GLP-1 Therapy for NAFLD and MASH: Emerging Evidence

Non-alcoholic fatty liver disease (NAFLD) — now increasingly called metabolic-associated steatotic liver disease (MASLD) — affects approximately 25% of the global population and is the most common liver disease in the United States. Its more severe form, metabolic-associated steatohepatitis (MASH, formerly NASH), can progress to cirrhosis and liver failure.

GLP-1 receptor agonists have emerged as one of the most promising treatments for NAFLD/MASH. For prescribers offering GLP-1 programs, understanding this emerging indication is increasingly important.

NAFLD/MASH is closely linked to metabolic syndrome — obesity, insulin resistance, dyslipidemia, and hypertension. GLP-1 agonists address multiple components of this metabolic cluster:

Weight loss: Fat accumulation in the liver is driven by excess caloric intake and obesity. Weight loss reduces hepatic fat content.

Insulin sensitization: Insulin resistance drives hepatic fat accumulation. GLP-1 agonists improve insulin sensitivity.

Direct hepatic effects: GLP-1 receptors are expressed in hepatic tissue. GLP-1 agonism may have direct anti-inflammatory and anti-fibrotic effects in the liver.

Lipid effects: GLP-1 agonists reduce triglycerides and improve lipid profiles, reducing the lipid substrate for hepatic fat accumulation.

The NASH trial of semaglutide (published in NEJM in 2021) was a landmark study:

Design: 320 patients with NASH and liver fibrosis (stage F1–F3). Randomized to semaglutide 0.1, 0.2, or 0.4 mg daily (subcutaneous) vs. placebo for 72 weeks.

Results:

• NASH resolution without worsening fibrosis: 59% (0.4 mg) vs. 17% (placebo)
• Fibrosis improvement: 43% (0.4 mg) vs. 33% (placebo) — not statistically significant
• Significant improvements in liver enzymes, weight, and metabolic markers

Significance: The NASH resolution rate was impressive, but the lack of significant fibrosis improvement was a limitation. This led to the design of larger Phase 3 trials.

The ESSENCE trial is a Phase 3 trial of semaglutide 2.4 mg weekly (the Wegovy dose) in patients with MASH and liver fibrosis. Results from the first part of the trial (52 weeks) were published in 2024:

• MASH resolution without worsening fibrosis: 62.9% (semaglutide) vs. 34.3% (placebo)
• Fibrosis improvement by ≥1 stage: 36.8% (semaglutide) vs. 22.4% (placebo)

These results led to FDA approval of semaglutide for MASH in adults with liver fibrosis — a significant new indication.

The SYNERGY-NASH trial examined tirzepatide in patients with MASH:

• MASH resolution: 44–62% (tirzepatide, dose-dependent) vs. 10% (placebo)
• Fibrosis improvement: 55% (highest dose) vs. 30% (placebo)

Tirzepatide has also received FDA approval for MASH.

Given the strong results with semaglutide and tirzepatide, retatrutide is being studied in MASH. The triple mechanism (GLP-1/GIP/glucagon) may produce even greater hepatic benefits. Phase 2 data is expected in 2026.

Patients presenting for GLP-1 weight management therapy should be screened for NAFLD/MASH:

• Liver enzymes (ALT, AST) — elevated in MASH
• FIB-4 score (calculated from age, AST, ALT, platelet count) — screens for advanced fibrosis
• Liver ultrasound — detects hepatic steatosis
• Fibroscan (transient elastography) — assesses liver stiffness/fibrosis

For patients with known NAFLD/MASH on GLP-1 therapy:

• Monitor liver enzymes every 3–6 months
• Repeat FIB-4 or Fibroscan annually
• Monitor for signs of liver decompensation

Document the NAFLD/MASH indication in the medical record. This strengthens the clinical rationale for GLP-1 prescribing and may support insurance coverage.

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This content is for informational and educational purposes only. It does not constitute medical advice. Prescribers should review current prescribing information and use clinical judgment.