University of Wisconsin–Madison researchers have developed a new way of measuring the volume and activity of beta cells—the source of the hormone insulin. The findings were published in the journal Diabetes.
Weibo Cai, PhD, and his colleagues used PET imaging to identify minute levels of a radioactive chemical in the mouse pancreas. Dr. Cai, Associate Professor of Radiology at UW and senior author of the study, reports that this new test measure how actively the cells make insulin, instead of simply measuring the quantity of beta cells.
He believes this test may be used to evaluate treatments or cell transplantations that are intended to slow or reverse diabetes.
A shortage of insulin due to the death or inactivity of the beta cells is the cause of type 1 diabetes. The same problem can also cause type 2 diabetes. However, type 2 diabetes can also result from insufficient response to insulin.
“In some conditions you can have an adequate number of beta cells, but not all of them are functioning,” Dr.Cai said. “We measure volume and get a product of function times volume, which is what everybody wants to know.”
After filing a provisional patent through the Wisconsin Alumni Research Foundation, Dr. Cai is now planning human studies. The goal is FDA approval of the new method to determine the quantity and condition of the beta cells.
The first trials would examine the distribution and potential toxicity of the radioactive manganese chloride that used as a tracer. The tracer has a short half-life, so the exposure to radiation is no greater than what is now used in the many PET scans used to detect cancer.
The new method will not replace blood sugar testing. Instead, it may be used to track the effectiveness of medicines and other measures intended to dampen the immune assault that kills beta cells.
Dr. Cai noted that the the new test may have advantages over earlier methods. Some magnetic resonance techniques can give information about the quantity and function of beta cells, but the dose of manganese chloride is at least 1 million times higher than the new PET technique. This suggests an advantage in the form of lower toxicity.
In addition, other tests detect beta cells by identifying receptors that are unique to those cells.
“[However], even if cells are not functioning, the receptors are still there,” Dr. Cai said. “That does not tell you if they are making insulin. Our test is based on the calcium channel, a portal that the cell uses to exchange chemicals with its environment. The cell has to be active to take up manganese chloride, therefore it’s functioning. If you have more functioning beta cells, then you have more insulin.”
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