GLP-1 Drugs and the Liver: How Incretin-Based Therapies May Treat Fatty Liver Disease | Research

The takeaway

GLP-1 receptor agonists and newer dual/triple agonists show promise for treating MASH (fatty liver disease), though it's debated whether they help the liver directly or through weight loss.

Phase III trials underway
GLP-1 agonists for MASH have progressed from successful phase II studies into pivotal phase III clinical trials

What the researchers found

GLP-1 receptor agonists have shown promise in treating MASH (formerly NASH) in phase II trials and are now in phase III testing. Newer dual and triple agonists combining GLP-1 with glucagon and/or GIP activity have demonstrated improvements in weight, insulin resistance, and non-invasive liver markers. However, it remains unclear whether these drugs act directly on liver disease or primarily work through upstream weight loss and metabolic improvements. The authors suggest that combining gut hormone agonists with agents that directly target fibrosis (like FGF21 or pan-PPAR agonists) may be the most effective strategy.

Why it matters

MASH is a leading cause of liver disease worldwide, driven primarily by obesity and insulin resistance. The GLP-1 drug class — including semaglutide and tirzepatide — represents one of the most promising therapeutic approaches, but the field is still working out which combinations work best. This review maps the current landscape of incretin-based liver therapies and identifies the key open questions that will shape clinical trials for years to come.

How the study worked

This is a narrative review article that synthesizes evidence from published clinical trials (phase IIa, IIb, and early phase III) of GLP-1 receptor agonists and multi-agonist peptides in patients with MASH. It evaluates both the direct and indirect mechanisms of action and discusses combination therapy strategies.

What this study cannot tell us

As a narrative review, this paper does not perform quantitative analysis or meta-analysis of the trials discussed. The optimal ratios of GLP-1, GIP, and glucagon agonism in multi-agonist drugs remain unresolved. The review acknowledges significant uncertainty about whether GIP agonism or antagonism is the better approach, and notes that combination therapies bring cumulative side-effect and cost concerns.

How to read the evidence

This is a narrative review synthesizing phase II and early phase III clinical trial data. While it summarizes strong clinical evidence, it does not perform its own quantitative analysis.

When this study was published

Published in 2023 in the Journal of Hepatology, this review captures the state of the field as MASH trials entered their most advanced stages. The landscape continues to evolve rapidly with new trial readouts.

The bigger picture

The explosion of GLP-1 drugs for weight loss and diabetes has opened an unexpected therapeutic frontier: liver disease. MASH affects hundreds of millions of people globally and currently has very few approved treatments. If incretin-based therapies prove effective — especially in combination with anti-fibrotic agents — it would represent one of the most significant expansions of the GLP-1 drug class beyond its original metabolic indications.

Questions still open

Do GLP-1 agonists have direct anti-inflammatory or anti-fibrotic effects on liver cells, or is the benefit entirely mediated by weight loss?
What is the optimal ratio of GLP-1, GIP, and glucagon receptor activity in multi-agonist drugs for treating liver disease specifically?
Will the side-effect burden of combination therapies (gut hormones plus anti-fibrotic agents) be acceptable for long-term use in MASH patients?

Common questions

What is MASH and why is it so hard to treat?

MASH (metabolic dysfunction-associated steatohepatitis, formerly called NASH) is a severe form of fatty liver disease where fat buildup leads to inflammation and liver scarring. It's driven by obesity and insulin resistance, and until very recently there were no approved drugs specifically targeting it. The liver damage can progress silently to cirrhosis and liver failure.

Could someone already on semaglutide or tirzepatide for weight loss also be helping their liver?

Possibly. Clinical trial data suggest that GLP-1 drugs improve liver health markers in people with fatty liver disease, likely through weight loss and improved insulin sensitivity. Whether there are also direct liver-protective effects is still being studied, but the weight loss alone may provide significant liver benefits.

Read the original research

Incretins (GLP-1 receptor agonists and dual/triple agonists) and the liver.

Journal of hepatology, 79(6), 1557-1565

View on PubMed ↗Publisher’s paper ↗

Citation

Newsome, Philip N; Ambery, Phil. (2023). Incretins (GLP-1 receptor agonists and dual/triple agonists) and the liver.. Journal of hepatology, 79(6), 1557-1565. https://doi.org/10.1016/j.jhep.2023.07.033