published_or_final_version / Botany / Master / Master of Philosophy

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Revised; Originally published: 05/2008 / The article provides information about different types of dietary fats and promotes consumption of healthy fats in moderation as part of a balanced diet. The prevalence of fat-free products in grocery stores may give some health-conscious consumers the perception that all dietary fats are unhealthy. However, fats are absolutely vital for proper physiological functioning, and it is imperative that fats are included in a healthy diet. Fats are classified as saturated, monounsaturated, or polyunsaturated. Both types of unsaturated fats, when consumed in moderation, can help lower cholesterol and decrease the risk of heart disease, especially when they replace saturated and trans fats. We provide tips for selecting healthier fats, along with a guide for consuming appropriate portions of fat.

The goal of this work was to characterize avian skeletal muscle (SKM) glucose and fatty acid uptake. English sparrows (Passer domesticus) were used for the following studies: 1. Characterization of glucose uptake, 2. Identification and localization of glucose transporters, 3. Characterization of free fatty acid uptake, and 4. Reciprocal inhibition of glucose and free fatty acids. The results are summarized as follows. Isolated SKM incubated for 60 minutes with insulin, IGF-1, caffeine or AICAR demonstrated no increase in glucose transport. Interestingly, uptake was decreased in the presence of incremental unlabeled glucose suggesting the presence of glucose transporters (GLUT) and by phloretin, an inhibitor of transport proteins, decreased transport. The SKM glycogen content was low, which is supportive of the observed minimal glucose uptake. These findings suggest that GLUT expression may differ in birds as compared to mammals. GLUT1 and GLUT3 gene expression, but not GLUT4, were found in all tissues examined and share a high degree of homology with published chicken sequences. In addition, GLUT3 and GLUT4 proteins were not detected, whereas GLUT1 protein was abundant in blood-tissue barriers. Sparrows have high plasma ketone body levels suggestive of a high rate of free fatty acid (FFA) oxidation. In vitro uptake of radiolabeled oleic acid (OA) was maximal at 60 minutes and competitively inhibited by unlabeled OA suggesting a facilitative process. Radiolabeled OA uptake was not increased by IGF-1, caffeine and AICAR, whereas insulin increased uptake at 60 minutes. Inhibitors of protein-mediated substrate transport increased OA uptake by 60 minutes (DIDS and phloretin) whereas a specific inhibitor of long chain FFA transport, sulfo-N-succinimidyl oleate, decreased its uptake at 2.5 min. In reciprocal inhibition studies, 20mM unlabeled glucose and OA inhibited the uptake of their radiolabeled counterparts. Glucose (20mM) significantly decreased labeled OA uptake 36% and 20mM OA significantly decreased labeled glucose transport by 49%. These data begin to elucidate why avian skeletal muscle may not take up glucose to an appreciable extent and further, why avian skeletal muscle is insulin resistant.

Evidence obta1ned by various assay techniques has demonstrated that the plasma insulin level in maturity-onset diabetes is either normal or elevated (l, 2). Since pat1ents suffering from this disease also exhibit diminished responsiveness to the effects of exogenous 1nsul1n (3), their condition appears to be attributed to either failure of the target tissues to respond adequately to the hormone, or lack of metabolically active insulin. Recent investigations have established that insulin exerts a dual action on the glucose metabolism of mammals in vivo, decreasing the blood sugar both by inhibiting hepatic glucose production and by enhancing peripheral glucose utilization (4-9). Insulin unresponsiveness may be due to a failure of one or both of these actions. The localization of the defect in glucose metabolism is essential in fully understanding and correcting the impaired metabolism of the maturity-onset diabetic. Current evidence also indicates that an increase in plasma free fatty acid (FFA) concentration precedes other metabolic changes in maturity-onset diabetes (10, 11). FFA are released into the plasma by the adipose tissue (12). A widely-accepted hypothesis postulates a causal and inverse relationship between glucose uptake and FFA release by the adipose tissue. [...]

Aquaculture feeds, traditionally composed mainly of fishmeal and fish oil, currently represent the largest cost to fish farmers. With aquaculture growing at an average of 8.8% per year and limited supply of fishmeal and fish oil, suitable alternatives must be found. In addition to increasing sustainability and lowering production costs, the use of plant and/or animal ingredients has the potential to lower flesh levels of persistent organic pollutants (POPs) such as polychlorinated biphenyls. Fish oil and to a lesser extent fishmeal, are considered to be the largest source POPs in farmed fish. Using alternative feed ingredients however, can compromise fish growth and the flesh quality of the final product. Lipid sources including flaxseed oil, canola oil, poultry fat and the protein sources canola protein concentrate, soy protein concentrate and poultry by-product meal were examined as alternatives to fish oil and fishmeal in one on-farm field study and one laboratory feeding trial with Atlantic salmon (Salmon salar) and two laboratory feeding trials conducted on sablefish (Anoplopoma fimbria), a relatively new marine aquaculture species. The nutritive value of the alternative ingredients was assessed on the basis of fish growth performance, proximate composition, fatty acid composition and apparent digestibility coefficients. Sensory attributes were evaluated in the sablefish studies while flesh POP levels were determined in both species. The use of alternative dietary lipids showed no negative effects on fish performance. However replacement of fishmeal with plant proteins in some cases, negatively affected fish growth. Flesh levels of persistent organic pollutants were significantly decreased (p<0.05) with the use of alternative dietary lipids, and flesh levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were also depressed. Activated carbon treated anchovy oil and finishing diets were examined in the Atlantic salmon laboratory feeding trial and were effective at lowering flesh POP levels while providing high levels of EPA and DHA. The use of alternative feed ingredients will soon be inevitable in aquaculture feeds. The current research shows alternative lipids and proteins can be incorporated successfully in sablefish and Atlantic salmon feeds with minimal effects on fish growth and quality.

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid (n-3 PUFA) required for fetal neurodevelopment. Increased DHA levels are associated with 17β-estradiol levels, as DHA is higher in women relative to men and in pregnant relative to non-pregnant women, suggesting a maternal adaptation to supply DHA to the fetus. DHA can be synthesized in the body from shorter n-3 PUFA through sequential elongation-desaturation, with Δ6-desaturase being the rate-limiting enzyme. The goal of the present thesis was to characterize the mechanism underlying higher DHA in situations of altered 17β-estradiol status by examining the expression of DHA synthesis enzymes in rodent models. Fatty acid composition of several lipid classes was measured by gas chromatography and enzyme expression was measured by RT-qPCR and immunoblotting. Hepatic Δ6-desaturase and phospholipid DHA was higher in female relative to male, and in pregnant relative to non-pregnant rats. Similarly, 17β-estradiol supplementation of ovariectomized rats resulted in increased hepatic Δ6-desaturase expression and DHA content, while ovariectomy itself had no effects on DHA levels despite controlling for hyperphagia. Mice deficient in the DNA binding activity of estrogen receptor α (ERα) had no differences in hepatic Δ6-desaturase or DHA levels. These results suggest that 17β-estradiol mediates the higher DHA levels in females and during pregnancy through increasing hepatic Δ6-desaturase expression, although the effects of removing 17β-estradiol signalling through ovariectomy or ERα disruption are less clear. This work helps to explain findings of altered DHA status in response to changes in 17β-estradiol concentrations, possibly resulting in more appropriately tailored dietary DHA recommendations. Also, increased understanding of the regulation of DHA synthesis may improve DHA yields in agri/aquaculture and enable increased content of DHA in the food supply.

Chemical, physical and sensory properties of omega-3 fatty acid enriched chicken frankfurters developed with flax oil and microencapsulated fish oil at 1.2%, 2.4% and 3.6% were evaluated. Four replicate batches of frankfurters were produced for texture profile analysis and TBARS for assessment of lipid oxidation over four weeks of refrigerated storage. Gas chromatograph analysis indicated that omega-3 fatty acid levels increased (p<0.05) with flax and fish oils treatments resulting in a shift in omega-6/omega-3 with no increase in lipid oxidation over the storage period. The two highest levels of fish oil resulted in increased redness, hardness, gumminess and chewiness (p<0.05) with the highest fish oil having the lowest rating for acceptability. 1.2 and 2.4% flax oil and 1.2% fish oil samples were softer and juicier than commercial frankfurters. Addition of oils high in omega-3 fatty acids to chicken-based frankfurters can result in product resistant to oxidation and acceptable to consumers.

The objectives of this study were to evaluate the effect of rumen-protected fish oil (RPFO) and rumen-protected marine algae (RPMA) supplements on ovarian function of lactating dairy cows on pasture or in confinement during the estrus and ovulation synchronization period. Thirty-six Holstein cows were assigned to one of the two feeding systems and fed with lipid supplements from 30d before to 100d after calving. The resumption of cyclicity and onset of estrus were not influenced by LS. Mean daily number of the large follicles was similar across the treatments. During the Ovsynch period, RPFO treated cows had larger follicles (?10mm; P<0.05). Ovulation was delayed in RPFO and RPMA group but the number of ovulation was not altered. The number and diameter of CL were greater in the RPMA group. Progesterone concentrations were greater in the RPMA group on pasture (P<0.05). These findings indicate that RPMA supplementation improves the ovarian function.