Hypoadiponectinemia in lean lactating women: Prolactin inhibits adiponectin secretion from human adipocytes

Prolactin effects on the pathogenesis of diabetes mellitus

BACKGROUND

Prolactin (PRL) is a pituitary hormone promoting lactation in response to the suckling reflex. Beyond its well-known effects, novel tissue-specific and metabolic functions of PRL are emerging.

AIMS

To dissect PRL as a critical mediator of whole-body gluco-insulinemic sensitivity.

METHODS

PubMed-based search with the following terms 'prolactin', 'glucose metabolism', 'type 2 diabetes mellitus', 'type 1 diabetes mellitus', 'gestational diabetes mellitus' was performed.

DISCUSSION

The identification of the PRL-glucose metabolism network poses the basis for unprecedented avenues of research in the pathogenesis of diabetes mellitus type 1 or 2, as well as of gestational diabetes. In this regard, it is of timely relevance to define properly the homeostatic PRL serum levels since glucose metabolism could be influenced by the circulating amount of the hormone.

RESULTS

This review underscores the basic mechanisms of regulation of pancreatic β-cell functions by PRL and provides a revision of articles which have investigated the connection between PRL unbalancing and diabetes mellitus. Future studies are needed to elucidate the burden and the role of PRL in the regulation of glucose metabolism and determine the specific PRL threshold that may impact the management of diabetes.

CONCLUSION

A careful evaluation and context-driven interpretation of PRL levels (e.g., pregnancy, PRL-secreting pituitary adenomas, drug-related hyper- and hypoprolactinemia) could be critical for the correct screening and management of glucometabolic disorders, such as type 1 or 2 as well as gestational diabetes mellitus.

Severe Hyperprolactinemia Promotes Brown Adipose Tissue Whitening and Aggravates High Fat Diet Induced Metabolic Imbalance

BACKGROUND

The association of high serum prolactin and increased body weight is positive but controversial, therefore we hypothesized that additional factors such as diets and the impact of prolactin on brown adipose tissue may condition its metabolic effects.

METHODS

We used LacDrd2KO females with lifelong severe hyperprolactinemia due dopamine-D2 receptor deletion from lactotropes, and slow onset of metabolic disturbances, and compared them to their respective controls (Drd2 ^loxP/loxP ). Food intake, and binge eating was evaluated. We then challenged mice with a High Fat (HFD) or a Control Diet (CD) for 8 weeks, beginning at 3 months of age, when no differences in body weight are found between genotypes. At the end of the protocol brown and white adipose tissues were weighed, and thermogenic and lipogenic markers studied, using real time PCR (Ucp1, Cidea, Pgc1a, Lpl, adiponectin, Prlr) or immunohistochemistry (UCP1). Histochemical analysis of brown adipose tissue, and glucose tolerance tests were performed.

RESULTS

Hyperprolactinemic mice had increased food intake and binge eating behavior. Metabolic effects induced by a HFD were exacerbated in lacDrd2KO mice. Hyperprolactinemia aggravated HFD-induced body weight gain and glucose intolerance. In brown adipose tissue pronounced cellular whitening as well as decreased expression of the thermogenic markers Ucp1 and Pgc1a were observed in response to high prolactin levels, regardless of the diet, and furthermore, hyperprolactinemia potentiated the decrease in Cidea mRNA expression induced by HFD. In subcutaneous white adipose tissue hyperprolactinemia synergistically increased tissue weight, while decreasing Prlr, Adiponectin and Lpl mRNA levels regardless of the diet.

CONCLUSIONS

Pathological hyperprolactinemia has a strong impact in brown adipose tissue, lowering thermogenic markers and evoking tissue whitening. Furthermore, it modifies lipogenic markers in subcutaneous white adipose, and aggravates HFD-induced glucose intolerance and Cidea decrease. Therefore, severe high prolactin levels may target BAT function, and furthermore represent an adjuvant player in the development of obesity induced by high fat diets.

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.

Metabolic effects of prolactin and the role of dopamine agonists: A review

Prolactin is a polypeptide hormone that is well known for its role in reproductive physiology. Recent studies highlight its role in neurohormonal appetite regulation and metabolism. Elevated prolactin levels are widely associated with worsening metabolic disease, but it appears that low prolactin levels could also be metabolically unfavorable. This review discusses the pathophysiology of prolactin related metabolic changes, and the less commonly recognized effects of prolactin on adipose tissue, pancreas, liver, and small bowel. Furthermore, the effect of dopamine agonists on the metabolic profiles of patients with hyperprolactinemia are discussed as well.

Hyperprolactinemia using domperidone in prepubertal gilts: Effects on hormonal status, mammary development and mammary and pituitary gene expression

Objectives of this experiment were to determine if the domperidone protocol previously used for gestating gilts can also lead to hyperprolactinemia in growing gilts, and to assess the effects of such a protocol on hormonal status, mammary development and gene expression in mammary and pituitary tissue of gilts at puberty. The impact on future lactation performance was also determined. At 75 ± 3 kg body weight (BW), gilts were divided between: 1) controls (CTL), receiving daily intramuscular (IM) injections of canola oil (1.1 mL) for 29 d (n = 41), and 2) treated (DOMP), receiving daily IM injections with 0.5 mg/kg BW of the dopamine receptor antagonist domperidone for 29 d (n = 40). In addition to that daily injection, treated gilts also received twice daily IM injections with 0.5 mg/kg BW of domperidone over the first 3 d of treatment. Fifteen gilts per treatment were sacrificed at 210 ± 5 d of age to collect mammary glands (for compositional analysis and gene expression) and the anterior pituitary (for gene expression). Remaining gilts were bred and allowed to farrow. Blood was sampled at the onset of treatment and on days 14 and 30. Gilts that farrowed were also blood sampled on days 3 and 20 of lactation. Blood was assayed for prolactin (PRL), leptin, insulin-like growth factor 1 (IGF-1), urea, free fatty acids and glucose. Concentrations of PRL increased after 14 d and 30 d of treatment (P < 0.01) and were lesser on day 3 of lactation in DOMP than CTL gilts (P < 0.01). At puberty, there were tendencies (P < 0.10) for total parenchymal protein and DNA to be greater in DOMP than CTL gilts. Treatment did not affect mRNA abundance of PRL or the long form of the PRL receptor genes in the pituitary gland at puberty but expression level of the dopamine receptor D2 and PRL genes was much lower in pubertal than late-pregnant gilts (P < 0.001). Furthermore, many genes related with PRL had a much greater expression level in late pregnancy than at puberty. On day 20 of lactation, CTL sows had greater concentrations of urea than DOMP sows (P < 0.01). The growth rate of litters was not affected by treatment nor was milk composition (P > 0.10). Even though PRL concentrations were increased with treatment, the absence of effect on mammary development was either due to timing relative to developmental stage, whereby treatment was initiated when gilts were too young, or was because all PRL receptors may have been saturated thereby preventing biological action of additional PRL.

Lactation Versus Formula Feeding: Insulin, Glucose, and Fatty Acid Metabolism During the Postpartum Period

Milk production may involve a transient development of insulin resistance in nonmammary tissues to support redistribution of maternal macronutrients to match the requirements of the lactating mammary gland. In the current study, adipose and liver metabolic responses were measured in the fasting state and during a two-step (10 and 20 mU/m²/min) hyperinsulinemic-euglycemic clamp with stable isotopes, in 6-week postpartum women who were lactating (n = 12) or formula-feeding (n = 6) their infants and who were closely matched for baseline characteristics (e.g., parity, body composition, and intrahepatic lipid). When controlling for the low insulin concentrations of both groups, the lactating women exhibited a fasting rate of endogenous glucose production (EGP) that was 2.6-fold greater and a lipolysis rate that was 2.3-fold greater than the formula-feeding group. During the clamp, the groups exhibited similar suppression rates of EGP and lipolysis. In the lactating women only, higher prolactin concentrations were associated with greater suppression rates of lipolysis and lower intrahepatic lipid and plasma triacylglycerol concentrations. These data suggest that whole-body alterations in glucose transport may be organ specific and facilitate nutrient partitioning during lactation. Recapitulating a shift toward noninsulin-mediated glucose uptake could be an early postpartum strategy to enhance lactation success in women at risk for delayed onset of milk production.

Plasma Prolactin and Progesterone Levels and the Risk of Gestational Diabetes: A Prospective and Longitudinal Study in a Multiracial Cohort

Objective: Prolactin and progesterone are implicated in glucose homeostasis in and outside of pregnancy. However, their associations with gestational diabetes (GDM) risk were not well-understood. This study investigates this question in a prospective and longitudinal cohort. Methods: This is a nested case-control study of 107 incident GDM cases and 214 matched non-GDM controls within the NICHD Fetal Growth Studies-Singleton Cohort. Blood samples were collected at gestational weeks 10-14, 15-26, 23-31, and 33-39. The odds ratios (OR) of GDM were estimated using conditional logistic regression. The longitudinal changes in prolactin and progesterone were estimated using linear mixed-effects models. Results: Compared to controls, cases have significantly higher prolactin levels at weeks 10-14 (median: 50.4 vs. 42.1 ng/mL), and significantly lower progesterone levels at weeks 10-14 (median: 109.4 vs. 126.5 nmol/L). Prolactin levels at weeks 10-14 were significantly and positively associated with GDM risk; the adjusted ORs across increasing quartiles were 1.00, 1.13, 1.80, 2.33 (p-trend = 0.02). A similar but slightly attenuated association was observed at weeks 15-26 (p-trend = 0.05). Progesterone was not associated with GDM risk at either time points. Longitudinal changes in prolactin and progesterone between the first two visits were not associated with GDM risk. In addition, prolactin was significantly and positively associated with insulin and C-peptide levels at weeks 10-14, and significantly and inversely associated with C-peptide levels at weeks 15-26; progesterone was significantly and inversely associated with glucose and insulin levels. Conclusions: This study provided the first prospective evidence of a positive association between prolactin levels in early pregnancy and GDM risk.

The level of bile salt-stimulated lipase in the milk of Chinese women and its association with maternal BMI

This study aimed to investigate the bile salt-stimulated lipase (BSSL) concentration in the milk of Chinese women and its correlation with maternal body mass index (BMI), gestational diabetes mellitus (GDM) and gestational hypertensive disorder (GHD). The BSSL levels in the milk samples were measured by enzyme-linked immunosorbent assay (ELISA). BSSL level in colostrum milk of mothers with full-term infants was positively correlated with pregnancy week and negatively correlated with maternal pre-pregnancy BMI and BMI late in pregnancy. Moreover, the BSSL concentration in mature milk was positively correlated with BMI gain during pregnancy. The BSSL concentration in colostrum milk was lower in GDM mothers than in normal mothers. The BSSL helps infants digest fat in early life and its level was associated with lactation. The changes in BSSL characteristics with maternal BMI and GDM in this study may have clinical implications regarding the effects of pregnancy weight and metabolism on the nutrition and health of the offspring.

Metabolic and Endocrine Role of Adipose Tissue During Lactation

The adipose tissue serves an essential role for survival and reproduction in mammals, especially females. It serves primarily as an energy storage organ and is directly linked to the reproductive success of mammals. In wild animals, adipose tissue function is linked to seasonality of the food supply to support fetal growth and milk production. Adipose tissue depots in ruminants and non-ruminants can secrete many signal molecules (adipokines) that act as hormones and as pro- and anti-inflammatory cytokines. The visceral adipose tissue especially appears to be more endocrinologically active than other adipose depots. The endocrine function is important for the overall long-term regulation of energy metabolism and plays an important role in the adaptation to lactation in many mammalian species, including humans. Furthermore, endocrine signals from adipose tissue depots contribute to fertility modulation, immune function, and inflammatory response. Energy homeostasis is modulated by changes in feed intake, insulin sensitivity, and energy expenditure, processes that can be influenced by adipokines in the brain and in peripheral tissues.

Maternal metabolic adaptations to pregnancy among young women in Cebu, Philippines

OBJECTIVES

Evidence that fetal development has long-term impacts on health has increased interest in maternal-fetal nutrient exchange. Although maternal metabolism is known to change during gestation to accommodate fetal nutrient demands, little is known about these modifications outside of a Western, clinical context. This study characterizes maternal metabolic adaptations to pregnancy, and their associations with offspring birth weight (BW), among women living in the Philippines.

METHODS

Fasting glucose, triglycerides, insulin, leptin, and adiponectin were assessed in 808 participants in the Cebu Longitudinal Health and Nutrition Survey (Metropolitan Cebu, Philippines). Cross-sectional relationships between metabolites and hormones and gestational and lactational status were evaluated. Among the subset of currently pregnant women, associations between maternal glucose and triglycerides and offspring BW were also examined.

RESULTS

Women in their second and third trimesters had significantly lower fasting glucose and adiponectin compared to nulliparous women, and leptin levels and triglyceride levels were notably higher late in pregnancy (all P < .05). Among pregnant women, fasting glucose was a positive predictor of offspring BW, but only in males (P = .012, R²  = .28). Hormones and metabolites in post-partum women trend back toward levels found in nulliparous women, with some differences by breastfeeding status.

CONCLUSIONS

We find evidence for marked changes in maternal lipid and carbohydrate metabolism during pregnancy, consistent with known adaptations to support fetal growth. The finding of sex-specific relationships between maternal glucose and offspring BW adds to evidence for greater impacts of the maternal-gestational environment on biology and health in male offspring.

Chronic hyperprolactinemia evoked by disruption of lactotrope dopamine D2 receptors impacts on liver and adipocyte genes related to glucose and insulin balance

We studied the impact of high prolactin titers on liver and adipocyte gene expression related to glucose and insulin homeostasis in correlation with obesity onset. To that end we used mutant female mice that selectively lack dopamine type 2 receptors (D2Rs) from pituitary lactotropes (lacDrd2KO), which have chronic high prolactin levels associated with increased body weight, marked increments in fat depots, adipocyte size, and serum lipids, and a metabolic phenotype that intensifies with age. LacDrd2KO mice of two developmental ages, 5 and 10 mo, were used. In the first time point, obesity and increased body weight are marginal, although mice are hyperprolactinemic, whereas at 10 mo there is marked adiposity with a 136% increase in gonadal fat and a 36% increase in liver weight due to lipid accumulation. LacDrd2KO mice had glucose intolerance, hyperinsulinemia, and impaired insulin response to glucose already in the early stages of obesity, but changes in liver and adipose tissue transcription factors were time and tissue dependent. In chronic hyperprolactinemic mice liver Prlr were upregulated, there was liver steatosis, altered expression of the lipogenic transcription factor Chrebp, and blunted response of Srebp-1c to refeeding at 5 mo of age, whereas no effect was observed in the glycogenesis pathway. On the other hand, in adipose tissue a marked decrease in lipogenic transcription factor expression was observed when morbid obesity was already settled. These adaptive changes underscore the role of prolactin signaling in different tissues to promote energy storage.

Changes in Maternal Plasma Adiponectin from Late Pregnancy to the Postpartum Period According to the Mode of Delivery: Results from a Prospective Cohort in Rio de Janeiro, Brazil

INTRODUCTION

Maternal plasma adiponectin is inversely related to insulin resistance, atherosclerosis and child health. However, little is known about its concentrations in the perinatal period, especially according to mode of delivery. Our aim is to evaluate the association between mode of delivery and changes in maternal plasma adiponectin from 3rd trimester of pregnancy to 30-45 days postpartum.

METHODS

A cohort was recruited in Rio de Janeiro, Brazil, with four waves of follow-up: 5-13th, 22-26th, 30-36th gestational weeks and 30-45 days postpartum. Eligible subjects should be between 20-40 years of age, be free of chronic and infectious diseases and presenting with a singleton pregnancy. The mode of delivery was classified as vaginal (VD) or cesarean (CS). Plasma adiponectin concentration (μg/mL) was measured using commercial ELISA kits. Statistical analyses included the Wilcoxon rank-sum test and the multiple linear mixed effects model.

RESULTS

A total of 159 participated in the study. Median adiponectin concentrations were higher for the VD group (n = 99; 8.25, IQR: 5.85-11.90) than for the CS group (n = 60; 7.34, IQR: 4.36-9.76; p = 0.040) in the postpartum samples but were not different between the two groups in the 3rd trimester. Women who underwent CS had a lower rate of increase in adiponectin concentration from the 3rd trimester to 30-45 days postpartum compared to those who underwent VD (β = -.15, 95% CI: -.28-.02, p = 0.030).

CONCLUSION

The CS procedure was associated with lower maternal circulating concentrations of adiponectin at 30-45 days postpartum, compared to the VD.

Placental origins of adverse pregnancy outcomes: potential molecular targets: an Executive Workshop Summary of the Eunice Kennedy Shriver National Institute of Child Health and Human Development

Although much progress is being made in understanding the molecular pathways in the placenta that are involved in the pathophysiology of pregnancy-related disorders, a significant gap exists in the utilization of this information for the development of new drug therapies to improve pregnancy outcome. On March 5-6, 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health sponsored a 2-day workshop titled Placental Origins of Adverse Pregnancy Outcomes: Potential Molecular Targets to begin to address this gap. Particular emphasis was given to the identification of important molecular pathways that could serve as drug targets and the advantages and disadvantages of targeting these particular pathways. This article is a summary of the proceedings of that workshop. A broad number of topics were covered that ranged from basic placental biology to clinical trials. This included research in the basic biology of placentation, such as trophoblast migration and spiral artery remodeling, and trophoblast sensing and response to infectious and noninfectious agents. Research findings in these areas will be critical for the formulation of the development of future treatments and the development of therapies for the prevention of a number of pregnancy disorders of placental origin that include preeclampsia, fetal growth restriction, and uterine inflammation. Research was also presented that summarized ongoing clinical efforts in the United States and in Europe that has tested novel interventions for preeclampsia and fetal growth restriction, including agents such as oral arginine supplementation, sildenafil, pravastatin, gene therapy with virally delivered vascular endothelial growth factor, and oxygen supplementation therapy. Strategies were also proposed to improve fetal growth by the enhancement of nutrient transport to the fetus by modulation of their placental transporters and the targeting of placental mitochondrial dysfunction and oxidative stress to improve placental health. The roles of microRNAs and placental-derived exosomes, as well as messenger RNAs, were also discussed in the context of their use for diagnostics and as drug targets. The workshop discussed the aspect of safety and pharmacokinetic profiles of potential existing and new therapeutics that will need to be determined, especially in the context of the unique pharmacokinetic properties of pregnancy and the hurdles and pitfalls of the translation of research findings into practice. The workshop also discussed novel methods of drug delivery and targeting during pregnancy with the use of macromolecular carriers, such as nanoparticles and biopolymers, to minimize placental drug transfer and hence fetal drug exposure. In closing, a major theme that developed from the workshop was that the scientific community must change their thinking of the pregnant woman and her fetus as a vulnerable patient population for which drug development should be avoided, but rather be thought of as a deprived population in need of more effective therapeutic interventions.

Hyperprolactinemia induced by hCG leads to metabolic disturbances in female mice

The metabolic syndrome is a growing epidemic; it increases the risk for diabetes, cardiovascular disease, fatty liver, and several cancers. Several reports have indicated a link between hormonal imbalances and insulin resistance or obesity. Transgenic (TG) female mice overexpressing the human chorionic gonadotropin β-subunit (hCGβ+ mice) exhibit constitutively elevated levels of hCG, increased production of testosterone, progesterone and prolactin, and obesity. The objective of this study was to investigate the influence of hCG hypersecretion on possible alterations in the glucose and lipid metabolism of adult TG females. We evaluated fasting serum insulin, glucose, and triglyceride levels in adult hCGβ+ females and conducted intraperitoneal glucose and insulin tolerance tests at different ages. TG female mice showed hyperinsulinemia, hypertriglyceridemia, and dyslipidemia, as well as glucose intolerance and insulin resistance at 6 months of age. A 1-week treatment with the dopamine agonist cabergoline applied on 5-week-old hCGβ+ mice, which corrected hyperprolactinemia, hyperandrogenism, and hyperprogesteronemia, effectively prevented the metabolic alterations. These data indicate a key role of the hyperprolactinemia-induced gonadal dysfunction in the metabolic disturbances of hCGβ+ female mice. The findings prompt further studies on the involvement of gonadotropins and prolactin on metabolic disorders and might pave the way for the development of new therapeutic strategies.

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.

The modulation of adiponectin by STAT5-activating hormones

Adiponectin is a hormone secreted from adipocytes that plays an important role in insulin sensitivity and protects against metabolic syndrome. Growth hormone (GH) and prolactin (PRL) are potent STAT5 activators that regulate the expression of several genes in adipocytes. Studies have shown that the secretion of adiponectin from adipose tissue is decreased by treatment with PRL and GH. In this study, we demonstrate that 3T3-L1 adipocytes treated with GH or PRL exhibit a reduction in adiponectin protein levels. Furthermore, we identified three putative STAT5 binding sites in the murine adiponectin promoter and show that only one of these, located at -3,809, binds nuclear protein in a GH- or PRL-dependent manner. Mutation of the STAT5 binding site reduced PRL-dependent protein binding, and supershift analysis revealed that STAT5A and -5B, but not STAT1 and -3, bind to this site in response to PRL. Chromatin immunoprecipitation (IP) analysis demonstrated that only STAT5A, and not STAT1 and -3, bind to the murine adiponectin promoter in a GH-dependent manner in vivo. Adiponectin promoter/reporter constructs were responsive to GH, and chromatin IP analysis reveals that STAT5 binds the adiponectin promoter in vivo following GH stimulation. Overall, these data strongly suggest that STAT5 activators regulate adiponectin transcription through the binding of STAT5 to the -3,809 site that leads to decreased adiponectin expression and secretion. These mechanistic observations are highly consistent with studies in mice and humans that have high GH or PRL levels that are accompanied by lower circulating levels of adiponectin.

Lactation and Progression to Type 2 Diabetes Mellitus After Gestational Diabetes Mellitus: A Prospective Cohort Study

BACKGROUND

Lactation improves glucose metabolism, but its role in preventing type 2 diabetes mellitus (DM) after gestational diabetes mellitus (GDM) remains uncertain.

OBJECTIVE

To evaluate lactation and the 2-year incidence of DM after GDM pregnancy.

DESIGN

Prospective, observational cohort of women with recent GDM. (ClinicalTrials.gov: NCT01967030).

SETTING

Integrated health care system.

PARTICIPANTS

1035 women diagnosed with GDM who delivered singletons at 35 weeks' gestation or later and enrolled in the Study of Women, Infant Feeding and Type 2 Diabetes After GDM Pregnancy from 2008 to 2011.

MEASUREMENTS

Three in-person research examinations from 6 to 9 weeks after delivery (baseline) and annual follow-up for 2 years that included 2-hour, 75-g oral glucose tolerance testing; anthropometry; and interviews. Multivariable Weibull regression models evaluated independent associations of lactation measures with incident DM adjusted for potential confounders.

RESULTS

Of 1010 women without diabetes at baseline, 959 (95%) were evaluated up to 2 years later; 113 (11.8%) developed incident DM. There were graded inverse associations for lactation intensity at baseline with incident DM and adjusted hazard ratios of 0.64, 0.54, and 0.46 for mostly formula or mixed/inconsistent, mostly lactation, and exclusive lactation versus exclusive formula feeding, respectively (P trend = 0.016). Time-dependent lactation duration showed graded inverse associations with incident DM and adjusted hazard ratios of 0.55, 0.50, and 0.43 for greater than 2 to 5 months, greater than 5 to 10 months, and greater than 10 months, respectively, versus 0 to 2 months (P trend = 0.007). Weight change slightly attenuated hazard ratios.

LIMITATION

Randomized design is not feasible or desirable for clinical studies of lactation.

CONCLUSION

Higher lactation intensity and longer duration were independently associated with lower 2-year incidences of DM after GDM pregnancy. Lactation may prevent DM after GDM delivery.

PRIMARY FUNDING SOURCE

National Institute of Child Health and Human Development.

Lower levels of human milk adiponectin predict offspring weight for age: a study in a lean population of Filipinos

Prior studies have reported a significant, inverse association between adiponectin in human milk and offspring growth velocity. Less is known about this association in populations characterised by a loss of weight for age z-scores (WAZs) in early life. We investigated the association between maternal body composition and milk adiponectin in a sample of Filipino mothers. We then tested for an association between milk adiponectin and size for age in their infants. A total of 117 Filipino mothers nursing infants from 0 to 24 months were recruited from Cebu, Philippines. Anthropometrics, interviews and milk samples were collected and analysed using standard protocols. Mean milk adiponectin in this sample was 7.47 ± 5.75 ng mL(-1) . Mean infant WAZ and weight for length (WLZ) decreased with age. Maternal body composition was not associated with milk adiponectin content. Milk adiponectin had a significant, positive association with infant WAZ and WLZ. Prior reports have found an inverse association between milk adiponectin and infant WAZ. Here, we report that in lean populations with lower milk adiponectin, there is a positive association with infant WAZ, possibly reflecting pleiotropic biological functions of adiponectin for post-natal growth. This study increases the understanding of normal biological variation in milk adiponectin and the consequences of low levels of milk adiponectin for offspring growth.

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.

Lactation intensity and fasting plasma lipids, lipoproteins, non-esterified free fatty acids, leptin and adiponectin in postpartum women with recent gestational diabetes mellitus: the SWIFT cohort

OBJECTIVES

Lactation may influence future progression to type 2 diabetes after gestational diabetes mellitus (GDM). However, biomarkers associated with progression to glucose intolerance have not been examined in relation to lactation intensity among postpartum women with previous GDM. This study investigates whether higher lactation intensity is related to more favorable blood lipids, lipoproteins and adipokines after GDM pregnancy independent of obesity, socio-demographics and insulin resistance.

METHODS

The Study of Women, Infant Feeding, and Type 2 Diabetes (SWIFT) is a prospective cohort study that recruited 1035 women diagnosed with GDM by the 3-h 100g oral glucose tolerance tests (OGTTs) after delivery of a live birth in 2008-2011. Research staff conducted 2-h 75 g OGTTs, and assessed lactation intensity, anthropometry, lifestyle behaviors and socio-demographics at 6-9 weeks postpartum (baseline). We assayed fasting plasma lipids, lipoproteins, non-esterified free fatty acids, leptin and adiponectin from stored samples obtained at 6-9 weeks postpartum in 1007 of the SWIFT participants who were free of diabetes at baseline. Mean biomarker concentrations were compared among lactation intensity groups using multivariable linear regression models.

RESULTS

Increasing lactation intensity showed graded monotonic associations with fully adjusted mean biomarkers: 5%-8% higher high-density lipoprotein cholesterol (HDL-cholesterol), 20%-28% lower fasting triglycerides, 15%-21% lower leptin (all trend P-values < 0.01), and with 6% lower adiponectin, but only after adjustment for insulin resistance (trend P-value = 0.04).

CONCLUSION

Higher lactation intensity was associated with more favorable biomarkers for type 2 diabetes, except for lower plasma adiponectin, after GDM delivery. Long-term follow-up studies are needed to assess whether these effects of lactation persist to predict progression to glucose intolerance.

Supplementation with conjugated linoleic acids extends the adiponectin deficit during early lactation in dairy cows

Decreasing insulin sensitivity (IS) in peripheral tissues allows for partitioning nutrients towards the mammary gland. In dairy cows, extensive lipid mobilization and continued insulin resistance (IR) are typical for early lactation. Adiponectin, an adipokine, promotes IS. Supplementation with conjugated linoleic acids (CLA) in rodents and humans reduces fat mass whereby IR and hyperinsulinemia may occur. In dairy cows, CLA reduce milk fat, whereas body fat, serum free fatty acids and leptin are not affected. We aimed to investigate the effects of CLA supplementation on serum and adipose tissue (AT) adiponectin concentrations in dairy cows during the lactation driven and parity modulated changes of metabolism. High yielding cows (n=33) were allocated on day 1 post partum to either 100 g/day of a CLA mixture or a control fat supplement (CON) until day 182 post partum. Blood and subcutaneous (sc) AT (AT) biopsy samples were collected until day 252 post partum to measure adiponectin. Serum adiponectin decreased from day 21 pre partum reaching a nadir at calving and thereafter increased gradually. The distribution of adiponectin molecular weight forms was neither affected by time, parity nor treatment. Cows receiving CLA had decreased serum adiponectin concentrations whereby primiparous cows responded about 4 weeks earlier than multiparous cows. The time course of adiponectin concentrations in sc AT (corrected for residual blood) was similar to serum concentrations, without differences between CLA and CON. CLA supplementation attenuated the post partum increase of circulating adiponectin thus acting towards prolongation of peripartal IR and drain of nutrients towards the mammary gland.

Correlation between serum adiponectin and clinical characteristics, biochemical parameters in Indian women with polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common disorder. PCOS women are at a high risk for insulin resistance and metabolic syndrome (MS). Adiponectin is positively related to insulin sensitivity. It has a preventive role in atherogenesis and MS. The present work was conducted to study the correlation between serum adiponectin levels and clinical characteristics and biochemical parameters in PCOS patients.

MATERIALS AND METHODS

A prospective study in 49 newly diagnosed (as per Rotterdam criteria) Indian PCOS women was conducted. PCOS women were clinically examined and investigated for biochemical parameters.

RESULTS

The mean serum adiponectin was 12 ± 9.4 μg/mL (range 0.47-45). Hypoadiponectinemia (serum adiponectin <4 μg/mL) was present in 22% patients. Age and adiponectin correlated significantly and inversely (r = -0.42, P = 0.027). Overweight/obese patients had lower mean adiponectin levels than normal weight (11.62 ± 9.5 vs 13.58 ± 9.5, P = 0.56). It was significantly lower in patients with acanthosis nigricans (AN) as compared with those without AN (8.4 ± 5.9 vs 15 ± 11, P = 0.038). Hirsute patients showed lower mean adiponectin levels than nonhirsute (10 ± 7.3 vs 13 ± 10, P = 0.57). A positive, insignificant correlation was observed between serum adiponectin and cholesterol, low-density lipoprotein, follicle stimulating hormone (FSH), thyroid stimulating hormone, levels. A negative insignificant correlation existed between serum adiponectin and luteinizing hormone (LH), LH: FSH ratio, prolactin, dehydroepiandrosterone, testosterone, triglyceride, high-density lipoprotein, fasting blood glucose, fasting insulin, and Homeostasis Model Assessment.

CONCLUSION

Hypoadiponectinemia is present in one-fifth of women with PCOS. Adiponectin levels decrease as age advances. Low levels of adiponectin possibly contributes to the development of dermal manifestation (AN) of insulin resistance.

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.

Adiponectin links adipose tissue function and monocyte inflammatory responses during bovine metabolic stress

The periparturient period of dairy cows is characterized by intense lipid mobilization from adipose tissue leading to increased plasma concentrations of nonesterified fatty acids (NEFA). High NEFA are a predisposing factor for inflammatory based diseases. A major component of these diseases is uncontrolled macrophage/monocyte inflammatory responses. Changes in the endocrine activity of adipose tissue during the periparturient period could impact macrophage function by modifying the secretion of adipokines including adiponectin. Currently, the effects of adiponectin on monocyte activation in dairy cattle are unknown. In humans and rodents, this adipokine regulates monocyte phenotype and alterations in its plasma levels are linked with the development of inflammatory diseases. The objectives of this study were to establish associations between plasma adiponectin expression dynamics and different markers of lipid mobilization during the periparturient period of dairy cows and to characterize the effects of adiponectin on the inflammatory response of bovine monocytes. Plasma adiponectin, NEFA, BHB, albumin, and subcutaneous and retroperitoneal fat depots depth were measured during the periparturient period of dairy cows. In vitro, bovine monocytes were cultured with adiponectin to assess changes in pro-inflammatory responses following LPS stimulation. Results from this study demonstrate that alterations in plasma adiponectin levels in periparturient cattle are inversely correlated with the concentrations of plasma NEFA, an important marker of lipid mobilization. Furthermore, adiponectin exposure significantly decreased monocyte expression of TNFα after LPS stimulation thus markedly reducing their inflammatory response. Reduced plasma adiponectin during the periparturient period could predispose dairy cows to the development of uncontrolled monocyte inflammatory responses.

Prolactin and adipose tissue

The pituitary lactogenic hormone prolactin (PRL) exerts various physiological actions in humans and rodents via its binding to a membrane receptor. Beside its role in lactation and reproduction, accumulating evidence suggests that PRL has a crucial impact on energy balance by acting on two key players, the pancreas and the adipose tissue. Adipose tissue is now recognized as an endocrine organ and its metabolic activity appears to play an important role in pathophysiology such as obesity and diabetes. White adipocytes store excess of energy in the form of triglycerides for future need while brown adipocytes metabolize lipids and glucose to produce heat, highlighting their different metabolic functionality. The plasticity of white adipose tissue, by the emergence of beige adipocytes, appears to be essential in energy homeostasis. PRL receptor deficient mice provided direct evidence that PRL signaling is involved in the regulation of adipogenesis affecting energy balance and metabolic adaptation most notably during development. Moreover, it was demonstrated that PRL signaling participates to brown adipose tissue differentiation and function, opening novel understanding of hormonal regulation of energy balance. This review summarizes our current knowledge about PRL signaling and its role on adipose tissue.

Drug-induced hypo- and hyperprolactinemia: mechanisms, clinical and therapeutic consequences

INTRODUCTION

The altered profiles of prolactin secretion in the anterior hypophysis, generated by pathological, pharmacological or toxicological causes, have special consequences on multiple functions in both genders.

AREAS COVERED

This selective review presents the main mechanisms controlling prolactin secretion, focusing on the interplay of various neurotransmitters or xenobiotics, but also on the role of psychic or posttraumatic stress. A detailed analysis of several pharmacotherapeutic groups with hyperprolactinemic effects emphasize on the relevance of the pharmacokinetic/pharmacodynamic mechanisms and the clinical significance of the long term administration.

EXPERT OPINION

Accurate monitoring and evaluation of the hyperprolactinemia induced by xenobiotics is strongly recommended. The typical antipsychotics and some of the atypical agents (amisulpride, risperidone, paliperidone), as well as some antidepressants, antihypertensives and prokinetics, are the most important groups inducing hyperprolactinemia. The hyperprolactinemic effects are correlated with their affinity for dopamine D2 receptors, their blood-brain barrier penetration and, implicitly, the requested dose for adequate occupancy of cerebral D2 receptors. Consequently, integration of available pharmacokinetic and pharmacodynamic data supports the idea of therapeutic switch to non-hyperprolactinemic agents (especially aripiprazole) or their association, for an optimal management of antipsychotic-induced hyperprolactinemia. Possible alternative strategies for counteracting the xenobiotics-induced hyperprolactinemia are also mentioned.

Adiponectin deficit during the precarious glucose economy of early lactation in dairy cows

In rodents and primates, insulin resistance develops during pregnancy and fades after parturition. In contrast, dairy cows and other ruminants maintain insulin resistance in early lactation (EL). This adaptation favors mammary glucose uptake, an insulin-independent process, at a time when the glucose supply is scarce. Reduction in circulating levels of the insulin-sensitizing hormone adiponectin promotes insulin resistance in other species, but whether it contributes to insulin resistance in EL dairy cows is unknown. To address this question, plasma adiponectin was measured in high-yielding dairy cows during the transition from late pregnancy (LP) to EL. Plasma adiponectin varied in quadratic fashion with the highest levels in LP, a maximal reduction of 45% on the day after parturition and a progressive return to LP values over the next 8 wk. Adiponectin circulated nearly exclusively in high molecular weight complexes in LP, and this distribution remained unaffected in EL. The reduction of plasma adiponectin in EL occurred without changes in adiponectin mRNA in adipose tissue but was associated with repression of the expression of proteins associated with the endoplasmic reticulum and involved in assembly of adiponectin oligomers. Finally, EL increased the expression of the adiponectin receptor 1 in muscle and adiponectin receptor 2 in liver but had no effect on the expression of these receptors in adipose tissue and in the mammary gland. These data suggest that reduced plasma adiponectin belongs to the subset of hormonal adaptations in EL dairy cows facilitating mammary glucose uptake via promotion of insulin resistance.

Changes in circulating adiponectin and metabolic hormone concentrations during periparturient and lactation periods in Holstein dairy cows

Although our previous report demonstrated that adiponectin and AdipoR1 gene expressions changed among different lactation stages in the bovine mammary gland, its in vivo kinetics remain unclear in ruminant animals. In this study, we investigated the changes in circulating concentrations of adiponectin, as well as other metabolic hormones and metabolites, (i) during the periparturient period and (ii) among different lactation stages, in Holstein dairy cows. In experiment 1, serum adiponectin concentrations increased after parturition. Serum insulin concentrations were lower in the postpartum than prepartum period, whereas serum growth hormone (GH) concentrations increased in the postpartum period. Serum nonesterified fatty acids (NEFA) levels were increased during the postpartum period and were dependent on the parity. In experiment 2, there was no significant difference in plasma adiponectin concentrations among lactational stages. Plasma insulin concentrations tended to be lower in early lactation while plasma GH levels tended to be higher. Plasma NEFA concentrations were significantly lower in mid- and late-lactation stages than non-lactation stages. These findings indicate that elevation of serum adiponectin might be involved in energy metabolism just around parturition, and might exert its action through regulation of receptor expression levels in target tissues in each lactational stage in Holstein dairy cows.

Randomized pilot study of cabergoline, a dopamine receptor agonist: effects on body weight and glucose tolerance in obese adults

AIM

Dopaminergic hypofunction and hyperprolactinaemia have been implicated in the pathogenesis of obesity and glucose intolerance. The aim of this pilot study was to determine the efficacy of cabergoline, a dopamine receptor agonist, on body weight and glucose tolerance in obese non-diabetic persons with normal plasma prolactin levels.

METHODS

This 16-week double blind, placebo-controlled pilot study randomized non-diabetic obese adults (body mass index 30-42 kg/m(2) ) to placebo or cabergoline (0.25 mg twice weekly for 4 weeks followed by 0.5 mg twice weekly for the next 12 weeks). Of 40 subjects enrolled, 29 completed 16 weeks: 16 randomized to placebo and 13 to cabergoline. All subjects were counselled on a 500 kcal/day calorie deficit diet. A 75-g oral glucose tolerance test was performed at baseline and at 16 weeks.

RESULTS

As expected, prolactin levels decreased after cabergoline (p < 0.001). Weight loss was similar after placebo compared with cabergoline treatment: 1.0 vs. 1.2% body weight, respectively. Fasting glucose levels did not differ between groups after treatment, however, 90-min postprandial glucose and insulin decreased in the cabergoline group only (p = 0.029). HOMA-IR (homeostasis model of assessment) increased by 40% after placebo and 1.5% after cabergoline treatment.

CONCLUSIONS

This pilot study suggests that cabergoline therapy may improve glucose tolerance independent of weight loss, however, a larger, longer term study of dopamine receptor agonist therapy in obese individuals is warranted to confirm this finding.

Nutritional and hormonal modulation of adiponectin and its receptors adipoR1 and adipoR2

Adiponectin is the most abundant plasma protein synthesized mostly by adipose tissue and is an insulin-sensitive hormone, playing a central role in glucose and lipid metabolism. Adiponectin effects are mediated via two receptors, adipoR1 and adipoR2. Several hormones and diet components that are involved in insulin resistance may impair insulin sensitivity at least in part by decreasing adiponectin and adiponectin receptors. Adiponectin expression and serum levels are associated with the amount and type of fatty acids and carbohydrate consumed. Other food items, such as vitamins, alcohol, sodium, green tea, and coffee, have been reported to modify adiponectin levels. Several hormones, including testosterone, estrogen, prolactin, glucocorticoids, catecholamines, and growth hormone, have been shown to inhibit adiponectin production, but the studies are still controversial. Even so, adiponectin is a potential therapeutic target in the treatment of diabetes mellitus and other diseases associated with hypoadiponectinemia.

Serum prolactin concentrations determine whether they improve or impair β-cell function and insulin sensitivity in diabetic rats

BACKGROUND

Prolactin improves glucose homeostasis by increasing β-cell mass under certain conditions such as pregnancy, whereas hyperprolactinaemia due to a pituitary gland adenoma tumour exacerbates insulin resistance. However, previous studies have not evaluated how prolactin modulates β-cell function and insulin sensitivity at different dosages. Here, we determined that chronic intraperitoneal injections of different dosages of prolactin have opposite effects on insulin resistance and β-cell function and mass in 90% pancreatectomized diabetic male rats, and the mechanisms were explored.

METHODS

Diabetic rats were divided into three groups according to the dose of intraperitoneally injected prolactin for 4 weeks: (1) low dose of prolactin (25 µg/kg bw/12 h), (2) high dose of prolactin (250 µg/kg bw/12 h), and (3) vehicle. As a non-diabetic control group, sham-operated rats were injected with vehicle.

RESULTS

Chronic high- and low-dose prolactin injections elevated serum prolactin levels by 2.5- and 11.8-fold, respectively. Both dosages promoted β-cell mass by increasing β-cell proliferation and neogenesis through the potentiation of phosphorylation of signal transducer and activator of transcription 5 and decreased menin expression in diabetic rats. However, only the low-dose prolactin injection potentiated glucose-stimulated insulin secretion though glucokinase and glucose transporter 2 induction in the diabetic rats. In addition, low-dose prolactin decreased hepatic glucose output in hyperinsulinaemic states, indicating an improvement in hepatic insulin resistance. However, the high-dose prolactin injection exacerbated whole-body and hepatic insulin resistance in diabetic rats.

CONCLUSIONS

In contrast to the normal adaptive increases in glucose-stimulated insulin secretion through expanded β-cell mass and insulin sensitivity realized with moderately increased prolactin levels, high levels of prolactin exacerbate insulin resistance and impair the insulin-secretory capacity in diabetic mice.

Insulin sensitivity in late gestation and early postpartum period: the role of circulating maternal adipokines

OBJECTIVE

Early postpartum period is characterised by a dramatic decrease in insulin resistance and significant metabolic alterations. The aims of this study were to determine the changes in circulating maternal concentrations of total adiponectin, adiponectin multimers, leptin and resistin before and after the delivery and to explore their relationship with insulin sensitivity.

METHODS

Twenty-seven normal pregnant women at term were included in this longitudinal study. Blood samples were taken before and 4 days after elective caesarean section. Total adiponectin, adiponectin multimers, leptin, resistin, glucose, insulin and prolactin were measured in maternal serum. Adiponectin multimers were measured before and after the delivery in eight women.

RESULTS

(1) The mean maternal serum total adiponectin concentration was significantly higher before than after delivery while the relative distribution of circulating maternal adiponectin multimers did not change after delivery; (2) the median maternal serum concentration of leptin was significantly higher in the antepartum than in the postpartum period; (3) the median maternal serum resistin concentration was comparable before and after delivery; (4) multiple linear regression analysis revealed that antepartum insulin sensitivity was associated with maternal low body mass index, and low glucose concentrations in glucose challenge test, as well as with maternal age and increased leptin concentrations. Postpartum insulin sensitivity was associated with decreased circulating resistin concentrations.

CONCLUSIONS

Despite increase in insulin sensitivity, early postpartum period is characterised by a decrease in maternal circulating total adiponectin and by steady concentrations of resistin and adiponectin multimers compared to the late third trimester.

Increase of high molecular weight adiponectin in hypertensive pregnancy was correlated with brain-type natriuretic peptide stimulation on adipocyte

BACKGROUND

High-molecular weight (HMW)-adiponectin is an active multimer for insulin sensitivity and anti-inflammatory reactions. We compared the ratio of serum total and HMW-adiponectin with brain-type natriuretic peptide (BNP) and other adipocytokines in normal pregnancy and pregnancy-induced hypertension (PIH). Effect of BNP on the secretion of adiponectin from cultured adipocytes was also examined.

METHODS

The three study groups consisted of 44 non-pregnant women, 40 normal (healthy) pregnant women over 28weeks gestation and 29 patients with severe PIH. Adiponectin (protease-pretreated for HMW), BNP-N-terminal, leptin, and monocyte chemoattractant protein (MCP)-1 were measured with ELISA. Pre-adipocytes were differentiated to matured adipocytes and cultured with recombinant-BNP addition.

RESULTS

HMW-to-total adiponectin ratio (HMW-ratio) was lower in normal pregnancy than in non-pregnant, and significantly higher in PIH than normal pregnancies. BNP-N-terminal showed positive correlation with HMW-adiponectin and HMW-ratio. Leptin and MCP-1 showed positive correlation with HMW-adiponectin, but not with HMW-ratio. Adiponectin in the supernatant of adipocyte cultures and intracellular cyclic-GMP was increased in dose-dependent manner in response to BNP.

CONCLUSION

The observed increase in the HMW-adponectin ratio in subjects with PIH may reflect a functional increase of adiponectin in the pathophysiology of PIH. Additionally, this increase seemed to be related to BNP via stimulation of adipocytes.

The influence of a high-fat dietary environment in the fetal period on postnatal metabolic and immune function

Few reports show whether a high-fat (HF) dietary environment in the fetal period affects immune function or the development of lifestyle-related disease at maturity. We examined the influence of an HF dietary environment in the fetal period on postnatal metabolic and immune function. A total of 16 pregnant mice were given control (CON) diet and 16 were given HF diet in the gestational period, from mating to delivery. After delivery lactating mice were given either CON or HF diet, resulting in four groups. After weaning, the offspring mice were given the same diet that their mothers received during lactation. HF dietary intake in the postnatal period increased fat pad weights, serum glucose, and leptin levels. An HF diet in the fetal period resulted in fewer splenic lymphocytes, a thinner thymic cortex, and impaired antigen-specific immune reactions. Furthermore, tumor necrosis factor (TNF)-alpha production and serum triglyceride levels were elevated in the fetal HF group. In addition, the HF-HF group showed a consistent decrease in ovalbumin (OVA)-specific IgG and elevation of IgE, associated with advanced fatty changes in the liver. Results from this study suggest that HF environment during the fetal period induces epigenetic propensity toward obesity and immunological burden in part due to increased adipose tissue mass, significant reduction in the number of immune cells and decreased activities of immune cells.

Identification of new putative susceptibility genes for several psychiatric disorders by association analysis of regulatory and non-synonymous SNPs of 306 genes involved in neurotransmission and neurodevelopment

A fundamental difficulty in human genetics research is the identification of the spectrum of genetic variants that contribute to the susceptibility to common/complex disorders. We tested here the hypothesis that functional genetic variants may confer susceptibility to several related common disorders. We analyzed five main psychiatric diagnostic categories (substance-abuse, anxiety, eating, psychotic, and mood disorders) and two different control groups, representing a total of 3,214 samples, for 748 promoter and non-synonymous single nucleotide polymorphisms (SNPs) at 306 genes involved in neurotransmission and/or neurodevelopment. We identified strong associations to individual disorders, such as growth hormone releasing hormone (GHRH) with anxiety disorders, prolactin regulatory element (PREB) with eating disorders, ionotropic kainate glutamate receptor 5 (GRIK5) with bipolar disorder and several SNPs associated to several disorders, that may represent individual and related disease susceptibility factors. Remarkably, a functional SNP, rs945032, located in the promoter region of the bradykinin receptor B2 gene (BDKRB2) was associated to three disorders (panic disorder, substance abuse, and bipolar disorder), and two additional BDKRB2 SNPs to obsessive-compulsive disorder and major depression, providing evidence for common variants of susceptibility to several related psychiatric disorders. The association of BDKRB2 (odd ratios between 1.65 and 3.06) to several psychiatric disorders supports the view that a common genetic variant could confer susceptibility to clinically related phenotypes, and defines a new functional hint in the pathophysiology of psychiatric diseases.

Evaluation of insulin sensitivity in hyperprolactinemic subjects by euglycemic hyperinsulinemic clamp technique

The background and aim of the study is to evaluate insulin sensitivity in hyperprolactinemic subjects via euglycemic hyperinsulinemic clamp technique. Sixteen hyperprolactinemic subjects and 12 healthy subjects were included in the study. HOMA-B and HOMA-IR values of groups were calculated. Euglycemic hyperinsulinemic clamp technique was performed in both groups, and the M value of the groups was defined. Mann-Whitney U and chi-square tests were used in statistical analysis. Basal insulin level of hyperprolactinemic patients were higher than the control group (6.85 +/- 4.68; 3.66 +/- 0.88 microU/ml respectively; P < 0.05). Mean HOMA-IR and HOMA-B values of patients were higher than control group (1.49 +/- 1.30; 0.78 +/- 0.27 respectively; P = 0.02 and 136.28 +/- 72.53; 64.77 +/- 23.31, respectively, P < 0.001). M values of the patients were statistically lower than the control group (5.64 +/- 2.36; 7.05 +/- 1.62 kg/mg/min respectively; P < 0.05). (1) Hyperprolactinemic patients were more insulin resistant than control subjects. (2) Insulin resistance in hyperprolactinemic patients is not associated with obesity or anthropometric parameters such as fat content, waist circumference and BMI.

The effects of hyperprolactinemia on bone and fat

Many patients with prolactin secreting pituitary tumors have decreased bone mineral. The bone loss is associated with an increase in bone resorption and is secondary to prolactin-induced hypogonadism. In both sexes trabecular bone in the spine and hip is more affected than cortical bone in the distal radius. Normalization of prolactin and restoration of gonadal function increases bone density but is not associated with normalization of bone mass. It is not known whether the bone loss in hyperprolactinemic subjects represents a failure to achieve peak bone mass or is due to accelerated bone loss. Despite low bone density hyperprolactinemic subjects do not demonstrate increased fractures. The association between prolactin, weight gain and obesity suggests that prolactin may also be a modulator of body composition and body weight. It is not known whether hyperprolactinemia associated weight gain is due to stimulation of lipogenesis or due to disruption of central nervous system dopaminergic tone. Hyperprolactinemia is also associated with insulin resistance and endothelial dysfunction which may improve after normalization of prolactin. The clinical significance of these findings and the precise role of prolactin in regulation of weight and metabolism remain to be elucidated.

Physiological, pharmacological, and nutritional regulation of circulating adiponectin concentrations in humans

Adiponectin is an adipocyte hormone that links visceral adiposity with insulin resistance and atherosclerosis. It is unique among adipocyte-derived hormones in that its circulating concentrations are inversely proportional to adiposity, and low adiponectin concentrations predict the development of type 2 diabetes and cardiovascular disease. Consequently, in the decade since its discovery, adiponectin has generated immense interest as a potential therapeutic target for the metabolic syndrome and diabetes. This review summarizes current research regarding the regulation of circulating adiponectin concentrations by physiological, pharmacological, and nutritional factors, with an emphasis on human studies. In humans, plasma adiponectin concentrations are influenced by age and gender, and are inversely proportional to visceral adiposity. In vitro studies suggest that adiponectin production may be determined primarily by adipocyte size and insulin sensitivity, with larger, insulin-resistant adipocytes producing less adiponectin. While adiponectin concentrations are unchanged after meal ingestion, they are increased by significant weight loss, such as after bariatric surgery. In addition, adiponectin production is inhibited by a number of hormones, including testosterone, prolactin, glucocorticoids and growth hormone, and by inflammation and oxidative stress in adipose tissue. Smoking decreases, while moderate alcohol consumption increases, circulating adiponectin concentrations. Dietary fatty acid composition in rodents influences adiponectin production via ligand-activated nuclear receptors (PPARs); however, current evidence in humans is equivocal. In addition to PPAR agonists (such as thiazolidinediones and fibrates), a number of pharmacological agents (angiotensin receptor type 1 blockers, ACE inhibitors, and cannabinoid receptor antagonists) used in treatment of the metabolic syndrome also increase adiponectin concentrations in humans.

Postpartum adiponectin concentration, insulin resistance and metabolic abnormalities among women with pregnancy-induced disturbances

The authors compared postpartum adiponectin levels among women with prior pregnancy-induced disturbances and assessed their association with homeostasis model assessment for insulin resistance (HOMA-IR), the metabolic syndrome (MS), and the Framingham risk score (FRS). Women delivering in 1998 through 2001 and who had gestational diabetes mellitus (n=22), gestational hypertension (n=32), or preeclampsia (n=34) were examined 1 to 2 years after delivery and were grouped-matched to controls (n=29) by age and prepregnancy body mass index. HOMA-IR was increased, adiponectin values were decreased, and there was a higher MS prevalence in women with prior gestational diabetes mellitus (all P<.05). Adiponectin levels were inversely related to HOMA-IR (r=-0.45; P<.0001) and FRS (r=-0.25; P=.007), and a significant trend for decreasing adiponectin values with increased number of MS components was noted (P trend <.0001). Adiponectin concentration remained a significant correlate of FRS and MS irrespective of pregnancy history; a concentration <10.5 microg/mL provided the optimal cutoff to distinguish those with or without MS. Thus, a lower postpartum adiponectin concentration identifies women at increased cardiovascular risk regardless of pregnancy history.

What can we learn from rodents about prolactin in humans?

Prolactin (PRL) is a 23-kDa protein hormone that binds to a single-span membrane receptor, a member of the cytokine receptor superfamily, and exerts its action via several interacting signaling pathways. PRL is a multifunctional hormone that affects multiple reproductive and metabolic functions and is also involved in tumorigenicity. In addition to being a classical pituitary hormone, PRL in humans is produced by many tissues throughout the body where it acts as a cytokine. The objective of this review is to compare and contrast multiple aspects of PRL, from structure to regulation, and from physiology to pathology in rats, mice, and humans. At each juncture, questions are raised whether, or to what extent, data from rodents are relevant to PRL homeostasis in humans. Most current knowledge on PRL has been obtained from studies with rats and, more recently, from the use of transgenic mice. Although this information is indispensable for understanding PRL in human health and disease, there is sufficient disparity in the control of the production, distribution, and physiological functions of PRL among these species to warrant careful and judicial extrapolation to humans.

Hypoadiponectinemia as a marker of adipocyte dysfunction -- Part I: the biology of adiponectin

Adiponectin is the most abundantly secreted adipocyte-derived peptide hormone, possessing an array of antidiabetogenic and cardiovascular protective effects. Acting through 2 distinct membrane receptors, adiponectin receptors 1 and 2 (which utilize 5'-adenosine monophosphate-activated protein kinase phosphorylation, p38 mitogen-activated protein kinase, and peroxisome proliferator-activated receptor alpha as key cell signaling elements), adiponectin increases hepatic and skeletal muscle sensitivity to insulin, enhances fatty acid oxidation, suppresses monocyte-endothelial interaction, supports endothelial cell growth, lowers blood pressure, and moderates adipose tissue growth. The secretion of adiponectin can be suppressed by adipose factors, which are turned on once fat cell mass increases, such as cytokines, adipose renin-angiotensin system, and increased oxidative stress. Inhibition of adiponectin secretion results in the loss of an array of mechanisms, which under normal conditions of fat cell homeostasis provide protection from insulin resistance, diabetes, and atherosclerosis.

Prolactin/Leptin interactions in the control of food intake in rats

Recent evidence suggests that the peptide hormone prolactin (PRL) modulates energy balance through a number of mechanisms, including acting in the brain to increase food intake. In the current studies, we first demonstrated that chronic infusions of PRL into the lateral ventricles increased food intake in cycling rats without disrupting estrous cyclicity. In subsequent experiments the hypothesis that at least part of PRL's ability to increase food intake resulted from PRL-induced leptin resistance was tested. Female rats given chronic infusions of PRL (5 microg/h) into the cerebral ventricles for 10 d did not show a reduction in food intake or body weight after a central injection of 4 microg murine leptin, whereas the expected reduction in both of these parameters was seen in vehicle-infused rats. Leptin injections were without effect on these parameters, whether they were administered to free feeding PRL-infused rats or after 24-h food deprivation. This lack of a behavioral response to leptin was accompanied by an attenuation in Fos induction and phosphorylation of signal transducer and activator of transcription 3 after leptin administration in PRL-infused rats in both the ventromedial hypothalamus and paraventricular hypothalamic nucleus.

Adiponectin activates adenosine monophosphate-activated protein kinase and decreases luteinizing hormone secretion in LbetaT2 gonadotropes

Metabolic dysregulation is associated with reproductive disorders, but the underlying mechanisms are not clearly understood. Adiponectin is an adipocyte-derived secretory factor that improves insulin sensitivity. Results from animal models indicate that overexpression of adiponectin impairs female fertility. We hypothesized that adiponectin regulates reproduction by altering the hypothalamic-pituitary axis. Mouse LbetaT2 immortalized gonadotrope cells express both adiponectin receptors 1 and 2. Adiponectin increases phosphorylation of AMP-activated protein kinase (AMPK), a downstream target of adiponectin receptors, and reduces basal and GnRH-stimulated LH secretion, acutely. The repression of LH secretion can be mimicked by 5-aminoimidazole-4-carboxamide-1-beta-riboside, an AMP analog, suggesting the involvement of AMPK. A dominant-negative AMPK mutant or compound C, a selective AMPK inhibitor, potentiates basal LH secretion and abolishes the inhibitory effect of adiponectin. Chronic activation of AMPK by 5-aminoimidazole-4-carboxamide-1-beta-riboside decreases cellular LH levels, and expression of dominant-negative AMPK increases cellular LH levels, suggesting a second effect of AMPK to regulate LH synthesis. Lastly, intravenous injection of an adenovirus expressing adiponectin into male mice reduces serum LH levels without changing FSH levels. In conclusion, our results suggest that adiponectin decreases LH secretion in pituitary gonadotropes in an AMPK-dependent manner.

Prolactin and the hyperphagia of lactation

The nutritional needs of developing young place a large energetic demand on lactating females. In this paper some of the mechanisms through which lactating rats meet these demands are described. Emphasis is placed on the mechanisms that drive increased food intake in suckled rats that are independent of milk delivery and negative energy balance. Evidence is presented to suggest that prolactin (PRL), released from the pituitary in response to suckling stimulation, acts centrally to stimulate food intake during lactation. Brain areas in which PRL may act to stimulate food intake as well as its interactions with other hormones and neuropeptides involved in energy balance are discussed.