GLP-1R Signaling Directly Activates Arcuate Nucleus Kisspeptin Action in Brain Slices but Does not Rescue Luteinizing Hormone Inhibition in Ovariectomized Mice During Negative Energy Balance.
Level 5 - mechanism / opinion, no new human data
Preclinical animal and ex vivo tissue experiment (no human data)
PubMed 28144621 · doi:10.1523/ENEURO.0198-16.2016
What was done
In ovariectomized mice and hypothalamic brain slices, researchers assessed whether glucagon-like peptide 1 (GLP-1) fiber projections contact arcuate nucleus (ARC) kisspeptin (Kiss1) neurons and whether these neurons express Glp1r mRNA. They measured electrophysiological responses (action potentials and membrane potential) of ARC Kiss1 neurons exposed to the GLP-1R agonist liraglutide. They also evaluated brainstem preproglucagon mRNA changes after a 48-hour fast, tested if liraglutide restored suppressed luteinizing hormone (LH) during fasting, and tested if chronic central infusion of the GLP-1R antagonist exendin(9-39) altered ARC Kiss1 mRNA or plasma LH in fed mice.
What was found
GLP-producing fibers directly apposed ARC Kiss1 neurons, which expressed Glp1r mRNA. In brain slices, liraglutide depolarized the membrane and increased action potential firing in ARC Kiss1 cells. Brainstem preproglucagon mRNA decreased after a 48-hour fast. However, liraglutide administration did not prevent LH suppression in fasted mice, and central GLP-1R antagonism with exendin(9-39) in fed mice caused no change in ARC Kiss1 mRNA or plasma LH. The abstract reports no numerical values.
Why it matters
This study shows that direct activation of ARC kisspeptin neurons by GLP-1R signaling is insufficient on its own to sustain or rescue pituitary LH secretion during acute energy restriction, indicating that metabolic regulation of the reproductive axis involves additional compensatory pathways.
Limits
The study is restricted to female ovariectomized mice and ex vivo brain slices, precluding direct clinical translation. Sample sizes, effect sizes, and specific quantitative data are omitted from the abstract. Intact gonadal states and other hypothalamic metabolic circuits were not characterized.
Cited by
- contradicts In underfed mice, GLP-1 administration decreases kisspeptin, causing sex hormones to drop.