Immunomodulatory role of prolactin in diabetes development

Study of Association of Serum Prolactin Levels with Insulin Resistance in Type 2 Diabetes Mellitus Patients

Objective

Prolactin (PRL) regulates glucose metabolism and insulin sensitivity. The study aimed to evaluate the role of PRL in glucose homeostasis and its association with insulin resistance in patients with diabetes mellitus (DM).

Methods and Materials

This cross-sectional, observational study included 100 patients (25-60 years) with T2DM. Primary information including demographics, anthropometric measurements, and biochemical measures (complete blood count, glucose parameters, liver and kidney function test, lipid profile, thyroid function test, serum fasting insulin levels, serum PRL levels) was collected.

Results

A total of 100 patients, 50 men and 50 women (25 premenopausal and 25 postmenopausal), were enrolled in this study. The correlation between serum cholesterol and PRL was found to be statistically non-significant (P = 0.129) in men and significant (P = 0.041) in women. There was an inverse relationship between fasting plasma glucose and serum PRL levels in both men (r = -0.88; P < 0.0001) and women patients (r = -0.768; P < 0.0001). Negative correlation between postprandial plasma glucose and PRL was found to be statistically significant (r = -0.398; P = 0.048) in postmenopausal women. The comparison in both men and women indicated an inverse correlation between serum PRL and glycated haemoglobin levels. There was a significant negative correlation between homeostasis model assessment-estimated insulin resistance (HOMA-IR) and PRL levels in both men (r = -0.362; P = 0.039) and women patients (r = -0.362; P = 0.003). Homeostasis model assessment of β cell function (HOMA-β), which directly correlates with residual pancreatic beta cell function, was positively correlated with prolactin levels, irrespective of gender and menopausal status of female subjects.

Conclusion

Serum PRL levels correlate with improved glycaemic control.

Prolactin is a Key Factor for Nonalcoholic Fatty Liver Disease in Obese Children

This study investigates whether serum prolactin (PRL) is a key factor for nonalcoholic fatty liver disease (NAFLD) in children. A total of 691 obese childred participated in this study and were divided into a NAFLD group (n=366) and simple obesity (SOB) group (n=325) according to the hepatic ultrasound results. The two groups were matched for gender, age, pubertal development, and body mass index (BMI). All patients underwent an OGTT test, and fasting blood samples were collected to measure prolactin. Stepwise logistic regression was performed to identify significant predictors of NAFLD. Serum prolactin levels were significantly lower in NAFLD subjects than in the SOB subjects [82.4 (56.36, 118.70) vs. 99.78 (63.89, 153.82), p<0.001] (mIU/l). NAFLD was strongly associated with insulin resistance (HOMA-IR) and prolactin, with lower levels of prolactin increasing the risk of NAFLD (adjusted ORs=1.741; 95% CI: 1.059-2.860) across the prolactin concentration tertiles after adjustment for confounders. Low serum prolactin levels are associated with the presence of NAFLD; thus, increased circulating prolactin might be a compensatory response for obesity in children.

Modulatory role of prolactin in type 1 diabetes

Objectives

Patients with type 1 diabetes mellitus have been reported to have elevated prolactin levels and a possible relationship between prolactin levels and the development of the disease has been proposed. However, some studies show that prolactin mediates beneficial functions in beta cells. Therefore, we review information on the roles of prolactin in type 1 diabetes mellitus.

Content

Here we summarize the functions of prolactin in the immune system and in pancreatic beta cells, in addition, we describe studies related to PRL levels, its regulation and alterations of secretion in patients with type 1 diabetes mellitus.

Summary

Studies in murine models have shown that prolactin protects beta cells from apoptosis, stimulates their proliferation and promotes pancreatic islet revascularization. In addition, some studies in patients with type 1 diabetes mellitus have shown that elevated prolactin levels correlate with better disease control.

Outlook

Prolactin treatment appears to be a promising strategy to improve beta-cell vascularization and proliferation in transplantation and immunotherapies.

Associations between Prolactin, Diabetes, and Cognitive Impairment: A Literature Review

BACKGROUND

Converging evidence indicates prolactin (PRL) and diabetes play an important role in the pathophysiology of cognitive impairment. However, little is known about the mechanisms responsible for the effects of PRL and diabetes on cognitive impairment.

SUMMARY

We summarize and review the available literature and current knowledge of the association between PRL and diabetes on aspects of cognitive impairment.

KEY MESSAGES

The phosphatidylinositol 3-kinase/protein kinase B pathway is central to the molecular mechanisms underlying how PRL and diabetes interact in cognitive impairment. Further work is needed to identify the interaction between PRL and diabetes, especially in the molecular aspects of cognitive impairment, which can suggest novel strategies for cognitive dysfunction treatment.

The interplay between prolactin and cardiovascular disease

Hyperprolactinemia can be caused by several conditions and its effects on the hypothalamic-pituitary-gonadal axis are understood in more detail. Nevertheless, in recent decades, other metabolic effects have been studied and data pointed to a potential increased cardiovascular disease (CVD) risk. A recent study showed a decrease in total and LDL- cholesterol only in men with prolactinoma treated with dopamine agonists (DA) supporting the previous results of a population study with increased CVD risk in men harboring prolactinoma. However, other population studies did not find a correlation between prolactin (PRL) levels and CVD risk or mortality. There is also data pointing to an increase in high-density lipoprotein levels, and decreases in triglycerides, carotid-intima-media thickness, C-reactive protein, and homocysteine levels in patients with prolactinoma on DA treatment. PRL was also implicated in endothelial dysfunction in pre and postmenopausal women. Withdrawal of DA resulted in negative changes in vascular parameters and an increase in plasma fibrinogen. It has been shown that PRL levels were positively correlated with blood pressure and inversely correlated with dilatation of the brachial artery and insulin sensitivity, increased homocysteine levels, and elevated D-dimer levels. Regarding possible mechanisms for the association between hyperprolactinemia and CVD risk, they include a possible direct effect of PRL, hypogonadism, and even effects of DA treatment, independently of changes in PRL levels. In conclusion, hyperprolactinemia seems to be associated with impaired endothelial function and DA treatment could improve CVD risk. More studies evaluating CVD risk in hyperprolactinemic patients are important to define a potential indication of treatment beyond hypogonadism.

Relation between self-perceived stress, psychopathological symptoms and the stress hormone prolactin in emerging psychosis

BACKGROUND

Psychosocial stress and the stress hormone prolactin are assumed to play an important role in the pathogenesis of schizophrenia and related psychoses, and have been frequently observed to be increased in antipsychotic-naïve patients with a clinical high risk for psychosis (CHR-P) or first episode of psychosis (FEP). The aim of this study was to further elucidate the relationships between self-perceived stress, psychopathological symptoms and prolactin levels in these patients.

METHODS

In this cross-sectional study, 45 healthy controls, 31 CHR-P patients and 87 FEP patients were recruited from two different study centers. Prolactin was measured under standardized conditions between 8 and 10 am. All patients were antipsychotic-naïve and not taking any prolactin influencing medication. Self-perceived stress during the last month was measured with the perceived stress scale (PSS-10) immediately before blood taking.

RESULTS

Both CHR-P and FEP patients showed significantly higher levels of self-perceived stress and prolactin than controls. Hyperprolactinemia (i.e. prolactin levels above the reference range) was observed in 26% of CHR-P and 45% of FEP patients. Self-perceived stress was significantly positively associated with affective symptoms, but not with other symptoms. There was no significant association between self-perceived stress and prolactin levels.

CONCLUSION

Our results confirm that CHR-P and FEP patients have higher stress levels than healthy controls and frequently have hyperprolactinemia, independent of antipsychotic medication. However, although it is well established that prolactin increases in response to stress, our results do not support the notion that increased prolactin levels in these patients are due to stress.

The Effect of Pituitary Gland Disorders on Glucose Metabolism: From Pathophysiology to Management

This review aims to explore, present, and discuss disorders of glucose metabolism implicated in pituitary gland diseases, the appropriate interventions, as well as the therapeutic challenges that may arise. Pituitary pathologies may dysregulate glucose homeostasis, as both the excess and deficiency of various pituitary hormones can affect glucose metabolism. Increased circulating levels of growth hormone, glucocorticoids or prolactin have been shown to mainly provoke hyperglycemic states, while hypopituitarism can be associated with both hyperglycemia and hypoglycemia. Addressing the primary cause of these disorders with the use of surgery, medical treatment or radiotherapy forms the cornerstone of current management strategies. Physicians should bear in mind that some such medications have an unfavorable effect on glucose metabolism too. When unsuccessful, or until the appropriate treatment of the underlying pituitary problem, the addition of established antidiabetic therapies might prove useful. Further studies aiming to discover more accurate and effective drug preparations in combination with optimal lifestyle management models will contribute to achieving a more successful glycemic control in these patients.

Prolactin effect on blood glucose and insülin in breastfeeding women

INTRODUCTION

Prolactin plays a significant role in lactation and prolactin levels are increasing physiologically in pregnancy and breastfeeding period. There might be different mechanisms during breastfeeding between prolactin and insülin levels. In order to highlighten this mechanisms we compared the plasma levels of glucose, insülin, prolactin, C-peptid in basal situations and after taking 75 gr carbonhydrate, 20 gr protein, 23 gr fat in breastfeeding and in non lactating women.

MATERIAL AND METHODS

Participiants and measurements: The study population included 12 breastfeeding women and 11 healthy non lactating women as a control group. We collected information on age, history of gestational diabetes mellitus, family history of diabetes mellitus, natality, the symptoms of hypoglycemia. Weight, height and waist circumference were measured and body mass index (BMI) was calculated as weight (kg)/height (m²).

RESULTS

Prolactin was inversely correlated with HbA1c and 2. hour C peptide (p=0.005, r=-0.564; p=0.008, r=-0.539). Prolactin was not significantly correlated with HOMA-IR, HOMA-IS, AUC-I or AUC-G. Prolactin levels were higher in breastfeeding women (median:34.98 μg/L) than in non lactating women (median:12.21 μg/L, p<0.001). There was a significant association between age and fasting glucose (p=0.018, r=-0.665), 2. hour glucose (p=0.049, r=0.578) in breastfeeding women.

DISCUSSION

In our study, we displayed prolactin was inversely correlated with HbA1c and 2. hour C peptide. Some studies in the past demonstrated that higher prolactin levels had importantly lower prevelance of type 2 diabetes. Our findings supported this situation.

Circulating prolactin concentrations and risk of type 2 diabetes in US women

AIMS/HYPOTHESIS

Prolactin, a multifunctional hormone, is involved in regulating insulin sensitivity and glucose homeostasis in experimental studies. However, whether circulating concentrations of prolactin are associated with risk of type 2 diabetes remains uncertain.

METHODS

We analysed the prospective relationship between circulating prolactin concentrations and type 2 diabetes risk in the Nurses' Health Study (NHS) and NHSII with up to 22 years of follow-up. Total plasma prolactin was measured using immunoassay in 8615 women free of type 2 diabetes and cardiovascular disease at baseline blood collection (NHS 1989-1990; NHSII 1996-1999) and a subset of 998 NHS women providing a second blood sample during 2000-2002. Baseline bioactive prolactin was measured in a subset of 2478 women using the Nb2 bioassay. HRs were estimated using Cox regression.

RESULTS

A total of 699 incident type 2 diabetes cases were documented during 156,140 person-years of follow-up. Total plasma prolactin levels were inversely associated with type 2 diabetes risk; the multivariable HR comparing the highest with the lowest quartile was 0.73 (95% CI 0.55, 0.95; p_trend = 0.02). The associations were similar by menopausal status and other risk factors (p_interaction > 0.70). Additional adjustment for sex and growth hormones, adiponectin, and inflammatory and insulin markers did not significantly alter the results. The association of plasma bioactive prolactin with type 2 diabetes risk was non-significantly stronger than that of total prolactin (HR comparing extreme quartiles, 0.53 vs 0.81 among the subset of 2478 women, p_difference = 0.11). The inverse association of total prolactin with type 2 diabetes was significant during the first 9 years after blood draw but waned linearly with time, whereas for bioactive prolactin, the inverse relationship persisted for a longer follow-up time after blood draw.

CONCLUSIONS/INTERPRETATION

A normally high circulating total prolactin concentration was associated with a lower type 2 diabetes risk within 9-10 years of follow-up since blood draw in US women. Our findings are consistent with experimental evidence, suggesting that among healthy women, prolactin within the biologically normal range may play a protective role in the pathogenesis of type 2 diabetes.

Ablation of prolactin receptor increases hepatic triglyceride accumulation

Increasing prevalence of non-alcoholic fatty liver disease (NAFLD) worldwide has necessitated a more thorough understanding of it and expanded the scope of research in this field. Women are more resistant to NAFLD than men despite equal exposure to major risk factors, such as obesity or hyperlipidemia. Female resistance is hormone-dependent, as evidenced by the sharp increase in NAFLD incidence in post-menopausal women who do not take hormone replacement therapy. Here, we found that the estrogen-responsive pituitary hormone prolactin (PRL), through specific PRL receptor (PRLR), down-regulates hepatic triglyceride (TG) accumulation. PRL was demonstrated to significantly down-regulate hepatic TG accumulation in female mice and protect male mice from liver steatosis induced by high-fat diet. Interestingly, Ad-shPRLR injected mice, whose hepatic PRLR abundance was effectively decreased at the protein levels, exhibited significantly aggravated liver steatosis. PRL could decrease the expression of stearoyl-coenzyme A desaturase 1 (SCD1), the rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids, in animal models and multiple hepatic cell lines. Following knockdown of PRLR, the changes to PRL-triggered SCD1 expression disappeared. Thus, PRL acted as a previously unrecognized master regulator of liver TG metabolism, indicating that modification of PRL via PRLR might serve as a potential therapeutic target for NAFLD.

The effects of hyperprolactinemia and its control on metabolic diseases

INTRODUCTION

Hyperprolactinaemia has been implicated in the pathogenesis of obesity and glucose intolerance and is reportedly associated with impaired metabolic profile and metabolic syndrome in approximately one third of patients.

AREAS COVERED

Suppression of dopaminergic tone has been proposed as a potential mechanism responsible for weight gain and metabolic abnormalities in such patients. Dopamine receptor type 2 (D₂R) is abundantly expressed on human pancreatic β-cell and adipocytes, suggesting a regulatory role for peripheral dopamine in insulin and adipose functions. Medical treatment with the dopamine-agonists bromocriptine and cabergoline has been shown to significantly improve gluco-insulinemic and lipid profile, also reducing the prevalence of metabolic syndrome. In patients with concomitant hypogonadism, simultaneous correction of both PRL excess and testosterone deficiency is mandatory to improve insulin resistance and metabolic abnormalities.

EXPERT COMMENTARY

Hyperprolactinemia promotes metabolic alterations. Control of PRL excess by dopamine agonists is mandatory to induce weight loss and to improve metabolic profile, and replacement treatment for concomitant hypogonadism effectively ameliorates insulin resistance and metabolic syndrome.

Impact of Gender on the Association between Low Serum Prolactin and Left Ventricular Mass in Subjects with Prediabetes

BACKGROUND

Low circulating prolactin hormone was associated with increased risk for type 2 diabetes mellitus. An inverse association of serum prolactin with cardiac remodeling was also previously suggested. Thus, the first question arises whether low serum prolactin is associated with adverse cardiac remodeling in subjects with prediabetes and if so what the impact of gender is? Second, could serum prolactin be considered a predictor of cardiac morbidity in those subjects? This study was conducted to assess prolactin level variations in relation to echocardiographic indices of cardiac remodeling among adult men and women with prediabetes.

METHODS

This cross sectional study enrolled 80 subjects with prediabetic; 40 men and 40 women. Anthropometric measurements, plasma glucose, lipid profile, homeostasis model assessment of insulin resistance, white blood cells count, prolactin and echocardiography were assessed.

RESULTS

Prolactin was significantly lower in men than in women with prediabetes. Left ventricular mass (LVM) was significantly higher in men than in women with prediabetes. The proportion of left ventricular hypertrophy (LVH) in men with prediabetes was 45% compared with 22.5% in women (P=0.03). We also found inverse independent associations of serum prolactin with LVM and LVH in men, but not in women.

CONCLUSION

In prediabetes, physiologically low serum prolactin is an independent predictor of increased LVM and LVH in adult men, but not in women. Prolactin may be a potential diagnostic biomarker for cardiac remodeling in adult men with prediabetes.

Assessment of circulating betatrophin concentrations in lean glucose-tolerant women with polycystic ovary syndrome

The aims of the current study were to investigate the betatrophin levels in lean glucose-tolerant women with polycystic ovary syndrome (PCOS), and to explore the relationships between these levels and antropometric, hormonal and metabolic parameters. The study population consisted of 50 lean (body mass index [BMI] < 25 kg/m²) women diagnosed with PCOS using the Rotterdam criteria, and 60 age- and BMI-matched healthy controls without any features of clinical or biochemical hyperandrogenism. Before recruitment, glucose tolerance was evaluated in all of the subjects using the 2-h 75 g oral glucose-tolerance test, and only those exhibiting normal glucose tolerance were enrolled. Serum betatrophin levels were significantly higher in women with PCOS (median 322.3; range 44.7-1989.3 ng/L) compared to the controls (median 199.9; range 6.2-1912.9 ng/L; p = .005). In the control group, no significant correlation was evident between betatrophin levels and clinical or biochemical parameters. In the PCOS group, betatrophin levels were positively correlated with prolactin levels (r = .286, p = .046) and negatively correlated with BMI (r = -.283, p = .049), waist/hip ratio (r = -.324, p = .023), and low-density lipoprotein cholesterol levels (r = -.385, p = .006). Impact statement What is already known on this subject: Several studies have suggested that primary alteration in beta-cell function is a pathophysiological feature of PCOS, and insulin resistance is the most significant predictor of beta-cell dysfunction independent of obesity. Betatrophin is a circulating protein that is primarily expressed in the liver in humans. Early experimental investigations demonstrated that overexpression of betatrophin significantly promoted pancreatic beta-cell proliferation, insulin production and improved glucose tolerance. Few studies have investigated the association between PCOS and betatrophin. However, in contrast to our study, the authors included overweight/obese patients and glucose tolerance was not evaluated before recruitment. What the results of this study add: Our results showed that serum betatrophin levels were significantly higher in lean glucose-tolerant PCOS women than in age- and BMI-matched healthy controls. What are the implications of these findings for clinical practice and/or further research: Elevated betatrophin levels in PCOS women, in the absence of obesity and glucose intolerance, may reflect a compensatory mechanism in order to counteract metabolic syndrome-related risk factors.

Circulating Prolactin and Risk of Type 2 Diabetes: A Prospective Study

Prolactin plays an important role in maintaining a normal glucose homeostasis during pregnancy and beyond. Studies investigating the association between prolactin and type 2 diabetes beyond pregnancy are rare and none is prospective. We aimed to examine whether prolactin associates with type 2 diabetes prospectively in a Chinese population. In 2009, 2,377 participants aged 40 years or older were enrolled from Shanghai, China. Among 1,596 diabetes-free participants at baseline, 1,510 completed the follow-up investigation in 2013. Participants who had a fasting plasma glucose ≥126 mg/dL and/or a 2-hour plasma glucose ≥200 mg/dL during a 75-g oral glucose tolerance test had a definite diagnosis of type 2 diabetes or received antidiabetic therapies during follow-up were classified as having type 2 diabetes. During a mean follow-up of 3.7 years, 189 new cases of type 2 diabetes were documented. After multivariate adjustment, women in the highest quartile of prolactin showed the lowest risk for diabetes compared with those in the lowest quartile (hazard ratio = 0.48, 95% confidence interval: 0.26, 0.90). However, such significant associations were not observed in men. Prolactin may be a mediator in the pathogenesis of type 2 diabetes in women; however, more studies are needed to elucidate the underlying sex-specific mechanism.

Prevalence of autoimmune disease in patients with prolactinomas and non-functioning pituitary adenomas

PURPOSE

Prolactin can affect autoimmune response and evidence suggests that hyperprolactinemia can primarily precipitate autoimmunity. We postulate that patients with prolactinomas are more prone to autoimmune disease (AID).

METHODS

We conducted a retrospective case-control study comparing prevalence of AID in 100 prolactinoma patients (PRL-P, cases) and 100 age- and gender-matched non-functioning pituitary adenoma patients (NFPA-P, controls) assessed at the Neuroendocrine Clinics of the McGill University Health Centre between January 2005 and December 2014. Comparisons were done using a conditional logistic regression (CLR) analysis. Multiple imputation was used to account for missing data values.

RESULTS

Sixty-eight women and 32 men were in each group. Median age was 37 years for PRL-P and 46 years for NFPA-P. AID was diagnosed in 28/100 cases and 16/100 controls. Autoimmune thyroid disease was the most common AID reported in both groups, representing 70 and 61% of the AID diagnoses respectively. CLR analysis revealed a multiplicative interaction effect between AID prevalence and age (p 0.004). Odds ratios for AID in PRL-P compared to NFPA-P increase with age and become significant at age 43, reaching 4.17 (95% CI 1.26, 13.82) at age 45 and 8.09 (95% CI 1.96, 33.43) at age 50 (p 0.05).

CONCLUSION

Our data showed a higher prevalence of AID in both PRL-P and NFPA-P than in a reference population. In both groups, prevalence of AID increased with age, given a multiplicative interaction effect. A significant higher prevalence of autoimmunity in PRL-P compared with NFPA-P occurs after age 43. These associations may have significant implications for the management of prolactinoma patients.

Bayesian modeling suggests that IL-12 (p40), IL-13 and MCP-1 drive murine cytokine networks in vivo

Background

Cytokine-hormone network deregulations underpin pathologies ranging from autoimmune disorders to cancer, but our understanding of these networks in physiological/pathophysiological states remains patchy. We employed Bayesian networks to analyze cytokine-hormone interactions in vivo using murine lactation as a dynamic, physiological model system.

Results

Circulatory levels of estrogen, progesterone, prolactin and twenty-three cytokines were profiled in post partum mice with/without pups. The resultant networks were very robust and assembled about structural hubs, with evidence that interleukin (IL)-12 (p40), IL-13 and monocyte chemoattractant protein (MCP)-1 were the primary drivers of network behavior. Network structural conservation across physiological scenarios coupled with the successful empirical validation of our approach suggested that in silico network perturbations can predict in vivo qualitative responses. In silico perturbation of network components also captured biological features of cytokine interactions (antagonism, synergy, redundancy).

Conclusion

These findings highlight the potential of network-based approaches in identifying novel cytokine pharmacological targets and in predicting the effects of their exogenous manipulation in inflammatory/immune disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0226-3) contains supplementary material, which is available to authorized users.

Serum vaspin and adiponectin levels in patients with prolactinoma

BACKGROUND

Studies investigating serum vaspin and adiponectin levels in patients with prolactinoma are inconclusive. The aim of this study was to evaluate serum vaspin and adiponectin levels in patients with prolactinoma and healthy controls.

METHODS

A total of 42 prolactinoma patients (Group 1, 21 patients; Group 2, 21 patients) and 30 healthy controls were enrolled in the study. Group 1 consisted of newly diagnosed patients who were never treated or had not received a dopamine agonist (DA) within 6 months prior to screening. Group 2 consisted of prolactinoma patients who were on DA treatment for at least 6 months at the time of screening. The control group (group 3) consisted of healthy controls.

RESULTS

Patients with prolactinoma had higher homeostasis model assessment of insulin resistance and lower quantitative insulin sensitivity check index values in comparison to healthy controls (p < 0.001 for both). Serum levels of adiponectin and vaspin were also significantly lower in prolactinoma patients when compared to the control group (p < 0.01 and p < 0.001, respectively). Following adjustment for confounding factors, the respective odds ratios for prolactinoma in patients in the lower subgroup compared with those in the higher subgroup for adiponectin and vaspin were 2.733 (0.621-12.035; p > 0.05) and 5.041 (1.191-21.339; p < 0.05).

CONCLUSION

This is the first study to demonstrate the presence of low vaspin levels in patients with prolactinomas. Further studies are needed to help establish the roles of vaspin and adiponectin in prolactinoma patients.

Prolactin serum levels correlate with inflammatory status in drug-naïve first-episode schizophrenia

OBJECTIVES

The present study was to examine the relationship between serum levels of prolactin and the inflammatory status in drug-naïve, first-episode schizophrenia patients with normal weight.

METHODS

Patients with normal weight, drug-naïve, first-episode schizophrenia and healthy controls were enrolled in the study. Serum levels of prolactin (PRL) were measured using electrical chemiluminescence immunoassay. Serum levels of interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were examined using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Sixty patients with normal weight, drug-naïve, first-episode schizophrenia and 60 healthy controls were enrolled. The schizophrenia group had higher serum levels of PRL, IL-1β, IL-6 and TNF-α compared with the control group. There was a gender difference of hyperprolactinemia in schizophrenia group. There were positive relationships between serum levels of PRL and serum levels of IL-1β, IL-6 and TNF-α within the schizophrenia group. Within the schizophrenia group, TNF-α was the strongest predictor among the three cytokines for serum levels of prolactin after controlling for gender, age, education, smoking status and disease duration.

CONCLUSIONS

Patients with normal weight, drug-naïve, first-episode schizophrenia present elevated serum levels of PRL, which might be related to the up-regulated inflammatory status in this patient population.

The effect of glucagon-like peptide-1 in the management of diabetes mellitus: cellular and molecular mechanisms

Incretins, such as glucagon-like peptide-1 (GLP)-1, have been shown to elevate plasma insulin concentration. The purpose of this study is to investigate the cellular and molecular basis of the beneficial effects of GLP-1. Normal and diabetic male Wistar rats were treated with GLP-1 (50 ng/kg body weight) for 10 weeks. At the end of the experiment, pancreatic tissues were taken for immunohistochemistry, immunoelectron microscopy and real-time polymerase chain reaction studies. Samples of blood were retrieved from the animals for the measurement of enzymes and insulin. The results show that treatment of diabetic rats with GLP-1 caused significant (P < 0.05) reduction in body weight gain and blood glucose level. GLP-1 (10(-12)-10(-6) M) induced significant (P < 0.01) dose-dependent increases in insulin release from the pancreas of normal and diabetic rats compared to basal. Diabetes-induced abnormal liver (aspartate aminotransferase and alanine aminotransferase) and kidney (blood urea nitrogen and uric acid) parameters were corrected in GLP-1-treated rats compared to controls. GLP-1 treatment induced significant (P < 0.05) elevation in the expression of pancreatic duodenal homeobox-1, heat shock protein-70, glutathione peroxidase, insulin receptor and GLP-1-receptor genes in diabetic animals compared to controls. GLP-1 is present in pancreatic beta cells and significantly (P < 0.05) increased the number of insulin-, glutathione reductase- and catalase-immunoreactive islet cells. The results of this study show that GLP-1 is co-localized with insulin and seems to exert its beneficial effects by increasing cellular concentrations of endogenous antioxidant genes and other genes involved in the maintenance of pancreatic beta cell structure and function.

Evaluation of body weight, insulin resistance, leptin and adiponectin levels in premenopausal women with hyperprolactinemia

The effects of hyperprolactinemia on metabolic parameters are not clear and a few data evaluating adiponectin levels in prolactinoma and idiopathic hyperprolactinemia exist. The aim of this study was to evaluate the effects of hyperprolactinemia on body weight, insulin resistance, beta cell function, and leptin and adiponectin levels in premenopausal women with hyperprolactinemia. Forty premenopausal women with prolactinoma or idiopathic hyperprolactinemia were compared to 41 age-matched healthy premenopausal women with regard to body weight, body mass index, waist and hip circumferences, waist to hip ratio, fasting plasma glucose, insulin levels, insulin resistance measured by homeostasis model assessment (HOMA)-insulin resistance index, beta cell function measured by HOMA-β index, leptin and adiponectin levels. Plasma insulin levels and HOMA indexes (both insulin resistance and beta indexes) were significantly higher in hyperprolactinemic women. The other parameters were similar between both groups. There was a positive correlation between prolactin levels and fasting plasma glucose in hyperprolactinemic women. The results of this study showed that high prolactin levels may be associated with hyperinsulinemia and insulin resistance in premenopausal women. This effect seems to be independent of body weight, leptin and adiponectin levels. High prolactin levels may directly stimulate insulin secretion from pancreas and directly cause hepatic and whole-body insulin resistance.

PRLR regulates hepatic insulin sensitivity in mice via STAT5

Insulin resistance is one of the major contributing factors in the development of metabolic diseases. The mechanisms responsible for insulin resistance, however, remain poorly understood. Although numerous functions of the prolactin receptor (PRLR) have been identified, a direct effect on insulin sensitivity has not been previously described. The aim of our current study is to investigate this possibility and elucidate underlying mechanisms. Here we show that insulin sensitivity is improved or impaired in mice injected with adenovirus that overexpress or knock down PRLR expression, respectively. Similar observations were obtained in in vitro studies. In addition, we discovered that the signal transducer and activator of transcription-5 pathway are required for regulating insulin sensitivity by PRLR. Moreover, we observed that PRLR expression is decreased or increased under insulin-resistant (db/db mice) or insulin-sensitive (leucine deprivation) conditions, respectively, and found that altering PRLR expression significantly reverses insulin sensitivity under both conditions. Finally, we found that PRLR expression levels are increased under leucine deprivation via a general control nonderepressible 2/mammalian target of rapamycin/ribosomal protein S6 kinase-1-dependent pathway. These results demonstrate a novel function for hepatic PRLR in the regulation of insulin sensitivity and provide important insights concerning the nutritional regulation of PRLR expression.

Circulating prolactin associates with diabetes and impaired glucose regulation: a population-based study

OBJECTIVE

Prolactin is a major stimulus for the β-cell adaptation during gestation and guards postpartum women against gestational diabetes. Most studies of the role of prolactin on glucose metabolism have been conducted in humans and animals during pregnancy. However, little is known concerning the association between circulating prolactin and glucose metabolism outside pregnancy in epidemiological studies. We aimed to determine whether the variation of circulating prolactin concentration associates with diabetes and impaired glucose regulation (IGR) in a cross-sectional study.

RESEARCH DESIGN AND METHODS

We recruited 2,377 participants (1,034 men and 1,343 postmenopausal women) without hyperprolactinemia, aged 40 years and older, in Shanghai, China. Diabetes and IGR were determined by an oral glucose tolerance test. Multinomial logit analyses were performed to evaluate the relationship of prolactin with diabetes and IGR.

RESULTS

Prolactin levels decreased from normal glucose regulation to IGR to diabetes. Multinomial logit analyses, adjusted for potential confounding factors, showed that high circulating prolactin was associated with lower prevalence of diabetes and IGR. The adjusted odds ratios (95% CI) for IGR and diabetes for the highest compared with the lowest quartile of prolactin were 0.54 (95% CI 0.33-0.89) and 0.38 (0.24-0.59) in men and 0.54 (0.36-0.81) and 0.47 (0.32-0.70) in women.

CONCLUSIONS

High circulating prolactin associates with lower prevalence of diabetes and IGR in the current study. Further studies are warranted to confirm this association.

Serum prolactin concentrations as risk factor of metabolic syndrome or type 2 diabetes?

BACKGROUND

To investigate potential associations of serum prolactin concentration (PRL) with metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM), previously observed in small and selected study samples, in a large population-based cohort.

METHODS

Data from 3,993 individuals (2,027 women) aged 20-79 years from the population-based Study of Health of Pomerania (SHIP) were used to analyse cross-sectional and longitudinal associations of PRL with MetS and T2DM risk in age- and multivariable-adjusted Poisson regression models. PRL were log-transformed and modelled as continuous (per standard deviation (SD) increase) and categorical predictor (sex-specific quartiles) variable, separately for men and woman.

RESULTS

Cross-sectional analyses showed an inverse association between low PRL concentrations and prevalent T2DM risk in men and women after multivariable-adjustment (men: Q1 vs. Q4: relative risk (RR), 1.55; 95% confidence interval (CI), 1.13 - 2.14; women: Q1 vs. Q4: RR, 1.70; 95% CI, 1.10 - 2.62). Likewise, higher PRL concentrations were associated with significantly lower T2DM risk (RR per SD increase in log-PRL: 0.83; 95% CI, 0.72 - 0.95 in men, and 0.84; 95% CI, 0.71 - 0.98 in women, respectively). An inverse association between PRL and MetS risk was not retained after multivariable adjustment. Longitudinal analyses yielded no association of PRL with incident MetS or T2DM.

CONCLUSION

The present study is the first large population-based study reporting a cross-sectional inverse association between PRL and prevalent T2DM in both genders. But the absent longitudinal associations do not support a causal role of PRL as a risk factor of incident MetS or T2DM.

Properties of antibodies to a synthetic peptide representing an epitope shared by receptors of the type I cytokine family

Previous works from our laboratory demonstrated that the monoclonal antibody (MAb) called R7B4 is directed to an epitope shared by various receptors corresponding to the type I cytokine receptor family, containing the common motif WSXWS or the homologous F(Y)GEFS. Later a consensus peptide significantly recognized by the MAb was identified and synthesized (sequence HGYWSEWSPE). In the present work, an homologous of the consensus sequence (HHGYWSEWSPE) was conjugated to PADRE adjuvant to produce Ab that could simulate theMAb activity, that is, acting as hormone and/or cytokine antagonists. The covalently conjugated peptide-PADRE was a better immunogen than the consensus peptide alone according to the reactivity of sera from C57BL/6 immunized mice and, besides, no Ab to PADRE were detected. Furthermore, Ab to consensus peptide elicited after peptide-PADRE inoculation into mice behaved as immunomodulatory agents, since they improved the humoral response to a foreign antigen (in this case ovalbumin). In addition, the Ab inhibited the in vitro proliferation of various cell lines, mainly cells derived from human and mouse breast cancer. Thus, immunization with the conjugate peptide-PADRE prepared under the experimental conditions described herein originated immunomodulatory Ab that, in the future, could be tested in some pathological conditions.

Prolactin and autoimmunity

Sex hormones, especially estrogen and prolactin (PRL), have an important role in modulating the immune response. PRL is secreted from the pituitary gland as well as other organs and cells particularly lymphocytes. PRL has an immune stimulatory effect and promotes autoimmunity. PRL interferes specifically with B cell tolerance induction, enhances proliferative response to antigens and mitogens and increases the production of immune globulins, cytokines and autoantibodies. Hyperprolactinemia (HPRL) in women present with clinical manifestations of galactorrhea, primary or secondary amenorrhea, delayed menarche or a change in the menses either in the amount or in the regularity. Furthermore in the last 2 decades multi-organ and organ specific autoimmune diseases like systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS), Hashimoto's thyroiditis (HT), multiple sclerosis (MS), psoriasis, hepatitis C patients, Behçet's disease, peripartum cardiomyopathy (PPCM) and active celiac disease were discussed to be associated with HPRL. There is data showing correlation between PRL level and diseases activity in few diseases. Genetic factors may have a role in humans as in animal models. The PRL isoforms based on the differences in the amino acid sequence and size of the cytoplasmic domain have an important effect on the bioactivity on prolactin receptors (PRL-Rs).

Reproductive immunology: a focus on the role of female sex hormones and other gender-related factors

Reproductive immunology has attracted the attention of researchers interested in fertility and pregnancy as well as those interested in immunity and autoimmunity. Over the past couple of decades, a wealth of data on the immune-reproductive interactions has been generated. This issue of the Journal will examine several topics including the role of immune factors in the induction of anti-Ro antibody-mediated autoimmunity in neonates and the immunological effects of gender and sex hormones. The possible implications of the research reviewed here for the development of novel therapeutic approaches are also addressed.

Prolactin, systemic lupus erythematosus, and autoreactive B cells: lessons learnt from murine models

The predominant prevalence of autoimmune diseases in women of reproductive age has led to the investigation of the effects of sex hormones on immune regulation and in autoimmune diseases, in particular the prototypic systemic autoimmune disease lupus. The female hormone prolactin has receptors beyond the reproductive axis including immune cells, and it is thought to promote autoimmunity in human and murine lupus. Induced hyperprolactinemia in experimental lupus models, regardless of gender, exacerbates disease activity and leads to premature death. Prolactin treatment in mice that are not prone to develop lupus leads to the development of a lupus-like phenotype. Persistent mild-moderate hyperprolactinemia alters the selection of the naïve B cell repertoire. Recent studies demonstrate that prolactin impairs all three mechanisms of B cell tolerance induction (negative selection, receptor editing, and anergy) and thereby contributes to the pathogenesis of autoimmunity. The effects of prolactin are genetically determined as shown by the differential response to the hormone in the different mice strains. Bromocriptine, a drug that inhibits prolactin secretion, abrogates some of the immune effects of this hormone. Further research is required to elucidate molecular mechanisms involved in immune effects of prolactin and to develop novel targeted treatments for SLE patients with prolactin-responsive disease.

Dual effects of hyperprolactinemia on carrageenan-induced inflammatory paw edema in rats

OBJECTIVES

The effects of short-term 5-day and long-term 30-day hyperprolactinemia induced by domperidone (1.7 mg/kg/day, s.c.) or ectopic pituitary graft on the acute inflammatory response induced by carrageenan were evaluated in male rats. Both models of hyperprolactinemia effectively increased serum prolactin (PRL) levels.

METHODS

The volume in milliliters of inflammatory edema was measured by plethysmography 1, 2, 3, 4, 6, 8 and 24 h after carrageenan injection. The areas under the inflammatory time-response curves were compared. Additionally, the effects of hyperprolactinemia on body weight and serum corticosterone levels were evaluated.

RESULTS

In both domperidone-treated and pituitary graft-implanted animals, short-term 5-day hyperprolactinemia increased the inflammatory response, while long-term 30-day hyperprolactinemia had anti-inflammatory effects. Body weight was not affected by either short- or long-term hyperprolactinemia.

CONCLUSION

These results show that PRL has biphasic effects on the carrageenan-induced inflammatory response.

Immunomodulatory, beta-cell, and neuroprotective actions of fenugreek oil from alloxan-induced diabetes

Immunological disorders and nephropathy are among the most frequent and serious complications of diabetes mellitus. This shows that fewer infiltrated inflammatory cells evidenced by reverted back to near the normal value of white blood cell, mean corpuscular volume, and lymphocytes counts as interleukin-6 in pancreas. Also, fenugreek oil significantly improved blood glucose levels, glucose intolerance, and insulin sensitivity compared to the diabetic group. The pancreatic islet and less beta-cells damage were observed after the administration of fenugreek oil to diabetic rats. Moreover, diabetic rats showed low activities of superoxide dismutase, catalase, glutathione peroxidase, and reduced glutathione content in kidney, which were restored to near normal levels by treatment with fenugreek oil. The increased levels of lipid peroxidation, creatinine, albumin, and urea in diabetic rats decreased significantly in diabetic rats treated with fenugreek oil. Diabetic rats treated with fenugreek oil restored almost a normal architecture of pancreas and kidney. In conclusion, this study reveals the efficacy of fenugreek oil in the amelioration of diabetes, hematological status, and renal toxicity which may be attributed to its immunomodulatory activity and insulin stimulation action along with its antioxidant potential.