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theses

Obesity is associated with many medical disorders including type 2 diabetes and certain cancers. During obesity there is increased infiltration of classically activated (M1) macrophages into adipose tissue which is associated with the development of insulin resistance and eventually type 2 diabetes. Macrophages require glutamine to survive but have limited expression of glutamine synthetase (GS), the only enzyme capable of producing glutamine de novo, thus glutamine must be obtained from external sources. During obesity blood flow is limited in adipose tissue hence bringing to question where M1 macrophages obtain their glutamine. Mature adipocytes express high amounts of GS and are known to release glutamine. Therefore glutamine from adipocytes may contribute to the infiltration of M1 macrophages into adipose tissue during obesity. We found that murine RAW264.7 macrophages express low levels of GS and have an absolute requirement for large amounts of exogenous glutamine for proliferation and secretion of proinflammatory cytokines MCP-1 (monocyte chemoattractant protein-1) and MIP-1α (macrophage inflammatory protein-1α). To determine if adipocyte-derived glutamine could support macrophage viability and function, mature 3T3-L1 murine adipocytes and RAW264.7 cells were cocultured for up to 48h in media without added glutamine and with a chemical inhibitor of GS. RAW264.7 cells survived and proliferated in the absence of exogenous glutamine when cocultured with mature 3T3-L1 adipocytes but did not survive in the absence of added glutamine when cocultured with 3T3-L1 preadipocytes or with mature 3T3-L1 adipocytes where GS was inhibited. In addition, when mature 3T3-L1 cells were cocultured with RAW264.7 cells in the absence of glutamine and with the GS inhibitor, the secretion of RANTES (regulated on activation normal T cell expressed and secreted) and Eotaxin-1 were negatively affected while secretion of MCP-1 was slightly affected. The lower secretion of RANTES, Eotaxin-1 and MCP-1 may have been due to RAW264.7 cells in cocultures dying in the absence of glutamine. These findings support the notion that glutamine produced by adipocytes may contribute to the viability and cytokine secretion of adipose tissue macrophages during obesity which may lead to the development of insulin resistance and type 2 diabetes.

ETD_5030

M.S.

Includes bibliographical references

by Samantha Ann Dori

doi:10.7282/T3XG9P6P

ETD graduate

The author owns the copyright to this work.