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Current Hypothesis for the Relationship between Dietary Rice Bran Intake, the Intestinal Microbiota and Colorectal Cancer Prevention

View Article: PubMed Central - PubMed

ABSTRACT

Globally, colorectal cancer (CRC) is the third most common form of cancer. The development of effective chemopreventive strategies to reduce CRC incidence is therefore of paramount importance. Over the past decade, research has indicated the potential of rice bran, a byproduct of rice milling, in CRC chemoprevention. This was recently suggested to be partly attributable to modification in the composition of intestinal microbiota when rice bran was ingested. Indeed, previous studies have reported changes in the population size of certain bacterial species, or microbial dysbiosis, in the intestines of CRC patients and animal models. Rice bran intake was shown to reverse such changes through the manipulation of the population of health-promoting bacteria in the intestine. The present review first provides an overview of evidence on the link between microbial dysbiosis and CRC carcinogenesis and describes the molecular events associated with that link. Thereafter, there is a summary of current data on the effect of rice bran intake on the composition of intestinal microbiota in human and animal models. The article also highlights the need for further studies on the inter-relationship between rice bran intake, the composition of intestinal microbiota and CRC prevention.

No MeSH data available.


Related in: MedlinePlus

A schematic summary of the relationship between dietary rice bran intake, microbial dysbiosis and colorectal cancer (CRC). (1) Microbial dysbiosis may lead to CRC mainly through the induction of intestinal inflammation and DNA damage. (2) Inflammation may be exacerbated by certain pathogenic intestinal bacteria such as Enterococcusfaecalis, Fusobacteria nucleatum, and Streptococcus gallolyticus, while probiotic bacteria (Clostridium butyricum and Bacillus subtilis) exhibit an opposing effect. (3) DNA damage induced by intestinal bacteria can be elicited through the increased production of free radicals such as superoxide (by Enterococcusfaecalis) and production of genotoxins such as colibactin (by Escherichia coli). (4) Further, inflammation may lead to an increase in proinflammatory cytokine production by immune cells through respiratory burst. This effect may cause DNA damage through oxidation. This suggests a relationship between inflammation and DNA damage induced by microbial dysbiosis. (5) The consumption of rice bran may reverse microbial dysbiosis through the expansion of the population of health-promoting bacteria, such as Bifidobacteria and Lactobacillus, in the intestine. This may potentially ameliorate the detrimental and cancer-causing effects of microbial dysbiosis. (6) In addition, rice bran intake has a beneficial effect on intestinal health because rice bran contains chemicals that were previously shown to exhibit cancer chemo-preventive effect, by eliciting an increased production of short-chain fatty acids (SCFAs) and inhibiting the activity of β-glucuronidase. In the figure, arrow-headed lines indicate “promotion” and bar-headed lines indicate “inhibition”.
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nutrients-08-00569-f001: A schematic summary of the relationship between dietary rice bran intake, microbial dysbiosis and colorectal cancer (CRC). (1) Microbial dysbiosis may lead to CRC mainly through the induction of intestinal inflammation and DNA damage. (2) Inflammation may be exacerbated by certain pathogenic intestinal bacteria such as Enterococcusfaecalis, Fusobacteria nucleatum, and Streptococcus gallolyticus, while probiotic bacteria (Clostridium butyricum and Bacillus subtilis) exhibit an opposing effect. (3) DNA damage induced by intestinal bacteria can be elicited through the increased production of free radicals such as superoxide (by Enterococcusfaecalis) and production of genotoxins such as colibactin (by Escherichia coli). (4) Further, inflammation may lead to an increase in proinflammatory cytokine production by immune cells through respiratory burst. This effect may cause DNA damage through oxidation. This suggests a relationship between inflammation and DNA damage induced by microbial dysbiosis. (5) The consumption of rice bran may reverse microbial dysbiosis through the expansion of the population of health-promoting bacteria, such as Bifidobacteria and Lactobacillus, in the intestine. This may potentially ameliorate the detrimental and cancer-causing effects of microbial dysbiosis. (6) In addition, rice bran intake has a beneficial effect on intestinal health because rice bran contains chemicals that were previously shown to exhibit cancer chemo-preventive effect, by eliciting an increased production of short-chain fatty acids (SCFAs) and inhibiting the activity of β-glucuronidase. In the figure, arrow-headed lines indicate “promotion” and bar-headed lines indicate “inhibition”.

Mentions: As an overall summary, microbial dysbiosis in the intestine would mainly lead to CRC via intestinal inflammation and the induction of DNA damage. Intestinal inflammation can be contributed by the increased intestinal abundance of pathogenic bacterial species. However, the increased presence of health-promoting probiotic bacteria may ameliorate intestinal inflammation. This therefore indicates the importance of the expansion of the intestinal population of probiotic bacteria in the reduction of intestinal inflammation. Pathogenic bacteria such as Enterococcus faecalis and Escherichia coli may also contribute to DNA damage via the increased production of superoxide free radicals and genotoxins, respectively. In addition, intestinal inflammation may further contribute to DNA damage through the induction of respiratory burst in immune cells, promoting the release of ROS and RNS which can cause DNA damage. The intake of rice bran would potentially ameliorate these molecular events as it may lead to an increased intestinal abundance of health-promoting bacteria, counteracting microbial dysbiosis. In addition, rice bran intake may lead to an increased intestinal production of SCFAs and the reduction of cancer-causing enzymatic activities of certain intestinal bacteria. In other words, rice bran would exert beneficial effects on intestinal health and potentially CRC prevention via an interaction with the intestinal microbiota. A graphical representation of the relationship between dietary rice bran intake, the compositional changes of intestinal microbiota and CRC is shown in Figure 1.


Current Hypothesis for the Relationship between Dietary Rice Bran Intake, the Intestinal Microbiota and Colorectal Cancer Prevention
A schematic summary of the relationship between dietary rice bran intake, microbial dysbiosis and colorectal cancer (CRC). (1) Microbial dysbiosis may lead to CRC mainly through the induction of intestinal inflammation and DNA damage. (2) Inflammation may be exacerbated by certain pathogenic intestinal bacteria such as Enterococcusfaecalis, Fusobacteria nucleatum, and Streptococcus gallolyticus, while probiotic bacteria (Clostridium butyricum and Bacillus subtilis) exhibit an opposing effect. (3) DNA damage induced by intestinal bacteria can be elicited through the increased production of free radicals such as superoxide (by Enterococcusfaecalis) and production of genotoxins such as colibactin (by Escherichia coli). (4) Further, inflammation may lead to an increase in proinflammatory cytokine production by immune cells through respiratory burst. This effect may cause DNA damage through oxidation. This suggests a relationship between inflammation and DNA damage induced by microbial dysbiosis. (5) The consumption of rice bran may reverse microbial dysbiosis through the expansion of the population of health-promoting bacteria, such as Bifidobacteria and Lactobacillus, in the intestine. This may potentially ameliorate the detrimental and cancer-causing effects of microbial dysbiosis. (6) In addition, rice bran intake has a beneficial effect on intestinal health because rice bran contains chemicals that were previously shown to exhibit cancer chemo-preventive effect, by eliciting an increased production of short-chain fatty acids (SCFAs) and inhibiting the activity of β-glucuronidase. In the figure, arrow-headed lines indicate “promotion” and bar-headed lines indicate “inhibition”.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037554&req=5

nutrients-08-00569-f001: A schematic summary of the relationship between dietary rice bran intake, microbial dysbiosis and colorectal cancer (CRC). (1) Microbial dysbiosis may lead to CRC mainly through the induction of intestinal inflammation and DNA damage. (2) Inflammation may be exacerbated by certain pathogenic intestinal bacteria such as Enterococcusfaecalis, Fusobacteria nucleatum, and Streptococcus gallolyticus, while probiotic bacteria (Clostridium butyricum and Bacillus subtilis) exhibit an opposing effect. (3) DNA damage induced by intestinal bacteria can be elicited through the increased production of free radicals such as superoxide (by Enterococcusfaecalis) and production of genotoxins such as colibactin (by Escherichia coli). (4) Further, inflammation may lead to an increase in proinflammatory cytokine production by immune cells through respiratory burst. This effect may cause DNA damage through oxidation. This suggests a relationship between inflammation and DNA damage induced by microbial dysbiosis. (5) The consumption of rice bran may reverse microbial dysbiosis through the expansion of the population of health-promoting bacteria, such as Bifidobacteria and Lactobacillus, in the intestine. This may potentially ameliorate the detrimental and cancer-causing effects of microbial dysbiosis. (6) In addition, rice bran intake has a beneficial effect on intestinal health because rice bran contains chemicals that were previously shown to exhibit cancer chemo-preventive effect, by eliciting an increased production of short-chain fatty acids (SCFAs) and inhibiting the activity of β-glucuronidase. In the figure, arrow-headed lines indicate “promotion” and bar-headed lines indicate “inhibition”.
Mentions: As an overall summary, microbial dysbiosis in the intestine would mainly lead to CRC via intestinal inflammation and the induction of DNA damage. Intestinal inflammation can be contributed by the increased intestinal abundance of pathogenic bacterial species. However, the increased presence of health-promoting probiotic bacteria may ameliorate intestinal inflammation. This therefore indicates the importance of the expansion of the intestinal population of probiotic bacteria in the reduction of intestinal inflammation. Pathogenic bacteria such as Enterococcus faecalis and Escherichia coli may also contribute to DNA damage via the increased production of superoxide free radicals and genotoxins, respectively. In addition, intestinal inflammation may further contribute to DNA damage through the induction of respiratory burst in immune cells, promoting the release of ROS and RNS which can cause DNA damage. The intake of rice bran would potentially ameliorate these molecular events as it may lead to an increased intestinal abundance of health-promoting bacteria, counteracting microbial dysbiosis. In addition, rice bran intake may lead to an increased intestinal production of SCFAs and the reduction of cancer-causing enzymatic activities of certain intestinal bacteria. In other words, rice bran would exert beneficial effects on intestinal health and potentially CRC prevention via an interaction with the intestinal microbiota. A graphical representation of the relationship between dietary rice bran intake, the compositional changes of intestinal microbiota and CRC is shown in Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Globally, colorectal cancer (CRC) is the third most common form of cancer. The development of effective chemopreventive strategies to reduce CRC incidence is therefore of paramount importance. Over the past decade, research has indicated the potential of rice bran, a byproduct of rice milling, in CRC chemoprevention. This was recently suggested to be partly attributable to modification in the composition of intestinal microbiota when rice bran was ingested. Indeed, previous studies have reported changes in the population size of certain bacterial species, or microbial dysbiosis, in the intestines of CRC patients and animal models. Rice bran intake was shown to reverse such changes through the manipulation of the population of health-promoting bacteria in the intestine. The present review first provides an overview of evidence on the link between microbial dysbiosis and CRC carcinogenesis and describes the molecular events associated with that link. Thereafter, there is a summary of current data on the effect of rice bran intake on the composition of intestinal microbiota in human and animal models. The article also highlights the need for further studies on the inter-relationship between rice bran intake, the composition of intestinal microbiota and CRC prevention.

No MeSH data available.


Related in: MedlinePlus