Researchers at Cincinnati Children's Hospital Medical Center have conducted the first study to detect the presence of a protein in human milk that may explain the association between breastfeeding and reduced risk of obesity later in life.
The protein is adiponectin, which is secreted by fat cells and affects how the body processes sugars and lipids -- fatty substances in the blood. It's been suggested that adiponectin is involved in the metabolic syndrome, which includes insulin resistance, obesity, type 2 diabetes and coronary artery disease and occurs in 20-25 percent of adults. Higher levels of adiponectin have been associated with less disease.
If adiponectin is present in human milk, the Cincinnati Children's researchers theorized, the protein could have an influence over the metabolic "programming" of infants. That is, it could affect adiposity, or "fatness," later in life.
The Cincinnati Children's researchers analyzed samples of human milk collected from anonymous donor mothers as part of the Research Human Milk Bank at Cincinnati Children's and found levels of adiponectin that were "quite high -- higher than many proteins found in human milk," says Lisa Martin, PhD, the study's lead author.
"This study is an important first step in developing molecular research focused on understanding the relationship between human milk constituents and later metabolism. Exposures early in life, during the period of extreme growth and development, may have an impact on adult disease."
The researchers also confirmed the presence of leptin in human milk. Leptin is another protein produced by fat that appears to play an important role in the regulation of body fat. Leptin is a satiety hormone, involved in the state of being "full."
Adiponectin levels, however, are substantially greater than leptin in human milk, according to Dr. Martin, a researcher in the Center for Epidemiology and Biostatistics at Cincinnati Children's and in the Division of Human Genetics. "Whether the greater quantity of adiponectin has biological significance remains to be seen," she says.
The study will be presented May 2 at the annual meeting of the Pediatric Academic Societies in San Francisco.