Randle Cycle in Practice: a student exercise to teach glucose- and fatty acid metabolism in fasted, fed and exercised states

Here we describe an approach and overall concept of how to train undergraduate university students to understand basic regulation and integration of glucose and fatty acid metabolism in response to fasting, intake of carbohydrates, and aerobic exercise. During lectures and both theoretical and practical sessions, the students read, analyze, and discuss the fundamentals of the Randle cycle. They focus on how metabolism is regulated in adipose tissue, skeletal muscle, and liver at a molecular level under various metabolic conditions. Subsequently, students perform one of four different trials: 1) overnight fast followed by ingestion of jelly sandwiches and lemonade ad libitum for up to 15 minutes; 2) overnight fast followed by ingestion of a chocolate bar and a soda; 3) overnight fast followed by ingestion of carrots; and 4) light fast and aerobic exercise for 2 hours, while monitoring glucose and fatty acid levels. The data from these trials clearly show that glucose levels are kept constant at around 5 mM, while fatty acid levels rise to 300-700 µM after an overnight fast. Upon carbohydrate intake, glucose levels increase, whereas fatty acid levels are reduced. In response to aerobic exercise, the glucose level is kept constant at 5 mM, while fatty acid levels increase over time. Collectively, the data clearly recapitulate the essence of the Randle cycle. The exercise shows the great pedagogical value of experiments within practical courses to help students gain knowledge of energy metabolism and regulation of biochemical pathways. In an active learning environment, students successfully tackled physiological assignments, enhancing constructive communication and collaboration among peers. NEW & NOTEWORTHY Explore our study on how undergraduates learn about glucose and fatty acid metabolism through a blend of lectures and dynamic practical experiments. Our paper highlights how students delve into the Randle cycle and its regulation in various metabolic scenarios, gaining insights through hands-on trials. This innovative approach not only deepens understanding but also enhances collaborative skills. Dive into our findings to see how active learning shapes future scientists.