Learned preference and aversion for complete and isoleucine-devoid diets in rats

Naito-Hoopes, Mikako; McArthur, Laura H.; Gietzen, Dorothy W.; Rogers, Quinton R.

doi:10.1016/0031-9384(93)90142-3

Cited by 27 publications

(10 citation statements)

References 24 publications

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“…Although it is possible that protein status is sensed generally, several lines of observation suggest that mechanisms exist for the sensing of individual amino acids. For instance, it is wellestablished that diets that are severely amino acid imbalanced induce aversive responses, leading to decreased food intake (16,26). However, if offered a choice between two diets that are imbalanced for different amino acids, rats will effectively self-select between these two diets to meet their amino acid requirements, even though each diet would be aversive if offered alone (11).…”

Section: Discussionmentioning

confidence: 99%

Amino acids inhibit Agrp gene expression via an mTOR-dependent mechanism

Morrison¹,

Xi²,

White³

et al. 2007

American Journal of Physiology-Endocrinology and Metabolism

155

115

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Metabolic fuels act on hypothalamic neurons to regulate feeding behavior and energy homeostasis, but the signaling mechanisms mediating these effects are not fully clear. Rats placed on a low-protein diet (10% of calories) exhibited increased food intake ( P < 0.05) and hypothalamic Agouti-related protein ( Agrp) gene expression ( P = 0.002). Direct intracerebroventricular injection of either an amino acid mixture (RPMI 1640) or leucine alone (1 μg) suppressed 24-h food intake ( P < 0.05), indicating that increasing amino acid concentrations within the brain is sufficient to suppress food intake. To define a cellular mechanism for these direct effects, GT1–7 hypothalamic cells were exposed to low amino acids for 16 h. Decreasing amino acid availability increased Agrp mRNA levels in GT1–7 cells ( P < 0.01), and this effect was attenuated by replacement of the amino acid leucine ( P < 0.05). Acute exposure to elevated amino acid concentrations increased ribosomal protein S6 kinase phosphorylation via a rapamycin-sensitive mechanism, suggesting that amino acids directly stimulated mammalian target of rapamycin (mTOR) signaling. To test whether mTOR signaling contributes to amino acid inhibition of Agrp gene expression, GT1–7 cells cultured in either low or high amino acids for 16 h and were also treated with rapamcyin (50 nM). Rapamycin treatment increased Agrp mRNA levels in cells exposed to high amino acids ( P = 0.01). Taken together, these observations indicate that amino acids can act within the brain to inhibit food intake and that a direct, mTOR-dependent inhibition of Agrp gene expression may contribute to this effect.

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Section: Discussionmentioning

confidence: 99%

Amino acids inhibit Agrp gene expression via an mTOR-dependent mechanism

Morrison¹,

Xi²,

White³

et al. 2007

American Journal of Physiology-Endocrinology and Metabolism

155

115

View full text Add to dashboard Cite

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“…associated with foods containing the limiting IAA [11, 101, 103, 141, 142] are preferred. Hedonic centers in the BG, including the NAcc, will be stimulated likely via the LH.…”

Section: Learned Responses Aversion and Preferencementioning

confidence: 99%

“…Also, IAA-deficient rats learn to associate the positive effects of gastric infusions that provide repletion of the limiting IAA, with the place where these infusions were given [102]; this shows that spatial learning, a HIP function, can be involved in conditioned preferences. We [105, 142] used the Sclafani [143] method for determining preferences for flavored water paired with test foods. Although the appropriate associations are made, aversions are achieved more quickly than preferences.…”

Section: Learned Responses Aversion and Preferencementioning

confidence: 99%

“…519–522), which covers a series of choice experiments. Since those first experiments, many choice studies have been done; they show that animals will eat just about anything else, rather than an IAA-deficient or imbalanced diet, reviewed in [35, 54, 142]. Hrupka [144] showed that rats adapted to a lysine-supplemented wheat gluten diet (which is deficient in the IAA, lysine) selected a higher level of supplemental lysine (at a difference of 0.01 %) without reducing their food intake.…”

Section: Learned Responses Aversion and Preferencementioning

confidence: 99%

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The Brain's Response to an Essential Amino Acid-Deficient Diet and the Circuitous Route to a Better Meal

Gietzen

Aja

2012

Mol Neurobiol

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The essential (indispensable) amino acids (IAA) are neither synthesized nor stored in metazoans, yet they are the building blocks of protein. Survival depends on availability of these protein precursors, which must be obtained in the diet; it follows that food selection is critical for IAA homeostasis. If even one of the IAA is depleted, its tRNA becomes quickly deacylated and the levels of charged tRNA fall, leading to disruption of global protein synthesis. As they have priority in the diet, second only to energy, the missing IAA must be restored promptly or protein catabolism ensues. Animals detect and reject an IAA-deficient meal in 20 min, but how? Here, we review the molecular basis for sensing IAA depletion and repletion in the brain’s IAA chemosensor, the anterior piriform cortex (APC). As animals stop eating an IAA-deficient meal, they display foraging and altered choice behaviors, to improve their chances of encountering a better food. Within 2 h, sensory cues are associated with IAA depletion or repletion, leading to learned aversions and preferences that support better food selection. We show neural projections from the APC to appetitive and consummatory motor control centers, and to hedonic, motivational brain areas that reinforce these adaptive behaviors.

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“…COR, the threonine-corrected diet, was identical to THR-DEV except that it was supplemented with threonine (6 g/kg) in order to correct the balance of the amino acid mixture ; ILEU-DEV, the isoleucine-devoid diet, was deficient in isoleucine instead of threonine but otherwise well balanced for the other indispensable amino acids (Naito-Hoopes et al 1993); PO %, was protein free;…”

mentioning

confidence: 99%

Rebalancing essential amino acids intake by self-selection in the rat

Fromentin

Nicolaı̈dis

1996

Br J Nutr

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The purpose of the present study was to assess whether rats are capable of selecting the right proportions of two diets that are individually inappropriate in terms of essential amino acid composition to satisfy their amino acid requirements. Rats were offered a choice of one protein-free regimen and another devoid of only one essential amino acid (either threonine or isoleucine) set up in such a way as to provide amino acid balance if they were consumed in 1/3 and 2/3 proportions respectively. Preliminary experiments had established that all our diets were aversive by themselves except for the 60 g casein/kg diet. Rats did reach almost the necessary proportion with, according to published standards (National Research Council, 1978), some excess in isoleucine intake. In addition, given access to two aversive diets that were each nutritionally inadequate, rats showed no aversion and gained body weight when they had the opportunity to consume both of them. Beyond the capacity that rats have of rebalancing their micronutrient intake, the present experiment brings out the idea that the imbalance-induced aversion: preference ratio may be completely upset when this omnivore has access to more than one feed.

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Learned preference and aversion for complete and isoleucine-devoid diets in rats

Cited by 27 publications

References 24 publications

Amino acids inhibit Agrp gene expression via an mTOR-dependent mechanism

Amino acids inhibit Agrp gene expression via an mTOR-dependent mechanism

The Brain's Response to an Essential Amino Acid-Deficient Diet and the Circuitous Route to a Better Meal

Rebalancing essential amino acids intake by self-selection in the rat

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