Nutrition during the perinatal period programs body growth. Growth hormone (GH) secretion from the pituitary regulates body growth and is controlled by Growth Hormone Releasing Hormone (GHRH) neurons located in the arcuate nucleus of the hypothalamus. We observed that dietary restriction during the early postnatal period (i.e. lactation) in mice influences postnatal growth by permanently altering the development of the somatotropic axis in the pituitary gland. This alteration may be due to a lack of GHRH signaling during this critical developmental period. Indeed, underfed pups showed decreased insulin-like growth factor I (IGF-I) plasma levels, which are associated with lower innervation of the median eminence by GHRH axons at 10 days of age relative to normally fed pups. IGF-I preferentially stimulated axon elongation of GHRH neurons in in vitro arcuate explant cultures from 7 day-old normally fed pups. This IGF-I stimulating effect was selective since other arcuate neurons visualized concomitantly by neurofilament labeling, or AgRP immunochemistry, did not significantly respond to IGF-I stimulation. Moreover, GHRH neurons in explants from age-matched underfed pups lost the capacity to respond to IGF-I stimulation. Molecular analyses indicated that nutritional restriction was associated with impaired activation of AKT. These results highlight a role for IGF-I in axon elongation that appears to be cell selective and participates in the complex cellular mechanisms that link underfeeding during the early postnatal period with programming of the growth trajectory.

Objective Individuals born with intrauterine growth retardation (IUGR) are more prone to cardio-metabolic diseases as adults, and environmental changes during the perinatal period have been identified as potentially crucial factors. We have studied in a preclinical model early-onset molecular alterations present before the development of a clinical phenotype. Methods We used a preclinical mouse model of induced IUGR, in which we modulated the nutrition of the pups during the suckling period, to modify their susceptibility to cardio-metabolic diseases in adulthood. Results Mice born with IUGR that were overfed (IUGR-O) during lactation rapidly developed obesity, hepatic steatosis and insulin resistance, by three months of age, whereas those subjected to nutrition restriction during lactation (IUGR-R) remained permanently thin and highly sensitive to insulin. Mice born with IUGR and fed normally during lactation (IUGR-N) presented an intermediate phenotype and developed insulin resistance by 12 months of age. Molecular alterations to the insulin signaling pathway with an early onset were observed in the livers of adult IUGR-N mice, nine months before the appearance of insulin resistance. The implication of epigenetic changes was revealed by ChIP sequencing, with both posttranslational H3K4me3 histone modifications and microRNAs involved. Conclusions These two changes lead to the coherent regulation of insulin signaling, with a decrease in Akt gene transcription associated with an increase in the translation of its inhibitor, Pten. Moreover, we found that the levels of the implicated miRNA19a-3p also decreased in the blood of young adult IUGR mice nine months before the appearance of insulin resistance, suggesting a possible role for this miRNA as an early circulating biomarker of metabolic fate of potential use for precision medicine.