Regulation of Lipolysis in Human Neonatal Adipose Tissue

Abstract

Lipolytic response to conditions producing alterations in carbohydrate metabolism was tested on human newborn subcutaneous adipose tissue in vitro. Glycerol release from intact adipose tissue fragments or n isolated adipose tissue cells was used to indicate the rate of lipolysis. The addition of glucose increased glycerol release in isolated cells (p < 0.01–0.025) and in intact tissue fragments (p < 0.0005–0.0025) from subcutaneous adipose tissue in neonates, but did not affect the glycerol release in the same tissue in adults. Lipolysis was also significantly increased after addition of pyruvate (p < 0.025). Oligomycin and reduced oxygen tension diminished the stimulatory effect of glucose on lipolysis. Basal glycerol release was often elevated in newborns in whom the adipose tissue glycogen content was higher than in normal newborn infants of the same age.

Transcriptional Landscaping Identifies a Beige Adipocyte Depot in the Newborn Mouse

“…Our findings indicate the probable existence of metabolic reprogramming during the maturation of subcutaneous adipose tissue, shifting from the burning of fat as heat and energy to the accumulation of lipids as energy storage. This metabolic shift is in good agreement with the previously observed intensive lipid catabolism and fatty acid release from the subcutaneous adipose tissue in newborn mammals, including human infants [14,19,25,54], and the potential of the subcutaneous adipose tissue-derived adipocytes to transform into beige adipocytes in response to cold stress [44,72].…”

“…Of note, the loss of the thermogenic fat in the subcutaneous fat depots is accelerated in childhood obesity [52], and obesity reduces the potential of beige adipocyte differentiation [53]. As thermogenic fat also has lipolytic activity and provides free fatty acids for energy production by the liver and by the BAT, the presence of thermogenic cells in the subcutaneous fat depot contributes to the intense fat oxidation observed after birth in mammals [14,19,25,54]. The similarities between subcutaneous WAT in the newborn and BAT make it plausible that the infant subcutaneous fat depot is actually composed of beige fat cells.…”