This study will help us understand how bacteria may cause obesity. Particularly types of bacteria in mice that were strongly linked to metabolic syndrome.
Expressed TLR4 only in intestinal epithelium
Metabolic syndrome is a cluster of conditions including obesity around the waist, high blood sugar and increased blood pressure which is a risk factor for heart disease, strokes and diabetes. Toll-like receptor 4 (TLR4) is a protein that receives chemical signals to activate inflammation.
Lacks TLR4 only in white blood cells
This experiment will help to determine whether TLR4, specifically in the intestinal epithelium, will cause the development of metabolic syndrome. The research team ran experiments on both normal mice and mice genetically modified to lack TLR4 in their intestinal epithelium Results showed that those lacking TLR4 showed symptoms consistent with metabolic syndrome (weight gain, increased body and liver fat and insulin resistance)
The researchers then changed the diet of both groups of mice to a high fat diet to find out whether diet would affect the development of metabolic syndrome Again, the Genetically modified mice gained significantly more weight and had greater body and liver fat than the normal mice
To confirm the role of TLR4 expression in the intestinal epithelium, the researchers genetically modifies three more groups of mice. 1 - This group expressed TLR4 only in the intestinal epithelium 2 - This group lacked TLR4 in all body cells 3 - This group lacked TLR4 only in white blood cells Belly and small intestine fat was higher in mice lacking TLR4 only in the intestinal epithelium.
Lacks TLR4 in all body cells
The experiments provides evidence that deleting TLR4 specifically from the intestinal epithelium is required for developing metabolic syndrome. They found that specific clusters of bacteria that contribute to the development of metabolic syndrome were expressed differently in the deficient mice than in the normal mice. The bacteria expressed genes that made them "less hungry" and thus less able to digest the nutrients present in their given food which contributed to obesity.