| 1AimTo investigate and evaluate the effects of low frequency (2Hz) electroacupuncture at the point Zusanli (ST36) on fasting blood glucose (FBG), fasting serum insulin (FI), oral glucose tolerance test (OGTT), quantitative insulin sensitivity check index (QUICKI), serum glucagon-like peptide-1(GLP-1) and pancreatic β cell histology in diet and streptozotocin (STZ) induced T2DM Wistar rats.2MethodFirstly to create the T2DM rat model,30eight week old male Wistar rats were randomly divided into a model group (n=20) and a control group (n=10). Insulin resistance was induced by high fat high sugar diet for four weeks while the control group was raised on regular lab chow. Model rats were then given an intraperitoneal injection of STZ (30mg/kg) to directly damage the pancreatic (3cells and induce T2DM. After a two week stabilisation period an OGTT was performed to evaluate the success of the model. Rats from the model group that met the requirements for inclusion were then further divided into two groups: acupuncture treatment (n=8) and model comparison (n=8). The acupuncture group received two courses of low frequency2Hz1mA electroacupuncture treatment at Zusanli, each course consisted of ten consecutive days of treatment with a two day break between each course. Model comparison and control groups were also restrained on treatment days using the same technique as the acupuncture group but treatment was not administered. During the treatment period both the model and acupuncture group continued to feed on high fat high sugar rat chow. After the treatment an OGTT was again performed on all rats. Blood samples were collected before gavage (Omin) and at the30minute point (30min) to observe fasting serum insulin and circulating serum GLP-1. The following day after OGTT and sample collection was completed, all rats were anaesthetized and the pancreas removed. Pancreatic tissue was preserved in formalin and embedded in paraffin wax. The tissue was then cut onto slides and H/E stained for histological examination.3ResultsOGTT:After treatment the model (P=0.01) and treatment (P=0.00) groups had a significantly higher blood sugar curve when compared with the control group. Before treatment the model and acupuncture group showed a high similarity (P=0.99), but after the treatment period had finished the model group’s mean blood glucose curve had risen and although no statistically significant difference between the two groups was observed (P=.33), there was not the same level of similarity. This would suggest a trend that a larger sample size could more accurately assess.FBG:After treatment the FBG levels between each group were significantly different (P=0.01) with the model group rising significantly higher than both acupuncture (P=0.05) and control (P=0.02) groups. More importantly the acupuncture group maintained a similar FBG level, which although significantly higher than the control group (P=0.01) was also borderline significantly lower than the model group (P=0.05). The ANCOVA analysis using before treatment FBG levels as the covariate showed the model group to be significantly higher than both the treatment (P=0.00) and control group (P=0.00) but more importantly the treatment and control groups showed no difference (P=0.96). This indicates that in this experiment electroacupuncture successfully prevented the increased FBG levels seen in the model group caused by the continued high fat high sugar diet.FI:Before and after treatment there was no statistically significant between the groups fasting insulin levels.QUICKI:QUICKI scores for before treatment in the model and acupuncture groups were similar with no significant difference, whereas compared with the control group the model’s QUICKI score had significantly dropped (P=0.02) and the acupuncture group had a borderline significance drop (P=0.05). This result confirms the success of the model as not only the blood glucose levels are high there is also significantly reduced insulin sensitivity. After treatment ANCOVA analysis shows insulin sensitivity in the model group continued to deteriorate whereas the treatment group improved to the point where pairwise comparison showed no difference between the treatment and control groups (P=0.54). These results supported previous studies which demonstrated electroacupuncture’s ability to restore insulin sensitivity. Although the model group deteriorated, it was not statistically different from the acupuncture group (P=0.12) however the trend would suggest that a larger sample size might demonstrate a difference and is worth further investigation.GLP-1:When compared with the control group, successful model rats prior to group division had a significantly higher30minute post meal blood serum GLP-1level (P=0.01), which confirms a previous report that STZ injection raises the serum levels of GLP-1in Wistar rats. After treatment GLP-1levels showed no significant difference between the groups, however the acupuncture group’s mean was higher than other groups which would require a larger sample size and further research.Pancreatic (3cell Histology:Under an optical microscope the control and acupuncture groups showed similar even tissue distribution with comparatively clear structure to the islets. The acupuncture group showed minor signs of fibrous tissue formation with some islets containing swollen β cells. The model group showed heavy deformation of the islets with fibrous tissue formation evident. Examined islets showed extensive swelling of (3cell cytoplasm.4Conclusion(1)Low frequency electroacupuncture at Zusanli controls the advancement of T2DM in diet and STZ induced Wistar rats by improving insulin sensitivity, β cell quality and blood sugar stability.(2) Due to small sample size the effects of electroacupuncture at Zusanli on circulating GLP-1are still unclear and require further investigation.(3) Intraperitoneal injection of STZ can cause fasting serum GLP-1and meal response to rise significantly in Wistar rats. (4) Feeding Wistar rats with high fat high sugar rat chow and administering a single intraperitoneal injection of STZ (30mg/kg) can create T2DM rat models with a relatively high success rate of80%. |
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