Zoe Ireland

Maternal creatine : does it reach the fetus and improve survival after an acute hypoxic episode in the spiny mouse (Acomys cahirinus)?

OBJECTIVE We hypothesized that elevating creatine in the maternal diet would reach fetal and placental tissues and improve fetal survival after acute hypoxia at birth. STUDY DESIGN Pregnant spiny mice were fed a control or 5% creatine-supplemented diet from day 20 of gestation (term, approximately 39 days). On days 37-38, intrauterine hypoxia was induced by placement of the isolated uterus in a saline solution bath for 7.5-8 minutes, after which fetuses were expelled from the uterus and resuscitation was attempted by manual palpation of the chest. Total creatine content (creatine + phosphocreatine) of placental, fetal, and maternal organs was measured. RESULTS The maternal creatine diet significantly increased total creatine content in the placenta, fetal brain, heart, liver, and kidney and increased the capacity of offspring to survive birth hypoxia. Maternal creatine improved postnatal growth after birth hypoxia. CONCLUSION This study provides evidence that creatine has potential as a prophylactic therapy for pregnancies that are classified as high risk for fetal hypoxia.

Developmental changes in the expression of creatine synthesizing enzymes and creatine transporter in a precocial rodent, the spiny mouse

BackgroundCreatine synthesis takes place predominately in the kidney and liver via a two-step process involving AGAT (L-arginine:glycine amidinotransferase) and GAMT (guanidinoacetate methyltransferase). Creatine is taken into cells via the creatine transporter (CrT), where it plays an essential role in energy homeostasis, particularly for tissues with high and fluctuating energy demands. Very little is known of the fetal requirement for creatine and how this may change with advancing pregnancy and into the early neonatal period. Using the spiny mouse as a model of human perinatal development, the purpose of the present study was to comprehensively examine the development of the creatine synthesis and transport systems.ResultsThe estimated amount of total creatine in the placenta and brain significantly increased in the second half of pregnancy, coinciding with a significant increase in expression of CrT mRNA. In the fetal brain, mRNA expression of AGAT increased steadily across the second half of pregnancy, although GAMT mRNA expression was relatively low until 34 days gestation (term is 38–39 days). In the fetal kidney and liver, AGAT and GAMT mRNA and protein expression were also relatively low until 34–37 days gestation. Between mid-gestation and term, neither AGAT or GAMT mRNA or protein could be detected in the placenta.ConclusionOur results suggest that in the spiny mouse, a species where, like the human, considerable organogenesis occurs before birth, there appears to be a limited capacity for endogenous creatine synthesis until approximately 0.9 of pregnancy. This implies that a maternal source of creatine, transferred across the placenta, may be essential until the creatine synthesis and transport system matures in preparation for birth. If these results also apply to the human, premature birth may increase the risk of creatine deficiency.

Neuroprotective properties of melatonin in a model of birth asphyxia in the spiny mouse (Acomys cahirinus).

Birth asphyxia is associated with disturbed development of the neonatal brain. In this study, we determined if low-dose melatonin (0.1 mg/kg/day), administered to the mother over 7 days at the end of pregnancy, could protect against the effects of birth asphyxia in a precocial species – the spiny mouse (Acomys cahirinus). At 37 days of gestation (term is 38–39 days), pups were subjected to birth asphyxia (7.5 min uterine ischemia) and compared to Cesarean section-delivered controls. At 24 h of age, birth asphyxia had increased markers of CNS inflammation (microglia, macrophage infiltration) and apoptosis (activated caspase-3, fractin) in cortical gray matter, which were reduced to control levels by prior maternal melatonin treatment. Melatonin may be an effective prophylactic agent for use in late pregnancy to protect against hypoxic-ischemic brain injury at birth.

Maternal creatine supplementation from mid-pregnancy protects the diaphragm of the newborn spiny mouse from intrapartum hypoxia-induced damage

We hypothesized that maternal creatine supplementation from mid-pregnancy would protect the diaphragm of the newborn spiny mouse from the effects of intrapartum hypoxia. Pregnant mice were fed a control or 5% creatine-supplemented diet from mid-gestation. On the day before term, intrapartum hypoxia was induced by isolating the pregnant uterus in a saline bath for 7.5–8 min before releasing and resuscitating the fetuses. Surviving pups were placed with a cross-foster dam, and diaphragm tissue was collected at 24 h postnatal age. Hypoxia caused a significant decrease in the cross-sectional area (∼19%) and contractile function (26.6% decrease in maximum Ca2+-activated force) of diaphragm fibers. The mRNA levels of the muscle mass-regulating genes MuRF1 and myostatin were significantly increased (2-fold). Maternal creatine significantly attenuated hypoxia-induced fiber atrophy, contractile dysfunction, and changes in mRNA levels. This study demonstrates that creatine loading before birth significantly protects the diaphragm from hypoxia-induced damage at birth.

Creatine pretreatment prevents birth asphyxia-induced injury of the newborn spiny mouse kidney

Background:Acute kidney injury (AKI) is a major complication for infants following an asphyxic insult at birth. We aimed to determine if kidney structure and function were affected in an animal model of birth asphyxia and if maternal dietary creatine supplementation could provide an energy reserve to the fetal kidney, maintaining cellular respiration during asphyxia and preventing AKI.Methods:Pregnant spiny mice were maintained on normal chow or chow supplemented with creatine from day 20 gestation. On day 38 (term ~39 d), pups were delivered by cesarean section (c-section) or subjected to intrauterine asphyxia. Twenty-four hours after insult, kidneys were collected for histological or molecular analysis. Urine and plasma were also collected for biochemical analysis.Results:AKI was evident at 24 h after birth asphyxia, with a higher incidence of shrunken glomeruli (P < 0.02), disturbance to tubular arrangement, tubular dilatation, a twofold increase (P < 0.02) in expression of Ngal (early marker of kidney injury), and decreased expression of the podocyte differentiation marker nephrin. Maternal creatine supplementation prevented the glomerular and tubular abnormalities observed in the kidney at 24 h and the increased expression of Ngal.Conclusion:Maternal creatine supplementation may prove useful in ameliorating kidney injury associated with birth asphyxia.

Creatine supplementation during pregnancy: summary of experimental studies suggesting a treatment to improve fetal and neonatal morbidity and reduce mortality in high-risk human pregnancy

While the use of creatine in human pregnancy is yet to be fully evaluated, its long-term use in healthy adults appears to be safe, and its well documented neuroprotective properties have recently been extended by demonstrations that creatine improves cognitive function in normal and elderly people, and motor skills in sleep-deprived subjects. Creatine has many actions likely to benefit the fetus and newborn, because pregnancy is a state of heightened metabolic activity, and the placenta is a key source of free radicals of oxygen and nitrogen. The multiple benefits of supplementary creatine arise from the fact that the creatine-phosphocreatine [PCr] system has physiologically important roles that include maintenance of intracellular ATP and acid–base balance, post-ischaemic recovery of protein synthesis, cerebral vasodilation, antioxidant actions, and stabilisation of lipid membranes. In the brain, creatine not only reduces lipid peroxidation and improves cerebral perfusion, its interaction with the benzodiazepine site of the GABAA receptor is likely to counteract the effects of glutamate excitotoxicity – actions that may protect the preterm and term fetal brain from the effects of birth hypoxia. In this review we discuss the development of creatine synthesis during fetal life, the transfer of creatine from mother to fetus, and propose that creatine supplementation during pregnancy may have benefits for the fetus and neonate whenever oxidative stress or feto-placental hypoxia arise, as in cases of fetal growth restriction, premature birth, or when parturition is delayed or complicated by oxygen deprivation of the newborn.

Behavioural effects of near-term acute fetal hypoxia in a small precocial animal, the spiny mouse (Acomys cahirinus)

We have previously developed a model of near-term intra-uterine hypoxia producing significant neonatal mortality (37%) in a small laboratory animal – the spiny mouse – which has precocial offspring at birth. The aim of the present study was to determine if this insult resulted in the appearance of behavioural abnormalities in those offspring which survived the hypoxic delivery. Behavioural tests assessed gait (using footprint patterns), motor coordination and balance on an accelerating rotarod, and spontaneous locomotion and exploration in an open field. We found that the near-term acute hypoxic episode produced a mild neurological deficit in the early postnatal period. In comparison to vaginally delivered controls, hypoxia pups were able to remain on the accelerating rotarod for significantly shorter durations on postnatal days 1–2, and in the open field they travelled significantly shorter distances, jumped less, and spent a greater percentage of time stationary on postnatal days 5 and 15. No changes were observed in gait. Unlike some rodent models of cerebral hypoxia-ischaemia, macroscopic examination of the brain on postnatal day 5 showed no gross cystic lesions, oedema or infarct. Future studies should be directed at identifying hypoxia-induced alterations in the function of specific brain regions, and assessing if maternal administration of neuroprotective agents can prevent against hypoxia-induced neurological deficits and brain damage that occur at birth.

Maternal dietary creatine supplementation does not alter the capacity for creatine synthesis in the newborn spiny mouse.

We have previously reported that maternal creatine supplementation protects the neonate from hypoxic injury. Here, we investigated whether maternal creatine supplementation altered expression of the creatine synthesis enzymes (arginine:glycine amidinotransferase [AGAT], guanidinoaceteate methyltransferase [GAMT]) and the creatine transporter (solute carrier family 6 [neurotransmitter transporter, creatine] member 8: SLC6A8) in the term offspring. Pregnant spiny mice were fed a 5% creatine monohydrate diet from midgestation (day 20) to term (39 days). Placentas and neonatal kidney, liver, heart, and brain collected at 24 hours of age underwent quantitative polymerase chain reaction and Western blot analysis. Maternal creatine had no effect on the expression of AGAT and GAMT in neonatal kidney and liver, but mRNA expression of AGAT in brain tissues was significantly decreased in both male and female neonates born to mothers who were fed the creatine diet. SLC6A8 expression was not affected by maternal dietary creatine loading in any tissues. Maternal dietary creatine supplementation from midgestation in the spiny mouse did not alter the capacity for creatine synthesis or transport.

Effects of birth asphyxia on neonatal hippocampal structure and function in the spiny mouse

Studies of human neonates, and in animal experiments, suggest that birth asphyxia results in functional compromise of the hippocampus, even when structural damage is not observable or resolves in early postnatal life. The aim of this study was to determine if changes in hippocampal function occur in a model of birth asphyxia in the precocial spiny mouse where it is reported there is no major lesion or infarct. Further, to assess if, as in human infants, this functional deficit has a sex‐dependent component. At 37 days gestation (term = 39 days) spiny mice fetuses were either delivered immediately by caesarean section (control group) or exposed to 7.5 min of in utero asphyxia causing systemic acidosis and hypoxia. At 5 days of age hippocampal function was assessed ex vivo in brain slices, or brains were collected for examination of structure or protein expression. This model of birth asphyxia did not cause infarct or cystic lesion in the postnatal day 5 (P5) hippocampus, and the number of proliferating or pyknotic cells in the hippocampus was unchanged, although neuronal density in the CA1 and CA3 was increased. Protein expression of synaptophysin, brain‐derived neurotrophic factor (BDNF), and the inositol trisphosphate receptor 1 (IP3R1) were all significantly increased after birth asphyxia, while long‐term potentiation (LTP), paired pulse facilitation (PPF), and post‐tetanic potentiation (PTP) were all reduced at P5 by birth asphyxia. In control P5 pups, PPF and synaptic fatigue were greater in female compared to male pups, and after birth asphyxia PPF and synaptic fatigue were reduced to a greater extent in female vs. male pups. In contrast, the asphyxia‐induced increase in synaptophysin expression and neuronal density were greater in male pups. Thus, birth asphyxia in this precocial species causes functional deficits without major structural damage, and there is a sex‐dependent effect on the hippocampus. This may be a clinically relevant model for assessing treatments delivered either before or after birth to protect this vulnerable region of the developing brain.

Short-Term Dose–Response Characteristics of 2-Iminobiotin Immediately Postinsult in the Neonatal Piglet After Hypoxia-Ischemia

Background and Purpose— To determine the optimal dose of 2-iminobiotin (2-IB) for the treatment of moderate to severe asphyxia in a neonatal piglet model of hypoxia-ischemia. Methods— Newborn piglets were subjected to a 30-minute hypoxia-ischemia insult and randomly treated with vehicle or 2-IB (0.1 mg/kg, 0.2 mg/kg, or 1.0 mg/kg). aEEG background and seizure activity were scored after hypoxia-ischemia every 4 h until 24 h and at 48 h and neurobehavioral scores were obtained. Brain tissue was collected and processed for analysis of caspase-3 activity, histology, and tyrosine nitration. Results— A dose range of 0.1 to 1.0 mg/kg/dose of 2-IB improved short-term outcome as demonstrated by an increased survival with a normal aEEG and decreased nitrotyrosine staining in the 2-IB–treated animals, indicating decreased cellular damage. Neurobehavior, caspase-3 activity in thalamus, and histology scores were not significantly different. Conclusions— Based on survival with a normal aEEG, 0.2 mg/kg 2-IB is likely to be the most appropriate dose for use in future clinical trials in neonates with perinatal hypoxia-ischemia.