Scientists find obesity health risk 'trigger'

SCIENTISTS believe they may have uncovered a key reason why obese people have a raised risk of health complications such as type two diabetes.

They blame a specific protein, "pigment epithelium-derived factor" (PEDF), which is secreted by fat cells.

The Australian and US research on mice suggests blocking some of PEDF's action may reverse some complications, raising hopes of new drug treatments.

The study appears in the journal Cell Metabolism.

Because PEDF is produced by fat cells people who are overweight have higher levels of the protein in the bloodstream.

The latest research shows that the protein sends a signal to other tissues in the body, triggering development of insulin resistance, a condition that often leads to type two diabetes, in the muscle and liver.

Raised PEDF levels were also linked to a release of fats into the bloodstream, raising the risk of complications such as heart disease.

In tests on obese mice, the researchers found that treatments designed to block the action of PEDF lowered the animals' blood fat level and reversed some of their insulin resistance.

Fat cells are known to play an important role in regulating the body's metabolism by releasing hormones and other chemicals into the bloodstream.

This pattern of secretion is also known to change with the size of the fat cells.

The latest study set out to identify which of these secretions had a profound general impact on metabolism.

The researchers took particular interest in PEDF because it was already known that levels of the protein were raised in people with type two diabetes, and metabolic syndrome, a collection of health risk factors that include too much belly fat, a high level of cholesterol as well as high blood pressure.

They found that of all the molecules secreted by fat cells PEDF was among the most abundant.

They also showed that PEDF levels fell in obese mice when they lost weight, either by using diet or drugs.

When lean mice in the experiments were injected with PEDF, they showed signs of developing insulin resistance and inflammation in both muscle and the liver.

And in the long term, PEDF raised fat levels in the animals' blood.

These fats were transported into the muscle and liver, where they accumulated, raising the risk of insulin resistance still further. BBC