Remission of impaired glucose tolerance by anthocyanin supplementation: a randomized, double-blind, and...

Anthocyanin supplementation is a promising nutritional intervention for prediabetes, whereas the efficacy varies due to the heterogeneity of diseases. Efficacy of the anthocyanin supplementation in impaired glucose tolerance (IGT) is evaluated and possible mechanisms are further explored.

This study aimed to investigate the effect of anthocyanin supplementation on pancreatic islet function in individuals with IGT.

A 12-wk randomized, double-blind, placebo-controlled (anthocyanin 160 mg/d or placebo) trial was conducted with routine lifestyle guidance involving 68 IGT participants. The primary outcome was β-cell function: disposition index (DI). Secondary outcomes included other oral glucose tolerance test (OGTT)-derived indices, insulin sensitivity, anthropometric measures, and levels of skin advanced glycation end products (AGEs) measured by skin autofluorescence. Analyses followed intention-to-treat principle.

For the primary outcome, there were no significant between-group differences in DI, with the adjusted mean differences of 61.3 [95% confidence interval (CI): -27.4, 150.0; P = 0.174]. The IGT reversion rate (defined as 2-h OGTT glucose <7.8 mmol/L) was significantly higher in the anthocyanin group than in the placebo group (55.9% compared with 29.4%, P = 0.013). In parallel with a greater improvement in Matsuda index, with an adjusted difference of 4.6 (95% CI: 2.5, 6.7; P = 0.003). Additionally, skin AGEs decreased significantly only in the anthocyanin group. The reduction in skin AGEs was positively correlated with the decrease in postprandial glucose AUC (r = 0.302, P = 0.001) and negatively with improved Matsuda index (r = -0.344, P < 0.001).

Anthocyanin supplementation could significantly reverse IGT by improving insulin sensitivity. The reduction of skin AGEs by anthocyanins might play a critical role in the dietary management of IGT. This trial was registered at chictr.org.cn as ChiCTR2400079566 (https://www.chictr.org.cn/showproj.aspx?proj=210725).