Aging Livers Hide Their Weaknesses Until Stress Pushes Mitochondria to the Brink

The human liver is famously forgiving. It filters toxins, balances energy stores and regenerates lost tissue for decades, often keeping its architecture and routine blood chemistry looking deceptively healthy well into old age. Yet a comprehensive review published in Frontiers in Cell and Developmental Biology argues that this apparent stability conceals a growing fragility, one that is centered not on any single failing molecule but on the slow erosion of mitochondrial resilience. Led by Hanxi Chen, Shi Chen and Zhengtao Liu of Zhejiang Chinese Medical University and Zhejiang Shuren University, the authors synthesized transcriptomic, proteomic and metabolomic evidence from rodents, non-human primates and humans to propose that liver aging is best understood as a set of coordinated pathway-level disturbances rather than a collection of isolated biomarkers. Their central claim is provocative: chronological age alone is an incomplete proxy for how a liver will actually behave when life, or a transplant surgeon, puts it under pressure.

The clinical stakes are far from abstract. Organ shortages have made older donor livers a routine part of transplantation, and outcomes still track donor age in ways that stubbornly resist prediction. A registry-based analysis of more than 111,000 liver transplants cited in the review found that when older grafts went to younger recipients, five-year graft survival fell to 69.9 percent, compared with 77.8 percent for young-to-old combinations. Grafts from donors over 60 to 70 years fared particularly poorly in high-risk recipients with MELD scores of 35 or above, and in living donation, use of donors aged 50 and older carried a 61 percent increased hazard of graft failure. The paradox that frustrates clinicians is that age alone incompletely predicts post-transplant behavior. Some older livers retain substantial reserve while others collapse under metabolic overload, inflammatory injury or impaired recovery, which is precisely why the authors argue for a biologically grounded, module-based framework rather than another hunt for a single decisive marker.

That framework rests on five interrelated biological modules that emerged from converging multi-omics evidence: lipid stress and metabolic remodeling, diminished oxidative reserve, proteostatic strain, inflammatory sensitization, and reduced recovery capacity. Each module is supported by different layers of molecular data, and each connects back to mitochondria, the organelles that power fatty-acid oxidation, oxidative phosphorylation, redox homeostasis and detoxification in hepatocytes. The logic is that impaired mitochondrial metabolic flexibility, weakened redox buffering, disrupted organelle crosstalk and failing quality-control systems provide the common substrate on which all five disturbances build. Critically, the authors stress that these modules remain partly compensated at baseline. Molecular age-related changes accumulate quietly while histology and standard blood tests look normal, and only become conspicuous when the liver is challenged by metabolic overload, ischemia-reperfusion injury, cold preservation or ex vivo machine perfusion.

The lipid stress module illustrates how the pieces interlock. Multi-omics studies across mouse strains, diets and ages show that age-associated hepatic phenotypes are shaped not just by time but by genotype and diet, with alterations in fatty-acid handling, lipid-droplet distribution, peroxisomal programs and FGF21 and FABP4 signaling narrowing metabolic flexibility even when baseline function appears preserved. One mechanistic study linked senescence-associated 13-hydroxyoctadecadienoic acid, an oxidized lipid mediator, to age-related steatosis by showing that it directly inhibits catalase, a key antioxidant enzyme. That finding stitches lipid stress to the oxidative reserve module: aged rodent and primate livers repeatedly show altered glutathione balance, elevated reactive oxygen and nitrogen species, increased malondialdehyde, mitochondrial DNA damage and changes in catalase, superoxide dismutase and respiratory-chain proteins. In other words, lipid overload and antioxidant decline are not separate problems but two faces of the same mitochondrial vulnerability.

Proteostatic strain adds a third thread. Rodent phosphoproteomic data and primate single-nucleus studies converge on altered chaperone, protein-degradation and endoplasmic reticulum stress pathways, suggesting that the energetic cost of maintaining protein quality rises with age even in hepatocytes that look intact. The review links this to lipid and redox stress through a mechanistic chain: excess mitochondrial calcium and reactive oxygen species increase ER protein-folding demand, while ATP limitation weakens chaperone and degradation capacity, so proteostatic strain may act as a downstream amplifier of metabolic overload rather than an isolated defect. Inflammatory sensitization operates at the multicellular level. Single-cell studies identify altered endothelial, macrophage, neutrophil and hepatocyte programs in aged liver, and challenge models show that IL-1α signaling between liver sinusoidal endothelial cells and hepatocytes, along with Cxcl2-positive macrophage recruitment of neutrophils, can amplify ischemia-reperfusion injury in old livers. Finally, recovery capacity, the ability to restore metabolic, synthetic and structural homeostasis after injury, is compromised by dysregulated Hedgehog signaling, reduced hepatocyte plasticity and extracellular matrix remodeling, meaning two grafts can absorb similar early stress yet diverge sharply in lactate clearance, bile production and survival.

Why does mitochondria sit at the center rather than the periphery of this network? The review describes a feedback architecture in which lipid overload increases mitochondrial calcium loading and ROS generation, which promotes ER stress and inflammatory signaling; the resulting proteostatic and inflammatory burden then consumes energy and limits repair, further impairing mitochondrial quality control and metabolic flexibility in a self-reinforcing loop. This structure generates testable predictions. A liver carrying combined lipid stress and low redox reserve should show a larger stress-induced rise in mitochondrial, ER-stress and inflammatory readouts and a slower recovery trajectory than a liver with only one abnormal module. The authors are careful to note that mitochondrial vulnerability is the interface connecting the modules, not a separate module itself and not a validated measure of biological age, but it offers a unifying hypothesis for why aging livers with identical birthdays and similar biopsies can behave so differently under duress.

Not all evidence carries equal weight, and the review is unusually candid about this. Rodent studies provide most of the mechanistic depth, with large mouse multi-omics datasets and naturally aged models showing distributed remodeling across lipid metabolism, immune signaling, stress-kinase networks and protein-state regulation. Non-human primate data, though limited in scale and often drawn from female animals, strengthen confidence that ER stress, degradation pathways and hepatocyte pro-senescence programs are conserved rather than rodent-specific artifacts. Human baseline evidence remains the weakest layer: transcriptomic signals of aging are entangled with steatosis, fibrosis, metabolic disease and medication history, and matched human tri-omics datasets are scarce. Spatial and single-cell studies add a crucial caveat about anatomy, showing that hepatocytes do not age uniformly across the lobule. Pericentral cells preferentially accumulate large lipid droplets while periportal cells show more prominent mitochondrial and epigenetic disturbance, which means small biopsies or bulk assays can miss biologically important local variation.

This is where transplantation and machine perfusion enter as natural experiments. Procurement, cold preservation, reperfusion and metabolic reactivation impose rapid, defined swings in oxygen availability and energetic demand, converting modest baseline differences into clinically meaningful ones. Hypothermic oxygenated perfusion and normothermic machine perfusion have already proven their clinical value in randomized trials, reducing early allograft dysfunction, biliary strictures and organ discard, but their scientific value here lies in the sampling window they create. During HOPE, early perfusate flavin mononucleotide, a marker of mitochondrial injury, was higher in grafts that developed early allograft dysfunction, and in a 50-graft validation cohort the five-minute value yielded an area under the curve of 0.744 for early allograft dysfunction and 0.890 for one-year mortality. During NMP, serial perfusate transaminases, lactate dehydrogenase, von Willebrand factor and platelet changes associated with early dysfunction, while perfusate IL-6, TNF-α and IL-10 correlated with postoperative bilirubin, intensive-care stay or graft loss, and bile pH, bicarbonate and glucose tracked biliary viability.

The authors insist these signals are promising readouts, not decision rules. No published study has validated a combined panel across perfusion protocols, and none of the fluid-based markers is aging-specific; they reflect donor comorbidity, ischemia, procurement and preservation strategy as well as age-related vulnerability. The module framework is explicitly hypothesis-generating rather than outcome-validated, and the review warns against merging FMN trajectories, cytokine measurements and biliary chemistry from different cohorts into a clinical scoring system without prospective, matrix-matched validation. What the framework does offer is translational logic: tissue biopsies capture pathway state, serial perfusate captures stress and recovery kinetics, bile captures cholangiocyte function, and post-transplant outcomes provide the ultimate clinical anchor. Future priorities include paired tissue-fluid biobanks, attention to circadian timing and pre-analytical handling of metabolites, spatially informed biopsy interpretation, and explicit separation of immediate procurement injury from genuine recovery behavior in sampling schedules.

The bigger picture is a conceptual shift in how aging science approaches one of medicine’s hardest assessment problems. Rather than seeking a molecular birth certificate for the liver, the review proposes mapping which vulnerability modules are active in a given organ and how they will respond to defined stress. Candidate intervention targets, including FGF21 and FABP4 in lipid metabolism, the 13-HODE-catalase axis in antioxidant buffering and Hedgehog signaling in regenerative reserve, remain experimental, and the authors caution that any therapeutic claim requires direct evidence of benefit against clinically meaningful endpoints. But the reframing itself is consequential: if the most stable features of liver aging are process-level changes that become functionally visible under stress, then machine perfusion may be not just a preservation technology but a stress-testing platform, a controlled environment in which the hidden mitochondrial biography of an aging liver can finally be read before it matters.

Subject of Research: Mitochondrial vulnerability and multi-omics biological modules of the aging liver and their translational relevance to transplantation

Article Title: Multi-omics perspectives on mitochondrial vulnerability in the aging liver: biological modules and translational implications

Article References: Chen, H., Lu, W., Wang, K., Fang, R., Lee, S., Chen, S., & Liu, Z. (2026). Multi-omics perspectives on mitochondrial vulnerability in the aging liver: biological modules and translational implications. Frontiers in Cell and Developmental Biology, 14, Article 1954948. https://doi.org/10.3389/fcell.2026.1954948

Image Credits: AI Generated

DOI: 10.3389/fcell.2026.1954948

Keywords: liver aging, mitochondria, multi-omics, machine perfusion, liver transplantation, oxidative stress, proteostasis, inflammation, biomarkers, FGF21, ischemia-reperfusion injury, hepatocytes