title: Palmitate alters the rhythmic expression of molecular clock genes and orexigenic neuropeptide Y mRNA levels within immortalized, hypothalamic neurons.
abstract: The control of energy homeostasis within the hypothalamus is under the regulated control of homeostatic hormones, nutrients and the expression of neuropeptides that alter feeding behavior. Elevated levels of palmitate, a predominant saturated fatty acid in diet and fatty acid biosynthesis, alter cellular function. For instance, a key mechanism involved in the development of insulin resistance is lipotoxicity, through increased circulating saturated fatty acids. Although many studies have begun to determine the underlying mechanisms of lipotoxicity in peripheral tissues, little is known about the effects of excess lipids in the brain. To determine these mechanisms we used an immortalized, clonal, hypothalamic cell line, mHypoE-44, to demonstrate that palmitate directly alters the expression of molecular clock components, by increasing Bmal1 and Clock, or by decreasing Per2, and Rev-erbα, their mRNA levels and altering their rhythmic period within individual neurons. We found that these neurons endogenously express the orexigenic neuropeptides NPY and AgRP, thus we determined that palmitate administration alters the mRNA expression of these neuropeptides as well. Palmitate treatment causes a significant increase in NPY mRNA levels and significantly alters the phase of rhythmic expression. We explored the link between AMPK and the expression of neuropeptide Y using the AMPK inhibitor compound C and the AMP analog AICAR. AMPK inhibition decreased NPY mRNA. AICAR also elevated basal NPY, but prevented the palmitate-mediated increase in NPY mRNA levels. We postulate that this palmitate-mediated increase in NPY and AgRP synthesis may initiate a detrimental positive feedback loop leading to increased energy consumption.
authors: Department of Physiology, University of Toronto, Canada.
authors: Laura J
authors: LJ
authors: Fick
authors: Gordon H
authors: GH
authors: Fick
authors: Denise D
authors: DD
authors: Belsham
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D056930:ARNTL Transcription Factors / Q000235:genetics; D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics*; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000235:genetics*; D004734:Energy Metabolism / Q000235:genetics; D005786:Gene Expression Regulation; D015694:Gene Products, rev / Q000235:genetics; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009478:Neuropeptide Y / Q000235:genetics*; D009479:Neuropeptides / Q000235:genetics; D018774:Oncogene Proteins v-erbA / Q000235:genetics; D000068797:Orexins; D010168:Palmitates / Q000378:metabolism* / Q000494:pharmacology; D056950:Period Circadian Proteins / Q000235:genetics; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis
chemical_list: D056930:ARNTL Transcription Factors; C538961:Bmal1 protein, mouse; D015694:Gene Products, rev; D047908:Intracellular Signaling Peptides and Proteins; D009478:Neuropeptide Y; D009479:Neuropeptides; D018774:Oncogene Proteins v-erbA; D000068797:Orexins; D010168:Palmitates; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D056926:CLOCK Proteins; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases