CXCL16 is a marker of inflammation, atherosclerosis, and acute coronary syndromes in humans.

OBJECTIVES: This study was designed to determine the association of CXCL16 with inflammation, atherosclerosis, and acute coronary syndromes. BACKGROUND: Vascular inflammation coincides with uptake of modified lipoproteins in the pathogenesis of atherosclerosis. CXCL16 is a protein that shares scavenger receptor function, promoting uptake of modified lipids, with the activities of an inflammatory chemokine. However, the role of CXCL16 in atherosclerosis remains uncertain. METHODS: The effect of inflammatory stimuli on CXCL16 gene and protein expression was studied in macrophages, mice, and humans, and the association of sol-CXCL16 with risk factors, atherosclerosis, and acute coronary syndromes was determined in humans. RESULTS: Endotoxin induction of CXCL16 in human macrophages was attenuated by aspirin, nuclear factor (NF)-kappa-B inhibition and peroxisome proliferator-activated receptor (PPAR)-gamma agonists. Experimental human endotoxemia (n = 6) led to an 8-fold increase in whole-blood CXCL16 messenger ribonucleic acid (p < 0.001) and a 1.7-fold increase in soluble (sol)-CXCL16 (p < 0.001), a cleaved active chemokine. Rosiglitazone-blocked endotoxin induced sol-CXCL16 in mice (p = 0.001), and pioglitazone (n = 28), compared to placebo (n = 28), lowered plasma sol-CXCL16 in metabolic syndrome subjects (p < 0.05). In a nested case-control study of acute and chronic coronary artery disease (n = 699), sol-CXCL16 levels correlated with inflammatory and metabolic risk factors and were associated with chronic coronary artery disease (odds ratio [OR] [95% confidence interval], above vs. below median; 1.60 [1.01 to 2.58]; p = 0.04) and acute coronary syndromes (OR 2.52 [1.32 to 4.82], p = 0.005) following adjustment for established risk factors, medications, and C-reactive protein levels. CONCLUSIONS: Our findings suggest that CXCL16 may play a pro-inflammatory role in human atherosclerosis, particularly in acute coronary syndrome.

Diet-dependent cardiovascular lipid metabolism controlled by hepatic LXRalpha.

The high-cholesterol/high-fat Western diet has abetted an epidemic of atherosclerotic cardiovascular disease, the leading cause of death in industrialized nations. Liver X receptors (LXRs) are oxysterol sensors that are required for normal cholesterol and triglyceride homeostasis, yet synthetic LXR agonists produce undesirable hypertriglyceridemia. Here we report a previously unrecognized role for hepatic LXRalpha in the links between diet, serum lipids, and atherosclerosis. A modest increase in hepatic LXRalpha worsened serum lipid profiles in LDL-receptor null mice fed normal chow but had the opposite effect on lipids and afforded strong protection against atherosclerosis on a Western diet. The beneficial effect of hepatic LXRalpha was abrogated by a synthetic LXR agonist, which activated SREBP-1c and its target genes. Thus, the interplay between diet and hepatic LXRalpha is a critical determinant of serum lipid profiles and cardiovascular risk, and selective modulation of LXR target genes in liver can ameliorate hyperlipidemia and cardiovascular disease.

An inflammatory cascade leading to hyperresistinemia in humans.

BACKGROUND: Obesity, the most common cause of insulin resistance, is increasingly recognized as a low-grade inflammatory state. Adipocyte-derived resistin is a circulating protein implicated in insulin resistance in rodents, but the role of human resistin is uncertain because it is produced largely by macrophages. METHODS AND FINDINGS: The effect of endotoxin and cytokines on resistin gene and protein expression was studied in human primary blood monocytes differentiated into macrophages and in healthy human participants. Inflammatory endotoxin induced resistin in primary human macrophages via a cascade involving the secretion of inflammatory cytokines that circulate at increased levels in individuals with obesity. Induction of resistin was attenuated by drugs with dual insulin-sensitizing and anti-inflammatory properties that converge on NF-kappaB. In human study participants, experimental endotoxemia, which produces an insulin-resistant state, causes a dramatic rise in circulating resistin levels. Moreover, in patients with type 2 diabetes, serum resistin levels are correlated with levels of soluble tumor necrosis factor alpha receptor, an inflammatory marker linked to obesity, insulin resistance, and atherosclerosis. CONCLUSIONS: Inflammation is a hyperresistinemic state in humans, and cytokine induction of resistin may contribute to insulin resistance in endotoxemia, obesity, and other inflammatory states.