Diets Deficient in Indispensable Amino Acids Rapidly Decrease the Concentration of the Limiting Amino Acid in the Anterior Piriform Cortex of Rats

Abstract

Diets deficient in an indispensable amino acid have long been known to suppress food intake in rats. Detection of dietary deficiency takes place in the anterior piriform cortex (APC). Recent studies showed that the response to amino acid deficiency takes as little as 15 min to develop, but few data exist to correlate the concentration of amino acids in the APC with this rapid response. The purpose of this study was to measure the concentration of amino acids in the APC in a behaviorally relevant time frame. Rats were preconditioned by consumption of a basal diet for 7-10 d, and then given a test diet with either a control or deficient amino acid profile. Both the threonine- and leucine-deficient diets reliably depleted threonine and leucine concentration in the APC within 30 min, respectively. The control diets and a diet lacking the dispensable amino acid glycine did not lead to amino acid depletion. In combination with previous studies, the present results show that the decrease in the concentration of indispensable amino acids in the APC may be the initial sensory signal for recognition of dietary amino acid deficiency.

Central Amino Acid Sensing in the Control of Feeding Behavior

“…In contrast, regional differences in the concentration of BCAA and AAA following the ingestion of amino acid imbalanced diets have been described. In this context, while the concentration of the limiting amino acid decreases in discrete sites, including the pyriform cortex, locus coeruleus, and the nucleus of the solitary tract, hypothalamic areas are protected from this deficiency (39–41). Collectively, these data indicate that amino acid concentrations in the brain are not a simple reflection of the plasma amino acid profile but vary selectively in discrete sites under specific dietary contexts.…”

Acute tryptophan depletion in humans: a review of theoretical, practical and ethical aspects

“…The initial sensor of this effect, which can occur within 30 minutes, seems to be altered essential amino acid levels in the anterior piriform cortex, and the effect is mediated by serotonin 3 receptors. [42][43][44] Although the decline in food intake is mediated by serotonin receptors, the effect is not specific to amino acid imbalances involving tryptophan, so any effect might also apply to studies with phenylalanine/tyrosine deficient mixtures. The significance for human ATD studies of the ingestion of amino acid mixtures with an unphysiological imbalance of amino acids is not known.…”

Anticatabolic activity of alpha-ketoglutaric acid in growing rats

“…A change in the blood amino acid (AA) profile may be the initial sensory signal for recognition of dietary AA deficiency which has long been known to suppress feed intake in rats (Koehnle et al, 2004). Nevertheless, a PFD decreases N excretion by increasing the rate of reutilization of amino acids from endogenous proteins for protein synthesis (Nielsen et al, 1994).…”