Pipeline H - Energy metabolism
We designed a pipeline focusing on whole-body energy balance regulation in mice. All phenotyping assays comprise in-vivo testing of parameters affecting energy homeostasis. Imbalances between energy uptake and energy expenditure result in rather immediate changes of endogenous energy stores. In some cases it may be advisable to also challenge energy balance regulation by feeding a high energy diet, low ambient temperatures, or adding running wheels or treadmills. It is highly recommended to continuously monitor body mass, body composition, blood glucose levels, or other suitable blood parameters to generate data for time course analysis. This can be facilitated or refined by implanting transponders that monitor physiological parameters such as core or peripheral body temperature, locomotor activity, or allow the online monitoring of blood glucose levels.
The Energy Metabolism pipeline comprises a few tests that are also implemented in other pipelines such as the Screening Pipeline but they provide important additional information regarding disease progression (e.g. glucose levels in blood) or are required as co-variates for data analysis (e.g. body mass or body composition) or to determine baseline conditions (e.g. indirect calorimetry). Implantation of transponders to monitor physiological functions offers the possibility to follow up changes in body temperature, locomotor activity, and blood glucose levels with high time resolution and precision. However, surgery, analgesia and the monitoring of successful recovery are important prerequisites for the preparation of a study. The test Energy Balance Regulation comprises the combination of indirect calorimetry to monitor energy expenditure and features of classical metabolic cages that allow the precise measurement of food uptake, and the collection of feces and urine. This test is designed to monitor food uptake of single caged mice over a period of 3-5 days. In parallel, all egested feces is collected, desiccated, and energy content is determined by bomb calorimetry. The aim of the test is to generate exact data for both sides of the energy balance equation. Energy uptake: food consumption, energy uptake and apparent energy assimilation efficiency. Energy expenditure: indirect calorimetry allows the monitoring daily energy expenditure (additional data: locomotor activity, rearing behavior, respiratory exchange ratio, lipid and carbohydrate oxidation rates). The direct measurement of exhaled volatile, mainly organic molecules has recently opened a new and non-invasive window into mouse (and human) metabolism (breath analysis). Finally, cold challenges induced by varying ambient temperature can be conducted to investigate thermoregulatory capacities.