1 Department of Obstetrics and Gynaecology, University of Thessalia, 22 Papakiriazi Street, 41222 Larissa, State Departments of 2 Obstetrics and Gynaecology and 3 General Surgery, Larissa and 4 Department of Biological Chemistry, University of Ioannina, Ioannina, Greece
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Abstract |
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Key words: body mass index/leptin/oestradiol/ovariectomy/ovary
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Introduction |
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Since obesity is one of the symptoms in a significant proportion of women with polycystic ovary syndrome (PCOS), several studies have investigated changes in leptin concentrations in this syndrome (Brzechffa et al., 1996; Chapman et al., 1997
; Laughlin et al., 1997
; Mantzoros et al., 1997
; Rouru et al., 1997
). Although the results are conflicting, it has become evident that leptin may play a role in certain cases of PCOS and may act as a link between fat and reproduction. Recent studies have detected leptin receptor mRNA in the human ovary and specific binding of leptin in ovine granulosa cells (Cioffi et al., 1996
; Spicer and Francisco, 1997
), whereas experiments in vitro have shown that leptin may directly affect follicle stimulating hormone (FSH)-induced production of oestradiol by rat granulosa cells (Zachow and Magoffin, 1997
). A possible relationship between oestrogen and leptin has been recently postulated. In rats, ovariectomy reduced significantly serum leptin values and the expression of ob gene in certain sites of white adipose tissue, changes which were reversed by oestradiol supplement (Shimizu et al., 1997
; Yoneda et al., 1998
). In humans, lower concentrations of leptin have been found in postmenopausal compared to premenopausal women and in men compared to pre- or postmenopausal women, while during the normal menstrual cycle the concentrations of leptin are higher in the luteal than in the follicular phase (Hardie et al., 1997
; Shimizu et al., 1997
; Messinis et al., 1998
).
The present study was undertaken to examine further the relationships between gonadal steroids and leptin in normal women by investigating changes in leptin concentrations following bilateral ovariectomy.
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Materials and methods |
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Statistical analysis
For the purpose of the statistical analysis, hormone results were transformed into logarithms in order to achieve an approximately normal distribution of the data. However, in the results the arithmetic means are presented. For comparisons within the same group, statistical analysis was performed using one-way analysis of variance (ANOVA) and paired t-test as appropriate, while for comparisons between groups two-way ANOVA was used (effects of time and of women). Correlations between various parameters were calculated by using simple and multiple linear regression.
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Results |
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Serum oestradiol values (mean ± SEM) on day 0 did not differ significantly between groups 1 (286 ± 57 pmo/l), 2 (270 ± 71 pmol/l) and 3 (227 ± 38 pmol/l), although they were lower in group 3. Oestradiol values decreased significantly in groups 1 and 2 at 12 h from the operation (P < 0.05) and further up to day 8 with no significant difference between the two groups at any point (Figure 1). In group 3, however, serum oestradiol values showed a temporal but significant increase on day 1 (P < 0.05), decreasing slightly on day 2 and then increasing gradually up to day 7 (500 ± 78 pmol/l, P < 0.01, Figure 1
). Oestradiol values were significantly higher in group 3 than in groups 1 and 2 during the whole postoperative period (Figure 1
). Serum concentrations of progesterone (mean ± SEM) were on day 0 significantly higher in group 2 (16.9 ± 1.2 nmol/l) than in group 1 (4.5 ± 0.6 nmol/l, P < 0.01) and group 3 (1.2 ± 0.2 nmol/l, P < 0.01). After the operation, in groups 1 and 2 progesterone values decreased rapidly during the first 24 h, particularly in group 2 and gradually thereafter up to postoperative day 8 with no significant difference between the two groups at any point (Figure 1
). In group 3, serum progesterone values showed a temporal but significant increase 12 h from the operation (P < 0.01) remaining low throughout the rest of the postoperative period (Figure 1
). The described changes in FSH, LH, oestradiol and progesterone concentrations during the postoperative period in group 3 (Figure 1
) resemble those seen during the mid- to late follicular phase of the normal menstrual cycle.
A slight but non-significant decrease in body weight (mean ± SEM) was noted on postoperative day 8 compared with day 0 in group 1 (0.53 ± 0.20 kg) and group 2 (0.71 ± 0.30 kg) with no significant difference between the two groups. In group 3, the decrease in body weight on day 7 (3.2 ± 0.2 kg) was significantly greater than in groups 1 and 2 (P < 0.01). BMI values were available in groups 1 and 2 on days 0 and 8 and in group 3 on days 0, 4, 5, 6 and 7. BMI (mean ± SEM) did not change significantly on postoperative day 8 compared with the value on day 0 both in group 1 (26.1 ± 1.1 and 26.3 ± 1.1 kg/m2 respectively) and group 2 (26.7 ± 0.7 and 26.9 ± 0.8 kg/m2 respectively), while it decreased significantly in group 3 from day 0 (28.2 ± 1.5 kg/m2) to day 7 (26.3 ± 1.5 kg/m2, P < 0.001). A significant decrease in BMI was also seen in group 3 from day 0 to day 4 (27.3 ± 1.5 kg/m2, P < 0.001) and from day 4 to day 7 (P < 0.001). Serum leptin concentrations before and after the operation correlated significantly with BMI in groups 1 and 2 combined (r = 0.632, P < 0.001, n = 28, Figure 2b). A significant positive correlation between leptin and BMI was also found in group 3 before and after the operation (r = 0.892, P < 0.001, n = 30) (Figure 2a
). Serum leptin values correlated significantly with oestradiol values from postoperative days 47 in group 3 (r = 0.480, P < 0.05, n = 24, Figure 3a
) and from day 0 to day 8 in group 1 (r = 0.467, P < 0.001, n = 91, Figure 3c
). In group 2, the correlations between leptin and oestradiol values were not significant. Significant positive correlations were also found between serum leptin and progesterone concentrations from postoperative day 0 to day 8 in group 1 (r = 0.239, P < 0.05, n = 91, Figure 3d
) and group 2 (r = 0.217, P < 0.05, n = 91, Figure 3d
) and from day 0 to day 7 in group 3 (r = 0.323, P < 0.05, n = 54, Figure 3b
). When multiple regression analysis was performed in group 3, the significant positive correlation between leptin and oestradiol shown in Figure 3a
was eliminated and leptin correlated significantly only with BMI. When leptin values on days 0 and 8 of groups 1 and 2 were combined, by simple regression analysis they correlated significantly with BMI (r = 0.602, P < 0.01, n = 28), progesterone (r = 0.601, P < 0.01, n = 28) and oestradiol values (r = 0.386, P < 0.05, n = 28). When multiple regression analysis was applied, the significant correlation of leptin with oestradiol was eliminated, while the correlation of leptin with progesterone and BMI were preserved. Oestradiol values correlated significantly with those of progesterone on days 0 and 8 in groups 1 and 2 (r = 0.520, P < 0.01, n = 28) and in group 3 from days 47 (r = 0.405, P < 0.05, n = 24). No significant correlations were found between BMI and oestradiol or progesterone values in all three groups of women.
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Discussion |
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After the temporal increase, leptin values declined rapidly in all three groups of women up to postoperative day 4 to concentrations that were significantly lower than before the operation. At the same time, changes in oestradiol values varied considerably among groups, indicating that leptin changes during the immediate period following ovariectomy are independent of oestradiol. These results contradict data in rats in which treatment with oestrogen reversed the significant reduction in serum leptin concentrations and in the expression of ob gene in white adipose tissue that was seen 28 weeks after ovariectomy (Shimizu et al., 1997; Yoneda et al., 1998
). It is evident, therefore, that factors other than oestradiol controlled leptin secretion during the postoperative period in the present study. Such factors could be changes in food intake, reduction in fat stores and body weight and consequently in BMI and decrease in motor activity. These factors, however, are interrelated and, although fat stores were not measured in the present study, only a small reduction in body weight with no significant changes in BMI was seen in the groups of ovariectomized women 1 week after the operation. Since body weight measurements were not available in the ovariectomized women during the greater part of the postoperative period, one cannot exclude the possibility that a significant reduction in body weight occurred in these women during the first 4 days after the operation at a time when great restrictions in food intake were applied. Although dramatic changes in leptin values in response to changes in food intake are not expected in normal or obese subjects (Korbonits et al., 1997
), a recent study has shown that even a 4% reduction in body weight over a period of 7 days resulted in a 61% decrease in leptin values in men and women (Dubuc et al., 1998
). These data, together with the significant positive correlations between leptin values and BMI that were seen in our patients during the postoperative period, indicate that changes in leptin values following the operation were predominantly determined by changes in this parameter.
The possibility, however, that oestradiol itself can affect leptin production in women is not excluded. A significant positive correlation between leptin and oestradiol values was seen during the second half of the postoperative period in the cholocystectomized women and this is in accordance with data in mid- to late follicular phase of the normal menstrual cycle (Messinis et al., 1998). At the same time, leptin and oestradiol values increased significantly in this group of women, even though BMI continued to decline. Furthermore, high affinity binding of 17ß-oestradiol in the cytoplasmic fraction of various white adipose tissues has been demonstrated in rats (Wade and Gray, 1978
).
The finding that in ovariectomized women a significant independent association was found between progesterone and leptin values suggests that this steroid may also participate in the production of leptin by adipocytes. Significant positive correlations of leptin with progesterone were also found in a previous study during the normal menstrual cycle (Hardie et al., 1997). It is possible, therefore, that oestradiol during the follicular phase of the cycle primes the adipocytes to the stimulating effect of progesterone. This could explain the significantly higher values of leptin in the early to midluteal compared with the mid- to late follicular phase of the cycle seen in the present and in previous studies (Hardie et al., 1997
; Shimizu et al., 1997
; Messinis et al., 1998
). The rapid decline of luteal phase leptin values after ovariectomy to concentrations similar to those of the follicular phase supports this assumption. The possibility that the ovaries may contribute to the circulating leptin concentrations in women cannot be excluded despite the fact that in this study leptin values declined both in the ovariectomized and the non-ovariectomized women. Recent data have suggested that the pre-ovulatory follicle itself may be an important source of leptin (Cioffi et al., 1997
). Oestradiol and progesterone, therefore, may act within the follicle to increase leptin production at that site. On the other hand, leptin produced inside the ovary might act as a paracrine factor to affect steroid synthesis in the follicle and corpus luteum, since both binding of leptin and a direct effect of this substance on steroidogenesis have been demonstrated in vitro (Spicer and Francisco, 1997
; Zachow and Magoffin, 1997
). Alternatively, however, changes in leptin concentrations on days 04 in the group of cholocystectomized women could simply reflect the stage of the cycle in these women, i.e. early to midfollicular phase, during which a decline in leptin values has been recently described, although the mechanism is not clear (Messinis et al., 1998
).
From a physiological point of view, these results support the hypothesis that leptin may be the missing link between body fat and reproduction (Conway and Jacobs, 1997). Apart from the relationship with gondal steroids, this protein may also affect reproduction through other mechanisms, such as by controlling early development of embryos before implantation (Antczak and Van Blerkon, 1997).
In conclusion, the present study confirms previous data that leptin concentrations are higher in the luteal than the follicular phase of the cycle. The results demonstrate for the first time that leptin concentrations following a laparotomy decline rapidly from the first to the fourth postoperative day both in ovariectomized and non-ovariectomized women. Although BMI seems to be the predominant factor responsible for these changes, it is also possible that oestradiol and progesterone are involved in the mechanism which controls the production of leptin during the normal menstrual cycle.
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Acknowledgments |
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Notes |
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References |
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Antczak, M. and Van Blerkom, J. (1997) Oocyte influences on early development: the regulatory proteins leptin and STAT3 are polarized in mouse and human oocytes and differentially distributed within the cells of the preimplantations stage embryo. Mol. Hum. Reprod., 3, 10671086.[Abstract]
Barash, I.A., Cheung, C.C., Weigle, D.S. et al. (1996) Leptin is a metabolic signal to the reproductive system. Endocrinology, 137, 31443147.[Abstract]
Brzechffa, P.R., Jakimiuk, A.J., Agarwal, S.K. et al. (1996) Serum immunoreactive leptin concentrations in women with polycystic ovary syndrome. J. Clin. Endocrinol. Metab., 81, 41664169.[Abstract]
Caro, J.F., Sinha, M.K., Kolaczynski, J.W. et al. (1996a) Leptin: the tale of an obesity gene. Diabetes, 45, 14551462.[ISI][Medline]
Caro, J.F., Kolaczynski, J.W., Nyce, M.R. et al. (1996b) Decreased cerebrospinal-fluid/serum leptin ratio in obesity. A possible mechanism for leptin resistance. Lancet, 348, 159161.[ISI][Medline]
Chapman, I.M., Wittert, G.A. and Norman, R.J. (1997) Circulating leptin concentrations in polycystic ovary syndrome. Relation to anthropometric and metabolic parameters. Clin. Endocrinol., 46, 175181.[ISI][Medline]
Chehab, F.F., Lim, M.E. and Lu, R. (1996) Correction of the sterility defect in homozygous obese female mice by treatment with the human recombinant leptin. Nature Genet., 12, 318320.[ISI][Medline]
Cioffi, J.A., Shafer, A.W., Zupancic, T.J. et al. (1996) Novel B219/0B receptor isoforms: possible role of leptin in hematopoiesis and reproduction. Nature Med., 2, 585589.[ISI][Medline]
Cioffi, J.A., Van-Blerkom, J., Antczak, M. et al. (1997) The expression of leptin and its receptors in pre-ovulatory human follicles. Mol. Hum. Reprod., 3, 467472.[Abstract]
Conway, G.S. and Jacobs, H.S. (1997) Leptin: a hormone of reproduction. Hum. Reprod., 12, 633635.
Diamond, F.B. Jr., Eichler, D.C., Duckett, G. et al. (1997) Demonstration of a leptin binding factor in human serum. Biochem. Biophys. Res. Commun., 233, 818822.[ISI][Medline]
Dubuc, G.R., Phinney, S.D., Stern, J.S. and Havel, P.J. (1998) Changes of serum leptin and endocrine and metabolic parameters after 7 days of energy restriction in men and women. Metabolism, 47, 429434.[ISI][Medline]
Halaas, J.L., Gajawala, K.S., Maffei, M. et al. (1995) Weight-reducing effects of the plasma protein encoded by the obese gene. Science, 269, 543546.[ISI][Medline]
Hardie, L., Trayhurn, P., Abramovich, D. and Fowler, P. (1997) Circulating leptin in women: a longitudinal study in the menstrual cycle and during pregnancy. Clin. Endocrinol., 47, 101106.[ISI][Medline]
Korbonits, M., Trainer, P.J., Little, J.A. et al. (1997) Leptin levels do not change acutely with food administration in normal or obese subjects, but are negatively correlated with pituitaryadrenal activity. Clin. Endocrinol., 46, 751757.[ISI][Medline]
Laughlin, G.A., Morales, A.J. and Yen, S.S.C. (1997) Serum leptin levels in women with polycystic ovary syndrome: The role of insulin resistance/hyperinsulinemia. J. Clin. Endocrinol. Metab., 82, 16921696.
Licinio, J., Mantzoros, C., Negrao, A.B. et al. (1998) Human leptin levels are pulsatile and inversely related to pituitaryadrenal function. Nature Med., 3, 575579.[ISI]
Mantzoros, C.S., Dunaif, A. and Flier, J.S. (1997) Leptin concentrations in the polycystic ovary syndrome. J. Clin. Endocrinol. Metab., 82, 16871691.
Messinis, I.E., Milingos, S., Kollios, K. et al. (1996) Changes in pituitary response to gonadotropin-releasing hormone following bilateral ovariectomy in women treated with follicle-stimulating hormone. Gynecol. Endocrinol., 10, 383390.[ISI][Medline]
Messinis, I.E., Milingos, S., Zikopoulos, K. et al. (1998) Leptin concentrations in the follicular phase of spontaneous cycles and cycles superovulated with follicle stimulating hormone. Hum. Reprod., 13, 11521156.[Abstract]
Montague, C.T., Farooki, I.S., Whitehead, J.P. et al. (1997) Congenital leptin deficiency is associated with severe early-onset obesity in humans. Nature, 387, 903908.[ISI][Medline]
Murakami, T., Iida, M. and Shima, K. (1995) Dexamethasone regulates obese expression in isolated rat adipocytes. Biochem. Biophys. Res. Commun., 214, 12601267.[ISI][Medline]
Rouru, J., Anttila, L., Koskinen, P. et al. (1997) Serum leptin concentrations in women with polycystic ovary syndrome. J. Clin. Endocrinol. Metab., 82, 16971700.
Schwartz, M.W., Peskind, E., Raskind, M. et al. (1996) Cerebrospinal fluid leptin levels: relationship to plasma levels and to adiposity in humans. Nature Med., 2, 589593.[ISI][Medline]
Shimizu, H., Shimonura, Y., Nakanishi, Y. et al. (1997) Estrogen increases in vivo leptin production in rats and human subjects. J. Endocrinol., 154, 285292.[Abstract]
Spicer, L.J. and Francisco, C.C. (1997) The adipose obese gene product, leptin: evidence of a direct inhibitory role in ovarian function. Endocrinology, 138, 33743379.
Wade, G.N. and Gray, J.M. (1978) Cytoplasmic 17 ß-[3H]estradiol binding in rat adipose tissues. Endocrinology, 103, 16951701.[Abstract]
Yoneda, N., Saito, S., Kimura, M. et al. (1998) The influence of ovariectomy on ob gene expression in rats. Horm. Metab. Res., 30, 263265.[ISI][Medline]
Zachow, R.J. and Magoffin, D.A. (1997) Direct intraovarian effects of leptin: impairment of the synergistic action of insulin-like growth factor-I on follicle-stimulating hormone-dependent estradiol-17ß production by rat ovarian granulosa cells. Endocrinology, 138, 847850.
Zhang, Y., Proenca, R., Maffei, M. et al. (1994) Positional cloning of the mouse obese-gene and its human homologue. Nature, 372, 425432.[ISI][Medline]
Submitted on August 28, 1998; accepted on January 7, 1999.