Alcohol-Induced Oxidative Stress and Gut–Liver–Brain Crosstalk: Expanding the Paradigm from ALD to MetALD

Alcohol-associated liver disease (ALD) includes a spectrum from steatosis and steatohepatitis to cirrhosis and hepatocellular carcinoma driven by oxidative stress, immune activation, and systemic inflammation. Ethanol metabolism through alcohol dehydrogenase, aldehyde dehydrogenase, and cytochrome P450 2E1 generates reactive oxygen and nitrogen species, leading to mitochondrial dysfunction, hepatocellular injury, and activation of inflammatory and fibrogenic pathways. Beyond hepatic effects, ALD engages the gut–liver–brain axis, where microbial dysbiosis, blood–brain barrier disruption, and neuroinflammation contribute to cognitive impairment and cerebrovascular risk. The emerging concept, metabolic dysfunction-associated steatotic liver disease and increased alcohol intake (MetALD), presents the synergistic impact of alcohol and metabolic comorbidities, enhancing oxidative injury and fibrosis. This review summarizes key mechanisms connecting oxidative stress to multisystem pathology and highlights the need for precision therapies targeting redox imbalance, immune dysregulation, and gut–brain–liver interactions to improve outcomes in ALD and MetALD.