Feeding the machine
Dr. Jane Shearer's research helps us to understand how our bodies cope with the food we put into them.
Story by Julie Sedivy/Illustration by Genevieve Simms
AHFMR Scholar Dr. Jane Shearer describes her research as a laboratory version of the movie Super Size Me. In that documentary, filmmaker Morgan Spurlock eats all of his meals at McDonald's for a month and winds up with a weight gain of 11 kg, elevated cholesterol levels, and many other symptoms. To study the effects of diet on health, Dr. Shearer feeds the rats in her lab their own McDiet—a bright pink-coloured mixtures of sugar and lard—and observes how it affects their health.
It takes only four weeks on this diet for rats to develop aspects of type 2 diabetes, a disorder in which patients become resistant to insulin. When the bloodstream is flooded with fuels such as glucose and fat, insulin is released to help clear them. However, an excess of these fuels can cause the insulin pathway to malfunction so that a normal amount of insulin does not stimulate the cells to process the fuels. Because insulin levels serve as a signal to other systems in the body, insulin resistance can cause biochemical changes that have far-reaching consequences. One of these effects is that more fatty acids circulate in the blood, which increases the risk of cardiovascular disease.
By making her rats insulin resistant, Dr. Shearer can then study how systems in the body interact and test the effects of potential treatments. Rather than focus on one specific pathway or organ system, she is interested in the effects of nutrition "all the way from the level of the genes up to the whole body and its physiological function." Much of her work has focused on how the balance of glucose and fatty acids in the blood relates to the functioning of the heart and liver as well as skeletal muscles.
In keeping with her "big-picture" approach, Dr. Shearer often looks at more than one system at a time when hunting for clues about how fuels are processed in the body. For example, by injecting a tracing substance into an animal, she can label and track fats and glucose in order to study where they go and what factors affect their metabolism.
Using tracers in live tissue, Dr. Shearer discovered important differences between how glucose and fatty acids are metabolized. A particular enzyme (a type of protein) called AMP kinase stimulates the uptake of both, but it does so in different ways. Moreover, different kinds of muscle tissue absorb glucose and fatty acids when this enzyme is at work. Glucose is taken up faster by muscle tissue with a large percentage of fast-twitch fibers—muscle that generates short bursts of strength or speed. However, muscle tissue with a high concentration of slow-twitch fibers—muscle that allows for prolonged aerobic activity—does a better job of taking up fatty acids. These are findings that Dr. Shearer says "I never would have had if I hadn't been able to look at both circulation and fuel uptake in tissues, side by side."
Dr. Shearer agrees that, although the scientific payoff is high, maintaining an interdisciplinary approach can be challenging, especially for students who need to master a range of techniques and conceptual frameworks. Fortunately, her research style is well suited to the lab environment of the Faculty of Kinesiology at the University of Calgary. The world-class facility is designed according to an open lab concept intended to foster collaboration among experts, where faculty share lab resources and jointly supervise students.
Given the recent rise in rates of obesity and type 2 diabetes, it has never been more important to study the connection between diet and health. Dr. Shearer concedes that treating obesity in humans is more complex than in animals. However, by shedding light on how metabolism works, her research promises to point the way to possible treatments.
Task force on obesity
Dr. Jane Shearer is a member of a task force on obesity and related diseases established by the Faculty of Kinesiology at the University of Calgary. Her work focuses on the the genetic mechanisms behind obesity and diabetes, as well as the study of the diabetic heart since cardiovascular disease is the leading cause of death for diabetics.
Other members of the task force will tackle the problem of obesity from such angles as nutrition, exercise physiology, and obesity in society.
Source: University of Calgary Faculty of Kinesiology