Animal only
This mouse study investigated the molecular mechanisms by which tirzepatide (TZP), a dual GIP/GLP-1 receptor agonist, affects the liver in metabolic dysfunction-associated steatotic liver disease (MASLD). Male C57BL/6J mice (n=32) were fed a high-fat, high-fructose (HFHFr) diet to induce MASLD and then randomized to receive no treatment, semaglutide (Sema), or TZP. Researchers combined RNA sequencing and liquid chromatography-mass spectrometry (LC-MS) to generate hepatic transcriptomic and proteomic profiles, with key targets validated by PCR and immunoblotting. The study found that HFHFr feeding produced hyperglycemia, insulin resistance, elevated liver enzymes, and hepatic steatosis and inflammation. Both TZP and Sema were associated with improvements in these parameters; TZP was associated with reductions in pro-inflammatory markers (MCP-1, IL-1β, TNF-α, GSDMD) and partial restoration of IL-10. Integrated omics analysis implicated the CCL2/CCR2 chemokine axis and PI3K-AKT signaling pathway as key molecular signatures associated with TZP's hepatic effects. Key limitations include the exclusive use of an animal model, a small sample size, and the mechanistic (non-causal) nature of omics associations.
BMC gastroenterology · Jun 2026DOI ↗ Animal only
This animal study compared the anti-atherosclerotic effects of tirzepatide (a dual GIP/GLP-1 receptor agonist) and semaglutide (a selective GLP-1 receptor agonist) in ApoE knockout mice. Mice were treated with streptozotocin to induce diabetes and divided into early diabetes, late diabetes, and non-diabetic groups, each receiving either agent or saline for 12 weeks. The study found that in the early diabetes group, both tirzepatide and semaglutide significantly reduced aortic plaque formation compared to controls, with modest improvements in blood glucose and lipid levels. No significant vascular effects were observed in the late diabetes or non-diabetic groups in terms of plaque reduction. Tirzepatide more broadly reduced inflammatory markers—including Mcp-1, Il-6, I-cam, and Cd68—compared to semaglutide. Anti-inflammatory effects were also detected in non-diabetic mice, suggesting possible vascular protective mechanisms independent of metabolic control. The authors conclude that dual incretin receptor agonism may offer cardiovascular benefits, though the specific contribution of GIP signaling requires further investigation. Key limitations include the use of an animal model, which may not translate directly to human cardiovascular disease.
Scientific reports · Apr 2026DOI ↗ Animal only
This animal study investigated the anti-obesity effects of three GLP-1 receptor agonist peptides — semaglutide, tirzepatide, and retatrutide — in melanocortin 4 receptor knockout (MC4R KO) mice, a model of genetically driven obesity caused by disruption of the POMC-MC4R signaling pathway. All three compounds were administered for 21 days, after which body weight, body composition, metabolic markers, liver health, and gene expression were assessed. The study found that all three GLP-1 analogs produced statistically significant reductions in body weight, with tirzepatide showing the greatest effect (approximately 31.6%), followed by retatrutide (approximately 24.1%) and semaglutide (approximately 19.7%). All three agents reduced both fat and lean mass, improved plasma insulin levels and insulin resistance (HOMA-IR), lowered cholesterol, and reduced markers of liver damage (AST and ALT) as well as liver hypertrophy. Gene expression analysis showed suppression of fatty acid synthesis genes, but no significant effect on inflammatory gene expression. Energy expenditure was reduced by all agents; only tirzepatide significantly decreased the respiratory quotient. A key limitation is that this is a mouse model study, and findings may not directly translate to humans. The authors suggest MC4R KO mice are a valid model for studying obesity-related drug efficacy.
International journal of obesity (2005) · Feb 2026DOI ↗ Animal only
This study investigated whether milk-derived small extracellular vesicles (sEVs) could serve as oral delivery vehicles for two GLP-1 receptor agonists (GLP-1RAs): semaglutide and tirzepatide. Researchers loaded both peptides onto sEVs in vitro and administered them orally to diabetic db/db mice—a well-established mouse model of type 2 diabetes. The study found that both peptides were efficiently incorporated into the sEV carrier system and that oral administration of the loaded vesicles effectively reduced blood glucose levels in the diabetic mice. The authors compared this approach to the existing SNAC (sodium N-[8-(2-hydroxybenzoyl) amino] caprylate) technology used in the commercially approved oral semaglutide formulation (Rybelsus), arguing that sEVs offer broader applicability across multiple peptide drugs, not just semaglutide. Key limitations include the exclusive use of an animal model with no human pharmacokinetic or efficacy data, a relatively small and homogeneous study design, and the early-stage, preclinical nature of the platform. Translation to humans remains undemonstrated.
Journal of extracellular biology · Nov 2025DOI ↗ Animal only
This study describes the development and validation of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytical method for measuring tirzepatide — a dual GIP/GLP-1 receptor agonist — in rat plasma. Researchers used protein precipitation with methanol for sample preparation, a peptide C18 column for chromatographic separation, and positive electrospray ionization with multiple reaction monitoring for detection, using semaglutide as an internal standard. The method demonstrated good linearity (1–1000 ng/mL), with intra- and inter-day accuracy and precision meeting regulatory criteria. Stability under various storage and handling conditions was also confirmed. The validated method was then applied to a pharmacokinetic study in rats administered tirzepatide intravenously and subcutaneously at 0.3 mg/kg. The study reports terminal half-lives of approximately 10 hours via both routes and estimates subcutaneous bioavailability at roughly 62%. Key limitations include the exclusive use of a rat model, a single dose level, and a small number of animals typical of preclinical PK studies, meaning findings may not translate directly to humans. The authors suggest the method could be adapted for quantifying other structurally similar peptide therapeutics.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences · Oct 2025DOI ↗ Animal only
This preclinical study investigated whether three GLP-1-based receptor agonists — semaglutide (GLP-1 receptor agonist), tirzepatide (dual GLP-1/GIP receptor agonist), and retatrutide (triple GIP/GLP-1/glucagon receptor agonist) — could alter the interoceptive (subjective-like) effects of alcohol in rats. Using an operant drug discrimination paradigm in both male and female rats, researchers trained animals to distinguish alcohol from vehicle, then tested whether these compounds disrupted that learned discrimination. The study found that acute administration of all three agents attenuated alcohol's discriminative stimulus effects, suggesting modulation of how alcohol "feels" internally. Repeated semaglutide treatment maintained this effect over a 15-day period, and the effect reversed within three days of cessation. The authors suggest these findings may help explain clinically observed reductions in alcohol craving and drinking in humans receiving GLP-1 receptor agonists. Limitations include the exclusive use of animal models, meaning direct translation to human subjective alcohol experience remains uncertain, and the study does not assess long-term outcomes or dependence-related endpoints.
Psychopharmacology · Jul 2025DOI ↗ Animal onlyPreprint
This preclinical study examined whether three incretin-based receptor agonists — semaglutide (GLP-1 receptor agonist), tirzepatide (dual GLP-1/GIP receptor agonist), and retatrutide (triple GIP/GLP-1/glucagon receptor agonist) — could alter the interoceptive (subjective) effects of alcohol in rats using an operant drug discrimination paradigm. Male and female rats were trained to discriminate alcohol from saline, then tested after acute or repeated drug administration. The study found that acute administration of all three compounds reduced alcohol's discriminative stimulus effects, suggesting each compound modulated how the animals internally perceived alcohol. Repeated semaglutide treatment sustained this effect across a 15-day period, though discrimination returned to baseline levels within three days of stopping treatment. The authors interpret these findings as potentially relevant to understanding why GLP-1 receptor agonists reduce drinking behavior in humans, hypothesizing that blunting alcohol's subjective effects may be a contributing mechanism. Key limitations include the exclusive use of an animal model, meaning translation to human subjective experience remains uncertain, and the study does not establish clinical efficacy or safety in people with alcohol use disorder.
Unknown journal · Apr 2025DOI ↗