Long-term effects of early postnatal food restriction on growth hormone secretion in rats

Background: Malnutrition in early life retards growth permanently in both humans and rats, but the underlying mechanism is unclear. The purpose of this study was to test the hypothesis that early postnatal food restriction induces long-term changes in the growth hormone-insulin-like growth factor I (GH-IGF-I) axis. Methods: We examined the effect of increasing litter size to 20 during lactation [food restriction (FR)] on growth and spontaneous GH secretion and serum IGF-I levels in 14- to 15-week-old rats. Results: No catch up in body weight (BW; p <.05), total length (TTL; p < .001), or tail length (TL; females, p <.02; males, p <.001) was observed in the adult female and male FR rats. Spontaneous 6-hour rat GH (rGH) secretory profiles showed significantly increased (p <.05) mean baseline rGH plasma concentrations in the male adult FR versus control (CON) rats (38.0 ± 3.6 versus 26.4 ± 2.5 ng/mL). Serum IGF-I levels in the male adult FR rat were significantly (p <.01) reduced (751.3 ± 50.3 versus 985 ± 55.5 ng/mL) compared with male controls. rGH secretory pattern in the adult female FR rat and serum IGF-I concentrations were not different from female controls. Conclusions: FR during lactation leads to incomplete catch-up growth in adult female and male rats. In the adult male FR rat, increased baseline rGH secretion and reduced serum IGF-I concentrations might explain the slow growth.