A recent discovery by Columbia University Medical Centre has revealed that rather than gut bacteria, as earlier believed, it was the bone cells that were responsible for appetite regulation.
The CUMC researchers had focused on bone function for several years and in 2007 made a major discovery. Their research revealed that our skeletons functioned as an endocrine organ and the bone cells released hormones that were known to be crucial in regulating energy metabolism.
In initial studies the team discovered that bone cells released a hormone called osteocalcin, which controlled the regulation of blood sugar. They noted that disabling a certain gene in the bone-forming cells (osteoblasts) of mice, caused the animal's appetite to drop significantly.
"Since osteocalcin does not regulate appetite, we knew that a second bone hormone had to be involved in this process," professor Stavroula Kousteni, who led the study said, New Atlas reported.
The researchers found that the second hormone was lipocalin 2, a protein known to contribute to obesity and previously linked to activating neurons in the brain involved in appetite suppression. Lipocalin 2 was thought to be secreted by fat cells (adipocytes), however, the CUMC research revealed that the levels of the hormone to be 10 times higher in osteoblasts than previously found in adipocytes.
Nature published the study online on 8 March.
"In recent years, studies at CUMC and elsewhere have shown that bone is an endocrine organ and produces hormones that affect brain development, glucose balance, kidney function, and male fertility," says study leader Stavroula Kousteni, PhD, associate professor of physiology and cellular biophysics (in medicine) at CUMC, News Medical reported.
"Our findings add a critical new function of bone hormones to this list-appetite suppression - which may open a wholly new approach to the treatment of metabolic disorders."