Cardiovascular risk and renal injury profile in subjects with type 2 diabetes and non-albuminuric diabetic kidney disease

Background: In the last years, the classical pattern of diabetic kidney disease (DKD) has been partially overcome, because of the uncovering of a new DKD phenotype with significant renal dysfunction without presence of albuminuria: the non-albuminuric DKD (NA-DKD). To date, the cardiovascular risk associated with this phenotype is still debated. We investigated the cardiovascular risk and renal injury profile of NA-DKD subjects in comparison with other DKD phenotypes.Methods: Pulse wave velocity (PWV), intima-media thickness, presence of carotid atherosclerotic plaque, renal resistive index (RRI), and a panel of urinary biomarkers of kidney injury were evaluated in 160 subjects with type 2 diabetes, stratified according to estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (UACR) into four groups: controls (UACR < 30 mg/g and eGFR >= 60 mL/min/1.73 m(2)), A-DKD (Albuminuric-DKD, UACR >= 30 mg/g and eGFR >= 60 mL/min/1.73 m(2)), NA-DKD (UACR < 30 mg/g and eGFR < 60 mL/min/1.73 m(2)), AL-DKD (Albuminuric and Low eGFR-DKD; UACR >= 30 mg/g and eGFR < 60 mL/min/1.73 m(2)).Results: Subjects with NA-DKD showed a higher PWV (11.83 +/- 3.74 m/s vs. 10.24 +/- 2.67 m/s, P = 0.045), RRI (0.76 +/- 0.11 vs. 0.71 +/- 0.09, P = 0.04), and prevalence of carotid atherosclerotic plaque (59% vs. 31%, P = 0.009) compared with controls. These characteristics were similar to those of subjects with AL-DKD, whereas the profile of A-DKD subjects was closer to controls. After multiple regression analyses, we found that RRI, that is in turn influenced by eGFR (beta = - 0.01, P = 0.01), was one of the major determinants of PWV (beta = 9.4, P = 0.02). Urinary TreFoil Factor 3, a marker of tubular damage, was higher in NA-DKD subjects vs. controls (1533.14 +/- 878.31 ng/mL vs. 1253.84 +/- 682.17 ng/mL, P = 0.047). Furthermore, after multiple regression analyses, we found that urinary osteopontin was independently associated with PWV (beta = 2.6, P = 0.049) and RRI (beta = 0.09, P = 0.006).Conclusions: Our data showed a worse cardiovascular and renal injury profile in NA-DKD subjects. This finding emphasizes the central role of eGFR in the definition of cardiovascular risk profile of diabetic subjects together with albuminuria.