Advertisement

Serum creatine kinase response to exercise during dexamethasone-induced insulin resistance in Quarter Horses with polysaccharide storage myopathy

Anna M. FirshmanPresent address is Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

Search for other papers by Anna M. Firshman in
Current site
Google Scholar
PubMed
Close
 BVSc, PhD
,
Stephanie J. ValbergDepartment of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

Search for other papers by Stephanie J. Valberg in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
Tami L. KargesDepartment of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

Search for other papers by Tami L. Karges in
Current site
Google Scholar
PubMed
Close
 BSc
,
Luke E. BenedictDepartment of Medicine, College of Medicine, University of Minnesota, Minneapolis, MN 55108.

Search for other papers by Luke E. Benedict in
Current site
Google Scholar
PubMed
Close
 MD
,
Erin J. AnnandaleDepartment of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

Search for other papers by Erin J. Annandale in
Current site
Google Scholar
PubMed
Close
 MS
, and
Elizabeth R. SeaquistDepartment of Medicine, College of Medicine, University of Minnesota, Minneapolis, MN 55108.

Search for other papers by Elizabeth R. Seaquist in
Current site
Google Scholar
PubMed
Close
 MD

Abstract

Objective—To determine effects of dexamethasone on insulin sensitivity, serum creatine kinase (CK) activity 4 hours after exercise, and muscle glycogen concentration in Quarter Horses with polysaccharide storage myopathy (PSSM).

Animals—4 adult Quarter Horses with PSSM.

Procedure—A 2 × 2 crossover design was used with dexamethasone (0.08 mg/kg) or saline (0.9% NaCl) solution administered IV every 48 hours. Horses were exercised on a treadmill daily for 3 wk/treatment with a 2-week washout period between treatments. Serum CK activity was measured daily 4 hours after exercise. At the end of each treatment period, serum cortisol concentrations were measured, a hyperinsulinemic euglycemic clamp (HEC) technique was performed, and muscle glycogen content was determined.

Results—Mean ± SEM serum cortisol concentration was significantly lower after 48 hours for the dexamethasone treatment (0.38 ± 0.08 mg/dL), compared with the saline treatment (4.15 ± 0.40 mg/dL). Dexamethasone significantly decreased the rate of glucose infusion necessary to maintain euglycemia during the HEC technique, compared with the saline treatment. Muscle glycogen concentrations and mean CK activity after exercise were not altered by dexamethasone treatment, compared with the saline treatment.

Conclusions and Clinical Relevance—Dexamethasone significantly reduced whole-body insulin-stimulated glucose uptake in Quarter Horses with PSSM after a 3-week period but did not diminish serum CK response to exercise or muscle glycogen concentrations in these 4 horses. Therefore, a decrease in glucose uptake for 3 weeks did not appear to alleviate exertional rhabdomyolysis in these horses. It is possible that long-term treatment may yield other results. (Am J Vet Res 2005;66:1718–1723)

Abstract

Objective—To determine effects of dexamethasone on insulin sensitivity, serum creatine kinase (CK) activity 4 hours after exercise, and muscle glycogen concentration in Quarter Horses with polysaccharide storage myopathy (PSSM).

Animals—4 adult Quarter Horses with PSSM.

Procedure—A 2 × 2 crossover design was used with dexamethasone (0.08 mg/kg) or saline (0.9% NaCl) solution administered IV every 48 hours. Horses were exercised on a treadmill daily for 3 wk/treatment with a 2-week washout period between treatments. Serum CK activity was measured daily 4 hours after exercise. At the end of each treatment period, serum cortisol concentrations were measured, a hyperinsulinemic euglycemic clamp (HEC) technique was performed, and muscle glycogen content was determined.

Results—Mean ± SEM serum cortisol concentration was significantly lower after 48 hours for the dexamethasone treatment (0.38 ± 0.08 mg/dL), compared with the saline treatment (4.15 ± 0.40 mg/dL). Dexamethasone significantly decreased the rate of glucose infusion necessary to maintain euglycemia during the HEC technique, compared with the saline treatment. Muscle glycogen concentrations and mean CK activity after exercise were not altered by dexamethasone treatment, compared with the saline treatment.

Conclusions and Clinical Relevance—Dexamethasone significantly reduced whole-body insulin-stimulated glucose uptake in Quarter Horses with PSSM after a 3-week period but did not diminish serum CK response to exercise or muscle glycogen concentrations in these 4 horses. Therefore, a decrease in glucose uptake for 3 weeks did not appear to alleviate exertional rhabdomyolysis in these horses. It is possible that long-term treatment may yield other results. (Am J Vet Res 2005;66:1718–1723)