Fig 1.
Schema of experimental schedule.
Experimental protocol used to induce diabetes with streptozocin (STZ). All rats were administered daily with DA-9701 or vehicle by oral gavage for 2 weeks. Oral glucose tolerance tests (OGTT) and liquid gastric emptying assessments were performed at weeks 3 and 4. The study was completed with solid gastric emptying measurements after sacrifice of the rats.
Fig 2.
Effects of STZ on OGTT and body weight in rats.
(A) OGTT at 3 and 4 weeks in control and STZ-treated rats. Control groups at 3 weeks (●) and 4 weeks (○) showed stable glucose levels post-OGTT, while STZ-treated rats at 3 weeks (■) and 4 weeks (□) exhibited elevated glucose levels. Data are shown as mean ± standard error of the mean (5–8 mice per group). Control (3 weeks) vs. STZ (3 weeks) – p < 0.05, **** - p < 0.0001, #-Control (4 weeks) vs. STZ (4 weeks). (B) Body weight of control and STZ-treated rats was measured weekly over a 4-week period, with the STZ-treated group showing lower body weight compared to the control group (6–7 mice per group).
Fig 3.
Liquid and solid gastric emptying in the control and STZ-treated rats at 2 and 4 weeks.
(A) Plasma acetaminophen levels as a measure of liquid gastric emptying show increased emptying in STZ-treated rats at 2 weeks (n = 5/group; *p < 0.05). (B) Plasma acetaminophen measurement after 4 weeks indicates continued enhanced liquid gastric emptying in STZ-treated rats (n = 6–11/group; **p < 0.01, ****p < 0.0001). (C) Solid gastric emptying is significantly accelerated in STZ-treated rats at 2 weeks (*p < 0.05). (D) At 4 weeks, STZ treatment maintains faster solid gastric emptying compared to control (*p < 0.05) (n = 4–6/group).
Fig 4.
Efficacy of DA-9701 in STZ-induced diabetic rats on gastric emptying and glucose levels.
(A) Liquid gastric emptying measured by plasma acetaminophen at three and 4 weeks post-STZ with and without DA-9701 treatment (n = 5/group). DA-9701 normalized emptying rates in STZ rats. (B) Comparison of solid gastric emptying in diabetic rats 2 weeks after vehicle or DA-9701 administration (n = 5/group). A marked increase in solid gastric emptying was observed in the STZ-only group, which was significantly modulated by the addition of DA-9701 (**p < 0.01). (C) Blood glucose levels from 0 minutes to 120 minutes after oral glucose administration (1 g/kg) in overnight-fasted rats, comparing the effects of DA-9701 and vehicle treatments in STZ-induced diabetic and control groups. The AUC for glucose variability highlighted the role of DA-9701 in reducing glucose spikes in STZ-treated rats (n = 5–10/group). (D) At 4 weeks, OGTT results demonstrated a significant effect of DA-9701 on glucose regulation in STZ-treated rats, with the AUC inset indicating improved glucose management.
Fig 5.
Effects of DA-9701 on cellular and molecular markers in STZ-induced diabetic rats.
(A) Immnunostaining for c-Kit (green) and immunoblot analysis for c-Kit and β-Actin. STZ treatment upregulated c-Kit expression, which was significantly modulated by DA-9701 (*p < 0.05, **p < 0.01). (B) MDA concentration was measured to assess oxidative stress. STZ treatment resulted in elevated MDA levels, indicating increased oxidative stress; however, subsequent administration of DA-9701 mitigated this effect. The expression of oxidative stress-related genes (Ogg1, Gpx, and Cat) was measured using qRT-PCR. STZ treatment upregulated oxidative stress-related genes expression, which were significantly reduced by DA-9701 (*p < 0.05, **p < 0.01, ***p < 0.001). (C) Immunoblot analysis showed that expression of p-ERK1/2 and PCNA was upregulated in STZ-induced diabetic rats. All analyses were performed using gastric tissues from control and diabetic rats treated with vehicle or DA-9701 (6 mg/kg) daily for 2 weeks.
Fig 6.
Effects of DA-9701 on insulin secretion in STZ-induced diabetic group and control group.
Insulin levels (ng/mL) were measured at 0, 15, and 30 minutes post-glucose administration in control and STZ-induced diabetic groups treated with either vehicle or DA-9701. DA-9701 significantly increased insulin secretion at 15 and 30 minutes in both control and STZ-treated groups compared to their respective vehicle-treated groups (*p < 0.05).
Fig 7.
A schematic showing a mechanism by which DA-9701 normalizes rapid gastric emptying.
Administration of STZ led to a series of events that induce hyperglycemia, which in turn increased oxidative stress, resulting in the activation of ERK1/2. This activation induced the upregulation of c-Kit, ultimately causing rapid gastric emptying. The administration of DA-9701 likely counteracted these effects, leading to the normalization of gastric emptying rates.