SIAH1 and Hyperglycemia: However, in vivo (4 week-STZ injected diabetic mice), the duration of hyperglycemia is relatively longer and hence upregulation of endogenous TGF-β is also longer, suggesting that HIPK2 protein expression under these in vivo conditions is likely to be upregulated at the posttranslational level (stabilization through decreases in SIAH1).