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Team:Hong Kong HKUST/projectdescription
From 2013.igem.org
The conversion of carbohydrates or protein into fat uses 10 times more calories of energy than simply storing fat in a fat cell*. This brought us attention to one method of burning calories - increase energy expenditure by converting fat into glucose. However, mammals cannot convert fatty acids into carbohydrate due to lack of glyoxylate enzymes, while plants and bacteria can. We planned to introduce glyoxylate enzymes into mammalian cells and introduce an artificial futile cycle.
While the consequence of introducing nonnative cycle unknown, James C. Liao’s group at UCLA recently has introduced glyoxylate shunt into mammalian liver cell to investigate fatty acid metabolism. They concluded that although fatty acids could not be converted into glucose in mammalian cells, human hepatocytes expressing the glyoxylate shunt have increased fatty acid oxidation and mice expressing the shunt were resistance to diet-induced obesity.
In addition to constitutive glyoxylate shunt introduced, HKUST 2013 team plans to elaborate Liao’s group work by introducing inducible system that allows tunable fatty acid uptake by sensing fatty acid concentrations. This inducible system prevents risk of fatty acid deficiency, where glyoxylate shunt no longer functions in a normal
range of fatty acid concentration.
HKUST team plans to investigate four different sensing mechanisms using: 1) fatty acid metabolism regulator protein (FadR), 2) peroxisome proliferator-activated
receptor-alpha (PPAR-alpha) 3) liver- fatty acid binding protein (FABP1) and 4) binding immunoglobulin protein, HSP5 or glucose regulated protein (GRP78). The four sensing mechanisms will be measured and compared.
After construction of constitutive glyoxylate shunt, the most sensitive inducible circuit or promoter will be fused to regulate the glyoxylate shunt. The fatty acids will be quantified to compare uptake of fatty acids between wild type cells and cells expressing glyoxylate shunt. The uptake of fatty acids will be further compared between cells containing constitutive and inducible glyoxylate shunt.
*http://science.howstuffworks.com/life/cellular-microscopic/fat-cell2.htm
