Hypothalamus proteomics from mouse models with obesity and anorexia reveals therapeutic targets of appetite regulation.
OBJECTIVE
This study examined the proteomic profile of the hypothalamus in mice exposed to a high-fat diet (HFD) or with the anorexia of acute illness. This comparison could provide insight on the effects of these two opposite states of energy balance on appetite regulation.


METHODS
Four to six-week-old male C56BL/6J mice were fed a normal (control 1 group; n=7) or a HFD (HFD group; n=10) for 8 weeks. The control 2 (n=7) and lipopolysaccharide (LPS) groups (n=10) were fed a normal diet for 8 weeks before receiving an injection of saline and LPS, respectively. Hypothalamic regions were analysed using a quantitative proteomics method based on a combination of techniques including iTRAQ stable isotope labeling, orthogonal two-dimensional liquid chromatography hyphenated with nanospray ionization and high-resolution mass spectrometry. Key proteins were validated with quantitative PCR.


RESULTS
Quantitative proteomics of the hypothalamous regions profiled a total of 9249 protein groups (q<0.05). Of these, 7718 protein groups were profiled with a minimum of two unique peptides for each. Hierachical clustering of the differentiated proteome revealed distinct proteomic signatures for the hypothalamus under the HFD and LPS nutritional conditions. Literature research with in silico bioinformatics interpretation of the differentiated proteome identified key biological relevant proteins and implicated pathways. Furthermore, the study identified potential pharmacologic targets. In the LPS groups, the anorexigen pro-opiomelanocortin was downregulated. In mice with obesity, nuclear factor-κB, glycine receptor subunit alpha-4 (GlyR) and neuropeptide Y levels were elevated, whereas serotonin receptor 1B levels decreased.


CONCLUSIONS
High-precision quantitative proteomics revealed that under acute systemic inflammation in the hypothalamus as a response to LPS, homeostatic mechanisms mediating loss of appetite take effect. Conversely, under chronic inflammation in the hypothalamus as a response to HFD, mechanisms mediating a sustained 'perpetual cycle' of appetite enhancement were observed. The GlyR protein may constitute a novel treatment target for the reduction of central orexigenic signals in obesity.
Clinical and Experimental Sciences Unit, University of Southampton, Southampton, UK.
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Manousopoulou
Centre of Basic Research, Biomedical Research Foundation of the Academy of Athens, Greece.
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Koutmani
Centre of Basic Research, Biomedical Research Foundation of the Academy of Athens, Greece.
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Karaliota
Clinical and Experimental Sciences Unit, University of Southampton, Southampton, UK.
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Woelk
Information Technologies in Medicine and Biology, Department of Informatics and Telecommunications, University of Athens, Athens, Greece.|Wyss Institute of Biological Inspired Engineering, Boston, MA, USA.
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Manolakos
Centre of Basic Research, Biomedical Research Foundation of the Academy of Athens, Greece.|Wyss Institute of Biological Inspired Engineering, Boston, MA, USA.
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Karalis
Clinical and Experimental Sciences Unit, University of Southampton, Southampton, UK.|Institute for Life Sciences, University of Southampton, Southampton, UK.|Cancer Sciences and CES Unit, University of Southampton, Southampton, UK.
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Garbis
D000818:Animals; D000855:Anorexia / Q000097:blood / Q000139:chemically induced / Q000235:genetics*; D001069:Appetite Regulation; D019295:Computational Biology; D059305:Diet, High-Fat / Q000009:adverse effects; D004195:Disease Models, Animal; D015536:Down-Regulation; D007031:Hypothalamus / Q000378:metabolism*; D007249:Inflammation / Q000139:chemically induced / Q000235:genetics; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008070:Lipopolysaccharides / Q000009:adverse effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009478:Neuropeptide Y / Q000235:genetics / Q000378:metabolism; D009765:Obesity / Q000097:blood / Q000139:chemically induced / Q000235:genetics*; D011333:Pro-Opiomelanocortin / Q000235:genetics / Q000378:metabolism; D020543:Proteome / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044302:Receptor, Serotonin, 5-HT1B / Q000235:genetics / Q000378:metabolism; D018009:Receptors, Glycine / Q000235:genetics / Q000378:metabolism
C000603631:HTR1B protein, mouse; D007328:Insulin; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009478:Neuropeptide Y; D020543:Proteome; D012333:RNA, Messenger; D044302:Receptor, Serotonin, 5-HT1B; D018009:Receptors, Glycine; C408089:glycine receptor, alpha4-subunit; D011333:Pro-Opiomelanocortin