# Serum Growth Differentiation Factor 8 (Myostatin) Concentrations in Cats with Early-Stage Chronic Kidney Disease

## TL;DR

This study found that GDF8 levels in cats with early-stage kidney disease are not higher than in healthy cats, but they decrease with muscle loss and age.

## Contribution

The study is the first to evaluate serum GDF8 concentrations in cats with early-stage CKD, revealing its potential as a muscle mass marker.

## Key findings

- GDF8 levels were not different between healthy and early-stage CKD cats.
- GDF8 levels decreased with advanced muscle wasting and increased age.
- No association was found between GDF8 and kidney function markers.

## Abstract

Chronic kidney disease (CKD) is a progressive and prominent disease in cats. Muscle wasting is a common consequence of CKD, with weight loss occurring in the earlier stages of kidney disease. Growth differentiation factor 8 (GDF8) is a protein regulator of muscle growth that promotes muscle breakdown and inhibits muscle synthesis. In people with CKD, GDF8 has been shown to be elevated in serum blood samples. These levels, however, have not been evaluated before in cats with CKD. In this study, GDF8 levels were measured in serum blood samples from healthy cats and cats with International Renal Interest Society stage 1 and stage 2 CKD using a multispecies enzyme-linked immunosorbent assay. GDF8 levels were not different amongst healthy and CKD cats. GDF8 levels were also not different across other markers of kidney function. GDF8 levels decreased with advanced muscle wasting, identifying GDF8 as a potential marker of muscle mass in cats. GDF8 levels also decreased with the age of the cats. With variability in GDF8 production and excretion and potential influence from tissues outside the kidney, further investigation of the role of GDF8 in muscle regulation and cats with CKD is warranted.

Weight loss occurs with chronic kidney disease (CKD) and is present in the early stages. Growth differentiation factor 8 (GDF8), also known as myostatin, is a negative regulator of muscle growth, and circulating GDF8 concentrations are increased in people with CKD. The objective of this study was to evaluate if serum GDF8 concentrations in cats with early CKD are increased compared to healthy cats. Associations of GDF8 with age, sex, body weight, body condition score (BCS), muscle condition score (MCS), and selected renal parameters were also examined. Serum GDF8 in healthy (n = 10), International Renal Interest Society (IRIS) stage 1 CKD (n = 5), and IRIS stage 2 CKD (n = 10) cats was quantified using a commercially available sandwich ELISA. GDF8 was not different amongst healthy cats (2137 ± 740 pg/mL) and cats with IRIS stage 1 (1785 ± 530 pg/mL) and IRIS stage 2 (1961 ± 638 pg/mL; p = 0.608) CKD. GDF8 was moderately correlated with MCS (rs = 0.517, 95% CI 0.006–0.814, p = 0.049) and inversely correlated with age (r = −0.429, 95% CI −0.705 to −0.041, p = 0.032), but no association was found with the selected renal parameters, body weight, or BCS.