A sweet danger: the silent link between hyperinsulinemia and gastric cancer

Hyperinsulinemia (HI), a compensatory response to insulin resistance commonly associated with obesity and preceding Type 2 Diabetes Mellitus, represents a critical link between metabolic dysfunction and both cancer risk and progression. While its systemic effects are well-documented, its specific impact on gastric cancer (GC) risk and prognosis requires deeper investigation. HI promotes oncogenesis by activating the PI3K/AKT and MAPK/ERK signaling pathways, which are often dysregulated in GC through the overexpression of insulin receptor isoform A as well as oncogenic mutations in their key regulatory proteins, leading to increased cell proliferation, angiogenesis, and therapy resistance. In addition, the intricate crosstalk between these cascades and other signaling pathways, including NF-kB, JAK/STAT, WNT/β-catenin, fosters a pro-inflammatory milieu, the transition to mesenchymal phenotype, and tumor microenvironment remodeling. This review synthesizes two decades of research to elucidate the biochemical mechanisms by which elevated insulin levels provide the necessary stimuli and metabolic energy for tumor survival. We further evaluate clinical management strategies, emphasizing the potential of dietary interventions and pharmacological approaches to modulate the course of disease. Notably, a meta-analysis of existing literature indicates that metformin use is strongly associated with a reduced GC risk (Hazard Ratio, HR: 0.67, p = 0.008), and better outcomes including lower recurrence (HR: 0.61, p < 0.0001), all-cause mortality (HR: 0.61, p = 0.0002), and cancer-specific mortality (HR: 0.80, p = 0.0003). Despite the limitations of our findings, our review indicates that the pharmacological control of HI, and the underlying mutational pattern and pathway alterations it promotes, should be considered relevant in oncological management of GC patients.