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1.
Gen Comp Endocrinol ; 168(1): 36-45, 2010 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-20399211

RESUMO

An adiposity-associated rise in leptin occurs at the time of delayed embryonic development in Cynopterus sphinx. The aim of present study was to examine the mechanism by which leptin may inhibit progesterone, and therefore could be responsible for delayed development. The study showed a significant increase in circulating leptin level during the period of increased fat accumulation, which coincided with significant decrease in serum progesterone level and delayed embryonic development in C. sphinx. The study showed increased Ob-R expression in the corpus luteum and in the utero-embryonic unit during the period of delayed embryonic development. The in vitro study showed suppressive effect of leptin on progesterone synthesis. The effect of high dose of leptin on ovarian steroidogenesis was found to be mediated through decreased expression of StAR and LH-R proteins in the ovary. The treatment with leptin caused increased expression of STAT 3 and iNOS proteins in the ovary, which correlated with decreased expression of StAR protein in the ovary. The inhibitory effects of leptin on progesterone synthesis in the ovary are thus mediated through STAT 3 and iNOS-NO signaling pathways. This study further demonstrated low expression of PCNA coinciding with the increased concentration of the leptin receptor in the utero-embryonic unit and high circulating leptin level during November. In conclusion, adiposity associated increased leptin level during November-December might play role in suppressing progesterone synthesis in the corpus luteum as well as suppressing the rate of cell-proliferation in the utero-embryonic unit thereby causing delayed embryonic development in C. sphinx.


Assuntos
Leptina/farmacologia , Leptina/fisiologia , Animais , Corpo Lúteo/efeitos dos fármacos , Corpo Lúteo/metabolismo , Desenvolvimento Embrionário/efeitos dos fármacos , Feminino , Immunoblotting , Imuno-Histoquímica , Leptina/sangue , Nitratos/metabolismo , Óxido Nítrico Sintase Tipo II/metabolismo , Nitritos/metabolismo , Ovário/efeitos dos fármacos , Ovário/metabolismo , Gravidez , Progesterona/sangue , Progesterona/metabolismo , Radioimunoensaio , Receptores do LH/metabolismo , Receptores para Leptina/metabolismo , Fator de Transcrição STAT3/metabolismo , Transdução de Sinais/efeitos dos fármacos
2.
Reproduction ; 138(6): 935-44, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19690096

RESUMO

The aim of the present study was to evaluate the seasonal variation in serum melatonin levels and their relationship to the changes in the serum progesterone level, ovarian steroidogenesis, and embryonic development during two successive pregnancies of Cynopterus sphinx. Circulating melatonin concentrations showed two peaks; one coincided with the period of low progesterone synthesis and delayed embryonic development, whereas the second peak coincided with regressing corpus luteum. This finding suggests that increased serum melatonin level during November-December may be responsible for delayed embryonic development by suppressing progesterone synthesis. The study showed increased melatonin receptors (MTNR1A and MTNR1B) in the corpus luteum and in the utero-embryonic unit during the period of delayed embryonic development. The in vitro study showed that a high dose of melatonin suppressed progesterone synthesis, whereas a lower dose of melatonin increased progesterone synthesis by the ovary. The effects of melatonin on ovarian steroidogenesis are mediated through changes in the expression of peripheral-type benzodiazepine receptor, P450 side chain cleavage enzyme, and LH receptor proteins. This study further showed a suppressive impact of melatonin on the progesterone receptor (PGR) in the utero-embryonic unit; this effect might contribute to delayed embryonic development in C. sphinx. The results of the present study thus suggest that a high circulating melatonin level has a dual contribution in retarding embryonic development in C. sphinx by impairing progesterone synthesis as well as by inhibiting progesterone action by reducing expression of PGR in the utero-embryonic unit.


Assuntos
Quirópteros/embriologia , Desenvolvimento Embrionário , Melatonina/fisiologia , Animais , Células Cultivadas , Quirópteros/sangue , Quirópteros/metabolismo , Ritmo Circadiano/fisiologia , Embrião de Mamíferos , Desenvolvimento Embrionário/fisiologia , Feminino , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Hormônios Esteroides Gonadais/biossíntese , Melatonina/sangue , Melatonina/metabolismo , Melatonina/farmacologia , Gravidez , Progesterona/sangue , Receptores de Melatonina/metabolismo , Receptores de Melatonina/fisiologia
3.
Reprod Fertil Dev ; 19(5): 626-33, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17601410

RESUMO

The present study was undertaken in the fruit bat Cynopterus sphinx, which breeds twice in quick succession at Varanasi, India. Its gestation period varies significantly in the two successive pregnancies of the year owing to delayed embryonic development during the first (winter) pregnancy. The primary aim of the present study was to determine the role of metabolic factors in delayed embryonic development in the fruit bat C. sphinx. Variation in bodyweight, fat deposition, oxygen (O(2)) consumption rate, basal metabolic rate (BMR), body temperature (Tb) and hepatic succinate dehydrogenase (SDH) activity, along with circulating levels of thyroid hormones (tri-iodothyronine and thyroxine), were examined as metabolic factors during the two successive pregnancies in C. sphinx. The increase in bodyweight observed in November was due to accumulation of white adipose tissue in the posterior abdominal region. A significant decline in O(2) consumption rate, BMR, Tb and SDH activity was found in early winter in November-December, which coincides closely with the period of fat accumulation and with the period of delayed embryonic development in C. sphinx. A significantly higher O(2) consumption rate, BMR, Tb and SDH activity was noted during the second pregnancy in, when embryonic development was relatively faster. Thyroid hormone levels were high during the period of embryonic delay compared with levels during the remaining months. The results of the present study suggest that the delayed embryonic development in C. sphinx during early winter may be due to a low O(2) consumption rate, BMR, Tb and SDH activity in November-December. The energy saved by suppressing embryonic development in this species may be advantageous for fat accumulation. Increased thyroid hormone levels during the early winter period might facilitate fat accumulation in C. sphinx.


Assuntos
Tecido Adiposo Branco/metabolismo , Quirópteros/embriologia , Quirópteros/metabolismo , Desenvolvimento Embrionário/fisiologia , Animais , Metabolismo Basal/fisiologia , Temperatura Corporal/fisiologia , Peso Corporal/fisiologia , Feminino , Tamanho do Órgão/fisiologia , Consumo de Oxigênio/fisiologia , Gravidez , Estações do Ano , Succinato Desidrogenase/metabolismo , Tiroxina/sangue , Tri-Iodotironina/sangue , Útero/anatomia & histologia , Útero/metabolismo
4.
Braz J Med Biol Res ; 37(11): 1637-44, 2004 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-15517078

RESUMO

The causes of luteal phase progesterone deficiency in polycystic ovary syndrome (PCOS) are not known. To determine the possible involvement of hyperinsulinemia in luteal phase progesterone deficiency in women with PCOS, we examined the relationship between progesterone, luteinizing hormone (LH) and insulin during the luteal phase and studied the effect of metformin on luteal progesterone levels in PCOS. Patients with PCOS (19 women aged 18-35 years) were treated with metformin (500 mg three times daily) for 4 weeks prior to the test cycle and throughout the study period, and submitted to ovulation induction with clomiphene citrate. Blood samples were collected from control (N = 5, same age range as PCOS women) and PCOS women during the late follicular (one sample) and luteal (3 samples) phases and LH, insulin and progesterone concentrations were determined. Results were analyzed by one-way analysis of variance (ANOVA), Duncan's test and Karl Pearson's coefficient of correlation (r). The endocrine study showed low progesterone level (4.9 ng/ml) during luteal phase in the PCOS women as compared with control (21.6 ng/ml). A significant negative correlation was observed between insulin and progesterone (r = -0.60; P < 0.01) and between progesterone and LH (r = -0.56; P < 0.05) concentrations, and a positive correlation (r = 0.83; P < 0.001) was observed between LH and insulin. The study further demonstrated a significant enhancement in luteal progesterone concentration (16.97 ng/ml) in PCOS women treated with metformin. The results suggest that hyperinsulinemia/insulin resistance may be responsible for low progesterone levels during the luteal phase in PCOS. The luteal progesterone level may be enhanced in PCOS by decreasing insulin secretion with metformin.


Assuntos
Hipoglicemiantes/uso terapêutico , Insulina/sangue , Fase Luteal/sangue , Hormônio Luteinizante/sangue , Metformina/uso terapêutico , Síndrome do Ovário Policístico/tratamento farmacológico , Progesterona/sangue , Adolescente , Adulto , Análise de Variância , Estudos de Casos e Controles , Clomifeno/uso terapêutico , Feminino , Fármacos para a Fertilidade Feminina/uso terapêutico , Humanos , Hiperinsulinismo/sangue , Hiperinsulinismo/complicações , Hiperinsulinismo/tratamento farmacológico , Indução da Ovulação , Síndrome do Ovário Policístico/sangue , Progesterona/deficiência
5.
Braz. j. med. biol. res ; 37(11): 1637-1644, Nov. 2004. tab, graf
Artigo em Inglês | LILACS | ID: lil-385867

RESUMO

The causes of luteal phase progesterone deficiency in polycystic ovary syndrome (PCOS) are not known. To determine the possible involvement of hyperinsulinemia in luteal phase progesterone deficiency in women with PCOS, we examined the relationship between progesterone, luteinizing hormone (LH) and insulin during the luteal phase and studied the effect of metformin on luteal progesterone levels in PCOS. Patients with PCOS (19 women aged 18-35 years) were treated with metformin (500 mg three times daily) for 4 weeks prior to the test cycle and throughout the study period, and submitted to ovulation induction with clomiphene citrate. Blood samples were collected from control (N = 5, same age range as PCOS women) and PCOS women during the late follicular (one sample) and luteal (3 samples) phases and LH, insulin and progesterone concentrations were determined. Results were analyzed by one-way analysis of variance (ANOVA), Duncan's test and Karl Pearson's coefficient of correlation (r). The endocrine study showed low progesterone level (4.9 ng/ml) during luteal phase in the PCOS women as compared with control (21.6 ng/ml). A significant negative correlation was observed between insulin and progesterone (r = -0.60; P < 0.01) and between progesterone and LH (r = -0.56; P < 0.05) concentrations, and a positive correlation (r = 0.83; P < 0.001) was observed between LH and insulin. The study further demonstrated a significant enhancement in luteal progesterone concentration (16.97 ng/ml) in PCOS women treated with metformin. The results suggest that hyperinsulinemia/insulin resistance may be responsible for low progesterone levels during the luteal phase in PCOS. The luteal progesterone level may be enhanced in PCOS by decreasing insulin secretion with metformin.


Assuntos
Humanos , Feminino , Adolescente , Adulto , Hipoglicemiantes/uso terapêutico , Insulina/sangue , Fase Luteal/sangue , Hormônio Luteinizante/sangue , Metformina/uso terapêutico , Síndrome do Ovário Policístico/tratamento farmacológico , Progesterona/sangue , Análise de Variância , Estudos de Casos e Controles , Clomifeno/uso terapêutico , Fármacos para a Fertilidade Feminina/uso terapêutico , Hiperinsulinismo/sangue , Hiperinsulinismo/complicações , Hiperinsulinismo/tratamento farmacológico , Indução da Ovulação , Síndrome do Ovário Policístico/sangue , Progesterona/deficiência
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