TNFα and IL-1α are thought to contribute to impaired anabolism in a variety of clinical states, including sepsis, cancer cachexia and the AIDS wasting syndrome. We asked whether cytokines exert direct effects on hepatic production of IGFBP-1, an important modulator of IGF bioavailability. C57BL/6 mice were treated with 100 μg/kg of recombinant IL-1α or TNFα by intraperitoneal injection. Western ligand blotting and immunoprecipitation with specific antisera revealed that serum levels of IGFBP-1 (but not IGFBP- 2, -3, -4, -5 or -6) are increased -4 fold 2 h after treatment and then decline. Northern blotting confirms that hepatic IGFBP-1 mRNA abundance also is increased acutely in both IL-1α- and TNFα-treated animals. Similar results obtained in adrenalectomized mice indicate that adrenal activation is not required for this effect. Cell culture studies show that cytokines exert direct effects on the production of IGFBP-1 by HepG2 hepatoma cells, increasing IGFBP-1 levels in conditioned medium and the abundance of IGFBP-1 mRNA -3-fold. In contrast, transient transfection studies with IGFBP-1 promoter/luciferase reporter gene constructs show that IGFBP-1 promoter activity is reduced after 18 hr cytokine treatment. We conclude that IL-1α and TNFα increase circulating levels of IGFBP-1, reflecting direct effects on hepatic IGFBP-1 mRNA abundance. Stimulation of hepatic IGFBP-1 production may contribute to alterations in IGF bioactivity and impaired anabolism in clinical conditions where cytokine production is high. Additional studies are required to identify specific mechanisms mediating effects of cytokines on hepatic production of IGFBP-1.
- Insulin-like growth factor binding protein
- Interleukin- 1
- Tumor necrosis factor