Fig. 5.

Effect of leptin treatment on intra-islet vascularization. Islets were transplanted into the anterior chamber of the eye of 4-wk-old ob/ob mice. At the age of 3 mo, the mice received daily i.p. injections of leptin. (A) Leptin administration had a rapid effect on blood vessel diameters, as demonstrated by in vivo imaging of the same islet before treatment (Left) and after 1 wk of treatment (Right). The vasculature was visualized by tail vein injection of dextran-FITC. The same vessel segments could be identified and their diameters measured at different time points (red lines). Note that angiogenesis is evident after leptin administration (arrows). (B) Longitudinal analysis of individual vessel diameters showing vessel morphological changes before, during, and after leptin treatment. (Upper) Traces of 20 vessel segments from islet grafts in the ob/ob mouse over time. (Lower) Bar graph showing corresponding average monthly diameter increases. Confocal images are representative and shown as MIPs. Values are average ± SEM. ***P < 0.001; ****P < 0.0001. (Scale bars: 100 µm.)