The renoprotective effect through the tubuloglomerular feedback mechanism (TGF) with the Sodium-glucose cotransporter2 inhibitor (SG) attracts attention. We investigated whether the improvement of TGF can be estimated from urinary glucose (UG) and urinary sodium (UNa) excretion, and from other parameters by assessing the changes of urinary findings in patients using SG (Dapagliflozin, Canagliflozin, Empagliflozin). Type 2 diabetes patients with SG who UG and UNa excretion were measured regularly were enrolled in this study. To correct for a postprandial increase of UG due to elevated plasma glucose(PG) levels, the creatinine-corrected UG (cUG: mg/mgCr) was calculated as follows. (The average PG level (AG mg/dl) = 28.7 × HbA1c- 46.7 (Diabetes Care 2008 Aug; 31(8): 1473-1478), the estimated UG (eUG) = UG × AG/PG). Then cUG was corrected for urinary creatinine excretion.) We analyzed these data at before, after 1, 3, 6, and 12 months (M) of SG treatment. Eighteen patients (14 men and 4 women, aged 54.9 ± 6.9 years, eGFR > 100 in 3 and < 60 in 2 patients) were investigated these parameters. Uric acid (UA), urine pH(pH) decreased after treatment, eGFR remained below baseline throughout the study period (p< 0.05). About the mean (SE) UNa/cUG ratio, no differences were observed in this study(1M 2.9 (0.5)/3M2.6 (0.5)/6M2.3 (0.5)/12M 2.6 (0.4)). The UNa/cUG ratio was negatively correlated with HbA1c and eGFR. eGFR decreased more markedly in the patients with a baseline eGFR>100. eGFR was negatively correlated with the UNa/cUG ratio and UA(p<0.05). The renoprotective effect according to TGF improvement might be obtained in the patients whom cUG excretion increased remarkably, furthermore UA decreased and pH was lower. If the UNa/cUG ratio exceeds 2.6, the intraglomerular pressure cannot be improved sufficiently because salt intake is higher and UNa excretion increases independently of UG excretion. The UNa/UG ratio can be used to estimate improvement of TGF by SG in clinical practice.
C. Watanabe: None. Y. Mori: None.