New insights into gut bacteria and their connection to metabolic syndrome have been uncovered by scientists.
A study on Metabolic syndrome entitled “Intestinal Epithelial Cell Toll-like Receptor 5 Regulates the Intestinal Microbiota to Prevent Low-Grade Inflammation and Metabolic Syndrome in Mice” was published in the journal Gastroenterology by Benoit Chassaing, part of Dr. Andrew Gewirtz’group at Georgia State University. In this study the researchers found that healthy bacteria that live in the gut may help treat or prevent metabolic syndrome.
Obesity is considered a worldwide epidemic, since is estimated that 1.4 billion people suffer from the disease and the number is rising each year. Obesity affects all socioeconomic backgrounds and ethnic groups, and is a risk factor for developing metabolic syndrome. Metabolic syndrome is a mixture of risk factors, such as central obesity, insulin resistance, dyslipidaemia and hypertension that in combination can lead to type 2 diabetes mellitus and cardiovascular disease. It has been described that changes in gut microbiota composition may lead to several gastrointestinal tract chronic inflammatory diseases, such as Crohn’s disease and ulcerative colitis.
People with metabolic syndrome are twice as likely to develop heart disease and five times as likely to develop diabetes as the general population, according to the National Institutes of Health.
According to the American Heart Association and the National Institutes of Health reports, respectively, around 34% of American adults have metabolic syndrome and subjects with metabolic syndrome have 2 and 5 times more the risk to develop, respectively, heart disease and diabetes when compared to the general population.
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In previous studies, this group of researchers described how changes in the bacteria from the intestine play a role in metabolic syndrome. Now, in their present work, the authors found the mechanisms that could explain the previous observations. As Dr. Andrew Gewirtz, a professor at the Institute for Biomedical Sciences at Georgia State said in the press release “It’s the loss of TLR5 on the epithelium,” he explains, “the cells that line the surface of the intestine and their ability to quickly respond to bacteria. That ability goes away and results in a more aggressive bacterial population that gets closer in and produces substances that drive inflammation.”
It has been shown that mice deficient in Toll-like receptor 5 (TLR5-null mice), which binds flagellin, a protein of bacterial flagella, have the composition of their intestinal microbiota altered when compared with wild-type mice; they develop low-grade inflammation, metabolic syndrome, and are susceptible to colitis. The differential role of TLR5 in the intestinal epithelial cell (IEC) and the dendritic cell (DC) is not well understood.
Animal husbandry conditions can be mimicked by changing the composition of bacteria from the intestine instead of removing the TLR5. The researchers generated mice with specific deletion of Tlr5 in IECs or DCs and compared with co-housed siblings, used as controls. Then the authors compared using the composition of the bacteria in the intestine of the test mice, as well as responses to pathogenic bacteria and administration of high-fat diets. Dr. Ruth Ley from the Departments of Microbiology and Molecular Biology at Cornell and author of the study explained the results: “They confirm the concept that altered microbiota can promote low-grade inflammation and metabolic syndrome and advance the underlying mechanism. We showed that the altered bacterial population is more aggressive in infiltrating the host and producing substances, namely flagellin and lipopolysaccharide, that further promote inflammation.”
The role of fat in the diet has been noted in other studies relating to metabolic syndrome as well. Recently, according to a new study published in the Canadian Medical Association Journal entitled “Mediterranean diets and metabolic syndrome status in the PREDIMED randomized trial” a Mediterranean diet that includes nuts and olive oil may revert metabolic syndrome. In this study, the researchers followed participants that were on a low-fat diet, a Mediterranean diet supplemented with nuts, or a Mediterranean diet supplemented with extra-virgin olive oil for an average of 4.8 years. They found that participants who followed the Mediterranean diets had lower levels of glucose in the blood and decreased abdominal waists. At the beginning of the study, 64% of participants had metabolic syndrome but in the end of the study, 28.2% of the participants under the Mediterranean diets did not present the diagnostic criteria for metabolic syndrome.
This study suggests that a Mediterranean diet supplemented with extra virgin olive oil or nuts may be useful in reducing the risks of central obesity and hyperglycemia in people at high risk of cardiovascular disease.