A New Marker for Type-2 Diabetes?

Elevated levels of a molecule called RBP4 (retinol binding protein 4) is an indication of an early stage of the development of insulin resistance , the main cause of type 2 diabetes, as also cardiovascular disease and metabolic syndrome, according to a recent study.

Researchers at Beth Israel Deaconess Medical Center (BIDMC), say their findings offer a potential new target, and also offers an early method of identifying individuals who are at risk of developing the disease. This could help to create better screening tests for insulin resistance, in assessing the effects of diet and exercise programs on diabetes, and also in formulating new therapies targeted at lowering the levels of the protein.

Barbara Kahn, MD, Chief of the Division of Diabetes, Endocrinology and Metabolism at BIDMC and Professor of Medicine at Harvard Medical School says, type 2 diabetes is gaining epidemic propotions in the Western world ,and is and for the first time in a century threatening to reduce life span in the U.S.

Insulin resistance results when the body's muscles, fat and liver cells become unable to respond to the hormone insulin, which is necessary for the body to take up sugar from blood and convert it into energy.This results in an elevated level of glucose in the bloodstream.

Insulin resistance not only predisposes individuals to type 2 diabetes, it also operates as a major risk factor for cardiovascular disease.

An investigator in the Kahn laboratory, Dr.Timothy Graham, says it is often not possible to distinguish individuals with or without insulin resistance. In a previous study conducted on animals, Kahn's laboratory made the discovery that RBP4, a protein secreted from fat cells, formerly recognized for its role in the transport of vitamin A only, can induce insulin resistance.

The researchers were eager to discover if the same applied to humans, and their study revealed that RBP4 might possibly be used as a screening test, but could not confirm if RBP4 is simply a marker for insulin resistance or if it actually causes insulin resistance.

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. The researchers also found that elevated levels of RBP4 were associated with a higher body mass index, elevated hip-to-waist ratio, higher triglyceride levels, decreased HDL cholesterol and increased blood pressure. These factors are part of the metabolic syndrome, and indicate a higher risk of cardiac disease.

The good news is that moderate exercises three to four times a week, for 60 minutes at a stretch , lowered RBP4, a protocol, says Kahn, many people could follow. She says her team is interested in doing a study to see if lowering RBP4 levels can help diabetics, but as RBP4 is required for vitamin A metabolism, it cannot be completely eliminated, but reduced to normal levels.

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Experts say the possibility of an early disease marker for type 2 diabetes is exciting.The findings may also encourage people to exercise more.

More information about insulin resistance and pre-diabetes can be obtained from the National Institute of Diabetes and Digestive and Kidney Diseases.

This study was funded by the National Institutes of Health, the American Diabetes Association, the Swedish Diabetes Association, and the Takeda Pharmaceutical Company, Ltd.