The skeleton has recently emerged as an additional player in the control of whole-body
glucose metabolism; however, the mechanism behind this is not clear.
METHODS: Here we employ mice lacking
neuropeptide Y, Y1 receptors solely in cells of the early osteoblastic lineage (Y1f3.6Cre), to examine the role of osteoblastic Y1 signalling in glycaemic control.
RESULTS: Y1f3.6Cre mice not only have a high bone
mass phenotype, but importantly also display altered
glucose homeostasis; significantly decreased pancreas weight, islet number and pancreatic
insulin content leading to elevated
glucose levels and reduced
glucose tolerance, but with no effect on
insulin induced
glucose clearance. The reduced
glucose tolerance and elevated bone mass was corrected in Y1f3.6Cre mice by bone marrow transplant from wildtype animals, reinforcing the osteoblastic nature of this pathway. Importantly, when fed a high fat diet, Y1f3.6Cre mice, while equally gaining
body weight and fat mass compared to controls, showed significantly improved
glucose and
insulin tolerance.
Conditioned media from Y1f3.6Cre osteoblastic cultures was unable to stimulate
insulin expression in MIN6 cells compared to
conditioned media from wildtype osteoblast, indicating a direct signalling pathway. Importantly,
osteocalcin a secreted osteoblastic factor previously identified as a modulator of insulin secretion was not altered in the Y1f3.6Cre model.
CONCLUSION: