The translatability of studies in rodent models to humans are subject to the differences in physiology between humans and mice, and the experimental conditions used when collecting data. One major factor affecting physiology often overlooked is the effect of ambient temperature. The majority of rodent housing is maintained between 20-22°C, the thermoneutral temperature of lightly clothed humans. However, mice have a much higher thermoneutral zone of ~30°C1. Thus, the aim of this project is to investigate the impact of housing temperature on the metabolism of mice fed normal chow or an obesogenic high fat diet.
Male C57Bl6 mice were housed at 22°C or a 29°C and fed either chow or a high fat diet (HFD; 60% calories as fat) for 12 weeks. During this dietary intervention, oral glucose tolerance test (oGTT), EchoMRI, and indirect calorimetry experiments were conducted. 2-way ANOVA was used for statistical analysis.
Body fat mass increased with HFD (effect of diet, p<0.05), and was further increased at thermoneutrality (22°C Chow 11.3±1.2, HFD 28.1±1.6%; 29°C Chow 14.0±1.4%, HFD 33.4±1.6%; effect of temperature, p<0.05). Lean mass was not different with diet or temperature. During an oGTT, mice fed a HFD were similarly glucose intolerant compared to chow mice regardless of housing temperature. Interestingly, animals housed at 29°C had higher insulin levels at 15 min post glucose load with both diets which reached statistical significance in the HFD mice (p<0.05). Not unexpectedly, indirect calorimetry showed that mice held at 22°C had ~45% higher energy expenditure and higher food intake than mice held at 29°C, regardless of diet.
This data show that animals housed at different temperatures do show differences in whole body energy metabolism and glucose homeostasis that could impact on the translatability of results to human disease.