Abstract
Purpose: :
Elevated GGT is a risk factor for insulin resistance as well as cataract formation. We investigated the hypothesis that a co-ordinate lenticular GGT and glutathione (GSH) response occurs with development of experimental type 1 (T1) and type 2 (T2) diabetes.
Methods: :
T1 diabetes was induced by Streptozocin (STZ) treatment in Sprague-Dawley rats and T2 diabetes developed by 16 weeks in Zucker diabetic fatty (ZDF) rats. The pre- and post diabetic plasma and lens levels of GGT and GSH were compared. Plasma samples and whole lenses were obtained from 8-10 rats prior to and 6 to 8 weeks post diabetes detection. The Accu-Chek® plasma glucose concentration, plasma and lens GGT and GSH levels were determined by standard colorimetric assays.
Results: :
The GGT activity in the T1 diabetic rat plasma was 5-fold higher (p=0.002) than in control non-diabetic plasma. There was a close association between elevated plasma glucose and increased GGT (r = .0615; slope= 0.534) in STZ diabetic rats. The GGT and GSH levels in T1 diabetic lens were significantly lower (p’s<0.01) than in control non-diabetic lens. The GGT activity in plasma of control ZDF rats was 2-fold lower than in diabetic STZ rats. T2 plasma GGT levels tended to be inversely related to the plasma glucose concentration (r =.0215; slope= -.051). The levels of GGT and GSH in lens were lower in diabetic versus non-diabetic ZDF rats.
Conclusions: :
The results suggest that the T1 and T2 diabetic rat models are dissimilar with regard to the relationships between elevated plasma glucose and GGT levels. The results suggest that a co-ordinate reduction in GGT and GSH levels occurs in diabetic rat lens.
Keywords: diabetes • cataract • pathology: experimental