Skeletal muscle glycolytic capacity and phosphofructokinase regulation in horses with polysaccharide storage myopathy.

The research investigates whether a disease in horses known as polysaccharide storage myopathy (PSSM) is caused by a defect in the process of glycolysis or the regulation of an enzyme called phosphofructokinase. The study found no abnormalities or deficiencies in either of these areas, suggesting that these are not responsible for PSSM in horses.

Objective of the Research

• The primary objective of this research was to determine whether polysaccharide storage myopathy (PSSM) in horses, specifically Quarter Horses, is due to a defect in the glycolytic process or in the allosteric regulation of an enzyme referred to as phosphofructokinase (PFK).

Research Method

• The researchers conducted muscle biopsy samples from 6 Quarter Horses diagnosed with PSSM and another 8 from Quarter Horse or Thoroughbred control horses.
• They established the maximal activity of glycogenolytic and glycolytic enzymes through a spectrophotometric method.
• The researchers also determined the maximal activity of PFK under two different conditions of acidity (pH), with pH 8.0 and 7.0. They also varied the concentrations of activators and inhibitors added to the reaction mixture for the PFK enzyme.
• The relative activity of the PFK was then calculated using the measured activity at pH 7 divided by the maximum PFK activity.

Research Findings

• The study found no notable deficiencies in either glycogenolytic or glycolytic enzyme activities in horses affected by PSSM.
• The relative activity of PFK in horses with PSSM did not show any striking difference when compared to control horses, regardless of the activators or inhibitors used in the experiment.

Conclusions

• The research concludes that, within the group of horses with PSSM studied, they did not find any discernible deficiencies or abnormalities in either the glycogenolytic or glycolytic enzymes or in the allosteric regulation of PFK.
• The findings imply that although PSSM appears clinically and histologically similar to glycogenolytic/glycolytic enzyme deficiencies found in humans and other animal species, these abnormalities in the metabolic pathway do not lead to PSSM in horses.