There was
no significant difference in the rCBF between the AGL (medium dose) and vehicle groups during ischemia (Fig. 3). After reperfusion, rCBF levels remained higher in the AGL group, achieving statistical significance during the later phase. The BDNF levels in the whole forebrain were significantly elevated in the AGL group compared with the vehicle group (Fig. 4). In the forebrain, there were significant elevations in the cortex, and the thalamostriatum. The BDNF levels in the hippocampus did not achieve a significant difference. On selleck screening library analysis of the volumes of infarcted lesions in the acute phase (Fig. 5A), the reduction in the AGL (medium dose)-treated group did not achieve a significant difference, selleck as compared with vehicle alone (Fig. 5B). There was no significant difference in the edema index between the groups (data not shown). In the chronic phase, the volumes of infarcted lesions were not different between the groups (Fig. 5B). On assessment of neurological function, the SND score was not different between the groups, for seven days after ischemia (Fig. 5C). It was demonstrated that chronic, prophylactic treatment with AGL increased BDNF levels in the brain, and protected the brain against ischemic stroke. The pharmacokinetics and the efficacy profiles of AGL on glucose/insulin/glucagon levels in plasma after acute or chronic administration have been extensively studied in diabetic and normal animals
(Moritoh et al., 2008 and Lee et al., 2008), with a mean half-life
of 3.6 h in normal rats, and 28 h in normal monkeys. After a single gavage (0.5 mg/kg) of AGL in normal rats, maximum inhibition (90%) of DPP-4 occurred at 30 min, which declined to 40% at 12 h, and disappeared within 24 h (Lee et al., 2008). We discontinued the treatment 24 h before the onset of ischemia to exclude, or at least minimize, any direct effects of AGL on cerebral ischemia. It is well known that hyperglycemia is an exacerbating factor in ischemic stroke in patients with DM-2. However, normal blood glucose levels were not reduced by chronic, prophylactic treatment with AGL. AGL actually has only a minor effect on individuals with normal blood glucose levels. Administration of extremely high doses of AGL (100 mg/kg) showed no effect on fasting plasma glucose or insulin levels in normal mice (Lee et al., 2008), confirming that the effects of Parvulin AGL on insulin secretion and insulin resistance are dependent in the presence of hyperglycemia. Functional deterioration improved in both the chronic AGL- and vehicle-treated groups on entering the chronic phase, obliterating the initial difference between the groups. Because the rate of passage of biological time correlates inversely to [body weight]2, as represented by longevity and heart/respiration rate (Calder, 1983), 15–30 min in mice is regarded as from 30 min to 1 h in rats (Yanamoto et al., 2004), and 3–6 h in humans (Yanamoto et al., 2012).