DOWN-REGULATION OF CCAAT ENHANCER BINDING-PROTEIN-ALPHA, BINDING-PROTEIN-BETA AND BINDING-PROTEIN-DELTA IN ADIPOSE-TISSUE BY INTRACEREBROVENTRICULAR LEPTIN IN RATS/

In our previous report, intracerebroventricular (i.c.v.) administratio n of leptin caused fat depletion by an induced adipocyte-apoptosis in addition to influencing lipid metabolism. To uncover the biochemical m echanisms that mediate this response, the present study was designed t o determine whether CCAAT/enhancer binding proteins (C/EBP)alpha, -bet a and -delta play a role in the leptin-induced fat depletion. Expressi ons of C/EBP alpha, -beta and -delta in epididymal fat tissues were ex amined by Western immunoblot and in situ immunocytochemical analysis a fter 5 days of i.c.v. treatment. Young and old rats (3 and 8 months ol d) were treated with or without 5 mu g/day leptin. The expression of C /EBP alpha, -beta and -delta was decreased by i.c.v. leptin treatment in young rats as compared with controls (P < 0.05). However, leptin di d not influence the expression of C/EBP alpha, -beta and -delta in adi pose tissues of 8-month-old rats. The basal level of expression of C/E BP beta was greater in 8-month-old rats than in 3-month-old rats, (P < 0.05) whereas the basal expression of C/EBP alpha and -delta was not different between age groups. These results were confirmed by in situ immunocytochemical analysis. The present study suggests that leptin-in duced down-regulation of C/EBP alpha, -beta and -delta might influence adipocyte differentiation and growth in a number of ways. (C) 1998 El sevier Science B.V. All rights reserved.