Changes in Lipid Profile and Heart Tissues of Wistar Rats Induces by Using Monosodium Glutamate as Food Additive

Experimental Animals

The experiment was conducted on 8 normal adult male albino rats with an average weight from 94- 100 g. the animals were kept in standard neat metallic and well ventilated cages. They maintained on standard healthy laboratory conditions at temperature of 18-24°C and an appropriate humidity and lighting. They had access to 12hr of darkness and 12 hours of daylight. All rats had free access to drinking water and food.

Experimental Design

During the experimental period, they were fed with standard pellet during the experimental period. They were fed with standard pellet diet (consisting of 60% starch, 20% casein, 10% cotton seed oil, 4% salt mixture, 5%cellulose, and 1% vitamin mixture). After the adaptation period of 14 days, the rats were distributed into 4 equal groups, each contained 3 rats. Group I (G1) represented the healthy control animals and received distilled water. The second group (G2, low dose) received 0.5 g MSG, third group (G3, mid dose) received1.0 g MSG, and fourth group (G4, high dose) received 1.5 g MSG with daily supply of drinking water for 3 weeks.

Preparation of Monosodium Glutamate

0.5 g of MSG was dissolved in 2ml of water for group one (low dose). 1g of MSG was dissolved in 2ml of water for group two (medium dose).1.5 g of MSG was dissolved in 2ml of water for group three (high dose).

Blood Collection and Samples Preparation

Pre samples has been taken from the eye of each groups by heparinized capillary tube and kept in specific labeled plain container. Serums were separates by centrifuge at 5000 rpm for 5 minutes and stored in freezer until analysis. At the end of the experimental period of 3 weeks, blood was collected from each rat individually for biochemical assay. The animals were fasted for twelve hours prior to blood collection. All animals were anesthetized by chloroform and blood samples were collected immediately from their heart using heart puncture technique with the aid of disposable sterile syringe and needle (Sigma). Blood samples were then transferred into capped tubes with no anticoagulant,. The blood was allowed to clot at room temperature for 30 minutes prior to centrifugation at 2500 rpm for 20 minutes using centrifuge to obtain the serum for biochemical analysis. The yellow serum supernatant was removed. The spectrophotometer Analyzer was used to determine the concentration of serum triglycerides, total cholesterol, low density lipoproteins (LDL) and high density lipoprotein (HDL). This machine is a fully automated and composed of an analytical unit which produces chemical reactions in samples, an operation unit which inputs and outputs analytical conditions, and a control unit which controls each function required for operation of the instrument.

Methods

Serum Cholesterol: It was determined according to method described by Meiattini, et al. and Allain, et al. [12, 13]. Serum Triglyceride: It was determined according to method described by Friedman and Young; Fassati and Prencips [14, 15]. Serum high density protein (HDP): It was determined according to method described by Burstein, et al. and Grove [16, 17]. Serum low density protein (LDP): It was determined according to method described by Salah, et al. [18].

Histology Sample Processing

Statistical analysis: the heart tissue was fixed in 4%formldehyed for sample preservative , then the tissue was dehydrated by passing it through increasing of ethyl alcohol ( from 0 to 100%) this step called (processing ). After replacement occurs, the alcohol was replaced with xylene, which is miscible with alcohol. This step is called (clearing), then, tissue was embedded in paraffin wax which becomes hardened was sectioned using rotary microtome. The sections where rehydrated by passing through xylene, and then decreasing strength of alcohol (100% to 0%) and finally water, and stain with heamoxlyin and eosin and then dehydrated again using xylene, then mounted on the microscope slide, a cover slip was placed on top, to protect the sample which read under microscope in 40X.

Data was statistically analyzed by using one-way analysis of variance and the unpaired t-test.

Lipid Profile

Table 1 indicated that mean values of free cholesterol

for G1, G2, G3 and G4 are100.6±0.55, 117.3±0.6, 164.7±0.49

and 210.7±0.25 mg/dl, respectively. These results are

clearly illustrated that the cholesterol level was

significance increased in low, mild and high doses

compared with control at level P ≤ 0.05. The findings are

agree with those results obtained by Saeed [19]. The level

of cholesterol obtained for G2 and G3 within normal range

(125- 200 mg/dl), but cholesterol level of G4 is greater

than those finding by Huizen [9]. Therefore, these treated

rats are subjected to cardiovascular disease such as

coronary heart disease and stroke due to increasing the

concentration of SMG. Whereas, mean values of

Triglyceride for G1, G2, G3 and G4 are118.6±1.66,

$$ 6 0. 7 \pm 0. 6 8, \mathrm {a n d} 1 7 7. 3 9 \pm 2 0 \mathrm {a n d} 2 2 5. 3 \pm 6 3 \mathrm {m g / d l}, $$

respectively. These results are clearly illustrated that the

triglyceride levels are significance increased in low, mild

and high doses compared with control at level P ≤ 0.05.

These findings are similar to those results obtained by

Saeed [20]. The level of triglyceride obtained for G2 is low

while for G3 and G4 is higher than those values reported

by Huizen [9]. Therefore, when consumed calories are

greater than requirement of body, then liver forms

triglycerides from the excess energy and these are stored

as fat. While mean values of LDL-C for G1, G2, G3 and G4 are

37.6±0.7, 55.3±0.77, 59.6 ±0.9 and 69.8±0.42 mg/dl,

respectively. These findings are indicated that mean value

of LDL-Cholesterol was significance increased in low, mild

and high dose compared with control at level P ≤ 0.05.

The range of LDL-C obtained is 55.3 – 69.8 mg/dl which is

lower than range (38 – 85 mg/dl) reported by Colpo [11].

If the LDL concentration is high in blood, then it is

precipitate in artery (arterial disease). Therefore, LDL is

known as bad cholesterol. Mean values of HDL-C for G1,

G2, G3 and G4 are 43.71±0.09, 41.18±0.73, and 43.90±0.57

and 65.75±0.64 mg/dl, respectively. These findings are

indicated that HDL-C was significance decreased in G2 and

G3, but increased in high in G4 compared with control (G1)

at level P ≤ 0.05. These results are contradicted to

previous study which reported significance decrease in

the concentrations of serum HDL in G2 and G3but,

increasing in G4 [20]. This contradiction may be due to

immaturity of rats or short period of experiment. The

range of HDL-C obtained is 41.2 – 65.8 mg/dl which

greater than normal range (21 – 54mg/dl) reported by

(HEART-UK- www.heartuk.org.uk). The ratio of

cholesterol to HDL for G1, G2, G3, and G4 is 2.28, 2.84, .75

and 3.19, respectively. The results are indicated that ratio

of cholesterol to HDL is increased with increasing doses of

Figure 1: represents control (not treated with monosodium glutamate. There is no change in heart tissues of Wistar rats. Figure 2 showed slightly change in heart myofibers of Wister rat treated with low dose (0.5g). Figure 3 indicated degenerations change on heart tissues of Wister rat treated with medium dose (1.0g). Figure 4 indicated congestions change and hemorrhage on heart tissues of Wister rat treated with high dose (1.5g).

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