Discovery that insulin is produced in the brain raises possibility of Type 3 diabetes. Does High Circulating Insulin Drive Body Fat Accumulation? Answers from Genetically Modified Mice. The house mouse Mus musculus is an incredible research tool in the biomedical sciences, due to its ease of care and its ability to be genetically manipulated. Although mice aren't humans, they resemble us closely in many ways, including how insulin signaling works. Genetic manipulation of mice allows researchers to identify biological mechanisms and cause-effect relationships in a very precise manner. One way of doing this is to create "knockout" mice that lack a specific gene, in an attempt to determine that gene's importance in a particular process. Another way is to create transgenic mice that express a gene of interest, often modified in some way. A third method is to use an extraordinary (but now common) tool called "Cre-lox" recombination (1), which allows us to delete or add a single gene in a specific tissue or cell type.
I attended an interesting talk this week by Dr. Another interesting model is the liver-specific insulin receptor knockout (LIRKO) mouse. Fat Tissue Insulin Sensitivity and Obesity. In this post, I'll discuss a few more facts pertaining to the idea that elevated insulin promotes the accumulation of fat mass. Insulin Action on Fat Cells Over the Course of Fat Gain The idea that insulin acts on fat cells to promote obesity requires that insulin suppress fat release in people with more fat (or people who are gaining fat) to a greater extent than in lean people. As I have written before, this is not the case, and in fact the reverse is true. The fat tissue of obese people fails to normally suppress fatty acid release in response to an increase in insulin caused by a meal or an insulin injection, indicating that insulin's ability to suppress fat release is impaired in obesity (1, 2, 3).
The reason for that is simple: the fat tissue of obese people is insulin resistant. There has been some question around the blogosphere about when insulin resistance in fat tissue occurs. The question was first investigated by Dr. But they went further. The Case of Diazoxide Conclusion.