Nutrition-dependent control of insect development by insulin-like peptides

• Insulin-like peptides (ILPs) are encoded by multiple genes in insects.
• Insect ILPs are mainly produced by the brain medial neurosecretory cells (mNSCs).
• Transcription and secretion of ILPs are regulated by multiple nutritional signals.
• Insect ILPs regulate body and tissue growth by systemic as well as local actions.
• Activities of secreted ILPs are regulated by several binding proteins in hemolymph.

In metazoans, members of the insulin-like peptide (ILP) family play a role in multiple physiological functions in response to the nutritional status. ILPs have been identified and characterized in a wide variety of insect species. Insect ILPs that are mainly produced by several pairs of medial neurosecretory cells in the brain circulate in the hemolymph and act systemically on target tissues. Physiological and biochemical studies in Lepidoptera and genetic studies in the fruit fly have greatly expanded our knowledge of the physiological functions of ILPs. Here, we outline the recent progress of the structural classification of insect ILPs and overview recent studies that have elucidated the physiological functions of insect ILPs involved in nutrient-dependent growth during development.