Effects of food restriction and pregnancy on the expression of insulin-like growth factor-1 and -II in tissues from guinea pigs

Abstract

The insulin-like growth factor (IGF) system is subjected to pregnancy-associated changes in the circulation and is suggested to be of importance for partitioning of nutrients between the mother and the foetus. Interestingly, maternal undernutrition alters the pregnancy-associated changes, with possible adverse consequences for the mother and the foetus. However, it is not known how malnutrition and pregnancy alter the expression of mRNA for IGFs locally in different tissues. The aims of this study were to investigate where IGF-I and IGF-II are expressed in guinea pigs and how this expression is altered during food restriction and pregnancy. Ad libitum-fed and food-restricted (fed 70% of the ad libitum-fed intake four weeks before pregnancy and throughout the study) guinea pigs were mated. On day 40 of pregnancy and on the corresponding day for virginal females the animals were killed. mRNA for IGF-I and IGF-II was analysed in various organs/tissues by solution hybridisation. mRNA for IGF-I was expressed in high amounts in uterus, liver and adipose tissues. The expression was not affected by food restriction, but was increased in liver and adipose tissue and decreased in uterus by pregnancy. mRNA for IGF-II was expressed in high amounts in the placenta and liver. In the placenta the expression was decreased by food restriction. Pregnancy increased the levels of mRNA for IGF-II in the liver. Food-restricted dams had smaller foetuses and placentas. In conclusion, this study indicates an important role for the adipose tissue during gestation, not only as an energy store but also as an endocrine tissue expressing IGF-I. The decreased expression of IGF-II in the placenta due to food restriction is suggested to have adverse effects on placental structure and function.