Goals

The program in energy balance is broadly concerned with the exchange of energy between humans and their environment and with the many ways that environmental stressors affect energy exchange. The program aims in particular at elucidating the molecular, cellular, and physiological mechanisms by which physical activity, nutrition, and temperature influence the body’s intake, distribution, and use of energy, through their effects on various tissues (muscle, adipose) and on blood flow and regulation of blood volume. Research investigates these mechanisms and their effects in both young and older adults. Environmental stressors and metabolic processes both change as people age, in ways that have important consequences for health and well being.

Of central concern to the program are biological responses to exercise. First, exercise increases the heat load in the body, an outcome that may be biologically beneficial to body temperature regulation in cool environments but potentially harmful in hot ones. Second, exercise consumes considerable energy; because active skeletal muscle has a high metabolic rate, total energy expenditure depends greatly on muscle mass. Third, exercise engages cardiovascular mechanisms that regulate blood flow and the distribution of fluid in the body. Finally, lack of exercise, or inactivity, can contribute to energy imbalance, obesity, and, as a consequence, to a greater propensity to develop type 2 diabetes – a particular problem in older individuals. An important goal of the program is to understand better the role of disuse (with aging and inactivity) in the development of obesity and type 2 diabetes.

Current Research

Pierce scientists are studying the ways that physical activity affects glucose and fat metabolism and how these effects are altered by diet or by defects in use and storage of energy that commonly occur in aging and with obesity. Goals are to understand the key metabolic pathways in energy production (for example, in the breakdown of fats and carbohydrates) and to discover how these pathways can adapt successfully to exercise training in older and in obese individuals. At the cellular level, scientists are studying how regimens of exercise modify the molecular regulation of oxygen consumption and the storage use of energy in skeletal muscle fibers. At physiological level, scientists are studying how long-term exercise leads to adaptations in muscle structure, oxidative capacity, and fuel consumption. Community-based studies of older people integrate the findings obtained from cellular and physiological research to determine the functional as well as physiological effects of exercise training on overall body composition and glucose metabolism in aging, and hence the effects on health and well-being.

Pierce scientists are also studying how the cardiovascular system maintains the appropriate volume of fluid in the body and how exercise and heat production increase blood flow, especially in skeletal muscle and in the skin. More specifically, scientists are studying both acute (neural) and long-term (endocrine) regulation of fluid volume and arterial blood pressure, as well the effects of environmental stressors such as exercise and temperature. At the physiological level, scientists are studying how reproductive hormones in women act on the kidneys to regulate fluid retention and maintain water balance. These processes are central to maintaining cardiovascular function, blood pressure, and body temperature. At the tissue level, scientists are studying how contraction of skeletal muscle during exercise increases the delivery of oxygen and nutrients through the microcirculation; parallel research studies how neural control of peripheral circulation helps maintain systemic blood pressure. At the cellular level, scientists are studying the electrical and biochemical signaling pathways that control the distribution and magnitude of blood flow into networks of capillaries.

This combination of programmatically directed research, addressing issues at the cellular, physiological, and functional levels, affords a unique opportunity to understand energy balance and metabolic disorders in relation to cardiovascular regulation of temperature, body fluids, and oxygen transport. Understanding how organisms respond and adapt to environmental stressors will, in turn, enhance our ability to design specific, proactive interventions, based on diet and exercise, to improve human health and function. Aging and obesity are often associated with hypertension and diabetes, and these disorders can cause profound maladaptive changes, both directly and indirectly, to the heart and blood vessels. A key long-term goal is to determine how much and what kind of exercise are needed to improve and/or maintain health and daily function in older age.