Plasma Activin A concentrations are not a useful biomarker for detecting insulin dysregulation and predicting laminitis risk in ponies.

BACKGROUND

Circulating insulin concentrations are used to quantify risk of laminitis in currently non-laminitic ponies. Basal serum activin A (AA) concentration has previously been positively correlated with serum insulin concentrations 60 minutes (T60) following an oral sugar test (OST) in ponies with equine metabolic syndrome. Therefore, circulating AA might be a useful marker for insulin dysregulation (ID) and laminitis risk.

OBJECTIVES

To explore the relationship between circulating AA concentrations at baseline (T0) and T60 in ponies that developed laminitis within six months and non-laminitic ponies.

METHODS

Case-control study. Forty-three ponies that developed laminitis (PLP) during a four-year surveillance period were selected from a larger cohort; 43 ponies from the same cohort that remained non-laminitic (NLP) were selected as controls. Plasma AA concentrations were measured using a validated ELISA at T0 and T60 and compared between groups at both time points using a Wilcoxon signed ranks test. Correlations with other previously measured metabolic markers were investigated using Spearman's rank correlation coefficients.

RESULTS

There was a significant difference between T0 plasma AA (median 8.8; interquartile range [6.2, 13.1]ng/mL) and T60 (13.1; [8.8, 20.1]ng/mL) within the NLP group (P= <0.001) and between plasma AA at T0 (7.4 [5.5, 12.4]ng/mL) and T60 (12.3 [6.9, 16.6]ng/ml) in the PLP group (P= <0.001). There were no significant correlations between plasma AA (T0 or T60) and any other measured metabolic marker. Single timepoints and retrospective analysis were the main limitations.

CONCLUSION

Plasma AA concentration is not a useful marker for ID or predicting laminitis development in ponies.