A body of laboratory research by Robert S. Chapkin, PhD, Regents Professor and University Faculty Fellow at Texas A & M University and a former AICR grantee, is unveiling how dietary omega-3 fats and other healthful food compounds may influence the colon's immune system. His recent studies investigating the dynamic relationships between diet and human biology are providing new insights into colon cancer prevention.
In a recent review of the evidence surrounding omega-3s, published last month in Molecular Aspects of Medicine, Chapkin concludes that the fatty acids can alter the immune response by targeting specialized regions of the cell referred to as lipid rafts.
Lipid rafts are transient regions of cholesterol and fats that are interspersed among the layers of cell membranes. They serve as staging areas for a variety of cellular processes, such as the immune response.
Using a mouse model, Chapkin and his collaborators showed that when mice ate omega-3s, present in fatty fish such as salmon, the fatty acids were incorporated into the cell's lipid rafts. Once there, the omega-3s rearranged the molecules that participate in cell signaling, preventing the cells from initiating a pro-inflammatory cascade of events that may trigger disease.
"The lipid rafts are like rooms in a house that get larger when someone – like omega-3s – inhabits the rooms," said Chapkin. The extra space in the enlarged rooms enables the occupants – such as key signaling molecules – to communicate differently, says Chapkin, "This communication dampens the ability of certain immune cells to respond and this can suppress the immune response, which is beneficial in some circumstances."
In some cases, inflammation is necessary for good health, such as when the body is fighting an infection. But chronic inflammation, which brings a continuous stream of inflammatory compounds, is a risk factor for colon cancer.
"The inflammatory environment of the intestine can be tweaked, tipping the balance toward a more favorable one."
This research suggests, says Chapkin, "The inflammatory environment of the intestine can be tweaked, tipping the balance toward a more favorable one."
There is no established recommendation for omega-3 intake and, says Chapkin, there are insufficient data to conclusively identify the optimal amount. In fact, some studies show that the high amounts of omega 3s – found only in supplements – actually interfere with the white blood cells' ability to fend off foreign invaders.
Chapkin's research extends to the health benefits of dietary fiber, as well. At the 2011 AICR Research Conference this month, Chapkin presented evidence that suggests omega-3s and fiber exert a powerful synergistic effect.
Dietary fiber is metabolized by the beneficial bacteria in the colon, a process referred to as fermentation. Butyrate is a product of the fermentation of pectin, a type of fiber present in many fruits and vegetables. When omega-3s and butyrate interact in animal models, there is a protective effect in the intestine. Levels of apoptosis, or programmed cell death, of pre-cancerous colon cells increase, offering protection against colon cancer.
These two dietary components – omega-3s and fiber – work together in a way that heightens or facilitates their chemoprotective properties, says Chapkin. He and his colleagues are now trying to determine how these whole food components promote the death of cancer cells that might be propagating in someone's intestine.
"The colon is the only tissue in the body that is impacted by this because the colon is the only place where fiber is fermented," says Chapkin. "This combination is targeting the colon."
Chapkin's next research will examine the effects of omega-3 fatty acids and fiber on intestinal stem cells, cells that have the potential to transform into different types of cells. Eventually, he hopes to conduct human studies to substantiate his findings.
On a typical day, an adult American spends an estimated 2.5 hours eating and drinking, according to a U.S. Department of Agriculture study released earlier this month.
The average person spends slightly less than half of the 2.5 hours eating and drinking as the primary activity. During the remaining time, eating and drinking accompanies another activity, such as watching television, working, or traveling.People age 65 and older spent considerably more time in primary eating and drinking than other age groups, and teens age 15-17 spent the least amount of time in both primary and secondary eating/drinking.
Sources: Economic Research Service, US Department of Agriculture. "Time spent eating and drinking varies by age." November 17, 2011.
Emails, phone calls, and online support may help obese adults lose weight – and keep it off – as effectively as in-person counseling, suggests a new two-year study published last week in The New England Journal of Medicine.
In the study, 415 obese participants were divided into one of two weight-loss programs: One group was provided with weight-loss support remotely; through the telephone, a Website and email. The second group was given in-person support, along with the same three remote forms of support. Another group, the control, was given only minimal weight-loss support, such as brochures.
Participants in the two interventions were encouraged to lose 5 percent of their starting weight within six months, then to maintain their lower weight.
Over the course of two years, participants received monthly email summarizing their progress and sessions with weight-loss coaches. For the first three months, everyone was offered in-person sessions with coaches. Afterwards, the group receiving only remote support was provided with monthly telephone calls. The in-person support group was offered two monthly sessions. Both groups had access to a Website where users could input and receive feedback on their calorie intake and exercise.
At the end of the study, the difference between the two interventions was not significant. The percentage of people who lost five percent or more of their starting weight was more than double among those in the weight-loss programs compared to the control. Approximately 40 percent of participants in the remote support and in-persons support lost and kept off 5 percent of their initial weight. About 19 percent of those in the control group achieved the goal.
Source: Appel LJ, et al. "Comparative Effectiveness of Weight-Loss Interventions in Clinical Practice." N Engl J Med. 2011 Nov 15
Numerous studies have linked high consumption of broccoli and other cruciferous vegetables with health benefits; including cancer protection. Now, a new study published in Cell has uncovered one way in which these vegetables influence the gut's immune function.
When cruciferous vegetables are metabolized, one product is indole-3-carbinol (I3C), a chemical cousin to sulforaphane.
In the Cell study, researchers found that I3C binds with a receptor called AhR, which, in turn, regulates specialized immune cells in the intestine. First, the researchers found that mice lacking AhR experienced greater weight loss, colon abnormalities, and fewer specialized immune cells than the animals with AhR.
Then the researchers removed any vegetables from the animals' diet, which meant no I3C.
Without I3C, similar symptoms appeared as when there was no AhR. Also, the normal balance of gut bacteria skewed to the disease-causing microbes.
The findings point to how dietary compounds act through AhR to maintain healthy immune function in the intestine.
Source: Li Y, Innocentin S, Withers DR, Roberts NA, Gallagher AR, Grigorieva EF, Wilhelm C, Veldhoen M. "Exogenous Stimuli Maintain Intraepithelial Lymphocytes via Aryl Hydrocarbon Receptor Activation." Cell, 2011 Oct 28;147(3):629-40.
Milk thistle is an herb that has a long history of medical use, including for liver disorders. Its flavonoid silibinin is being studied for its chemoprevention activity. A new cell study now offers one way in which silibinin may act against lung cancer: by preventing the formation of compounds involved in inflammation.
The study, published in the journal Molecular Carcinogenesis, added silibinin to the growth environment of mouse lung cancer cells. After cells were given a mixture to prompt inflammatory compounds, the researchers found that silibinin blocked signaling pathways needed to form harmful compounds.
Relative to comparison cells, the cells treated with silibinin showed reduced expression of inflammatory enzymes – such as COX2. Silibinin also appeared to reduce the migration of lung cancer cells, thereby preventing its spread.
Source: Tyagi A, Agarwal C, Dwyer-Nield LD, Singh RP, Malkinson AM, Agarwal R. "Silibinin Modulates TNF-a and IFN-g Mediated Signaling to Regulate COX2 and iNOS Expression in Tumorigenic Mouse Lung Epithelial LM2 Cells." Mol Carcinog. 2011 Aug 31.