The effects of hypoxis hemerocallidea on blood glucose levels in rats with Type 2 diabetes
Elshawesh, Mohamed Abdallah
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About 180 million people have been estimated to suffer from type 2 diabetes (T2DM) in 2006 and the annual death rate due to this disease was 3 million by that time. More than 400 medicinal plants used for the treatment of diabetes mellitus have been recorded, but only a small number of these plants have received scientific and medical evaluation to assess their efficacy. The most common plant used to treat diabetes mellitus is Hypoxis hemerocallidea (HH). The present study was undertaken to investigate the effects of Hypoxis hemerocallidea (HH) on T2DM in rats. Male Wistar rats weighing 200-250 g were used in this experiment. Hypoxis hemerocallidea (HH) corm was used as plant material in the experiment. The study was based on three parts, an acute diabetes study, chronic diabetes study and insulin secretion study. In the acute study, the rats were randomly divided into 2 groups (control and diabetes). The saline solution was added to different concentrations of HH corm to produce concentration of (50, 200, 400, 800 mg/ml). Diabetes was induced by intraperitoneal injections of STZ (65mg/kg). Two weeks after the injection (STZ 65 mg/kg), different concentrations of HHS was administered intraperitoneally after an overnight fast. The blood glucose levels were monitored in the diabetic and control rats at, 30, 60, 120, 180 and 240 minutes post injection. In the chronic study, the rats were randomly divided into 6 different groups (control, HFD, DM, DM-HH, DM-PTHH, and HH). Diabetes mellitus was then induced in the groups of diabetic rats by intraperitoneal injections of STZ (40 mg/kg) and rats were fed a high fat diet (HFD). The body weight of the rats were measured weekly for 7 weeks. An intraperitoneal glucose tolerance test (IPGTT) was performed at the end of week 6. At the end of week 7, rats were killed and serum sample were collected for determination of fatty acid and insulin. Liver and pancreatic tissue was collected for histological evaluation. In the insulin secretion study, Hypoxis hemerocallidea was tested for its effects on insulin secretion by pancreatic islet cells exposed to low (3mM) and high (20mM) glucose medium. Results of the acute study indicated that HHS at a dose 800 mg/ml decreased blood glucose levels fastest in both normal and diabetic rats reaching significance after 30 minutes and 60 minutes respectively and remained below the baseline value until 240 minutes. In the chronic study, it was illustrated that HH had no effect in normal rats on any of the parameters evaluated. Animals in the DM group gained weight the first two weeks, but thereafter began to lose weight. At the end of seven weeks the animals gained significantly less weight than the rest. Animals fed a HFD have more visceral fat compared to the control group. The visceral fat gain occurred in the absence of a significant increase in body weight. We found a markedly lower fasting glucose level in HH treated diabetic animals compared to untreated DM animals. At time zero the blood glucose level of the HFD group (5.8±0.5mmol/l) and the HH group (4.9±0.7mmol/l) were in the normal range, and were not significantly different (P > 0.05) from the control group (5.0±0.2mmol/l). After glucose load peak blood glucose levels was measured after 30 minutes in the control group (9.0±0.6mmol/l), the HFD group (9.8±0.4 mmol/l), the DM-HH group (21±5.7 mmol/l) and the DM-HHPT group (27.8±5.3 mmol/l). In the HH group the blood glucose level reached a peak at 60 minutes (7.6±0.6 mmol/l). In the DM group two peaks were recorded one after 10 minutes (27.2±7.1mmol/l) and another after 60 minutes (31±5.2 mmol/l). In the groups control, HFD, DMHH, DM-HHPT and HH groups the blood glucose level after 120 minutes were not significantly different from the time zero value. The blood glucose level after 120 minutes in the DM group (28.2±7.1 mmol/L) was significantly higher (P ≤ 0.01) than from the time zero value. Serum fatty acid levels were increased in all groups fed a high fat diet. The serum insulin levels in the HFD group (6.2 ± 0.76 μUI/ml protein; P ≤ 0.05 ), the DM group (2.0 ± 0.9 μUI/ml protein; P ≤ 0.001), the DMHH group (3.4 ± 0.7 μUI/ml protein; P ≤ 0.001) and the DM-HHPT group (3.0 ± 1.1 μUI/ml protein; P ≤ 0.001) were significantly lower than the control group. The β-cell function in the HFD group (62 ± 8 %; P ≤ 0.001), the DM group (3 ± 1 %; P ≤ 0.001), the DM-HH (11 ± 9 %; P ≤ 0.001) group and the DM-HHPT group (4 ± 2 %; P ≤ 0.001) were significantly lower than the control group. The histological observation of the liver and the pancreas in rats after 7 weeks on different dietary regimes showed some morphological changes within the liver and pancreas parenchyma of some rats. In the insulin secretion study, glucose stimulated insulin secretion in low (3mM) and high (2mM) glucose concentration. Furthermore, insulin secretion was significantly higher when the glucose concentration was increased from 3mM to 20 mM (1.10 ± 0.13 μUI/ml protein and 1.5 ± 0.17 mIU/mg protein respectively P≤ 0.01). In the presence of low HH (100 µg/ml), there was a marked increase in insulin secretion when exposure to high glucose compared to low glucose concentration, while in the presence of high HH (500 µg/ml), there was no significant different in insulin secretion in the presence of low or high glucose. In conclusion, the results of this experimental study indicate that a concentration 800 mg/kg of HHS produces maximal hypoglycaemic effect in fasted normal and diabetic rats. HH has an antidiabetic activity as it lowers serum glucose levels in T2DM rats and significantly increases glucose tolerance. It also increases body weight of diabetic rats. HH treatment was found to improve insulin secretion in pancreatic islet cells.