Dietary Proteins and Satiety-Related Neuronal Pathways in the Brain
This review presents recent findings regarding the neuroregulation of appetite by the ingestion of dietary proteins and amino acids, at both the peripheral and central levels. Protein is considered to be a strong inhibitor of food intake in omnivores, displaying the most marked appetite suppressant effects of the three macronutrients. Eating a high-protein diet does not induce a conditioned food aversion but rather experience-enhanced satiety. Moreover, the relatively poor palatability of dietary proteins is not the principal mechanism causing a reduction in energy intake. The input signals associated with amino acid ingestion originate from visceral and metabolic mechanisms and involve both indirect (mainly vagus-mediated) and direct information (plasma levels of nutrients and hormones) recorded by the central nervous system. At the peripheral level, the satiety effect of dietary proteins appears to be mediated by anorexigenic hormones such as CCK, GLP-1, and PYY. There is also some evidence that circulating leucine levels may impact food intake. Indeed, leucine is associated with mechanisms involving mTOR and AMPK, both of which are energy sensors active in the regulation of energy intake, at least in the arcuate nucleus but probably also in other brain areas. How information arising from the ingestion of dietary protein leads to the control of food intake is a highly complex process that is not yet fully understood, particularly regarding the involvement of certain brain regions such as the area postrema and hypothalamus. In the central nervous system, high-protein diets trigger the activation of noradrenergic/adrenergic neurons in the NTS and melanocortin neurons in the ARC. At the same time, our studies have shown that the APC, a brain area known to sense any deficiency in indispensable amino acids, does not appear to be involved in the detection of dietary protein intake.
KeywordsDietary Protein Nucleus Tractus Solitarius Conditioned Taste Aversion Plasma Amino Acid Satiety Effect
Brain derived neurotrophic factor
Cholecystokinin (formerly called pancreozymin), a food intake suppressing peptide hormone released by the gastrointestinal tract during digestion
Nucleus tractus solitarius
Arcuate nucleus of the hypothalamus
Anterior piriform cortex
A type of enteroendocrine cell found in the mucosal epithelium that lines the lumen of the small intestine. I-cells secrete a wide variety of gut hormones, including cholecystokinin.
Glucagon-like peptide 1
Indispensable amino acid
Central nervous system
Conditioned taste aversion
α Melanocyte stimulating hormone
Mammalian target of rapamycin
AMP-activated protein kinase
The authors thank Patrick Even, Claire Gaudichon and Dalila Azzout for valuable input on the manuscript.
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