Amelioration of accelerated diabetic mesangial expansion by treatment with a PKC beta inhibitor in diabetic db/db mice, a rodent model for type 2 diabetes.

Activation of protein kinase C (PKC) is implicated as an important mechanism by which diabetes causes vascular complications. We have recently shown that a PKC beta inhibitor ameliorates not only early diabetes-induced glomerular dysfunction such as glomerular hyperfiltration and albuminuria, but also overexpression of glomerular mRNA for transforming growth factor beta1 (TGF-beta1) and extracellular matrix (ECM) proteins in streptozotocin-induced diabetic rats, a model for type 1 diabetes. In this study, we examined the long-term effects of a PKC beta inhibitor on glomerular histology as well as on biochemical and functional abnormalities in glomeruli of db/db mice, a model for type 2 diabetes. Administration of a PKC beta inhibitor reduced urinary albumin excretion rates and inhibited glomerular PKC activation in diabetic db/db mice. Administration of a PKC beta inhibitor also prevented the mesangial expansion observed in diabetic db/db mice, possibly through attenuation of glomerular expression of TGF-beta and ECM proteins such as fibronectin and type IV collagen. These findings provide the first in vivo evidence that the long-term inhibition of PKC activation in the renal glomeruli can ameliorate glomerular pathologies in diabetic state, and thus suggest that a PKC beta inhibitor might be an useful therapeutic strategy for the treatment of diabetic nephropathy.