Prolactin and lactation as modifiers of diabetes risk in gestational diabetes

Reproductive risk factors across the female lifecourse and later metabolic health

Metabolic health is characterized by optimal blood glucose, lipids, cholesterol, blood pressure, and adiposity. Alterations in these characteristics may lead to the development of type 2 diabetes mellitus or dyslipidemia. Recent evidence suggests that female reproductive characteristics may be overlooked as risk factors that contribute to later metabolic dysfunction. These reproductive traits include the age at menarche, menstrual irregularity, the development of polycystic ovary syndrome, gestational weight change, gestational dysglycemia and dyslipidemia, and the severity and timing of menopausal symptoms. These risk factors may themselves be markers of future dysfunction or may be explained by shared underlying etiologies that promote long-term disease development. Disentangling underlying relationships and identifying potentially modifiable characteristics have an important bearing on therapeutic lifestyle modifications that could ease long-term metabolic burden. Further research that better characterizes associations between reproductive characteristics and metabolic health, clarifies underlying etiologies, and identifies indicators for clinical application is warranted in the prevention and management of metabolic dysfunction.

Periportal hepatocyte proliferation at midgestation governs maternal glucose homeostasis in mice

The maternal liver is challenged by metabolic demands throughout pregnancy. However, hepatocyte dynamics and their physiological significance in pregnancy remain unclear. Here, we show in mice that hepatocyte proliferation is spatiotemporally regulated in each liver lobular zone during pregnancy, with transient proliferation of periportal and pericentral hepatocytes during mid and late gestation, respectively. Using adeno-associated virus (AAV)-8-mediated expression of the cell cycle inhibitor p21 in hepatocytes, we show that inhibition of hepatocyte proliferation during mid, but not late, gestation impairs liver growth. Transcriptionally, genes involved in glucose/glycogen metabolism are downregulated in late pregnancy when midgestational hepatocyte proliferation is attenuated. In addition, hepatic glycogen storage is abolished, with concomitant elevated blood glucose concentrations, glucose intolerance, placental glycogen deposition, and fetal overgrowth. Laser capture microdissection and RNA-seq analysis of each liver lobular zone show zone-specific changes in the transcriptome during pregnancy and identify genes that are periportally expressed at midgestation, including the hyaluronan-mediated motility receptor (Hmmr). Knockdown of Hmmr in hepatocytes by AAV8-shHmmr suppresses periportal hepatocyte proliferation at midgestation and induces impaired hepatic glycogen storage, glucose intolerance, placental glycogen deposition and fetal overgrowth. Our results suggest that periportal hepatocyte proliferation during midgestation is critical for maternal glycogen metabolism and fetal size.

Undernutrition-induced substance metabolism and energy production disorders affected the structure and function of the pituitary gland in a pregnant sheep model

Introduction

Undernutrition spontaneously occurs in ewes during late gestation and the pituitary is an important hinge in the neurohumoral regulatory system. However, little is known about the effect of undernutrition on pituitary metabolism.

Methods

Here, 10 multiparous ewes were restricted to a 30% feeding level during late gestation to establish an undernutrition model while another 10 ewes were fed normally as controls. All the ewes were sacrificed, and pituitary samples were collected to perform transcriptome, metabolome, and quantitative real-time PCR analysis and investigate the metabolic changes.

Results

PCA and PLS-DA of total genes showed that undernutrition changed the total transcriptome profile of the pituitary gland, and 581 differentially expressed genes (DEGs) were identified between the two groups. Clusters of orthologous groups for eukaryotic complete genomes demonstrated that substance transport and metabolism, including lipids, carbohydrates, and amino acids, energy production and conversion, ribosomal structure and biogenesis, and the cytoskeleton were enriched by DEGs. Kyoto encyclopedia of genes and genomes pathway enrichment analysis displayed that the phagosome, intestinal immune network, and oxidative phosphorylation were enriched by DEGs. Further analysis found that undernutrition enhanced the lipid degradation and amino acid transport, repressing lipid synthesis and transport and amino acid degradation of the pituitary gland. Moreover, the general metabolic profiles and metabolic pathways were affected by undernutrition, repressing the 60S, 40S, 28S, and 39S subunits of the ribosomal structure for translation and myosin and actin synthesis for cytoskeleton. Undernutrition was found also to be implicated in the suppression of oxidative phosphorylation for energy production and conversion into a downregulation of genes related to T cell function and the immune response and an upregulation of genes involved in inflammatory reactions enriching phagosomes.

Discussion

This study comprehensively analyses the effect of undernutrition on the pituitary gland in a pregnant sheep model, which provides a foundation for further research into the mechanisms of undernutrition-caused hormone secretion and metabolic disorders.

The relationship between pregnancy count and duration of breast-feeding with metabolic syndrome (Fasa Persian cohort study)

BACKGROUND

Changes that occur during pregnancy and after that during breastfeeding induce some symptoms similar to metabolic syndrome (MetS) risk factors. This study aims to determine the relationship between pregnancy, as well as the duration of breastfeeding and MetS controlling the effect of other risk factors like hypertension, glucose intolerance, triglyceride, central obesity, and reduction of high-density lipoprotein in women of Fasa Persian Cohort Study.

MATERIALS AND METHODS

In this cross-sectional study, 5015 women aged 35-70 years were investigated in the Sheshdeh region from 2016 to 2021, and the information related to the disease symptoms was collected through questionnaires, examinations, and laboratory tests. MetS was calculated based on two guidelines according to adult treatment panel III (ATP III) and international diabetes federation (IDF) methods. For reporting the data, the odds ratio with its 95% confidence interval was used. In order to eliminate the effect of confounders, logistic regression was used.

RESULTS

Prevalence of MetS showed a descending trend in women with up to two pregnancies and it reached 22.6% and 22.4% using ATPIII and IDF methods respectively, while with an increase in the number of pregnancies of more than two, MetS prevalence was ascending. The prevalence of MetS did not have any specific trend across various breastfeeding duration groups. Multivariate analysis approved that the odds ratio of developing MetS in comparison with women who had two pregnancies was significantly increasing trend when the pregnancy counts increased.

CONCLUSION

The chance of developing MetS based on both IDF and ATP III methods after adjustment for confounding effects would grow with an increase in the number of pregnancies to more than two and breast-feeding of more than seven years. It is recommended that women with more than two pregnancies or the long duration of breast-feeding women undergo a specialized examination to investigate and control MetS problems so that future diseases could be prevented.

Lactation duration and lifetime progression to metabolic syndrome in women according to their history of gestational diabetes: a prospective longitudinal community-based cohort study

BACKGROUND

Despite the many signs of progress in pharmacotherapies, metabolic syndrome (MetS) is one of the main public-health burdens worldwide. Our study aimed to compare the effect of breastfeeding (BF) in women with and without gestational diabetes mellitus (GDM) on MetS incidence.

METHODS

Of females who participated in the Tehran Lipid and glucose study, women who met our inclusion criteria were selected. The Cox proportional hazards regression model, with adjustment of potential confounders, was done to evaluate the relationship between duration of BF and incident of MetS in women with a GDM history compared to non-GDM.

RESULTS

Out of 1176 women, there were 1001 non-GDM and 175 GDM. The median follow-up was 16.3 (11.9, 19.3) years. Results of the adjusted model illustrated that the total BF duration was negatively associated with MetS incidence risk (hazard ratio (HR) 0.98, 95% CI 0.98-0.99) in total participants indicating that per one-month increase of BF duration, the hazard of MetS reduced by 2%. The HR of MetS in Comparison between GDM and non-GDM women demonstrated significantly more reduced MetS incidence with a longer duration of exclusive BF (HR 0.93, 95% CI 0.88-0.98).

CONCLUSIONS

Our findings illustrated the protective effect of BF, especially exclusive BF, on MetS incidence risk. BF is more effective in reducing the risk of MetS among women with a history of GDM than among women without such a history.

Prolactin in Pregnancies Affected by Pre-Existing Maternal Metabolic Conditions: A Systematic Review

Women affected by maternal pregestational diabetes mellitus (type 1 or type 2) or by polycystic ovary syndrome experience an increased risk of pregnancy complications, as well as suboptimal lactation outcomes. The hormone prolactin plays important roles in pregnancy and postpartum, both as a metabolic and lactogenic hormone. We aimed to explore, through a systematic review, the relationship between pregestational maternal metabolic conditions and prolactin levels in pregnancy and postpartum. MEDLINE via OVID, CINAHL Plus, and Embase were searched from inception to 9 May 2022. Eligible studies included women who were pregnant or up to 12 months postpartum and had a pre-existing diagnosis of type 1 or type 2 diabetes mellitus or polycystic ovary syndrome; with reporting of at least one endogenous maternal serum prolactin level during this time. Two independent reviewers extracted the data. Eleven studies met the eligibility criteria. The studies were too diverse and heterogeneous to enable meta-analysis. Overall, prolactin levels appeared to be lower in pregnancies affected by type 1 diabetes mellitus. There was little data in polycystic ovary syndrome or type 2 diabetes pregnancy, but prolactin increment across pregnancy in polycystic ovary syndrome emerged as an area for future study. During postpartum, lactation difficulties in women with metabolic disease present before pregnancy are well-described, but the relationship to prolactin remains unclear. Overall, preliminary evidence suggests that pre-existing maternal metabolic disease may alter prolactin dynamics in pregnancy and postpartum. Further well-designed studies in modern cohorts, with standardised collection and serial sampling across pregnancy and postpartum, are required to clarify these associations.

Human Placental Lactogen in Relation to Maternal Metabolic Health and Fetal Outcomes: A Systematic Review and Meta-Analysis

Human placental lactogen (hPL) is a placental hormone which appears to have key metabolic functions in pregnancy. Preclinical studies have putatively linked hPL to maternal and fetal outcomes, yet-despite human observational data spanning several decades-evidence on the role and importance of this hormone remains disparate and conflicting. We aimed to explore (via systematic review and meta-analysis) the relationship between hPL levels, maternal pre-existing and gestational metabolic conditions, and fetal growth. MEDLINE via OVID, CINAHL plus, and Embase were searched from inception through 9 May 2022. Eligible studies included women who were pregnant or up to 12 months post-partum, and reported at least one endogenous maternal serum hPL level during pregnancy in relation to pre-specified metabolic outcomes. Two independent reviewers extracted data. Meta-analysis was conducted where possible; for other outcomes narrative synthesis was performed. 35 studies met eligibility criteria. No relationship was noted between hPL and gestational diabetes status. In type 1 diabetes mellitus, hPL levels appeared lower in early pregnancy (possibly reflecting delayed placental development) and higher in late pregnancy (possibly reflecting increased placental mass). Limited data were found in other pre-existing metabolic conditions. Levels of hPL appear to be positively related to placental mass and infant birthweight in pregnancies affected by maternal diabetes. The relationship between hPL, a purported pregnancy metabolic hormone, and maternal metabolism in human pregnancy is complex and remains unclear. This antenatal biomarker may offer value, but future studies in well-defined contemporary populations are required.

Breastfeeding effect on glucose tolerance assessment in women with previous gestational diabetes mellitus: A randomized controlled trial

AIMS

To test whether breastfeeding during the oral glucose tolerance test (OGTT) affects glucose and insulin outcomes (main outcome: 120 min plasma glucose).

METHODS

A randomized crossover trial was conducted in 20 women with prior gestational diabetes mellitus. Each woman undertook two OGTTs in the first 3 months after delivery, breastfeeding the infant in one and avoiding breastfeeding in the other. Glucose and insulin were measured at 0, 30, 60 and 120 min. Statistics included: T-test for paired data, general linear model (GLM) for repeated measures. Analysis of covariance (ANCOVA) was used to adjust for glucose and insulin values at 0 min. Statistical dispersion for GLM and ANCOVA outcomes is expressed as standard error.

RESULTS

In the OGTTs with breastfeeding, higher values were observed for overall glucose and insulin concentrations, glucose and insulin peaks and individual time points of glucose (at 0, 30 and 60 min) and insulin (at 0 and 60 min) but without differences at 120 min (glucose 6.7 ± 0.3 vs. 6.9 ± 0.3 mmol/L, p = 0.506). The rate of abnormal tests was not different. ANCOVA confirmed higher postchallenge glucose values in the OGTT with breastfeeding and similar glucose values at 120 min.

CONCLUSIONS

According to the results of this randomized trial, we conclude that breastfeeding during the OGTT resulted in similar 120 min glucose concentration and glycaemic status categorization. However, breastfeeding during the OGTT led to clear differences in glucose and insulin values in the first hour, that warrant further studies.

Lactogenic hormones in relation to maternal metabolic health in pregnancy and postpartum: protocol for a systematic review

INTRODUCTION

Maternal metabolic disease states (such as gestational and pregestational diabetes and maternal obesity) are reaching epidemic proportions worldwide and are associated with adverse maternal and fetal outcomes. Despite this, their aetiology remains incompletely understood. Lactogenic hormones, namely, human placental lactogen (hPL) and prolactin (PRL), play often overlooked roles in maternal metabolism and glucose homeostasis during pregnancy and (in the case of PRL) postpartum, and have clinical potential from a diagnostic and therapeutic perspective. This paper presents a protocol for a systematic review which will synthesise the available scientific evidence linking these two hormones to maternal and fetal metabolic conditions/outcomes.

METHODS AND ANALYSIS

MEDLINE (via OVID), CINAHL and Embase will be systematically searched for all original observational and interventional research articles, published prior to 8 July 2021, linking hPL and/or PRL levels (in pregnancy and/or up to 12 months postpartum) to key maternal metabolic conditions/outcomes (including pre-existing and gestational diabetes, markers of glucose/insulin metabolism, postpartum glucose status, weight change, obesity and polycystic ovary syndrome). Relevant fetal outcomes (birth weight and placental mass, macrosomia and growth restriction) will also be included. Two reviewers will assess articles for eligibility according to prespecified selection criteria, followed by full-text review, quality appraisal and data extraction. Where possible, meta-analysis will be performed; otherwise, a narrative synthesis of findings will be presented.

ETHICS AND DISSEMINATION

Formal ethical approval is not required as no primary data will be collected. The results will be published in a peer-reviewed journal and presented at conference meetings, and will be used to inform future research directions.

PROSPERO REGISTRATION NUMBER

CRD42021262771.

Prolactin in relation to gestational diabetes and metabolic risk in pregnancy and postpartum: A systematic review and meta-analysis

CONTEXT

Pre-clinical evidence suggests that prolactin has important metabolic functions in pregnancy and postpartum, in addition to lactogenic actions.

OBJECTIVE

To explore the relationship between prolactin and maternal metabolic outcomes in human pregnancy and postpartum, particularly in relation to gestational diabetes mellitus (GDM).

DATA SOURCES

MEDLINE via OVID, CINAHL plus, Embase.

STUDY SELECTION

Eligible studies included women who were pregnant or up to 12 months postpartum, reporting at least one maternal serum prolactin level in relation to key metabolic outcomes including GDM, glycaemic parameters, obesity, and gestational weight gain.

DATA EXTRACTION

Two independent reviewers extracted data.

DATA SYNTHESIS

Twenty-six articles were included. Meta-analysis showed no relationship between maternal prolactin levels and GDM status, with a weighted mean difference of -2.14 ng/mL (95% CI -12.54 to 8.27 ng/mL, p=0.7) between GDM and controls in early pregnancy (n=3 studies) and -3.89 ng/mL (95% CI, -15.20 to 7.41 ng/mL, p=0.5) in late pregnancy (n=11 studies). In narrative synthesis of other outcomes (due to study heterogeneity and/or lack of data), prolactin levels were not associated with maternal glycaemic or weight-related parameters during pregnancy, but in the postpartum period (particularly with lactation) a high-prolactin environment was associated with low circulating insulin and beta-cell function, and increased insulin sensitivity.

CONCLUSIONS

Current evidence from human studies does not clearly support a relationship between prolactin and metabolic parameters during pregnancy, including with GDM status. Elevated prolactin was associated with lower insulin and beta-cell function and higher insulin sensitivity in the post-partum period, but the direction of causality remains unclear.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier [CRD42021262771].

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.

Metabolic Conditions Including Obesity, Diabetes, and Polycystic Ovary Syndrome: Implications for Breastfeeding and Breastmilk Composition

Breastfeeding is internationally recognized as the recommended standard for infant nutrition, informed by evidence of its multiple benefits for both mother and baby. In the context of common metabolic conditions such as polycystic ovary syndrome, diabetes (type 1, type 2, and gestational), and obesity, breastfeeding may be particularly beneficial for both mother and infant. However, there is evidence of delayed lactogenesis and reduced breastfeeding rates and duration in women with these conditions, and the effects of altered maternal metabolic environments on breastmilk composition (and potentially infant outcomes) are incompletely understood. In this review, we explore the relationships between maternal metabolic conditions, lactogenesis, breastfeeding, and breastmilk composition. We examine relevant potential mechanisms, including the central role of insulin both in lactogenesis and as a milk-borne hormone. We also describe the bioactive and hormonal components of breastmilk and how these may link maternal and infant health.

Metabolomic Biomarkers in Gestational Diabetes Mellitus: A Review of the Evidence

Gestational diabetes mellitus (GDM) is the fastest growing type of diabetes, affecting between 2 to 38% of pregnancies worldwide, varying considerably depending on diagnostic criteria used and sample population studied. Adverse obstetric outcomes include an increased risk of macrosomia, and higher rates of stillbirth, instrumental delivery, and birth trauma. Metabolomics, which is a platform used to analyse and characterise a large number of metabolites, is increasingly used to explore the pathophysiology of cardiometabolic conditions such as GDM. This review aims to summarise metabolomics studies in GDM (from inception to January 2021) in order to highlight prospective biomarkers for diagnosis, and to better understand the dysfunctional metabolic pathways underlying the condition. We found that the most commonly deranged pathways in GDM include amino acids (glutathione, alanine, valine, and serine), carbohydrates (2-hydroxybutyrate and 1,5-anhydroglucitol), and lipids (phosphatidylcholines and lysophosphatidylcholines). We also highlight the possibility of using certain metabolites as predictive markers for developing GDM, with the use of highly stratified modelling techniques. Limitations for metabolomic research are evaluated, and future directions for the field are suggested to aid in the integration of these findings into clinical practice.

Prolactin-Induced Adaptation in Glucose Homeostasis in Mouse Pregnancy Is Mediated by the Pancreas and Not in the Forebrain

Adaptive changes in glucose homeostasis during pregnancy require proliferation of insulin-secreting beta-cells in the pancreas, together with increased sensitivity for glucose-stimulated insulin secretion. Increased concentrations of maternal prolactin/placental lactogen contribute to these changes, but the site of action remains uncertain. Use of Cre-lox technology has generated pancreas-specific prolactin receptor (Prlr) knockouts that demonstrate the development of a gestational diabetic like state. However, many Cre-lines for the pancreas also express Cre in the hypothalamus and prolactin could act centrally to modulate glucose homeostasis. The aim of the current study was to examine the relative contribution of prolactin action in the pancreas and brain to these pregnancy-induced adaptations in glucose regulation. Deletion of prolactin receptor (Prlr) from the pancreas using Pdx-cre or Rip-cre led to impaired glucose tolerance and increased non-fasting blood glucose levels during pregnancy. Prlr^lox/lox /Pdx-Cre mice also had impaired glucose-stimulated insulin secretion and attenuated pregnancy-induced increase in beta-cell fraction. Varying degrees of Prlr recombination in the hypothalamus with these Cre lines left open the possibility that central actions of prolactin could contribute to the pregnancy-induced changes in glucose homeostasis. Targeted deletion of Prlr specifically from the forebrain, including areas of expression induced by Pdx-Cre and Rip-cre, had no effect on pregnancy-induced adaptations in glucose homeostasis. These data emphasize the pancreas as the direct target of prolactin/placental lactogen action in driving adaptive changes in glucose homeostasis during pregnancy.

First trimester secreted Frizzled-Related Protein 4 and other adipokine serum concentrations in women developing gestational diabetes mellitus

Background

The aim of this study was to evaluate whether soluble frizzled-related protein 4 (sFRP4) concentration in the first trimester of pregnancy is individually, or in combination with Leptin, Chemerin and/or Adiponectin, associated with the development of gestational diabetes (GDM).

Methods

In a nested case-control study, 50 women with GDM who spontaneously conceived and delivered a live-born infant were matched with a total of 100 uncomplicated singleton control pregnancies based on body mass index (± 2 kg/m²), gestational age at sampling (exact day) and maternal age (± 2 years). In serum samples, obtained between 70–90 days gestational age, sFRP4, Chemerin, Leptin and Adiponectin concentrations were determined by ELISA. Statistical comparisons were performed using univariate and multi-variate logistic regression analysis after logarithmic transformation of the concentrations. Discrimination of the models was assessed by the area under the curve (AUC).

Results

First trimester sFRP4 concentrations were significantly increased in GDM cases (2.04 vs 1.93 ng/ml; p<0.05), just as Chemerin (3.19 vs 3.15 ng/ml; p<0.05) and Leptin (1.44 vs 1.32 ng/ml; p<0.01). Adiponectin concentrations were significantly decreased (2.83 vs 2.94 ng/ml; p<0.01) in GDM cases. Further analysis only showed a weak, though significant, correlation of sFRP4 with Chemerin (R² = 0.124; p<0.001) and Leptin (R² = 0.145; p<0.001), and Chemerin with Leptin (R² = 0.282; p<0.001) in the control group. In a multivariate logistic regression model of these four markers, only Adiponectin showed to be significantly associated with GDM (odds ratio 0.12, 95%CI 0.02–0.68). The AUC of this model was 0.699 (95%CI 0.605–0.793).

Conclusion

In the first trimester of pregnancy, a multi-marker model with sFRP4, Leptin, Chemerin and Adiponectin is associated with the development of GDM. Therefore, this panel seems to be an interesting candidate to further evaluate for prediction of GDM in a prospective study.

Breastfeeding and Prevalence of Metabolic Syndrome among Perimenopausal Women

Little is known about the long-term benefits of breastfeeding for mother's metabolic health. This study aimed to investigate the links between breastfeeding duration and the prevalence of metabolic syndrome (MetS) and its components in perimenopausal women. The analysis included a group of 7621 women aged 55.4 ± 5.4 years. MetS and its components were defined according to the International Diabetes Federation guidelines. Women who breastfed for 13-18 months and beyond 18 months were at lower risk of MetS (odds ratio OR) = 0.76, 95% CI 0.60-0.95; p = 0.017 and OR = 0.79, 95% CI 0.64-0.98; p = 0.030, respectively) than those who never breastfed. Meanwhile, women who breastfed for 7-12 months showed increased glucose concentration (OR = 0.77, 95% CI 0.63-0.94; p = 0.012) compared with those who had never breastfed. The additional analysis involving parity showed that women who had given birth to two babies and breastfed them had lower odds of MetS than those who never breastfed (p < 0.05), although there was no significant difference among women who breastfed for >18 months. Women who had given birth to at least three children and breastfed for 1-6 and 13-18 months had lower odds of MetS and increased triglyceride concentration (p < 0.05). Moreover, participants having breastfed for 1-6 months were found to have a reduced risk of abdominal obesity compared with those who had not breastfed (p < 0.05). Breastfeeding is associated with lower prevalence of MetS in perimenopausal women and can be recommended as a way of reducing the risk of MetS and its components.

Lactation and maternal risk of diabetes: Evidence from the Mexican Teachers' Cohort

One postpartum behaviour that may be protective against diabetes is lactation due to its potential role in resetting maternal metabolism after pregnancy. However, the role of lactation in maternal risk of diabetes has not been investigated in Latin American populations, where rates of breastfeeding are suboptimal and diabetes incidence is increasing. Therefore, our aim was to estimate the association between mean duration of lactation per child and maternal incidence of diabetes. We followed 66,573 women from the Mexican Teachers' Cohort free of diabetes at baseline. Incident diabetes was ascertained through triennial questionnaires and lactation history was asked in baseline questionnaire. We used Cox proportional hazards regression models to estimate the hazard ratio (HR) for diabetes by mean duration of lactation per child. We examined the dose-response association between lactation per child and diabetes with restricted cubic splines. We found that 3,168 incident cases of diabetes were diagnosed during 157,510 person years of follow-up. In comparison with women who did not breastfed, women with a mean lactation per child of 3 to <6 months and 6 to <12 months had HRs of 0.81 (95% CI [0.65, 0.99]) and 0.73 (95% CI [0.59, 0.91]), respectively (p for quadratic term 0.004). There was no further decline in risk of diabetes after ≥12 months of lactation per child. The dose-response association between lactation and diabetes was linear up to 9 months of lactation. Our findings suggest that lactation is associated with reduced incidence of diabetes, indicating considerable potential for diabetes prevention on a population level.

Time for a New Perspective on Prolactin in Metabolism

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

Effect of lactation on the recurrence rate of gestational diabetes mellitus: a retrospective cohort study

PURPOSE

To examine the impact of lactation on the recurrence rate of gestational diabetes mellitus (GDM).

METHODS

Retrospective cohort study performed in a single teaching hospital on data between 2009 and 2016. The study group consisted of women who had a diagnosis of GDM and breastfed exclusively for ≥ 1 month. The control group consisted of women who had a diagnosis of GDM and did not breastfeed or added formula < 1 month postpartum. Data regarding breastfeeding duration, timing and amount of formula supplementation were obtained by a telephone questionnaire. We hypothesized that the recurrence of GDM would be lower in women who breastfed exclusively for ≥ 1 month. Therefore, to detect a decrease from 50 to 30% in the recurrence rate of GDM with alpha (one-sided) of 0.05 and 80% power, a sample size of 168 (84 per group) was needed.

RESULTS

Overall, 229 women were found eligible; 139 and 90 in the study and control groups, respectively. Except for parity, baseline demographic and obstetric variables were not different between the two groups. After adjusting for parity, the incidence of GDM in subsequent pregnancy was significantly lower among the study compared to the control group [48 (34.5%) and 41 (45.6%), respectively; one-tailed p = 0.043; RR 0.56; 95% CI 0.35-0.90)]. The cesarean delivery (CD) rate was significantly lower as well [28 (20.1%) and 31 (34.4%), respectively; two-tailed p = 0.02; RR 0.48, 95% CI 0.26-0.89)].

CONCLUSION

Exclusive lactation for ≥ 1 month reduced the recurrence rate of GDM and possibly the risk of CD in the subsequent pregnancy.

Decreased beta-cell function in breastfeeding obese and non-obese women: A prospective observational study

BACKGROUND & AIMS

Obesity is associated with lower breastfeeding rates. The underlying pathophysiological mechanisms are not well-understood, but there is increasing evidence on an association between parameters of maternal glucose metabolism and prolactin concentrations. In this cross-sectional observational study we investigate the relationship between breastfeeding, maternal obesity, and maternal glucose metabolism postpartum with beta cell function as a primary outcome measure.

METHODS

We investigated 106 women (44% obese) prospectively recruited during the pregnancy, who underwent a 75 g - 2 h oral glucose tolerance test (OGTT) between the 3rd and 5th months postpartum. At this time point, we tested the relationship between breastfeeding status, maternal prolactin concentrations, maternal obesity, and fasting and dynamic indices of glucose metabolism using multivariate logistic regression in a post hoc analysis of prospective observational data.

RESULTS

During the study visit at a mean of 122 (SE 9.3) days after delivery, 47% of obese women and 68% of non-obese women were breastfeeding (p < 0.05). Lactation and higher prolactin concentrations were associated with lower prepregnancy weight and lower postpartum insulin concentrations. Prehepatic beta-cell function was decreased in both obese (mean (SD); 0.16 (0.04) vs. 0.19 (0.05), p < 0.05) and non-obese (0.12 (0.05) vs. 0.16 (0.06), p < 0.01), lactating women. Obese lactating women have significantly lower first (1135.1 (306.7) pmol/L vs. 1517.3 (475.8) pmol/L, p < 0.01) and second phase insulin secretion (mean (SD), 300.2 (70.7) pmol/L vs. 393.1 (115.5) pmol/L, p < 0.01) as shown by Stumvoll indices when comparing to obese non-lactating women. Prehepatic beta-cell function and Stumvoll 1st phase insulin secretion index, but not BMI, were independently and negatively associated with breastfeeding and circulating prolactin concentrations.

CONCLUSIONS

Beta-cell function during lactation relates to breastfeeding and circulating prolactin concentrations independently of obesity. The well-known positive effects of lactation on maternal and offspring outcomes might reflect a causative relationship of higher breastfeeding rates in metabolically healthier women.

Lactation Duration and Progression to Diabetes in Women Across the Childbearing Years: The 30-Year CARDIA Study

Importance

Lactation duration has shown weak protective associations with incident diabetes (3%-15% lower incidence per year of lactation) in older women based solely on self-report of diabetes, studies initiated beyond the reproductive period are vulnerable to unmeasured confounding or reverse causation from antecedent biochemical risk status, perinatal outcomes, and behaviors across the childbearing years.

Objective

To evaluate the association between lactation and progression to diabetes using biochemical testing both before and after pregnancy and accounting for prepregnancy cardiometabolic measures, gestational diabetes (GD), and lifestyle behaviors.

Design, Setting, and Participants

For this US multicenter, community-based 30-year prospective cohort study, there were 1238 women from the Coronary Artery Risk Development in Young Adults (CARDIA) study of young black and white women ages 18 to 30 years without diabetes at baseline (1985-1986) who had 1 or more live births after baseline, reported lactation duration, and were screened for diabetes up to 7 times during 30 years after baseline (1986-2016).

Exposures

Time-dependent lactation duration categories (none, >0 to 6 months, >6 to <12 months, and ≥12 months) across all births since baseline through 30 years.

Main Outcomes and Measures

Diabetes incidence rates per 1000 person-years and adjusted relative hazards (RH) with corresponding 95% CIs, as well as proportional hazards regression models adjusted for biochemical, sociodemographic, and reproductive risk factors, as well as family history of diabetes, lifestyle, and weight change during follow-up.

Results

Overall 1238 women were included in this analysis (mean [SD] age, 24.2 [3.7] years; 615 black women). There were 182 incident diabetes cases during 27 598 person-years for an overall incidence rate of 6.6 cases per 1000 person-years (95% CI, 5.6-7.6); and rates for women with GD and without GD were 18.0 (95% CI, 13.3-22.8) and 5.1 (95% CI, 4.2-6.0), respectively (P for difference < .001). Lactation duration showed a strong, graded inverse association with diabetes incidence: adjusted RH for more than 0 to 6 months, 0.75 (95% CI, 0.51-1.09); more than 6 months to less than 12 months, 0.52 (95% CI, 0.31-0.87), and 12 months or more 0.53 (0.29-0.98) vs none (0 days) (P for trend = .01). There was no evidence of effect modification by race, GD, or parity.

Conclusions and Relevance

This study provides longitudinal biochemical evidence that lactation duration is independently associated with lower incidence of diabetes. Further investigation is required to elucidate mechanisms that may explain this relationship.

Planned birth at or near term for improving health outcomes for pregnant women with gestational diabetes and their infants

BACKGROUND

Gestational diabetes is a type of diabetes that occurs during pregnancy. Women with gestational diabetes are more likely to experience adverse health outcomes such as pre-eclampsia or polyhydramnios (excess amniotic fluid). Their babies are also more likely to have health complications such as macrosomia (birthweight > 4000 g) and being large-for-gestational age (birthweight above the 90th percentile for gestational age). Current clinical guidelines support elective birth, at or near term in women with gestational diabetes to minimise perinatal complications, especially those related to macrosomia.This review replaces a review previously published in 2001 that included "diabetic pregnant women", which has now been split into two reviews. This current review focuses on pregnant women with gestational diabetes and a sister review focuses on women with pre-existing diabetes (Type 1 or Type 2).

OBJECTIVES

To assess the effect of planned birth (either by induction of labour or caesarean birth), at or near term (37 to 40 weeks' gestation) compared with an expectant approach for improving health outcomes for women with gestational diabetes and their infants. The primary outcomes relate to maternal and perinatal mortality and morbidity.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (15 August 2017), and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised trials comparing planned birth, at or near term (37 to 40 weeks' gestation), with an expectant approach, for women with gestational diabetes. Cluster-randomised and non-randomised trials (e.g. quasi-randomised trials using alternate allocation) were also eligible for inclusion but none were identified.

DATA COLLECTION AND ANALYSIS

Two of the review authors independently assessed study eligibility, extracted data and assessed the risk of bias of the included study. The quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

The findings of this review are based on a single trial involving 425 women with gestational diabetes. The trial compared induction of labour with expectant management (waiting for the spontaneous onset of labour in the absence of any maternal or fetal issues that may necessitate birth) in pregnant women with gestational diabetes at term. We assessed the overall risk of bias as being low for most domains, apart from performance, detection and attrition bias (for outcome perineum intact), which we assessed as being at high risk. It was an open-label trial, and women and healthcare professionals were not blinded.There were no clear differences between women randomised to induction of labour and women randomised to expectant management for maternal mortality or serious maternal morbidity (risk ratio (RR) 1.48, 95% confidence interval (CI) 0.25 to 8.76, one trial, 425 women); caesarean section (RR 1.06, 95% CI 0.64 to 1.77, one trial, 425 women); or instrumental vaginal birth (RR 0.81, 95% CI 0.45 to 1.46, one trial, 425 women). For the primary outcome of maternal mortality or serious maternal morbidity, there were no deaths in either group and serious maternal morbidity related to admissions to intensive care unit. The quality of the evidence contributing to these outcomes was assessed as very low, mainly due to the study having high risk of bias for some domains and because of the imprecision of effect estimates.In relation to primary neonatal outcomes, there were no perinatal deaths in either group. The quality of evidence for this outcome was judged as very low, mainly due to high risk of bias and imprecision of effect estimates. There were no clear differences in infant outcomes between women randomised to induction of labour and women randomised to expectant management: shoulder dystocia (RR 2.96, 95% CI 0.31 to 28.21, one trial, 425 infants, very low-quality evidence); large-for-gestational age (RR 0.53, 95% CI 0.28 to 1.02, one trial, 425 infants, low-quality evidence).There were no clear differences between women randomised to induction of labour and women randomised to expectant management for postpartum haemorrhage (RR 1.17, 95% CI 0.53 to 2.54, one trial, 425 women); admission to intensive care unit (RR 1.48, 95% CI 0.25 to 8.76, one trial, 425 women); and intact perineum (RR 1.02, 95% CI 0.73 to 1.43, one trial, 425 women). No infant experienced a birth trauma, therefore, we could not draw conclusions about the effect of the intervention on the outcomes of brachial plexus injury and bone fracture at birth. Infants of women in the induction-of-labour group had higher incidences of neonatal hyperbilirubinaemia (jaundice) when compared to infants of women in the expectant-management group (RR 2.46, 95% CI 1.11 to 5.46, one trial, 425 women).We found no data on the following prespecified outcomes of this review: postnatal depression, maternal satisfaction, length of postnatal stay (mother), acidaemia, intracranial haemorrhage, hypoxia ischaemic encephalopathy, small-for-gestational age, length of postnatal stay (baby) and cost.The authors of this trial acknowledge that it is underpowered for their primary outcome of caesarean section. The authors of the trial and of this review note that the CIs demonstrate a wide range, therefore making it inappropriate to draw definite conclusions.

AUTHORS' CONCLUSIONS

There is limited evidence to inform implications for practice. The available data are not of high quality and lack power to detect possible important differences in either benefit or harm. There is an urgent need for high-quality trials evaluating the effectiveness of planned birth at or near term gestation for women with gestational diabetes compared with an expectant approach.

IL-37 and 38 signalling in gestational diabetes

Gestational diabetes mellitus (GDM) is still a clinical challenge around world. Inflammation contributes to the pathogenesis of GDM, the precise underlying mechanism remains to be explored. IL-37 and 38 play important role in autoimmunity, but their role in the development of GDM is unclear. Using histopathology and immunohistochemistry, the thickness of the umbilical artery, the area of capillaries within the placental chorionic villi, and the production of IL-37/38 were determined. Placental mRNA of IL-37/IL-38 from GDM and Non-GMD was measured using qRT-PCR. serum IL-37/IL38 levels were evaluated, using ELISA. IL-37 was reduced 49%, 48% or 57% in chorionic villi of placentas (P<0.05), umbilical artery (P<0.05), or umbilical vein (P<0.05) from GDM women, respectively, compared to that from non-GDM women. In contrast, IL-38 was increased 3.3, 2.6, or 2.6 fold in chorionic villi (P<0.01), umbilical artery (P<0.05), umbilical vein (P<0.05) from GDM women, respectively, compared to that from non-GDM women. IL-37 in GDM placentas or serum was reduced ∼52% or 33%, compared to that from Non-GDM subjects, respectively; whereas IL-38 in the GDM placentas or serum was increased by 1.6 fold or 1.3 fold, compare to that from Non-GDM, respectively. Our data suggest that IL-37 protect pregnant women from the development of GDM. IL-38 produced in the chorionic villi and umbilical cords may be a response to local inflammation during the development of GDM. Such a dysregulated micro-environment may contribute to the development of GDM via an immune-mediated mechanism. These data may provide useful information for the intervention for GDM.

Potential protective effect of lactation against incidence of type 2 diabetes mellitus in women with previous gestational diabetes mellitus: A systematic review and meta-analysis

Lactation may protect women with previous gestational diabetes mellitus (GDM) from developing type 2 diabetes mellitus, but the results of existing studies are inconsistent, ranging from null to beneficial. We aimed to conduct a systematic review to gather available evidence. Databases MEDLINE, CINAHL, PubMed, and EMBASE were searched on December 15, 2015, without restriction of language or publication year. A manual search was also conducted. We included observational studies (cross-sectional, case-control, and cohort study) with information on lactation and type 2 diabetes mellitus incidence among women with previous GDM. We excluded case studies without control data. Data synthesis was conducted by random-effect meta-analysis. Fourteen reports of 9 studies were included. Overall risk of bias using RoBANS ranged from low to unclear. Longer lactation for more than 4 to 12 weeks postpartum had risk reduction of type 2 diabetes mellitus compared with shorter lactation (OR 0.77, 95% CI 0.01-55.86; OR 0.56, 95% CI 0.35-0.89; OR 0.22, 95% CI 0.13-0.36; type 2 diabetes mellitus evaluation time < 2 y, 2-5 y, and >5 y, respectively). Exclusive lactation for more than 6 to 9 weeks postpartum also had lower risk of type 2 diabetes mellitus compared with exclusive formula (OR 0.42, 95% CI 0.22-0.81). The findings support the evidence that longer and exclusive lactation may be beneficial for type 2 diabetes mellitus prevention in women with previous GDM. However, the evidence relies only on observational studies. Therefore, further studies are required to address the true causal effect.

Lactation is associated with altered metabolomic signatures in women with gestational diabetes

AIMS/HYPOTHESIS

Lactation for >3 months in women with gestational diabetes is associated with a reduced risk of type 2 diabetes that persists for up to 15 years postpartum. However, the underlying mechanisms are unknown. We examined whether in women with gestational diabetes lactation for >3 months is associated with altered metabolomic signatures postpartum.

METHODS

We enrolled 197 women with gestational diabetes at a median of 3.6 years (interquartile range 0.7-6.5 years) after delivery. Targeted metabolomics profiles (including 156 metabolites) were obtained during a glucose challenge test. Comparisons of metabolite concentrations and ratios between women who lactated for >3 months and women who lactated for ≤3 months or not at all were performed using linear regression with adjustment for age and BMI at the postpartum visit, time since delivery, and maternal education level, and correction for multiple testing. Gaussian graphical modelling was used to generate metabolite networks.

RESULTS

Lactation for >3 months was associated with a higher total lysophosphatidylcholine/total phosphatidylcholine ratio; in women with short-term follow-up, it was also associated with lower leucine concentrations and a lower total branched-chain amino acid concentration. Gaussian graphical modelling identified subgroups of closely linked metabolites within phosphatidylcholines and branched-chain amino acids that were affected by lactation for >3 months and have been linked to the pathophysiology of type 2 diabetes in previous studies.

CONCLUSIONS/INTERPRETATION

Lactation for >3 months in women with gestational diabetes is associated with changes in the metabolomics profile that have been linked to the early pathogenesis of type 2 diabetes.

Early diabetes screening in women with previous gestational diabetes: a new insight

BACKGROUND

Gestational diabetes mellitus (GDM) is a risk factor for the development of diabetes mellitus (DM). However, there is a low return rate for this screening, so it is important to search for earlier methods for evaluation after delivery, to increase the number of pregnant women screened, so you can start the treatment or prevention of these early comorbidities. To determine the accuracy of the 75 g 2-h oral glucose tolerance test (OGTT) performed between 48-72 h after delivery for the diagnosis of DM using the OGTT after 6 weeks as the gold standard criterion, and to identify the optimal cutoff points for this exam for diabetes screening after a pregnancy complicated by GDM.

METHODS

82 women with previous GDM underwent an OGTT between 48-72 h postpartum and repeated the test 6 weeks after delivery.

RESULTS

The prevalence of DM and prediabetes based on the first OGTT was 3.7 and 32.9 %, respectively, and 8.5 and 20.7 %, respectively, at the second OGTT. For those with DM, the area under the curve (AUC) based on the fasting plasma glucose (FPG) was 0.77 (95 % CI 0.61-0.92), and based on 2-h OGTT was 0.82 (95 % CI 0.66-0.97). For patients with prediabetes, the AUC based on the FPG was 0.73 (95 % CI 0.59-0.86) and based on the 2-h OGTT was 0.74 (95 % CI 0.61-0.87). Using a FPG cutoff value of 78 mg/dl (4.3 mmol/L) and a 2-h OGTT cutoff value of 130 mg/dl (7.2 mmol/L) for DM, the specificity was 58.7 and 60 %, the sensitivity was 71.4 and 85.7 %, the positive predictive value was 13.9 and 16.7 and the negative predictive value was 95.7 and 97.9 %, respectively.

CONCLUSIONS

OGTT performed early in postpartum is a useful tool for identifying women with previous GDM who must perform an OGTT 6 weeks after delivery.

Maternal Serum Prolactin and Prediction of Postpartum β-Cell Function and Risk of Prediabetes/Diabetes

OBJECTIVE

The insulin resistance of mid- to late pregnancy poses a physiologic stress test for the pancreatic β-cells, which must respond by markedly increasing their secretion of insulin. This response is achieved through an expansion of β-cell mass induced by the hormones prolactin and human placental lactogen (HPL). Conversely, the furan fatty acid metabolite 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) has recently emerged as a negative regulator of β-cell function in pregnancy. Given their respective roles in the β-cell response to the stress test of gestation, we hypothesized that antepartum prolactin, HPL, and CMPF may relate to a woman's underlying glucoregulatory physiology and hence to her metabolic status after pregnancy.

RESEARCH DESIGN AND METHODS

Three hundred and sixty-seven women underwent measurement of fasting serum prolactin, HPL, and CMPF in the late-2nd/early-3rd trimester, followed by an oral glucose tolerance test (OGTT) at 3 months postpartum that enabled assessment of glucose tolerance, insulin sensitivity/resistance, and β-cell function (Insulin Secretion-Sensitivity Index-2 [ISSI-2]).

RESULTS

The postpartum OGTT identified 301 women with normal glucose tolerance (NGT) and 66 with prediabetes or diabetes. Serum prolactin in pregnancy was higher in women with postpartum NGT compared with those with postpartum prediabetes/diabetes (mean 98.2 vs. 80.2 ng/mL, P = 0.0003), whereas HPL and CMPF did not differ between the groups. On multiple linear regression analyses, antepartum prolactin was an independent determinant of postpartum ISSI-2 (β = 0.0016, t = 2.96, P = 0.003). Furthermore, higher serum prolactin in pregnancy independently predicted a lower risk of postpartum prediabetes/diabetes (odds ratio 0.50, 95% CI 0.35-0.72, P = 0.0002).

CONCLUSIONS

Serum prolactin in pregnancy predicts postpartum β-cell function and risk of prediabetes/diabetes.

Evaluation of Circulating Determinants of Beta-Cell Function in Women With and Without Gestational Diabetes

CONTEXT

Gestational diabetes (GDM) arises in women in whom there is insufficient β-cell compensation for the insulin resistance of late pregnancy. The mechanisms underlying both normal antepartum β-cell adaptation and its aberrancy in GDM are unclear. Preclinical studies have suggested that the hormones prolactin and human placental lactogen (HPL) may stimulate β-cell mass, whereas the furan fatty acid metabolite 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) has recently emerged as a potential negative regulator of β-cell function. However, there has been limited study of these factors in humans.

OBJECTIVE

Our objective was to systematically evaluate HPL, prolactin, and CMPF in relation to glucose homeostasis and β-cell function in women with and without GDM.

DESIGN/SETTING/PARTICIPANTS

Three-hundred-and-ninety-five women underwent an oral glucose tolerance test in late pregnancy, enabling assessment of GDM status, glycemia (area-under-the-glucose-curve on oral glucose tolerance test [AUCglucose]), β-cell function (Insulin Secretion-Sensitivity Index-2, insulinogenic index/homeostatic model assessment of insulin resistance [HOMA-IR]), insulin sensitivity/resistance (Matsuda index, HOMA-IR), and circulating HPL, prolactin, and CMPF.

RESULTS

Serum concentrations of HPL, prolactin, and CMPF were similar between women with GDM (n = 105) and women without GDM (n = 290). However, on multiple linear regression analyses, CMPF emerged as a significant predictor of AUCglucose in women with GDM (t = 4.75, P < .0001) but not in their peers (P = .60). Furthermore, CMPF independently predicted lower Insulin Secretion-Sensitivity Index-2 (t = -2.28, P = .02) and lower insulinogenic index/HOMA-IR (t = -2.22, P = .03) in women with GDM but not in the non-GDM group (both P = .93). Neither HPL nor prolactin was significantly associated with AUCglucose, β-cell function, or insulin sensitivity.

CONCLUSION

CMPF is a potential circulating determinant of β-cell dysfunction and hyperglycemia in women with GDM.

Insulin: pancreatic secretion and adipocyte regulation

Insulin is the primary acute anabolic coordinator of nutrient partitioning. Hyperglycemia is the main stimulant of insulin secretion, but other nutrients such as specific amino acids, fatty acids, and ketoacids can potentiate pancreatic insulin release. Incretins are intestinal hormones with insulinotropic activity and are secreted in response to food ingestion, thus integrating diet chemical composition with the regulation of insulin release. In addition, prolactin is required for proper islet development, and it stimulates β-cell proliferation. Counterintuitively, bacterial components appear to signal insulin secretion. In vivo lipopolysaccharide infusion acutely increases circulating insulin, which is paradoxical as endotoxemia is a potent catabolic condition. Insulin is a potent anabolic orchestrator of nutrient partitioning, and this is particularly true in adipocytes. Insulin dictates lipid accretion in a dose-dependent manner during preadipocyte development in adipose tissue-derived stromal vascular cell culture. However, in vivo studies focused on insulin's role in regulating adipose tissue metabolism from growing, and market weight pigs are sometimes inconsistent, and this variability appears to be animal, age and depot dependent. Additionally, porcine adipose tissue synthesizes and secretes a number of adipokines (leptin, adiponectin, and so forth) that directly or indirectly influence insulin action. Therefore, because insulin has an enormous impact on agriculturally important phenotypes, it is critical to have a better understanding of how insulin homeostasis is governed.

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.

60 YEARS OF NEUROENDOCRINOLOGY: The hypothalamo-prolactin axis

The hypothalamic control of prolactin secretion is different from other anterior pituitary hormones, in that it is predominantly inhibitory, by means of dopamine from the tuberoinfundibular dopamine neurons. In addition, prolactin does not have an endocrine target tissue, and therefore lacks the classical feedback pathway to regulate its secretion. Instead, it is regulated by short loop feedback, whereby prolactin itself acts in the brain to stimulate production of dopamine and thereby inhibit its own secretion. Finally, despite its relatively simple name, prolactin has a broad range of functions in the body, in addition to its defining role in promoting lactation. As such, the hypothalamo-prolactin axis has many characteristics that are quite distinct from other hypothalamo-pituitary systems. This review will provide a brief overview of our current understanding of the neuroendocrine control of prolactin secretion, in particular focusing on the plasticity evident in this system, which keeps prolactin secretion at low levels most of the time, but enables extended periods of hyperprolactinemia when necessary for lactation. Key prolactin functions beyond milk production will be discussed, particularly focusing on the role of prolactin in inducing adaptive responses in multiple different systems to facilitate lactation, and the consequences if prolactin action is impaired. A feature of this pleiotropic activity is that functions that may be adaptive in the lactating state might be maladaptive if prolactin levels are elevated inappropriately. Overall, my goal is to give a flavour of both the history and current state of the field of prolactin neuroendocrinology, and identify some exciting new areas of research development.

Interventions to modify the progression to type 2 diabetes mellitus in women with gestational diabetes: a systematic review of literature

PURPOSE OF REVIEW

Gestational diabetes mellitus (GDM) increases the lifetime risk of developing type 2 diabetes mellitus (T2DM) in the mother. We undertook a systematic review to assess the effectiveness of interventions that delay or prevent the onset of T2DM in women with previous gestational diabetes.

RECENT FINDINGS

Diet and lifestyle interventions show differing effects on women with GDM and their long-term risk of T2DM. Pharmacological interventions, such as metformin, appear to have a beneficial role. Breastfeeding may have a protective role by reducing the risk of progression to T2DM. The findings were limited by the small number of heterogeneous studies that varied in their population, intervention, outcome and duration of follow-up.

SUMMARY

Women with GDM should be informed about the future risk of T2DM and the potential benefit with lifestyle interventions. Further studies are needed prior to routine use of metformin as a preventive strategy for T2DM in women with GDM.

Beneficial effects of breastfeeding in women with gestational diabetes mellitus

Gestational diabetes mellitus (GDM) increases the future risk of developing type 2 diabetes mellitus (T2DM). There is now a growing evidence that breastfeeding has short- and long-term health benefits for mothers with GDM. Mothers with GDM who breastfeed have improved lipid and glucose metabolic profiles for the first 3 months after birth. However, women with GDM are less likely to breastfeed and, if they do, breastfeeding is usually continued for a shorter duration compared with women without GDM. One long-term prospective study followed women with GDM from delivery for up to 19 years postpartum, and found that breastfeeding for ≥3 months reduced the risk of T2DM and delayed the development of T2DM by a further 10 years compared with breastfeeding for <3 months. However, the physiological mechanisms underlying the protective effects of breastfeeding are still unknown, even though it is important to gain a full understanding of the pathways involved in these effects. Therefore, the purpose of this review is to provide a comprehensive analysis of the recent developments in the field of GDM and breastfeeding. We reviewed data from animal experiments and human studies. We also provide insight into the molecular pathways and describe promising topics for future research.

Prolactin receptor gene polymorphisms are associated with gestational diabetes

AIMS

Human placental lactogen (hPL) acts via the prolactin receptor (PRLR) on maternal β-cells to mediate increases in β-cell mass and function during normal pregnancy. This interaction between hPL and PRLR is essential to maintain normal glucose homeostasis and to address the increased metabolic demands of pregnancy. Given the importance of the PRLR-hPL axis in pancreatic islet cell adaptation to pregnancy, we hypothesized that genetic variation in the PRLR gene could influence risk of development of gestational diabetes mellitus (GDM). DNA samples from 96 mothers affected by GDM and 96 unaffected cases were genotyped for 8 selected single nucleotide polymorphisms (SNPs) in PRLR.

RESULTS

Significant associations were identified in two SNPs analyzed. The minor alleles of PRLR SNPs rs10068521 and rs9292578 were more frequently observed in GDM cases than controls and were associated with a 2.36-fold increased risk for GDM in those carrying the minor allele.

CONCLUSION

SNPs of the PRLR gene 5' UTR and promoter region are associated with increased risk for GDM in a population of Chilean subjects.

Relationship between lactation duration and insulin and glucose response among women with prior gestational diabetes

BACKGROUND

Few studies have investigated whether favorable effects of lactation persist after weaning and protect women with prior gestational diabetes mellitus (GDM) against later development of insulin resistance and insulin secretion defects.

OBJECTIVE

To investigate the impact of lactation duration on insulin and glucose response among women with prior GDM.

DESIGN/METHODS

The study group comprised 144 women with a history of GDM between 2003 and 2010. Plasma insulin and glucose concentrations were obtained from a 75 g oral glucose tolerance test (OGTT). Total lactation duration (exclusive breastfeeding and breast and bottle-feeding) for all infants was self-reported in months.

RESULTS

Mean age was 36.5±5.0 years. Time between delivery and metabolic testing was 4.0±1.9 years. Women breastfed for an average of 13.9±16.8 months. Most women (80.6%) reported a history of lactation. Women who lactated had higher homeostasis model assessment for insulin sensitivity (HOMA-IS) and Matsuda indices and lower fasting and 2-h post-OGTT insulin concentrations as well as area under the curve (AUC) for insulin (P≤0.01 for all). Compared with women who lactated for <10 months, women who lactated for ≥10 months had improved insulin sensitivity-secretion index, higher HOMA-IS and Matsuda indices, lower fasting and 2-h post-OGTT insulin concentrations as well as AUC for insulin, and lower incidence of impaired glucose intolerance (P≤0.05 for all). In multiple linear regression analyses, lactation duration emerged as an independent predictor of fasting insulin concentrations (β=-0.02) and insulin sensitivity indices (β=0.02) (P≤0.05 for all).

CONCLUSIONS

These results suggest that longer duration of lactation is associated with improved insulin and glucose response among women with prior GDM.

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.