Intestinal Bacteria May Lead to Weight Gain, Metabolic Syndrome
If you are trying to lose weight, in addition to watching what goes into your gut, it may be important to know what is already there. Scientists from Emory University have found that the bacteria that reside in the intestines may also play an important role in whether the body uses the food for fuel, or stores it as extra fat.
Andrew Gewirtz and a team of researchers from Emory, Cornell University, and the University of Boulder studied laboratory mice that were lacking a protein called toll-like receptor 5 (TLR5) in their intestinal cells that caused an excess of bacteria – about three to four times that of normal mice.
The mice with the genetic mutation were about 15% heavier than healthy mice. The mice also had a higher level of inflammation which can promote a condition called the metabolic syndrome, a cluster of risk factors that can lead to heart disease and type 2 diabetes.
TLR5 normally is present in the intestines to guard against overgrowth of bacteria. When the intestine has too many pathogens, it triggers an inflammatory state in an attempt to compensate. This makes the cells less sensitive to insulin, which removes glucose from the blood and transports it to the cells where it is used for fuel. If the cells are resistant to insulin, the glucose continues to circulate, causing high blood sugar and type 2 diabetes.
"We don't think the bacteria are directly making the mice eat more, but the bacteria are causing low-grade inflammation, which causes insulin resistance and then makes the mice eat more," says Gewirtz.
To test this theory, the researchers gave the TLR5-deficient mice an unrestricted diet and they did eat about 10% more than normal mice. When the researchers limited food intake, which should have caused a lower glucose level, the mice were still less sensitive to insulin.
If the same situation occurs in humans, this study suggests that some people may eat more, not because of “undisciplined eating”, but because of changes in their intestinal bacteria. A human’s intestinal bacteria population are thought to be acquired from birth, but influenced over the years by the use of antibiotics, diet, water supplies, and sanitation and hygiene.
Some recent research has found that probiotics, “healthy” bacteria that manipulate the balance of the microflora in the intestine by reducing the growth of “harmful” bacteria, may play a role in fighting obesity and controlling inflammation.
The findings from the study are published online March 4 in the journal Science.