Abstract Body: Type 2 diabetes mellitus (T2DM) patients have a higher risk of heart failure and cause cardiomyopathy without other cardiac disease. There is no specific biomarker for discriminating patients with diabetic cardiomyopathy (DCM). In this study, we investigated the cereblon (CRBN) level in mice and human samples to determine its potential as a biomarker for early detection of diabetic cardiomyopathy (DCM). C57BL/db/db male mice at 6 and 8 weeks of age, as the early DCM model with obesity and T2DM were investigated. We confirmed that mitochondrial function was decreased in the 8 weeks old db/db mice without alterations of cardiac function and structures. Compared to the control mice, CRBN protein level was significantly increased and phosphorylation of AMPK, a negative regulator by CRBN, was significantly decreased in the heart tissue of 8 weeks old db/db mice. Blood CRBN level was also significantly increased in both 6 and 8 weeks old db/db mice compared with control mice. In blood of diabetic patients, CRBN level was significantly correlated with IL-6, IL-1b, TNF-a, IGFBP-7, and adiponectin, which are previously reported biomarkers of DCM. However, CRBN level was not correlated with cardiac troponin I, NT-proBNP, and ST2, which are biomarkers of myocardial injury and heart failure. Furthermore, the CRBN level showed a higher tendency in patients with diastolic dysfunction without systolic dysfunction compared to patients with normal function and systolic dysfunction, although the difference was not statistically significant. In conclusion, cardiac mitochondrial dysfunction occured and CRBN levels of heart and blood increased prior to cardiac functional and structural changes in the early DCM mouse model, and CRBN might serve as a potential biomarker for the early detection of DCM in T2DM patients.