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[Energy metabolism in the perinatal period (author's transl)]
Insights
Neonatal hypoglycemia in newborn rats is caused by depleted liver glycogen and insufficient gluconeogenesis due to a lack of essential substrates. This leads to profound hypoglycemia when glycogen stores are exhausted after birth.
Area of Science:
- Biochemistry
- Neonatal Physiology
- Metabolic Regulation
Background:
- Neonatal hypoglycemia is common in fasted newborns, but its origins are not fully understood.
- Studies in newborn rats indicate immediate post-birth liver glycogenolysis and gluconeogenesis.
- Enzyme activity changes are linked to hormonal shifts (glucagon rise, insulin fall) due to birth stress.
Purpose of the Study:
- To investigate the causes of neonatal hypoglycemia in fasting newborn rats.
- To understand the regulatory mechanisms of hepatic gluconeogenesis in neonates.
- To compare these mechanisms across different species, including humans.
Main Methods:
- Analysis of liver glycogenolysis and gluconeogenesis in newborn rats.
- Measurement of key enzyme activities (phosphorylase, glycogen synthetase, phosphoenolpyruvate carboxykinase).
- Assessment of substrate availability for gluconeogenesis (free fatty acids, ketone bodies, lactate, amino acids).
Main Results:
- Profound hypoglycemia develops in fasting newborn rats between 6 and 16 hours post-birth after liver glycogen depletion.
- Hepatic gluconeogenesis is insufficient to meet energy demands due to a lack of substrates.
- Hormonal changes (increased glucagon, decreased insulin) influence enzyme activity post-birth.
Conclusions:
- Fasting neonatal hypoglycemia in rats results from exhausted glycogen stores and impaired gluconeogenesis.
- Substrate availability is critical for maintaining glucose homeostasis in newborns.
- Understanding these mechanisms is crucial for addressing neonatal hypoglycemia in humans.
Abstract:
Neonatal hypoglycemia is of frequent occurrence in fasted newborn babies or animals but the origin of this hypoglycemia is not fully understood. Studies performed in newborn rats have shown that liver glycogenolysis and gluconeogenesis occur immediately after birth and that the increase in the activities of key regulatory enzymes (phosphorylase, glycogen synthetase and phosphoenolpyruvate carboxykinase) results probably from the rise of plasma glucagon and the fall of plasma insulin induced by the "stress" of birth. When the liver glycogen stores have been exhausted, i.e. between 6 and 16 hours after birth, a profound hypoglycemia develops in fasting newborn rats. The inability of hepatic gluconeogenesis to produce sufficient glucose to meet the energy requirement of the newborn tissues results from a lack of fat-derived (free fatty acids and ketone bodies) and gluconeogenic (lactate, amino acids) substrates. The stage of appearance and the mechanisms regulating gluconeogenesis in other species including human are discussed.