In situ lipolytic regulation in subjects born small for gestational age
OBJECTIVE:Subjects born small for gestational age (SGA) who are prone to develop insulin resistance in adulthood display an abnormal development pattern of the adipose tissue during fetal and postnatal life. Since the lipolytic activity of the adipose tissue is critical in the development of insulin resistance, the purpose of this study was to investigate whether SGA itself might affect lipolysis regulation.STUDY DESIGN:We studied the effect of catecholamines, by local injection of isoproterenol, and the effect of insulin, using two-step infusion at 8 and 40 mU/m2/min, on the in situ lipolysis of the subcutaneous abdominal adipose tissue of 23 subjects born SGA and 23 born appropriate for gestational age (AGA), using the microdialysis technique.RESULTS:Under isoproterenol infusion, the increase in dialysate glycerol concentration was significantly 1.5-fold higher in the SGA than in the AGA group (P=0.02) and induced a 20% increase in the plasma FFA concentration (P=0.04), whereas no significant increase was observed in the AGA group. The antilipolytic action of insulin on dialysate glycerol concentration was similar in both groups throughout the insulin infusion.CONCLUSION:Subjects born SGA demonstrated a hyperlipolytic reactivity to catecholamines, which might be regarded as an additional deleterious component of the insulin resistance associated with SGA. In contrast, being born SGA does not directly affect the antilipolytic action of insulin, showing that it does not play a major role in causing the long-term metabolic complications associated with reduced fetal growth.