The physiological effects of creatine supplementation in fetal sheep before, during, and after umbilical cord occlusion and global hypoxia

Abstract

The aim of this study was to investigate the effects of direct creatine infusion on fetal systemic metabolic and cardiovascular responses to mild acute in utero hypoxia. Pregnant ewes (n=28) were surgically instrumented at 118 days gestation (dGa). A constant intravenous infusion of creatine (6 mg.kg-1.h-1) or isovolumetric saline (1.5 ml.h-1) began at 121 dGa. After 10 days, fetuses were subjected to 10-minute umbilical cord occlusion (UCO) to induce mild global hypoxia (saline-UCO, n=8; creatine-UCO, n=7) or sham UCO (saline-control, n=6; creatine-control, n=7). Cardiovascular, arterial blood gases and metabolites, and plasma creatine were monitored prior to, during, and then for 72 hours following the UCO. Total creatine content in discrete fetal brain regions was also measured. Fetal creatine infusion increased plasma concentrations 5-fold but had no significant effects on any measurement pre-UCO. Creatine did not alter fetal physiology during the UCO or in the early recovery stage, up to 24 hours after UCO. During the late recovery stage, 24-72 hours after UCO, there was a significant reduction in the arterial oxygen pressure and saturation in creatine fetuses (PUCO x TREATMENT = 0.02 and 0.04, respectively). At 72 hours after UCO, significant creatine loading was detected in cortical grey matter, hippocampus, thalamus and striatum (PTREATMENT = 0.01-0.001). In the striatum, the UCO itself increased total creatine content (PUCO = 0.019). Overall, fetal creatine supplementation may alter oxygen flux following an acute hypoxic insult. Increasing total creatine content in the striatum may also be a fetal adaptation to acute oxygen deprivation.

The Effects of In Utero Fetal Hypoxia and Creatine Treatment on Mitochondrial Function in the Late Gestation Fetal Sheep Brain

“…Full details on the surgical preparation and methodology for this fetal sheep experiment have been previously published [ 32 ]. The animals included in that study provide the tissue samples studied in detail in this paper.…”

“…We have recently characterized a near-term fetal sheep model of in utero hypoxia where the fetus was treated with a direct continuous infusion of creatine prior to, during, and following global hypoxia produced by a 10-minute umbilical cord occlusion (UCO) [ 32 ]. These experiments were conducted at ~130 dGA, when fetal the sheep is considered to be at a level of physiological maturity equivalent to the near-term human fetus [ 33 ].…”

“…This study found that fetal creatine treatment increased plasma concentrations 5-fold after 4 days of continuous infusion, with no effect on basal blood gases, pH, glucose or lactate concentrations, nor on the fetal response during UCO, or during the early recovery stage (up to 24 hours after the insult). Creatine treated fetuses did however display changes to arterial oxygenation in 24-72 hours after UCO [ 32 ]. Importantly, at 13 days after commencing creatine treatment, significant creatine loading was detected in the grey matter, hippocampus, thalamus, and striatum [ 32 ].…”

“…Creatine treated fetuses did however display changes to arterial oxygenation in 24-72 hours after UCO [ 32 ]. Importantly, at 13 days after commencing creatine treatment, significant creatine loading was detected in the grey matter, hippocampus, thalamus, and striatum [ 32 ].…”

“…The aim of the current study was to test the efficacy of prior creatine loading on mitochondrial respiratory activity and the incidence of neuropathology in key regions of the fetal brain, using tissue samples collected from [ 32 ]. We hypothesized that regional differences in mitochondrial function would be evident, and that prophylactic creatine treatment would mitigate mitochondrial dysfunction following hypoxia, thereby reducing fetal brain injury, an outcome that has been documented in this fetal model on several previous occasions [ 7 , 34 – 36 ].…”