Pre-Dialysis Serum Myostatin Concentration Is Independently Associated with Intradialytic Muscle Cramps in Hemodialysis Patients

Muscle cramps are among the most common acute complications of hemodialysis (HD), often occurring even in the absence of electrolyte disturbances. Most cramps are painful and may cause patients to fear future dialysis sessions. We hypothesized that susceptibility to muscle cramps may be related to impaired skeletal muscle myokine secretion. No significant differences in pre-dialysis myokine levels were observed between patients with and without muscle cramps (myostatin 36.2 vs. 86.9 (p = 0.09), fibronectin type III domain-containing protein 5 (FNDC5) 0.6 vs. 0.6 (p = 0.61), interleukin-6 (IL-6) 2.4 vs. 2.0 (p = 0.4). However, after adjustment for lean tissue mass (LTM) and lean tissue index (LTI), myostatin levels were significantly lower in patients with cramps (0.80 [0.35–1.84] vs. 1.49 [0.45–6.31], respectively, (p = 0.048) for LTM, and 2.26 [1.04–4.06] vs. 3.89 [1.52–19.47], respectively, (p = 0.04) for LTI). In multivariable logistic regression analysis, log2-transformed myostatin concentration was independently and inversely associated with muscle cramps after adjustment for dialysis vintage, body mass index (BMI), and extracellular water. No association was found between muscle cramps and ultrafiltration volume or serum sodium and potassium levels. The study included 67 hemodialysis patients (HD patients), of whom 39 experienced repeated muscle cramps during dialysis. Muscle cramps were defined as painful involuntary muscle contractions lasting more than one minute during or shortly after a dialysis session. Plasma levels of myokines—myostatin, FNDC5, and IL-6—were assessed. Pre-dialysis myostatin, but not FNDC5 or IL-6, was independently associated with the occurrence of intradialytic muscle cramps. Further studies are needed to confirm its clinical utility.