October 26, 2012

Obese yet Metabolically Healthy


Obesity and insulin sensitivity seem like oil and water in the recipe of diabetes. But a study published in the online journal Nature Medicine has identified a process that preserves insulin sensitivity in obesity.

Researchers studied mice with genetically modified fat cell expression of mitoNEET. “mitoNEET” is a protein in the outer membrane of the mitochondria. Researchers wanted to see if manipulating mitoNEET would affect the energy yielding capacity of the mitochondria.

They found that by stimulating mitoNEET, the mitochondria enhanced fat uptake and storage, increasing the mass of fat cells. Although the fat cells increased in size, the insulin sensitivity of the cell did not suffer. This was quite puzzling to researchers because obesity and insulin sensitivity are not typically observed together.

The study also found that mitoNEET inhibits mitochondrial iron transport thus lowering the rate of beta cell oxidation. This increased the production of adiponectin.  Adiponectin is shown to enhance insulin sensitivity.

On the flip side, a reduction in mitoNEET expression  increased the iron content of the mitochondria which led to less weight gain on a high-fat diet. However, this reduction in mitoNEET expression also caused more beta cell oxidation and glucose impairment.

At the risk of bringing this down to the level of a Jerry Springer show, if your body is looking to pack on weight while sustaining insulin sensitivity – mitoNEET does the job. The implication of mitoNEET is not immediately known in how it can help in weight loss, but it certainly has a pivotal role in fat cell metabolism. I wonder if mitoNEET is a brown fat cell characteristic. Brown fat, now that does a body good!

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