Scholarly article on topic 'Effect of ethanolic extract of Lepidium meyenii Walp on serum hormone levels in ovariectomized rats'

Effect of ethanolic extract of Lepidium meyenii Walp on serum hormone levels in ovariectomized rats Academic research paper on "Biological sciences"

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Academic research paper on topic "Effect of ethanolic extract of Lepidium meyenii Walp on serum hormone levels in ovariectomized rats"

Research Article

Effect of ethanolic extract of Lepidium meyenii Walp on serum hormone levels in ovariectomized rats

Yongzhong Zhang, Longjiang Yu1, Wenwen Jin1, Mingzhang Ao1

Department of Pharmacology, Medical School, Wuhan University of Science and Technology, Wuhan, 1School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan,

Received: 22-07-2013 Revised: 21-08-2013 Accepted: 15-05-2014

Correspondence to: Dr. Yongzhong Zhang, E-mail: zyzcolin_1228@163.com

ABSTRACT

Objective: To evaluate the effect of long-term ethanol extract of Lepidium meyenii (Maca) on serum hormone levels in ovariectomized (OVX) rats and compare them with the effect of diethylstilbestrol.

Materials and Methods: Fifty female Sprague-Dawley rats were ovariectomized or sham operated. Both sham and OVX control groups (n = 10, respectively) received the vehicle. The remaining OVX rats were oral administrated with ethanol extract of Maca (0.096, or 0.24g/kg; n = 10, respectively) and diethylstilbestrol (0.05 mg/kg; n = 10). The treatment continued for 28 weeks. At week 12 and week 28, the blood of rats was collected and serum hormone levels, including estradiol (E2), testosterone (T) and follicle-stimulating hormone (FSH) were measured by radioimmunoassay.

Results: At week 12, the levels of serum E2 were slightly higher in Maca groups than that in OVX group; T levels were significantly decreased; and FSH levels were advanced slightly in Maca groups than that in sham group. After 28 weeks administration, serum E2 levels in Maca-treated animals did not differ significantly from sham control, the low dose of Maca increased serum E2 levels, and Maca prevented increase in serum FSH levels compared with OVX group.

Conclusions: Long-term Maca supply modulates endocrine hormone balance in OVX rats, especially it decreases enhanced FSH levels. It is proposed that Maca may become a potential choice for postmenopausal women.

KEY WORDS: Lepidium meyenii, maca, ovariectomized rats, serum hormone

Introduction

The global population of postmenopausal women is on the rise and expected to increase from 470 million in 1990 to 1.2 billion by the year 2030.111 Most of them suffer from menopausal symptoms, such as hot flushes, tender breasts, vaginal dryness, reduced bone mineral density, etc. Hormone replacement therapy (HRT) has been proven to be efficacious in alleviating such symptoms.121 However, the findings from the Women's Health Initiative Trial suggest that long-term HRT use increases the risk of breast cancer, endometrial cancer, thromboembolic events and vaginal bleeding and the overall health risks exceed its benefits.13,41

Alternative treatments are being sought and the potential role of traditional herb medicines in particular seem worth investigating.151

Lepidium meyenii (Maca) is the cruciferous herb native to the South America that grows exclusively above 3500 m in the central Andes. Traditionally it has been used to increase physical endurance, for male impotence and female hormonal imbalances.161 Much research has been published in recent years to show the aphrodisiac effects of Maca. We have demonstrated osteoprotective effect of ethanol extract of L. meyenii on ovariectomized rats.171 But few studies have been carried out to evaluate its effect in female hormonal imbalance. The present study was conducted to investigate the effect of ethanol extract of L. meyenii (Maca) on serum hormone levels in ovariectomized rats.

Materials and Methods

Preparation of ethanolic extract of Lepidium meyenii

Pulverized root of L. meyenii (standardized 0.6% macamides and macaenes) was obtained from Lima, Peru, through Chinese Maya Bioengineer Co, Hubei.

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DOI: 10.4103/0253-7613.135955

Official permission of Government of Peru was taken to import a medicinal plant for study in China. The plant was authenticated by Irma Fernandez, Botanist, Department of Pharmaceutical Sciences, Universidad Peruana Cayetano Heredia. The voucher specimen (PA.247) was placed in School of Life Science and Technology, Huazhong University of Science and Technology.

The powdered tuber 400 g was extracted with 95% ethanol (3 x 1500 mL) at room temperature for 2 days. The preparation was filtrated and evaporated using a rotary evaporator at 40°C to get an extract at a yield of 19.2% by weight of the starting materials, before use, the extract was further diluted with distilled water to obtain different concentrations and kept at 4°C for 24 h.

Animals

Fifty 90-day-old female Sprague-Dawley rats were purchased from Tongji Medical College (Wuhan, China). They were housed under controlled conditions (room temperature 22-24°C; relative humidity 50-55%; 12 h light/dark cycle), and had free access to tap water and standard solid food containing 1.22% calcium and 0.43% phosphorus throughout the whole experimental period. All experimental designs and procedures were approved by the Animal Ethics Committee for Animal Care and Use at Huazhong University of Science and Technology.

Experimental Methods

The animals were randomly divided into 5 groups of 10 each. After 7 days of acclimatization, the 4 groups were ovariectomized and the remaining group was sham operated. The rats were anesthetized with pentobarbital sodium (40 mg/kg i.p.), and the ovaries were removed bilaterally. Sham-operation was performed in the same manner but with only exposure of ovaries. They were administrated prophylactic penicillin G (4000 IU/kg i.p.) for three days. A week later, both sham and ovariectomized control (OVX) groups received the vehicle (equivalence of distilled water) through gastric tube. The remaining ovariectomized groups were administrated with ethanolic extract of L. meyenii (receiving 0.096 g/kg b.w. and 0.24 g/kg b.w., respectively) and diethylstilbestrol (0.05 mg/kg) daily. Diethylstilbestrol (DES) was used as a positive control. The treatment continued for 28 weeks. Body weight of all animals was measured weekly. At week 12 of administration, the rats were anesthetized with ether and blood samples were obtained from caudal veins (0.8 ml/rat approximately). The samples were centrifuged (1000 x g for 10 min) and serum estradiol (E2), testosterone (T) and follicle-stimulating hormone (FSH) levels were measured by radioimmunoassay (JiuDing Medical Bio-engineering Co., Tianjin, China). At the end of the treatment phase (28 weeks), the rats were anesthetized and sacrificed by withdrawing blood from common carotid artery and the hormone levels were assessed as mentioned above. The weight of the uterus was also measured at the end of the study period.

Statistical Analysis

All data were presented as mean ± S.E.M and analyzed using the statistical package for the social sciences software (SPSS version 12.0). Differences between groups were determined by

t-test and one-way analysis of variance (ANOVA) and P < 0.05 was considered statistically significant.

Results

Effect of L. Meyenii on Body and Uterine Weights in Rats

The body and uterine weights of five groups are presented in Table 1. An increase in body weight was seen in all groups at 12 and 28 weeks as compared to baseline. The increase in body weight in L. meyenii extract treated groups was comparable to both sham and OVX control groups at 12 and 28 weeks. In DES group, at the end of 28 weeks, a significant decrease in body weight was observed as compared to sham and OVX control groups. The wet weight of the uteri in the OVX and L. meyenii treated groups was significantly lower (P < 0.01) as compared to sham group while the uterine weights of DES-treated group were significantly higher than that of OVX group (P < 0.05). Effect of L. Meyenii on Serum Hormone Levels

A significant decrease in serum estradiol (E2) levels was seen at the end of 28 weeks (P < 0.05) and in serum testosterone (T) levels at the end of 12 and 28 weeks in OVX control (P < 0.05) as compared with sham control group. A corresponding significant increase in FSH levels was observed (P < 0.01) throughout the study period in OVX control as compared with sham control. In groups treated with the two doses of L. meyenii,no significant change in E2 and FSH levels at 12 weeks was seen and at low dose of L. meyenii (0.096 g/kg), significant decrease in testosterone levels was observed (P < 0.05) as compared with OVX control group. At 28 weeks, significant increase in E2 levels of low dose of L. meyenii extract was observed as compared with OVX control (P < 0.05). The decrease in FSH levels with both doses at 28 weeks was also highly significant (P < 0.01). On the other hand, in DES group, there was a statistically significant increase in E2 level and statistically significant decrease in T and FSH levels as compared with OVX control group at both 12 and 28 weeks (P < 0.05).

Discussion

In the present study, we evaluated the effect of ethanol extract of L. meyenii on serum hormone levels in OVX rats and compared them with the effect of DES. It is well known that postmenopausal syndrome results from estrogenic hormone deficiency. OVX rats are commonly used for postmenopausal studies.181 Our results showed that both serum E2 and T concentrations decreased when the rats were ovariectomized, but the degression of serum E2 was not fast; it did not decrease significantly until 28 weeks after operation [Table 2]. On the contrary, serum T level reduced quickly in OVX rats, which suggests that most serum testosterone is synthesized from the ovaries. FSH is a hormone synthesized in pituitary gland and its secretion is under tight negative feedback control by E2. Consequently, lower serum E2 is accompanied by a compensatory increase in FSH concentration.191 Our results confirmed that FSH levels were elevated in OVX rats. The change of serum hormone in OVX rats was similar to that in postmenopausal women.1101

The serum E2 levels were not significantly decreased in the L. meyenii-treated groups in OVX rats by week 12.

Table 1:

Effect of ethanol extract of L. meyenii on body and uterine weight in OVX rats (n=10 per group)

Weight (gm) Sham OVX L. meyenii (g/kg) DES

control control

0.096 0.24

BW at baseline 192.2±6.22 193.3±17.8 201.2±25.9 193.0±12.1 186.8±16.0

BW at 12 weeks 227.3±14.3 242.9±22.5 246.1±28.4 240.1±18.1 225.1±15.1

BW at 28 weeks 276.4±26.6 282.8±27.3 294.1±32.4 274.7±23.7 251.1±16.2a c

Uterine weight (mg/g BW) 2.536±1.04 1.031±0.92b 1.276±0.85b 1.509±0.67a 1.97±0.518c

Values are mean±S.E.M, BW = Body weight, OVX = Ovariectomized, DES = Diethylstilbestrol, aP<0.05 vs. sham, bP<0.01 vs. sham, cP<0.05 vs OVX

Table 2:

Effect of ethanol extract of L. meyenii on serum hormone levels in OVX rats (n=10 per group)

Sham OVX L. meyenii (g/kg) DES

0.096 0.24

12 week

E2 (mg/L) 19.37±8.22 15.20±7.86 16.78±6.37 18.61±8.45 23.62±9.59c

T(ng/L) 42.4±10.1 25.4±9.2b 14.8±7.3b' c 27.7±21.6 10.2±2.1b'd

FSH (IU/L) 1.97±0.51 3.78±0.63b 3.65±1.69 2.95±1.75 2.14±0.85d

28 week

E2 (mg/L) 11.88±6.26 7.29±2.81a 10.28±3.33c 8.28±2.98 11.66±2.33d

T(ng/L) 21.5±7.6 9.7±4.7b 7.3±6.1b 10.9±4.1b 4.7±0.1b'd

FSH (IU/L) 3.14±1.00 8.05±3.04b 3.92±1.21d 3.69±2.66d 2 0.53±0.79d

All values are expressed as mean±S.E.M, OVX = Ovariectomized, DES = Diethylstilbestrol, aP<0.05 vs sham, bP<0.01 vs sham, cP<0.05 vs OVX, dP<0.01 vs OVX.

However, by week 28, the L. meyenii low-dose increased serum E2 level treatment, and L. meyenii prevented the increase in serum FSH levels at the end of the treatment. It was surprising to note that the high dose L. meyenii did not affect E2 levels. Meanwhile, uterine weights of L. meyenii groups increased slightly, which suggests that it may exhibit weakly estrogenic activity. However, other studies take the view that L. meyenii does not act in a hormone-like fashion to improve postmenopausal symptoms.[11] In the study by Stojanovska et al,[12] a double-blind, placebo-controlled, randomized, parallel trial carried out in postmenopausal women treated with Maca had reported a widespread improvement in psychological symptoms, including anxiety and depression, and lowers measures of sexual dysfunction, but no differences were seen in serum concentrations of E2, FSH and LH among baseline, Maca treatment and placebo. However, the duration of Maca treatment was only 6 weeks. Therefore, the subject of whether or not the estrogenic activity of Maca plays an important role in improving postmenopausal symptoms needs further attention.

The mechanisms regulating the hormonal actions are unclear at present. To our knowledge, the biological activity of L. meyenii may be due to one or more of the phytochemicals present in the extract. Carbohydrate, lipid, protein, fiber, inorganic salt, amino acid, fatty acid, and sterol content of the hypocotyls of L. meyeniihave been described.[13] Additionally, it also contains alkaloids, steroids, macaene and macamide, while some investigators suggest that L. meyenii exerts hormonal balancing effect through Maca alkaloids, which act on the hypothalamus-pituitary axis and the adrenals,[14] but, there is no supporting evidence. Further experiments are needed to

assess which compound, of the several Maca's components, is responsible of the observed in vivo effects.

In conclusion, our study indicated that long-term treatment with L. meyenii (Maca) modulated hormone levels in ovariectomized rats. Especially, it decreased enhanced FSH levels. However, its underlying mechanism has not yet been elucidated and further studies will be needed.

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Cite this article as: Zhang Y, Yu L, Jin W, Ao M. Effect of ethanolic extract of Lepidium meyenii Walp on serum hormone levels in ovariectomized rats. Indian J Pharmacol 2014;46:416-9.

Source of Support: Nil. Conflict of Interest: No.

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