Abstract
BackgroundEnergy homeostasis is regulated by the hypothalamus but fails when animals are fed a high-fat diet (HFD), and leptin insensitivity and obesity develops. To elucidate the possible mechanisms underlying these effects, a microarray-based transcriptomics approach was used to identify novel genes regulated by HFD and leptin in the mouse hypothalamus.ResultsMouse global array data identified serpinA3N as a novel gene highly upregulated by both a HFD and leptin challenge. In situ hybridisation showed serpinA3N expression upregulation by HFD and leptin in all major hypothalamic nuclei in agreement with transcriptomic gene expression data. Immunohistochemistry and studies in the hypothalamic clonal neuronal cell line, mHypoE-N42 (N42), confirmed that alpha 1-antichymotrypsin (α1AC), the protein encoded by serpinA3, is localised to neurons and revealed that it is secreted into the media. SerpinA3N expression in N42 neurons is upregulated by palmitic acid and by leptin, together with IL-6 and TNFα, and all three genes are downregulated by the anti-inflammatory monounsaturated fat, oleic acid. Additionally, palmitate upregulation of serpinA3 in N42 neurons is blocked by the NFκB inhibitor, BAY11, and the upregulation of serpinA3N expression in the hypothalamus by HFD is blunted in IL-1 receptor 1 knockout (IL-1R1−/−) mice.ConclusionsThese data demonstrate that serpinA3 expression is implicated in nutritionally mediated hypothalamic inflammation.
Highlights
Energy homeostasis is regulated by the hypothalamus but fails when animals are fed a high-fat diet (HFD), and leptin insensitivity and obesity develops
Transcriptomics Transcriptomic data revealed the regulation of serpinA3N gene expression in total dissected hypothalamic tissue from mice maintained on a Low-fat diet (LFD) or HFD for 1 or 4 weeks and either challenged with vehicle or leptin
Analysis of the gene expression data by two-way Analysis of variance (ANOVA) confirmed that serpinA3N gene expression increased with time on the diet and there was no interaction between diet and time for the arcuate nuclei (ARC) and Dorsomedial nuclei of the hypothalamus (DMH) but there was for the VMH (P < 0.05) indicating that the age of the animals may lead to increases in serpinA3N gene expression in the ARC, VMH and DMH over the 16 weeks of the experiment (Fig. 3c–e)
Summary
Energy homeostasis is regulated by the hypothalamus but fails when animals are fed a high-fat diet (HFD), and leptin insensitivity and obesity develops. Sergi et al Genes & Nutrition (2018) 13:28 been identified as important in energy balance regulation: orexigenic neurons expressing neuropeptide Y (NPY) and agouti-related peptide (AgRP) and anorexigenic neurons expressing proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Both orexigenic and anorexigenic neurons express leptin receptors, highlighting the importance of this hormones in the system. Leptin acts on multiple levels in hypothalamic neurons, effecting gene transcription, post-translational processing as well as membrane polarisation to inhibit AgRP/NPY neurons while activating POMC/CART neurons, resulting in a stable body weight [11]. The ability of leptin to regulate feeding behaviour as well as peripheral glucose homeostasis is diminished as a result of hypothalamic insensitivity to this hormone [12,13,14,15,16]
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