Pre- and early postnatal enriched environmental experiences prevent neonatal hypoxia-ischemia late neurodegeneration via metabolic and neuroplastic mechanisms.

Prenatal and early postnatal periods are important for brain development and neural function. Neonatal insults such as hypoxia-ischemia (HI) causes prolonged neural and metabolic dysregulation, affecting central nervous system maturation. There is evidence that brain hypometabolism could increase the risk of adult-onset neurodegenerative diseases. However, the impact of non-pharmacologic strategies to attenuate HI-induced brain glucose dysfunction is still underexplored. This study investigated the long-term effects of early environmental enrichment in metabolic, cell, and functional responses after neonatal HI. Thereby, male Wistar rats were divided according to surgical procedure, sham, and HI (performed at postnatal day 3), and the allocation to standard (SC) or enriched condition (EC) during gestation and lactation periods. In-vivo cerebral metabolism was assessed by means of [18 F]-FDG micro-positron emission tomography, and cognitive, biochemical, and histological analyses were performed in adulthood. Our findings reveal that HI causes a reduction in glucose metabolism and glucose transporter levels as well as hyposynchronicity in metabolic brain networks. However, EC during prenatal or early postnatal period attenuated these metabolic disturbances. A positive correlation was observed between [18 F]-FDG values and volume ratios in adulthood, indicating that preserved tissue by EC is metabolically active. EC promotes better cognitive scores, as well as down-regulation of amyloid precursor protein in the parietal cortex and hippocampus of HI animals. Furthermore, growth-associated protein 43 was up-regulated in the cortex of EC animals. Altogether, results presented support that EC during gestation and lactation period can reduce HI-induced impairments that may contribute to functional decline and progressive late neurodegeneration.

Long-term changes in metabolic brain network drive memory impairments in rats following neonatal hypoxia-ischemia.

BACKGROUND AND PURPOSE: Hypoxia and cerebral ischemia (HI) events are capable of triggering important changes in brain metabolism, including glucose metabolism abnormalities, which may be related to the severity of the insult. Using positron emission microtomography (microPET) with [18F]fluorodeoxyglucose (18F-FDG), this study proposes to assess abnormalities of brain glucose metabolism in adult rats previously submitted to the neonatal HI model. We hypothesize that cerebral metabolic outcomes will be associated with cognitive deficits and magnitude of brain injury. METHODS: Seven-day-old rats were subjected to an HI model, induced by permanent occlusion of the right common carotid artery and systemic hypoxia. 18F-FDG-microPET was used to assess regional and whole brain glucose metabolism in rats at 60 postnatal days (PND 60). An interregional cross-correlation matrix was utilized to construct metabolic brain networks (MBN). Rats were also subjected to the Morris Water Maze (MWM) to evaluate spatial memory and their brains were processed for volumetric evaluation. RESULTS: Brain glucose metabolism changes were observed in adult rats after neonatal HI insult, limited to the right brain hemisphere. However, not all HI animals exhibited significant cerebral hypometabolism. Hippocampal glucose metabolism was used to stratify HI animals into HI hypometabolic (HI-h) and HI non-hypometabolic (HI non-h) groups. The HI-h group had drastic MBN disturbance, cognitive deficit, and brain tissue loss, concomitantly. Conversely, HI non-h rats had normal brain glucose metabolism and brain tissue preserved, but also presented MBN changes and spatial memory impairment. Furthermore, data showed that brain glucose metabolism correlated with cognitive deficits and brain volume outcomes. CONCLUSIONS: Our findings demonstrated that long-term changes in MBN drive memory impairments in adult rats subjected to neonatal hypoxic ischemia, using in vivo imaging microPET-FDG. The MBN analyses identified glucose metabolism abnormalities in HI non-h animals, which were not detected by conventional 18F-FDG standardized uptake value (SUVr) measurements. These animals exhibited a metabolic brain signature that may explain the cognitive deficit even with no identifiable brain damage.