Fetal glucose metabolism

Circulating follistatin in relation to energy metabolism

Recently, substantial evidence has emerged that the liver contributes significantly to the circulating levels of follistatin and that circulating follistatin is tightly regulated by the glucagon-to-insulin ratio. Both observations are based on investigations of healthy subjects. These novel findings challenge the present view of circulating follistatin in human physiology, being that circulating follistatin is a result of spill-over from para/autocrine actions in various tissues and cells. Follistatin as a liver-derived protein under the regulation of glucagon-to-insulin ratio suggests a relation to energy metabolism. In this narrative review, we attempt to reconcile the existing findings on circulating follistatin with the novel concept that circulating follistatin is a liver-derived molecule regulated by the glucagon-to-insulin ratio. The picture emerging is that conditions associated with elevated levels of circulating follistatin have a metabolic denominator with decreased insulin sensitivity and/or hyperglucagoneimia.

Fuel metabolism in pregnancy and in gestational diabetes mellitus

Fuel metabolism during pregnancy and in gestational diabetes mellitus (GDM) is reviewed with emphasis on carbohydrate and fat metabolism. In early pregnancy, insulin secretion in response to glucose is increased, peripheral insulin sensitivity is normal or increased, glucose tolerance is normal or slightly enhanced. In addition, there is maternal fat accumulation. During late pregnancy, there is increased fetal growth and increased fetal demand for nutrients. Maternal responses to these demands consist of an accelerated switch from carbohydrate to fat utilization that is facilitated by peripheral insulin resistance and by high blood levels of lipolytic hormones. In patients with GDM, insulin resistance is either comparable or greater than in nondiabetic pregnancy whereas insulin secretion appears to be compromised. Important short term consequences of GDM are perinatal complications, whereas long term complications include an increased rate of development of maternal non-insulin-dependent diabetes mellitus.

Metabolic changes in the rat liver during pregnancy. II. Tricarboxylic acid cycle

During pregnancy the rat liver shows alterations in metabolism which apparently do not to occur in the non-pregnant animal. In our study, the following metabolite concentrations and enzyme activities in the liver of pregnant and non-pregnant rats were measured after fasting periods of 6 and 12 h: malate, fumarate, isocitrate, alpha-keto-glutarate, glutamate, malate-dehydrogenase, fumarate-hydratase, glutamate-dehydrogenase, isocitrate-dehydrogenase, aspartate-aminotransferase and after 12 h fast, the concentrations of acetyl coenzyme A and citrate. These results are discussed with regard to their possible importance for the maternal and fetal energy supply.

Glucose and oxygen metabolism in normally oxygenated and spontaneously hypoxemic fetal lambs

Whole blood glucose and oxygen concentration were measured in chronically catheterized fetal lambs, some of whom had implanted common umbilical artery flow transducers. Ten of the fetuses were well oxygenated (femoral arterial PaO2 less than 18 torr) and 13 fetuses had evidence of chronic hypoxemia (femoral arterial PaO2 less than 18 torr). The mean glucose uptake (54.0 +/- 7.6 S.E.M. mM. per kilogram per day), umbilical blood flow (230 +/- 13 S.E.M. ml. per kilogram per minute), and glucose/oxygen ratio (0.503) were the same in both fetal groups. The oxygenated fetuses had higher glucose levels at ang given maternal glucose concentration than the hypoxemic animals (p less than 0.001y and showed a correlation between glucose again across the placental circulation and the transplacental driving force for glucose (p less than 0.002). The hypoxemic fetuses, who had a higher per kilogram oxygen consumption than the oxygenated fetuses (p less than 0.05), showed no correlation between the amount of glucose taken up and the transplacental glucose concentration gradient.

Fetal carbohydrate metabolism: its clinical importance

A basic understanding of fetal nutrition and metabolism is essential in the clinical management of the obstetric patient. The fetus depends upon a constant infusion of glucose for energy production and growth. Maternal glucose is the prime source of this nutrient. Alterations in maternal carbohydrate homeostasis will lead to changes in fetal metabolism. In diabetes mellitus, hyperglycemia may produce hyperinsulinemia and macrosomia. The growth-retarded fetus may have a decreased supply of maternal glucose and reduced amounts of hepatic glycogen and adipose tissue. The fetus must depend upon these stores for survival during periods of intrauterine hypoxia. In the newborn period, hypothermia and hypoxia may rapidly deplete energy reserves. With this information, the clinician may more knowledgeably manage dietary demands in the antepartum patient, fetal distress during labor, and the immediate newborn period.