daf-2

The effect of daf-2/InsR on growth following starvation is largely but not entirely daf-16-dependent.

Both compounds induced DAF-16 nuclear translocation and upregulated SKN-1 expression.

Reduced insulin/IGF signaling (IIS) in Caenorhabditis elegans increases starvation resistance in a daf-16/FoxO-dependent fashion, but it is unclear whether the effects of reduced IIS are entirely dependent on daf-16/FoxO.

Further genetic experiments in daf-2 and daf-16 mutants revealed a dual mechanism: a DAF-16-independent capacity to lower ROS, coupled with a strict DAF-16 dependence for inducing antioxidant enzymes.

We reduced IIS by adult-onset daf-2 RNAi in wild-type and heritable RNAi-deficient ( hrde-1 ) backgrounds, allowing either spontaneous or UV-induced germline mutations to accumulate over multiple generations.

Targeted genetic analysis and transcriptional analysis uncovered that this metabolic disruption requires the insulin-like receptor daf-2 and aak-2, and further CBZ specifically and consistently upregulates the Δ9-desaturases, most prominently fat-6 and fat-7, identifying them as the key effector enzymes.

Notably, daf-16 is dispensable for reproduction following extended starvation, and daf-2 loss preserves reproductive success independent of daf-16.

The antioxidant genes of the DAF-2/SKN-1 pathway were activated by Cryptococcus_T038 and _T248 and H. opuntiae_W164 in C. elegans strain LD1171 (GCS-1p::GFP) and by Cryptococcus_T038, H. opuntiae_W164, and S. boulardii_SB in C. elegans strain CF1553 (SOD-3p::GFP).

Collectively, our findings highlight that cycloastragenol reprograms lipid metabolism by down-regulating the insulin-like receptor (daf-2)/phosphatidylinositol 3-kinase (age-1)/NHR-49 signaling while simultaneously enhancing the activity of the AAK-2/NAD-dependent protein deacetylase (SIR-2.1) pathway.

Mechanistically, PS-45 inhibited DAF-16 nuclear translocation and dysregulated insulin/IGF-1 signaling genes (daf-2, age-1, pdk-1, akt-1, and daf-16).

When DAF-2 activity is reduced or inhibited in C. elegans, DAF-16 and SKN-1 are activated and translocate to the nucleus to promote stress resistance and prolong lifespan.

Under conditions of oxidative stress, RT-qPCR analysis revealed that PSG treatment significantly up-regulated the expression of key antioxidant gene skn-1 and longevity-associated gene daf-16.

When DAF-2 activity is reduced or inhibited in C. elegans, DAF-16 and SKN-1 are activated and translocate to the nucleus to promote stress resistance and prolong lifespan.

Mutant worms in IIS (daf-2, daf-16, and sod-3) or autophagy-related genes (unc-51, atg-3, and atg-13) abolished the lifespan reduction.

On the contrary, BCL-11 deficiency compromises the cytoprotective properties of daf-2 signaling upon animal exposure to stress.

Notably, the neuroprotective effects of BSP were completely abolished in mutants of key insulin signaling pathway genes (daf-2, age-1, akt-1, akt-2, daf-16) and the AMPK homologous gene aak-2, indicating that its efficacy is associated with the insulin/AMPK-autophagy regulatory axis.

Moreover, CSS modulated serotonergic signaling by increasing tph-1 and ser-6 expression, linking its effects to serotonin-mediated regulation of fat metabolism.

The mechanistic data indicated that cycloastragenol suppresses the nuclear hormone receptor family member NHR-49 and the delta(9)-fatty-acid desaturase 7 (FAT-7) enzyme, and activates the 5'-AMP-activated protein kinase catalytic subunit alpha-2 (AAK-2) and the protein skinhead 1 (SKN-1) signaling.

Mutations in daf-2, age-1, pdk-1, akt-1, daf-16, and ftn-1 significantly altered PS-45-induced aging phenotypes and ferroptotic stress, identifying the DAF-2-AGE-1-PDK-1-AKT-DAF-16-FTN-1 axis as a central regulatory pathway.

By examining worms deficient in the ILP member INS-7 under glucose-present and glucose-absent conditions, we uncovered a previously unrecognized DAF-2-AKT/SGK signaling output that drives reversible growth arrest specifically under glucose-present conditions, while allowing normal development in the absence of glucose, in a manner independent of DAF-16.