Fasting, but not adrenalectomy, reduces transport of leptin into the brain

Food deprivation and adrenalectomy are associated with low concentrations o f leptin in blood and the absence of obesity. Because leptin is known to cr oss the blood-brain barrier (BBB) by a saturable transport system, we exami ned whether fasting and adrenalectomy (ADX) also act at the BBB. Multiple-t ime regression analysis showed that fasting, but not ADX, significantly dec reased the entry of leptin into mouse brain. After 3 days of food deprivati on, the influx of leptin became indistinguishable from that of the vascular control (albumin); 5 h of refeeding significantly reversed this reduced ra te of influx. Thus, the results indicate that the BBB provides a dynamic si te for the regulation of physiological processes involving leptin. (C) 2000 Elsevier Science Inc. All rights reserved.