Quantitative analysis of carbon fluxes for fat biosynthesis in wild-type and IRS-1 knockout brown adipocytes

Excessive fat synthesis and the subsequent dysregulation of lipid metabolism constitute the major pathological factors of obesity and type 2 diabetes through triggering insulin resistance. Thus, controlling fat synthesis by identifying key sites for regulation of lipogenesis and modulating the lipogenic fluxes may provide novel approaches to intervention of the diseases. As a first step to quantitative investigation of lipogenic fluxes from various carbon sources as related to insulin signaling, relative contribution of glucose, glutamine, and acetoacetate to fat biosynthesis in wild-type (WT) and insulin receptor substrate-i knockout (IRS-1 KO) brown adipocytes were analyzed by stable-isotope labeling, GC/MS, and flux estimation. Glutamine contributed more to fatty acid synthesis than glucose in WT cells while glucose's contribution was heavier in IRS-1 KO cells. Unlike the straightforward pathway for lipogenesis from glucose, two possibilities for glutamine's route to fatty acid synthesis have been proposed: glutaminolysis pathway through conventional tricarboxylic acid cycle and a pathway via reductive carboxylation of a-ketoglutarate to isocitrate. These pathways were integrated into a metabolic network model for quantitative estimation of individual lipogenic fluxes. Incubation of the cells with [U-13C] glutamine for 6 hrs led to metabolic and isotopic steady state where individual fluxes of the model were estimated with 95% confidence by least-square fit method.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Yoo, Hyun-Tae, 1973-

Advisor dc:contributor.advisor

• Gregory Stephanopoulos.

• Chemistry.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/30238

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/30238