Neurochemical changes in the developing rat hippocampus during prolonged hypoglycemia.
Hypoglycemia is common during development and is associated with the risk of neurodevelopmental deficits in human infants. The effects of hypoglycemia on the developing hippocampus are poorly understood. The sequential changes in energy substrates, amino acids and phosphocreatine were measured from the hippocampus during 180 min of insulin-induced hypoglycemia (blood glucose < 2.5 mmol/L) in 14-day-old rats using in vivo(1)H NMR spectroscopy. Hypoglycemia resulted in neuroglycopenia (brain glucose < 0.5 micromol/g). However, the phosphocreatine/creatine (PCr/Cr) ratio was maintained in the physiological range until approximately 150 min of hypoglycemia, indicating that energy supply was sufficient to meet the energy demands. Lactate concentration decreased soon after the onset of neuroglycopenia. Beyond 60 min, glutamine and glutamate became the major energy substrates. A precipitous decrease in the PCr/Cr ratio, indicative of impending energy failure occurred only after significant depletion of these amino acids. Once glutamate and glutamine were significantly exhausted, aspartate became the final energy source. N-acetylaspartate concentration remained unaltered, suggesting preservation of neuronal/mitochondrial integrity during hypoglycemia. Correction of hypoglycemia normalized the PCr/Cr ratio and partially restored the amino acids to pre-hypoglycemia levels. Compensatory neurochemical changes maintain energy homeostasis during prolonged hypoglycemia in the developing hippocampus.
Rao
Raghavendra
R
Division of Neonatology, Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota, USA. raoxx017@umn.edu
Ennis
Kathleen
K
Long
Jeffery D
JD
Ugurbil
Kamil
K
Gruetter
Rolf
R
Tkac
Ivan
I
D000818:Animals; D000831:Animals, Newborn; D001923:Brain Chemistry / Q000502:physiology*; D002908:Chronic Disease; D004734:Energy Metabolism / Q000502:physiology*; D005947:Glucose / Q000172:deficiency; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006019:Glycolysis / Q000502:physiology; D006624:Hippocampus / Q000254:growth & development* / Q000378:metabolism* / Q000503:physiopathology; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007003:Hypoglycemia / Q000378:metabolism* / Q000503:physiopathology; D007228:Infant Nutrition Disorders / Q000378:metabolism / Q000503:physiopathology; D007231:Infant, Newborn; D019344:Lactic Acid / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D009474:Neurons / Q000378:metabolism; D010085:Oxidative Phosphorylation; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D010725:Phosphocreatine; D005973:Glutamine; D019344:Lactic Acid; D018698:Glutamic Acid; D005947:Glucose