Arteriosclerosis, thrombosis, and vascular biology
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Arterioscler. Thromb. Vasc. Biol. · Nov 2007
ReviewInflamed adipose tissue: a culprit underlying the metabolic syndrome and atherosclerosis.
The metabolic syndrome is associated with a dysregulated adipose tissue; in part a consequence of adipose cell enlargement and the associated infiltration of macrophages. Adipose cell enlargement leads to a proinflammatory state in the cells with reduced secretion of adiponectin and with increased secretion of several cytokines and chemokines including interleukin (IL)-6, IL-8, and MCP-1. MCP-1 has been shown to play an important role for the associated recruitment of macrophages into the adipose tissue. ⋯ In particular tumor necrosis factor (TNF) alpha, but also IL-6, has been shown to induce these effects in preadipocytes and this is associated with an increased Wnt signaling maintaining the cells in an undifferentiated and proinflammatory state. The proinflammatory state in the adipose tissue also leads to a local insulin resistance including an impaired inhibitory effect of insulin on FFA release. The insulin resistance further supports the proinflammatory state because insulin, by itself, is both antilipolytic and antiinflammatory by antagonizing cytokine-induced activation of STAT signaling.
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Arterioscler. Thromb. Vasc. Biol. · Nov 2007
Angptl4 upregulates cholesterol synthesis in liver via inhibition of LPL- and HL-dependent hepatic cholesterol uptake.
Dysregulation of plasma lipoprotein levels may increase the risk for atherosclerosis. Recently, angiopoietin-like protein 4, also known as fasting-induced adipose factor Fiaf, was uncovered as a novel modulator of plasma lipoprotein metabolism. Here we take advantage of the fasting-dependent phenotype of Angptl4-transgenic (Angptl4-Tg) mice to better characterize the metabolic function of Angptl4. ⋯ The hypertriglyceridemic effect of Angptl4 is attributable to inhibition of LPL-dependent VLDL lipolysis by converting LPL dimers to monomers, and Angptl4 upregulates cholesterol synthesis in liver secondary to inhibition of LPL- and HL-dependent hepatic cholesterol uptake.