Diabetes mellitus and obesity are increasing in prevalence, and are associated with increased risk for atherosclerotic cardiovascular disease. Activation of inflammatory processes in visceral fat is thought to contribute to the link between insulin resistance and atherosclerosis. The specific mechanisms involved in this inflammation, however, remain unclear. The hypothesis to be tested in the proposed research is that the 12/15-lipoxygenase (12/15-LO) pathway is important in mediating inflammatory changes in visceral fat, including cytokine production and macrophage infiltration, seen in states of insulin resistance.
One specific aim i s to evaluate the impact of varying degrees of insulin resistance on 12/15-LO pathway activation in visceral fat and in macrophages within visceral fat. Genetically insulin-resistant mice, which are heterozygous null at the insulin receptor and insulin receptor substrate-1 gene loci on the C57BL/6 background, will be fed along with wild-type C57BL/6 mice either a standard chow diet or a """"""""western"""""""" diet which is high in saturated fat and precipitates or worsens insulin resistance. After either 15 or 30 weeks of feeding, visceral adipocytes and macrophages from visceral fat will be harvested, inflammatory gene expression will be measured using quantitative real-time PCR, and cytokine proteins will be studied by immunoassay. Trafficking of macrophages into visceral fat will be quantitated by fluorescence-activated cell sorting and immunohistochemistry. It is expected that more severely insulin-resistant animals will demonstrate higher levels of inflammatory activation.
A second aim i s to determine the importance of 12/15-LO activity in the inflammatory gene expression, cytokine production, and macrophage trafficking associated with insulin resistance. Mice which either have a deletion at the 12/15-LO gene locus or are transgenic for 12/15-LO, both on the C57BL/6 background, will be fed along with wild-type C57BL/6 mice either chow or the western diet. The techniques outlined above will be used to measure markers of inflammation. It is expected that visceral fat inflammatory activation in response to insulin resistance will vary directly with the genetically predetermined activity of 12/15-LO. This research has potential to identify the currently unclear inflammatory processes activated by insulin resistance in fat, and therefore facilitate specific targeted therapy to reduce development of atherosclerosis in the setting of diabetes and pre-diabetes. The ability to apply such measures to the population at large could greatly impact the currently increasing incidence of coronary events and cardiovascular mortality. ? ? ? ?
