TTN and metabolic dysfunction-associated steatotic liver disease: During muscle proteolysis, titin is degraded into a smaller 25 kDa fragment to form titin N-terminal fragment (TNTF) which is excreted in the urine and is an effective biomarker used to assess muscle proteolytic degradation and atrophy in clinical situations such as interstitial lung disease [20], non-alcoholic fatty liver disease [21], and post-intensive care syndrome [22].