Insulin sensitivity and skeletal muscle glucose transport in horses with equine polysaccharide storage myopathy.

The study focuses on horses with an inherited muscle disorder called equine polysaccharide storage myopathy (PSSM) and investigates their insulin sensitivity and glucose metabolism. It was observed that these horses had higher glycogen content and required more glucose to maintain normal blood sugar levels.

Objective of the Study

• The main aim of the study was to understand the in vivo insulin sensitivity and glucose responses in horses affected by equine polysaccharide storage myopathy (PSSM). This analysis was done using a method called euglycemic hyperinsulinemic clamp.
• In addition, the study also sought to determine the levels of muscle glucose transporters (GLUT1 and GLUT4) and the insulin receptor in the muscle tissues of these horses using Western blot analysis.

Key Findings

• Comparing to healthy horses, horses with PSSM showed 1.8-fold higher glycogen content in their muscles. Plus, the polysaccharide analyzed in equine PSSM was less branched.
• During the clamp test, it was observed that these horses required a higher rate of glucose infusions to maintain euglycemia (normal levels of glucose in blood).
• Although the content of GLUT1 (one type of glucose transporter) was lower in horses with PSSM, they displayed no differences in the total amounts of GLUT4 (another kind of glucose transporter) and insulin receptors compared to control horses.

Conclusion

• The researchers concluded that PSSM represents a unique disorder where increased insulin sensitivity and elevated glucose response, which normally would lead to glycogen storage, results in increased muscle glycogen synthesis. This is largely irrespective of increased GLUT4 or insulin receptor quantities.
• Thus, PSSM could be characterized by metabolic abnormalities including heightened insulin sensitivity and unusual glucose metabolism patterns.