Chinese bayberry (Myrica rubra Sieb. et Zucc.) leaves proanthocyanidins inhibit intestinal glucose transport in human Caco-2 cells.

Background: The hypoglycemic effects of Chinese bayberry leaves proanthocyanidins (BLPs) have been demonstrated. It is unclear, nevertheless, whether BLPs reduced postprandial blood glucose levels by regulating glucose uptake and glucose transport. Method: This study investigated the effect of BLPs (25, 50, and 100 µg/mL) on glucose uptake and glucose transport in human intestinal epithelial cells (Caco-2 cells). The uptake of 2-Deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl) amino]-D-glucose (2-NBDG) and disaccharidases activity in Caco-2 cells were measured. The glucose transport ability across the cell membrane was determined using the established Caco-2 monolayer model. The transcript and protein levels of key glucose transporters were analyzed using real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting, respectively. Results: The results showed that BLPs significantly decreased glucose uptake and disaccharidases activity (p < 0.05). Otherwise, BLPs treatment obviously inhibited glucose transport across the Caco-2 monolayer in both simulated-fast (5 mM glucose) and simulated-fed (25 mM glucose) conditions. It was attributed to the suppression of glucose transporter2 (GLUT2) and sodium-dependent glucose cotransporter 1 (SGLT1) by BLPs. BLPs were found to significantly downregulated the transcript level and protein expression of glucose transporters (p < 0.05). Meanwhile, the mRNA expression of phospholipase C (PLC) and protein kinase C (PKC) involved in the signaling pathway associated with glucose transport were decreased by BLPs. Conclusion: These results suggested that BLPs inhibited intestinal glucose transport via inhibiting the expression of glucose transporters. It indicated that BLPs could be potentially used as a functional food in the diet to modulate postprandial hyperglycemia.

Study of the Biotransformation of Tongmai Formula by Human Intestinal Flora and Its Intestinal Permeability across the Caco-2 Cell Monolayer.

Tongmai formula (TMF) is a well-known Chinese medicinal preparation that contains isoflavones as its major bioactive constituents. As traditional Chinese medicines (TCMs) are usually used by oral administration, their fate inside the intestinal lumen, including their biotransformation by human intestinal flora (HIF) and intestinal absorption deserves study. In this work TMF extract was incubated with human intestinal bacteria under anaerobic conditions and the changes in the twelve main constituents of TMF were then investigated. Their intestinal permeabilities, i.e., the transport capability across the intestinal brush border were investigated with a human colon carcinoma cell line (Caco-2) cell monolayer model to predict the absorption mechanism. Meanwhile, rapid HPLC-DAD methods were established for the assay. According to the biotransformation curves of the twelve constituents and the permeability coefficients, the intestinal absorption capacity of the typical compounds was elevated from the levels of 10(-7) cm/s to 10(-5) cm/s from those of the original compounds in TMF. Among them the main isoflavone glycosides puerarin (4), mirificin (6) and daidzin (7) were transformed into the same aglycone, daidzein (10). Therefore it was predicted that the aglycone compounds might be the real active ingredients in TMF. The models used can represent a novel path for the TCM studies.

Study on transcription and expression of IL-8 in human Caco-2 cells induced by VvhA recombinant protein / 中华微生物学和免疫学杂志

Objective To investigate the effect of VvhA recombinant protein to the expression of IL-8 in human intestinal epithelial Caco-2 cells. Methods The VvhA recombinant protein(rVvhA) was ex-pressed by prokaryotic expression vector pET-28a (+)-whA in E. coli BL21 (DE3) , purified by Ni~(2+)-NTA affinity chromatography refoldod by stepwise deliquation together with dialysis methods and identified by Western blot. The cytotoxic of rVvhA to human Caco-2 cells was measured by CCK-8. The transcription of IL-8 mRNA in human Caco-2 cells induced by rVvhA was determined by RT-PCR, and the expression of IL-8 in human Caco-2 cells induced by rVvhA was determined by ELISA assay. Results rVvhA was purified with high purity up to 95%. The viability of human Caco-2 cells treated with 1.5 HU/ml rVvhA was inhibi-ted significantly (P < 0.05). The rVvhA can induce human Caco-2 cells to increase the transcription and expression of IL-8 in dose- and time-dependent manner. The transcription of IL-8 gene in human Caco-2 cells treated with 0.6 HU/ml rVvhA in 30 min can be up-regulated significantly, and the expression of IL-8 in human Caco-2 cells treated with rVvhA in 4 h can be increased significantly. Conclusion rVvhA has cy-totoxic to human Caco-2 and can increase the expression of IL-8, it might play a major role in the inflamma-tory reaction of rVvhA-exposed cells.