Objective 1 - Define how dietary fatty acids and exercise alter peripheral biological rhythms and metabolic dysfunction. • Subobjective 1.A. Define whether long-chain n3 polyunsaturated fatty acids correct the obesity-mediated peripheral circadian clock dysfunction. • Subobjective 1.B. Define the extent to which exercise overrides peripheral clock dysfunction and metabolic dysfunction. Objective 2 - Define the impact of diet timing on colonic bile acid pathways and inflammation. Objective 3 - Define the impact of dietary fiber composition on colonic bile acid pathways and inflammation. Objective 4 - Define the mechanisms and the influence of daily physical activity timing to improve bone health. • Subobjective 4.A. Determine the mechanisms through which the timing of exercise alters the diurnal pattern of bone turnover, bone cell physiology, calcium utilization, and bone structure. • Subobjective 4.B. Determine the efficacy of morning vs evening exercise to maximize bone anabolic effects.
Disruption of biological rhythms in peripheral organs by environmental cues leads to metabolic dysfunction and disorders, including obesity. Food and physical exercise can drive the biological rhythms in peripheral organs. This project will examine the ability of dietary components (dietary fatty acids and fiber), exercise, and the timing of food consumption and exercise to correct the disrupted biological rhythms in peripheral organs and restore metabolic homeostasis. This project will address three questions: (1) Do changes in dietary fatty acid composition and exercise override the disrupted peripheral biological rhythms and restore metabolic homeostasis? (2) Does the timing of food intake and dietary fiber composition regulate bile acid pathways and attenuate colonic inflammation? (3) Does the timing of physical exercise make differences in regulating the diurnal pattern of bone metabolism and improving bone formation? Rodent studies will be performed to address each of these questions. In addition, a human clinical trial will be performed to translate question 3 results to humans. This project takes innovative approaches to addressing these questions in the context of modifying the diurnal patterns to promote health. Results from this research will provide valuable information of how dietary fatty acids and exercise minimize metabolic dysfunction and prevent associated disorders, a greater understanding of food timing and dietary fiber in regulating bile acid pathways and informing guidance for reducing colonic inflammation, and a greater understanding of timing of exercise training in improving bone health, particularly to people with bone loss associated with advancing age.
Objective 1. Research continued on investigating the effects of diet on metabolic health in rodent models of obesity. All mammals exhibit biological rhythms that control daily physiological functions (for example, fast vs. eating); obesity disrupts these rhythms. Fish oil prevents obesity and improves insulin sensitivity in mice. Fish oil is a rich source of long chain n3-polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA). Time-restricted feeding (also known as intermittent fasting) restores biological rhythms in rodent models of disturbed metabolism. ARS scientists are currently investigating the benefits of (1) DHA and (2) time-restricted feeding in restoring the daily biological rhythms disrupted by obesity. As a subordinate project of Objective 1, ARS scientists have extended their biological rhythm research to investigate biological rhythm alterations in a mouse model of breast cancer. Childhood obesity is a risk factor of breast cancer in women. Findings from this investigation will further our knowledge on cancer metabolism and its disruption in biological rhythms and build the foundation for clinical trials on cancer prevention in humans. Objective 2. Research continued on investigating whether time-restricted feeding (without reducing energy intake) reduces colonic inflammation in a mouse model of obesity. It has been shown that time-restricted feeding improves colon health. However, the molecular impact of time-restricted feeding on colonic inflammation remains to be determined. ARS scientists have initiated a study to determine whether time-restricted feeding reduces inflammation and early cancer markers in the colon in a mouse model of obesity. Objective 3. Dietary fiber may protect against colonic inflammation and cancer. However, the mechanisms remain to be determined. ARS scientists are finishing a study in mice to determine whether an increase in dietary resistant starch reduces inflammation and early cancer markers in the colon in a mouse model of obesity. As subordinate projects of Objective 3, (1) ARS scientists have been analyzing plasma samples collected from a mouse study which investigated the underlying metabolic basis of diet-related obesity and colon cancer risk. (2) ARS scientists have been analyzing the samples collected from a cell model which was designed to determine the molecular impact of the high fat diet on the function of intestinal barrier. (3) ARS scientists initiated a mouse study to determine whether an increase in dietary sorghum bran reduces inflammation and early cancer markers in the colon in a mouse model of obesity. Objective 4. While it is well-known that exercise improves bone health, ARS scientists are developing a clinical study to determine the best time of day for postmenopausal women to exercise and enhance bone health. The protocol will be submitted for Institutional Review Board review. Scientists completed a study investigating the influence of the time of day of exercise on bone metabolism in rats with estrogen deficiency – a model of human menopause. This study provides mechanistic insights into the relationship between the time of day for exercise and improvements in bone health. Investigating the impact of the daily timing of exercise on bone will aid in developing effective exercise strategies to improve bone health in postmenopausal women. As a subordinate project of Objective 4, ARS scientists are collaborating with a scientist at Mount Sinai School of Medicine and analyzing bone samples collected from a study investigating the role of follicle-stimulating hormone, a hormone regulating the development, growth, and reproductive processes of the body, in regulating bone mass and body composition across the lifespan of mice. Studies show that follicle-stimulating hormone is a potential therapeutic target for preventing osteoporosis and obesity.
1. Voluntary running improves bone health by reducing bone resorption. A sedentary lifestyle is a risk factor for obesity, which is associated with bone loss. Exercise improves metabolism in obesity by increasing energy expenditure. ARS scientists in Grand Forks, North Dakota, found that voluntary running reduces body fat mass and decreases blood concentrations of TRAP-5b (a marker of bone resorption) in dose-response manners in a mouse model of obesity. Findings from this study indicate that running protects against bone loss by preventing bone resorption in obesity. This research provides insight into the role of exercise in reducing the risk of obesity-mediated bone loss and is of interest to scientists in government, academia, and industry. Understanding the roles of exercise in protection against bone loss in obesity will build the foundation for clinical trials on quantitative exercise and promotion of bone health in humans.
2. Adequacy of calcium and vitamin D reduces inflammation and bacterial dysfunction in the colon. Adoption of an obesogenic diet low in calcium and vitamin D (CaD) leads to increased obesity, colonic inflammation, and cancer. However, the underlying mechanisms remain to be elucidated. ARS scientists in Grand Forks, North Dakota, along with collaborators, demonstrated that CaD adequacy reduces colonic inflammation, cancer signaling, and bacterial dysfunction in mice fed a Western-style diet. These findings provide direct molecular evidence on the connection of CaD and colon health. This research provides mechanistic, nutritional insight into the roles of dietary nutrients (e.g., CaD) in preventing colonic inflammation and cancer. These findings will build the foundation for clinical trials evaluating the role of diet in disease prevention and colon health promotion in humans. The research will have impact for scientists in government, academia, and industry studying the roles of diet in colon health.
3. Butyrate inhibits colon cancer cell proliferation. Intake of dietary fiber may protect against colon cancer. The anticancer property of dietary fiber is associated with an increased production of short chain fatty acids (SCFAs) during dietary fiber fermentation in the colon. However, the mechanisms remain to be determined. ARS scientists in Grand Forks, North Dakota, along with collaborators, demonstrated butyrate is a key SCFA protecting against human colon cancer cell proliferation in a human cell culture model. This research provides mechanistic and nutritional insight into the roles of SCFAs in preventing colonic inflammation and cancer. Understanding the roles of SCFA in inhibiting colon cancer cell proliferation will build the foundation for dietary fiber selection in disease prevention and health promotion in humans. This work is of interest to health professionals, basic and clinical scientists, and the general public.
4. Selenium adequacy may reduce the risk of type 2 diabetes. Although dietary selenium deficiency or excess selenium induces type 2 diabetes–like symptoms, little is known about the impact of suboptimal body selenium status on the risk of type 2 diabetes. ARS scientists in Grand Forks, North Dakota, along with collaborators, found that suboptimal body selenium status caused type 2 diabetes development in a mouse model of diabetes. These findings indicate that suboptimal selenium intake may also increase the risk of type 2 diabetes development in humans. This research provides mechanistic, nutritional insight into the roles of dietary selenium in preventing type 2 diabetes. The research will have impact for scientists in government, academia, and industry studying the roles of dietary selenium in prevention of type 2 diabetes.
5. Inhibiting differentiation of bone marrow fat cells does not prevent bone loss in high-fat diet induced obese mice. Bone forming cells and fat cells are derived from a same stem cell origin and the current evidence indicates that decreasing bone marrow fat accumulation increases bone formation. ARS scientists in Grand Forks, North Dakota, demonstrated that knockout of peroxisome proliferator-activated receptor (PPAR) gamma, a protein needed for fat cell development, from bone marrow did not prevent bone loss induced by a high-fat diet. The work is of interest to basic scientists as it provides scientific mechanisms for further studying the role of marrow fat in bone metabolism. The findings are also of interest to the general public in preventing obesity and improving bone health.
6. Geranylgeraniol reduces the risk of type 2 diabetes and improves bone health. Many natural products and their bioactive compounds can reduce high blood sugar in type 2 diabetes mellitus and improve bone health. ARS scientists in Grand Forks, North Dakota, along with collaborators, demonstrated that supplementation of geranylgeraniol, a bioactive compound found in fruits and vegetables, reduces blood sugar concentrations, increases concentrations of serum bone formation markers, and decreases concentrations of bone resorption markers in obese mice. Furthermore, geranylgeraniol supplementation reduces inflammation and changes the composition of gut microbes. These findings indicate that geranylgeraniol is beneficial to bone and modifies the gut microbe composition and function. The research demonstrates the role of dietary bioactive compound in reducing the risk of type 2 diabetes; it is of interest to researchers in basic and clinical areas, industry, and the general public in using dietary bioactive compounds to improve health.
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