Limited impact on glucose homeostasis of leptin receptor deletion from insulin- or proglucagon-expressing cells

Abstract

Aims/hypothesisThe adipose tissue-derived hormone leptin plays an important role in the maintenance of body weight and glucose homeostasis. Leptin mediates its effects by interaction with leptin receptors (LepRb), which are highly expressed in the hypothalamus and other brain centres, and at lower levels in the periphery. Previous studies have used relatively promiscuous or inefficient Cre deleter strains, respectively, to explore the roles of LepR in pancreatic β and α cells. Here, we use two newly-developed Cre lines to explore the role of leptin signalling in insulin and proglucagon-expressing cells.MethodsLeptin receptor expression was measured in isolated mouse islets and highly-purified islet cells by RNASeq and quantitative RT-PCR. Mice lacking leptin signalling in pancreatic β, or in α and other proglucagon-expressing cells, were generated using Ins1Cre- or iGluCre-mediated recombination respectively of flox'd leptin receptor alleles. In vivo glucose homeostasis, changes in body weight, pancreatic histology and hormone secretion from isolated islets were assessed using standard techniques.ResultsLeptin receptor mRNA levels were at or below the level of detection in wild-type adult mouse isolated islets and purified cells, and leptin signalling to Stat3 phosphorylation was undetectable. Whereas male mice further deleted for leptin receptors in β cells exhibited no abnormalities in glucose tolerance up to 16 weeks of age, females transiently displayed improved glucose tolerance at 8 weeks (11.2 ± 3.2% decrease in area under curve; p < 0.05), and improved (39.0 ± 13.0%, P < 0.05) glucose-stimulated insulin secretion in vitro. No differences were seen between genotypes in body weight, fasting glucose or β/α cell ratio. Deletion of LepR from α-cells, a minority of β cells, and a subset of proglucagon-expressing cells in the brain, exerted no effects on body weight, glucose or insulin tolerance, nor on pancreatic hormone secretion assessed in vivo and in vitro.Conclusions/interpretationThe use here of a highly selective Cre recombinase indicates that leptin signalling plays a relatively minor, age- and sex-dependent role in the control of β cell function in the mouse. No in vivo role for leptin receptors on α cells, nor in other proglucagon-expressing cells, was detected in this study.

Gcg CreERT2 knockin mice as a tool for genetic manipulation in pancreatic alpha cells

“…BAC transgenes include long flanking sequences on both sides of the Cre inserted into the Gcg gene, and thereby confer better control of Gcg -Cre gene expression by cis elements similar to the endogenous Gcg gene. Nevertheless, it was reported that approximately 20% of beta cells were labelled with Cre reporter in one of the BAC transgenic lines [29]. This is in contrast to our two new mouse models, in which activation of Cre reporter in beta cells was negligible (<1%), even in the Gcg iCre mice in which the targeted Gcg gene locus was disarranged by a duplication mutation.…”

The transcription factor Pax6 is required for pancreatic β cell identity, glucose-regulated ATP synthesis, and Ca2+ dynamics in adult mice

“…Relative gene expression was assessed using SYBR Green (Invitrogen), and expression of each gene was normalized and expressed as n -fold change in mRNA expression versus Cre − , calculated using the 2 ΔΔCt method (60). …”

Adiponectin, Leptin, and Fatty Acids in the Maintenance of Metabolic Homeostasis through Adipose Tissue Crosstalk

“…While previous studies show that the β-cell expresses leptin receptors (Seufert et al, 1999), Soedling and colleagues recently reported that leptin receptor mRNA expression in isolated β-cells was at or below the level of detection and, using a newly developed Cre to specifically target Leptin receptor deletion to the β-cell, the authors reported no metabolic abnormalities (Soedling et al, 2015). Contrary to these findings, previous studies in isolated pancreatic islets from rodents and humans (Emilsson et al, 1997; Fehmann et al, 1997; Kieffer et al, 1997) showed that the pancreatic β-cell is a major target of leptin.…”