Endotoxaemia leads to major increases in inflammatory adipokine gene expression in white adipose tissue of mice

The proposition that white adipose tissue is involved in the inflammatory response and metabolic dysregulation of endotoxaemia has been examined. Mice were injected with lipopolysaccharide (LPS; 25 mg/kg) and epididymal, perirenal and subcutaneous adipose tissue removed 4 or 24 h later. The expression of genes encoding key inflammation-related adipokines was measured by real-time polymerase chain reaction. At 24 h after the administration of LPS, there was no change in leptin mRNA level, and adiponectin mRNA fell. However, major increases in TNF alpha, MCP-1 (up to 40-fold) and IL-6 (up to 250-fold) mRNA levels were evident; a substantial elevation in these mRNAs occurred by 4 h, and adipose tissue IL-6 protein also increased (three- to eightfold). At 24 h, the responses in the subcutaneous depot were much lower than in epididymal and perirenal adipose tissue, but at 4 h, the subcutaneous tissue showed major increases in IL-6, MCP-1 and TNF alpha gene expression. In contrast to the inflammatory adipokines, the mRNA level of two macrophage markers, F4/80 and MAC-1, was unaltered in adipose tissue during endotoxaemia. Expression of the hypoxia-sensitive transcription factor, HIF-1 alpha, gene was increased at both 4 and 24 h, and HIF-1 alpha protein was elevated at 4 h, suggesting that the tissue was hypoxic. It is concluded that white adipose tissue may play an important role in the production of inflammatory mediators in endotoxaemia.