# Evaluation of myeloid-related protein 126, cardiac troponin C and serum amyloid A as potential plasma biomarkers of health and disease in sea turtles

## TL;DR

This study evaluates three proteins as potential biomarkers to assess the health of sea turtles, finding that myeloid-related protein 126 shows promise in distinguishing healthy from diseased individuals.

## Contribution

The study introduces myeloid-related protein 126 as a novel potential biomarker for sea turtle health.

## Key findings

- Myeloid-related protein 126 levels were significantly lower in healthy and recovered turtles compared to moribund ones.
- Cardiac troponin C was higher in moribund turtles but not predictive of health status.
- Serum amyloid A showed high variability but no significant correlations with health indicators.

## Abstract

Sea turtle health assessments can be strengthened by developing conserved biomarkers that discriminate between healthy and diseased states. Serum amyloid A, myeloid-related protein 126 and cardiac troponin C (CTNC) were explored as potential biomarkers of sea turtle health. Plasma concentrations initially quantified using a targeted SPARCL™ assay significantly differed between moribund (n = 15) and recovered (n = 5) loggerhead turtles (Caretta caretta). There was a negative correlation between myeloid-related protein 126 and packed cell volume (r = −0.612, P = 0.005) and total solids (r = −0.497, P = 0.03) and between and Fulton’s body condition index (r = −0.684, P = 0.001). Serum amyloid A showed a relatively high interquartile range (IQR) in moribund turtles and no significant correlations with clinical parameters. Myeloid-related protein 126 and cardiac troponin C were further evaluated by an enzyme-linked immunosorbent assay in a larger dataset of loggerhead, Kemp’s ridley (Lepidochelys kempii) and green (Chelonia mydas) turtles. Plasma myeloid-related protein 126 was significantly lower in captive healthy (n = 7) and recovered (n = 23) turtles than in moribund (n = 25) and nesting green (n = 58) turtles. Green turtles with fibropapillomatosis (n = 10) were not significantly different from any group. Discriminating values between healthy/recovered and moribund turtles were 1.89 and 1.97 ng/ml by receiver operating characteristic and logistic regression analyses, respectively. Myeloid-related protein 126 decreased in successfully rehabilitated turtles (n = 18 turtles; n = 67 blood samples) and was negatively correlated with body condition score (r = −0.672, P < 0.001) and packed cell volume (r = −0.443, P = 0.009). Cardiac troponin C was significantly higher (P = 0.049) in moribund turtles (n = 16) compared to healthy/recovered turtles (n = 7) and in moribund samples (n = 11) compared to recovered samples (n = 11) in serially sampled turtles (P = 0.015), but was not predictive of health status. Myeloid-related protein 126 represents a strong biomarker candidate in sea turtles. Cardiac troponin C warrants further evaluation in a larger dataset and serum amyloid A requires examination of variables affecting pathophysiologic responses in sea turtles.