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Palatability-induced hyperphagia increases hypothalamic Dynorphin peptide and mRNA levels
C C Welch1, E M Kim, M K Grace
1Department of Medicine, VA Medical Center, Minneapolis, MN 55417, USA.
Brain Research
|May 20, 1996
Summary
Highly palatable diets rich in fat and sucrose increase hypothalamic dynorphin synthesis, particularly when overconsumed. Caloric restriction of these diets, however, decreases opioid precursor and peptide levels in the hypothalamus.
Area of Science:
- Neuroscience
- Endocrinology
- Nutritional Science
Background:
- Opioid systems play a role in regulating food intake.
- The effects of highly palatable diets on hypothalamic opioid signaling are not fully understood.
Purpose of the Study:
- To investigate the impact of a high-fat, high-sucrose diet on hypothalamic opioid peptide and mRNA levels in rats.
- To determine if caloric intake or diet composition drives changes in opioid signaling.
Main Methods:
- Rats were fed either a control diet (CHO) or a palatable diet (Fat/Sucrose) under various feeding conditions: ad libitum, pair-fed to CHO, or restricted intake.
- Hypothalamic levels of pro-dynorphin, pro-enkephalin, and pro-opiomelanocortin (POMC) mRNA, as well as dynorphin A1-17, Met-enkephalin, and beta-endorphin, were quantified.
Main Results:
- Ad libitum intake of the Fat/Sucrose diet increased caloric consumption and body weight compared to the CHO diet.
- The Fat/Sucrose diet elevated pro-dynorphin mRNA and dynorphin A1-17 levels, but not other measured opioids.
- Pair-feeding or caloric restriction of the Fat/Sucrose diet attenuated these increases, with restricted intake reducing pro-dynorphin, pro-enkephalin, and POMC mRNA levels.
Conclusions:
- Hypothalamic dynorphin synthesis is stimulated by palatable diets high in fat and sucrose, potentially due to overconsumption of calories.
- Caloric restriction of palatable diets leads to decreased levels of specific opioid precursors and peptides in the hypothalamus.