The hunger games of skeletal metabolism

Gastrointestinal peptides and adipokines are critical signalling molecules involved in controlling whole-body energy homeostasis. These circulating hormones regulate a variety of biological responses such as hunger, satiety and glucose uptake. In vivo experiments have established that these hormones also regulate bone metabolism, while associations between these hormones and bone mass have been observed in human clinical studies. With a focus on recent research, this review aims to describe the roles that gastrointestinal peptides (ghrelin, peptide YY, glucose-dependent insulinotropic polypeptide, glucagon-like peptide 1 and glucagon-like peptide 2) and adipokines (leptin and adiponectin) have in bone metabolism and to examine their effects on bone in situations of altered metabolism, such as obesity. As the prevalence of obesity continues to increase, there is a growing interest in understanding the interactions between nutritional regulators from the gut and adipose tissue and their influence on bone mass.