Effect of high-fat and low-fiber meals on the cell proliferation activity of colorectal mucosa

Effects of Increasing Levels of Defatted Rice Bran on Intestinal Physical Barrier and Bacteria in Finishing Pigs

The aims of this study were to assess the effects of increasing levels of DFRB as a replacement for corns on intestinal physical barrier function and bacteria of finishing pigs. A total of 35 castrated finishing pigs (age: 158.5 ± 2.0 d, initial body weight: 62.9 ± 0.8 kg) were randomly divided into five dietary treatments (seven replicates/treatment) for a 28-day experimental period, i.e., a control diet with basal diet, and four experimental diets in which maize was replaced by 7%, 14%, 21%, and 28% DFRB, respectively. The results showed that serum endotoxins concentration and diamine oxidase (DAO) activity were both increased (linear, p = 0.0004, 0.001, respectively) with DFRB level. However, compared with control group, serum endotoxins concentration and DAO activity were not different in pigs fed with 7% DFRB in the diet. There was a quadratic response in serum D-lactate concentration to the increased DFRB (quadratic, p = 0.021). In the cecum, thickness of the intestinal wall significantly increased with increasing levels of DFRB in the diets (linear, p = 0.033), while crypt depth/thickness of the intestinal wall ratio significantly decreased with increasing level of DFRB in the diets (linear, p = 0.043). In the jejunum, total bacteria, Escherichia coli, and Bifidobacterium all responded quadratically to increasing levels of DFRB in the diets (quadratic, p = 0.003, 0.001, 0.006, respectively). Additionally, there was no difference in Escherichia coli in pigs fed 0%, 7%, and 14% DFRB diets. In the colon, there were quadratic responses in C. perfringens to the increased DFRB (quadratic, p = 0.023). C. perfringens reduced as the DFRB concentration increased from 0% to 14% and then increased. When D-lactate, total bacteria, Escherichia coli, Bifidobacterium, and C. perfringens were considered, the optimal substitution level of DFRB were 12.00%, 11.84%, 7.50%, 8.92%, and 15.92%, respectively. In conclusion, 7% DFRB had a beneficial effect on intestinal wall thickness, Bifidobacterium and C. perfringens, and had no adverse effect on intestinal permeability and Escherichia coli.

Methylation of promoter region of CDX2 gene in colorectal cancer

The incidence of colorectal cancer is on the increase owing to changes in daily diet. In the present study, the methylation status of caudal type homeobox transcription factor 2 (CDX2) gene in lesion tissue of colorectal cancer (CRC) was investigated. Additionally, the correlation between the promoter methylation of CDX2 gene, CRC and gene expression in patients with CRC and normal population was examined. Between April 2014 and May 2015 78 cases with CRC were enrolled in the study. Using methylation-specific polymerase chain reaction (PCR), the promoter methylation of CDX2 in normal tissues and colorectal tissues was examinned. Through the fluorescence quantitative PCR technique, the expression levels of CDX2 gene were determined in a normal population and lesion tissue of patients with CRC. At the same time, we evaluated the levels of the CDX2 gene product in the normal population and lesion tissue of patients with CRC. The results showed that the methylation rate of the promoter region of CDX2 gene in normal colorectal tissue was 43.5%, whereas that in the lesion tissue of CRC was 78.5%. The result was statistically significant (P<0.05). The quantity of mRNA and protein expression of CDX2 gene in colorectal and normal tissue was significantly different (P<0.05). In conclusion, the methylation of the CDX2 gene promoter region was associated with risk of CRC, i.e., methylation of the promoter region of CDX2 gene favors the occurrence of CRC.

Dietary fiber decreases colonic epithelial cell proliferation and protein synthetic rates in human subjects

Although it has been proposed that high fiber consumption can prevent proliferative diseases of the colon, the clinical data to support this hypothesis have been inconsistent. To provide a more robust measure of the effects of fiber on colonic mucosal growth than previous studies, we evaluated both cell proliferation and colonic mucosal protein synthesis in nine healthy volunteers after they consumed a typical Western diet (<20 g fiber/day) or a Western diet supplemented with wheat bran (24 g/day) in a randomized crossover design. Biopsies taken from the sigmoid colon were used to assess mucosal proliferation by determining proliferating cell nuclear antigen (PCNA) in crypt cells and to assess mucosal protein synthetic rate using stable isotopically labeled leucine infusion. Fiber supplementation produced a 12% decrease in labeling index (%crypt cells stained with PCNA) (P < 0.001) and an 11% decrease in mucosal protein fractional synthetic rate (FSR; P < 0.05). Moreover, mucosal protein FSR correlated directly with labeling index (r2= 0.22, P < 0.05). These data demonstrate that increased wheat bran consumption decreases colonic mucosal proliferation and support the potential importance of dietary fiber in preventing proliferative diseases of the colon.

Serum bile acids and risk factors for colorectal cancer

The ratio of deoxycholic acid to chenodeoxycholic acid in the serum of 62 men was inversely related to body mass index and to saturated fat intake after adjustment for body mass index, smoking, and age conversely, this ratio was associated positively with the intake of fibre from grains.

Fecal levels of short-chain fatty acids and bile acids as determinants of colonic mucosal cell proliferation in humans

We studied the correlation between fecal levels of short-chain fatty acids (SCFA), bile acids (BA), and colonic mucosal proliferation in humans on a free diet. Subjects [n = 43: 27 men and 16 women; 61 +/- 7 and 59 +/- 6 (SE) yr old, respectively] were outpatients who previously underwent resection of at least two sporadic colon polyps. Mucosal proliferation was determined by [3H]thymidine incorporation in vitro in three colorectal biopsies obtained without cathartics and was expressed as labeling index (LI). BA were analyzed in feces by mass spectrometry and SCFA by gas chromatography. We found that increasing levels of BA in feces did not correlate with higher LI. On the contrary, higher levels of SCFA were significantly associated with lower LI in the colonic mucosa (P for trend = 0.02). In conclusion, in humans on a free diet, intestinal proliferation seems to be regulated by the levels of SCFA in feces and not by BA. Because a lower intestinal proliferation is associated with a decreased colon cancer risk, treatments or diets that increase colonic levels of SCFA might be beneficial for colonic mucosa.

Dairy foods and prevention of colon cancer: human studies

Colon cancer is the commonest gastrointestinal cancer and the second leading cause of cancer deaths in the United States. Recent approaches to lowering the incidence of colon cancer have included attempts at dietary prevention and chemoprevention. International and national incidence rates for colon cancer suggest an inverse relationship with dietary calcium and/or vitamin D intake (or sun exposure). Several human intervention studies have suggested that supplemental calcium administration will change proliferative indices of risk for colon cancer from high to lower risk patterns. The principal current hypothesis for the action of calcium implies that calcium may precipitate or bring out of solution fatty acids and bile acids that are potentially toxic to the colorectal epithelium. Both calcium administration and dairy food administration are associated with lowering aqueous fecal concentrations of bile acids and fatty acids accompanied by a highly significant lowering of cytotoxicity in studies in vitro. There is biochemical and biological evidence in cell culture systems that exposure to calcium and/or vitamin D reduces the oncogenic properties of colon cancer cells. A recent blinded study of the administration of low-fat dairy foods demonstrated a significant improvement in several parameters of proliferation as well as in two differentiation markers from a high to a lower risk pattern. Furthermore, administration of calcium also has been shown to reduce the incidence of recurrent adenomatous polyps in individuals at increased risk for colon polyp formation because of the presence of prior colon adenomata. These combined data suggest that administration of supplemental calcium or low-fat dairy foods may have a significant effect upon colonic polyp and perhaps colon cancer incidence.

Rectal epithelial proliferation in persons with or without a history of adenoma and its association with diet and lifestyle habits

BACKGROUND

Rectal epithelial proliferation (REP) measurements are used as a biomarker of risk for colorectal neoplasia and response to chemoprevention. The authors evaluated REP in screenees with and without a history of adenoma and its association with demographic and adenoma characteristics, diet, and other lifestyle habits.

METHODS

Long term lifestyle habits were evaluated and proliferation assessed by in vitro bromodeoxyuridine labeling of rectal biopsies in 223 screenees, 132 of whom had adenomas removed > 3 years previously. Analyses included the total population, screenees with a previous history of adenomas and adenoma free screenees separately, and a subgroup of 55 matched adenoma cases and controls.

RESULTS

Crypt proliferation measurements were not elevated in screenees with a history of adenomas compared with adenoma free screenees (mean total labeling index [LI] of 4.8% and 4.9%, respectively). This was confirmed by the case-control analysis, in which the LI of the most superficial crypt compartment was lower in the adenoma cases (P=0.05). Moreover, their total LI correlated negatively with the number of adenomas removed previously (P < 0.01). Proliferation was more frequent in the most superficial crypt compartments of female adenoma free screenees than in female screenees with a history of adenomas (P=0.02), and in men age > 65 years compared with younger men (P=0.06). In the total population, negative Spearman rank correlations were found between total LI and long term dietary intake of calcium (correlation coefficient [r]=-0.15; P=0.02), LI of the two most superficial crypt compartments and intake of fiber (r=-0.18; P=0.01), water (r=-0.12; P=0.08), and carbohydrates (not significant). A positive correlation was found between LI of the most superficial crypt compartment and cigarette smoking (r=0.4; P=0.02).

CONCLUSIONS

REP measurements did not discriminate between screenees with a history of adenomas and adenoma free screenees. Long-term lifestyle habits, gender, and age were associated with REP levels and need to be considered when evaluating human intervention studies.

Mitotic activity in colorectal mucosa of healthy subjects in two Italian areas with different dietary habits

The proliferative activity was evaluated in colorectal biopsies of 39 healthy subjects living in two distinct geographical areas, Trieste in northern and Florence in central Italy. Subjects living in Trieste had a significantly higher mitotic activity compared with subjects living in Florence (mitoses/cells counted x 100 were 0.17 +/- 0.04 in Trieste and 0.089 +/- 0.02 in Florence). The results of a dietary questionnaire also showed that subjects in Trieste consumed significantly fewer starches, fibers, nitrites, and proteins. However, no correlation was evident between the consumption of these nutrients and intestinal proliferation.

Protective mechanisms of dietary fibers in nutritional carcinogenesis

Fibers in foods are complex carbohydrates. There are several types of fiber, but, for the purpose of mechanistic insight into their mode of protective action in carcinogenesis, classification into two broad types, soluble and insoluble fibers, is warranted. Soluble fibers are present in fruits, vegetables, and certain grains like oats. This type of fiber undergoes metabolism in the small intestine and especially in the large intestine through bacterial enzymes, converting it to products that increase stool size only moderately. But, they have appreciable effects in modifying the metabolism of colon carcinogens like azoxymethane to yield detoxified products and, thus, reducing colon carcinogenesis. In contrast, insoluble fibers present in sizeable amounts in bran cereals, like wheat or rice, are not significantly metabolized by enzymes in the intestinal flora. Such fibers increase stool size substantially through several mechanisms, including higher water retention. The larger bulk dilutes carcinogens, especially tumor promoters such as secondary bile acids, resulting in lower risk of colon cancer in animals and in humans. Evidence in animal models and in humans also indicates that fiber may lower the risk of breast cancer, possibly via an endocrine mechanism. Based on these concepts, increased intake of total fiber, but especially of wheat bran cereal fiber, to yield a daily stool in adults of about 200 grams can significantly reduce the risk of colon cancer and, to a lesser but definite extent, of breast cancer. Thus, adequate fiber intake from cereals, fruits, and vegetables can help prevent important types of human cancer.