The relationship between prolactin (PRL), leptin, nitric oxide (NO), and cytokines in patients with hyperprolactinemia

Metabolic effects of prolactin

Over the last years, the metabolic role of PRL has emerged. PRL excess is known to promote weight gain, obesity, metabolic syndrome, and impairment in gluco-insulinemic and lipid profiles, likely due to the suppression of physiologic dopaminergic tone. Prolactin receptors and dopamine receptors type 2 have been demonstrated to be expressed on both human pancreatic β- cell and adipocytes, supporting a key role of prolactin and dopamine in peripheral metabolic regulation. Medical treatment with the dopamine agonists bromocriptine and cabergoline has been demonstrated to decrease the prevalence of metabolic syndrome and obesity, and significantly improve gluco-insulinemic and lipid profiles. In hyperprolactinemic men with concomitant hypogonadism, correction of hyperprolactinaemia and testosterone replacement has been proven to restore metabolic impairment. In turn, low prolactin levels have also been demonstrated to exert a detrimental effect on weight gain, glucose and lipid metabolism, thus leading to an increased prevalence of metabolic syndrome. Therefore, PRL values ranging from 25 to 100 mg/L, in absence of other recognizable pathological causes, have been proposed to represent a physiological response to the request for an increase in metabolic activity, and nowadays classify the so-called HomeoFIT- PRL as a promoter of metabolic homeostasis. The current review focuses mainly on the effects of hyperprolactinemia and its control by medical treatment with DAs on the modulation of food intake, body weight, gluco-insulinemic and lipid profile. Furthermore, it provides the latest knowledge about the metabolic impact of hypoprolactinemia.

The tumour microenvironment of pituitary neuroendocrine tumours

The tumour microenvironment (TME) includes a variety of non-neoplastic cells and non-cellular elements such as cytokines, growth factors and enzymes surrounding tumour cells. The TME emerged as a key modulator of tumour initiation, progression and invasion, with extensive data available in many cancers, but little is known in pituitary tumours. However, the understanding of the TME of pituitary tumours has advanced thanks to active research in this field over the last decade. Different immune and stromal cell subpopulations, and several cytokines, growth factors and matrix remodelling enzymes, have been characterised in pituitary tumours. Studying the TME in pituitary tumours may lead to a better understanding of tumourigenic mechanisms, identification of biomarkers useful to predict aggressive disease, and development of novel therapies. This review summarises the current knowledge on the different TME cellular/non-cellular elements in pituitary tumours and provides an overview of their role in tumourigenesis, biological behaviour and clinical outcomes.

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.

Profile of leptin, adiponectin, and body fat in patients with hyperprolactinemia: Response to treatment with cabergoline

INTRODUCTION

Though hypoadiponectinemia and leptin resistance have been proposed as potential factors for weight gain in patients with hyperprolactinemia (HPL), the effects of HPL and cabergoline on these adipocyte-derived hormones are not clear. Aims of this study were (i) to assess the alterations of body fat, leptin, and adiponectin in patients with HPL (ii) effect of cabergoline treatment on these parameters.

METHODS

Nineteen consecutive patients with prolactinoma (median prolactin [PRL] 118.6 (interquartile range: 105.3) μg/L) and 20 controls were studied in a nonrandomized matched prospective design. The controls were age, gender, and body mass index (BMI) matched. Anthropometric data, metabolic variables, leptin, and adiponectin were studied at baseline and 3 and 6 months after cabergoline treatment.

RESULTS

Patients with prolactinoma had increased level of fasting plasma glucose (P < 0.001) as compared to age-, gender-, and BMI-matched healthy controls. Estradiol concentration of controls was higher than that of patients (P = 0.018). Patients with prolactinoma had higher levels of leptin (P = 0.027) as compared to healthy controls without a significant difference in adiponectin levels. There was a significant decrease of body weight at 3 months (P = 0.029), with a further decline at 6 months (P < 0.001) of cabergoline therapy. Furthermore, there was a significant decrement of BMI (P < 0.001), waist circumference (P = 0.003), waist-hip ratio (P = 0.03), total body fat (P = 0.003), plasma glucose (P < 0.001), leptin levels (P = 0.013), and an increase in estradiol concentration (P = 0.03) at 6 months of cabergoline treatment.

CONCLUSION

Patients with prolactinoma have adverse metabolic profile compared to matched controls. Normalization of PRL with cabergoline corrects all the metabolic abnormalities.

Effect of chronic cabergoline treatment and testosterone replacement on metabolism in male patients with prolactinomas

INTRODUCTION

Hyperprolactinemia and hypogonadism are reportedly associated with an impaired metabolic profile. The current study aimed at investigating the effects of testosterone replacement and cabergoline (CAB) treatment on the metabolic profile in male hyperprolactinemic patients.

PATIENTS AND METHODS

Thirty-two men with prolactinomas, including 22 with total testosterone (TT) <8 nmol/l (HG, 69%) and 10 with TT >8 nmol/l (non-HG, 31%), were entered in the study. In all patients, metabolic parameters were assessed at diagnosis and after 12- and 24-month treatment.

RESULTS

Compared to non-HG patients, at baseline the HG patients had higher waist circumference (WC). TT significantly correlated with body mass index (BMI). Twelve-month CAB induced PRL normalization in 84%. HG prevalence significantly decreased (28%) and non-HG prevalence significantly increased (72%). Anthropometric and lipid parameters, fasting insulin (FI), insulin sensitivity index (ISI0), homeostatic model assessment of insulin secretion (HOMA-β) and homeostatic model assessment of insulin resistance (HOMA-IR) significantly improved compared to baseline. TT was the best predictor for FI. Percent change (Δ) of TT significantly correlated with ΔCholesterol, ΔWeight and ΔBMI. Compared to non-HG patients, the HG patients had a higher weight, BMI, WC and HOMA-β. In HG, testosterone replacement was started. After 24 months, PRL normalized in 97%. HG prevalence significantly decreased (6%) and non-HG prevalence significantly increased (94%). Anthropometric and lipid parameters, FI, ISI0, HOMA-β and HOMA-IR significantly improved compared to baseline, with FI, ISI0, HOMA-β and HOMA-IR further ameliorating compared to the 12-month evaluation. Compared to non-HG patients, the HG patients still had a higher weight, BMI and WC.

CONCLUSIONS

In hyperprolactinemic hypogonal men, proper testosterone replacement induces a significant improvement in the metabolic profile, even though the amelioration in the lipid profile might reflect the direct action of CAB.

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.

Higher doses of cabergoline further improve metabolic parameters in patients with prolactinoma regardless of the degree of reduction in prolactin levels

OBJECTIVE

Currently available studies that fully analyse the metabolic parameters in patients with prolactinoma are scarce and discordant. The aim of this study was to evaluate the metabolic effects of cabergoline (CAB) treatment in patients with newly diagnosed prolactinoma in relation to disease control and CAB dosage.

DESIGN

This is a retrospective clinical-based therapy analysis.

PATIENTS

Forty-three patients with prolactinoma (eight men, 35 women), aged 33·65 ± 11·23 years, were evaluated metabolically at baseline and after 12 months of CAB treatment.

MEASUREMENTS

Body mass index (BMI), systolic and diastolic blood pressure, waist circumference (WC), lipid profile, haemoglobinA1c (HbA1c), glucose and insulin levels (and their areas under the curve, AUC) after an oral glucose tolerance test, homoeostasis model assessment of insulin resistance (Homa-IR) index, insulin sensitivity index (ISI) Matsuda, oral disposition index (DIo) and visceral adiposity index (VAI) were measured at baseline and after 12 months of treatment.

RESULTS

Twelve months of CAB reduced WC (P < 0·001), total (P = 0·001) and low-density lipoprotein \terol (P < 0·001), triglycerides (P = 0·024), fasting insulin (P < 0·001), AUCINSULIN (P < 0·001), HbA1c (P = 0·022), Homa-IR (P < 0·001) and VAI (P < 0·001), with a concomitant increase in high-density lipoprotein cholesterol (P < 0·001) and in ISI Matsuda (P < 0·001), regardless of the degree of reduction in prolactin levels. The patients receiving higher doses (>0·50 mg/week) of CAB showed lower BMI (P = 0·009), fasting insulin (P = 0·001), Homa-IR (P < 0·001) and VAI (P = 0·018) and higher ISI Matsuda (P = 0·002) and DIo (P = 0·011), compared with those on lower doses.

CONCLUSIONS

A significant metabolic improvement was observed in patients with prolactinoma after 12 months of CAB treatment, especially when higher doses were used, highlighting the importance of considering the metabolic profile in these patients and the role of active treatment with high CAB doses.

Cancer biomarker profiling in patients with chronic hepatitis C virus, liver cirrhosis and hepatocellular carcinoma

The detection and diagnosis of hepatocellular carcinoma (HCC) at an early stage may significantly affect the prognosis of HCC patients. Thus, it is necessary to always identify novel putative markers for improving diagnosis. Hepatocarcinogenesis correlates with pathological hepatic angiogenesis. However, each tumor-induced angio-genetic process is influenced by the microenvironment through several pro- and anti-angiogenic factors released from tumor cells, tumor-associated inflammatory cells and/or from the extracellular matrix, and modulated by various signal pathways. In this study, we evaluated the profiling of angiogenic factors using Bio-Plex Pro™ Human Cancer Biomarker Panel 1, a 16-plex magnetic bead-based assay, in sera of patients with chronic hepatitis C (CHC) virus, liver cirrhosis (LC) and HCC. Our results demonstrated: i) high levels of hepatocyte growth factor (HGF) and prolactin only in LC and HCC patients, ii) high levels of soluble human epidermal growth factor receptor‑2 (sHER-2/neu; ErbB-2), sIL-6Ra, leptin (LEP) and platelet endothelial cell adhesion molecule‑1 (PECAM-1) in CHC, LC and HCC patients and iii) that sIL-6R correlated with the fibrosis stage in CHC patients, with Child‑Pugh score in those patients with LC and with tumor size in those patients with HCC, confirming that this protein may be used as a predictor of liver damage and of inflammatory process leading to fibrosis, cirrhosis, and subsequently to cancer. Moreover, an interactomic study conducted using the Ingenuity Pathway Analysis (IPA) software proved the existence of a correlation between 5 significant proteins [ErbB-2, sIL-6Ra, prolactin (PRL), HGF and LEP] which are involved in the same metabolic pathways.

Effect of cabergoline on metabolism in prolactinomas

INTRODUCTION

Hyperprolactinemia has been implicated in the pathogenesis of obesity and glucose intolerance and is reportedly associated with an impaired metabolic profile. The current study aimed at investigating the effects of 12- and 60-month treatment with cabergoline (CAB) on metabolic syndrome (MetS) in patients with prolactinomas.

PATIENTS AND METHODS

61 patients with prolactinomas (13 men, 48 women, 41 with microadenoma, 20 with macroadenoma), aged 34.4 ± 10.3 years, entered the study. In all patients, prolactin (PRL) and metabolic parameters were assessed at diagnosis and after 12 and 60 months of continuous CAB treatment. MetS was diagnosed according to NCEP-ATP III criteria.

RESULTS

Compared to baseline, CAB induced a significant decrease in PRL with complete normalization in 93% of patients after the 60-month treatment. At baseline, MetS prevalence was significantly higher in patients with PRL above (34.5%) than in those with PRL lower (12.5%) than the median (129 μg/l, p = 0.03). MetS prevalence significantly decreased after 12 (11.5%, p = 0.039) and 60 (5.0%, p = 0.001) months compared to baseline (28.0%). At both evaluations the lipid profile significantly improved compared to baseline. Fasting insulin and homeostatic model assessment of insulin resistance significantly decreased after 1 year of CAB (p = 0.012 and p = 0.002, respectively) and further improved after 60 months (p = 0.000). The visceral adiposity index significantly decreased after the 60-month treatment (p = 0.000) compared to baseline. At the 5-year evaluation CAB dose was the best predictor of percent decrease in fasting insulin (t = 2.35, p = 0.022).

CONCLUSIONS

CAB significantly reduces MetS prevalence and improves the adipose tissue dysfunction index. The improvement in PRL, insulin sensitivity and other metabolic parameters might reflect the direct effect of CAB.

The association of serum prolactin concentration with inflammatory biomarkers - cross-sectional findings from the population-based Study of Health in Pomerania

OBJECTIVE

Prolactin (PRL) is involved in immune regulation and may contribute to an atherogenic phenotype. Previous results on the association of PRL with inflammatory biomarkers have been conflicting and limited by small patient studies. Therefore, we used data from a large population-based sample to assess the cross-sectional associations between serum PRL concentration and high-sensitivity C-reactive protein (hsCRP), fibrinogen, interleukin-6 (IL-6), and white blood cell (WBC) count.

DESIGN AND POPULATION

From the population-based Study of Health in Pomerania (SHIP), a total of 3744 subjects were available for the present analyses.

METHODS AND MEASUREMENTS

PRL and inflammatory biomarkers were measured. Linear and logistic regression models adjusted for age, sex, body-mass-index, total cholesterol and glucose were analysed.

RESULTS

Multivariable linear regression models revealed a positive association of PRL with WBC. Multivariable logistic regression analyses showed a significant association of PRL with increased IL-6 in non-smokers [highest vs lowest quintile: odds ratio 1·69 (95% confidence interval 1·10-2·58), P = 0·02] and smokers [OR 2·06 (95%-CI 1·10-3·89), P = 0·02]. Similar results were found for WBC in non-smokers [highest vs lowest quintile: OR 2·09 (95%-CI 1·21-3·61), P = 0·01)] but not in smokers. Linear and logistic regression analyses revealed no significant associations of PRL with hsCRP or fibrinogen.

CONCLUSIONS

Serum PRL concentrations are associated with inflammatory biomarkers including IL-6 and WBC, but not hsCRP or fibrinogen. The suggested role of PRL in inflammation needs further investigation in future prospective studies.

Leptin in hepatocellular carcinoma

The risk factors for hepatocellular carcinoma (HCC) development have been established, and include chronic hepatitis B and C, heavy alcohol consumption, and aflatoxins. In fact, 5%-30% of patients with HCC still lack a readily identifiable risk factor. It has been reported that the majority of ‘‘cryptogenic’’ HCC may be attributed to nonalcoholic fatty liver disease, the hepatic presentation of the metabolic syndrome (MS). Obesity is associated with the development of the MS. Recently, adipose tissue has been considered as an endocrine organ because of its capacity to secrete a variety of cytokines, which are collectively known as the adipokines. Leptin, the product of the obese gene, is mainly produced by adipose tissue. Since leptin was first characterized in 1994, accumulated literature has demonstrated the involvement of this adipokine in several areas of human physiology. After binding to its receptor, leptin initiates a cascade of signaling events and subsequent cellular effects. In addition to being the regulatory mediator of energy homeostasis, several in vitro studies have demonstrated the fibrogenic role of leptin in the liver. Furthermore, the deregulated expression of leptin and its receptor have been demonstrated to be associated with a variety of metabolic disorders as well as human cancers. Most importantly, direct evidence supporting the inhibitory and/or activating role of leptin in the process of carcinogenesis and progression of human HCC has been accumulating rapidly. This review aims to provide important insights into the potential mechanisms of leptin in the development of HCC. Hopefully, further investigations will shed light on a new therapeutic target in HCC.