The team, led by Jie Gao and colleagues at the State Key Laboratory of Animal Nutrition and Feeding within the Chinese Academy of Agricultural Sciences, worked with eighteen castrated male Large White pigs weighing around seventy kilograms. The animals were split into three groups: an untreated control, a group injected with diquat, and a group fed a diet containing 800 milligrams of lipoic acid per kilogram before receiving the same diquat challenge. Diquat is a bipyridine herbicide widely used in research to trigger oxidative stress; inside cells it hijacks molecular oxygen to generate superoxide radicals and hydrogen peroxide, mimicking the damage that modern farming stressors, from early weaning to poor diets, can inflict on porcine liver. Fourteen days after the injection, the researchers collected liver samples to examine tissue in its recovery phase, a window that most previous studies overlooked.

The technical scale of the analysis is impressive. Using tandem mass tag labeling combined with liquid chromatography-tandem mass spectrometry, the team identified 7,271 hepatic proteins and accurately quantified 5,326 of them. A parallel label-free ubiquitylome analysis detected 1,651 ubiquitination sites across 594 proteins, with 1,208 sites quantified. Ubiquitination is a post-translational modification in which a small regulatory protein is attached to lysine residues on target proteins, often marking them for degradation by the proteasome but sometimes altering their activity or location. Because the ubiquitin system is increasingly recognized as a master switch for ferroptosis, cataloguing these tags provided a direct readout of how stressed liver cells reorganize their survival machinery.

Ferroptosis itself is a relatively recently characterized form of regulated cell death, driven by iron-dependent lipid peroxidation. Unlike apoptosis, it culminates in the catastrophic oxidation of cellular membranes. The liver, as the body’s principal iron storage organ, is especially vulnerable. When free ferrous iron accumulates in the cytoplasm, it catalyzes the Fenton reaction, converting hydrogen peroxide into highly destructive hydroxyl radicals. Prior work has already tied ferroptosis to liver injury in pigs and in models of metabolic and ischemic liver disease, but the upstream regulation of the pathway, particularly through ubiquitination, remained murky.

Two proteins emerged from the molecular fog as the study’s central characters. The first is ferritin heavy chain 1, or FTH1, the functional core of ferritin, the cell’s iron vault. FTH1 possesses ferroxidase activity, converting dangerous ferrous iron into its safer ferric form and sequestering it within the ferritin shell, thereby preventing the Fenton reaction from running unchecked. The researchers found that lipoic acid supplementation increased FTH1 abundance in recovering livers, a trend confirmed by parallel reaction monitoring, an independent mass spectrometry method, and by Western blotting, though the Western blot difference reached only marginal statistical significance with a p-value of 0.054.

The second protagonist is poly(rC)-binding protein 1, known as PCBP1, a cytosolic iron chaperone that grabs ferrous iron through conserved cysteine residues and delivers it to ferritin for safe storage. The ubiquitylome data revealed that lipoic acid promoted ubiquitination of PCBP1 at lysine 314, a residue the authors showed is highly conserved across species, hinting at an evolutionarily important function. Co-immunoprecipitation experiments on liver tissue confirmed that total PCBP1 ubiquitination was significantly higher in lipoic acid-fed pigs than in the diquat-only group. What this ubiquitination does to PCBP1’s iron-binding activity is not yet resolved, and the authors are explicit that functional verification of the K314 site will be a centerpiece of their future work.

The cellular story was reinforced by experiments in THLE-2 cells, an immortalized human liver epithelial line. When the cells were stressed with hydrogen peroxide, lipoic acid treatment at 200, 400, and 800 micromolar concentrations significantly blunted the stress-induced drop in FTH1 and the surge in intracellular ferrous iron, in a dose-dependent fashion. The treatment also preserved cell viability, reduced malondialdehyde, a lipid peroxidation byproduct, and restored the activities of total and copper-zinc superoxide dismutase. The authors acknowledge that cross-species differences between human cells and the porcine model are a limitation and plan to validate the findings in primary pig hepatocytes.

One of the more counterintuitive results came from the antioxidant measurements. Fifteen days after the diquat challenge, livers of the stressed pigs showed elevated, not depressed, activity of catalase, superoxide dismutase, and glutathione peroxidase, along with higher total antioxidant capacity. Rather than contradicting earlier reports of diquat toxicity, the authors interpret this as a compensatory overshoot: after acute oxidative shock subsides, the body’s Nrf2-driven antioxidant program remains cranked up, pumping out protective enzymes to mop up lingering peroxides. Histological sections supported the idea of a recovery phase, showing mild microvacuoles, some binucleated hepatocytes, and slight sinusoidal congestion but no outright necrosis. Lipoic acid-fed pigs generally landed between the controls and the stressed animals on most indices, suggesting the supplement gently steered the overactivated antioxidant system back toward balance rather than flipping it abruptly.

At the pathway level, the enrichment analyses added further texture. Differentially expressed proteins in lipoic acid-supplemented pigs were significantly enriched in mineral absorption and, notably, in the ferroptosis pathway itself, while gene ontology terms for iron ion transport, ferric iron binding, and iron homeostasis appeared repeatedly at both the protein and ubiquitination levels. The ubiquitinome also lit up the AMPK and FoxO signaling pathways, which the authors speculate may act as upstream hubs governing the E3 ubiquitin ligases, such as Parkin and HUWE1, that in other contexts have been shown to degrade ferroptosis regulators like ACSL4 and the transferrin receptor. Which specific ligases or deubiquitinases modify PCBP1 in response to lipoic acid remains an open question the team is chasing next.

The practical implications extend beyond the laboratory. Heat stress, weaning, mycotoxins, and transport all impose oxidative burdens on swine, costing the industry real money in growth performance and welfare. By establishing that a dietary additive can tune the ubiquitination of iron-handling proteins and thereby suppress ferroptosis, the study offers a mechanistic rationale for lipoic acid as a functional feed additive, not merely a generic antioxidant. It also demonstrates, more broadly, that post-translational modifications deserve a seat at the table when nutritionists evaluate how supplements actually work. Whether the same iron-sequestration strategy can be exploited in human liver disease, where ferroptosis is implicated in conditions from steatohepatitis to acute liver failure, is an enticing question, and one that this porcine ubiquitylome has now made considerably easier to ask.

Subject of Research: The role of ubiquitination in alpha-lipoic acid-mediated suppression of ferroptosis during hepatic oxidative stress recovery in finishing pigs

Article Title: Ubiquitylome analysis reveals the protective effect of α-lipoic acid via the ferroptosis pathway during recovery after hepatic oxidative stress in finishing pigs

Article References: Gao, J., Cui, Y., Li, C., Bao, W., Hao, Y., Piao, X., Meng, Q., & Gu, X. (2026). Ubiquitylome analysis reveals the protective effect of α-lipoic acid via the ferroptosis pathway during recovery after hepatic oxidative stress in finishing pigs. Stress Biology, 6(1), Article 68. https://doi.org/10.1007/s44154-026-00341-1

Image Credits: AI Generated

DOI: 10.1007/s44154-026-00341-1

Keywords: alpha-lipoic acid, ferroptosis, ubiquitination, oxidative stress, liver, FTH1, PCBP1, iron homeostasis, pigs, proteomics, diquat, feed additive