Prolactin receptors in Rip‐cre cells, but not in AgRP neurones, are involved in energy homeostasis

Abstract

Among its many functions, prolactin has been implicated in energy homeostasis, particularly during pregnancy and lactation. The arcuate nucleus is a key site in the regulation of energy balance. The present study aimed to examine whether arcuate nucleus neuronal populations involved in energy homeostasis are prolactin responsive and whether they can mediate the effects of prolactin on energy homeostasis. To determine whether Agrp neurones or Rip-Cre neurones are prolactin responsive, transgenic mice expressing the reporter td-tomato in Agrp neurones (td-tomato/Agrp-Cre) or Rip-Cre neurones (td-tomato/Rip-Cre) were treated with prolactin and perfused 45 minutes later. Brains were processed for double-labelled immunohistochemistry for pSTAT5, a marker of prolactin-induced intracellular signalling, and td-tomato. In addition, Agrp-Cre mice and Rip-Cre mice were crossed with mice in which the prolactin receptor gene (Prlr) was flanked with LoxP sites (Prlr mice). The Prlr construct was designed such that Cre-mediated recombination resulted in deletion of the Prlr and expression of green fluorescent protein (GFP) in its place. In td-tomato/Rip-Cre mice, prolactin-induced pSTAT5 was co-localised with td-tomato, indicating that there is a subpopulation of Rip-Cre neurones in the arcuate nucleus that respond to prolactin. Furthermore, mice with a specific deletion of Prlr in Rip-Cre neurones had lower body weights, increased oxygen consumption, increased running wheel activity and numerous cells in the arcuate nucleus had positive GFP staining indicating deletion of Prlr from Rip-Cre neurones. By contrast, no co-localisation of td-tomato and pSTAT5 was observed in td-tomato/Agrp-Cre mice after prolactin treatment. Moreover, Prlr /Agrp-Cre mice had no positive GFP staining in the arcuate nucleus and did not differ in body weight compared to littermate controls. Overall, these results indicate that Rip-Cre neurones in the arcuate nucleus are responsive to prolactin and may play a role in the orexigenic effects of prolactin, whereas prolactin does not directly affect Agrp neurones.

Chronic high prolactin levels impact on gene expression at discrete hypothalamic nuclei involved in food intake

“…Increases in Npy and Agrp gene expression in the ARN emerge at 10 months of age and may be related to the development of leptin resistance in this nucleus. The effect of hyperprolactinemia on Agrp is concordant with the increased levels of Agrp in ARN described during lactation, but is most likely an indirect effect because PRLRs are absent from AGRP neurons . Finally, Npy mRNA levels were increased in the DMN of lacDrd2KO mice, as has been shown during lactation in rats .…”

“…The effect of hyperprolactinemia on Agrp is concordant with the increased levels of Agrp in ARN described during lactation, 54 but is most likely an indirect effect because PRLRs are absent from AGRP neurons. 55 Finally, Npy mRNA levels were increased in the DMN of lacDrd2KO mice, as has been shown during lactation in rats. 56 The DMN controls food intake and if destroyed, hyperphagia and obesity ensue.…”

Pancreatic prolactin receptor signaling regulates maternal glucose homeostasis

“…In their model, loss of PRLR signaling in β cells resulted in GDM, reduced β cell proliferation and impaired β cell mass expansion during pregnancy (Banerjee et al 2016). The RIP-Cre has been shown to have significant Cre activity outside of the pancreas, including the hypothalamus (Wicksteed et al 2010, Ladyman et al 2017. Adding to the potential confusion, RIP-Cre has been demonstrated to develop glucose intolerance and impaired insulin secretion independent of a floxed target gene (Lee et al 2006).…”

Leptin Receptors in RIP-Cre25Mgnneurons Mediate Anti-Dyslipidemia Effects of Leptin in Insulin-Deficient Male Mice

“…However, the mice ectopically express Cre recombinase in the central nervous system (CNS) (Song et al, 2010;Wicksteed et al, 2010) due to the nature of genetically-engineering methods in the early era (Harno et al, 2013;Magnuson and Osipovich, 2013). Because RIP-Cre 25Mgn mice express Cre recombinase in unique and distinct neurons from conventional hypothalamic neurons such as AgRP neurons (Campbell et al, 2017;Choudhury et al, 2005), the transgenic mice have been utilized for studies investigating the role of hypothalamic neurons that are genetically-uncategorized by conventional genes, in particular studies focusing on the regulation of metabolism (Kong et al, 2012;Ladyman et al, 2017;Wang et al, 2018a;Wang et al, 2014).…”

“…RIP-Cre 25Mgn neurons regulate energy expenditure through thermogenesis (Kong et al, 2012;Wang et al, 2018a) and glucose metabolism (Ladyman et al, 2017;Wang et al, 2014) in the presence of insulin.…”