|WANG, MINQIAN - Rutgers University|
|ZHANG, LIQING - Virginia Tech|
|ARANGO-ARGOTY, GUSTAVO - Virginia Tech|
|XIAO, WEIDONG - Temple University Medical School|
|YAM, KIT - Rutgers University|
Submitted to: Molecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2017
Publication Date: 8/3/2017
Citation: Wang, M., Firrman, J., Zhang, L., Arango-Argoty, G., Tomasula, P.M., Liu, L.S., Xiao, W., Yam, K. 2017. Apigenin impacts growth of the gut microbiota and alters gene expression of Enterococcus. Molecules. 22(8):1292.
Interpretive Summary: Apigenin is a nutrient, known as a flavonoid, found in fruits and vegetables such as celery, parsley, oranges, onions, and cilantro. Laboratory tests on human cells have shown apigenin to have some anti-inflammatory and anti-carcinogenic activities, but these have not been substantiated by human clinical trials. Once inside the digestive tract, a small amount of apigenin is absorbed in the small intestine, with the remainder then coming in contact with the large community of bacteria living in the large intestine, referred to as the gut microbiota. Even though it is known that the gut microbiota respond to changes in the diet, it was unknown if a single flavonoid could affect the gut microbiota. In the first study of its type, ARS researchers at Wyndmoor, PA, evaluated the ability of apigenin to cause changes in the growth of gut bacteria, first by looking at its effects on an individual bacterial species, Enterococcus, and then on this same species in the complete community of bacteria from a human donor. Apigenin slowed down the growth of Enterococcus when it was the sole bacterial culture and may be capable of damaging Enterococcus, but this was not observed in the community setting. This shows that apigenin works differently in a community setting, where there are hundreds of types of bacteria, some of which may degrade apigenin. In conclusion, this research shows that apigenin may injure Enterococcus and slow its growth when tested as an individual species. It also demonstrates how the gut microbiota as a community may be shaped by apigenin.
Technical Abstract: Apigenin is a major dietary flavonoid widely distributed in plants with many bioactivities. Apigenin reaches the colon region intact and interacts with the human gut microbiota; however, there is little research on how apigenin affects gut bacteria. This study investigated the effect of pure apigenin on human gut bacteria, at both single strain and community levels. The effect of apigenin on the single gut bacteria strains, Bacteroides galacturonicus, Bifidobacterium catenulatum, Lactobacillus rhamnosus GG, and Enterococcus caccae, was examined by measuring their anaerobic growth profiles. The effect of apigenin on a gut microbiota community was studied by culturing fecal inoculum under in vitro conditions simulating the human ascending colon. 16S rRNA gene sequencing and GC-MS analysis quantified changes in the community structure. Single molecule RNA sequencing was used to reveal the response of Enterococcus caccae to apigenin. Enterococcus caccae was effectively inhibited by apigenin when cultured alone; however, genus Enterococcus was enhanced when tested in a community setting. Single molecule RNA sequencing found that Enterococcus caccae responded to apigenin by up- regulating genes involved in DNA repair, stress response, cell wall synthesis, and protein folding. Taken together, these results demonstrate that apigenin effects both growth and gene expression of Enterococcus caccae.