Impact of Mlkl or Ripk3 deletion on age-associated liver inflammation, metabolic health, and lifespan

Chronic, low-grade inflammation is a hallmark of aging and various age-related diseases, including metabolic dysfunction-associated steatotic liver disease (MASLD). The prevalence of metabolic dysfunction-associated steatohepatitis (MASH), an advanced form of MASLD, increases with age and contributes to morbidity and mortality among the elderly. This study investigates the role of necroptosis, a programmed cell death pathway that promotes inflammation, in liver inflammaging and age-associated MASLD by utilizing genetic ablation models of two key necroptosis proteins, Mlkl or Ripk3. The absence of Mlkl or Ripk3 significantly reduced liver inflammation, steatosis, and fibrosis in aged male mice, supporting the role of necroptosis in age-associated MASLD. Additionally, Mlkl or Ripk3 deletion impacted other non-necroptotic cellular processes that drive inflammation and MASLD, such as cellular senescence, apoptosis, and autophagy in aged liver. Levels of plasma TNFα and IL6, key proinflammatory cytokines associated with inflammaging, are reduced in Mlkl^-/- or Ripk3^-/- aged mice, supporting a systemic effect of necroptosis inhibition on inflammation. Proteomic analysis of liver tissues emphasizes the critical role of lipid and immune regulatory processes in maintaining liver homeostasis when Mlkl or Ripk3 is absent in aging liver. While Mlkl deletion did not affect the lifespan of mice, Ripk3 deletion shortened it. Additionally, Mlkl deficiency improved insulin sensitivity, whereas Ripk3 deficiency exacerbated glucose intolerance in aged mice. Thus, selective inhibition of Mlkl, not Ripk3, represents a potential therapeutic avenue for mitigating age-related liver disease and enhancing metabolic outcomes in the elderly.