Gastric bypass surgery can help obese patients lose weight. It also has an intriguing ability to lessen, in some cases cure, diabetes.
Now scientists have uncovered evidence to explain why some patients who undergo gastric bypass often see their diabetes symptoms disappear within days of surgery.
In studying mice, researchers in France found that the surgery creates a "double intestine," increasing the body's ability to regulate blood sugars.
"Up to now, the intestine had been considered like a machine to assimilate nutrients. We've now begun to realize that it is a complex endocrine organ," Gilles Mithieux of Institut National de la Sante et de la Recherche Medicale in France said.
Researchers of the study, published in Cell Metabolism Tuesday, found that increasing the blood sugar production in the small intestine lowers the production in the liver and increases insulin sensitivity.
This regulation occurs via the portal vein, which carries blood sugar from the digestive tract to the liver. It sends a signal to the brain to decrease hunger, but also to lower blood sugar synthesis in the liver, improving symptoms of diabetes.
In bypass surgery, the upper portion of the small intestine closest to the stomach is replaced with the lower part, which then receives all the nutrients from the stomach.
The change in position causes the lower part of the small intestine to behave more like the upper part and also produce blood sugar. The sugar flows to the portal vein.
Researchers found that bypass surgery was ineffective in mice lacking GLUT 2, a glucose transporter needed for sensing glucose in the portal vein, and in those whose portal veins had lost their nerve supply.
Lap-band surgery is another way of inducing weight loss, but it doesn't affect the intestine and therefore lacks the metabolic benefits of bypass surgery.
The new findings support the idea that gastric bypass may be used to treat diabetes in obese patients, and possibly in diabetics in general, Mithieux said.
