Increased leptin and white adipose tissue hypoplasia are sexually dimorphic in Lif null/Igf-I haploinsufficient mice.

We previously showed cooperation of leukemia inhibitory factor (LIF) and insulin-like growth factor I (IGF-I) during development. Mice doubly deficient in LIF and IGF-I died at birth. We now analyze the possible combined influence of both factors on postnatal growth. The haploinsufficiency of the Igf-I gene on a Lif null background caused a marked reduction in body mass index and white adipose tissue only in female mice. These animals had increased leptin, increased serum IGF-I and apparent substitution of white adipose tissue by brown adipose tissue. The complex interrelationships between LIF and IGF-I in regulating weight thus involve sexually dimorphic effects on adipose tissue differentiation and circulating leptin.