Urinary cystatin C as a potential risk marker for cardiovascular disease and chronic kidney disease in patients with obesity and metabolic syndrome

Background and Objectives: Obesity and metabolic syndrome (MS) increase the risk of cardiovascular disease (CVD), chronic kidney disease (CKD), and all-cause mortality. Serum cystatin C (S-CysC), a marker of GFR, has been shown to be associated with CVD and CKD. This study was designed to elucidate the association of urinary CysC (U-CysC), a marker of renal tubular dysfunction, with CVD and CKD risk factors in patients with obesity and MS. Design, setting, participants, & measurements: The U-CysC-creatinine ratio (UCCR) was examined in 343 Japanese obese outpatients enrolled in the multi-centered Japan Obesity and Metabolic Syndrome Study. Results: UCCR was positively correlated with urine albumin-creatinine ratio (UACR) and S-CysC and negatively correlated with estimated GFR (eGFR). Among obese patients, UCCR was significantly higher in MS patients than in non-MS patients. UCCR had significant correlations with the number of components of MS and arterial stiffness, all of which are CVD predictors, similarly to UACR (P < 0.05). Interestingly, diet- and exercise-induced weight reduction for 3 months significantly decreased only UCCR among all of the renal markers examined (P < 0.01), in parallel with the decrease in BMI, HbA1c, and arterial stiffness, suggesting the beneficial effect of weight reduction on renal tubular dysfunction. Conclusions: This study demonstrates that UCCR is significantly associated with renal dysfunction, the severity of MS, arterial stiffness, and weight change in obese patients. The data of this study suggest that UCysC could serve as a CVD and CKD risk factor in patients with obesity and MS.