The objectives of the present study were to examine the effects of dietary fat type and level of energy intake on hypothalamic leptin binding affinity and membrane fatty acid composition, circulating leptin levels, and body weight homeostasis in rats. Animals were fed diets containing tallow, safflower oil, or menhaden oil (20% wt/wt) for 10 wks, ad libitum or at 60% of ad libitum intakes. Specific leptin binding could not be detected in hypothalamic membrane homogenates; hypothalamic leptin levels were unaffected by diet or energy intake. Levels of tracer exceeding assay reference values were found in homogenates, suggesting intra-membrane binding. Excess tracer levels were weakly associated (p < 0.07) with the sum of hypothalamic phospholipid monounsaturates. Restriction lowered weight gain and food intakes (p < 0.0001 for both). In hypothalamic phospholipids, energy restriction lowered levels of 18:3(n-3) and increased levels of 20:1(n-9), 20:4(n-6), and 22:4(n-6) (p < 0.05, p < 0.02, p < 0.05, and p < 0.04, respectively). Fat type and energy level interactively affected hypothalamic levels of 20:4(n-6), 22:5(n-3) and 22:6(n-3) (p < 0.05, p < 0.006, and p < 0.05, respectively). Restriction lowered circulating leptin levels (p < 0.0001); overall plasma leptin levels were marginally associated (p < 0.07) with hypothalamic 16:0 concentrations. The results of the study support previous findings suggesting that leptin binding at the level of the hypothalamic membrane may not be detectable. The results also support the lack of a dietary fat effect on plasma leptin levels and levels of certain hypothalamic fatty acids, such as 20:4(n-6), 22:4(n-6), and 22:5(n-3), with energy restriction. The findings of the study suggest a link between increased membrane fluidity, increased binding affinity, and lower circulating leptin levels, promoting the possibility that the biological actions of leptin can be controlled through dietary effects on
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.33001 |
| Date | January 2001 |
| Creators | Heshka, Jodi T. |
| Contributors | Jones, Peter J. H. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (School of Dietetics and Human Nutrition.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001846601, proquestno: MQ75316, Theses scanned by UMI/ProQuest. |
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