Effects of "Bioactive" amino acids leucine, glutamate, arginine and tryptophan on feed intake and mRNA expression of relative neuropeptides in broiler chicks

Songbo Wang,Qingyan Jiang,Ping Gao,Gang Shu,Lina Wang,Paul Khondowe,Yongliang Zhang,Shengfeng Chen,Jianjian Yu,Qianyun Xi,Xiaotong Zhu

doi:10.1186/2049-1891-3-27

Abstract

Feed intake control is vital to ensuring optimal nutrition and achieving full potential for growth and development in poultry. The aim of the present study was to investigate the effects of L-leucine, L-glutamate, L-tryptophan and L-arginine on feed intake and the mRNA expression levels of hypothalamic Neuropeptide involved in feed intake regulation in broiler chicks. Leucine, glutamate, tryptophan or arginine was intra-cerebroventricularly (ICV) administrated to 4d-old broiler chicks respectively and the feed intake were recorded at various time points. Quantitative PCR was performed to determine the hypothalamic mRNA expression levels of Neuropeptide Y (NPY), agouti related protein (AgRP), pro-opiomelanocortin (POMC), melanocortin receptor 4 (MC4R) and corticotrophin releasing factor (CRF). Our results showed that ICV administration of L-leucine (0.15 or 1.5 μmol) significantly (P < 0.05) increased feed intake up to 2 h post-administration period and elevated both hypothalamic NPY and AgRP mRNA expression levels. In contrast, ICV administration of L-glutamate (1.6 μmol) significantly (P < 0.05) decreased feed intake 0.25, 0.5 and 2 h post-injection, and increased hypothalamic CRF and MC4R mRNA expression levels. Meanwhile, both L-tryptophan (10 or 100 μg) and L-arginine (20 or 200 μg) had no significant effect on feed intake. These findings suggested that L-leucine and L-glutamate could act within the hypothalamus to influence food intake, and that both orexigenic and anorexigenic Neuropeptide genes might contribute directly to these effects.

Highlights

Metabolic fuels, including amino acids, could act on hypothalamic neurons to regulate feeding behavior and energy homeostasis, but the signaling mechanisms mediating these effects are not fully clear [1]
ICV injection of leucine increased feed intake and hypothalamic Neuropeptide Y (NPY) and agouti related protein (AgRP) mRNA expression To determine the effects of ICV injection of leucine on feed intake, 0.15 μmol and 1.5 μmol of leucine were administered
The anorexigenic Neuropeptide POMC and corticotrophin releasing factor (CRF), and the melanocortin receptor MC4R, had their mRNA expression levels reduced though the reduction did not reach statistically significant levels for both doses of leucine used

Summary

Introduction

Metabolic fuels, including amino acids, could act on hypothalamic neurons to regulate feeding behavior and energy homeostasis, but the signaling mechanisms mediating these effects are not fully clear [1]. An essential amino acid, likely represents a physiological signal of hypothalamic amino acid availability [8]. It enters the brain more quickly than other amino acids, and it is the most potent activator of the amino-acid-sensitive mTORC1 pathway in mammals [8,9]. Leucine intracerebroventricular (ICV) injection led to a decrease in food intake in mammals, by increasing hypothalamic mTOR signaling [5]. The effect of ICV injection of leucine on hypothalamic orexigenic and anorexigenic Neuropeptide remained to be elucidated

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