Background: Serum cystatin C (sCys C) has been proposed as a marker of kidney function with advantages compared to creatinine. It is unclear whether renal damage begin in prediabetes (PDM), when sCys C could be a promisor marker of early kidney dysfunction. We investigated whether sCys C differed between normoglycemic (NG) and PDM subjects and contributed to the detection of kidney dysfunction.

Methods: A cross-sectional analysis of 947 nondiabetic participants (mean age 45.7 years) from the Brazilian Longitudinal Study of Adult Health was performed. sCys C (determined by ELISA) and CKD-EPI eGFR were compared between NG and PDM (fasting plasma glucose: 100-125 mg/dL or 2-hour post-load: 140-199 mg/dL or A1c: 5.7-6.4%). PDM were stratified in 4 groups according to altered sCys C and albumin excretion rate (AER): normal sCys C and AER (G1), abnormal sCys C and normal AER (G2), normal sCys C and abnormal AER (G3) and abnormal sCys C and AER (G4) were compared using ANOVA.

Results: PDM subjects (n = 671) had anthropometric and biochemical data higher than NG (n=276), higher sCys C levels [0.67 (0.41-0.95) vs. 0.48 (0.31-0.81), p<0.001] and lower eGFR (96.3±17.4 vs. 100.6±17.1 mL/min/1.73m2, p<0.001). In eGFR categories (60-<90, 90-<125 and ≥125 mL/min/1.73m2), sCys C were always higher in PDM subjects than in NG. Comparing NG individuals, hyperfiltrants had lower sCys C than normofiltrants (p=0.03) but not than mildly reduced eGFR individuals (p=0.12). Considering the PDM groups, eGFR gradually dropped from G1 to G4 (96.8±17.4 vs. 96.2±16.9 vs. 94.0±17.2 vs. 77.2±25.4 mL/min/1.73m2, p-trend = 0.06) and, as expected, mean eGFR in G4 was lower than in G1 (p=0.017).

Conclusion: Our data confirmed that sCys C is increased in PDM. Reduced sCys C only in NG hyperfiltrant subjects could suggest an inability of hyperfiltrant PDM to excrete Cys C. No statistical evidence that sCys C could be an early marker of kidney dysfunction in prediabetes was found; prospective studies should address its utility to detect dysfunction before AER elevation.

Disclosure

J.I.F. Branda: None. B. Almeida: None. S.R.G. Vivolo: None.

© 2019 by the American Diabetes Association.
2019
Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at http://www.diabetesjournals.org/content/license.