Anti-ghrelin immunoglobulins modulate ghrelin stability and its orexigenic effect in obese mice and humans.

Obese individuals often have increased appetite despite normal plasma levels of
the main orexigenic hormone ghrelin. Here we show that ghrelin degradation in the
plasma is inhibited by ghrelin-reactive IgG immunoglobulins, which display
increased binding affinity to ghrelin in obese patients and mice.
Co-administration of ghrelin together with IgG from obese individuals, but not
with IgG from anorectic or control patients, increases food intake in rats.
Similarly, chronic injections of ghrelin together with IgG from ob/ob mice
increase food intake, meal frequency and total lean body mass of mice. These data
reveal that in both obese humans and mice, IgG with increased affinity for
ghrelin enhances ghrelin's orexigenic effect, which may contribute to increased
appetite and overeating.