Browsing by Subject "HCA-7"

Background and aim: Colorectal cancers (CRC) are the third most common type of cancer in men and the second most common in women worldwide. The risk for CRC is influenced by lifestyle factors, especially diet. The effect of diet on CRC risk is thought to be mediated by the liquid phase of the feces called fecal water (FW); the components in food or produced from food by the microbiome must be in soluble form to have an effect on the colon epithelial cells, especially on the proliferating cells at the bottom of the colonic crypts, and consequently on CRC risk. In this study, we examined how viability of cells from human colon cancer cell line HCA-7 was affected, when the cells were exposed to FW extracted from fecal samples from study participants eating diets with emphasis on either animal or plant protein sources. Additionally we tested, whether body mass index (BMI), pH of the FW, amount of N-nitroso compounds in feces (NOC), or intake of fiber, protein, calcium or energy correlate with viability. Materials and methods: 146 healthy voluteers (age 20–69, BMI 18,5–35) were randomly assigned to three intervention diet groups for 12 weeks. Protein content of the diets (target 17 E%) came from animal and plant sources in proportion of 70/30 % (ANIMAL-group, n=46), 50/50 % (50/50-group, n=44) and 30/70 % (PLANT-group, n=44). Food consumption was assessed using 4-day food records kept by the participants before and at the end of the intervention period. Fecal samples were collected from the same time periods. Fecal samples were diluted with water in ratio of 1:1 and homogenized, homogenate was ultracentrifuged, pH of the supernatant i.e. FW was measured and finally the FW was filtered sterile using a 0,22 μm filter. HCA-7-cells were first incubated roughly 24 h on 96-well cell culture plate in growth medium so that the cells were attached to the plate. Then three parallel FW samples in three different dilution (10 vol-%, 20 vol-% and 30 vol-%) from each study participant were added on to the plate, and the plate was further incubated exactly 24 h. After that, the amount of living cells was measured colorimetrically using WST-8-reagent. Viability (%) was determined by calculating the proportion of living cells in sample containing wells compared to the living cells in the control wells. Statistical significance of the differences of viability between the diet groups was tested by analysis of covariance (ANCOVA) using the viability at the baseline as covariate. Correlations were analyzed using Pearson’s correlation test. Results: FW samples were obtained from134 study participants. There was a statistically significant difference in viability between the groups’ means in samples with FW content of 30 vol-% (ANCOVA p=0,005). Viability (%) was smallest in the PLANT-group (co-variate adjusted mean 30,0 ± 1,9), and in the reciprocal comparison it differed from both the ANIMAL-group (37,8 ± 1,8; p = 0,011, Bonferroni correction) and the 50/50-group (37,1 ± 1,8; p = 0,021). At the end of the study, there were statistically significant correlation (p < 0,05) between viability and BMI in all of the FW contents (10 vol-%: Pearson correlation coefficient R = 0,210; 20 vol-%: R = 0,366; 30 vol-%: R = 0,319), pH of the FW in the FW contents of 20 vol-% (R = 0,204) and 30 vol-% (R = 0,249). The intake of protein (g/d) correlated in contents of 10 vol-% (R = 0,199) and 30 vol-% (R = 0,181). Also, the intake of protein in proportion to energy intake (E%) correlated in contents of 10 vol-% (R = 0,179) and 30 vol-% (R = 0,236). The intake of fiber, calcium and the amount of NOC:s in feces did not correlate with viability. Conclusions: In this study, the FW from the PLANT group reduced the viability of HCA-7 cells in vitro compared to the FW of the 50/50 ja the ANIMAL groups. This could indicate that increasing the consumption of plant-based protein sources and decreasing that of animal proteins may decrease the risk of CRC. To strengthen the current results, the exposure experiments should be replicated also using different colon cancer cell lines and a normal-like control cell line.