Effect of simulated microgravity on the antidiabetic properties of wheatgrass (Triticum aestivum) in streptozotocin-induced diabetic rats

Abstract

Microgravity affects plant growth and content. A three-dimensional clinostat was used at 4 rotations/min to rotate the seeds of Triticum aestivum cultivar (Ammon) in three dimensions for 7 days, following which the antioxidant activities of ethanolic extracts were evaluated using both nitric oxide- and hydrogen peroxide-scavenging activities. The antidiabetic activities of ethanolic extracts were evaluated by measuring the concentration of plasma glucose, insulin, C peptide, and glycated hemoglobin (HbA1c); determining the number of β cells in the pancreatic islets; and performing the glucose tolerance test. Furthermore, the effects of the ethanolic extracts on the lipid profile and liver function were estimated. After rats were sacrificed, their pancreases were isolated and used for histopathological processing. The results indicated that the antioxidant potential and antioxidant metabolite content were significantly increased under microgravity conditions in comparison to those under normal gravity conditions. Rats treated with an extract of wheatgrass (T. aestivum) germinated over a period of 6-10 days under microgravity (WGM) showed a significant reduction in the levels of serum glucose, HbA1C, urea, creatinine, aspartate aminotransferase and alanine aminotransferase, and insulin resistance compared to rats treated with an extract of wheatgrass germinated under gravity. Additionally, the total cholesterol and low-density lipoprotein cholesterol levels were significantly decreased. In contrast, high-density lipoprotein cholesterol, C-peptide, and insulin levels rose significantly after treatment with T. aestivum germinated under microgravity. WGM is a promising potential diabetic treatment without side effects with a low manufacturing cost.

Keywords: Medicinal chemistry; Type 1 diabetes.

Fig. 1. Triticum aestivum growth under gravity and microgravity conditions and the effect of simulated microgravity on the total phenolic content, total flavonoid content, vitamin C content, and total antioxidant activities in wheatgrass extract.

a shows T. aestivum growth under gravity conditions. b shows T. aestivum growth under microgravity conditions simulated by a three-dimensional clinostat. c shows the total phenolic content of ethanolic extracts of T. aestivum under gravity and microgravity conditions. d shows the total flavonoid content of ethanolic extracts of T. aestivum under gravity and microgravity conditions. e shows the vitamin C content of ethanolic extracts of T. aestivum under gravity and microgravity conditions. f shows the hydrogen peroxide- and nitric oxide radical-scavenging activities of ethanolic extracts of T. aestivum under gravity and microgravity conditions. The values are expressed as the mean ± SEM of seven rats in each group. Data in c–e were analyzed by using two-way ANOVA, followed by Tukey’s multiple comparison test with the level of significance set at P < 0.05. *, **, ***, **** = P < 0.05, P < 0.01, P < 0.001, and P < 0.0001, respectively. Data in f were analyzed by using two-way ANOVA, followed by Tukey’s multiple comparison test with the level of significance set at P < 0.05. a refers to microgravity versus a reference compound ascorbic acid; b refers to gravity versus a reference compound ascorbic acid; and c refers to microgravity versus a gravity.

Fig. 2. The effects of ethanolic extracts of T. aestivum germinated under gravity and microgravity conditions on oral glucose tolerance tests over 2 h and fasting blood glucose levels over 30 days in experimental rats.

a shows the effect of ethanolic extracts of T. aestivum under gravity and microgravity conditions on the results of the oral glucose tolerance test (OGTT). b shows the effect of ethanolic extracts of T. aestivum under gravity and microgravity conditions on fasting blood glucose levels in experimental rats. The values are expressed as the mean ± SEM of seven rats in each group. Data were analyzed by using two-way ANOVA followed by Tukey’s multiple comparison test with the level of significance set at P < 0.05. a refers to treatment versus normal control; b refers to treatment versus diabetic control; c refers to microgravity versus gravity.

Fig. 3. The effects of ethanolic extracts of T. aestivum germinated under gravity and microgravity conditions on body weight in experimental rats after 30 days.

a shows changes in body weight in untreated nondiabetic rats on days 0 and 30. b shows changes in body weight in untreated diabetic rats on days 0 and 30. c shows changes in diabetic rats treated with the ethanolic extract of T. aestivum germinated under microgravity conditions on days 0 and 30. d shows changes in diabetic rats treated with the ethanolic extract of T. aestivum germinated under gravity condition group on days 0 and 30. e shows changes in diabetic rats treated with metformin on days 0 and 30. All values represent the mean ± SD. All comparisons were performed between the same group of animals on days 0 and 30. Data were analyzed by using two-way ANOVA, followed by Tukey’s multiple comparison test with the level of significance set at P < 0.05. *, ***, **** = P < 0.05,  , P < 0.001, and P < 0.0001, respectively.

Fig. 4. Effect of treatment with ethanolic extracts of T. aestivum under gravity and microgravity conditions for 30 days on C-peptide, serum insulin, and glycated hemoglobin (HbA1c) levels in experimental rats.

a shows the effect of ethanolic extracts of T. aestivum germinated under gravity and microgravity conditions on body weight in experimental rats. b shows the effect of ethanolic extracts of T. aestivum germinated under gravity and microgravity conditions on C-peptide levels in experimental rats. c shows the effect of ethanolic extracts of T. aestivum germinated under gravity and microgravity conditions on serum insulin levels in experimental rats. The values are expressed as the mean ± SEM of seven rats in each group. Data were analyzed by using two-way ANOVA, followed by Tukey’s multiple comparison test with the level of significance set at P < 0.05. a refers to treatment versus normal control, b refers to treatment versus diabetic control, and c refers to microgravity versus gravity.

Fig. 5. Effect of treatment with ethanolic extracts of T. aestivum under gravity and microgravity conditions for 30 days on liver and kidney functions and lipid profiles in experimental rats.

a shows the effect of ethanolic extracts of T. aestivum under gravity and microgravity conditions on biomarkers of kidney function in experimental rats. b shows the effect of ethanolic extracts of T. aestivum under gravity and microgravity conditions on the lipid profiles of experimental rats. c shows the effect of ethanolic extracts of T. aestivum under gravity and microgravity conditions on biomarkers of liver function in experimental rats. The values are expressed as the mean ± SEM of seven rats in each group. Data were analyzed by using two-way ANOVA, followed by Tukey’s multiple comparison test with the level of significance set at P < 0.05. a refers to treatment versus normal control, b refers to treatment versus diabetic control, and c refers to microgravity versus gravity.

Fig. 6. Photomicrographs of H&E-stained histological slides of pancreatic specimens.

a Normal histological appearance of the islets of Langerhans from the pancreases of rats in the control group. b The pancreases of rats in the diabetic control group showed degeneration, necrotic changes, and islet shrinkage. c The appearance of pancreas sections from rats administered the ethanolic extract of T. aestivum under gravity conditions showed improved islet morphology. d The appearance of pancreas sections from rats administered the ethanolic extract of T. aestivum under microgravity conditions showed the normal structure of the pancreatic islets of Langerhans. e shows that there were no pathological changes in the islets of Langerhans of the pancreas in diabetic rats treated with metformin. Original magnification was ×400. f The pancreatic β cell number per islet in different treatment groups. Groups were compared to the control untreated group. As shown in the figure, microgravity extract treatment had a highly significant effect on the pancreatic β cell number per islet compared to the normal untreated control group. Data were compared against data for the normal control by using one-way ANOVA with Bonferroni’s multiple comparisons test with the level of significance at P < 0.05. *, ***, ****, ns = P < 0.05, P < 0.001, P < 0.0001, and nonsignificant, respectively.