Central and peripheral administrations of insulin-like growth factor-1 suppress food intake in chicks

Abstract

A number of studies have been made on the physiological actions of insulin-like growth factor-1 (IGF-1) in mammals and birds. In mammals, the effects of central administration of IGF-1 on food intake have been examined. For example, intracerebroventricular administration of IGF-1 significantly decreased food intake in diabetic rats, but not in sheep and nondiabetic rats. The chicken is known to be a hyperglycemic animal. Like satiety hormones, plasma IGF-1 levels are elevated postprandially in chickens. In this study, we hypothesized that IGF-1 is involved in the regulation of food intake in chickens. Intracerebroventricular administration of IGF-1 significantly suppressed food intake in chicks in a dose dependent manner. Both the mRNAs of IGF-1 and its receptor were expressed throughout the brain. However, the mRNA levels of IGF-1 were not influenced by fasting and refeeding in all regions of the brain. On the other hand, 6h of fasting significantly suppressed mRNA expression of hepatic IGF-1, and this effect was significantly reversed by 6h of refeeding. Furthermore, intravascular administration of IGF-1 significantly suppressed food intake in chicks. These findings suggest that IGF-1 may function as a satiety hormone in chickens.

Effects of Fasting and Refeeding on the mRNA levels of Insulin-like Growth Factor-binding Proteins in Chick Liver and Brain

“…However, McMurtry et al (1996) demonstrated that the half-life of free IGF-1 was 5.17 ± 0.27 min in broiler chickens. We previously confirmed that hepatic IGF-1 mRNA levels were significantly decreased by 6 h of fasting in 8-day-old broiler chicks (Fujita et al, 2017) and by 4 h of fasting in 14-day-old broiler chicks (unpublished data). These findings suggest that the plasma IGF-1 concentration may be significantly decreased under the 6-h fasted condition, which in turn stimulates appetite in broiler chicks.…”

“…In chickens, the rostral and caudal parts of the brainstem include the DVC and infundibular nucleus (the avian equivalent of mammalian ARC), respectively (Kuenzel and Masson, 1988). In addition, we have reported that the IGF-1 receptor is expressed in these parts of the brain in chicks (Fujita et al, 2017). The plasma IGF-1 concentration was significantly decreased by 48 h of fasting and reversed by 48 h of refeeding in layer chickens (Kita et al, 2002).…”

“…We previously demonstrated that intravascular administration of IGF-1 significantly suppressed food intake in chicks (Fujita et al, 2017). The dorsal vagal complex (DVC) and arcuate nucleus (ARC) receive and integrate peripheral satiety signals in mammals (Williams and Elmquist, 2012).…”

“…Additionally, we showed that the mRNA levels of IGF-1 in the liver were significantly increased upon refeeding and that the IGF-1 receptor is expressed throughout the brain (Fujita et al, 2017). Evidence demonstrates that IGF-1 crosses the blood-brain barrier (Reinhardt and Bondy, 1994;Armstrong et al, 2000;Nishijima et al, 2010).…”

“…Recently, we found that central and peripheral administration of IGF-1 significantly suppressed food intake in chicks (Fujita et al, 2017). Additionally, we showed that the mRNA levels of IGF-1 in the liver were significantly increased upon refeeding and that the IGF-1 receptor is expressed throughout the brain (Fujita et al, 2017).…”