Ep. Widmaier et al., LEPTIN CORTICOTROPIN-RELEASING HORMONE (CRH), AND NEUROPEPTIDE-Y (NPY) IN FREE-RANGING PREGNANT BATS, ENDOCRINE, 7(2), 1997, pp. 145-150
Leptin, the product of the obese gene first identified in mice, restor
es fertility in obese mice, and accelerates puberty in mice. We hypoth
esized that leptin's putative role in reproduction may extend to pregn
ancy and lactation. Leptin levels were determined in Myotis lucifugus,
the little brown bat, a free-ranging mammal with a seasonal breeding
cycle. The present study shows that plasma levels of leptin progressiv
ely rise during pregnancy, supporting a potential role for leptin in t
he maintenancy of pregnancy. In contrast, leptin was significantly low
er during lactation, a time when most mammals, including bats, demonst
rate reduced fertility. In addition to its possible roles in reproduct
ion, leptin appears important in regulation of energy balance. M. luci
fugus spontaneously fasts for up to 16 h each day during the active se
ason, which allowed us to test the hypothesis that acute fasting was a
ssociated with decreased leptin. Leptin was significantly lower in fas
ted (lactating) bats, compared to those that recently returned from ni
ghtly foraging. Although postprandial lactating bats had a significant
ly higher fat index than fasted bats, plasma leptin and body fat were
not significantly correlated, and were only weakly correlated (r(2) =
0.26) when both pregnant and lactating females were included in the an
alysis. Similar changes during pregnancy, lactation, and the daily fee
ding cycle were observed in the hypothalamic neuropeptide, corticotrop
in-releasing hormone (CRH), which is believed to play an important rol
e in energy balance and reproduction. By contrast, neuropeptide Y (NPY
) increased during pregnancy but did not change during fasting. These
results suggest that leptin's putative role in reproduction may extend
to pregnancy and lactation, and that spontaneous, acute fasting resul
ts in decreased circulating levels of leptin in M. lucifugus.