Sulfated Progesterone Metabolites That Enhance Insulin Secretion via TRPM3 Are Reduced in Serum From Women With Gestational Diabetes Mellitus.

Serum progesterone sulfates were evaluated in the etiology of gestational diabetes mellitus (GDM). Serum progesterone sulfates were measured using ultra-performance liquid chromatography-tandem mass spectrometry in four patient cohorts: 1) the Hyperglycemia and Adverse Pregnancy Outcomes study; 2) London-based women of mixed ancestry and 3) U.K.-based women of European ancestry with or without GDM; and 4) 11-13 weeks pregnant women with BMI ≤25 or BMI ≥35 kg/m2 with subsequent uncomplicated pregnancies or GDM. Glucose-stimulated insulin secretion (GSIS) was evaluated in response to progesterone sulfates in mouse islets and human islets. Calcium fluorescence was measured in HEK293 cells expressing transient receptor potential cation channel subfamily M member 3 (TRPM3). Computer modeling using Molecular Operating Environment generated three-dimensional structures of TRPM3. Epiallopregnanolone sulfate (PM5S) concentrations were reduced in GDM (P < 0.05), in women with higher fasting plasma glucose (P < 0.010), and in early pregnancy samples from women who subsequently developed GDM with BMI ≥35 kg/m2 (P < 0.05). In islets, 50 µmol/L PM5S increased GSIS by at least twofold (P < 0.001); isosakuranetin (TRPM3 inhibitor) abolished this effect. PM5S increased calcium influx in TRPM3-expressing HEK293 cells. Computer modeling and docking showed identical positioning of PM5S to the natural ligand in TRPM3. PM5S increases GSIS and is reduced in GDM serum. The activation of GSIS by PM5S is mediated by TRPM3 in both mouse and human islets.

Maternal glucose homeostasis is impaired in mouse models of gestational cholestasis.

Women with intrahepatic cholestasis of pregnancy (ICP), a disorder characterised by raised serum bile acids, are at increased risk of developing gestational diabetes mellitus and have impaired glucose tolerance whilst cholestatic. FXR and TGR5 are modulators of glucose metabolism, and FXR activity is reduced in normal pregnancy, and further in ICP. We aimed to investigate the role of raised serum bile acids, FXR and TGR5 in gestational glucose metabolism using mouse models. Cholic acid feeding resulted in reduced pancreatic ß-cell proliferation and increased apoptosis in pregnancy, without altering insulin sensitivity, suggesting that raised bile acids affect ß-cell mass but are insufficient to impair glucose tolerance. Conversely, pregnant Fxr-/- and Tgr5-/- mice are glucose intolerant and have reduced insulin secretion in response to glucose challenge, and Fxr-/- mice are also insulin resistant. Furthermore, fecal bile acids are reduced in pregnant Fxr-/- mice. Lithocholic acid and deoxycholic acid, the principal ligands for TGR5, are decreased in particular. Therefore, we propose that raised serum bile acids and reduced FXR and TGR5 activity contribute to the altered glucose metabolism observed in ICP.

Obeticholic acid improves fetal bile acid profile in a mouse model of gestational hypercholanemia.

Intrahepatic cholestasis of pregnancy (ICP) is characterized by elevated maternal circulating bile acid levels and associated dyslipidemia. ICP leads to accumulation of bile acids in the fetal compartment, and the elevated bile acid concentrations are associated with an increased risk of adverse fetal outcomes. The farnesoid X receptor agonist obeticholic acid (OCA) is efficient in the treatment of cholestatic conditions such as primary biliary cholangitis. We hypothesized that OCA administration during hypercholanemic pregnancy will improve maternal and fetal bile acid and lipid profiles. Female C57BL/6J mice were fed either a normal chow diet, a 0.5% cholic acid (CA)-supplemented diet, a 0.03% OCA-supplemented diet, or a 0.5% CA + 0.03% OCA-supplemented diet for 1 wk before mating and throughout pregnancy until euthanization on day 18. The effects of CA and OCA feeding on maternal and fetal morphometry, bile acid and lipid levels, and cecal microbiota were investigated. OCA administration during gestation did not alter the maternal or fetal body weight or organ morphometry. OCA treatment during hypercholanemic pregnancy reduced bile acid levels in the fetal compartment. However, fetal dyslipidemia was not reversed, and OCA did not impact maternal bile acid levels or dyslipidemia. In conclusion, OCA administration during gestation had no apparent detrimental impact on maternal or fetal morphometry and improved fetal hypercholanemia. Because high serum bile acid concentrations in ICP are associated with increased rates of adverse fetal outcomes, further investigations into the potential use of OCA during cholestatic gestation are warranted.NEW & NOTEWORTHY We used a mouse model of gestational hypercholanemia to investigate the use of obeticholic acid (OCA), a potent FXR agonist, as a treatment for the hypercholanemia of intrahepatic cholestasis of pregnancy (ICP). The results demonstrate that OCA can improve the fetal bile acid profile. This is relevant not only to women with ICP but also for women who become pregnant while receiving OCA treatment for other conditions such as primary biliary cholangitis and nonalcoholic steatohepatitis.

Ursodeoxycholic acid improves feto-placental and offspring metabolic outcomes in hypercholanemic pregnancy.

Perturbations in the intrauterine environment can result in lifelong consequences for metabolic health during postnatal life. Intrahepatic cholestasis of pregnancy (ICP) can predispose offspring to metabolic disease in adulthood, likely due to a combination of the effects of increased bile acids, maternal dyslipidemia and deranged maternal and fetal lipid homeostasis. Whereas ursodeoxycholic acid (UDCA) is a commonly used treatment for ICP, no studies have yet addressed whether it can also prevent the metabolic effects of ICP in the offspring and fetoplacental unit. We therefore analyzed the lipid profile of fetal serum from untreated ICP, UDCA-treated ICP and uncomplicated pregnancies and found that UDCA ameliorates ICP-associated fetal dyslipidemia. We then investigated the effects of UDCA in a mouse model of hypercholanemic pregnancy and showed that it induces hepatoprotective mechanisms in the fetal liver, reduces hepatic fatty acid synthase (Fas) expression and improves glucose tolerance in the adult offspring. Finally, we showed that ICP leads to epigenetic changes in pathways of relevance to the offspring phenotype. We therefore conclude that UDCA can be used as an intervention in pregnancy to reduce features of metabolic disease in the offspring of hypercholanemic mothers.

Obeticholic acid ameliorates dyslipidemia but not glucose tolerance in mouse model of gestational diabetes.

Metabolism alters markedly with advancing gestation, characterized by progressive insulin resistance, dyslipidemia, and raised serum bile acids. The nuclear receptor farnesoid X receptor (FXR) has an integral role in bile acid homeostasis and modulates glucose and lipid metabolism. FXR is known to be functionally suppressed in pregnancy. The FXR agonist, obeticholic acid (OCA), improves insulin sensitivity in patients with type 2 diabetes with nonalcoholic fatty liver disease. We therefore hypothesized that OCA treatment during pregnancy could improve disease severity in a mouse model of gestational diabetes mellitus (GDM). C57BL/6J mice were fed a high-fat diet (HFD; 60% kcal from fat) for 4 wk before and throughout pregnancy to induce GDM. The impact of the diet supplemented with 0.03% OCA throughout pregnancy was studied. Pregnant HFD-fed mice displayed insulin resistance and dyslipidemia. OCA significantly reduced plasma cholesterol concentrations in nonpregnant and pregnant HFD-fed mice (by 22.4%, P < 0.05 and 36.4%, P < 0.001, respectively) and reduced the impact of pregnancy on insulin resistance but did not change glucose tolerance. In nonpregnant HFD-fed mice, OCA ameliorated weight gain, reduced mRNA expression of inflammatory markers in white adipose tissue, and reduced plasma glucagon-like peptide 1 concentrations (by 62.7%, P < 0.01). However, these effects were not evident in pregnant mice. OCA administration can normalize plasma cholesterol levels in a mouse model of GDM. However, the absence of several of the effects of OCA in pregnant mice indicates that the agonistic action of OCA is not sufficient to overcome many metabolic consequences of the pregnancy-associated reduction in FXR activity.

Bile acids and their respective conjugates elicit different responses in neonatal cardiomyocytes: role of Gi protein, muscarinic receptors and TGR5.

Bile acids are recognised as bioactive signalling molecules. While they are known to influence arrhythmia susceptibility in cholestasis, there is limited knowledge about the underlying mechanisms. To delineate mechanisms underlying fetal heart rhythm disturbances in cholestatic pregnancy, we used FRET microscopy to monitor cAMP release and contraction measurements in isolated rodent neonatal cardiomyocytes. The unconjugated bile acids CDCA, DCA and UDCA and, to a lesser extent, CA were found to be relatively potent agonists for the GPBAR1 (TGR5) receptor and elicit cAMP release, whereas all glyco- and tauro- conjugated bile acids are weak agonists. The bile acid-induced cAMP production does not lead to an increase in contraction rate, and seems to be mediated by the RI isoform of adenylate cyclase, unlike adrenaline-dependent release which is mediated by the RII isoform. In contrast, bile acids elicited slowing of neonatal cardiomyocyte contraction indicating that other signalling pathways are involved. The conjugated bile acids were found to be partial agonists of the muscarinic M2, but not sphingosin-1-phosphate-2, receptors, and act partially through the Gi pathway. Furthermore, the contraction slowing effect of unconjugated bile acids may also relate to cytotoxicity at higher concentrations.

A progesterone-brown fat axis is involved in regulating fetal growth.

Pregnancy is associated with profound maternal metabolic changes, necessary for the growth and development of the fetus, mediated by reproductive signals acting on metabolic organs. However, the role of brown adipose tissue (BAT) in regulating gestational metabolism is unknown. We show that BAT phenotype is lost in murine pregnancy, while there is a gain of white adipose tissue (WAT)-like features. This is characterised by reduced thermogenic capacity and mitochondrial content, accompanied by increased levels of markers of WAT and lipid accumulation. Surgical ablation of BAT prior to conception caused maternal and fetal hyperlipidemia, and consequently larger fetuses. We show that BAT phenotype is altered from day 5 of gestation, implicating early pregnancy factors, which was confirmed by reduced expression of BAT markers in progesterone challenged oophorectomised mice. Moreover, in vitro data using primary BAT cultures show a direct impact of progesterone on expression of Ucp1. These data demonstrate that progesterone mediates a phenotypic change in BAT, which contributes to the gestational metabolic environment, and thus overall fetal size.

Bile acids and gestation.

There are numerous profound maternal physiological changes that occur from conception onwards and adapt throughout gestation in order to support a healthy pregnancy. By the time of late gestation, when circulating pregnancy hormones are at their highest concentrations, maternal adaptations include relative hyperlipidemia, hypercholanemia and insulin resistance. Bile acids have now been established as key regulators of metabolism, and their role in gestational changes in metabolism is becoming apparent. Bile acid homeostasis is tightly regulated by the nuclear receptor FXR, which has been shown to have reduced activity during pregnancy. This review focuses on the gestational alterations in bile acid homeostasis that occur in normal pregnancy, which in some women can become pathological, leading to the development of intrahepatic cholestasis of pregnancy. As well as their important role in maternal metabolic health, we will review bile acid metabolism in the feto-placental unit.