Urinary Titin on the First Postoperative Day Predicts Long-Term Skeletal Muscle Loss in Patients with Gastroenterological Cancer

Perioperative malnutrition is common in patients with gastroenterological cancer and contributes to postoperative skeletal muscle atrophy, which adversely affects their prognosis. Early assessment of skeletal muscle atrophy is crucial for improving postoperative outcomes. This study aimed to evaluate the efficacy of urinary titin as a biomarker for skeletal muscle atrophy. A prospective observational study was conducted, and a total of 34 gastroenterological cancer patients were included. Urinary titin levels were measured using ELISA at admission, postoperative days (POD) 1, 7, and 14, and at 6 months after surgery. Surgical procedure, operative time, cancer stage, postoperative complications, hospital stay, and preoperative and postoperative body composition were evaluated, along with nutritional status and grip strength from admission to 6 months after surgery. Changes in urinary titin levels were measured at the same time points as described above. Preoperatively, the mean urinary titin level was 5.03 pmol/mg Cr, slightly higher than in healthy subjects. Urinary titin peaked at 33.71 (24.30-66.58) pmol/mg/dL Cr on POD1 and was associated with serum free branched-chain amino acid concentrations. Urinary titin on POD1 was significantly correlated with a decrease in skeletal muscle mass (rs -0.361, <i>p</i> = 0.036) and body cell mass (rs -0.361, <i>p</i> = 0.038) at 6 months postoperatively. The grip strength at 6 months postoperatively tended to decrease (rs -0.342, <i>p</i> = 0.052). BMI and serum LDH at admission were associated with urinary titin on POD1 but were not correlated with skeletal muscle loss at 6 months, suggesting that urinary titin on POD1 is an independent biomarker of skeletal muscle atrophy. These data indicate that urinary titin on POD1 can predict long-term skeletal muscle atrophy.