Ellery Stacey J, Della Gatta Paul A, Bruce Clinton R, Kowalski Greg M, Davies-Tuck Miranda, Mockler Joanne C, Murthi Padma, Walker David W, Snow Rod J, Dickinson Hayley
The Ritchie Centre, Hudson Institute of Medical Research, Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia.
Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Burwood Campus, Melbourne, Australia.
Placenta. 2017 Apr;52:86-93. doi: 10.1016/j.placenta.2017.02.020. Epub 2017 Feb 24.
Creatine is an amino acid derivative that is involved in preserving ATP homeostasis. Previous studies suggest an important role for the creatine kinase circuit for placental ATP turnover. Creatine is obtained from both the diet and endogenous synthesis, usually along the renal-hepatic axis. However, some tissues with a high-energy demand have an inherent capacity to synthesise creatine. In this study, we determined if the term human placenta has the enzymatic machinary to synthesise creatine.
Eleven placentae were collected following elective term caesarean section. Samples from the 4 quadrants of each placenta were either fixed in formalin or frozen. qPCR was used to determine the mRNA expression of the creatine synthesising enzymes arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT), and the creatine transporter (SLC6A8). Protein expression of AGAT and GAMT was quantified by Western blot, and observations of cell localisation of AGAT, GAMT and SLC6A8 made with immunohistochemistry. Synthesis of guanidinoacetate (GAA; creatine precursor) and creatine in placental homogenates was determined via GC-MS and HPLC, respectively.
AGAT, GAMT and SLC6A8 mRNA and protein were detected in the human placenta. AGAT staining was identified in stromal and endothelial cells of the fetal capillaries. GAMT and SLC6A8 staining was localised to the syncytiotrophoblast of the fetal villi. Ex vivo, tissue homogenates produce both GAA (4.6 nmol mg proteinh) and creatine (52.8 nmol mg proteinh).
The term human placenta has the capacity to synthesise creatine. These data present a new understanding of placental energy metabolism.
肌酸是一种氨基酸衍生物，参与维持三磷酸腺苷（ATP）的稳态。先前的研究表明肌酸激酶循环在胎盘ATP周转中起重要作用。肌酸可从饮食和内源性合成中获取，通常沿着肾-肝轴进行。然而，一些能量需求高的组织具有合成肌酸的内在能力。在本研究中，我们确定足月人胎盘是否具有合成肌酸的酶机制。
在择期足月剖宫产术后收集11个胎盘。每个胎盘4个象限的样本分别用福尔马林固定或冷冻。采用定量聚合酶链反应（qPCR）测定肌酸合成酶精氨酸：甘氨酸脒基转移酶（AGAT）和胍基乙酸甲基转移酶（GAMT）以及肌酸转运体（SLC6A8）的mRNA表达。通过蛋白质印迹法定量AGAT和GAMT的蛋白表达，并用免疫组织化学法观察AGAT、GAMT和SLC6A8的细胞定位。分别通过气相色谱-质谱联用（GC-MS）和高效液相色谱法（HPLC）测定胎盘匀浆中胍基乙酸（GAA；肌酸前体）和肌酸的合成。
在人胎盘中检测到AGAT、GAMT和SLC6A8的mRNA和蛋白。在胎儿毛细血管的基质和内皮细胞中发现AGAT染色。GAMT和SLC6A8染色定位于胎儿绒毛的合体滋养层。在体外，组织匀浆可产生GAA（4.6 nmol·mg蛋白·h）和肌酸（52.8 nmol·mg蛋白·h）。
足月人胎盘具有合成肌酸的能力。这些数据为胎盘能量代谢提供了新的认识。
