LEPTIN DOES NOT REDUCE BODY-FAT CONTENT BUT AUGMENTS COLD DEFENSE ABILITIES IN THERMONEUTRALLY REARED RAT PUPS

A previous study showed that recombinant leptin markedly affects the b ody fat content and thermoregulatory energy expenditure of lean (+/+ a nd +/fa) suckling-age rats, and we wanted to find out whether leptin i n doses that halved body fat of cold-reared lean pups had any effect i n thermoneutrally reared lean pups, When +/+ pups were artificially re ared from 4 to 16 days of age at thermoneutrality and treated as befor e with leptin from day 7, their total metabolic rate throughout the tr eatment period was only 4% higher than that of the control littermates and their final body fat content only 4% lower (both P>0.05). We conc lude from comparisons of the results in +/+ pups at cold and thermoneu tral conditions that leptin does not stimulate, but rather disinhibits , sympathetically mediated thermoregulatory thermogenesis.