Endocrine Abstracts

Introduction: Glucocorticoids are vital for regulating metabolic processes, as well as use in medical treatments. However chronic glucocorticoid excess is known to cause negative metabolic effects including hyperglycaemia, muscle atrophy and fat accumulation. The effect on energy metabolism and metabolic rate remains undefined and merits investigation in both male and female mice.

Methods: 20 male and 20 female C57BL/6J mice were randomly assigned to a corticosterone (100 mg/l, approximately 300μg/day) or a vehicle control group. Mice were treated ad libitum via drinking water for 3 weeks, whilst being fed a standard chow diet. Mice were placed into a TSE Phenomaster system for the final week of treatment for indirect calorimetry assessment.

Results: Corticosterone treatment resulted in a typical phenotype of glucocorticoid excess with female mice experiencing significantly greater fat accumulation and bodyweight gain. Females treated with corticosterone exhibited increased energy expenditure (EE, 25±5.9%), oxygen consumption (21.7±10.0%) and carbon dioxide production (36.4±14.3%) during the day compared to controls, but males did not. However, corticosterone did significantly elevate the respiratory exchange ratio (RER) towards 1 in both males (10.7±5.7%) and females (11.8±7.0%) during the day. At night, when mice are naturally more active, female corticosterone mice no longer had elevated EE, oxygen consumption and carbon dioxide production compared to controls. However, RER remained elevated in females (7.6%±4.8%) and moderately so in males (3.2±2.6%), staying close to or exceeding 1 in both. Corticosterone treated mice were hyperphagic throughout with food and water intake peaking at night.

Conclusions: These findings provide further insights into the metabolic consequences of glucocorticoid excess in male and female mice. Whilst energy metabolism and metabolic rate are altered in both, the metabolic effects of glucocorticoid excess might be more pronounced in females.