Streptozocin Diabetes Elevates all Isoforms of TGF-β in the Rat Kidney

Transforming growth factor beta (TGF-beta) is a major promoter of diabetic nephropathy. While TGF-beta1 is the most abundant renal isoform, types 2 and 3 are present as well and have identical in vitro effects. Whole kidney extracts were studied 2 weeks after induction of streptozocin diabetes and in control rats. Mean glomerular area was 25% greater in the diabetic animals. TGF-beta1 showed a 2-fold increase in message with a 3-fold increase in protein. TGF-beta2 mRNA increased approximately 6% while its protein doubled. TGF-beta-message increased by 25%, producing a 35% increase in its protein. TGF-beta-inducible gene H3 mRNA was increased 35% in the diabetic animals, consistent with increased activity of this growth factor. All isoforms of TGF-beta are increased in the diabetic rat kidney. Future studies need to address the specific role that each isoform plays in diabetic nephropathy as well as the impact of therapies on each isoform.