LEPTIN GENE IS EXPRESSED IN RAT BROWN ADIPOSE-TISSUE AT BIRTH

The ob gene product leptin is secreted from adipose tissue, Leptin has dramatic effects on food intake and energy expenditure in rodents. Br own adipose tissue is the first form of adipose tissue to appear durin g development, and is present at birth in most species, The developmen t of a leptin feedback system in early life and the relative role of t he brown and white adipose tissues have not yet been revealed. We have investigated the expression of ob/leptin mRNA in brown adipose tissue around birth and with respect to feeding, Northern blotting analysis and in situ hybridization experiments demonstrated the presence of lep tin mRNA in brown adipose tissue at 0, 18, and 24 h after birth, The l eptin mRNA level was decreased at 8 h postpartum in fed animals and at 18 or 24 h in the absence of feeding. In addition, circulating leptin was detected in the plasma of newborn rats at 0, 10, or 24 h after bi rth, whereas it was not detectable in 10 h-old animals that did not su ckle at their mother. The presence at birth of ob mRNA and circulating leptin, as web as the early effect of suckling on ob mRNA levels, sug gests the precocious involvement of leptin in the control of food inta ke.