PurposeAcid-base transport in renal proximal tubules (PTs) is mainly sodium-dependent and conducted in coordination by the apical Na+/H+ exchanger (NHE3), vacuolar H+-adenosine triphosphatase (V-ATPase), and the basolateral Na+/HCO3- cotransporter. V-ATPase on PTs is well-known to play an important role in proton excretion. Recently we reported a stimulatory effect of insulin on these transporters. However, it is unclear whether insulin is involved in acid-base balance in PTs. Thus, we assessed the role of insulin in acid-base balance in PTs.MethodsV-ATPase activity was evaluated using freshly isolated PTs obtained from mice, and specific inhibitors were then used to assess the signaling pathways involved in the observed effects.ResultsV-ATPase activity in PTs was markedly enhanced by insulin, and its activation was completely inhibited by bafilomycin (a V-ATPase-specific inhibitor), Akt inhibitor VIII, and PP242 (an mTORC1/2 inhibitor), but not by rapamycin (an mTORC1 inhibitor). V-ATPase activity was stimulated by 1 nm insulin by approximately 20% above baseline, which was completely suppressed by Akt1/2 inhibitor VIII. PP242 completely suppressed the insulin-mediated V-ATPase stimulation in mouse PTs, whereas rapamycin failed to influence the effect of insulin. Insulin-induced Akt phosphorylation in the mouse renal cortex was completely suppressed by Akt1/2 inhibitor VIII and PP242, but not by rapamycin.ConclusionOur results indicate that stimulation of V-ATPase activity by insulin in PTs is mediated via the Akt2/mTORC2 pathway. These results reveal the mechanism underlying the complex signaling in PT acid-base balance, providing treatment targets for renal disease.

Objective Diabetes is a major risk factor for chronic kidney disease (CKD). In this study, we examined the effects of alogliptin on blood glucose control and the renal function in type 2 diabetes CKD patients. Methods We recruited 36 CKD patients with type 2 diabetes. The patients were followed up for six months after adding alogliptin. Blood biochemical, urine test and office BP values were obtained six months before and after the start of treatment. Results The mean HbA1c value was not decreased; however, the 1,5-AG values tended to improve (p= 0.1023). The mean eGFR was unchanged. There were no significant changes in the patients with an eGFR of 60 mL/min/1.73 m 2 or more (25 patients) or in the patients with an eGFR less than 60 mL/min/1.73 m 2 (11 patients). A total of 15 patients were identified to have rapidly declining diabetic nephropathy, with an annual reduction in eGFR of 5 mL/min/1.73 m 2 or more. The slope of the regression line for eGFR (-1.296 before starting treatment with alogliptin) was positive, increasing up to 0.08786. The eGFR values appeared to stop decreasing and positively reversed. The urinary albumin-to-creatinine ratio exhibited a downward trend. The effect on the renal function was independent of the levels of blood sugar, blood pressure and lipids. Conclusion We examined the ability of alogliptin to maintain the renal function in patients with CKD complicated by type 2 diabetes. Our study suggests that alogliptin can be safely administered in patients with CKD. However, although we expected alogliptin to demonstrate renal protective effects, were unable to detect statistically significant differences. One reason for this finding is that there are few registered cases.

An easy-to-use assessment for activated factor X (FXa) is lacking despite its pivotal role in the coagulation. Dielectric blood coagulometry (DBCM) was recently invented as a novel assessment tool for determining the whole blood coagulability by measuring the temporal change in the permittivity of blood. We previously reported that it could evaluate the global blood coagulability. This study aimed to apply the DBCM for assessing FXa activity and its inhibition by anticoagulants. We performed the DBCM analysis along with measurement of the FXa activity by a fluorometric assay in samples from healthy subjects, and identified a new index named maximum acceleration time (MAT) that had a correlation to the FXa activity. Next the DBCM analysis was performed using blood samples mixed with anticoagulants (unfractionated heparin, dalteparin, and edoxaban). Blood samples with three anticoagulants had different profiles of the temporal change in the permittivity, reflecting their different selectivity for FXa. We compared the MAT with the anti-FXa activity assay, and found that the prolongation of MAT was similarly correlated with the anti-FXa activity regardless of the type of anticoagulants. In conclusion, the DBCM has the possibility for evaluating the innate FXa activity and effect of anticoagulants focusing on their FXa inhibition.