MASH

MASH stands for metabolic dysfunction-associated steatohepatitis. It is the name adopted in 2023 by a consensus of international liver-research societies for the inflammatory, fibrosing form of fatty liver disease that was previously called NASH (nonalcoholic steatohepatitis). The rename was one output of a multi-society Delphi process that also replaced nonalcoholic fatty liver disease (NAFLD) with metabolic dysfunction-associated steatotic liver disease (MASLD). The consensus statement, rationale, and diagnostic criteria are published as Rinella et al., Hepatology 2023 (NLM 37363821).

What differentiates MASH from simple steatosis

MASLD encompasses the whole spectrum of steatotic liver disease associated with cardiometabolic risk factors. MASH is the subset of MASLD in which liver biopsy (or an accepted noninvasive proxy) shows not just hepatic steatosis but also hepatocellular injury, lobular inflammation, and often fibrosis. The histologic distinction matters because simple steatosis tends to progress slowly if at all, whereas MASH is the state from which meaningful fibrotic progression, cirrhosis, and hepatocellular carcinoma arise. The NAS (NAFLD Activity Score) histologic scoring system described by Kleiner and colleagues remains the reference framework for grading (Kleiner et al., Hepatology 2005 (NLM 15915461)); the 2023 nomenclature update kept those histologic criteria in place while changing the disease names.

Why MASH is a frequent reference point in peptide research

The GLP-1 and GIP receptor agonist classes have been studied for effects on liver fat content, biomarkers of hepatic injury, and MASH histologic endpoints in published trials, and the FGF21 pathway is a parallel research area. A reader encountering MASH in the Open Assay corpus is most often encountering a citation to published research on how a particular peptide or receptor agonist was evaluated in a MASH model or population. The relevance of the term is therefore bibliographic - it identifies the published disease context in which a peptide has been studied - rather than a claim that any RUO research peptide addresses MASH.

How Open Assay handles MASH-linked citations

Where a peptide page on Open Assay cites MASH research, the citation points to the specific published article or trial record, identifies the histologic or biomarker endpoint used, and does not extrapolate from that research to claims about research materials. Open Assay uses the current MASLD/MASH terminology for research published from 2023 forward and preserves the original NAFLD/NASH terminology when citing research from before the 2023 nomenclature change, noting the equivalence where useful.