A Signaling Role for Leptin in Puberty Onset in Female Rats?

Abstract

The brain might initiate puberty in response to adequate leptin signaling from the periphery. We studied the link between whole body fat, plasma leptin levels, and puberty onset, in both controls and food-restricted female Wistar rats from age 22 to 42 days. Body fat correlated positively with the prevailing plasma leptin levels (r = 0.776) and with the time of puberty onset, i.e. vaginal opening (VO) (r = 0.691). Blood samples collected every other day at ZT 2, 6, and 12, showed a diurnal rhythm in leptin levels with a nadir at ZT 6. Furthermore, leptin levels increased over the pubertal period. Food restriction (FR) delayed the time of VO considerably (median VO at 38 vs 28 d), and body fat and plasma leptin levels were lower in the FR group (p <0.01), although the positive correlation between body fat and leptin levels remained. Only the absolute, but not the relative amount of body fat increased with age. These data support the notion that leptin could indeed serve as the link between nutritional status and the reproductive axis, and in this way participate in the timing of puberty.