In vitro
This in vitro study examined the effects of three incretin-based therapies — semaglutide (GLP-1 receptor agonist), tirzepatide (dual GLP-1/GIP agonist), and cagrilintide (amylin analogue) — on mitochondrial function in C2C12 skeletal muscle myotubes under both normal and lipotoxic conditions. Lipotoxicity was induced using palmitic acid (PA), which significantly reduced basal oxygen consumption rate and ATP production in treated cells. The study used Seahorse XFp metabolic flux analysis, mitochondrial DNA copy number quantification (qPCR), and oxidative phosphorylation complex protein expression (western blotting), with key findings replicated in primary human skeletal muscle cells. The researchers found that semaglutide and cagrilintide transiently reduced basal respiration in healthy myotubes, while tirzepatide demonstrated more sustained improvements in mitochondrial respiration under both healthy and lipotoxic conditions. The study's primary limitations include its reliance on cell culture models, meaning findings may not directly translate to whole-organism physiology, and the use of a single lipotoxic stimulus. The partial replication in human primary cells adds some translational relevance, but in vivo validation remains absent.
Journal of cachexia, sarcopenia and muscle · Apr 2026DOI ↗ In vitroPreprint
This preprint describes a computational study aimed at designing improved semaglutide analogues — variants of the GLP-1 receptor agonist used in weight-loss and diabetes treatment — in the context of the underperforming CagriSema Phase III trial. The researchers used an automated "natural amino acid scanning" approach, systematically introducing single amino acid mutations across the semaglutide peptide backbone. Using the crystal structure of the GLP-1–GLP-1R complex (PDB: 4ZGM) as a structural template, they performed high-throughput computational modeling with Modeller and estimated binding affinities (Kd) using the Prodigy tool. From this pipeline, the study identified 564 computationally designed semaglutide analogues predicted to show improved binding affinity to the extracellular domain (ECD) of GLP-1R. The authors propose a conceptual "interfacial electrostatic scaffold" consisting of four salt bridges at the peptide–receptor interface as a framework for next-generation GLP-1R agonist development, drawing an analogy to the century-long iterative optimization of insulin. Key limitations include the fully computational nature of the study — no experimental validation (biochemical, cellular, or in vivo) is presented — and reliance on a single structural template and computational binding affinity estimators, which may not fully capture dynamic receptor behavior.
Unknown journal · Apr 2025DOI ↗