Intracellular interplay between cholecystokinin and leptin signalling for satiety control in rats

Hayato Koizumi,Masayuki Ikeda,Takatoshi Mochizuki,Weihong Pan,Shahid Mohammad,Tomoya Ozaki,Kiyokazu Muto,Juhyon Kim,Nanami Matsuba,Eri Morioka

doi:10.1038/s41598-020-69035-6

Abstract

Cholecystokinin (CCK) and leptin are satiety-controlling peptides, yet their interactive roles remain unclear. Here, we addressed this issue using in vitro and in vivo models. In rat C6 glioma cells, leptin pre-treatment enhanced Ca2+ mobilization by a CCK agonist (CCK-8s). This leptin action was reduced by Janus kinase inhibitor (AG490) or PI3-kinase inhibitor (LY294002). Meanwhile, leptin stimulation alone failed to mobilize Ca2+ even in cells overexpressing leptin receptors (C6-ObRb). Leptin increased nuclear immunoreactivity against phosphorylated STAT3 (pSTAT3) whereas CCK-8s reduced leptin-induced nuclear pSTAT3 accumulation in these cells. In the rat ventromedial hypothalamus (VMH), leptin-induced action potential firing was enhanced, whereas nuclear pSTAT3 was reduced by co-stimulation with CCK-8s. To further analyse in vivo signalling interplay, a CCK-1 antagonist (lorglumide) was intraperitoneally injected in rats following 1-h restricted feeding. Food access was increased 3-h after lorglumide injection. At this timepoint, nuclear pSTAT3 was increased whereas c-Fos was decreased in the VMH. Taken together, these results suggest that leptin and CCK receptors may both contribute to short-term satiety, and leptin could positively modulate CCK signalling. Notably, nuclear pSTAT3 levels in this experimental paradigm were negatively correlated with satiety levels, contrary to the generally described transcriptional regulation for long-term satiety via leptin receptors.

Highlights

Cholecystokinin (CCK) and leptin are satiety-controlling peptides, yet their interactive roles remain unclear
Leptin increased or decreased intrinsic Ca2+ oscillations depending on cell populations in primary cultures of ventromedial hypothalamus (VMH), which include the ventromedial nucleus (VMN) and arcuate nucleus (ARC) n eurons[40]
Since CCK ligand binding has been reported in C6 c ells[56], the present study analyzed the gene expression of CCK-1 and CCK-2 receptors using real time RT-PCR

Summary

Introduction

Cholecystokinin (CCK) and leptin are satiety-controlling peptides, yet their interactive roles remain unclear. Nuclear pSTAT3 was increased whereas c-Fos was decreased in the VMH Taken together, these results suggest that leptin and CCK receptors may both contribute to short-term satiety, and leptin could positively modulate CCK signalling. CCK-1 receptors are localized in peripheral and central machinery known to control satiety, and their dense expression has been found in the pylorus, nodose ganglion, nucleus tractus solitarius, and hypothalamic satiety-controlling centres[20]. The nodose ganglion neurons co-express ObRb and CCK-1 receptors, and their synergistic excitatory actions were identified in these n eurons[53,54] This suggests a direct interaction of these receptors within peripheral satiety controllers, it is still unclear as to how these receptors interact at the intracellular signalling level in the central nervous system.

Methods

Results

Conclusion