Anti-diabetic effects of astaxanthin-rich extract derived from Paracoccus carotinifaciens on pancreatic β cells

Astaxanthin is a natural pigment that is used as a dietary supplement. Many experiments have shown that astaxanthin has positive effects against various diseases including diabetes. Adonixanthin and adonirubin are biosynthetic intermediates of beta-carotene to astaxanthin and possess the same radical scavenging activity as astaxanthin. In this study, we evaluated the antidiabetic effect on pancreatic beta cells of astaxanthin-rich extract (ARE) derived from Paracoccus carotinifaciens, which contains several carotenoids such as astaxanthin, adonir-ubin, and adonixanthin. Specifically, we studied the effects on insulin secretion and cytoprotection as well as on intracellular reactive oxygen species (ROS) generation and mitochondrial superoxide production. As a result, pretreatment with ARE derived from P. carotinifaciens increased insulin secretion under the condition of 20 mM glucose stimulation in iGL cells. In addition, ARE derived from P. carotinifaciens significantly decreased strep-tozotocin (STZ)-induced cell death in INS-1 cells, and isobologram analysis revealed the synergistic effects among astaxanthin, adonixanthin, and adonirubin. We clarified that the production control of mitochondrial superoxide was involved in the mechanism of these effects. These findings suggest that ARE derived from P. carotinifaciens may be used to treat diabetes by increasing glucose-stimulated insulin secretion and protecting pancreatic beta cells.