Biochemical and genetic evaluation of the role of AMP-activated protein kinase in polysaccharide storage myopathy in Quarter Horses.

OBJECTIVE

To evaluate whether biochemical or genetic alterations in AMP-activated protein kinase (AMPK) play a role in the development of polysaccharide storage myopathy (PSSM) in Quarter Horses.

ANIMALS: 30 PSSM-affected and 30 unaffected (control) Quarter Horses.

PROCEDURES: By use of an established peptide phosphotransfer assay, basal and maximal AMPK activities were measured in muscle biopsy samples obtained from 6 PSSM-affected and 6 control horses. In 24 PSSM-affected and 24 control horses, microsatellite markers identified from the chromosomal locations of all 7 AMPK subunit genes were genotyped with a fluorescent DNA fragment analyzer. Alleles of 2 of the AMPK gamma subunit genes were genotyped via DNA sequencing. Allele frequencies of DNA markers in or near the AMPK subunit genes were measured in isolated genomic DNA.

RESULTS

No differences in basal or maximal muscle AMPK enzyme activities between PSSM-affected and control horses were detected. There were also no differences in allele frequencies for microsatellite markers near any of the 7 AMPK subunit genes between the 2 groups. Furthermore, previously known and newly identified alleles of 2 equine AMPK gamma subunit genes were also not associated with PSSM.

CONCLUSIONS AND CLINICAL RELEVANCE: These results have provided no evidence to indicate that AMPK plays a causative role in PSSM in American Quarter Horses.