Mechanisms in the adaptation of maternal β-cells during pregnancy

G-Protein-Coupled Estrogen Receptor (GPER) and Sex-Specific Metabolic Homeostasis

Obesity and metabolic syndrome display disparate prevalence and regulation between males and females. Human, as well as rodent, females with regular menstrual/estrous cycles exhibit protection from weight gain and associated chronic diseases. These beneficial effects are predominantly attributed to the female hormone estrogen, specifically 17β-estradiol (E2). E2 exerts its actions via multiple receptors, nuclear and extranuclear estrogen receptor (ER) α and ERβ, and the G-protein-coupled estrogen receptor (GPER, previously termed GPR30). The roles of GPER in metabolic homeostasis are beginning to emerge but are complex and remain unclear. The discovery of GPER-selective pharmacological agents (agonists and antagonists) and the availability of GPER knockout mice have significantly enhanced our understanding of the functions of GPER in normal physiology and disease. GPER action manifests pleiotropic effects in metabolically active tissues such as the pancreas, adipose, liver, and skeletal muscle. Cellular and animal studies have established that GPER is involved in the regulation of body weight, feeding behavior, inflammation, as well as glucose and lipid homeostasis. GPER deficiency leads to increased adiposity, insulin resistance, and metabolic dysfunction in mice. In contrast, pharmacologic stimulation of GPER in vivo limits weight gain and improves metabolic output, revealing a promising novel therapeutic potential for the treatment of obesity and diabetes.

Pancreas regeneration

The pancreas is made from two distinct components: the exocrine pancreas, a reservoir of digestive enzymes, and the endocrine islets, the source of the vital metabolic hormone insulin. Human islets possess limited regenerative ability; loss of islet β-cells in diseases such as type 1 diabetes requires therapeutic intervention. The leading strategy for restoration of β-cell mass is through the generation and transplantation of new β-cells derived from human pluripotent stem cells. Other approaches include stimulating endogenous β-cell proliferation, reprogramming non-β-cells to β-like cells, and harvesting islets from genetically engineered animals. Together these approaches form a rich pipeline of therapeutic development for pancreatic regeneration.

The Role of Hepatocyte Growth Factor (HGF) in Insulin Resistance and Diabetes

In obesity, insulin resistance (IR) and diabetes, there are proteins and hormones that may lead to the discovery of promising biomarkers and treatments for these metabolic disorders. For example, these molecules may impair the insulin signaling pathway or provide protection against IR. Thus, identifying proteins that are upregulated in IR states is relevant to the diagnosis and treatment of the associated disorders. It is becoming clear that hepatocyte growth factor (HGF) is an important component of the pathophysiology of IR, with increased levels in most common IR conditions, including obesity. HGF has a role in the metabolic flux of glucose in different insulin sensitive cell types; plays a key role in β-cell homeostasis; and is capable of modulating the inflammatory response. In this review, we discuss how, and to what extent HGF contributes to IR and diabetes pathophysiology, as well as its role in cancer which is more prevalent in obesity and diabetes. Based on the current literature and knowledge, it is clear that HGF plays a central role in these metabolic disorders. Thus, HGF levels could be employed as a biomarker for disease status/progression, and HGF/c-Met signaling pathway modulators could effectively regulate IR and treat diabetes.

Combined Metabolomic Analysis of Plasma and Urine Reveals AHBA, Tryptophan and Serotonin Metabolism as Potential Risk Factors in Gestational Diabetes Mellitus (GDM)

Gestational diabetes mellitus during pregnancy has severe implications for the health of the mother and the fetus. Therefore, early prediction and an understanding of the physiology are an important part of prenatal care. Metabolite profiling is a long established method for the analysis and prediction of metabolic diseases. Here, we applied untargeted and targeted metabolomic protocols to analyze plasma and urine samples of pregnant women with and without GDM. Univariate and multivariate statistical analyses of metabolomic profiles revealed markers such as 2-hydroxybutanoic acid (AHBA), 3-hydroxybutanoic acid (BHBA), amino acids valine and alanine, the glucose-alanine-cycle, but also plant-derived compounds like sitosterin as different between control and GDM patients. PLS-DA and VIP analysis revealed tryptophan as a strong variable separating control and GDM. As tryptophan is biotransformed to serotonin we hypothesized whether serotonin metabolism might also be altered in GDM. To test this hypothesis we applied a method for the analysis of serotonin, metabolic intermediates and dopamine in urine by stable isotope dilution direct infusion electrospray ionization mass spectrometry (SID-MS). Indeed, serotonin and related metabolites differ significantly between control and GDM patients confirming the involvement of serotonin metabolism in GDM. Clustered correlation coefficient visualization of metabolite correlation networks revealed the different metabolic signatures between control and GDM patients. Eventually, the combination of selected blood plasma and urine sample metabolites improved the AUC prediction accuracy to 0.99. The detected GDM candidate biomarkers and the related systemic metabolic signatures are discussed in their pathophysiological context. Further studies with larger cohorts are necessary to underpin these observations.

Prevalence and Determinants of Gestational Diabetes Mellitus: A Cross-Sectional Study in China

Objectives: This study aimed to identify the prevalence of gestational diabetes mellitus (GDM) and to examine its associations with social and behavioral factors, maternal body mass index (BMI), anemia, and hypertension. Methods: A cross-sectional analysis was performed on data collected from 2345 pregnant women from 16 hospitals in five selected provinces in mainland China.

RESULTS

Prevalence of GDM was as follows: overall: 3.7%; pregnant women in the first pregnancy: 3.4%; pregnant women in the second pregnancy: 4.6%. Compared with early pregnancy women, late-stage pregnant women were more likely to have GDM (OR = 4.32, 95% CI (1.82, 10.27)). Compared with 18-25 years old pregnant women, women aged 36-45 years were more likely to have GDM (OR = 3.98, 95% CI (1.41, 11.28). Compared with non-hypertensive patients, hypertensive patients were more likely to have GDM (OR = 6.93, 95% CI (1.28, 37.64)). However, second pregnancy, high maternal BMI, prolonged screen time (TV-viewing time, computer-using time, and mobile-phone using time), insufficient and excessive sleep duration, poor sleep quality, smoking, and secondhand smoke exposure were not significantly associated with an increased risk of GDM. Conclusions: Women in the second pregnancy do not appear to predict an increased risk for developing GDM than women in the first pregnancy. High-risk groups of GDM included women in their late pregnancy, aged 36-45 years old, and with hypertension. The findings will contribute to an improved understanding of social and behavioral determinants of GDM in Chinese population and contribute to the development of health-prevention promotion interventions to address GDM.

MicroRNAs in Pregnancy and Gestational Diabetes Mellitus: Emerging Role in Maternal Metabolic Regulation

PURPOSE OF THE REVIEW

This review focuses on the recent emergence of microRNAs (miRNAs) as metabolic and developmental regulators in pregnancy and their role in the development of gestational diabetes mellitus (GDM). MiRNAs are short and stable RNA sequences that repress protein synthesis through interference with messenger RNA translation.

RECENT FINDINGS

The placenta produces numerous miRNAs with some of them being released in the maternal circulation. These miRNA genes are encoded into specific clusters and expressed preferentially by placental cells, in a time-dependent manner. They were shown to be dysregulated in plasma and placenta from women suffering from GDM and associated with pregnancy and birth-related outcomes. The discovery of pregnancy-related miRNAs and their respective characterization will provide us with important information as to their function in maternal and placental metabolic regulation. More studies are needed to determine whether they will be useful for early screening of GDM.

Higher parity is associated with increased risk of Type 2 diabetes mellitus in women: A linear dose-response meta-analysis of cohort studies

AIM

The goal of this study is to investigate the association between higher parity and the risk of occurrence of type 2 diabetes mellitus (T2DM) in women and to quantify the potential dose-response relation.

METHODS

We searched MEDLINE, and EMBASE electronic databases for related cohort studies up to March 10th, 2016. Summary rate ratios (RRs) and 95% confidence intervals (CIs) for T2DM with at least 3 categories of exposure were eligible. A random-effects dose-response analysis procedure was used to study the relations between them.

RESULTS

After screening a total of 13,647 published studies, only 7 cohort studies (9,394 incident cases and 286,840 female participants) were found to be eligible for this meta-analysis. In the category analysis, the pooled RR for the highest number of parity vs. the lowest one was 1.42 (95% CI: 1.17-1.72, I²=71.5%, P_{heterogeneity}=0.002, Power=0.99). In the dose-response analysis, a noticeable linear dose-risk relation was found between parity and T2DM (P_{for nonlinearity test}=0.942). For every live birth increase in parity, the combined RR was 1.06 (95% CI: 1.02-1.09, I²=84.3%, P_{heterogeneity}=0.003, Power=0.99). Subgroup and sensitivity analyses yielded similar results. No publication bias was found in the results.

CONCLUSION

This meta-analysis suggests that higher parity and the risk of T2DM show a linear relationship in women.

Persistent influence of maternal obesity on offspring health: Mechanisms from animal models and clinical studies

The consequences of excessive maternal weight and adiposity at conception for the offspring are now well recognized. Maternal obesity increases the risk of overweight and obesity even in children born with appropriate-for-gestational age (AGA) birth weights. Studies in animal models have employed both caloric excess and manipulation of macronutrients (especially high-fat) to mimic hypercaloric intake present in obesity. Findings from these studies show transmission of susceptibility to obesity, metabolic dysfunction, alterations in glucose homeostasis, hepatic steatosis, skeletal muscle metabolism and neuroendocrine changes in the offspring. This review summarizes the essential literature in this area in both experimental and clinical domains and focuses on the translatable aspects of these experimental studies. Moreover this review highlights emerging mechanisms broadly explaining maternal obesity-associated developmental programming. The roles of early developmental alterations and placental adaptations are also reviewed. Increasing evidence also points to changes in the epigenome and other emerging mechanisms such as alterations in the microbiome that may contribute to persistent changes in the offspring. Finally, we examine potential interventions that have been employed in clinical cohorts.

Stress-induced adaptive islet cell identity changes

The different forms of diabetes mellitus differ in their pathogenesis but, ultimately, they are all characterized by progressive islet β-cell loss. Restoring the β-cell mass is therefore a major goal for future therapeutic approaches. The number of β-cells found at birth is determined by proliferation and differentiation of pancreatic progenitor cells, and it has been considered to remain mostly unchanged throughout adult life. Recent studies in mice have revealed an unexpected plasticity in islet endocrine cells in response to stress; under certain conditions, islet non-β-cells have the potential to reprogram into insulin producers, thus contributing to restore the β-cell mass. Here, we discuss the latest findings on pancreas and islet cell plasticity upon physiological, pathological and experimental conditions of stress. Understanding the mechanisms involved in cell reprogramming in these models will allow the development of new strategies for the treatment of diabetes, by exploiting the intrinsic regeneration capacity of the pancreas.

Gestational Diabetes Mellitus From Inactivation of Prolactin Receptor and MafB in Islet β-Cells

β-Cell proliferation and expansion during pregnancy are crucial for maintaining euglycemia in response to increased metabolic demands placed on the mother. Prolactin and placental lactogen signal through the prolactin receptor (PRLR) and contribute to adaptive β-cell responses in pregnancy; however, the in vivo requirement for PRLR signaling specifically in maternal β-cell adaptations remains unknown. We generated a floxed allele of Prlr, allowing conditional loss of PRLR in β-cells. In this study, we show that loss of PRLR signaling in β-cells results in gestational diabetes mellitus (GDM), reduced β-cell proliferation, and failure to expand β-cell mass during pregnancy. Targeted PRLR loss in maternal β-cells in vivo impaired expression of the transcription factor Foxm1, both G1/S and G2/M cyclins, tryptophan hydroxylase 1 (Tph1), and islet serotonin production, for which synthesis requires Tph1. This conditional system also revealed that PRLR signaling is required for the transient gestational expression of the transcription factor MafB within a subset of β-cells during pregnancy. MafB deletion in maternal β-cells also produced GDM, with inadequate β-cell expansion accompanied by failure to induce PRLR-dependent target genes regulating β-cell proliferation. These results unveil molecular roles for PRLR signaling in orchestrating the physiologic expansion of maternal β-cells during pregnancy.

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.

Sex of the baby and future maternal risk of Type 2 diabetes in women who had gestational diabetes

AIMS

Women who develop gestational diabetes mellitus have a chronic defect in the secretion of insulin by the pancreatic β cells that underlies both their diagnostic hyperglycaemia in pregnancy and their elevated lifetime risk of developing Type 2 diabetes in the future. It has recently emerged that carrying a male fetus is associated with poorer maternal β-cell function and an increased risk of gestational diabetes, whereas the development of gestational diabetes when carrying a girl (as compared with a boy) predicts a comparatively higher risk of early progression to Type 2 diabetes before any subsequent pregnancy. In this context, we sought to determine the impact of fetal sex on the long-term risk of Type 2 diabetes in women with gestational diabetes.

METHODS

Using population-based administrative databases, we identified all women in Ontario, Canada, with a singleton live-birth first pregnancy complicated by gestational diabetes between April 2000 and March 2010 (n = 23 363). We compared the risk of subsequent Type 2 diabetes after pregnancy in those who carried a girl (n = 11 229) vs. those who carried a boy (n = 12 134).

RESULTS

Over median 5.5 years follow-up, 5483 women (23.5%) were diagnosed with diabetes. Compared with those who carried a boy, women who had a girl had an elevated risk of subsequently developing diabetes (adjusted hazard ratio = 1.06, 95% CI 1.01-1.12).

CONCLUSIONS

Among women with gestational diabetes, those who are carrying a girl have a slightly higher overall future risk of Type 2 diabetes.

Replicative capacity of β-cells and type 1 diabetes

Efforts to restore β-cell number or mass in type 1 diabetes (T1D) must combine an intervention to stimulate proliferation of remaining β-cells and an intervention to mitigate or control the β-cell-directed autoimmunity. This review highlights features of the β-cell, including it being part of a pancreatic islet, a mini-organ that is highly vascularized and highly innervated, and efforts to promote β-cell proliferation. In addition, the β-cell in T1D exists in a microenvironment with interactions and input from other islet cell types, extracellular matrix, vascular endothelial cells, neuronal projections, and immune cells, all of which likely influence the β-cell's capacity for replication. Physiologic β-cell proliferation occurs in human and rodents in the neonatal period and early in life, after which there is an age-dependent decline in β-cell proliferation, and also as part of the β-cell's compensatory response to the metabolic challenges of pregnancy and insulin resistance. This review reviews the molecular pathways involved in this β-cell proliferation and highlights recent work in two areas: 1) Investigators, using high-throughput screening to discover small molecules that promote human β-cell proliferation, are now focusing on the dual-specificity tyrosine-regulated kinase-1a and cell cycle-dependent kinase inhibitors CDKN2C/p18 or CDKN1A/p21as targets of compounds to stimulate adult human β-cell proliferation. 2) Local inflammation, macrophages, and the local β-cell microenvironment promote β-cell proliferation. Future efforts to harness the responsible mechanisms may lead to new approaches to promote β-cell proliferation in T1D.

Pregnancy Hyperglycemia in Prolactin Receptor Mutant, but Not Prolactin Mutant, Mice and Feeding-Responsive Regulation of Placental Lactogen Genes Implies Placental Control of Maternal Glucose Homeostasis

Pregnancy is often viewed as a conflict between the fetus and mother over metabolic resources. Insulin resistance occurs in mothers during pregnancy but does not normally lead to diabetes because of an increase in the number of the mother's pancreatic beta cells. In mice, this increase is dependent on prolactin (Prl) receptor signaling but the source of the ligand has been unclear. Pituitary-derived Prl is produced during the first half of pregnancy in mice but the placenta produces Prl-like hormones from implantation to term. Twenty-two separate mouse genes encode the placenta Prl-related hormones, making it challenging to assess their roles in knockout models. However, because at least four of them are thought to signal through the Prl receptor, we analyzed Prlr mutant mice and compared their phenotypes with those of Prl mutants. We found that whereas Prlr mutants develop hyperglycemia during gestation, Prl mutants do not. Serum metabolome analysis showed that Prlr mutants showed other changes consistent with diabetes. Despite the metabolic changes, fetal growth was normal in Prlr mutants. Of the four placenta-specific, Prl-related hormones that have been shown to interact with the Prlr, their gene expression localizes to different endocrine cell types. The Prl3d1 gene is expressed by trophoblast giant cells both in the labyrinth layer, sitting on the arterial side where maternal blood is highest in oxygen and nutrients, and in the junctional zone as maternal blood leaves the placenta. Expression increases during the night, though the increase in the labyrinth is circadian whereas it occurs only after feeding in the junctional zone. These data suggest that the placenta has a sophisticated endocrine system that regulates maternal glucose metabolism during pregnancy.

Fetal sex and maternal risk of gestational diabetes mellitus: the impact of having a boy

OBJECTIVE

Retrospective analyses of perinatal databases have raised the intriguing possibility of an increased risk of gestational diabetes mellitus (GDM) in women carrying a male fetus, but it has been unclear if this was a spurious association. We thus sought to evaluate the relationship between fetal sex and maternal glucose metabolism in a well-characterized cohort of women reflecting the full spectrum of gestational glucose tolerance from normal to mildly abnormal to GDM.

RESEARCH DESIGN AND METHODS

A total of 1,074 pregnant women underwent metabolic characterization, including oral glucose tolerance test (OGTT), at mean 29.5 weeks' gestation. The prevalence of GDM, its pathophysiologic determinants (β-cell function and insulin sensitivity/resistance), and its clinical risk factors were compared between women carrying a female fetus (n = 534) and those carrying a male fetus (n = 540).

RESULTS

Women carrying a male fetus had lower mean adjusted β-cell function (insulinogenic index divided by HOMA of insulin resistance: 9.4 vs. 10.5, P = 0.007) and higher mean adjusted blood glucose at 30 min (P = 0.025), 1 h (P = 0.004), and 2 h (P = 0.02) during the OGTT, as compared with those carrying a female fetus. Furthermore, women carrying a male fetus had higher odds of developing GDM (odds ratio 1.39 [95% CI 1.01-1.90]). Indeed, male fetus further increased the relative risk of GDM conferred by the classic risk factors of maternal age >35 years and nonwhite ethnicity by 47 and 51%, respectively.

CONCLUSIONS

Male fetus is associated with poorer β-cell function, higher postprandial glycemia, and an increased risk of GDM in the mother. Thus, fetal sex potentially may influence maternal glucose metabolism in pregnancy.

Hyperglycemia and hepatic tumors in ICR mice neonatally injected with streptozotocin

Repeated, low-dose administration of streptozotocin (STZ) is widely used to induce insulin-dependent diabetes mellitus in mice. The authors adapted this method using neonatal mice and determined the long-term effects of STZ injection in the mice. After receiving intraperitoneal injections of STZ at postnatal day 3 (P3), P4 and P8, male and female mice were hyperglycemic by week 4. A clear sex difference was found, with blood glucose levels in STZ-treated males remaining higher than those in STZ-treated females until week 23. Whereas STZ-treated males remained hyperglycemic until week 23, STZ-treated females did not have significantly higher glucose levels than control mice after week 18. Additionally, STZ-treated mice had neoplastic lesions in their livers by week 4, with a progression in the severity of these lesions until week 24. The results confirm that, in addition to pancreatic beta cell toxicity, STZ has an oncogenic effect on the liver when administered to neonates.

Maternal outcomes and follow-up after gestational diabetes mellitus

Gestational diabetes mellitus reflects impaired maternal insulin secretion relative to demand prior to pregnancy, as well as temporary metabolic stressors imposed by the placenta and fetus. Thus, after delivery, women with gestational diabetes have increased risk of diabetes and recurrent gestational diabetes because of their underlying impairment, which may be further exacerbated by fat accretion during pregnancy and post-partum deterioration in lifestyle behaviours. This hypothetical model is discussed in greater detail, particularly the uncertainty regarding pregnancy as an accelerator of β-cell decline and the role of gestational weight gain. This report also presents risk estimates for future glucose intolerance and diabetes and reviews modifiable risk factors, particularly body mass and lifestyle alterations, including weight loss and breastfeeding. Non-modifiable risk factors such as race/ethnicity and insulin use during pregnancy are also discussed. The review concludes with current literature on lifestyle modification, recommendations for post-partum glucose screening, and future directions for research to prevent maternal disease.

Failure to increase insulin secretory capacity during pregnancy-induced insulin resistance is associated with ethnicity and gestational diabetes

OBJECTIVE

To assess changes in insulin resistance and β-cell function in a multiethnic cohort of women in Oslo, Norway, from early to 28 weeks' gestation and 3 months post partum and relate the findings to gestational diabetes mellitus (GDM).

METHOD

Population-based cohort study of 695 healthy pregnant women from Western Europe (41%), South Asia (25%), Middle East (15%), East Asia (6%) and elsewhere (13%). Blood samples and demographics were recorded at mean 15 (V1) and 28 (V2) weeks' gestation and 3 months post partum (V3). Universal screening was by 75 g oral glucose tolerance test at V2, GDM with modified IADPSG criteria (no 1-h measurement): fasting plasma glucose (PG) ≥5.1 or 2-h PG ≥8.5 mmol/l. Homeostatic model assessment (HOMA)-β (β-cell function) and HOMA-IR (insulin resistance) were calculated from fasting glucose and C-peptide.

RESULT

Characteristics were comparable across ethnic groups, except age (South Asians: younger, P<0.001) and prepregnant BMI (East Asians: lower, P=0.040). East and South Asians were more insulin resistant than Western Europeans at V1. From V1 to V2, the increase in insulin resistance was similar across the ethnic groups, but the increase in β-cell function was significantly lower for the East and South Asians compared with Western Europeans. GDM women compared with non-GDM women were more insulin resistant at V1; from V1 to V2, their β-cell function increased significantly less and the percentage increase in β-cell function did not match the change in insulin resistance.

CONCLUSION

Pregnant women from East Asia and South Asia were more insulin resistant and showed poorer HOMA-β-cell function than Western Europeans.

Loss of HGF/c-Met signaling in pancreatic β-cells leads to incomplete maternal β-cell adaptation and gestational diabetes mellitus

Hepatocyte growth factor (HGF) is a mitogen and insulinotropic agent for the β-cell. However, whether HGF/c-Met has a role in maternal β-cell adaptation during pregnancy is unknown. To address this issue, we characterized glucose and β-cell homeostasis in pregnant mice lacking c-Met in the pancreas (PancMet KO mice). Circulating HGF and islet c-Met and HGF expression were increased in pregnant mice. Importantly, PancMet KO mice displayed decreased β-cell replication and increased β-cell apoptosis at gestational day (GD)15. The decreased β-cell replication was associated with reductions in islet prolactin receptor levels, STAT5 nuclear localization and forkhead box M1 mRNA, and upregulation of p27. Furthermore, PancMet KO mouse β-cells were more sensitive to dexamethasone-induced cytotoxicity, whereas HGF protected human β-cells against dexamethasone in vitro. These detrimental alterations in β-cell proliferation and death led to incomplete maternal β-cell mass expansion in PancMet KO mice at GD19 and early postpartum periods. The decreased β-cell mass was accompanied by increased blood glucose, decreased plasma insulin, and impaired glucose tolerance. PancMet KO mouse islets failed to upregulate GLUT2 and pancreatic duodenal homeobox-1 mRNA, insulin content, and glucose-stimulated insulin secretion during gestation. These studies indicate that HGF/c-Met signaling is essential for maternal β-cell adaptation during pregnancy and that its absence/attenuation leads to gestational diabetes mellitus.

The effect of gestation and fetal mismatching on the development of autoimmune diabetes in non-obese diabetic mice

The impact of gestation and fetal-maternal interactions on pre-existent autoimmune beta cell destruction is widely unknown. The aim of this study was to investigate the influence of gestation per se and fetal mismatching on the onset of autoimmune diabetes in female non-obese diabetic (NOD) mice. We examined cumulative diabetes frequencies of NOD dams mated to syngeneic NOD, haploidentical CByB6F1/J and fully mismatched C57BL/6J male mice. Pregnancy from NOD males neither increased nor accelerated the diabetes onset of NOD dams (71% by age 28 weeks) compared to unmated female NOD mice (81% by age 28 weeks; P = 0·38). In contrast, delayed diabetes onset was observed when NOD dams were mated at 10 weeks of age with major histocompatibility complex (MHC) haploidentical CByB6F1/J male mice (38% at age 28 weeks; P = 0·01). Mating with fully MHC mismatched C57BL/6J male mice (72% diabetes by age 28 weeks; P = 0·22) or mating with the haploidentical males at the later time-point of age 13 weeks (64% versus 91% in unmated litter-matched controls; P = 0·13) did not delay diabetes significantly in NOD females. Because infusion of haploidentical male mouse splenocytes was found previously to prevent diabetes in NOD mice we looked for, but found no evidence of, persistent chimeric lymphocytes from haploidentical paternal origin within the dams' splenocytes. Gestation per se appears to have no aggravating or ameliorating effects on pre-existent autoimmune beta cell destruction, but pregnancy from MHC partially mismatched males delays diabetes onset in female NOD mice.