Melatonin Mediates Monochromatic Light‐induced Insulin‐like Growth Factor 1 Secretion of Chick Liver: Involvement of Membrane Receptors

Abstract

Monochromatic lights influenced the proliferation and differentiation of skeletal satellite cells in broilers by the enhancement of insulin-like growth factor 1 (IGF-1) secretion. However, whether melatonin (MEL)-mediated monochromatic lights influenced the IGF-1 secretion remains unclear. Newly hatched broilers, including intact, sham operation and pinealectomy groups, were exposed to blue (BL), green (GL), red (RL) and white light (WL) from a light-emitting diode system for 14 days. The results showed that GL effectively promoted the secretion of MEL and IGF-1, the expression of proliferating cell nuclear antigen and MEL receptor subtypes Mel1a, Mel1b and Mel1c in the liver compared to BL and RL in vivo. Moreover, those was a positive correlation between MEL and IGF-1 (r = 0.834). After pinealectomy, however, these parameters declined, and there were no differences between GL and other monochromatic light treatments. In vitro, exogenous MEL increased hepatocyte proliferation and IGF-1 secretion. Meanwhile, the MEL enhancements were suppressed by prazosin (selective Mel1c antagonist), followed by luzindole (nonselective Mel1a/Mel1b antagonist), but not suppressed by 4-phenyl-2-propionamideotetralin (selective Mel1b antagonist). These findings demonstrated that MEL mediated the monochromatic light-induced secretion of IGF-1 in chicks' livers by Mel1c and that Mel1a may be involved in this process.

Melatonin Receptor Mel1b‐ and Mel1c‐mediated Green Light Induced the Secretion of Growth Hormone in Anterior Pituitary of Chicks

“…There are currently three types of melatonin membrane receptors known in birds. These membrane receptors are widely distributed in various tissues and organs, such as the hypothalamus , tectum , eyeball , spleen , bursa of Fabricius , liver and gastrointestinal tract . The three membrane receptors play different roles in different tissues and organs.…”

“…Monochromatic light affected the protein expression of Pit-1 in the anterior pituitary (F (3,16) = 32.948) (Fig. 1C).…”

“…Monochromatic light affected the expression of Pit-1 (F (3,18) = 4.348) and GH (F (3,13) = 7.871) mRNA levels in the anterior pituitary ( Fig. 1A,B).…”

“…Meanwhile, the melatonin concentration in GL was the greatest and was significantly greater than those in WL, RL and BL by 6.44-22.35% (P = 0.000-0.016); the difference was not observed between RL and WL (P = 0.175). After pinealectomy, the level of plasma GH (F (3,10) = 0.376) and melatonin (F (3,11) = 0.518) in various monochromatic lights decreased significantly, especially in GL. However, the differences disappeared among the four light treatments (P > 0.05).…”

“…The productive performance of the avian is particularly sensitive to changes of the light environment. Previous studies have found that green light (GL) can significantly promote the growth , increase the secretion of liver insulin‐like growth factor‐1 (IGF‐1) , cause skeletal muscle satellite cells to proliferate , induce skeletal muscle growth and enhance immune function in the early stages of a broiler's life. However, how color of light information (different wavelength light) affects the growth and development of broilers is not fully understood.…”