Metabolism of Subcutaneous Adipose Tissue in the Immediate Postnatal Period of Human Newborns

Abstract

The activities of citrate cleavage enzyme (CCE; EC 4.1.3.8), malic enzyme (ME; EC 1.1.1.40), phosphoenol pyruvate carboxykinase (PEPK; EC 2.7.1.40), α-glycerophosphate dehydrogenase (GPD EC 1.1.1.8) and glucose-6-phosphate dehydrogenase (G-6-PD; EC 1.1.1.49) was measured in cytosol of subcutaneous adipose (white) tissue in human new borns and adults. ME activity was highest during the first day of life and then decreased. CCE was higher in the newborn adipose tissue than in adults. G-6-PD and GPD activities were higher in the neonate. No changes were noted with PEPK. Our results obtained on activities of enzymes involved in citrate breakdown (CCE) providing acetylCoA and furnishing ‘reduction potential’ for fatiy acid synthesis (ME, G-6-PD) suggest that fatty acid synthesis decreases rapidly after birth. This decrease in enzymes involved in fatty acid synthesis is faster than the decrease in enzymes involved in glycerol production

Changes in catecholamine-induced lipolysis in isolated human fat cells during the first year of life.

“…In the few studies published so far the methods used to determine lipolysis have proved insensitive and only a small number of subjects have been studied (21,22). Novak et al (23) reported that the adipose tissue ofnewborn infants is less sensitive to catecholamines than is adipose tissue from old persons.…”

Oxidation of Fatty Acids by Mitochondria Obtained from Newborn Subcutaneous (White) Adipose Tissue

“…This mechanism of desaturation has been described in both liver and adipose tissue and is related to fatty acid synthesis. In newborn adipose tissue, the synthesis of fatty acids is apparently more intensive than in adults [16]. Therefore, quantitative measurements of ogygen consumption obtained in mitochondrial systems contaminated with microsomes must consider this limitation.…”

Activity of Some Enzymes of Carbohydrate Metabolism in Human Subcutaneous Adipose Tissue in Newborns, Infants and Adults

“…But in newborns the difference between activity of the two enzymes is very low. In a recent work, Novak et al (12) have shown that no activity of G-6-PD could be detected in adult AT or in the AT obtained from infants older than 3 days. They were able to find this activity only in a part of newborns aged 0-3 days.…”

“…The latter has a special importance in the AT. Numerous studies deal with enzyme activities of glucose utilization in the AT of different animals (21,25) and of adult humans (20,23), but for newborns only few reports exist (12,18). Therefore, we have measured in the first part of our study one of the principal enzymes of glycolysis, pyruvate kinase (PK; EC 2.7.1.40), and two enzymes of pentose phosphate shunt, glucose-6-phosphate dehydrogenase (G-6-PD; EC 1.1.1.49) and phosphogluconate dehydro genase (6-PGD; EC 1.1.1.44), and changes of their activities during the ontoge nesis (newborns, infants, adults).…”