Ursodeoxycholic acid (UDcA) treatment can reduce itch and lower endogenous serum bile acids in intrahepatic cholestasis of pregnancy (ICP). We sought to determine how it could influence the gut environment in icp to alter enterohepatic signalling. the gut microbiota and bile acid content were determined in faeces from 35 pregnant women (14 with uncomplicated pregnancies and 21 with ICP, 17 receiving UDCA). Faecal bile salt hydrolase activity was measured using a precipitation assay. Serum fibroblast growth factor 19 (FGF19) and 7α-hydroxy-4-cholesten-3-one (C4) concentrations were measured following a standardised diet for 21 hours. Women with a high ratio of Bacteroidetes to Firmicutes were more likely to be treated with UDcA (fisher's exact test p = 0.0178) than those with a lower ratio. Bile salt hydrolase activity was reduced in women with low Bacteroidetes:Firmicutes. Women taking UDcA had higher faecal lithocholic acid (p < 0.0001), with more unconjugated bile acids than women with untreated ICP or uncomplicated pregnancy. UDCA-treatment increased serum FGF19, and reduced C4 (reflecting lower bile acid synthesis). During ICP, UDCA treatment can be associated with enrichment of the gut microbiota with Bacteroidetes. these demonstrate high bile salt hydrolase activity, which deconjugates bile acids enabling secondary modification to FXR agonists, enhancing enterohepatic feedback via FGF19.The serum and faecal bile acid composition is intimately related to biotransformation of bile acids by intestinal bacteria, and their subsequent enterohepatic circulation. Deconjugation of primary bile acids by bacterial bile salt hydrolase (BSH) enables unconjugated bile acids to be modified to secondary bile acids. Bile acids act as signalling molecules for many different end organs (e.g. liver, pancreas, adipose tissue, inflammatory cells), with individual bile acid species of differing ligand potency for different receptors (e.g. farnesoid X receptor (FXR), Takeda G-protein-coupled receptor 5 (TGR5)) 1-3 .Intrahepatic cholestasis of pregnancy (ICP) is predominantly a liver disorder specific to pregnancy, defined by pruritus and elevated serum bile acids beyond the normal asymptomatic hypercholanaemia of pregnancy. Fetal adverse outcomes are related to the extent of elevation of serum concentrations of total bile acids 4,5 . Women with ICP have increased rates of impaired glucose tolerance, gestational diabetes mellitus, and dyslipidaemia 6,7 .

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 are lipid-solubilising molecules that also regulate metabolic processes. Farnesoid X receptor (FXR) and Takeda G-protein coupled receptor 5 (TGR5) are two bile acid receptors with key metabolic roles. FXR regulates bile acid synthesis in the liver and influences bile acid uptake in the intestine. TGR5 is mainly involved in regulation of signalling pathways in response to bile acid uptake in the gut and therefore prandial response. Both FXR and TGR5 have potential as therapeutic targets for disorders of glucose and/or lipid homeostasis. Gestation is also known to cause small increases in bile acid concentrations, but physiological hypercholanaemia of pregnancy is usually not sufficient to cause any clinically relevant effects. This review focuses on how gestation alters bile acid homeostasis, which can become pathological if the elevation of maternal serum bile acids is more marked than physiological hypercholanaemia, and on the influence of FXR and TGR5 function in pregnancy on glucose and lipid metabolism. This will be discussed with reference to two gestational disorders: intrahepatic cholestasis of pregnancy (ICP), a disease where bile acids are pathologically elevated, and gestational diabetes mellitus (GDM), characterised by hyperglycaemia during pregnancy.

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 β-cell proliferation and increased apoptosis in pregnancy, without altering insulin sensitivity, suggesting that raised bile acids affect β-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.

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) UK-based European-ancestry women with or without GDM; 4) 11-13 week pregnant women with BMI≤25 or BMI≥35 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 TRPM3. Computer modelling using Molecular Operating Environment (MOE) generated 3D structures of TRPM3. Epiallopregnanolone sulfate (PM5S) concentrations were reduced: in GDM (p&lt;0.05); in women with higher fasting plasma glucose (p&lt;0.010); and in early pregnancy samples from women who subsequently developed GDM with BMI≥35 (p&lt;0.05). In islets, 50μM PM5S increased GSIS by at least 2-fold (P&lt;0.001); isosakuranetin (TRPM3-inhibitor) abolished this effect. PM5S increased calcium influx in TRPM3-expressing HEK293 cells. Computer modelling 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.

Serum progesterone sulfates were evaluated in the etiology of gestational diabetes mellitus (GDM). <p>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) UK-based European-ancestry women with or without GDM; 4)<u> </u>11-13 week pregnant women with BMI≤25 or BMI≥35 with subsequent uncomplicated pregnancies or GDM.</p> <p>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 TRPM3. Computer modelling using Molecular Operating Environment (MOE) generated 3D structures of TRPM3. </p> <p>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 (p<0.05). In islets, 50µM PM5S increased GSIS by at least 2-fold (P<0.001); isosakuranetin (TRPM3-inhibitor)<u> </u>abolished this effect. PM5S increased calcium influx in TRPM3-expressing HEK293 cells. Computer modelling and docking showed identical positioning of PM5S to the natural ligand in TRPM3. </p> 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.

Introduction: Serum progesterone sulfate (P4S) concentrations increase in pregnancy and bind receptors that influence glucose homeostasis. We hypothesized that P4S modulate glucose homeostasis in pregnancy. Methods: Serum P4S were assayed using ultra-performance liquid chromatography- tandem mass spectrometry. Samples were studied in three separate patient groups: women with GDM (n=20) and matched healthy controls (n=38); participants (average 28 weeks’ gestation) from the upper (n=93) and lower (n=94) quartiles of fasting plasma glucose in the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) Study; 11-13 week pregnant women with BMI≤25 or BMI≥35 who subsequently had uncomplicated pregnancies or developed GDM (n=50/group). Glucose-stimulated insulin secretion (GSIS) was quantified in isolated wild-type, Fxr-/- and Tgr5-/- mouse and human islets in the presence of P4S and TRPM3 inhibitor isosakuranetin (ISO). Intracellular calcium concentrations were measured after treatment with P4S in TRPM3 transfected HEK293. Computer modelling using Molecular Operating Environment generated 3D structures of TRPM3 and P4S binding. Results: Epiallopregnanolone sulfate (PM5S) concentrations were reduced in serum samples from the HAPO study participants with higher fasting plasma glucose (p&lt;0.01), in women with GDM (p&lt;0.05) and in early pregnancy samples from women with BMI ≥35 who subsequently developed GDM (P&lt;0.05). In wild-type and human islets, 50μM PM5S increased GSIS by at least 2-fold at 20mM glucose concentrations (P&lt;0.001). This effect was not abolished from islets obtained from Fxr-/- or Tgr-/- mice, however it was abolished by ISO. PM5S elicited Ca2+ influx in TRPM3-expressing HEK293 cells. Computer modelling and docking showed identical positioning of PM5S to cholesterol hemisuccinate in TRPM3. Conclusion: PM5S increases GSIS and concentrations are reduced in the serum of women with GDM. The increased GSIS is mediated by TRPM3. Disclosure H. Fan: None. F. Fraternali: None. K. F. Hunt: None. J. Bowe: None. C. Williamson: Consultant; Self; GlaxoSmithKline plc., Mirum Pharmaceuticals. A. Mitchell: None. M. Giorgi: None. P. M. Jones: None. D. R. Mccance: None. D. A. Andersson: None. S. Bevan: None. H. Marschall: None. I. Eberini: None. Funding Tommy’s; Guy’s and St Thomas’ Biomedical Research Centre; National Health Service

No abstract