Onetouch ultraeasy

OGTT was performed during the last week of the experiment. Rats were deprived of their respective diets overnight and then administered with 2 g glucose/kg body weight by oral gavage. Blood samples were collected from the tail vein at 0, 30, 60, 90 and 120 min after oral glucose loading and blood glucose levels were measured with a calibrated OneTouch UltraEasy glucometer (LifeScan). The total area under the curve (AUC) for OGTT was calculated by the trapezoid method.

OGTTs were performed preoperatively and repeated in postoperative weeks 2 and 4. Before the tests, the rats fasted overnight; glucose 1.5 g/kg bw (dissolved as a 50% solution) was administered by intragastric tube, and a drop of blood was taken from the tail vein at 0, 30, 60 and 120 min for measurement of blood glucose levels. Blood glucose was measured with a portable glucometer (ONETOUCH UltraEasy; LifeScan Inc., Wayne, PA, USA). The determined glucose values at the specified time points were used for calculation of the area under the curve (AUC_0-120) using the trapezoidal method according to the equation of AUC = 0.25 × (0 min blood glucose value + 4 × 30 min blood glucose value+ 3 × 120 min blood glucose value). Insulin determinations were made using serum from blood extracted from the angular vein, and insulin was measured by a rat-specific radioimmunoassay kit (Beijing FuRui Biotech, Co., Ltd., Beijing, China) according to the manufacturer's guidelines. Insulin sensitivity of the experimental animals was evaluated using the homeostasis model assessment – insulin resistence (HOMA-IR), HOMA-IR = fasting glucose × fasting insulin / 22.5.

Before experiments were performed, streptozotocin (STZ; Sigma-Aldrich; Merck KGaA, Darmstadt, Germany), which has been frequently used in the establishment of DR models (25 (link)), was dissolved in 0.1 M citrate buffer (pH 4.5). Rats were anesthetized with 1% pentobarbital sodium [40 mg/kg injected intraperitoneally (i.p.)] and received a 65 mg/kg i.p. injection of STZ. Rats in the healthy control group received an equivalent dose of the citrate buffer vehicle. Following 72 h of incubation, glucose levels were monitored using blood glucose meters (One Touch UltraEasy; Lifescan, Inc., Milpitas, CA, USA); animals with blood glucose levels >16.7 mM were considered to be diabetic. Subsequently, 20 µl appropriate lentiviral mixtures were injected into the vitreous cavities of both eyes. The mice were sacrificed with 1% pentobarbital sodium (80 mg/kg i.p.), and the eyeballs were removed and processed for histopathology. Isolated retinal tissues were fixed in 4% paraformaldehyde, followed by cryoprotection in 30% sucrose, dehydration in increasing concentrations of alcohol, paraffin embedding, sectioning (thickness, 2 µm), and staining with hematoxylin and eosin for microscopic observation (26 (link),27 (link)).