The Effect Of Acupuncture on the Feeding Center of Hypothalamus in Experimental Obese Rats

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INTRODUCTION

Many studies showed that acupuncture is effective in treatment of obesity.[ 1-3] It is indicated in the modern physiological research that there are appetite centers related to intake activity in hypothalamic nodes of the mammal[ 4], of which the lateral hypothalamus area (LHA) is the intake center (also called hunger center), acting on making a decision of starting intake activity, and the ventral medium nucleus of the hypothalamus (VMH) is the satiety center, acting on making a decision of stopping intake activity. In order to probe into the function of acupuncture on the central neural system during weight loss, discover the inter-relationships between central regulation and peripheral function, and perfect the contents of clinical researches, this paper focused on the experimental observation on the characters of electric activity of the nerve cell at unit time in LHA and VMH in experimental obese rats.
MATERIALS AND METHODS Materials

The experiment was performed in the Key Laboratory of Acupuncture and Moxibustion in Changhai Hospital, Second Military Medical University from June 2002 to January 2004. Fifty SD male weaning rats were employed, weighted about 50 g, at the age of 30 days, provided by the Animal Center of the University.
Methods Preparation of the Obese Model

The rats were fed with high-fat forage (4.8 cal/g).[ 5] During model preparation, the rats were free of intaking and drinking; the forage and water were shifted once daily. The success of the obese model was based that on mass increased by 20% compared with the mass of normal rats fed at the same time. Afterward, the obese-model rats were randomized into acupuncture group and obese group, 15 rats for each. In addition, the normal control of 15 rats was designed, fed with common granular forage. (Remark: a part of rats were eliminated naturally during the experiment).
Acupuncture Treatment

The rats in the acupuncture group entered treatment stage right after the success of model preparation. The treatment was given at 8:00 to 9:00 am everyday, once daily on the bilateral points of housanli and neiting alternatively, continuous for 12 times as one session. On housanli, even-needling method was applied by rotating the needle for 0.5 minute; on neiting, reducing method was done by rotating the needle for 0.5 minute, attached on G6805-B electric needling apparatus, at the frequency of 10 Hz, the intensity of 1 V, continuous wave for 5 minutes. Needling continuously for 12 days was taken as 1 session. During such period, the rats of every group were fed with common forage, being free of intaking and drinking; the forage and water were shifted once daily.

Observation of indexes: Mass of rats after model preparation (98 days) at the same time of every group and mass at the same time after one session acupuncture treatment(110 days) were taken as the standards of evaluation on therapeutic effects of acupuncture on weight loss. ( 2) Discharge frequency in LHA and VMH of rats of every group and the observation of electric activity of nerve cell in every group.

After the end of acupuncture treatment, the observation was done on unit discharge in LHA and VMH of rats in every group. The experiment time began at 8:00 am. The concrete methods of the observation of unit discharge in LHA and VMH were as follows: At the constant temperature, the mass was weighed. Afterward, the basic anesthesia was done with ether first, then the compound anesthesia was followed with abdominal injection with urethane at 1g/kg mass. After anesthesia, the catheterization was done at the trachea to prevent asphyxia. Afterward, the rat was supine and fixed on the stereotaxic instrument (KOPF-693 made in USA). The scalp was opened along the midline of the skull cap and the skull was exposed. Regulated horizontally, the anterior fontanelle, median raphe and lambdoid suture were at the same level. According to the illustration of SD rats cerebral stereotaxic alta of Bao et al[ 6], the projections of LHA and VMH were orientated on the skull cap at 1.0 mm-anterior fontanelle, 1.8 mm lateral to media raphe and 2.2 mm-lambdoid suture. A small foramen at 1 mm diameter was done with the animal bone driller. A self-made grass microelectrode (The internal resistance was over 10 M (and the tube was filled up 3 mol KCL with 20g/L pontamine sky blue staining solution added.) was assembled on the micro-propeller (KOPF-650 type made in USA) supporter, by which, LHA was pushed slightly to the intracranal part at the depth of 6.0-6.1 mm and VMH was inserted in the intracranal part at the depth of 6.9-7.1 mm. By amplification in grades with L-FDQ-1 nerve signal amplifier and electro-physiological instrument respectively, the unit discharge in LHA and VMH was induced automatically. The discharge frequency (Hz) was recorded by transforming the measure pattern of computer nerve pulsating signal into pulsating signal. At the end of the experiment, electricity was attached on the negative electrode for 10 minutes and the microelectrode record location was labeled. Afterward, the rat was sacrificed and the brain was collected for fixation and slice preparation and histological identification was carried on.

Statistical Analysis: SPSS 10.0 software was adopted to manage the data and the results were analyzed with t test.
RESULTS

Descriptive Statistics: Totally 50 rats were adopted, but due to unsuccessful preparation of the model 13 were lost. Thirty-seven rats entered the results analysis.

Statistical Inference (Table 1): Mass changes at the same stage before and after acupuncture in rats in 3 groups.

at=12.9, 14.8, P <0.01 _s the normal group; bt=10.1, 7.09, P <0.01 _s the obese group

Discharge frequency in LHA and VMH in rats of every group (Table 2)

By the histological identification, the regions recorded belonging to LHA and VMH were included in the statistics.

Lateral hypothalamus area, VWA: medium nudeus of hypothalamus; at=5.4, 4.86, 10.66, P <0.01 _s the obese group; bt=4.55, P <0.05, ct=13.01, P <0.01 _s the normal group; LHA
DISCUSSION

It was seen in the experimental results that after one session treatment with acupuncture, the mass of rats in the acupuncture group was reduced on average by 58 g (P <0.01), indicating extremely significant difference compared with the obese model group (P <0.01), and that was basically near to the results in the normal group (P >0.05), explaining that acupuncture, by regulating nerve and body fluid, reduces effectively the exceeded mass of obese rats to the normal level basically, which has verified the reliability of acupuncture on weight loss in clinic[ 5].

In addition, it was discovered in Table 1 that the mass in the obese group was still increased continuously fed with normal forage after stopping high-fat forage. The reasons of such result were inspired from Table 2. The excitatory state in the hunger center of obese rats was at a higher active level (P <0.01) and excitatory level in satiety center was relatively lower (P <0.01). It is explained that since childhood (30 days), the obese rats are fed with high-fat forage, which invigorates the strong appetite and hyperfeeding function, resulting in the excitability predominated in hunger center and the reducing tendency of excitatory level in satiety center. Even at an unreal hunger state, overeating behavior still existed, resulting in excessive calories and accumulation of fat, which is the main reason of food obesity. Besides, feeding high-fat forage instead of normal forage is probably one of the reasons of the hunger state. It was also observed that the intake amount was increased during the feeding. It is indicated in modern medical research that the activities between the hunger center and satiety center are inter-restricted[ 7] and inter-supplemented so as to maintain the intake dynamic equivalence. The obese patients destroy such dynamic equivalence, their appetite is the obstacle of weight loss, and therefore, it is very difficult for them to reduce weight only depending on their own subjective desire and willpower. The results of the research in this paper provides as the reference that the effective channel for obese patients to achieve weight loss by the integration of medical means and subjective consciousness as well as self-control capacity. It is also verified initially in this experiment that it is absolutely necessary for weight loss to be achieved by the adjustment of acupuncture and food quality. Much better weight loss results will be obtained by the integration of acupuncture treatment and changes of food components.

It was seen in Table 2 that after 1 session treatment with acupuncture, the electric activity in LHA was much lower than that in obese group and same as the normal group. The electric activity in VMH was much higher than that in obese group and higher than the normal group, explaining that acupuncture not only reduces excitability of LHA, but also increases excitability of VMH to achieve the predominated activity in the satiety center, weaken the activity of LHA and reduce its excitability so as to control the excessive appetite of obese rats[ 8], reduce calorie intake and provide the positive action on regulating the movement of gastro-intestine and absorption and promoting consumption and utilization of accumulated fat in the body. To conclude, the action of acupuncture on the adjustment of central nuclei in the hypothalamus is one of the main mechanisms of weight loss. Concerning the electric activity of VMH in acupuncture group being higher than the normal group, it is probably the short-term oscilation during central adjustment in the treatment for enhancing the results of weight loss. But the further study is required to verify this.
Table1. Mass changes at the same before and after acupuncture in rats in 3 groups

Legend for Chart:

A - Group
B - n
C - Before Acupuncture
D - After Acupuncture

A B C
D

Acupuncture 13 468.9 ± 11.0(a)
411.3 ± 17.6(b)

Obese 13 471.2 ± 8.7(a)
481.4 ± 17.2

Normal 11 398.5 ± 15.3
410.6 ± 16.8(b)

(a) t = 12.9, 14.8, P<0.01 _s the normal group;

(b) t = 10.1, 7.09, P<0.01 _s the obese group

Table 2: Discharge frequency in LHA and VMH in rats of every group

Legend for Chart:

A - Group
B - n
C - Before Acupuncture
D - After Acupuncture

A B C
D

Acupuncture 13 9.3 ± 3.8(a)
21.4 ± 4.2(ab)

Obese 13 21.5 ± 6.7
5.1 ± 1.4

Normal 11 9.2 ± 5.3(a)
14.6 ±2.3(c)

Lateral hypothalamus area, VWA: medium nudeus of hypothalamus;

(a) t = 5.4, 4.86, 10.66, P<0.01 _s the obese group;
(b) t = 4.55, P<0.05, (c) t = 13.01, P<0.01 _s the
normal group; LHA

REFERENCES

[1] Shiraishi T, Onoe M, Kojima TA, et al.Effects of bilateral auricular acupuncture stimulation on body weight in healthy volunteers and mildly obese patients. Exp Biol Med 2003,228(10):1201-7.

[2] Pittler MH, Ernst E. Complementary therapies for reducing body weight: a systematic review. Int J Obes Relat Metab Disord. 2005, 29(9): 1030-8.

[3] Cabioglu MT, Ergene N. Electroacupuncture therapy for weight loss reduces serum total cholesterol, triglycerides, and LDL cholesterol levels in obese women. Am J Chin Med. 2005;33(4):525-33.

[4] Bear MF, Connors BW, Paradiso CM. Neuroscience: Exploring the Brain. Beijing: Higher Education Press 1983: 185

[5] Liu ZC, Sun FM, Han Y, et al. Experimental research of acupuncture treating simple obeity. Acupuncture Res 1998,23(1):69-75

[6] Bao XM, Shu SY. Rat Brain Solid Orientation Atlas. Beijing: Peoples Hygiene Press 1991:32, 37

[7] Wan XC, Yang TZ, Xu CT. Modern Neurology. Beijing: Beijing University of science and technology. Peking Union College Press 1999:435

[8] Zhao M, Liu ZC, Su J. Acupuncture effect of experimental fat rat hypothalamus diet center. Acupuncture Res 1999, 24(2):98-101

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By Yue-sheng Xia, ND

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