"It is well known that protein
feeding decreases hunger sensation and subsequent food intake in animals and
humans," said study author Gilles Mithieux of INSERM and Universite Lyon
in France. However, the mechanism by which proteins exert their control over
appetite remained unclear, the researchers said. In fact, earlier studies have
found that a rise in dietary protein shows little effect on the major hormones
that regulate hunger, they added.
In a study of rats, Mithieux and
colleagues made the surprising discovery that diets heavy in protein spark the
production of glucose in the small intestine. That rise in glucose, sensed in
the liver and relayed to the brain, led the animals to eat less, they
reported.
"The current findings provide
an answer to the question of how protein-enriched meals decrease hunger and
reduce eating, unsolved up to now," according to the researchers.
"Our data also brings to light a novel concept of control of food intake,
involving the small intestine glucose metabolism as a key relay from the
macronutrient composition of the diet to the amount of food ingested."
The group found that protein
feeding of rats markedly increased the activity of genes involved in glucose
production in the animals' small intestine. Those activities led to glucose
synthesis and release into the portal vein--the vessel that conducts blood
from digestive and other organs to the liver--a phenomenon lasting after the
assimilation of glucose from the diet.
Furthermore, they found that the
flux in glucose detected by the liver glucose sensor activated parts of the
brain involved in the control of appetite, causing a decline in subsequent
food consumption.
"In addition to protein's
ability to diminish appetite, it had also been suggested that glucose
appearance in the portal vein, as occurs during meal assimilation, may induce
comparable consequences," Mithieux said. "Here, we connect these
previous observations by reporting that intestinal synthesis of glucose is
induced following food digestion in rats specifically fed a protein-enriched
diet."
"As in rats, diets high in protein suppress appetite in
people," the researchers added. The human intestine also synthesizes glucose.
"Therefore, glucose metabolism in the small intestine may be a new target
in the treatment of food intake disorders," they said.
*****
The
researchers included Gilles Mithieux, Pierre Misery, Bruno Pillot, Amandine
Gautier-Stein, Fabienne Rajas,and Carine Zitoun of the Institut National de la
Sante et de la Recherche Medicale, the Institut National de la Recherche
Agronomique, and the Universite Claude Bernard Lyon I, in Lyon, France;
Christine Bernard, of Institut National de la Sante et de la Recherche
Medicale and Universite Claude Bernard Lyon I, in Lyon, France; and Christophe
Magnan of Centre National de la Recherche Scientifique and Universite Paris in
Paris, France. The research was supported by INSERM, INRA and Universite
Paris.
Mithieux et al.: "PORTAL SENSING OF
INTESTINAL GLUCONEOGENESIS IS A MECHANISTIC LINK IN THE DIMINUTION OF FOOD
INTAKE INDUCED BY DIET PROTEIN." Publishing in Cell Metabolism, Vol. 2;
Issue: 5; November 005, pages 321-329. DOI 0.1016/j.cmet.2005.09.010
www.cellmetabolism.org
Source: worldhealth.net
