Role of insulin/insulin-like growth factor-1 signaling pathway genes on the lifespan of Caenorhabditis elegans

Aging process is influenced by the insulin/insulin-like growth factor-1 signaling (IIS) pathway or IGF-1 signaling pathway. Studies done on the genes of this pathway were found to affect longevity. However, no conclusive results have been drawn.The purpose of this systematic review is to summarize the function of genes involved in the IIS pathway of Caenorhabditis Elegans (C. elegans), a nematode commonly used as a model organism in molecular genetics and developmental biology. A literature search for relevant studies was done through PubMed and Scopus databases using MeSH keywords Caenorhabditis elegans, C. elegans, nematode, genes, RNA, DNA, IIS pathway, IGF pathway, lifespan, and longevity. The search was limited to studies that were published in the last ten years (2008-May 2018). After exclusion of duplicates, review papers, human, in vitro, and other organismal studies, a total of 76 research articles were selected for further assessments. Data relevant to the effects of IIS genes on the lifespan ofC. eleganswas independently extracted. Reduction of daf-2 and age-1 and overexpression of sir-2.1 were reported to promote increment of the lifespan of C. elegans.  Furthermore, differentially expressed genes that were involved in the protection against oxidative stress, pathogen attack, and toxicity includeins-18, numr-1/-2, sgk-1, and rgs-1. The knockdown of daf-2, age-1, and overexpression of sir-2.1 genes prolonged the lifespan of C. elegans while knockdown of daf-16, hsf-1, sir-2.1 as well as skn-1 shorten the lifespan of C. elegans.In conclusion, the differential expression of genes in the IIS pathway prolongs the lifespan of C. elegans.