Decreased placental and muscular expression of the fibroblast growth factor 19 in gestational diabetes mellitus

The Role of the FGF19 Family in the Pathogenesis of Gestational Diabetes: A Narrative Review

Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications. Understanding the pathogenesis and appropriate diagnosis of GDM enables the implementation of early interventions during pregnancy that reduce the risk of maternal and fetal complications. At the same time, it provides opportunities to prevent diabetes, metabolic syndrome, and cardiovascular diseases in women with GDM and their offspring in the future. Fibroblast growth factors (FGFs) represent a heterogeneous family of signaling proteins which play a vital role in cell proliferation and differentiation, repair of damaged tissues, wound healing, angiogenesis, and mitogenesis and also affect the regulation of carbohydrate, lipid, and hormone metabolism. Abnormalities in the signaling function of FGFs may lead to numerous pathological conditions, including metabolic diseases. The FGF19 subfamily, also known as atypical FGFs, which includes FGF19, FGF21, and FGF23, is essential in regulating metabolic homeostasis and acts as a hormone while entering the systemic circulation. Many studies have pointed to the involvement of the FGF19 subfamily in the pathogenesis of metabolic diseases, including GDM, although the results are inconclusive. FGF19 and FGF21 are thought to be associated with insulin resistance, an essential element in the pathogenesis of GDM. FGF21 may influence placental metabolism and thus contribute to fetal growth and metabolism regulation. The observed relationship between FGF21 and increased birth weight could suggest a potential role for FGF21 in predicting future metabolic abnormalities in children born to women with GDM. In this group of patients, different mechanisms may contribute to an increased risk of cardiovascular diseases in women in later life, and FGF23 appears to be their promising early predictor. This study aims to present a comprehensive review of the FGF19 subfamily, emphasizing its role in GDM and predicting its long-term metabolic consequences for mothers and their offspring.

Mechanism of BLIMP1/TRIM66/COX2 in human decidua participates in parturition†

The mechanism underlying the initiation of parturition remains unclear. Cyclooxygenase 2 and prostaglandins in decidual membrane tissue play an important role in the "parturition cascade." With the advancement of gestation, the expression of the transcriptional suppressor B lymphocyte-induced maturation protein 1 in the decidual membrane gradually decreases. Through chromatin immunoprecipitation sequencing, we found that B lymphocyte-induced maturation protein 1 has a binding site in the distal intergenic of PTGS2(COX2). Tripartite motif-containing protein 66 is a chromatin-binding protein that usually performs transcriptional regulatory functions by "reading" histone modification sites in chromatin. In this study, tripartite motif-containing protein 66 exhibits the same trend of expression as B lymphocyte-induced maturation protein 1 in the decidua during gestation. Moreover, the co-immunoprecipitation assay revealed that tripartite motif-containing protein 66 combined with B lymphocyte-induced maturation protein 1. This finding indicated that tripartite motif-containing protein 66 formed a transcription complex with B lymphocyte-induced maturation protein 1, which coregulated the expression of COX2. In animal experiments, we injected si-Blimp1 adenoviruses (si-Blimp1), Blimp1 overexpression plasmid (Blimp1-OE), and Trim66 overexpression plasmid (Trim66-OE) through the tail vein of mice. The results showed that B lymphocyte-induced maturation protein 1 and tripartite motif-containing protein 66 affected the initiation of parturition in mice. Therefore, the present evidence suggests that B lymphocyte-induced maturation protein 1 and tripartite motif-containing protein 66 partially participate in the initiation of labor, which may provide a new perspective for exploring the mechanism of term labor.

Adiponectin, A-FABP and FGF-19 Levels in Women with Early Diagnosed Gestational Diabetes

Background: Adiponectin, adipocyte fatty acid-binding protein (A-FABP), and fibroblast growth factor-19 (FGF-19) belong to proteins involved in glucose metabolism regulation. The aims of the study were to compare the plasma levels of these proteins in women with early diagnosed gestational diabetes mellitus (GDM) to those in healthy controls and to investigate their changes during pregnancy after early intervention. Methods: The study was undertaken as a case-control study. Early GDM diagnosis was based on repeated fasting plasma glucose ≥5.1 and <7.0 mmol/L during the first trimester of pregnancy and exclusion of overt diabetes. Age-matched controls comprised healthy pregnant and non-pregnant women. In addition to adipokines, clinical parameters and measures of glucose control were assessed. Results: Women with GDM (n = 23) had significantly lower adiponectin and higher A-FABP levels compared to healthy pregnant (n = 29) or non-pregnant (n = 25) controls, while no significant differences in FGF-19 between the groups were found. The therapeutic intervention shifted adiponectin and A-FABP levels in GDM women towards concentrations of healthy pregnant controls. Adipokines were associated with visceral adiposity and glucose control. Conclusion: Women with GDM showed altered adipokine production even in the first trimester of pregnancy. Early therapeutic intervention not only improved glucose control but also normalized impaired adipokine production.

FGF4, A New Potential Regulator in Gestational Diabetes Mellitus

Background: Gestational diabetes mellitus (GDM) is associated with adverse maternal and neonatal outcomes, however the underlying mechanisms remain elusive. The aim of this study was to find efficient regulator of FGFs in response to the pathogenesis of GDM and explore the role of the FGFs in GDM.

Methods: We performed a systematic screening of placental FGFs in GDM patients and further in two different GDM mouse models to investigate their expression changes. Significant changed FGF4 was selected, engineered, purified, and used to treat GDM mice in order to examine whether it can regulate the adverse metabolic phenotypes of the diabetic mice and protect their fetus.

Results: We found FGF4 expression was elevated in GDM patients and its level was positively correlated to blood glucose, indicating a physiological relevance of FGF4 with respect to the development of GDM. Recombinant FGF4 (rFGF4) treatment could effectively normalize the adverse metabolic phenotypes in high fat diet induced GDM mice but not in STZ induced GDM mice. However, rFGF4 was highly effective in reduce of neural tube defects (NTDs) of embryos in both the two GDM models. Mechanistically, rFGF4 treatment inhibits pro-inflammatory signaling cascades and neuroepithelial cell apoptosis of both GDM models, which was independent of glucose regulation.

Conclusions/interpretation: Our study provides novel insight into the important roles of placental FGF4 and suggests that it may serve as a promising diagnostic factor and therapeutic target for GDM.

Tissue-specific mechanisms of bile acid homeostasis and activation of FXR-FGF19 signaling in preterm and term neonatal pigs

The tissue-specific molecular mechanisms involved in perinatal liver and intestinal farnesoid X receptor (FXR)-fibroblast growth factor 19 (FGF19) signaling are poorly defined. Our aim was to establish how gestational age and feeding status affect bile acid synthesis pathway, bile acid pool size, ileal response to bile acid stimulation, genes involved in bile acid-FXR-FGF19 signaling and plasma FGF19 in neonatal pigs. Term (n = 23) and preterm (n = 33) pigs were born via cesarean section at 100% and 90% gestation, respectively. Plasma FGF19, hepatic bile acid and oxysterol profiles, and FXR target gene expression were assessed in pigs at birth and after a bolus feed on day 3 of life. Pig ileal tissue explants were used to measure signaling response to bile acids. Preterm pigs had smaller, more hydrophobic bile acid pools, lower plasma FGF19, and blunted FXR-mediated ileal response to bile acid stimulation than term pigs. GATA binding protein 4 (GATA-4) expression was higher in jejunum than ileum and was higher in preterm than term pig ileum. Hepatic oxysterol analysis suggested dominance of the alternative pathway of bile acid synthesis in neonates, regardless of gestational age and persists in preterm pigs after feeding on day 3. These results highlight the tissue-specific molecular basis for the immature enterohepatic bile acid signaling via FXR-FGF19 in preterm pigs and may have implications for disturbances of bile acid homeostasis and metabolism in preterm infants.NEW & NOTEWORTHY Our results show that the lower hepatic bile acid synthesis and ileum FXR-FGF19 pathway responsiveness to bile acids contribute to low-circulating FGF19 in preterm compared with term neonatal pigs. The molecular mechanism explaining immature or low-ileum FXR-FGF19 signaling may be linked to developmental patterning effects of GATA-4.

FGF15/FGF19 alleviates insulin resistance and upregulates placental IRS1/GLUT expression in pregnant mice fed a high-fat diet

INTRODUCTION

This study aimed to evaluate whether FGF19 can alleviate insulin resistance and change the expression of placental IRS1/GLUTs.

METHODS

Mice transgenic for Fgf15 (the murine homologue of human FGF19) were constructed, and human recombinant FGF19 was administered to pregnant high-fat diet mice. Then, glycolipid metabolism parameters and the weight of foetus and placenta were observed. The expression levels of key molecules of the insulin signalling pathway and glucose transporters in placentae were detected by qRT-PCR and western blotting. Primary trophoblasts and JAR cells were cultured in high-glucose medium, and FGF19 was added to observe its regulatory effects on IRS1/GLUTs.

RESULTS

Overexpressing FGF15 or exogenously administering FGF19 reduced the levels of fasting blood glucose, HOMA-IR, triglycerides, and free fatty acids in pregnant high-fat diet mice compared to control mice (P < 0.05). FGF15/FGF19 did not significantly affect placental weight, foetal weight or litter size (P > 0.05). In addition, FGF15/FGF19 upregulated the expression of p-IRS1 and GLUT4 in the placentae of high-fat diet mice and upregulated GLUT1 levels in the placentae of normal diet-fed mice (P < 0.05), while it did not significantly alter total IRS1 and GLUT3 levels (P > 0.05). Consistent with the results of the animal experiments, FGF19 increased the expression of p-IRS1 and GLUT4 in trophoblast cells cultured in high-glucose medium (P < 0.05).

DISCUSSION

Overexpressing FGF15 or administering FGF19 to pregnant high-fat diet mice can improve glycolipid metabolism and alleviate systemic and local insulin resistance. The possible underlying mechanism may involve upregulation of placental expression of p-IRS1 and GLUT4.

Circulating levels of fibroblast growth factor 21 in gestational diabetes mellitus: a meta-analysis

In recent times, the role of fibroblast growth factor 21 (FGF21) in patients with gestational diabetes mellitus (GDM) has been increasingly investigated. However, to our knowledge, no systematic analysis has been conducted yet to evaluate the relationship between FGF21 levels and GDM. Confirmed studies related to circulating FGF21 levels and GDM were searched from the databases of PubMed, ISI Web of Science, MEDLINE and EMBASE. Data were reported as standard mean difference (SMD) and associated 95% confidence intervals (CIs). Analysis were performed with Review Manager 5.2 and Stata version 11.0. A total of 392 cases and 435 controls in nine articles were included in this meta-analysis. The circulating FGF21 levels in pregnant women with GDM was higher than that in controls (random effects MD [95% CI] = 0.46, [0.07-0.86], p = 0.02). The result of multivariate meta-regression showed that sample size and point of sample collection contributed to heterogeneity (p = 0.033 and p = 0.047, respectively). Additionally, the results showed that there was no publication bias in this meta-analysis (Z = 1.36, p = 0.175; t = 1.24, p = 0.256, respectively). To conclude, this meta-analysis provides evidence that circulating FGF21 levels are higher in GDM subjects than controls, and it is important to clarify the relationship between circulating FGF21 levels and pregnant women with GDM in accurate prediction of GDM.

Association of Elevated Plasma FGF21 and Activated FGF21 Signaling in Visceral White Adipose Tissue and Improved Insulin Sensitivity in Gestational Diabetes Mellitus Subtype: A Case-Control Study

OBJECTIVE

To study the discrepancy of the insulin sensitivity alteration pattern, circulating fibroblast growth factor (FGF21) levels and FGF21 signaling in visceral white adipose tissue (vWAT) of gestational diabetes mellitus (GDM) subtypes.

METHODS

26 GDM women with either a predominant of insulin-secretion defect (GDM-dysfunction, n = 9) or insulin-sensitivity defect (GDM-resistance, n = 17) and 13 normal glucose tolerance (NGT) women scheduled for caesarean-section at term were studied. Blood and vWAT samples were collected at delivery.

RESULTS

The insulin sensitivity was improved from the 2^nd trimester to delivery in the GDM-resistance group. Elevated circulating FGF21 concentration at delivery, increased FGF receptor 1c and decreased klotho beta gene expression, enhanced ERK1/2 phosphorylation, and increased GLUT1, IR-B, PPAR-γ gene expression in vWAT were found in the GDM-resistance group as compared with the NGT group. The circulating FGF21 concentration was negatively correlated with fasting blood glucose (r = -0.574, P < 0.001), and associated with the GDM-resistance group (r = 0.574, P < 0.001) in pregnant women at delivery. However, we observed no insulin sensitivity alteration in GDM-dysfunction and NGT groups during pregnancy. No differences of plasma FGF21 level and FGF21 signaling in vWAT at delivery were found between women in the GDM-dysfunction and the NGT group.

CONCLUSIONS

Women with GDM heterogeneity exhibited different insulin sensitivity alteration patterns. The improvement of insulin sensitivity may relate to the elevated circulating FGF21 concentration and activated FGF21 signaling in vWAT at delivery in the GDM-resistance group.

Fibroblast Growth Factor 19 in Gestational Diabetes Mellitus and Fetal Growth

Fibroblast growth factor 19 (FGF19) has been implicated in glucose homeostasis. Gestational diabetes mellitus (GDM) enhances fetal insulin secretion and fetal growth. Girls weigh less and are more insulin resistant than boys at birth. We sought to assess whether FGF19 is associated with GDM and fetal growth and explore potential sex dimorphic associations. This was a nested case-control study in the Shanghai Birth Cohort, including 153 pairs of newborns of GDM versus euglycemic mothers matched by infant's sex and gestational age at birth. Cord plasma FGF19, insulin, C-peptide, proinsulin, IGF-I and IGF-II concentrations were measured. Cord plasma FGF19 concentrations were similar in GDM versus euglycemic pregnancies (mean ± SD: 43.5 ± 28.2 versus 44.5 ± 30.2 pg/mL, P=0.38). FGF19 was not correlated with IGF-I or IGF-II. FGF19 concentrations were positively correlated with birth weight (r=0.23, P=0.01) and length (r=0.21, P=0.02) z scores, C-peptide (r=0.27, P=0.002) and proinsulin (r=0.27, P=0.002) concentrations in females. Each SD increment in cord plasma FGF19 was associated with a 0.25 (0.07-0.43) increase in birth weight z score in females. In contrast, FGF19 was not correlated with birth weight or length in males. These sex dimorphic associations remained after adjusting for maternal and neonatal characteristics. The study is the first to demonstrate that GDM does not matter for cord blood FGF19 concentrations. The female specific positive correlation between FGF19 and birth weight is suggestive of a sex-dimorphic role of FGF19 in fetal growth. The observations call for more studies to validate the novel findings and elucidate the underlying mechanisms.

Developments in the study of gastrointestinal microbiome disorders affected by FGF19 in the occurrence and development of colorectal neoplasms

Colorectal neoplasms are a type of malignant digestive system tumor that has become the third-highest morbidity tumor in China and the fourth leading cause of cancer-related death worldwide. The role of the gastrointestinal (GI) microbiome in bile acid metabolism, inflammation, and insulin resistance and its strong correlation with the occurrence and development of colorectal neoplasms have gradually led to it becoming a target area of tumor research. Fibroblast growth factor (FGF) 19 is a hormone that is secreted in mainly the ileum and can regulate bile acid biosynthesis, improve inflammation, and regulate insulin resistance. The relationship of the GI microbiome, FGF19 and its carcinogenic activities in colorectal neoplasms enticed us to search for potential targets and research ideas for the clinical diagnosis and treatment of colorectal neoplasms.

FGF19 subfamily members: FGF19 and FGF21

Fibroblast growth factors (FGF) constitute a large family of proteins with pleiotropic effects on development, organogenesis, and metabolism. The FGF19 subclass includes growth factors circulating with the blood referred to as endocrine FGF. Representatives of the FGF19 subclass, including FGF19, FGF21, and FGF23, act via FGFR receptors. The proteins of FGF19 subfamily influence the enterohepatic circulation of bile, participate in glucose and lipid metabolism regulation, and maintenance of phosphorus and vitamin D3 homeostasis. FGF19 and FGF21 are activated under different physiological and pathological conditions.

Role of fibroblast growth factor 21 in gestational diabetes mellitus: A mini-review

Gestational diabetes mellitus (GDM) is defined as glucose intolerance with onset or first diagnosis during pregnancy, but not to the level of being diagnostic for diabetes in a nonpregnant adult. In GDM, whole-body insulin-dependent glucose disposal decreases by 40%-60% which necessitates a 200%-250% increase in insulin secretion to maintain normoglycaemia. GDM develops when a pregnant woman does not produce sufficient insulin to compensate for the reduced glucose disposal. Fibroblast growth factor 21 (FGF21) is a hormone that is expressed predominantly in the liver, but also in other metabolically active tissues such as pancreas, skeletal muscle and adipose tissue. In animals, FGF21 lowers blood glucose levels and inhibits glucagon secretion. In humans, circulating FGF21 levels are increased in insulin-resistant morbidities such as obesity and type 2 diabetes mellitus (T2DM). An elevated FGF21 level is also an independent predictor of T2DM. GDM and T2DM are proposed to have similar underlying pathophysiologies, raising the question of whether a similar relationship exists between FGF21 and GDM as it does with T2DM. There are a limited number of studies investigating FGF21 levels in patients with GDM. Moreover, recent clinical trials investigating the therapeutic potential of FGF21 have highlighted a major gap in our understanding of the biology of FGF21. This review evaluates what is currently known about FGF21 and GDM and highlights important gaps that warrant further research.

Decreased placental and muscular expression of the fibroblast growth factor 19 in gestational diabetes mellitus

Aims/Introduction

Fibroblast growth factor (FGF)19 has been shown to improve glycemic homeostasis and lipid metabolism in animal models. In humans, decreased FGF19 level has been described in diabetes. The present study aimed to investigate the expression of FGF19 in gestational diabetes mellitus (GDM) patients.

Materials and Methods

Samples for measurement were obtained from 20 women with GDM and 25 healthy controls. The messenger ribonucleic acid (mRNA) and protein expression levels of FGF19, FGF21 and co‐receptor β‐klotho (KLB) in the placenta, rectus muscle and subcutaneous fat tissues were quantified by real‐time quantitative polymerase chain reaction, western blot and immunohistochemistry, respectively.

Results

Women with GDM had significantly lower mRNA and protein expressions of FGF19 than control women in the placenta (mRNA 0.33 ± 0.05 vs 0.72 ± 0.09; protein 0.34 ± 0.13 vs 0.85 ± 0.20) and rectus muscle (mRNA 0.83 ± 0.11 vs 1.28 ± 0.19; protein 0.78 ± 0.24 vs 1.23 ± 0.39). However, there were no significant differences between GDM women and controls with respect to the expression levels of FGF21 and β‐klotho in the placenta and rectus muscle. There were almost no detectable FGF19 and FGF21 expressions in subcutaneous fat tissue. Furthermore, β‐klotho expression levels were not different between the GDM and control group in subcutaneous fat.

Conclusions

FGF19 expressions are decreased in the placenta and rectus muscle of women with GDM. This might contribute to the pathophysiology or development of GDM.