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Subject: search.filters.subject.Linoleic acid -- Metabolism

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    The effect of synthetic and bovine conjugated linoleic acid on energy balance : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutritional Science at Massey University, Palmerston North, New Zealand
    (Massey University, 1999) Hayman, Ann
    Conjugated linoleic acid (CLA) is biologically active and has altered body composition in experimental animals. Dietary supplementation with synthetic CLA reduced body fat in mice and rats in a number of studies. The CLA used in previously published research contained mixed isomers, the majority of which were 9cl 1t-CLA and 10t12c-CLA. The biologically active isomer at the time of starting the trials described in this thesis was assumed to be 9cl 1t-CLA, due to the prevalence of this isomer in biological tissues. The two trials in this thesis were designed to investigate the effect of dietary CLA on energy balance. In the first (refer Abstract, section 2.1), synthetic CLA reduced body fat in male BALB/c mice in a dose response manner, over the range 0.25 to 1.0% w/w CLA in the diet. High levels (1.0% and 2.0%) caused a reduction in growth. In the second (refer Abstract, section 3.1) dietary treatments supplemented with synthetic CLA, or bovine CLA in milk fat, at levels similar to the 0.25% w/w synthetic CLA treatment found to be effective in reducing body fat in mice, had no effect on energy balance in female Sprague-Dawley rats. The CLA in milk fat contains approximately 86% of the 9cl 1t-CLA isomer while synthetic CLA contains approximately 37%.9cl 1t-CLA and 46 % 10t12c-CLA. Results from these two trials support recent evidence from research demonstrating 10t12c-CLA is the biologically active isomer, in relation to energy metabolism and body composition. 9cl 1t-CLA is the prevalent isomer of CLA found in the human diet. The CLA used previously published research was chemically synthesised and contained a considerably higher proportion of 10t12c-CLA then found in human food sources. PREVIOUS PUBLICATION: The study described in Chapter 2 has been previously published as an abstract and displayed as a poster presentation at the Pacific Partners in Nutrition Conference, held at Auckland, New Zealand, September, 1999 (Hayman, et al., 1999).
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    Effect of synthetic and bovine milk conjugated linoleic acid (CLA) on immune function : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition Science at Massey University
    (Massey University, 1999) Zhao, Hui
    CLA is a collective name for a mixture of positional and geometrical isomers of linoleic acid (c-9, c-12-octadecadioenic acid) which possess conjugated double bonds. CLA occurs in a variety of foods, but is present at higher concentrations in products from ruminants. Milk fat is the richest natural source of CLA. The objective of this research was to examine the immunomodulatory properties of CLA (both synthetic and natural CLA derived from bovine milk fat). Two experiments were conducted at the Milk and Health Research Centre, Massey University, Palmerston North, New Zealand. The aim of the first experiment was to investigate the dose effect of different concentrations of synthetic CLA (Tonalin) on immune function. Mice were fed either skim milk powder based diet or the same diet supplemented with 0.1, 0.25, 0.5, 1.0 or 2.0% synthetic CLA (Tonalin) by weight. Animals were immunised orally with a mixture of polio vaccine in sodium bicarbonate (25μl) and subcutaneously with Fluvax and Tetanus toxoid vaccine on days 7 and 21. After 4 weeks feeding, mice were euthanased by isoflurane overdose. Various immune parameters were measured and the results showed that synthetic CLA (Tonalin) enhanced a range of immune functions. Synthetic CLA stimulated PHA induced T lymphocyte proliferation at 0.25, 0.5 and 1.0% as compared with the control group (p < 0.05). Synthetic CLA enhanced macrophage phagocytosis in a dose dependent manner. Synthetic CLA enhanced antibody responses (mucosal and systemic) to vaccines (polio vaccine, Fluvax and Tetanus toxoid). Natural killer cell activity was significantly enhanced in mice fed 0.25 and 0.5% CLA. In general, 0.25% CLA was regarded as the best CLA level which achieved optimal immunoregulating effects. The aim of the second experiment was to examine the effect of natural CLA derived from milk fat on immune responses in mice. Mice were fed a skim milk powder (SMP) based diet. The control diet was skim milk powder only, without any CLA or milk fat supplementation. The dietary treatments were: ordinary milk fat, fractionated milk fat (1st stage), 0.2% synthetic CLA (Tonalin) and CLA enriched milk fat. Animals were fed these diets for 28 days. Mice were immunised orally with a mixture of polio vaccine/ovalbumin/cholera toxin in sodium bicarbonate on days 7, 14 and 21 and subcutaneously with Fluvax and ADT (Diptheria and Tetanus toxoid vaccine) on days 7 and 21. Natural CLA was found to stimulate PHA and Con A induced T lymphocyte blastogenesis. Supplementation with natural CLA also led to increased antibody responses to vaccines and increased CD25+ populations in peripheral blood in mice. Natural CLA also enhanced macrophage phagocytosis. Synthetic CLA enhanced a range of immune functions which is consistent with the results in the first experiment. It is noted that although the CLA content is low in milk fat, the natural CLA derived from milk fat expressed potent effects in enhancing the growth of immune cells and promoting a range of immune functions in mice. Key words: conjugated linoleic acid (CLA), lymphocyte, macrophage, immunity, milk fat