This Week In Biofilms And Microbiomes: Monday June 13, 2016
A round-up of what we read last week in the media's coverage of biofilms and microbiomes research.
Obesity is linked to changes in our gut microbiome, reports a new study published in Nature last week. In this mouse study, researchers at Yale University found that bacteria in the intestines produce a short-chain fatty acid called acetate, which works through the brain and nervous system to increase the production of insulin by the pancreas, which tells fat cells to store more energy, thus leading to obesity. In addition, acetate also increases levels of a hunger hormone called ghrelin, which could lead animals and people to eat even more. The researchers had previously noticed that high-fat diets stimulated increased levels of acetate in rodents’ blood streams, and that this increase triggered insulin secretion—but they didn’t know where the acetate was coming from. They further explored the link in the current study. Antibiotic-treated rats and germ-free mice produced relatively low levels of acetate, but restoring the animals’ normal gut microbiota led to increased acetate production; feeding the rodents a high-fat diet raised acetate levels even further. The team also showed that rather than directly stimulating pancreatic cells to secrete insulin, acetate triggers a signal from the brain to the pancreas via the vagus nerve—part of the parasympathetic nervous system that controls 'subconscious' operations such as heart rate and digestion. Cutting the vagus nerve or blocking its activity with drugs stopped acetate from boosting insulin levels. Finally, the research team closely examined the causal relationship between the gut microbiota and increased insulin. After transferring fecal matter from a group of obese rodents to healthy rodents, they observed a spike in acetate and insulin levels that could result in obesity. If researchers confirm the same process happens in people, then identifying the bacteria that make acetate and figuring out how to stop them could lead to new obesity treatments, says microbiome researcher Chad Trent of the New York University Langone Medical Center. The paper received a good press coverage by many outlets, including Medical Daily, Science Daily, Newsweek and The Scientist.
Disease process and antibiotic treatment could have a far greater impact on intestinal microbial diversity than surgical intervention, suggests a new study published in the journal Surgery. Researchers at the Children's Hospital Los Angeles obtained 43 samples of intestinal swabs from 29 patients, aged 5 days to 13 years old, during initial resection or later stoma closure. Bacterial 16s rRNA was extracted from these samples and compared using phylogenetic diversity whole tree alpha diversity and by comparing significantly different taxonomic groups. The findings revealed that for inflammatory and ischemic disorders that require prolonged courses of antibiotics, the microbiome of the intestinal lining remained altered even after the medical condition was clinically resolved. Intestine in children who had inflammatory and ischemic disorders had less bacterial diversity and different types of bacteria compared to children who needed intestine surgery that required only a few days of antibiotics such as in the case of obstructive conditions. The investigators also found that patients who underwent intestinal diversion, resulting in digested food passing through just part of their intestine, had little change to their intestinal flora when sites above and below the diversion were compared. “Alterations in the microbiome are linked to many disease states and may also be associated with increasing surgical complications and long term effects in the children we treat," said Tracy C. Grikscheit, MD, pediatric surgeon and principal investigator at The Saban Research Institute of Children's Hospital Los Angeles. "Now we need to determine if the disease process or the extended antibiotic regimen is responsible for the changes we identified so that we can effectively care for the medical condition while minimizing any unintended, and potentially, far-reaching effects." Read the press release covered by NewsWise.
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