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

Could low prolactin levels after radiotherapy predict the onset of hypopituitarism?

Both local and external cranial radiotherapy (RT) can induce neurotoxicity and vascular damage of the hypothalamic-pituitary area, which can promote neuroendocrine alterations. While anterior pituitary insufficiency after RT has been extensively characterized, data on the effect of RT on prolactin (PRL) secretion are limited and heterogeneous, with different patterns of PRL behavior described in the literature. A progressive decline in PRL levels, reflecting a time-dependent, slowly evolving radiation-induced damage to the pituitary lactotroph cells has been reported. To date, the association between hypopituitarism and hypoprolactinemia in patients undergoing RT has not yet been fully investigated. The few available data suggest that lower PRL levels can predict an extent damage of the pituitary tissue and a higher degree of hypothalamic dysfunction. However, most studies on the effect of RT on pituitary function do not properly assess PRL secretion, as PRL deficiency is usually detected as part of hypopituitarism and not systematically investigated as an isolated disorder, which may lead to an underestimation of hypoprolactinemia after RT. In addition, the often-inadequate follow-up over a long period of time may contribute to the non-recognition of PRL deficiency after RT. Considering that hypoprolactinemia is associated with various metabolic complications, there is a need to define appropriate diagnostic and management criteria. Therefore, hypoprolactinemia should enter in the clinical investigation of patients at risk for hypopituitarism, mainly in those patients who underwent RT.

Excessive free fatty acid sensing in pituitary lactotrophs elicits steatotic liver disease by decreasing prolactin levels

The pituitary is the central endocrine gland with effects on metabolic dysfunction-associated steatotic liver disease (MASLD). However, it is not clear whether the pituitary responds to free fatty acid (FFA) toxicity, thus dysregulating hepatic lipid metabolism. Here, we demonstrate that decreased prolactin (PRL) levels are involved in the association between FFA and MASLD based on a liver biospecimen-based cohort. Moreover, overloaded FFAs decrease serum PRL levels, thus promoting liver steatosis in mice with both dynamic diet intervention and stereotactic pituitary FFA injection. Mechanistic studies show that excessive FFA sensing in pituitary lactotrophs inhibits the synthesis and secretion of PRL in a cell-autonomous manner. Notably, inhibiting excessive lipid uptake using pituitary stereotaxic virus injection or a specific drug delivery system effectively ameliorates hepatic lipid accumulation by improving PRL levels. Targeted inhibition of pituitary FFA sensing may be a potential therapeutic target for liver steatosis.

Increased BMI associated with decreased breastfeeding initiation in Million Veteran Program participants

Background

Breastfeeding has been associated with maternal and infant health benefits but has been inversely associated with body mass index (BMI) prepartum. Breastfeeding and BMI are both linked to socioeconomic factors.

Methods

Data from parous female participants with available breastfeeding information from the Million Veteran Program cohort was included. BMI at enrollment and earliest BMI available were extracted, and polygenic scores (PGS) for BMI were calculated. We modeled breastfeeding for one month or more as a function of BMI at enrollment; earliest BMI where available pre-pregnancy; and PGS for BMI. We conducted Mendelian randomization for breastfeeding initiation using PGS as an instrumental variable.

Results

A higher BMI predicted a lower likelihood of breastfeeding for one month or more in all analyses. A +5 kg/m 2 BMI pre-pregnancy was associated with a 24% reduced odds of breastfeeding, and a +5 kg/m 2 genetically predicted BMI was associated with a 17% reduced odds of breastfeeding.

Conclusions

BMI predicts a lower likelihood of breastfeeding for one month or longer. Given the high success of breastfeeding initiation regardless of BMI in supportive environments as well as potential health benefits, patients with elevated BMI may benefit from additional postpartum breastfeeding support.

Postpartum development of metabolic dysfunction-associated steatotic liver disease in a lean mouse model of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is associated with increased postpartum risk for metabolic dysfunction-associated steatotic liver disease (MASLD). GDM-related MASLD predisposes to advanced liver disease, necessitating a better understanding of its development in GDM. This preclinical study evaluated the MASLD development in a lean GDM mouse model with impaired insulin secretion capacity. Lean GDM was induced by short-term 60% high-fat diet and low-dose streptozotocin injections (60 mg/kg for 3 days) before mating in C57BL/6N mice. The control dams received only high-fat diet or low-fat diet. Glucose homeostasis was assessed during pregnancy and postpartum, whereas MASLD was assessed on postpartum day 30 (PP30). GDM dams exhibited a transient hyperglycemic phenotype during pregnancy, with hyperglycaemia reappearing after lactation. Lower insulin levels and impaired glucose-induced insulin response were observed in GDM mice during pregnancy and postpartum. At PP30, GDM dams displayed higher hepatic triglyceride content compared controls, along with increased MAS (MASLD) activity scores, indicating lipid accumulation, inflammation, and cell turnover indices. Additionally, at PP30, GDM dams showed elevated plasma liver injury markers. Given the absence of obesity in this double-hit GDM model, the results clearly indicate that impaired insulin secretion driven pregnancy hyperglycaemia has a distinct contribution to the development of postpartum MASLD.

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.

Current Insights in Prolactin Signaling and Ovulatory Function

Prolactin (PRL) is a pleiotropic hormone released from lactotrophic cells of the anterior pituitary gland that also originates from extrapituitary sources and plays an important role in regulating lactation in mammals, as well as other actions. Acting in an endocrine and paracrine/autocrine manner, PRL regulates the hypothalamic-pituitary-ovarian axis, thus influencing the maturation of ovarian follicles and ovulation. This review provides a detailed discussion of the current knowledge on the role of PRL in the context of ovulation and ovulatory disorders, particularly with regard to hyperprolactinemia, which is one of the most common causes of infertility in women. Much attention has been given to the PRL structure and the PRL receptor (PRLR), as well as the diverse functions of PRLR signaling under normal and pathological conditions. The hormonal regulation of the menstrual cycle in connection with folliculogenesis and ovulation, as well as the current classifications of ovulation disorders, are also described. Finally, the state of knowledge regarding the importance of TIDA (tuberoinfundibular dopamine), KNDγ (kisspeptin/neurokinin B/dynorphin), and GnRH (gonadotropin-releasing hormone) neurons in PRL- and kisspeptin (KP)-dependent regulation of the hypothalamic-pituitary-gonadal (HPG) axis in women is reviewed. Based on this review, a rationale for influencing PRL signaling pathways in therapeutic activities accompanying ovulation disorders is presented.

Lactogenesis factors in the Asian population

The increasing incidence of disrupted lactogenesis in Asian populations underscores the importance of timely identification and efficient intervention. This study acknowledges the influence of ethnicity on genetic variations and aims to investigate the genetic mechanisms that contribute to lactogenesis in individuals of Asian descent. This study examines the possibilities of genetic screening as a means of applying preventive measures, with a particular focus on epigenetic techniques. Additionally, the analysis looks into the underlying mechanisms involved in milk production. This review discusses the intricate mechanisms underlying breast milk production and the potential influence of genetic variables on lactogenesis. Specifically, it explores the association between lactogenesis issues and genetic conditions such as depression, obesity, gestational hypertension, and gestational diabetes. These genetic factors could potentially be found by genetic screening as contributors to disruption in lactogenesis. This study aims to promote future investigation in the subject of genetic testing and its potential association with lactogenesis issues, despite the current scarcity of direct research on this topic. The statement posits that the progress made in genetic testing has the potential to provide novel insights into the timely identification and treatment of disrupted lactogenesis.

Breastfeeding is associated with a delayed decrease in postprandial maternal glucose concentration

BACKGROUND

Breastfeeding has long-term benefits in reducing the risk of diabetes; however, information about the acute influence on maternal glucose profile is scarce. Thus, the aim of the study was to assess maternal glucose fluctuations associated with breastfeeding episodes in women with normal glucose status.

METHODS

We performed an observational study of glucose fluctuations with breastfeeding episodes in 26 women with normal glucose status in fasting and postprandial state. Continuous glucose monitoring was performed using CGMS MiniMed Gold®/iPro2® (Medtronic, Dublin, Ireland) three months after delivery under real-life conditions. We compared fasting and postprandial periods of 150 minutes affected or not by a breastfeeding episode.

RESULTS

Mean glucose concentration of postprandial periods affected by breastfeeding was lower than not affected (-6.31 mg/dL [95% CI: -11.17, -1.62] P<0.01). Glucose concentration was significantly lower between 50 and 105 minutes after meal initiation (maximum difference -9.19 mg/dL [95% CI: -16.03, -2.16] at 91-95 min). Mean glucose concentrations of fasting periods affected by breastfeeding were similar to those not affected (-0.18 mg/dL [95% CI: -2.7, 0] P=0.831).

CONCLUSIONS

In women with normal glucose status, breastfeeding episodes are associated with a lower glucose concentration in the postprandial but not in the fasting state.

Furan fatty acid metabolite CMPF is associated with lower risk of type 2 diabetes, but not chronic kidney disease: a longitudinal population-based cohort study

BACKGROUND

Furan fatty acid metabolite 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) is a strong biomarker of fish and n-3 polyunsaturated fatty acid (PUFA) intake. The relationship of CMPF with human health has been controversial, especially for type 2 diabetes and chronic kidney disease.

OBJECTIVE

We performed a prospective cohort study to examine the association of serum CMPF with incident type 2 diabetes and chronic kidney disease.

METHODS

In the Guangzhou Nutrition and Health Study, during a median follow-up of 8.8 y, we used a multivariable-adjusted Poisson regression model to investigate the association of baseline serum CMPF with the incidence of type 2 diabetes (1470 participants and 170 incident cases) and chronic kidney disease (1436 participants and 112 incident cases). We also examined the association of serial measures of serum CMPF with glycemic and renal function biomarkers. Mediation analysis was also performed to examine the contribution of CMPF in the association between marine n-3 PUFAs and risk of type 2 diabetes or chronic kidney disease.

RESULTS

Each standard deviation increase in baseline serum CMPF was associated with an 18% lower risk of type 2 diabetes (relative risk: 0.82, 95% confidence interval [CI]: 0.68, 0.99) but was not associated with chronic kidney disease (relative risk: 0.95; 95% CI: 0.77-1.16). Correlation analyses of CMPF with glycemic and renal function biomarkers showed similar results. Mediation analysis suggested that serum CMPF contributed to the inverse association between erythrocyte marine n-3 PUFAs and incident type 2 diabetes (proportion mediated 37%, P-mediation = 0.022).

CONCLUSIONS

Our findings suggest that serum CMPF was associated with a lower risk of type 2 diabetes but not chronic kidney disease. This study also suggests that CMPF may be a functional metabolite underlying the protective relationship between marine n-3 PUFA intake and type 2 diabetes.

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.

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.

Pregnancy induces pancreatic insulin secretion in women with long-standing type 1 diabetes

INTRODUCTION

Pregnancy entails both pancreatic adaptations with increasing β-cell mass and immunological alterations in healthy women. In this study, we have examined the effects of pregnancy on β-cell function and immunological processes in long-standing type 1 diabetes (L-T1D).

RESEARCH DESIGN AND METHODS

Fasting and stimulated C-peptide were measured after an oral glucose tolerance test in pregnant women with L-T1D (n=17) during the first trimester, third trimester, and 5-8 weeks post partum. Two 92-plex Olink panels were used to measure proteins in plasma. Non-pregnant women with L-T1D (n=30) were included for comparison.

RESULTS

Fasting C-peptide was detected to a higher degree in women with L-T1D during gestation and after parturition (first trimester: 64.7%, third trimester: 76.5%, and post partum: 64.7% vs 26.7% in non-pregnant women). Also, total insulin secretion and peak C-peptide increased during pregnancy. The plasma protein levels in pregnant women with L-T1D was dynamic, but few analytes were functionally related. Specifically, peripheral levels of prolactin (PRL), prokineticin (PROK)-1, and glucagon (GCG) were elevated during gestation whereas levels of proteins related to leukocyte migration (CCL11), T cell activation (CD28), and antigen presentation (such as CD83) were reduced.

CONCLUSIONS

In summary, we have found that some C-peptide secretion, that is, an indirect measurement of endogenous insulin production, is regained in women with L-T1D during pregnancy, which might be attributed to elevated peripheral levels of PRL, PROK-1, or GCG.

The metabolic role of prolactin: systematic review, meta-analysis and preclinical considerations

INTRODUCTION

Hyperprolactinemia has been proven to induce hypogonadism and metabolic derangements in both genders, while the consequences of prolactin (PRL) deficiency have been poorly investigated.

AREAS COVERED

To systematically review and analyze data from clinical studies focusing on the metabolic consequences of abnormally high prolactin levels (HPRL) and low prolactin levels (LPRL). In addition, data from preclinical studies about underlying pathophysiological mechanisms were summarized and discussed.

EXPERT OPINION

PRL contributes to providing the correct amount of energy to support the mother and the fetus/offspring during pregnancy and lactation, but it also has a homeostatic role. Pathological PRL elevation beyond these physiological conditions, but also its reduction, impairs metabolism and body composition in both genders, increasing the risk of diabetes and cardiovascular events. Hence, hypoprolactinemia should be avoided as much as possible during treatment with dopamine agonists for prolactinomas. Patients with hypoprolactinemia, because of endogenous or iatrogenic conditions, deserve, as those with hyperprolactinemia, careful metabolic assessment.

Lactation alters the relationship between liver lipid synthesis and hepatic fat stores in the postpartum period

In mothers who are nursing their infants, increased clearance of plasma metabolites into the mammary gland may reduce ectopic lipid in the liver. No study to date has investigated the role of lactation on liver lipid synthesis in humans, and we hypothesized that lactation would modify fatty acid and glucose handling to support liver metabolism in a manner synchronized with the demands of milk production. Lactating (n = 18) and formula-feeding women (n = 10) underwent metabolic testing at 6-week postpartum to determine whether lactation modified intrahepatic triacylglycerols (IHTGs), measured by proton magnetic resonance spectroscopy. Subjects ingested oral deuterated water to measure fractional de novo lipogenesis (DNL) in VLDL-TG during fasting and during an isotope-labeled clamp at an insulin infusion rate of 10 mU/m²/min. Compared with formula-feeding women, we found that lactating women exhibited lower plasma VLDL-TG concentrations, similar IHTG content and similar contribution of DNL to total VLDL-TG production. These findings suggest that lactation lowers plasma VLDL-TG concentrations for reasons that are unrelated to IHTG and DNL. Surprisingly, we determined that the rate of appearance of nonesterified fatty acids was not related to IHTG in either group, and the expected positive association between DNL and IHTG was only significant in formula-feeding women. Further, in lactating women only, the higher the prolactin concentration, the lower the IHTG, while greater DNL strongly associated with elevations in VLDL-TG. In conclusion, we suggest that future studies should investigate the role of lactation and prolactin in liver lipid secretion and metabolism.

Prolactin and Maternal Metabolism in Women With a Recent GDM Pregnancy and Links to Future T2D: The SWIFT Study

CONTEXT

Prolactin is a multifaceted hormone known to regulate lactation. In women with gestational diabetes mellitus (GDM) history, intensive lactation has been associated with lower relative risk of future type 2 diabetes (T2D). However, the role of prolactin in T2D development and maternal metabolism in women with a recent GDM pregnancy has not been ascertained.

OBJECTIVE

We examined the relationships among prolactin, future T2D risk, and key clinical and metabolic parameters.

METHODS

We utilized a prospective GDM research cohort (the SWIFT study) and followed T2D onset by performing 2-hour 75-g research oral glucose tolerance test (OGTT) at study baseline (6-9 weeks postpartum) and again annually for 2 years, and also by retrieving clinical diagnoses of T2D from 2 years through 10 years of follow up from electronic medical records. Targeted metabolomics and lipidomics were applied on fasting plasma samples collected at study baseline from 2-hour 75-g research OGTTs in a nested case-control study (100 future incident T2D cases vs 100 no T2D controls).

RESULTS

Decreasing prolactin quartiles were associated with increased future T2D risk (adjusted odds ratio 2.48; 95% CI, 0.81-7.58; P = 0.05). In women who maintained normoglycemia during the 10-year follow-up period, higher prolactin at baseline was associated with higher insulin sensitivity (P = 0.038) and HDL-cholesterol (P = 0.01), but lower BMI (P = 0.001) and leptin (P = 0.002). Remarkably, among women who developed future T2D, prolactin was not correlated with a favorable metabolic status (all P > 0.05). Metabolomics and lipidomics showed that lower circulating prolactin strongly correlated with a T2D-high risk lipid profile, with elevated circulating neutral lipids and lower concentrations of specific phospholipids/sphingolipids.

CONCLUSION

In women with recent GDM pregnancy, low circulating prolactin is associated with specific clinical and metabolic parameters and lipid metabolites linked to a high risk of developing T2D.

Novel Biomolecules in the Pathogenesis of Gestational Diabetes Mellitus 2.0

Gestational diabetes mellitus (GDM) has become a major public health problem and one of the most discussed issues in modern obstetrics. GDM is associated with serious adverse perinatal outcomes and long-term health consequences for both the mother and child. Currently, the importance and purposefulness of finding a biopredictor that will enable the identification of women with an increased risk of developing GDM as early as the beginning of pregnancy are highly emphasized. Both “older” molecules, such as adiponectin and leptin, and “newer” adipokines, including fatty acid-binding protein 4 (FABP4), have proven to be of pathophysiological importance in GDM. Therefore, in our previous review, we presented 13 novel biomolecules, i.e., galectins, growth differentiation factor-15, chemerin, omentin-1, osteocalcin, resistin, visfatin, vaspin, irisin, apelin, FABP4, fibroblast growth factor 21, and lipocalin-2. The purpose of this review is to present the potential and importance of another nine lesser known molecules in the pathogenesis of GDM, i.e., 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), angiopoietin-like protein-8 (ANGPTL-8), nesfatin-1, afamin, adropin, fetuin-A, zonulin, secreted frizzled-related proteins (SFRPs), and amylin. It seems that two of them, fetuin-A and zonulin in high serum levels, may be applied as biopredictors of GDM.

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.

The beneficial metabolic actions of prolactin

The role of prolactin (PRL) favoring metabolic homeostasis is supported by multiple preclinical and clinical studies. PRL levels are key to explaining the direction of its actions. In contrast with the negative outcomes associated with very high (>100 μg/L) and very low (<7 μg/L) PRL levels, moderately high PRL levels, both within but also above the classically considered physiological range are beneficial for metabolism and have been defined as HomeoFIT-PRL. In animal models, HomeoFIT-PRL levels counteract insulin resistance, glucose intolerance, adipose tissue hypertrophy and fatty liver; and in humans associate with reduced prevalence of insulin resistance, fatty liver, glucose intolerance, metabolic syndrome, reduced adipocyte hypertrophy, and protection from type 2 diabetes development. The beneficial actions of PRL can be explained by its positive effects on main metabolic organs including the pancreas, liver, adipose tissue, and hypothalamus. Here, we briefly review work supporting PRL as a promoter of metabolic homeostasis in rodents and humans, the PRL levels associated with metabolic protection, and the proposed mechanisms involved. Finally, we discuss the possibility of using drugs elevating PRL for the treatment of metabolic diseases.

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

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

Gestational Diabetes Mellitus: Diagnostic Approaches and Maternal-Offspring Complications

Gestational diabetes mellitus (GDM) is the most common complication during pregnancy and is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. GDM is associated with adverse pregnancy outcomes and long-term offspring and maternal complications. For GDM screening and diagnosis, a two-step approach (1-hour 50 g glucose challenge test followed by 3-hour 100 g oral glucose tolerance test) has been widely used. After the Hyperglycemia and Adverse Pregnancy Outcome study implemented a 75 g oral glucose tolerance test in all pregnant women, a one-step approach was recommended as an option for the diagnosis of GDM after 2010. The one-step approach has more than doubled the incidence of GDM, but its clinical benefit in reducing adverse pregnancy outcomes remains controversial. Long-term complications of mothers with GDM include type 2 diabetes mellitus and cardiovascular disease, and complications of their offspring include childhood obesity and glucose intolerance. The diagnostic criteria of GDM should properly classify women at risk for adverse pregnancy outcomes and long-term complications. The present review summarizes the strengths and weaknesses of the one-step and two-step approaches for the diagnosis of GDM based on recent randomized controlled trials and observational studies. We also describe the long-term maternal and offspring complications of GDM.

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.

Lactation improves pancreatic β cell mass and function through serotonin production

Pregnancy imposes a substantial metabolic burden on women through weight gain and insulin resistance. Lactation reduces the risk of maternal postpartum diabetes, but the mechanisms underlying this benefit are unknown. Here, we identified long-term beneficial effects of lactation on β cell function, which last for years after the cessation of lactation. We analyzed metabolic phenotypes including β cell characteristics in lactating and non-lactating humans and mice. Lactating and non-lactating women showed comparable glucose tolerance at 2 months after delivery, but after a mean of 3.6 years, glucose tolerance in lactated women had improved compared to non-lactated women. In humans, the disposition index, a measure of insulin secretory function of β cells considering the degree of insulin sensitivity, was higher in lactated women at 3.6 years after delivery. In mice, lactation improved glucose tolerance and increased β cell mass at 3 weeks after delivery. Amelioration of glucose tolerance and insulin secretion were maintained up to 4 months after delivery in lactated mice. During lactation, prolactin induced serotonin production in β cells. Secreted serotonin stimulated β cell proliferation through serotonin receptor 2B in an autocrine and paracrine manner. In addition, intracellular serotonin acted as an antioxidant to mitigate oxidative stress and improved β cell survival. Together, our results suggest that serotonin mediates the long-term beneficial effects of lactation on female metabolic health by increasing β cell proliferation and reducing oxidative stress in β cells.

Prolactin as a neuroendocrine clue in sexual function of women across the reproductive life cycle: an expert point of view

Prolactin is a proteic hormone best known for its role in enabling the production of milk by female mammals. Secreted by the pituitary gland in response to the stimuli of eating, estrogen treatment, mating, ovulation and nursing, prolactin is involved in over 300 separate processes in a range of vertebrates, including humans. The hormone is released in a pulsatile manner and plays an essential role in metabolism, as well as in the regulation of the immune system and pancreatic development. Nevertheless, prolactin exerts other relevant roles, as it acts at the central nervous system level to modulate behavior, arousal and sexuality. In this experts' opinion, we aim to give insights into the main activities of prolactin to advance the ability of medical doctors and specialists in obstetrics and gynecology to provide more emphasis in their clinical practices to the link between prolactin and sexuality.

The Role of HIV Infection in the Pathophysiology of Gestational Diabetes Mellitus and Hypertensive Disorders of Pregnancy

Purpose of the Review: The main objective of this study is to investigate mechanisms associated with gestational diabetes mellitus (GDM) and hypertensive disorders of pregnancy (HDP) in HIV infected pregnant women by looking how placental hormones such as (progesterone and prolactin) and basic haemostatic parameters are regulated in HIV infected pregnancies.

Recent Findings: HIV/AIDS are a major global obstetric health burden that lead to increased rate of morbidity and mortality. HIV/AIDS has been associated with the pathophysiology of GDM and HDP. Increased risk of GDM due to highly active antiretroviral therapy (HAART) usage has been reported in HIV infected pregnancies, which causes insulin resistance in both pregnant and non-pregnant individuals. HAART is a medication used for lowering maternal antepartum viral load and pre-exposure and post-exposure prophylaxis of the infant. In pregnant women, HAART induces diabetogenic effect by causing dysregulation of placental hormones such as (progesterone and prolactin) and predispose HIV infected women to GDM. In addition to HIV/AIDS and GDM, Studies have indicated that HIV infection causes haemostatic abnormalities such as hematological disorder, deregulated haematopoiesis process and the coagulation process which results in HDP.

Summary: This study will help on improving therapeutic management and understanding of the pathophysiology of GDM and HDP in the absence as well as in the presence of HIV infection by reviewing studies reporting on these mechanism.

Association between variations of physiological prolactin serum levels and the risk of type 2 diabetes: A systematic review and meta-analysis

AIM

To determine the pooled association between variations of prolactin serum levels within the physiological range and the risk of type 2 diabetes mellitus (T2D).

METHODS

Pubmed, Scopus, Web of Science, and grey literature were searched for studies investigating the association between variations of prolactin serum levels in the normal range and the risk of T2D in adults. The risk of prevalent and incident T2D was summarized as the odds ratio or relative risk according to the quartile of prolactin serum concentration, using random-effects meta-analysis.

RESULTS

Of 2,014 articles identified, 6 met the inclusion criteria. Data were pooled from cross-sectional studies including 6,670 subjects and longitudinal studies involving 13,203 subjects. Men with prolactin levels in the fourth quartile versus those in the first quartile had decreased risk of prevalent T2D (OR 0.52; 95%CI 0.35-077). The same association was seen in women (OR 0.46; 95%CI 0.30-0.73). Conversely, prolactin levels in the fourth versus first quartile were not associated with the risk of incident T2D in men (RR 1.21; 95%CI 0.79-1.87) or women (RR 0.77; 95%CI 0.48-1.22).

CONCLUSION

Higher prolactin serum levels within the normal range were associated with reduced risk of prevalent but not incident T2D. Further studies are necessary to address whether this association is causal, but these findings raise the discussion regarding the optimal level of prolactin suppression in subjects undergoing therapy with dopaminergic agonists.

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.

Placental Lactogen as a Marker of Maternal Obesity, Diabetes, and Fetal Growth Abnormalities: Current Knowledge and Clinical Perspectives

Placental lactogen (PL) is a peptide hormone secreted throughout pregnancy by both animal and human specialized endocrine cells. PL plays an important role in the regulation of insulin secretion in pancreatic β-cells, stimulating their proliferation and promoting the expression of anti-apoptotic proteins. Cases of pregnancy affected by metabolic conditions, including obesity and diabetes, are related to alterations in the PL secretion pattern. Whereas obesity is most often associated with lower PL serum concentrations, diabetes results in increased PL blood levels. Disruptions in PL secretion are thought to be associated with an increased prevalence of gestational complications, such as placental dysfunction, diabetic retinopathy, and abnormalities in fetal growth. PL is believed to be positively correlated with birth weight. The impaired regulation of PL secretion could contribute to an increased incidence of both growth retardation and fetal macrosomia. Moreover, the dysregulation of PL production during the intrauterine period could affect the metabolic status in adulthood. PL concentration measurement could be useful in the prediction of fetal macrosomia in women with normal oral glucose tolerance test (OGTT) results or in evaluating the risk of fetal growth restriction, but its application in standard clinical practice seems to be limited in the era of ultrasonography.

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.

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.

Pure omega 3 polyunsaturated fatty acids (EPA, DPA or DHA) are associated with increased plasma levels of 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) in a short-term study in women

3-Carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) is a metabolite of furan fatty acids found in plasma and urine. Our data show that purified EPA, DPA and DHA may also be precursors of CMPF; however the metabolic pathway(s) remain unclear.

The effect of breastfeeding on postpartum glucose tolerance and lipid profiles in women with gestational diabetes mellitus

Background

We aimed to investigate the association of breastfeeding on postpartum glucose levels and lipid profiles in women diagnosed with gestational diabetes mellitus (GDM) and women without GDM.

Methods

We performed a secondary analysis of a cohort study of 243 women, 159 women with GDM and 84 normally glucose tolerant women between 2012 and 2017. At approximately 6-10 weeks postpartum, we measured fasting blood glucose and plasma lipid levels. Breastfeeding behaviour was self-defined as exclusive breastfeeding or not exclusive breastfeeding.

Results

The mean (SD) glucose in the group of women who breastfed exclusively was 4.6 (0.49) mmol/L, compared to 4.9 (0.58) mmol/L (95% CI 0.45, 0.15, p <  0.001) among women who did not exclusively breastfeed. Among women with GDM, the reduction in fasting glucose in women who were breastfeeding was 0.22 mmol/L (95% CI 0.39, 0.05, p = 0.004), and in women who were not GDM, the reduction was 0.14 mmol/L (95% CI 0.37, 0.09, p = 0.24,). After adjustment for GDM status in pregnancy, maternal body mass index (BMI), maternal age and ethnicity, and exclusive breastfeeding was associated with a decreased fasting glucose of 0.19 (95% CI 0.318, 0.061, p = 0.004). After similar adjustment, there was no significant difference in triglycerides, high density lipoprotein cholesterol or low-density lipoprotein cholesterol between women who were breastfeeding and women who were not breastfeeding.

Conclusions

Breastfeeding is associated with a reduction in fasting glucose levels postpartum, but not maternal lipid profile. Breastfeeding may play a role in reducing glucose intolerance in women who have had GDM.

Lrrc55 is a novel prosurvival factor in pancreatic islets

Pancreatic islets adapt to the increase in insulin demand during pregnancy by upregulating β-cell number, insulin synthesis, and secretion. These changes require prolactin receptor (PrlR) signaling, as mice with PrlR deletion are glucose intolerant with a lower β-cell mass. Prolactin also prevents β-cell apoptosis. Many genes participate in these adaptive changes in the islet, and Lrrc55 is one of the most upregulated genes with unknown function in islets. Because Lrrc55 expression increases in parallel to the increase in β-cell number and insulin production during pregnancy, we hypothesize that Lrrc55 might regulate β-cell proliferation/apoptosis (thus β-cell number) and insulin synthesis. Here, we found that Lrrc55 expression was upregulated by >60-fold during pregnancy in a PrlR-dependent manner, and this increase was restricted only to the islets. Overexpression of Lrrc55 in β-cells had minimal effect on β-cell proliferation and glucose-stimulated insulin secretion but protected β-cells from glucolipotoxicity-induced reduction in insulin gene expression. Moreover, Lrrc55 protects β-cells from glucolipotoxicity-induced apoptosis, with upregulation of prosurvival signals and downregulation of proapoptotic signals of the endoplasmic reticulum (ER) stress pathway. Furthermore, Lrrc55 attenuated calcium depletion induced by glucolipotoxicity, which may contribute to its antiapoptotic effect. Hence our findings suggest that Lrrc55 is a novel prosurvival factor that is upregulated specifically in islets during pregnancy, and it prevents conversion of adaptive unfolded protein response to unresolved ER stress and apoptosis in β-cells. Lrrc55 could be a potential therapeutic target in diabetes by reducing ER stress and promoting β-cell survival.

Screening Glucose Challenge Test in Pregnancy Can Identify Women With an Adverse Postpartum Cardiovascular Risk Factor Profile: Implications for Cardiovascular Risk Reduction

Background

The 1‐hour glucose challenge test (GCT) is routinely performed in pregnancy to screen for gestational diabetes mellitus. Remarkably, it has recently emerged that the GCT can also predict a woman's future risk of cardiovascular disease, although the mechanistic basis of this relationship is unclear. In this context we hypothesized that a higher GCT may identify women with an otherwise unrecognized adverse cardiovascular phenotype. Thus, we sought to evaluate the relationship between the antepartum GCT and subsequent postpartum cardiovascular risk factor profile.

Methods and Results

In this study 503 women completed a screening GCT in late second trimester and then underwent cardiometabolic characterization at 3 months postpartum, whereupon traditional (blood pressure, glucose, lipids) and nontraditional (apolipoprotein B, C‐reactive protein, adiponectin) cardiovascular risk factors were compared across GCT tertiles. At 3 months postpartum, each of the following risk factors progressively worsened from the lowest to middle to highest GCT tertile: fasting glucose (P=0.0002), 2‐hour glucose (P<0.0001), total cholesterol:high‐density lipoprotein cholesterol (P=0.0004), high‐density lipoprotein cholesterol (P=0.004), triglycerides (P=0.001), apolipoprotein B (P=0.001), and adiponectin (P=0.02). On multiple linear regression analyses, the GCT emerged as a significant independent predictor of higher fasting glucose (P=0.0006), 2‐hour glucose (P<0.0001), total cholesterol: high‐density lipoprotein cholesterol (P=0.0004), triglycerides (P=0.001), low‐density lipoprotein cholesterol (P=0.01), and apolipoprotein B (P=0.004) and of lower high‐density lipoprotein cholesterol (P=0.02) and adiponectin (P=0.0099). Moreover, these independent associations persisted after excluding women who had gestational diabetes mellitus.

Conclusions

The antepartum GCT can identify women with an adverse underlying cardiovascular risk factor phenotype.

Piecing together the puzzle of pancreatic islet adaptation in pregnancy

Pregnancy places acute demands on maternal physiology, including profound changes in glucose homeostasis. Gestation is characterized by an increase in insulin resistance, counterbalanced by an adaptive increase in pancreatic β cell production of insulin. Failure of normal adaptive responses of the islet to increased maternal and fetal demands manifests as gestational diabetes mellitus (GDM). The gestational changes and rapid reversal of islet adaptations following parturition are at least partly driven by an anticipatory program rather than post-factum compensatory adaptations. Here, I provide a comprehensive review of the cellular and molecular mechanisms underlying normal islet adaptation during pregnancy and how dysregulation may lead to GDM. Emerging areas of interest and understudied areas worthy of closer examination in the future are highlighted.

Pancreatic prolactin receptor signaling regulates maternal glucose homeostasis

Prolactin (PRL) signaling has been implicated in the regulation of glucose homeostatic adaptations to pregnancy. In this report, the PRL receptor (Prlr) gene was conditionally disrupted in the pancreas, creating an animal model which proved useful for investigating the biology and pathology of gestational diabetes including its impacts on fetal and placental development. In mice, pancreatic PRLR signaling was demonstrated to be required for pregnancy-associated changes in maternal β cell mass and function. Disruption of the Prlr gene in the pancreas resulted in fewer insulin producing cells, which failed to expand appropriately during pregnancy resulting in reduced blood insulin levels and maternal glucose intolerance. This inability to sustain normal blood glucose balance during pregnancy worsened with age and a successive pregnancy. The etiology of the insulin insufficiency was attributed to deficits in regulatory pathways controlling β cell development. Additionally, the disturbance in maternal blood glucose homeostasis, was associated with fetal overgrowth and dysregulation of inflammation and prolactin-associated transcripts in the placenta. Overall, these results indicate that the PRLR, acting within the pancreas, mediates maternal pancreatic adaptations to pregnancy and therefore its dysfunction may increase a woman's chances of becoming glucose intolerant during pregnancy.

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

AIMS/HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSIONS/INTERPRETATION

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

Increased serum 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) levels are associated with glucose metabolism in Chinese pregnant women

PURPOSE

Previous studies have found that 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) was associated with diabetes. This study aimed to investigate the relationship between abnormal increased CMPF levels and gestational diabetes mellitus (GDM).

METHODS

We recruited 828 pregnant women, and all of them underwent an oral glucose tolerance test (OGTT). We screened out 141 GDM patients and 230 pregnant women with normal glucose tolerance as controls. The serum CMPF concentration in participants was measured, and the relationship between the serum CMPF concentration and various parameters and biochemical indices was analyzed.

RESULTS

Compared with the serum levels in pregnant women with normal glucose tolerance, GDM patients exhibited markedly higher serum CMPF levels. The serum CMPF concentration showed an independent positive correlation with the blood glucose levels, glycated hemoglobin A1c(HbA1c), and the area under the glucose-time curve from the 2-h OGTT (AUC for glucose). Moreover, the CMPF concentration was independently negatively correlated with insulin secretion. However, CMPF was not significantly associated with lipid metabolism.

CONCLUSIONS

Elevated serum CMPF levels are detrimental to the development of hyperglycemia and islet β-cell functional failure in patients with GDM, which may promote the development of GDM.

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.

Furan fatty acids - Beneficial or harmful to health?

Furan fatty acids are found in plants, algae, and fish, and reported to have some positive health benefits, including anti-oxidant and anti-inflammatory activities, and inhibition of non-enzymatic lipid peroxidation. A major metabolite of furan fatty acids, 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), has been reported to be increased in patients who progress from prediabetes to type 2 diabetes, although CMPF is not necessarily associated with impaired glucose metabolism. Other studies report that CMPF levels are lower in subjects with diabetes than control subjects. Plasma CMPF levels increase in subjects who consume fish or fish oil, and in patients with renal failure. It is not known where furan fatty acids are converted to CMPF and it is speculated that this might be a result of microbiome activity. The plasma levels reported for CMPF in healthy, diabetic and patients with renal disease vary by factors of more than 100-fold within each of these three groups, so measurement error appears to be limiting the ability to interpret studies. This review explores these controversies and raises questions about whether CMPF is a marker for healthy diets or indeed associated with diabetes and renal health. The review concludes that, on balance, furan fatty acids are beneficial for health.

Circulating 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) levels are associated with hyperglycemia and β cell dysfunction in a Chinese population

Several recent clinical studies have suggested that the levels of circulating 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) are significantly higher in patients with gestational diabetes mellitus (GDM), impaired glucose tolerance (IGT), and type 2 diabetes mellitus (T2DM). This study recruited a total of 516 participants. The following patient populations were enrolled: 99 newly diagnosed cases with T2DM, 219 cases with prediabetes [82 with isolated impaired glucose tolerance (I − IGT), 66 with isolated impaired fasting glucose (I − IFG) and 71 with impaired glucose tolerance and impaired fasting glucose (IGT + IFG)], and 198 cases with normal glucose tolerance [NGT, including 99 first-degree relatives of type 2 diabetes patients (FDRs) and 99 non-FDRs]. We investigated the circulating CMPF levels in subjects with different glucose metabolism statuses and examined the potential link between CMPF and β cell function. Our results indicate that the serum CMPF levels were elevated in the prediabetes, T2DM, and FDRs groups compared to the NGT group. Additionally, the serum CMPF concentrations were independently and negatively associated with the triglyceride levels and Stumvoll first-phase insulin secretion index. Cumulatively, our findings suggest that the circulating CMPF levels can predict glycolipid metabolism disorders. Furthermore, elevated serum CMPF concentrations may determine hyperglycemia and β cell dysfunction.

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.

Prior lactation reduces future diabetic risk through sustained postweaning effects on insulin sensitivity

Breastfeeding for ≥12 mo is recommended for optimal infant nutrition but may hold maternal benefits as well. Indeed, lactation has been associated with lower long-term risk of diabetes in the mother, but the mechanism by which it imparts sustained postweaning effects on glucose tolerance remains unclear. In this context, we postulated that lactation could potentially induce postweaning beneficial effects on glucose tolerance by modifying the natural history of insulin sensitivity and/or pancreatic β-cell function over time. Thus, in this study, we evaluated the relationships between duration of lactation [≤3 mo (n = 70), 3-12 mo (n = 140), and ≥12 mo (n = 120)] and trajectories of insulin sensitivity/resistance, β-cell function, and glycemia over the first 3 yr postpartum in a cohort of 330 women comprising the full spectrum of glucose tolerance in pregnancy, who underwent serial metabolic characterization, including oral glucose tolerance tests, at 3 mo, 1 yr, and 3 yr postpartum. The prevalence of dysglycemia (pre-diabetes/diabetes) at 3 yr postpartum was lower in women who breastfed for ≥12 mo (12.5%) than in those who breastfed for ≤3 mo (21.4%) or for 3-12 mo (25.7%)(overall P = 0.028). On logistic regression analysis, lactation for ≥12 mo independently predicted a lower likelihood of prediabetes/diabetes at 3 yr postpartum (OR = 0.37, 95% CI 0.18-0.78, P = 0.009). Notably, lactation for ≥12 mo predicted lesser worsening of insulin sensitivity/resistance (P < 0.0001), fasting glucose (P < 0.0001), and 2-h glucose (P = 0.011) over 3 yr compared with lactation ≤3 mo but no differences in β-cell function (P ≥ 0.37). It has thus emerged that adherence to current breastfeeding recommendations reduces future diabetic risk through sustained postweaning effects on insulin sensitivity/resistance but not β-cell function.

Synthesis and Characterization of Urofuranoic Acids: In Vivo Metabolism of 2-(2-Carboxyethyl)-4-methyl-5-propylfuran-3-carboxylic Acid (CMPF) and Effects on in Vitro Insulin Secretion

CMPF (2-(2-carboxyethyl)-4-methyl-5-propylfuran-3-carboxylic acid) is a metabolite that circulates at high concentrations in type 2 and gestational diabetes patients. Further, human clinical studies suggest it might have a causal role in these diseases. CMPF inhibits insulin secretion in mouse and human islets in vitro and in vivo in rodents. However, the metabolic fate of CMPF and the relationship of structure to effects on insulin secretion have not been significantly studied. The syntheses of CMPF and analogues are described. These include isotopically labeled molecules. Study of these materials in vivo has led to the first observation of a metabolite of CMPF. In addition, a wide range of CMPF analogues have been prepared and characterized in insulin secretion assays using both mouse and human islets. Several molecules that influence insulin secretion in vitro were identified. The molecules described should serve as interesting probes to further study the biology of CMPF.

Histological and Metabolic State of Dams Suckling Small Litter or MSG-Treated Pups

Lactation is an important function that is dependent on changes in the maternal homeostasis and sustained by histological maternal adjustments. We evaluated how offspring manipulations during the lactational phase can modulate maternal morphologic aspects in the mammary gland, adipose tissue, and pancreatic islets of lactating dams. Two different models of litter-manipulation-during-lactation were used: litter sizes, small litters (SL) or normal litters (NL) and subcutaneous injections in the puppies of monosodium glutamate (MSG), or saline (CON). SL Dams and MSG Dams presented an increase in WAT content and higher plasma levels of glucose, triglycerides, and insulin, in relation to NL Dams and CON Dams, respectively. The MG of SL Dams and MSG Dams presented a high adipocyte content and reduced alveoli development and the milk of the SL Dams presented a higher calorie and triglyceride content, compared to that of the NL Dams. SL Dams presented a reduction in islet size and greater lipid droplet accumulation in BAT, in relation to NL Dams. SL Dams and MSG Dams present similar responses to offspring manipulation during lactation, resulting in changes in metabolic parameters. These alterations were associated with higher fat accumulation in BAT and changes in milk composition only in SL Dams.