Protective effect of hyperbaric oxygen on the reduction of glucose in Goto-Kakizaki rats with type II diabetes mellitus

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Objective To observe the effect of hyperbaric oxygen (HBO) on the reduction of glucose in Goto-Kakizaki (GK) rats with type Ⅱ diabetes mellitus,and to further explore its mechanism involved.Methods Seventy-two 5-month SPF male GK rats were randomly assigned to 3 groups:the model group,the metformin hydrochloride group and the HBO group,with each group further divided into 3 subgroups.Another 24 male healthy 5-month Wistar rats were chosen as the normal control group.The rats in the HBO group received HBO treatment by inhaling pure oxygen under a constant pressure of 0.15 MPa for 30 minutes,while the rats in group 2 were treated with gastric feeding of metformin hydrochloride 250 mg/( kg · d) once a day.At the same time,all the rats in the control group,the model group and the HBO group had gastric feeding of purified water 5 ml/(kg · d) once a day.The levels of fasting blood glucose and glucose transport protein ( GLUT-1 ) of all the rats were measured respectively after 1,2 and 3 weeks of treatment.Moreover,one Wistar rat in the control group and two in the HBO group were chosen to have dynamic glucose monitoring for 72 hours.Glucose level of all the animals in the 4 groups were measured 4 hours after fasting,every other day,and 2 rats were chosen from each group for observation of the changes in the ultrastructure of islet B cells in the pancreas under the electron microscope.Results Blood glucose level of the GK rats in the metformin hydrochloride group on day 7 was (9.71 ± 2.07 )mmol/L,that of the rats in the HBO group on day 7 was(9.79 ± 2.12) mmol/L,that of the rats in the model group on day 7 was (9.99 ± 2.31 ) mmol/L,and that of the rats in control group was (4.90 ± 0.56) mmol/L.No statistical significance could be noted,when comparisons were made between the groups (P ＞ 0.05 ).Following treatment on d 7,the level of serum glucose transport protein of the control group was (7.12 ± 2.11 )ng/L,that of the model group was (3.98 ± 1.25 )ng/L,that of the metformin hydrochloride group was (4.56 ± 1.76) ng/L and that of the HBO group was (4.37 ±0.68)ng/L.Significant statistical differences could be noted,when comparisons were made between the groups(P ＜ 0.01 ).Following treatment on day 14,the level of serum glucose transport protein for the control group was (7.06 ± 0.54) ng/L,that of the model group was (3.99 ± 0.85 ) ng/L,that of the metformin hydrochloride group was (5.06 ± 0.77) ng/L.Statistical differences could be detected in the level of glucose transport protein,when comparison were made between the control group,the model group and the metformin hydrochloride group (P ＜ 0.01 ).Conclusions HBO seemed to have the capacity of lowering glucose level of GK rats through enhancement in the level of glucose transport protein and improvement of the structure/function of the islet B cells. Key words: Hyperbaric oxygen; Type Ⅱ diabetes mellitus; Glucose transport protein; Dynamic glucose monitoring