Location: Immunity and Disease Prevention Research2015 Annual Report
Objective 1: Determine the differential metabolism and uptake of n-3 fatty acids from dietary phospholipid and triglyceride forms in different tissues. -Sub-objective 1A: Determine the differential uptake and accretion of PL and TG forms of DHA in different mouse tissues. - Sub-objective 1B: Compare the metabolism of PL and TG forms of DHA in different mouse tissues. - Sub-objective 1C: Determine whether the differential accretion of DHA in brain from the PL and TG forms will result in differences in mouse behavior. Objective 2: Compare the anti-inflammatory and immune-modulating ability of n-3 fatty acids from dietary phospholipid and triglyceride forms in different tissues. -Sub-objective 2A: Compare the anti-inflammatory and immune-modulating ability of PL and TG forms of DHA by using experimental allergic encephalopathy (EAE)as a mouse model of brain inflammation. - Sub-objective 2B: Compare the anti-inflammatory and immune-modulating ability of PL and TG forms of DHA in the prevention of diet-induced NAFLD in mice.
Proposed experiments will compare accretion, metabolism and health effects n-3 fatty acids from the phospholipid (PL) and the triglyceride (TG) forms in different mouse tissues. For objective 1, we will determine the dose dependent accretion and metabolism of the PL-DHA and TG-DHA in the mouse tissues and their effects on the behavioral responses. We hypothesize that tissue accretion of DHA will increase with its increased intake, and at a given dose it will be greater in the PL group than in the TG group for tissues which express mfsd2a transporter (brain and liver) and will be similar in tissues (heart, muscle, and adipose tissue) that do not express this transporter. We also hypothesize that concentration of DHA in different lipid classes and PL subclasses, and that of DHA metabolites will be a function of tissue DHA concentration, and that DHA will improve learning and memory, and decrease fear and anxiety induced stress; effects of PL-DHA will be greater than that of TG-DHA on the behavioral responses tested. For objective 2, we will compare anti-inflammatory and immune-modulating effects of single equivalent dose (based on the results of objective 1) of the PL- and TG-DHA on brain and liver. For studies with brain we will use the mouse model of experimental allergic encephalomyelitis (EAE), and for liver we will use the high fat and high sucrose diets fed mouse model of nonalcoholic fatty liver disease (NAFLD). We hypothesize that both forms of DHA will delay the onset and severity of EAE and NAFLD when compared with the control groups, and PL-DHA will be more effective than TG-DHA. We anticipate our results will support the proposed hypotheses, however, if DHA does not have any effect on the response variables tested, we may repeat some experiments by increasing the duration of feeding. Whether or not the two forms of DHA differ in their effects on the responses tested will be equally useful information. A variety of behavioral, biochemical, molecular, immunohistochemistry, flowcytometery, and other analytical methods will be used. The mouse models and the methods proposed here have been previously used in our or our collaborator’s laboratories.
This is the first report for this project which began in April of 2015 and continues research from 2032-51530-021-00D, "Diet, Inflammation and Prevention of Chronic Disease", which expired in April, 2015. Please see the report for the previous project for additional information. This project will compare the metabolism and health effects of the phospholipid and triglyceride forms of docosahexaenoic acid (DHA), an omega-3 fatty acid with many biological activities found in marine organisms, including cold water fish and krill. Assessing the relative benefits of these forms of DHA has become of interest recently because new sources of dietary supplements containing DHA (Krill Oil) contain the phospholipid form, while the usual supplements (and foods) contain the triglyceride form. The phospholipid form may have different absorption and transport properties, and may also have direct biological effects in the immune system lacked by the triglyceride form. Thus our experiments will focus on these questions using mouse model systems. New collaborations with scientists at the Mouse Biology Program at University of California Davis (UCD), the department of Neurology at UCD Medical Center, and with the ARS experts in the areas of metabolomics, inflammation, and behavior have been developed for this project. In consultation with the Mouse Biology Program (MBP) of UCD we have prepared the animal protocol and submitted it for approval by our Institutional Animal Care and Use Committee (IACUC). MBP staff will be responsible for the day-to-day care of the animals, conducting the behavioral tests, ultimate sacrifice of the animals and collection of the tissues. We have also received samples of the desired, purified lipids (triglyceride and phospholipid forms of DHA) from a specialty manufacturer and are testing the composition. If the purity is acceptable, we will then order the amounts needed for objective 1. Since feeding purified fatty acids raises the problem of fatty acid peroxidation, we had many discussions with scientists and diet preparation companies working in this area regarding the preparation and feeding of the diets without oxidation of the DHA. We feel that we have an acceptable solution to prepare pelleted diets with appropriate antioxidants to allow reliable delivery to the experimental animals. By the end of this fiscal year we anticipate having preparatory work complete and we will be in a position to initiate the animal studies.