Scientists have identified a receptor molecule present in the intestinal wall called Gpr4, that, when activated by wastes of gut bacteria, controls the movement of food through the intestine, thus regulating nutrient absorption and subsequently, gain weight.
The researchers disrupted communication between the bacteria and the hosts in two ways: raising normal mice under germ-free conditions so they lacked the bacteria, and genetically engineering other mice to lack Gpr41 so they were unable to respond to the bacteria.
In both cases, the mice weighed less and had a leaner build than their normal counterparts even though they all ate the same amount.
The researchers also found that in mice without Gpr41, the intestines passed food more quickly. They hypothesized that one action of Gpr41 is to slow down the motion that propels food forward, so that more nutrients can be absorbed. Thus, if the receptor cannot be activated, food is expelled more quickly, and the animal gets less energy from it.
The researchers suggest that the Gpr41 receptor may be a likely target for drugs that can fight a certain kind of obesity by slowing down the absorption of energy from the gut.