Original investigation
Insulin and glucose play a role in foam cell formation and function
1 Cardiovascular Research Center, University of Virginia, 415 Lane Road, Charlottesville, VA 22903, USA
2 Dept. Cell Biology, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
3 Pfizer, Inc., Groton, CT 06340, USA
4 Dept. of Medicine, University of California at San Diego, 9500 Gilman Road, La Jolla, CA 92093, USA
5 Dept. of Medicine, University of Minnesota, 420 Delaware St SE, Minneapolis, MN 55455, USA
6 Dept. of Internal Medicine/Division of Endocrinology, University of Virginia, PO Box 801409, Charlottesville, VA 22908, USA
Cardiovascular Diabetology 2006, 5:13 doi:10.1186/1475-2840-5-13
Published: 20 June 2006Abstract
Background
Foam cell formation in diabetic patients often occurs in the presence of high insulin and glucose levels. To test whether hyperinsulinemic hyperglycemic conditions affect foam cell differentiation, we examined gene expression, cytokine production, and Akt phosphorylation in human monocyte-derived macrophages incubated with two types of oxidized low density lipoprotein (LDL), minimally modified LDL (mmLDL) and extensively oxidized LDL (OxLDL).
Methods and results
Using Affymetrix GeneChip® arrays, we found that several genes directly related to insulin signaling were changed. The insulin receptor and glucose-6-phosphate dehydrogenase were upregulated by mmLDL and OxLDL, whereas insulin-induced gene 1 was significantly down-regulated. In hyperinsulinemic hyperglycemic conditions, modified LDL upregulated Akt phosphorylation and expression of the insulin-regulated aminopeptidase. The level of proinflammatory cytokines, IL-lβ, IL-12, and IL-6, and of a 5-lipoxygenase eicosanoid, 5-hydroxyeicosatetraenoic acid (5-HETE), was also increased.
Conclusion
These results suggest that the exposure of macrophages to modified low density lipoproteins in hyperglycemic hyperinsulinemic conditions affects insulin signaling and promotes the release of proinflammatory stimuli, such as cytokines and eicosanoids. These in turn may contribute to the development of insulin resistance.
