Urinary Titin Level Is a Novel Marker of Severe Sarcopenia and Dynapenia: Shimane CoHRE Study

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Background In an aging society, it is important to intervene and prevent sarcopenia and dynapenia from an early stage. However, biochemical markers for screening sarcopenia and dynapenia have not yet been established. In this study, we hypothesized that the urinary titin level in participants undergoing health checkups would be a useful marker for sarcopenia/dynapenia. Methods This study included 445 individuals who participated in a health checkup in Okinoshima Town, Shimane Prefecture, Japan, in June 2023. Skeletal muscle mass (SMI/skeletal muscle index), muscle strength (handgrip strength), and physical performance (usual gait speed) were measured. Urinary titin levels were determined using enzyme‐linked immunosorbent assay (ELISA) and corrected for creatinine. Results The participants' mean age was 75.3 ± 8.4 years, and 40% were men. The median urinary titin levels (interquartile range [IQR]) were 4.66 (2.91–8.37) pmol/mg Cr, and no difference was observed between men and women. Although urinary titin levels were not significantly correlated with SMI (r = 0.061, p = 0.199), they were negatively correlated with gait speed significantly (r = −0.201, p < 0.001) and handgrip strength, albeit at a borderline level (r = −0.093, p = 0.051). When classified into non‐sarcopenia, mild sarcopenia, and severe sarcopenia, urinary titin levels (IQR) were 4.60 (2.84–7.84), 4.36 (3.12–7.32), and 8.68 (4.74–11.70), respectively. Participants with severe sarcopenia had significantly higher levels than those in other groups (p < 0.01 vs. non‐sarcopenia, p < 0.05 vs. mild sarcopenia). The receiver operating characteristic (ROC) curve for severe sarcopenia showed the area under the curve (AUC) value of 0.69 (95% confidence interval [CI] 0.57–0.80). Urinary titin levels were also significantly higher in the dynapenia than in the non‐dynapenia (p < 0.001). Conclusions Urinary titin levels are good markers of physical performance and muscle strength. Elevated urinary titin levels were found in an elderly population with severe sarcopenia/dynapenia, suggesting that titin may be useful as a biochemical marker for a severe sarcopenia/dynapenia screening tool.