Characterization of adiponectin-receptor agonist dipeptide, Tyr-Pro, by in vitro and in silico analyses

Adiponectin plays a role in regulating glucose metabolism via binding to adiponectin receptor1/2 (AdipoR1/2)-mediated signaling in an insulin-independent manner. Although orally-active AdipoR agonist, AdipoRon, was successfully developed as a novel anti-diabetic drug, no natural food-derived compounds with AdipoR agonistic effect have been reported so far. The aim of this study is to develop an AdipoR1-agonistic peptide by in vitro and in silico analyses. Considering the structural property of AdipoRon, 15 synthetic dipeptides possessing aromatic and imino groups were subjected to glucose uptake experiments in L6 myotubes. Among them, Tyr-Pro (163 ± 6%, 1 µM, p < 0.05) significantly promoted glucose uptake by activating AMPK/GLUT4 axis similar to AdipoRon (162 ± 12%, 0.1 µM). No significant promotion effect of Pro-Tyr was observed, suggesting the importance of peptide sequence. In AdipoR1-knockdown cells, the effect of Tyr-Pro was diminished, indicating that Tyr-Pro may interact with AdipoR1 as an agonist. No significant effect of Pro-Tyr was observed, suggesting the importance of peptide sequence. In AdipoR1-knockdown cells, the effect of Tyr-Pro was diminished, indicating that Tyr-Pro may interact with AdipoR1 as an agonist. The molecular dynamics simulation of Tyr-Pro toward the AdipoR1 was also confirmed by CHARMM-GUI-aided in silico analysis, in which Tyr-Pro was stably positioned in the two possible binding sites (sites 1 and 2) of AdipoR1 embedded in a virtual phospholipid membrane (ΔG_bind: < -10 kcal/mol). In conclusion, the present study demonstrated the antidiabetic function of the Tyr-Pro as an AdipoR1 agonist.