title: Palatability-induced hyperphagia increases hypothalamic Dynorphin peptide and mRNA levels.
abstract: Opioid involvement in regulating the intake of highly palatable diets was studied by examining the effect of feeding either a cornstarch-based diet (CHO) or a high fat diet containing sucrose (Fat/Sucrose) on hypothalamic opioid levels. Rats received either CHO ad libitum, Fat/Sucrose ad libitum, Fat/Sucrose pair-fed to the caloric intake of CHO, or Fat/Sucrose at 60% of ad libitum Fat/Sucrose intake. Animals receiving Fat/Sucrose ad libitum consumed more calories and gained more weight than animals receiving CHO (P < 0.001). Relative to CHO, ad libitum intake of Fat/Sucrose elevated proDynorphin mRNA levels in the arcuate and Dynorphin A1-17 levels in the paraventricular nucleus (PVN) (P < 0.05), but did not affect arcuate mRNA levels of proEnkephalin or proOpiomelanocortin (POMC), or PVN levels of Met-Enkephalin or beta-Endorphin. Pair-feeding the Fat/Sucrose diet to the level of intake of the CHO diet resulted in levels of proDynorphin and Dynorphin A1-17 that were similar in the two diet groups. Pair-feeding Fat/Sucrose reduced mRNA levels of proDynorpin, proEnkephalin and POMC, and Dynorphin A1-17 levels, relative to ad libitum feeding of Fat/Sucrose. Met-Enkephalin and beta-Endorphin were not affected by dietary treatment. Feeding Fat/Sucrose at 60% of ad libitum intake resulted in mRNA levels of proDynorphin, proEnkephalin and POMC, and Dynorphin A1-17 levels that were similar to those observed in CHO group. Hypothalamic Dynorphin A1-17 and proDynorphin mRNA levels are stimulated by feeding a highly palatable diet rich in fat and sucrose. The increased synthesis may be due in part to a palatability-induced overconsumption of calories. Caloric restriction of the same diet decreases mRNA levels of proDynorphin, proEnkephalin and POMC, as well as levels of Dynorphin A1-17.
authors.affiliation: Department of Medicine, VA Medical Center, Minneapolis, MN 55417, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Welch
authors.forename: E M
authors.initials: EM
authors.lastname: Kim
authors.forename: M K
authors.initials: MK
authors.lastname: Grace
authors.forename: C J
authors.initials: CJ
authors.lastname: Billington
authors.forename: A S
authors.initials: AS
authors.lastname: Levine
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000378:metabolism; D015152:Blotting, Northern; D004032:Diet; D004399:Dynorphins / Q000096:biosynthesis*; D005518:Food Preferences / Q000523:psychology*; D006963:Hyperphagia / Q000523:psychology*; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D018847:Opioid Peptides / Q000096:biosynthesis; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D013649:Taste; D015430:Weight Gain / Q000502:physiology
chemical_list: D018847:Opioid Peptides; D012333:RNA, Messenger; D004399:Dynorphins