The IGF-1 senescence switch: a biphasic model for SASP-driven aging and precision senomodulation.

Insulin-like growth factor-1 (IGF-1) signaling plays a paradoxical role in aging, acting as both a mediator of tissue repair and a driver of chronic inflammation through the senescence-associated secretory phenotype (SASP). In this review, we propose a biphasic senescence switch model in which the temporal pattern of IGF-1 exposure, acute versus chronic, determines cellular fate. Transient IGF-1 signaling supports homeostasis and repair, whereas sustained activation promotes stable senescence via reactive oxygen species (ROS)-mediated DNA damage, p53/p21 pathway activation, and a potent pro-inflammatory SASP. Central to this process is IGF-binding protein-5 (IGFBP-5), which amplifies senescence in vascular and stromal cells by linking coagulation and inflammatory signals to p53-dependent arrest. The contrasting human conditions of IGF-1 deficiency (Laron syndrome) and excess (acromegaly) illustrate the lifespan and disease risks associated with dysregulated IGF-1 signaling. Emerging evidence highlights the role of extracellular vesicles in bypassing soluble IGFBP regulation, enabling paracrine propagation of senescence even under systemic IGF-1 modulation. Ultimately, we position the IGF-1/IGFBP axis as a prime target for precision senomodulation, advocating for combined strategies that temporally tune endocrine signaling with senolytic and senomorphic therapies to mitigate chronic inflammation, delay age-related dysfunction, and extend healthspan.