Gut-brain connection elucidates how overeating results in obesity: study.
Washington: A recent study conducted in Baylor College of Medicine has revealed that there is a strong connection between your gut and brain which leads to weight gain by the consumption of those extra servings.
The research was published in the 'Journal of Clinical Investigation'.
Mice consuming a high-fat diet show increased levels of gastric inhibitory polypeptide (GIP), a hormone produced in the gut that is involved in managing the body's energy balance.
The study found out that the excess GIP travels through the blood to the brain where it inhibits the action of leptin, the satiety hormone; consequently, the animals continue eating and gain weight. Blocking the interaction of GIP with the brain restores leptin's ability to inhibit appetite and results in weight loss in mice.
Researchers know that leptin, a hormone produced by fat cells, is important in the control of body weight both in humans and mice. Leptin works by triggering in the brain the sensation of feeling full when we have eaten enough, and we stop eating. However, in obesity resulting from consuming a high-fat diet or overeating, the body stops responding to leptin signals it does not feel full, and eating continues, leading to weight gain.
"My colleagues and I started looking for what causes leptin resistance in the brain when we eat fatty foods. Using cultured brain slices in Petri dishes we screened blood circulating factors for their ability to stop leptin actions. After several years of efforts, we discovered a connection between the gut hormone GIP and leptin." said Dr Makoto Fukuda, corresponding author and assistant professor of paediatrics at Baylor College of Medicine
GIP is one of the incretin hormones produced in the gut in response to eating and known for its ability to influence the body's energy management. To determine whether GIP was involved in leptin resistance, Fukuda and his colleagues first confirmed that the GIP receptor, the molecule on cells that binds to GIP and mediates its effects, is expressed in the brain.
The researchers evaluated the effect blocking the GIP receptor would have on obesity by infusing directly into the brain a monoclonal antibody developed by Dr Peter Ravn at AstraZeneca that effectively prevents the GIP-GIP receptor interaction. This significantly reduced the bodyweight of high-fat-diet-fed obese mice.
"In summary, when eating a balanced diet, GIP levels do not increase and leptin works as expected, triggering in the brain the feeling of being full when the animal has eaten enough and the mice stop eating," Fukuda said.
"But, when the animals eat a high-fat diet and become obese, the levels of blood GIP increase. GIP flows into the hypothalamus where it inhibits leptin's action. Consequently, the animals do not feel full, overeat and gain weight. Blocking the interaction of GIP with the hypothalamus of obese mice restores leptin's ability to inhibit appetite and reduces body weight," added Fukuda.
Although more research is needed, the researchers speculate that these findings might one day be translated into weight loss strategies that restore the brain's ability to respond to leptin by inhibiting the anti-leptin effect of GIP.