Cardio-protective properties of Momordica charantia in Albino Rats

Cardio-protective properties of Momordica charantia in Albino Rats Sheriff OL, Yusuf FA Abstract: Momordica charantia, commonly known as bitter gourd, is used as a vegetable by the Asian community in Africa. It is frequently used as an anti-diabetic herb for the management of disease in the Ayurvedic system of Medicine. This present study was aimed at evaluating possible cardio-protective properties of M. charantia by determining its effect on blood cholesterol levels in albino rats. The study involved 25 rats and they were divided into 5 groups each comprising of 5 rats. The aqueous extract of M. Charantia was administered orally with syringes and cannula to 4 groups at different doses (80mg/kg, 100mg/kg, 120mg/kg and 140mg/kg body weights per day, respectively) and the last group served as the control and were given drug vehicle (normal saline) only. After two weeks of administration, the 25 rats were sacrificed and blood samples were collected and assayed for total blood cholesterol, triglyceride, highdensity lipoprotein and low-density lipoprotein levels. Results indicated that M. charantia plant extract increased significantly (P<0.05) the low density lipoprotein levels in the experimental group B (100mg/kg), and significantly reduced low density lipoprotein levels (P<0.05) in the experimental group A (80mg/kg), when compared to the control group. This study showed that M. charantia plant extract has cardio-protective properties by its dose-dependent effects on blood cholesterol.


Introduction
Finding healing powers in plants is an ancient idea.People on all continents have long applied poultices and imbibed infusions of hundreds, if not thousands, of indigenous plants, dating back to prehistory 1 .
It is estimated that there are 250,000 to 500,000 species of plants on Earth 2 .Relatively small percentages (1 to 10%) of these are used as foods by both humans and other animal species.It is possible that even more are used for medicinal purposes 3 .Momordica charantia (MC), a member of the Cucurbitaceae family, is known as bitter melon, bitter gourd, balsam pear, karela, and pare.It grows in tropical areas of the Amazon, East Africa, Asia, India, South America, and the Caribbean and is used traditionally as both food and medicine.Several studies revealed that this plant has antiulcer, anti-diabetic, antifungal, anti-leukemic, antiprotozoan, antibacterial, anti-fertility, antiviral, and hypoglycemic effects 3, 4, 5 .
Cholesterol is a waxy steroid metabolite found in the cell membrane and transported in the blood plasma of animals 6 .It is an essential structural component of mammalian cell membranes and also an important component for the manufacture of bile acids, steroid hormones and fat soluble vitamins 7 .Cholesterol, being amphipathic, is transported in the surface monolayer of the lipoprotein particle.
There are several lipoproteins within the blood; these include chylomicrons, very-low density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL).The lipoprotein particles are molecular addresses that determine the start-and endpoint for cholesterol transport.
The more cholesterol and less protein a lipoprotein has, the less dense it is.The LDL molecules are the major carriers of cholesterol in the blood 8 .
Studies have shown that having large numbers of HDL particles correlates with better health outcomes; in contrast to having small numbers which has been associated with atheromatous disease progression within the arteries 2 .Low HDL cholesterol is an independent cardiovascular risk factor.
Clinical evidence also indicates that a low level of HDL is a major risk factor of atherosclerosis.
Raising HDL significantly reduces this risk, making HDL levels an important target of treatment, particularly in patients with pre-existing atherosclerosis.
Both LDL and HDL cholesterol levels are important factors to determining the risk for coronary artery disease.An increase in coronary artery disease is associated with increased LDL and decreased HDL cholesterol levels 10 .
As high LDL and low HDL are both independent risk factors for heart disease, the ratio of the two numbers is a useful tool to evaluate cardiovascular risk.Numerous natural substances have been shown to positively affect the HDL/LDL ratio.
Triglycerides are esters composed of a glycerol bound to three fatty acids.They are major components of VLDL and chylomicrons and play an important role in metabolism as energy sources and transporters of dietary fat.High levels in the bloodstream have been linked to some cardiovascular diseases 11 .
Despite the widespread usage of this plant in folk medicine in the management of many health conditions, only a few, nonrandomized clinical studies have investigated the effects of MC in humans 12, 13,   16, 15 .It is therefore crucial to conduct more studies which will shed more light on its other physiological effects.This study therefore seeks to assess possible cardio-protective properties of MC by determining its effect on the blood cholesterol level in rats.

Materials and methods:
Experimental protocol: Twenty-five albino rats (mean weight 150-180g) were maintained under standard laboratory conditions and were allowed free access to food and water ad libitum.Animals were divided randomly into five groups.Control (distilled water): group A, MC (80mg/kg for 14 days); group B, MC (100mg/kg for 14 days), group C, MC (120mg/kg for 14 days); and group D, MC (140mg/kg for 14 days).

Extract, route and blood collection:
The leaves of MC were aired and dried and milled into pow-der.1.5 kg of the sample was percolated in 13 liters of water for about 48 hours, after which it was filtered and evaporated using water bath to give about 220g of a dark solid extract which was stored at 4 0 C temperature before physiological studies were made before oral administration.
After two weeks of administration, the 25 rats were sacrificed by cervical dislocation after being anaesthetized with chloroform.Blood samples were obtained through cardiac puncture.
Statistical analysis: All results were expressed as mean±SEM.Data was analysed by one-way analysis of variance (ANOVA) and Duncan New Multiple Range Test (DMRT).Differences in means were considered significant at P<0.05.All analysis was performed using SPSS Version 17.

Results
Effect of Momordica charantia (MC) on total cholesterol: Administration of MC caused insignificant changes in the total cholesterol levels in experimental groups after 14 days of treatment when compared to the control group (fig1).Effect of Momordica charantia on LDL-C: The measured levels of LDL-C showed significant changes in the groups A (80mg/kg) and B (100mg/kg).It was significantly lowered in group A (1.1 mmol/L) and signicantly raised in group B, when compared with the control.The other experimental groups showed no significant changes when compared to the control (fig 4).

Discussion
The study revealed insignificant changes in total cholesterol level in MC administered rats as com-pared with controls.The blood triglyceride levels and HDL-C levels exhibited insignificant increases and decreases while the LDL-C levels showed significant changes at different doses of administration.These results suggest that MC, when administered orally and at doses employed, has a significant dose/duration modulating effect on blood cholesterol levels.
The normal total cholesterol levels seen in our study indicates that MC possibly has no effect on total cholesterol levels.This is contrary to findings of Chaturvedi et al; 2004 16 , who reported that rats exposed to MC for 30 days had significantly low-ered total blood cholesterol levels.This differing result is probably due to the difference in duration and dose of administration.It therefore appears that the effect of MC on total cholesterol levels in rats is both dose and duration dependent, with the duration factor being more pronounced.
The triglyceride level usually provides a useful index for cardiovascular risk assessment in experimental studies.The observed levels in control and experimental rats suggest that the administration of MC at doses and duration used had no effect on blood levels.This is contrary to results by Chatuvedi and Ahmed et al in which triglyceride levels showed a dose-dependent response to the MC extract 16,17 .It may therefore be plausible to note that the levels of blood triglyceride may be associated with the insensitivity of triglyceride to MC in-vivo, which is likely due to the short duration of treatment.
The LDL-C level in this study showed significant increase and decrease at differing doses.Experimental rats in group B showed significantly lowered LDL-C levels.This corresponds to results observed in studies carried out by Chaturvedi   (2005) in which LDL-C levels where found to be low, even in the groups on 80mg/kg dose 18 .This is probably due to the lowering effect of MC on apolipoprotein B (Apo B) secretion by the liver, with a consequent reduction in LDL-C levels 19 .
Experimental rats in group B showed significantly increased LDL-C blood levels.This also corresponds to results in studies by Chaturvedi in which LDL-C levels increased significantly after administration of higher doses of MC 18 .
Serum lipids are important markers for overall cardiovascular risk.According to the Centres for Disease Control and Prevention (CDC), an estimated 106.9 million American adults have elevated total blood cholesterol levels; approximately 47.9 percent of men and 49.7 percent of women 20 .
The World health Organization states that 18 percent of stroke events and about 56 percent of heart disease is attributable to total cholesterol levels above 3.2 mmol/l, which amounts to about 4.4 million deaths 21 .
According to the lipid hypothesis, abnormal cho- lesterol levels (hypercholesterolemia)-that is, higher concentrations of LDL and lower concentrations of functional HDL, are strongly associated with cardiovascular disease 22 .High levels of cholesterol in blood, depending on how it is transported within lipoproteins, are strongly associated with progression of atherosclerosis.LDL molecules are the major carriers of cholesterol in blood.When there is high level of cholesterol, the molecules are oxidized and taken up by macrophages, which become engorged and form foam cells.These cells often become entrapped in the walls of blood vessels and contribute to atherosclerotic plaque formation.These plaques are the main causes of heart attacks, strokes and other serious medical problems 19 .
As high LDL and low HDL are both independent risk factors for heart disease, the ratio of the two numbers is a useful tool to evaluate cardiovascular risk 11 .In fact, one study showed that a 1 percent greater LDL value is associated with slightly more than a 2 percent increase in coronary artery disease The HDL/LDL ratio which is a biomarker for cardiovascular disease was increased in rats given MC at longer duration of treatment.This was evidenced by the significant decrease in LDL levels at lower doses of administration of the extract.This development was shown to be mostly duration dependent and it appears that longer duration of treatment may play an important role in the development of higher HDL/LDL ratios.
In conclusion, administration of MC, at doses and duration employed in this study, had dose-dependent cardio-protective properties via its effect on the blood cholesterol levels.However, there is an indication that higher doses should be discouraged.
Momordica charantia on Triglyceride: The effect of MC on triglyceride is shown in fig 2. Triglyceride levels for the treated groups A, B, C and D (1.4, 1.6, 1.2,1.6 mmol/L) were not significantly different from the compared controls after 14 days of treatment.Effect of Momordica charantia on HDL-C: The effect of MC on HDL-C was depicted in fig 3. Administration of MC had no significant impact on HDL as evidenced by measured values of 0.5, 1.0, 0.5, 1.0 mmol/L for groups A, B, C, and D respectively.
over 6 years, and a 1 percent lower HDL value is associated with a 3 to 4 percent increase in coronary artery disease, even at total cholesterol levels less than 200 mg/dl.Additionally, low HDL levels are associated with increased heart attacks and death from coronary artery disease10 .Numerous natural substances have also been shown to positively affect the HDL/LDL ratio23-24 .

Table 1 : Total Cholesterol level in Control and Experimental ratsTable 2 :
Triglyceride level in Control and Experimental rats