Renal connective tissue growth factor correlates with glomerular basement membrane thickness and prospective albuminuria in a non-human primate model of diabetes: possible predictive marker for incipient diabetic nephropathy.
Diabetic renal disease is characterized by accumulation of extracellular matrix, glomerulosclerosis, and tubulointerstitial fibrosis. Connective tissue growth factor (CTGF) is implicated in these changes, as it contributes to new matrix synthesis and is increased in the diabetic kidney. CTGF also inhibits mesangial matrix degradation through up-regulation of the tissue inhibitor of matrix metalloproteinase 1 (TIMP-1). In a non-human primate model of diabetes, we determined whether the level of renal CTGF protein before development of albuminuria correlated with renal matrix and TIMP-1 changes and whether renal CTGF predicts progression to albuminuria.


METHODS
In a group of diabetic (n=9) and control (n=6) baboons after a 5-year duration of diabetes, renal tissue CTGF and TIMP-1 were detected by immunohistochemistry and compared with glomerular basement membrane (GBM) thickness and mesangial volume measurements from electron photomicrographs of renal biopsies. Urinary albumin levels were measured at 5 and 10 years of diabetes.


RESULTS
GBM thickness, CTGF protein, and TIMP-1 protein were increased after 5 years of diabetes (each P<.05). Tubular fibronectin scores correlated with tubular CTGF scores (r=0.72, P=.002). In diabetic animals, GBM thickness correlated with tubular and total CTGF levels (P=.002 and P=.04, respectively), whereas mesangial cell and total matrix volume correlated with glomerular TIMP-1 (P=.02 and P=.01, respectively). Tubular CTGF scores (P=.008) and GBM thickness (P=.03) at 5 years in diabetes each predicted the degree of albuminuria at 10 years.


CONCLUSIONS
These results suggest that early increases in renal CTGF protein contribute to incipient diabetic nephropathy and that renal CTGF may have utility as an early marker for progression to dysfunction in the diabetic kidney.
Thomson
Sally E
SE
Discipline of Medicine, University of Sydney, Sydney, Australia.
McLennan
Susan V
SV
Kirwan
Paul D
PD
Heffernan
Scott J
SJ
Hennessy
Annemarie
A
Yue
Dennis K
DK
Twigg
Stephen M
SM
D000419:Albuminuria / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D055513:Connective Tissue Growth Factor; D003922:Diabetes Mellitus, Type 1 / Q000150:complications* / Q000473:pathology; D003928:Diabetic Nephropathies / Q000175:diagnosis* / Q000473:pathology; D004195:Disease Models, Animal; D018450:Disease Progression; D050533:Glomerular Basement Membrane / Q000473:pathology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000032:analysis*; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis*; D008297:Male; D048529:Papio hamadryas; D011379:Prognosis; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000032:analysis
D015415:Biomarkers; C526317:CCN2 protein, human; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D019715:Tissue Inhibitor of Metalloproteinase-1; D055513:Connective Tissue Growth Factor