Nephrin expression is reduced in human diabetic nephropathy: evidence for a distinct role for glycated albumin and angiotensin II.
We studied the distribution of nephrin in renal biopsies from 17 patients with diabetes and nephrotic syndrome (7 type 1 and 10 type 2 diabetes), 6 patients with diabetes and microalbuminuria (1 type 1 and 5 type 2 diabetes), and 10 normal subjects. Nephrin expression was semiquantitatively evaluated by measuring immunofluorescence intensity by digital image analysis. We found an extensive reduction of nephrin staining in both type 1 (67 +/- 9%; P < 0.001) and type 2 (65 +/- 10%; P < 0.001) diabetic patients with diabetes and nephrotic syndrome when compared with control subjects. The pattern of staining shifted from punctate/linear distribution to granular. In patients with microalbuminuria, the staining pattern of nephrin also showed granular distribution and reduction intensity of 69% in the patient with type 1 diabetes and of 62 +/- 4% (P < 0.001) in the patients with type 2 diabetes. In vitro studies on human cultured podocytes demonstrated that glycated albumin and angiotensin II reduced nephrin expression. Glycated albumin inhibited nephrin synthesis through the engagement of receptor for advanced glycation end products, whereas angiotensin II acted on cytoskeleton redistribution, inducing the shedding of nephrin. This study indicates that the alteration in nephrin expression is an early event in proteinuric patients with diabetes and suggests that glycated albumin and angiotensin II contribute to nephrin downregulation.
Doublier
Sophie
S
Department of Internal Medicine, University of Turin, Center for Experimental Research and Medical Sciences, Turin, Italy.
Salvidio
Gennaro
G
Lupia
Enrico
E
Ruotsalainen
Vesa
V
Verzola
Daniela
D
Deferrari
Giacomo
G
Camussi
Giovanni
G
D000328:Adult; D000368:Aged; D000419:Albuminuria / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology*; D001706:Biopsy; D015153:Blotting, Western; D002478:Cells, Cultured; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D003928:Diabetic Nephropathies / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression / Q000187:drug effects*; D017127:Glycation End Products, Advanced; D006801:Humans; D007668:Kidney / Q000737:chemistry / Q000648:ultrastructure; D008297:Male; D008565:Membrane Proteins; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009404:Nephrotic Syndrome / Q000378:metabolism; D011506:Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000032:analysis / Q000187:drug effects / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012709:Serum Albumin / Q000494:pharmacology / Q000502:physiology*; D014018:Tissue Distribution; D000093423:Glycated Serum Albumin
D017127:Glycation End Products, Advanced; D008565:Membrane Proteins; D011506:Proteins; D012333:RNA, Messenger; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D012709:Serum Albumin; C113267:nephrin; D000804:Angiotensin II; D003571:Cytochalasin B; D000093423:Glycated Serum Albumin