etal., et - INFLIBNETshodhganga.inflibnet.ac.in/bitstream/10603/99241/9/09_chapter 3.pdf · University campus, were used for the study. Coconut was dehusked, broken carefully and

Chapter 3

Effect of tender coconut water on blood pressure and lipid

metabolism in rats fed high fructose diet

Coronary heart disease is one of the leading causes of morbidity and

mortality worldwide. Dyslipidemia is an important element in the linkage

between hypertension and coronary heart disease. Hypertension and

hypercholesterolemia are important modifiable risk factors for cardiovascular

diseases. High blood pressure has been associated with elevated atherogenic

blood lipid fractions (Bonaa and Thelli, 1991 ). Recent evidence suggests that

hypertension may interact with other risk factors such as dyslipidemia in

development of coronary heart disease (Gaziano et J, 1999).

Hypercholesterolemia and hypertension are both associated with endothelial

dysfunction and oxidative stress and their coexistence is associated with an

increase of cardiac events in epidemiological studies (Martin tf al, 2001;

Forstermann, 2006). Both life style and hereditary factors are known to be

related to the development of hypertension (Muratani etal., 2000).

Dietary fructose exerts a number of adverse metabolic effects in

experimental animals and in humans including hypertriglyceridaemia (Amann

et-al, 1981), hyperinsulinaemia (Zavaroni et af 1982) and hypertension

(Reaven, 1988). The fructose-hypertensive rat model represents an acquired

form of systolic hypertension (Verma et aP, 1997). With dietary fructose

consumption in the form of sucrose increasing in industrialized and developing

88

countries (Anderson, 1982), the potential public health implications are

important. The metabolic mechanisms underlying the effects of dietary fructose

are not well understood.

As mentioned in the introduction, work has been going on in the

laboratory to investigate the effect of tender coconut water (TCW) on various

aspects of health and disease. A study, carried out using isoproterenol treated

rats with induced myocardial infarction, indicated that (TCW) has significant

beneficial effect on lowering blood cholesterol and it has cardioprotective

action (Anurag and Rajamohan, 2003). Significant hepatoprotective and

antioxidant effects were observed in CC14 treated rats (Anthony and

Rajamohan, 2003).

Recently there has been focus on blood pressure lowering effects of

dietary plants. Epidemiologic studies suggest that higher intakes of potassium,

calcium, magnesium (Mc Carron d: aF, 1984 ), peptides from fish or milk

proteins (Kawasaki et al, 2000), antioxidants (Block etaf, 2001), polyphenols

(Keli et, al, 1996), polyunsaturated fatty acids (Holm et aP, 2001 ), and food

components (Iwase et Bi, 2000) are beneficial for preventing hypertension and

cardiovascular diseases (Keli d af, 1996). The tender coconut water (TCW)

presents a series of nutritional and therapeutic properties. TCW contains

several biologically active components which can influence lipid levels. These

include free amino acid L-Arginine, Vitamin C, minerals such as calcium,

magnesium and potassium. In addition to hypolipidemic and antioxidant

89

properties the blood pressure lowering effects of these biologically active

components are discussed in detail in the introduction. In view of these, we

studied the effect of TCW on blood pressure and lipid metabolism in high

fructose fed hypertensive rats. The results of these studies are discussed in this

chapter.

3.1 Materials and Methods

Chemicals

All biochemicals used for the study were obtained from Sigma

Chemicals, St.Louis, USA. Fructose was purchased from SRL Pvt Ltd.

Mumbai. Other chemicals used were of analytical grade.

Collection of tender coconut water

Fresh coconuts of tender stage (5-6 months maturity) harvested from

the coconut trees (Cocos nucifera L.) of West Coast Tall variety, grown on the

University campus, were used for the study. Coconut was dehusked, broken

carefully and liquid endosperm was collected and used for each day

experiment.

Experimental Animals

Male albino rats of Sprague Dawley strain weighing 150-170 g were

used for the study. The animals were individually housed under hygienic

conditions in polypropylene cages under 12 hour light and dark cycle and fed

with standard semi-synthetic diet and water ad libitum. Throughout the

90

experiment, temperature of the animal room was maintained at 25±1 °C. The

rats were trained for the first week to become acclimated to the procedure of

indirect blood pressure measurement.

Experimental Groups

A total of 24 rats were divided into 4 groups of 6 rats each as follows:

Composition of the diet is given in Table 1.

Group 1 - Control

Group 2 - Control + TCW

Group 3 - High fructose fed (hypertensive) rats

Group 4 - High fructose fed (hypertensive) rats + TCW

Table 1 Composition of the diet (g/lOOg)

Ingredients Control diet High fructose diet

Com starch 71 -

Fructose - 71

Casein 16 16

Groundnut oil 8 8

Salt mixture3 4 4

Vitamin mixtureb1 1

Composition of 1 Kg salt mixture3 :

30.5 g MgS04, 65.2 g NaCl, 105.7 g KCl, 200.2 g KH2P04, 38.8 g MgC03,

512.4 g CaC03, 0.8 g KI, 0.9 g NaF, 1.4 g CuS04, 0.4 g MnS04 and 0.5 g

CONH3 _

91

Composition of 1 Kg vitamin mixtureb:

3 g thiamine mononitrate, 3 g riboflavin, 3 g pyridoxine hydrochloride,

3 .5 g nicotinamide, 15 g d-calcium pantothenate, 8 g folic acid, 1 g d-biotin, 5

mg cyanocobalamin, 0.6 g vitamin A acetate, 25 g tocopherol acetate and 1 O g

choline chloride.

The first and second group of rats received the control diet. The third

and fourth group of rats received high fructose diet (71 % ) for two weeks to

induce hypertension. From third week onwards rats of second and fourth group

received TCW ( 4ml/100 g of body weight) for 3 weeks by gastric intubation.

All other rats received same volume of distilled water. Body weight, food

intake and blood pressure were measured every 3 days. At the end of fifth

week, animals were fasted overnight and they were sacrificed by decapitation.

Blood was collected and tissues (heart, liver, kidney and aorta) were removed

to ice cold containers for various estimations. Before killing, 24 hour urine

samples were collected thrice from rats of each group in metabolic cages, and

used for estimation of urinary nitrite. For histopathological examination, the

liver and aorta were removed and fixed in 10% buffered neutral formalin. The

study protocol was approved by the animal welfare committee of University of

Kerala.

3.2 Results

The following biochemical parameters were studied:

92

3.2.1 Composition of tender coconut water (TCW) used for the study

(Table 2).

Table 2 Concentration of total sugar, total protein, L-Arginine, vitamin C,

polyphenols, selenium and minerals in TCW

Constituents TCW

Total sugar (%) 4.6

Total protein (mg/dl) 146

L-Arginine (mg/di) 32

Vitamin C (mg/dl) 26

Polyphenols (mg/dl) 3.75

Selenium (mg/dl) 0.001

Sodium (mg/dl) 40

Potassium (mg/dl) 220

Magnesium (mg/dl) 16

Calcium (mg/dl) 32

3.2.2 Change in body weight and liver weight

The diet consumption (11 ± 1.3 g/day) and gain in body weight (61 ±

6.5g) were similar in all the four groups. High fructose fed rats showed an

increase in liver weight. On the other hand, the liver weight was lower in rats

fed tender coconut water (TCW) when compared to high fructose fed control

rats (Table 3).

93

Table 3 Change in Liver weight

Groups Liver weight

(g/100 g body weight)

1 6.72±0.85b

2 6.42± 0.59 b

3 7.45±0.SOa

4 6.84±0.43b

F ratio 2.93

Values are mean± SD for six rats. P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.3 Systolic and diastolic blood pressure

Fig. (2 and 3) shows weekly systolic and diastolic blood pressure of

control rats, control rats+ TCW, high fructose fed hypertensive rats (HFF) and

high fructose fed hypertensive rats + TCW. All the group of rats showed

similar systolic blood pressure at the beginning of the experiment. The fructose

fed rats displayed a continuous increase in systolic and diastolic blood pressure

during the first three weeks. Administration of tender coconut water during the

subsequent three weeks markedly reduced the blood pressure. There was a

progressive decrease in blood pressure from third week onwards.

94

Fig. 2 Effect of tender coconut water on systolic blood pressure

Systolic blood pressure

160 a

b a

140 b b h h

120

100

80

60

40

20

0

0 2 3 4

Weeks

Values are mean ± SD for six rats.

a

5

h

CJ Group 1

12! Group 2

• Group 3

ICI Group 4

P< 0.05, • indicates that the results are significantly different from group I, b indicates that the results are significantly different from group 3.

Fig. 3 Effect of tender coconut water on diastolic blood pressure

Diastolic blood pressure

ci :c

E E

120

100

80

60

40

20

0

; -

�·

- �

' � i':,

; ;

�· ���

; ; �� �·

0 1

Values are mean ± SD for six rats.

a b a a

i� b b � b

b f � �

�-i':,

� ; ; ; �

'.

I I

2 3 4 5

Weeks

b

I

r:31 Group 1

11111 Group 2

D Group 3

lffil Group 4

P< 0.05, • indicates that the results are significantly different from group I, b indicates that the results are significantly different from group 3.

95

3.2.4 Concentration of serum total cholesterol, lipoprotein cholesterol and

atherogenic index

Fructose fed control rats showed increased concentration of serum total

cholesterol, LDL + VLDL cholesterol and higher ratio of atherogenic index

(Total cholesterol/HDL cholesterol) compared to normal rats. Administration

of tender coconut water to fructose fed rats showed decreased serum total

cholesterol, LDL+ VLDL cholesterol, lower ratio of atherogenic index and

higher level ofHDL cholesterol (Table 4).

Table 4 Concentration of serum total cholesterol, lipoprotein cholesterol

and atherogenic index

Groups

1

2

3

4

F ratio

Total

Cholesterol

68.0±4.8b

67.5±3.4b

99.5±3.1 a

78.9±1.4b

115.5

Values are mean ± SD for six rats.

VLDL+LDL

Cholesterol

21.2±3.8b

21.8±2.9b

68.1±3.3a

32.9±1.Sb

339.8

HDL

Cholesterol

46.8±2.6b

45.6±2.7b

31.3±3.la

46.2±1.0b

56.4

Atherogenic

index

1.44±0.11 b

l.47±0.14b

3.19±0.24a

1.68±0.26b

204.7

P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

96

3.2.5 Concentration of cholesterol in tissues

Cholesterol in liver, heart, kidney and aorta increased in fructose fed rats

compared to normal rats. TCW supplementation resulted in decreased levels of

cholesterol in liver, heart, kidney and aorta of fructose fed rats (Fig 4 ).

Fig. 4 Concentration of Cholesterol in tissues

Cholesterol

700 a

rn Liver a

600 11 Heart

500 fill Kidney

"C 400 11111 Aorta

300

200

100

Group 1 Group 2 Group 3 Group 4

Values are mean ± SD for six rats. P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.6 Concentration of triglycerides in serum and tissues

Triglycerides in serum, liver, heart, kidney and aorta increased in fructose

fed rats compared to normal rats. While tender coconut water supplementation

resulted in decreased levels of serum and tissue triglycerides in fructose fed rats

(Table 5).

97

Table 5 Concentration of triglycerides in serum (mg/di) and tissues (mg/

100g wet tissue)

Groups Serum Liver Heart Kidney Aorta

1 7.02±0.32b 221.5±3.7b 50.8±2.44b 60.7±5.43b 925.6±8.21 b

2 6.91±0.25b 212.9±3.2

b 43.7±4.72b 61.35±3.8b

924.46±6.35b

3 12.4±0.76a

423.6±6.7a

73.7±5.52a

95.65±3.8a

1043.2±1 l.2a

4 9.06±0.28b

238.2±2.8b

59.07±2.31 b 70.2±4.lOb 956.07±9 .03

b

F ratio 195.82 284.11 41.28 57.35 160.46

Values are mean ± SD for six rats. P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2. 7 Concentration of phospholipids in tissues

Phospholipids in liver, heart and kidney were increased in fructose fed

rats compared to normal rats. While tender coconut water supplementation

resulted in decreased levels of phospholipids in liver, heart and kidney of

fructose fed rats (Fig. 5).

98

Fig. 5 Concentration of phospholipids in tissues

Phospholipid

� Liwr

11 Heart 3500

a, 3000 �

b b a a a b llll Kidney

2500 :i:,

C) 2000

8 1500

C> E

1000

500

0

b�--�

Group 1 Group 2 Group 3 Group 4

Values are mean± SD for six rats . P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.8 Activity of HMG CoA Reductase in liver

HMG CoA reductase activity in liver was lower in fructose fed rats when

compared to normal rats. On the other hand, feeding tender coconut water in fructose

fed rats caused higher activity of this enzyme (Table 6).

Table 6 Activity of HMG CoA Reductase in liver

Groups HMG CoA Reductase#

1 2.80±0.25b

2 2.98±0.24b

3 4.68±0.48a

4 3.65±0.34b

F ratio 36.34

Values are mean± SD for six rats. # Ratio ofHMG CoA to mevalonate, lower ratio indicates higher enzyme activity. P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

99

3.2.9 Activity of LPL in heart and adipose tissue

Activity of lipoprotein lipase in heart and adipose tissue was significantly

lower in fructose fed rats compared to normal rats. Feeding tender coconut

water significantly increased the activities of this enzyme (Table 7).

Table 7 Activity of LPL* in heart and adipose tissue

Groups Heart Adipose tissue

1 31.95±3.01 b

157.5±6.13b

2 30.75±1.11 b

156.3±1.70b

3 26.05±0.65a

13 l.7±3.09a

4 29.42±0.35b

143.7±3.50b

F ratio 9.57 37.47

Values are mean ± SD for six rats. * micromoles of glycerol liberated I houri g protein.P< 0.05, • indicates that the results are significantly different from group 1,b indicates that the results are significantly different from group 3.

3.2.10 Activity of plasma lecithin : cholesterol acyltransferase (LCAT)

Activity of plasma LCAT was significantly lower in fructose fed rats

compared to normal rats. Feeding tender coconut water significantly increased

the activity of this enzyme (Fig. 6).

100

Fig. 6 Activity of plasma LCA T*

35

30

h

LCAT

h

Group 1 Group 2 Group 3 Group 4

Values are mean ± SD for six rats. * Ratio of ester cholesterol to free cholesterol during incubation. Higher ratio indicateshigher enzyme activity.P< 0.05, • indicates that the results are significantly different from group I, b indicates

that the results are significantly different from group 3.

3.2.11 Activities of lipogenic enzymes

Activities of hepatic lipogenic enzymes glucose-6-phosphate

dehydrogenase, malic enzyme and isocitrate dehydrogenase were significantly

higher in fructose fed rats compared to normal rats. The activities of lipogenic

enzymes decreased in fructose fed rats given tender coconut water (Table 8).

101

Table 8 Activities of lipogenic enzymes in liver

Groups Glucose-6-phosphate Malic enzymeP Isocitrate

dehydrogenasea

dehydrogenase1

I 40.96±3.41b

98.9±4.2b

105.3±2.8b

2 37.75± 1.36b

97.9±2.9b

103.7±1.6b

3 73.48±4.20a

185.3±4.3a

153.6±4.Sa

4 49.7±3.43b

122.8±5.4b

121.9±5.4b

F ratio 145.86 550.15 216.77

Values are mean ± SD for six rats. " amount of enzyme which causes an increase of 1.0 in OD/min/g protein. � amount of enzyme which causes an increase of 0.0 I in OD/min/g protein. 1 mg NAD reduced/30s/ mg protein. P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.12 Activities of Glutamate oxaloacetate transaminase (SGOT) and

Glutamate pyruvate transaminase (SGPT) in serum

Increased activities of SGOT and SGPT in the serum were observed in

fructose fed control rats when compared to normal rats. Fructose fed rats given

tender coconut water showed decreased activities of these enzymes (Table 9).

102

Table 9 Activities of SGOT and SGPT in serum

Groups SGOT SGPT

(IU/L) (IU/L)

1 23.7±1.Sb

21.4±1.2b

2 23.9±1.6b

22.2±1.3b

3 46.5±4.4a

35.9±1.3a

4 27.4±1.9b

27.2±1.Sb

F ratio 102.2 143.6

Values are mean ± SD for six rats. P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.13 Activity of Alkaline phosphatase (ALP) in serum

Increased activity of ALP in the serum was observed in fructose fed

control rats when compared to normal rats. Fructose fed rats given tender

coconut water showed decreased activity of this enzyme (Fig. 7).

103

Fig. 7 Activity of Alkaline Phosphatase in serum

Alkaline phosphatase

14 a

12 b b ....... b.,. . .,. . .,. ....... .,. . .,. . .,.

10 ....... .,. . .,. . .,. ....... . .,. . .,. ., .... .,. ....... . ...... .,. • .,..I' .,. . ., . .,.

8 ....... . ...... . .,. . .,. .,. . .,. . .,. ....... . ...... .,.•rl'•rl' J'•,1'.•,/' ....... ....... . .,. . .,. .,. . .,. . .,

6 ....... . .......,. . .,. . ., .,.., . .,.•'\,•'\,• ....... .,. . .,. . .,. r/'•,1'•,?, ....... ....... .,. . .,. . .,. rl'•,l'•,1'

4 ....... . ...... ...... .,. .,. . .,. . .,. ....... . ...... ., . .,. . .,. ,l'•rl'•.I' ....... •'\,•'\,• .,. . .,. . .,. .,. . .,. . .,.

2 ....... ........ ,1'•,/'•,1' ,I'•,/'• .. ....... ....... .,. . .,. . .,. .,. . .,. . .,. ....... . ...... .,. ...... rl'•.f•rl' ·":·":· ·":·":·

Group 1 Group 2 Group 3 Group 4

Values are mean± SD for six rats. P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.14 Activities of nitric oxide synthase in liver, concentration of plasma

L-arginine and serum nitrite

The activities of nitric oxide synthase in liver, concentration of plasma

L-Arginine and serum nitrite were significantly lower in fructose fed control

rats when compared to normal rats. On the other hand, tender coconut water

feeding significantly increased the nitric oxide synthase activity, plasma L-

Arginine and serum nitrite levels (Table 10).

104

Table 10 Activities of nitric oxide synthase (units/ mg protein) in liver,

concentration of plasma L-arginine (µ mol/ml) and serum nitrite (µ mol/1)

Groups Nitric oxide synthase Plasma L-Arginine Serum nitrite

1 0.89± 0.05b 0.132± 0.002b 11.65±0.88b

2 0.92±0.04b O. l 35±0.002b 1 l.91±0.76b

3 0.42±0.04a 0.125±0.004a 10.24±0.27a

4 l.06±0.12b 0.183±0.013b l l.97±0.72b

F ratio 84.63 60.30 5.44

Values are mean ± SD for six rats P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.15 Concentration of urinary nitrite

The levels of urinary nitrite was significantly lower in fructose fed

control rats when compared to normal rats. Compared to fructose fed rats

urinary nitrite was higher in TCW administered fructose fed rats (Table 11).

Table 11 Concentration of urinary nitrite (mg/di)

Groups Urinary nitrite

1 30.57± 2.lb

2 32.07± 1.50b

3 23.67±0.87a

4 38.2± 1.23b

F ratio 63.92

Values are mean ± SD for six rats P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

105

3.2.16 Concentration of blood urea

The concentration of blood urea significantly increased in fructose fed

control rats compared to normal rats. Tender coconut water supplementation

significantly reduced the blood urea levels in fructose fed rats (Fig. 8).

Fig. 8 Concentration of blood urea

45 40 35 30

� 25 e 20

15 10

5

b

Blood Urea

a

b b

0 4--_.=..,.,..,._�____.,...,,_,,=-�-'---'--='L__�-=..,.-=----�

Group1 Group 2 Group 3 Group 4

Values are mean ± SD for six rats P< 0.05, • indicates that the results are significantly different from group 1, b indicates that the results are significantly different from group 3.

3.2.17 Histopathological Studies

Histopathological studies of liver shows accumulation of fat,

cytoplasmic degeneration in hepatocytes and microvesicular changes in the

liver while aorta shows lipid accumulation in elastic fibers of fructose fed

control rats. Supplementation with tender coconut water lowered fatty

accumulation in these tissues (Plate 2 & 3).

106

Plate 2: ~ight microscopic appearance of the liver sections stained with

Hematoxylin-Eosin (x 100)

107

1. Control

The liver architecture is normal with cords of hepatocytes with normal cytoplasm and

central nuclei. There are no inflammatory cells in the portal tract nor in the parenchyma. There are

no signs of cellular damage.

2. Control + TCW

The liver architecture is same as normal. No hepatic damage and fatty infiltration. No signs of

cellular damage.

3. Fructose fed hypertensive rats

Portal inflammation and fatty infiltration is noticed.

4. Fructose fed hypertensive rats + TCW

No hepatocellular damage and inflammatory infiltration. Lower lipid accumulation (LA).

Plate 3: Light microscopic appearance of the aorta sections stained with

Hematoxylin-Eosin (x 400)

1. Control

Structure of normal aorta consist of Intima (IA) - Innermost layer lined by endothelial cells,

Media (MA)- contains elastic fibers (EF) and Adventitia- consist of fibrous outer covering. No

abnormal features.

2. Control + TCW

Same as that of control. No fatty infiltration, fatty deposits and medial hypertrophy.

3. Fructose fed hypertensive rats

In hypertensive rats thickness of aorta is increased. Space between the layers of aorta is increased.

It indicates the lipid accumulation (LA) between the layers. Deposits ofmucopolysaccharides.

4. Fructose fed hypertensive rats + TCW

Thickness of aorta is reduced and medial hypertrophy is reversed. Lower lipid accumulation. No

deposits of mucopolysaccharides.

108

3.3 Discussion

The results from this study indicated that TCW feeding had a significant

antihypertensjve and lipid lowering effect in fructose fed rats. Rats maintained

on high fructose diet developed high systolic and diastolic blood pressure, as

compared to rats fed standard starch diet, confirming the results of previous

studies (Hwang etal, 1987; Suzuki et a1, 1997; Cosenzi et a.f, 1999). TCW

feeding significantly decreased the systolic and diastolic blood pressure which

was significantly raised by a high fructose diet as supported by Alleyne tta1,

(2005).

TCW feeding caused decreased levels of total cholesterol, VLDL+

LDL, cholesterol, triglycerides, higher levels of HDL cholesterol and lower

atherogenic index. Concentration of tissue cholesterol, triglycerides and

phospholipids were lower in rats fed TCW. These results are in accordance

with our previous findings in TCW fed rats with induced myocardial infarction

(Anurag and Rajamohan, 2003). Accumulation of cholesterol, triglycerides,

phospholipids and decreased HDL levels are consistent with previous reports

(Srividhya and Anuradha, 2002; Nandhini et al, 2001 ). Fructose induced

hypertriglyceridemia is a result of enhanced lipogenesis (Zakim et a.f, 1967;

Sullivan et al, 1971), over production of VLDL and decreased triglyceride

clearance (Bar-On and stein, 1967). The rise in HDL cholesterol in TCW

treated rats may be due to delayed clearance or due to increased HDL

109

synthesis. Stimulation of LPL is reported to increase HDL production and

decrease VLDL constituents (Mochizuki et-al, 1998).

TCW feeding resulted in higher activity of HMG CoA reductase in the

liver, which indicates increased cholesterolgenesis. Contrary to this effect,

cholesterol level in the serum and tissues were lower in rats administered

TCW. This observation suggests that the cholesterol lowering effect of TCW is

not due to decreased synthesis. The lowering of cholesterol in serum and liver

may be due to the increased degradation of cholesterol as reported by previous

studies (Sandhya and Rajamohan, 2006).

The lower activities of glucose-6-phosphate dehydrogenase, isocitrate

dehydrogenase and malic enzyme in TCW fed rats which provide NADPH for

fatty acid synthesis indicate decreased synthesis of triglycerides which

correlate with the lower level of the lipid in the serum and tissue. In addition,

the activity of lipoprotein lipase in heart and adipose tissue were higher in rats

fed TCW. This enzyme is involved in the uptake of triglyceride rich

lipoproteins (chylomicrons and VLDL) by the extrahepatic tissues. The

increase in the activity of this enzyme indicates increased clearance of

triglycerides from the circulation and which correlates with the lower levels of

triglycerides in serum. Several authors have reported increased hepatic

lipogenesis as a consequence of dietary fructose (Boogaerts etal, 1984 ). High

fructose feeding has shown to increase the availability of long chain fatty acids

required for synthesis of triglycerides by upregulating the hepatic lipogenic

110

enzymes (Fiebig et al, 1998). Significant reduction in the activity of LPL could

be another reason for hypertriglyceridemia (Bar-On and Stein, 1987). Fructose

feeding is reported to decrease the ability of insulin to stimulate the activity of

LPL (Anurag and Anuradha, 2000).

The activity of plasma LCAT showed an increase in TCW fed rats. This

enzyme 1s believed to be involved in the transport of cholesterol from the

tissues to the liver for its catabolism. The decreased concentration of

cholesterol in the tissues agrees with increased activity of this enzyme. The

decreased activity of LCAT indicates impairement in HDL synthesis as well as

triglyceride metabolism in fructose fed rats (Hallfrisch eta! 1983 ).

Histopathological studies of liver and aorta reveals very less fatty

accumulation in fructose fed rats supplemented with TCW. The activities of

SGPT, SGOT and alkaline phosphatase increased, while supplementation of

TCW led to decreased enzyme activities. This observation indicates that fatty

infiltration and degeneration of liver cells caused by feeding high fructose diet

were significantly reduced by TCW.

Tender coconut water contains several factors which possess

hypolipidemic property. Analysis carried out by us indicates that TCW

contains 32 mg % L-Arginine, 26 mg % Vitamin C, 32 mg % calcium, 16 mg%

magnesium, 40 mg% sodium and 220 mg% potassium. Several workers

reported that the L-Arginine has significant hypolipidemic and antiatherogenic

effect (Hadzieva et al, 2000; Miguez et al, 2004 ). Studies carried out using

111

TCW in rats induced myocardial infarction showed significant hypolipidemic

action (Anurag and Rajamohan, 2003). L - Arginine infusion has shown to

produce peripheral vasodilation and have antihypertensive effects (Defronzo

and Ferranninni, 1991; Hishikawa eta.� 1992). L-Arginine infusion has been

reported to prevent fructose induced hypertension (Aydin el:af, 2002). Dietary

supplementation with L-Arginine has been reported to reverse dysfunctional

arginine/ nitric oxide pathway in endothelium (pieper eta1, 1997). L-Arginine

is shown to stimulate the body's production of growth hormones reported to

have cardioprotective action (Isgaard eta'/., 1997).

Reports indicate that L- Arginine's antiatherogenic activity is mediated

via the formation of nitric oxide (Loscalzo , 2000). Supplementation with L­

Arginine blocks the progression of plaques via restoration of NOS substrate

availability and reduction of vascular oxidative stress (Dhawan et al', 2005).

Feeding TCW to fructose fed rats showed increased activity of nitric oxide

synthase. Endothelial NOS activity is reported to have decreased in fructose

fed rats (Yasuhiro eta.P, 2002). Increased plasma L-Arginine, serum nitrite and

urinary nitrite indicate increased production of nitric oxide. Concentration of

blood urea was significantly reduced in TCW fed group compared to high

fructose fed hypertensive rats. Urinary nitrite excretion is an indicator of nitric

oxide formation during oral administration of L-Arginine in rats (Boger et.al,

1996). Reports indicate that plasma ADMA (asymmetric dimethylarginine), an

endogenous NOS inhibitor levels are elevated m animals with

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hypercholesterolemia (Boger et a#, 2000). Oral L-Arginine supplementation

stimulates NO synthesis to overcome the inhibitory effects of high ADMA,

probably due to normalization of the L-Arginine I ADMA ratio and thereby

improves the endothelial function. In addition, NO availability has been shown

to modulate metabolism of lipoproteins. Negative correlation between plasma

concentrations of NO metabolic products, and plasma total and LDL

cholesterol levels has been reported (Bode-Boger eta1, 1996).

In addition to L-Arginine TCW is also rich in minerals such as

calcium, magnesium and potassium which have been reported to have

hypolipidemic and antihypertensive effects. Compared to potassium levels (220

mg % ) the sodium content ( 40 mg % ) of TCW is very low which may prove

beneficial in hypertension. High potassium diets have been reported to prevent

hypertensive endothelial injury and intimal thickening. The high potassium

diet, by protecting endothelial cells, can greatly decrease the cholesterol ester

deposition during hypercholesterolemia and hypertension (Tobian et ai, 1990).

The direct effect of K on blood pressure regulation would be through its effect

on natriuresis, baroreceptor sensitivity, the renin angiotensin system (RAS),

vasodilation, and sympathetic nervous system activation. Alternate

mechanisms include the role of K in inhibition of free - radical formation

(McCabe, 1994 ), vascular smooth muscle proliferation and arterial thrombosis

(Lin and Young, 1994 ). Potassium has been reported to decrease urmary

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calcium excretion and increase body calcium balance, by increasing renal

calcium resorption (Leman etaf, 1991).

Calcium supplementation has also been shown to decrease blood

pressure in hypertension (Sallinen etal, 1996). NO synthase produces NO from

L-arginine through calcium dependent process. NO is responsible for the

acetylcholine mediated vascular relaxation. Accelerated degradation of NO

may lead to impaired vasodilation and hence increased blood pressure (Newaz

et a! 1999). Calcium supplementation decreases the intestinal absorption of fat

and lowers serum lipoprotein and cholesterol concentrations (Reid, 2004 ).

Several studies have indicated that magnesium plays a role in the etiology

of hypertension (Nadler el a9, 1993). Increased magnesium intake may improve

dyslipidemia, oxidative stress and insulin sensitivity (Olatunji and Soladoye,

2006). Magnesium administration, concomitant with potassium, assists tissue

replenishment of potassium (Shils, 1969; Dyckner and Wester, 1979). Proposed

mechanisms involve stimulation of vascular prostacyclin release (Watson etaf,

1986), renal vasodilation (Rude, 1989), vascular responsiveness (Lee, 1984 ),

acceleration of the cell membrane sodium pump (Saito et al, 1988) and

antagonism of arterial calcium uptake (Altura and Altura, 1986). The role of

calcium in regulating vascular tone is dependent on magnesium. Magnesium

deficiency has been reported to increase the susceptibility of lipoproteins to

lipid peroxidation (Rayssiguier etaQ, 1993 a, b) which results in a high rate of

free-radical formation (Weglicki ef at, 1996), which inactivates the

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endothelium-derived relaxation factor, NO, which when undergoes degradation

by superoxide anions could contribute to the enhancement of the arterial

contractile response, resulting in the development and maintenance of

hypertension (Yang, 1998).

The presence of ascorbic acid and minerals like calcium, potassium and

magnesium also help in hypolipidemic action of TCW. Studies indicate that

Vitamin C can reduce the amount of cholesterol and triglycerides in all

lipoprotein classes and can increase intracellular tetrahydrobiopterin (BH4) and

subsequent enhancement of NOS activity (Carr etiJ, 2005; Frei et al, 1997).

Vitamin C is reported to decrease systolic and diastolic blood pressure and

endothelial dysfunction (Trout, 1991 ). The mechanisms involve scavenging

intracellular superoxide, activation of smooth muscle guanylyl cyclase, release

of NO from tissue, direct reduction of nitrite to NO and a decrease in low

density lipoprotein (Chen ef al, 2002; Salonen eta9, 1988; Frei efaf, 1989).

The results indicate that feeding TCW significantly reduced the

hypertension induced by high fructose diet. Hyperlipidemia associated with

fructose induced hypertension was also ameliorated by TCW administration

which may be due to the presence of biologically active components.

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