SMAD3 and diabetic kidney disease: By deleting Smad3 from db/db mice, we found that Smad3 knockout (KO)‐db/db mice were protected from DKD, with significantly reduced levels of albumin to creatinine, serum creatinine and histological injury in kidney, including mesangial matrix expansion and thickness of glomerular basement membrane over 12‐32 weeks.16