Location: Jean Mayer Human Nutrition Research Center On Aging
2017 Annual Report
Objectives
ENERGY METABOLISM: 1: Determine the effects of specific dietary composition factors, including macronutrient type, fiber & food form on hunger, satiety & energy regulation. 2: Demonstrate effective methods for sustainable weight control & prevention of obesity in adult population groups spanning a range of ages & demographics. 3: Develop new methodology for improving the accuracy & precision of assessment of energy & nutrient intakes & energy requirements in adults.
OBESITY AND METABOLISM: 1: Determine the mechanistic roles of the intestinal and hepatic proteins ACSL5 and plin2 in fatty acid metabolism, especially in delivery of dietary triacylglycerol to tissues and tissue lipogenic metabolism.
2: Determine the physiologic actions and consequences of ACSL5 in diet-induced obesity and obesity associated metabolic complications.
BODY COMPOSITION: 1: Develop and validate stable isotope methodology to that can be utilized to investigate energy regulation related to sarcopenic obesity and frailty in the elderly. 2: Validate energy dispersive X-ray fluorescence methodologies for studying the prevalence of zinc deficiency and implications of zinc deficiency in the elderly.
Approach
LAB NAME: ENERGY METABOLISM
The mission of the Obesity and Energetics Laboratory is to understand the effects of lifestyle factors on energy metabolism and weight regulation. 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. Studies in our laboratory include in-depth biological examinations of the impact of different dietary factors on biochemical and neurological factors involved in energy regulation and body composition, chemical studies of food composition, and randomized controlled trials testing practical interventions that can be scaled for population-wide benefits.
LAB NAME: OBESITY AND METABOLISM
To address the role of acyl CoA synthetase 5 (ACSL5) and perilipin 2 (plin2) in intestinal enterocytes and hepatocytes we have generated conditional lines of knockout of ACSL5 and plin2 mice allowing us to disrupt in a tissue specific manner. We will investigate the physiological effects of ablation of ACSL5 and plin2 in mouse hepatocytes and enterocytes and the response to a high caloric diet in vivo. In these animal studies we will determine body composition, energy expenditure, insulin glucose homeostasis, fat absorption, hepatic steatosis, and in liver and intestine tissues gene expression will be determine. In isolated hepatocytes studies in our mice we will triglyceride (TG) accumulation, and TG oxidation. The studies in this project will provide novel insights that will allow researchers to direct therapeutic strategies to protect against the development of obesity and associated complications.
LAB: BODY COMPOSITION
Simple monitoring of isotope clearance in breath CO2 can provide detailed information on the metabolism of labeled food and help us understand the connection between food composition and energy management. Our approach includes the use of a single stable isotope administration (C-13 palmitic acid or carbohydrate) and monitoring its disappearance in breath CO2 for several days. We use both mathematical modeling and clinical validation. Repeated measurements of C-13 in breath CO2 provide us with a profile of the timing and efficiency of oxidation of the labeled fuel.
The development and validation of new tools for field use include a new portable analytical device that can measure zinc content in fingernail clippings. The methodology used is non-destructive energy dispersive X-ray fluorescence (XRF). Preliminary results show that zinc measurement in protein (fingernails) is a better indicator for zinc status than zinc measurements in plasma. This is because plasma values can be easily affected by resent food intake or infection. This methodology will be tested in nursing home residents. It will become an addition to a set of portable devices that we have developed for the evaluation of nutrition status, hydration, and frailty in the field. The instruments are designed to evaluate status as well as to assess the efficacy of treatments and nutrition programs in older adults.
Progress Report
ENERGY METABOLISM LAB: In addition to describing the papers published in our accomplishments, the laboratory has been working on its clinical trials, which are designed to test whether more effective and sustainable methods for weight loss can be achieved in challenging populations, including military families and worksite employees.
Our work in military families, funded by a partnership with Department of Defense scientists, is going well, and we continue to enroll adult dependents of active duty military personnel for a 2-year weight management intervention that randomizes participants to two different interventions. This study is the first of its kind to attempt to develop a successful and scalable method for weight management in military families. We follow best practices by having separate teams for intervention delivery and outcomes with data accessible only by the outcomes team. A presentation of recruiting data and weight data to the Department of Defense in 2017 that was not broken down by randomization showed clinically significant weight loss that is higher than previous weight loss results in similar populations. This was combined with low drop out for the population, and the results were very favorably received. Work is now ongoing in 5 states (Massachusetts, Connecticut, Colorado, Kentucky and New York), and 9 military bases have expressed an interest in working with us. Our next goal is to finish study recruiting during 2018 so that study-wide results will be available in 2020.
Our second randomized trial is a large 12-site 18-month worksite intervention being conducted in Massachusetts, in which sites are randomized to an active control (both weight management and healthy living interventions are offered on a non-randomized basis) or a wait-listed control. Our previously-published pilot worksite weight management intervention demonstrated very impactful weight loss in worksites and is potentially scalable, and this powered study is designed to see whether similar results are obtained in a larger trial. As in our military study, we follow best practices by having separate teams for intervention delivery and outcomes with data accessible only by the outcomes team. All 12 sites were successfully recruited during the past year, the interventions are currently active, and final measurements will be taken in early 2018.
Progress was also made in our International Obesity Consortium studies. We have completed data collection for a study of restaurant meals in our international sites, and after significant logistical challenges the sample meals were successfully imported to the U.S. for composition analysis. Data analyses for this novel and timely study are currently ongoing.
OBESITY METABOLISM LAB: Previously, we generated mouse lines of plin2 int-/- (mice in which plin2 expression was ablated within intestinal enterocytes) and plin2 loxP/loxP (mice expressing plin2 in all tissues). Over the last year we investigated both whether the absence of plin2 expression within intestinal enterocytes affects dietary triglyceride absorption as well as the potential effects of this absence on body fat accumulation. Our experiments demonstrated that ablation of piln2 within intestinal enterocytes had no effect on either the body’s ability to absorb dietary fat within enterocytes or fat accumulation within the body.
We continued our studies on a line of mice that we generated in which ACSL5 expression was ablated within intestinal enterocyte. Our previous data have suggested that in a line of mice in which ACSL5 was ablated within all tissues, increased rates of systemic energy expenditure was secondary to increased expression of the hepatic hormone FGF21. The hormone FGF21 was secreted into the blood, which modulated adipocyte metabolism to increase rates of adipocyte thermogenesis. However, further studies have demonstrated that ablation of ACSL5 expression specifically within intestinal enterocytes protected against diet-induced obesity in response to a high fat diet did not result in increased hepatic expression of FGF21. Preliminary studies do indicate that the protection against diet-induced obesity associated with intestinal ACSL5 ablation was not due to malabsorption of dietary fat but rather likely due to increased metabolic rate. Investigation of the pattern of gene expression within the intestine does not support a role for increased fat oxidation within the intestine as an explanation for the observed phenotype. We hypothesize that the increased rates of systemic energy expenditure in these are altered rates of thermogenesis in adipose tissue. Over the next year we will be continuing our studies in mice with intestinal deficiency of ACSL5 to elucidate the mechanistic basis for the observed protection against diet-induced obesity.
Accomplishments
1. ENERGY METABOLISM LAB: All calories are not the same: high fiber calories are beneficial. There continues to be intense controversy in the scientific community and in the media over whether all calories are the same, and resolving this issue is necessary to inform recommendations on eating patterns for sustainable weight management. ARS-funded researchers in Boston, Massachusetts, conducted a randomized controlled trial on whether calories from high-fiber whole grain cereals differ from those in low-fiber refined grains and found substantial differences. On average there was an almost 100 kcal/day benefit from consuming whole grains versus refined grains, because consumption of refined grains caused an increase in metabolic rate and an increase in fecal energy losses. These results provide strong evidence that all calories are not the same, and in particular that whole grains have fewer net calories, providing important benefits to weight management.
2. ENERGY METABOLISM LAB: No effect of glycemic load was found on metabolic rate. One of the big controversies in nutrition science has been whether low glycemic load (a.k.a. low carbohydrate) diets benefit weight management by increasing metabolism so that fewer calories are available for fat deposition. ARS-funded researchers in Boston, Massachusetts, conducted a randomized controlled trial and found that there was no effect of low versus high glycemic load diets on metabolic rate, thus refuting this suggested benefit. Providing correct information on topics of public interest in nutrition and weight management is important including when no differences are found, as in this case, because it helps focus consumers on other ways to help manage weight that are more effective.
3. ENERGY METABOLISM LAB: Worksite weight management interventions vary widely from ineffective to clinically impactful. The majority of U.S. adults are employed, and therefore worksites represent an important opportunity for implementing weight management interventions to reduce the obesity epidemic. Moreover, programs delivered to employees can potentially have an even broader reach, since employees are likely to bring home these weight management strategies to their families. ARS-funded researchers in Boston, Massachusetts, conducted a systematic review to evaluate the effectiveness of published worksite weight management interventions. The review demonstrated that, on average, worksite weight management interventions have not been clinically effective (defined as 5-10% weight loss in overweight or obese individuals) but there was a remarkably wide variability in program effectiveness and some were clinically effective. This review highlights the importance of investigating why some interventions are more effective than others, so that scalable and clinically effective interventions can be made available for routine use in American worksites.
4. OBESITY METABOLISM LAB: Absence of a specific protein within the intestine of mice protects against the development of diet-induced obesity and associated metabolic complications. Alterations in intestinal metabolism are thought to be involved in the development of obesity and increase the risk of developing type 2 diabetes mellitus. ARS-funded researchers in Boston, Massachusetts, demonstrated that when mice were genetically modified to not express the protein acyl CoA synthetase 5 within intestinal cells and then these mice were fed a high caloric diet, they demonstrated significant protection against the accumulation of body fat and metabolic complications that predispose the development of diabetes. These studies suggest that the absence of acyl CoA synthetase 5 within intestinal cells increased the body’s ability to burn calories. The discovery that reduced expression of acyl CoA synthetase 5 within intestinal cells increased the mice’s ability to metabolize fat provides researchers with a therapeutic target to develop diets and drugs to ameliorate obesity and its complications, such as diabetes.
Review Publications
Karl, J.P., Roberts, S.B., Schaefer, E.J., Gleason, J.A., Fuss, P., Rasmussen, H., Saltzman, E., Das, S. 2015. Effects of carbohydrate quantity and glycemic index on resting metabolic rate and body composition during weight loss. Obesity. 23(11):2190-2198.
Karl, J.P., Meydani, M., Barnett, J.B., Vanegas, S.M., Goldin, B., Rasmussen, H., Saltzman, E., Chen, C., Das, S., Jonnalagadda, S.S., Meydani, S.N., Roberts, S.B. 2017. Substituting whole grains for refined grains in a 6-week randomized trial favorably affects energy balance parameters in healthy men and post-menopausal women. American Journal of Clinical Nutrition. 105:589-599. doi: 10.3945/ajcn.116.139683.
