Chapter 39 - Amylin and Calcitonin Gene-Related Peptide

Abstract

Calcitonin gene-related peptide (CGRP) and amylin are homologous 37 amino acid peptides. This chapter deals with the extraskeletal actions of CGRP and amylin. In skeletal muscle the primary effects appear to be inhibition of glycogen synthesis and stimulation of glycogenolysis. Thus, muscle glycogen stores are decreased by amylin or CGRP, and this is accompanied by diminished glucose uptake and increased glycolysis, leading to increased lactate production. Also, CGRP is one of the most potent vasodilators known and its receptors are distributed widely throughout the vascular system. CGRP is also distributed throughout the nervous system, being found in sensory, motor, and autonomic nerves, as well as in the hypothalamus, thalamus, and hippocampus. Following this, the study describes effects of CGRP and amylin on osteoclasts and on bone mass, highlighting that the effects of amylin and CGRP on the total amount of mineralized tissue in bone have been assessed in several experimental systems, including local injections, systemic administration, and more recently, in genetically modified animals. Furthermore, the study deals with effects of CGRP and amylin on calcium metabolism. Finally, it sheds light on the significance of amylin and CGRP in bone physiology, suggesting that because most of the CGRP gaining access to bone does so via sensory nerves, it is likely that this peptide is involved in the response of bone to injury and to other stimuli, such as exercise. The association of CGRP-containing nerves with healing and growing bone supports this contention.