Myofibrillar Myopathy (MFM) in Horses: A Functional Nutrition Perspective

Myofibrillar myopathy (MFM) represents a significant challenge in equine health management, particularly when approaching it from a functional nutrition standpoint. This condition, characterized by progressive muscle dysfunction, shares several similarities with Polysaccharide Storage Myopathy Type 2 (PSSM2) and is starting to be recognized as having mitochondrial dysfunction at its core. Let's explore this condition in depth, focusing on nutritional approaches that may help manage affected horses.

Understanding Myofibrillar Myopathy

Myofibrillar myopathy in horses involves the breakdown of myofibrils, the fundamental contractile units within muscle fibers. The condition manifests through various symptoms including muscle atrophy, weakness, exercise intolerance, and abnormal gait. Diagnostically, it's characterized by distinctive pathological changes in muscle tissue, with disruption and aggregation of myofibrillar proteins.

The MFM-PSSM2 Connection

The relationship between MFM and PSSM2 has become increasingly apparent in recent research. While traditional PSSM1 is linked to a specific glycogen synthase mutation, PSSM2 variants represent a more complex group of myopathies that include MFM. Both conditions share similar clinical presentations, including:

• Exercise intolerance

• Muscle stiffness and pain

• Reluctance to move forward

• Atypical hind limb gait abnormalities

• Poor muscle development despite training

Notably, both conditions can present without overt episodes of tying-up.

Mitochondrial Exhaustion as a Critical Factor

Mitochondrial dysfunction appears to be a central factor in the expression of MFM in horses. These cellular powerhouses are responsible for generating ATP, the energy currency that muscles rely on for contraction and relaxation. In MFM-affected horses, several mitochondrial issues may be present:

1. Reduced mitochondrial density in affected muscle tissue

2. Impaired mitochondrial function and energy production

3. Increased oxidative stress damaging mitochondrial membranes

4. Disrupted calcium homeostasis affecting mitochondrial activity

5. Compromised mitochondrial biogenesis (the creation of new mitochondria)

This mitochondrial exhaustion creates a cascade effect, where energy production becomes insufficient, leading to protein misfolding, aggregation, and eventually, myofibrillar damage.

Functional Nutrition Approaches for MFM

Addressing MFM through functional nutrition requires a multi-faceted approach targeting mitochondrial health, inflammation reduction, and muscle recovery:

1. Optimizing Fat Metabolism

Since affected horses often struggle with carbohydrate metabolism, shifting energy sources toward fat can be beneficial:

• High-quality, anti-inflammatory fats. However depending on the case, liver support may be needed before the horse can efficiently metabolize fats (see our blog post on horses and their missing gallbladder for more info.)

• Medium-chain triglycerides for easier utilization

• Gradual introduction to allow metabolic adaptation

  
  

2. Mitochondrial Support Nutrients

Several nutrients directly support mitochondrial function:

• Coenzyme Q10 (ubiquinol) - critical for electron transport chain

• L-carnitine - facilitates fatty acid transport into mitochondria

• D-Ribose - supports ATP regeneration

• B vitamins, especially B2 (riboflavin) and B3 (niacin) - essential for energy production

  
  

3. Antioxidant Protection

Combating oxidative stress protects mitochondrial membranes:

• Vitamin E (natural sources only, and only after testing blood values of Vitamin E AND Selenium.)

• Selenium (region-appropriate supplementation)

• Polyphenol-rich foods

• Glutathione precursors

  
  

4. Anti-inflammatory Support

Reducing systemic inflammation helps preserve muscle integrity:

• Omega-3 Fatty Acids

• Specialized herbal support

• Avoidance of pro-inflammatory feeds (excessive omega-6, high sugar/starch)

  
  

5. Protein Quality and Timing

Supporting muscle repair requires strategic protein provision:

• Essential amino acids, particularly branched-chain amino acids

• Lysine, methionine, and threonine adequacy

• Small, frequent feedings to maintain amino acid availability

  
  

Practical Implementation

A functional nutrition approach for MFM-affected horses typically includes:

1. Lower NSC (non-structural carbohydrate) forage as the foundation, eliminate all conventional grains

2. Strategic and bio-individually appropriate fat supplementation for energy needs

3. Targeted micronutrient support for mitochondrial function

4. Phased exercise protocols working within capability

5. Regular monitoring of muscle enzymes and clinical symptoms

6. Individual adjustments based on response

   
   

Beyond Nutrition: The Exercise Connection

While nutrition forms the foundation, appropriate exercise remains crucial for MFM management. The focus should be on:

• Gradual conditioning that works within current capabilities. Don't underestimate the power of the working walk!

• Emphasis on low-intensity, consistent movement

• Careful, 30-40 minutes of low intensity warm-up and cool down for every ride.

• Avoiding eccentric exercises that challenge compromised muscles

Despite being a significant challenge with parallels to PSSM2 and mitochondrial dysfunction at its core, a functional nutrition approach targeting mitochondrial health, appropriate energy sources, and strategic antioxidant support offers promising management strategies for horses affected by MFM. By understanding the complex interplay between nutrition, metabolism, and muscle function, we can develop customized approaches that can help improve quality of life and functionality in horses with this challenging condition.

Myofibrillar myopathy (MFM) represents a significant challenge in equine health management, particularly when approaching it from a functional nutrition standpoint.