Prolactin signaling modulates stress-induced behavioral responses in a preclinical mouse model of migraine.

OBJECTIVE: The aim of this study was to determine if prolactin signaling modulates stress-induced behavioral responses in a preclinical migraine model. BACKGROUND: Migraine is one of the most complex and prevalent disorders. The involvement of sex-selective hormones in migraine pathology is highly likely as migraine is more common in women and its frequency correlates with reproductive stages. Prolactin has been shown to be a worsening factor for migraine. Normally prolactin levels are low; however levels can surge during stress. Dopamine receptor agonists, which suppress pituitary prolactin release, are an effective migraine treatment in a subset of patients. Previously, we showed that administration of prolactin onto the dura mater induces female-specific behavioral responses, suggesting that prolactin may play a sex-specific role in migraine. METHODS: The effects of prolactin signaling were assessed using a preclinical migraine model we published recently in which behavioral sensitization is induced by repeated stress. Plasma prolactin levels were assessed in naïve and stressed CD-1 mice (n = 3-5/group) and transgenic mice with conditional deletion of the Prlr in Nav1.8-positive sensory neurons (Prlr conditional knock-out [CKO]; n = 3/group). To assess the contribution of prolactin release during stress, naïve or stressed male and female CD-1 mice were treated with the prolactin release inhibitor bromocriptine (2 mg/kg; n = 7-12/group) or vehicle for 5 days (8-12/group) and tested for facial hypersensitivity following stress. Additionally, the contribution of ovarian hormones in regulating the prolactin-induced responses was assessed in ovariectomized female CD-1 mice (n = 6-10/group). Furthermore, the contribution of Prlr activation on Nav1.8-positive sensory neurons was assessed. Naïve or stressed male and female Prlr CKO mice and their control littermates were tested for facial hypersensitivity (n = 8-9/group). Immunohistochemistry was used to confirm loss of Prlr in Nav1.8-positive neurons in Prlr CKO mice. The total sample size is n = 245; the full analysis sample size is n = 221. RESULTS: Stress significantly increased prolactin levels in vehicle-treated female mice (39.70 ± 2.77; p < 0.0001). Bromocriptine significantly reduced serum prolactin levels in stressed female mice compared to vehicle-treated mice (-44.85 ± 3.1; p < 0.0001). Additionally, no difference was detected between female stressed mice that received bromocriptine compared to naïve mice treated with bromocriptine (-0.70 ± 2.9; p = 0.995). Stress also significantly increased serum prolactin levels in male mice, although to a much smaller extent than in females (0.61 ± 0.08; p < 0.001). Bromocriptine significantly reduced serum prolactin levels in stressed males compared to those treated with vehicle (-0.49 ± 0.08; p = 0.002). Furthermore, bromocriptine attenuated stress-induced behavioral responses in female mice compared to those treated with vehicle (maximum effect observed on day 4 post stress [0.21 ± 0.08; p = 0.03]). Bromocriptine did not attenuate stress-induced behavior in males at any timepoint compared to those treated with vehicle. Moreover, loss of ovarian hormones did not affect the ability of bromocriptine to attenuate stress responses compared to vehicle-treated ovariectomy mice that were stressed (maximum effect observed on day 4 post stress [0.29 ± 0.078; p = 0.013]). Similar to CD-1 mice, stress increased serum prolactin levels in both Prlr CKO female mice (27.74 ± 9.96; p = 0.047) and control littermates (28.68 ± 9.9; p = 0.041) compared to their naïve counterparts. There was no significant increase in serum prolactin levels detected in male Prlr CKO mice or control littermates. Finally, conditional deletion of Prlr from Nav1.8-positive sensory neurons led to a female-specific attenuation of stress-induced behavioral responses (maximum effect observed on day 7 post stress [0.32 ± 0.08; p = 0.007]) compared to control littermates. CONCLUSION: These data demonstrate that prolactin plays a female-specific role in stress-induced behavioral responses in this preclinical migraine model through activation of Prlr on sensory neurons. They also support a role for prolactin in migraine mechanisms in females and suggest that modulation of prolactin signaling may be an effective therapeutic strategy in some cases.

Prolactin Response to Metformin in Cabergoline-Resistant Prolactinomas: A Pilot Study.

INTRODUCTION: Cabergoline is the treatment of choice for prolactinomas. However, 10-20% of prolactinomas are resistant to cabergoline. Metformin, a biguanide widely used in the treatment of diabetes mellitus, has been shown to reduce prolactin secretion in various pituitary tumor-cell lineages both in vitro and in vivo and in human pituitary adenomas in vitro. The aim of this study is to test the effects of metformin addition to cabergoline treatment on prolactin levels in patients with resistant prolactinomas. SUBJECTS AND METHODS: This is a prospective study performed in an outpatient clinic in a reference center. Ten adult patients (26-61 years) with prolactinomas (7 M), persistent hyperprolactinemia (38-386 ng/mL) under cabergoline treatment (2-7 mg/week) for at least 6 months (6-108 months), features of metabolic syndrome, and not taking metformin were included. Metformin (1.0-2.5 g v.o./day) was given according to patients' tolerance. Cabergoline doses were kept unchanged. Serum prolactin levels were measured before and after short- (30-60 days) and long-term (120-180 days) metformin treatment. RESULTS: Mean prolactin levels did not show any significant changes (148 ± 39 vs. 138 ± 42 vs. 133 ± 39 ng/mL, before, at 30-60 days, and at 120-180 days, respectively, p = 0.196) after metformin (mean dose: 1.25 g/day; range: 1.0-2.0 g/day). No patient reached a normal prolactin level during metformin treatment. Two patients were considered partial responders for exhibiting prolactin decreases ≥50% at a single time point during metformin. CONCLUSION: Metformin addition to ongoing high-dose cabergoline treatment in patients with cabergoline-resistant prolactinomas failed to show a consistent inhibitory effect in serum prolactin levels.

Risk of Breast Cancer With Prolactin Elevating Antipsychotic Drugs: An Observational Study of US Women (Ages 18-64 Years).

PURPOSE/BACKGROUND: Antipsychotic drugs are well established to alter circulating prolactin levels by blocking dopamine D2 receptors in the pituitary. Prolactin activates many genes important in the development of breast cancer. Prior studies have found an association with antipsychotic use and risk of breast cancer. METHODS/PROCEDURES: The IBM MarketScan Commercial and Medicaid Databases were used to establish a large, observational cohort of women taking antipsychotics drugs compared with anticonvulsants or lithium. A new user design was used that required 12 months of insurance enrollment before the first antipsychotic or anticonvulsant/lithium prescription. Invasive breast cancer was identified using diagnostic codes. Multivariable Cox proportional hazards models were used to evaluate the risk of breast cancer with antipsychotic drug exposure controlling for age and other risk factors. FINDINGS/RESULTS: A total of 914 cases (0.16%) of invasive breast cancer were identified among 540,737 women. Exposure to all antipsychotics was independently associated with a 35% increased risk of breast cancer (aHR [adjusted hazard ratio], 1.35; 95% confidence interval, 1.14-1.61). Category 1 drugs (high prolactin) were associated with a 62% increased risk (aHR, 1.62; 95% CI, 1.30-2.03), category 2 drugs a 54% increased risk (aHR, 1.54; 95% CI, 1.19-1.99), and category 3 drugs were not associated with breast cancer risk. IMPLICATIONS/CONCLUSIONS: In the largest study of antipsychotics taken by US women, a higher risk between antipsychotic drug use and increased risk for breast cancer was observed, with a differential higher association with antipsychotic categories that elevate prolactin. Our study confirms other recent observational studies of increased breast cancer risk with antipsychotics that elevate prolactin.

Examining Side Effect Variability of Antipsychotic Treatment in Schizophrenia Spectrum Disorders: A Meta-analysis of Variance.

Side effects of antipsychotic drugs play a key role in nonadherence of treatment in schizophrenia spectrum disorders (SSD). While clinical observations suggest that side effect variability between patients may be considerable, statistical evidence is required to confirm this. Here, we hypothesized to find larger side effect variability under treatment compared with control. We included double-blind, placebo-controlled, randomized controlled trials (RCTs) of adults with a diagnosis of SSD treated with 1 out of 14 antipsychotics. Standard deviations of the pre-post treatment differences of weight gain, prolactin levels, and corrected QT (QTc) times were extracted. The outcome measure was the variability ratio of treatment to control for individual antipsychotic drugs and the overall variability ratio of treatment to control across RCTs. Individual variability ratios were weighted by the inverse-variance method and entered into a random-effects model. We included N = 16 578 patients for weight gain, N = 16 633 patients for prolactin levels, and N = 10 384 patients for QTc time. Variability ratios (VR) were significantly increased for weight gain (VR = 1.08; 95% CI: 1.02-1.14; P = .004) and prolactin levels (VR = 1.38; 95% CI: 1.17-1.62; P < .001) but did not reach significance for QTc time (VR = 1.05; 95% CI: 0.98-1.12; P = 0.135). We found marked differences between individual antipsychotics and increased variability in side effects in patients under treatment with antipsychotics suggesting that subgroups of patients or individual patients may benefit from treatment allocation through stratified or personalized medicine.

The impact of metformin on prolactin levels in postmenopausal women.

WHAT IS KNOWN AND OBJECTIVE: Metformin-induced reduction in prolactin levels is more pronounced in users of hormonal contraception than in non-users. The current study was aimed at investigating whether physiological concentrations of estradiol determine the impact of metformin on lactotrope secretory function. METHODS: We studied two matched groups of postmenopausal women with elevated prolactin levels. Twenty-three women were on hormone replacement therapy (group 1), while the remaining ones (group 2, n = 23) did not use sex hormones. Because of coexistent prediabetes, all individuals received metformin (2.55-3 g daily) for the following six months. Circulating levels of total prolactin, monomeric prolactin, thyrotropin, gonadotropins, free thyroid hormones and estradiol were determined at the beginning and at the end of the study. RESULTS AND DISCUSSION: Compared with group 1, group 2 was characterized by higher gonadotropin levels and lower estrogen levels. Although metformin reduced monomeric prolactin levels in both study groups, this effect was more pronounced in group 1 than in group 2. Only in group 1, metformin decreased total prolactin levels, while only in group 2 the drug reduced FSH levels. Metformin treatment did not affect circulating levels of the remaining hormones. The impact of metformin on total and monomeric prolactin levels correlated with baseline prolactin levels and with the degree of improvement in insulin sensitivity. WHAT IS NEW AND CONCLUSION: The obtained results indicate that the impact of metformin on lactotrope secretory function is partially determined by the estrogen status of patients.

Vitamin D status determines the impact of metformin on circulating prolactin levels in premenopausal women.

WHAT IS KNOWN AND OBJECTIVE: Metformin was found to normalize secretory function of overactive pituitary cells. Its effect on circulating thyrotropin levels was more pronounced in women receiving exogenous vitamin D. The aim of the current study was to investigate whether vitamin D status determines the impact of metformin on prolactin levels in premenopausal women with hyperprolactinaemia. METHODS: The study population consisted of three groups of women with prediabetes and elevated prolactin levels: vitamin D-naïve women with vitamin D insufficiency (group 1; n = 19), women receiving vitamin D preparations because of vitamin D deficiency (group 2 n = 20), as well as vitamin D-naïve women with normal vitamin D status (group 3 n = 23). All participants were then treated with metformin (2.55-3 g daily). Circulating levels of glucose, insulin, prolactin, thyrotropin, free thyroid hormones, gonadotropins, estradiol, calcium and 25-hydroxyvitamin were determined at baseline and six months later. RESULTS AND DISCUSSION: At baseline, prolactin levels were higher in group 1 than in the remaining groups of patients. Although metformin decreased glucose levels and improved insulin sensitivity in all treatment groups, this effect was more pronounced in groups 2 and 3. Only in subjects with 25-hydroxyvitamin D levels within the reference range, metformin reduced prolactin levels. The impact on prolactin levels correlated with 25-hydroxyvitamin D levels and with the improvement in insulin sensitivity. The drug produced a neutral effect on circulating levels of thyrotropin, free thyroid hormones, gonadotropins, estradiol, calcium and 25-hydroxyvitamin D. WHAT IS NEW AND THE CONCLUSION: The results of the current study suggest that the impact of metformin on secretory function of overactive lactotropes depends on the vitamin D status of patients.

PBK/TOPK Inhibitor Suppresses the Progression of Prolactinomas.

Background: Prolactinoma is the most common type of pituitary tumors, and its resultant tumor occupying and hormone disturbance greatly damage the health of patients. In this study, we investigated a protein kinase-PDZ Binding Kinase (PBK)/T-LAK Cell-Originated Protein Kinase (TOPK) as a candidate protein regulating prolactin (PRL) secretion and tumor growth of prolactinomas. Methods: Downloaded prolactinoma transcriptome dataset from Gene Expression Omnibus (GEO) database, and screened differentially expressed genes (DEGs) between normal pituitary tissues and prolactinoma tissues. Then, Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of DEGs were performed, a protein-protein interaction (PPI) network was constructed and the hub genes were identified. After a literature search, TOPK was presumed as an candidate target regulating the prolactinoma. We found a specific inhibitor of TOPK to investigate its effects on the proliferation, migration, apoptosis and PRL secretion of pituitary tumor cells. Finally, the regulation of TOPK inhibitor on its downstream target-p38 Mitogen Activated Protein Kinase (p38 MAPK) was detected to explore the potential mechanism. Results: A total of 361 DEGs were identified, and 20 hub genes were screened out. TOPK inhibitor HI-TOPK-032 could suppress the proliferation & migration and induce apoptosis of pituitary tumor cells in vitro, and reduce PRL secretion and tumor growth in vivo. HI-TOPK-032 also inhibited the phosphorylation level of the downstream target p38 MAPK, suggesting that TOPK inhibitors regulate the development of prolactinoma by mediating p38 MAPK. Conclusion: Our study of identification and functional validation of TOPK suggests that this candidate can be a promising molecular target for prolactinoma treatment.

Calcium-Prolactin Secretion Coupling in Rat Pituitary Lactotrophs Is Controlled by PI4-Kinase Alpha.

The role of calcium, but not of other intracellular signaling molecules, in the release of pituitary hormones by exocytosis is well established. Here, we analyzed the contribution of phosphatidylinositol kinases (PIKs) to calcium-driven prolactin (PRL) release in pituitary lactotrophs: PI4Ks - which control PI4P production, PIP5Ks - which synthesize PI(4, 5)P2 by phosphorylating the D-5 position of the inositol ring of PI4P, and PI3KCs - which phosphorylate PI(4, 5)P2 to generate PI(3, 4, 5)P3. We used common and PIK-specific inhibitors to evaluate the strength of calcium-secretion coupling in rat lactotrophs. Gene expression was analyzed by single-cell RNA sequencing and qRT-PCR analysis; intracellular and released hormones were assessed by radioimmunoassay and ELISA; and single-cell calcium signaling was recorded by Fura 2 imaging. Single-cell RNA sequencing revealed the expression of Pi4ka, Pi4kb, Pi4k2a, Pi4k2b, Pip5k1a, Pip5k1c, and Pik3ca, as well as Pikfyve and Pip4k2c, in lactotrophs. Wortmannin, a PI3K and PI4K inhibitor, but not LY294002, a PI3K inhibitor, blocked spontaneous action potential driven PRL release with a half-time of ~20 min when applied in 10 µM concentration, leading to accumulation of intracellular PRL content. Wortmannin also inhibited increase in PRL release by high potassium, the calcium channel agonist Bay K8644, and calcium mobilizing thyrotropin-releasing hormone without affecting accompanying calcium signaling. GSK-A1, a specific inhibitor of PI4KA, also inhibited calcium-driven PRL secretion without affecting calcium signaling and Prl expression. In contrast, PIK93, a specific inhibitor of PI4KB, and ISA2011B and UNC3230, specific inhibitors of PIP5K1A and PIP5K1C, respectively, did not affect PRL release. These experiments revealed a key role of PI4KA in calcium-secretion coupling in pituitary lactotrophs downstream of voltage-gated and PI(4, 5)P2-dependent calcium signaling.

The Impact of Ethinyl Estradiol on Metformin Action on Prolactin Levels in Women with Hyperprolactinemia.

BACKGROUND: Metformin reduced prolactin levels only in women with hyperprolactinemia. OBJECTIVE: The purpose of this case-control study was to compare metformin action on lactoctrope function between women receiving oral contraceptive pills and women not using hormonal contraception. METHODS: The study included two groups of matched women with elevated prolactin levels and new-onset prediabetes or diabetes. The first group consisted of 20 women using oral contraceptive pills for at least 12 months before entering the study, while the second group included 20 patients not using any hormonal contraception. Over the whole study period, all women were treated with metformin (1.7-3 g daily). Circulating levels of glucose, insulin, prolactin, thyrotropin, free thyroid hormones, adrenocorticotropic hormone, gonadotropins and insulin-like growth factor-1 were measured at the beginning and at the end of the study (16 weeks later). RESULTS: Thirty-eight patients completed the study. Metformin reduced plasma glucose levels and improved insulin sensitivity but the latter effect was stronger in women receiving oral contraceptive pills than in women not using any contraception. Although metformin treatment decreased plasma prolactin levels in both study groups, this effect was stronger in women taking oral contraceptive pills. Only in this group of women, metformin increased plasma luteinizing hormone levels. The changes in plasma prolactin correlated with their baseline insulin sensitivity and the effect of metformin on insulin sensitivity. Metformin did not affect plasma levels of thyrotropin, free thyroxine, free triiodothyronine, follicle-stimulating hormone, adrenocorticotropic hormone and insulin-like growth factor-1. CONCLUSIONS: The obtained results suggest that the effect of metformin on overactive lactotropes depends on estrogen levels.

Prolactin ordering patterns in psychiatric inpatients and the impact this has on patient management.

OBJECTIVE: Guidelines stipulate that baseline prolactin be ordered prior to commencing antipsychotic treatment to facilitate investigation of any subsequent hyperprolactinaemic symptoms. The aim was to observe when and why prolactin levels are ordered for psychiatry inpatients commencing or continuing antipsychotics and how this alters clinical management. METHODS: Psychiatry inpatients admitted to the Alfred Hospital, Melbourne, Australia, in 2018 with the diagnoses of psychosis, schizophrenia, schizo-affective disorder or bipolar affective disorder were retrospectively analysed. Results and clinical history data were collected in patients in whom prolactin was ordered during or within 12 months of the relevant admission. RESULTS: Of 592 patients admitted during this period, 90 had prolactin ordered. Eight (8.9%) of the 90 tests were for hyperprolactinaemic symptoms, while the remainder were routine blood work. The results altered clinical management in 10 of the 90 (11.1%) patients. Of these 10, 8 were symptomatic. In the six patients with first episode psychosis, only one had prolactin ordered prior to antipsychotic commencement. CONCLUSIONS: Adherence to guideline recommendations of baseline prolactin testing was poor. When established on antipsychotics, measuring prolactin rarely changed management in asymptomatic patients; however, it did in those with hyperprolactinaemic symptoms. Measuring prolactin in asymptomatic patients on antipsychotics appears unhelpful.

Prolactin response to antipsychotics: An inpatient study.

BACKGROUND: Antipsychotic medication, stress, gender, and age are factors that influence prolactin levels in patients with psychosis. The aim of the study was to investigate the level of prolactin response to antipsychotic treatment in acute patients, taking into account the total duration of psychosis. METHODS AND FINDINGS: The study was conducted on 170 acute patients with schizophrenia spectrum disorders and bipolar disorder. Subjects were divided into three subgroups according to the duration of the psychosis (less than 5 years, between 5 and 10 years and more than 10 years of disorder duration). The initial prolactin response under antipsychotic treatment was measured, while the severity of the psychiatric symptoms was assessed with the BPRS (Brief Psychiatric Rating Scale). Hyperprolactinemia was found in 120 (70.6%) patients, amongst which 80 (66.7%) were females and 40 (33.3%) were males. The average increase in prolactinemia was 2.46 times the maximum value in women, and 1.59 times in men. Gender (ß = 0.27, p<0.0001), type of antipsychotic medication according to potency of inducing hyperprolactinemia (ß = -0.23, p<0.003), and the duration of psychosis over 10 years (ß = -0.15, p = 0.04) significantly predicted prolactin levels, when age, diagnosis, antipsychotic category (conventional/atypical/combinations of antipsychotics), and BPRS total scores were controlled for. CONCLUSIONS AND RELEVANCE: Prolactin levels in patients treated with antipsychotic medication appeared to depend on patients' gender, on the type of antipsychotic medication according to potency of inducing hyperprolactinemia, and on the duration of the psychosis. An increase in prolactin levels was associated with female gender, while the use of prolactin sparing antipsychotics and a duration of psychosis over 10 years were associated with lower prolactin levels.

Time for a New Perspective on Prolactin in Metabolism.

The pituitary hormone prolactin (PRL) regulates a variety of functions beyond reproduction. The association between physiological (pregnancy) and pathological (prolactinoma) hyperprolactinemia and metabolic alterations led to the concept of this hormone being diabetogenic. However, large cohort clinical studies have recently shown that low circulating PRL levels are associated with metabolic disease and represent a risk factor for type 2 diabetes (T2D), whereas high PRL levels are beneficial. Moreover, PRL acts on the pancreas, liver, adipose tissue, and hypothalamus to maintain and promote metabolic homeostasis. By integrating basic and clinical evidence, we hypothesize that upregulation of PRL levels is a mechanism to maintain metabolic homeostasis and, thus, propose that the range of PRL levels considered physiological should be expanded to higher values.

Amisulpride: Real-World Evidence of Dose Adaptation and Effect on Prolactin Concentrations and Body Weight Gain by Pharmacokinetic/Pharmacodynamic Analyses.

BACKGROUND: Amisulpride is an antipsychotic used in a wide range of doses. One of the major adverse events of amisulpride is hyperprolactinemia, and the drug might also induce body weight gain. OBJECTIVE: The aims of this work were to characterize the pharmacokinetics of amisulpride in order to suggest optimal dosage regimens to achieve the reference range of trough concentrations at steady-state (Cmin,ss) and to describe the relationship between drug pharmacokinetics and prolactin and body weight data. METHODS: The influence of clinical and genetic characteristics on amisulpride pharmacokinetics was quantified using a population approach. The final model was used to simulate Cmin,ss under several dosage regimens, and was combined with a direct Emax model to describe the prolactin data. The effect of model-based average amisulpride concentrations over 24 h (Cav) on weight was estimated using a linear model. RESULTS: A one-compartment model with first-order absorption and elimination best fitted the 513 concentrations provided by 242 patients. Amisulpride clearance significantly decreased with age and increased with lean body weight (LBW). Cmin,ss was higher than the reference range in 65% of the patients aged 60 years receiving 400 mg twice daily, and in 82% of the patients aged > 75 years with a LBW of 30 kg receiving 200 mg twice daily. The pharmacokinetic/pharmacodynamic model included 101 prolactin measurements from 68 patients. The Emax parameter was 53% lower in males compared with females. Model-predicted prolactin levels were above the normal values for Cmin,ss within the reference range. Weight gain did not depend on Cav. CONCLUSIONS: Amisulpride treatment might be optimized when considering age and body weight. Hyperprolactinemia and weight gain do not depend on amisulpride concentrations. Modification of the amisulpride dosage regimen is not appropriate to reduce prolactin concentrations and alternative treatment should be considered.

Effects of milking frequency and domperidone injections on milk production and prolactin signaling in the mammary gland of dairy cows.

Eleven mid-lactation Holstein cows were milked twice daily during the first 2 experimental weeks. During wk 3 to 10, the cows were differentially milked: right quarters were milked thrice daily (3×) and left quarters were milked once daily (1×). During wk 11 to 14, all quarters were milked twice daily. After 4 wk of differential milking, the cows received daily i.m. injections of the dopamine antagonist domperidone (DOMP; 300 mg; n = 6) or of dimethyl sulfoxide as the control (CTL; n = 5) for 8 wk (wk 7-14). During the differential milking period (wk 3-6), milk production was greater for quarters milked 3× than for those milked 1× but did not differ between DOMP and CTL cows. During the differential milking + injection period (wk 7-10), milk production continued to differ according to milking frequency. However, DOMP injection did not have an effect or interact with milking frequency on milk production. During the injection period (wk 11-14), milk production remained greater in the quarters previously milked 3× and milk production increased in DOMP injected cows but not in CTL cows. Injections of DOMP increased prolactin concentration, which was greater in the serum of DOMP cows than in that of CTL cows during the differential milking + injection and the injection periods. The expression of genes that are directly related to milk synthesis (CSN2, LALBA, and ACACA) was greater in the 3× quarters than in the 1× quarters. In addition, DOMP increased CSN2 expression during the injection period. The expression of both isoforms of the PRLR gene was greater in the 3× quarters during the differential milking + injection and the injection periods. At the protein level, injections of DOMP tended to increase the number of long PRLR isoform during the differential milking + injection period. The number of short PRLR isoform was greater in the 1× quarters than in the 3× quarters during the differential milking, the differential milking + injection, and the injection periods. The total amount of STAT3 protein was greater in the 1× quarters during the differential milking and the differential milking + injection periods. The amount of phosphorylated STAT3 protein was greater in the 1× quarters during the differential milking period. The total amount of phosphorylated STAT5 protein was greater in the 3× quarters during the differential milking and the differential milking + injection periods. The results of this experiment support the hypothesis that the responsiveness of the mammary gland to PRL is modulated by milking frequency, although the underlying mechanism remains to be determined.

Investigating the potential role of BDNF and PRL genotypes on antidepressant response in depression patients: A prospective inception cohort study in treatment-free patients.

BACKGROUND: Brain-derived neurotrophic factor (BDNF) is associated with response to antidepressant drugs in mood and anxiety disorders. Prolactin (PRL) is a pituitary hormone with behavioural effects, acting as a neurotrophic factor within the brain and may be involved in antidepressant response. OBJECTIVES: To investigate the relationship between BDNF and PRL genotypes with antidepressant drug response. METHODS: Prospective inception cohort of 186 Russian treatment-free participants (28 men and 158 women) between 18 and 70 years clinically diagnosed with depressive disorder who initiated antidepressant medication. DNA polymorphisms were genotyped for PRL rs1341239, BDNF rs6265 and rs7124442. Primary outcome was measured by differences in Hamilton Depression Rating Scale (∆HAM-D) scores between baseline/week two, week two/week four, and baseline/week four. Linear regression and independent t-test determined the significance between polymorphisms and ∆HAM-D. RESULTS: Comparisons between genotypes did not reveal any significant differences in scores during the first two weeks of treatment. In the latter two weeks, BDNF rs7124442 homozygous C patients responded significantly worse in comparison to homozygous T patients during this period. Further analysis within women and in post-menopausal women found a similar comparison between alleles. LIMITATIONS: Study lasted four weeks, which may be considered short to associate genuine antidepressant effects. CONCLUSIONS: Patients taking tricylic antidepressants were noted to have a significant improvement in ∆HAM-D compared to patients taking SSRIs. Homozygous C BDNF rs712442 patients were found to respond significantly worse in the last two weeks of treatment.

Myostatin regulates pituitary development and hepatic IGF1.

Circulating myostatin-attenuating agents are being developed to treat muscle-wasting disease despite their potential to produce serious off-target effects, as myostatin/activin receptors are widely distributed among many nonmuscle tissues. Our studies suggest that the myokine not only inhibits striated muscle growth but also regulates pituitary development and growth hormone (GH) action in the liver. Using a novel myostatin-null label-retaining model (Jekyll mice), we determined that the heterogeneous pool of pituitary stem, transit-amplifying, and progenitor cells in Jekyll mice depletes more rapidly after birth than the pool in wild-type mice. This correlated with increased levels of GH, prolactin, and the cells that secrete these hormones, somatotropes and lactotropes, respectively, in Jekyll pituitaries. Recombinant myostatin also stimulated GH release and gene expression in pituitary cell cultures although inhibiting prolactin release. In primary hepatocytes, recombinant myostatin blocked GH-stimulated expression of two key mediators of growth, insulin-like growth factor (IGF)1 and the acid labile subunit and increased expression of an inhibitor, IGF-binding protein-1. The significance of these findings was demonstrated by smaller muscle fiber size in a model lacking myostatin and liver IGF1 expression (LID-o-Mighty mice) compared with that in myostatin-null (Mighty) mice. These data together suggest that myostatin may regulate pituitary development and function and that its inhibitory actions in muscle may be partly mediated by attenuating GH action in the liver. They also suggest that circulating pharmacological inhibitors of myostatin could produce unintended consequences in these and possibly other tissues.

Differences in multihormonal responses to the dopamine agonist apomorphine between unipolar and bipolar depressed patients.

BACKGROUND: A large number of studies suggest that dopaminergic function may be impaired in depressed patients, particularly in bipolar patients. The dopamine D2/D1 agonist apomorphine (APO) can be useful in the evaluation of dopaminergic function. However, most studies show conflicting results in APO test responses when evaluating unipolar and bipolar depressed patients. Thus, the objective of this study was to apply the APO test to assess whether hypothalamic-pituitary dopaminergic function is altered in unipolar and bipolar depression. METHODS: We evaluated multihormonal responses to APO test (0.75 mg subcutaneous) in 134 drug-free DSM-IV major depressed inpatients (54 with bipolar depression [BD] and 80 with unipolar depression [UD]), compared with 36 healthy controls (HCs). We also examined the cortisol response to the dexamethasone suppression test (DST, 1 mg orally) in all subjects. RESULTS: No significant differences in prolactin (PRL), cortisol, adrenocorticotropin (ACTH) or growth hormone (GH) baseline values were found across the three groups. ACTH/cortisol and GH responses to APO were also comparable. BD patients showed lower PRL suppression to APO than did UD patients and HCs (both p < 0.00001). Although responses to DST were comparable between UD and BD patients, the former exhibited higher post-DST cortisol levels than did HCs (p < 0.05). CONCLUSIONS: Our results suggest that BD patients, unlike UD patients, have altered post-synaptic D2 receptor sensitivity at the pituitary level. This alteration does not seem secondary to hypercortisolemia. These findings, if confirmed by other studies with larger samples, may support the use of dopamine agents in BD patients treatment.

Effect of Kisspeptin on Serum Prolactin and Gonadotropins Levels in Balb-c Mice with Induced Chronic Stress.

OBJECTIVE: To determine and compare effects of kisspeptin on serum prolactin, luteinizing hormone and follicle stimulating hormone levels in Balb-c mice with and without exposure to chronic restraint stress. STUDY DESIGN: An animal experimental study. PLACE AND DURATION OF STUDY: Shifa College of Medicine / Shifa International Hospital Islamabad, in collaboration with National Institute of Health, Islamabad and Centre for Research in Experimental and Applied Medicine Laboratory, Army Medical College, Rawalpindi, from April 2014 to June 2015. METHODOLOGY: Mice divided into three groups, each containing 30 mice. Control group (group A) received intraperitoneal injection of saline, group B was administered with intraperitoneal injection of saline and restrained stress, and group C was administered with both stress and kisspeptin 100 ng daily for four weeks. Restraint stress was applied to groups B and C for three hours per day by immobilising individual mice in wire-mesh restrainers. At the end of four weeks blood sampling was done. Serum luteinizing hormones (LH), serum follicular stimulating hormone (FSH) and serum prolactin (PRL) were analysed by ELISA. RESULTS: Serum prolactin level increased in group B (stressed) and group C (stressed + kisspeptin treated) as compared to control group; and decreased in group C as compared to group B. Serum LH and FSH in group B was decreased as compared to control, and it was increased in group C as compared to control and group B. CONCLUSION: Administration of kisspeptin increases level of gonadotropins and reduces stress-induced hyperprolactinemia, which may improve fertility despite stress in animal.