Effects of adrenomedullin on tumour necrosis factor alpha, interleukins, endothelin-1, leptin, and adiponectin in the epididymal fat and soleus muscle of the rat.

Adrenomedullin (ADM) is a peptide hormone, which participates in the development of metabolic syndrome. In this study, we have investigated the interaction of ADM and cytokines, endothelin-1 (EDN-1) and adipokines in the epididymal fat and the soleus muscle. Epididymal fat and soleus muscles from adult male Sprague-Dawley rat were incubated with ADM at concentration of 100 nM for the study of the gene expression and secretion of tumour necrosis factor (TNF-α), EDN-1, leptin, adiponectin, interleukin 1β (IL-1β), and IL-6. The effects of TNF-α and EDN-1 on ADM gene expression and secretion were also investigated. The results showed that ADM decreased the gene expression and protein secretion of TNF-α in both the epididymal fat and the soleus muscle and decreased IL-1β gene expression and secretion in the soleus muscle. It also decreased endothelin gene expression and adiponectin gene expression and release and increased IL-6 and leptin gene expression and secretion in the epididymal fat. These effects were effectively blocked by the calcitonin gene-related peptide (CGRP) receptor antagonist, hCGRP8-37, but not by the ADM receptor antagonist, hADM22-52. The reduction of inflammatory cytokines and EDN-1 may help to decrease insulin resistance and increase glucose uptake. As TNF-α also increases ADM levels in the epididymal fat and the soleus muscle and EDN-1 also increases ADM levels in the epididymal fat, they may form a feedback loop with ADM in these tissues. The increase in leptin and the decrease in adiponectin by ADM in the epididymal fat may have opposite effects on metabolism.