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Since adipocytes export fatty acids and glycerol and don't use them as an energy source, what is the main source of energy for adipocytes?

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Adipocytes use glucose as an energy source. They express the insulin-responsive glucose transporter GLUT4 just like muscle cells so that when blood glucose levels rise they are primed to take the glucose up for fatty acid biosynthesis, but they also use glucose as a fuel molecule.

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  • $\begingroup$ Thank you! And in the fasting state, which fuel they use? Glucose too? $\endgroup$ – user5354 Jan 10 '14 at 18:31
  • $\begingroup$ In the fasting state blood glucose levels will be maintained by the liver via gluconeogenesis, so yes. During fasting the main function of the adipocytes is fat mobilisation and release of fatty acids (and glycerol, used by the liver as a substrate for gluconeogenesis). $\endgroup$ – Alan Boyd Jan 11 '14 at 13:47
  • $\begingroup$ But if adipocyte's GLUT4 recepetors are not being stimulated by insulin in the fasting state, how can they uptake glucose? Does hydrolysis of the ester link between a fatty acid and the glycerol releases energy? $\endgroup$ – user5354 Jan 11 '14 at 20:43
  • $\begingroup$ @AlanBoyd, this is an interesting question, do you have any reference for the statement that glucose is the main energy source of (white) adipocytes? They are capable of fatty acid oxidation too (see for example jlr.org/content/17/5/516.short) but I have not seen any data on the relative importance of glucose vs fatty acids. $\endgroup$ – Roland Jun 6 '15 at 6:18
  • $\begingroup$ @AlanBoyd, also, to my knowledge, human adipose tissue does not synthesize (much) fatty acids from glucose. See for example ncbi.nlm.nih.gov/pubmed/1113680 $\endgroup$ – Roland Jun 6 '15 at 6:21

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