OR24-5 Zebrafish in Utero Glucose Exposure Induces Lipid Dysregulation That Is Abrogated by Acetyl CoA Carboxylase or Glycolysis Inhibition
Authors: Cox Carol , Gibert Yann , Speed Joshua , Konadu Bridget 
Published: November 2022

Abstract

Background and Aim
One in ten pregnancies suffer from Gestational Diabetes Mellitus (GDM). GDM exposes fetus to high uterine glucose that causes fetal hyperglycemia. At birth Fetal hyperglycemia results in hypoglycemia, macrosomia, and larger than normal infants and these infants are predisposed to a number of metabolic disorders such as obesity, Type 2 Diabetes and non-alcoholic fatty liver disease (NAFLD) in adulthood. Although in-utero glucose exposure provides evidence for fetal lipid dysregulation linked to metabolic disorders in adults, the molecular mechanisms are still unclear. Increase in circulating insulin and glucose are implicated in the enhanced activation of hepatic De novo lipogenesis (DNL) in dyslipidemia, hence, we aim to investigate the potential beneficial effect of the pharmacological inhibition of DNL or glycolysis in our well-characterized zebrafish model of fetal hyperglycemia that mimics the metabolic disorders in human GDM against lipid derangement mediated by excess glucose in embryos in a short term and avoid the long-term outcome of obesity.

Methods
We developed a zebrafish model of fetal hyperglycemia by exposing embryos to high glucose (4.5% w/v) during the last day of embryogenesis from 96 to 120 hours post-fertilization (hpf). Glucose level was detected in embryo homogenates by glucometer. Insulin expression was visualized by whole-mount in-situ Hybridization. Gene expression of glycolytic (Hexokinase) and lipogenic [Acetyl-CoA Carboxylase (acca)] markers by RT-qPCR and malonyl CoA levels (product of DNL) by ELISA were also assessed. Lipid accumulation was detected by Oil-Red-O staining (ORO) and quantified by spectrophotometry. Pharmacological intervention using metformin or ND646 (known inhibitors of acca) or 2-Deoxyglucose, 2DG (Known inhibitor of Hexokinase) with glucose for 24hours were utilized to attenuate fetal hyperglycemia-mediated lipid accumulation in embryos.

Results
Zebrafish embryos exposed to high glucose for 24 hours are transiently hyperglycemic while normoglycemia is restored 24 hours after removal from glucose media. At 120 hpf embryos exposed to high-glucose demonstrated increased insulin, hexokinase, and acca expression compared to untreated controls. We also observed a significant reduction in malonyl CoA levels in ND 646 and metformin cotreated embryos with glucose compared to controls. Interestingly, quantification of ORO staining revealed a significant increase in lipid deposition in glucose treated embryos compared to controls at 120 hpf (0.2±0.01 vrs 0.13±0.005), which was significantly attenuated in embryos co-treated with glucose and 2-DG- (0.15±0.003) or metformin- (0.11±0.007) compared to glucose-treated embryos. Similarly, a moderate reduction in ORO staining was observed in embryos that were co-treated with glucose and ND646 (0.17 ± 0.006).

Conclusion and significance
Together our results show that embryonic glucose exposure leads to increased lipid accumulation which can be rescued by blocking glycolysis or de novo lipogenesis. Intervening glycolysis and de novo lipogenesis could be a promising therapeutic approach for modulating fetal hyperglycemia-related lipid dysregulations.
Presentation: Monday, June 13, 2022 12:00 p.m. - 12:15 p.m.