title: Expression of cytoskeletal proteins during the course of experimental diabetic nephropathy.
abstract: OBJECTIVE
  Diabetic nephropathy is characterised by structural changes known to be associated in non-diabetic nephropathies with the expression of the cytoskeletal proteins a-smooth muscle actin and vimentin. We aimed to investigate the expression of cytoskeletal proteins in experimental diabetic nephropathy.
  
  
  METHODS
  Rats were made diabetic by an injection of streptozotocin (45 mg/kg). Groups of rats (n = 6) and their respective controls (n = 4) were killed at different time intervals. (days 7, 15, 30, 60, 90 and 120). We also studied two groups of diabetic rats treated with a long-acting insulin; the first (n = 8) was treated from the induction of diabetes and the second (n = 8) received insulin from day 15 onward. At each time-point, kidney function, proteinuria and histology were evaluated. Cytoskeletal proteins and collagens III and IV deposition was determined by immunohistochemistry. Changes in the transcription of the cytoskeletal proteins was determined by northern blot analysis.
  
  
  RESULTS
  Although normal glomeruli did not express alpha-smooth muscle actin until late in the time course, it was detected in diabetic mesangium from day 7 onward. In the interstitium, it appeared in a perivascular and peritubular distribution. Vimentin was detectable within normal glomerular epithelial cells and increased rapidly (days 7 and 15) in diabetic rats. Vimentin also appeared early within the lining of the peritubular capillaries and damaged diabetic tubules. These changes were associated with a delayed increased transcription of alpha-smooth muscle actin and vimentin. Treatment with insulin (early or late) attenuated and reversed respectively the expression of cytoskeletal proteins and collagens within diabetic kidneys. Close correlations were noted between the number of alpha-smooth muscle actin positive cells within diabetic glomeruli and mesangial expansion (r = 0.46, p < 0.02) as well as interstitial alpha-smooth muscle actin positive cells and interstitial fibrosis (r = 0.51, p < 0.002).
  
  
  CONCLUSIONS
  Changes in the expression of cytoskeletal proteins within the kidneys of diabetic rats suggest a role for alpha-smooth muscle actin and vimentin in the pathogenesis of diabetic kidney disease.
authors.affiliation: Sheffield Kidney Institute, Northern General Hospital Trust, UK.
authors.forename: T
authors.initials: T
authors.lastname: Sanai
authors.forename: T
authors.initials: T
authors.lastname: Sobka
authors.forename: T
authors.initials: T
authors.lastname: Johnson
authors.forename: M
authors.initials: M
authors.lastname: el-Essawy
authors.forename: E C
authors.initials: EC
authors.lastname: Muchaneta-Kubara
authors.forename: O
authors.initials: O
authors.lastname: Ben Gharbia
authors.forename: S
authors.initials: S
authors.lastname: el Oldroyd
authors.forename: A M
authors.initials: AM
authors.lastname: Nahas
mesh_terms: D000199:Actins / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D003094:Collagen / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D003928:Diabetic Nephropathies / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D007328:Insulin / Q000627:therapeutic use; D007668:Kidney / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D007678:Kidney Glomerulus / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D012079:Renal Circulation; D014158:Transcription, Genetic; D014746:Vimentin / Q000032:analysis / Q000096:biosynthesis
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D007328:Insulin; D014746:Vimentin; D003094:Collagen