Caffeic acid inhibits the uptake of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) by inducing the efflux transporters expression in Caco-2 cells.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is formed as a by-product of the Maillard reaction during cooking and frying of protein-rich foods at high temperatures. PhIP is metabolized in the liver by cytochrome P450 1A1/2 to carcinogenic metabolite N-hydroxy PhIP, which can form DNA adduct. The ATP binding cassette (ABC) transporters, P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) are capable of transporting the food-borne procarcinogen PhIP back to the intestinal lumen. In the present study, the uptake and efflux of PhIP were assessed by determining apparent bidirectional permeability coefficients and efflux ratio. The efflux ratio of PhIP with 10 µM caffeic acid was significantly increased compared with control. The mRNA levels of efflux transporters were measured to evaluate the effect of caffeic acid in the presence of PhIP on efflux-mediated transport of PhIP. Caco-2 cells exposed to 10 µM caffeic acid for 3 and 6 h also exhibited higher mRNA levels of P-gp and BCRP than those of control. In contrast, the mRNA level of MRP2 was only slightly induced after 3 h and 6 h. Therefore, caffeic acid at low concentration is expected to be used not only as an antioxidant, but also as an inhibitor of the absorption of food borne carcinogen heterocyclic amines. However, further studies, especially in vivo studies, are required to confirm these results.

Dietary Chlorella protects against heterocyclic amine-induced aberrant gene expression in the rat colon by increasing fecal excretion of unmetabolized PhIP.

The food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the most abundant heterocyclic amines formed by cooking meat and fish at high temperature. PhIP induces colorectal adenoma risk in male rats when administered orally. This study used male Fisher 344 rats to investigate the impact of dietary Chlorella on PhIP metabolism and aberrant colonic gene expression following short-term PhIP treatment. High-performance liquid chromatography analysis revealed that fecal excretion of unmetabolized PhIP was significantly increased in rats whose diets were supplemented with Chlorella compared to rats in a PhIP-only group (P<0.001). Quantitative realtime PCR confirmed that the increase in beta-catenin and cyclin D1 mRNA in the colon induced by PhIP was ameliorated in rats pre-fed with Chlorella (P=0.052 for beta-catenin; P=0.005 for cyclin D1). The increase in DNA shearing that is a hallmark of caspase-8-mediated apoptosis by PhIP was also significantly diminished in the colons of rats pre-fed Chlorella (P=0.012). These results suggested that administering dietary Chlorella with a Western-style diet concomitantly or immediately before mutagen exposure might be beneficial in blocking the absorption of food mutagens such as PhIP.

Effect of acupuncture on the activity of gastrointestinal electricity / 中国针灸

Based on the summarization of literatures on regulation of gastrointestinal electricity with acupuncture, the regulation effect of acupuncture, its influencing factors and its mechanism were analyzed in this article. It is found that the regulation effect can be influenced by many factors such as different acupuncture techniques, frequency, point selection, manipulations and the physical condition of the object. The effect of acupuncture appears great variety, which manifests as reinforced, inhibited or a kind of two-way regulation. And it is also held that the effect of acupuncture relies on the integrity of the nerve system. Nuclei, neurotransmitters, body fluid and gastrointestinal hormone also take part in the acupuncture effect. Therefore, studies on mechanism of acupuncture effect on gastrointestinal electricity should be strengthened in the future.