title: Long-term therapeutic effect of vitamin D analog doxercalciferol on diabetic nephropathy: strong synergism with AT1 receptor antagonist.
abstract: The intrarenal renin-angiotensin system (RAS) plays a key role in the development of diabetic nephropathy. Recently, we showed that combination therapy with an AT(1) receptor blocker (ARB) and an activated vitamin D analog produced excellent synergistic effects against diabetic nephropathy, as a result of blockade of the ARB-induced compensatory renin increase. Given the diversity of vitamin D analogs, here we used a pro-drug vitamin D analog, doxercalciferol (1alpha-hydroxyvitamin D(2)), to further test the efficacy of the combination strategy in long-term treatment. Streptozotocin-induced diabetic DBA/2J mice were treated with vehicle, losartan, doxercalciferol (0.4 and 0.6 microg/kg), or losartan and doxercalciferol combinations for 20 wk. Vehicle-treated diabetic mice developed progressive albuminuria and glomerulosclerosis. Losartan alone moderately ameliorated kidney injury, with renin being drastically upregulated. A similar therapeutic effect was seen with doxercalciferol alone, which markedly suppressed renin and angiotensinogen expression. The losartan and doxercalciferol combination most effectively prevented albuminuria, restored glomerular filtration barrier structure, and dramatically reduced glomerulosclerosis in a dose-dependent manner. These effects were accompanied by blockade of intrarenal renin upregulation and ANG II accumulation. These data demonstrate an excellent therapeutic potential for doxercalciferol in diabetic renal disease and confirm the concept that blockade of the compensatory renin increase enhances the efficacy of RAS inhibition and produces synergistic therapeutic effects in combination therapy.
authors.affiliation: Division of Biological Sciences, Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Dilip K
authors.initials: DK
authors.lastname: Deb
authors.forename: Juan
authors.initials: J
authors.lastname: Kong
authors.forename: Gang
authors.initials: G
authors.lastname: Ning
authors.forename: Yurong
authors.initials: Y
authors.lastname: Wang
authors.forename: George
authors.initials: G
authors.lastname: Li
authors.forename: Yunzi
authors.initials: Y
authors.lastname: Chen
authors.forename: Zhongyi
authors.initials: Z
authors.lastname: Zhang
authors.forename: Stephen
authors.initials: S
authors.lastname: Strugnell
authors.forename: Yves
authors.initials: Y
authors.lastname: Sabbagh
authors.forename: Cynthia
authors.initials: C
authors.lastname: Arbeeny
authors.forename: Yan Chun
authors.initials: YC
authors.lastname: Li
mesh_terms: D000419:Albuminuria / Q000209:etiology / Q000517:prevention & control; D000804:Angiotensin II / Q000378:metabolism; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000808:Angiotensinogen / Q000378:metabolism; D000818:Animals; D016207:Cytokines / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D003928:Diabetic Nephropathies / Q000209:etiology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D004872:Ergocalciferols / Q000494:pharmacology*; D005355:Fibrosis; D050533:Glomerular Basement Membrane / Q000187:drug effects / Q000473:pathology; D018836:Inflammation Mediators / Q000378:metabolism; D019808:Losartan / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000473:pathology; D051379:Mice; D008811:Mice, Inbred DBA; D050199:Podocytes / Q000187:drug effects / Q000473:pathology; D012083:Renin / Q000378:metabolism; D012084:Renin-Angiotensin System / Q000187:drug effects* / Q000235:genetics; D013997:Time Factors; D014815:Vitamins / Q000494:pharmacology*
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D016207:Cytokines; D004872:Ergocalciferols; D018836:Inflammation Mediators; D014815:Vitamins; D000808:Angiotensinogen; D000804:Angiotensin II; C042533:1 alpha-hydroxyergocalciferol; D012083:Renin; D019808:Losartan