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Tirzepatide and muscle composition changes in people with type 2 diabetes (SURPASS-3 MRI): a post-hoc analysis of a randomised, open-label, parallel-group, phase 3 trial

Sattar N, Neeland IJ, Dahlqvist Leinhard O, Fernández Landó L, Bray R, Linge J, Rodriguez A

The lancet. Diabetes & endocrinology, 2025

2,942 participants

Abstract

BACKGROUND: Substantial weight reduction is often associated with loss of muscle mass. Tirzepatide has been associated with significant reductions in body weight in type 2 diabetes trials and a beneficial effect on body fat distribution in the SURPASS-3 MRI substudy. This post-hoc exploratory analysis studied the association of tirzepatide treatment with changes in thigh muscle volume, muscle volume Z score, and muscle fat infiltration, and aimed to contextualise the results using longitudinal MRI data from UK Biobank participants.

METHODS: SURPASS-3 was a randomised, open-label, parallel-group, phase 3 trial. The multicentre (45 sites) and multinational (eight countries) MRI substudy of SURPASS-3 enrolled insulin-naive adults (aged ≥18 years) with type 2 diabetes who were on treatment with metformin with or without a sodium-glucose co-transporter-2 (SGLT-2) inhibitor, had an HbA1c of 7·0-10·5% (53-91 mmol/mol), a BMI of at least 25 kg/m2, and a fatty liver index of at least 60. Participants were randomly assigned (1:1:1:1) to receive subcutaneous injection once per week of tirzepatide (5, 10, or 15 mg), or subcutaneous injection once per day of titrated insulin degludec. Thigh muscle fat infiltration, muscle volume, and muscle volume Z score (invariant to sex, height, weight, and BMI) were quantified by MRI at baseline and week 52. In this post-hoc analysis, we assessed the differences between mean baseline and week 52 muscle composition values in the tirzepatide groups…

How strong is the evidence?

Evidence Hub reads this as a secondary / pooled analysis, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 2,942 participants or records.

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