Enhanced insulin sensitivity using electroacupuncture on bilateral Zusanli acupoints (ST 36) in rats

Improvement of insulin resistance by Chlorella in fructose-rich chow-fed rats

Chlorella is a type of unicellular fresh water algae. In an attempt to develop new agents for handling insulin resistance, Chlorella was employed to screen the effect on insulin resistance in rats induced by fructose-rich chow. A single oral administration of Chlorella for 90 min decreased the plasma glucose in a dose-dependent manner in rats receiving 4-week fructose-rich chow. In addition, chronic treatment with Chlorella for 15 days also lowered plasma glucose in the same manner. Then, the insulin action on glucose disposal rate was measured using the glucose-insulin index, values of the areas under the curves of glucose and insulin during the intraperitoneal glucose tolerance test (IPGTT). Oral administration (three times daily for 5 days) of Chlorella to rats receiving 4 weeks of fructose-rich chow abolished the elevated value of the glucose-insulin index, indicating that Chlorella has an ability to improve insulin resistance. An increase of insulin sensitivity by Chlorella was further evaluated using the plasma glucose lowering action of exogenous insulin in streptozotocin-induced diabetic rats (STZ-diabetic rats). Oral administration of Chlorella three times daily to STZ-diabetic rats increased the response to exogenous insulin 15 days later. The obtained results suggest that oral administration of Chlorella has the ability to improve insulin sensitivity, which may be used as an adjuvant therapy for patients with insulin resistance.

Electroacupuncture stimulation using different frequencies (10 and 100 Hz) changes the energy metabolism in induced hyperglycemic rats

PURPOSE: To investigate the effect of 10 and 100 Hz peripheral electro-estimulation (electroacupuncture, EAc) at Zusanli (ST-36) and Zhongwan (CV-12) acupoints on blood glucose and lactate levels and tissue (liver and kidney) concentrations of lactate in hyperglycemic induced anesthetized rats. METHODS: Thirty-six rats were randomly assigned to 3 groups (n=12): G1: basal (anesthesia: ketamine (90mg kg-1 body weight)+ xylazine (10mg/kg-1 body weight, i.p.); G2: anesthesia+EA10Hz EAc and G3: anesthesia+EA100Hz EAc). EAc stimulation was delivered for 30 min at 10 mA at selected acupoints. Blood and tissue (kidney, liver) samples were collected at the end of the EAc application (n=6, T30) and 30 minutes later (n=6, T60) for biochemical analysis. G1 samples were collected at the same timepoints. ANOVA followed by Tukey's Multiple Comparison Test was used for statistical analyses. RESULTS: Glycemia decreased significantly (p<0.001) in G2/G3 rats in all timepoints. Kidney and liver lactate concentrations decreased significantly (p>0.001) in G2/G3 rats at T-60 and at T30 timepoints in G2 compared with G1 rats. Lactacedemia decreased significantly at T30 timepoint in G2 compared with G1 rats. G1/G3 tissue lactate levels were not different. CONCLUSIONS: Electroacupuncture (10 Hz) applied to St-36 and CV-12 acupoints decreases glycemia and lactacedemia and liver and kidney lactate concentrations. We hypothesize that the decrease in lactate levels may be related to greater energy production due to enhanced lactate to pyruvate conversion. Higher frequency (100 Hz) failed to promote the same effect.

Increase in plasma glucose lowering action of rosiglitazone by electroacupuncture at bilateral Zusanli acupoints (ST.36) in rats

OBJECTIVES

Hypoglycemia induced by electroacupuncture (EA) is due to an increase of insulin secretion and/or mediation of beta-endorphin. We applied EA at the Zusanli (ST.36) acupuncture point (acupoint) in combination with rosiglitazone (TZD) administration to evaluate their effect on plasma glucose and to explore possible mechanisms of action.

METHODS

Thirty six normal adult Wistar rats were randomly divided into four groups: the 0.1 mg/kg TZD group (0.1TZD), 0.1 mg/kg TZD and EA group (0.1TZD + EA), EA group, and control group. In other experiments, streptozotocin was used to induce type 2 diabetes mellitus in neonatal rats; these were then randomly divided into a 0.1TZD group, 0.1TZD + EA group, and EA group and changes in plasma glucose and insulin concentrations evaluated.

RESULTS

A marked hypoglycemic response was observed in the normal rat 0.1TZD, 0.1TZD + EA and EA groups, with the response more significant in the 0.1TZD + EA group than in the 0.1TZD group. Among the diabetic animals, the hypoglycemic responses in the 0.1TZD + EA and EA groups were greater than in the 0.1TZD group. In both the normal and diabetic rats, insulin secretion was increased by EA or 0.1TZD + EA treatment, but not by 0.1TZD.

CONCLUSIONS

The plasma glucose lowering action of rosiglitazone was increased by EA in both normal and diabetic rats, indicating that the application of EA may enhance the hypoglycemic action of this insulin sensitizer.

Intense electroacupuncture normalizes insulin sensitivity, increases muscle GLUT4 content, and improves lipid profile in a rat model of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is associated with hyperandrogenism and insulin resistance, possibly reflecting defects in skeletal muscle and adipocyte insulin signaling. Low-frequency (2 Hz) electroacupuncture (EA) increases insulin sensitivity in female rats with dihydrotestosterone (DHT)-induced PCOS, but the mechanism is unclear. We hypothesized that low-frequency EA regulates mediators involved in skeletal muscle glucose uptake and metabolism and alters the lipid profile in rats with DHT-induced PCOS. To test this hypothesis, we implanted in prepubescent female rats 90-day continuous-release pellets containing DHT (PCOS). At 70 days of age, the rats were randomly subdivided into two groups: one received low-frequency EA (evoking muscle twitches) for 20-25 min five times/wk for 4-5 wk; the other did not. Controls were implanted with pellets containing vehicle only. All three groups were otherwise handled similarly. Lipid profile was measured in fasting blood samples. Insulin sensitivity was determined by euglycemic hyperinsulinemic clamp, soleus muscle protein expression of glucose transporter 4 (GLUT4), and phosphorylated and nonphosphorylated Akt, and Akt substrate of 160 kDa was determined by Western blot analysis and GLUT4 location by immunofluorescence staining. PCOS EA rats had normalized insulin sensitivity, lower levels of total high-density lipoprotein and low-density lipoprotein cholesterol, and increased expression of GLUT4 in different compartments of skeletal muscle compared with PCOS rats. Total weight and body composition did not differ in the groups. Thus, in rats with DHT-induced PCOS, low-frequency EA has systemic and local effects involving intracellular signaling pathways in muscle that may, at least in part, account for the marked improved insulin sensitivity.

Acupuncture: is it effective for treatment of insulin resistance?

Insulin resistance (IR) is closely associated with obesity, type 2 diabetes mellitus (T2DM), hypertension, polycystic ovary syndrome (PCOS), non-alcohol fatty liver diseases (NAFLD) and metabolic syndrome and is also a risk factor for serious diseases such as cardiovascular diseases. Pharmacological treatments available for IR are limited by drug adverse effects. Because acupuncture has been practiced for thousands of years in China, it has been increasingly used worldwide for IR-related diseases. This review analyses 234 English publications listed on the PubMed database between 1979 and 2009 on the effectiveness of acupuncture as a treatment for IR. These publications provide clinical evidence, although limited, in support of the effectiveness of acupuncture in IR. At this stage, well-designed, evidence-based clinical randomized controlled trial studies are therefore needed to confirm the effects of acupuncture on IR. Numerous experimental studies have demonstrated that acupuncture can correct various metabolic disorders such as hyperglycemia, overweight, hyperphagia, hyperlipidemia, inflammation, altered activity of the sympathetic nervous system and insulin signal defect, all of which contribute to the development of IR. In addition, acupuncture has the potential to improve insulin sensitivity. The evidence has revealed the mechanisms responsible for the beneficial effects of acupuncture, though further investigations are warranted.

Acute effect of electroacupuncture at the Zusanli acupoints on decreasing insulin resistance as shown by lowering plasma free fatty acid levels in steroid-background male rats

Background

Insulin sensitivity has been enhanced by electroacupuncture (EA) in rats, but the EA phenomenon in an insulin resistant state is still unclear. This study reports the use of a large dose of prednisolone to evaluate the effects of EA in a state of insulin resistance.

Methods

The plasma levels of free fatty acids (FFAs) were estimated in steroid-background rats (SBRs) and compared with those in healthy rats treated with normal saline. In addition, plasma glucose and endogenous insulin levels were assayed to calculate the homeostasis model assessment (HOMA) index. Intravenous glucose tolerance test (IVGTT) was carried out to compare glucose tolerance. The SBRs were randomly divided into EA-treatment and non-EA treatment groups and 15-Hz EA was applied to the bilateral Zusanli acupoints to investigate its effects on insulin resistance. In addition to an insulin challenge test (ICT) and IVGTT, the plasma levels of FFAs were measured and western blot was performed to help determine the effects of EA on the insulin resistant state.

Results

The plasma levels of FFAs increased markedly in SBRs, the HOMA index was markedly higher, and glucose tolerance was impaired. EA improved glucose tolerance and insulin sensitivity by decreasing the plasma levels of FFAs. Further, the insulin signaling proteins (IRS1) and glucose transporter isoform protein (GLUT4) in skeletal muscle inhibited by prednisolone recovered after EA.

Conclusion

Insulin resistance was successfully induced by a large dose of prednisolone in male rats. This insulin resistance can be improved by 15 Hz EA at the bilateral Zusanli acupoints, as shown by decreased plasma levels of FFAs.

Electro-acupuncture improves responsiveness to insulin via excitation of somatic afferent fibers in diabetic rats

The effects of electro-acupuncture (EA) on plasma concentration of glucose and on responsiveness to insulin were examined in an animal model of diabetes, the streptozotocin-treated rat. Two weeks after treatment with streptozotocin, rats were anesthetized with urethane-chloralose and subjected to the EA for 10 min delivered to the tibialis anterior muscle of one side. The stimulation produced no significant changes in plasma glucose concentration. In contrast, EA increased the response of plasma glucose to insulin (0.2 U kg(-1)). The effect of EA on the responsiveness to insulin was abolished by section of both sciatic and femoral nerves ipsilateral to the side of the EA. These results show that EA in diabetic rats has no effect on plasma glucose concentration while it augments the responsiveness to insulin, and we show that this occurs via a mechanism that involves the somatic afferent nerves.

Electroacupuncture restores learning and memory impairment induced by both diabetes mellitus and cerebral ischemia in rats

Previous investigations have demonstrated that electroacupunctural stimulation can ameliorate primary and secondary symptoms such as peripheral neuropathy and diabetic encephalopathy in diabetic rats. In this study, we investigated whether electroacupuncture could improve learning and memory which was typically impaired in diabetic rats with cerebral ischemia. Furthermore, we investigated the mechanisms underlying its effects using passive avoidance test, active avoidance test, Morris water maze and electrophysiology. Electroacupuncture increased the step-down latency in passive avoidance test and accurate rate in active avoidance test, decreased the escape latency in Morris water maze. After electroacupuncture treatment, the long-term potentiation (LTP) impaired by both diabetes and cerebral ischemia was restored significantly. These results suggest that electroacupuncture can ameliorate learning and memory capacity impaired by hyperglycemia and ischemia. LTP plays a very important role in this beneficial effect.

Low-frequency electro-acupuncture and physical exercise improve metabolic disturbances and modulate gene expression in adipose tissue in rats with dihydrotestosterone-induced polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a complex endocrine and metabolic disorder associated with ovulatory dysfunction, hyperandrogenism, abdominal obesity, and insulin resistance. Pharmacotherapy is often unsatisfactory. This study evaluates the effects of low-frequency electro-acupuncture (EA) and physical exercise on metabolic disturbances and adipose tissue mRNA expression of selected genes in a rat PCOS model characterized by insulin resistance and adiposity. Dihydrotestosterone (inducing PCOS) or vehicle (control) was administrated continuously, beginning before puberty. At age 10 wk, PCOS rats were randomly divided into three groups; PCOS, PCOS EA, and PCOS exercise. PCOS EA rats received 2-Hz EA (evoking muscle twitches) three times/wk during 4-5 wk. PCOS exercise rats had free access to a running wheel for 4-5 wk. EA and exercise improved insulin sensitivity, measured by clamp, in PCOS rats. Exercise also reduced adiposity, visceral adipocyte size, and plasma leptin. EA increased plasma IGF-I. Real-time RT-PCR revealed increased expression of leptin and IL-6 and decreased expression of uncoupling protein 2 in visceral adipose tissue of PCOS rats compared with controls. EA restored the expression of leptin and uncoupling protein 2, whereas exercise normalized adipose tissue leptin and IL-6 expression in PCOS rats. Thus, EA and exercise ameliorate insulin resistance in rats with PCOS. This effect may involve regulation of adipose tissue metabolism and production because EA and exercise each partly restore divergent adipose tissue gene expression associated with insulin resistance, obesity, and inflammation. In contrast to exercise, EA improves insulin sensitivity and modulates adipose tissue gene expression without influencing adipose tissue mass and cellularity.

Acupuncture in polycystic ovary syndrome: current experimental and clinical evidence

This review describes the aetiology and pathogenesis of polycystic ovary syndrome (PCOS) and evaluates the use of acupuncture to prevent and reduce symptoms related with PCOS. PCOS is the most common female endocrine disorder and it is strongly associated with hyperandrogenism, ovulatory dysfunction and obesity. PCOS increases the risk for metabolic disturbances such as hyperinsulinaemia and insulin resistance, which can lead to type 2 diabetes, hypertension and an increased likelihood of developing cardiovascular risk factors and impaired mental health later in life. Despite extensive research, little is known about the aetiology of PCOS. The syndrome is associated with peripheral and central factors that influence sympathetic nerve activity. Thus, the sympathetic nervous system may be an important factor in the development and maintenance of PCOS. Many women with PCOS require prolonged treatment. Current pharmacological approaches are effective but have adverse effects. Therefore, nonpharmacological treatment strategies need to be evaluated. Clearly, acupuncture can affect PCOS via modulation of endogenous regulatory systems, including the sympathetic nervous system, the endocrine and the neuroendocrine system. Experimental observations in rat models of steroid-induced polycystic ovaries and clinical data from studies in women with PCOS suggest that acupuncture exert long-lasting beneficial effects on metabolic and endocrine systems and ovulation.

Proposal open for discussion: defining agreed diagnostic procedures in experimental diabetes research

BACKGROUND

Animal experimentation has a long tradition in diabetes research and has provided invaluable benefits with regard to insulin discovery and treatment assessment.

METHODS

The review focuses on chemical-induced diabetes in rats and surveys the protocols of diabetes induction, diabetes diagnosis, and glucose tolerance evaluation in a selection of recent research.

RESULTS

This brief review of techniques in experimental diabetes highlights that there is no uniformity, whereas standardisation of procedures is desirable so that comparability will exist among experiments carried out in different settings.

CONCLUSIONS

On this basis, questions are put and standards are proposed. It would be a platform to promote the exchange of ideas through expert consultation about practical issues related to animal research and a basis on which standards can be set according to user requirements and animal respect.

Enhanced insulin-hypoglycemic activity in rats consuming a specific glycoprotein extracted from maitake mushroom

AIM

Intraperitoneal glucose tolerance (ipGTT) and insulin challenge (ICT) tests were implemented to evaluate whether a specific glycoprotein extract of maitake mushroom (Grifola frondosa) known as SX-fraction enhances insulin sensitivity in spontaneously hypertensive rats (SHR).

METHODS

SHR were divided randomly into a control group, a group receiving the antidiabetic drug, pioglitazone, in their diet, and three groups consuming three different concentrations of SX-Fraction derived from maitake mushroom in their food. The response of circulating glucose and insulin concentrations was examined at different time periods during an ipGTT. The major action of exogenous insulin during the ipGTT occurred within a 15-min period following injection of regular insulin. Accordingly, hypoglycemic activity was evaluated in SHR with and without glucose challenge over a short time frame in the ICT.

RESULTS

Evidence gathered from the ipGTT and ICT tests suggests that the SX-fraction of Maitake in a proper dosage as well as pioglitazone enhance insulin sensitivity. Ingestion of SX-fraction produced a lower-circulating level of glucose after challenge despite no rise in circulating insulin. Compared to control, significantly lower-circulating glucose levels were seen in the groups consuming pioglitazone and higher doses of SX-fraction at 7.5 min after insulin challenge whether or not glucose was given concomitantly.

CONCLUSION

SHR in the pioglitazone and SX-fraction groups showed improved glucose tolerance despite no elevation of circulating insulin concentrations and showed enhanced sensitivity to exogenous insulin. Thus, a glycoprotein extract from Maitake mushroom (SX-fraction) should be considered as an alternative method for improving insulin sensitivity.