Glucose stimulates the release of bombyxin, an insulin-related peptide of the silkworm Bombyx mori

The effects of starvation and feeding on the release of bombyxin, a peptide of insulin superfamily in insects, from the larval brain of the silkworm B ombyx mori were investigated. Following starvation, the bombyxin titer in t he hemolymph of larvae decreased, whereas its content in the brain increase d. On the other hand, refeeding of the starved larvae resulted in an increa se in the hemolymph bombyxin titer and a rapid decrease in the hormone leve l in the brain. These results indicate that the release of bombyxin from th e brain is suppressed by starvation and stimulated by feeding. The hemolymp h glucose titer also changed sharply upon starvation and refeeding, and a c lose relationship was observed between the changes in glucose concentration s and bombyxin titers in the hemolymph. The injection of glucose into starv ed larvae could mimic the effect of refeeding on the release of bombyxin, s uggesting that glucose serves as the signal for the "fed" state of the anim al. It is likely that glucose is a common nutritional signal for inducing t he release of mammalian and insect insulins. (C) 2000 Academic Press.