March 18, 2011
Using Lambs To Weigh-In On Obesity
(Ivanhoe Newswire)-- The results of a new study on obesity in sheep and lambs may lend a hand in understanding obesity in humans. The new study is the first to show a definite link between obesity in a mother and obesity in her child in mammals that bear "mature offspring." Since humans also bear mature offspring, the results of this study are the first that can possibly be applied to humans.
While the relationship between maternal obesity and offspring obesity has been proven in rats, rats do not bear mature offspring-- their young are born immature, and therefore a link between maternal and offspring obesity in rats cannot be applied to humans.
However, in the new study, by researchers at the Center for Pregnancy and Newborn Research, University of Texas and the University of Wyoming, lambs were used for the research. Scientists regulated the diets of sheep for 60 days before conception and throughout their pregnancy: Half the ewes were fed a normal diet, and half received a diet to produce obesity. After giving birth, the scientists monitored the appetite and weight gain of their offspring, observation which continued for 19 months.
One area in which the newborn lambs were monitored was hormone levels. Researchers took blood samples from the lambs and tested leptin levels. Leptin is a hormone that regulates appetite and is produced by fat cells. In lambs born to obese mothers, scientists saw no peak in leptin levels, but in lambs born to mothers with normal body weight, leptin levels peaked six to nine days after birth.
After analyzing blood samples from one-day-old lambs, scientists observed higher cortisol levels in obese sheep. The scientists now suspect exposure to high levels of cortisol in the womb may be the reason leptin levels did not peak in lambs of obese mothers.
Professor Peter Nathanielsz, lead author of the research, was quoted as saying, "Given the epidemic of obesity both in the developed and developing world, the search for environmental factors occurring around the time of birth which predispose the offspring of overweight mothers to lifelong obesity is important"¦ Seeing these hormonal changes in lambs"¦is advancing our understanding of what programs appetite. We are getting closer to understanding what causes obesity in humans."
SOURCE: Journal of Physiology, Published March 15, 2011