Semaglutide-induced weight loss improves mitochondrial energy efficiency in skeletal muscle

Abstract

Objective: Glucagon-like peptide 1 receptor agonists (e.g. semaglutide) potently induce weight loss and thereby reducing obesity-related complications. However, weight regain occurs when treatment is discontinued. An increase in skeletal muscle oxidative phosphorylation (OXPHOS) efficiency upon diet-mediated weight loss has been described, which may contribute to reduced systemic energy expenditure and weight regain. We set out to determine the unknown effect of semaglutide on muscle OXPHOS efficiency.

Methods: C57BL/6J mice were fed a high-fat diet for 12 weeks before receiving semaglutide or vehicle for 1 or 3 weeks. The rate of ATP production and O₂ consumption were measured by a high-resolution respirometry and fluorometry to determine OXPHOS efficiency in skeletal muscle at these 2 timepoints.

Results: Semaglutide treatment led to significant reductions in fat and lean mass. Semaglutide improved skeletal muscle OXPHOS efficiency, measured as ATP produced per O₂ consumed (P/O) in permeabilized muscle fibers. Mitochondrial proteomic analysis revealed changes restricted to two proteins linked to complex III assembly (Lyrm7 and Ttc1, p <0.05 without multiple corrections) without substantial changes in the abundance of OXPHOS subunits.

Conclusions: These data indicate that weight loss with semaglutide treatment increases skeletal muscle mitochondrial efficiency. Future studies could test whether it contributes to weight regain.

Keywords: OXPHOS; energy efficiency; mitochondria; obesity; semaglutide; weight loss.

Figure 1.. Semaglutide induces weight loss in overweight mice.

(A) Schematic of the experimental design. Twenty-week-old C57BL/6J mice were fed 42% HFD diet for 12 weeks before semaglutide (3 nmol/kg of body weight/day) intervention. Semaglutide was subcutaneously injected daily for 1 or 3 weeks. Vehicle groups received an equal volume of PBS. (B) Body weight was recorded every week. (C) Percent change in body weight after semaglutide treatment was calculated from the baseline of 12-wk HFD. (D) Fat mass was determined by NMR before and after treatment. (E) Percentage change in fat mass was analyzed by NMR. (F) Lean mass was determined by NMR before and after treatment. (G) Percentage change in lean mass was calculated by NMR. (H) After the completion of semaglutide treatment, gastrocnemius muscles were harvested, and wet weight was measured. Data are represented as mean± SEM. * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001 significant difference vs. corresponding controls. ## p<0.01, ### p<0.001 significant difference vs. vehicle3wk. N=8 and 9 for vehicle-1wk and vehicle-3wk, respectively, and N=11 for both semaglutide 1-wk and 3-wk.

Figure 2.. Semaglutide treatment increases skeletal muscle OXPHOS energy efficiency.

A small piece of red gastrocnemius was collected and permeabilized in the buffer with saponin (30 μg/ml). (A and B) The rate of ATP production (JATP) was determined by fluorometer. (C and D) Mitochondrial O₂ consumption (JO₂) was analyzed by high-resolution respirometry. (E and F) OXPHOS efficiency was determined as P/O ratio. (G and H) Abundance of OXPHOS subunits in whole lysate of gastrocnemius muscle was determined by Western blot. Data are represented as mean± SEM. * p<0.05 significant difference vs. corresponding controls. N=10 and 13 for vehicle-1wk and vehicle-3wk and N=10 and 14 for semaglutide 1-wk and 3-wk, respectively.

Figure 3.. Semaglutide-induced increase in mitochondrial OXPHOS efficiency is NOT observed when quantified in isolated mitochondria from skeletal muscle.

Mitochondria were isolated from whole gastrocnemius muscle. (A and B) The rate of ATP production (JATP) was determined by fluorometer. (C and D) Mitochondrial O₂ (JO₂) consumption was analyzed by high-resolution respirometry. (E and F) OXPHOS efficiency was determined as P/O ratio. (G and H) Abundance of OXPHOS subunits in isolated mitochondria from gastrocnemius muscle was determined by Western blot. Data are represented as mean± SEM. N=12 and 13 for vehicle-1wk and vehicle-3wk, respectively, and N=15 for both semaglutide 1-wk and 3-wk.

Figure 4.. Semaglutide treatment does not alter skeletal muscle mitochondrial supercomplexes formation.

(A-F) Mitochondrial supercomplexes formations were analyzed by Native PAGE and quantified. (G) Representative mitochondrial morphology analyzed by electron microscopy. All data are from 3-wk semaglutide treatment. N=6 for both vehicle and semaglutide for Native PAGE.

Figure 5.. Semaglutide-induced weight loss does not robustly influence the abundances of OXPHOS subunits.

(A) Relative abundance of mitochondrial lipids. (B) Principal component analysis of mitochondrial proteomic data. (C) Volcano plot of differentially abundant mitochondria proteins between vehicle (Veh) and semaglutide (Sema) groups. (D-H) Heatmap of abundance of OXPHOS subunits determined by mass spectrometry. All data are from 3-wk semaglutide treatment. N=6 for both vehicle and semaglutide.