In Vivo Quantitative Visualization Analysis of the Effect of C-Peptide on Glomerular Hyperfiltration in Diabetic Rats by Using Multiphoton Microscopy

Objective: The purpose of this study was to visualize glomerular hyperfiltration in rats at the early stage of diabetes under in vivo conditions and to quantitatively examine the effect of C-peptide on filtration. Methods: Type 1 diabetes was induced by streptozotocin (50mg/kg) in Wistar rats. The rats were divided into four groups: control, control plus C-peptide, early diabetes, and early diabetes plus C-peptide. C-peptide was continuously infused (50pmol/kg/min). Filtration was visualized by a bolus shot of various sizes of dextrans (3k to 70kDa) conjugated with Texas Red and observed with a multiphoton microscope under inhaled anesthesia. Relative sieving coefficients were used to quantify filtration. Results: Almost all smaller particles (3-10kDa) were filtered both in control and diabetic rats. Filtration of larger particles (40-70kDa) was seen in normal rats but was more apparent in diabetic rats, where it was progressive according to the duration of diabetes. C-peptide administration restored the leakage of larger particles to the level seen for the control. Conclusions: We visualized and analyzed hyperfiltration and confirmed that C-peptide has a nephroprotective effect. Furthermore, we found that the leakage of larger particles increased as the duration of diabetes increased.