Prolactin effect on blood glucose and insülin in breastfeeding women

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.

Influence of Breastfeeding on the State of Meta-Inflammation in Obesity-A Narrative Review

Obesity has become an emerging health issue worldwide that continues to grow in females of reproductive age as well. Obesity, as a multisystem and chronic disease, is associated with metabolic inflammation, which is defined as chronic low-grade systemic inflammation mediated by, i.a., adipose tissue macrophages. Lactation has been proven to have a beneficial influence on maternal health and could help restore metabolic balance, especially in the state of maternal obesity. In this review, we aimed to analyze the influence of breastfeeding on chronic low-grade meta-inflammation caused by obesity. We performed a comprehensive literature review using the PubMed, Science Direct, and Google Scholar electronic databases. For this purpose, we searched for "metabolic inflammation"; "meta-inflammation"; "obesity"; "breastfeeding"; "fetal programming"; "energy metabolism"; "postpartum"; "immunity"; "immune system"; and "inflammation" keyword combinations. While the clinical impact of breastfeeding on maternal and offspring health is currently well known, we decided to gain insight into more specific metabolic effects of adiposity, lipid, and glucose homeostasis, and immunological effects caused by the activity of cytokines, macrophages, and other immune system cells. Further research on the immunological and metabolic effects of breastfeeding in obese patients is key to understanding and potentially developing obesity therapeutic strategies.

Prolactin does not seem to mediate the improvement on insulin resistance markers and blood glucose levels related to breastfeeding

Introduction

The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide. Strategies to decrease this risk should be strongly encouraged. Lactation has been associated, for the mother, with reduction in future T2DM risk in several studies. The mechanisms behind this phenomenon, however, are poorly understood. The aims of this study were, first, to compare blood glucose levels and markers of insulin resistance (MIR) in early postpartum women with overweight/obesity according to their breastfeeding status and, second, to evaluate whether prolactin (PRL) levels could mediate improvements in these parameters.

Methods

The prospective study followed 95 women older than 18 years from early pregnancy for up to 60 to 180 days postpartum. All participants had a BMI > 25 kg/m2 and a singleton pregnancy. At each visit, questionnaires and clinical and biochemical evaluations were performed. Participants were divided into two groups according to the breastfeeding status as "yes" for exclusive or predominant breastfeeding, and "no" for not breastfeeding.

Results

Breastfeeding women (n = 44) had significantly higher PRL levels [47.8 (29.6-88.2) vs. 20.0 (12.0-33.8), p< 0.001]. They also had significantly lower fasting blood glucose levels [89.0 (8.0) vs. 93.9 (12.6) mg/dl, p = 0.04], triglycerides (TG) [92.2 (37.9) vs. 122.4 (64.4) mg/dl, p = 0.01], TG/HDL ratio [1.8 (0.8) vs. 2.4 (1.6) mg/dl, p = 0.02], TyG index [8.24 (0.4) vs. 8.52 (0.53), p = 0.005], fasting serum insulin [8.9 (6.3-11.6) vs. 11.4 (7.7-17.0), p = 0.048], and HOMA-IR [2.0 (1.3-2.7) vs. 2.6 (1.6-3.9), p = 0.025] in the postpartum period compared to the non-breastfeeding group. Groups were homogeneous in relation to prevalence of GDM, pre-gestational BMI, as well as daily caloric intake, physical activity, and weight loss at postpartum. Linear regression analysis with adjustments for confounders showed a statistically significant association of breastfeeding with fasting blood glucose [-6.37 (-10.91 to -1.83), p = 0.006], HOMA-IR [-0.27 (-0.51 to -0.04), p = 0.024], TyG index [-0.04 (-0.06 to -0.02), p = 0.001], and TG/HDL ratio [-0.25 (-0.48 to -0.01), p = 0.038]. Mediation analysis showed that PRL did not mediate these effects. Sensitivity analyses considering different cutoffs for PRL levels also did not show modification effect in the mediation analyses.

Conclusion

Breastfeeding was associated with improvement in glucose metabolism and MIR 60 to 180 days after birth in overweight and obese women, even when adjusted for confounders. PRL levels were not found to mediate the association between breastfeeding and improvement in MIR.

Self-management of type 2 diabetes mellitus in pregnancy and breastfeeding experiences among women in Thailand: Study protocol

Women with type 2 diabetes mellitus are at a higher risk of pregnancy complications. Although traditional beliefs and practices influence diabetes management and breastfeeding, recommendations integrating Thai cultural beliefs in maternal care are lacking. The purpose of this study is to describe diabetes self-management in pregnancy and breastfeeding experiences in women with preexisting type 2 diabetes mellitus from Thailand. A convergent parallel mixed-methods study will be conducted. Data will be collected from 20 pregnant women with preexisting type 2 diabetes mellitus in Thailand who are either primigravida or multigravida, aged 20-44 years old, speak the Thai language, and provide consent. The National Institute on Minority Health and Health Disparities Framework's sociocultural and behavioral domains guides the research aims. Data will be collected two times. The first time is during pregnancy (T1); study participants will complete questionnaires and engage in an interview about diabetes self-management, breastfeeding confidence, and breastfeeding intention. The second time is at 4-6 weeks postpartum (T2); study participants will be interviewed about their breastfeeding experiences. We will review and extract maternal health outcomes including body mass index, gestational weight gain, and glycated hemoglobin for T1 as well as fasting plasma glucose for T2. Qualitative data will be analyzed using directed content analysis. Quantitative data will be analyzed using descriptive statistics. Data sources will be triangulated with relative convergence in the results. This proposed study is significant because the findings will be used as a preliminary guide to developing a culturally tailored approach to enhance health outcomes of Thai women with diabetes in pregnancy and postpartum periods.

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].

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.

Risk factors of hyperprolactinemia induced by risperidone and olanzapine and their correlations with plasma glucose and lipids

Background

Hyperprolactinemia is a common adverse reaction in patients with schizophrenia who take antipsychotic drugs; it often leads to treatment non-compliance in patients and has an adverse effect on their prognosis.

Aims

This study aimed to explore the risk factors of elevated prolactin (PRL) caused by risperidone (RIS) and olanzapine (OLZ) and the relationship between PRL and fasting plasma glucose and lipids.

Methods

Patients with schizophrenia were divided into two groups: 264 patients who were taking RIS and 175 patients who were taking OLZ. These two groups were further divided according to serum PRL levels: an elevated PRL group (>30 ng/mL) and a normal PRL group (PRL ≤30 ng/mL). The demographics, medication dosage, fasting plasma glucose, total cholesterol and triglycerides were compared in the two groups. Logistic regression analysis was performed to explore the risk factors of elevated PRL levels.

Results

Compared with the OLZ group, the RIS group had a greater number of patients with elevated PRL (155/264 vs 58/175). Either the RIS or the OLZ group, the proportion of elevated PRL was greater in female patients (RIS: χ²=6.76, p=0.009; OLZ: χ²=12.98, p<0.001) and with higher doses of the related drugs (RIS: U=-3.73, p<0.001; OLZ: U=-2.31, p=0.021). In patients taking RIS, the elevated PRL subgroup took the drug for a longer period (U=-2.76, p=0.006) and had lower triglyceride levels (U=2.76, p=0.006). In patients taking OLZ, the elevated PRL subgroup had lower fasting plasma glucose levels (U=2.29, p=0.022). Logistic regression analysis showed that gender, dose and fasting glucose levels were significantly associated with elevated PRL levels (RIS: p=0.001, OLZ: p<0.001; RIS: p<0.001; OLZ: p=0.003; RIS: p=0.020, OLZ: p=0.001, respectively).

Conclusion

Compared with OLZ, RIS had a greater effect on PRL in patients with schizophrenia, and in patients with schizophrenia taking RIS or OLZ, gender and dose were significantly correlated with the PRL value. Moreover, the plasma glucose level of the group with elevated PRL was lower than that of the group with normal PRL. The results also showed that high serum PRL may be associated with a favourable glucose metabolic profile in patients with schizophrenia taking RIS or OLZ. Further studies are warranted to confirm this association.

Trial registration number

NCT02640911.