Protein can help you to lose weight
Frequently recommended in weight loss diets, dietary proteins have demonstrated their appetite-suppressing effects.
In Lyon a team of researchers working under Gilles Mithieux, the Director of l’Unité Inserm 855 ‘Nutrition and the Brain’, helped to explain the biological mechanisms responsible for this special property of protein that controls hunger. The researchers described in detail the chain reactions caused by the digestion of proteins that can deliver to the brain a message of satiety, even quite a long while after the meal. These results, published in the scientific journal Cell, might make it possible to plan a better management of obese or overweight patients and to create for them the best diet plan.
The research team of Inserm, CNRS and Université Claude Bernard at Lyon has managed to explain in detail the feeling of satiety experienced several hours after a high protein meal. Their research helps to explain the exchanges between the digestive system and the brain, initiated by food proteins that are mainly found in meat, fish, eggs or certain cereal products.
In earlier studies, researchers have shown that ingestion of dietary proteins triggers glucose synthesis in the intestine after the assimilation of meals (a feature called gluconeogenesis). The glucose that is released into the blood circulation (portal vein) is detected by the nervous system which sends an ‘appetite suppressant’ signal to the brain. Better known for its action in the liver and kidneys to feed other organs with sugar, gluconeogenesis delivers an ‘appetite suppressant’ message to the intestine between meals, which affects us with the feeling we know as “satiety”.
With the help of this new research the researchers can accurately describe how protein digestion causes a double loop of chain reactions involving the peripheral ventral (via the vagus nerve) and the dorsal (via the spinal cord) nervous systems. A detailed exploration of the biological mechanism identified specific receptors (μ-opioid receptors) present in the nervous system of the portal vein, at the end of the intestine. These receptors are inhibited by the presence of oligopeptides, products of the digestion of proteins.
Initially, oligopeptides act on the μ-opioid receptors that send a message through the vagus nerve and the spinal pathway to those areas of the brain that have a specialized role of decoding such messages. The brain then sends a return message that triggers gluconeogenesis in the intestine. The latter then initiates sending the “appetite suppressant” message to those areas of the brain that control food intake, such as the hypothalamus.
The identification of these receptors and their role in the intestinal gluconeogenesis will allow the scientists to consider new therapeutic leads in the treatment of obesity. The challenge now is to determine how to act on the μ-opioid receptors and sustainably regulate satiety. According to Gilles Mithieux, the leader of the research team, ‘Solicited too strongly, these receptors can become unresponsive. We should, therefore, find the best way to inhibit them moderately in order to keep their long-term beneficial effect in controlling food intake.’