Objective 1: Determine the effect of consuming dietary sources of fat with varied saturation and chain length on the physiological responses of satiety, lipid oxidation, and energy metabolism. Sub-objective 1A: Determine the acute effects of consuming dietary fats of varied saturation and chain length on satiety, thermogenesis and energy utilization in healthy individuals. Sub-objective 1B: Determine the chronic effects of consuming dietary fats of varied saturation and chain length on satiety, energy utilization, and body composition. Objective 2: Determine the role of long chain omega 3 (LCn3) fatty acids in modulating the function of bone cells and the contribution of RANKL/RANK/OPG pathway in obesity-induced changes in bone metabolism in animal and cell models. Sub-objective 2A1: Define the role of LCn3 in preventing adiposity-induced bone loss. Sub-objective 2B: Define the optimal ratio of n6/n3 in improving bone quality and quantity in an obesity animal model. Objective 3: Define the influences of dietary fatty acids and energy balance upon conversion of alpha-linolenic acid (ALA; 18:3n3) to LCn3. Sub-Objective 3A: Determine the effects of saturated fatty acids (SFA) content upon mechanisms of ALA disposition under eucaloric conditions. Sub-Objective 3B: Determine the effects of SFA content upon mechanisms of ALA disposition in rodents under hypercaloric conditions. Objective 4: Define the extent to which consuming rainbow trout bred for elevated LCn3 content reduces CVD risk markers, such as platelet reactivity and related eicosanoids, in people.
Fat is an essential part of a healthy diet. However, the fatty acid compositions of dietary fats are often overlooked in designing healthy diets. Many Americans consume diets high in saturated fatty acids (SFA) and low in unsaturated fatty acids, including long-chain omega-3 fatty acids (LCn3). This imbalance may contribute to obesity and exacerbate osteoporosis and cardiovascular disease (CVD). The aim of our work is to provide robust data that will inform evidence-based recommendations for the appropriate levels and composition of dietary fats to maintain health and prevent disease. We will accomplish this aim by completing four research objectives that will clarify how the fatty acid profile of dietary fat contributes to health, or conversely, to disease progression. These objectives will use a combination of clinical translational studies in humans and mechanistic studies in rodents and isolated cells. Objective 1 addresses the role of dietary fats in the development of obesity by studying their effects on the modulation of satiety and energy metabolism; Objective 2 addresses the roles of specific fatty acids in preventing bone structure deterioration and promoting bone health in obesity; Objective 3 addresses the impacts of dietary fatty acids and energy balance on LCn3 metabolism; Objective 4 addresses the impact of consuming LCn3-rich rainbow trout on CVD risk markers in humans. We will fulfill these objectives through a combination of clinical translational and mechanistic studies involving human volunteers and rodent models.
Objective 1A. In this clinical trial we are evaluating the energetic and satiety responses to dietary fat intake in humans. Specifically, in an acute study, we are evaluating the responses to saturated fat, monounsaturated fat, and polyunsaturated fat containing high linoleic acid, high alpha-linolenic acid, or long chain omega-3 fatty acids. Participants are given a test meal and their energetic responses (energy expenditure, thermic effect of food, and beta-oxidation of fat) and satiety (gut hormones and subjective responses) are determined over 4 hours. The protocol has been developed and reviewed by Center scientists; Institutional Review Board (IRB) approval received; initiation of trial is underway. An amendment submitted to the IRB to add the determination of fatty acid binding protein polymorphisms to the study has been approved. These data will be used as a covariate in assessing responses. Objective 1B. In this clinical trial we are evaluating the energetic and satiety responses to dietary fat intake in humans. Specifically, in a chronic feeding trial, we are evaluating the responses to saturated fat, monounsaturated fat, and polyunsaturated fat containing high linoleic acid, high alpha-linolenic acid, or long chain omega-3 fatty acids (LCn3). Participants will be given a 4 week dietary intervention after which their energetic responses (energy expenditure, thermic effect of food, and beta-oxidation of fat) and satiety (gut hormones and subjective responses) will be determined over 4 hours. We will determine fatty acid binding protein (FABP) polymorphisms to be used as a covariate in assessing responses. The protocol has been developed and IRB approval is pending. A Headquarters supported post-doc will be hired in the late summer to work on this project with emphasis on the FABP assessment and interpretation. Objective 2A1. An animal study was conducted to define the role of LCn3 in preventing adiposity-induced bone loss in mice. Six-Sixty male C57BL/6 mice were assigned randomly to 6 treatment groups and fed either a 10% fat control diet or a 45% high-fat diet with three levels (0, 1, or 3%) of LCn3 from fish oil. Animals were fed the experimental diets for 6 months. Body weight, body composition, feed intake, bone structure, serum markers and expression of genes related to bone metabolism have been measured and being currently analyzed. Objective 2A2. An animal study was initiated to define the role of bone marrow adipocytes in high-fat induced bone loss in mice. PPAR-gamma floxed (f/f) and a breeding pair of Osx-1-Cre line mice have been obtained from the Jax Lab. Currently, PPAR-gamma floxed (f/f) or PPAR-gamma KO mice are being generated with genotyping selection through in-house breeding of PPAR-gamma floxed (f/f) and Osx-1-Cre mice. Then, forty-eight six-wk old PPAR-gamma floxed (f/f) or PPAR-gamma KO mice will be randomized to one of the 4 dietary treatments (n=12): a normal-fat (10% as fat) control diet (as soybean oil, SO) or a 45% high-fat diet (10% as SO + 35% as lard). After 6 months of feeding, mice will be sacrificed and functional change including gene expression of adipocytes, osteoblasts, and osteoclasts will be evaluated. Serum bone formation and resorption markers will be determined. Objective 3. We furthered our studies to determine whether the content of dietary saturated fatty acids (SFA), vs the monounsaturated fatty acid oleic acid, decreases the metabolism of the n-3 polyunsaturated fatty acid (PUFA) alpha-linolenic acid (ALA) to longer chain (LC) polyunsaturated fatty acids. Our data demonstrate that in adult mice, a high oleic acid diet reduced liver content of the n-3 fatty acid ALA but also that of the n-6 fatty acid linoleic acid but did not decrease the levels of their LCPUFA metabolites. On the other hand, the SFA diet increased kidney levels of n-3 LCPUFA but not n-6 LCPUFA by 32%. The high-oleic acid diets induced fatty liver in contrast to the SFA diet. Kinetic studies examining ALA metabolism were not able to be commenced due to the lack of commercially available 14C-ALA. We tested the extent to which medium chain (MC) SFA vs LCSFA (palmitic acid and stearic acid) modified obesity-related disease outcomes in mice fed obesogenic diets for 16 weeks. Our data demonstrate that while all animals became obese with both types of SFA sources, the MCSFA-fed animals had better insulin sensitivity and had less fat deposition in the liver. Markers of inflammatory stress and PUFA metabolism are being analyzed. We developed a novel means of characterizing and analyzing phospholipid biomarkers in human plasma. Specific types of phospholipids, a class of fats circulating in the blood, are often used as biomarkers for cardiovascular disease, diabetes, and Alzheimer’s disease. A drawback to the use of these biomarkers is that they are chemically very similar. These phospholipids often are the same size but have different types of fatty acids attached to them. Using an instrument called a hybrid quadrupole linear ion trap mass spectrometer, we developed an analytical method to identify and quantify these phospholipids that have the same size but different structure. This method is rapid and provides more detailed information regarding bloods lipids. This work will assist clinical and basic scientists in improving biomarker analysis for human disease. This work is submitted for publication. Objective 4. In this clinical trial, we are comparing the efficacy of fish with differing long chain n3 fatty acid contents to reduce cardiovascular disease (CVD) risk markers in obese people with elevated CVD risk. Specifically, we are comparing diploid and triploid farm-raised rainbow trout and tilapia. To date, all fish have been obtained and the fatty acid profile determined. IRB approval has been obtained and we are actively recruiting for the study.
1. Eating farmed Atlantic salmon improves blood lipid profiles. The effect of eating farmed salmon on cardiovascular disease risk was studied by assessing serum lipoprotein levels, size and density in people who ate increasing amounts of farmed Atlantic salmon. The results indicate that even eating 3 ounces of salmon twice a week modified serum lipoprotein particle size and concentration in a manner associated with reduced cardiovascular disease risk.
2. Improving the resistant starch content of potatoes. Resistant starch (RS) has properties which may provide health benefits. ARS scientists at Grand Forks, North Dakota in collaboration with scientists from North Dakota State University conducted a study to determine the contributions of cultivar, cooking method and service temperature on the RS contents of potatoes. Results showed that RS content varied by preparation method but not potato variety. Baked potatoes had higher RS contents than boiled; chilled potatoes had more RS than either hot or reheated. These results may assist consumers to make healthy dietary choices.
3. High-fat diet induced obesity increases bone loss in systemic chronic inflammation. Does obesity further compromise bone structure resulting from systemic chronic inflammation? ARS scientists at Grand Forks, North Dakota investigated whether obesity worsens bone structure and markers of bone metabolism in mice with chronic inflammation. They demonstrated that chronic systemic inflammation increases bone resorption and decreases bone mass and obesity induced by a high-fat diet further compromises bone microstructure. These findings suggest that reducing excessive adiposity can be beneficial to bone health in chronic inflammation states such as aging and postmenopausal estrogen deficiency.
4. Moderate exercise improves bone mass of obese rats. Weight reduction is recommended to reduce obesity-related health disorders but some studies suggest that weight loss through “dieting” may compromise bone health. ARS scientists at Grand Forks, North Dakota investigated how weight loss through dietary energy restriction and/or physical activity affects body adiposity, bone structure and markers of bone turnover differently. They demonstrated that energy restriction is the most effective means to decrease obesity but the combination of exercise and caloric restriction is better for improving bone mass.
5. Bone marrow fat cells play an important role in bone formation. Do bone marrow fat cells influence bone formation and resorption? ARS scientists at Grand Forks, North Dakota investigated how bone marrow fat cells affect the number and function of osteoblasts, bone forming cells, in mice specifically lacking bone marrow fat cells. They demonstrated that eliminating bone marrow fat cells increased the population of osteoblasts during bone remodeling. The findings will help understand how obesity affect bone metabolism.
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Raatz, S.K., Johnson, L.K., Picklo, M.J. 2015. Consumption of honey, sucrose, and high fructose corn syrup produce similar metabolic effects in glucose tolerant and glucose intolerant individuals. Journal of Nutrition. 145:2265-72.
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Al-Naqeb, G., Rousova, J., Kubatova, A., Picklo, M.J. 2016. Pulicaria jaubertii E. Gamal-Eldin reduces triacylglyceride content and modifies cellular antioxidant pathways in 3T3-L1 adipocytes. Chemico-Biological Interactions. 253:48-59.
Akbar, M., Cao, J.J., Lu, Y., Nardo, D., Chen, M., Elshikha, A.S., Ahamed, R., Brantly, M., Holliday, L., Song, S. 2016. Alpha-1 antitrypsin gene therapy prevented bone loss in ovariectomy induced osteoporosis mouse model. Human Gene Therapy. DOI: 10.1089/hum.2016.029.
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