Determining the variables and mechanisms that govern aging is important for facilitating healthy aging. Dietary fats, specifically cholesterol, possibly play a critical role in the aging of organisms. Additionally, dietary cholesterol may influence the reproduction of organisms. The insulin signalling/IGF pathway plays a vital role in longevity in C. elegans. Nevertheless, the relationship between cholesterol metabolism and the insulin/IGF signalling pathway is well known. Hence, cholesterol metabolism possibly has an indirect impact on the aging process of organisms. In this study, wild-type C. elegans and an insulin receptor mutant, daf-2(-), were employed to investigate the effect of cholesterol on aging and egg laying. For the lifespan study, synchronised L4 larvae of wild type and daf-2(-) were exposed to 10 µg/mL cholesterol, a concentration twice the standard level routinely used for the maintenance of C. elegans. Life span assays were conducted using three biological replicates, each consisting of ten worms per plate. The egg laying of the above C. elegansstrains was assayed at 7 different concentrations ranging from 2.5 µg/mL to 17.5 µg/mL of cholesterol, using 30 L4 larvae per treatment (n=30). Survival plots of the lifespan assay were created using the Kaplan-Meier estimator. Despite its negative impact on the life span of wild-type C. elegans, cholesterol has no significant effect on the life span of daf-2 mutants, suggesting that cholesterol-mediated lifespan shortening is DAF-2 mediated. Egg laying data was statistically analysed using one-way ANOVA followed by the Tukey post HSD pairwise comparison, showing that there was a progressive increase in the egg laying starting from 7.5 µg/mL and effects maximised at the 15µg/mL concentration. The lower dose (2.5 µg/mL) and the highest concentration (17.5 µg/mL) did not exert a significant effect on egg laying in wild type C. elegans. No discernible changes in daf-2(-) egg laying were seen at any cholesterol concentration. Hence, both life span reduction at 10 µg/mL concentration of cholesterol and the enhancement of the egg laying are both DAF-2 dependent, while the effects on egg laying showed a dose dependency.
Keywords: Life span, Egg laying, Cholesterol, C. elegans, Insulin signaling
