Drosophila insulin-like peptide-6 (dilp6) expression from fat body extends lifespan and represses secretion of Drosophila insulin-like peptide-2 from the brain

Reduced insulin/IGF signaling extends lifespan in diverse species, including Drosophila melanogaster where the genome encodes seven insulin-like peptides (dilp1-7). Of these, reduced dilp2 expressed in the brain has been associated with longevity assurance when over-expression of dfoxo in fat bodies extends lifespan. Here, we show that the insulin-regulated transcription factor dFOXO positively modulates dilp6 mRNA in adult fat body. Over-expression of dilp6 in adult fat body extends lifespan and increases longevity-associated metabolic phenotypes. Adult fat body dilp6 expression represses dilp2 and dilp5 mRNA in the brain, and the secretion of DILP2 into the hemolymph. The longevity benefit of expressing dfoxo in fat body, and the nonautonomous effect of fat body dfoxo upon brain dilp expression, is blocked by simultaneously repressing dilp6 by RNAi in fat body. dilp6 thus appears to bridge dFOXO, adipose tissue and brain endocrine function to regulate Drosophila longevity.