Influence of Weight Loss on Skeletal Muscle Mitochondrial Function in the Mature Horse
Authors: Zambito J, Nichols C, Barnes K, Spooner H, Hollander J
Journal: Equine Veterinary Journal
Summary
# Editorial Summary: Weight Loss and Equine Muscle Mitochondrial Function Obesity-related metabolic complications in horses are well documented, yet the mechanisms by which weight loss restores cellular function remain poorly characterised. Zambito and colleagues examined how reducing body condition score from obese (7–8) to moderate (5) affected mitochondrial populations within the middle gluteal muscle of eight light-type horses, specifically comparing subsarcolemmal (SSM) and interfibrillar (IFM) mitochondria through differential centrifugation and enzyme assays. Weight loss produced meaningful physiological improvements: plasma nitrate markers decreased and erythrocyte glutathione increased, whilst lipid peroxidation was significantly reduced (P = 0.01–0.02), indicating improved oxidative stress status. Critically, interfibrillar mitochondria demonstrated greater sensitivity to weight loss than their subsarcolemmal counterparts, with complex IV activity showing the most pronounced changes—a finding suggesting that IFM dysfunction may be a key pathological feature of equine obesity. These findings imply that monitoring mitochondrial responsiveness during weight management programmes could help practitioners tailor interventions for obese horses and better predict metabolic recovery, particularly in those intended for performance.
Read the full abstract on the publisher's site
Practical Takeaways
- •Weight loss in obese horses improves cellular oxidant status and reduces lipid peroxidation, supporting metabolic health benefits of conditioning programs
- •Different mitochondrial populations respond distinctly to weight loss, which may explain variable performance recovery rates in individual horses during rehabilitation
- •Monitoring weight loss progression by BCS rather than absolute weight may be more physiologically relevant for assessing metabolic improvements in obese horses
Key Findings
- •Interfibrillar mitochondria (IFM) showed significantly decreased electron transport chain complex activity with weight loss, particularly complex IV, while subsarcolemmal mitochondria (SSM) were less affected
- •Plasma nitrate decreased and erythrocyte glutathione increased during weight loss from BCS 7-8 to BCS 5, indicating improved oxidant status
- •Lipid peroxidation decreased with both BCS reduction and percent weight loss, with greater baseline amounts in SSM than IFM
- •Mitochondrial number (citrate synthase activity) remained unchanged during weight loss, suggesting altered function rather than mitochondrial proliferation