GLP-1 and muscle research: July 21-27, 2026

GLP-1 and GIP receptor agonism does not directly drive skeletal muscle atrophy or impair myogenesis in primary human myotubes Preprint

Preprint · 2026-07-23 · Ditchfield C et al.

This preprint used primary human myotubes isolated from older adults with obesity to test whether semaglutide or GIP directly causes muscle atrophy or impairs myogenesis. Neither treatment altered atrophy-related gene expression, the secretome, myotube thickness, or differentiation. Semaglutide did reduce glycolytic and total ATP production rates with reduced lactate secretion, though mitochondrial parameters were unaffected. GIP modestly increased myotube thickness after eight days. The authors conclude that lean mass loss with incretin-based therapies is unlikely to be driven by direct pharmacological action on skeletal muscle. Note: this is a preprint and a cell-culture study.

Why it matters: Directly addresses the mechanistic question of whether GLP-1 and GIP receptor agonists cause muscle loss through a direct effect on muscle cells, pointing instead toward indirect factors such as caloric restriction and reduced mechanical loading.

What this means for you: This adds to the case for maintaining resistance training during GLP-1 therapy, since lean mass loss appears more likely to reflect reduced mechanical loading than a direct drug effect on muscle.

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The MUSCLE-GLP1-CKD study: design and rationale of a prospective real-world cohort evaluating muscle health during GLP-1 receptor agonist therapy in chronic kidney disease and type 2 diabetes Preprint

Preprint · 2026-07-23 · Macía-Heras M et al.

This preprint describes the design and rationale of MUSCLE-GLP1-CKD, a prospective real-world observational cohort study following adults with CKD stages 3a–4 and type 2 diabetes for 12 months. Participants initiating semaglutide will be compared to non-exposed controls, with the primary outcome being the 12-month change in appendicular skeletal muscle mass index measured by bioelectrical impedance analysis. Secondary outcomes include handgrip strength, Short Physical Performance Battery scores, gait speed, sarcopenia status, and cardiometabolic variables. The authors note that the impact of GLP-1 receptor agonists on muscle in moderate-to-advanced CKD remains insufficiently characterized. Note: this is a preprint describing a study protocol; no results are yet available.

Why it matters: This is one of the first prospectively designed, real-world studies to systematically track muscle mass, strength, and physical function during GLP-1 receptor agonist therapy in a population at particularly high risk for sarcopenia.

What this means for you: This is one more reason to monitor grip strength and functional performance regularly during GLP-1 therapy, especially for those with kidney disease or other sarcopenia risk factors.

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Negative effects of semaglutide on bone in obese mice.

Cell reports. Medicine · 2026-06-18 · Eisner K et al.

This mouse study found that semaglutide reduced femur mass, stiffness, and strength in obese male C57BL/6J mice, and these decrements were more pronounced than in mice calorically restricted to the same degree of weight loss. Markers of osteoblast activity were also lower in semaglutide-treated animals. In a follow-up cohort, bone parameters did not recover six weeks after drug discontinuation compared to vehicle. The authors call for clinical investigations to determine whether similar effects occur in humans. Note: this is an animal study.

Why it matters: The finding that semaglutide may reduce bone strength beyond what caloric restriction alone explains raises a concern about skeletal integrity that is distinct from, but closely related to.

What this means for you: Worth discussing with a prescribing clinician, particularly for individuals already at elevated risk for bone loss.

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Dronedarone hydrochloride reverses obesity-related metabolic syndrome while preserving skeletal muscle mass Preprint

Preprint · 2026-07-23 · Lei J et al.

This preprint reports that dronedarone hydrochloride, an anti-arrhythmic drug, reduced food intake, visceral and subcutaneous fat, and reversed steatohepatitis in diet-induced and ob/ob obese mice. In head-to-head comparisons with semaglutide, tirzepatide, and empagliflozin, dronedarone achieved comparable glycemic control and fat reduction but, unlike the comparators, fully preserved skeletal muscle mass. The abstract states that muscle loss accounted for up to 40% of reduced weight with GLP-1 receptor agonists in this model. Note: this is a preprint and an animal study; no human data are presented.

Why it matters: The direct comparison of skeletal muscle mass preservation between dronedarone and GLP-1/GIP receptor agonists in an animal model quantifies the lean mass loss concern and highlights it as a distinguishing feature of current therapies.

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