Assessment of prenatal cerebral and cardiac metabolic changes in a rabbit model of fetal growth restriction based on ¹³C-labelled substrate infusions and <i>ex vivo</i> multinuclear HRMAS

Background We have used a previously reported rabbit model of fetal growth restriction (FGR), reproducing perinatal neurodevelopmental and cardiovascular impairments, to investigate the main relative changes in cerebral and cardiac metabolism of term FGR fetuses during nutrient infusion. Methods FGR was induced in 9 pregnant New Zealand rabbits at 25 days of gestation: one horn used as FGR, by partial ligation of uteroplacental vessels, and the contralateral as control (appropriate for gestation age, AGA). At 30 days of gestation, fasted mothers under anesthesia were infused i.v. with 1-13C-glucose (4 mothers), 2-13C-acetate (3 mothers), or not infused (2 mothers). Fetal brain and heart samples were quickly harvested and frozen down. Brain cortex and heart apex regions from 30 fetuses were studied ex vivo by HRMAS at 4°C, acquiring multinuclear 1D and 2D spectra. The data were processed, quantified by peak deconvolution or integration, and normalized to sample weight. Results Most of the total 13C-labeling reaching the fetal brains/hearts (80–90%) was incorporated to alanine and lactate (cytosol), and to the glutamine-glutamate pool (mitochondria). Acetate-derived lactate (Lac C2C3) had a slower turnover in FGR brains (~ -20%). In FGR hearts, mitochondrial turnover of acetate-derived glutamine (Gln C4) was slower (-23%) and there was a stronger accumulation of phospholipid breakdown products (glycerophosphoethanolamine and glycerophosphocholine, +50%), resembling the profile of non-infused control hearts. Conclusions Our results indicate specific functional changes in cerebral and cardiac metabolism of FGR fetuses under nutrient infusion, suggesting glial impairment and restricted mitochondrial metabolism concomitant with slower cell membrane turnover in cardiomyocytes, respectively. These prenatal metabolic changes underlie neurodevelopmental and cardiovascular problems observed in this FGR model and in clinical patients, paving the way for future studies aimed at evaluating metabolic function postnatally and in response to stress and/or treatment.背景 我们采用此前已报道的胎儿生长受限（FGR）兔模型，该模型可重现围产期神经发育与心血管功能损伤，旨在探究足月FGR胎兔在营养输注过程中脑与心脏代谢的主要相对变化。 方法 于妊娠25天时，对9只妊娠新西兰兔诱导FGR：通过部分结扎子宫胎盘血管，将单侧子宫角构建为FGR模型组，对侧子宫角作为适于胎龄（AGA）对照。妊娠30天时，对麻醉状态下的禁食母兔进行静脉输注（i.v.）：其中4只母兔输注1-13C-葡萄糖，3只输注2-13C-乙酸盐，剩余2只不进行输注。快速采集胎兔脑组织与心脏样本并冷冻保存。对30例胎兔的大脑皮层及心尖区域样本，于4℃下采用高分辨魔角旋转核磁共振波谱（HRMAS）进行离体分析，采集多核一维及二维波谱。数据经处理后，通过峰反褶积或积分进行定量，并以样本重量进行归一化。 结果 总计80%~90%的13C标记物可被整合至胎兔脑组织与心脏的胞质丙氨酸、乳酸，以及线粒体谷氨酰胺-谷氨酸池中。乙酸盐来源的乳酸（Lac C2C3）在FGR胎兔脑组织中的周转速率较慢（约降低20%）。在FGR胎兔心脏中，乙酸盐来源的谷氨酰胺（Gln C4）的线粒体周转速率较慢（降低23%），且磷脂降解产物（甘油磷酸乙醇胺与甘油磷酸胆碱）的积累量显著升高（升高50%），该代谢特征与未输注营养的对照胎兔心脏一致。 结论 本研究结果表明，在营养输注条件下，FGR胎兔的脑与心脏代谢存在特异性功能改变：分别提示神经胶质功能受损与线粒体代谢受限，同时伴随心肌细胞膜周转速率减慢。这些产前代谢变化可解释本FGR模型及临床患者中观察到的神经发育与心血管问题，为后续评估出生后代谢功能以及探究应激与/或治疗干预对代谢的影响相关研究奠定了基础。