別府 英博

Obesity markedly increases the risk of colorectal cancer. Recently, the preventive effects of edible mushrooms on triglyceride elevation and visceral fat accumulation have been reported. Here, the effects of Pleurotus eryngii (Eringi) and Hypsizygus marmoreus (Bunashimeji) on azoxymethane (AOM)-induced aberrant crypt foci (ACF precancerous lesions) in the colorectums of mice fed a high-fat diet were examined. Eringi (ER) and Bunashimeji (BU) mushroom powder samples were used. Six-week-old male C57BL/6J mice received an intraperitoneal injection of AOM (10 mg/kg) once a week for two weeks, and were sacrificed and dissected at 6 weeks after the start of the experiment. After the initiation of the experiment, they received a normal diet (ND), high-fat diet (HFD), HFD + ER (1 or 5% of diet), or HFD + BU (1 or 5% of diet). As a result, body and fat weights were significantly lower in the 5% ER and BU groups than in the HFD group. Liver triglyceride levels were also significantly lower in the 5% ER and BU groups. Total liver cholesterol levels were significantly lower in the 5% ER group. The numbers of ACF (especially large ACF) showed strong inhibitory effects in both ER and BU groups. Measurement of the cell proliferation marker Ki-67 labeling index in the colonic mucosa demonstrated more significant suppression in both ER and BU groups than in the HFD group. These results suggest that the simultaneous intake of ER and BU may inhibit colorectal tumorigenesis in HFD-fed mice.

Aloe-emodin (1, 8-dihydroxy-3-hydroxyl-methylanthraquinone AE) and emodin (1,3,8-trihydroxy-6-methylanthraquinone EM) are anthraquinone derivatives that have been detected in some medical plants and share similar anthraquinone structures. AE and EM have been shown to exhibit anticancer activities in various cancer cell lines however, the inhibitory effects of these derivatives on the growth of cancer cells were previously reported to be different. Gastric cancer is the second most common cause of cancer cell death worldwide. In the present study, we examined the inhibitory effects of 0.05 mM AE and 0.05 mM EM on the proliferation of the MKN45 human gastric cancer cell line. The proliferation of MKN45 cells was significantly inhibited in AE- and EM-treated groups 24 h and 48 h after treatment. Furthermore, the inhibitory effects of EM were stronger than those of AE. The cell cycle of MKN45 cells were arrested in G0/G1 phase or G0/G1 and G2/M phases by AE and EM, respectively. However, an analysis of intracellular polyamine levels and DNA fragmentation revealed that the mechanisms underlying cell death following cell arrest induced by AE and EM differed.

Aloe vera gel exhibits protective effects against insulin resistance as well as lipid-lowering and anti-diabetic effects. The anti-diabetic compounds in this gel were identified as Aloe-sterols. Aloe vera gel extract (AVGE) containing Aloe-sterols has recently been produced using a new procedure. We previously reported that AVGE reduced large-sized intestinal polyps in Apc-deficient Min mice fed a high fat diet (HFD), suggesting that Aloe vera gel may protect against colorectal cancer. In the present study, we examined the effects of Aloe vera gel powder (AVGP) and AVGE on azoxymethane-induced colorectal preneoplastic aberrant crypt foci (ACF) in mice fed a HFD. Male C57BL/6J mice were given a normal diet (ND), HFD, HFD containing 0.5% carboxymethyl cellulose solution, which was used as a solvent for AVGE (HFDC), HFD containing 3% or 1% AVGP, and HFDC containing 0.0125% (H-) or 0.00375% (L-) AVGE. The number of ACF was significantly lower in mice given 3% AVGP and H-AVGE than in those given HFD or HFDC alone. Moreover, 3% AVGP, H-AVGE and L-AVGE significantly decreased the mean Ki-67 labeling index, assessed as a measure of cell proliferation in the colonic mucosa. In addition, hepatic phase II enzyme glutathione S-transferase mRNA levels were higher in the H-AVGE group than in the HFDC group. These results suggest that both AVGP and AVGE may have chemopreventive effects on colorectal carcinogenesis under the HFD condition. Furthermore, the concentration of Aloe-sterols was similar between 3% AVGP and H-AVGE, suggesting that Aloe-sterols were the main active ingredients in this experiment.