Palatability-induced hyperphagia increases hypothalamic Dynorphin peptide and mRNA levels

• Published in: Brain research 1996-05, Vol.721 (1), p.126-131
• Main Authors: Welch, Catherine C., Kim, Eun-Mee, Grace, Martha K., Billington, Charles J., Levine, Allen S.
• Format: Article
• Language: English
• Subjects: Animals; Arcuate Nucleus of Hypothalamus - metabolism; Biological and medical sciences; Blotting, Northern; Diet; Dynorphins - biosynthesis; Fat; Feeding. Feeding behavior; Food Preferences - psychology; Fundamental and applied biological sciences. Psychology; Highly palatable diet; Hyperphagia - psychology; Hypothalamus - metabolism; Male; Opioid; Opioid peptide; Opioid Peptides - biosynthesis; Opioid rnRNA; Paraventricular Hypothalamic Nucleus - metabolism; Radioimmunoassay; Rats; Rats, Sprague-Dawley; RNA, Messenger - biosynthesis; Sucrose; Taste; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Weight Gain - physiology
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/0006-8993(96)00151-5

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 A 1–17 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 β-Endorphin. Pair-feeding the Fat/Sucrose diet to the level of intake of the CHO diet resulted in levels of proDynorphin and Dynorphin A 1–17 that were similar in the two diet groups. Pair-feeding Fat/Sucrose reduced mRNA levels of proDynorpin, proEnkephalin and POMC, and Dynorphin A 1–17 levels, relative to ad libitum feeding of Fat/Sucrose. Met-Enkephalin and β-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 A 1–17 levels that were similar to those observed in CHO group. Hypothalamic Dynorphin A 1–17 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 A 1–17.