Epiallopregnanolone Sulfate Is Reduced in Gestational Diabetes Mellitus and Induces Glucose-Stimulated Insulin Secretion

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<0.01), in women with GDM (p<0.05) and in early pregnancy samples from women with BMI ≥35 who subsequently developed GDM (P<0.05). In wild-type and human islets, 50μM PM5S increased GSIS by at least 2-fold at 20mM glucose concentrations (P<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