Proteomic effects of short-term liraglutide vs. placebo in a blinded crossover RCT: Implications for efficacy, safety, and comparison with semaglutide.

BACKGROUND: Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert cardiometabolic benefits beyond weight loss, yet their systemic proteomic mechanisms remain incompletely defined. We profiled short-term liraglutide-induced protein changes and compared them with published semaglutide signatures. METHODS: In a randomized, double-blind, placebo-controlled, crossover trial (NCT02944500), 20 adults with obesity received liraglutide 3 mg daily or placebo for 5 weeks, separated by a 3-week washout. Plasma and serum samples underwent SomaScan v4.1 profiling of 6249 proteins. Mixed-effects models tested Time×Treatment interactions with and without weight adjustment. Results were benchmarked against the 30-protein semaglutide STEP 1/2 signature. RESULTS: Liraglutide significantly modulated 124 proteins (57 FDR < 0.05); 85 % of effects persisted after weight adjustment, indicating largely weight-independent actions. Upregulated proteins included pancreatic enzymes (PNLIP, CTRB1/2, PRSS2), while endothelial and fibrotic markers (ACE, NOS3, FAP) were downregulated. Myostatin (MSTN) was strongly suppressed (log₂ fold change -0.41; p = 1.7 × 10), with concurrent rises in its inhibitors WFIKKN2 and BMPR1A. Liraglutide shared 70-75 % directional overlap with semaglutide, with 25-30 % unique effects enriched in vascular, neurodevelopmental, and musculoskeletal pathways. A semaglutide-based classifier distinguished liraglutide from placebo (AUC = 0.82; sensitivity 0.89; specificity 0.60). Downregulated proteins were genetically linked to coronary artery disease and type 2 diabetes (FDR < 0.05). CONCLUSIONS/INTERPRETATION: Short-term liraglutide reproduces the core GLP-1RA proteomic fingerprint while uniquely suppressing myostatin and vascular remodeling pathways. These rapid, largely weight-independent molecular responses indicate early cardioprotective and myostatin-inhibitor signaling changes that could be relevant for future muscle-preserving strategies, supporting individualized GLP-1RA use beyond weight loss alone.