RESUMEN
Type-2 diabetes mellitus (T2DM) is an expanding global health problem, involving defective insulin secretion by pancreatic ß-cells and peripheral insulin resistance, leading to impaired glucose regulation. Galectin-1-an endogenous lectin with affinity for N-acetyllactosamine (LacNAc)-containing glycans-has emerged as a regulator of inflammatory and metabolic disorders. However, the role of galectin-1 in glucose homeostasis and pancreatic ß-cell function, independently of hypercaloric diets, has not been explored. Here, we identified a phenotype compatible with T2DM, involving alterations in glucose metabolism and pancreatic insulin release, in female but not male mice lacking galectin-1 (Lgals1-/-). Compared with age-matched controls, Lgals1-/- female mice exhibited higher body weight and increased food intake ad libitum as well as after fasting and acute re-feeding. Although fasted serum insulin levels and insulin sensitivity were similar in both genotypes, Lgals1-/- female mice presented altered glucose tolerance and higher basal glucose levels depending on the fasting period. Insulin response to glucose overload was impaired, while pancreatic insulin content was enhanced in the absence of galectin-1. Accordingly, recombinant galectin-1 enhanced glucose-stimulated insulin release in vitro. Our study identifies a role for galectin-1 in regulating glucose metabolism through modulation of pancreatic insulin secretion, highlighting novel opportunities to control T2DM.
Asunto(s)
Resistencia a la Insulina , Insulina , Animales , Femenino , Galectina 1/genética , Galectina 1/metabolismo , Glucosa/metabolismo , Homeostasis , Insulina/metabolismo , Secreción de Insulina , Masculino , RatonesRESUMEN
To study the pathological effects of continuous hyperprolactinemia on food intake mechanisms we used female mice that lack dopamine D2 receptors in lactotropes (lacDrd2KO). These mice had lifelong hyperprolactinemia, increased food intake, and gradual development of obesity from 5 to 10 months of age. Ongoing endogenous prolactin signaling in lacDrd2KO mice was evidenced by increased basal phosphorylation of STAT5b in hypothalamic areas related to food intake, such as the arcuate (ARN), dorsomedial (DMN), and ventromedial nuclei. In the ARN of young lacDrd2KO mice there were higher Prlr mRNA levels and in obese 10-month-old lacDrd2KO mice increased expression of the orexigenic genes Neuropeptide Y (Npy) and Agouti-related peptide, compared to controls. Furthermore, Npy expression was increased in the DMN, probably contributing to increased food intake and decreased expression of Uncoupling protein-1 in brown adipose tissue, both events favoring weight gain. Leptin resistance in obese lacD2RKO mice was evidenced by its failure to lower food intake and a dampened response of STAT3 phosphorylation, specifically in the mediobasal hypothalamus. Our results suggest that pathological chronically high prolactin levels, as found in psychiatric treatments or patients with prolactinomas, may impact on specific hypothalamic nuclei altering gene expression, leptin response, and food intake.
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Núcleo Arqueado del Hipotálamo/efectos de los fármacos , Núcleo Arqueado del Hipotálamo/metabolismo , Ingestión de Alimentos/efectos de los fármacos , Prolactina/farmacología , Animales , Glucemia/efectos de los fármacos , Ensayo de Inmunoadsorción Enzimática , Inmunohistoquímica , Insulina/sangre , Ratones , Ratones Noqueados , Reacción en Cadena en Tiempo Real de la Polimerasa , Factor de Transcripción STAT5/genética , Factor de Transcripción STAT5/metabolismoRESUMEN
A multistep signaling cascade originates in brain centers that regulate hypothalamic growth hormone-releasing hormone (Ghrh) and somatostatin expression levels and release to control the pattern of GH secretion. This process is sexually fine-tuned, and relays important information to the liver where GH receptors can be found. The temporal pattern of pituitary GH secretion, which is sex-specific in many species (episodic in males and more stable in females), represents a major component in establishing and maintaining the sexual dimorphism of hepatic gene transcription. The liver is sexually dimorphic exhibiting major differences in the profile of more than 1000 liver genes related to steroid, lipid, and foreign compound metabolism. Approximately, 90% of these sex-specific liver genes were shown to be primarily dependent on sexually dimorphic GH secretory patterns. This proposes an interesting scenario in which the central nervous system, indirectly setting GH profiles through GHRH and somatostatin control, regulates sexual dimorphism of liver activity in accordance with the need for sex-specific steroid metabolism and performance. We describe the influence of the loss of sexual dimorphism in liver gene expression due to altered brain function. Among other many factors, abnormal brain sexual differentiation, xenoestrogen exposure and D2R ablation from neurons dysregulate the GHRH-GH axis, and ultimately modify the liver capacity for adaptive mechanisms. We, therefore, propose that an inefficient brain control of the endocrine growth axis may underlie alterations in several metabolic processes through an indirect influence of sexual dimorphism of liver genes.
Asunto(s)
Encéfalo/fisiopatología , Sistema Endocrino/fisiopatología , Hepatopatías/fisiopatología , Hígado/fisiopatología , Caracteres Sexuales , Animales , Epigénesis Genética , Femenino , Humanos , Hepatopatías/genética , MasculinoRESUMEN
We studied the impact of high prolactin titers on liver and adipocyte gene expression related to glucose and insulin homeostasis in correlation with obesity onset. To that end we used mutant female mice that selectively lack dopamine type 2 receptors (D2Rs) from pituitary lactotropes (lacDrd2KO), which have chronic high prolactin levels associated with increased body weight, marked increments in fat depots, adipocyte size, and serum lipids, and a metabolic phenotype that intensifies with age. LacDrd2KO mice of two developmental ages, 5 and 10 mo, were used. In the first time point, obesity and increased body weight are marginal, although mice are hyperprolactinemic, whereas at 10 mo there is marked adiposity with a 136% increase in gonadal fat and a 36% increase in liver weight due to lipid accumulation. LacDrd2KO mice had glucose intolerance, hyperinsulinemia, and impaired insulin response to glucose already in the early stages of obesity, but changes in liver and adipose tissue transcription factors were time and tissue dependent. In chronic hyperprolactinemic mice liver Prlr were upregulated, there was liver steatosis, altered expression of the lipogenic transcription factor Chrebp, and blunted response of Srebp-1c to refeeding at 5 mo of age, whereas no effect was observed in the glycogenesis pathway. On the other hand, in adipose tissue a marked decrease in lipogenic transcription factor expression was observed when morbid obesity was already settled. These adaptive changes underscore the role of prolactin signaling in different tissues to promote energy storage.
Asunto(s)
Adipocitos/metabolismo , Hepatocitos/metabolismo , Hiperprolactinemia/genética , Hígado/metabolismo , Obesidad/genética , Receptores de Dopamina D2/genética , Animales , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice , Ensayo de Inmunoadsorción Enzimática , Hígado Graso/genética , Hígado Graso/metabolismo , Femenino , Expresión Génica , Glucosa/metabolismo , Prueba de Tolerancia a la Glucosa , Homeostasis/genética , Hiperprolactinemia/metabolismo , Inmunohistoquímica , Insulina/metabolismo , Lactotrofos/metabolismo , Lipogénesis/genética , Ratones , Ratones Noqueados , Proteínas Nucleares/genética , Obesidad/metabolismo , Radioinmunoensayo , Reacción en Cadena en Tiempo Real de la Polimerasa , Receptores de Prolactina/genética , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Factores de Transcripción/genética , Regulación hacia ArribaRESUMEN
Growth hormone (GH) is fundamental for growth and glucose homeostasis, and prolactin for optimal pregnancy and lactation outcome, but additionally, both hormones have multiple functions that include a strong impact on energetic metabolism. In this respect, prolactin and GH receptors have been found in brown, and white adipocytes, as well as in hypothalamic centers regulating thermogenesis. This review describes the neuroendocrine control of the function and plasticity of brown and beige adipocytes, with a special focus on prolactin and GH actions. Most evidence points to a negative association between high prolactin levels and the thermogenic capacity of BAT, except in early development. During lactation and pregnancy, prolactin may be a contributing factor that limits unneeded thermogenesis, downregulating BAT UCP1. Furthermore, animal models of high serum prolactin have low BAT UCP1 levels and whitening of the tissue, while lack of Prlr induces beiging in WAT depots. These actions may involve hypothalamic nuclei, particularly the DMN, POA and ARN, brain centers that participate in thermogenesis. Studies on GH regulation of BAT function present some controversies. Most mouse models with GH excess or deficiency point to an inhibitory role of GH on BAT function. Even so, a stimulatory role of GH on WAT beiging has also been described, in accordance with whole-genome microarrays that demonstrate divergent response signatures of BAT and WAT genes to the loss of GH signaling. Understanding the physiology of BAT and WAT beiging may contribute to the ongoing efforts to curtail obesity.
RESUMEN
Background: The association of high serum prolactin and increased body weight is positive but controversial, therefore we hypothesized that additional factors such as diets and the impact of prolactin on brown adipose tissue may condition its metabolic effects. Methods: We used LacDrd2KO females with lifelong severe hyperprolactinemia due dopamine-D2 receptor deletion from lactotropes, and slow onset of metabolic disturbances, and compared them to their respective controls (Drd2 loxP/loxP ). Food intake, and binge eating was evaluated. We then challenged mice with a High Fat (HFD) or a Control Diet (CD) for 8 weeks, beginning at 3 months of age, when no differences in body weight are found between genotypes. At the end of the protocol brown and white adipose tissues were weighed, and thermogenic and lipogenic markers studied, using real time PCR (Ucp1, Cidea, Pgc1a, Lpl, adiponectin, Prlr) or immunohistochemistry (UCP1). Histochemical analysis of brown adipose tissue, and glucose tolerance tests were performed. Results: Hyperprolactinemic mice had increased food intake and binge eating behavior. Metabolic effects induced by a HFD were exacerbated in lacDrd2KO mice. Hyperprolactinemia aggravated HFD-induced body weight gain and glucose intolerance. In brown adipose tissue pronounced cellular whitening as well as decreased expression of the thermogenic markers Ucp1 and Pgc1a were observed in response to high prolactin levels, regardless of the diet, and furthermore, hyperprolactinemia potentiated the decrease in Cidea mRNA expression induced by HFD. In subcutaneous white adipose tissue hyperprolactinemia synergistically increased tissue weight, while decreasing Prlr, Adiponectin and Lpl mRNA levels regardless of the diet. Conclusions: Pathological hyperprolactinemia has a strong impact in brown adipose tissue, lowering thermogenic markers and evoking tissue whitening. Furthermore, it modifies lipogenic markers in subcutaneous white adipose, and aggravates HFD-induced glucose intolerance and Cidea decrease. Therefore, severe high prolactin levels may target BAT function, and furthermore represent an adjuvant player in the development of obesity induced by high fat diets.
Asunto(s)
Intolerancia a la Glucosa , Hiperprolactinemia , Adiponectina/farmacología , Tejido Adiposo Pardo/metabolismo , Animales , Dieta Alta en Grasa/efectos adversos , Femenino , Intolerancia a la Glucosa/metabolismo , Hiperprolactinemia/metabolismo , Hiperprolactinemia/patología , Ratones , Obesidad/metabolismo , Prolactina/metabolismo , ARN Mensajero/metabolismo , Aumento de PesoRESUMEN
Prolactin-secreting adenomas are the most frequent type among pituitary tumors, and pharmacological therapy with dopamine agonists remains the mainstay of treatment. But some adenomas are resistant, and a decrease in the number or function of dopamine D2 receptors (D2Rs) has been described in these cases. D2R knockout [Drd2(-/-)] mice have chronic hyperprolactinemia and pituitary hyperplasia and provide an experimental model for dopamine agonist-resistant prolactinomas. We described previously that disruption of D2Rs increases vascular endothelial growth factor (VEGF) expression. We therefore designed two strategies of antiangiogenesis using prolactinomas generated in Drd2(-/-) female mice: direct intra-adenoma mVEGF R1 (Flt-1)/Fc chimera (VEGF-TRAP) injection for 3 weeks [into subcutaneously transplanted pituitaries from Drd2(-/-) mice] and systemic VEGF neutralization with the specific monoclonal antibody G6-31. Both strategies resulted in substantial decrease of prolactin content and lactotrope area, and a reduction in tumor size was observed in in situ prolactinomas. There were significant decreases in vascularity, evaluated by cluster of differentiation molecule 31 vessel staining, and proliferation (proliferating cell nuclear antigen staining) in response to both anti-VEGF treatments. These data demonstrate that the antiangiogenic approach was effective in inhibiting the growth of in situ dopamine-resistant prolactinomas as well as in the transplanted adenomas. No differences in VEGF protein expression were observed after either anti-VEGF treatment, and, although serum VEGF was increased in G6-31-treated mice, pituitary activation of the VEGF receptor 2 signaling pathway was reduced. Our results indicate that, even though the role of angiogenesis in pituitary adenomas is contentious, VEGF might contribute to adequate vascular supply and represent a supplementary therapeutic target in dopamine agonist-resistant prolactinomas.
Asunto(s)
Inhibidores de la Angiogénesis/uso terapéutico , Neoplasias Hipofisarias/tratamiento farmacológico , Prolactinoma/tratamiento farmacológico , Proteínas Recombinantes de Fusión/uso terapéutico , Receptor 1 de Factores de Crecimiento Endotelial Vascular/metabolismo , Animales , Anticuerpos Monoclonales/metabolismo , Proliferación Celular/efectos de los fármacos , Dopamina/metabolismo , Femenino , Hiperplasia , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microvasos/efectos de los fármacos , Neovascularización Patológica/tratamiento farmacológico , Neovascularización Patológica/metabolismo , Neovascularización Patológica/patología , Hipófisis/irrigación sanguínea , Hipófisis/metabolismo , Hipófisis/patología , Neoplasias Hipofisarias/irrigación sanguínea , Neoplasias Hipofisarias/metabolismo , Neoplasias Hipofisarias/patología , Prolactina/sangre , Prolactinoma/irrigación sanguínea , Prolactinoma/metabolismo , Prolactinoma/patología , Receptores de Dopamina D2/genética , Receptores de Factores de Crecimiento Endotelial Vascular , Factor A de Crecimiento Endotelial Vascular/inmunología , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
Dopamine D2 receptor (D2R) participation in prolactin regulation is well documented, but the role of D2Rs in the control of other hormones involved in growth, food intake and glucose metabolism has not been extensively studied. The study of D2R knockout mice (Drd2(-/-)) puts forward new insights into the role of the D2R in growth hormone (GH)-releasing hormone-GH regulation, peptides involved in food intake, glucose homeostasis, as well as in prolactinoma development. The expected phenotype of chronic hyperprolactinemia and prolactinoma development was found in the Drd2(-/-) mouse, and this model constitutes a valuable tool in the study of dopamine-resistant prolactinomas. Unexpectedly, these mice were growth retarded, and the importance of functional hypothalamic D2Rs in the neonatal period was revealed. In the Drd2(-/-) mouse there was a failure of high neonatal GH levels and therefore the expansion of pituitary somatotropes was permanently altered. These mice also had increased food intake, and a sexually dimorphic participation of the D2R in food intake regulation is suggested. The effect described is probably secondary to D2R regulation of prolactin secretion. Furthermore, the negative modulation of D2Rs on α-melanocyte-stimulating hormone release and positive action on the hypothalamic expression of orexins reveals the complex D2R regulation of food intake. Finally, pancreatic D2Rs inhibit glucose-stimulated insulin release. Lack of dopaminergic inhibition throughout development in the Drd2(-/-) mouse may exert a gradual deteriorating effect on insulin homeostasis, so that eventually glucose intolerance develops. These results highlight the complex endocrine actions of the D2Rs at different levels, hypothalamus, pituitary or pancreas, which function to improve fitness, reproductive success and survival.
Asunto(s)
Sistema Endocrino/fisiología , Metabolismo/genética , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/fisiología , Animales , Ingestión de Alimentos/genética , Ingestión de Alimentos/fisiología , Sistema Endocrino/metabolismo , Hormona del Crecimiento/metabolismo , Hormona Liberadora de Hormona del Crecimiento/metabolismo , Ratones , Ratones Noqueados , Prolactina/metabolismo , Receptores de Dopamina D2/metabolismoRESUMEN
Many sex differences in liver gene expression originate in the brain, depend on GH secretion and may underlie sex disparities in hepatic disease. Because epigenetic mechanisms may contribute, we studied promoter methylation and microRNA abundance in the liver, associated with expression of sexual dimorphic genes in mice with selective disruption of the dopamine D2 receptor in neurons (neuroDrd2KO), which decreases hypothalamic Ghrh, pituitary GH, and serum IGFI and in neonatally androgenized female mice which have increased pituitary GH content and serum IGFI. We evaluated mRNA levels of the female predominant genes prolactin receptor (Prlr), alcohol dehydrogenase 1 (Adh1), Cyp2a4, and hepatocyte nuclear transcription factor 6 (Hnf6) and the male predominant gene, Cyp7b1. Female predominant genes had higher mRNA levels compared to males, but lower methylation was only detected in the Prlr and Cyp2a4 female promoters. In neuroDrd2KO mice, sexual dimorphism was lost for all genes; the upregulation (feminization) of Prlr and Cyp2a4 in males correlated with decreased methylation of their promoters, and the downregulation (masculinization) of Hnf-6 mRNA in females correlated inversely with its promoter methylation. Neonatal androgenization of females evoked a loss of sexual dimorphism only for the female predominant Hnf6 and Adh1 genes, but no differences in promoter methylation were found. Finally, mmu-miR-155-5p, predicted to target Cyp7b1 expression, was lower in males in association with higher Cyp7b1 mRNA levels compared to females and was not modified in neuroDrd2KO or TP mice. Our results suggest specific regulation of gene sexually dimorphic expression in the liver by methylation or miRNAs.
Asunto(s)
Alcohol Deshidrogenasa/genética , Hidrocarburo de Aril Hidroxilasas/genética , Familia 2 del Citocromo P450/genética , Familia 7 del Citocromo P450/genética , Hormona del Crecimiento/farmacología , Factor Nuclear 6 del Hepatocito/genética , Receptores de Prolactina/genética , Esteroide Hidroxilasas/genética , Alcohol Deshidrogenasa/metabolismo , Animales , Hidrocarburo de Aril Hidroxilasas/metabolismo , Familia 2 del Citocromo P450/metabolismo , Familia 7 del Citocromo P450/metabolismo , Epigénesis Genética/efectos de los fármacos , Epigénesis Genética/fisiología , Femenino , Regulación de la Expresión Génica/efectos de los fármacos , Hormona del Crecimiento/metabolismo , Factor Nuclear 6 del Hepatocito/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Regiones Promotoras Genéticas/genética , Receptores de Prolactina/metabolismo , Caracteres Sexuales , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Esteroide Hidroxilasas/metabolismoRESUMEN
[This corrects the article DOI: 10.1155/2014/608497.].
RESUMEN
Preclinical and clinical studies support that Notch signaling may play an important oncogenic role in cancer, but there is scarce information for pituitary tumors. We therefore undertook a functional study to evaluate Notch participation in pituitary adenoma growth. Tumors generated in Nude mice by subcutaneous GH3 somatolactotrope cell injection were treated in vivo with DAPT, a γ-secretase inhibitor, thus inactivating Notch signaling. This treatment led to pituitary tumor reduction, lower prolactin and GH tumor content and a decrease in angiogenesis. Furthermore, in silico transcriptomic and epigenomic analyses uncovered several tumor suppressor genes related to Notch signaling in pituitary tissue, namely Btg2, Nr4a1, Men1, Zfp36 and Cnot1. Gene evaluation suggested that Btg2, Nr4a1 and Cnot1 may be possible players in GH3 xenograft growth. Btg2 mRNA expression was lower in GH3 tumors compared to the parental line, and DAPT increased its expression levels in the tumor in parallel with the inhibition of its volume. Cnot1 mRNA levels were also increased in the pituitary xenografts by DAPT treatment. And the Nr4a1 gene was lower in tumors compared to the parental line, though not modified by DAPT. Finally, because DAPT in vivo may also be acting on tumor microenvironment, we determined the direct effect of DAPT on GH3 cells in vitro. We found that DAPT decreases the proliferative, secretory and migration potential of GH3 cells. These results position selective interruption of Notch signaling as a potential therapeutic tool in adjuvant treatments for aggressive or resistant pituitary tumors.
Asunto(s)
Adenoma/patología , Neoplasias Hipofisarias/patología , Receptores Notch/antagonistas & inhibidores , Adenoma/metabolismo , Animales , Línea Celular Tumoral , Diaminas/farmacología , Femenino , Ratones Endogámicos BALB C , Ratones Desnudos , Neoplasias Hipofisarias/metabolismo , Prolactina/metabolismo , Ratas , Receptores Notch/metabolismo , Transducción de Señal , Tiazoles/farmacología , Carga TumoralRESUMEN
Liver sexual gene dimorphism, which depends mainly on specific patterns of GH secretion, may underlie differential susceptibility to some liver diseases. Because GH and prolactin secretion are regulated by dopaminergic pathways, we studied the participation of brain and lactotrope dopamine 2 receptors (D2Rs) on liver gene sexual dimorphism, to explore a link between the brain and liver gene expression. We used global D2R knockout mice (Drd2(-/-)) and conducted a functional dissection strategy based on cell-specific Drd2 inactivation in neurons (neuroDrd2KO) or pituitary lactotropes. Disruption of neuronal D2Rs (which impaired the GH axis) decreased most of male or female-predominant class I liver genes and increased female-predominant class II genes in males, consistent with the positive (class I) or negative (class II) regulation of these genes by GH. Notably, sexual dimorphism was lost for class I and II genes in neuroDrd2KO mice. Disruption of lactotrope D2Rs did not modify class I or II genes in either sex, because GH axis was preserved. But surprisingly, 1 class II gene (Prlr) and female-predominant class I genes were markedly up-regulated in lacDrd2KO females, pointing to direct or indirect effects of prolactin in the regulation of selected female-predominant liver genes. This suggestion was strengthened in the hyperprolactinemic Drd2(-/-) female mouse, in which increased expression of the same 4 liver genes was observed, despite a decreased GH axis. We hereby demonstrate endocrine-mediated D2R actions on sexual dimorphic liver gene expression, which may be relevant during chronic dopaminergic medications in psychiatric disease.
Asunto(s)
Encéfalo/metabolismo , Hígado/metabolismo , Hipófisis/metabolismo , Receptores de Dopamina D2/metabolismo , Animales , Femenino , Regulación de la Expresión Génica/fisiología , Hormona del Crecimiento/sangre , Hormona del Crecimiento/metabolismo , Lactotrofos/metabolismo , Masculino , Ratones , Ratones Noqueados , Neuronas/metabolismo , Proteínas/genética , Proteínas/metabolismo , Receptores de Dopamina D2/genética , Caracteres SexualesRESUMEN
Neonatal androgenization masculinizes the GH axis and thus may impact on liver gene regulation. Neonatal testosterone administration to female mice decreased (defeminized) female predominant GH-dependent liver gene expression (Hnf6, Adh1, Prlr, Cyp3a41) and did not modify male predominant genes (Cyp7b1, Cyp4a12, Slp). Female predominance of Cis mRNA, an inhibitor of episodic GH signaling pathway, was unaltered. At birth, Cyp7b1 promoter exhibited a higher methylation status in female livers, while the Hnf6 promoter was equally methylated in both sexes; no differences in gene expression were detected at this age. In adulthood, consistent with sex specific predominance, lower methylation status was determined for the Cyp7b1 promoter in males, and for the Hnf6 promoter in females, and this last difference was prevented by neonatal androgenization. Therefore, early steroid treatment or eventually endocrine disruptor exposure may alter methylation status and sexual dimorphic expression of liver genes, and consequently modify liver physiology in females.
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Andrógenos/farmacología , Hormona del Crecimiento/genética , Factor Nuclear 6 del Hepatocito/genética , Hígado/efectos de los fármacos , Esteroide Hidroxilasas/genética , Testosterona/farmacología , Animales , Animales Recién Nacidos , Familia 7 del Citocromo P450 , Metilación de ADN/efectos de los fármacos , Femenino , Regulación del Desarrollo de la Expresión Génica , Hormona del Crecimiento/metabolismo , Factor Nuclear 6 del Hepatocito/metabolismo , Hígado/crecimiento & desarrollo , Hígado/metabolismo , Masculino , Ratones , Regiones Promotoras Genéticas/efectos de los fármacos , Caracteres Sexuales , Transducción de Señal , Esteroide Hidroxilasas/metabolismo , Virilismo/genéticaRESUMEN
Prolactin, a pleiotropic hormone secreted by lactotropes, has reproductive and metabolic functions. Chronically elevated prolactin levels increase food intake, but in some hyperprolactinemic states such as in the global dopamine D2 receptor (D2R) knockout mouse, food intake is not increased. Here, we conduct a cell-specific genetic dissection study using conditional mutant mice that selectively lack D2Rs from pituitary lactotropes (lacDrd2KO) to evaluate the role of elevated prolactin levels without any confounding effect of central D2Rs on motor and reward mechanisms related to food intake. LacDrd2KO female mice exhibited chronic hyperprolactinemia, pituitary hyperplasia, and a preserved GH axis. In addition, lacDrd2KO female but not male mice showed increased food intake by 3 months of age, and from 5 months onward their body weights were heavier. Marked increments in fat depots, adipocyte size, serum triglycerides, and nonesterified fatty acid levels and a decrease in lipolytic enzymes in adipose tissue were seen. Furthermore, lacDrd2KO female mice had glucose intolerance but a preserved response to insulin. In the hypothalamus, Npy mRNA expression was increased, and Pomc and Ppo mRNA levels were unaltered (in contrast to results in global D2R knockout mice). Thus, the orexigenic effect of prolactin and its action on hypothalamic Npy expression were fully evidenced, leading to increased food intake and adiposity. Our results highlight the metabolic role of prolactin and illustrate the value of studying cell-specific mutant mice to disentangle the pathophysiological mechanisms otherwise masked in null allele mutants or in animals treated with pervasive pharmacological agents.
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Adiposidad/genética , Peso Corporal/genética , Ingestión de Alimentos/genética , Hipófisis/metabolismo , Receptores de Dopamina D2/genética , Tejido Adiposo/metabolismo , Animales , Ciclo Estral , Femenino , Genotipo , Intolerancia a la Glucosa , Prueba de Tolerancia a la Glucosa , Insulina/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Prolactina/sangreRESUMEN
The role of angiogenesis in pituitary tumor development has been questioned, as pituitary tumors have been usually found to be less vascularized than the normal pituitary tissue. Nevertheless, a significantly higher degree of vasculature has been shown in invasive or macropituitary prolactinomas when compared to noninvasive and microprolactinomas. Many growth factors and their receptors are involved in pituitary tumor development. For example, VEGF, FGF-2, FGFR1, and PTTG, which give a particular vascular phenotype, are modified in human and experimental pituitary adenomas of different histotypes. In particular, vascular endothelial growth factor, VEGF, the central mediator of angiogenesis in endocrine glands, was encountered in experimental and human pituitary tumors at different levels of expression and, in particular, was higher in dopamine agonist resistant prolactinomas. Furthermore, several anti-VEGF techniques lowered tumor burden in human and experimental pituitary adenomas. Therefore, even though the role of angiogenesis in pituitary adenomas is contentious, VEGF, making permeable pituitary endothelia, might contribute to adequate temporal vascular supply and mechanisms other than endothelial cell proliferation. The study of angiogenic factor expression in aggressive prolactinomas with resistance to dopamine agonists will yield important data in the search of therapeutical alternatives.
RESUMEN
Dopamine and estradiol interact in the regulation of lactotroph cell proliferation and prolactin secretion. Ablation of the dopamine D2 receptor gene (Drd2(-/-)) in mice leads to a sexually dimorphic phenotype of hyperprolactinemia and pituitary hyperplasia, which is stronger in females. TGF-ß1 is a known inhibitor of lactotroph proliferation. TGF-ß1 is regulated by dopamine and estradiol, and it is usually down-regulated in prolactinoma experimental models. To understand the role of TGF-ß1 in the gender-specific development of prolactinomas in Drd2(-/-) mice, we compared the expression of different components of the pituitary TGF-ß1 system, including active cytokine content, latent TGF-ß-binding protein isoforms, and possible local TGF-ß1 activators, in males and females in this model. Furthermore, we evaluated the effects of dopamine and estradiol administration to elucidate their role in TGF-ß1 system regulation. The expression of active TGF-ß1, latent TGF-ß-binding protein isoforms, and several putative TGF-ß1 activators evaluated was higher in male than in female mouse pituitary glands. However, Drd2(-/-) female mice were more sensitive to the decrease in active TGF-ß1 content, as reflected by the down-regulation of TGF-ß1 target genes. Estrogen and dopamine caused differential regulation of several components of the TGF-ß1 system. In particular, we found sex- and genotype- dependent regulation of active TGF-ß1 content and a similar expression pattern for 2 of the putative TGF-ß1 activators, thrombospondin-1 and kallikrein-1, suggesting that these proteins could mediate TGF-ß1 activation elicited by dopamine and estradiol. Our results indicate that (1) the loss of dopaminergic tone affects the pituitary TGF-ß1 system more strongly in females than in males, (2) males express higher levels of pituitary TGF-ß1 system components including active cytokine, and (3) estradiol negatively controls most of the components of the system. Because TGF-ß1 inhibits lactotroph proliferation, we propose that the higher levels of the TGF-ß1 system in males could protect or delay the development of prolactinomas in Drd2(-/-) male mice.
Asunto(s)
Hipófisis/metabolismo , Prolactinoma/metabolismo , Factor de Crecimiento Transformador beta1/metabolismo , Animales , Femenino , Regulación de la Expresión Génica/fisiología , Genotipo , Integrinas/genética , Integrinas/metabolismo , Masculino , Ratones , Ratones Noqueados , Neoplasias Hipofisarias/metabolismo , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/metabolismo , Factores Sexuales , Trombospondina 1/genética , Trombospondina 1/metabolismo , Calicreínas de Tejido/genética , Calicreínas de Tejido/metabolismo , Factor de Crecimiento Transformador beta1/genéticaRESUMEN
Parasitism during development impairs normal growth and delays the onset of puberty through altered hormone profiles, including insulin-like growth factor one (IGF-1). As mammary gland development during prepuberty is strongly dependent on IGF-1, we determined if antiparasitic treatment during this stage of growth improved mammary gland development. One group of Holstein heifers was treated monthly, rotationally with antiparasitic drugs from birth to 70 weeks of age, a second group was untreated. Treated heifer calves had between 56% and 65% less EPG counts than untreated ones. Presence of Ostertagia, Cooperia, Haemonchus and Trichostrongylus was demonstrated. Treatment effectively advanced the onset of puberty and increased IGF-1 levels. At 20, 30, 40 and 70 weeks of age biopsies from the mammary gland were taken and histological sections were prepared and stained with hematoxylin-eosin. Pictures were analyzed to compare parenchyma area in relation to total mammary tissue between groups. Mammary samples from treated heifers had higher ratios of parenchyma/total area than untreated ones. As mammary development during prepuberty is crucial for mammary performance during lactation, these results add new evidence to the importance of gastrointestinal parasite control in heifers.
Asunto(s)
Antiparasitarios/administración & dosificación , Enfermedades de los Bovinos/tratamiento farmacológico , Helmintiasis Animal/tratamiento farmacológico , Glándulas Mamarias Animales/crecimiento & desarrollo , Infecciones por Nematodos/veterinaria , Maduración Sexual/fisiología , Animales , Bovinos , Enfermedades de los Bovinos/prevención & control , Heces/parasitología , Femenino , Helmintiasis Animal/prevención & control , Factor I del Crecimiento Similar a la Insulina/análisis , Glándulas Mamarias Animales/citología , Infecciones por Nematodos/tratamiento farmacológico , Infecciones por Nematodos/prevención & control , Recuento de Huevos de Parásitos/veterinaria , TiempoRESUMEN
Abnormal exposure to steroid hormones within a critical developmental period elicits permanent alterations in female reproductive physiology in rodents, but the impact on the female GH axis and the underlying sexual differences in hepatic enzymes have not been described in detail. We have investigated the effect of neonatal androgenization of female mice (achieved by s.c. injection of 100 µg testosterone propionate (TP) on the day of birth: TP females) on the GHRH-somatostatin-GH axis and downstream GH targets, which included female and male predominant liver enzymes and secreted proteins. At 4 months of age, an organizational effect of neonatal testosterone was evidenced on hypothalamic Ghrh mRNA level but not on somatostatin (stt) mRNA level. Ghrh mRNA levels were higher in males than in females, but not in TP females. Increased expression in TP females correlated with increased pituitary GH content and somatotrope population, increased serum and liver IGF-I concentration, and ultimately higher body weight. Murine urinary proteins (MUPs) that were excreted at higher levels in male urine, and whose expression requires pulsatile occupancy of liver GH receptors, were not modified in TP females and neither was liver Mup 1/2/6/8 mRNA expression. Furthermore, a male predominant liver gene (Cyp2d9) was not masculinized in TP females either, whereas two female predominant genes (Cyp2b9 and Cyp2a4) were defeminized. These data support the hypothesis that neonatal steroid exposure contributes to the remodeling of the GH axis and defeminization of hepatic steroid-metabolizing enzymes, which may compromise liver physiology.
Asunto(s)
Hormona del Crecimiento/metabolismo , Hígado/metabolismo , Testosterona/metabolismo , Virilismo/metabolismo , Animales , Hidrocarburo de Aril Hidroxilasas/análisis , Peso Corporal/fisiología , Sistema Enzimático del Citocromo P-450/análisis , Familia 2 del Citocromo P450 , Femenino , Hormona del Crecimiento/análisis , Hipotálamo/efectos de los fármacos , Hipotálamo/metabolismo , Factor I del Crecimiento Similar a la Insulina/análisis , Hígado/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos C57BL , Hipófisis/efectos de los fármacos , Hipófisis/metabolismo , Prolactina/sangre , Proteínas/análisis , Esteroide Hidroxilasas/análisis , Testosterona/farmacología , Virilismo/inducido químicamenteRESUMEN
The relationship between antidopaminergic drugs and glucose has not been extensively studied, even though chronic neuroleptic treatment causes hyperinsulinemia in normal subjects or is associated with diabetes in psychiatric patients. We sought to evaluate dopamine D2 receptor (D2R) participation in pancreatic function. Glucose homeostasis was studied in D2R knockout mice (Drd2(-/-)) mice and in isolated islets from wild-type and Drd2(-/-) mice, using different pharmacological tools. Pancreas immunohistochemistry was performed. Drd2(-/-) male mice exhibited an impairment of insulin response to glucose and high fasting glucose levels and were glucose intolerant. Glucose intolerance resulted from a blunted insulin secretory response, rather than insulin resistance, as shown by glucose-stimulated insulin secretion tests (GSIS) in vivo and in vitro and by a conserved insulin tolerance test in vivo. On the other hand, short-term treatment with cabergoline, a dopamine agonist, resulted in glucose intolerance and decreased insulin response to glucose in wild-type but not in Drd2(-/-) mice; this effect was partially prevented by haloperidol, a D2R antagonist. In vitro results indicated that GSIS was impaired in islets from Drd2(-/-) mice and that only in wild-type islets did dopamine inhibit GSIS, an effect that was blocked by a D2R but not a D1R antagonist. Finally, immunohistochemistry showed a diminished pancreatic beta-cell mass in Drd2(-/-) mice and decreased beta-cell replication in 2-month-old Drd2(-/-) mice. Pancreatic D2Rs inhibit glucose-stimulated insulin release. Lack of dopaminergic inhibition throughout development may exert a gradual deteriorating effect on insulin homeostasis, so that eventually glucose intolerance develops.