The effects of GIP, GLP-1 and GLP-2 on markers of bone turnover: a review of the gut–bone axis

Bone is a dynamic tissue continuously undergoing remodeling processes of resorption and formation to maintain bone mass and health. Food intake and the release of the gut-derived incretin hormones, including glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) and its 'sister hormone' glucagon-like peptide 2 (GLP-2), appear to regulate bone turnover processes in the postprandial state as part of the so-called gut-bone axis. The effects of these gut hormones on bone metabolism depend on their circulating concentrations. While at physiological concentrations, elicited by nutrient intake, GIP seems to be the main contributor to postprandial bone resorption; supraphysiological concentrations of gut hormones induce more potent and robust antiresorptive effects. This review provides an overview of the literature describing the role of gut-derived hormones in the regulation and maintenance of bone tissue. In addition, we describe the effects of gut hormone-based treatment modalities on bone health and discuss the potential of gut hormone-based strategies for the treatment of bone disorders in the future.