Leptin can be considered as a peripheral signal which informs the centers about the
mass of energy stores. Studies done on the human adult population have demonstrated
that degree of adiposity and insulin levels play a major role as determinants of leptin
circulating levels. The aim of this study was to evaluate which factors may influence
leptin levels at birth. We examined the role played by baby size and by the metabolic
environment the fetus was exposed to during pregnancy. We considered 85 newborns from
normal (n = 60), gestational (GDM, n = 17) and pregestational (IDDM = 8) diabetes
mellitus mothers. At delivery, blood was taken from the umbilical cord vein. Babies
from normal and GDM mothers were subdivided into AGA (appropriate for gestational
age) and LGA (large for gestational age). There was no difference in leptin levels
between babies from normal or GDM mothers belonging to the same weight category, but
leptin levels were always higher in LGA than in AGA newborns, and highly correlated
with birth weight (r = 0.34, P = 0.001). Moreover, IDDM mothers gave birth to newborns
with significantly higher levels of leptin and insulin when compared with normal and
GDM mothers. Diabetes of both GDM and IDDM mothers was clinically well controlled
(HbA1c was 4.0 and 7.2, respectively). The correlation between leptin and insulin
was significant only when newborns from IDDM mothers were included in the regression
analysis (r = 0.39, P = 0.0002). Our results suggest that degree of adiposity is one
of the main regulators of leptin concentration in the human newborn and that babies
exposed to an altered, though clinically controlled, metabolic environment, as in
IDDM mothers, have increased levels of leptin.
Key words
Leptin - Newborns - Birth weight - Gestational diabetes - Insulin dependent diabetes
(IDDM)
