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Combination therapy with AT1 blocker and vitamin D analog markedly ameliorates diabetic nephropathy: blockade of compensatory renin increase.

ABSTRACT: The renin-angiotensin system (RAS) plays a critical role in the development of diabetic nephropathy, and blockade of the RAS is currently used for treatment of diabetic nephropathy. One major problem for the current RAS inhibitors is the compensatory renin increase, which reduces the efficacy of RAS inhibition. We have shown that vitamin D exerts renoprotective actions by transcriptionally suppressing renin. Here we demonstrated that combination therapy with an AT1 receptor blocker and a vitamin D analog markedly ameliorated renal injury in the streptozotocin (STZ)-induced diabetes model due to the blockade of the compensatory renin rise by the vitamin D analog, leading to more effective RAS inhibition. STZ-treated diabetic DBA/2J mice developed progressive albuminuria and glomerulosclerosis within 13 weeks, accompanied by increased intrarenal production of angiotensin (Ang) II, fibronection, TGF-beta, and MCP-1 and decreased expression of slit diaphragm proteins. Treatment of the diabetic mice with losartan or paricalcitol (19-nor-1,25-dihydroxyvitamin D(2), an activated vitamin D analog) alone moderately ameliorated kidney injury; however, combined treatment with losartan and paricalcitol completely prevented albuminuria, restored glomerular filtration barrier structure, and markedly reduced glomerulosclerosis. The combined treatment suppressed the induction of fibronection, TGF-beta, and MCP-1 and reversed the decline of slit diaphragm proteins nephrin, Neph-1, ZO-1, and alpha-actinin-4. These were accompanied by blockade of intrarenal renin and Ang II accumulation induced by hyperglycemia and losartan. These data demonstrate that inhibition of the RAS with combination of vitamin D analogs and RAS inhibitors effectively prevents renal injury in diabetic nephropathy.

SUBMITTER: Zhang Z

PROVIDER: S-EPMC2562415 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:IntroductionRenin-angiotensin system (RAS) blockade using angiotensin-converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB) is first-line therapy for IgA nephropathy (IgAN). There is a paucity of information on the predictors and magnitude of response to this treatment.MethodsIn a prospective study, treatment-naive patients with IgAN with urinary protein ≥ 1 g/d and estimated glomerular filtration rate (eGFR) ≥ 30 ml/min per 1.73 m2 received supportive treatment including ACEi (ramipril) or ARB (losartan) in patients intolerant to ACEi, and optimal blood pressure (BP) control to ≤130/80 mm Hg, with a follow-up of 6 months. The primary outcome was remission of proteinuria. Complete remission (CR) was defined as proteinuria < 0.5 g/d and partial remission (PR) as proteinuria < 1g/d with at least a 50% decline from the baseline with stable renal function (≤ 25% reduction in eGFR).ResultsA total of 96 patients were analyzed, with a mean age of 33.3 ± 10.2 years, baseline eGFR 74.0 ± 30.9 ml/min per 1.73 m2, and urinary protein 2.6 ± 1.2 g/d. In all, 71.9% patients received ≥ 75% of the maximum approved dose of ACEi/ARB. Remission was observed in 36.5% (CR, 6.3%) patients at 3 months and in 55.2% (CR, 31.3%) at 6 months. Patients who failed to achieve remission had lower baseline eGFR (P = 0.002) and serum albumin levels (P< 0.001), asymptomatic hyperuricemia (P < 0.001), and higher proteinuria (P = 0.076). E1 (P= 0.053) and T1/T2 (P = 0.009) lesions were more frequent on histology. The ACEi/ARB had to be discontinued in 17 (17.7%) patients. These patients were older (P= 0.085) with lower eGFR (P < 0.002) and serum albumin levels (P = 0.001) and more E1 (P = 0.012) and T1/T2 (P = 0.001) lesions on histology.ConclusionMeticulous supportive therapy with optimal use of ACEi/ARB achieved remission in half of IgAN patients in this study. Increasing the treatment duration to 6 months improved remission rates. Patients with severe clinical and histological disease were less likely to tolerate and respond to treatment with RAS blockade.

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Combination therapy with AT1 blocker and vitamin D analog markedly ameliorates diabetic nephropathy: blockade of compensatory renin increase.

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