Retatrutide reshapes metabolism in obesity and type 2 diabetes, study finds

Study: Retatrutide And Lipid And Metabolite Profiles In Participants With Obesity With Or Without Type 2 Diabetes. Image Credit: khomkrit sangkatechon / Shutterstock

A recent study published in The Journal of Clinical Endocrinology & Metabolism showed that retatrutide treatment altered metabolites associated with insulin resistance and fatty acid oxidation (FAO) among people with obesity with or without type 2 diabetes (T2D). These changes were consistent with improved metabolic health. The findings support further large-scale investigations for retatrutide use to improve overall health among people with commonly observed comorbidities such as obesity and T2D. If validated in subsequent trials across diverse populations, such treatments could help reduce the burden of cardiometabolic disease and improve patients' overall quality of life worldwide.

Retatrutide is a synthetic drug that simultaneously acts on multiple receptors. By engaging glucagon-like peptide-1 (GLP-1), glucagon (GCG), and glucose-dependent insulinotropic polypeptide (GIP) receptors simultaneously, the drug may modulate blood glucose levels and energy balance. Scientists are exploring retatrutide effects for obesity and T2D treatment. In phase 2 clinical trials, this drug improved body weight, body fat, and glycated hemoglobin (HbA1c) levels in people with obesity, with or without T2D. Participants also showed reduced waist circumference, blood pressure, fasting blood glucose, and insulin levels, along with nearly complete elimination of liver fat in a prior MASLD substudy. Retatrutide was generally well-tolerated, with no major safety concerns reported.

Phase 2 Trial Metabolomics Analysis

In the present study, researchers performed a post-hoc exploratory analysis to measure fasting plasma lipidome and metabolome changes among retatrutide recipients. They also explored the biochemical alterations underlying metabolic changes in the participants.

The study analyzed fasting plasma samples obtained from two previously conducted phase 2 randomized controlled trials (RCTs). These trials included individuals living with obesity, with or without T2D. The obesity trial included individuals with body mass index (BMI) between 27 and 30 kg m-² and at least one weight-related condition, as well as individuals with BMI ≥30 kg m-². In this trial, participants subcutaneously received retatrutide (1.0 mg, 4.0 mg, 8.0 mg, 12 mg) or placebo once weekly for 48 weeks.

The T2D trial comprised individuals with HbA1c ranging from 7.0 to 10.5% and BMI ranging from 25 to 50 kg m-². These individuals were treated with metformin or diet and exercise for ≥3.0 months before the trial. Participants received weekly subcutaneous injections of retatrutide at 0.5 mg, 4.0 mg, 8.0 mg, or 12 mg, placebo, or 1.5 mg dulaglutide over 36 weeks.

The post-hoc analysis comprised 282 participants in the obesity trial and 213 T2D patients. The researchers collected samples at study initiation, week 24, and week 48 from participants in the obesity trial. The sample collection time points were baseline, week 24, and week 36 for participants in the T2D trial. The team performed liquid chromatography-tandem mass spectrometry (LC-MS/MS) to monitor metabolic and lipidomic changes following retatrutide therapy. They used mixed models for statistical analysis. They also performed a mediation analysis to assess the treatment's contribution to the observed changes.

Fatty Acid Oxidation And Insulin Resistance

Retatrutide, in higher doses, altered metabolite concentrations. The researchers noted prominent changes in acetylcarnitine (C2), 3-hydroxybutyrate (3-HB), medium- and long-chain acylcarnitines (ACs), and free carnitine (C0). As key players in mitochondrial fatty acid metabolism, they work together to shuttle, process, and regulate fatty acids for energy production. While C2 and 3-HB increased and C0 decreased, several medium- and long-chain acylcarnitines initially increased, with FAO-related responses attenuating by week 48. The joint changes in 3-HB and the C2/C0 ratio accounted for approximately 23% of the weight-lowering treatment effects in participants without T2D. In T2D patients, the effects were weaker, accounting for less than 13%.

Retatrutide treatment also led to changes in branched-chain amino acids (BCAAs) and their catabolic products linked to insulin resistance. The drug lowered levels of 2-aminoadipic acid (2-AAA), triglycerides (TGs) enriched in short- and saturated-chain fatty acids, and urate in both trial populations, while 2-hydroxybutyrate (2-HB) was lowered more robustly in the T2D cohort and mainly by week 48 in the obesity trial.

At 24 weeks, participants in the obesity trial showed dose-dependent metabolic shifts. Researchers observed notable increases of nearly 198% in 3-HB and 95% in the C2/C0 ratio at the 12 mg dose in these participants. Valine and alanine levels declined markedly. By week 48, FAO-related responses had weakened, whereas insulin resistance-associated metabolic changes persisted. In T2D participants, increases in 3-HB and the C2/C0 ratio were much smaller, although reductions in BCAAs were comparable to those observed in the obesity cohort.

Retatrutide treatment was also associated with lower levels of the inflammatory marker 2,3-dinor-11β-PGF2α in the T2D cohort, where lipid mediators were assayed. The reduction was sustained through 36 weeks in the 8 mg and 12 mg dose groups. In parallel, levels of the PPARγ agonist 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) increased by approximately 40% at week 36 with both higher-dose regimens.

Retatrutide Biomarker Findings Need Validation

The study findings demonstrate that retatrutide treatment altered metabolites related to insulin resistance and fatty acid oxidation in ways consistent with improved metabolic health and a lower cardiovascular risk profile based on biomarker changes, rather than demonstrated reductions in cardiovascular events.

These findings link previously reported robust clinical outcomes with underlying biochemical mechanisms, although the post-hoc exploratory analysis remains hypothesis-generating and does not prove causality. 

Future studies should determine whether retatrutide’s metabolic effects arise from direct tissue actions or secondary weight-loss mechanisms. Researchers should also investigate its potential cardiovascular, neuroprotective, and bariatric surgery-like benefits as hypotheses for future research.

Download your PDF copy by clicking here.