August 16th, 2012

Gut Bacteria Tied to Metabolic Syndrome

Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

Action Points
• Certain bacteria in the gut may be associated with various
components of the metabolic syndrome, a study in an Old Order Amish community showed.
• Point out that all of the study participants belonged to one of three groups defined by the presence of separate communities containing six to 12 genera of bacteria.

Certain bacteria in the gut may be associated with various components of the metabolic syndrome, a study in an Old Order Amish community showed.

All of the study participants belonged to one of three groups defined by the presence of separate communities containing six to 12 genera of bacteria, according to Claire Fraser, PhD, of the University of Maryland School of Medicine in Baltimore, and colleagues. Each genus can contain several individual bacterial species.

Although none of the three bacterial communities were associated with body mass index or any of the metabolic syndrome components, 26 of the individual bacterial species were associated either positively or negatively with BMI, serum triglycerides, HDL cholesterol, total cholesterol, fasting glucose levels, and C-reactive protein, the researchers reported online in PLoS One.
That suggests "that certain members of the gut microbiota may play a role in these metabolic derangements," they wrote, adding that the cross-sectional nature of the data precludes an assessment of the causality of the relationships.

"Follow-up longitudinal studies can begin to address whether specific gut bacterial taxa play a causal role in the predisposition to or development of the metabolic syndrome, as well as the utility of interventions that modulate the composition of the gut microbiota to mitigate the risk of cardiovascular complications associated with metabolic syndrome," they wrote.
Obesity is believed to be caused by both environmental and genetic factors, and some studies have linked obesity to gut bacteria, with a range of proposed mechanisms. However, results from the various studies have been conflicting depending on the population studied.
Fraser and colleagues explored the issue among men and women belonging to the Old Order Amish sect in Lancaster County, Pa. Within the community, there is a high degree of uniformity of genetic background, socioeconomic status, and lifestyle, which reduces potential confounders.

The researchers collected stool samples from 310 adults ages 20 to 80 (64% female). Women had a higher average age and BMI and were more likely to have at least one component of the metabolic syndrome (38.9% versus 26.8%), which was defined by elevated BMI, blood pressure, fasting triglycerides, and fasting glucose, and low fasting HDL cholesterol.

Among the 203 genera of bacteria identified, there were three communities of interacting bacteria. The participants were assigned to one of three groups depending on which community was most prevalent in the gut -- 47% had a community dominated by Prevotella, 39% had a community dominated by various genera from the phylum Firmicutes, most commonly Oscillospira, and 14% had a community dominated by Bacteroides.

After adjustment for age and sex, none of the bacterial communities were associated with BMI or the components of the metabolic syndrome, but 26 bacterial species from the phyla Bacteroidetes, Firmicutes, and Actinobacteria and the order Clostridiales were related to various metabolic syndrome traits.