Circulating adiponectin levels during human endotoxaemia

Adiponectin, an adipocytokine secreted by fat tissue, may prevent development of diabetes type II, as high adiponectin levels are linked with insulin sensitivity. In contrast, tumour necrosis factor (TNF)-alpha, which is also produced by fat tissue, leads to insulin resistance and furthermore inhibits adiponectin mRNA production and secretion of the protein. However, adiponectin also negatively regulates TNF-alpha levels. Therefore, we set out to test whether an infusion of endotoxin would influence circulating adiponectin levels in healthy human subjects. Twenty-three healthy human subjects were injected with endotoxin (2 ng/kg body weight); eight of these subjects were also injected with saline and served as controls. Plasma levels of adiponectin, TNF-alpha and interleukin-6 were measured at 0, 1.5, 2, 4, 8 and 24 h. TNF-alpha and interleukin-6 levels peaked at 1.5 h and 2 h, respectively. Control subjects injected with saline showed a decrease in adiponectin plasma levels with time (P < 0.05) presumably owing to the effect of fasting or physical inactivity. However, there was no change in adiponectin plasma levels in endotoxin injected subjects, thus the effect of fasting was opposed. In conclusion, circulating adiponectin levels are reduced during a resting and fasting state, an effect reversed by endotoxin injection.