Skip to main content
ARS Home » Pacific West Area » Davis, California » Western Human Nutrition Research Center » Obesity and Metabolism Research » Research » Research Project #426826

Research Project: Improving Public Health by Understanding Diversity in Diet, Body, and Brain Interactions

Location: Obesity and Metabolism Research

2017 Annual Report

Objective 1: Compare metabolic, physiologic, and behavioral responses to consumption of a high quality vs. typical American diet pattern. Sub-objective 1A. Determine if a diverse, DGA-based nutrient-rich diet elicits a superior metabolic profile in persons at-risk for metabolic disease, compared to the typical U.S. diet that strays from the DGA with respect to saturated fats, added sugars, fiber, and dairy servings. Sub-objective 1B. Determine if chronic stress, stress system responsiveness, and diet quality interact to influence metabolic health. Sub-objective 1C. Determine the effect of diet quality and physical activity level on the plasma metabolomic response to a mixed macronutrient challenge. Sub-objective 1D. Determine if combining assessment of dietary intake using the 24-h recalls, physical activity assessments, anthropomorphic measures and fasting biomarkers of hepatic lipogenesis will improve prediction of insulin sensitivity assessments over the use of fasting glucose and insulin. Objective 2: Discover interrelationships between metabolically important tissues that contribute to metabolic health and energy homeostasis. Sub-objective 2A. Characterize the gut (fecal) microbial populations in response to dietary interventions based on the Dietary Guidelines or the typical American diet, and determine how they are related to metabolic outcomes. Determine the contribution of gut microbiota to the systemic metabolome. New Sub-objectives 2B and 2C as of 1-31-2017 to reflect change in personnel expertise: Sub-objective 2B. - Identify and validate pathways that regulate plasma TMAO levels and susceptibility to cardiometabolic disease. Sub-objective 2C- Identify resident Gut Microbial Taxa that regulate plasma TMAO levels and atherosclerosis susceptibility. Objective 3: Identify physiological and psychological processes that influence behavior related to food intake. Sub-objective 3A. Link individual differences in eating behavior with metabolomics and endocrinology of hunger and satiety. Sub-objective 3B. Vulnerability and resilience to stress may be determined by metabolic responses to stress: implications for stress-eating.

We will use a multidisciplinary approach to test molecular, physiologic, and metabolic responses to diet patterns, specific nutrients, and physical activity levels to determine effects on or associations with chronic disease risks. We posit that consumption of a diet, patterned on the Dietary Guidelines for Americans (DGA), will rapidly improve cardiometabolic risk factors, improve gut barrier function and reduce metabolic dysfunction. Also, individual differences in chronic stress and stress system responsiveness will partially explain variation in metabolic responses to the DGA diet. A randomized, food-controlled trial will be conducted to test these hypotheses. We will also conduct a cross-sectional study using metabolomics to map an individual’s metabolic flexibility and link this phenotypic trait to lifestyle, including markers of health status, physical activity parameters, diet quality, food preferences and food choices. As part of this study, we will administer a meal challenge to test the hypothesis that behavioral phenotypes can be identified based on responses of known and putative satiety signals to the meal. Using the cross-sectional approach and metabolomic analyses, we will develop basal and stress-induced metabolite profiles to identify differential stress-response signatures. Ancillary studies will be conducted to examine underlying mechanisms that might explain metabolic dysfunction. To examine gut microbiota and metabolites in more depth, samples of adipose, liver, intestinal content, and blood from ‘healthy’ and ‘unhealthy’ obese undergoing gastric bypass surgery will be used to derive phenotypic signatures spanning several biological systems and adipose tissue structure/function to test the hypothesis that phenotypic signatures can predict improvement in insulin resistance and inflammation. Using a murine model of diet-induced obesity, we will test the hypothesis that obesity disrupts the normal association between peripheral nervous system (PNS) sensing of ambient temperature and communication to the brain to coordinate temperature-control of feeding and energy expenditure. This study will include functional tests in vivo, and PNS expression of temperature-sensing TRP channels will be evaluated in dorsal root ganglion ex vivo. Finally, cultured muscle cells will be used to examine the hypothesis that incomplete mitochondrial combustion of fatty acids in tissue such as muscle leads to increased acylcarnitine accumulation, and select acylcarnitines promote cell stress responses will be evaluated.

Progress Report
Progress was made on all three objectives, which fall under National Program 107, Component 3: Scientific Basis for Dietary Guidance and Component 4: Prevention of Obesity and Obesity-Related Diseases. Progress focuses on the conduct of two important human trials that were designed to address the variability in human metabolism as it relates to dietary intervention or to habitual dietary intake. A randomized controlled trial to examine the health benefits of a diet pattern based on the Dietary Guidelines for Americans was completed this year. Partial support for this study is from subordinate project 2032-51530-022-20T with Dairy Research Institute. Progress continues on the exploratory objectives that address sub-objective 1B, related to stress responsivity. Laboratory analyses to support this sub-objective are near completion. Progress continues on the exploratory objectives that address sub-objective 2A that is related to metabolomics derived from the human ‘host’ and those derived from the resident microbial community living in the gut. Samples for microbiota analysis have been sent to our ARS collaborator in Little Rock, Arkansas, and targeted metabolomics analyses being performed in-house by ARS scientists in Davis, California are about 50% complete. A cross-sectional phenotyping study is now in its third year and we anticipate that 195 subjects will be enrolled out of a total of 400 participants needed over the course of the four-year project. Of those enrolled, 172 have completed the study and others are in progress. The phenotyping study serves as the foundation for sub-objectives 1C, 1D, and 3A. Partial support for sub-objective 3A is from subordinate project 58-2032-6-010-F with Arla Foods. Results for all measurements taken during interactions with study volunteers are entered in a secure database. Preliminary results combining whole body energetics with metabolic regulators of energy metabolism from the first 50 subjects were presented at an international meeting. Data generation examining the relationship between metabolomics describing energy pathways and glucose metabolism are in progress with 75% of the second 50 subjects completed. In partial fulfillment of Sub-objective 2B, which aims to identify and validate pathways that regulate plasma, Trimethylamine N-oxide (TMAO) levels and susceptibility to cardiometabolic disease, the targeted metabolomics assays have been developed and validated on a variety of samples. Samples from the in-house dietary intervention study and the cross-sectional study will be assayed over the next 12 months. To identify resident gut microbial taxa that regulate plasma TMAO levels and atherosclerosis susceptibility (sub-objective 2C), samples are being collected from mice and will be analyzed during the next fiscal year. The endocannabinoid system (ECS) is a neurometabolic system that acts in the brain, and may be an important appetite regulator that is being studied in sub-objective 3A. The link between this system and appetite was explored in a subordinate project conducted by ARS scientists in Davis, California, and collaborators from the Department of Nutrition, University of California, Davis. The association between blood levels of endocannabinoid compounds, self-reported appetite and satiety, and craving for fat-rich and sweet-tasting foods was analyzed in a study of craving during the menstrual cycle in healthy, young women. Different endocannabinoid compounds had different associations with cravings: this study demonstrated that it is important to measure the complete endocannabinoid profile to understand how these compounds influence eating and appetite regulation. For agreement 58-5306-03-037F, with the University of Copenhagen, Denmark, profiles of oxylipins and global metabolomics were quantified in two strains of mice on high fat diets with variable durations of cold stress. We used cold exposure to activate brown fat. This led to increased basal metabolic rate which resulted in increased activity of an enzyme (soluble epoxide hydrolase), critical in lipid metabolism and thought to play a role in dilation of the blood vessels, blood pressure regulation, and inflammatory processes. We also discovered that specific metabolite classes showed gender-specific exaggerations. Results have been transmitted to the collaborator, and manuscript preparation is in progress. In a second study, humans with high and low levels of intrascapular brown fat were identified and metabolite profiles were performed on brown and white fat biopsies. Discrete metabolic patterns were found between brown versus white adipose. Both white and brown fat from subjects with low brown fat had distinct metabolic patterns when compared to these fat samples by their high brown fat counterparts. Collection and incorporation of additional gene expression data are underway and will be combined with these results for manuscript preparation. Identifying factors leading to variability in phenotypic responses in tissue and plasma metabolomes are fundamental questions within the parent project which are enriched by this subordinate project. For no-funds to ARS agreement (log# 0047113), with University of California Davis (UC Davis), the Lipid Mediators Advancement Core was formed as a subcomponent of the West Coast Central Comprehensive Metabolomics Research Center (WC3MRC), and is housed at the Western Human Nutrition Research Center (WHNRC), co-located on the UC Davis campus. To support research into whole grain impacts on energy metabolism and gut microbiota, ARS researchers in Davis, California validated mass spectrometry-based quantitative short chain fatty acid (SCFA) analyses with robust quality assurance protocols. The methods have been used to study the impact of genetic manipulation of wheat to enhance butyrate production by gut microbes after consumption. Butyrate improves insulin sensitivity and increases energy expenditure. The method has been expanded to allow the co-extraction and analysis of SCFAs and bile acids, and will be used to facilitate human phenotyping (sub-objectives 1C, 1D, and 3A). The analysis of plasma SCFAs has also been validated by ARS researchers in Davis, California, and its application to translational research objectives exploring whole grain consumption and glucose control await appropriate resources. In collaboration with WC3MRC staff, novel 96-well plate sample preparation approaches have been developed and validated that allow the quantification of a broader spectrum of low abundance lipid mediators in a single analytical run, increasing the efficiency while improving the sensitivity of methods available. Further activities included efforts with collaborative research partners that will enhance and inform interpretation of phenotypic changes within a nutritional context (objective 1) and support the discovery of cross-talk between metabolically active tissues (objective 2). As examples; ARS researchers in Davis, California provided advanced analytical chemistry support to optimize pre-analytical sample handling for improving quality of metabolomics data, and metabolomic analyses for studies on zinc status and plasma triglycerides, omega-3 fatty acid feeding and endocannabinoid profiles, vitamin A status and plasma signaling lipids and bile acids, endocannabinoid-dependent modulation of inflammatory regulation and mediator profiles in cell culture, obesity and plasma lipid markers of hepatic lipid health. All methods developed in this reporting year were fundamental advancements which will support the phenotyping objectives. For agreement 2032-51530-022-44I with the National Institute of Health, mice expressing the genes ApoE3*Leiden and cholesteryl ester transfer protein (CETP) are being bred with 100 Diversity Outbred mice. The offspring of this cross will be fed a standardized diet and phenotyped for TMAO levels and microbiota composition. Subsequently the mice are then placed on a high fat, high cholesterol diet for 12 weeks. This will result in an increase in circulating lipid levels and the mice are phenotyped for atherosclerosis, TMAO levels and microbiota composition. We anticipate the feeding study to be completed by March of 2018 with data generation being performed over the next year. For agreement 2032-51530-022-39R, with the company Sonomaceuticals, the Chardonnay grape pomace powders have been successfully prepared by the cooperator, and ARS scientists at Davis, California have obtained final approval to conduct a human study using these Chardonnay grape pomace powders.

1. Following the Dietary Guidelines for Americans (DGA) improves health. The Dietary Guidelines for Americans (DGA) include recommendations for diet patterns that support public health and prevent premature disease, but to date the majority of evidence used as the basis for these recommendations are gleaned from observational studies or studies examining component food groups, but not for a complete diet pattern. ARS scientists in Davis, California have completed a study in adult women at risk for metabolic disease who were given all foods and beverages for one of two different diet patterns: one was based on all recommendations set forth by the DGA and the other was based on the average diet consumed by Americans as described in the, "What We Eat in America" survey. Important features of this study were that the body weight of each participant was maintained throughout the study and clinical measures of blood glucose control, blood pressure, and circulating lipids were measured. The results showed that in response to the DGA diet, systolic blood pressure and total cholesterol levels decreased, whereas there were no differences between the diet patterns in terms of the response in blood glucose control. These results provide important evidence to be used by the Dietary Guidelines Advisory Committee in preparation for revising the 2020 Dietary Guidelines.

2. The cardiovascular benefit of extra virgin olive oils (EVOO). It is not known if the health benefits associated with extra virgin olive oils (EVOO) are related to the total antioxidant capacity of the oil, or if such benefits may be associated with the concentrations of specific natural products with unique health-promoting effects which can vary by olive variety and cultivation practice. Two antioxidants found in EVOO, oleocanthal and oleacin, have unique anti-inflammatory properties, are found in different proportions depending on the olive variety, and are responsible for the spicy taste of some oils. ARS scientists in Davis, California collaborated with colleagues from the University of California Davis, and the National and Kapodistrian University of Athens, Greece, to compare the impact of acute oleocanthal-rich versus phenolic-equivalent, but oleocanthal-poor, EVOO consumption on platelet reactivity (a measure of the tendency for these blood cells to clump and form clots). Results of this study show that ~3 tablespoons of oleocanthal-rich EVOOs could reduce platelet reactivity in about 60% of healthy men tested. Further, a broad chemical survey of small molecules in the blood of the study volunteers discriminated the 60% who were responsive from the 40% who were not responsive before and during the study. Ultimately, this study showed that the observed platelet aggregation response to EVOO depended on the concentration and ratio of specific chemicals called phenolics in EVOO, not the oil antioxidant capacity; if supported by further research, these results can be used by health care professionals to refine dietary recommendations to reduce cardiovascular risk, and will support olive producers in stratifying the market for olives with different properties.

3. Endocrine associations with craving during the menstrual cycle. Although it is commonly known that some women experience food cravings during the menstrual cycle, little is known about who will and who will not experience cravings. Understanding cravings could uncover novel pathways regulating eating cues and obesity. Scientists in Davis, California aimed to begin to define underlying biological reasons for cravings that occur during the luteal phase, and conducted a study with healthy young women who had normal menstrual cycles to focus on sex steroid hormones and other hormones that are known to have an overall effect on food intake. They found that higher blood levels of leptin, a hormone produced by fat cells, was associated with reduced sweet food intake. Further, women who reported craving more sweet tasting foods had higher levels of estrogen (a hormone released from the ovaries) and the ratio of estrogen to leptin in blood. These associations led to the conclusion that healthy women experience cravings differently during the luteal phase, and ovarian hormones and leptin concentrations may be possible drivers of craving or intake of sweet foods.

Review Publications
Hartiala, J., Schwartzman, W.S., Gabbay, J., Ghazalpour, A., Bennett, B.J., Allayee, H. 2017. The genetic architecture of coronary artery disease: current knowledge and future opportunities. Current Atherosclerosis Reports. 19(2):6. doi: 10.1007/s11883-017-0641-6.
Krishnan, S., Tyron, R.R., Horn, W.F., Welch, L., Keim, N.L. 2016. Estradiol, SHBG and leptin interplay with food craving and intake across the menstrual cycle. Physiology and Behavior. 165:304-312. doi: 10.1016/j.physbeh.2016.08.010.
Oaks, B., Stewart, C., Laugero, K.D., Adu-Afarwuah, S., Lartey, A., Vosti, S., Ashorn, P., Dewey, K. 2016. Maternal plasma cholesterol and duration of pregnancy: a prospective cohort study in Ghana. Maternal and Child Nutrition. doi: 10.1111/mcn.12418.
Cooper, D.N., Kable, M.E., Marco, M.L., De Leon, A., Rust, B.M., Baker, J.E., Horn, W.F., Burnett, D., Keim, N.L. 2017. The effects of moderate whole grain consumption on fasting glucose and lipids, gastrointestinal symptoms, and microbiota. Nutrients. 9(2):173. doi: 10.3390/nu9020173.
Widaman, A.M., Witbracht, M.G., Forester, S.M., Laugero, K.D., Keim, N.L. 2016. Chronic stress is associated with indicators of diet quality in habitual breakfast skippers. Journal of the Academy of Nutrition and Dietetics. 116(11):1776-1784. doi: 10.1016/j.jand.2016.03.016.
Widaman, A., Keim, N.L., Burnett, D.D., Miller, B., Witbract, M.G., Widaman, K.F., Laugero, K.D. 2017. A potential tool for clinicians; evaluating a computer-led dietary assessment method in overweight and obese women during weight loss. Nutrients. doi: 10.3390:nu9030218.
Oakes, B.M., Laugero, K.D., Stewart, C.P., Adu-Afarwuah, S., Lartey, A., Ashorn, P., Vosti, S., Dewey, K.G. 2016. Late-pregnancy salivary cortisol concentrations of Ghanaian women participating in a randomized controlled trial of prenatal lipid-based nutrient supplements. Journal of Nutrition. 146(2):343-352.
Agrawal, K., Melliou, E., Li, X., Pedersen, T.L., Wang, S.C., Magiatis, P., Newman, J.W., Holt, R.R. 2017. Oleocanthal-rich extra virgin olive oil demonstrates acute anti-platelet effects in healthy men in a randomized trial. Journal of Functional Foods. 36:84-93. doi: 10.1016/j.jff.2017.06.046.
Hazard, B., Zhang, X., Naemeh, R., Hamilton, K.M., Rust, B., Raybould, H.E., Newman, J.W., Martin, R., Dubcovsky, J. 2015. Mutations in durum wheat SBEII genes conferring increased amylose and resistant starch affect grain yield components, semolina and pasta quality and fermentation responses in rats. Crop Science. 55(6):2813–2825. doi: 10.2135/cropsci2015.03.0179.
Olmstead, K.I., Lafrano, M.R., Fahrmann, J., Grapov, D., Viscarra, J.A., Newman, J.W., Oliver, F., Crocker, D.E., Filipp, F.V., Ortiz, R.M. 2017. Insulin induces a shift in lipid and primary carbon metabolites in a model of fasting-induced insulin resistance. Metabolomics. 13:60. doi: 10.1007/s11306-017-1186-y.
Stewart, C.P., Oakes, B.M., Laugero, K.D., Ashorn, U., Harjunmaa, U., Kumwenda, C., Chaima, D., Maleta, K., Ashorn, P., Dewey, K.G. 2015. Maternal cortisol and stress are associated with birth outcomes, but are not affected by lipid-based micronutrient supplements during pregnancy: an analysis of data from a randomized controlled trial in rural Malawi. BMC Pregnancy & Childbirth. 15:346. doi: 10.1186/s12884-015-0793-8.
Keim, N.L., Martin, R.J. 2015. Dietary whole grain-microbiota interactions: insights into mechanisms for human health. Advances in Nutrition. 5:556–557. doi: 10.3945/an.114.006536.