Elsevier

Molecular Metabolism

Volume 10, April 2018, Pages 14-27
Molecular Metabolism

Original Article
Rapid sensing of l-leucine by human and murine hypothalamic neurons: Neurochemical and mechanistic insights

https://doi.org/10.1016/j.molmet.2018.01.021Get rights and content
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open access

Highlights

  • A neurochemically diverse group of mouse and human hypothalamic neurons rapidly sense and respond to l-leucine.

  • Leucine can produce neuronal activation or neuronal inhibition via distinct and novel Ca2+ signaling mechanisms.

  • Leucine activates 25% ARH POMC neurons.

  • Leucine inhibits 10% ARH NPY/AGRP neurons and reduces AGRP secretion from fasted mediobasal hypothalamic slices.

Abstract

Objective

Dietary proteins are sensed by hypothalamic neurons and strongly influence multiple aspects of metabolic health, including appetite, weight gain, and adiposity. However, little is known about the mechanisms by which hypothalamic neural circuits controlling behavior and metabolism sense protein availability. The aim of this study is to characterize how neurons from the mediobasal hypothalamus respond to a signal of protein availability: the amino acid l-leucine.

Methods

We used primary cultures of post-weaning murine mediobasal hypothalamic neurons, hypothalamic neurons derived from human induced pluripotent stem cells, and calcium imaging to characterize rapid neuronal responses to physiological changes in extracellular l-Leucine concentration.

Results

A neurochemically diverse subset of both mouse and human hypothalamic neurons responded rapidly to l-leucine. Consistent with l-leucine's anorexigenic role, we found that 25% of mouse MBH POMC neurons were activated by l-leucine. 10% of MBH NPY neurons were inhibited by l-leucine, and leucine rapidly reduced AGRP secretion, providing a mechanism for the rapid leucine-induced inhibition of foraging behavior in rodents. Surprisingly, none of the candidate mechanisms previously implicated in hypothalamic leucine sensing (KATP channels, mTORC1 signaling, amino-acid decarboxylation) were involved in the acute activity changes produced by l-leucine. Instead, our data indicate that leucine-induced neuronal activation involves a plasma membrane Ca2+ channel, whereas leucine-induced neuronal inhibition is mediated by inhibition of a store-operated Ca2+ current.

Conclusions

A subset of neurons in the mediobasal hypothalamus rapidly respond to physiological changes in extracellular leucine concentration. Leucine can produce both increases and decreases in neuronal Ca2+ concentrations in a neurochemically-diverse group of neurons, including some POMC and NPY/AGRP neurons. Our data reveal that leucine can signal through novel mechanisms to rapidly affect neuronal activity.

Keywords

l-leucine sensing
Hypothalamus
Calcium imaging
Pluripotent
Metabolism

Abbreviations

ARH
arcuate nucleus of the hypothalamus
MBH
mediobasal-hypothalamus
hPSC
human induced pluripotent stem cells

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