Exogenous melatonin alleviates abnormal glucose metabolism in the breast muscle under long-term light exposure through the parasympathetic pathway.

INTRODUCTION

Human beings and animals have been exposed to long-term artificial lighting environments to induce glucose metabolism disorder. Melatonin (MT) is involved in the regulation of glucolipid metabolism, and can prevent skeletal muscle wasting as well as sarcopenia-associated diseases. However, the effect of exogenous MT on skeletal muscle glucose metabolism and the involvement of the parasympathetic pathway have not been clarified.

OBJECTIVES

To investigate the role of parasympathetic regulatory pathway in the mediating the effects of exogenous MT on skeletal muscle glucose metabolism following long-term light exposure.

METHODS

This study established rapid growth period broiler models, while characterized muscle histological analysis, glucose metabolism indexes and related genes expression through parasympathetic activation, exogenous MT administration and exogenous MT with parasympathetic inhibition experiments.

RESULTS

Long-term light exposure inhibited muscle glycogen synthesis, promoted muscle glycogen decomposition, increased anaerobic glycolysis, decreased aerobic respiration and induced the injury in breast muscle. Parasympathetic activation and exogenous MT caused a marked improvement in muscle glycogen accumulation, aerobic glycolysis and the injury in breast muscle. The exogenous MT beneficial functions were alleviated by parasympathetic inhibition. Furthermore, parasympathetic activation and exogenous MT administration protected cecal microbiota homeostasis, by improving stability of the gut microbiota community and increasing the relative abundance of Lactobacillus. Lactobacillus abundance was positively associated with muscle glycogen accumulation.

CONCLUSION

Taken together, this study highlighted the role of the novel parasympathetic regulatory pathway in the effects of exogenous MT in maintaining glucose metabolism homeostasis and restoring the damage in skeletal muscle with long-term light exposure. The results indicate that gut microbiota are involved in the MT-parasympathetic regulatory network. This study filles the gap in autonomic nervous-endocrine regulation under long light exposure, and provides a new insight to alleviate long light exposure-induced glucose metabolism disorders to improve the growth and health of humans and animals.