Effects of laboratory housing conditions on neurobiology of energy balance in mice

Preclinical research with animals plays a vital role in the understanding the regulation of body weight, appetite and energy balance. Laboratory housing conditions can greatly affect experimental outcomes, however, these factors are often overlooked. Indeed, rodents raised in small litters are more prone to develop obesity and metabolic derangements than rodents raised in normal litters. In addition, housing mice either individually or socially from weaning till adulthood can greatly reduce growth and affect energy balance regulation, and metabolic health, but in a sex-dependent fashion. It has been hypothesized that the lack of social thermoregulation may be partly responsible for these effects. However, increasing environmental temperature close to thermoneutrality (28°C) does not ameliorate these effects. This emphasize that laboratory housing conditions, the number of mice in a cage and their sex must be reported as they can profoundly affect experimental outcomes in preclinical studies. The establishment of social dominance relationships can also potentially affect energy balance regulation in mice in a sex-dependent fashion, although this has been studied only in an exploratory analysis and conclusions cannot be drawn. Finally, in ingestive behviour studies in mice, meals are often defined using arbitrary criteria, but the effects that these can have on meal related parameters are not known. Investigation of feeding behaviour and meal-related parameters in mice is possible through automated breakpoint analysis and the use of arbitrary intermeal intervals to define meals should be carefully evaluated.