 significantly different from Ctrl samples incubated with the same glucose concentrations without iron; # p ≤ 0.05 significantly different from Ctrl + Glucose 20 mM. Abbreviations: AUC, area under the curve; Ctrl, control (MEM).

Figure 7

The effect on MIN6 cell insulin secretion after incubation with two different glucose concentrations (5.5 mM and 20 mM). Unformulated abscisic acid (free ABA), unformulated thinned nectarine extract (free TNE), ascorbyl palmitate/DSPE-PEG nanoformulated abscisic acid (NF-ABA), ascorbyl palmitate/DSPE-PEG nanoformulated thinned nectarine extract (NF-TNE), and MEM (Ctrl) were used as treatments. The data represent the mean ± SEM, n = 4. Data were analyzed with one-way ANOVA followed by Tukey’s multiple comparison test; * p ≤ 0.05, significantly different from the Ctrl sample at the same glucose concentrations. Abbreviations: AUC, area under the curve; Ctrl, control.

Figure 8

The effect on MIN6 cell insulin secretion after incubation with two different glucose concentrations (5.5 mM and 20 mM) and high iron levels (100 μM). Unformulated abscisic acid (free ABA), unformulated thinned nectarine extract (free TNE), ascorbyl palmitate/DSPE-PEG nanoformulated abscisic acid (NF-ABA), ascorbyl palmitate/DSPE-PEG nanoformulated thinned nectarine extract (NF-TNE), and MEM (Ctrl) were used as treatments. The data represent the mean ± SEM, n = 4. Data were analyzed with one-way ANOVA followed by Tukey’s multiple comparison test; ** p ≤ 0.01, **** p ≤ 0.0001 significantly different from the Ctrl sample at the same glucose concentrations. Abbreviations: AUC, area under the curve; Ctrl, control.