Examination of the Postprandial Bone Remodeling in Persons With Reduced GIP-Receptor Activity

The bone tissue of the human adult body is in a constant process of break-down (resorption) and rebuilding (formation), a process called bone remodeling. The extent to which bone remodeling happens varies during the day, especially a decrease in the bone resorption is observed after eating. The overall purpose of this study is to examine the possible role of the hormone Glucose-dependent Insulinotropic Polypeptide (GIP) in Bone Remodeling. GIP is released from cells in the gut after eating, and previous studies have shown an effect of GIP on bone tissue. In addition, it has been observed that the risk of bone fracture is 60% higher in women with a mutation in the GIP receptor, when compared to women with a normal functioning GIP receptor. In the present study humans with a mutation in their GIP receptor is compared to humans with a normal functioning GIP receptor. The study population will be examined during a meal stimulation test, where blood will be sampled regularly. The blood samples will be examined for markers of bone resorption among other markers of bone remodeling, GIP and other gut hormones. The hypothesis for the present study is that GIP secreted after meal ingestion inhibits bone resorption. Thus it is expected that the decrease in resorption is less pronounced in the humans carrying the GIP-receptor mutation, compared to humans with a normal functioning GIP receptor.