A cluster of neurons in the brain that control hunger and appetite also regulate bone mass, according to researchers at Yale School of Medicine.
“We have found that the level of your hunger could determine your bone structure,” explained one of the senior authors, Tamas L. Horvath. “The less hungry you are, the lower your bone density, and surprisingly, the effects of these neurons on bone mass are independent of the effect of the hormone leptin on these same cells.”
Reporting their findings in the journal Cell Reports, the team said they focused on neurons located in the hypothalamus which control feeding and compulsive behaviours. These are known as agouti-related peptide (AgRP) neurons.
The researchers used mice that were genetically-engineered so their cells selectively interfered with the AgRP neurons, revealing that these same cells are also involved in determining bone mass.
The study showed that when the AgRP circuits were impaired, this resulted in bone loss and osteopenia (reduced bone mineral density) in mice. This is similar to osteoporosis in women, the scientists said. And when the team enhanced AgRP neuronal activity in mice, this actually promoted increased bone mass.
“Taken together, these observations establish a significant regulatory role for AgRP neurons in skeletal bone metabolism independent of leptin´s action,” commented co-senior author Dr. Karl Insogna. “Based on our findings, it seems that the effect of AgRP neurons on bone metabolism in adults is mediated at least in part by the sympathetic nervous system, but more than one pathway is likely involved.”
Insogna added: “There are other mechanisms by which the AgRP system can affect bone mass, including actions on the thyroid, adrenal and gonad systems. Further studies are needed to assess the hormonal control of bone metabolism as a pathway modulated by AgRP neurons.”