Antidiabetic potential of purple and red rice (Oryza sativa L.) bran extracts

Authors: Boue, Stephen; Daigle, Kim; Chen, Ming Hsuan; Cao, Heping; HEIMAN, MARK - Microbiome Theraputics

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2016
Publication Date: 6/10/2016
Citation: Boue, S.M., Daigle, K.W., Chen, M.H., Cao, H., Heiman, M.L. 2016. Antidiabetic potential of purple and red rice (Oryza sativa L.) bran extracts. Journal of Agricultural and Food Chemistry. 64(26):5345-5353. https://pubs.acs.org/doi/10.1021/acs.jafc.6b01909.
DOI: https://doi.org/10.1021/acs.jafc.6b01909

Interpretive Summary: Rice bran contains several bioactive components that have been linked to the promotion of human health. Brown rice bran contains lipophilic components that include the tocotrienols and gamma-oryzanol. Pigmented or colored rice bran contains different phenolic compounds including anthocyanins (purple rice) and proanthocyanidins (red rice). Some of these bioactive compounds individually have been shown to promote glucose uptake and aid in glucose balance in animal studies. However, only recently has rice bran been examined for its potential to aid in glucose management. In this study, bran extracts were examined for their ability to stimulate glucose uptake in mouse fat cells (adipocytes). Exposure of adipocytes to red bran and purple bran extracts significantly increased glucose uptake, however the brown rice extract did not increase glucose uptake. Glucose uptake was increased 2.7-fold by exposure to 50 ug/mL of the red bran extract, and 2.4-fold by exposure to 50 ug/mL of the purple bran extract. On a molecular level, increased levels of glucose transporters were detected in both purple and red bran extracts. Thus, the stimulative effect of pigmented bran extracts on glucose uptake was attributed to increased gene expression of glucose transporters. Also, three red bran fractions from a stimulated glucose uptake, with both the 50% ethanol and 70% acetone fractions displaying higher activity with proanthocyanidins a component of these two fractions. Overall, the two pigmented rice bran extracts in this study exhibited strong stimulatory effects on glucose uptake. These results indicate potential benefits of red and purple bran extracts as an intervention to prevent hyperglycemia.

Technical Abstract: Rice bran contains several bioactive components that have been linked to the promotion of human health. Brown rice bran contains lipophilic components that include the tocotrienols and gamma-oryzanol. Pigmented or colored rice bran contains different phenolic compounds including anthocyanins (purple rice) and proanthocyanidins (red rice). Some of these bioactive compounds individually have been shown to promote glucose uptake and aid in glucose homeostasis in animal studies. However, only recently has rice bran been examined for its potential to aid in glucose management. In this study, bran extracts were examined for their ability to stimulate glucose uptake in 3T3-L1 adipocytes. Exposure of adipocytes to red bran and purple bran extracts significantly increased basal glucose uptake, however the brown rice extract did not increase glucose uptake. Basal glucose uptake was increased 2.7-fold by exposure to 50 ug/mL of the red bran extract, and 2.4-fold by exposure to 50 ug/mL of the purple bran extract. On a molecular level, polymerase chain reaction showed significantly increased levels of glucose transporters GLUT1 and GLUT4 in both purple and red bran extracts. Thus, the stimulative effect of pigmented bran extracts on glucose uptake was attributed to increased gene expression of glucose transporters. Also, three red bran fractions from a Sephadex column stimulated glucose uptake, with both the 50% ethanol and 70% acetone fractions displaying higher activity with proanthocyanidins a component of these two fractions. Overall, the two pigmented rice bran extracts in this study exhibited strong stimulatory effects on glucose uptake. These results indicate potential benefits of red and purple bran extracts as an intervention to prevent hyperglycemia.