Association of Difference Between eGFR From Cystatin C and Creatinine and Serum GDF-15 With Adverse Outcomes in Diabetes Mellitus.

BACKGROUND: Protein catabolism and chronic inflammation drive sarcopenia and frailty in individuals with diabetes mellitus and chronic kidney disease (CKD). The difference between estimated glomerular filtration rates derived from cystatin C and creatinine (eGFRcys and eGFRcr, respectively), termed eGFRdiff, along with growth differentiation factor-15 (GDF-15) levels, have emerged as markers of metabolic and inflammatory dysregulation. Lower eGFRdiff and elevated GDF-15 levels are associated with sarcopenia, frailty, CKD progression and mortality. However, their interplay and respective impacts on CKD progression and mortality remain unclear. METHODS: A total of 638 Japanese individuals with diabetes mellitus were stratified into tertiles based on eGFRdiff. Serum GDF-15 levels were measured using enzyme-linked immunosorbent assays. The relationships between eGFRdiff and GDF-15 were assessed using Spearman's correlation coefficients. Multivariate ordered logistic regression was used to evaluate the association between eGFRdiff and GDF-15 tertiles, with GDF-15 as the dependent variable and eGFRdiff as the independent variable, adjusting for covariates including age, sex, urinary albumin-to-creatinine ratio (UACR) and eGFRcr or eGFRcys. Cox proportional hazards models with restricted cubic splines were used to examine associations between eGFRdiff and GDF-15 (independent variables) with CKD progression (≥ 30% decline in eGFRcr from baseline) and mortality (dependent variables). These models were adjusted for age, sex, glycated haemoglobin, UACR and eGFRcr. RESULTS: The median age was 65 years (interquartile range: 58-73), and 53.9% of participants were male. Over median follow-up periods of 5.3 years for CKD progression and 5.4 years for mortality, 75 participants (11.8%) experienced CKD progression and 44 (6.9%) died. GDF-15 levels inversely correlated with eGFRdiff (r = -0.35, p < 0.001). Higher eGFRdiff values were associated with lower odds of being in a higher GDF-15 tertile (odds ratio 0.86; 95% confidence interval [CI]: 0.76-0.97; p = 0.01). Both lower eGFRdiff and higher GDF-15 levels were independently associated with adverse outcomes: CKD progression (GDF-15, hazard ratio [HR] 1.36, 95% CI: 1.02-1.81, p < 0.05; eGFRdiff, HR 0.67, 95% CI: 0.58-0.78, p < 0.0001) and mortality (GDF-15, HR 2.35, 95% CI: 1.63-3.41, p < 0.0001; eGFRdiff: 0.80, 95% CI: 0.65-0.99, p < 0.05). CONCLUSIONS: Both eGFRdiff and GDF-15 were independently associated with adverse outcomes in individuals with diabetes mellitus. GDF-15 showed a stronger association with mortality, whereas eGFRdiff was more strongly linked to CKD progression. These findings underscore the potential utility of these markers in risk stratification for diabetes-related complications and may guide individualized interventions in clinical practice.