Meeting Abstract
Basal metabolic rate (BMR) quantifies the cost of body maintenance at thermoneutral zone, whereas resting metabolic rate (RMR), measured below thermoneutrality, includes also costs of thermoregulation. It is still unclear whether intra-specific variation in BMR, (i.e. in the magnitude of obligatory heat production) affects the need for extra heat production during cold stress. We studied the total amount of major thermogenic protein – UCP1 in brown adipose tissue (TOTUCP1) in mice selected towards either high (HBMR) or low (LBMR) BMR, and acclimated to 30 °C, 23 °C and 4 °C. We showed previously that the capacity of non-shivering thermogenesis (NST) is higher in LBMR then HBMR mice acclimated to 23 °C and 4 °C. Conversely, BMR of HBMR mice is 50% higher at 30 °C, but the lines did not differ with respect to RMR at 23 °C. Here, we showed that TOTUCP1 is higher in LBMR than HBMR mice at all temperatures, which provides molecular underpinning of the between-line difference in NST. Because this effect of selection is observed even at thermoneutral zone, we hypothesize that it reveals the presence of genetically-based, inverse correlation between BMR and the constitutive level of thermogenic capacity determined by UCP1. We attribute the between line difference in BMR at 30 °C to higher heat production of enlarged visceral organs of HBMR mice, which below thermoneutrality can be used for thermoregulation. On the other hand, lower BMR-related heat production of LBMR mice must be to a larger extend supported by NST. We discuss implications of our finding for evolution of endothermy. Financial support: National Science Centre, Poland, grant 2014/15/B/NZ8/00244 for P.B.
