Antihyperlipidemic and antiatherogenic activities of Terminalia pallida Linn. fruits in high fat diet-induced hyperlipidemic rats.

Hyperlipidemia contributes significantly in the manifestation and development of atherosclerosis and coronary heart disease (CHD). Although synthetic lipid-lowering drugs are useful in treating hyperlipidemia, there are number of adverse effects. So the current interest has stimulated the search for new lipid-lowering agents with minimal side effects from natural sources. The present study was designed to investigate the antihyperlipidemic and antiatherogenic potentiality of ethanolic extract of Terminalia pallida fruits in high fat diet-induced hyperlipidemic rats. T. pallida fruits ethanolic extract (TPEt) was prepared using Soxhlet apparatus. Sprague-Dawley male rats were made hyperlipidemic by giving high fat diet, supplied by NIN (National Institute of Nutrition), Hyderabad, India. TPEt was administered in a dose of 100 mg/kg.b.w./day for 30 days in high fat diet-induced hyperlipidemic rats. The body weights, plasma lipid, and lipoprotein levels were measured before and after the treatment. TPEt showed significant antihyperlipidemic and antiatherogenic activities as evidenced by significant decrease in plasma total cholesterol, triglycerides, low-density lipoprotein cholesterol, and very low-density lipoprotein cholesterol levels coupled together with elevation of high-density lipoprotein cholesterol levels and diminution of atherogenic index in high fat diet-induced hyperlipidemic rats. There was a significantly reduced body weight gain in TPEt-treated hyperlipidemic rats than in the control group. The present study demonstrates that TPEt possesses significant antihyperlipidemic and antiatherogenic properties, thus suggesting its beneficial effect in the treatment of cardiovascular diseases.

Hyperlipidemia is characterized by elevated serum total cholesterol, low density and very low density lipoprotein cholesterol levels. Hyperlipidemia-associated lipid disorders are considered to cause atherosclerotic cardiovascular disease.[1] Among these hypercholesterolemia and hypertriglyceridemia are closely related to ischemic heart disease. Currently available hypolipidemic drugs have been associated with a number of side effects.[2] Herbal therapy for hyperlipidemia has minimal side effects and economic effective in reducing the lipid levels.[3] Terminalia pallida (TP) fruit has been in use for treatment of diabetes by tribal people.[45] Decoction of this fruit given as a drink cures diarrhea. TP fruit's ethanolic extract (TPEt) possess significant anti-ulcer and antihyperglycemic activities.[67]

Materials and Methods

Collection of plant material

TP fruits were collected from Tirumala hills, Andhra Pradesh, India, and identified (Voucher No. 158) by taxonomist of the Department of Botany, S.V. University, Tirupati. They were shade dried and powdered.

Preparation of terminalia pallida ethanolic extract

TP fruit powder was extracted with 7 volumes of 95% ethanol in Soxhlet apparatus at 60-70°C for 6 h. The filtrate was distilled and concentrated under reduced pressure at low temperature (40°C) in Buchi rotavapour R-200. A dark brown, semi-solid residue was obtained. It was stored at 4°C and used for further studies.

Induction of hyperlipidemia

Sprague-Dawley male rats with an average body weight of 160-180 g were made hyperlipidemic by giving high-fat diet (HFD) obtained from National Institute of Nutrition, Hyderabad, for 15 days. The HFD contained Cholesterol (2%), Cholic acid (1%), Dalda (20%), and Coconut oil (6%) as major constituents. Hyperlipidemia was confirmed by measuring the levels of serum lipids and lipoproteins in the rats.

Experimental design

The rats were divided into 2 groups with 6 in each group.

Group 1-Hyperlipidemic rats treated with vehicle alone

Group 2-Hyperlipidemic rats treated with 100 mg TPEt/kg b.w./day for 30 days.

The vehicle or TPEt were administered to the rats using a gastric force feeding needle. Both groups of rats were fed HFD during the first 15 days of the treatment, after that HFD was replaced with normal standard diet for the second 15 days of the treatment. Body weights, serum lipids, and lipoprotein levels were measured on the 16th day and 31st day after the treatment.

Biochemical parameters

Serum Triglycerides (TG), total cholesterol (TC), and HDL-cholesterol (HDL-C) were estimated according to the methods of Zlatkis et al.,[8] Foster and Dunn,[9] and Burstein et al.,[10] respectively. The serum levels of VLDL and LDL cholesterol were calculated using Friedewald formula.[11] The atherogenic index (AI) was calculated by using the following formula.[12]

Statistical analysis

All values are expressed as Mean ± S.D. The data were statistically analyzed by Student's t test .

Results

After feeding HFD, there was a significant rise in the levels of serum TG, TC, LDL and VLDL cholesterol along with a decrease in HDL cholesterol in the rats [Table 1]. Treatment with TPEt for first 15 days resulted in a significant decrease in the levels of serum TG, TC, LDL and VLDL cholesterol of group 2 rats despite feeding on HFD during the period of treatment. In group 1 rats, serum TG, TC, LDL and VLDL cholesterol levels were further increased during this period. After withdrawal of HFD, continuation of the treatment of group 2 animals with TPEt for the next 15 days has resulted in a further significant decrease in the levels of serum TG, TC, LDL and VLDL cholesterol to normal levels whereas in group 1 animals serum lipids and lipoprotein levels remained higher than those in the controls [Table 2].

Table 1

Plasma lipid profile in normal and high.fat diet.fed rats

Table 2

Effect of TPEt treatment on plasma lipid profile in normal and HFD induced hyperlipidemic rats (Mean ± S.D)

TPEt-treated animals showed decrease in AI and increased percentage of protection against atherogenicity caused by HFD [Table 3]. There was a significant increase in body weights of rats upon HFD feeding for 15 days. TPEt supplemented group had significantly lower body weight gain than control group after 15 and 30 days of the treatment [Table 4].

Table 3

Atherogenic index and percentage of protection against atherogenicity upon treatment with TPEt in HFD induced hyperlipidemic rats

Table 4

Effect of TPEt treatment on body weights (g) of control and treated rats

Discussion

HFD-fed hyperlipidemic rat model has earlier been reported as an ideal in vivo model for testing antihyperlipidemic drugs.[1314] Havel and Rapaport[15] reported that enriched fatty diets cause elevation of plasma TC and LDL cholesterol. High levels of TC and most importantly LDL cholesterol are predictors of atherosclerosis.[16] Bainton et al. showed that triglycerides are directly or indirectly related to coronary heart diseases.[17] In the present study, treatment with TPEt markedly decreased serum TG, TC, and LDL cholesterol, which indicates its use in treating coronary heart diseases.

In the present study, TPEt treatment increased the levels of HDL cholesterol. Higher HDL levels are documented to be physiologically beneficial.[18] Persons with low HDL cholesterol are necessarily at risk for premature CHD as reported by Rader et al.[19] and Ascherio and Willet.[20] A 1% decrease in HDL-C is associated with a 3%-4% increase in the risk of heart disease. It could not be explained how TPEt-treated group showed a significantly reduced body weight gain compared with the control group. AI, defined as the ratio of TC - HDL-C/HDL-C, is believed to be an important risk factor for atherosclerosis.[21] TPEt significantly decreased the ratio in HFD-fed rats indicating its antiatherogenic property.

From the above study, it is clear that TPEt can be utilized for providing dietary management in the prevention of atherosclerosis in hyperlipidemic patients.