Endocrine Abstracts

Maternal cold exposure induced by winter shearing promotes fetal growth, particularly that of the liver by increasing maternal glucose supply to the fetus. A major component of the fetal liver is glycogen which is rapidly mobilized at birth in order to provide an endogenous energy source. Hepatic glyocgen content is regulated in part by the lipid activated transcription factor, peroxisome proliferator-activated receptor alpha (PPARα), whilst insulin-like growth factor (IGF)-II regulates glycogen synthase. The aim of the present study was to determine the effect of maternal CE on hepatic glycogen content in the newborn and whether its abundance was related to PPARα or IGF-II mRNA abundance.

Fifthteen multiparous ewes of similar body weight were entered into the study of which eight were shorn (S) at 70 days gestation and seven remained unshorn (US). All mothers were fed to fully meet the metabolisable energy requirements of an US sheep. The offspring were humanely euthanased at one day of age to enable liver sampling in which the relative abundance of PPARα and IGF-II mRNA to 18S rRNA were determined using RT-PCR and are expressed in arbitrary units (a.u.) whilst liver glycogen content was measured enzymatically.

Despite CE offspring having larger livers (S 128±11; US 110±11 g (P<0.05)) they had a reduced glycogen content (S 67±21; US 132±11 mmol (P<0.01)) in conjunction with a decreased mRNA abundance for IGF-II (S 75±7; US 191±27 a.u. (P<0.01)) and PPARα (S 5±0.09; US 14±1 a.u. (P<0.05)). In addition PPARα mRNA abundance was positively correlated (P<0.01) with hepatic glycogen content.

In conclusion, maternal CE has a pronounced effect on liver mass and content which may be related to a decrease in mRNA abundance for IGF-II and PPARα that act to promote glycogen mobilization in the newborn.