Metabolic adaptations in neonatal mother-deprived rabbits

Abstract

[EN] In order to study the metabolic adaptation in response to 48 h transient doe-litter separation (DLS) in young rabbits (5 rabbits/d group) between postnatal 9 and 11 d, plasma concentrations of thyroid hormones T3 and T4, insulin, leptin, glucose, triglycerides (TG), and free fatty acids (FFA) were examined before (6-8 d), during (9-11 d), and after separation (12-16 d). T3 concentrations in newborn control rabbits gradually increased from 0.6 ng/mL at postnatal 6 d to 1.0 ng/mL at postnatal 16 d, whereas those of T4 remained fairly constant (25 ng/mL) up to postnatal 14 d, when T4 gradually declined to 8 ng/mL. T3 values of DLS newborn rabbits did not differ from those of controls at postnatal 10 and 11 d, but were lower (P<0.05) at postnatal 12 d, while T4 concentrations in DLS animals increased, although not significantly, between postnatal 10 and 12 d compared to controls. Insulin concentrations in young control rabbits ranged between 0.6 and 1.0 mg/L in the early postnatal days, whereas those for leptin averaged 2-3 ng/mL. Insulin and leptin values in DLS newborn rabbits were lower (P<0.05) at postnatal 10 and 11 d, but thereafter rebounded to levels close to those of controls. Glycaemia showed a comparable trend in both groups, ranging between 170 and 190 mg/dL up to postnatal 14 d, but thereafter decreased (P<0.05) to values of 120-130 mg/dL independently of treatment. Concentrations of TG varied greatly from day to day around a mean value of 300 mg/dL, whereas those of FFA remained at approximately the same steady-state levels from postnatal 6 to 16 d, averaging 0.8 mM without any significant differences between groups. In conclusion, these findings confirm that newborn rabbits can cope with the metabolic stress of starvation associated with DLS by lowering insulin and leptin concentrations while maintaining those of thyroid hormones, an overall endocrine response which, together with temporary increase of glucorticoids, successfully maintains an adequate energy balance.