Health Research Report
159th Issue Date 15 JUL 2013
Compiled By Ralph Turchiano
In this issue: (Very few reports over last 14 days)
- Harvard and USC scientists show how DHA resolves inflammation
- The dark side of artificial sweeteners
- How cranberries impact infection-causing bacteria
Harvard and USC scientists show how DHA resolves inflammation
New research in The FASEB Journal suggests that fish oil DHA is used to create Maresins, which cause macrophages to ‘turn off’ inflammation
Bethesda, MD—Chronic inflammation is a major factor in a wide range of problems from arthritis to cardiovascular disease, and DHA (found in fish oil) is known to temper this problem. A new research report appearing in the July 2013 issue of The FASEB Journal, helps explain why DHA is important in reducing inflammation, and provides an important lead to finding new drugs that will help bring people back to optimal health. Specifically, researchers found that macrophages (a type of white blood cell) use DHA to produce “maresins,” which serve as the “switch” that turns inflammation off and switches on resolution.
“We hope that the results from this study will enable investigators to test the relevance of the maresin pathway in human disease,” said Charles N. Serhan, Ph.D., a researcher involved in the work from the Brigham & Women’s Hospital and Harvard Medical School in Boston, Mass. “Moreover, we hope to better understand resolution biology and its potential pharmacology so that we can enhance our ability to control unwanted inflammation and improve the quality of life.”
To make this discovery, Serhan and colleagues deconstructed the biosynthetic pathway for maresin biosynthesis and found that human macrophages are responsible for converting DHA to the novel epoxide intermediate “13S, 14S-epoxy-maresin.” Then, they learned how to synthesize the molecule and found that maresins caused macrophages to change their “type” so they no longer caused inflammation (switching them from M1 to M2 phenotypes).
“We’ve known for a long time that DHA tames inflammation, now, we learn exactly how DHA works: via new substances called maresins,” said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. “We encounter inflammation almost daily, but our body has ways of turning it off. This is an important step toward understanding exactly this happens. You’re likely to be hearing a lot more about maresins if, or when, new therapies arise from this discovery.”
The dark side of artificial sweeteners
More and more Americans are consuming artificial sweeteners as an alternative to sugar, but whether this translates into better health has been heavily debated. An opinion article published by Cell Press on July 10th in the journal Trends in Endocrinology & Metabolism reviews surprising evidence on the negative impact of artificial sweeteners on health, raising red flags about all sweeteners—even those that don’t have any calories.
“It is not uncommon for people to be given messages that artificially-sweetened products are healthy, will help them lose weight or will help prevent weight gain,” says author Susan E. Swithers of Purdue University. “The data to support those claims are not very strong, and although it seems like common sense that diet sodas would not be as problematic as regular sodas, common sense is not always right.”
Consumption of sugar-sweetened drinks has been linked to obesity, type 2 diabetes, and metabolic syndrome—a group of risk factors that raises the risk for heart disease and stroke. As a result, many Americans have turned to artificial sweeteners, which are hundreds of times sweeter than sugar but contain few, if any, calories. However, studies in humans have shown that consumption of artificially sweetened beverages is also associated with obesity, type 2 diabetes, and metabolic syndrome as well as cardiovascular disease. As few as one of these drinks per day is enough to significantly increase the risk for health problems.
Moreover, people who regularly consume artificial sweeteners show altered activation patterns in the brain’s pleasure centers in response to sweet taste, suggesting that these products may not satisfy the desire for sweets. Similarly, studies in mice and rats have shown that consumption of noncaloric sweeteners dampens physiological responses to sweet taste, causing the animals to overindulge in calorie-rich, sweet-tasting food and pack on extra pounds.
Taken together, the findings suggest that artificial sweeteners increase the risk for health problems to an extent similar to that of sugar and may also exacerbate the negative effects of sugar. “These studies suggest that telling people to drink diet sodas could backfire as a public health message,” Swithers says. “So the current public health message to limit the intake of sugars needs to be expanded to limit intake of all sweeteners, not just sugars.”
How cranberries impact infection-causing bacteria
Research points to potential role for cranberry derivatives in implantable medical devices
Consuming cranberry products has been anecdotally associated with prevention of urinary tract infections (UTIs) for over 100 years. But is this popular belief a myth, or scientific fact?
In recent years, some studies have suggested that cranberries prevent UTIs by hindering bacteria from sticking to the walls of the urinary tract, thanks to phytochemicals known as proanthocyanidins (PACs). Yet the mechanisms by which cranberry materials may alter bacterial behaviour have not been fully understood.
Now, researchers in McGill University’s Department of Chemical Engineering are shedding light on the biological mechanisms by which cranberries may impart protective properties against urinary tract and other infections. Two new studies, spearheaded by Prof. Nathalie Tufenkji, add to evidence of cranberries’ effects on UTI-causing bacteria. The findings also point to the potential for cranberry derivatives to be used to prevent bacterial colonization in medical devices such as catheters.
In research results published online last month in the Canadian Journal of Microbiology, Prof. Tufenkji and members of her laboratory report that cranberry powder can inhibit the ability of Proteus mirabilis, a bacterium frequently implicated in complicated UTIs, to swarm on agar plates and swim within the agar. The experiments also show that increasing concentrations of cranberry powder reduce the bacteria’s production of urease, an enzyme that contributes to the virulence of infections.
These results build on previous work by the McGill lab, showing that cranberry materials hinder movement of other bacteria involved in UTIs. A genome-wide analysis of an uropathogenic E. coli revealed that expression of the gene that encodes for the bacteria’s flagellar filament was decreased in the presence of cranberry PACs.
The team’s findings are significant because bacterial movement is a key mechanism for the spread of infection, as infectious bacteria literally swim to disseminate in the urinary tract and to escape the host immune response.
“While the effects of cranberry in living organisms remain subject to further study, our findings highlight the role that cranberry consumption might play in the prevention of chronic infections,” Tufenkji says. “More than 150 million cases of UTI are reported globally each year, and antibiotic treatment remains the standard approach for managing these infections. The current rise of bacterial resistance to antibiotics underscores the importance of developing another approach.”
Another recent study led by Tufenkji in collaboration with McGill professor Showan Nazhat, a biomaterials expert at the Department of Mining and Materials Engineering, finds that cranberry-enriched silicone substrates impaired the spread of Proteus mirabilis. Those results, published online in the journal Colloids and Surfaces B: Biointerfaces, point to potential use for cranberry derivatives to hinder the spread of germs in implantable medical devices such as catheters, which are frequently implicated in UTIs.
“Based on the demonstrated bioactivity of cranberry, its use in catheters and other medical devices could someday yield considerable benefits to patient health,” Tufenkji says.