Acute and prolonged effects of TNF-α on the expression and secretion of inflammation-related adipokines by human adipocytes differentiated in culture

Abstract

The pro-inflammatory cytokine TNF-α has multiple effects on adipocyte function, including the production of adipokines. In this paper, we have examined the acute vs prolonged effects of TNF-α on the expression and secretion of key inflammation-related adipokines by human adipocytes. Adipocytes differentiated in culture were treated with TNF-α for 1–24 h, mRNA quantitated by real-time polymerase chain reaction (PCR) and secreted adipokines by ELISA. Treatment of adipocytes with TNF-α for up to 24 h had little effect on MIF, MT-2 and PAI-1 mRNA levels. TNF-α decreased adiponectin, adipsin, haptoglobin and leptin mRNA levels by 24 h, but adiponectin and haptoglobin mRNA was initially increased. In contrast, TNF-α induced rapid and substantial increases in expression of the genes encoding IL-6, MCP-1, NGF and TNF-α itself; IL-6 and TNF-α mRNA levels peaked at 2 h with 75-fold and 600-fold increases, respectively. The elevated MCP-1, NGF and VEGF mRNA levels were sustained between 4 and 24 h. The adipokine secretion pattern largely paralleled cellular mRNA levels; IL-6 (transiently), MCP-1, NGF and VEGF release were stimulated by TNF-α, with an accelerating rate of MCP-1 secretion over 24 h. TNF-α has rapid and substantial effects on the synthesis of key inflammation-related adipokines in human adipocytes, with highly gene-specific responses.