Journal of Ethnopharmacology 88 (2003) 73–77

Effect of soluble dietary fibre fraction ofTrigonella foenumgraecum on glycemic, insulinemic, lipidemic and platelet

aggregation status of Type 2 diabetic model rats

J.M.A. Hannana, B. Rokeyaa, O. Faruquea, N. Naharb,M. Mosihuzzamanb, A.K. Azad Khana, L. Ali a,∗

a Biomedical Research Group, Bangladesh Institute of Research & Rehabilitation in Diabetes,Endocrine & Metabolic Disorders (BIRDEM), 122, Kazi Nazrul Islam Avenue, Dhaka 1000, Bangladesh

b Department of Chemistry, University of Dhaka, Dhaka 1000, Bangladesh

Accepted 7 May 2003

Abstract

The soluble dietary fibre (SDF) fraction ofTrigonella foenum graecum (Tf-sdf) has previously been shown to reduce postprandial elevationin blood glucose level of Type 2 model diabetic rats by delaying the digestion of sucrose. The Tf-sdf has now been investigated for its chroniceffect on serum fructosamine, insulin and lipid levels, and on platelet aggregation in Type 2 diabetic rats. Tf-sdf was administered orally twicedaily at a dose of 0.5 g kg−1 for 28 days. It lowered the serum fructosamine level (P < 0.05) with no significant change in the insulin levelas compared with the control. Atherogenic lipids, i.e. triglycerides, cholesterol and LDL-cholesterol were found to decrease significantlyin Tf-sdf fed rats (P < 0.01). HDL-cholesterol showed an opposite trend (P = 0.024), but serum non-esterified fatty acid (NEFA) valuesparalleled the atherogenic lipids (P = 0.001). No significant effect on platelet aggregation (%) was found although there was a tendency tolower the aggregation (P = 0.069). It is concluded that Tf-sdf has a beneficial effect on dyslipidemia and has a tendency to inhibit plateletaggregation in Type 2 model diabetic rats.© 2003 Elsevier Ireland Ltd. All rights reserved.

Keywords: Trigonella foenum graecum; Soluble dietary fibre; Diabetes mellitus; Oral hypoglycemic agent; Fructosamine; Insulin; Hypolipidemic effect;Platelet aggregation; Streptozotocin diabetic rats

1. Introduction

The seeds ofTrigonella foenum graecum are reportedto possess hypoglycemic properties in both animal (Shaniet al., 1974; Ribes et al., 1984; Ajabnoor and Tilmisany,1988; Amin et al., 1988) and human subjects (Madaret al., 1988; Madar and Arad, 1989; Sharma et al., 1990). Wehave previously shown that the whole powder, its methanolextract, and the residue remaining after methanol extractionhave significant hypoglycemic effects when fed simulta-neously with glucose. The water extract of the methanolextractive-free residue of the seed powder, which containsalmost exclusively the soluble dietary fraction ofTrigonellafoenum graecum (Tf-sdf), showed significant hypoglycemicactivity at different prandial states (Ali et al., 1995a,b).Tf-sdf was found to be effective in Type 2 as well as in Type

∗ Corresponding author. Tel.:+880-2-8611138/8617130/8613700;fax: +880-2-8613004.

E-mail addresses: lali@dab-bd.org, lali@citechco.net (L. Ali).

1 (where insulin secretory capacity is almost absent) modelrats. It showed no effect on the fasting blood glucose levelsof nondiabetic and diabetic model rats. However, it showeda significant hypoglycemic effect (P < 0.05) in Type 2model rats when fed simultaneously with glucose (Aliet al., 1995a,b). We have also shown that its hypoglycemicactivity may be related to lowering of carbohydrate absorp-tion through inhibition of disaccharidase enzyme in the gut(Faruque et al., 1998). In the present study, we investigatedthe effect of Tf-sdf on serum fructosamine, insulin and lipidlevels, and on platelet aggregation in the Type 2 rats afterchronic feeding.

2. Materials and methods

2.1. Plant materials and preparation of test sample

Seeds of the plant were purchased from local mar-ket and botanically authenticated and voucher specimens

0378-8741/$ – see front matter © 2003 Elsevier Ireland Ltd. All rights reserved.doi:10.1016/S0378-8741(03)00190-9

74 J.M.A. Hannan et al. / Journal of Ethnopharmacology 88 (2003) 73–77

were deposited in the National Herbarium, Bangla-desh.

Trigonella foenum graecum seeds were dried at 40◦Cand finely powdered. The powder (300 g) was extractedwith aqueous 80% ethanol (3× 400 ml, 30 min each time)by refluxing and the aqueous 80% ethanol extract was dis-carded. The remaining residue (100 g) was further extractedwith chloroform (3× 750 ml, 30 min each time) at roomtemperature. From the remaining residue, a soluble dietaryfibre (SDF) was prepared (25.2 g) by the Theander andWesterlund method (Theander and Westerlund, 1986).

2.2. Experimental animals

Long–Evans male rats (weighing 180–200 g) bred atBIRDEM laboratory were used. Type 2 rat model weredeveloped by intra-peritoneal injection of Streptozotocin(90 mg kg−1 body weight, dissolved in 0.1 citrate buffer,pH 4.5) to 48–72-h-old pups (Bonner-Weir et al., 1981).

Ten rats (n = 10) were fed with Tf-sdf (0.5 g kg−1 bodyweight) twice daily for 4 weeks and another 10 were usedas control. Values of serum fructosamine, insulin and lipidsof control and treated groups at 0 day were matched.

2.3. Blood collection

Blood was collected from the abdominal aorta under pen-tobarbital anesthesia. Serum and plasma were separated andstored at−20◦C until the estimation of fructosamine, in-sulin and lipids.

2.4. Measurement of platelet aggregation

Blood samples were drawn from abdominal aorta afterpentobarbital anesthesia. The anticoagulant used was sodiumcitrate (38 g l−1, 1 vol. anticoagulant for 9 vol. of blood).Platelet-rich plasma (PRP) and platelet-poor plasma (PPP)were prepared by centrifugation. Platelet aggregation kinet-ics in 200 ul of PRP was measured by optical aggregometryusing two different doses of ADP (12 and 14�M) as in-ducer. Platelet aggregation was expressed as percentage ofthe PPP transmission value.

2.5. Biochemical analysis

Serum fructosamine levels were measured by using spec-trophotometric method, serum insulin by Rat insulin ELISAkit (Crystal Chem Inc., USA) and lipids (TG, total choles-terol, HDL-cholesterol, LDL-cholesterol and NEFA) weremeasured in plasma by enzymatic-colorimetric method.

2.6. Statistical analysis

All analyses were done using the Statistical Package forSocial Sciences (SPSS) for Windows 7.5. Results are ex-

pressed as Mean± S.D. Unpaired Student’t-test was per-formed for statistical comparison.

3. Results

3.1. Serum fructosamine

Fructosamine level was significantly lowered in Tf-sdfgroup (mmol l−1, control versus Tf-sdf, 91.08±7.20 versus71.99± 6.35; P < 0.05) (Fig. 1a).

3.2. Serum insulin

Serum insulin did not differ significantly between the twogroups (ng ml−1, 166.09± 9.02 in control versus 149.83±17.03 in Tf-sdf) (Fig. 1b).

3.3. Plasma lipids

Atherogenic lipids were lowered significantly comparedto control (mg dl−1, M ± S.D., control versus Tf-sdf; TG:70.78±17.45 versus 30.89±8.72,P = 0.001; total choles-terol: mg dl−1, 66.34±4.16 versus 52.22±5.81,P = 0.001;LDL-cholesterol: mg dl−1, 16.40 ± 7.4 versus 6.12 ± 6.9,P = 0.014) (Fig. 2a–c). HDL-cholesterol level (mg dl−1)increased from 35.78± 5.31 to 41.89± 5.11 (P = 0.024)

Fru

cto

sam

ine (

mm

ol/

l)

0

20

40

60

80

100

120

Control Tf-sdf

Seru

m in

sulin

(ng

/ml)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

*

(a)

(b)

Fig. 1. Effect of Tf-sdf on serum fructosamine and serum insulin levels.Values are mean± S.D. (n = 10). ∗P < 0.05.

J.M.A. Hannan et al. / Journal of Ethnopharmacology 88 (2003) 73–77 75

Control Tf-sdf

Tot

alC

hole

ste

rol(

mg/

dl)

0

20

40

60

80

Control Tf-sdf

TG

(mg/

dl)

0

20

40

60

80

100

Control Tf-sdf

LDL-

chol

este

rol(

mg/

dl)

0

5

10

15

20

25

Control Tf-sdf

HD

L-ch

oles

tero

l

0

10

20

30

40

50

*

*

**

**

(a)

(c) (d)

(b)

Fig. 2. Effect of Tf-sdf on lipid profiles. Values are mean± S.D. (n = 10). ∗P < 0.05, ∗∗P < 0.01.

Control Tf-sdf

NE

FA(m

mol

/l)

0.0

0.1

0.2

0.3

0.4

0.5

**

Fig. 3. Effect of Tf-sdf on NEFA level. Values are mean±S.D. (n = 10).∗∗P < 0.01.

(Fig. 2d). NEFA values (mmol l−1) were significantly low-ered (0.32± 0.11 versus 0.14± 0.05, P = 0.001) (Fig. 3).

3.4. Platelet aggregation

Tf-sdf fraction resulted in a lowering tendency of plateletaggregation in Type 2 rats (%, control versus Tf-sdf, ADP(12�M): 55.96± 10.75 versus 44.17± 11.11, P = 0.078;ADP (14�M): 57.29 ± 14.04 versus 44.64 ± 8.28, P =0.069) (Fig. 4).

4. Discussion

We have shown earlier that Tf-sdf fraction can effec-tively reduce postprandial rise of glucose in rats (Ali et al.,1995a,b). The serum fructosamine data in the present

76 J.M.A. Hannan et al. / Journal of Ethnopharmacology 88 (2003) 73–77

ADP concentration

12 micro-M 14 micro-M

Plat

elet

aggr

egat

ion

(%)

0

20

40

60

80ControlTf-sdf

Fig. 4. Effect of Tf-sdf on platelet aggregation. Values are mean± S.D.

(n = 10).

study reflects the glycemic status of the rats for the last2–3 weeks and it demonstrates, more conclusively, theanti-hyperglycemic properties of the Tf-sdf fraction. It hasalso been shown earlier that Tf-sdf fraction does not stimu-late insulin secretion during a single feeding (Rokeya et al.,1998), this has been further confirmed in this study at achronic feeding state. Findings from the present as well asprevious studies, therefore, suggest that the hypoglycemicactivity of Tf-sdf is not related to stimulation of insulin se-cretion. Thus, this material may lead to postprandial glucosereduction without any extra load on the pancreatic B cells.

High levels of total cholesterol and, more importantly,LDL-cholesterol in blood are major coronary risk factors(National Cholesterol Education Program Expert Panel,1994). Administration of Tf-sdf fraction lowered both totalcholesterol and LDL-cholesterol in Type 2 diabetic rats.Several studies show that an increase in HDL-cholesterolis associated with a decrease in coronary risk and mostof the drugs that decrease total cholesterol also decreaseHDL-cholesterol (Wilson, 1990). In the present study,the Tf-sdf, while lowering LDL-cholesterol, increasedthe HDL-cholesterol fraction significantly. Recent studiesshow that triglycerides are also independent risk factorsfor coronary heart disease (Bainton et al., 1992; NationalCholesterol Education Program Expert Panel, 1994) and inthe present study the agent decreased the triglyceride levelssignificantly. Tf-sdf fraction may reduce the triglyceridesby decreasing the non-esterified fatty acids (NEFA) inType 2 rats. NEFA may influence platelet aggregation andvascular changes by accelerating the rate of prostacyclinin plasma (Reinila, 1981; Gjesdal et al., 1976). The plantfraction showed a tendency to lower the platelet aggrega-

tion that might be due to the reduction of NEFA. Hence,the resulting benefit of the agent not only helps to combathyperglycemia, but also helps to prevent dyslipidemia—animportant risk factor for the micro- and macro-vascularcomplications of diabetes.

It has been previously shown by us that Tf-sdf frac-tion effectively inhibits carbohydrate absorption in the gut.Therefore, the hypolipidemic action of the fraction could bethe result of retardation of carbohydrate and fat absorptiondue to the presence of bioactive fibre in the agent.

In conclusion, Tf-sdf has got promising antihyper-glycemic or hypolipidemic effects and it has also a tendencyto reduce platelet aggregation in diabetic rats.

Acknowledgements

We gratefully acknowledge the financial support of In-ternational Program for the Chemical Sciences (IPICS),International Foundation of Sciences (IFS) and DiabeticAssociation of Bangladesh in conducting this study. Weare grateful to Prof. Salar Khan, National Herbarium,Bangladesh for the identification of the plant.

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