Supplementary Material for: Sitagliptin Extends Lifespan of Caenorhabditis elegans by Inhibiting IIS and Activating DR-like Signaling Pathways

Introduction: The discovery of longevity molecules that delay aging and prolong lifespan has always been a dream of humanity. Sitagliptin phosphate (SIT), an oral dipeptidyl peptidase-4 (DPP-4) inhibitor, is an oral drug commonly used in the treatment of type 2 diabetes (T2D). In addition to being anti-diabetic, previous studies have reported that SIT has shown potential to improve health. However, whether SIT plays a role in the amelioration of aging and the underlying molecular mechanism remain undetermined. Methods: Caenorhabditis elegans (C. elegans) was used as a model of aging. Lifespan assays were performed with adult-stage worms on NGM plates containing FUDR with or without the specific concentration of SIT. The period of fast body movement, body bending rates and pharyngeal pumping rates were recorded to assess the health-span of C. elegans. Gene expression was confirmed by GFP fluorescence signal of transgenic worms and qPCR. In addition, the intracellular ROS levels were measured using a free radical sensor H2DCF-DA. Results: We found that SIT significantly extended lifespan and health-span of C. elegans. Mechanistically, we found that several age-related pathways and genes were involved in SIT-induced lifespan extension. The transcription factors DAF-16/FOXO, SKN-1/NRF2 and HSF-1 played important roles in SIT-induced longevity. Moreover, our findings illustrated that SIT induced survival benefits by inhibiting the insulin/insulin-like signaling (IIS) pathway and activating the dietary restriction (DR)-related and mitochondrial function-related signaling pathways. Conclusion: Our work may provide a theoretical basis for the development of anti-T2D drugs as anti-aging drugs, especially for the treatment of age-related disease in diabetic patients.