Effect of Freeze Dried Extract of Olea europaea on the Pituitary–Thyroid Axis in Rats
2
SHORT COMMUNICATION Effect of Freeze Dried Extract of Olea europaea on the Pituitary–Thyroid Axis in Rats A. A. Al-Qarawi, 1 * M. A. Al-Damegh 2 and S. A. ElMougy 1 1 Department of Veterinary Medicine, College of Agriculture and Veterinary Medicine, King Saud University, PO Box 1482, Saudi Arabia 2 Girl’s College of Education, Scientific Department, Buraydah, Qassim Branch, Saudi Arabia The effect of an aqueous extract of olive (Olea europaea) leaf on the thyroid activity was studied. The results suggest a stimulatory action of the extract on the thyroid, unrelated to the pituitary. Copyright # 2002 John Wiley & Sons, Ltd. INTRODUCTION Between 1948 and 1954, the olive leaf was used both empirically as well as in experimental and clinical studies for its hypotensive action. Zarzuelo et al. (1991) studied the vasodilator effect of olive leaf; while in 1993, Duarte et al. studied the effect of oleuropeoside (isolated from Olea europaea) in isolated guinea-pig atria. Later in 1995, Olea europaea was found to influence the rat isolated ileum and trachea (Fehri et al., 1995). Olive leaf was reported to have a significant hypoglycaemic activity (Gonzalez et al., 1992). Recently, oleuropein, the bitter principle of olives, was found to enhance nitric oxide production by mouse macrophages (Visioli et al., 1998). Olive oil had an overall lowering activity on serum fatty acids (Campbell and Dorn, 1992) in dogs. These properties initiated a stepwise experiment into the possible effect of olive leaf extracts directly on the thyroid gland or/and on the pituitary. Material and Methods Plant material. The plant material consisted of the leaves of Olea europaea collected in December–January 1998 in AlTaif, Saudi Arabia. On arrival the sample was ground and soaked in distilled water and kept at 4 °C for 48 h. The extract was then separated by filtration and subsequently lyophillized and refrigerated at 4 °C until used. Serum thyroxine (T 4 ) triiodothyronine (T 3 ) and thyrotrophic (TSH) assay. Plasma levels of thyroxine (T 4 ), triiodothyronine(T 3 ) and thyrotropic (TSH) hor- mones were determined using Coat-a-Count I 125 -radio- immunoassay kits provided from the Diagnostic Products Corporation. Design of the experiment. Male mature Wistar rats weighing 125–150 g were divided into four groups. One group was kept as a control and given a daily oral dose of distilled water. The three other groups were given an oral dose of 100 mg, 250 mg and 500 mg of the lyophyllized aqueous extract of the olive leaf for 14 consecutive days. On day 15 the rats were bled from the inner canthus and the plasma was separated for the various hormonal assays. Statistical analysis. Student’s t-test was performed for comparing different sets of data. Results Table 1 reveals that after 14 days of treatment with the aqueous extract of Olea europeae leaves, the TSH level in the blood decreased sharply and significantly. Serum T 3 increased but to differing degrees. The increase in T 3 was dose dependent and approximately three times the control values. Although the T 4 increased the values were not significant. Discussion The results suggest that an aqueous extract prepared from olive leaves has a thyroid stimulating activity. This property may explain (a) the hypolipidaemic effect of olive leaves, because levels of serum lipids, including Table 1. Effect of the aqueous extract Olea europaea leaves on serum TSH, T 3 and T 4 Treatment TSH(mIU/mL) T 3 (nmol/L) T 4 (ng/dL) Control 0.8 0.055 1.2 0.11 0.9 0.071 100 mg 0.2 0.001 b 1.8 0.35 1.0 0.31 250 mg 0.2 0.001 c 2.3 0.38 b 1.1 0.29 500 mg 0.2 0.001 c 3.0 0.70 a 1.3 0.24 Values are mean SEM. a p < 0.05. b p < 0.01. c p < 0.001. PHYTOTHERAPY RESEARCH Phytother. Res. 16, 286–287 (2002) Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ptr.855 Copyright # 2002 John Wiley & Sons, Ltd. * Correspondence to: Dr A. A. Al-Qarawi, Department of Veterinary Medicine, College of Agriculture and Veterinary Medicine, King Saud University, P.O. Box 1482, Saudi Arabia. Received 27 May 1999 Accepted 12 April 2000
Transcript of Effect of Freeze Dried Extract of Olea europaea on the Pituitary–Thyroid Axis in Rats
����� ���������
Effect of Freeze Dried Extract of Olea europaeaon the Pituitary–Thyroid Axis in Rats
A. A. Al-Qarawi,1* M. A. Al-Damegh2 and S. A. ElMougy1
1Department of Veterinary Medicine, College of Agriculture and Veterinary Medicine, King Saud University, PO Box 1482, Saudi Arabia2Girl’s College of Education, Scientific Department, Buraydah, Qassim Branch, Saudi Arabia
The effect of an aqueous extract of olive (Olea europaea) leaf on the thyroid activity was studied. Theresults suggest a stimulatory action of the extract on the thyroid, unrelated to the pituitary. Copyright �2002 John Wiley & Sons, Ltd.
INTRODUCTION
Between 1948 and 1954, the olive leaf was used bothempirically as well as in experimental and clinical studiesfor its hypotensive action. Zarzuelo et al. (1991) studiedthe vasodilator effect of olive leaf; while in 1993, Duarteet al. studied the effect of oleuropeoside (isolated fromOlea europaea) in isolated guinea-pig atria. Later in1995, Olea europaea was found to influence the ratisolated ileum and trachea (Fehri et al., 1995). Olive leafwas reported to have a significant hypoglycaemic activity(Gonzalez et al., 1992). Recently, oleuropein, the bitterprinciple of olives, was found to enhance nitric oxideproduction by mouse macrophages (Visioli et al., 1998).Olive oil had an overall lowering activity on serum fattyacids (Campbell and Dorn, 1992) in dogs. Theseproperties initiated a stepwise experiment into thepossible effect of olive leaf extracts directly on thethyroid gland or/and on the pituitary.
Material and Methods
Plant material. The plant material consisted of theleaves of Olea europaea collected in December–January1998 in AlTaif, Saudi Arabia. On arrival the sample wasground and soaked in distilled water and kept at 4°C for48 h. The extract was then separated by filtration andsubsequently lyophillized and refrigerated at 4°C untilused.
Serum thyroxine (T4) triiodothyronine (T3) andthyrotrophic (TSH) assay. Plasma levels of thyroxine(T4), triiodothyronine(T3) and thyrotropic (TSH) hor-mones were determined using Coat-a-Count I125-radio-immunoassay kits provided from the Diagnostic ProductsCorporation.
Design of the experiment. Male mature Wistar ratsweighing 125–150 g were divided into four groups. One
group was kept as a control and given a daily oral dose ofdistilled water. The three other groups were given an oraldose of 100�g, 250 �g and 500 �g of the lyophyllizedaqueous extract of the olive leaf for 14 consecutive days.On day 15 the rats were bled from the inner canthus andthe plasma was separated for the various hormonalassays.
Statistical analysis. Student’s t-test was performed forcomparing different sets of data.
Results
Table 1 reveals that after 14 days of treatment with theaqueous extract of Olea europeae leaves, the TSH levelin the blood decreased sharply and significantly. SerumT3 increased but to differing degrees. The increase in T3was dose dependent and approximately three times thecontrol values. Although the T4 increased the values werenot significant.
Discussion
The results suggest that an aqueous extract prepared fromolive leaves has a thyroid stimulating activity. Thisproperty may explain (a) the hypolipidaemic effect ofolive leaves, because levels of serum lipids, including
Table 1. Effect of the aqueous extract Olea europaea leaveson serum TSH, T3 and T4
��������� ����� ��� ������ �� ���� ���
������� ���� ����� ���� ���� ���� �������� �� ���� ������ ���� ���� ���� ������� �� ���� ����� ���� ����� ���� ������� �� ���� ����� ���� ����� ���� ����
!��"�# ��� ����� �$%�� �� ������ �� ����� �� ������
PHYTOTHERAPY RESEARCHPhytother. Res. 16, 286–287 (2002)Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ptr.855
Copyright � 2002 John Wiley & Sons, Ltd.
* Correspondence to: Dr A. A. Al-Qarawi, Department of VeterinaryMedicine, College of Agriculture and Veterinary Medicine, King SaudUniversity, P.O. Box 1482, Saudi Arabia.
Received 27 May 1999Accepted 12 April 2000
cholesterol, are known to be lowered by increased levelsof circulating thyroid hormones (Tepperman, 1981) and(b) the hypoglycaemic activity of olive leaves (Gonzalezet al., 1992) which could be brought about as a result ofincreased thyroid activity (Felig et al., 1981). In thepresent investigation, the results indicate that the actionof the olive leaf extract was mediated either directly onthe thyroid gland as seen in a significant rise in the levelof T3 and a non-significant increase in T4or/and throughperipheral conversion to T3. It is well known that T4 is themajor secretory product of the thyroid and that 20% ofthe daily production rate of T3 is derived from the thyroid
secretion and 80% from peripheral T4 conversion. Thisconversion is brought about by 5� deiodinase (Bennettand Plum, 1996). Therefore, the aqueous extract of theolive leaf could have exhibited a stimulatory influence onthe 5� deiodinase thus increasing the peripheral conver-sion of T4 to T3. The significant decreased level of TSHcould have been brought about through a direct inhibitoryaction on the pituitary, or through the feedback mechan-ism of an increased level of T4 or/and an increased uptakeof the TSH by the thyroid. This requires furtherinvestigation to distinguish between the three possiblemechanisms of thyroid stimulation.
References
&������ '�( )�"� *� ���+� � ������ �� � ����� ���, ����-�&� ��"����#. ������/ ����0�����
���1���� 2�( 3��� 4� ����� $55� �# �5 ���� #"�6�7�� �8� �����89� �8� �� #��"� ��� "�����"# 5���: � 8� �� �����;�8��# 8� ���#� � � � � � ��� ��. ���0����
3"���� '( )���< =( >��<"��� ?( '8����< '( )���<;!8< �8�� *(������� '� ����� $55� �# �5 ���"��1��#8�� 8� 8#�������"8���;18� ���8�� ������ � � ��. ���0����
*�,�8 &( %��� �( ?8� ,� '%( ����8#�� '�� ����� $55� �# �5�� � ����� � �� �@��� � �� �,� ��� 8#������ 8��"� ������ ,��� �� ���� � � � �. ���0����
*��8� )( &�@��� '3( &����"# ?$( *��,��� �?� ����� !������"����# ��� � �������$� % 4��7;8��. A�7 B��C�
4��<���< %( >��<"��� ?( 4���< %'( ���8��� %)( '8����< '(=#"�� �� ����� :1���: ���8 � �898�: �5 ��89� ���5� ������� � ��. ���0����
��11����� '� ������ ������� ��� !������� �� �����# ��,���� B��� &��C. �,8 ����
!8#8��8 *( &����#�� �( 4���8 �� ����� =��"��1�8�( �,� �8����1�8� 81�� �5 ��89�#( ��,�� �# �8��8 �@8�� 1���" �8�� �:��"#� �� ��1,���#� %�� ��� ��. ���0��+�
>��<"��� ?( 3"���� '( '8����< '( 4��<���< %( ���8��� %)������ !�#��8����� �55� � �5 ��89� ���5� ������ � � ��. ���0����
OLEA EUROPAEA ON PITUITARY - THYROID AXIS 287
Copyright � 2002 John Wiley & Sons, Ltd. Phytother. Res. 16, 286–287 (2002)
