Abstract
Oxidation of fatty acids is a major pathway supporting energy requiring processes in the early postnatal period. This is documented by an increase in free fatty acids (FFA), glycerol and ketone bodies in the blood. FFA and glycerol arise from intensive triglyceride breakdown in white adipose tissue. Activation of lipolysis requires ATP. Decreased lipolysis is seen in vitro after the first 24-48 hr of life. Since FFA can uncouple mitochondrial respiration, the early accumulation of FFA known to occur in adipose tissue could lead to a secondary depression of lipolysis due to inadequate ATP generation.
Carnitine acts as a coupling agent in mammalian brown fat mitochondria. Its effect on lipolysis (glycerol release) was measured in fragments of human newborn and adult subcutaneous (white) adipose tissue. In the neonate, L-carnitine (2.5mM) enhanced glycerol release with or without stimulation by a phosphodiesterase inhibitor (theophylline, 10−M) or a beta-agonist (isoproterenol, 10−5M)(p≤0.05); deoxycarnitine (2.5mM) decreased lipolysis under similar conditions (p ≤ 0.05). In the adult, L-carnitine increased lipolysis only in presence of isoproterenol (p≤O.05) while deoxycarnitine had no effect.
Carnitine is contained in milk. These studies suggest a deficiency of carnitine might decrease the availability of FFA as fuel for essential metabolic needs, particularly in the small or ill neonate with inadequate oral intake.
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Novak, M., Penn-Walker, D. & Monkus, E. LIPOLYTIC ACTION OF L-CARNITINE IN VITRO IN HUMAN NEWBORN SUBCUTANEOUS ADIPOSE TISSUE. Pediatr Res 8, 365 (1974). https://doi.org/10.1203/00006450-197404000-00151
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DOI: https://doi.org/10.1203/00006450-197404000-00151