Research Project: Energy Met.: Novel Approaches to Facilitating Successful Energy Regulation in Aging--Obesity & Met.: Role of Adipocyte Metabolism in the Development of Obesity and Associated Metabolic Complications

Location: Jean Mayer Human Nutrition Research Center On Aging

2023 Annual Report

Objectives
Energy Metabolism: Objective 1: Determine nutritional factors, including meal patterns and novel dietary composition factors (e.g., types of dietary fiber and salt), that influence adherence to calorie restriction regimens to improve weight regulation and reduce metabolic aging. Sub-objective 1A: Identify significant dietary and biobehavioral predictors of weight, body fat change, and adherence to a calorie restriction regimen. Sub-objective 1B: Determine the effects of changing from a typical (high) to a recommended (low) level of dietary sodium on energy regulation in adults. Objective 2: Evaluate the effectiveness, sustainability, and acceptability of different approaches to weight control and prevention of obesity in diverse adult population groups. Objective 3: Develop new methodology for improving the accuracy and precision of assessment of energy and nutrient intake in adults. Objective 4: Identify positive and negative influences of specific food culture parameters, including attitudes to healthy food and external pressures to overeat, on energy regulation and risk of obesity in different population groups. Obesity and Metabolism: Objective 1: To determine the relative role and mechanisms by which ACSL4 expression in white and brown adipocytes modulates adipocyte oxygen consumption, systemic energy expenditure and the development of diet-induced obesity and associated metabolic complications. Sub-objective 1A: To determine how adipocyte ACSL4 expression in response to a high fat diet (HFD) compromises white adipose tissue function and whole-body systemic metabolism Sub-objective 1B: To determine whether ACSL4, 4-hydroxy-trans-2, 3-nonenal (4-HNE) and/or mitochondrial-derived reactive oxygen species (ROS) play compulsory roles in mediating diet-induced perturbations in gWAT, adipocyte mitochondrial function and cellular bioenergetics Sub-objective 1C: To determine the role of ACSL4 in promoting HFD-induced brown adipocyte dysfunction and DIO Objective 2: To determine the role and mechanisms by which interferon related factor 8 (IRF8) adipocyte expression is regulated in diet-induced obesity and modulates the development of diet-induced obesity and associated metabolic complications.

Approach
Energy Metabolism: The mission of the Energy Metabolism Laboratory is to understand the effects of lifestyle factors and dietary composition on energy metabolism and weight regulation, and extend our research to underserved and global populations. Our research examines dietary and behavioral variables that influence both energy intake and metabolism throughout the adult lifecycle, and our focus is to develop and test effective lifestyle interventions for implementing sustainable, healthy weight control at all ages while continuing to advance the science of nutrition and energy regulation. Studies in our laboratory include in-depth biological examinations of the impact of different dietary factors on energy regulation and body composition, development of new approaches to tracking dietary intake, and randomized controlled trials testing practical interventions that can be scaled for population-wide benefits in different population groups. Obesity and Metabolism: Excessive dietary intake of nutrients above the body’s energetic needs results in obesity and associated metabolic complications. Adipocyte dysfunction, which occurs with increased storage of triacylglycerol in adipocytes, is important in the development of diet-induced obesity (DIO) and associated metabolic complications. Obesity-associated adipocyte dysfunction is associated with features of premature aging such as p53 activation and increased adipose tissue inflammation. In this project plan, we propose to use mouse models to determine the role of specific proteins within adipocytes in the development of obesity and/or associated metabolic complications. Within cells, acyl-CoA synthetases (ACSL) converts fatty acids to fatty acid acyl CoA. Each of the five known ACSL isoforms has been hypothesized to direct acyl-CoAs to specific metabolic fates; we want to determine the role of acyl CoA synthetase 4 (ACSL4) in obesity-associated adipocyte metabolism. In a preliminary study, we investigated and observed that mice with adipocyte deficiency of ACSL4 are protected against DIO, p53 activation, and exhibit increased systemic energy expenditure (EE). In Objective 1 of our project plan we propose to determine the underlying DIO associated mechanisms by which ACSL4 modulates adipocyte and systemic EE and associated metabolic and inflammatory complications. In separate preliminary studies we have discovered that deficiency of interferon related factor 8 (IRF8), specifically within adipocytes of mice, protects against the development of DIO-associated hepatic steatosis and reduced fasting blood glucose. The goals of Objective 2 of this proposal is to elucidate the mechanisms by which adipocyte expression of IRF8 is regulated and the role of adipocyte IRF8 in DIO-associated detrimental alterations in adipose tissue such as adipose tissue inflammation and systemic metabolism.

Progress Report
Energy Metabolism. A. In support of Aim 1, we evaluated whether self-selected diet composition predict short- (12 months) and long-term (24 months) adherence to calorie restriction (CR). Using the Geometric Framework for Nutrition (GFN) methodology, we have completed analyses of how self-selected dietary intake changes during CR and are currently preparing this research for publication. B. In support of Aim 2 we are collaborating with the Friedman School of Nutrition at Tufts to develop and test interventions for healthy nutrition and weight management in Head Start employees. This project uses a participatory approach to intervention development and starts with qualitative interviews with Head Start employees and stakeholders to define the parameters for intervention, and the preparatory informant interviews and surveys have been completed to inform the intervention. C. In support of Aim 3 we previously published ahead of schedule a study that pilot tested COCO Nutritionist, our new app that is the first to be able to use natural spoken language to reduce the burden of food logging by eliminating the need to log food and find suitable food codes -- steps that are time consuming and have been previously conducted by participants or nutritionists working with them. COCO nutritionist extracts amounts and types of foods from natural language and automatically maps them to USDA food codes. In our pilot test there was no significant difference in energy intake between values obtained with the new method and gold standard values obtained by 24h multiple pass dietary recall. Since food logging is a central component of nationally recommended programs for weight management, this work represents an important advance, and will be extended in future work by our group. D. In support of Aim 4 we have fully completed our initial round of data collection and a 12-month follow-up of U.S. participants. The value of this data lies in its unique contribution to understanding the different ways in which weight can be successfully managed. Obesity and Metabolism. As one step to determine how adipocyte expression of acyl CoA synthetase 4 (ACSL4) regulated adipocyte gene expression and high fat diet induced obesity, we fed mice with adipocyte specific deficiency of ACSL4 and wild type mice expressing ACSL4 with a high fat diet. We then isolated gonadal adipocytes from the two different lines of mice and performed RNAseq to determine how ACSL4 expression regulated expression of genes. Our study demonstrated that gonadal adipocytes from mice with adipocyte ACSL4 specific deficiency had a 50-fold reduction in the expression of the enzyme tryptophan hydroxylase 2 (TPH2). Since mice with adipocyte ACSL4 were protected against high fat diet induced obesity, we compared the expression of TPH2 in isolated gonadal adipocytes from wild type mice fed a low fat and high fat diet. We observed that in adipocytes isolated from mice fed a low-fat diet, TPH2 mRNA expression was reduced 50-fold as compared adipocytes isolated from mice fed the high fat diet. The enzyme, TPH2, has previously been reported to be expressed in the brain where it was demonstrated to be the rate limiting enzyme in the synthesis of serotonin. To investigate the role of increased TPH2 expression in adipocytes, we injected adeno-associated viruses (AAV) that expressed TPH2 directly into gonadal fat cells and fed the mice a low-fat chow diet. While we noted no increase in total body fat, we noted increased weights of gonadal fat pads where we injected the AAV into fat cells and also increased brown adipose depot weights in these mice. Additionally, the size of adipocytes, consistent with increased fat storage, were enlarged in gonadal adipose tissue depot of mice with adipocyte TPH2 overexpression. In mice withTPH2 overexpression in gonadal fat cells, we noted increased systemic glucose intolerance and insulin resistance. In brown adipose tissue, TPH2 in gonadal fat cells was associated with significantly decreased expression of uncoupling protein 1 (UCP1) which is critical for the ability of brown fat to burn calories. Serotonin levels were increased in gonadal adipose depot and circulating levels of serotonin were increased and approached significance (p-0.67). Our data suggest that increased levels of the enzyme TPH2 in adipocytes result in increased adipose tissue and circulating levels of serotonin which affect adipocyte size, systemic glucose metabolism, and potentially energy expenditure.

Accomplishments
1. Identifying biological factors that contribute to obesity. As obesity continues to be identified as one of the country’s greatest public health challenges, understanding contributing biological factors is important. An enzyme associated with obesity, known as tryptophan hydroxylase 2 (TPH2) is being studied by ARS-funded researchers in Boston, Massachusetts, as a possible factor in altering the regulation of blood glucose associated obesity. The researchers observed that when mice were fed a high caloric diet the expression of TPH2 increased along with that of a neurotransmitter also associated with increased fat cell size and increased accumulation of fat. The researchers are now pursuing diets that would regulate TPH2 expression to improve the regulation of blood glucose levels that may prevent fat cells from increasing in size. This discovery could have significant influence in reducing obesity.

Review Publications
Fassini, P., Das, S., Magerowski, G., Marchini, J.S., Araujo da Silva Jr, W., Rozatte da Silva, I., de Souza Ribiero Salguiero, R., Dias Machado, C., Marques Miguel Suen, V., Alonso-Alonso, M. 2020. Noninvasive neuromodulation of the prefrontal cortex in young women with obesity: a randomized clinical trial. International Journal of Obesity. 44:1279-1290. https://doi.org/10.1038/s41366-020-0545-3.
Roberts, S., Das, S., Sayer, R., Caldwell, A.E., Wyatt, H.R., Mehta, T., Gorczyca, A.M., Oslund, J.L., Peters, J.C., Friedman, J., Chiu, C., Greenway, F., Donnelly, J.E., Dao, M., Cuevas, A.G., Affuso, O., Wilkinson, L., Thomas, D., Manalac, R., Bachiashvili, V., Hill, J.O. 2022. Study protocol - an online International Weight Control Registry to inform precision approaches to healthy weight management. International Journal of Obesity. https://doi.org/10.1038/s41366-022-01158-4.
Dorling, J.L., Belsky, D.W., Racette, S.B., Das, S., Ravussin, E., Redman, L.M., Hochsmann, C., Huffman, K.M., Kraus, W.E., Kobor, M.S., Macisaac, J.L., Lin, D.T., Corcoran, D.L., Martin, C.K. 2021. Association between the FTO rs9939609 single nucleotide polymorphism and dietary adherence during a 2-year caloric restriction intervention: exploratory analyses from CALERIE phase 2. Experimental Gerontology. https://doi.org/10.1016/j.exger.2021.111555.
Das, S., Silver, R., Vail, T.A., Chin, M.K., Blanchard, C.M., Dickinson, S.L., Ceglia, L., Saltzman, E., Xiwei, C., Allison, D.B., Roberts, S. 2023. Randomized controlled trial of a novel lifestyle intervention used with or without meal replacements in work sites. Obesity. https://doi.org/10.1002/oby.23636.
Silver, R., Das, S., Kramer, A.F., Chui, K.K., Roberts, S. 2023. No effect of calorie restriction or dietary patterns on spatial working memory during a two-year intervention: a secondary analysis of the CALERIE trial. Journal of Nutrition. https://doi.org/10.1016/j.tjnut.2023.01.019.
Yuan, M., Hu, F., Li, Y., Cabral, H., Das, S., Deeney, J.T., Moore, L.L. 2023. Dairy foods, weight change, and risk of obesity during the menopausal transition. Journal of Nutrition. https://doi.org/10.1016/j.tjnut.2023.01.001.
Roberts, S., Flaherman, V. 2023. Dietary energy. Advances in Nutrition. https://doi.org/10.1093/advances/nmac092.
Corby, M.K., Hochsmann, C., Dorling, J.L., Bhapkar, M., Pieper, C.F., Racette, S.B., Das, S., Redman, L.M., Kraus, W.E., Ravussin, E. 2022. Challenges in defining successful adherence to calorie restriction goals in humans: results from CALERIE 2. Experimental Gerontology. https://doi.org/10.1016/j.exger.2022.111757.
Taetzsch, A.G., Roberts, S., Bukhari, A., Lichtenstein, A.H., Gilhooly, C., Martin, E., Krauss, A.J., Hatch-Mcchesney, A., Das, S. 2020. Eating timing: Associations with dietary intake and metabolic health. Journal of the Academy of Nutrition and Dietetics. https://doi.org/10.1016/j.jand.2020.10.001.